平顶飞秒激光经圆锥透镜在熔融石英中成丝及超连续辐射

实验研究了平顶飞秒激光经圆锥透镜后在熔融石英中的成丝及超连续辐射.与高斯飞秒激光的成丝对比发现,平顶飞秒激光可以获得在圆锥透镜焦深区域内强度分布更为均匀的等离子体细丝,这一特征更有利于飞秒激光在固体介质中进行微纳加工等领域的应用.并且,在不损伤熔融石英的条件下,平顶飞秒激光成丝可以获得更高能量、更高转换效率的超连续辐射,这是因为若产生光强相近的细丝,平顶飞秒激光所需的初始激光能量更高,此激光能量下产生的细丝长度更长、均匀性更好.     

用显微拉曼扫描成象(mapping)法测集成电路中CoSi_2电极引起的应力

用显微拉曼扫描成象（ｍａｐｐｉｎｇ）法测集成电路中ＣｏＳｉ２电极引起的应力李碧波黄福敏张树霖（北京大学物理系北京１００８７１高玉芝张利春（北京大学微电子所北京１００８７１）ＳｔｒｅｓＩｎｄｕｃｅｄｂｙＣｏＳｉ２ＧｒｏｗｎｏｎＰｏｌｙｃｒｙｓｔａｌｉｎ...     

环状连续强激光下光学薄膜的瞬温和热畸变

详细研究了非冷却光学薄膜元件在环形激光光束辐照下的瞬态温度分布和随后的热畸变，并且用泰曼干涉仪实际测量了连续波氧碘激光辐照各种非冷却光学元件的热畸变量并与理论计算相比较，分析结果表明理论和实验相一致。     

准晶体中八方晶系点群的对称性与矩阵表示

从理论上对准晶体中八方晶系各点群进行了研究.运用八方晶系各点群的极赤投影图,列出了各点群的所有对称操作;填出了固有点群822的群乘表.运用坐标变换和群论在自定义的八方坐标系中,推导出八方晶系点群所有对称操作的矩阵.这32个3×3矩阵的结构是相当简洁的,它们的矩阵元只有5种可能取值:0,±1,±2.其中2是反映八方晶系准晶体所具有的准周期性的特殊无理数.     

ROBUST GLOBAL EXPONENTIAL STABILITY OF UNCERTAIN IMPULSIVE SYSTEMS

By using the quasi-Lyapunov function, some sufficient conditions of global exponential stability for impulsive systems are established, which is the basis for the following discussion. Then, by employing Riccati inequality and Hamilton-Jacobi inequality approach, some sufficient conditions of robust exponential stability for uncertain linear/nonlinear impulsive systems are derived, respectively. Finally, some examples are given to illustrate the applications of the theory.     

Ni-Si多层膜中固态非晶化反应的热力学与动力学过程

研究了Ni/非晶Si(a-Si)多层组分调制膜(ML)中界面上的固相反应。根据计算的亚稳自由能图,对界面上固相反应形成非晶态进行了热力学与动力学的分析。提出了Ni/a-Si多层膜中的固相反应的动力学模型。 关键词：     

External cavity diode laser around 657 nm

Operating a laser diode in an external cavity, which provides frequency-selective feedback, is a very effective method to tune the laser frequency to a range far from its free running frequency. For the Ca atomic Ramsey spectroscopy experiment, we have constructed a 657-nm laser system based on the Littman-Metcalf configuration with a 660-nm commercial laser diode. Continuously 10-GHz tuning range was achieved with about 100-kHz spectral linewidth, measured with beat-note spectrum of two identical laser systems.     

Dynamical Convergence Trajectory in Networks

It is well known that topology and dynamics are two major aspects to determine the function of a network. We study one of the dynamic properties of a network： trajectory convergence, i.e. how a system converges to its steady state. Using numerical and analytical methods, we show that in a logical-like dynamical model, the occurrence of convergent trajectory in a network depends mainly on the type of the fixed point and the ratio between activation and inhibition links. We analytically proof that this property is induced by the competition between two types of state transition structures in phase space： tree-like transition structure and star-like transition structure. We show that the biological networks, such as the cell cycle network in budding yeast, prefers the tree-like transition structures and suggest that this type of convergence trajectories may be universal.     

上海市黄瓜上市高峰量预报因子的选择和模型的建立

本文通过对上海市黄瓜上市高峰期产量预报因子的选择和模型的建立,摸索出上海市蔬菜上市的规律,对保证城市蔬菜均衡供应具有一定的意义。众所周知,黄瓜产量不仅与品种、栽培措施有关,而且与气象因素有着相当密切的关系.黄瓜生长期中,各种气象因子对其上市高峰量的影响是不同的。以往都是凭经验来确定某气象因子的时段.(所谓时段,是指某一段相隔一定天数的时间).这种方法所得到的结果并非最佳因子;而用这些因子组建的回归方程就带有极大的主观性,影响预测的结果.因此,为避免不     

晶体学与准晶体学点群的母子群关系

依据群论，得出了准晶体学点群的直积或半直积推导算式；依据结晶学理论，绘出了五角、八角、十角和十二角晶系各点群的极赤投影图.据此推导出了每一个准晶体学点群的全部最大子群，从而推导并绘制出了三维晶体学和准晶体学点群之间的母子群关系(60个点群的“家谱”).该“家谱”以最大子群链的图解形式直观地给出了每个点群的最小母群和最大子群. 关键词： 准晶体 晶体 点群 最大子群 最小母群 群链