Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “trending”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,351 records · Page 75
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Aircraft optimization by a system approach: Achievements and trends

Recently emerging methodology for optimal design of aircraft treated as a system of interacting physical phenomena and parts is examined. The methodology is found to coalesce into methods for hierarchic, non-hierarchic, and hybrid systems all dependent on sensitivity analysis. A separate category of methods has also evolved independent of sensitivity analysis, hence suitable for discrete problems. References and numerical applications are cited. Massively parallel computer processing is seen as enabling technology for practical implementation of the methodology.

Sobieszczanski-Sobieski, Jaroslaw↗
NASA NTRS1992

Precision and radiosonde validation of satellite gridpoint temperature anomalies. I - MSU channel 2. II - A tropospheric retrieval and trends during 1979-90

Monthly 2.5-deg gridpoint anomalies in the Tiros-N satellite series Microwave Sounding Unit channel 2 brightness temperatures during 1979-1988 are evaluated with multiple satellites and radiosonde data for their climate temperature monitoring capability. The MSU anomalies are computed about a 10-yr mean annual cycle at each gridpoint, with the MSUs intercalibrated to a common arbitrary level. The monthly gridpoint anomaly agreement between concurrently operating satellites reveals single-satellite precision generally better than 0.07 C in the tropics and better than 0.15 C at higher latitudes. The removal from channel 2 of the temperature influence above the 30-kPa level is addressed, providing a sharper and thus potentially more useful weighting function for monitoring lower tropospheric temperatures.

Spencer, Roy W.↗
NASA NTRS1992

Technology trends in high temperature pressure transducers: The impact of micromachining

This paper discusses the implications of micromachining technology on the development of high temperature pressure transducers. The introduction puts forth the thesis that micromachining will be the technology of choice for the next generation of extended temperature range pressure transducers. The term micromachining is defined, the technology is discussed and examples are presented. Several technologies for high temperature pressure transducers are discussed, including silicon on insulator, capacitive, optical, and vibrating element. Specific conclusions are presented along with recommendations for development of the technology.

Mallon, Joseph R., Jr.↗
NASA NTRS1992

Relationship between mechanical-property and energy-absorption trends for composite tubes

U.S. Army helicopters are designed to dissipate prescribed levels of crash impact kinetic energy without compromising the integrity of the fuselage. Because of the complexity of the energy-absorption process it is imperative for designers of energy-absorbing structures to develop an in-depth understanding of how and why composite structures absorb energy. A description of the crushing modes and mechanisms of energy absorption for composite tubes and beams is presented. Three primary crushing modes of composite structures including transverse shearing, lamina bending, and local buckling are described. The experimental data presented show that fiber and matrix mechanical properties and laminate stiffness and strength mechanical properties cannot reliably predict the energy-absorption response of composite tubes.

Farley, Gary L.↗
NASA NTRS1992

Aircraft optimization by a system approach - Achievements and trends

Recently emerging methodology for optimal design of aircraft treated as a system of interacting physical phenomena and parts is examined. The methodology is found to coalesce into methods for hierarchic, non-hierarchic, and hybrid systems all dependent on sensitivity analysis. A separate category of methods has also evolved independent of sensitivity analysis, hence suitable for discrete problems. References and numerical applications are cited. Massively parallel computer processing is seen as enabling technology for practical implementation of the methodology.

Sobieszczanski-Sobieski, Jaroslaw↗
NASA NTRS1992

Compositional trends in rock-forming elements of Comet Halley dust

The VEGA 1 and 2 spacecraft flew by Comet P/Halley in 1986 carrying, among other instruments, two mass spectrometers to measure the elemental composition of dust particles emitted from the comet. Most particles seem to be a mixture of silicates of variable magnesium-iron composition and organic matter. Comprehensive study of data and consideration of the mass of dust particles reveal cometary grains of 'unusual' composition: magnesium-rich and iron-rich particles. Magnesium-rich particles are most likely magnesium carbonates, which could not have formed under conditions of equilibrium condensation but rather require formation by aqueous alteration. The composition of the iron-rich particles can also be related to secondary processes in the comet.

Fomenkova, M. N.↗
NASA NTRS1992

Infrared spectra of obscuring dust tori around active galactic nuclei. I - Calculational method and basic trends

Using a new 2D radiative transfer algorithm, we have calculated the thermally reradiated infrared spectra of the compact dust tori which are thought to surround many AGN. These tori radiate anisotropically. Face-on tori may be from one-half to a few orders of magnitude brighter than edge-on tori throughout the infrared. Their spectra at nearly all viewing angles are basically 'bumps' which are about 50 percent wider than blackbodies and peak in the mid-infrared at a wavelength determined mainly by the flux of nuclear radiation on the inner edge of the torus. The infrared color temperatures are hotter for face-on tori than edge-on tori by about 100 K. The 10 micron silicate feature often associated with dust can appear in absorption, emission, or not at all. There is a rough tendency for absorption features to be more prominent for edge-on tori than for face-on tori.

Pier, Edward A.↗
NASA NTRS1992

Space Shuttle payload accommodation and trends in customer demands

This paper will review payload demands for Shuttle resources and services in the pre-Space Station Freedom time frame. Requests for flight in both the Orbiter cargo bay and middeck will be considered. Factors limiting more efficient use of the Shuttle will also be discussed.

Hedin, Daniel L.↗
NASA NTRS1993

Atmospheric methyl bromide - Trends and global mass balance

A decadal time series of global CH3Br concentrations in the earth's atmosphere is presented. It is shown that average concentrations are about 10 pptv and during the last 4 yr may be increasing at 0.3 +/- 0.1 pptv/yr. It is estimated that the atmospheric lifetime of CH3Br that is due to reaction with OH is about 2 yr, which results in a calculated global emission rate of about 100 Gg/yr. Ocean supersaturations of 140-180 percent are observed, and atmospheric concentrations over the open oceans are higher than at comparably located coastal sites. The ocean source is estimated to be about 35 Gg/yr. The remaining emissions must come from other natural sources and anthropogenic activities.

Khalil, M. A. K.↗
NASA NTRS1992

Search for deterministic pulse trends in gamma ray burst temporal profiles

Most cosmic gamma-ray burst temporal profiles appear to be comprised of several individual pulses, many of which overlap. It is advantageous to deconvolve the temporal structures into their constituent pulses, and thereby investigate the shape, intensity and temporal distributions of the pulses as a function of energy. Such fundamental pulse descriptors would provide constraints for theoretical modeling of the burst emission process, such as indications of source size, optical depth and geometry, as a function of time. We have developed a deconvolution algorithm which treats sequences of pulse shapes that change deterministically. The algorithm, a generalization of autoregressive techniques, has been applied to a few bright bursts observed by BATSE. Results indicate that, even within short intervals, constituent pulses are not self-similarly shaped, nor do pulse shapes evolve in a simple manner throughout a burst. Hence, the direction of our future work on pulse deconvolution will focus on analysis methods which allow pulse shape to vary.

Norris, J. P.↗
NASA NTRS1993

Simulations of the trend and annual cycle in stratospheric CO2

Literature data on mid-latitude balloon soundings of CO2 and aircraft sampling in the lower polar stratosphere during the winter are used as a fundamental test of tracer transport in the middle atmospheric version of the GISS GCM (Rind et al., 1990) to predict the propagation into the stratosphere of the annual increase and annual cycle of CO2. The results predict significant propagation of the CO2 annual cycle into the lower stratosphere, an effect which must be accounted for when interpreting observations.

Hall, Timothy M.↗
NASA NTRS1993

Noise Trends of a 0.5 M (20 In.) Diameter Supersonic Throughflow Fan as Measured in an Unmodified Compressor Aerodynamic Test Facility

The tone noise levels of a supersonic throughflow fan were measured at subsonic and supersonic axial duct Mach numbers. The noise in the inlet plenum showed no blade passing and harmonic tones at subsonic or supersonic axial flow conditions. At subsonic axial flow conditions, the supersonic throughflow fan showed no inlet plenum tones at fan operating conditions where tone noise had been previously measured for a subsonic fan design. This lower inlet-quadrant noise level for the supersonic throughflow fan was the result of high subsonic inlet velocities acting to reduce the noise propagating out the inlet. The fan noise, which was prevented from propagating upstream by the high subsonic inlet velocities, appeared to increase the noise in the exhaust duct at subsonic throughflow conditions. The exhaust duct noise decreased at supersonic axial throughflow Mach numbers, with the lowest blade passing and harmonic tones levels being observed at the design axial Mach number of 2.0. Multiple pure tone noise was observed in the inlet duct at subsonic axial flow Mach numbers but was seen only in the exhaust duct at supersonic axial flow conditions.

Dittmar, James H.↗
NASA NTRS1933

Trend of airplane flight characteristics

This report describes the development of airplane characteristics since the war and indicates the direction development should take in the immediate future. Some of the major topics include: the behavior of an airplane about its lateral, vertical, and longitudinal axes. Behavior at large angles of attack and landing characteristics are also included.

Von Koppen, Joachim↗