Other materials stories that may be of interestPublished on April 30th, 2013 | By: Eileen De Guire
Recent innovations in LEDs have improved the energy efficiency of streetlights, but, until now, their glow still wastefully radiated beyond the intended area. A team of researchers from Taiwan and Mexico has developed a new lighting system design that harnesses high-efficiency LEDs and ensures they shine only where they’re needed, sparing surrounding homes and the evening sky from unwanted illumination. The team reported their findings in the open-access journal Optics Express. The proposed lamp is based on a novel three-part lighting fixture. The first part contains a cluster of LEDs, each of which is fitted with a special lens, called a Total Internal Reflection lens, that focuses the light so the rays are parallel to one another instead of intersecting. These lens-covered LEDs are mounted inside a reflecting cavity, which “recycles” the light and ensures that as much of it as possible is used to illuminate the target. Finally, as the light leaves the lamp it passes through a diffuser or filter that cuts down on unwanted glare. The combination of collimation and filtering also allows researchers to control the beam’s shape: the present design yields a rectangular light pattern ideally suited for street lighting, the researchers say. In addition to cutting light pollution and glare, the new model could also save energy. A general LED street light could reduce power consumption by 40 to 60 percent. The increased efficiency of the proposed design would likely save an additional 10 to 50 percent. Furthermore, the module would be simple to fabricate, since it comprises just four parts, including a type of LED bulb commonly used in the lighting industry.
The union of theory and practice makes broadband, low-loss optical devices practical, which is why two groups of Penn State engineers collaborated to design optical metamaterials that have custom applications that are easily manufactured. In the past, to control the optics of metamaterials, researchers used complicated structures including 3-dimensional rings and spirals that are difficult if not impossible to manufacture in large numbers and small sizes at optical wavelengths. From a practical perspective, simple and manufacturable nanostructures are necessary for creating high-performance devices. “We must design nanostructures that can be fabricated,” says Theresa S. Mayer, Distinguished Professor of Electrical Engineering and co-director of Penn State’s nanofabrication laboratory. Designing materials that can allow a range of wavelengths to pass through while blocking other wavelengths is far more difficult than simply creating something that will transmit a single frequency. Minimizing the time domain distortion of the signal over a range of wavelengths is necessary, and the material also must be low loss. The design team looked at existing fishnet structured metamaterials and applied nature-inspired optimization techniques based on genetic algorithms. They optimized the dimensions of features such as the size of the fishnet and the thicknesses of the materials. One of the transformative innovations made by the researchers was the inclusion of nanonotches in the corners of the fishnet holes, creating a pattern that could be tuned to shape the dispersion over large bandwidths.
University of Nebraska-Lincoln materials engineers have developed a structural nanofiber that is both strong and tough, a discovery that could transform everything from airplanes and bridges to body armor and bicycles. Their findings are featured on the cover of the American Chemical Society’s journal, ACS Nano. “Our discovery adds a new material class to the very select current family of materials with demonstrated simultaneously high strength and toughness,” says the team’s leader, Yuris Dzenis, McBroom Professor of Mechanical and Materials Engineering and a member of UNL’s Nebraska Center for Materials and Nanoscience. Dzenis and colleagues developed an exceptionally thin polyacrilonitrile nanofiber, a type of synthetic polymer related to acrylic, using electrospinning. Dzenis suggests that toughness comes from the nanofibers’ low crystallinity. In other words, it has many areas that are structurally unorganized. These amorphous regions allow the molecular chains to slip around more, giving them the ability to absorb more energy.
Resistive memory cells (ReRAM) are regarded as a promising solution for future generations of computer memories. They will dramatically reduce the energy consumption of modern IT systems while significantly increasing their performance. Unlike the building blocks of conventional hard disk drives and memories, these novel memory cells are not purely passive components but must be regarded as tiny batteries. This has been demonstrated by researchers of Jülich Aachen Research Alliance. The new finding radically revises the current theory and opens up possibilities for further applications. The research group has already filed a patent application for their first idea on how to improve data readout with the aid of battery voltage. In complex experiments, the scientists from Forschungszentrum Jülich and RWTH Aachen University determined the battery voltage of typical representatives of ReRAM cells and compared them with theoretical values. This comparison revealed other properties (such as ionic resistance) that were previously neither known nor accessible.”The demonstrated internal battery voltage of ReRAM elements clearly violates the mathematical construct of the memristor theory. This theory must be expanded to a whole new theory–to properly describe the ReRAM elements,” says Eike Linn, a specialist for circuit concepts.
(Berkeley National Lab/YouTube) A worldwide race is on for scientists to develop ever more powerful X-ray microscopes. With ultra-high resolution X-ray optics at ultra-bright synchrotrons—such as the 120-meter-long Hard X-Ray Nanoprobe (HXN) being developed for the National Synchrotron Light Source II (NSLS-II) at Brookhaven Lab—researchers will see structure and chemistry deep inside natural and engineered materials as they address some of the biggest questions in materials science, physics, chemistry, environmental sciences, and biology. Unprecedented capabilities, however, bring critical technical challenges, but scientists at Brookhaven Lab are on the job. In this video of the 486th Brookhaven Lecture, Yong Chu illustrates unique challenges and innovative approaches for X-ray microscopy at the nanoscale. He also discusses measurement capabilities for the first science experiments at NSLS-II. Chu joined the Photon Sciences Directorate at Brookhaven Lab as group leader for the HXN beamline at NSLS-II in 2009.
The innovative research of a Montana State University student, Neerja Zambare, a senior from Pune, India, majoring in both chemical engineering and biological engineering, was selected as one of the country’s undergraduate researchers for her poster about a bio-cement that effectively plugs cracks near wells and drilling sites. Zambare exhibited her research poster, “Biofilm induced biomineralization in a radial flow reactor,” at the Council on Undergraduate Research’s Posters on the Hill Exhibition April 23-24 in Washington, D.C., one of the country’s most prestigious undergraduate research fairs. Zambare was accompanied by Robin Gerlach, MSU professor of chemical and biological engineering and Zambare’s research mentor. Gerlach said Zambare convinced him that she would be the right person to join his lab group in the Center for Biofilm Engineering. The group trained her and then asked her to join a project that the lab had been working on for some time—a bacterium that makes calcium carbonate and has potential applications in sealing ponds, plugging cracks emitting carbon dioxide near carbon sequestration wells as well as abandoned wells.
(arXiv) Two modifications have been made to a miniature ceramic anvil high pressure cell (mCAC) designed for magnetic measurements at pressures up to 12.6 GPa in a commercial superconducting quantum interference (SQUID) magnetometer. Replacing the Cu-Be piston in the former mCAC with a composite piston composed of the Cu-Be and ceramic cylinders reduces the background magnetization significantly smaller at low temperatures, enabling more precise magnetic measurements at low temperatures. A second modification to the mCAC is the utilization of a ceramic anvil with a hollow in the center of the culet surface. High pressures up to 5 GPa were generated with the “cupped ceramic anvil” with the culet size of 1.0 mm.
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