Physical Sciences

Magnetostrictive valves for cryogenic applications would be actuated by superconducting flux tubes (SFTs), according to a proposal. The reasoning behind this proposal closely tracks that of the proposal to use SFTs in magnetostrictive heat switches, as reported in the preceding article.

A report describes experiments using multiwavelength pyrometry to determine the surface temperature of the end tip inside a BeO cylinder that is part of a probe designed to measure high-temperature gases. The cylinder is heated by the gas into which it is inserted, and the gas temperature...

"Tribology for Aerospace Applications" is a textbook and reference source written for designers of rotating machinery; users and designers of such mechanical components as bearings, gears, and seals; tribologists; university and industrial researchers; and students of machine design. The book incorporates...

An ultrasonic instrument has been developed for measuring the sizes of bubbles in the human body. A primary example is that of bubbles associated with decompression sickness (the "bends"); these bubbles consist mostly of nitrogen and can occur in both blood vessels and extravascular tissues. The bubbles can lodge...

A report describes a program to develop a multi-function telescope to be carried aboard spacecraft of the planned X2000 series of planetary missions. [A related multi-function telescope was described in "Telescope for Imaging and Laser Communication" (NPO-20388), NASA Tech Briefs,...

A report describes an experimental investigation that revealed a previously unknown type of spatial alignment of quantum dots (QDs) in InxGa1 -xAs/GaAs multilayer structures. Multilayer arrays of QDs (in the form of nanometer-sized InxGa1-xAs islands) were formed by alternately depositing...

This paper sets the ultimate limit on the maximum amount of optical data pulses that can be sent through a single fiber in a given period under the wavelength-division-multiplexed (WDM) format. The discovery in 1973 that optical soliton on a single wavelength beam can exist in fiber is one of...

A report discusses the design of fast stochastic observers for spacecraft pointing control. In this special context, "observers" signifies mathematical algorithms, implemented on computers aboard spacecraft, through which one processes sensory data (principally, the outputs of star trackers and...

To reduce response times and save lives in operating rooms, community trauma centers, and remote combat care facilities, a team of scientists working on behalf of Lyndon B. Johnson Space Center (JSC) has developed an artificial-intelligence alarm-management software system that detects...

A method of designing purging flows of clean, dry gases to maintain acceptably low levels of contamination in enclosed volumes has been developed. The method is applicable to diverse enclosures that must be kept clean, including housings of precise optical instruments, clinical facilities, facilities for...

A report describes direct numerical simulations of single- and two-phase, temporally developing transitional mixing layers at Reynolds numbers (based on the initial vorticity thickness and mean velocity difference) from 200 to 600. As many as 300 × 332 ×180 grid points were used to discretize the...

A report describes direct numerical simulations of a droplet-laden mixing layer (e.g., evaporating droplets of a hydrocarbon fuel in air) undergoing a transition to mixing turbulence. The governing equations are those of Lagrangian transport of discrete droplets through a flowing gas, which...

A report describes experiments that generated evidence of thermodynamic instability of nanometer-size islands (quantum dots) in InxGa1–xAs grown on GaAs. InxGa1–xAs/GaAs specimens were grown by metal-organic chemical vapor deposition, using various partial pressures of AsH3....

A method of controlling the crystal-growth habit in directional freezing has been devised. A substance can be purified by directional-freeze crystallization, wherein (1) the liquid phase of the substance is partially frozen, causing impurities to become preferentially concentrated in the...

A theoretical model that predicts the time-dependent behavior of a pyrotechnically actuated mechanism and a computer program that implements the model have been developed. The model and program are especially applicable to a pyrotechnic device known as the NASA Standard Initiator (NSI)....