基于多Markov链的效果评估模型研究

基于单Markov链的扫雷作战效果评估模型是一个理论意义大于实际的模型,离实际的多Markov扫雷过程还有相当的距离.文中从正交分解的角度,指出Markov评估模型只能进行定性评估.提出了用于定性评估的多Markov模型,从"分解基"相关性的角度提出了多链模型结构选择的方式,实现了基于遗传算法的模型解法,计算结果表明:在引入先验知识后,能在小样本数据条件下取得较为准确的评估结果.     

海水中时谐水平电偶极子的准近场定位

将海水看作无穷大的半空间,提出了基于准近场的时谐水平电偶极子的定位方法．在准近场条件下,只需在海水中布置两个双轴电场传感器测得相应位置的电场强度,运用所提出的反演定位方法和迭代算法,就能精确地确定偶极子在海水中的位置．给出了仿真计算,结果表明该反演定位方法具有极高的定位精度．     

水底涡压力场的计算与分析

水底涡主要是由于海流绕过海底凸起物后形成的,经扰动,旋涡脱体,随水流动.计算结果表明,水底涡的速度分布规律与龙卷风速度分布规律相同,在水底引起负压分布,其分布规律与舰船水压场类似,难以滤除,很容易引起水压引信误动.     

基于单个矢量水听器的二维波达方向估计

提出了一种基于单个矢量水听器的二维波达方向估计方法，该矢量水听器由三个空间轴向垂直的振速水听器和一个声压水听器构成．利用时延数据，以时间变元为旋转因子．构造了两个具有相同阵形的子阵，采用ESPRIT实现了对目标信号的波达方向估计．具有较好的估计精度，能实现方向余弦的自动配对，不造成波达方向的模糊性．计算机仿真实验结果证明了该方法的有效性。     

A30赵家沟桥大跨径连续箱梁施工技术

大跨径连续箱梁的施工技术是大跨径连续箱梁桥的一个难题。在施工过程中必须按照各种施工技术规格，各方面配合才能很好的完成。A30赵家沟桥在施工方案设计、施工步骤、技术要素等各方面做出了优秀的成绩。     

A NEW GENERATING METHOD FOR THE MACHINING OF A CYLINDRICALGEAR WITH SYMMETRIC ARCUATE TOOTH TRACE

Objective To introduce a new generating method for the machining of a cylindrical gear with symmetric arcuate tooth trace. Methods Adopting this method, the key problems of mismatch control and manufacturing of symmetric arcuate tooth trace gears are solved by using suitable cutter tilt and a new generating method with double-edge gear-wheel cutter. The machining principle is analyzed and the mathematical model of generating motion is established. Then the tooth flank equation and differential geometrical parameters are discussed. Results The minim alteration of cutter tilt will make the contact flank area change so as to satisfy the special requirements. It is easy to realize the tip relief of gearing by altering coefficients of every moving axis. Because the tooth has the arc shape, the symmetrical arcuate cylindrical gears have higher overall strength and it is easy to perform the flank grinding for high precision. Conclusion This new generating method has higher productivity. It is easy to get a perfect contact zone and fully give play to the potential bearing capacity of the gears. The symmetrical arcuate cylindrical gears can be used in highly durable and heavy duty gearing applications.     

分界面上基于矢量水听器阵列空间谱DOA估计

矢量水听器通常由三个空间轴向垂直的振速水听器和一个声压水听器构成，可同时测量声信号的振速和声压．为了了解复杂分界面上矢量水听器阵列的定向性能，根据分界面上平面波的反射模型，提出了改进的Bartlett和Capon空间谱，建立了统一框架，并且在绝对硬边界典型界面下，分析了基于矢量水听器阵列的定向性能．给出了具体算例．     

一种新型数控铣床总体方案初探

在分析大型回转曲面零件机械加工方法的基础上，本文提出一种新型数控铣床的总体方案。该机床刚性好，加工精度高，功能强，生产率高，控制系统稳定、可靠，价格便宜，具有推广价值和应用前景。     

The mispricing of transportation initial public offerings in the Chinese mainland and Hong Kong

The main objective of this study is to determine the level of mispricing of transportation IPOs in the Chinese mainland and Hong Kong. A subsidiary objective is to test the hypothesis that there is a strong positive correlation between the initial day returns that are required for new equity issues and the level of ex ante uncertainty associated with the IPO. By applying a standard methodology in finance for assessing the existence and scale of mispricing, the study finds significant underpricing for transportation IPOs in the Chinese mainland and Hong Kong. There is also evidence that freight-related IPOs are subject to more severe underpricing than non-freight related IPOs, and that water-transport IPOs are underpriced more than IPOs of other types of transport business. It is concluded that there does exist support for the hypothesis that the level of ex ante uncertainty is strongly associated with the level of mispricing and that this explains cross-sectional differences in the degree of underpricing of IPOs. In this respect, the results from the Chinese mainland and Hong Kong are consistent with the results of similar studies conducted elsewhere.     

真实感海洋视景仿真中的图形技术

介绍了真实感海洋视景的组成和仿真中所采用的图形技术。从仿真的实时性和真实感出发,着重介绍了实体对象的建模、海空气候环境模型、海洋自然环境模型及海洋场要素的可视化,并研究了提高仿真实时性所采用的光照模型和LOD模型与多级纹理映射相结合的方法。这些算法可以实现动态、逼真的三维真实感海洋环境,方法简单、实用。