激光加工气膜孔对定向凝固高温合金薄壁持久性能的影响

采用定向凝固无余量精铸工艺制造的接近于空心涡轮叶片形状和壁厚的管状薄壁（δ＝１．２ｍｍ）试样，研究了激光加工孔对定向凝固高温合金薄壁持久性能的影响。结果表明，在９００℃／３７０ＭＰａ下，与没有孔的薄壁试样相比，有一排孔的试样持久性能没有明显降低，有两排孔的试样持久寿命略有下降。显微分析表明，激光加工孔对组织没有明显的影响，只是稍微减小了承载面积，而且只有在出现两排激光孔时才有所表现。     

空间激光通信系统光斑小目标跟踪算法研究

在空间激光通信链路中，大气湍流、结构设计误差、平台扰动等因素为链路的精确对准和精密跟踪带来了困难。为提高激光链路的跟踪精度，首先对光斑跟踪过程中的影响因素进行研究分析，继而对跟踪算法做出改进。针对跟踪目标特性，设计了一种自适应模板目标相关跟踪算法，并搭建了基于粗精复合轴跟踪系统的实验平台，开展了实验验证。结果表明：与当前常用跟踪算法相比，该设计处理速度可达 1 kfps，目标跟踪位置与真实位置基本重合，目标跟踪准确率高于98%，在处理速度、跟踪准确率与算法鲁棒性上均有较大提升，具有一定的实用性。     

星载激光测高地面数据处理设计研究

星载激光测高技术是对地观测系统中最为核心和前沿的信息获取技术之一,因其具有探测方向性好、测距精度高等特点,在地球科学领域中体现出了巨大的应用潜力。在ICESat/GLAS测高地面数据处理系统的基础上,针对将于今年发射的高分七号卫星的载荷特点,设计了一套星载激光测高地面数据处理系统软件。该软件可实现对星载激光测高数据的地面处理并生成3级数据产品,包含激光能量计算、波形分解和激光脚点定位等,以及相应各级产品的数据质量控制处理。利用高分七号仿真数据对该软件进行相应的性能测试,测试结果表明:该系统软件基本满足需求,已初步具备星载激光测高地面数据处理能力。     

基于多核计算机集群系统的网格分区策略

网格分区技术是提高并行计算效率的重要手段。基于图的分区技术(如Metis等)已经可以完全做到负载平衡,但是随着计算机集群系统的发展,节点间的通讯成为并行计算中的重要时间消耗部分。为此,提出一种适用于非结构网格的新分区策略(MC Partition method),减少了节点间的通讯规模,结果表明,这种分区方法可以较大的提高并行计算效率。     

线性调频半导体激光衍射光栅干涉仪

介绍一种以线性调频半导体激光为光源的衍射光栅干涉仪。激光与光栅上衍射的±１级衍射波会合，由于有光程差而发生光拍频，测量拍频信号的相位移则可测得光栅的位移。设计了一种克服激光波长漂移和空气折射率变化影响的对称差动光路，使这种方法达到实用化的程度，分辨力达到纳米级。此外，还介绍了应用于接触干涉仪的实验情况。     

激光功率与底面状态对选区激光熔化球化的影响

为研究激光功率与底面状态对选区激光熔化熔池流动的影响，基于离散单元法建立了选区激光熔化铺粉模型，采用粒径分布与实验相符的马氏体时效钢粉末分别铺展到平坦底面和增材底面上，将计算获得的粉末分布导入到基于有限体积法建立的选区激光熔化熔池计算流体力学模型中，研究激光功率和基板底面粗糙度对熔池流动和熔道表面形貌的影响。采用激光单道扫描实验验证铺粉模型和选区激光熔化模型。结果表明：随着激光功率的降低，单位长度的球化数量增加；由于增材底面使熔池润湿性变差，同时又对熔池流动行为产生扰动，使得增材粗糙底面上熔道的球化数量增加。选区激光熔化铺粉模拟及激光单道扫描模拟结果与实验结果吻合较好。本研究可为选区激光熔化工艺中工艺参数的选择提供理论指导。     

激光伪随机编码的最小周期识别算法改进研究

目前激光制导武器使用的伪随机编码,基本都是利用移位寄存器加上特定的反馈函数来实现的,只要识别出其最小周期就可以利用准同步干扰方式进行干扰。对有限位伪随机码的特点进行研究和分析,介绍了一种新的计算小数之间的整数比的方法,并提出了对现有最小周期识别算法的改进算法。进行了仿真验证,结果表明:改进后的算法优于现有其他方法。     

提高长线传输数字波形质量的技术措施

从两方面论述数字编码波形在长线上传输的影响因素及其改善措施。通过分析并经实验表明，长线的分布电容影响通常居诸因素之首位。改进长线驱动电路，在一定程度上，可改善其传输波形之质量。另外，可利用长线传输波形的同时，还传输供总线接口电路需要的电源能量，满足总线浮空隔离的要求，有效地抑制了共模干扰。此项技术适用于远距多路串行总线的数据采集系统。     

Toward understanding the active SETI debate: Insights from risk communication and perception

Insights from the robust field of risk communication and perception have to date been almost totally absent from the policy debate regarding the relative risks and merits of Active SETI or Messaging to Extraterrestrial Intelligence (METI). For many years, the practice (or proposed practice) of Active SETI has generated a vigorous and sometimes heated policy debate within the scientific community. There have also been some negative reactions in the media toward the activities of those engaged in Active SETI. Risk communication is a scientific approach to communication regarding situations involving potentially sensitive or controversial situations in which there may be high public concern and low public trust. The discipline has found wide acceptance and utility in fields such as public health, industrial regulation and environmental protection. Insights from the scientific field of risk communication (such as omission bias, loss aversion, the availability heuristic, probability neglect, and the general human preference for voluntary over involuntary risks) may help those who have participated in either side of the debate over Active SETI to better understand why the debate has taken on this posture. Principles of risk communication and risk perception may also help those engaged in Active SETI to communicate more effectively with other scientists, the public, with the media, and with policy makers regarding their activities and to better understand and respond to concerns expressed regarding the activity.     

Selective laser melting of Al–8.5Fe–1.3V–1.7Si alloy: Investigation on the resultant microstructure and hardness

This article presents the microstructure and hardness variation of an Al–8.5Fe–1.3V–1.7Si(wt%, FVS0812) alloy after selective laser melting(SLM) modification. Three zones were distinguished across the melting pool of the SLM-processed FVS0812 alloy: the laser melted zone(LMZ), the melting pool border, and the heat affected zone(HAZ) in the previously deposited area around the melting pool. Inside the LMZ, either an extremely fine cellular-dendritic structure or a mixture zone of the a-Al matrix and nanoscale Al_(12)(Fe,V)_3Si particles appeared. With a decreased laser beam scanning speed, the cellular-dendritic structure zone within the LMZ shrank significantly while the mixture zone expanded. The a-Al and Al_(12)(Fe,V)_3Si mixture zone was also observed in the HAZ, but another phase, submicron h-Al_(13)Fe_4 particles with rectangular or hexagonal shapes,formed along the melting pool border. Microhardness tests indicated that the hardness of the SLM-processed FVS0812 samples far exceeded that of the as-cast FVS0812 alloy.