Special Coverage

Distributed Propulsion Concepts and Superparamagnetic Energy Harvesting Hummingbird Engine
Aerofoam
Wet Active Chevron Nozzle for Controllable Jet Noise Reduction
Magnetic Relief Valve
Locking Mechanism for a Flexible Composite Hinge
Active Aircraft Pylon Noise Control System
Unmanned Aerial Systems Traffic Management
Method of Bonding Dissimilar Materials
Sonar Inspection Robot System
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Using Light To Treat Mucositis and Help Wounds Heal

Arrays of LEDs would generate biostimulatory radiation. A continuing program of research and development is focusing on the use of controlled illumination by light-emitting diodes (LEDs) to treat mucositis and to accelerate healing of wounds. The basic idea is to illuminate the affected area of a patient with light of an intensity, duration, and wavelength (or combination of wavelengths) chosen to produce a therapeutic effect while generating only a minimal amount of heat.

Posted in: Briefs, Bio-Medical, Medical

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Error-Detecting Counters for FPGA and ASIC State Machines

Inconsistencies between main and auxiliary counts would be detected. Error-detecting counters have been proposed as parts of fault-tolerant finite state machines that could be implemented in field-programmable gate arrays (FPGAs) and application-specific integrated circuits that perform sequential logic functions. The use of error-detecting counters would complement the fault-tolerant coding schemes described in “Fault-Tolerant Coding for State Machines” (NPO-41050), in this issue on page 55. Counters are often used in state machines in cases in which it is necessary to represent large numbers of states and/or to count clock cycles between certain states. To ensure reliability, it is necessary to ensure that the counters are as free of faults as are the other parts of the state machines.

Posted in: Briefs, TSP, Semiconductors & ICs

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Dot-in-Well Quantum-Dot Infrared Photodetectors

The goal is to develop high-performance radiation-hard QDIPs for focal plane arrays. Dot-in-well (DWELL) quantum-dot infrared photodetectors (QDIPs) [DWELL-QDIPs] are subjects of research as potentially superior alternatives to prior QDIPs. Heretofore, there has not existed a reliable method for fabricating quantum dots (QDs) having precise, repeatable dimensions. This lack has constituted an obstacle to the development of uniform, high- performance, wavelength- tailorable QDIPs and of focal-plane arrays (FPAs) of such QDIPs. However, techniques for fabricating quantum-well infrared photodetectors (QWIPs) having multiple-quantum- well (MQW) structures are now well established. In the present research on DWELL-QDIPs, the arts of fabrication of QDs and QWIPs are combined with a view toward overcoming the deficiencies of prior QDIPs. The longer-term goal is to develop focal-plane arrays of radiation- hard, highly uniform arrays of QDIPs that would exhibit high performance at wavelengths from 8 to 15 μm when operated at temperatures between 150 and 200 K.

Posted in: Briefs, TSP, Electronics & Computers

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Integrated Microbatteries for Implantable Medical Devices

Extremely small batteries could operate for years at nanoampere discharge rates. Integrated microbatteries have been proposed to satisfy an anticipated need for long-life, low-rate primary batteries, having volumes less than 1 mm3, to power electronic circuitry in implantable medical devices. In one contemplated application, such a battery would be incorporated into a tubular hearing-aid device to be installed against an eardrum. This device is based on existing tube structures that have already been approved by the FDA for use in human ears.

Posted in: Briefs, TSP, Electronics & Computers

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Increasing Discharge Capacities of Li-(CF)n Cells

Electrolyte additive could open new applications for Li-(CF)n batteries. An electrolyte additive has shown promise as a means of increasing the sustainable rates of discharge and, hence, the discharge capacities, of lithium- poly (carbon monofluoride) electrochemical power cells. Lithium- poly (carbon monofluoride) [Li-(CF)n] cells and batteries offer very high specific energies — practical values of about 600 W.h/g and a theoretical maximum value of 2,180 W·h/kg. However, because Li-(CF)n cells and batteries cannot withstand discharge at high rates, they have been relegated to niche applications that involve very low discharge currents over times of the order of hundreds to thousands of hours. Increasing the discharge capacities of Li- (CF)n batteries while maintaining high practical levels of specific energy would open new applications for these batteries.

Posted in: Briefs, TSP, Electronics & Computers

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Creep Analysis of Lead-Free Solders Undergoing Thermal Loading

Finite element material models are used to evaluate the reliability of lead-free solders. Lead and its compounds have been widely used for many years in the electronics industry. However, the global demand to reduce the use of hazardous materials has compelled electronics manufacturers to consider the use of lead-free materials in future products. This transition has heightened the necessity for new finite element material models that can be used to evaluate the reliability of lead-free solders.

Posted in: Briefs, Electronics & Computers

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Oxidation Behavior of Carbon Fiber-Reinforced Composites

OXIMAP is a numerical (FEA-based) solution tool capable of calculating the carbon fiber and fiber coating oxidation patterns within any arbitrarily shaped carbon silicon carbide composite structure as a function of time, temperature, and the environmental oxygen partial pressure. The mathematical formulation is derived from the mechanics of the flow of ideal gases through a chemically reacting, porous solid. The result of the formulation is a set of two coupled, non-linear differential equations written in terms of the oxidant and oxide partial pressures. The differential equations are solved simultaneously to obtain the partial vapor pressures of the oxidant and oxides as a function of the spatial location and time. The local rate of carbon oxidation is determined at each time step using the map of the local oxidant partial vapor pressure along with the Arrhenius rate equation. The non-linear differential equations are cast into matrix equations by applying the Bubnov- Galerkin weighted residual finite-element method, allowing for the solution of the differential equations numerically.

Posted in: Briefs, TSP, Software

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