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Self-Healing Wire Insulation
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Space Optical Communications Using Laser Beams
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Active Response Gravity Offload and Method
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nBn Infrared Detector Containing Graded Absorption Layer

Potential applications include environmental monitoring, firefighting, law enforcement, and medical diagnosis. It has been proposed to modify the basic structure of an nBn infrared photodetector so that a plain electron-donor-type (n-type) semiconductor contact layer would be replaced by a graded n-type III–V alloy semiconductor layer (i.e., ternary or quarternary) with appropriate doping gradient. The abbreviation “nBn” refers to one aspect of the unmodified basic device structure: There is an electron-barrier (“B”) layer between two n-type (“n”) layers, as shown in the upper part of the figure. One of the n-type layers is the aforementioned photon-absorption layer; the other n-type layer, denoted the contact layer, collects the photocurrent.

Posted in: Briefs, Physical Sciences

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Ultra-Broad-Band Optical Parametric Amplifier or Oscillator

Potential applications include wavelength-multiplexing communications and generating reference frequencies. A concept for an ultra-broad-band optical parametric amplifier or oscillator has emerged as a by-product of a theoretical study in fundamental quantum optics. The study was originally intended to address the question of whether the two-photon temporal correlation function of light [in particular, light produced by spontaneous parametric down conversion (SPDC)] can be considerably narrower than the inverse of the spectral width (bandwidth) of the light. The answer to the question was found to be negative. More specifically, on the basis of the universal integral relations between the quantum two-photon temporal correlation and the classical spectrum of light, it was found that the lower limit of two-photon correlation time is set approximately by the inverse of the bandwidth. The mathematical solution for the minimum two-photon correlation time also provides the minimum relative frequency dispersion of the down-converted light components; in turn, the minimum relative frequency dispersion translates to the maximum bandwidth, which is important for the design of an ultra-broad-band optical parametric oscillator or amplifier.

Posted in: Briefs, Physical Sciences

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Atomic References for Measuring Small Accelerations

These systems may be used in military and geological applications. Accelerometer systems that would combine the best features of both conventional (e.g., mechanical) accelerometers and atom interferometer accelerometers (AIAs) have been proposed. These systems are intended mainly for use in scientific research aboard spacecraft but may also be useful on Earth in special military, geological, and civil-engineering applications.

Posted in: Briefs, TSP, Physical Sciences

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Enhancing SERS by Means of Supramolecular Charge Transfer

Sensors based on this method could detect chemical and biological hazards. In a proposed method of sensing small quantities of molecules of interest, surface enhanced Raman scattering (SERS) spectroscopy would be further enhanced by means of intermolecular or supramolecular charge transfer. There is a very large potential market for sensors based on this method for rapid detection of chemical and biological hazards.

Posted in: Briefs, TSP, Physical Sciences

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Error-Rate Bounds for Coded PPM on a Poisson Channel

It is now possible to calculate tight bounds at high SNR. Equations for computing tight bounds on error rates for coded pulse-position modulation (PPM) on a Poisson channel at high signal-to-noise ratio have been derived. These equations and elements of the underlying theory are expected to be especially useful in designing codes for PPM optical communication systems.

Posted in: Briefs, Information Sciences

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Biomorphic Multi-Agent Architecture for Persistent Computing

Computing systems would reconfigure themselves to continue functioning despite failures of components. A multi-agent software/hardware architecture, inspired by the multicellular nature of living organisms, has been proposed as the basis of design of a robust, reliable, persistent computing system. Just as a multicellular organism can adapt to changing environmental conditions and can survive despite the failure of individual cells, a multi-agent computing system, as envisioned, could adapt to changing hardware, software, and environmental conditions. In particular, the computing system could continue to function (perhaps at a reduced but still reasonable level of performance) if one or more component(s) of the system were to fail.

Posted in: Briefs, Information Sciences

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Using Covariance Analysis To Assess Pointing Performance

A Pointing Covariance Analysis Tool (PCAT) has been developed for evaluating the expected performance of the pointing control system for NASA’s Space Interferometry Mission (SIM). The SIM pointing control system is very complex, consisting of multiple feedback and feedforward loops, and operating with multiple latencies and data rates. The SIM pointing problem is particularly challenging due to the effects of thermomechanical drifts in concert with the long camera exposures needed to image dim stars.

Posted in: Briefs, TSP, Information Sciences

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