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331.
首先分析了进气道等效圆波导中发动机等效“半球+ 平面扇形金属叶片”终端的不连续性,根据电磁场互易定理和物理光学法( P O) 计算了这种终端的反射系数;然后利用“传输模式叠加法”计算了进气道的雷达散截面( R C S) 。计算结果与实验结果比较吻合,优于文献给出的计算结果。这种方法采用模式迭加求和,避免了普通模式法需进行大型矩阵计算以及对计算机内存的过高要求。 相似文献
332.
本文研究了在图象模式识别过程中引入人工智能的知识学习、知识表达和知识推理的理论和技术,设计并实现了一个应用于遥感图片解译的计算机视觉专家系统。 为使系统具有较高的智能化程度,本文提出了一种新的推理方法——多重推理法,它具有处理某些不完全知识和错误知识的能力,并且推理过程所运用的部分知识(规则)是从已知样本中自动归纳学习生成的。 相似文献
333.
334.
对直升机动力学的现状与发展的分析 总被引:4,自引:2,他引:4
对以旋翼动力学和飞行动力学为主体的直升机动力学研究进展回顾。主要讨论与飞行力学有关的旋翼气动力模型,旋翼结构动力学、气动弹性力学、飞行动力学模型与控制以及飞行操纵与品质等方面的进展,分析它们的现状,供有关直升机研究人员参考。 相似文献
335.
针对某型航空发动机火焰筒大修时出现的裂纹、烧伤及侵蚀问题,开展了火焰筒第4~6段换段修理工艺试验。通过分析火焰筒的结构,确定了用新段替换相应的故障段的方法对火焰筒进行修复。在拆分故障段时,尽量减小保留段壁厚的局部减薄量;在重新装配时,避免在原电阻焊点处再次焊接;通过采取以上工艺措施,实现了火焰筒的换段修理。同时进行了电阻焊焊接拉伸试验、撕破检查、金相组织检查等工艺验证试验。换段修理的火焰筒通过了发动机试车考核验证。换段工艺方法也可作为批生产过程中部分段制造有缺陷时的补救方案。 相似文献
336.
N.F. Allard V.A. Alekseev 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
The spectra of many cool DZ white dwarfs show extremely broad resonance lines of ionized calcium and magnesium in the optical and ultraviolet region. When the line center is strongly saturated, these wings may become a significant source of additional opacity in cool white dwarf atmospheres. The omission of this opacity results in systematic errors in the predicted flux distribution and hence in the effective temperatures and element abundances. In a continuation of Homeier et al. (2007) and Allard et al. (2012), where we presented absorption spectra of Na–He in cool white dwarfs, we extend this work to the Ca+–He system. 相似文献
337.
N.F. Allard A. Nakayama F. Stienkemeier J.F. Kielkopf G. Guillon A. Viel 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
The detection of Li I lines is the most decisive spectral indicator of substellarity for young brown dwarfs with masses below about 0.06 solar mass. Due to the weakness of the Li resonance lines, it is important to be able to model precisely both their core widths and their wing profiles. This allows an adequate prediction of the mass at which Li lines reappear in the spectra of brown dwarfs for a given age, or reversely an accurate determination of the age of a cluster. We report improved line profiles and the dependence of line width on temperature suitable for modeling substellar atmospheres that were determined from new LiHe molecular potential energies. Over a limited range of density and temperature, comparison with laboratory measurements was used to validate the potential energies which support the spectral line profile theory. 相似文献
338.
J.E. Mendoza-Torres 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
We analyze five solar Explosive Events observed in the Si iv emission line at 139.37 nm during SUMER/SoHO raster scans near disk center. The Doppler velocities from −45 km s−1 to +45 km s−1 were sorted into eleven symmetrically organized velocity bins, five equally-sized bins on each side and one bin for the line at rest. The radiance values along the NS oriented slit around the maximum of each EE are used to build one-dimensional distributions. We study these distributions and their development in space and time for different velocity bins to unveil the 3D-structure and evolution of Explosive Events. The spatial radiance distributions for the EE maximum and around it were made. For some Explosive Events the dispersion direction is not oriented orthogonally to the slit direction; consequently, the blueshifted emission is in a linear way offset from the redshifted emission by several pixels. The largest offset (∼5″) is observed between distributions whose velocities differ by ∼36 km s−1. The linear relation agrees with an scenario of flows inside magnetic arcs. 相似文献
339.
孙中山先生的民生主义学说是其三民主义思想的重要组成部分,这一思想的形成经历了一个历史过程。从理论渊源来看,既有中国传统政治思想中民本主义思想的影响,也有对西方资本主义政治经济学有关内容的吸纳,还受到社会主义思想的影响。民生主义提出后,在不同的政治势力之间引发了激烈的争论,这种争论也推动了孙中山三民主义的不断发展演变。民生主义学说对于当代中国民生问题具有重要的启示和借鉴意义。 相似文献
340.
Dipak Debnath Sandip K. Chakrabarti Anuj Nandi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
The Galactic black hole candidate H 1743-322 exhibited two X-ray outbursts in rapid succession: one in August 2010 and the other in April 2011. We analyze archival data of this object from the PCA instrument on board RXTE (2–25 keV energy band) to study the evolution of its temporal and spectral characteristics during both the outbursts, and hence to understand the behavioral change of the accretion flow dynamics associated with the evolution of the various X-ray features. We study the evolution of QPO frequencies during the rising and the declining phases of both the outbursts. We successfully fit the variation of QPO frequency using the Propagating Oscillatory Shock (POS) model in each of the outbursts and obtain the accretion flow parameters such as the instantaneous shock locations, the shock velocity and the shock strength. Based on the degree of importance of the thermal (disk black body) and the non-thermal (power-law) components of the spectral fit and properties of the QPO (if present), the entire profiles of the 2010 and 2011 outbursts are subdivided into four different spectral states: hard, hard-intermediate, soft-intermediate and soft. We attempt to explain the nature of the outburst profile (i.e., hardness-intensity diagram) with two different types of mass accretion flow. 相似文献