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251.
二、拉沃奇金科研生产联合体拉沃奇金科研生产联合体(NPO LA)是俄罗斯另一家大型航天公司。该公司在发展俄航天技术,特别是在行星际空间探索中起着重要的作用,同时还从事科学卫星和地球观测卫星的研制。2.1发展简况拉沃奇金联合体建于1937年4月,当时主要是设计制造军用飞机。S. 相似文献
252.
Bhanu B. Sungkee Lee Das S. 《IEEE transactions on aerospace and electronic systems》1995,31(4):1268-1291
This paper describes an adaptive approach for the important image processing problem of image segmentation that relies on learning from experience to adapt and improve the segmentation performance. The adaptive image segmentation system incorporates a feedback loop consisting of a machine learning subsystem, an image segmentation algorithm, and an evaluation component which determines segmentation quality. The machine learning component is based on genetic adaptation and uses (separately) a pure genetic algorithm (GA) and a hybrid of GA and hill climbing (HC). When the learning subsystem is based on pure genetics, the corresponding evaluation component is based on a vector of evaluation criteria. For the hybrid case, the system employs a scalar evaluation measure which is a weighted combination of the different criteria. Experimental results for pure genetic and hybrid search methods are presented using a representative database of outdoor TV imagery. The multiobjective optimization demonstrates the ability of the adaptive image segmentation system to provide high quality segmentation results in a minimal number of generations 相似文献
253.
254.
255.
钱津 《郑州航空工业管理学院学报(管理科学版)》2006,24(1):15-19
马克思在《资本论》中提出了国际价值概念,这具有重要的学术研究意义。国际价值在马克思的阐述中是与国民劳动的强度和生产率相连的,是建立在劳动价值论基础上的。世界劳动表现的国际价值,更明确地揭示表面上有区别的各个国家的劳动的内在的统一性。国际价值的存在并不改变价值规律适用范围的普遍性。 相似文献
256.
Strapdown INS error model for multiposition alignment 总被引:1,自引:0,他引:1
Dohyoung Chung Jang Gyu Lee Chan Gook Park Heung Won Park 《IEEE transactions on aerospace and electronic systems》1996,32(4):1362-1366
The relationship between quaternion errors and tilt angles from true navigation frame to analytic platform frame is newly derived for strapdown inertial navigation system (SDINS). Using the relationship it is shown that the quaternion error model for attitude and velocity is equivalent to the conventional perturbation error model. Based upon the equivalency, the quaternion errors during a multiposition alignment are determined and analyzed. Furthermore, it is shown that the heading rotation of 180 deg achieves the minimal quaternion error for 2-position ground alignment 相似文献
257.
Direct initiation of detonations in gaseous mixtures of C2H2-O2, H2-O2 and H2-Cl2 in the pressure range of 10–150 torr using flash photolysis was studied. Similar to blast initiation using a concentrated powerful energy source, it was found that for photochemical initiation, there exists a certain threshold of flash intensity and energy for each mixture at any given initial pressure and composition below which a deflagration is formed. At the critical threshold, however, a fully developed detonation is rapidly formed in the immediate vicinity of the window of incident UV radiation. However, at super critical flash energies, the amplitude of the detonation formed decreases and combustion of the entire irradiated volume approaches a constant volume explosion. It was found that photo-chemical initiation requires both a certain minimum peak value of the free radical concentration generated by the photo-dissociation as well as an appropriate gradient of this free radical distribution. The minimum peak radical concentration permits rapid reaction rates for the generation of strong pressure waves, while the gradient is necessary for the amplification of the shock waves to a detonation. If the gradient is absent and the free radicals are uniformly distributed in the mixture, then the entire volume simply explodes as in a constant volume process. The present study reveals that the mechanism of photochemical initiation is one of proper temporal synchronization of the chemical energy release to the shock wave as it propagates through the mixture. In analogy to the LASER, the term SWACER is introduced to represent this mechanism of Shock Wave Amplication by Coherent Energy Release. There are strong indications that this SWACER mechanism is universal and plays the main role in the formation of detonations whenever a powerful concentrated external source is not used to generate a strong shock wave in the explosive. 相似文献
258.
Beamspace ML bearing estimation incorporating low-angle geometry 总被引:1,自引:0,他引:1
A problem in low-angle radar tracking, namely, bearing estimation in the presence of a strong specular multipath component that arrives within the beamwidth of the direct path signal, is studied. Three-dimensional beamspace domain maximum likelihood (3D-BDML) is a computationally simple ML bearing estimation algorithm applicable in this scenario which operates in a 3-D beamspace. A variation of 3D-BDML incorporating the multipath geometry as a priori information is presented. In symmetric 3D-BDML the pointing angle of the center beam is equal to the bisector angle between the direct path ray and the image ray, which may be estimated a priori given only the radar height and the target range. The effect of the inclusion of a priori information on the performance of 3D-BDML is analyzed in terms of the dependence on the relative phase difference between the direct and specular path signals, the sensitivity to error in the bisector angle estimate, and the results of operation when no specular multipath component is present in the data. In addition, computationally simple schemes for coherently incorporating multifrequency data into 3D-BDML are investigated 相似文献
259.
根据风切变对飞机飞行影响的机理,以及FAA对CATⅠ类着陆最坏条件下的边界要求,推导了风切变的危险程度判据。通过计算,分析了垂直风切变与水平风切变对飞行性能的影响的异同,并通过对危险判据与性能恶化参数的相关性研究,提出了适用于机载风切变探测告警系统的告警准则。 相似文献
260.
Stark L. Tendick F. Kim W. Anderson R. Hisey M. Mills B. Matsunaga K. An Nguyen Ramos C. Tyler M. Zahalak G. Amick M. Baker B. Brown N. Brown T. Chang J. Jyh-Horng Chen Chik J. Cohen D. Cox D. Dubey J. Ellis K. Engdahl E. Frederickson C. Halamka J. Hauser R. Jacobs J. Lee C. Lee D. Liu A. Ninomiya R. Rudolph J. Schafer S. Schendel E. So G. Takeda M. Tam L. Thompson M. Wood E. Woodruff T. 《IEEE transactions on aerospace and electronic systems》1988,24(5):542-551
With major emphasis on simulation, a university laboratory telerobotics facility permits problems to be approached by groups of graduate students. Helmet-mounded displays provide realism; the slaving of the display to the human operator's viewpoint gives a sense of `telepresence' that may be useful for prolonged tasks. Using top-down 3-D model control of distant images allows distant images to be reduced to a few parameters to update the model used for display to the human operator in a preview model to circumvent, in part, the communication delay. Also, the model can be used as a format for supervisory control and permit short-term local autonomous operations. Image processing algorithms can be made simpler and faster without trying to construct sensible images from the bottom. Control studies of telerobots lead to preferential manual control modes and, in this university environment, to basic paradigms for human motion and thence, perhaps, to redesign of robotic control, trajectory path planning, and rehabilitation prosthetics. Speculation as to future industrial drives for this telerobotic field suggests efficient roles for government agencies such as NASA 相似文献