Texas A&M Engineering News

Real world data questions long held travel behavior theories

Thu, 01 Feb 2018 00:00:00 CST

Time is money and traffic earns nothing but road rage, lost productivity and an increased gas bill. Dr. Mark Burris, the Herbert D. Kelleher Professor at Texas A&M University, seeks to save travelers time, money and frustration with his travel behavior research.

The more accurately researchers can predict future travel, the better they can plan and build the necessary infrastructure quickly and affordably. In doing so, Burris and his team at Texas A&M strive to reduce travelers’ time and frustration in traffic while also saving tax dollars.

“My focus is to improve our understanding of how cost impacts someone’s travel,” said Burris. “How it impacts the route they take, the mode they use, the time of day they choose and more.”

Traditionally, much of this information was based on surveys completed by travelers about past trips and potential future travel. More recently, the technological advances that monitor new travel choices like “high occupancy toll lanes” and “managed lanes” provide real data that reveals more detailed information about travel behavior. This kind of information is very useful in understanding how travelers regard their travel times, and how much they would be willing to pay to reduce those travel times.

The Harris County Toll Road Authority, Texas Department of Transportation, and Houston TranStar supplied data from the Katy Freeway in Houston that Burris and his team used for this research. The Katy Freeway includes four managed lanes, two in each direction, in the middle of the freeway.

During most of the day, carpools and buses can use these lanes for free, while single occupant vehicles have to pay a toll. The toll varies based on the time of the day and the correlating traffic congestion peaks. This freeway is one of only a few worldwide that had the ability to identify travelers in both the managed lanes and the regular lanes. Note the data were anonymized so it was impossible to know who used the roadway, just that a specific vehicle had used the roadway.

When analyzing the data collected from the Katy Freeway, Burris and his team found surprising results. About 11 percent of travelers were paying to use the managed lanes at times when the regular freeway lanes were traveling at the same speed or faster than the managed lanes – a behavior that no models ever predicted. Also based on these data, little evidence was found supporting the notion that travelers would be willing to pay for more reliable travel times in the managed lanes.

Farinoush Sharifi, a master’s student in transportation engineering, is studying this anomaly in her master’s thesis.

“To make it clear, many people believe that paying a toll to use a lane will bring them shorter travel time,” said Sharifi. “However, by looking into the Katy Managed Lanes study we have found that there are times users pay to travel on the toll lane but go slower than the toll-free lanes.”

Sharifi and Burris are working to understand the reasons for these uneconomical travel decisions using pattern recognition methods. Burris also found that the vast majority (84 percent) of freeway travelers with transponders only used the regular lanes, a small percentage of people (3 percent) only used the managed lanes and 13 percent utilized both. Thus, most travelers are not choosing between these lanes every day (as models assume), but rather have chosen the lanes they will travel well in advance and do not alter that choice regardless of travel conditions.

After collecting and analyzing this data, Burris and his team have begun exploring travel behavior in new and innovative ways. Partnering with a psychologist and a behavioral economist, Burris is now working to find ways to model travel behavior decisions in laboratory studies.

“This real-world data has led to some very surprising findings that put my research at the forefront of this field,” said Burris. “This improves our understanding of how travelers’ value different travel options and should dramatically change how we model travel behavior. Combined, this allows transportation agencies to better predict and prepare for future travel demand.”

These advances in understanding traveler behavior come at the same time great advances in automobile technology are occurring. Automated and connected vehicles will also greatly impact travel behavior.

Burris has teamed up with Texas A&M Hagler Institute for Advanced Study fellow Dr. Kumares Sinha and doctoral student Arezoo Samimi to examine some of these potential impacts. They are developing a traffic simulation model of El Paso to determine the travel time and emissions impacts of having connected vehicles in the traffic stream. These vehicles will have information on travel times to their destination and can help the traveler choose the best route – or reroute when an incident occurs.

In theory, this should reduce travel times and emissions. However, if too many vehicles reroute at once it could have negative overall impacts on travel. Their research will examine these potential impacts and strategies that combine data from connected vehicles and travel behavior to maximize potential benefits of connected vehicles.

Polymer movement: key to next-generation coatings

Tue, 23 Jan 2018 00:00:00 CST

Researchers in the Department of Materials Science and Engineering at Texas A&M University, led by doctoral student Victor Selin and Dr. Svetlana Sukhishvili, are making headway in understanding fundamental principles that will help to create the next generation of biomedical coatings.

Medical devices, such as orthopedic implants, often need their surfaces modified with protective coatings. These devices have random shapes, which requires the use of a simple method to controllably coat the surface. These coatings can provide the surface of the objects with antireflection properties or make them able to release therapeutic compounds that kill bacteria and/or control the growth of mammalian cells.

The group is working to gain a fundamental understanding of the growth and behavior of multilayer polymer films to create functional films on the surface of different materials and aims to be able to control their properties and structures. These properties are important because they dictate how such films interact with aqueous and salinated solutions. Their work has revealed that by simple manipulations during film buildup, these properties can be easily controlled.

“By demonstrating how one can control the mobility of individual polymer chains layer-by-layer, we hope to facilitate practical applications of these films as a platform for functionalization of surfaces of biomedical devices,” Selin said.

Using several techniques, the group established a quantitative picture of the internal structure and polymer chain dynamics of these films. These experiments allowed the group to correlate the film properties with the behavior of individual polymer chains.

“The knowledge we are developing is needed to learn how to design surface coatings that will be able to controllably release multiple therapeutic agents,” Selin said. “Our research provides a better understanding of the relationship between assembly conditions and the internal structure of resulting films, and therefore significantly contributes to the existing fundamental knowledge in polymer physics and materials science.”

This research is part of a National Science Foundation research project focusing on the studies of layer-by-layer coatings led by Dr. Svetlana Sukhishvili, a professor in the materials science and engineering department at Texas A&M, in close collaboration with Dr. John Akner, a lead instrument scientist at Oak Ridge National Laboratory, who is an expert in neutron scattering techniques.

Insects may hold the key to more effective coatings and lubrication systems

Mon, 22 Jan 2018 00:00:00 CST

Dr. Jun Kyun Oh was highlighted in the Materials Today journal for his work which was funded by the National Science Foundation that aims to understand how forces at the molecular level determine adhesion kinetics and dynamics.

Oh, a former student in the Department of Materials Science and Engineering and postdoctoral researcher in the Artie McFerrin Department of Chemical Engineering at Texas A&M University, investigated the structural properties of the hind leg femur-tibia joint in adult katydids, or bush crickets.

“We showed that the katydid hind leg femur-tibia joint had unique surfaces and nanoscale textures,” Oh said. “Importantly, the sheared surfaces at this joint showed no sign of wear or damage, even though it had undergone thousands of external shearing cycles.”

The potential of their bioinspired research is leading to further studies to develop more effective coatings and lubrication systems.

“The research will seek to determine the main features of surface morphology of different characteristics of insect joints and how these features influence the adhesion between insect joints,” Oh said. It will also establish the role of their internal nanostructure on their mechanical properties such as stiffness and hardness.”

Oh is collaborating with Dr. Spencer Behmer, professor in the Department of Entomology, and Richelle Marquess, a student of Behmer’s.

Shape memory alloy research featured in Wired magazine

Fri, 19 Jan 2018 00:00:00 CST

Aircraft with shapeshifting wings may seem like the stuff of movies, but with the use of shape memory alloys (SMAs), it may be a reality in the near future. Dr. Darren Hartl, associate professor in the Department of Aerospace Engineering at Texas A&M University, whose research is featured in Wired magazine, is part of a team working on using SMAs to shift parts of an aircraft in mid-flight.

Shape memory alloys would allow engineers to design an aircraft that could change in response to variables, such as temperature, humidity and barometric pressure. Because shockwaves behave differently in these variables, this would in effect help minimize the sonic boom that is created when these shockwaves come off an aircraft and combine together as they head toward the ground. Reduce the sonic boom and you just might see supersonic flight over land in the near future.

Read the entire Wired article here.

Li recognized for work on irradiation damage and irradiation-resistant materials

Thu, 18 Jan 2018 00:00:00 CST

Jin Li, a graduate student in the Department of Materials Science and Engineering at Texas A&M University, has been awarded the American Vacuum Society (AVS) – Applied Surface Science Division 1^st Place Student Award. This honor is in recognition of his work focusing on the understanding of irradiation damage, as well as design irradiation-resistant materials.

“Nuclear energy as a clean power source provides about 13 percent of electricity generated worldwide (about 20 percent in the U.S. in 2016),” Li said. “The development of clean and renewable energy is of great importance for next-generation nuclear reactors, however, there are not any materials immune to irradiation damage to date. Therefore, the understanding of the irradiation damage is the key to the design of advanced materials for advanced nuclear reactors.”

Li, the lead researcher behind the project, works with experiment design, sample fabrication, in situ irradiation and data analysis, among other things.

“The impact of this work is apparent to the nuclear materials community regarding the potential discovery of radiation tolerant nanomaterials, which are designed for advanced nuclear reactors,” Li said.

Li studied under Dr. Xinghang Zhang, a former professor in the Department of Mechanical Engineering. His Ph.D. thesis focused on radiation damage and mechanical behavior of nanostructured metals. He published six first-author articles in premier materials science journals, such as Nano Letters and Acta Materialia. He also has two papers that are under review and more than 15 other co-author papers, including four in Acta Materialia, two in Nano Letters and one in Progress in Materials Science. Li is now a postdoctoral fellow at Purdue University.

Li received the award during the AVS 64^th International Symposium in October.

Texas A&M researchers make advances in control of chameleon-like material for next-generation computers

Elizabeth Thomson — Fri, 12 Jan 2018 00:00:00 CST

Researchers from Texas A&M University report significant advances in their understanding and control of a chameleon-like material that could be key to next-generation computers that are even more powerful than today’s silicon-based machines.

The existing paradigm of silicon-based computing has given us a range of amazing technologies, but engineers are starting to discover silicon’s limits. As a result, for computer science to keep advancing it is important to explore alternative materials that could enable different ways to do computation, according to Dr. Patrick J. Shamberger, assistant professor in the Department of Materials Science and Engineering. Vanadium dioxide is one example.

“It’s a very interesting, chameleon-like material that can easily switch between two different phases, from being an insulator to being a conductor, as you heat and cool it or apply a voltage,” said Dr. Sarbajit Banerjee, professor with joint appointments in the Departments of Chemistry and Materials Science and Engineering. “And if you think about those two phases as being analogous to a zero and a one, you can come up with some interesting new ways of information processing.”

Banerjee and Shamberger are corresponding authors of a paper describing their work, which was published in the January 2018 issue of Chemistry of Materials.

“Before vanadium dioxide can be used in computing, we need to better control its transition from insulator to conductor and back again,” Shamberger said. In the paper the team describes doing just that by adding tungsten to the material.

Among other things, the researchers showed that tungsten allows the transition to occur over two very different pathways. The result is that the transition from insulator to conductor happens easily and quickly, while the transition from conductor back to insulator is more difficult.

“Think of it as driving from point A to point B and back again. Going there you take a superhighway, but coming back you’re on back roads,” Banerjee said.

Essentially the addition of tungsten allows the vanadium oxide to switch quickly in one direction and much more slowly in the other, phenomena that could be exploited in future computers.

“It provides an additional ‘knob’ to tune how you go back and forth between the two states,” said Erick J. Braham, a graduate student at Texas A&M who was the first author on the paper.

The team has also found that the addition of tungsten allows them to better control, or tune, the different temperatures where the transitions occur.

Banerjee notes the interdisciplinary nature of the work, which involved four groups with expertise ranging from computational materials science to electron microscopy, has been key.

“We’ve really looked at this puzzle from different ends to try to make sense of exactly what’s going on,” he said. “It’s been very exciting.”

Additional authors from Texas A&M are Dr. Raymundo Arroyave from materials science and engineering; Nathan A. Fleer, graduate student in chemistry and materials science and engineering; Dr. Diane Sellers, assistant research scientist in chemistry and materials science and engineering; Ruben Villarreal, graduate student in materials science and engineering; and Katie E. Farley and Emily Emmons, both former graduate students. Authors from the University of Illinois at Chicago are Dr. Reza Shahbazian-Yassar, professor, and Hasti Asayesh-Ardakani, a visiting researcher. Their work was supported by the National Science Foundation and the Air Force Office of Scientific Research.

Gaharwar wins Biomedical Engineering Society Cellular and Molecular Bioengineering Rising Star Award

Thu, 11 Jan 2018 00:00:00 CST

Dr. Akhilesh K. Gaharwar was selected to receive the 2018 Biomedical Engineering Society (BMES) Cellular and Molecular Bioengineering (CMBE) Rising Star Award at the 2018 CMBE Annual Conference--Discovering the Keys: Transformative and Translational Mechanobiology, which was held Jan. 2-6, 2018 in Key Largo, Florida.

The BMES-CMBE Special Interest Group brings together researchers with diverse scientific and clinical interests with a common goal of understanding and engineering molecules, cells, their interactions and microenvironments in the pursuit of controlling biological processes and improving the practice of medicine. In 2018, the conference theme focused on addressing key challenges in mechanobiology and how to advance the study of pathophysiology and improve human health.

Gaharwar is one of eight awardees selected internationally for the Rising Star award, which is given to exceptional junior principal investigators. The awardees are invited to give a podium presentation at the conference. Gaharwar’s talk titled “Widespread changes in transcriptome profile of human mesenchymal stem cells by two-dimensional (2-D) nanosilicates,” focused on understanding how nanomaterials interact with human stem cells.

For additional information visit the BMES-CMBE Conference website or Gaharwar’s lab website.

Evaluating electrodes: Researchers identify concepts to measure battery performance

Tue, 09 Jan 2018 00:00:00 CST

How do we know if a new battery is good? Batteries that perform well are invaluable to a number of resources that we use daily, such as cell phones and laptops, but also those that we are utilizing more frequently than ever before, such as drones and electric vehicles. Researchers in the Texas A&M University College of Engineering have identified two factors that can be used to measure the performance of batteries.

Yuan Yue, lead author of the published manuscript and a graduate student in the Department of Materials Science and Engineering, and Dr. Hong Liang, the Oscar S. Wyatt Jr. Professor in the Department of Mechanical Engineering and affiliated faculty member in materials science and engineering, collected and analyzed experimental data from over 250 scholarly articles published in the last decade. The duo began analyzing the structures and performance of the V₂O₅ electrode to derive key characteristics that could be used to optimize batteries.

“To be used as an electrode, V₂O₅ has three modes of lithium ion intercalation,” Liang said. “We know from using the fundamentals of electrochemistry that the electrochemical performance of a battery is dominated by how lithium ions move in and out of structures through a process called intercalation.”

Liang and Yue found that the two concepts of high capacity band and total capacity retention were the key to evaluating the electrochemical performance of V₂O₅ electrodes.

“The most significant and exciting part of this research is finding the right path to optimize the design of batteries,” Yue said. “Construction of the new concept about the maximum ability of the specific capacity of a V₂O₅ electrode shines enormous light to the field.”

The conclusions of their work allow for further development of finding the optimal way to design a lithium-ion battery electrode.

“The hints are, for example, using hierarchical-structures to increase power level, adding carbon materials or ions to increase energy density and using porous current collectors to increase capacity,” Liang said. “Those general strategies will bring broad impacts to the significant efforts in developing better electrode materials from both academic and industrial researchers.”

The development of improved lithium-ion battery cells could be used for power sources of cell phones, drones, electric vehicles, laptops and smart grids in the future.

In recognition of his work, Yue was awarded the 2017-2018 Texas A&M Energy Institute Fellowship.

The criteria identified can be illustrated in the figure shown above. It’s like the peak of a mountain that gets struck by a light. To make a high performance battery, we need to identify the peak value such that the optimum performance is achieved.

Hwang uncovers new details about the ‘vehicles’ inside the body

Tue, 02 Jan 2018 00:00:00 CST

Similar to roadways across the country, every cell in our body has a network of paths, and a professor at Texas A&M University has zoomed in to the molecular level to research the proteins that travel along this transportation system.

Dr. Wonmuk Hwang, associate professor in the Department of Biomedical Engineering, researches motor proteins, which act as vehicles to carry cargo inside a cell in the body. His latest research has been focused on kinesin, the smallest protein in the human body that can walk with two “legs” and carry material throughout the body on intracellular filaments called microtubules.

His findings have been recently published in a paper in the journal eLife. The goal of the research was to study how kinesins process fuel to generate that walking motion.

“If you compare this with the macroscopic gasoline engine, you burn the gas, you generate the heat and you power the car,” Hwang said. “This is a molecular motor (in the human body), so the energy source is not just burning the fuel but actually, when fuel binds to this kinesin motor, there is binding energy associated and burning. After burning you have to exhaust the product.”

Hwang said each step in the energy binding, burning and exhausting processes plays a role in the movement of the kinesin in specific phases of its walking pattern. The energy for the movement comes from adenosine triphosphate (ATP) molecules, which Hwang said are the main fuel of the body.

“When you eat something, the end product of the energy you take in is converted into ATP to be used in the cell,” he said.

According to Hwang, one surprise from his research findings was how the kinesins obtain the ATP. Instead of the ATP binding to the protein in random encounters, Hwang said the kinesins have loops on their surfaces that capture nearby fuel and then assist in the burning and discarding of the pieces.

Kinesins play a vital role in many cellular processes, and understanding how they function can have multiple biomedical applications. Hwang said his research served dual purposes — laying the foundation for applications down the road and the advancement of knowledge.

Hwang said one of the future applications of the research is in anti-cancer drugs. A subset of kinesins are key players in cell division, and knowledge about their movement can help scientists and engineers develop drugs that will inhibit the kinesins from walking and dividing cancer cells.

“If you know where to target then people can start to screen for drugs that particularly bind to those domains to modify or control those motors,” Hwang said.

While the protein and their distinct bipedal walking motion were discovered in the mid-1980s, how the motor worked remained a mystery.

“Compared to the engine of a vehicle, whose working principles are understood well enough to improve its design to fit its purpose, the lack of knowledge about how kinesins walk makes it difficult to utilize these nanoscale machines for biotechnology applications,” Hwang said.

Hwang has worked since 2008 on the project and collaborated with researchers at Harvard University and Vanderbilt University to carry out computer simulations that were unprecedented in scale, and discovered how the fuel processing steps are achieved.

Looking forward, Hwang said he would like to further characterize properties of kinesins and find how the “legs” communicate with each other to facilitate the bipedal motion.

“It’s not like our legs where there’s a nervous system and so forth — it’s just molecules,” Hwang said. “People don’t know how communication between the ‘feet’ happens, because you have to make them coordinated. How does the protein know when it’s making a step? There must be some communication.”

Civil engineering research paves the way for innovative bridge systems

Tue, 02 Jan 2018 00:00:00 CST

The state of Texas has more bridges than any other state in the nation, with over 50,000 total. Maintaining structurally sound, shorter- and longer-span bridges was the driving force in two collaborative projects recently completed by Dr. Mary Beth Hueste and the Texas Department of Transportation (TxDOT).

Hueste, a Zachry Department of Civil Engineering professor at Texas A&M and Texas A&M Transportation Institute (TTI) research engineer, is dedicated to furthering the understanding of the use of new materials and designs for bridge structures, with a focus on prestressed concrete bridge systems. Prestressed members are put into a state of compression using high-strength steel tendons before external loads are applied.

“The use of precast, prestressed concrete bridge girders in Texas and other parts of the U.S. has proven to provide economical bridge systems that have a number of benefits,” Hueste said. “Producing the girders at the precast plant leads to enhanced quality because there is more control of the materials and the manufacturing process at the plant during fabrication. By investigating new bridge systems that utilize precast girders, TxDOT and other bridge owners have additional options for bridge designs that can be selected when the site conditions or other factors make precast concrete the optimal alternative.”

Continuous prestressed concrete girder bridges

The first project centered on continuous prestressed concrete girder bridges. Most Texas bridge structures are constructed with precast concrete girders with a cast-in-place concrete bridge deck. The bridge girders are fabricated at a precast plant where they are prestressed to avoid cracking of the concrete and to achieve longer span lengths compared to conventional reinforced concrete bridges. However, the precast girder units are limited to 160 feet due to weight and length restrictions on transporting them from the plant to the bridge site. This project’s primary focus was to develop innovative and economical alternatives for longer-span bridges, with main spans up to 300 feet.

Hueste was the research supervisor on this project. She worked alongside Dr. John Mander, Zachry professor in design and construction integration and TTI research engineer, and Reza Baie, Anagha Parkar, Akshay Parchure, Jennifer Prouty and Tristan Sarremejane, civil engineering graduate students employed by TTI.

Hueste and her team of researchers found that with in-span spliced girder technology and continuous prestressing installed at the bridge site, the span length of precast concrete girder bridges can be nearly doubled. In-span splicing involves connecting the precast girder sections at optimal locations within the span such that the overall span length between bridge supports is greater than the length of the individual girder segments.

Hueste and her team constructed a full-scale spliced girder specimen in the laboratory where they conducted extensive testing to confirm that the splice connections performed satisfactorily.

“Full-scale testing allowed us to verify that the splice-connection detail between precast girder segments is structurally sound under the design service loads,” Hueste said. “In addition, we applied even larger loadings to ensure that the connection details will provide sufficient strength up to ultimate load conditions.”

The research study led to a comprehensive set of recommendations for the design of continuous spliced precast girders, along with detailing guidelines for in-span spliced connections.

Spread prestressed concrete slab beam bridges

The central focus of this second project was to investigate a new bridge system for short-span bridges with spans up to about 50 feet.

Conventional slab beam bridges have precast concrete slab beams placed immediately adjacent to one another with a cast-in-place topping slab. While this bridge system is commonly used for short-span bridges due to its shallow profile, it is more expensive than typical prestressed I-beam bridges.

This project examined the use of slab beams that are spread apart with less expensive precast concrete panels between beams and a cast-in-place concrete deck. The goal was to investigate the design, constructability and performance of this new bridge system, and to provide guidance for future designs.

Hueste was the research supervisor on this project. She worked alongside Mander; Dr. Gary Fry, adjunct associate professor; and Tevfik Terzioglu, Dongqi Jiang and Joel Petersen-Gauthier, civil engineering graduate research assistants employed by TTI. In addition, a number of undergraduate students assisted during various stages of the project.

In order to better understand the spread slab beam bridge system, the team built a full-scale prototype with widely spaced beams at the Texas A&M RELLIS Campus. There they were able to assess constructability and in-service performance. Additionally, they tested a second spread slab beam bridge with closely spaced beams recently constructed on U.S. Highway 69 in Denison, Texas. Both bridges were instrumented, and field testing was conducted using heavily loaded vehicles to evaluate load distribution behavior.

The measured data from field testing, along with comprehensive modeling and analysis, were used to develop design expressions to determine the distribution of load for this bridge system. The researchers found that the spread slab beam bridge system provides another viable design option for short-span bridges that may be more cost-effective than traditional slab beam bridges.

“Our research with TxDOT has helped to further the potential for precast, prestressed concrete bridge systems,” Hueste said. “Both projects used full-scale testing to evaluate the performance of new short- and longer-span bridge systems. These investigations are crucial for providing guidance to bridge engineers to ensure that these new bridge types will perform as expected.”