An Immersed Boundary Method with Formal Second-Order Accuracy and Reduced Numerical Viscosity

A formally second-order accurate immersed boundary method is presented and tested in this paper. We apply this new scheme to simulate the flow past a circular cylinder and study the effect of numerical viscosity on the accuracy of the computation by comparing the numerical results with those of a first-order method. The numerical evidence shows that the new scheme has less numerical viscosity and is therefore a better choice for the simulation of high Reynolds number flows with immersed boundaries.     

两种含钆双1:11杂多配合物的合成、表征、稳定性及驰豫性质

以两种稀土杂多配合物K15[Gd（BW11O39）2]和K17[Gd（CuW11O39）2]作为研究对象，采用元素分析、红外光谱对其结构进行表征，并用电导法对其稳定性、溶解性进行研究，测试其在水中及运铁蛋白溶液中的弛豫效率．结果表明这两种稀土杂多配合物的弛豫效率远高于目前临床常用的造影剂Gd—DTPA，是比较好的潜在的磁共振成像造影剂候选化合物．     

Single-machine scheduling with learning and forgetting effects

Scheduling with learning effects has been widely studied in the past decade. With the increasingly moving toward shorter product cycle times in many production lines, workers in this changeable environment must constantly learn new skill and technology. As a result, the forgetting effect might occur in these situations. In this paper, we propose a model with the consideration of both the learning and forgetting effects. We show some single-machine problems remain polynomially solvable under the proposed model.     

梯形透过率光栅远场光强分布及光栅方程的解析推导

二值化梯形透过率光栅是一种具有离轴衍射级次的二维光栅,其各衍射点光强信息和位置信息的确定对该新型光栅的实际应用具有重要意义。然而,目前尚无相关解析理论对其进行合理的描述。为了解决上述问题,通过二维傅里叶变换方法获得了该光栅各个衍射级次光强分布的解析表达式,并根据二维光栅的结构特征给出了在透射式和反射式情况下该光栅满足的光栅方程。这为该新型光栅的光线追迹计算打下了理论基础。最后,将解析表达式计算结果与采用X-Lab软件标量衍射模块计算的数值模拟结果进行比较,验证解析理论的正确性。     

硅基低位错密度厚锗外延层的UHV/CVD法生长

利用超高真空化学气相淀积系统, 基于低温缓冲层和插入应变超晶格的方法, 在Si(100)衬底上外延出厚度约为880 nm的纯Ge层. 采用X射线双晶衍射、高分辨透射电镜、原子力显微镜和光致发光谱分别表征了其结构及光学性质. 测试结果显示外延Ge的X射线双晶衍射曲线半高宽为273", 表面均方根粗糙度为0.24 nm, 位错密度约为1.5×10⁶ cm². 在室温下观测到外延Ge的直接带跃迁光致发光, 发光峰值位于1540 nm. 表明生长的Si基Ge材料具有良好的结晶质量, 可望在Si基光电子器件中得到应用.     

Si1−xGex/Si multi-quantum well phototransistor for near-infrared operation

For the first time in the literature, we report the monolithic integration of SiGe near-infrared phototransistor and planar hetero-junction bipolar transistor (HBT). The phototransistor is made with SiGe/Si multi-quantum well structure (MQW_PHT). At room temperature, the MQW_PHT reveals an optical responsivity of 1904 mW/A at 0.85 μm and 1.25 mW/A at 1.3 μm under the reversed bias of V_CE=1.5 V. For electrical DC and microwave performance, the SiGe HBT has a current gain of 160 and a cut-off frequency (f_T) of 25 GHz, respectively.     

Properties of vertex cover obstructions

We study properties of the sets of minimal forbidden minors for the families of graphs having a vertex cover of size at most k. We denote this set by O(k-VERTEX COVER) and call it the set of obstructions. Our main result is to give a tight vertex bound of O(k-VERTEX COVER), and then confirm a conjecture made by Liu Xiong that there is a unique connected obstruction with maximum number of vertices for k-VERTEX COVER and this graph is C_2k+1. We also find two iterative methods to generate graphs in O((k+1)-VERTEX COVER) from any graph in O(k-VERTEX COVER).     

利用结构相关性方法研究碳氢键活化反应C-H+M■的机理

本文利用结构相关(?)方法对碳氢键活化反应的氧化加成反应机理进行了研究.建立了反应的过渡态,并对反应途径进行了描述.根据所得到的反应途径对碳氢键活化研究中的一些问题进行了解释.