<var>Using 3D scanning, 3D simulation, and CAD, engineers at the Queensland University of Technology have created a patient-specific contoured mattress that successively supports patients in the operating room.</var>
Paige Little is an expert on using state-of-the-art imaging technology to understand ideal body position and support for enhancing the quality of sleep. It&rsquo;s the kind of research used to improve beds for the home. But in 2018, Little was contacted by a consultant who asked for something more serious. Could she design a customized, patient-specific surgical mattress for a 10-year-old about to undergo spinal surgery?

The patient had Morquio syndrome, a disorder that causes skeletal abnormalities and neuromuscular scoliosis. She would need to lie safely on her stomach and the front of her body for the duration of the surgery.

&ldquo;Intraoperative patient position is always a critical factor in spinal surgery, particularly in the case of prone patient positioning, where the anatomy and physiology of the torso is such that additional pressure may have adverse effects on the cardiopulmonary system as well as causing skin and muscle necrosis,&rdquo; Little said. &ldquo;Optimal patient positioning for spine surgery is vital for surgical success and the minimization of complications intra and postoperatively.&rdquo;

Little, an associate professor at the school of mechanical, medical, and process engineering at Queensland University of Technology, is up to the challenge. Using an innovative digital workflow involving 3D surface scanning, 3D simulation and computer-aided design (CAD), she successfully created a customized theater mattress with the patient&rsquo;s specific body-contour requirements. The operation was a success, and the surgical team praised the mattress and its positive impact on patient outcome.
<img alt="" src="~/getmedia/3cd9331a-8fc6-47de-8bf9-c54a38524afa/patient-img1.jpg" /> <var>Dr Paige Little at Research Centre Qld Children&rsquo;s Hospital.</var>

<h5>Patient-specific design</h5>

Little&rsquo;s goal was to create a customized mattress to hold the patient safely and reduce possible skin damage during the surgery procedure. By using digital simulation tools and CAD, she was able to create a patient-specific surgical mattress that fit the contours of the patient&rsquo;s body. This made it easier for the surgeon to relieve load bearing on prominent anatomical features during the surgery because the support surface was tailored to the patient&rsquo;s anatomy for the lengthy procedure.

&ldquo;The design process is based in CAD, and for many of the mattresses I have designed, I use Solidworks to create the mattress contours,&rdquo; Little said. &ldquo;We have recently explored the use of CNC machining to create the surface contours in the polyurethane foam, and with high spindle speeds it is possible to machine this foam using standard tooling. The machining is very successful with well-defined surface contours, and relatively little post-process cleaning is needed to remove dust waste. The foams do not require freezing to machine them. They also do not release toxic fumes or particulate matter.&rdquo;

Topographic scanning of the entire patient was required to create a mattress contour. &ldquo;The contour is not a replica of the patient&rsquo;s anatomy, but rather is custom-designed using the topographic scan as a basis,&rdquo; Little said. &ldquo;The design process cannot be parameterized&mdash;the design is created for each patient using CAD methods to alleviate pressure on the skin surface over areas that are delicate, or regions of the anatomy that cannot bear load for long periods of time. For some corrective surgeries, the patient may be lying stationary for many hours.&rdquo;

Manufacture is currently a manual, just-in-time process. The process may benefit from CNC machining or robotic manufacturing, especially for mattress contours that are for large or tall individuals or have deep cutouts and/or overhangs.

Sealy of Australia then manufactured the final mattress product. Technicians used the 3D model to hand-cut and piece together multiple layers of soft hypo-allergenic foam to conform exactly to the patient&rsquo;s anatomy.

The custom mattress is effectively contoured to the patient&rsquo;s anterior anatomy during surgery. Intraoperative monitoring indicated the patient was not under undue cardiovascular strain over the course of the operation &ldquo;and she successfully remained in the prone position for the entire eight-hour operation,&rdquo; Little said. &ldquo;Immediately postoperatively, there was no evidence of excessive interface pressure between the patient and the support, suggesting the custom-fit mattress successfully distributed the patient&rsquo;s body weight, alleviating regions of excessive pressure.&rdquo;
<img alt="" src="~/getmedia/a3cf9bdb-f951-4224-a7dc-5c8ec7269b24/patient-img2.jpg" /><var>Sealy of Australia R&amp;D manager Daniel Green exams form that contours to the patient&rsquo;s torso.</var>

<h5>Moving Forward</h5>

Since the first use of the surgical mattress, Little has designed 11 other supportive mattresses for pediatric patients with unique anatomies requiring support during surgery&mdash;all with successful results.

The next step is to continue showcasing the mattresses to a broader clinical audience so other patients can benefit from the use of customized body supports during surgery. &ldquo;Their surgical teams will also gain confidence in reducing the risks of complications due to extended periods of weight-bearing in patients with unique conditions,&rdquo; Little said.

The digital workflow she used to design the mattresses can also be applied to the design and advanced manufacturing of other custom-fit devices to assist in treatment and/or rehabilitation of patients. &ldquo;These same techniques&mdash;3D topographic scanning, 3D simulation, and CAD methods&mdash;can be applied to the design of customized corrective/rehabilitation orthoses,&rdquo; Little said, &ldquo;or to the custom design of supports for radiation therapy to ensure the patient is positioned in a repeatable position between treatment appointments.&rdquo;

Using 3D scanning, 3D simulation, and CAD, engineers at the Queensland University of Technology have created a patient-specific contoured mattress that successively supports patients in the operating room.

<var>Using 3D scanning, 3D simulation, and CAD, engineers at the Queensland University of Technology have created a patient-specific contoured mattress that successively supports patients in the operating room.</var>

Paige Little is an expert on using state-of-the-art imaging technology to understand ideal body position and support for enhancing the quality of sleep. It&rsquo;s the kind of research used to improve beds for the home. But in 2018, Little was contacted by a consultant who asked for something more serious. Could she design a customized, patient-specific surgical mattress for a 10-year-old about to undergo spinal surgery?

The patient had Morquio syndrome, a disorder that causes skeletal abnormalities and neuromuscular scoliosis. She would need to lie safely on her stomach and the front of her body for the duration of the surgery.

&ldquo;Intraoperative patient position is always a critical factor in spinal surgery, particularly in the case of prone patient positioning, where the anatomy and physiology of the torso is such that additional pressure may have adverse effects on the cardiopulmonary system as well as causing skin and muscle necrosis,&rdquo; Little said. &ldquo;Optimal patient positioning for spine surgery is vital for surgical success and the minimization of complications intra and postoperatively.&rdquo;
Little, an associate professor at the school of mechanical, medical, and process engineering at Queensland University of Technology, is up to the challenge. Using an innovative digital workflow involving 3D surface scanning, 3D simulation and computer-aided design (CAD), she successfully created a customized theater mattress with the patient&rsquo;s specific body-contour requirements. The operation was a success, and the surgical team praised the mattress and its positive impact on patient outcome.

Patient Support Via Customized Surgical Mattresses

<var>Hydrogen seems like an ideal fuel, but a feasibility analysis reveals the factors that will determine its success.</var>
Hydrogen has the highest energy density by weight of any fuel. So it only makes sense that compressed hydrogen gas is being considered as a carbon-free replacement for diesel in heavy-duty trucks. A hydrogen-fueled truck fleet would substantially reduce greenhouse gas emissions and other pollutants from the freight industry.

Before that can happen, engineers need to work out the optimum technology to make hydrogen economical as well as clean.

​&ldquo;Hydrogen technology is currently expensive because of relatively low deployment. Once it is more common, the refueling infrastructure cost should decrease significantly. Hydrogen refueling infrastructure can be implemented immediately. It has the potential to be very economical,&rdquo; said Wahiba Yaici, a research scientist at the CanmetENERGY Research Centre, Natural Resources Canada in Ottawa, Ontario.

The cost of hydrogen itself looms as the main element in the acceptance of compressed hydrogen. It is rarely found isolated and must go through processes to extract it. Each hydrogen production method involves separating hydrogen from some compound. Common extraction processes include natural gas reforming, biomass gasification, and coal gasification. So-called green hydrogen is produced by using renewable energy such as solar and wind to power the electrolysis of water or other hydrogen-making reactions.
<img alt="A truck cab with visible hydrogen fuel tank" src="~/getmedia/c92a71b0-061d-466a-b7d5-8b3ffeabf1ff/hydrogen-img1.jpg" /><var>Generally, green hydrogen is more expensive than hydrogen produced by other methods, but it also has the advantage of producing zero carbon emissions.</var>

Storing hydrogen is another issue. Hydrogen at a fueling station can be stored either as a gas or a liquid. Storing hydrogen as a gas typically requires high-pressure tanks at 5,000 to 10,000 psi. Storage as a liquid requires cryogenic temperatures, as the boiling point of hydrogen at one atmosphere pressure is &minus;252.8 &deg;C (-423 &deg;F).

The main options for onboard hydrogen storage in vehicles are gaseous storage at 5,000 psi or at 10,000 psi in thermally insulated tanks or in materials with superior chemical properties, like metal hydrides or organic compounds,&rdquo; Yaici said.

To address the hydrogen refueling scenario for big trucks, Yaici teamed with Michela Longo, an associate professor at the Politecnico di Milano in Italy, to write a paper, &ldquo;Hydrogen Gas Refueling Infrastructure for Heavy-Duty Trucks: A Feasibility Analysis,&rdquo; for the ASME Journal of Energy Resources Technology. Both authors are mechanical engineers. The pair chose to pursue hydrogen because it can be used as fuel in modified internal combustion engines (ICEs), reducing the need to purchase new vehicles. Existing diesel engines can easily be modified to burn hydrogen. This is in contrast to the fuel-cell-powered vehicles most people think of when talking hydrogen; fuel cells combine hydrogen and oxygen, yielding water, heat, and electricity used to power an electric motor that drives the vehicle.

This paper investigates the feasibility of developing a nationwide network of hydrogen refueling infrastructure to help convert the long-haul, heavy-duty (LHHD) truck fleet from diesel fuel to hydrogen. Diesel is currently the main fuel used to transport freight over the road.

The team carried out a technical analysis to estimate the number of hydrogen refueling stations needed to convert the fleet of LHHD vehicles to hydrogen. They also did an economic analysis to evaluate the final selling price of hydrogen.

According to Yaici, &ldquo;Results from the techno-economic study showed that hydrogen prices can vary significantly.&rdquo; On average, they found hydrogen to cost 239 percent more than diesel due to the diverse costs of the various production methods for hydrogen. Hydrogen also has about 2.6 times the energy density of diesel fuel by weight, which serves as an equalizer. Energy density by volume is another matter because at the operating temperature of trucks, diesel is a liquid while hydrogen is a gas, giving it a lower energy density by volume if it is not liquefied by cryogenics. Regardless of the hydrogen production method, the process can occur at a central facility or locally where it is needed.

&ldquo;A central system can increase the scope of production by producing hydrogen at large facilities that take advantage of bulk processes to reduce costs per unit,&rdquo; Yaici said. &ldquo;Nevertheless, hydrogen must be transported to its destination via pipeline or trucks. This will increase the operational fees. A distributed process, one where hydrogen is produced on demand locally, eliminates the need to deliver hydrogen over long distances.&rdquo;
<img alt="A hydrogen &quot;gas&quot; pump accompanied by a small array of solar panels" src="~/getmedia/7f96ca95-97e5-4062-9f56-5da4b3d880e5/hydrogen-img2.jpg" />
Hydrogen stations are built to refuel vehicles in similar manner to those used by diesel stations. Each refueling station will consist of a compressor, storage tanks, and at least one dispenser. Yaici pointed out the versatility of the feasibility study. &ldquo;The methodology and models proposed can be used for studying the techno-economics of hydrogen refueling stations in any country and for other types of ICE fleets or fuel cell vehicles,&rdquo; he said.

This includes refueling stations for vehicle fleets powered by renewable fuels such as renewable natural gas or biofuels. Engineering analyses such as this one will help shape the future of transportation.

Hydrogen seems like an ideal fuel, but a feasibility analysis reveals the factors that will determine its success.

<var>Hydrogen seems like an ideal fuel, but a feasibility analysis reveals the factors that will determine its success.</var>
Hydrogen has the highest energy density by weight of any fuel. So it only makes sense that compressed hydrogen gas is being considered as a carbon-free replacement for diesel in heavy-duty trucks. A hydrogen-fueled truck fleet would substantially reduce greenhouse gas emissions and other pollutants from the freight industry.

Before that can happen, engineers need to work out the optimum technology to make hydrogen economical as well as clean.

Putting Hydrogen to the Economic Test

Interview with Moncef Krarti

Moncef Krarti, head of the Building System Program at the University of Colorado, Boulder, discusses ways to turn down the temperature on hot, overcrowded urban areas.

Cooling Cities by Combating Heat Islands

Infographic: Pneumatic Help for Grasping

<div class="infogram-embed" data-id="_/JNK9h2xLuaalwUNVZqrN" data-title="Pneumatically-Powered Help for Grasping" data-type="interactive">&nbsp;</div>
 
&nbsp;

Researchers hope this pneumatic grip glove could soon help relieve industrial workers of some pain.

Workers who must repeat forceful actions with their hands&mdash;whether operating industrial hand tools or typing on a keyboard&mdash;are often subject to carpal tunnel syndrome and other cumulative trauma disorders, which not only are painful but also diminish grip strength. Naveen Chandrashekar, a professor of mechanical and mechatronics engineering at the University of Waterloo in Ontario, and graduate student Daniel Loewen, now chief technology officer at ioAirFlow in Winnipeg, looked for a way to reduce the force needed by workers operating hand tools, which would lean to less wear and tear on the hands and wrists.

Pneumatic Help for Grasping

October-December 2022

<var>What if your car was as vulnerable to hack into as your laptop? The reality is cars today are basically a computer on wheels. According to Car and Driver, 40 percent of a new car&rsquo;s cost is driven by electronic components. The New York Times reported that a modern vehicle could contain more than 3,000 computer chips. Electronics are such an essential part of a car&rsquo;s design that the shortage of semiconductors due to supply chain disruption from the pandemic has impacted auto assembly lines worldwide, creating a lack of new vehicles on the market.</var> 
 
By introducing computer systems into vehicles, hackers have found ways to exploit their vulnerabilities. In 2015, Black Hat security researchers Charlie Miller and Chris Valasek hacked a Jeep Cherokee via its infotainment system. Miller and Valasek exploited how the vehicle autogenerated its Wi-Fi password based on the time when the car&rsquo;s multimedia system would turn on. Through the infotainment system, the hackers could manipulate the air conditioner, the radio, the windshield wipers, and even the transmission. On a road test with Wired magazine, the hackers cut the transmission as the vehicle was driving 70 mph on the highway. This past February, German teenager David Colombo identified a vulnerability in the TeslaMate, a third-party application used by Tesla owners to analyze car performance. By hacking the app, Colombo was able to unlock doors, turn on and off the headlights, and control the radio. He was even able to track in real-time the location of the car. 
 
<img alt="" src="~/getmedia/5329b926-0216-4ace-bdb7-ec2d9631e42a/cyber1@2x.jpg" /> 
<var>&ldquo;We have connected vehicles today that exposed multiple internet access points to the internet. There is the infotainment system, but also smart sensors and various devices connected to smart roads and smart cities,&rdquo; said Francesco Pascale, solution lead of embedded IIoT and device management at Almaviva Digitaltec.</var> 
 
Pascale, along with Marco Lombardi and Domenico Santaniello, professors at the Department of Industrial Engineering at the University of Salerno, recently authored a study on how cyberattacks can be detected in connected vehicles. The study &ldquo;Two-Step Algorithm to Detect Cyber-Attack Over the Can-Bus: A Preliminary Case Study in Connected Vehicles&rdquo; was published in the ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part B: Mechanical Engineering. The paper highlights how connected vehicles today receive over-the-air updates, transmit diagnostic information, and provide streaming entertainment options. These vehicle-to-everything connections make many cars vulnerable to being hacked. &ldquo;Some types of cyberattacks can be targeted to take possession of sensitive data, but the most dangerous ones, as seen in past years, can aim to compromise the car motor functions or, even worse, to take possession of it while driving. It is not difficult to think that autonomous vehicles can become attractive targets for hackers in the not-too-distant future,&rdquo; Pascale said. Last year, the European Union Agency for Cybersecurity (ENSIA) published the Cybersecurity Challenges in the Uptake of Artificial Intelligence in Autonomous Driving report, highlighting the security challenges future autonomous vehicles face and how the artificial intelligence systems can be exploited. Possible attack scenarios include tampering with the car&rsquo;s computer vision, jamming or blinding the sensors, hijacking communication channels, and information disclosure. To help identify these attacks, Pascale, Lombardi, and Santaniello propose to analyze the data flow that moves via the communication channels between various electronic control units (ECUs) inside the vehicle CAN-Bus, the internal communication system. Using a two-step algorithm that first performs a spatial-temporal analysis of the data and then a probabilistic analysis, the algorithm can understand if a given stream of data in a particular time box can be considered an attack or not with a certain probability. 
 
<img alt="" src="~/getmedia/f2df193b-96e5-44bb-a29b-ed7445863ad5/cyber2@2x.jpg" /> 
 
&ldquo;This methodology has been expanded to include the recognition of real-world scenarios, such as city traffic, driving on a motorway, extra-urban roads with animals, etc., in order to have even more precision and accuracy in the analysis,&rdquo; Pascale said. The current algorithm is part of the Italian patent n.102021000009548, soon extending internationally. The patent will become part of MinervaS, a startup organization creating solutions for vehicles and energy systems, promoted by the University of Salerno. The global market for automotive cybersecurity is expected to increase significantly over the next decade. The projected market value will reach $5.3 billion by 2026. Drivers want smart and connected cars, providing detailed information about their trips and entertainment while driving. Companies such as SafeRide and Synopsys offer cybersecurity suites that help protect vehicles from cyber threats. According to Pascale, dealing with cyberattacks is a delicate approach. &ldquo;An immediate solution could be to exclude the node that generated the attack from the system (virtually disconnect the ECU from the CAN-Bus). However, this solution is not always applicable because, at times, it could be a node belonging to a critical system such as everything concerning the mechanics of the vehicle; if the attack is carried out while driving, this would involve a risk for the health of people at the internal of the same,&rdquo; Pascale said. Another approach could be to block the vehicle to avoid possible damage automatically. However, the problem with this approach is that if the attack targets a non-critical part, blocking the car may not be warranted. According to Pascale, &ldquo;the right approach would be to consider the weight of the attack with respect to the node that is attacked and evaluate the risk associated with each and on the basis of that foresee targeted actions.&rdquo; As cars become smarter and more connected, cybersecurity will continue to play an essential role in vehicles and their safety. 
 
&nbsp;

New research from the University of Salerno provides methods on how to detect and protect connected vehicles from cyberattacks.

<var>What if your car was as vulnerable to hack into as your laptop? The reality is cars today are basically a computer on wheels. According to Car and Driver, 40 percent of a new car&rsquo;s cost is driven by electronic components. The New York Times reported that a modern vehicle could contain more than 3,000 computer chips. Electronics are such an essential part of a car&rsquo;s design that the shortage of semiconductors due to supply chain disruption from the pandemic has impacted auto assembly lines worldwide, creating a lack of new vehicles on the market.</var> 
 
By introducing computer systems into vehicles, hackers have found ways to exploit their vulnerabilities. In 2015, Black Hat security researchers Charlie Miller and Chris Valasek hacked a Jeep Cherokee via its infotainment system. Miller and Valasek exploited how the vehicle autogenerated its Wi-Fi password based on the time when the car&rsquo;s multimedia system would turn on. Through the infotainment system, the hackers could manipulate the air conditioner, the radio, the windshield wipers, and even the transmission. On a road test with Wired magazine, the hackers cut the transmission as the vehicle was driving 70 mph on the highway. This past February, German teenager David Colombo identified a vulnerability in the TeslaMate, a third-party application used by Tesla owners to analyze car performance. By hacking the app, Colombo was able to unlock doors, turn on and off the headlights, and control the radio. He was even able to track in real-time the location of the car.

Advancing Cybersecurity in Connected Vehicles

<var>Lidar, or light detection and ranging, is a popular remote sensing method used for measuring the exact distance to an object. These imaging systems are increasingly used in the development of autonomous vehicles (AVs). However, final technology implementation cannot yet be achieved because major AV manufacturers are only now starting to select providers for data collection units that can be introduced in commercial vehicles.</var>

One of the biggest unknowns in the development of AVs is how adverse weather conditions challenge the development of safe and reliable advanced autonomous systems for sensing and perception. How does the diffraction of light through rain, fog, and snow limit lidar performance? 
 
Although many AV developers are hopeful that automotive lidar sensors will be safe and effective in all weather conditions, a quantitative analysis of these effects is lacking. Currently, testing for autonomous vehicles is primarily performed in sunny environments. Testing conducted in good weather cannot be assumed to correlate directly with performance quality under extreme weather conditions, which could result in false detection caused by the backscattered intensity, thereby reducing the reliability of the sensor. Thus, the sensitivity of lidar to weather is a major drawback to commercialization. 
 
To help resolve this issue, researchers at Frostburg State University in Frostburg, Md., led by Jamil Abdo, associate professor of mechanical engineering and department chair, tested lidar sensors in adverse weather to understand how extreme weather impacts lidar performance. 
 
<img alt="" src="~/getmedia/b2a54a21-306a-4e32-ba61-9b2045095f9a/selfdriving1@2x.jpg" /> 
<var>The results were presented in &ldquo;Effective Range Assessment of Lidar Imaging Systems for Autonomous Vehicles Under Adverse Weather Conditions with Stationary Vehicles&rdquo; in ASME&rsquo;s Journal of Risk and Uncertainty in Engineering Systems.</var>

<h4>Approach and Methodology</h4>

Abdo and his team designed an experiment to evaluate lidar performance under adverse weather conditions. Data sets were recorded under these conditions to determine the effective range to estimate the maximum range at which the lidar sensors can return points. 
 
The testing set-up and algorithms were developed for two commercial lidar sensors&mdash;Velodyne VLP-32 and Ouster OS1-32. Weather resistance of the set-up was an important consideration. The weatherproof platform was designed so that the sensors units were located about three feet high off the ground. 
 
We wrote programs to interface with these lidar units and to analyze the data,&rdquo; Abdo said. &ldquo;These programs allowed us to count the number of points in a region of space.&rdquo; 
 
The team selected a remote area for testing to ensure that other cars did not drive by, affecting the data. The test was also designed to meet the goals of ease of testing and reproducibility in testing locations. 
 
&ldquo;Even though the western Maryland area around Frostburg is a great location for testing, it was very hard to have a reproducible weather condition,&rdquo; Abdo said. &ldquo;We had to use design-of-experiment techniques to account for nondesirable factors such as noise during the testing.&rdquo; 
 
Abdo decided the best way to test the lidar units was in a worst-case scenario with two cars heading directly toward each other, recreated by driving a car straight toward the test platform. &ldquo;This is the worst-case scenario for car detection as when the car faces the lidar sensor, its cross-section is the smallest with respect to the sensor,&rdquo; Abdo said. 
 
Two types of tests were performed under various weather conditions. The first involved stationary tests where the car stopped every 7.5 meters for a few seconds before driving forward another 7.5 meters. The second method conducted testing with the car moving toward the lidar units at varying speeds of five mph, 10 mph, and 20 mph. 
 
Test results showed that both dense fog and heavy rain severely impacted lidar sensors&rsquo; object detection and operating range detection. Light rain had minimal effect on lidar performance, and snow had no negative impact. 
 
<img alt="" src="~/getmedia/37843adc-af7c-457e-b410-f484b00c2f6c/selfdriving2@2x.jpg" />

<h4>Moving Forward</h4>

Determining the influence of weather on lidar sensor performance is a critical step toward improving the safety levels for autonomous driving under adverse weather conditions &ldquo;because such analyses provide reliable information for adapting vehicle behavior,&rdquo; Abdo said. 
 
The AV industry has already taken notice of Abdo&rsquo;s work. Three major lidar manufacturers have contacted Abdo since he published the team&rsquo;s research/findings in September 2021, he said. The team has also received funds from Maryland Industrial Partners (MIPS) and Intelligent Fusion Company to support the second phase of research activities. 
 
For this work, &ldquo;Lidar performance in rain, snow, fog, smog, and dust will be investigated using dynamic sensors and moving targets,&rdquo; Abdo stated. &ldquo;We also plan to explore object tracking&mdash;for example, other vehicles and any potential obstacles&mdash;with lidar systems.&rdquo;

Explore how adverse weather conditions can impact autonomous vehicles&rsquo; lidar cameras.

<var>Lidar, or light detection and ranging, is a popular remote sensing method used for measuring the exact distance to an object. These imaging systems are increasingly used in the development of autonomous vehicles (AVs). However, final technology implementation cannot yet be achieved because major AV manufacturers are only now starting to select providers for data collection units that can be introduced in commercial vehicles.</var> 
One of the biggest unknowns in the development of AVs is how adverse weather conditions challenge the development of safe and reliable advanced autonomous systems for sensing and perception. How does the diffraction of light through rain, fog, and snow limit lidar performance?

How Self-Driving Cars See in Extreme Weather

Interview with Luca Capriotti

Luca Capriotti, former president of the International Youth Nuclear Congress, shares his passion for nuclear energy and beliefs that it can become a viable, safe power source to be used globally and responsibly in the future.

The Future of Power is Nuclear

Infographic: Sodium-Cooled Fast Reactor

&nbsp;
<div class="infogram-embed" data-id="_/GNZqhKYA24E6kz9OqOfZ" data-title="Infographic-RD Pulse-v02" data-type="interactive">&nbsp;</div>

<var>Most nuclear reactors in operation today use water as a coolant, but one promising alternative looks to replace water with liquid sodium. Sodium can be heated to high temperatures before boiling, which means that a sodium-cooled reactor can operate at atmospheric pressure and can use a thinner reactor vessel. These reactors also will produce less radioactive waste. Explore the diagram of a sodium-cooled fast reactor below.</var>

Sodium-Cooled Fast Reactor

July-September 2022

<var>Through a complete review of published research over the last 60 years, researchers aim to propel development of new head injury metrics forward.</var>

Metrics that help engineers design safer helmets and vehicles to prevent fatalities went mostly unchanged for about 50 years. Now, researchers are looking for better metrics to help prevent brain injuries&mdash;from mild concussions to traumatic damage.

In &ldquo;A Review of Head Injury Metrics Used in Automotive Safety and Sports Protective Equipment,&rdquo; published in the ASME Journal of Biomedical Engineering, authors Stefan Duma and Bethany Rowson examined every major metric that has been published over the past 60 years, including some of the original work done at Wayne State University in the 1960s and 1970s that examined skull fractures and were used for early football helmet and vehicle design standards. This effort summarizes existing head injury metrics and their applications for head and brain injuries.

Duma is Harry C. Wyatt Professor of Engineering and director of the Institute for Critical Technology and Applied Science (ICTAS) at Virginia Tech and Rowson is a former Virginia Tech research assistant professor. The team defined a metric as any variable or combination of variables that is &ldquo;used to assess injury severity, while a criterion is any quantitative value that is considered a threshold for injury or is assigned a predicted risk of injury.&rdquo;

The Virginia Tech team has about 30 years of history in automobile safety. About 20 years ago, they started working more in the sports and football area. Today, about 40 faculty and students at Virginia Tech work on brain-related research.
<img alt="" src="~/getmedia/03352d6a-8cb5-41f8-aedf-96603cdaf6a8/brain-img1.jpg" />
&ldquo;When you look at brain injury, a lot of the same tools are used when we evaluate vehicle safety as well as athletic player safety,&rdquo; Duma said. &ldquo;So, it made a lot of sense for us to do a detailed systematic review of brain injury criteria and head injury criteria that are used in both auto safety and sports biomechanics.&rdquo;

According to the review, the first head injury metrics to be included in safety standards were meant to reduce severe head injuries and fatalities. After the National Operating Committee on Standards for Athletic Equipment implemented football helmet standards in 1974, fatal head injuries in football dropped by approximately 74 percent, the authors noted. Similarly, with the implementation of mandatory Federal Motor Vehicle Safety Standards in 1968, the fatality rate of motor vehicle occupants dropped by 81 percent. Implementation of both standards saved thousands of lives, Duma added.

&ldquo;When we started using some of these metrics, we had a big reduction in injury rates. But there was not a lot of change for about 50 years, so it kind of stayed steady,&rdquo; he said. &ldquo;And now we&rsquo;re in a much more dynamic time where people are looking at much more complex and effective injury criteria. And the ultimate hope is that we can reduce more brain injuries.&rdquo;

Duma and Rowson noted that injury metrics are based on translational motion, rotational motion, or a combination of the two, and figuring out how to limit the amount of energy that is transferred during an event to an individual&rsquo;s head. Once metrics have been tested, evaluated, and analyzed, engineers are able to use them to better design cars and helmets that minimize injury and fatality risks.

While there have been numerous proposed brain injury metrics, the authors stated that few have been implemented in safety standards for vehicles or sports protective equipment. And those are still based off experimental data collected in the 1950s and 1960s, which was used to develop the Wayne State Tolerance Curve, which is the relationship between linear head acceleration, duration of acceleration, and incidence of head injury.
<img alt="" src="~/getmedia/358e7bd2-da97-4ca8-a6c8-620b30021700/brain-img2.jpg" />
&ldquo;If you start with reducing fatalities, which a lot of the initial work has done, now what we want to do is reduce concussions and brain injuries,&rdquo; he said. &ldquo;So, the real focus now and into the future is what metric is going to be best to help designers reduce concussion.&rdquo;

A tremendous amount of research is already underway worldwide into concussions, but &ldquo;there&rsquo;s a great deal still to be discovered in that space and a lot of questions to answer, [such as] why there are different injury rates,&rdquo; Duma said. &ldquo;This paper can help provide the foundation to examine some of these trends by using some of these different metrics.&rdquo;

But one major drawback to existing research is how limited the data is for different populations. Historically, most brain injury analysis in sports focused on male football players, Duma noted.

&ldquo;For about the past five years, we&rsquo;ve begun to focus much more on gender and sex differences in brain injury,&rdquo; he said. &ldquo;We&rsquo;ve really expanded that effort into women&rsquo;s lacrosse, rugby and soccer, really looking at understanding brain injury differences between men and women. And that&rsquo;s where a lot of the research is right now.&rdquo;

Duma and Rowson cautioned that as these new metrics are developed, they must be effectively evaluated against real world datasets without sampling bias, such as actual injury rates from a population, and head impact data from both high- and low-risk individuals.

&ldquo;The thing that I&rsquo;m really interested in is a simple question, which is how much is too much? How many times, how often, what&rsquo;s the frequency, what&rsquo;s the magnitude? We really just don&rsquo;t know [the answer to] that simple question,&rdquo; Duma explained. &ldquo;So, the idea is if we can better determine that, then we can really start to scope firm limits on head impact exposure for all sports and all activities.&rdquo;

Through a complete review of published research over the last 60 years, researchers aim to propel development of new head injury metrics forward.

<var>Through a complete review of published research over the last 60 years, researchers aim to propel development of new head injury metrics forward.</var>

Metrics that help engineers design safer helmets and vehicles to prevent fatalities went mostly unchanged for about 50 years. Now, researchers are looking for better metrics to help prevent brain injuries&mdash;from mild concussions to traumatic damage.

In &ldquo;A Review of Head Injury Metrics Used in Automotive Safety and Sports Protective Equipment,&rdquo; published in the ASME Journal of Biomedical Engineering, authors Stefan Duma and Bethany Rowson examined every major metric that has been published over the past 60 years, including some of the original work done at Wayne State University in the 1960s and 1970s that examined skull fractures and were used for early football helmet and vehicle design standards. This effort summarizes existing head injury metrics and their applications for head and brain injuries.

Duma is Harry C. Wyatt Professor of Engineering and director of the Institute for Critical Technology and Applied Science (ICTAS) at Virginia Tech and Rowson is a former Virginia Tech research assistant professor. The team defined a metric as any variable or combination of variables that is &ldquo;used to assess injury severity, while a criterion is any quantitative value that is considered a threshold for injury or is assigned a predicted risk of injury.&rdquo;

The Virginia Tech team has about 30 years of history in automobile safety. About 20 years ago, they started working more in the sports and football area. Today, about 40 faculty and students at Virginia Tech work on brain-related research.

Advancing Head Injury Metrics Research

<var>Researchers at Vanderbilt University have invented a nitrogen gas-powered thruster that is worn on the back that can correct falls as they start, restoring balance and averting potential injury.</var>

Falls can lead to severe and fatal injuries, particularly for elderly people. According to the U.S. Centers for Disease Control and Prevention, millions of people fall each year, with one in five suffering serious injury.

Michael Goldfarb, a professor of mechanical engineering at Vanderbilt University, has first-hand experience dealing with this health risk. &ldquo;As my parents grew older, both had experiences with fall risk that really limited their quality of life,&rdquo; he said. &ldquo;My father, in particular, had Parkinson&rsquo;s disease.&rdquo;

Goldfarb began thinking about new ways to correct occasional states of imbalance. Robotic exoskeletons can offer balance assistance, but have design challenges, such as having to coordinate a recovery response with the user. To avoid requiring a large frame or other structure (which would impede independence), he decided to focus on building a backpack-worn system that can apply forces directly to a person&rsquo;s body using a thruster.

&ldquo;This research challenge seemingly has not received much attention and therefore there were a lot of unknowns,&rdquo; Goldfarb said. &ldquo;Correcting a fall is a shared task between the person falling and the device helping to arrest the fall. What is the distribution of shared effort? How much force is appropriate to correct an impending fall? For how long is the force required? Can the magnitude of assistance required be provided by a compact cold-gas thruster?&rdquo;

Goldfarb and fellow researchers Almaskhan Baimyshev and Michael Finn-Henry then set out to create a lightweight, cold-gas thruster (CGT) jetpack that senses when a fall has been initiated and can provide a restoring force to help the person recover his or her balance. 
 
<img alt="" src="~/getmedia/5f7e2c63-99d6-45e1-9aef-b2ae61af4793/fall-img1.jpg" /> 
 
The prototype consists of four key features:

<ul>
	<li>Gas thruster subsystem: The compressed gas tank and converging-and-diverging nozzle use nitrogen because the non-toxic gas has a high molecular weight (which increases thrust) and is available at a low cost.</li>
</ul>
&nbsp;

<ul>
	<li>Gas valve subsystem: A custom high-throughput, fast-acting solenoid valve activates the CGT in the event of an impending fall.</li>
</ul>
&nbsp;

<ul>
	<li>Nozzle servo subsystem: A servo system controls the angle of the nozzle (and therefore the thrust vector) about the axis of rotation.</li>
</ul>
&nbsp;

<ul>
	<li>Cold-gas thruster embedded system and control hardware: The embedded system provides sensing and control of the CGT prototype, including a microcontroller and six-axis inertial measurement unit.</li>
</ul>
&nbsp;

To test the system, the team created a &ldquo;rocking block&rdquo; model as a simple approximation of a standing human. The CGT was able to restore the rocking block to its original stability when released from all initial angles well outside of its unassisted basin of stability, indicating promise as a wearable device for preventing or mitigating falls for people at fall risk.

Among the design challenges the team faced was developing a low-power, compact, very-high-throughput, fast-acting valve that can release 1,500-psi cold gas with a response time of a few milliseconds. Another challenge was detecting the onset of a fall and predicting when (and eventually in what direction) to fire the thruster to arrest the fall.

&ldquo;We also wanted to confine the sensing and actuation elements of the system to the backpack,&rdquo; said Goldfarb. &ldquo;All sensing required to make these decisions should ideally be on the backpack&mdash;for example, detection should not depend on external cameras or sensors worn on other parts of the body.&rdquo;

The CGT is a first-of-its-kind device. The team was pleasantly surprised by the control authority the thruster provides (the ability to provide substantial corrective assistance) and its soft but firm correction when arresting a fall.

&ldquo;One thing I really appreciate about it is that it combines what are sometimes considered disparate fields of mechanical engineering, including fluid mechanics, nozzle design, electropneumatic valve design, dynamics of multi-link rigid-body systems, and control theory,&rdquo; Goldfarb said. &ldquo;The work has also entailed substantial aspects of mechatronic design, particularly associated with the onboard sensing and control of the CGT.&rdquo;

The team published their results in the paper, &ldquo;Feasibility of a Wearable Cold-Gas Thruster for Fall Prevention&rdquo; in the August 2022 issue of the ASME Journal of Dynamic Systems, Measurement, and Control.
<img alt="" src="~/getmedia/2bac9e64-c06b-4fdd-b9dc-780f84efafab/fall-img2.jpg" />
<h5>Future Development</h5>

Goldfarb is currently developing a single degree-of-freedom system, which is directed at arresting backward falls.&nbsp;

&ldquo;For what it&rsquo;s worth, we were told by people who are experts in satellite thrusters that we would never be able to get the magnitude of thrust we were seeking,&rdquo; said Goldfarb. &ldquo;Our experiments proved them wrong.&rdquo;&nbsp;

The team recently tried the device on human subjects and it was effective in correcting balance. A current challenge is determining what algorithm to use for detecting an impending fall in a human. &ldquo;Much research has been conducted to detect a fall that has occurred, but almost none for how to detect an impending fall,&rdquo; said Goldfarb. &ldquo;We have enjoyed this research to date and will be delighted if our work eventually contributes to interventions that improve independence and quality of life for people who are at fall risk.&rdquo;

Researchers at Vanderbilt University have invented a nitrogen gas-powered thruster that is worn on the back that can correct falls as they start, restoring balance and averting potential injury.

<var>Researchers at Vanderbilt University have invented a nitrogen gas-powered thruster that is worn on the back that can correct falls as they start, restoring balance and averting potential injury.</var>

Falls can lead to severe and fatal injuries, particularly for elderly people. According to the U.S. Centers for Disease Control and Prevention, millions of people fall each year, with one in five suffering serious injury.

Michael Goldfarb, a professor of mechanical engineering at Vanderbilt University, has first-hand experience dealing with this health risk. &ldquo;As my parents grew older, both had experiences with fall risk that really limited their quality of life,&rdquo; he said. &ldquo;My father, in particular, had Parkinson&rsquo;s disease.&rdquo;

Goldfarb began thinking about new ways to correct occasional states of imbalance. Robotic exoskeletons can offer balance assistance, but have design challenges, such as having to coordinate a recovery response with the user. To avoid requiring a large frame or other structure (which would impede independence), he decided to focus on building a backpack-worn system that can apply forces directly to a person&rsquo;s body using a thruster.

&ldquo;This research challenge seemingly has not received much attention and therefore there were a lot of unknowns,&rdquo; Goldfarb said. &ldquo;Correcting a fall is a shared task between the person falling and the device helping to arrest the fall. What is the distribution of shared effort? How much force is appropriate to correct an impending fall? For how long is the force required? Can the magnitude of assistance required be provided by a compact cold-gas thruster?&rdquo;

Goldfarb and fellow researchers Almaskhan Baimyshev and Michael Finn-Henry then set out to create a lightweight, cold-gas thruster (CGT) jetpack that senses when a fall has been initiated and can provide a restoring force to help the person recover his or her balance.

Backpack Could Reduce the Risk of Fall

Paul P. Palies, director of the Combustion and Propulsion for Aviation Research Center at the University of Tennessee Space Institute, discusses the prospects for fueling aircraft with hydrogen.

Flying with Hydrogen

Ro-Bats, Bat-Bots, and Other Bat-like Robots

&nbsp;
<div class="infogram-embed" data-id="1b84054c-e967-4c9d-8c33-068ada31088e" data-title="Ro-Bats, Bat-Bots, and Other Bat-like Robots" data-type="interactive">&nbsp;</div>

For these engineers, the allure of biologically inspired flight still remains strong.

January-March 2023

Geothermal cooling via a closed-loop thermal heat sink system shows promise in improving solar performance in hot regions. 
 
Finding ways to enhance and improve the efficacy of photovoltaic (PV) systems is critical as the use of green power solutions continues to grow around the world. The concept behind one such solution to improve the performance of photovoltaic solar modules came to Ignacio Valiente-Blanco, a mechanical engineering professor in the Department of Signal Theory and Communications at the University of Alcalá (UAH) in Madrid, when he was hiking in the mountains near his home in Spain. 
 
&ldquo;I had been thinking for some time about how to improve this,&rdquo; Valiente-Blanco said. During that particularly warm day, when temperatures climbed to about 97 &deg;F (36 &deg;C), &ldquo;We found a small lake supplied by an underground aquifer. I was surprised about how cold the water was compared to the very warm environment. Then, it hit me. Why not use the cold temperatures underground to cool down solar panels in a sustainable and stable way?&rdquo; 
 
The epiphany resulted in a novel cooling system for photovoltaics that uses the underground as a heat sink that was both theoretically described and experimentally validated in &ldquo;Efficiency Improvement of Photovoltaic Solar Modules by Cooling Using an Underground Heat Exchanger,&rdquo; published in ASME&rsquo;s Journal of Solar Energy Engineering in December 2022. Valiente-Blanco led a team of six researchers and two technicians on this two-year effort. 
 
<img alt="" src="~/wwwasmeorg/media/Magazines/RDPulse/Spring-2023/Cool-Water-Boosts-Solar-Efficiency-1.png" /> 
&nbsp; 
Playing It Cool 
 
&ldquo;Commercial solar panels present very low-efficiency levels, typically in the range of 15 percent to 25 percent,&rdquo; explained Valiente-Blanco. &ldquo;Moreover, they dramatically lose efficiency when their temperature increases during operation, especially in the summer season.&rdquo; 
 
PV cells are dark so they can absorb as much solar energy as possible. But since only a fraction of the sun&rsquo;s radiation is converted to electricity, most of it is transformed into heat. 
 
&ldquo;Solar cells typically show a reduction in efficiency as they get hotter, thus the importance of cooling the solar panels, which can reach temperatures above 70 &deg;C (~160 &deg;F) given the right conditions,&rdquo; explained doctoral student Diego López-Pascual. The ideal operating temperature for solar photovoltaics is around 77 &deg;F (25 &deg;C). Such overheating can also result in &ldquo;potential power losses in the panels between 12 percent and 27 percent, limiting the productivity of photovoltaic facilities all around the world,&rdquo; according to the report. 
 
It also leads to problems related to thermal cycling and performance degradation, the researchers wrote. These fluctuations affect the life and amortization costs of solar panels, with typical degradation rates falling around 0.7% per year. 
 
Cooling solutions are nothing new either. In the report, the team points to two main technology buckets, passive and active. Passive technologies, such as finned heat dissipators and heat pipe systems, don&rsquo;t consume energy during operation and are more widely researched and deployed. Active tech, ranging from forced air ventilation and single-phase water cooling to and water evaporation, often can do a better job at reducing temperatures, but at a cost. 
 
&ldquo;During our initial research, we found that most of the active cooling alternatives explored showed at least one of three main issues,&rdquo; López-Pascual said. &ldquo;They required a lot of additional power to actuate the cooling system, they used large amounts of water, or they presented very heavy modifications to the solar panel.&rdquo; 
 
<img alt="" src="~/getmedia/76c289c2-4610-438e-9633-60b163553e94/Printing-Better-Cheaper-Heat-Exchangers-article-2.png" /> 
&nbsp; 
Closing the Circuit 
 
Limited research has been done on geothermal cooling for solar panels, according to the research team, but given the stability of low temperatures at a certain depth underground, its promise is significant. 
 
&ldquo;The underground typically sits at a constant temperature through the year past a certain depth. This temperature is similar to the yearly average ambient temperature in the region,&rdquo; said López-Pascual. Depending on location, underground temperatures are usually between 50 &deg;F (10 &deg;C) and 68 &deg;F (20 &deg;C) between 5 meters and 15 meters underground, according to the report. 
 
The UAH team&rsquo;s cooling system takes advantage of this by using the ground as a heat sink. It&rsquo;s a relatively simple working concept, López-Pascual said. 
 
&ldquo;By circulating a water-based coolant through the solar panel&rsquo;s heat exchanger, the panel is cooled. This warm water is then pumped to another heat exchanger installed underground where the extracted heat is dissipated given the colder and more stable temperature of the ground,&rdquo; he explained. &ldquo;Water then flows back towards the solar panel, completing the circuit and ensuring that the solar panel stays significantly colder,&rdquo; while also improving its efficiency. 
 
The second heat exchanger is in an underground borehole that stays at a constant temperature of 15.7 &plusmn; 0.5 &deg;C (or about 60 &deg;F) at a 15-meter depth, the researchers noted. 
 
Part of the additionally generated power is used to pump the coolant through the heat exchange system. However, since it&rsquo;s closed-circuit and relatively close in height to the solar module itself, the amount of energy consumed is &ldquo;relatively low&rdquo; compared to the additional energy the solar module creates due to the cooling system, still resulting in a net power gain, the researchers state. 
 
&ldquo;Since our system presents a closed circuit using the stable underground temperature as a heat sink, pumping power is significantly reduced and there is no water consumption required after filling the circuit,&rdquo; López-Pascual said. &ldquo;We also achieved a modular heat exchanger design that allowed us to extract great amounts of heat from the panel without heavy and complex adaptations.&rdquo; 
 
Plus, the closed-loop nature of the system limits the chances of contaminating nearby soil and water with coolant. 
 
Put to the Test 
 
To further prove the technology&rsquo;s viability, Valiente-Blanco&rsquo;s team built a prototype that was integrated into an isolated photovoltaic facility in Alcalá de Henares, north of Madrid, making use of two ATERSA model Ultra 270 P polycrystalline silicon solar panels. 
 
Peak power production of these panels is 270 W, with a power temperature coefficient of 0.43 percent per degree Celsius change in temperature. One of the panels remained unaltered for a control, while the other was outfitted with the prototype cooling system. 
 
For the heat exchanger installed on the back of the panel, six flattened U-shaped copper tubes were molded into a quasi-rectangular shape to increase the contact surface with the panel, then all the copper tubing was covered with polyethylene foam. A mix of 80 percent water and 20 percent ethylene glycol carried the heat from the panels to another copper-tube heat exchanger in a borehole. 
 
Testing occurred from July to September 2021 and showed promising results. The prototype improved net power generation of the outfitted solar panel by a max of 12.4 percent, with daily averages of about 9.8 percent. A coolant flow rate at 1.84 liters per minute per square meter of the solar module kept its temperature down by up to 14 &deg;C as well. Testing also showed that the increase in power generation depended on the pump&rsquo;s efficiency, the amount of solar radiation, and ambient temperature. The system was more effective at boosting power gains on days where solar radiation and ambient temperature were higher. 
 
Valiente-Blanco&rsquo;s team is already working on next-generation prototypes as well. &ldquo;One of our active research lines is focused on applying this concept to concentration photovoltaics, where the thermal management problem is even more critical. We are also thinking about new ways to take advantage of the excess heat,&rdquo; he said. 
 
Although the team has done some initial estimates on cost-effectiveness, a full in-depth study hasn&rsquo;t happened yet, but will once testing is completed. 
 
&ldquo;As part of my PhD thesis, we developed a thermo-electrical calculation model that allows us to predict with good accuracy the system&rsquo;s behavior under different environmental conditions,&rdquo; López-Pascual said. &ldquo;Even though the year-long test campaign is not yet completed, we had enough data to confirm the accuracy of the calculation model. We then used it to estimate a 5.9 percent increase in net energy output through the year compared to the same solar panel without the cooling system.&rdquo; 
 
And considering manufacturing costs, installation, and maintenance, this increase in energy production would make the system profitable for electricity production installations of just a few megawatts, and even more as the size of the installation increases, he added. 
 
As the development phase continues, the UAH team is working on optimizing system performance and reducing costs, Valiente-Blanco said. 
 
&ldquo;A couple of companies have already contacted us interested in the development. We are looking forward to seeing what the future brings for us,&rdquo; he added. 
 
Louise Poirier is senior editor at Mechanical Engineering magazine. 
 
&nbsp;

Geothermal cooling via a closed-loop thermal heat sink system shows promise in improving solar performance in hot regions.

Geothermal cooling via a closed-loop thermal heat sink system shows promise in improving solar performance in hot regions. 
 
Finding ways to enhance and improve the efficacy of photovoltaic (PV) systems is critical as the use of green power solutions continues to grow around the world. The concept behind one such solution to improve the performance of photovoltaic solar modules came to Ignacio Valiente-Blanco, a mechanical engineering professor in the Department of Signal Theory and Communications at the University of Alcalá (UAH) in Madrid, when he was hiking in the mountains near his home in Spain.

Cool Water Boosts Solar Efficiency

Conductive flakes enable an economical additive manufacturing method to yield results. 
&nbsp; 
&nbsp; 
The standard manufacturing and assembly processes for heat exchangers can be expensive and time-consuming. They also limit the geometric configurations that can be considered during the design process. 
 
Additive manufacturing (AM), when viable, can be a more efficient manufacturing process and gives engineers much more design freedom, often allowing them to create features that standard machining cannot. 
 
Researchers are looking for ways to build high-performance heat exchangers using AM. However, most metal-based AM processes are so expensive that commercial production is not viable. 
 
Looking to see if another approach might work, a research team led by Gregory F. Nellis, a professor at the University of Wisconsin (UW), designed and built an efficient and cost-effective heat exchanger using lower-cost, deposition-based AM processes. The team successfully printed a heat exchanger using fused deposition modeling that has sufficient thermal conductivity to outperform standard heat exchangers, at a more affordable cost. 
 
<img alt="" src="~/getmedia/e72dd379-9a34-430c-8cd7-64f1e6854ec4/Printing-Better-Cheaper-Heat-Exchangers-article-1.png" /> 
&nbsp; 
Higher performance, less cost 
&nbsp; 
Nellis&rsquo;s plan was to use AM to create a two-fluid heat exchanger in which air exchanges heat with a liquid. Performance results from testing with this prototype would then be assessed against an industry-standard copper/aluminum heat exchanger manufactured with conventional equipment. 
&nbsp; 
Nellis and his team&mdash;UW engineering professors Tim Osswald and Natalie Rudolph, Jake Boxleitner (a graduate student at the time, now employed at Brayton Energy), and Tom Mulholland (a doctoral student who now works with Samsung) &mdash; employed fused deposition modeling (FDM), a much less-expensive AM process, to manufacture several heat exchanger prototypes. The AM material developed by the team consisted of a composite polymer&nbsp;filled with conductive&nbsp;flakes to provide high conductivity in the direction of heat flow. 
&nbsp; 
First attempts using these AM methods focused on fabricating extended surfaces with aerodynamic shapes that bridge the air-side gap formed between two water channel walls. That build did not meet the performance targets. 
 
One of the key challenges was maintaining a continuous tool path within each build layer to allow uninterrupted extrusion and therefore defect-free water channel walls. 
 
&ldquo;It was tough coming up with a heat exchanger that was reliably leak-tight while still having high performance,&rdquo; Nellis said. &ldquo;It took us a while to understand that we needed designs where the nozzle extruding the filament never stopped. Any time the nozzle stopped&mdash;for example, to add a fin or some other feature&mdash;we would inevitably get a leak. Once we established this as a constraint, the design evolved quickly toward a final version that could achieve commercially relevant performance.&rdquo; 
 
Using a Design-of-Experiment approach, the team created simulations for unique geometric configurations, using three different frontal air velocities per geometry. The design variables were constrained based on several factors, including manufacturing limits. 
 
The team relied on UW&rsquo;s Center for High Throughput Computing to carry out many parallel simulations of heat exchanger designs and moved quickly toward an optimal solution. The team also developed a rapid method for screening various polymer/filler combinations to ensure the right combination of properties and printability (both the design and material are now patented). 
 
The final result of the process was the development of a simple heat exchanger that performed on par with the computer models. The 3D-printed model can be easily modified as manufacturing capabilities improve, resulting in higher performance. 
 
Test results were especially encouraging: The measured heat transfer rate for the model exceeded that of the industry-standard copper/aluminum heat exchanger of the same size and at the same operating conditions by 12 percent and exceeded the heat transfer rate of the conventional industry-standard stainless-steel heat exchanger by 285 percent. 
 
&ldquo;One of the nicest surprises was how quickly we could iterate on a design using additive manufacturing,&rdquo; said Nellis. &ldquo;It was sometimes possible to modify a design one day, print it overnight, test it the next day, and modify it again. The design/build/test cycle was greatly accelerated compared to other manufacturing technologies.&rdquo; 
&nbsp; 
Beating the heat 
&nbsp; 
Nellis used the FDM process to create an air-cooled, two-fluid heat exchanger technology that is cost-effective to manufacture and competes well with standard commercial HVAC. 
 
&ldquo;Our work has led to an understanding of the fundamental design constraints that must be respected for this combination of manufacturing technique and application,&rdquo; he said. 
 
Nellis has been contacted by several companies about commercialization of his process, which has potential impacts for other fields outside of HVAC. 
 
&ldquo;I think any multifluid device that must be low cost could be manufactured using deposition-based AM processes and therefore benefit from our research,&rdquo; he said.&nbsp; 
 
From Nellis&rsquo;s perspective, the best aspect of the project was how the most interesting and important work happened at the intersection of different fields. 
 
&ldquo;It was a lot of fun for Jake and I, with expertise in heat exchanger design, to meet regularly with the manufacturing team&mdash;Tom Mulholland, Natalie Rudolph, and Tim Osswald,&rdquo; he said. &ldquo;Often, we would together find a solution that was better than either team could have found in isolation, because together we could see the bigger picture.&rdquo; 
 
Mark Crawford is a technology writer in Corrales, N.M.

Conductive flakes enable an economical additive manufacturing method to yield results.

Conductive flakes enable an economical additive manufacturing method to yield results. 
&nbsp; 
&nbsp; 
The standard manufacturing and assembly processes for heat exchangers can be expensive and time-consuming. They also limit the geometric configurations that can be considered during the design process. 
Additive manufacturing (AM), when viable, can be a more efficient manufacturing process and gives engineers much more design freedom, often allowing them to create features that standard machining cannot. 
Researchers are looking for ways to build high-performance heat exchangers using AM. However, most metal-based AM processes are so expensive that commercial production is not viable. 
Looking to see if another approach might work, a research team led by Gregory F. Nellis, a professor at the University of Wisconsin (UW), designed and built an efficient and cost-effective heat exchanger using lower-cost, deposition-based AM processes. The team successfully printed a heat exchanger using fused deposition modeling that has sufficient thermal conductivity to outperform standard heat exchangers, at a more affordable cost.

Printing Better, Cheaper Heat Exchangers

Using Smart Trains to Find Defective Rails

Francesco Lanza di Scalea, professor of experimental mechanics, NDE and SHM Laboratory, Department of Structural Engineering, University of California, San Diego, La Jolla, Calif., discusses the use of ultrasonic high-speed inspection of train track rails to detect internal defects and potentially avoid costly damages.

Better Grip for Laparoscopy

To pull objects from the tightest spaces, researchers devise a clever little claw.

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To pull objects from the tightest spaces, researchers devise a clever little claw.

April-June 2023

July-September 2023

October-December 2023

Engineers are always trying to squeeze more power out of engines, and those in the military have added incentive. Military researchers looking to increase the power and thrust of a commercial compact jet engine turned to ceramics to meet the increased turbine inlet temperature that prevented them from using metals. Using finite element analysis and 3D printing, they showed that a turbine rotor made of silicon nitride could handle the higher temperatures and still provide increased power and thrust. 
 
&ldquo;We wanted to take something that was a small-scale engine that was already fairly power-dense to begin with and try to make it more power dense,&rdquo; said U.S. Air Force Lt. Col. Brian Bohan. &ldquo;There&rsquo;s a big gap in the commercial sector for this scale. We were trying to come up with ways to make an engine as powerful as some of the more expensive military engines, but at a more cost-effective price point.&rdquo; 
 
Bohan, formerly on the faculty at the U.S. Air Force Institute of Technology, was advisor and a co-author to Bryan T. Leicht, the lead author of &ldquo;Manufacturing a Ceramic Turbine Rotor for a Compact Jet Engine,&rdquo; published in the August 2023 issue of ASME&rsquo;s Journal of Turbomachinery. 
 
Bohan said the work began with the idea of bolstering engines for small unmanned aircraft, or drones, that would be powerful enough to keep up with a regular jet engine and cheap enough to make it cost effective. But the work soon concentrated on a more generic purpose. 
 
&ldquo;There are hobby-class engines at the small scale, and then you have military engines that are designed for small scale,&rdquo; he said. &ldquo;But they are $70,000 to $80,000 apiece. If you&rsquo;re trying to design an engine for somewhere in between those levels, you really have no options. That led to &lsquo;How do we get more power out of these commercial hobby-class engines, and how do we get something better out of the small scale?&rsquo;&rdquo; 
 
The researchers worked with a JetCat P400, which at $12,500 was a more affordable test object. But achieving the higher power density required increasing the turbine inlet temperature, which would exceed the maximum temperature limitations of its metallic turbine rotor. The authors also noted that traditional blade cooling methods could not be used because of its small size. 
 
So they turned to ceramics, which can withstand higher temperatures while maintaining strength. A drop-in replacement ceramic turbine would allow temperatures to rise from 765˚ C in the stock engine to 1,200˚ C and improve thrust and power by a factor of 1.44, noted the authors. 
 
<img alt="" src="~/getmedia/175d63af-af60-4585-813f-1b4dd5081cef/turbo_145_8_081009_f014-(2).jpg" /> 
3D-printed rotor made from alumina. 
 
The preferred material is silicon nitride, which the researchers determined could work through the use of finite element analysis. The problem is that the material is still being developed for use in additive manufacturing. For a test, the researchers 3D printed an alumina rotor using digital light projection. Bohan believes the results can be duplicated with silicon nitride when it becomes available. 
 
&ldquo;There&rsquo;s not a ton on ceramic 3D printing out there,&rdquo; he said. &ldquo;It is still pretty new. We started the process with cast ceramics, looking at different mold materials. We exhausted every possible option with molding and casting, mainly due to the complexity of the part. We could make a mold, but we could not get the part to dry successfully because we have very thin blades and a very thick hub. The two dry at very different rates.&rdquo; 
 
Their work improved when they obtained access to an ADMATEC Admaflex 300 DLP printer. Although engineers at Oak Ridge National Laboratory are working with silicon nitride for additive manufacturing, its current unavailability forced them to use an alumina resin for proof of concept. Both materials have a similar density and maximum service temperature, but silicon nitride outperforms in strength and fracture toughness through its unique interlocking grain structure, according to the authors. It provides greater resistance to failure from thermal shock and/or mechanical loads. 
 
<img alt="" src="~/getmedia/1de2e778-d724-4b8c-930b-0c0be16ddc34/turbo_145_8_081009_f015-(2).jpg" /> 
Combined thermal and centrifugal stress plot of the alumina turbine rotor design under idle power conditions within a jet engine. 
 
Bohan said there were still some obstacles to overcome with the 3D printer due to limitations of the printer and the thickness required. After the part is printed it is put into a tank of water to dissolve out binding materials. If the thickness is too great, water cannot penetrate far enough into the part. 
 
&ldquo;We had to do some design variations to get to a final net shape that both met our requirements, as well as the thickness requirements for manufacturing to fully dissolve the binder,&rdquo; Bohan said. &ldquo;Just coming up with the balance of both of those was tricky.&rdquo; 
 
Bohan said much of the work on printing ceramics for aviation is focused on large-scale applications such as single turbine blades for large engines. That would be difficult for smaller engines simply because of their size. 
 
For now, he said the team is encouraged that they were able to make a part that looks correct. &ldquo;I wasn&rsquo;t sure that we were going to get to that point,&rdquo; he said. &ldquo;It is in the wrong material, but the process of using the printer is identical between different materials. We may have to run the oven at different temperatures for different materials, but the actual manufacturing process should be the same, or fairly close.&rdquo; 
 
John Kosowatz is senior editor.

Air Force engineers 3D print turbine blades suitable for a drone engine.

Engineers are always trying to squeeze more power out of engines, and those in the military have added incentive. Military researchers looking to increase the power and thrust of a commercial compact jet engine turned to ceramics to meet the increased turbine inlet temperature that prevented them from using metals. Using finite element analysis and 3D printing, they showed that a turbine rotor made of silicon nitride could handle the higher temperatures and still provide increased power and thrust. 
 
&ldquo;We wanted to take something that was a small-scale engine that was already fairly power-dense to begin with and try to make it more power dense,&rdquo; said U.S. Air Force Lt. Col. Brian Bohan. &ldquo;There&rsquo;s a big gap in the commercial sector for this scale. We were trying to come up with ways to make an engine as powerful as some of the more expensive military engines, but at a more cost-effective price point.&rdquo;

Ceramic Boost for Small Jet Engines

To the annoyance of parents everywhere, children love playing with tape measures. They will lock the extended tape in place and notice how a slight curve keeps the metal strip rigid. Then they will release the lock and delight in how a spring retracts the tape with a satisfying thwack. 
 
Roboticists at the University of California, Los Angeles have been playing with tape measures, too. They have discovered that the rigid but bendy tape can be used as a new type of limb that acts something like a spider monkey&rsquo;s arm or an octopus&rsquo;s tentacle. 
 
The limb is extremely simple. A metal tape rolls through a hooked end piece and returns to a spool at the base. The spool can either let out more tape to extend the limb or pull the tape in to retract it. By hooking the end piece over a branch or pipe, the arm can pull the robot up. In tests, the system can climb shelves or ladders at 1.5 body lengths per second. 
 
&ldquo;The final goal envisioned for this project is a three- or four-limbed robot capable of moving freely in 3D space using its extendable limbs,&rdquo; wrote Justin Quan and Dennis Hong in their paper, &ldquo;Flexible Long-Reach Robotic Limbs Using Tape Springs for Mobility and Manipulation,&rdquo; published in the June 2023 issue of Journal of Mechanisms and Robotics. In time, robots sporting this system could shoot out and retract limbs to travel anywhere these arms can reach. 
 
&nbsp;
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To the annoyance of parents everywhere, children love playing with tape measures. They will lock the extended tape in place and notice how a slight curve keeps the metal strip rigid. Then they will release the lock and delight in how a spring retracts the tape with a satisfying thwack. 
 
Roboticists at the University of California, Los Angeles have been playing with tape measures, too. They have discovered that the rigid but bendy tape can be used as a new type of limb that acts something like a spider monkey&rsquo;s arm or an octopus&rsquo;s tentacle.

A new type of robotic arm takes its inspiration from the toolbox favorite.

Made to Measure

Members of teams with high levels of psychological safety feel free to express ideas and opinions. This feeling of safety promotes creativity and innovation. However, little evidence exists that shows how best to facilitate or build psychological safety within teams, especially in an educational context. Scarlett Miller, professor of engineering design and industrial engineering and director of the Center for Research in Design and Innovation at The Pennsylvania State University, recently led a team of researchers that published a study on this topic in the ASME Journal of Mechanical Design. She discusses the impact of interventions aimed at improving psychological safety in engineering design student teams.

Scarlett Miller of Penn State discusses how engineering teams can build psychological safety in their members.

Comfortable Enough to Innovate

Extremely cold, sub-zero weather conditions can kill, even after only a short time. Poorly insulated clothing can result in life-threatening respiratory and cardiovascular problems, as well as frostbite and hypothermia. 
 
People survive longer in severe cold if they wear clothing and outerwear that are specially designed for cold-weather conditions. Knowing the amount of a time a person can survive for a set of environmental conditions is critical for developing new fabrics and clothing that extend survival time. 
 
To improve the design of advanced, cold-weather fabrics, researchers at the Department of Mechanical Engineering at the Indian Institute of Technology in New Delhi undertook a series of experiments to evaluate how three key factors&mdash;ambient temperature, fabric insulation, and metabolic heat (heat generated by a person as a function of the physical work performed)&mdash;impact survival time. Their research is described in a paper published by the Journal of Heat and Mass Transfer in July 2023. 
 
Testing ambient temperature, fabric insulation, and metabolic heat 
 
Previous studies have shown that if metabolic heat generation is lower than the heat loss to the environment, the human body core temperature starts to drop. If the body core temperature decreases below 27 &deg;C, the chances of death become higher. &ldquo;Therefore, the time taken to decrease body core temperature from 37 &deg;C to 27 &deg;C could be considered the survival time of a human,&rdquo; stated mechanical engineers Vikrant Dupade, B. Premachandran, R.S. Rengasamy, and Prabal Talukdar in their research paper. 
 
Extending survival time is the main goal when exploring new ways to design and test clothing for extreme cold-weather conditions. To better understand the influence of ambient temperature, fabric insulation, and metabolic heat on the loss of body heat, the research team designed an experiment to test the thermal effectiveness of fabric combinations in cold-weather conditions. 
 
A guarded hot plate instrument was placed inside a cold chamber capable of maintaining the ambient temperature between 210 K and 310 K (-63 &deg;C and 36 &deg;C). A piece of layered artificial skin placed on the hot plate with same thermal diffusivity as human skin represented the human body core. 
 
Fabric combinations that were placed on top of the artificial skin consisted of several nonwoven layers underneath an outer layer made of breathable material. The insulating layers consisted of knitted fabric (fabric insulation &frac14; 0.53 clo [clothes thermal insulation]) and high loft nonwovens. Different thicknesses were used to vary the thermal insulation. The fabric ensemble was overlain by a windproof fabric. &ldquo;This top layer shields the fabric ensemble from air, rain, and snow while transferring perspiration, in the form of vapor, to the atmosphere,&rdquo; the research team wrote. 
 
The team then performed experiments on a set of layers of extreme cold weather clothing using the guarded hot plate instrument inside the climatic chamber. Survival time was measured at three different subzero temperatures, three different fabric insulation combinations, and three metabolic heats:
<ul>
	<li>Ambient temperatures of 213 K (-60 &deg;C), 233 K (-40 &deg;C), and 253 K (-20 &deg;C)</li>
	<li>Fabric insulations of 1.2 clo, 1.88 clo, and 2.56 clo (clothes thermal insulation)</li>
	<li>Metabolic activities of sleeping, sitting, and standing</li>
</ul>
 
&quot;In the first set of experiments, the nonwoven with 4-mm thickness and a thermal insulation of 0.67 clo was placed over the knitted fabric with thermal insulation of 0.53 clo,&rdquo; Dupade wrote. &ldquo;This process was repeated for the other two fabric assemblies that had two and three layers of nonwoven, which had total insulation of 1.88 clo and 2.56 clo, respectively.&rdquo; 
 
Each set of experiments was performed three times. The transient temperature profiles at different locations of the fabric assembly were measured continuously. Further, a one-dimensional heat transfer model was developed to carry out the numerical simulation. 
 
Results and conclusions 
 
The team compared both the experimental and numerically simulated transient temperature profiles inside the fabric assembly for all possible combinations of ambient temperature, fabric insulation, and metabolic heat. They found that for ambient temperature, survival time increased by 204 percent for an increase in ambient temperature of 9.4 percent and by 744 percent for an increase in ambient temperature of 18.8 percent. Increasing fabric insulation by 56 percent increased survival time by 190 percent, while increasing insulation by 113 percent improved survival time by 512 percent. 
 
Parametric analysis showed that the ambient temperature is the most influential parameter affecting the survival time, followed by fabric insulation. Metabolic heat did not have a significant effect on survival time. 
 
The survival time for humans exposed to extreme cold-weather conditions increases significantly with an increase in ambient temperature and fabric thermal insulation. &ldquo;Prior knowledge of the survival time for people exposed to extremely cold climatic conditions will be helpful in designing better cold weather clothing,&rdquo; concluded the team. 
 
Mark Crawford is a technology writer in Corrales, N.M.

Frigid temperatures can be lethal. New research sets a baseline for manufacturers developing insulated fabrics.

Extremely cold, sub-zero weather conditions can kill, even after only a short time. Poorly insulated clothing can result in life-threatening respiratory and cardiovascular problems, as well as frostbite and hypothermia. 
 
People survive longer in severe cold if they wear clothing and outerwear that are specially designed for cold-weather conditions. Knowing the amount of a time a person can survive for a set of environmental conditions is critical for developing new fabrics and clothing that extend survival time. 
 
To improve the design of advanced, cold-weather fabrics, researchers at the Department of Mechanical Engineering at the Indian Institute of Technology in New Delhi undertook a series of experiments to evaluate how three key factors&mdash;ambient temperature, fabric insulation, and metabolic heat (heat generated by a person as a function of the physical work performed)&mdash;impact survival time. Their research is described in a paper published by the Journal of Heat and Mass Transfer in July 2023.

Surviving the Cold

January-March 2024

Most large-scale solar power facilities are huge fixed-tilt installations, with rows upon rows of them covering acres of land. But a newer concept is agrivoltaics, which involves installing solar panels on land already in use for agriculture or livestock. Making the most of such space has led to the development of a novel solar installation geometry, called the vertical bifacial (VBF) array, which was pioneered by German company Next2Sun. 
 
Unlike the massive fixed-tilt installations that require large steel canopies to hold photovoltaic panels above the ground, as their name suggests, VBF panels have an upright orientation and are installed closer to the surface. These walls of panels allow for easier passage of machinery, animals, and people without the need to worry about clearance height, effectively increasing both the land&rsquo;s usage and the owner&rsquo;s return on investment. 
 
But because of their geometry, VBF installations do yield slightly less energy&mdash;about 5 to 10 percent less&mdash;than traditional monofacial fixed-tilt arrays. Power generation peaks for VBF arrays are different as well, given their vertical orientation, in the mid-morning and mid-afternoon, instead of solar noon for fixed-tilt installations. A team of researchers at Rutgers University has used modeling simulations to explore how changes in design can improve the energy output of VBF installations to make them competitive with conventional photovoltaic installations. 
 
This research is detailed in &ldquo;Design Considerations for Vertical Bifacial Agrivoltaic Installations,&rdquo; published in the <a href="https://asmedigitalcollection.asme.org/solarenergyengineering" target="_blank">ASME Journal of Solar Energy Engineering</a> in December. 
 
&nbsp;
<h3>Improvements unlocked</h3>
 
When laboratories shut down during the pandemic, the Rutgers team had to pivot toward a new research area that was doable within the new normal, recalled W. Ross Rucker, a post-doctoral researcher in the Department of Materials Science and Engineering at Rutgers, who completed part of this work for his doctorate. 
 
&ldquo;Modeling agrivoltaics fit neatly into that since a lot of the work could be done in our homes or outside in the fresh air,&rdquo; he said. &ldquo;We had originally started somewhat niche, looking at integrating solar panels into greenhouses, before joining up with the Rutgers Agrivoltaic Program [RAP] and researching more general applications.&rdquo; 
 
When considering how array design attributes affect energy output, the Rutgers team included such criteria as module height, inter-row spacing, inverter connection where rows are either wired together or separately, and inclusion of bypass diodes. 
 
Another consideration was cell density&mdash;either single-high modules or double-high modules, where two landscape-oriented modules are stacked vertically. &ldquo;Single-high modules built with bypass diodes and installed in New Brunswick, N.J., offered a small increase in power output, up to roughly 1.16 percent when rows were spaced 6.1 meters apart, with diminishing gains as the rows were spaced further apart,&rdquo; the paper stated. 
 
However, going to a double-high VBF installation resulted in a nearly doubled annual electrical output per acre, the researchers found. When increasing row spacing from 6.1 meters to 12.2 meters, VBF installations that used double-high racking and bypass diodes saw an output increase of more than 80 percent, when compared to single-high installations with row spacing at 6.1 meters. This increased to 95 percent when the double-high installations had row spacing of 24.4 meters. 
 
&ldquo;Row spacing is a vital consideration when you are planning out a VBF array, especially if you decide to stack up multiple rows of panels, and even more if you&rsquo;re going to be using the space to grow crops too,&rdquo; Rucker said. &ldquo;A lot of the light they collect is going to be coming from a sideways angle, and if they&rsquo;re too close together, the shadows cast by the panels are going to be blocking each other in a major way.&rdquo; 
 
But another major consideration for stacked rows is that the bottom modules be wired independently from the top modules&mdash;otherwise, the inter-row shading effects will reduce system electrical output, added Dunbar P. Birnie, III, a professor and Corning Saint-Gobain Malcolm G. McLaren Chair in the Department of Materials Science and Engineering at Rutgers and co-author on the study. 
 
&ldquo;We do expect somewhat lower energy production than other standard array types, but the VBF arrays seem to have the most ideal &lsquo;ease of farming&rsquo; because they don&rsquo;t impede the motion of farming equipment,&rdquo; he said. 
 
<img alt="Rutgers University Agrivoltaics" src="~/getmedia/2970f108-48a1-4ad2-ac97-495031bfb224/Rutgers-Agrivoltaics.jpg" /> 
The Rutgers Agrivoltaic Program installation is one-of-a-kind, featuring vertical bifacial solar voltaic arrays in varying row spacing and module heights. With more variations, the Rutgers team will be able to learn more in the future about solar generation and its connection to farming. 
 
Photo: A. J. Both/Rutgers University 
 
&nbsp;
<h3>In-field testing</h3>
 
Although this research has so far been based just on modeling, the RAP has built several experimental arrays at sites in New Jersey&mdash;including a VBF installation at the Rutgers Animal Farm in New Brunswick that is mostly complete. 
 
Birnie and Rucker&rsquo;s research supported both planning and design of the new arrays for the one-of-a-kind RAP installation, which features VBF solar voltaic arrays with varying row spacing and module heights to provide researchers the opportunity to test and learn more about agrivoltaics. 
 
&ldquo;During the design process for those arrays, we decided to include a vertical bifacial array. This gave extra meaning to our modeling and highlighted differences in electrical output that might be expected for different wiring patterns,&rdquo; Birnie said. 
 
RAP is funded by the U.S. Department of Energy through a grant under the Foundational Agrivoltaic Research for Megawatt Scale (FARMS) funding program, which aims to develop replicable models for agrivoltaics. 
 
VBF will be a better choice over traditional arrays farther away from the equator, and as research continues to show more about unexpected sources of improved output in VBF arrays, Rucker believes it may only be a few more years before VBF arrays become more universal. 
 
&ldquo;Our new VBF array is coming online soon and will allow us to evaluate differences in row spacing&mdash;one of the variables tested in our paper,&rdquo; Birnie said. &ldquo;As with new technologies in general, there is expected to be cost reduction with time as more installations are built. We hope to collaborate with VBF array installations at different latitudes to test the latitude and climate differences.&rdquo; 
 
Initial modeling also didn&rsquo;t simulate albedo light, or light that is reflected from the ground back onto the panels, &ldquo;because we thought it would be a lot of processing for a very small effect,&rdquo; Rucker said. &ldquo;At the urging of the reviewers, we went back to add those calculations to the model and it made a pretty significant difference.&rdquo; 
 
Although albedo typically has a relatively small effect for fixed-tilt and single-axis tracker arrays, Birnie added that he was also surprised by the quantity of light that could be available from upward scattered albedo effects. 
 
&ldquo;Comparison with real output production data is critical and will help us fine tune the albedo, glass surface reflection, and thermal effects in our modeling,&rdquo; Birnie said. 
 
The study&rsquo;s data indicates that VBF arrays can produce competitive amounts of electricity per acre when designed properly, further noting that &ldquo;Rows of double-high modules stacked in landscape orientation and placed 6.1 meters apart produce more than 159 MWh/year/acre and still leave plenty of space for farming operations.&rdquo; 
 
For now, field studies on electrical production, crop studies, and animal studies are all underway at RAP testing installations. Birnie and Rucker are also looking into non-ideal situations and how they can affect the overall productivity of the arrays, such as rotating the array away from perfect cardinal directions and certain farmer-friendly adaptations that trade off some photovoltaic efficiency for day-to-day operational conveniences. 
 
&ldquo;Modeling the vertical panels has been really fascinating. They&rsquo;re so different from traditional arrays yet so simple,&rdquo; Rucker said. &ldquo;The applications they have in agrivoltaics are going to be game-changing, I believe.&rdquo; 
 
 
Louise Poirier is senior editor at Mechanical Engineering magazine.

Energy output of vertical bifacial solar panel arrays can be vastly improved with the help of specific design considerations.

Most large-scale solar power facilities are huge fixed-tilt installations, with rows upon rows of them covering acres of land. But a newer concept is agrivoltaics, which involves installing solar panels on land already in use for agriculture or livestock. Making the most of such space has led to the development of a novel solar installation geometry, called the vertical bifacial (VBF) array, which was pioneered by German company Next2Sun. 
 
Unlike the massive fixed-tilt installations that require large steel canopies to hold photovoltaic panels above the ground, as their name suggests, VBF panels have an upright orientation and are installed closer to the surface. These walls of panels allow for easier passage of machinery, animals, and people without the need to worry about clearance height, effectively increasing both the land&rsquo;s usage and the owner&rsquo;s return on investment.

Two-Sided Panel Optimizes Agrivoltaics

Due to its visibility in athletes and returned service members, traumatic brain injury (TBI) has received widespread attention. But it&rsquo;s an injury that is still poorly understood. While studies suggest that some people are more vulnerable to TBI than others or that the direction of head motion and the nature of the impact affects the chances of injury, these ideas have not yet been confirmed by studying human brain motion. 
 
Now, engineers at Washington University in St. Louis have designed an experiment using magnetic resonance elastography (MRE) that directly assesses how skull motion direction impacts in vivo human brain deformation. 
 
MRE is a process that has been used for years to learn about material properties, such as stiffness and damping, in soft tissue. It is based on measuring shear waves that pass through the tissue. For brain experiments, waves are induced by vibrating the head; previous studies have shown that some approaches to generating these waves have worked better than others. 
 
&ldquo;This probably applies to head impacts as well as harmonic vibrations, because you can approximate any input as the sum of harmonic components,&rdquo; said lead researcher Phil Bayly, a mechanical engineering professor at Washington University in St. Louis. &ldquo;We then needed a metric to compare the effects of different kinds of inputs. This metric needed to be non-dimensional and physically meaningful, which we determined was the ratio of strain energy (SE) to kinetic energy (KE).&rdquo; 
 
Bayly and his colleague, Ruth Okamoto, analyzed the strain energy and kinetic energy in the brain using MRE displacement data obtained by harmonic excitation of the head at five frequencies and in two different directions. One direction was created by occipital excitation applied to the back of the skull, which produces an anterior-posterior skull displacement motion&mdash;essentially, nodding motion. The other direction was due to lateral excitation applied to the right temple, producing left-right skull displacement plane that looks like shaking &ldquo;no.&rdquo; 
 
When SE and KE are computed using the same harmonic displacement data, the SE/KE ratio serves as a nondimensional &ldquo;transfer function&rdquo; between excitation and deformation. &ldquo;This is a potentially simple and powerful dimensionless metric that can be used to compare the brain&rsquo;s response to different types of loading,&rdquo; Bayly said. 
 
The subject group consisted of 32 healthy people without self-reported neurological conditions ranging in age from 20 years old to 68 years old. Structural images of their brains were taken using an MRI scanner prior to application of skull vibrations. 
 
Skull vibrations were then induced with a deformable actuator placed at either the lateral (right temple) or occipital (back of skull) position; vibrations were induced at 20, 30, 50, 70, and 90 Hz using acoustic pressure waves. 
 
Phase-contrast and magnitude images were taken at each frequency using an echo-planar imaging process. Image data analysis also included rigid-body displacements, wave displacements and strains, and energy quantities. 
 
Results showed that ratio of strain energy to kinetic energy (SE/KE) depended strongly on both direction and frequency. SE/KE was approximately four times larger for lateral excitation than for occipital excitation and was largest at the lowest excitation frequencies studied. 
 
Okamoto and Bayly, along with five coauthors, reported their results in &ldquo;Effect of Direct Motion and Frequency of Skull Motion on Mechanical Vulnerability of the Human Brain,&rdquo; published in the November 2023 issue of ASME Journal of Biomechanical Engineering. 
 
&nbsp;
<h3>Response to loads</h3>
 
 
&ldquo;SE/KE ratio is a simple but revealing index of the brain&rsquo;s mechanical vulnerability to skull motion,&rdquo; Bayly said. &ldquo;The brain really does deform more readily when you rotate about neck axis in a sideways motion, compared to being in neck flexion-extension.&rdquo; 
 
Like many other solid structures&mdash;for example, aircraft frames or automobile bodies&mdash;the brain deforms more readily in response to loads in different directions and frequencies. 
 
&ldquo;This can be measured using advanced MR imaging methods that rely on exciting vibrations and waves in tissue, imaging the displacement fields with motion sensitive MRI, and analyzing the displacement fields to extract velocity strain, strain energy and kinetic energy,&rdquo; Bayly said. 
 
In future studies, Bayly and Okamoto will look more closely at what other factors determine vulnerability of the brain to skull motion. &ldquo;What role do the size and shape of the brain play? Is it different in children or older adults? I think the SE/KE ratio can be used to understand the propensity of any compliant object to deform under dynamic loading,&rdquo; he said. 
 
 
Mark Crawford is a technology writer in Corrales, N.M.

Researchers find that a blow to the side of the head causes more potential brain injury that one that hits straight-on.

Due to its visibility in athletes and returned service members, traumatic brain injury (TBI) has received widespread attention. But it&rsquo;s an injury that is still poorly understood. While studies suggest that some people are more vulnerable to TBI than others or that the direction of head motion and the nature of the impact affects the chances of injury, these ideas have not yet been confirmed by studying human brain motion. 
 
Now, engineers at Washington University in St. Louis have designed an experiment using magnetic resonance elastography (MRE) that directly assesses how skull motion direction impacts in vivo human brain deformation.

Direct Impact

Chatbots that are trained on a set of human-generated writing samples and can reply to prompts with sentences and even paragraphs that mimic their training, have become familiar to most users of the internet. One of these models, ChatGPT, is familiar enough that it&rsquo;s how most people understand large language models (LLM) that seemingly learn, comprehend, and then generate language. But these models also may carry great promise for the physical sciences, including applied mechanics. 
 
That&rsquo;s the premise of a paper written by a team of researchers from the University of California, Santa Barbara; University of New Hampshire; and Northwestern University. &ldquo;These emergent capabilities are exciting for science because they vastly lower the barrier to effective scientific data mining,&rdquo; they wrote in &ldquo;Perspective: Large Language Models in Applied Mechanics.&rdquo; The article appeared in the October 2023 issue of the ASME Journal of Applied Mechanics. 
 
LLMs such as ChatGPT and PaLM have the ability to perform sophisticated text comprehension as well as produce replies in the form of essays, poems, and other formats. 
 
&ldquo;Alongside their broader societal impacts, these capabilities carry great promise for the physical sciences, including applied mechanics,&rdquo; the team reported. The paper summarized recent developments in these models, their possible use in mechanics and adjacent fields, and what they could be used for in applied mechanics in the future. 
 
One issue the team addressed is the degree to which these LLMs are limited in their usefulness. LLMs have been known to produce artifacts called hallucinations, in which the model produces a reply to a prompt that is linguistically correct but is also nonsensical or erroneous. For instance, lawyers have been caught using LLMs to help write their briefs due to the inclusion of citations to imaginary court cases. Other problems with the output of the models include multi-state reasoning errors, interpretability, and lack of originality. What do these limitations mean for the adoption of LLMs to applied mechanics? 
 
Such limitations must be addressed before LLMs can be helpful to mechanical engineers and physical scientists, the authors stated. &ldquo;This tendency threatens any use of LLMs as knowledge bases, and cuts into their advantage over more traditional information retrieval engines,&rdquo; they wrote. 
 
Proponents of language models within applied mechanics have devised a way to mitigate this issue, however. Researchers suggested that retrieval-augmented generation first retrieve documents related to a query and then prompt the LLM to generate text based on those documents. 
 
Once a mechanics-specific language model can be trained, applied across its entire training corpus, and used to retrieve relevant documents, a second LLM can then be used to synthesize these results into a coherent response. Researchers are working on similar &ldquo;workarounds&rdquo; for multi-step reasoning errors, interpretability, and lack of originality. 
 
&nbsp;
<h3>Data extraction</h3>
 
 
There are several key emergent capabilities of LLMs that represent promising directions for their use in applied mechanics. For example, information extraction is the first and perhaps most immediate capability in information extraction, especially those that are generated solely by a prompt (called zero-shot learning) or when the prompt is accompanied by one or more examples of the expected output (called few-shot learning). 
 
&ldquo;With little or no supervision, very large language models (VLLMs) can perform sophisticated reading comprehension tasks over a large number of documents,&rdquo; the team reported. This capability alone allows for quick iteration on extraction tasks, allowing scientists to efficiently experiment with what information might be helpful to extract at scale from the literature. 
 
But zero- and few-shot learning is not the only bright spot on the researchers&rsquo; list, which also included normalizing representations, assisted programming, knowledge recall, and hypothesis generation. 
 
The authors of the paper in the ASME Journal of Applied Mechanics were Neal R. Brodnik, Caelin Muir, McLean P. Echlin, Tresa M. Pollock, and Samantha Daly of the University of California Santa Barbara; Samuel Carton and Satanu Ghosh of the University of New Hampshire; and Doug Downey of Northwestern University. 
 
Looking to the future, the researchers said LLMs have capabilities that scientists can apply to the field of mechanics. Industry expects to see LLMs get better as researchers and developers make the technology not only efficient but scalable. Yet, challenges remain. 
 
The ability of VLLMs to extract information, for example, offers &ldquo;unprecedented ability to perform complex reading comprehension tasks at scale, higher impact results may arise from using VLLMs for hypothesis generation, or otherwise.&rdquo; 
 
However, one of the biggest open questions that still remains is when applying LLMs to mechanics, which of these capabilities is likely to produce the most effective results in terms of the overall goals of the field? And that answer will decide the role of LLMs in applied mechanics going forward. 
 
&ldquo;These answers will remain unknown until mechanics-based LLMs are actually built and applied,&rdquo; the authors concluded. 
 
 
Cathy Cecere is membership content program manager.

Tools that act like ChatGPT could help engineers digest large stacks of information.

Chatbots that are trained on a set of human-generated writing samples and can reply to prompts with sentences and even paragraphs that mimic their training, have become familiar to most users of the internet. One of these models, ChatGPT, is familiar enough that it&rsquo;s how most people understand large language models (LLM) that seemingly learn, comprehend, and then generate language. But these models also may carry great promise for the physical sciences, including applied mechanics. 
 
That&rsquo;s the premise of a paper written by a team of researchers from the University of California, Santa Barbara; University of New Hampshire; and Northwestern University. &ldquo;These emergent capabilities are exciting for science because they vastly lower the barrier to effective scientific data mining,&rdquo; they wrote in &ldquo;Perspective: Large Language Models in Applied Mechanics.&rdquo; The article appeared in the October 2023 issue of the ASME Journal of Applied Mechanics.

How Language Models May Shape Engineering

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Engineers studied which types of falls caused the most serious injuries for riders.

Crashing Electric Scooters

April-June 2024

Biomechanical engineers often use biological bone for studies, especially for implants and corrective surgeries. However, biological bone is expensive to source and ship, varies in quality and cost, and can arrive in a degraded or diseased state that is unsuitable for research. 
 
For nearly 40 years, SynboneVR has developed synthetic bones used in biomechanical research as a way to offset some of the cost and risk of using biological bone. Biomechanical engineers continue to rely on these synthetic bones as standards for comparison in their own orthopedic design work. However, there is no prior research that summarizes the mechanical properties of these synthetic bones in order to understand their general performance, or how well they represent biological bone. 
 
&ldquo;Many researchers use these artificial bones in their research, but there is little information about how well they represent real human bones,&rdquo; said Radovan Zdero, professor of biomechanical engineering at Western University in London, Ont. 
 
To investigate this more thoroughly, Zdero and his research partners&mdash;Aleksandar Djuricic and Emil H. Schemitsch of the Orthopedic Biomechanics Lab at Victoria Hospital in London, Ont.&mdash;launched a literature search to delve deeper into the mechanical properties of synthetic bones. Their search was successful in finding relevant data on ballistics, dentistry, orthopedics, and materials science testing that used samples of SynboneVR bone as surrogates. 
 
The study was published in the ASME Journal of Biomechanical Engineering. 
 
 
 
&ldquo;Our review of this data, pros and cons, and future work recommendations will hopefully assist biomechanical engineers and physicists who use these synthetic bones as they develop experimental testing regimes and computational models,&rdquo; Zdero said. 
 
SynboneVR has been creating synthetic bone, as well as bones in basic anatomical shapes, for medical education for decades. These bones are made from polyurethane of various densities and architectures to simulate hard &ldquo;cortical&rdquo; and spongy &ldquo;cancellous&rdquo; bone. 
 
&ldquo;The first challenge was to find all the relevant articles we wanted to survey and present in a very practical and useful way to potential readers,&rdquo; Zdero said. 
 
Research papers were only included if they characterized mechanical properties of intact synthetic bones that were previously unreported, validated mechanical properties of intact or implanted synthetic bones against biological bone, and optimized mechanical properties of intact or implanted synthetic bones to make them more realistic by varying their geometry or material. 
 
The team was interested in three characteristics of the synthetic bone. One was a comparison of tissue-level mechanical properties of synthetic versus human bone. Another was the organ-level mechanical properties of implanted synthetic versus human bones. And the team tracked screw pullout results for synthetic versus biological bone. 
 
Zdero, Djuricic, and Schemitsch conducted transverse and longitudinal tests to evaluate elastic modulus, plastic yield stress, ultimate stress, and tortional stress (where appropriate). Metal screw insertion and pullout tests were also conducted, measuring peak torque at stripping, peak axial force at stripping, and peak force at pullout. Ballistics tests were done by propelling bullets against synthetic shapes. 
 
The researchers also compared the performance of synthetic bone according to types of bone shapes, including mandible, humerus, ulna, pelvis, femur, tibia, and calcaneus. 
 
&nbsp;
<h3>A Challenging Undertaking</h3>
 
Comparing mechanical results between synthetic bone and biological bone was extremely difficult to do because of the differences in test set-ups, loading protocols, bone preparation techniques, investigation goals, and reported results that were used in the older studies. 
 
&ldquo;It was surprising that some of these artificial bone models are very poor representations of real bone, while others are excellent representations of real bone,&rdquo; Zdero said. &ldquo;In addition, we found that the mechanical properties of some of these artificial bone models have not been studied at all nor validated.&rdquo; 
 
This variability would have been minimized if the researchers had used standard protocols relevant to biomechanical studies from organizations like the American Society for Testing and Materials and International Organization for Standardization. The differences in research approaches made it difficult to derive meaningful conclusions from comparing synthetic bones to biological bones. 
 
&ldquo;Reasons for this may be the large variation in the geometry and properties of biological bones, lack of consistent reporting about the quality of biological bones, and different ways researchers prepared, mechanically tested, or computationally analyzed synthetic or biological bones,&rdquo; Zdero said. 
 
A clear result from the data analysis showed that synthetic bones almost always had a much smaller coefficient of variation versus biological bones. This shows that the manufacturing methods used to create synthetic bone had high consistency, while simultaneously showing the high inter-specimen variation common among biological bones. 
 
&ldquo;Consequently, this attribute of these synthetic bones is compelling to most investigators who wish to reduce confounding variables that may affect statistical comparisons between groups,&rdquo; Zdereo said. 
 
The researchers thought more biomechanical properties should have been tested in the past synthetic bone studies that they had evaluated. To add value and reliability to future research, Zdero recommends that more tissue-level properties such as tensile and shear modulus and strength, fracture toughness, friction coefficient, fatigue life, and hardness be evaluated. 
 
Few of the papers optimized the mechanical performance of synthetic bones by altering their geometric or material parameters. In general, no particular geometric or material variable can change synthetic bone performance to perfectly match biological bone. 
 
&ldquo;However, successful optimization usually involves adjusting geometric and material parameters at the same time,&rdquo; Zdero said. &ldquo;In this regard, experimental studies plus finite element models could be design tools for concurrently investigating the effect of numerous variables.&rdquo; 
 
Zdero and his colleagues are the first researchers to compile and interpret the artificial bone properties provided by SynboneVR products. &ldquo;Our work has outlined specific practical ways to improve the mechanical properties of these artificial bones for future researchers,&rdquo; Zdero said. &ldquo;We also hope that the SynboneVR company will improve on the mechanical properties of their artificial bones and that biomedical engineers will perform validation studies on those artificial bones that have yet to be evaluated.&rdquo; 
 
 
Mark Crawford is a technology writer in Corrales, N.M.

Researchers rely on artificial bone material to stand in for the real thing. Up to now, however, no one has looked at how well the two materials match.

Biomechanical engineers often use biological bone for studies, especially for implants and corrective surgeries. However, biological bone is expensive to source and ship, varies in quality and cost, and can arrive in a degraded or diseased state that is unsuitable for research. 
 
For nearly 40 years, SynboneVR has developed synthetic bones used in biomechanical research as a way to offset some of the cost and risk of using biological bone. Biomechanical engineers continue to rely on these synthetic bones as standards for comparison in their own orthopedic design work. However, there is no prior research that summarizes the mechanical properties of these synthetic bones in order to understand their general performance, or how well they represent biological bone.

Synthetic Bone Versus Reality 

Some people are good at certain things, others not so much. That&rsquo;s as true in mechanical engineering as in any other field that requires specialized skills and knowledge. But what distinguishes an average proficient person from a true expert in, for example, the essential engineering skill of computer-aided design (CAD)? Is it simply a matter of experience, or are other factors such as an individual&rsquo;s particular approach to a certain task involved? How can we speed up the process of turning the merely competent into CAD superstars? 
 
Alison Olechowski, assistant professor in the University of Toronto&rsquo;s Department of Mechanical and Industrial Engineering, decided to find out. Working with graduate students James Chen and Yuanzhe Deng, she designed a study to characterize the differences and similarities in CAD modeling approaches, patterns, and strategies between proficient and expert users. The work was published in the ASME Journal of Mechanical Design. 
 
&ldquo;My research group is interested in improving CAD collaboration and understanding how mechanical engineering designers can work together with CAD to design innovative new products,&rdquo; Olechowski said. &ldquo;But when we started digging into that problem, we realized that we&rsquo;re lacking an understanding of how engineers design individually in CAD, and that&rsquo;s an important first building block. A lot of the existing research on CAD collects data from student or novice users, but very little exists for what we call proficient or intermediate or expert users. So, we designed an experiment where we would have engineering designers join us on a cloud-based tool.&rdquo; 
 
Olechowski and her colleagues defined a set of descriptions of novice, proficient, and expert CAD users and then recruited a group of designers. &ldquo;We invited folks to self-identify in those different levels of expertise. But what our experiment let us do is that we could then verify that,&rdquo; Olechowski explained. &ldquo;We also asked the expert users to report the number of years of experience that they had with CAD. Those who self-reported as expert had significantly more experience than those who were proficient.&rdquo; 
 
Participants were given engineering drawings from which to create a 3D parametric CAD model in four steps in a given amount of time. 
 
&ldquo;We had a number of metrics about the effectiveness, speed, and the quality of their design, and we could compare these things, so we could we look at the models that resulted from the experiments in and of themselves,&rdquo; Olechowski said. &ldquo;But we also looked at all the clicks, the design choices that were made by the users. Because there are many different ways to arrive at one final CAD model.&rdquo; 
 
The researchers found that years of experience definitely make a big difference. &ldquo;We didn&rsquo;t find one golden approach to building a CAD model, but we did notice some differences in user actions and how experts perform as differing from proficient users,&rdquo; Olechowski said. &ldquo;The experts were able to initially form a smart strategy and see the problem through from beginning to end, so that in the end their behavior had less iterations, they had to revise less.&rdquo; 
 
The merely proficient users, however, were found to use more of a trial-and-error process to arrive at their final goals. 
 
&ldquo;It&rsquo;s kind of a chicken and an egg thing, but we noticed that the experts were much more effective at reading the engineering drawings that they were given and then translating that into the model,&rdquo; Olechowski said. &ldquo;It reminds me of studies that have been done in the past about chess experts. Apparently, if you ask a group of non-chess players and chess experts to memorize where the pieces are on a board that just has randomly placed pieces, they can remember them about as well. But if you put the pieces in an actual gameplay scenario, the experts can remember those much better than the novices can, because they have those connections made and that experience built.&rdquo; 
 
Olechowski and her colleagues believe that one explanation for the gap between the experts and the merely proficient is the difference between what psychologists call declarative vs. procedural knowledge. Declarative knowledge is basically all about following the instructions and knowing the specific commands and various procedures to do a task, while procedural knowledge goes beyond that to incorporate different strategies or choices. 
 
&ldquo;If we think about the trajectory from a novice to an expert, so much of the way that we teach CAD is through declarative knowledge,&rdquo; she noted. &ldquo;That&rsquo;s the way most software programs are taught. &lsquo;This is what the buttons do, these are the features and the capabilities.&rsquo; Whereas it&rsquo;s hard to learn procedural expertise. It takes time.&rdquo; 
 
Ideally, she said, some kind of apprenticeship-style education would help, or being partnered with a great mentor, but such approaches aren&rsquo;t always possible. &ldquo;People are busy, and timelines are tight, so you might not get taught that procedural knowledge. And it&rsquo;s not really written up in books either.&rdquo; 
 
It&rsquo;s not yet clear how the results of this study might translate to CAD usage in other areas of engineering, or in architecture, in which problem solving might involve a higher degree of creativity. In this particular study, Olechowski said, &ldquo;They have to figure out how to do the design, but they don&rsquo;t have to be creative in what the design is. I would imagine that maybe an architecture audience would be more interested in more open-ended problems.&rdquo; 
 
She&rsquo;s looking at such questions for further exploration. &ldquo;Engineers are often trained to think about quality and manufacturability and cost from the very start,&rdquo; she observed. &ldquo;My understanding of architects is that they allow themselves to let go of some of those things, at least initially. So yeah, there are probably some differences there.&rdquo; 
 
Other angles to examine are the role of aptitudes such as a talent for spatial thinking, and the techniques of CAD users with more experience in newer additive manufacturing methods contrasted with those with more traditional subtractive manufacturing approaches&mdash;and how to find ways that designers with different talents and strategies, strengths and weaknesses, might work together better instead of possibly clashing over how to complete a project. 
 
Clearly, there&rsquo;s no magic formula to make any engineer a CAD expert, but it&rsquo;s clear that experience is one part of it. This study is an important first step in understanding and facilitating the mysterious process of transforming an average user into a CAD Jedi Master. 
 
 
Mark Wolverton is a technology writer in Narbeth, Pa.

Many people consider themselves to be proficient in applications such as computer assisted design. But true experts operate on a totally different level.&nbsp;

Some people are good at certain things, others not so much. That&rsquo;s as true in mechanical engineering as in any other field that requires specialized skills and knowledge. But what distinguishes an average proficient person from a true expert in, for example, the essential engineering skill of computer-aided design (CAD)? Is it simply a matter of experience, or are other factors such as an individual&rsquo;s particular approach to a certain task involved? How can we speed up the process of turning the merely competent into CAD superstars? 
 
Alison Olechowski, assistant professor in the University of Toronto&rsquo;s Department of Mechanical and Industrial Engineering, decided to find out. Working with graduate students James Chen and Yuanzhe Deng, she designed a study to characterize the differences and similarities in CAD modeling approaches, patterns, and strategies between proficient and expert users. The work was published in the ASME Journal of Mechanical Design.

Many people consider themselves to be proficient in applications such as computer assisted design. But true experts operate on a totally different level.

What Makes a CAD Expert?

Electronic waste is a growing problem in many parts of the world. One region that has taken steps to rein in waste is the European Union, which has set tough new standards with the intent of creating a so-called circular economy where old products become the building blocks for new ones. To see how this proposal would affect mechanical engineers, Núria Boix Rodríguez and Claudio Favi looked at mechatronic products, which combine mechanical and electronic components. Boix Rodríguez, now a postdoctoral researcher at KU Leuven in Belgium, discusses the role mechanical engineers could play in designing machines that can extend their service lives through repairability.

Núria Boix Rodríguez, postdoctoral researcher at KU Leuven, says engineering design can prepare industry for Europe&rsquo;s circular economy action plan.

Design to Disassemble

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Jeffrey Winters is editor in chief of Mechanical Engineering magazine.

Forget the skyhook. Researchers have developed a mechanism that can walk over to an object, climb on top, and hold on.

The Creeping Claw

July-September 2024

Skin-based bioelectronics applications are becoming more common in healthcare markets, but one challenge is keeping these devices in contact with bodies that are in constant motion. This conformal contact with the skin allows for bio-signal acquisition, especially for curvilinear areas of the body, so that the devices can send health data to external networks.&nbsp; 
 
Raudel Avila, assistant professor of mechanical engineering at Rice University, was determined to develop an improved geometrical and mechanical design for bioelectronics that improves wearability, efficiency, and comfort. &nbsp; 
 
&ldquo;Conventionally, bioelectronics are typically fabricated on a planar surface that is then deformed to match a required curvature in the body,&rdquo; Avila said. &ldquo;I realized we could make the bioelectronic device curve from the start and place it in the locations of interest in the body. This idea is particularly important when you are dealing with very sensitive or fragile skin, such as neonatal intensive care (NICU) or pediatric intensive care (PICU) patients.&rdquo;&nbsp; 
 
Because this field of research often benefits from cross-collaboration, Avila worked closely with material scientists and biomedical engineers. The team consisting of Sun Soo Kwak (Korea Advanced Institute of Science and Technology), Jean Won Kwak (Stanford University), John A. Rogers (Northwestern University), and Yonggang Huang (Northwestern) developed soft skin-integrated &ldquo;holey&rdquo; bioelectronic devices with enhanced mechanics to monitor health metrics in NICU and PICU patients. &nbsp; 
 
The research was reported in the April 2024 issue of Journal of Applied Mechanics.&nbsp; 
 
Bioelectronic devices with soft polymeric encapsulations and internal rigid electronic components result in a mechanically hybrid composite structure, with intrinsically soft mechanics for integration with biological tissues through mechanical compliance. For accurate signal acquisition and sensing on limbs, chest, forehead, and other curved regions of the body, bioelectronic devices are pressed and bent to closely match the skin morphology, causing additional interfacial stresses. &nbsp; 
 
<img alt="Bioelectronics" src="~/getmedia/a51ce77a-409a-4ec1-a382-ed387b9d7aeb/Bioelectronics.jpg" /> 
This 3D finite element model shows the stress distribution of a curved biosensor running across the top of a thigh. Credit: Raudel Avila 
 
 
Avila engineered a mechanical design strategy based on conformal curvature matching, with stiff substrate islands housing commercial electronic components and circuits. &nbsp; 
 
The team used finite element modeling of the skin curvature, encapsulation, and internal electronic layouts to quantify the spatial distribution of the underlying stresses at the skin interface, based on a mismatch curvature angle &theta; between the device and skin. &nbsp; 
 
&ldquo;Selected cases of &theta; = 30 deg and 60 deg can reduce the normal and shear stresses by up to 45 percent and 70 percent, respectively,&rdquo; Avila said. &nbsp; 
 
They also leveraged geometry and mechanics to design better bioelectronics form factors for applications such as continuous physiological monitoring of NICU and PICU patients. &nbsp; 
 
&ldquo;We are using traditional concepts from mechanics of materials to ensure that, for the multi-material layout that combines soft elastomers and rigid electronics, low flexural and torsional stiffness can be achieved to accommodate various bending and twisting deformations,&rdquo; he said.&nbsp; 
 
The biggest research challenge was to systematically understand how geometrical, mechanical, and material parameters affect the interfacial stresses on the skin. These parameters further influence the magnitude of the normal and interfacial stresses. By performing numerical simulations, the team was able to identify how parameters such as the Young&rsquo;s modulus of the encapsulation elastomers, the bending angle and device curvature, and the placement and layout of the internal electronic layouts influence the distribution of the interfacial stresses during bioelectronic placement on the skin. &nbsp; 
 
The somatosensory pressure (approximately 20 kPa) of skin is the metric the team used to evaluate if the user/patient can feel or sense the device during operation. This threshold value is very important because it is related to the comfort and wearability of the bioelectronic device during operation. &nbsp; 
 
&ldquo;We do not want devices to get in the way of people or affect the way they perform a task,&rdquo; Avila said. &ldquo;One of the biggest surprises of this work was achieving curved bioelectronic designs, with curved angles of up to 60 degrees, that never reach this somatosensory pressure. This means that, even when deformed, the device remains imperceptible to the user, which is very important in clinical settings for NICU and PICU patients.&rdquo;&nbsp; 
 
Avila and his team of collaborators demonstrated how curvature-matching designs for the bioelectronic&ndash;skin interface can reduce the resulting normal and shear stresses generated from device adhesion and skin stretching during dynamic motions. &nbsp; 
 
&ldquo;Our proposed curvature-matching design strategy can inform the future design of user-specific bioelectronics for integration with complex anatomical structures,&rdquo; Avila said.&nbsp; 
 
For example, these concepts can be applied for bioelectronics placed on high-curvature locations like pressure monitoring of residual limbs in amputees. &ldquo;Hopefully, the translational impact of our user-specific/curvature-specific bioelectronics will go beyond hospitals and clinics to enable other applications in different industries.&rdquo;&nbsp; 
 
 
Mark Crawford is a technology writer in Corrales, N.M.

To improve the communication between patients and bioelectronic devices, the interface between the two should follow the curve of the body. Researchers have developed a curvature-matching design strategy that can enhance wearability during skin motion.

Skin-based bioelectronics applications are becoming more common in healthcare markets, but one challenge is keeping these devices in contact with bodies that are in constant motion. This conformal contact with the skin allows for bio-signal acquisition, especially for curvilinear areas of the body, so that the devices can send health data to external networks.&nbsp; 
 
Raudel Avila, assistant professor of mechanical engineering at Rice University, was determined to develop an improved geometrical and mechanical design for bioelectronics that improves wearability, efficiency, and comfort. &nbsp;

Contact is Key to Bioelectronics

Bridge safety may be improved by using remote wireless sensors and finite element models for structural health monitoring (SHM) by providing a fuller picture of bridge integrity. This is according to a recently published study from the University of Pittsburgh&#39;s Swanson School of Engineering. &nbsp; 
 
Led by Piervincenzo (Piero) Rizzo, associate professor of civil and environmental engineering, the researchers compared model data to field data gathered from three similar concrete box bridges with existing wireless sensors. The team compared those field results against finite element models, which simulate various loading or impact conditions, including the vibrations, displacement, and deformation a truck creates. &nbsp; 
 
&ldquo;The scope of studies like this one is to understand how a specific structure responds to traffic load to wind loads, or to other manmade or natural events,&rdquo; said Rizzo. &nbsp; 
 
Funding for such studies is important to meet the increasing interest in bridge monitoring, he added. The Federal government mandates that every bridge is inspected at least once every two years. Tracking issues such as corrosion, concrete spalling, or cracking may provide advance warning of potential issues between physical inspections. &nbsp;&nbsp; 
 
Bridges expand or contract when the temperature increases or decreases. Monitoring over a one- or two-year period, during all four seasons, provides a clearer picture on the uniformity of expansion or contraction, and insight into the safety of the structure and operation of the bridge, Rizzo said.&nbsp; 
 
&ldquo;There are different ways of how we can monitor and inspect structures,&rdquo; he continued. &ldquo;To some extent, it&#39;s like tools and instruments to detect and monitor the health of a person,&rdquo; similar to how different tests such as bloodwork or ultrasounds can help diagnose different human health issues. &nbsp; 
 
&ldquo;You cannot go there and start cutting parts and see how the damaged bridge would respond when a truck crosses across the bridge,&rdquo; Rizzo said of the challenges to bridge monitoring. &nbsp;&ldquo;We use computer models to simulate the different scenarios and how [they] would be translated into the real world,&rdquo; he added. &nbsp; 
 
Looking at a specific load of a truck including all relevant data of its design and its weight, the team calculated mathematical models and compared those predictions with the experimental values obtained by the existing sensors already placed on the three concrete box bridges. &nbsp;Rizzo&rsquo;s team had no input on the type or placement of these already existing sensors. &nbsp;&nbsp; 
 
The results showed that finite element models along with the data-driven methodologies have the potential to identify damages and anomalies in the three box girder bridges with relative accuracy. The results verified expectations, minus one or two non-consequential outliers.&nbsp; 
 
<img alt="" src="~/getmedia/00b8b7a0-cc61-422d-b665-665e3ec90227/bridges-article.jpg" /> 
Cross section of (from top) Somerset Bridge, Cooks Mill Bridge, and Tonolaway Creek Bridge, with locations of sensors shown in red. Image: Rizzo, et al. 
 
 
A peer review process in 2020 resulted in Rizzo&rsquo;s team finding about 70 bridges in the U.S. that already had some sort of monitoring devices on them. While he doesn&rsquo;t have additional data to say for sure, he thinks there are many more sensors already applied to bridges. &nbsp; 
 
&ldquo;I am 99.9 percent sure that there are more than 70 bridges that have been monitored at some time in their lifespan,&rdquo; said Rizzo. &nbsp;Those potential additional bridges may provide additional valuable field data to advance future efforts in wireless sensor monitoring for infrastructure. &nbsp; 
 
&ldquo;The very interesting thing is that these mathematical models that we developed could be adapted to other similar bridges&mdash;bridges that are a bit longer or a bit wider,&rdquo; Rizzo said. He noted the value of such studies by academia to help provide complementary tools to the infrastructure industry. &nbsp;A model and remote wireless sensor approach also provides flexibility to adapt and address whatever issues may be affecting different types of bridges in different locations and conditions. &nbsp; 
 
&nbsp;&ldquo;Tell me what you need to look at and I&#39;ll tell you the best cost-effective solution,&rdquo; Rizzo said. &nbsp; 
 
 
Nancy Kristof is a technology writer in Denver.&nbsp;

A combo of wireless sensors and computer models reveals bridge integrity issues unseen by conventional inspections.

Bridge safety may be improved by using remote wireless sensors and finite element models for structural health monitoring (SHM) by providing a fuller picture of bridge integrity. This is according to a recently published study from the University of Pittsburgh&#39;s Swanson School of Engineering. &nbsp; 
 
Led by Piervincenzo (Piero) Rizzo, associate professor of civil and environmental engineering, the researchers compared model data to field data gathered from three similar concrete box bridges with existing wireless sensors. The team compared those field results against finite element models, which simulate various loading or impact conditions, including the vibrations, displacement, and deformation a truck creates. &nbsp;

Diagnosing Bridge Health

Researchers Hanxun Jin and Horacio D. Espinosa recently examined some advances in self-assembly techniques that have the potential to fabricate load-bearing mechanical metamaterials in &ldquo;Mechanical Metamaterials Fabricated From Self-Assembly: A Perspective,&rdquo; published in April in the ASME Journal of Applied Mechanics.&nbsp; 
 
Espinosa is a professor in the Department of Mechanical Engineering at Northwestern University. Jin was a postdoctoral researcher in the Division of Engineering and Applied Science at the California Institute of Technology when the paper was published; currently, Jin is a senior research scientist at Washington University in St. Louis.&nbsp;

Engineers are finding a growing number of applications for mechanical metamaterials, which feature unique mechanical properties that are determined by their structure.

Engineers are finding a growing number of applications for mechanical metamaterials, which feature unique properties that are determined by their structure.

Fabricating Mechanical Metamaterials

<img alt="" src="~/getmedia/5f0fee73-a6a6-4e38-be24-21a8dbf56ba6/Infographic-oct24-Image-01.gif" style="height:480px;weight:640px;" /> 
&nbsp; 
 
One popular alternative is the vertical-axis wind turbine that utilizes the Savonius design, which features a pair of simple hollow half cylinders. &nbsp; 
 
<img alt="" src="~/getmedia/d2d4c87a-a27d-4dea-bd65-3174c59be8c1/Infographic-oct-dec24-Image-02.jpg" /> 
&nbsp; 
 
The design is simple and cheap, but because the cylinders are pushed by drag rather than aerodynamic lift the way long wind turbine blades are, the Savonius turbine captures only one-third the power of a commercial wind turbine. In fact, it&rsquo;s the least efficient design for a wind turbine.&nbsp; 
 
<img alt="" src="~/getmedia/fbb73475-860b-451b-8dc1-ef6e74cbb9ff/Infographic-oct-dec24-Image-03.jpg" /> 
&nbsp; 
 
Recently, Man Mohan and Ujjwal K. Saha, mechanical engineering researchers at the Indian Institute of Technology at Guwahati, looked at ways to optimize the Savonius turbine. They hit upon using a genetic algorithm to produce various new shapes that could be tested in a computational fluid dynamics software package. The best performing shapes would become the seeds of another set of slightly altered blades. They repeated the steps until they found the optimized shape: a pair of L-shape scoops, slightly offset.&nbsp; 
 
<img alt="" src="~/getmedia/1655dc3b-f0b7-411a-a439-43a2fe5c6e3c/Infographic-oct-dec24-Image-04.jpg" /> 
&nbsp; 
 
While the simulations were promising, the real test of the new design involved building a scale model and placing it in a wind tunnel. Compared to a Savonius turbine made with simple, semicircular scoops, the optimized wind turbine performed more than 14 percent better under peak conditions and worked better in high winds. &nbsp; 
 
<img alt="" src="~/getmedia/caa9378b-a61e-441d-bd37-ba0528207704/Infographic-oct-dec24-Image-05.jpg" /> 
 
The paper, &ldquo;Evolving a Novel Blade Shape of a Savonius Wind Rotor Using an Optimization Technique Coupled with Numerical Simulations and Wind Tunnel Tests,&rdquo; was published in the April 2024 Journal of Energy Resources Technology.&nbsp; 
 
 
Jeffrey Winters is editor in chief of Mechanical Engineering magazine.

The horizontal-axis wind turbine has become an efficient and economical means to produce electricity. Some of the largest machines can produce as much as 15 MW when running at full capacity. But such turbines can be too complicated for small-scale operations or for capturing wind power in urban settings.&nbsp;

One popular alternative is the vertical-axis wind turbine that utilizes the Savonius design, which features a pair of simple hollow half cylinders.

The horizontal-axis wind turbine has become an efficient and economical means to produce electricity. Some of the largest machines can produce as much as 15 MW when running at full capacity. But such turbines can be too complicated for small-scale operations or for capturing wind power in urban settings.

A Better Shape to Catch the Wind

October-December 2024

Digital twin technology (DT) has been successfully deployed in fields as varied as aviation, manufacturing, and oil and gas. But civil engineering, especially for field-related applications, has not been a venue for DT, in part because it relies on a variety of external technologies and approaches that were developed for other engineering fields. The most frequent and consistent use of DT in civil engineering projects is in the operations and maintenance phase, whereas building information modeling (BIM) is pervasively utilized in the first phase of planning/design.&nbsp; 
 
To better understand how DT can be more uniformly applied in civil engineering, a research team led by Ruda Zhang, assistant professor of civil and environmental engineering at the University of Houston, conducted an in-depth literature review to develop a phase-based approach for using DT in the architecture, engineering, and construction (AEC) industry. The team also established a five-level rating system for defining the complexity and depth of the DT being used within these phases.&nbsp; 
 
&ldquo;Our systematic literature review studied the conventional techniques employed at each civil engineering phase,&rdquo; Zhang said. &ldquo;We then identified enabling technologies such as computer vision for extended sensing and the Internet of Things for reliable integration. Our goal is to show how DT is an important tool across the entire lifecycle of civil engineering projects and hopefully nudge researchers to think more holistically in their quest to integrate DT in civil engineering applications.&rdquo; &nbsp; 
 
Taiwo A. Adebiyi and Nafeezat A. Ajenifuja, both at the University of Houston, authored the paper with Zhang. The study, &ldquo;Digital Twins and Civil Engineering: Reorienting Adoption Strategies,&rdquo; appeared in the Journal of Computing and Information Science in Engineering in October 2024. &nbsp; 
 
&nbsp;
<h3>Three phases&nbsp;</h3>
 
One reason for the slow pace of DT adoption in civil engineering is the profession&rsquo;s resistance to change and the complexity of its projects. Every civil engineering project must go through three distinct and sequential phases: planning/design, construction, and operations and maintenance. Each of these phases utilizes AI in different ways, making it difficult to integrated the flow of DT across phases. The team researched how each phase uses DT and explored the different concepts/frameworks for phase-based DT applications.&nbsp;
<h4> 
Planning/Design Phase: Five Levels of BIM Growth&nbsp;</h4>
 
The integration of DT with BIM systems has been transformative for planning and design. The long-established practice of BIM has gradually evolved into a powerful digital tool. &nbsp; 
 
&ldquo;BIM has evolved from its inherent static configuration to an integrated dynamic powerhouse as an enabler for DT development in the built environment,&rdquo; Zhang said. BIM has grown from a rudimentary virtual reality &nbsp; program to include simulation, sensor technologies, and &nbsp;artificial intelligence (AI), all of which enable an advanced DT in the built environment.&nbsp;
<h4> 
Construction: Sensing, Internet of Things &nbsp;</h4>
 
How DT in deployed in the construction phase depends the other digital technologies being used, including sensing and the Internet of Things. &nbsp; 
 
&ldquo;Sensing technologies paved the way for real-time construction monitoring, enabling improved productivity, hazard identification, construction waste management, and clash detection,&rdquo; Zhang said. &ldquo;Laser scanners, RGB cameras, and depth cameras are used for mapping sensors; however, laser scanners are limited by the lack of color information&mdash;hence their combination with digital cameras to obtain colorized 3D point clouds.&rdquo;&nbsp;
<h4> 
Operations and Maintenance: Structural Health &nbsp;</h4>
 
Structural health monitoring (SHM) is an important application that relies on advanced DT technologies. SHM is segmented into two categories: diagnosis and prognosis. Most of the DT work done in this phase is diagnostic (damage detection, localization, and evaluation) with fewer advances in the prognosis category (for example, residual life prediction). Nonetheless, &ldquo;the advent of several miniaturized or sensor-based SHM systems directly attached to modern structures has paved the way for real-time monitoring of the structures via model updating and parameter estimations, otherwise known as system identification,&rdquo; Zhang said.&nbsp; 
 
When these and other DT tools are in place, the prognosis of aspect of SHM will become more attainable, &ldquo;including prediction, learning, management, optimization, and other context-specific functionalities&mdash;all of which are encompassed in a virtual duplicate of a physical infrastructure tagged DT,&rdquo; Zhang added.&nbsp; 
 
&nbsp;
<h3>A competitive tool&nbsp;</h3>
 
Zhang&rsquo;s research shows how BIM, sensing, and IoT are essential technologies/processes for developing highly sensitive digital twin technology for civil engineering applications. DT capabilities include data acquisition and processing through sensing technologies, data processing such as feature extraction via machine-learning methods, and data interpretation from extracted features or raw data using computer vision.&nbsp; 
 
Two other functions needed for effective DT development are uncertainty quantification and model updating. &nbsp; 
 
&ldquo;Model updating is a must for an accurate depiction of the digital states of the corresponding physical states of an asset,&rdquo; Zhang said. &ldquo;However, the need for continuous model updates can be computationally expensive due to the repetitive need for evaluations.&rdquo;&nbsp; 
 
More research is needed to determine the most efficient approach for model updates for the DT development of structural systems. For both uncertainty quantification and model updates, randomization of parameters for probabilistic evaluations is critical.&nbsp; 
 
If DT can be as advanced in civil engineering as it is in aviation and manufacturing, especially for mission planning optimization, &ldquo;it will become a competitive tool for sustainable and resilient civil engineering amidst the mounting environmental and social challenges in the AEC profession,&rdquo; Zhang concluded.&nbsp; 
 
Mark Crawford is a technology writer in Corrales, N.M.&nbsp;

The technology has uses beyond the aviation and manufacturing sectors. A new study found all three phases of civil engineering projects&mdash;planning/design, construction, and operation and maintenance&mdash;can find value in digital twins.

Digital twin technology (DT) has been successfully deployed in fields as varied as aviation, manufacturing, and oil and gas. But civil engineering, especially for field-related applications, has not been a venue for DT, in part because it relies on a variety of external technologies and approaches that were developed for other engineering fields. The most frequent and consistent use of DT in civil engineering projects is in the operations and maintenance phase, whereas building information modeling (BIM) is pervasively utilized in the first phase of planning/design.

Digital Twins Can Support Civil Engineering Projects

Gears are key components in automotive transmissions. Electrification of automotive powertrains over the coming years will pressure gear manufacturers to increase gear production. Any improvements that can maximize efficiency in the gear production chain will be in high demand for keeping up with market growth and reducing production costs. &nbsp; 
 
One way to do this is by improving the gear-grinding process. Grinding is important because it eliminates surface flaws, maximizes load capacity, and minimizes running noise. However, standard grinding of high-performance gears is a &ldquo;wet&rdquo; process&rdquo; that is time-consuming and requires multiple steps. Wet grinding typically uses a large amount of lubricant. Energy consumption for lubrification and cooling represents almost two-thirds of the total energy consumption of a typical grinding machining center&mdash;a cost that gear manufacturers would love to eliminate.&nbsp; 
 
To make dry grinding (no lubricants) more viable and cost-effective, a research team led by Erica Liverani, a senior assistant professor in the Department of Industrial Engineering at the University of Bologna in Italy, compared the high-performance gears made with conventional wet grinding with two other processes: superfinishing and dry grinding. By adjusting a variety of parameters, Liverani&rsquo;s team developed a dry grinding system that outperformed the other two methods. &nbsp; 
 
&ldquo;This shows that the complete elimination of lubricant in gear production is possible, leading to a more sustainable process without compromising gear performance,&rdquo; she said.&nbsp; 
 
Liverani and six coauthors published a paper on the topic, &ldquo;Dry Grinding: A More Sustainable Manufacturing Process for the Production of Automotive Gears,&rdquo; in the October 2024 issue of the Journal of Manufacturing Science and Engineering.&nbsp; 
 
&nbsp;
<h3>Ready, set&mdash;grind &nbsp;</h3>
 
The material and manufacturing processes that were used prior to grinding were the same in all cases, followed by grinding performed by the same manufacturer. &ldquo;The dimensional accuracy, roughness, microstructure, residual stress state, and wear resistance of gear flanks were then analyzed to compare the overall performance of each grinding process,&rdquo; Liverani said.&nbsp; 
 
Three grinding processes were selected based on current manufacturing standards and new requirements for carbon neutrality: &nbsp; 
 
Wet grinding (WG) served as a benchmark&nbsp; 
 
Dry hard finishing (DHG) performed without the use of lubricants &nbsp; 
 
Superfinishing (SF), a wet process that increases micro-pitting &nbsp; 
 
After grinding, all gears were analyzed with an optical microscope and scanning electron microscope for microstructure evaluation, an optical profiler for the acquisition of the surface topography and roughness, a Klingelnberg measuring system for evaluation of geometric errors, and an X-ray diffraction analysis for residual stress measurement. Finally, wear tests were performed to evaluate the influence of grinding on gear durability.&nbsp; 
 
<img alt="" src="~/getmedia/134c0c26-16b9-4bec-a00a-7d00d2961a99/gear-grinding-1.jpg" />
<div style="text-align: center;">Microscope images of gear teeth ground through different methods: a) wet grinding, b) and c) dry grinding, and d) and e) super finishing. Scuffing and micro-pitting are highlighted with white and black arrows, respectively. Image: Alessandro Fortunato, et al. in the Journal of Manufacturing Science and Engineering.</div>
&nbsp;

<h3> 
Cycle parameters&nbsp;</h3>
 
In terms of dimensional accuracy, roughness, and microstructure, &ldquo;the goal was to &nbsp;identify the best combination of parameters for achieving the best level of surface integrity,&rdquo; Liverani said. &ldquo;The grinding cycle parameters and grinding wheel specifications were changed depending on the grinding process being used.&rdquo;&nbsp; 
 
The results show that dry grinding can produce gears with acceptable geometric accuracy, no microstructure defects, and greater wear resistance than gears finished with conventional wet grinding or superfinishing. Findings include:&nbsp;
<ul>
	<li>No significant variations were found in the geometric accuracy of gears due to the grinding processes over the tested parameter range.</li>
	<li>Wet grinding and superfinishing achieved lower roughness, which could be detrimental for wear resistance.</li>
	<li>No significant variations were found in the microstructures of gears due to the grinding processes.</li>
	<li>Correct selection of process parameters allowed ground surfaces to be obtained without burns or a white layer.</li>
	<li>Dry-ground gears show slight tensile residual stresses in the flank surface, but a higher hardness was measured below the same surface with respect to wet grinding conditions.&nbsp;</li>
</ul>
&nbsp; 
<img alt="" src="~/getmedia/1d2a62f4-fe9c-447b-85fe-9a9a2d844c39/gear-grinding-2.jpg" />
<div style="text-align: center;">A schematic and photos of the experimental setup (a and b) and images of the gears ground in the experiment (c and d). Images: Alessandro Fortunato, et al. in the Journal of Manufacturing Science and Engineering.</div>

<h3 style="text-align: center;">&nbsp;</h3>

<h3> 
Stronger wear resistance</h3>
 
The flank profile of gears subject to dry grinding shows slight tensile values as a result of a high thermal gradient, which also causes microstructural defects if grinding parameters are not optimized. &nbsp; 
 
&ldquo;Nonetheless, in the tested conditions of this study, high hardness and beneficial topography assume a higher weight with respect to residual stresses, and wear tests revealed that dry ground gears have the longest durability,&rdquo; Liverani said. &ldquo;Based on these results, dry grinding could be an alternative to conventional wet grinding that satisfies the mechanical and geometric requirements of car manufacturers, while improving wear resistance, reducing waste, and increasing the sustainability of gear production in the strategic automotive market.&rdquo;&nbsp; 
 
Perhaps the greatest discovery was that the wear resistance of gears finished with dry grinding was considerably greater than that of gears finished with wet grinding or superfinishing. &ldquo;This is a fundamental advantage for electric vehicles, where noise must be minimized,&rdquo; Liverani said. &ldquo;The elimination of lubricant makes this solution more sustainable, improving wear resistance without compromising geometric accuracy.&rdquo;&nbsp; 
 
Mark Crawford is a technology writer in Corrales, N.M.

Researchers at the University of Bologna in Italy have developed a method of dry grinding for automotive gears&mdash;without using oils and other lubricants.

Gears are key components in automotive transmissions. Electrification of automotive powertrains over the coming years will pressure gear manufacturers to increase gear production. Any improvements that can maximize efficiency in the gear production chain will be in high demand for keeping up with market growth and reducing production costs. &nbsp; 
 
One way to do this is by improving the gear-grinding process. Grinding is important because it eliminates surface flaws, maximizes load capacity, and minimizes running noise. However, standard grinding of high-performance gears is a &ldquo;wet&rdquo; process&rdquo; that is time-consuming and requires multiple steps. Wet grinding typically uses a large amount of lubricant. Energy consumption for lubrification and cooling represents almost two-thirds of the total energy consumption of a typical grinding machining center&mdash;a cost that gear manufacturers would love to eliminate.

A More Sustainable Way to Make Automotive Gears

The first large-scale implementation of an air-conditioning system was at the Sackett-Wilhelms Lithographing &amp; Publishing Company in Brooklyn in 1902, which used the then-new invention to limit the amount of moisture absorbed by paper. Today, most factories are climate controlled. But not all factory owners optimize their heating, ventilation, and air conditioning (HVAC) systems for energy efficiency. &nbsp; 
 
Forooza Samadi, assistant director of the Alabama Industrial Training and Assessment Center and assistant professor of mechanical engineering at the University of Alabama in Tuscaloosa, recently studied ways factories could cut costs and carbon emissions. She was coauthor on the paper, &ldquo;Strategic Evaluation of Sustainable Practices for HVAC Systems in Small- and Medium-Sized U.S. Manufacturers,&rdquo; published in the ASME Journal of Engineering for Sustainable Buildings and Cities in August 2024. Here, she described some of her findings.

Manufacturers rely on heating, cooling, and ventilation systems to provide optimal environments for their equipment&mdash;and workers. University of Alabama researcher Forooza Samadi describes ways companies can optimize these systems.

Q&A: Improving Efficiency in HVAC Systems

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It&rsquo;s not all about power&mdash;a robotic arm needs the right technique and architecture to hurl an object efficiently.

Robot Throwing

January-March 2025

April-June 2025

Over the last decade there has been keen interest in developing marine hydrokinetic systems, especially underwater kites, for use as utility-scale renewable energy sources. &nbsp; 
 
That interest might seem unexpected, as kites are commonly thought of as airborne playthings. But in this instance, kites are generically lifting bodies moving through flowing fluids and tethered to base stations. A kite moving in cyclic patterns perpendicular to the prevailing flow can travel much faster than the flow itself. If a turbine is attached to the kite, it can capture much more power than a stationary turbine of the same size. &nbsp; 
 
The U.S. Navy in particular is interested in developing autonomous underwater vehicles (AUVs) that can support very high payloads and extended missions. These vehicles would be faced with unprecedented energy requirements, &ldquo;necessitating mechanisms for harvesting a portion of the marine energy made available along the mission,&rdquo; said Chris Vermillion, an associate professor of mechanical engineering at the University of Michigan in Ann Arbor who is an expert in this field. &nbsp; 
 
In a scenario Vermillion sketched out, an underwater kite could be deployed from the AUV parked on the seabed. As the kite executes figure-8 orbits at speeds that are several times that of the prevailing flow, it could generate electricity to recharge the UAV&rsquo;s battery.&nbsp; 
 
One factor that has hampered the development of power kites up to now involved the tether, specifically the drag induced as the tether moves through the fluid. An AUV parked on relatively deep seabeds would require very long (a kilometer or more) tether to reach areas of favorable flow. And every meter of that moving tether is susceptible to drag.&nbsp; 
 
To better understand the dynamics of ultralong tethers (ULTs), Vermillion and his research team at North Carolina State University (where he was an associate professor until 2024) ran a computation study that explored how to use advanced control techniques and physical morphing to overcome the drag effects of operating on a long tether. 
 
The results of their study were published as &ldquo;Drag-Mitigating Dynamic Flight Path Design and Sensitivity Analysis for an Ultra-Long Tether Underwater Kite&rdquo; in the January 2025 issue of ASME Journal of Dynamic Systems, Measurement, and Control.&nbsp; 
 
&nbsp;
<h3>Tether Drag Mitigation&nbsp;</h3>
 
Vermillion conducted the computational study to determine the relationship between path shape and tether drag at varying tether lengths in order to develop meaningful insights regarding the operation of systems that require ultralong tethers to reach viable flow resources.&nbsp; 
 
Tether drag mitigation is characterized through the use of a novel metric termed effective tether length, which characterizes the total length of tether engaged in drag production. The researchers also looked for ways to reduce the energy losses associated with tether drag.&nbsp; 
 
All analyses were based on a flight controller that simultaneously followed an adjustable figure-8 path and limited tether tension based on structural constraints&mdash;&ldquo;which is important since the required tether diameter and associated drag depend on the peak tension,&rdquo; Vermillion said.&nbsp; 
 
The experiments showed that tether drag is the primary loss associated with ULT applications. &ldquo;We learned that, through careful flight path design, only a fraction of the tether is actually engaged in motion while the majority of the tether is approximately stationary,&rdquo; he added.&nbsp; 
 
For a well-designed path, the team discovered that the mean effective tether length is much less than the total tether length. A high-performance path shape can reduce the effect of tether drag by over 50 percent.&nbsp; 
 
&ldquo;Additionally, given the impact of tether drag on system performance, physical tether drag mitigation strategies have a large impact on system performance when applied to a relatively small portion of the tether,&rdquo; Vermillion said. &nbsp; 
 
<img alt="Power kites" src="~/getmedia/bcfb1d43-e055-441e-9355-583e12e10623/Power-Kites.jpg" /> 
 
&nbsp;
<h3>Adaptive Controls&nbsp;</h3>
 
Although the initial model had an appropriate structure, several of the component models were &ldquo;pretty far off&rdquo; in terms of lift and drag characterizations. The kite&rsquo;s fuselage and tether were large contributors to these uncertainties. 
 
&ldquo;It took a number of experimental campaigns to ultimately validate the model that we used,&rdquo; Vermillion said. &ldquo;Even then, our team felt that it was important that the control strategies we employed on an ULT kite be adaptive, such that the algorithm could adjust the kite&rsquo;s figure-8 flight profile on the fly in order to minimize the effective tether length and maximize the power output. We ultimately settled on a variant of iterative learning control for performing this adaptation.&rdquo;&nbsp; 
 
One of the biggest surprises was that for kites whose tether lengths exceeded a few hundred meters, the power projections under an optimized flight path actually far exceeded the &ldquo;theoretical optimum&rdquo; predicted by a very simple model that has been used for decades to benchmark kite systems. This is a result of the fact that the simple benchmark model derives a theoretical optimum based on an assumption that the tether is a straight line. &nbsp; 
 
Under that assumption, the entire tether is moving, with the midpoint of the tether moving at half the speed of the kite (and the quarter tether point moving at one quarter of the kite&rsquo;s speed, the three-quarter point moving at three quarters of the kite&rsquo;s speed, etc.). Such a &ldquo;rigid&rdquo; tether is actually very inefficient, since the entirety of the tether is contributing significant drag. &nbsp; 
 
&ldquo;By tailoring the kite&rsquo;s path to keep most of the tether motionless, simulations predict that the kite&rsquo;s power output can far exceed that of the straight-tether assumption&mdash;something that had not been established in the literature up to the point of our team&rsquo;s study,&rdquo; Vermillion said.&nbsp; 
 
Mechanical engineers will be interested in the specific control strategies for UTL kites. An innovative element in this study was the use of iterative learning control (ILC) to maximize an economic objective in continuous time. &nbsp; 
 
&ldquo;Traditionally,&rdquo; Vermillion said, &ldquo;ILC has been used to improve tracking performance in manufacturing applications where a precise toolpath has been defined, and the goal is to track this path as closely as possible. However, in the kite application, the optimal flight path is in fact unknown. Indeed, the objective is no longer to track a prescribed path as quickly as possible, but to figure out the optimal path for maximizing the average power generation over a figure-8 pattern.&rdquo; &nbsp;&nbsp; 
 
The lab is focused on combining controller adaptation with physical reconfiguration and adaptation in real time. &nbsp; 
 
&ldquo;The reality is that a lot of performance gains can be realized through real-time controller adaptation, but some aspects of performance can only be improved with a different physical design,&rdquo; Vermillion said. &ldquo;By incorporating real-time physical adaptation into a system, both the control variables and physical design parameters [for example, wing geometry, rotor coning angle] can be adjusted as the operating environment changes. Of course, real-time reconfigurability comes at a cost, and our team is working to quantify the cost and benefit of this reconfigurability within an integrated multidisciplinary design optimization tool.&rdquo;&nbsp; 
 
 
Mark Crawford is a technology writer in Corrales, N.M.&nbsp;

A proof-of-concept computer model points to a way to reduce the drag effects of ultra-long tethers on underwater kites. Such kites could be used to generate electricity in deep-marine conditions.&nbsp;

Over the last decade there has been keen interest in developing marine hydrokinetic systems, especially underwater kites, for use as utility-scale renewable energy sources. &nbsp; 
 
That interest might seem unexpected, as kites are commonly thought of as airborne playthings. But in this instance, kites are generically lifting bodies moving through flowing fluids and tethered to base stations. A kite moving in cyclic patterns perpendicular to the prevailing flow can travel much faster than the flow itself. If a turbine is attached to the kite, it can capture much more power than a stationary turbine of the same size. &nbsp;

A proof-of-concept computer model points to a way to reduce the drag effects of ultra-long tethers on underwater kites. Such kites could be used to generate electricity in deep-marine conditions.

Reducing Drag from Power Kites

Ice formation on aircraft is a major problem in the aviation industry. Icing is directly responsible for many aircraft incidents, which can compromise the safety of passengers and require expensive, time-consuming, and sometimes ineffective deicing methods. Traditional deicing either relies on hazardous chemicals or bulky pneumatic boot systems that use hot combustion gases from engines. These methods are not only energy-intensive and time-consuming, but also ineffective at removing snow and frost. Conventional steady-state heating systems, although simpler, consume large amounts of energy and are slow to respond. Also, with the rise of electrified aviation, minimizing electrical energy consumption is more critical than ever, as batteries provide limited on-board power.&nbsp; 
 
There has long been a need for a deicing solution that is simple, energy-efficient, fast, and effective across all forms of ice, snow, and frost&mdash;and now researchers at the University of Illinois at Urbana-Champaign have developed one. Their technology uses electrothermal pulses for the efficient and rapid removal of ice from aircraft wings.&nbsp; 
 
&ldquo;Our pulse interfacial defrosting, deicing, and desnowing [PID] method is based on electrothermal heating, but unlike conventional systems, it uses short, high-intensity power pulses instead of continuous heating,&rdquo; said Nenad Miljkovic, a professor of mechanical engineering at the university and lead researcher for the project. &ldquo;These pulses rapidly deliver heat to the ice/material interface, detaching ice with minimal energy input and within a short time window.&rdquo; &nbsp; 
 
Miljkovic and his team reported their findings in &ldquo;Aircraft Electrothermal Pulse Deicing,&rdquo; published in the January 2025 issue of the ASME Journal of Heat and Mass Transfer.&nbsp; 
&nbsp;
<h3>The Pulse Approach</h3>
 
This project targeted the icing problem for electric aviation and various energy systems. With traditional methods, combustion gases from the aircraft engine are used to remove ice from the leading edge of the aircraft with the help of a pneumatic booting system. However, since electric aircraft have no engines, this method is not feasible. &nbsp; 
 
&ldquo;We thought that, by leveraging pulsed electrothermal heating, we could address the core limitations of existing deicing technologies in a fundamentally better way,&rdquo; &nbsp;Miljkovic said.&nbsp;To test the feasibility of pulse deicing, the team developed a transient thermal-hydrodynamic numerical model to account for multiple phases and materials, specific and latent heating effects, melt layer hydrodynamics, and boundary layer effects. The model studied the relationships between heater thickness, substrate electrical insulation thickness, pulse duration, and pulse energy. &nbsp; 
 
The results were used to estimate the input conditions required for deicing, which were then integrated into an electrical model considering energy storage, power electronics, integration, and layout, to achieve overall volumetric and gravimetric power density optimization. &nbsp; 
 
&ldquo;We developed a two-dimensional finite difference method simulation to determine the power requirements for pulse deicing,&rdquo; Miljkovic said. &ldquo;The model couples the hydrodynamics of melt layer formation and ice removal with the thermodynamics and heat transfer of phase change [melting and refreezing], and the local shear rate on the ice material due to boundary layer formation on the aircraft.&rdquo;&nbsp; 
 
Deicing performance was analyzed with respect to system volumetric and gravimetric power density. &ldquo;In contrast to previous electrothermal approaches, our simulation results demonstrate that pulse electrothermal deicing is a feasible method for modern more-electric aircraft, demonstrating five times higher efficiency with time reduction to deice the surface,&rdquo; said Miljkovic.&nbsp; 
 
The thin melt layer created by pulse heating reduces the adhesion between the ice/wing interface, allowing aerodynamic forces to remove the bulk ice from the wing without melting. The researchers also found that PID limits the diffusion of the heat compared to traditional steady heating and that combining PID with surface wettability accelerates buildup removal. In addition, the system only needs to melt an ultrathin layer of ice&mdash;around one-tenth of a millimeter&mdash;to facilitate the sliding of the ice off the wing, which can take as little as five seconds. &nbsp; 
&nbsp;
<h3>Plenty of Variables&nbsp;</h3>
 
Materials selection, design, and integration each presented their own challenges and steep learning curves. Since this technique is based on electrothermal heating using thin-film materials, &ldquo;ensuring the materials are ready for real-world application proved tricky,&rdquo; Miljkovic said. &ldquo;These surfaces must endure harsh outdoor environments, including rain impact, shear from air and water flow, snow and ice, dust, gravel abrasion, temperature fluctuations, and UV radiation.&rdquo;&nbsp; 
 
Because aircraft deicing elements are located on the wing&rsquo;s exterior and are constantly exposed to these stresses, the researchers had to get creative with material selection. &ldquo;For example, developing accelerated durability testing protocols and evaluating long-term performance under such simulated conditions was one of the steepest technical challenges of the project,&rdquo; Miljkovic said.&nbsp; 
 
On the electrical side, the team designed a power converter that could function reliably in an aircraft environment, which was equally demanding. &ldquo;This was a relatively high-power application, with 3 kW pulses, so efficiency and thermal management were critical for safe and effective operation,&rdquo; Miljkovic said. &ldquo;The challenge was further intensified by the need to operate in elevated ambient temperatures, which required strategic heat spreading and loss minimization measures to protect the electronics and maintain reliable performance.&rdquo;&nbsp; 
 
The power converter design and development were essential parts of making PID viable. The heater material required specific voltage and power characteristics, so the electrical team designed a converter tailored to those needs. This ensured precise, high-efficiency delivery of energy to the heater during the pulse, enabling the system&rsquo;s overall performance.&nbsp; 
 
&ldquo;We have developed a PID method using a thin-film resistive heater,&rdquo; said Miljkovic. &ldquo;By supplying high power for short periods, we reduce energy consumption and improve the overall efficiency of the deicing system.&rdquo;&nbsp; 
&nbsp;
<h3>Innovation at the Forefront&nbsp;</h3>
 
This research demonstrates the importance of designing energy efficient thermal management systems. Aviation is often an extreme challenge for mechanical engineering design, with every subsystem onboard an aircraft optimized in multiple dimensions&mdash;for example, weight, surface profile, and energy efficiency. &ldquo;Energy efficiency should also be considered in all aspects of the design&mdash;from drag reduction to electrical power consumption,&rdquo; said Miljkovic. &nbsp; 
 
The PID system must also be able to withstand the harsh aircraft environment. The power converter, for example, went through extensive environmental testing that followed procedures outlined in the DO-160G standard for systems on aircraft. The standard ensures that new systems implemented on aircraft can withstand certain mechanical stresses including shocks, vibrations, and high ambient temperatures. &ldquo;Having to design with these tests in mind was a good learning opportunity for us, and we think others would also find it interesting,&rdquo; noted Miljkovic.&nbsp; 
 
Miljkovic&rsquo;s industry partner for the project is Ampaire. The ultimate goal of the project is to test the technology with Ampaire on a larger, industry-level scale. &ldquo;We are in the process of completing a ground-based demonstration of the integrated PID technology on a retired Cessna aircraft wing, with Ampaire leading the effort,&rdquo; said Miljkovic. &ldquo;Looking ahead, it would be exciting to see this technology tested in flight under actual icing conditions.&rdquo;&nbsp; 
 
The team is also optimistic that PID will continue to advance to higher technology readiness levels and eventually be developed into a commercial product deployable by aircraft manufacturers. Beyond aviation, Miljkovic anticipates that this technology could have broad applicability across other mechanical and engineering sectors facing similar ice and frost-related challenges, especially the HVAC and renewable energy sectors.&rdquo; &nbsp; 
 
 
Mark Crawford is a technology writer in Corrales, N.M.

Researchers who developed an electrothermal pulse deicing system say it could provide energy-efficient and rapid removal of ice from the wings of electrified aircraft.&nbsp;

Ice formation on aircraft is a major problem in the aviation industry. Icing is directly responsible for many aircraft incidents, which can compromise the safety of passengers and require expensive, time-consuming, and sometimes ineffective deicing methods. Traditional deicing either relies on hazardous chemicals or bulky pneumatic boot systems that use hot combustion gases from engines. These methods are not only energy-intensive and time-consuming, but also ineffective at removing snow and frost. Conventional steady-state heating systems, although simpler, consume large amounts of energy and are slow to respond. Also, with the rise of electrified aviation, minimizing electrical energy consumption is more critical than ever, as batteries provide limited on-board power.&nbsp; 
 
There has long been a need for a deicing solution that is simple, energy-efficient, fast, and effective across all forms of ice, snow, and frost&mdash;and now researchers at the University of Illinois at Urbana-Champaign have developed one. Their technology uses electrothermal pulses for the efficient and rapid removal of ice from aircraft wings.&nbsp; 
&nbsp;

Deicing Planes One Pulse at a Time

When artificial intelligence (AI), machine learning, and blockchain technologies first emerged, collocated servers could handle their computational demands. Today, however, these tools require large-scale facilities dedicated to housing critical data and computation services&mdash;data centers (DCs).&nbsp; 
 
According to researchers from the Department of Mechanical Engineering at Villanova University and QuantaCool Associates, the significant quantities of waste heat generated by DCs provide an opportunity. They reported their findings in &ldquo;Data Center Waste Heat Reuse: An Investment Analysis,&rdquo; first published in the December 2024 issue of the ASME Journal of Engineering for Sustainable Buildings and Cities. Author Aaron Wemhoff addressed the ways to upgrade and reuse the waste heat produced by DCs.&nbsp;

The growing demand for AI and other computational tools has created a challenge for engineers tasked with keeping largescale data centers cool. Perhaps the solution is not dumping the waste heat, but reusing it productively.

Data Center Waste Heat is a Resource 

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Engineers design a simple but flexible robotic gripper.&nbsp;

When most people hear the term robotic claw, they envision a cold, hard vise grip, the sort of thing that isn&rsquo;t suited for picking a grape or handling an egg. But roboticists have been developing hands for robots with all degrees of softness. The problem is, each design is a bit different and requires replacing the gripper every time the robot takes on a new task.&nbsp;

October-December 2022

In This Issue

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Patient Support Via Customized Surgical Mattresses

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Putting Hydrogen to the Economic Test

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Cooling Cities by Combating Heat Islands

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Pneumatic Help for Grasping

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