短脉冲载荷下金属材料的层裂破坏

 本文用点炮加载聚酯薄膜飞片撞击金属靶材料，飞片速度0.714~2.24 km/s，脉冲宽度40~80 ns，击靶压力为2.280~11.952 GPa。在回收的铝、铜和钢靶样品上观察到层裂现象。通过金相分析发现它们的破坏方式与在一般较长脉冲加载下的破坏方式相似，铝和铜以延性方式破坏；钢则以脆性方式破坏。一维和二维数值模拟结果表明通常的几种层裂判据在这个应力、应变和应变率范围内也基本上适用。     

一种新的$1/f$过程小波模型

给出了一种新的二进小波1/f过程模型,从理论上证明了一类谱指数为H的近似1/f过程可通过一簇平稳随机过程产生.由于所提方法利用了1/f过程小波系数的相关性,因而有效地减少了合成1/f过程的谱误差.数值实验结果表明,新模型很好地改进了已有模型.     

模糊事件贝叶斯公式

讨论了模糊事件的概率及其基本性质 ,并通过对经典贝叶斯公式的推广 ,提出了模糊事件的贝叶斯公式 .     

基于矩阵初等变换的n元函数极值的快速判别法

给出了 n元函数极值的一个充分条件 ,并结合矩阵的初等变换建立了 n元函数极值的一种快速判别法 ,最后给出了一个例子     

Synthesis and optoelectronic properties of silole‐containing polyfluorenes with binary structures

2,5‐Bis(2‐bromofluorene‐7‐yl)silole was prepared by a modified one‐pot synthesis with a reverse addition procedure, from which novel silole‐containing polyfluorenes with binary random and alternating structures (silole contents between 4.5 and 25% and high M_w up to 509 kDa were successfully synthesized. The well‐defined repeating unit of the alternating copolymer comprises a terfluorene and a silole ring. Optoelectronic properties including UV absorption, electrochemistry, photoluminescence (PL), and electroluminescence (EL) of the copolymers were examined. The different excitation energy transfers from fluorene to silole of the copolymers in solution and in the solid state were compared. The films of the copolymers showed silole‐dominant green emissions with high absolute PL quantum yields up to 83%. EL devices of the copolymers with a configuration of ITO/PEDOT/copolymer/Ba/Al displayed exclusive silole emissions peaked at around 543 nm and the highest EL efficiency was achieved with the alternating copolymer. Using the alternating copolymer and poly(9,9‐dioctylfluorene) as the blend‐type emissive layer, a maximum external quantum efficiency of 1.99% (four times to that of the neat film) was realized, which was a high efficiency so far reported for silole‐containing polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 756–767, 2007     

On Two Parallel Matched Gratings Demodulation Method of Fiber Grating Strain Sensor

The method of demodulation with two parallel matched fiber Bragg gratings( FBGs)system is introduced to enlarge the range of strain that can be detected by the FBG sensor system.     

On the structure of stationary sets

We isolate several classes of stationary sets of [k]ωand investigate implications among them. Under a large cardinal assumption, we prove a structure theorem for stationary sets.     

有限混合Gamma分布的拓扑稠密性证明

首先给出了有限混合Erlang分布在正实数轴上所有概率分布中稠密的理论证明,进而给出了混合Gamma分布具有稠密性的结论,说明有限混合Gamma分布具有广泛的适用性,可以用来刻画正实数轴上的任意随机变量.     

Fuzzy Model of Regional Economic Competitiveness in GIS Spatial Analysis: Case Study of Gansu, Western China

After more than 20 years of impressive development since the economic reforms in 1978, today western China is facing an increasing development gap between its regions, particularly between urban and rural areas. Using the fuzzy comprehensive evaluation model, this paper aims to demonstrate the evolution of the economic competitiveness levels base on two categories of geographical unity in the province of Gansu located in Northwest China between 2000 and 2004. The results of fuzzy modeling are integrated into GIS spatiotemporal analyses in order to identify the spatial variation of each significant change in terms of the regional economic development. Our research effectively illustrates that there is a particular spatial dynamic of the economic development from region to region. Although the cities have improved very well in their economic competitiveness, the rural areas and minority regions still have a lot of progress to be achieved.     

关于开紧映射与Arhangel’skiǐ的问题

首先构造一T_2的亚紧空间使其不是任一仿紧T_2空间的开紧映象,否定了A．Arhangel'skiǐ1962年提出的一个问题；其次利用构造开紧映射的方法指出存在具有G_δ对角线的T_2的次亚紧空间使其不具有G_δ~*对角线,肯定地回答了1999年R．Hodel提出的一个猜测．