基于球投影的面阵探测器扭转角测量与校正

为了消除基于面阵探测器的锥束X射线计算机断层成像(XCT,X-ray Computed Tomography)检测系统中探测器的安装误差对重建断层图像的影响,使投影坐标系准确建立,并与重建坐标系精确配准,提出了基于椭圆拟合的平板探测器位姿参数的估计方法.并在此基础上,从锥束XCT的近似重建算法FDK(Feldkamp)出发,结合空间坐标变换原理,改进了重建算法中投影地址的计算方式,使之能在存在安装误差的情况下准确计算投影地址,重建出正确的断层图像.该方法简单有效,计算量小,无需对系统硬件进行调整.实验结果表明,利用该方法可以有效地消除由于探测器位姿引起的图像伪影.     

Improvement of PPP-inferred tropospheric estimates by integer ambiguity resolution

Integer ambiguity resolution in Precise Point Positioning (PPP) can improve positioning accuracy and reduce convergence time. The decoupled clock model proposed by Collins (2008) has been used to facilitate integer ambiguity resolution in PPP, and research has been conducted to assess the model’s potential to improve positioning accuracy and reduce positioning convergence time. In particular, the biggest benefits have been identified for the positioning solutions within short observation periods such as one hour. However, there is little work reported about the model’s potential to improve the estimation of the tropospheric parameter within short observation periods. This paper investigates the effect of PPP ambiguity resolution on the accuracy of the tropospheric estimates within one hour.     

机载离心式制冷压缩机设计及特性分析

开发制冷量等级为50 kW的超级小型化离心式制冷压缩机是发展新一代战斗机蒸发循环系统的关键技术.由于小流量特点,工业中使用的大型离心式制冷压缩机设计经验不能完全适用于小型离心式制冷压缩机设计及工作特性的预测.基于试验,提出相关设计方案,通过建立小流量离心式压缩机效率、压比等的特性计算方程,对所设计的压缩机进行性能预测,经试验数据验证,计算结果与试验数据较为接近.该研究结果可为国内发展机载蒸发循环用离心式制冷压缩机提供技术支持.     

月球车车轮与模拟月壤相互作用试验

设计搭建了深空探测车车轮牵引特性试验台,制备了轮土试验用模拟月壤,在土槽中进行了模拟月壤的整备,重塑了就位月壤的力学特性.对不同轮齿类型的刚性车轮进行了牵引特性试验,分析了轮下模拟月壤的剪切破坏和车轮行驶阻力的表现形式.结果表明:增大轮上载荷能够提高挂钩牵引力,车轮的牵引效率随着滑转率的增加呈现先增加后降低的趋势;随着轮齿高度的增加,挂钩牵引力会随之增大,车轮的最大牵引效率有所降低;随着轮齿数目的增加,挂钩牵引力会随之增大,车轮的牵引效率变化不大;车轮转速在数值较低的范围内变化时,对牵引性能的影响较小.     

车辆视频检测感兴趣区域确定算法

利用最大方差阈值方法对灰度图像二值化后,对车辆底部阴影突变行检测,对感兴趣区域确定方法进行改进,实现了感兴趣区域的精确确定.通过计算精确确定后的感兴趣区域的灰度对称性和熵值归一化对称性测度,实现了车辆的精确检测,找到车辆的对称轴,并在车辆区域上边界一定范围内,进行灰度突变检测,实现了车辆上边界的准确定位.通过实验验证算法较好地实现了复杂环境下的车辆检测和上边界定位.     

小型钛合金压力容器的声发射评价

对三种结构形式的小型钛合金压力容器进行了声发射检测试验.通过对大量声发射检测数据的分析,结合容器结构特点提出了评价这三种小型钛合金压力容器声发射严重性的三条新判据.     

塑料复合薄膜超声波焊接工艺研究

对聚对苯二甲酸乙二醇酯(12μm PET)/流延聚乙烯(30μm PE)和聚酯(12μm PET)/聚丙烯(30μm CPP)两种复合薄膜进行超声波焊接工艺研究,发现焊接振幅、焊接时间、焊接压力都影响焊接接头的热合强度.结果表明,聚乙烯基复合薄膜焊接接头的热合强度明显高于聚丙烯基复合薄膜;采用大焊接振幅和短焊接时间的焊接方式或采用小焊接振幅和长焊接时间的焊接方式,能够得到相似的焊接质量;PET/CPP复合薄膜在适宜的焊接振幅范围内(5～7μm)的焊接接头热合强度高,PET/PE复合薄膜的焊接接头热合强度受焊接振幅的影响较小;随着焊接时间的延长,两种复合薄膜焊接接头的热合强度呈现先增加后减小的变化趋势;当焊接压力约为150 N时,两种复合薄膜的焊接接头热合强度均达到最大值.     

碳纤维复合材料构件少无缺陷制孔技术

碳纤维复合材料在航空航天领域有广泛的应用,其制孔技术是制约碳纤维复合材料应用的主要因素之一.本文列举了碳纤维复合材料制孔时常见的缺陷类型,以及国内外在制孔方面的研究现状,并总结了提高制孔质量的方法.     

QD128航改燃气轮机燃烧室数值模拟

应用计算流体动力学软件FLUENT,对QD128航改燃气轮机燃烧室进行了三维数值模拟计算分析。为了验证数值计算结果的合理性,首先,对以航空煤油为燃料的航机燃烧室进行了CFD数值模拟计算,并将采用3种湍流模型得到的CFD计算结果与航机燃烧室性能试验结果进行了对比,确定了适合燃烧室数值模拟计算的湍流模型Realizable k-ε;然后,采用Realizable k-ε湍流模型,对燃用天然气的QD128燃气轮机燃烧室进行了数值模拟计算,根据其计算结果,对QD128燃气轮机燃烧室出口温度场进行了优化,并对改进后的燃烧室进行了CFD计算,计算结果表明改进措施是有效的。     

Trajectory optimization of multiple asteroids exploration with asteroid 2010TK7 as main target

In this study, the Earth’s Trojan asteroid 2010 TK₇ is selected as the rendezvous target. The multiple flyby sequence of asteroid exploration was proposed by optimizing the probe’s orbit. Impulsive maneuvers and low-thrust propulsion were used respectively to design the trajectories of the multiple asteroids exploration mission. Under impulsive maneuvers, gravity assist technique was adopted to reduce fuel consumption. First a reference orbit with only 2010 TK₇ as the rendezvous target was designed. Then five asteroids near the reference orbit were selected as candidates. Finally, we obtained a multiple asteroids exploration sequence of three asteroids based on gravity assist technique and genetic algorithm, and an additional velocity impulse of 0.4?km/s was required. In the subsequent section, a sixth-degree inverse polynomial shape-based method is applied to the low-thrust trajectory design of 2010 TK₇, and the exploration sequence under the action of low-thrust propulsion was provided.