光纤受激调制不稳定性的谱理论

利用多重尺度微扰法,直接从包含非线性极化项的麦克斯韦方程组出发,得到了在频域描述光纤中的受激调制不稳定性的谐波耦合方程组,在此基础上,得出了受激调制不稳定性的谱分布的一些数字结果。     

Synthesis of ternary mesoporous Cu-Zn-SiO2 materials at ambient temperature and their application for the water gas shift reaction

A series of ternary mesoporous CuZnMCM-41 materials has been synthesized at ambient temperature and their structure was characterized by XRD, N₂ physical adsorption and TPR techniques. Their catalytic applications in CO water gas shift reaction were studied.     

A Globally Convergent and Efficient Method for Unconstrained Discrete-Time Optimal Control

Shift schemes are commonly used in non-convex situations when solving unconstrained discrete-time optimal control problems by the differential dynamic programming (DDP) method. However, the existing shift schemes are inefficient when the shift becomes too large. In this paper, a new method of combining the DDP method with a shift scheme and the steepest descent method is proposed to cope with non-convex situations. Under certain assumptions, the proposed method is globally convergent and has q-quadratic local conve rgence. Extensive numerical experiments on many test problems in the literature are reported. These numerical results illustrate the robustness and efficiency of the proposed method.     

非线性时滞差分方程的线性化振动性

本文分临界和非临界两种情形，建立了非线性时滞差分方程与其线性化方程振动性等价定理，推广和改进已有的工作．作为推论，修正了文[２］中主要定理的错误．     

提高双参量光纤传感器精度的一种方法

分析了光纤传感器进行双参量测量时，系数矩阵的态性对待测量精度的影响，提出采用对系数矩阵进行预处理的方法，使得处理后的矩阵由病态变成良态。用方法对文献「４」和文献「５」给出的系数矩阵分别进行了处理。处理后，文献「４」系数矩阵的条件数从３４２降低到４，文献「５」系数矩阵的条件数从１６１降低到３，传感器输出不确定主降低了两个数量级。     

催化裂解CH4制备碳纳米管的影响因素

以柠檬酸法制备的Fe MgO、Co MgO和Ni MgO为催化剂 ,CH4 为碳源气 ,H2 为还原气 ,在 873、973和 10 73K制备出碳纳米管 ,通过TEM和拉曼光谱表征 ,讨论了催化剂、制备温度、反应时间等因素对碳纳米管形貌、产率和内部结构的影响 .结果表明 :不同的催化剂在相同的温度下制备的碳纳米管的形态和内部结构有很大的差异 .其中Fe MgO催化剂制备的碳纳米管管径粗 ,且大小不均匀 ,而Ni MgO催化剂制备的碳纳米管管径较细、较均匀 .碳纳米管的产率随着裂解温度的变化而改变 .Fe MgO催化剂制备碳纳米管的产率随制备温度的升高而提高 ,而Ni MgO催化剂制备碳纳米管的产率随制备温度的升高而降低 .Fe MgO催化剂制备碳纳米管 ,在10 73K甚至更高的制备温度才能达到其最高产率 .Co MgO催化剂制备碳纳米管的产率在 973K左右产率较高 ,而用Ni MgO催化剂制备碳纳米管 ,则在 873K甚至更低的制备温度就能达到最高产率 .反应时间与碳纳米管的产率不成正比 ,有一最佳反应时间 ,如Ni MgO催化剂的最佳反应时间为 2h .     

The Constrained Solutions of Two Matrix Equations

We study the symmetric positive semidefinite solution of the matrix equation AX ₁ A ^T + BX ₂ B ^T = C, where A is a given real m×n matrix, B is a given real m×p matrix, and C is a given real m×m matric, with m, n, p positive integers; and the bisymmetric positive semidefinite solution of the matrix equation D ^T XD = C, where D is a given real n×m matrix, C is a given real m×m matrix, with m, n positive integers. By making use of the generalized singular value decomposition, we derive general analytic formulae, and present necessary and sufficient conditions for guaranteeing the existence of these solutions. Received December 17, 1999, Revised January 10, 2001, Accepted March 5, 2001     

Unexpected Synthesis of 2, 2＇-[1-（4-Methoxyphenoxy）propane-2, 2-diyl]bis（5-methoxy-3-methylbenzofuran）

A new bisbenzofuran analogue Ⅶ was achieved unexpectedly in one step procedure from 1-（4-methoxyphenoxy）acetone Ⅰ by using Amberlyst 15 resin as catalyst in excellent yield. The structure was elucidated by spectroscopy analysis including ^1H-NMR, ^13C-NMR, DEPT, ESI-MS, element analysis.