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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Light and buffer-gas frequency shifts in the Rb-85 maser frequency standard.

The effect of buffer gas and pumping light on the output frequency of the Rb-85 maser is discussed. In contrast to a primary standard, these frequency shifts can be used to advantage when it is necessary to operate the maser at a frequency which differs from the ground-state hyperfine frequency by a few kilohertz. Using appropriate mixtures of buffer gas and carefully shaped lamp spectral profiles, it is also possible to operate the maser exactly at the ground-state hyperfine frequency. It is pointed out that the short-term phase stability of the maser is not impaired by these shifts.

Stern, W. A.↗
NASA NTRS1971

Compatibility of buffered uranium carbides with tungsten.

Results of compatibility tests between tungsten and hyperstoichiometric uranium carbide alloys run at 1800 C for 1000 and 2500 hours. These tests compared tungsten-buffered uranium carbide with tungsten-buffered uranium-zirconium carbide. The zirconium carbide addition appeared to widen the homogeneity range of the uranium carbide, making additional carbon available for reaction. Reaction layers could be formed by either of two diffusion paths, one producing UWC2, while the second resulted in the formation of W2C. UWC2 acts as a diffusion barrier for carbon and slows the growth of the reaction layer with time, while carbon diffusion is relatively rapid in W2C, allowing equilibrium to be reached in less than 2500 hours at a temperature of 1800 C.

Phillips, W. M.↗
NASA NTRS1974

Fracture of composite plates containing periodic buffer strips

Fracture of a composite plate which consists of perfectly bonded parallel load carrying laminates and buffer strips is considered. Fatigue cracks appear and spread in main laminates or in buffer strips or in both perpendicular to the interfaces. The external load is applied to the plate parallel to the strips and away from the crack region. The problem is solved for fully imbedded cracks and for broken laminates or strips. Corresponding stress intensity factors are calculated.

Erdogan, F.↗
NASA NTRS1976

A 128K-bit CCD buffer memory system

A prototype system was implemented to demonstrate that CCD's can be applied advantageously to the problem of low power digital storage and particularly to the problem of interfacing widely varying data rates. 8K-bit CCD shift register memories were used to construct a feasibility model 128K-bit buffer memory system. Peak power dissipation during a data transfer is less than 7 W., while idle power is approximately 5.4 W. The system features automatic data input synchronization with the recirculating CCD memory block start address. Descriptions are provided of both the buffer memory system and a custom tester that was used to exercise the memory. The testing procedures and testing results are discussed. Suggestions are provided for further development with regards to the utilization of advanced versions of CCD memory devices to both simplified and expanded memory system applications.

Siemens, K. H.↗
NASA NTRS1978

Preliminary investigation of crack arrest in composite laminates containing buffer strips

The mechanical properties of some hybrid buffer strip laminates and the crack arrest potential of laminates containing buffer strips were determined. The hybrid laminates consisted of graphite with either S-glass, E-glass, or Kevlar. Unnotched tensile coupons and center-cracked fracture coupons were tested. Elastic properties, complete stress/strain curves, and critical stress intensity values are given. The measured elastic properties compare well with those calculated by classical lamination theory for laminates with linear stress/strain behavior. The glass hybrids had more delamination and higher fracture toughness than the all-graphite or the Kevlar hybrid.

Goree, J. G.↗
NASA NTRS1981

Common data buffer

Time-shared interface speeds data processing in distributed computer network. Two-level high-speed scanning approach routes information to buffer, portion of which is reserved for series of "first-in, first-out" memory stacks. Buffer address structure and memory are protected from noise or failed components by error correcting code. System is applicable to any computer or processing language.

Byrne, F.↗
NASA NTRS1979

Test evaluation of shock buffering concept for hydrodynamic ram induced by yawing projectile impacting a simulated integral fuel tank

A concept for containing the shock inputs due to hydrodynamic ram caused by an impacting projectile within a fuel cell is discussed. This is to provide a buffering layer of foam, flexible, rigid or a combination thereof, which is sealed from the liquid. A program is described in which this buffering concept was tested. The effectiveness of a novel muzzle-mounted, 'tumble', test device is shown.

Zabel, P. H.↗
NASA NTRS1980

Collisional narrowing by polyatomic buffer gases in an optically pumped CH3F laser

The gain linewidth of an optically pumped CH3F molecular laser is observed with the addition of various polyatomic buffer gases. This is interpreted as collisional (Dicke) narrowing. The measurement is the first observation of collisional narrowing by polyatomic buffer gases. It is also the first observation of the effect in a laser oscillator. The effect was observed using a heterodyne mixing technique at the laser emission frequency of 604 GHz. Collision cross sections for SF6-CH3F and CS2-CH3F are obtained.

Lawandy, N. M.↗
NASA NTRS1980

Detection of individual atoms in helium buffer gas and observation of their real-time motion

Single atoms are detected and their motion measured for the first time to our knowledge by the fluorescence photon-burst method in the presence of large quantities of buffer gas. A single-clipped digital correlator records the photon burst in real time and displays the atom's transit time across the laser beam. A comparison is made of the special requirements for single-atom detection in vacuum and in a buffer gas. Finally, the probability distribution of the bursts from many atoms is measured. It further proves that the bursts observed on resonance are due to single atoms and not simply to noise fluctuations.

Pan, C. L.↗
NASA NTRS1982

Venus - Chemical weathering of igneous rocks and buffering of atmospheric composition

Data from the Pioneer Venus radar mapper, combined with measurements of wind velocity and atmospheric composition, suggest that surface erosion on Venus varies with altitude. Calcium- and magnesium-rich weathering products are produced at high altitudes by gas-solid reactions with igneous minerals, then removed into the hotter lowlands by surface winds. These fine-grained weathering products may then rereact with the lower atmosphere and buffer the composition of the observed gases carbon dioxide, water vapor, sulfur dioxide, and hydrogen fluoride in some regions of the surface. This process is a plausible mechanism for the establishment in the lowlands of a calcium-rich mineral assemblage, which had previously been found necessary for the buffering of these species.

Nozette, S.↗
NASA NTRS1985

FIFO Buffer for Asynchronous Data Streams

Variable-rate, asynchronous data signals from up to four measuring instruments or other sources combined in first-in/first-out (FIFO) buffer for transmission on single channel. Constructed in complementary metal-oxide-semiconductor (CMOS) logic, buffer consumes low power (only 125 mW at 5V) and conforms to aerospace standards of reliability and maintainability.

Bascle, K. P.↗
NASA NTRS1985

Development anmd testing of electrophoresis solutions. Task I.1: Development of optimal buffer system

Two buffers were explored for testing: low ionic strength electrophoresis buffer with and without density gradient material. It was found that the electrophoresis routine was better tolerated when Ficoll was present. The results of a viability study of primary human fetal kidney (HFK-1) cells at the first passage are shown. Cell strain HFK-1 was used in several experiments at the first and second passage. The HFK consisted mainly of fibroblasts, and HFK-1 has a high epithelioid cell content. The chromosomes of HFK were examined and found to be euploid. The stock medium for cell electrophoresis is described. In this solution density gradient solutes such as sucrose and Ficoll are dissolved to bring the osmolarity to 0.30. Its ionic strength is less than 0.01M, and its conductivity is usually 0.0011 mho/cm. Methods for viability determination included direct microscopic counting of the percent cells attached and spread within 24 hr of plating test cultures or electrophoretically separated fractions. The Cytograf viability assay concept was tested, and shown that blue stained cells scatter less light into the 0.8 to 3.3 deg angular interval than do unstained cells.

Source record↗
NASA NTRS1985

The formation of stable pH gradients with weak monovalent buffers for isoelectric focusing in free solution

Two methods which utilize simple buffers for the generation of stable pH gradients (useful for preparative isoelectric focusing) are compared and contrasted. The first employs preformed gradients comprised of two simple buffers in density-stabilized free solution. The second method utilizes neutral membranes to isolate electrolyte reservoirs of constant composition from the separation column. It is shown by computer simulation that steady-state gradients can be formed at any pH range with any number of components in such a system.

Mosher, Richard A.↗
NASA NTRS1991

Y1Ba2Cu3O(6+delta) growth on thin Y-enhanced SiO2 buffer layers on silicon

SiO2 buffer layers as thin as 2 nm have been developed for use in the growth of Y1Ba2Cu3O(6+delta) thin films on silicon substrates. The SiO2 layers are formed through Y enhancement of silicon oxidation, and are highly stoichiometric. Y1Ba2Cu3O(6+delta) film growth on silicon with thin buffer layers has shown c orientation and Tc0 = 78 K.

Robin, T.↗
NASA NTRS1990

Synthetic laser range imagery using Z-buffering

A technique for simulating laser range imagers using Z-buffering and readily available 3D graphics hardware is described. This approach utilizes the graphics hardware features available for hidden surface removal to achieve faster than real-time speed. How Z-buffering works in graphics workstations, how it can be adapted to provide a simulation of laser range images, and the performance characteristics of this simulation on a computer are shown.

Norsworthy, Robert↗
NASA NTRS1993

Spacecraft optical disk recorder memory buffer control

This paper discusses the research completed under the NASA-ASEE summer faculty fellowship program. The project involves development of an Application Specific Integrated Circuit (ASIC) to be used as a Memory Buffer Controller (MBC) in the Spacecraft Optical Disk System (SODR). The SODR system has demanding capacity and data rate specifications requiring specialized electronics to meet processing demands. The system is being designed to support Gigabit transfer rates with Terabit storage capability. The complete SODR system is designed to exceed the capability of all existing mass storage systems today. The ASIC development for SODR consist of developing a 144 pin CMOS device to perform format conversion and data buffering. The final simulations of the MBC were completed during this summer's NASA-ASEE fellowship along with design preparations for fabrication to be performed by an ASIC manufacturer.

Hodson, Robert F.↗
NASA NTRS1994

The Buffer Diagnostic Prototype: A fault isolation application using CLIPS

This paper describes problem domain characteristics and development experiences from using CLIPS 6.0 in a proof-of-concept troubleshooting application called the Buffer Diagnostic Prototype. The problem domain is a large digital communications subsystems called the real-time network (RTN), which was designed to upgrade the launch processing system used for shuttle support at KSC. The RTN enables up to 255 computers to share 50,000 data points with millisecond response times. The RTN's extensive built-in test capability but lack of any automatic fault isolation capability presents a unique opportunity for a diagnostic expert system application. The Buffer Diagnostic Prototype addresses RTN diagnosis with a multiple strategy approach. A novel technique called 'faulty causality' employs inexact qualitative models to process test results. Experimental knowledge provides a capability to recognize symptom-fault associations. The implementation utilizes rule-based and procedural programming techniques, including a goal-directed control structure and simple text-based generic user interface that may be reusable for other rapid prototyping applications. Although limited in scope, this project demonstrates a diagnostic approach that may be adapted to troubleshoot a broad range of equipment.

Porter, Ken↗
NASA NTRS1996

The Effects of Acetate Buffer Concentration on Lysozyme Solubility

The micro-solubility column technique was employed to systematically investigate the effects of buffer concentration on tetragonal lysozyme solubility. While keeping the NaCl concentrations constant at 2%, 3%, 4%, 5% and 7%, and the pH at 4.0, we have studied the solubility of tetragonal lysozyme over an acetate buffer concentration range of 0.01M to 0.5M as a function of temperature. The lysozyme solubility decreased with increasing acetate concentration from 0.01M to 0.1M. This decrease may simply be due to the net increase in solvent ionic strength. Increasing the acetate concentration beyond 0.1M resulted in an increase in the lysozyme solubility, which reached a peak at - 0.3M acetate concentration. This increase was believed to be due to the increased binding of acetate to the anionic binding sites of lysozyme, preventing their occupation by chloride. In keeping with the previously observed reversal of the Hoffmeister series for effectiveness of anions in crystallizing lysozyme, acetate would be a less effective precipitant than chloride. Further increasing the acetate concentration beyond 0.3M resulted in a subsequent gradual decrease in the lysozyme solubility at all NaCl concentrations.

Forsythe, Elizabeth L.↗