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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Trends in parts susceptibility to single event upset from heavy ions

New test data from the Jet Propulsion Laboratory (JPL), The Aerospace Corporation, Rockwell International (ANAHEIM) and IRT have been combined with published data of JPL and Aerospace to form a nearly comprehensive body of single event upset (SEU) test data for heavy ion irradiations. This data has been arranged to exhibit the SEU susceptibility of devices by function, technology and manufacturer. Clear trends emerge which should be useful in predicting future device performance.

Nichols, D. K.↗
NASA NTRS1986

Aircraft research and development trends in the US and USSR

Research and development related to aircraft has shown significant progress in both the U.S. and the USSR. In some cases, the indications are that technological advances have resulted in new aircraft concepts and, in other cases, there are indications of particular national needs or objectives that have driven the required research and development to meet the need. The progression of aircraft development tends to reflect factors other than technology such as the political atmosphere, the world environment, and other contending national objectives. The trends in aircraft research and development in the U.S. and USSR will be traced from the early 1900's and, in a time-frame manner, will be related to other influencing factors.

Spearman, M. L.↗
NASA NTRS1987

Environmental trends in extinction during the Paleozoic

Extinction intensities calculated from 505 Paleozoic marine assemblages divided among six environmental zones and 40 stratigraphic intervals indicate that whole communities exhibit increasing extinction offshore but that genera within individual taxonomic classes tend to have their highest extinction onshore. The offshore trend at the community level results from a concentration of genera in classes with low characteristic extinction rates in nearshore environments. This finding is consistent with the ecologic expectation that organisms inhabiting unpredictably fluctuating environments should suffer more extinction than counterparts living under more predictably equitable conditions.

Sepkoski, J. John, Jr.↗
NASA NTRS1987

Mixing levels, the Apennine Front soil component, and compositional trends in the Apollo 15 soils

New compositional data (by INAA) for 29 samples of Apollo 15 soil fractions are presented along with data for six depth intervals of the bottom half of the double drive tube at station 2 on the Apennine Front. The compositional trends in the Apollo 15 soils are discussed in terms of four techniques used to determine the important components of the regolith: graphical techniques, factor analysis, chemical analysis of individual soil particles, and mixing models. The concept of 'mixing levels' is introduced, which states that a sample of lunar regolith can be considered as a mixture on several different compositional levels (I, igneous rock types; II, local rock types; III, soils), and it is shown that most attempts at modeling lunar soils as mixtures have been directed at level II. It is argued that only four components are required to account for the variation in concentrations of lithophile elements in the Apollo 15 samples: mare basalt, KREEP basalt, green glass, and Apennine front soil (best represented by the station 2 samples).

Korotev, Randy L.↗
NASA NTRS1987

Composition and origin of Nuevo Laredo Trend eucrites

The new bulk-rock analyses reported for the ALHA81001, Lakangaon and Nuevo Laredo eucritic meteorites indicate that the first of these resembles Ibitira in possessing lower Na concentrations than any other eucrite, while the other two are the lowest-Mg/Fe of all eucrites. The present data and those seen in the literature suggest that most of the ostensible Main Group eucrites actually belong to the Nuevo Laredo Trend, which is characterized by limited variations of incompatible element contents despite considerable variations in Mg/(Mg+Fe) ratio and V content.

Warren, Paul H.↗
NASA NTRS1986

Computational mechanics - Advances and trends; Proceedings of the Session - Future directions of Computational Mechanics of the ASME Winter Annual Meeting, Anaheim, CA, Dec. 7-12, 1986

The papers contained in this volume provide an overview of the advances made in a number of aspects of computational mechanics, identify some of the anticipated industry needs in this area, discuss the opportunities provided by new hardware and parallel algorithms, and outline some of the current government programs in computational mechanics. Papers are included on advances and trends in parallel algorithms, supercomputers for engineering analysis, material modeling in nonlinear finite-element analysis, the Navier-Stokes computer, and future finite-element software systems.

Noor, Ahmed K.↗
NASA NTRS1986

New measurements of photospheric magnetic fields in late-type stars and emerging trends

The magnetic fields of late-type stars are measured using the method of Saar et al. (1986). The method includes radiative transfer effects and compensation for line blending; the photospheric magnetic field parameters are derived by comparing observed and theoretical line profiles using an LTE code that includes line saturation and full Zeeman pattern. The preliminary mean active region magnetic field strengths (B) and surface area coverages for 20 stars are discussed. It is observed that there is a trend of increasing B towards the cooler dwarfs stars, and the linear correlation between B and the equipartition value of the magnetic field strength suggests that the photospheric gas pressure determines the photospheric magnetic field strengths. A tendency toward larger filling factors at larger stellar angular velocities is also detected.

Saar, S. H.↗
NASA NTRS1987

Digital image classification approach for estimating forest clearing and regrowth rates and trends

A technique is presented to monitor vegetation changes for a selected study area in Costa Rica. A normalized difference vegetation index was computed for three dates of Landsat satellite data and a modified parallelipiped classifier was employed to generate a multitemporal greenness image representing all three dates. A second-generation image was created by partitioning the intensity levels at each date into high, medium, and low and thereby reducing the number of classes to 21. A sampling technique was applied to describe forest and other land cover change occurring between time periods based on interpretation of aerial photography that closely matched the dates of satellite acquisition. Comparison of the Landsat-derived classes with the photo-interpreted sample areas can provide a basis for evaluating the satellite monitoring technique and the accuracy of estimating forest clearing and regrowth rates and trends.

Sader, Steven A.↗
NASA NTRS1987

TOMS: The Antarctic ozone hole and ozone trends

The Total Ozone Mapping Spectrometer (TOMS) instrument aboard Nimbus 7 has proved invaluable for the investigation of the recent rapid decline in the springtime total ozone over the Antarctic. The principle problem discussed is that of observing the atmosphere over long periods of time to determine whether or not trends and/or slow oscillations are taking place. Total ozone is an excellent summary parameter for the state of the stratosphere. It responds to temperature changes, and in the long term, is expected to respond to chemical changes. Thus, when changes take place in total ozone, such as the springtime Antarctic decrease it is a clear indication of an important problem, both because of environmental potential and scientific importance. TOMS is actually an overkill for this problem. Significantly more data is taken than is necessary. Tests have shown that maps produced on a 2 by 4 degree grid are essentially equivalent to those produced from the entire gridded data set. Because the critical aspect of the search for changes in ozone is continuous data, reflight of a polar orbiting TOMS is important. Included in the flight should be a stratospheric temperature sensor and, if possible, a modification to obtain some ozone altitude information. A critical aspect of the problem is timeliness of the data. This is the only drawback of the existing TOMS. It is expected that in the very near future the processing will be done within two weeks of real time. This is critical to the process of discovery of phenomena such as the Antarctic ozone hole.

Stolarski, Richard S.↗
NASA NTRS1987

Pattern recognition techniques for failure trend detection in SSME ground tests

The Space Shuttle Main Engine (SSME) is a complex power plant. To evaluate its performance 1200 hot-wire ground tests have been conducted, varying in duration from 0 to 500 secs. During the test some 500 sensors are sampled every 20 ms. The sensors are generally bounded by red lines so that an excursion beyond could lead to premature shutdown. In 27 tests it was not possible to effect an orderly premature shutdown, resulting in major incidents with serious damage to the SSME and test stand. The application of pattern recognition are investigated to detect SSME performance trends that may lead to major incidents. Based on the sensor data a set of (n) features is defined. At any time during the test, the state of the SSME is given by a point in the n-dimensional feature space. The history of a test can now be represented as a trajectory in the n-dimensional feature space. Portions of the normal trajectories and failed test trajectories would lie in different regions of the n-dimensional feature space. The latter can now be partitioned into regions of normal and failed tests. Thus, it is possible to examine the trajectory of a test in progress and predict if it is going into the normal or failure region.

Choudry, A.↗
NASA NTRS1987

Geometric versus finite element modeling current and future trends at Northrop

Engineering Automation at Northrop encompasses the various design and analytical phases of air vehicle development. Design systems addresses automation of engineering/tooling design and computer aided manufacturing processes. The analysis systems automate aeroelastic modeling and postprocessing analysis results. These systems interface with aircraft loft and geometric entities thru localized transfer techniques. However, total integration effort based on a geometric database nucleus with peripheral design, analytical and manufacturing systems is well underway. An outline of the present and future trends is presented to help channel the RPI effort in this direction.

Bajaj, Shiv K.↗
NASA NTRS1987

Atmospheric trends in methylchloroform and the global average for the hydroxyl radical

ALE-GAGE (Atmospheric Lifetime Experiment-Global Atmospheric Gases Experiment) data obtained over the seven-year period from July 1978 to June 1985 are presented and interpreted. The data, combined with knowledge of industrial emissions, are used in an optimal estimation inversion scheme to deduce a globally average methylchloroform atmospheric lifetime of 6.3(+ 1.2, - 0.9) years (1 sigma uncertainty) and a globally averaged tropospheric hydroxyl radical concentration of (7.7 + or - 1.4) x 10 to the 5th radicals/cu cm (1 sigma uncertainty). These results provide the most accurate estimates yet of the trends and lifetime of methylchloroform and of the global average for tropospheric hydroxyl radical levels.

Prinn, R.↗
NASA NTRS1987

Global trends of measured surface air temperature

The paper presents the results of surface air temperature measurements from available meteorological stations for the period of 1880-1985. It is shown that the network of meteorological stations is sufficient to yield reliable long-term, decadal, and interannual temperature changes for both the Northern Hemisphere and the Southern Hemisphere, despite the fact that most stations are located on the continents. The results indicate a global warming of about 0.5-0.7 C in the past century, with warming of similar magnitude in both hemispheres. A strong warming trend between 1965 and 1980 raised the global mean temperature in 1980 and 1981 to the highest level in the period of instrumental records. Selected graphs of the temperature change in each of the eight latitude zones are included.

Hansen, James↗
NASA NTRS1988

Current status and future trends in turbine application of thermal barrier coatings

This paper provides an overview of the current status and future trends in application of thermal barrier coatings (TBC) to turbine components, and in particular to high turbine airfoils. Included are descriptions of the favorable results achieved to date with bill-of-material applications of plasma deposited TBC, and recent experience with developmental coatings applied by electron beam-physical vapor deposition.

Sheffler, Keith D.↗
NASA NTRS1989

Trends In Susceptibility To Single-Event Upset

Report provides nearly comprehensive body of data on single-event upsets due to irradiation by heavy ions. Combines new test data and previously published data from governmental and industrial laboratories. Clear trends emerge from data useful in predicting future performances of devices.

Nichols, Donald K.↗
NASA NTRS1986

Recent trends related to the use of formal methods in software engineering

An account is given of some recent developments and trends related to the development and use of formal methods in software engineering. Ongoing activities in Europe are focussed on, since there seems to be a notable difference in attitude towards industrial usage of formal methods in Europe and in the U.S. A more detailed account is given of the currently most widespread formal method in Europe: the Vienna Development Method. Finally, the use of Ada is discussed in relation to the application of formal methods, and the potential for constructing Ada-specific tools based on that method is considered.

Prehn, Soren↗
NASA NTRS1988

The absence of a color-distance trend in comets

New near-IR J-H and H-K observations of 23 comets have been obtained in the heliocentric distance range of 1 to 6 AU. No evidence is found for a color-distance trend in the present sample. Significant differences between the grain populations in different comets are pointed out. The results indicate that the color distributions are unimodal, and that, unlike asteroids, the comets cannot be classified into distinct color-defined groups.

Jewitt, D.↗