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A "smart home" system uses computer-controlled cameras and wearable sensors to automatically detect falls and warn caregivers. Credit: Alamy stock image, Harald Richter Falls by elderly people can cause serious injury or death if sufferers remain on the ground for too long. By combining data from both wearable sensors and video surveillance, a team at KAUST has developed a statistical scheme that detects when senior citizens or others need help after falling1. Falls have distinct signs, such as sudden changes in acceleration, which make them trackable with technology. Over the last 20 years, researchers have tackled this problem with sensors that measure movements or computers that analyze shapes in video images. Both approaches, however, have trouble distinguishing mild slips from serious incidents and consequently have high false alarm rates. The University's Assistant Professor Ying Sun and co-workers used statistics to improve fall detection. While accelerometers in most wearable sensors use manually set thresholds to trigger an alert signal, the KAUST team used exponentially weighted moving average (EWMA) charts to dynamically monitor acceleration data over time. Any unusual changes to a person's movements are then identified as sharp deviations from the expected, averaged dataset. "The EWMA monitoring technique is effective in detecting falls because it is sensitive to small changes," explained Sun. "Its low computational cost also means it can be easily implemented in real time." The researchers integrated EWMA chart monitoring into a model 'smart home' environment containing multiple surveillance cameras to better spot significant fall events. This strategy uses computer vision algorithms to subtract backgrounds and imaging artefacts from the video data to focus purely on human shapes. Then, if the dynamic sensor registers an alarm, the software compares images of the fallen person to a database of body positions. "The classification stage is executed only when a potential fall is detected by the EWMA scheme," said Sun. "This significantly reduces false alarms." Experiments revealed the EWMA-based approach accurately distinguished dangerous stumbles from everyday events, such as picking up a dropped pencil. By feeding the characteristics of identified true fall events into a classification algorithm, the team trained the program to automatically diagnose real falls and alert family members or caregivers. Sun notes that this statistical-based method makes it simpler to achieve reasonable accuracy in small, unobtrusive computing devices. "We plan to consider more data inputs, such as heart rate and blood pressure provided by a smartwatch or a smartphone, for healthcare monitoring," Sun says. "By collaborating with clinics or nursing institutes, we hope to validate our approach with real data." Explore further: New method for the early detection of emerging problems in industrial processes


News Article | May 2, 2017
Site: www.eurekalert.org

Marine surveys estimating fish population density and diversity are crucial to our understanding of how human activities impact coral reef ecosystems and to our ability to make informed management plans for sustainability. KAUST researchers recently conducted the first baseline surveys of reefs in the southern Red Sea by comparing reefs off the coast of Saudi Arabia with those of Sudan1. "A major issue is that there is no established historical record for Red Sea ecosystems," said Dr. Darren Coker, who worked on the project with KAUST M.Sc. Alumnus Alexander Kattan and Professor Michael Berumen all of the University's Red Sea Research Center. "This means we can only hypothesize what the natural reef environment would have looked like before human interference through fishing began." Berumen's team systematically compared 14 Saudi reefs with 16 offshore reefs in Sudan. The reefs are around 200-300 Km apart and share almost identical environmental conditions in terms of sea temperature, climate and coral species. However, Saudi Arabia has a long-established history of fishing, while Sudan does not. "There is much more to the story than just the numbers of fish we see," said Berumen. "We collected and analyzed data between and within regions to look at fish abundance, biomass and community diversity across all the reefs surveyed." "To minimize potential bias, I conducted all the survey dives myself," said Kattan, who trained intensively to ensure he could correctly identify fish species and accurately estimate their size underwater. "A friend helped me practice in a pool by diving with different sizes and shapes of simulated fish on popsicle sticks! Because size estimates were converted into biomass, it was vital that I was able to gauge sizes correctly." The team found that the biomass of top predators in the Sudanese reefs was almost three times that of the Saudi reefs. The top predators were far rarer in Saudi Arabian waters, a phenomenon that the researchers attribute to fishing pressures. Furthermore, fish abundance was around 62 % higher in Sudan and biomass was 20 % higher. There was also slightly greater diversity on the Sudanese reefs. "This is the strongest evidence yet of the impact of fishing on Saudi Arabia's reefs," said Berumen. "While Saudi Arabia appears to have lost many larger fish, these species, including top predators, have not completely disappeared, so there is an opportunity to turn the situation around. Saudi's reefs could be restored to the condition of the almost pristine Sudanese reefs through careful management and protection, and they could one day thrive as eco-tourism sites."


« Proterra delivers 100th electric bus | Main | Lucid Air debuts in New York; completes first high speed stability test at 217 mph » Researchers at KAUST have developed and used a novel way of increasing the chemical reactivity of a two-dimensional molybdenum disulfide material to produce a cheap and effective catalyst for water splitting to produce hydrogen. This technique may also have potential benefits for other manufacturing industries. One route to hydrogen generation is by electrolysis: passing an electrical current through water via two electrodes to cause a chemical reaction that breaks the water molecule into its component hydrogen and oxygen atoms. The speed of this hydrogen evolution reaction can be increased using a catalyst on the electrodes. Platinum is a perfect material for the job, but is it very expensive. Two-dimensional layered transition metal dichalcogenide (TMD) materials such as Molybdenum disulfide (MoS ) have been recognized as one of the low-cost and efficient electrocatalysts for hydrogen evolution reaction (HER). The crystal edges that account for a small percentage of the surface area, rather than the basal planes, of MoS monolayer have been confirmed as their active catalytic sites. As a result, extensive efforts have been developing in activating the basal planes of MoS for enhancing their HER activity. Here, we report a simple and efficient approach—using a remote hydrogen-plasma process—to creating S-vacancies on the basal plane of monolayer crystalline MoS ; this process can generate high density of S-vacancies while mainly maintaining the morphology and structure of MoS monolayer. The density of S-vacancies (defects) on MoS monolayers resulted from the remote hydrogen-plasma process can be tuned and play a critical role in HER, as evidenced in the results of our spectroscopic and electrical measurements. Molybdenum disulfide is a two-dimensional material very similar to graphene. Previous experimental and theoretical results have verified its excellent catalytic potential and indicated that the hydrogen evolution reaction takes place at its jagged edges, while its flat surface planes remain chemically inert. Lain-Jong Li, Professor of Material Science and Engineering at KAUST, with colleagues from the National Chiao Tung University (Taiwan) and the National Applied Research Laboratories in Taiwan created their molybdenum disulfide using a process called chemical vapor deposition. A sample was then transferred to a graphite substrate and placed in a vacuum chamber in which the researchers created a hydrogen plasma. This process removed some of the sulfur atoms from the surface of the sample. By adjusting the sample’s time in the plasma, the team could control the density of these sulfur vacancies. The researchers confirmed the changes in catalytic activity and also found a useful offshoot of this process. Controlling the atomic composition of molybdenum disulfide could also lead to the development of electrical, optical and magnetic devices.


News Article | May 5, 2017
Site: www.rdmag.com

Hydrogen is one of the most promising clean fuels for use in cars, houses and portable generators. When produced from water using renewable energy resources, it is also a sustainable fuel with no carbon footprint. However, water-splitting systems require a very efficient catalyst to speed up the chemical reaction that splits water into hydrogen and oxygen, while preventing the gases from recombining back into water. Now an international research team, including scientists at the Department of Energy’s SLAC National Accelerator Laboratory, has developed a new catalyst with a molybdenum coating that prevents this problematic back reaction and works well in realistic operating conditions. A key part of the development centered on understanding how the molybdenum coating worked using experiments at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), a DOE Office of Science User Facility. The scientists reported their results April 13 in Angewandte Chemie. “When you split water into hydrogen and oxygen, the gaseous products of the reaction are easily recombined back to water and it’s crucial to avoid this,” said Angel Garcia-Esparza, lead author and currently a postdoctoral researcher from the Ecole Normale Supérieure de Lyon. “We discovered that a molybdenum-coated catalyst is capable of selectively producing hydrogen from water while inhibiting the back reactions of water formation.” The experiments demonstrated that their molybdenum coating strategy has applications in electrocatalysis and photocatalysis devices, added Garcia-Esparza. These are devices that help drive forward a reaction using electricity or light. Garcia-Esparza helped develop the new catalyst as a graduate student at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia under the direction of Kazuhiro Takanabe, an associate professor of chemical science at KAUST. Takanabe’s research group explored the stability, performance and function of many different elements before selecting molybdenum as the coating for a standard platinum-based catalyst. “Finding a coating that worked well in the acid electrolyte used for water splitting was a major challenge for my collaborators, because many materials quickly degrade in the acidic conditions,” said co-author Dimosthenis Sokaras, a staff scientist at SLAC. Of the coatings they tested, “Molybdenum was the best-performing material in acidic media, where the conditions for hydrogen evolution are favorable and facile,” Garcia-Esparza explained. Another major challenge was finding a way to measure the properties of their molybdenum-coated catalyst, because these molybdenum compounds are not stable when exposed to air. “Taking the catalyst out of water perturbs the identity of the material,” said Garcia-Esparza. “Therefore, it was necessary to study the electrocatalyst under working conditions, which is difficult.” So Garcia-Esparza spent a summer performing electrochemistry experiments at SSRL to characterize the new catalyst under operational conditions. “The idea was to work together to see how the molybdenum-coated catalyst performed and determine its electronic structure when it was operating,” said Sokaras. “We wanted to understand why the back reaction doesn’t happen.” They tested a bare platinum catalyst, with and without a molybdenum coating, during water electrolysis at SSRL, using in operando X-ray absorption spectroscopy with a custom-made electrochemical cell. “At SSRL, we were essentially able to do electrochemistry while analyzing the sample with synchrotron radiation,” Garcia-Esparza said. “The experiments performed at SLAC were the final piece of the puzzle to determine the local structure and state of the electrocatalyst under the operational conditions of hydrogen production.” “Our findings support that the molybdenum layer acts as a membrane to block the oxygen and hydrogen gases from reaching near the platinum surface, which prevents water formation,” Sokaras said. In addition, the research team explored photocatalysis applications. They built a photocatalytic water-splitting system using either a standard catalyst of platinum on strontium titanium oxide (Pt/SrTiO ) or the same catalyst coated with molybdenum. Both systems were tested at KAUST with the lights on and off — that is, with and without an energy source driving the water-splitting reaction. When the light was on, the standard Pt/SrTiO  catalyst increased hydrogen production for only six hours because the system lost efficiency due to the back reaction. When the lights were then turned off, the amount of hydrogen decreased with time — verifying that significant amounts of the gases were recombining to form water. In contrast, the molybdenum-coated catalyst continuously split water to generate increasing amounts of hydrogen gas for 24 hours, producing about twice as much hydrogen gas as the standard catalyst in one day. In addition, the amount of hydrogen remained stable in the dark, confirming that the coating inhibited water formation These results are promising, but more work still needs to be done before the catalyst can be used in a practical device. Sokaras said, “I think we’re far from actually talking about a commercial device, but it is certainly a huge improvement to have this new catalyst material that prevents the back reaction. Now we need to find a way to make the coating more stable so it produces hydrogen for even longer.” The research team included scientists from SSRL, King Abdullah University of Science and Technology, Fukuoka University, University of Tokyo, and the Center for High Pressure Science and Technology Advanced Research in Shanghai, China. The work was supported by King Abdullah University of Science and Technology.


« U of Illinois researchers develop new capabilities for genome-wide engineering of yeast | Main | Porsche Digital, Inc. opens location in Silicon Valley » Water-splitting systems require a very efficient catalyst to speed up the chemical reaction that splits water into hydrogen and oxygen, while preventing the two gases from recombining back into water. Now an international research team has developed a new catalyst with a molybdenum (Mo) coating that prevents this problematic back reaction and works well in realistic operating conditions. The research team included scientists from the Department of Energy’s SLAC National Accelerator Laboratory, King Abdullah University of Science and Technology, Fukuoka University, University of Tokyo, and the Center for High Pressure Science and Technology Advanced Research in Shanghai, China. The work was supported by King Abdullah University of Science and Technology. A paper on the work is published in the journal Angewandte Chemie. The researchers suggested that the molybdenum layer likely hinders oxygen gas permeation, impeding contact with the active platinum. Photocatalytic overall water splitting proceeded using MoO /Pt/SrTiO with inhibited water formation from H and O —the prevailing back reaction on the bare Pt/SrTiO photocatalyst. The Mo coating was stable in acidic media for multiple hours of overall water splitting by membrane-less electrolysis and photocatalysis. A key part of the development centered on understanding how the molybdenum coating worked using experiments at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), a DOE Office of Science User Facility. The experiments demonstrated that their molybdenum coating strategy has applications in electrocatalysis and photocatalysis devices, added Angel Garcia-Esparza, lead author and currently a postdoctoral researcher from the Ecole Normale Supérieure de Lyon. Garcia-Esparza helped develop the new catalyst as a graduate student at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia under the direction of Kazuhiro Takanabe, an associate professor of chemical science at KAUST. Takanabe’s research group explored the stability, performance and function of many different elements before selecting molybdenum as the coating for a standard platinum-based catalyst. Another major challenge was finding a way to measure the properties of their molybdenum-coated catalyst, because these molybdenum compounds are not stable when exposed to air. Taking the catalyst out of water perturbs the identity of the material, explained Garcia-Esparza. “Therefore, it was necessary to study the electrocatalyst under working conditions—which is difficult.” The researchers tested a bare platinum catalyst, with and without a molybdenum coating, during water electrolysis at SSRL, using in operando X-ray absorption spectroscopy with a custom-made electrochemical cell. In addition, the research team explored photocatalysis applications. They built a photocatalytic water-splitting system using either a standard catalyst of platinum on strontium titanium oxide (Pt/SrTiO ) or the same catalyst coated with molybdenum. Both systems were tested at KAUST with the lights on and off— that is, with and without an energy source driving the water-splitting reaction. When the light was on, the standard Pt/SrTiO catalyst increased hydrogen production for only six hours because the system lost efficiency due to the back reaction. When the lights were then turned off, the amount of hydrogen decreased with time—verifying that significant amounts of the gases were recombining to form water. In contrast, the molybdenum-coated catalyst continuously split water to generate increasing amounts of hydrogen gas for 24 hours, producing about twice as much hydrogen gas as the standard catalyst in one day. In addition, the amount of hydrogen remained stable in the dark, confirming that the coating inhibited water formation. The results are promising, but more work still needs to be done before the catalyst can be used in a practical device.


News Article | April 17, 2017
Site: www.greencarcongress.com

« KAUST team alters atomic composition of MoS2 to boost performance as water-splitting catalyst for H2 production | Main | GM adding more than 1,100 jobs, $14M to expand Cruise Automation self-driving operations in California » Lucid Motors made its global auto show debut at the New York International Auto Show, presenting the Lucid Air luxury electric sedan and also presenting its Alpha Speed Car test vehicle, which had just completed its first high-speed stability test at 217 mph (349.2 km/h). The 1,000 hp, 400-mile range Lucid Air was first unveiled in December 2016. (Earlier post.) The Air will be manufactured in Casa Grande, Arizona. The factory, first announced in November 2016, will come online in 2019 and build 10,000 vehicles in the first 12 months. By 2022 the company expects the factory to employ 2,000 full-time employees and manufacture up to 130,000 vehicles annually. The Lucid Air is priced from $52,500 after federal tax credits. The base Lucid Air will feature a 400-horsepower motor, rear-wheel drive, and a 240-mile range. Deliveries will begin in 2019. Customers can pre-order the Air at https://lucidmotors.com/car/reserve. In preparation for production, Lucid Air alpha prototypes are undergoing a rigorous development program. Lucid has designated one of these test prototypes as a high-performance test vehicle and has installed a roll-cage for safety purposes. The Alpha Speed Car will be used for evaluating at-the-limit performance. For the Alpha Speed Car’s first testing session, Lucid headed to TRC Ohio to use its 7.5-mile oval to evaluate high-speed behaviors, including vehicle stability and powertrain thermal management. The test, software-limited to 217 mph, was successful in demonstrating the capabilities of the car and in finding areas for improvement that could not be properly evaluated in static bench tests. The collected data will now be used to finesse thermal and aero computer simulations and to make further performance improvements that will be tested later this year at higher speeds. The company notes that high-speed capability does not compromise the mission to develop a highly efficient vehicle; rather, the focus on maximizing range provides the high power and aerodynamic efficiency that enables higher speeds. The testing program continues for the Alpha Speed Car and the rest of the Lucid Air alpha fleet. The company will provide more details as these tests progress.


However, water-splitting systems require a very efficient catalyst to speed up the chemical reaction that splits water into hydrogen and oxygen, while preventing the gases from recombining back into water. Now an international research team, including scientists at the Department of Energy's SLAC National Accelerator Laboratory, has developed a new catalyst with a molybdenum coating that prevents this problematic back reaction and works well in realistic operating conditions. A key part of the development centered on understanding how the molybdenum coating worked using experiments at SLAC's Stanford Synchrotron Radiation Lightsource (SSRL), a DOE Office of Science User Facility. The scientists reported their results April 13 in Angewandte Chemie. "When you split water into hydrogen and oxygen, the gaseous products of the reaction are easily recombined back to water and it's crucial to avoid this," said Angel Garcia-Esparza, lead author and currently a postdoctoral researcher from the Ecole Normale Supérieure de Lyon. "We discovered that a molybdenum-coated catalyst is capable of selectively producing hydrogen from water while inhibiting the back reactions of water formation." The experiments demonstrated that their molybdenum coating strategy has applications in electrocatalysis and photocatalysis devices, added Garcia-Esparza. These are devices that help drive forward a reaction using electricity or light. Garcia-Esparza helped develop the new catalyst as a graduate student at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia under the direction of Kazuhiro Takanabe, an associate professor of chemical science at KAUST. Takanabe's research group explored the stability, performance and function of many different elements before selecting molybdenum as the coating for a standard platinum-based catalyst. "Finding a coating that worked well in the acid electrolyte used for water splitting was a major challenge for my collaborators, because many materials quickly degrade in the acidic conditions," said co-author Dimosthenis Sokaras, a staff scientist at SLAC. Of the coatings they tested, "Molybdenum was the best-performing material in acidic media, where the conditions for hydrogen evolution are favorable and facile," Garcia-Esparza explained. Another major challenge was finding a way to measure the properties of their molybdenum-coated catalyst, because these molybdenum compounds are not stable when exposed to air. "Taking the catalyst out of water perturbs the identity of the material," said Garcia-Esparza. "Therefore, it was necessary to study the electrocatalyst under working conditions, which is difficult." So Garcia-Esparza spent a summer performing electrochemistry experiments at SSRL to characterize the new catalyst under operational conditions. "The idea was to work together to see how the molybdenum-coated catalyst performed and determine its electronic structure when it was operating," said Sokaras. "We wanted to understand why the back reaction doesn't happen." They tested a bare platinum catalyst, with and without a molybdenum coating, during water electrolysis at SSRL, using in operando X-ray absorption spectroscopy with a custom-made electrochemical cell. "At SSRL, we were essentially able to do electrochemistry while analyzing the sample with synchrotron radiation," Garcia-Esparza said. "The experiments performed at SLAC were the final piece of the puzzle to determine the local structure and state of the electrocatalyst under the operational conditions of hydrogen production." "Our findings support that the molybdenum layer acts as a membrane to block the oxygen and hydrogen gases from reaching near the platinum surface, which prevents water formation," Sokaras said. In addition, the research team explored photocatalysis applications. They built a photocatalytic water-splitting system using either a standard catalyst of platinum on strontium titanium oxide (Pt/SrTiO3) or the same catalyst coated with molybdenum. Both systems were tested at KAUST with the lights on and off—that is, with and without an energy source driving the water-splitting reaction. When the light was on, the standard Pt/SrTiO3 catalyst increased hydrogen production for only six hours because the system lost efficiency due to the back reaction. When the lights were then turned off, the amount of hydrogen decreased with time—verifying that significant amounts of the gases were recombining to form water. In contrast, the molybdenum-coated catalyst continuously split water to generate increasing amounts of hydrogen gas for 24 hours, producing about twice as much hydrogen gas as the standard catalyst in one day. In addition, the amount of hydrogen remained stable in the dark, confirming that the coating inhibited water formation These results are promising, but more work still needs to be done before the catalyst can be used in a practical device. Sokaras said, "I think we're far from actually talking about a commercial device, but it is certainly a huge improvement to have this new catalyst material that prevents the back reaction. Now we need to find a way to make the coating more stable so it produces hydrogen for even longer." Explore further: Using platinum-molybdenum carbide to catalytically release hydrogen to power a fuel cell More information: Angel T. Garcia-Esparza et al. An Oxygen-Insensitive Hydrogen Evolution Catalyst Coated by a Molybdenum-Based Layer for Overall Water Splitting, Angewandte Chemie International Edition (2017). DOI: 10.1002/anie.201701861


Atomically thin sheets consisting of transition metals associated with chalcogen atoms, such as sulfur, selenium and tellurium, are versatile alternatives to the more conventional silicon-based semiconductors. Depending on their metal component, these transition metal dichalcogenide monolayers have band gaps—energy barriers that limit electron flow through a material—that can be tuned to alter their electronic properties. The unique electronic properties of these monolayers have potential to improve a plethora of devices, including field-effect transistors, photodetectors and gas sensors. Semiconducting monolayers are proven to be ideal candidates as gas sensing materials because they have a high surface-to-volume ratio. For example, MoS2 has been incorporated in field-effect transistors to detect nitrogen monoxide. However, its performance is limited by its relatively low carrier mobility or by the velocity at which its electrons (or holes) move when subjected to an electric field. To overcome these shortcomings, KAUST Professor Udo Schwingenschlögl's team evaluated the potential of the platinum dichalcogenide PtSe2 for use in gas detectors via sophisticated computational techniques. "Monolayer PtSe2 experimentally shows a high carrier mobility, which can be advantageous for gas sensing," said Schwingenschlögl, adding that this material had not previously been considered for this purpose. This approach shows the interaction between monolayer and gas molecules at both structural and electronic levels. First, the researchers built a model monolayer composed of selenium atoms that formed octahedral arrangements with one platinum atom at their center. Next, they determined the optimal geometry adopted by individual gas molecules, such as NOx, NH3, H2O, CO2 and CO, upon adsorption. They assessed the capacity of these adsorbed molecules to transfer charge to the monolayer by examining adsorption-induced changes in the electronic properties. These calculations provided high adsorption energies, indicating strong affinity between monolayer and gas molecules. All adsorbed molecules altered the monolayer charge (see image), which is key for the gas-sensing ability of monolayer PtSe2. Furthermore, their interactions were more effective with monolayer PtSe2 than its MoS2 or carbon-based graphene analogues. "It was exciting to explain this difference at a molecular orbital level," said Schwingenschlögl. Calculations of electron transport revealed the high sensitivity of monolayer PtSe2 as a gas sensor. More information: Muhammad Sajjad et al. Superior Gas Sensing Properties of Monolayer PtSe, Advanced Materials Interfaces (2017). DOI: 10.1002/admi.201600911


News Article | May 8, 2017
Site: phys.org

By adapting the interaction between several independent radar transmissions in real time, KAUST researchers have shown that it is possible to vastly improve target identification and range using multiple input, multiple output (MIMO) radar systems. Radar is used extensively in civilian and military aviation to identify and monitor aircraft movements and potential meteorological dangers as well as being a critical component of flight control and surveillance systems. Radar works by transmitting a radio signal from an output antenna and monitoring a receiving antenna for any detected reflections—akin to shining a spotlight into darkness to see what might be out there. Radar systems are now very sophisticated, and with advanced signal processing, it is now possible to discriminate between different types of objects from considerable distance. MIMO radar promises a step change in performance by being able to more adaptively shape the output waveform to concentrate the power of the transmitted signal in a specific direction and by transmitting multiple types of signal adapted to better match a broader range of targets. "MIMO radar uses several transmitting and receiving antennas at the same time, where the user can choose a different transmitted signal for each antenna," explained lead researcher and graduate student Taha Bouchoucha. "Our work was on the transmitter side, developing a simple way of constructing the transmitted waveforms to steer the signal to a specific region in space." There has been extensive research into MIMO radar systems, but the stumbling block has been the computational complexity of designing each individual waveform to produce the desired combined "beam pattern" after the waveforms have interacted in space. Under the supervision of Mohamed-Slim Alouini and Tareq Al-Naffouri, Bouchoucha focused on finding ways to simplify and accelerate these calculations. "We took advantage of a mathematical framework called the two-dimensional Fourier transform combined with fast and efficient algorithms to generate the Fourier transform parameters," said Bouchoucha. "Waveform generation using our approach is inexpensive and practical, and it gives complete flexibility and freedom to focus the transmitted signal in a specific region in space." The computation scheme has already been filed with the United States Patent and Trademark Office as a significant breakthrough in MIMO technology. "Being part of this project as a master's student was a great experience," said Bouchoucha, who is now a doctoral researcher at the University of California Davis. "It was an exceptional research environment, with inspiring mentors and peers who helped me develop." More information: Taha Bouchoucha et al. DFT-Based Closed-Form Covariance Matrix and Direct Waveforms Design for MIMO Radar to Achieve Desired Beampatterns, IEEE Transactions on Signal Processing (2017). DOI: 10.1109/TSP.2017.2656840


Zhu Z.Y.,KAUST | Cheng Y.C.,KAUST | Schwingenschlogl U.,KAUST
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

Fully relativistic first-principles calculations based on density functional theory are performed to study the spin-orbit-induced spin splitting in monolayer systems of the transition-metal dichalcogenides MoS2, MoSe2, WS2, and WSe2. All these systems are identified as direct-band-gap semiconductors. Giant spin splittings of 148-456 meV result from missing inversion symmetry. Full out-of-plane spin polarization is due to the two-dimensional nature of the electron motion and the potential gradient asymmetry. By suppression of the Dyakonov-Perel spin relaxation, spin lifetimes are expected to be very long. Because of the giant spin splittings, the studied materials have great potential in spintronics applications. © 2011 American Physical Society.

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