基于FBM分形向量特征的图象匹配

由于自然景物图象的灰度与边缘特征不稳定，基于灰度与边缘的匹配算法对于这一类图象难以生效。本文通过分析ＦｒａｃｔａｌＢｒｏｗｎｉａｎＭｏｔｉｏｎ（ＦＢＭ）的Ｗｅｉｅｒｓｔｒａｓｓ－Ｍａｎｄｅｌｂｒｏｔ随机分形逼近函数的频谱，给出了分形向量特征的定义和快速判别图象的ＦＢＭ区域的方法。在ＦＢＭ区域内采用该特征进行匹配能克服复杂自然景物图象中灰度与边缘特征的不稳定性。实验表明采用ＦＢＭ分形向量特征的匹配方法能够获得比较传统匹配方法，例如平均绝对差算法以及特征匹配法更高的匹配定位精度和匹配概率     

接管断裂失效概率估算的抽样方法研究

提出了用分层抽样－重要性抽样复合法计算接管的断裂失效概率，并与直接抽样的ＭｏｎｔｅＣａｒｌｏ法进行了比较，结果表明：用复合法计算接管断裂失效概率不但精度高，而且大幅度节省机时，提高效率。     

非均匀弹性地基上梁横向振动的渐近解法

研究非均匀弹性地基上梁的横向振动，提供了一种既能保证较高精度、计算又非常简单的固有频率的渐近解法，作为算例，给出了非均匀弹性地基上悬臂梁固有频率的一级近似计算公式并将计算结果与连续质量有限元素法的计算结果作了比较。     

基于系统论的无人机蜂群再认识

无人机蜂群结合了无人机和集群作战的优势,是当前军事技术装备发展的热点,也是电子战研究的重点.受研究视角和实际演示项目的影响,人们对无人机蜂群的研究和认识还存在一定的局限.和传统单个无人机相比,无人机蜂群的特殊之处在于其系统特性.从系统论的角度研究无人蜂群,可以更加深刻地理解无人机蜂群的本质和优势,科学研判无人机蜂群的未...     

Precession–nutation correction for star tracker attitude measurement of STECE satellite

Space Technology Experiment and Climate Exploration(STECE) is a small satellite mission of China for space technology experiment and climate exploration. A new test star tracker and one ASTRO 10 star tracker have been loaded on the STECE satellite to test the new star tracker's measurement performance. However,there is no autonomous precession–nutation correction function for the test star tracker,which causes an apparent periodic deflection in the inter-boresight angle between the two star trackers with respect to each other of up to ±500 arcsec,so the precession and nutation effect needs to be considered while assessing the test star tracker. This paper researches on the precession–nutation correction for the test star tracker's attitude measurement and presents a precession–nutation correction method based on attitude quaternion data. The periodic deflection of the inter-boresight angle between the two star trackers has been greatly eliminated after the precession and nutation of the test star tracker's attitude data have been corrected by the proposed method and the validity of the proposed algorithm has been demonstrated. The in-flight accuracy of the test star tracker has been assessed like attitude noise and low-frequency errors after the precession–nutation correction.     

Microstructure evolution of a hypereutectic Nb–Ti–Si–Cr–Al–Hf alloy processed by directional solidification

In this work, the Nb–14Si–24Ti–10Cr–2Al–2Hf–0.1Y alloy(at.%) was processed by the liquid–metal-cooled directional solidification(DS) at 1750 C with withdrawal rates of 1.2, 6,18 mm/min and post heat treatment(HT) at 1450 C for 10 h. The microstructures of the directionally solidified and heat treated samples were investigated. The results show that the microstructure of directionally solidified alloy mainly consists of petaloid Nbss+ Nb5Si3eutectics and Ti-rich Nbss+ Nb5Si3+ Cr2Nb eutectics. With the increase of withdrawal rate, the primary Nb5Si3is eliminated, Nbss+ Nb5Si3eutectic cells turn round and connected with the microstructure refinement and Nbss+ Nb5Si3+ Cr2Nb eutectics turn to a river-like morphology. After heat treatment,Nbss+ Nb5Si3+ Cr2Nb eutectics disappeared and petaloid Nbss+ Nb5Si3eutectics turn to a specific fiber-mesh structure gradually, which is promoted by higher withdrawal rates. Furthermore,both the volume fraction of Cr2Nb and the content of Cr in Nbssof Nbss+ Nb5Si3eutectics change regularly with the increase of withdrawal rate and heat treatment at 1450 C for 10 h.     

Grinding behavior and surface appearance of（TiC_p＋ TiB_w）/Ti-6Al-4V titanium matrix composites

（TiCp＋ TiBw）/Ti-6Al-4V titanium matrix composites（PTMCs） have broad application prospects in the aviation and nuclear field. However, it is a typical difficult-to-cut material due to high hardness of the reinforcements, high strength and low thermal conductivity of Ti-6Al-4V alloy matrix. Grinding experiments with vitrified CBN wheels were conducted to analyze comparatively the grinding performance of PTMCs and Ti-6Al-4V alloy. Grinding force and force ratios, specific grinding energy, grinding temperature, surface roughness, ground surface appearance were discussed. The results show that the normal grinding force and the force ratios of PTMCs are much larger than that of Ti-6Al-4V alloy. Low depth of cut and high workpiece speed are generally beneficial to achieve the precision ground surface for PTMCs. The hard reinforcements of PTMCs are mainly removed in the ductile mode during grinding. However, the removal phenomenon of the reinforcements due to brittle fracture still exists, which contributes to the lower specific grinding energy and grinding temperature of PTMCs than Ti-6Al-4V alloy.     

Effect of dilution holes on the performance of a triple swirler combustor

A triple swirler combustor is considered to be a promising solution for future high temperature rise combustors. The present paper aims to study dilution holes including primary dilution holes and secondary dilution holes on the performance of a triple swirler combustor. Experimental investigations are conducted at different inlet airflow velocities(40–70 m/s) and combustor overall fuel–air ratio with fixed inlet airflow temperature(473 K) and atmospheric pressure. The experimental results show that the ignition is very difficult with specific performance of high ignition fuel–air ratio when the primary dilution holes are located 0.6H(where H is the liner dome height)downstream the dome, while the other four cases have almost the same ignition performance. The position of primary dilution holes has an effect on lean blowout stability and has a large influence on combustion efficiency. The combustion efficiency is the highest when the primary dilution holes are placed 0.9H downstream the dome among the five different locations.For the secondary dilution holes, the pattern factor of Design A is better than that of Design B.     

自动相关监视系统信息传输性能分析方法及测试平台构建

本研究目的在于提出一种在民用飞机机载自动相关监视系统(Automatic Dependent Surveillance,简称ADS)系统设计和试验过程中实时/非实时检测该系统端到端信息传输性能的分析方法,并进行相应的地面测试平台搭建设计。对口于飞机的机载系统,ADS监视系统信息传输性能分析平台能够快速准确定位ADS系统的试验故障,实现有效的排故和分析,直观地评估自相关监视系统的工作状态。这项研究的结果有助于推动机载合同式自动相关监视系统(Automatic Dependent Surveillance-Contract,简称ADS-C)和广播式自动相关监视系统(Automatic Dependent Surveillance-Broadcast,简称ADS-B)机上地面功能试验、民机机上地面试验、民机飞行试验等各项工作的开展。该平台在飞机交付以后,也有利于维护工作与客户支持工作的进行。     

滚转运动对乘波飞行器气动特性的影响

 乘波飞行器运动过程中的非定常气动特性是高超声速飞行中的重要物理问题之一。采用数值模拟方法模拟了乘波飞行器在固定迎角下绕其对称轴强迫滚转运动这一过程。比较了在不同频率和滚转角下乘波飞行器的气动特性。计算格式采用AUSM类格式中最新的AUSM+up格式。计算结果表明：AUSM+up能很好地模拟飞行器滚转运动这一非定常过程;滚转运动时,所设计的乘波飞行器能使高压气体很好地附着在乘波飞行器下表面从而使其具有较好的气动特性;当频率较大时,乘波飞行器由于角速度的诱导作用会导致升力出现迟滞现象;做滚转运动时,滚转力矩小于零,产生正阻尼,乘波飞行器不会产生“摇滚”运动。