Physical Sciences

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)....

Ceramic static-strain gauges capable of generating mechanical-strain signals much larger than spurious thermal signals have been invented. These gauges are intended for use at temperatures from room temperature to 1,250 °C. Heretofore, external circuits have been used to provide temperature...

Image-plane multidither sensing has been found to be suitable for adaptive wavefront correction in a large telescope in which the main optic is a precise reflector divided into lightweight, controllably actuated segments. In image-plane multidither sensing, the telescope is aimed at a star...

A two-photon microscope imaging spectrometer has been proposed for use in scanning confocal two-photon microscopy. The proposed instrument would solve a spectrum-overlap that sometimes arises, as explained below.

A report proposes the use of lightweight balloon-borne instrumentation systems for exploration in the vicinity of a lander on the surface of Mars. Each system would comprise instrumentation with a mass of about 0.2 kg and a balloon with a mass of about 0.8 kg and volume of about 50 m3. The...