Tech Briefs

Software for Fault-Tolerant Matrix Multiplication

Formal Linear Algebra Recovery Environment is a computer program for high-performance, fault-tolerant matrix multiplication. The program is based on an extension of the prior theory and practice of fault-tolerant matrix·matrix multiplication of the form C = AB. This extension provides low-overhead methods for detecting errors, not only in C, but also in A and/or B. These methods enable the detection of all errors as long as, in a given case, only one entry in A, B, or C is corrupted. The program also provides for following a low-overhead roll-back approach to correct errors once detected. Results of computational experiments have demonstrated that the methods implemented in this program work well in practice while imposing an acceptably low level of overhead, relative to high-performance matrix-multiplication methods that do not afford fault tolerance.

Posted in: Briefs, TSP, Software

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Routines for Computing Pressure Drops in Venturis

A set of computer- program routines has been developed for calculating pressure drops and recoveries of flows through standard venturis, nozzle venturis, and orifices. Relative to prior methods used for such calculations, the method implemented by these routines offers greater accuracy because it involves fewer simplifying assumptions and is more generally applicable to wide ranges of flow conditions. These routines are based on conservation of momentum and energy equations for real nonideal fluids, the properties of which are calculated by curve-fitting subroutines based on empirical properties data. These routines are capable of representing cavitating, choked, non-cavitating, and unchoked flow conditions for liquids, gases, and supercritical fluids. For a computation of flow through a given venturi, nozzle venturi, or orifice, the routines determine which flow condition occurs: First, they calculate a throat pressure under the assumption that the flow is unchoked or non-cavitating, then they calculate the throat pressure under the assumption that the flow is choked or cavitating. The assumption that yields the higher throat pressure is selected as the correct one.

Posted in: Briefs, Software

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Multisensor Instrument for Real-Time Biological Monitoring

Multiple parameters can be measured simultaneously by use of a single compact sensor head. The figure schematically depicts an instrumentation system, called a "fiber optic-based integration system" (FOBIS), that is undergoing development to enable real-time monitoring of fluid cell cultures, bioprocess flows, and the like. The FOBIS design combines a micro flow cytometer (MFC), a microphotometer (MP), and a fluorescence-spectrum- or binding-force-measuring micro-sensor (MS) in a single instrument that is capable of measuring multiple biological parameters simultaneously or sequentially. The fiber-optic-based integration system is so named because the MFC, the MP, and the MS are integrated into a single optical system that is coupled to light sources and photometric equipment via optical fibers. The optical coupling components also include a wavelength-division multiplexer and diffractive optical elements. The FOBIS includes a laser-diode- and fiber-optic-based optical trapping subsystem ("optical tweezers") with microphotometric and micro-sensing capabilities for noninvasive confinement and optical measurement of relevant parameters of a single cell or other particle.

Posted in: Briefs, TSP, Medical

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Controllable Sonar Lenses and Prisms Based on ERFs

Compact devices without moving parts would focus and steer acoustic beams.  Sonar-beam-steering devices of the proposed type would contain no moving parts and would be considerably smaller and less power-hungry, relative to conventional multiple-beam sonar arrays. The proposed devices are under consideration for installation on future small autonomous underwater vehicles because the sizes and power demands of conventional multiple-beam arrays are excessive, and motors used in single-beam mechanically scanned systems are also not reliable. 

Posted in: Briefs, TSP, Physical Sciences

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The StarLight Space Interferometer

Two papers describe the StarLight space interferometer — a Michelson interferometer that would be implemented by two spacecraft flying in formation. The StarLight formation flying interferometer project has been testing and demonstrating engineering concepts for a new generation of space interferometers that would be employed in a search for extrasolar planets and in astrophysical investigations. As described in the papers, the original StarLight concept called for three spacecraft, and the main innovation embodied is a modification that makes it possible to reduce complexity by eliminating the third spacecraft. The main features of the modification are (1) introduction of an optical delay line on one spacecraft and (2) controlling the flying formation such that the two spacecraft are located at two points along a specified parabola so as to define the required baseline of specified length (which could be varied up to 125 m) perpendicular to the axis of the parabola. One of the papers presents a detailed description of the optical layout and discusses computational modeling of the performance; the other paper presents an overview of the requirements for operation and design, the overall architecture, and subsystems.

Posted in: Briefs, TSP, Physical Sciences

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Champagne Heat Pump

Relatively safe and environmentally benign working fluids can be used.  The term "champagne heat pump" denotes a developmental heat pump that exploits a cycle of absorption and desorption of carbon dioxide in an alcohol or other organic liquid. Whereas most heat pumps in common use in the United States are energized by mechanical compression, the champagne heat pump is energized by heating.

Posted in: Briefs, TSP, Physical Sciences

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Freeze-Tolerant Condensers

Two designs offer similar advantages. Two condensers designed for use in dissipating heat carried by working fluids feature two-phase, self-adjusting configurations such that their working lengths automatically vary to suit their input power levels and/or heat-sink temperatures. A key advantage of these condensers is that they can function even if the temperatures of their heat sinks fall below the freezing temperatures of their working fluids and the fluids freeze. The condensers can even be restarted from the frozen condition.

Posted in: Briefs, TSP, Physical Sciences

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