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Silicon Nanowires for Anodes of Rechargeable Li Power Cells

Silicon nanowires have been investigated as alternatives to the graphite heretofore widely used as an anode material in rechargeable lithium-ion power cells. The theoretical specific charge capacity of graphite, corresponding to the maximum Li content (at a composition of LiC6) is 372 mA•hr/g. In contrast, the theoretical specific charge capacity of Si corresponding to the maximum Li content (at a composition of Li4.4Si) is much greater — 4.2 A•hr/g. In previous studies in which thin films of silicon on substrates were investigated for use as high-capacity anodes, it was found that charge capacities faded rapidly in charge/discharge cycling because large changes in volume (as much as 310 percent) associated with insertion and extraction of lithium ions caused cracking and crumbling of the films, as well as delamination of the films from the substrates. The basic idea of the present nanowire approach is to disperse the active anode material into regions having small volumes in order to reduce the sizes of the changes in volume in order to reduce the adverse effects of those changes.

Posted in: Briefs, Materials
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Composites Containing Nanostructured Shape-Memory Alloys

A continuing program of research is devoted to understanding composite materials that include nanostructured shape-memory alloy (SMA) constituents and to developing methods of fabricating components from such materials. This research is intended to improve the utilization of SMAs in microscopic structures and miniaturized devices.

Posted in: Briefs, Materials
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Films Containing Nanostructures and/or Reactive Scavengers

Several advances have been made in research in the art of tailoring polymeric films to be, variously, (1) much more effective as barriers to diffusion of liquids and gases than they would otherwise be or (2) porous, with pore sizes suitable for filtration of selected gases or liquids. The part of the research addressing the barrier problem has provided a scientific basis for reducing the permeabilities of paints and packaging films to small fractions of the permeabilities of corresponding paints and packaging materials now in common use. In this part of the research, consideration was given to two strategies, described below, that can be used separately or together.

Posted in: Briefs, Materials
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Perspective on Research in Laser Propulsion

A document summarizes the history of research on laser propulsion, starting with the first publication of the laser-propulsion concept in the year 1969, proceeding through studies of laser propulsion within the broader context of advanced propulsion systems in general, and culminating in proof-of-concept experiments and associated studies under the auspices of the Air Force Research Laboratory during the years 1996 through 2007. The document briefly discusses the basic physical principles and engineering concepts of laser propulsion as demonstrated in the proof-of-concept experiments, in which a model rocket denoted a laser lightcraft was lofted to altitudes exceeding 200 ft. (about 61 m). In these experiments, a CO2-laser beam of pulse energy of 400 J at a repetition rate of 25 Hz was used to vaporize a solid propellant (Delrin® polyoxymethylene) to generate thrust. There is a brief discussion of energy-conversion efficiency in laser propulsion. This is followed by an analysis of the concept of supplementing laser ablation energy, and thereby effectively increasing the energy-conversion efficiency, by incorporating a chemically energetic ingredient (ammonium nitrate) into the Delrin propellant. The document includes an extensive bibliography of research on laser propulsion.

Posted in: Briefs, Physical Sciences
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Some Advances in Understanding of Environmental Fatigue

A research program has yielded advances in understanding of numerous aspects of environmental crack propagation in aerospace aluminum alloys. From one perspective, the objective of this program was to quantitatively establish governing crack-tip-mechanics conditions and damage mechanisms pertinent to environmental crack propagation, using a combination of (1) high-spatial-resolution experimentation and (2) computational simulation based on continuum-mechanics mathematical models employing multiple length scales. From a slightly different perspective, the central goals of this research were to (1) develop means of accurate prediction of crack-tip stresses and plastic strains for incorporation into micromechanical descriptions of crack growth, (2) validate crack-tip-mechanics models by means of high-spatial-resolution experiments, and (3) resolve physical characteristics of damage attributable to accumulation of hydrogen at fatigue-crack tips.

Posted in: Briefs, Physical Sciences
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Cracking of Aluminum Panels Repaired With Composite Patches

An experimental study of the mechanical behavior of cracked aluminum specimens repaired with composite-material patches has yielded findings that may eventually contribute to the development of more- effective composite patches and of techniques for predicting and detecting failures in composite-patched aluminum aircraft panels. Some prior studies have addressed various aspects of composite-patch repair of aluminum specimens, but until now, little attention has been given to such important aspects of mechanical behavior and properties as the relationships among stress, strain, and growth of cracks through-out the lifetimes of specimens. In this study, effects of initiation and growth of cracks on the residual strengths of the patched specimens were characterized. This study established a correlation among damage modes, residual strengths, and evolution of strain inside and outside the patched areas.

Posted in: Briefs, Physical Sciences
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Software Virtual Networks Integrate Training and Operation of Wireless Net-Centric Warfare Systems

Military planners are aggressively developing network-centric warfare platforms that use wireless communications as a force multiplier. The aim of these programs is to provide warfighters with the best equipment and technology to achieve tactical dominance as soon as practical.

Posted in: Briefs, Information Technology
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Interview with Ray Alderman, Executive Director of VITA

Founded in 1984 to promote VMEbus technology, VITA is a non-profit organization of more than 125 vendor companies who share a common interest in real-time, modular embedded computing systems. In August 2008, VITA's Executive Director, Ray Alderman, agreed to speak with Embedded Technology's editor, Bruce Bennett, about the state of VME technology in 2008, how far it has come in its 30-year history, and where it is likely to go in the future.

Posted in: Articles, Articles, Electronics & Computers, Embedded software, People and personalities
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System-On-Module Standard

MEN Micro Inc. (Ambler, PA) has announced the ESMexpress® System-On-Module Standard, a new computing standard in development to be the ANSIVITA 59 (RSE Rugged System- On-Module Express) standard. In conjunction with the new standard, they have also an - nounced the XM1 featuring the first-generation Intel® Atom® processor (Z530 at 1.6 GHz or Z510 at 1.1 GHz) based on 45-nm technology coupled with 1 GB of soldered DDR2 SDRAM for significantly lower power dissipation, reduction in design costs, and space-saving design flexibility. ESMexpress combines this model with advanced cooling technologies, and the latest serial buses and rugged components to ensure safe, reliable operation in harsh environments found in areas as diverse as the railway, avionics, industrial automation, medical engineering and mobile industries.

ESMexpress provides for extreme resistance against shock and vibration. Eight screws secure the module to the carrier board. In addition, a mechanically robust connector specified for MIL and railway applications supports differential signals with up to 8 GHz, features a stacking height of 5 mm with a minimum tolerance of +/-0.3 mm, is equipped with fixed contacts for power supply, and is specified for an operating temperature range of -55°C to +125°C. The Intel-based XM1 offers a screened temperature range of -40°C to +85°C. The electrical signals are distributed on two 120-pin connectors and are only defined for modern serial buses. For PCI Express there are four single lane ports (4 ×1) and one port that can be configured as 1 ×16, 1 ×8, 2 ×4 or 2 ×1. Other ports include three 1-Gigabit Ethernet (also as 10- Gigabit), eight USB, three SATA, SDVO, LVDS, HD Audio, several utility signals, and a single 12V power supply.

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Posted in: Products, Products, Electronics & Computers
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FPGA Mezzanine Card Module

VMETRO (Houston, TX) has released a FPGA Mezzanine Card (FMC/VITA 57) module. The ADC510, available in air-cooled and conduction- cooled rugged versions, integrates two 12-bit 500MHz A/D chips for use in DSP applications such as signal intelligence (SIGINT), electronic counter measures (ECM), and radar. This design, based on the emerging VITA 57.1 standard, makes it easier for developers to integrate FPGAs into their embedded system designs.

The ADC510 supports two Texas Instruments ADS5463 ADC devices, with each device supporting a sampling rate up to 500 MSPS and providing 12-bits of digital output. The ADC device interfaces are routed to the FMC connector to enable an FPGA on a baseboard to directly control and receive data. There is a choice of sample clock sources for the ADC510 including an onboard source that supports sampling rates of 300, 320, 400, and 500 MSPS as well as the ability to utilize an external sample clock. Input and output triggers are provided to enable multiple ADC510 modules to be synchronized to increase the number of input channels.

For Free Info Visit Here.

Posted in: Products, Products, Electronics & Computers
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