卫星遥感影像外方位元素的误差传播研究

高分辨率卫星遥感影像的几何定位精度与影像外方位元素精度密切相关.文章针对单景影像直接对地定位和立体影像前方交会定位两种典型情况,对影像各外方位元素在目标几何定位中的误差传播规律进行分析比较,相关结论可供卫星姿控及相机载荷设计方参考.     

多点切触加工中的局部干涉分析

为了消除多点切触加工刀位计算的局部干涉,通过对中凹端铣刀和工件曲面之间的几何接触状况分析,得到了多点切触加工算法的局部干涉判别条件.利用微分几何得到了多点切触加工刀位中刀具和工件的交线在第一切触点处的曲率半径和刀具曲率半径的比值,结合局部干涉判别条件,得到无干涉的多点切触加工约束的解区域.结果表明无论曲面为何种样式,必须选择第二切触点在曲率较大的主方向附近的解区域中,再使用多点切触加工算法算出的刀位,才有可能不发生过切现象.      

基于空时DFT投影实现宽带信号二维角估计

 提出了一种基于空时DFT投影的宽带信号二维角估计算法. 该方法采用3个共面的均匀线阵,每一均匀线阵对宽带信号空间采样,然后进行空时二维DFT变换,在空时频率域对宽带信号进行投影变换,用MUSIC算法实现宽带来波信号方向余弦的估计. 利用3个方向余弦估值进行配对,然后求得来波的方位角和仰角估计. 该方法既保留了投影算法的优点,即不需要源的先验知识;不需变换矩阵和在低信噪比有好的性能,又避免二维谱峰搜索.仿真实验表明了算法是有效的.     

刀具磨损的偏最小二乘回归分析与建模

简述了偏最小二乘回归方法;对在不同切削条件下车削加工过程刀具后刀面磨损的多组实验数据,采用偏最小二乘回归方法,根据变量重要性指标分析和因子载荷分析,从8个变量及其组合中筛选出了6个用于建模的自变量,并以后刀具磨损量作为因变量,建立了对所选自变量(切削速度V、切削分力的均值F_x、F_y和F_z、分力比值F_y/F_x和F_z/F_x等)的偏最小二乘回归模型;采用建模数据覆盖的切削条件下的实验数据和建模数据未覆盖的切削条件下的实验数据,分别对模型进行了验证.结果表明,采用偏最小二乘回归方法选择的自变量是合理的,所建立的刀具磨损的回归模型可以较满意地计算出不同切削条件下刀具后刀面的磨损量.     

微小孔加工试验及刀具磨损机理

由于钛合金和印刷电路板的难加工性使得微小孔的加工精度和表面质量难以保证,刀具技术成为提高加工效率的主要障碍。本文应用3种不同涂层钻头对钛合金和印刷电路板进行微小孔钻削对比试验,研究了进给速度与切削力和扭矩的关系,分析了刀具的磨损特征以及孔的表面质量和孔入口处的毛刺情况。结果表明:钻削印刷电路板的临界进给速度为1 591.2 mm/m in,涂层对钻削力和扭矩的影响不明显;类金钢石(DLC)涂层硬质合金钻头比普通硬质合金钻头和T iC涂层硬质合金钻头更适合加工钛合金材料微小孔。     

刀具织构轮廓对碳纤维增强复合材料面下损伤影响的切削仿真研究

为减小碳纤维增强复合材料（CFRP）加工时的面下损伤深度,创建了基于二维Hashin准则的宏观连续动态切削CFRP有限元模型,分析了切削力和面下损伤深度与纤维方向角之间的变化趋势,通过引入织构刀具来降低切削力及面下损伤深度,比较了沟槽形织构刀具、圆形织构刀具、三角形织构刀具切削CFRP的切削力和面下损伤。结果表明,不同织构刀具的切削力和面下损伤深度随纤维方向角变化趋势一致,均在0°时最小,90°达到最大值;织构刀具相对传统无织构刀具切削CFRP时均降低了切削力和面下损伤深度,其中圆形织构刀具降低程度最大;仿真模型经实验验证准确有效。     

Cutting tool temperature prediction method using analytical model for end milling

Dramatic tool temperature variation in end milling can cause excessive tool wear and shorten its life, especially in machining of difficult-to-machine materials. In this study, a new analyt-ical model-based method for the prediction of cutting tool temperature in end milling is presented. The cutting cycle is divided into temperature increase and decrease phases. For the temperature increase phase, a temperature prediction model considering real friction state between the chip and tool is proposed, and the heat flux and tool-chip contact length are then obtained through finite element simulation. In the temperature decrease phase, a temperature decrease model based on the one-dimension plate heat convection is proposed. A single wire thermocouple is employed to mea-sure the tool temperature in the conducted milling experiments. Both of the theoretical and experi-mental results are obtained with cutting conditions of the cutting speed ranging from 60 m/min to 100 m/min, feed per tooth from 0.12 mm/z to 0.20 mm/z, and the radial and axial depth of cut respec-tively being 4 mm and 0.5 mm. The comparison results show high agreement between the physical cutting experiments and the proposed cutting tool temperature prediction method.     

星图匹配制导中的关键技术

为了提高新一代弹道导弹的快速、机动反击能力和射击精度，采用星光，惯性组合制导足最佳的选择。本论文给出了基于双星敏感器的、星图匹配制导系统的关键技术。提出了根据弹道设计导航星表．极大地简化了弹载星表；提出了一种适用于星光制导的凸多边形箅法，合理地减少了匹配的星对角距数目。这两项技术保证了星图匹配制导技术的实用性。提出了一种分离初始定位、定向误差及平台漂移误差方法。采用凸多边形的星图识别算法可同时获得多颗星的瞬时位置，结合恒星在像平面的位置可解算导弹在赤道惯性系和发射点惯性系的三轴姿态，最后，给出了导弹初始定位、定向误差的数学表达式。仿真结果表明了该方法的有效性。     

Keeping Ma’at: An astronomical approach to the orientation of the temples in ancient Egypt

For various reasons, Archaeoastronomy has not been one of the favourite disciplines of the Egyptologists in the past. Probably because of that, important questions such as the orientation of Egyptian temples and the relevance of astronomy in this respect had never been afforded with the necessary seriousness and deepness. The Egyptian–Spanish Mission for the Archaeoastronomy of ancient Egypt has, among its various priorities, the solution of this problem. In order to achieve that, we have measured the orientation of some 330 temples in the Valley, the Delta, the Oases and the Sinai so far. The aim is to find a correct and almost definitive answer to the question of whether the ancient Egyptian sacred constructions were astronomically aligned or not. Our data seem to answer this question in the affirmative sense. Besides, they offer a very interesting new perspective in the field of landscape archaeology, a new discipline hardly worked in Egypt so far, in which terrestrial landscape, dominated by the Nile, and celestial landscape, dominated by the sun and the stars, would combine in order to permit the establishment of Ma’at, the Cosmic Order, on Earth.     

挠性杆的镗加工技术

针对挠性杆的结构特点和加工难点,提出了有效的工艺措施,从装夹定位、刀具材料与几何参数选择、刃磨方法、切削用量的选择,以及挠性杆内应力的分析等方面详细地阐述了加工过程中的关键技术,解决了挠性杆镗削加工的技术难题。