Thermal metamorphism of primitive meteorites. IV - Comparison with trends for ten trace elements in terrestrial basalt BCR-1 heated at 500-1000 C
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Ikramuddin, M.↗
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Future trends in electrical energy generation economics in the United States
Developments related to the economics of coal-fired systems in the U.S. are mainly considered. The historical background of the U.S. electric generation industry is examined and the U.S. electrical generation characteristics in the year 1975 are considered. It is pointed out that coal-fired power plants are presently the largest source of electrical energy generation in the U.S. Questions concerning the availability and quality of coal are investigated. Currently there are plans for converting some 50 large oil and gas-fired generating plants to coal, and it is expected that coal will be the fuel used in almost all fossil-fired base load additions to generating capacity. Aspects of advanced energy conversion from coal are discussed, taking into account the performance and economic potential of the energy conversion systems.
Schmitt, R. W.↗
Flight simulators. Part 1: Present situation and trends. Part 2: Implications for training
The present situation and developments in the technology of flight simulators based on digital computers are evaluated from the standpoint of training airline flight crews. Areas covered are minicomputers and their advantages in terms of cost, space and time savings, software data packets, motion simulation, visual simulation and instructor aids. The division of training time between aircraft and simulator training and the possible advantages from increased use of simulators are evaluated.
Hass, D.↗
An analysis of the gust-induced overspeed trends of helicopter rotors
Equations for analyzing the potential gust-induced overspeed tendency of helicopter rotors are presented. A parametric analysis was also carried out to illustrate the sensitivity of rotor angular acceleration to changes in rotor lift, propulsive force, tip speed, and forward velocity.
Jenkins, J. L., Jr.↗
Measurement of soil moisture trends with airborne scatterometers
The author had identified the following significant results. Repeated looks at surfaces that maintain constant roughness can provide an estimate of soil moisture in the surface, when appropriate radar look angles are used. Significant influence due to differences in soil moisture can be detected in the 13.3 GHz and 1.6 GHz scatterometer returns. Effects of normal crop densities have little influence on the surface soil moisture estimate, when appropriate look angles are used. It appears that different look angles are optimum for different frequencies to avoid effects from vegetation. Considering the frequency and look angles used on the Seasat-A imaging radar, differences in soil moisture should produce as much as 9 db difference in return on that system.
Blanchard, B. J.↗
The crystallisation trends of spinels in tertiary basalts from Rhum and Muck and their petrogenetic significance
Spinels found in transitional olivine basalts from the Islands of Rhum and Muck in the British Tertiary Province are analyzed to determine their chemical variability and their relationship to silicate phases. Chemical zoning of the cores of spinels which spilled into the basaltic liquid may be due to a reaction between the spinel and the liquid resulting in more Fe- and Ti-rich spinels. In addition, a peritectic-type reaction seems to have occurred, causing the transformation of aluminum spinel to chrome spinel with precipitation of plagioclase. Changes in the basaltic liquid are reflected by these transformations in the spinel composition.
Ridley, W. I.↗
New trends in cosmology
A review of big-bang cosmology is presented, emphasizing the big-bang model, hypotheses on the origin of galaxies, observational tests of the big-bang model that may be possible with the Large Space Telescope, and the scale-covariant theory of gravitation. Detailed attention is given to the equations of general relativity, the redshift-distance relation for extragalactic objects, expansion of the universe, the initial singularity, the discovery of the 3-K blackbody radiation, and measurements of the amount of deuterium in the universe. The curvature of the expanding universe is examined along with the magnitude-redshift relation for quasars and galaxies. Several models for the origin of galaxies are evaluated, and it is suggested that a model of galaxy formation via the formation of black holes is consistent with the model of an expanding universe. Scale covariance is discussed, a scale-covariant theory is developed which contains invariance under scale transformation, and it is shown that Dirac's (1937) large-numbers hypothesis finds a natural role in this theory by relating the atomic and Einstein units.
Canuto, V. M.↗
Trends in modern system theory
The topics considered are related to linear control system design, adaptive control, failure detection, control under failure, system reliability, and large-scale systems and decentralized control. It is pointed out that the design of a linear feedback control system which regulates a process about a desirable set point or steady-state condition in the presence of disturbances is a very important problem. The linearized dynamics of the process are used for design purposes. The typical linear-quadratic design involving the solution of the optimal control problem of a linear time-invariant system with respect to a quadratic performance criterion is considered along with gain reduction theorems and the multivariable phase margin theorem. The stumbling block in many adaptive design methodologies is associated with the amount of real time computation which is necessary. Attention is also given to the desperate need to develop good theories for large-scale systems, the beginning of a microprocessor revolution, the translation of the Wiener-Hopf theory into the time domain, and advances made in dynamic team theory, dynamic stochastic games, and finite memory stochastic control.
Athans, M.↗
Trends in aerospace structures
Recent developments indicate that there may soon be a revolution in aerospace structures. Increases in allowable operational stress levels, utilization of high-strength, high-toughness materials, and new structural concepts will highlight this advancement. Improved titanium and aluminum alloys and high-modulus, high-strength advanced composites, with higher specific properties than aluminum and high-strength nickel alloys, are expected to be the principal materials. Significant advances in computer technology will cause major changes in the preliminary design cycle and permit solutions of otherwise too-complex interactive structural problems and thus the development of vehicles and components of higher performance. The energy crisis will have an impact on material costs and choices and will spur the development of more weight-efficient structures. There will also be significant spinoffs of aerospace structures technology, particularly in composites and design/analysis software.
Card, M. F.↗
Needs and trends in structural dynamics
The paper discusses dynamic analyses and testing of aerospace vehicles and the application of such analyses and testing to nonaerospace fields. Items covered in the section on dynamic analyses of aerospace vehicles include self-induced and forced oscillatory loads, approaches to dynamic modeling and analysis, nonlinear analyses, and integrated dynamics design and optimization. Items covered in the section on the dynamic testing of aerospace vehicles include integrated test philosophy, test facilities, and ways of improving performance and reducing costs. The nonaerospace applications that are discussed include ground and water transportation, medicine, and nuclear power plants.
Morosow, G.↗
Trends in Langley helicopter noise research
A broad perspective of needs in helicopter exterior and interior control is presented. Emphasis is given to those items which support noise certification of civil helicopters and which result in reduced environmental noise impact to community residents as well as to helicopter passengers. The activities described are related to the Langley responsibilities for helicopter acoustics as defined by NASA roles and missions.
Hubbard, H. H.↗
On volatile element trends in gas-rich meteorites
Ten volatile elements (and non-volatile Co) in co-existing light and dark portions of 5 gas-rich chondrites were studied. Patterns of distinct but non-uniform enrichment by dark admixing material are revealed. The dark admixing material is enriched in Cs; Bi and Tl covary in it. It is compositionally unique from known types of primitive materials and is apparently not derived by secondary processes from such materials.
Bart, G.↗
Trends in reliability modeling technology for fault tolerant systems
Reliability modeling for fault tolerant avionic computing systems was developed. The modeling of large systems involving issues of state size and complexity, fault coverage, and practical computation was discussed. A novel technique which provides the tool for studying the reliability of systems with nonconstant failure rates is presented. The fault latency which may provide a method of obtaining vital latent fault data is measured.
Bavuso, S. J.↗
Preliminary trend monitoring system data manager's guide
The functions and data base structures that the data base manager will be responsible for maintaining are documented. All normal and error sequences are included.
Turberville, L.↗
Platforms in space: Evolutionary trends
The problem of physical crowding and the proliferation of separate communication links and ground support systems for multiple free-flying satellites can be overcome by using space platforms and multiplexing the data streams. Pertinent features of the space shuttle orbiter payloads, the solar power satellite, and geostationary and geosynchronous platforms are discussed. Typical payload requirements data which are needed to allow meaningful study of payloads as candidates for platform implementation are cited and factors affecting the compatibility/grouping of payloads are outlined.
Butler, J. M., Jr.↗
Measurement of soil moisture trends with airborne scatterometers
There are no author-identified significant results in this report.
Blanchard, B. J.↗
Silicon solar cells for space use: Present performance and trends
A technology assessment of present performance levels and current fabrication methods and designs is presented.
Iles, P. A.↗
Trends in the automation of planetary spacecraft
The automation of planetary spacecraft at the Jet Propulsion Laboratory (JPL) is discussed. Factors affecting the development of spacecraft automation, such as predictable and repetitive functions and narrow time-window, are analyzed. The volume of command data transmitted to the spacecraft is considered, together with an examination of 'autonomy' (executing functions without outside control) in relation to the ground command activity needed during the mission. The role of the spacecraft's growing computational power in increasing vehicle autonomy is noted.
Bird, T. H.↗