摘要：三维空间的噪声主动控制技术是近年来噪声控制领域研究的一个热点问题,对于降低飞机或车辆里的噪声水平有很大意义。提出了一种对于噪声在三维空间里进行优化控制的方法,建立三维空间的几何控制模型,并且对几何模型进行区域划分,误差准则取所有区域的声压平方和,确定优化目标为误差准则取得最小值,计算出多点次级声源的强度。最后基于该方法设计的噪声主动控制系统进行数值仿真和实验验证,结果验证了该方法的正确性和有效性。

摘要：根据轻型空间相机光学系统的特点以及相机的焦深,优化设计了一种适用于该类相机的调焦机构。为了满足相机总体要求,综合考虑重量、外型尺寸、刚度、误差等各方面的因素,选择丝杠和连杆配合使用的双滑块机构,将丝杠的转动通过连杆机构转换成调焦镜沿光轴方向的直线运动,实现了通过调整像面移动来解决离焦的问题。对该调焦机构在调焦范围内的调焦精度进行了分析,介绍了该调焦机构的误差来源和计算方法。最后,对该调焦机构进行了振动试验和精度试验。优化设计后的调焦机构总重量为2.5 kg,外型尺寸为186 mm×144 mm×60 mm。振动试验和精度试验的结果表明,该调焦机构的基频为505 Hz,单向定位精度为0.008 mm,重复定位精度为0.002 5 mm,满足相机总体提出的刚度和精度要求。该调焦机构具有刚度高、结构紧凑、定位精度高等特点,能够满足空间调焦的设计要求。

摘要：从某空间相机的任务需求出发,提出了采用基于碳纤维复合材料的高精密桁架作为主次镜间的支撑结构,完成了相关设计和工程分析,并在加工制造过程中,对相关工艺流程进行了探索。确定了相关结构的制造工艺流程,实现了该结构的高精密加工。最后,深入开展了相关振动、力学和温度稳定性试验,搭建了基于光学测量方法的自动测试平台,排除了人为因素的影响,实现了快速多次自动测量,从而提高了测试精度。分析和试验结果表明:所研制的大型碳纤维桁架质量仅为13kg,基频达到119Hz,在重力、10℃温升和4℃温差条件下的变形均小于4″,各组件Φ864mm安装接口的平面度优于8μm,同时实现了高度轻量化和高稳定性。该桁架已成功应用于某空间相机中,提出的设计、试验方案和工艺流程可以作为其它同型空间相机结构设计的技术参考。

摘要：提出了一种新型超越离合器———双楔块式低副单向超越离合器.对该超越离合器的结构及工作原理进行了分析说明;对其主要性能如:自锁条件、强度条件、溜滑角、效率等给出相应的理论计算公式,为该超越离合器的设计提供了理论依据.并通过试验证明了理论设计计算公式是正确性,同时也证明了该超越离合器所传递的转矩得到了很大提高,并且具有磨损小、寿命长和抗冲击能力强等优点.

摘要：In this study,diodo boron dipyrromethene(BODIPY)is employed a8 the energy donor and 3,4,9,10-perylene tetracarboxylic dianhydride(PDA)as the energy acceptor,enabling the synthesis of two new compounds:a BODIPY-perylene dyad named P1,and a triad named *** investigate the impact of the energy donor on the photophysical processes of the system,P1 comprises one diodo-BODIPY unit and one PDA unit,whereas P2 contains two diodo-BODIPY moieties and one PDA *** to the good spectral complementarity between diiodo-BODIPY and PDA,these two compounds exhibit excellent light-harvesting capabilities in the 400-620 nm ***-state fluorescence spectra demonstrate that when preferentially exciting the diodo-BODIPY moiety,it can effectively transfer energy to PDA;when selectively exciting the PDA moiety,quenching of PDA fluorescence is observed in both P1 and *** transient absorption results show that both compounds can efficiently generate triplet excited states,which are located on the PDA *** lifetimes of the triplet states for these two compounds are 103 and 89μs,respectively,significantly longer than that of *** results from the photooxidation experiments reveal that both P1 and P2 demonstrate good photostability and photooxidation capabilities,with P2 showing superior photooxidative *** photooxidation rate constant for P2 is 1.3 times that of P1,and its singlet oxygen quantum yield is 1.6 times that of *** results obtained here offer valuable insights for designing new photosensitizers.

摘要：Background People recently realized that it is important for artificial vascular biodegradable graft to bionically mimic the functions of the native vessel. In order to overcome the high risk of thrombosis and keep the patency in the clinical small-diameter vascular graft （SDVG） transplantation, a double-layer bionic scaffold, which can offer anticoagulation and mechanical strength simultaneously, was designed and fabricated via electrospinning technique. Methods Heparin-conjugated polycaprolactone （hPCL） and polyurethane （PU）-collagen type I composite was used as the inner and outer layers, respectively. The porosity and the burst pressure of SDVG were evaluated. Its biocompatibility was demonstrated by the 3-（4,5-dimethyl-2-thiazol）-2,5-diphenyl-2H tetrazolium bromide （MTT） test in vitro and subcutaneous implants in vivo respectively. The grafts of diameter 2.5 mm and length 4.0 cm were implanted to replace the femoral artery in Beagle dog model. Then, angiography was performed in the Beagle dogs to investigate the patency and aneurysm of grafts at 2, 4, and 8 weeks post-transplantation. After angiography, the patent grafts were explanted for histological analysis. Results The double-layer bionic SDVG meet the clinical mechanical demand. Its good biocompatibility was proven by cytotoxicity experiment （the cell＇s relative growth rates （RGR） of PU-collagen outer layer were 102.8%, 109.2% and 103.5%, while the RGR of hPCL inner layer were 99.0%, 100.0% and 98.0%, on days 1, 3, and 5, respectively） and the subdermal implants experiment in the Beagle dog. Arteriography showed that all the implanted SDVGs were patent without any aneurismal dilatation or obvious anastomotic stenosis at the 2nd, 4th, and 8th week after the operation, except one SDVG that failed at the 2nd week. Histological analysis and SEM showed that the inner layer was covered by new endothelial-like cells. Conclusion The double-layer bionic SDVG is a promising candidate as a replacement of native smal

摘要：在远距离目标轨迹测量系统中,当前的长焦相机由于CCD尺寸限制一般视场角度较小,无法实现对目标的可靠捕获。在对比当前的几种大视场拼接成像方法后,针对远距离目标测量系统的要求提出了一种通过控制单个相机进行圆锥旋转来模拟4相机阵列实现大视场成像的方法。设计了实验样机对该方法进行验证。首先根据该成像方法设计了相机运动控制方案和相应的机械结构,然后设计了相机的触发控制以及图像数据的传输和处理流程,最后使用该样机进行了实验。实验中样机经校准后采集到了相对位置正确的子视场图像,并拼接获得了大视场图像。使用视场角度为1.02°的小视角相机,实现了4个有一定程度重合的子视场2×2拼接,最终获得了1.93°的大视角。该方法为远距离目标测量系统中的目标捕获子系统设计提供了新思路。

摘要：针对地面航天器对接动力学全物理仿真试验台,提出采用质量惯量模拟技术模拟航天器的质量、惯量特性,以便灵活的适应不同吨位航天器对接试验。设计了杠铃式质量惯量模拟结构。介绍了杠铃式模拟件的结构特点,确定调整参数,调整范围,对模拟误差进行了分析。结果表明杠铃式质量惯量模拟件模拟准确,调整简单、方便。

摘要：质子交换膜燃料电池系统在氢气循环的运行过程中,阴极侧空气中的氮气和水会穿过质子交换膜渗透到阳极并逐渐积累,降低阳极的氢气浓度,影响燃料电池系统的发电性能。通过研究电堆结构参数和运行参数对氮气和水从阴极渗透到阳极的传输过程,发现氮气的渗透主要受膜厚度、膜湿度和气体压力的影响,而水的渗透除了膜厚影响以外,还受电流的大小的影响。这些结果为氢气循环条件下燃料电池系统稳定运行和制定合理的尾气排放策略提供理论依据和设计参数。

摘要：为了提高超燃冲压发动机隔离段耐反压能力以及缩短隔离段长度,设计了一种带等宽度平直斜楔的隔离段,斜楔放置在隔离段进口下壁面厚附面层一侧,在Ma=1.98非对称的隔离段进口来流条件下完成吹风实验.实验结果表明,隔离段加等宽度平直斜楔后可在相同的反压下使激波串相对长度从13.87缩短至11.12,比基准隔离段激波串长度缩短了19.8%.同样的隔离段加斜楔后能够承受的最大反压从来流静压的3.55倍上升到3.85倍,提高了8.45%左右.