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151.
Multiple-model estimation with variable structure- part VI: expected-mode augmentation 总被引:2,自引:0,他引:2
Rong Li X. Jilkov V.P. Ru J. 《IEEE transactions on aerospace and electronic systems》2005,41(3):853-867
A new class of variable-structure (VS) algorithms for multiple-model (MM) estimation is presented, referred to as expected-mode augmentation (EMA). In the EMA approach, the original set of models is augmented by a variable set of models intended to match the expected value of the unknown true mode. These models are generated adaptively in real time as (globally or locally) probabilistically weighted sums of mode estimates over the model set. This makes it possible to cover a large continuous mode space by a relatively small number of models at a given accuracy level. The paper presents new theoretical results for model-set design, a general formulation of the EMA approach, along with theoretical analysis and justification, and three algorithms for its practical implementation. The performance of the proposed EMA algorithms is evaluated via simulation of a generic maneuvering target tracking problem. 相似文献
152.
不同厚度试样的疲劳裂纹扩展试验及断口微观分析表明,恒幅加载低应力比飞行模拟载荷条件下具有明显的厚度影响。考查了模型对厚度影响的预测能力。Newman的模型具有预测厚度影响的潜力,广义改进的wellenborg模型不含有厚度影响的考虑,即使通过调整约束系数α的方法也不能计及厚度的影响。厚度对裂纹增长影响的物理原因及模型化有待于进一步研究。 相似文献
153.
J.G. Luhmann S.A. Ledvina D. Odstrcil M.J. Owens X.-P. Zhao Yang Liu Pete Riley 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
The problem of modeling solar energetic particle (SEP) events is important to both space weather research and forecasting, and yet it has seen relatively little progress. Most important SEP events are associated with coronal mass ejections (CMEs) that drive coronal and interplanetary shocks. These shocks can continuously produce accelerated particles from the ambient medium to well beyond 1 AU. This paper describes an effort to model real SEP events using a Center for Integrated Space weather Modeling (CISM) MHD solar wind simulation including a cone model of CMEs to initiate the related shocks. In addition to providing observation-inspired shock geometry and characteristics, this MHD simulation describes the time-dependent observer field line connections to the shock source. As a first approximation, we assume a shock jump-parameterized source strength and spectrum, and that scatter-free transport occurs outside of the shock source, thus emphasizing the role the shock evolution plays in determining the modeled SEP event profile. Three halo CME events on May 12, 1997, November 4, 1997 and December 13, 2006 are used to test the modeling approach. While challenges arise in the identification and characterization of the shocks in the MHD model results, this approach illustrates the importance to SEP event modeling of globally simulating the underlying heliospheric event. The results also suggest the potential utility of such a model for forcasting and for interpretation of separated multipoint measurements such as those expected from the STEREO mission. 相似文献
154.
X. Zhang Z. Zeren M. Parrot R. Battiston J. Qian X. Shen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
ULF/ELF electric field perturbations in the ionosphere have been widely observed by the satellites. In this paper, we develop a method of Logarithm Electric Field Intensity (LEFI) to automatically distinguish this kind of disturbances based on the spectrum intensity and its damping exponent with frequency in electromagnetic signals. This method is applied to DEMETER data processing around Chile earthquakes with magnitude larger than 6.0. It is found that 2/3 earthquakes have shown obvious ULF/ELF electric field perturbations in this region. The temporal and spatial distributions of electron density and temperature were compared with that of electric field, which proved the existence of irregularities above epicentral area. Finally, the coupling mechanism of earthquake-ionosphere is discussed based on multi-parameter analysis. 相似文献
155.
Numerically robust implementation of multiple-model algorithms 总被引:1,自引:0,他引:1
Standard implementation of multiple-model (MM) estimation algorithms may suffer from numerical problems, especially numerical underflows, which occur when the true model is vastly different from one or more models used in the algorithm. This may be devastating to the performance of the MM algorithm. Numerical robust implementations of some of the most popular MM algorithms are presented. Simulation results are provided to verify the proposed implementation and to compare with the implementations with a lower bound 相似文献
156.
G. Qin S. QiuH. Ye A. HeL. Sun X. LinH. Li X. XuH. Zeng 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
Three “SZ” Atmospheric Composition Detectors (ACDs) on board spacecraft “SZ-2”, “SZ-3” and “SZ-4” were launched on 10th January 2001, 26th March 2002 and 31st December 2002 separately. A large quantity of thermospheric composition data at the orbital altitude ranging from 330 to 362 km were collected from the in-situ measurement of ACDs. The spacecrafts’ lifetime was just in the second peak period of the 23rd solar cycle which includes two peaks and the solar activity value F10.7 was from 89 to 228. During this period, several intense geomagnetic disturbances happened. 相似文献
157.
L Mei C D Zhou J Q Lan Z G Wang W C Wu X M Xue 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(9):171-177
The frontal cortex is recognized as the highest adaptive control center of the human brain. The principle of the "frontalization" of human brain function offers new possibilities for brain research in space. There is evolutionary and experimental evidence indicating the validity of the principle, including it's role in nervous response to gravitational stimulation. The gravitational field is considered here as one of the more constant and comprehensive factors acting on brain evolution, which has undergone some successive crucial steps: "encephalization", "corticalization", "lateralization" and "frontalization". The dominating effects of electrical responses from the frontal cortex have been discovered 1) in experiments under gravitational stimulus; and 2) in processes potentially relating to gravitational adaptation, such as memory and learning, sensory information processing, motor programing, and brain state control. A brain research experiment during space flight is suggested to test the role of the frontal cortex in space adaptation and it's potentiality in brain control. 相似文献
158.
The concept of the Darboux point at which an extremal loses its global optimality is extended to the case of discontinuous control. Using Contensou's domain of maneuverability, the condition for optimal switching at a corner is derived and the optimality of the trajectory in the neighborhood of a Darboux point is analyzed. The theory is applied to the problems of minimum-fuel planar and noncoplanar deorbit from elliptical orbits for atmospheric entry at a prescribed angle. In each case, the global optimal trajectory is assessed and it is found that in these nonlinear problems the Darboux point and the conjugate point are distinct. The global optimality is always lost before local optimality. 相似文献
159.
A logic-based track formation procedure was presented by C.B. Chang et al. (1984). In addition to the conventional gating logic, it utilized the negative log-likelihood function (goodness of fit or sum of residuals) to further reduce the false track acceptance probability. An analytical technique for the evaluation of the effectiveness of this reduction is presented. The exact solution in closed form and a Gaussian approximation are given and compared. It is shown that the goodness of fit provides an additional reduction of the false track acceptance probability by a factor of two to three 相似文献
160.
A. Pedersen N. Cornilleau-Wehrlin B. De la Porte A. Roux A. Bouabdellah P. M. E. Décréau F. Lefeuvre F. X. Sène D. Gurnett R. Huff G. Gustafsson G. Holmgren L. Woolliscroft H. ST. C. Alleyne J. A. Thompson P. H. N. Davies 《Space Science Reviews》1997,79(1-2):93-106
In order to get the maximum scientific return from available resources, the wave experimenters on Cluster established the Wave Experiment Consortium (WEC). The WEC's scientific objectives are described, together with its capability to achieve them in the course of the mission. The five experiments and the interfaces between them are shown in a general block diagram (Figure 1). WEC has organised technical coordination for experiment pre-delivery tests and spacecraft integration, and has also established associated working groups for data analysis and operations in orbit. All science operations aspects of WEC have been worked out in meetings with wide participation of investigators from the five WEC teams. 相似文献