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881.
S.K. Bhan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(2):95-98
The utility of Landsat data in geosciences has been established beyond doubt. In this paper utility of Landsat data in mineral exploration has been highlighted.The geologic and geomorphic interpretation of Landsat data brought out two very significant and characteristic features in scene 152-046 in the southern part of Orissa. One was distinct tonal anomaly and other was occurance of flat planated surface devoid of vegetation and drainage on top of hills. This when checked on ground at Gandhmardan was found to be bauxite bearing lateritic plateau. When this known information was extrapolated over other regions in scenes 151-046 and 152-046, all other bauxitic — lateritic plateaus were picked up very easily on Landsat imagery.The information was further extrapolated in the southern scene No.152-047 where without doing much detailed geologic and geomorphic interpretation almost all other bauxitic — lateritic bodies occuring in the region were picked up. This proves the utility of Landsat data in mineral exploration.Moreover delineation of extent of such bodies could be done very accurately on Landsat imagery thus saving considerable time in the exploration programme. 相似文献
882.
According to the informational theory of emotions, emotions in humans depend on the power of some need (motivation) and the estimation by the subject of the probability (possibility) of the need satisfaction (the goal achievement). Low probability of need satisfaction leads to negative emotions, actively minimized by the subject. Increased probability of satisfaction, as compared to earlier forecast, generates positive emotions, which the subject tries to maximize, i.e. to enhance, to prolong, to repeat. The informational theory of emotions encompasses their reflective function, the laws of their appearance, the regulatory significance of emotions, and their role in organization of behavior. The level of emotional stress influences the operator's performance. A decrease in the emotional tonus leads to drowsiness, lack of vigilance, missing of significant signals and to slower reactions. An extremely high stress level disorganizes the activity, complicates it with a trend toward incorrect actions and reactions to insignificant signals (false alarms). The neurophysiological mechanisms of the influence of emotions on perceptual activity and operator performance as well as the significance of individuality are discussed. 相似文献
883.
In the above-titled paper (see ibid., vol.AES-23, p.568-82, July 1987) M.I. Dadi and J.R. Marks II studied the relative efficiencies of the Neyman-Pearson optimal detector with respect to the linear and sign detectors, for the detection of a constant signal in additive Laplace noise. By applying the central limit theorem, they derived expressions for three types of asymptotic relative efficiencies (AREs). However, as noted in the above paper, the Gaussian approximation to the sign detector fails to yield the correct asymptotic efficiency. The commenter derives the correct ARE of the optimal detector with respect to the sign detector for the Laplace noise 相似文献
884.
885.
Oli P.V.S. Nagarajan N. Rayan H.R. 《IEEE transactions on aerospace and electronic systems》1993,29(3):696-705
The concept of meridian orbits is briefly reviewed. It is shown that, if a satellite in the meridian orbit makes an odd number (>1) of revolutions per day, then the satellite passes over the same set of meridians twice a day. Satellites in such orbits pass over the same portion of the sky twice a day and every day. This enables a user to adopt a programmed mode of tracking, thereby avoiding a computational facility for orbit prediction, look angle generation, and auto tracking. A constellation of 38 or more satellites placed in a 1200-km altitude circular orbit is favorable for global communications due to various factors. It is shown that appropriate phasing in right ascension of the ascending node and mean anomaly results in a constellation wherein each satellite appears over the user's horizon one satellite after another. Visibility and coverage plots are provided to verify the continuous coverage 相似文献
886.
M. K. Tleulinov 《Russian Aeronautics (Iz VUZ)》2009,52(2):158-164
A method of direct integration with respect to time is proposed to solve dynamic problems of structural mechanics and comparison with the well-known methods is presented. 相似文献
887.
V. F. Pavlov V. A. Kirpichev N. I. Yakovenko D. V. Ivanov 《Russian Aeronautics (Iz VUZ)》2007,50(4):442-445
Residual stresses and endurance strength of specimens with stress concentrators are considered. The results obtained make it possible to predict the fatigue limit of strengthened parts with concentrators in the case of tension-compression. 相似文献
888.
N. P. Velikanova 《Russian Aeronautics (Iz VUZ)》2009,52(4):413-418
The results of low-cycle fatigue tests of smooth cylindrical specimens made of the EI698-VD nickel-base high-temperature alloy
widely used in aircraft engine industry are considered statistically. The influence of such factors as an initial level of
mechanical properties, operating time and temperature of tests is evaluated. The experimental data on low-cycle fatigue (LCF)
are used when determining the cyclic life for disks. 相似文献
889.
Radar Imaging of Mercury 总被引:1,自引:0,他引:1
John K. Harmon 《Space Science Reviews》2007,132(2-4):307-349
Earth-based radar has been one of the few, and one of the most important, sources of new information about Mercury during
the three decades since the Mariner 10 encounters. The emphasis during the past 15 years has been on full-disk, dual-polarization
imaging of the planet, an effort that has been facilitated by the development of novel radar techniques and by improvements
in radar systems. Probably the most important result of the imaging work has been the discovery and mapping of radar-bright
features at the poles. The radar scattering properties of these features, and their confinement to permanently shaded crater
floors, is consistent with volume backscatter from a low-loss volatile such as clean water ice. Questions remain, however,
regarding the source and long-term stability of the putative ice, which underscores the need for independent confirmation
by other observational methods. Radar images of the non-polar regions have also revealed a plethora of bright features, most
of which are associated with fresh craters and their ejecta. Several very large impact features, with rays and other bright
ejecta spreading over distances of 1,000 km or more, have been traced to source craters with diameters of 80–125 km. Among
these large rayed features are some whose relative faintness suggests that they are being observed in an intermediate stage
of degradation. Less extended ray/ejecta features have been found for some of the freshest medium-size craters such as Kuiper
and Degas. Much more common are smaller (<40 km diameter) fresh craters showing bright rim-rings but little or no ray structure.
These smaller radar-bright craters are particularly common over the H-7 quadrangle. Diffuse areas of enhanced depolarized
brightness have been found in the smooth plains, including the circum-Caloris planitiae and Tolstoj Basin. This is an interesting
finding, as it is the reverse of the albedo contrast seen between the radar-dark maria and the radar-bright cratered highlands
on the Moon. 相似文献
890.
Maskery M. Krishnamurthy V. 《IEEE transactions on aerospace and electronic systems》2007,43(3):843-863
The problem of deploying countermeasures (CM) against antiship missiles is investigated from a network centric perspective in which multiple ships coordinate to defend against a known missile threat. Using the paradigm of network enabled operations (NEOPS), the problem is formulated as a transient stochastic game with communication where the appropriate strategy takes the form of an optimal stationary correlated equilibrium. Under this strategy, ships cooperate through real-time communication to satisfy both local and collective interests. The use of communication results in a performance improvement over the noncommunicating, Nash equilibrium scenario. This framework allows us to develop a theoretical foundation for NEOPS and captures the trade-off between information exchange and performance, while generalizing the standard Nash equilibrium solution for the missile deflection game given in [1], The NEOPS equilibrium strategy is characterized as the solution to an optimization problem with linear objective and bilinear constraints, which can be solved calculating successive improvements starting from an initial noncooperative (Nash) solution. The communication overhead required to implement this strategy is associated with the mutual information between individual action probability distributions at equilibrium. Numerical results illustrate the trade-off between communication and performance. 相似文献