Tech Briefs

Less-Complex Method of Classifying MPSK

Nearly optimal performance can be obtained with less computation. An alternative to an optimal method of automated classification of signals modulated with M-ary phase-shift-keying (M-ary PSK or MPSK) has been derived. The alternative method is approximate, but it offers nearly optimal performance and entails much less complexity, which translates to much less computation time.

Posted in: Information Sciences, Briefs, TSP

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The Spatial Standard Observer

Degrees of visibility and discriminability of targets in images can be estimated. The spatial standard observer is a computational model that provides a measure of the visibility of a target in a uniform background image or of the visual discriminability of two images. Standard observers have long been used in science and industry to quantify the discriminability of colors. Color standard observers address the spectral characteristics of visual stimuli, while the spatial standard observer (SSO), as its name indicates, addresses spatial characteristics. The SSO is based on a model of human vision. The SSO was developed in a process that included evaluation of a number of earlier mathematical models that address optical, physiological, and psychophysical aspects of spatial characteristics of human visual perception. Elements of the prior models are incorporated into the SSO, which is formulated as a compromise between accuracy and simplicity. The SSO operates on a digitized monochrome still image or on a pair of such images. The SSO consists of three submodels that operate sequentially on the input image(s):

Posted in: Information Sciences, Briefs

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Solving the Swath Segment Selection Problem

Several techniques for solving the problem have been tested and compared. Several artificial-intelligence search techniques have been tested as means of solving the swath segment selection problem (SSSP) ? a real-world problem that is not only of interest in its own right, but is also useful as a test bed for search techniques in general. In simplest terms, the SSSP is the problem of scheduling the observation times of an airborne or spaceborne synthetic aperture radar (SAR) system to effect the maximum coverage of a specified area (denoted the target), given a schedule of downlinks (opportunities for radio transmission of SAR scan data to a ground station), given the limit on the quantity of SAR scan data that can be stored in an onboard memory between downlink opportunities, and given the limit on the achievable downlink data rate. The SSSP is NP complete (short for “nondeterministic polynomial time complete” ? characteristic of a class of intractable problems that can be solved only by use of computers capable of making guesses and then checking the guesses in polynomial time).

Posted in: Information Sciences, Briefs, TSP

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Covering a Crucible With Metal Containing Channels

Metal is deposited on a sacrificial pattern that defines the channels. In a procedure that partly resembles the lost-wax casting process, a crucible made of a brittle material (ceramic, quartz, or glass) is covered with a layer of metal containing channels. The metal cover and the channels can serve any or all of several purposes, depending upon the application: Typically, the metal would serve at least partly to reinforce the crucible. The channels could be used as passages for narrow objects that could include thermocouples and heat-transfer strips. Alternatively or in addition, channels could be used as flow paths for liquid or gaseous coolants and could be positioned and oriented for position or direction-selective cooling. In some cases, the channels could be filled with known gases and sealed so that failure of the crucibles could be indicated by instruments that detect the gases.

Posted in: Manufacturing & Prototyping, Briefs, TSP

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Thermal Spore Exposure Vessels

Thermal masses are minimized to enable rapid heating and cooling. Thermal spore exposure vessels (TSEVs) are laboratory containers designed for use in measuring rates of death or survival of microbial spores at elevated temperatures. A major consideration in the design of a TSEV is minimizing thermal mass in order to minimize heating and cooling times. This is necessary in order to minimize the number of microbes killed before and after exposure at the test temperature, so that the results of the test accurately reflect the effect of the test temperature.

Posted in: Medical, Briefs, TSP

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Enumerating Spore-Forming Bacteria Airborne With Particles

Complementary data are obtained by use of two instruments and correlated. A laboratory method has been conceived to enable the enumeration of: Cultivable bacteria and bacterial spores that are, variously, airborne by themselves or carried by, parts of, or otherwise associated with, other airborne particles; and Spore-forming bacteria among all of the aforementioned cultivable microbes.

Posted in: Medical, Briefs, TSP

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Holographic Plossl Retroreflectors

Lightweight, inexpensive holographic optical elements would be used in place of lenses. Goddard Space Flight Center, Greenbelt, Maryland Holographic retroreflectors that function equivalently to Plossl eyepieces have been developed and used in free-space optical communication systems that utilize laser beams. Plossl eyepieces are well known among telescope designers. They have been adopted for use as retroreflectors and as focusing elements (for reception) and collimating elements (for transmission) in optical communication systems. A retroreflector that incorporates a Plossl eyepiece is termed a cat’s eye retroreflector (see figure).

Posted in: Tech Briefs, ptb catchall, Photonics, Briefs, TSP

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