Special Coverage


Filled Skutterudites as Thermoelectric Materials

The highest known thermoelectric figure of merit was observed in one of these materials. Filled skutterudites have shown promise as semiconducting materials with superior thermoelectric properties at temperatures up to at least 650 °C. This finding is a breakthrough in a continuing investigation of the potential utility of skutterudites as thermoelectric materials. Previous results of this investigation were reported in several articles in NASA Tech Briefs; namely, "Skutterudite Compounds for Power Semiconductor Devices" (NPO-19378), NASA Tech Briefs, Vol. 20, No. 3 (March 1996), page 60; "Two Potentially Useful Ternary Skutterudite Compounds" (NPO-19409), NASA Tech Briefs, Vol. 20, No. 11 (November 1996), page 66; and "Preparation and Some Properties of n-Type IrxCo1 — xSb3" (NPO-19852), NASA Tech Briefs, Vol. 20, No. 11 (November 1996), page 94.

Posted in: Materials, Briefs, TSP


Camera Images Hydrogen Fires in Three Wavelength Bands

The camera filters and processing can be customized for other multispectral imaging applications. A special-purpose multispectral video camera has been designed to provide an enhanced capability for viewing hydrogen fires. Hydrogen fires do not emit sufficient visible light to be seen by the unaided human eye, but they do emit strongly at other wavelengths — especially in the infrared and near-infrared portions of the spectrum. Therefore, like some other video cameras developed previously for the same purpose, this camera is designed to respond to infrared light emitted by hot water molecules in hydrogen flames. Going beyond previous designs, this camera provides a combination of imaging in three wavelength bands and processing of the three images, all for the purposes of (1) reducing spurious responses to background light and solar radiation, and (2) synthesizing an image of a hydrogen flame overlaid on an ordinary visible-light image of the scene that contains the flame.

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


Instrument Measures Fluorescence From Chlorophyll in Plants

Effective discrimination against solar background radiation is achieved without critical optical and mechanical parts. An optoelectronic instrument, known as a plant fluorescence sensor, is being developed for use as a working tool in agricultural settings. This instrument is a remote, passive monitor that provides a means of discerning plant stress at very early stages. With sufficient warning, the user could provide timely applications of fertilizer, water, and/or pesticide to achieve maximum crop yield at minimum cost. Figure 1 presents two views of the plant fluorescence sensor. The instrument is the subject of U. S. Patent 5,567,947.

Posted in: Test & Measurement, Briefs


Initialized Fractional Calculus

Initialization functions are essential to a revised formulation suitable for engineering and scientific applications. The fractional calculus (which admits of integrals and derivatives of non-integer order) dates back almost to the origin of the better-known ordinary (integer-order) calculus, but thus far has been treated more as a mathematical curiosity than as a scientific and engineering tool. Increasingly many physical processes are found to be best described using fractional differential equations. These processes include: viscoelasticity, rheology, electrochemistry, fractal processes, and many diffusion processes. The application of the fractional calculus to scientific and engineering problems has been inhibited by difficulties that arise from the basic definitions given heretofore for integrals and derivatives of arbitrary order. These difficulties are associated with the initialization problem, which is explained below.

Posted in: Information Sciences, Briefs, TSP


Protein Pairing

Posted in: Blog


High-Performance Processor of Hyperspectral Images

Efficient algorithms analyze pixel spectra to estimate abundances of materials. The Remote Sensing Hyperspectral Engine (RSHE) is a special-purpose, portable computer that performs high-performance processing of hyperspectral image data collected by a remote-sensing optoelectronic apparatus. Typically, the remote-sensing apparatus is airborne or spaceborne, the images are of terrain, and the purpose of collecting and analyzing the image data is to estimate the spatially varying abundances of materials of interest. Remote-sensing applications in which the RSHE could prove beneficial include assessment of crops, exploration for minerals, identification of military targets, urban-planning studies, environmental assessment, and large-area search-and- rescue operations.

Posted in: Tech Briefs, Photonics, Briefs


Hand-Held Optoelectronic Particulate Monitors

Data on concentrations and sizes are obtained from diffraction of light. Optoelectronic instruments are being developed for use in measuring the concentrations and sizes of microscopic particles suspended in air. The instruments could be used, for example, to detect smoke, explosive dust in grain elevators, or toxic dusts in industrial buildings. Like some older, laboratory-bench-style particulate monitors, these instruments are based on diffraction of light by particles. However, these instruments are much smaller; exploiting recent advances in optics, electronics, and packaging, they are miniaturized into compact, hand-held units.

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