Ross P.W.,NSTec |
Cardenas M.,NSTec |
Griffin M.,NSTec |
Mead A.,NSTec |
And 3 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013
Strip velocity measurements of gated X-ray imagers are presented using an ultra-short pulse laser. Obtaining time-resolved X-ray images of inertial confinement fusion shots presents a difficult challenge. One diagnostic developed to address this challenge is the gated X-ray imagers. The gated X-ray detectors (GXDs) developed by Lawrence Livermore National Laboratory and Los Alamos National Laboratory use a microchannel plate (MCP) coated with a gold strip line, which serves as a photocathode. GXDs are used with an array of pinholes, which image onto various parts of the GXD image plane. As the pulse sweeps over the strip lines, it creates a time history of the event with consecutive images. In order to accurately interpret the timing of the images obtained using the GXDs, it is necessary to measure the propagation of the pulse over the strip line. The strip velocity was measured using a short pulse laser with a pulse duration of approximately 1-2 ps. The 200nm light from the laser is used to illuminate the GXD MCP. The laser pulse is split and a retroreflective mirror is used to delay one of the legs. By adjusting the distance to the mirror, one leg is temporally delayed compared to the reference leg. The retroreflective setup is calibrated using a streak camera with a 1 ns full sweep. Resolution of 0.5 mm is accomplished to achieve a temporal resolution of ∼5 ps on the GXD strip line. © 2013 SPIE. Source
Milardovich N.,Laboratorio Of Electricidad |
Prevosto L.,Grupo de Descargas Electricas |
Advanced Electromagnetics | Year: 2014
A numerical investigation on the harmonic disturbances in low-voltage cables feeding large LED loads is reported. A frequency domain analysis on several commerciallyavailable LEDs was performed to investigate the signature of the harmonic current injected into the power system. Four-core cables and four single-core cable arrangements (three phases and neutral) of small, medium, and large conductor cross sections, with the neutral conductor cross section approximately equal to the half of the phase conductors, were examined. The cables were modelled by using electromagnetic finite-element analysis software. High harmonic power losses (up to 2.5 times the value corresponding to an undistorted current of the same rms value of the first harmonic of the LED current) were found. A generalized ampacity model was employed for re-rating the cables. It was found that the cross section of the neutral conductor plays an important role in the derating of the cable ampacity due to the presence of a high-level of triplen harmonics in the distorted current. The ampacity of the cables should be derated by about 40 %, almost independent of the conductor cross sections. The calculation have shown that an incoming widespread use of LED lamps in lighting could create significant additional harmonic losses in the supplying low-voltage lines, and thus more severe harmonic emission limits should be defined for LED lamps. © 2014, Tarbiat Modares University. All rights reserved. Source
Now, scientists who've been cultivating gumweed on the Reno campus think they are on the verge of producing diesel fuel, and perhaps someday jet fuel, from the sticky cousin of the sunflower that grows across much of Nevada's high desert and doesn't compete for acreage with animal feed or food crops used to make ethanol. Glenn Miller, an environmental sciences professor in UNR's College of Agriculture, Biotechnology and Natural Resources, is leading the project in the second year of a four-year, $500,000 grant from the U.S. Department of Agriculture. Miller didn't know much about gumweed when Darrell Lemaire, a mining engineer, secured the DOE grant in 1980 and approached him about doing some research in his lab. "He read chemical abstracts for recreation," Miller recalled. "He built a big house up in the rocks (above campus) with a wine cellar 50 feet down. He gave me a couple bottles—of Gumweed Extract, 1981-82, 1982-83." The two scientists began growing gumweed on campus about 10 years ago and their project evolved from the premise that biofuels shouldn't be competing with food crops in Nebraska and Kansas. Gumweed, also known as tar weed, requires little water to grow. "You could grow it in places like Nevada where you are not growing soybeans or corn," Miller said. Lemaire, 89, published his findings in a 1982 book, Cultivation of Hydrocarbon Producing Plants Native to the Western U.S., and the Whole Plant Utilization of the Oils and Byproducts. "This was after the Carter years when Jimmy Carter wore sweaters whenever he addressed the nation from the White House to indicate to everybody we were running out of energy," Miller said. Miller said UNR researchers have successfully produced fuel by extracting hydrocarbons from the weed's oil and are in the process of getting it tested as a diesel fuel. Now it's a question of refining the process to determine if farmers can make money on it. In recent years, environmentalists have argued that ethanol adds to global warming by removing millions of acres of land from conservation reserve programs for use in corn production, and has led to higher food costs worldwide as more corn is used for fuel. Bill Payne, dean of UNR's College of Agriculture, said the gumweed research addresses those concerns while anticipating current low oil prices won't last forever. "As prices once again reach $80 or more per barrel, this type of technology will look increasingly attractive to an industrial world struggling to reduce its carbon emissions," Payne said. Hongfei Lin, a collaborator in UNR's College of Engineering, is trying to find a more cost-effective way to convert biomass into fuel. Instead of adding hydrogen to biomass, he's exploring utilization of oxidation—the same process involved when substances come in contact with oxygen molecules, such as when a fresh cut apple turns brown or a copper penny turns green. Lin estimates that if gumweed was raised on just 10 percent of the thousands of square miles in Nevada where sagebrush currently grows, it could produce an estimated 400 million to 600 million gallons of biofuels annually. Gumweed has been used many different ways historically. Native Americans used it for medicinal purposes and early pioneers chomped on it as a substitute for chewing gum. "I have tried eating the stuff," Miller said. "It tastes terrible. I don't think there's any future in that." Explore further: With cellulosic ethanol, there is no food vs. fuel debate according to MSU scientist
Druker A.,UNR |
Druker A.,CONICET |
Vermaut P.,Ecole Nationale Superieure de Chimie de Paris |
Ochin P.,CNRS East Paris Institute of Chemistry and Materials Science |
And 2 more authors.
Acta Microscopica | Year: 2013
In Fe-Mn-Si alloys, the shape memory effect (SME) is related to a stress-induced martensitic transformation. The transformation proceeds from the austenite phase, normally retained at room temperature, to a hexagonal-close-packed martensite: (FCC) → (HCP). However, when ribbons of a Fe-14Mn-6Si-8Cr-5.5Ni alloy are manufactured by rapid solidification, the high temperature ferritic phase can be retained. As a consequence, not only decreases the materials capacity to recover its shape, but weakens the material, as well. In melt-spinning techniques, the thickness of the ribbons as well as the stable or metastable phases that result from the process, depend mainly on the gas ejection pressure, liquid temperature, and wheel temperature and rotation speed. In this work, we used optical microscopy and transmission and scanning electron microscopy, to investigate the microstructures obtained for various melt-spinning process variables. We also analyzed the effect of heat treatments applied in order to stabilize the austenite at room temperature and to optimize the shape memory behavior. Source
News Article | December 19, 2015
A team of researchers from the University of Nevada in Reno (UNR) and the University of Arkansas in Little Rock (UALR) announced on Dec. 15 that they plan to develop a wearable robotic device that would assist visually impaired individuals to navigate past obstacles in their surroundings. The technological breakthrough is being developed with the $820,000 grant awarded by the National Institute of Health's (NIH) National Eye Institute division. The National Robotics Initiative grant will give the research team three years to complete the project. The team is led by Yantao Shen, Assistant Professor at the University of Nevada and his research partner, Professor Cang Ye from the UALR Department of Systems Engineering and composed of their postdoctoral, graduate and undergraduate students "The miniaturized system will contribute to the lives of visually impaired people by enabling them to identify and move objects, both for navigational purposes or for more simple things such as grasping a door handle or picking up a glass," Shen, lead researcher, said. He also noted that they hoped to expand the potential applications for the robotic hand. "Space exploration, military surveillance, law enforcement and search and rescue" can also benefit from the technology. "It is a big success for Dr. Shen and a clear evidence of the continuous growth of our biomedical engineering and autonomous systems programs, which have become major areas of focus for the College of Engineering," Manos Maragakis, Dean of UNR's College of Engineering said. Along with France's Pixium Vision and other advances to help the blind "see," it seems that we are taking another step further to improving the lives of our visually impaired brothers that will make even Louis Braille proud. We truly are in the age when physical disabilities are no longer a hindrance through the aid of technological advances.