施瓦希-德希特时空中标量场辐射的反射系数和透射系数

采用以阶梯形势垒代替施瓦希-德希特时空中视界附近的势垒的方法,计算了此时空中标量场辐射的反射系数和透射系数。结果表明在此时空中,标量场的反射系数趋于零,而透射系数接近于1,即所有的标量场都将透过势垒而传播到无穷远。     

矿井MIMO信道模型的空间相关性研究

建立了矿井MIMO信道的模型,推导出该信道模型的空间相关性函数,分析了发送天线端天线间距和接收端天线间距对空间相关性的影响,在此MIMO信道模型的基础上,讨论了矿井的MIMO信道的空间相关性对系统误码率的影响,仿真结果表明,煤矿井下MIMO信道空间相关性越高,系统的误码率就越大。     

An adaptive spacetime discontinuous Galerkin method for cohesive models of elastodynamic fracture

This paper describes an adaptive numerical framework for cohesive fracture models based on a spacetime discontinuous Galerkin (SDG) method for elastodynamics with elementwise momentum balance. Discontinuous basis functions and jump conditions written with respect to target traction values simplify the implementation of cohesive traction–separation laws in the SDG framework; no special cohesive elements or other algorithmic devices are required. We use unstructured spacetime grids in a h‐adaptive implementation to adjust simultaneously the spatial and temporal resolutions. Two independent error indicators drive the adaptive refinement. One is a dissipation‐based indicator that controls the accuracy of the solution in the bulk material; the second ensures the accuracy of the discrete rendering of the cohesive law. Applications of the SDG cohesive model to elastodynamic fracture demonstrate the effectiveness of the proposed method and reveal a new solution feature: an unexpected quasi‐singular structure in the velocity response. Numerical examples demonstrate the use of adaptive analysis methods in resolving this structure, as well as its importance in reliable predictions of fracture kinetics. Copyright © 2009 John Wiley & Sons, Ltd.     

一类新的射影平坦的Finsler度量

利用Hamel射影平坦方程获得了一类新的Finsler度量F=αФ(b²,s)在开子集U⊂Rⁿ上射影平坦的充要条件,此类度量包含了由Bryant构造的Sⁿ上具有正常旗曲率K=1,且测地线为大圆周的Finsler度量.     

一类Randers度量

研究了一类特殊的Randers度量,找到了这类度量与黎曼度量α逐点射影等价的几个方程.     

A new result on stability analysis for stochastic neutral systems

This paper discusses the mean-square exponential stability of stochastic linear systems of neutral type. Applying the Lyapunov–Krasovskii theory, a linear matrix inequality-based delay-dependent stability condition is presented. The use of model transformations, cross-term bounding techniques or additional matrix variables is all avoided, thus the method leads to a simple criterion and shows less conservatism. The new result is derived based on the generalized Finsler lemma (GFL). GFL reduces to the standard Finsler lemma in the absence of stochastic perturbations, and it can be used in the analysis and synthesis of stochastic delay systems. Moreover, GFL is also employed to obtain stability criteria for a class of stochastic neutral systems which have different discrete and neutral delays. Numerical examples including a comparison with some recent results in the literature are provided to show the effectiveness of the new results.     

量子de Sitter时空的两种创生观

在两种不同边界条件下,用WKB法重解了量子de Sitter模型的Whee-ler-Dewitt方程.讨论了波函数的物理意义.并指出不同边界条件实际上对应着不同的de Sitter时空创生观.     

几种DOA估计算法的性能分析

在其他条件相同的情况下比较了Bartlett，Capon和Music算法的性能。Bartlett算法使波束形成的输出功率相对于某个输入信号为最大；Capon算法使噪声以及来自非信源方向的任何干扰所贡献的功率为最小，但又能保持信源方向上信号功率不变；Mustc算法是一种超分辨的方法，属于特征结构的子空间方法，因而有较高的分辨率。仿真结果征明了在其他条件相同的情况下，Music算法的性能量化。     

气相流化床工艺冷凝态操作冷剂浓度的控制

分析了冷凝态操作中异戊烷浓度对露点温度和反应负荷的影响,通过理论计算,总结生产经验得出了确定露点温度和反应负荷的方法以及冷凝态操作时生产负荷控制的最佳范围。     

球对称稳态时空中标量场辐射的反射系数和透射系数

采用以方形势垒代替球对称稳态时空中视界附近的势垒的方法,计算了球对称稳态时空中标量场辐射的反射系数和透射系数,发现在此种类型的时空中,标量场的投射系数均接近于1,即所有的标量场都将透过势垒而传播到无穷远。