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111.
J. Park K.W. Min V.P. Kim H. Kil H.J. Kim J.J. Lee E. Lee S.J. Kim D.Y. Lee M. Hairston 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(4):650-654
The global distribution of low-latitude plasma blobs was investigated by in-situ plasma density measurements from the Korea Multi-Purpose Satellite-1 (KOMPSAT-1) and Defense Meteorological Satellite Program (DMSP) F15. In the observations, blobs occurred in the longitude sector where the activity of the equatorial plasma bubble (EPB) was appreciable, and additional blobs were found at the lower (KOMPSAT-1) altitude as in the EPBs. However, several notable differences exist between the distributions of EPBs and blobs. First, KOMPSAT-1 found few blobs around 0°E in March and June, as did DMSP F15 from 30°W to 120°E for every season. Second, the overall occurrences in December and March at the DMSP F15 (840 km) altitude were somewhat lower than expected from those of the EBPs. Third, at the DMSP F15 altitude, the occurrence probability of plasma blobs was less controlled by yearly variations in the solar activity. These results imply that topside ionospheric conditions as well as the existence of EPBs control further development of blobs. Additionally, it was found that the blob latitudes became higher as the yearly solar activity increased. Moreover, most of the blobs were encountered in the winter hemisphere, possibly due to the low ambient density. 相似文献
112.
For pt.I, see ibid., vol.28, no.3, p.829-840 (1992). In the central-limit control (CLC), the multiloop controls are employed to regulate the output voltage and track the central weighted current, thus equalizing the output current of each converter module (CM). The current distribution error (CDE) between the output current of each CM is used as a criterion in judging system performance. The prediction and simulation results of this control scheme are illustrated. When incorporated with the maximum current limit, the proposed control method can determine the number of required converters in the active state for each load condition. As a result, the efficiency of a system can be increased significantly. A comparison between the performances of the system under master-slave control (MSC) and CLC is given 相似文献
113.
four widely used self-oscillating dc-to-square-wave parallel inverters which employ an inductor-capacitor tuned network to determine the oscillation frequency are reduced to a common equivalent RLC network. The techniques of singular-point analysis and state-plane interpretations are employed to describe the steady-state and transient ient behavior of these circuits and to elucidate the three possible modes of operation: quasi-harmonic, relaxation, and discontinuous. Design guidelines are provided through a study of the influence of circuit parameter variations on the characteristics of oscillation and on frequency stability. Several examples are provided to illustrate the usefulness of this analysis when studying such problems as transistor emitter-to-base junction breakdown during oscillations and the design of starting circuits to insure self-excited oscillations in these inverters. 相似文献
114.
Lee F.C.Y. Wilson T.G. Feng S.Y.M. 《IEEE transactions on aerospace and electronic systems》1973,(4):571-584
A familiar two-transistor saturable-core parallel inverter is modeled as a nonlinear negative resistance in parallel with energy-storage elements. The techniques of singular-point analysis are combined with piecewise linear techniques to permit determination of solution trajectories on the phase plane. Clear insight is provided, not only into steady-state oscillation, but also into transient behavior of the circuit. Experimental results confirming the analytical model are included. 相似文献
115.
In this study, a process for establishing design requirements and selecting alternative con-figurations for the conceptual phase of aircraft design has been proposed. The proposed process uses system-engineering-based requirement-analysis techniques such as objective tree, analytic hier-archy process, and quality function deployment to establish logical and quantitative standards. Moreover, in order to perform a logical selection of alternative aircraft configurations, it uses advanced decision-making methods such as morphological matrix and technique for order prefer-ence by similarity to the ideal solution. In addition, a preliminary sizing tool has been developed to check the feasibility of the established performance requirements and to evaluate the flight perfor-mance of the selected configurations. The present process has been applied for a two-seater very light aircraft (VLA), resulting in a set of tentative design requirements and two families of VLA configurations: a high-wing configuration and a low-wing configuration. The resulting set of design requirements consists of three categories: customer requirements, certification requirements, and performance requirements. The performance requirements include two mission requirements for the flight range and the endurance by reflecting the customer requirements. The flight performances of the two configuration families were evaluated using the sizing tool developed and the low-wing configuration with conventional tails was selected as the best baseline configuration for the VLA. 相似文献
116.
R. J. Lillis D. A. Brain S. W. Bougher F. Leblanc J. G. Luhmann B. M. Jakosky R. Modolo J. Fox J. Deighan X. Fang Y. C. Wang Y. Lee C. Dong Y. Ma T. Cravens L. Andersson S. M. Curry N. Schneider M. Combi I. Stewart J. Clarke J. Grebowsky D. L. Mitchell R. Yelle A. F. Nagy D. Baker R. P. Lin 《Space Science Reviews》2015,196(1-4):357-358
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119.
J T Lett A B Cox A C Lee 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1986,6(11):295-303
Aspects of experiments on radiation-induced lenticular opacification during the life spans of two animal models, the New Zealand white rabbit and the rhesus monkey, are compared and contrasted with published results from a life span study of another animal model, the beagle dog, and the most recent data from the ongoing study of the survivors from radiation exposure at Hiroshima and Nagasaki. An important connection among the three animal studies is that all the measurements of cataract indices were made by one of the authors (A.C.L.), so variation form personal subjectivity was reduced to a minimum. The primary objective of the rabbit experiments (radiations involved: 56Fe, 40Ar and 20Ne ions and 60Co gamma photons) is an evaluation of hazards to astronauts from galactic particulate radiations. An analogous evaluation of hazards from solar flares during space flight is being made with monkeys exposed to 32, 55, 138 and 400 MeV protons. Conclusions are drawn about the proper use of animal models to simulate radiation responses in man and the levels of radiation-induced lenticular opacification that pose risks to man in space. 相似文献
120.
Siouris G.M. Jang Gyu Lee Jae Weon Choi 《IEEE transactions on aerospace and electronic systems》1995,31(2):730-738
The development of a pitch pointing control system for an advanced high performance fighter aircraft using eigenstructure assignment and command generator tracking schemes is presented. A desired eigenstructure is first chosen to achieve a desired decoupling (i.e., pitch attitude and flight path angle), and to obtain a desired damping and rise time. The command generator tracker is next used to ensure zero steady-state error-to-step commands. The stability robustness to the parameter variations of the closed-loop system is evaluated in the sense of the conditioning of the achieved eigenstructure by using singular value analysis technique. The analysis and synthesis techniques for the pitch pointing control system are illustrated by applying the techniques to F-15 aircraft as a part of the NASA/USAF program named ACTIVE (Advanced Controls for integrated Vehicles) 相似文献