Asymptotics of derivatives of orthogonal polynomials on the real line

We show that uniform asymptotics of orthogonal polynomials on the real line imply uniform asymptotics for all their derivatives. This is more technically challenging than the corresponding problem on the unit circle. We also examine asymptotics in the L ₂ norm. Research supported by NSF grant DMS0400446 and US-Israel BSF grant 2004353.     

A note on cycle spectra of line graphs

We show that line graphs G=L(H) with σ₂(G)≥7 contain cycles of all lengths k, 2rad(H)+1≤k≤c(G). This implies that every line graph of such a graph with 2rad(H)≥Δ(H) is subpancyclic, improving a recent result of Xiong and Li. The bound on σ₂(G) is best possible.     

ε－次可微多目标规划的最优性条件

本文主要从多目标规划相应的加权问题出发，讨论了在ε－次可微的条件下，凸多目标规划问题η－有效解存在的必要条件与充分条件．     

波导中入射脉冲的重建

本文用时域有限差分算法给出了波导中入射场的重建方法，研究了波导中脉冲传播的吸收边界条件。用本文的方法，只要测量出波导出口面上任一位置的场随时间的变化曲线，即可实现入射场的精确重建。     

关于隧道二极管电路

隧道二极管的伏安特性是一条“N”形的曲线，含有隧道二极管的电路是一种非线性电路。研究非线性电路的一种有效方法是分段线性化法,它的特点是把非线性的求解过程分成几个线性区段，对每一个线性区段再应用线性电路的分析方法。本文完整地阐述了分段线性化法的步骤，对如何建立线性化后的方程，进行了较详细的讨论，并在每一个线性区段，建立求解工作点的一组线性方程。最后求解这些方程，它们的有效解就是隧道二极管电路实际的工作点。     

“边沿跟踪法”抗距离欺骗干扰的计算机仿真

介绍了一种脉冲雷达的距离跟踪方案，研究了距离欺骗干扰的原理。分析了抗距离欺骗干扰的各种方法中存在的问题。提出了“边沿跟踪法”抗距离欺骗干扰的方案，用计算机仿真的方法对该方案进行了验证。仿真结果表明，“边沿跟踪法”可以有效地对抗距离欺骗干扰。     

微波检测模块

从微波电路、运放及数字电路、脉冲检测等方面介绍了微波检测模块，给出了有关数据并对问题进行了讨论。     

A comparative study of inflow conditions for two‐ and three‐dimensional spatially developing mixing layers using large eddy simulation

A series of spatially developing mixing layers are simulated using the large eddy simulation (LES) technique. A hyperbolic tangent function and data derived from boundary layer simulations are used to generate the inflow condition, and their effects on the flow are compared. The simulations are performed in both two and three dimensions. In two‐dimensional simulations, both types of inflow conditions produce a layer that grows through successive pairings of Kelvin–Helmholtz (K–H) vortices, but the composition ratio is lower for the hyperbolic tangent inflow simulations. The two‐dimensional simulations do not undergo a transition to turbulence. The three‐dimensional simulations produce a transition to turbulence, and coherent structures are found in the post‐transition region of the flow. The composition ratio of the three‐dimensional layers is reduced in comparison to the counterpart two‐dimensional runs. The mechanisms of growth are investigated in each type of simulation, and amalgamative pairing interactions are found in the pre‐transition region of the three‐dimensional simulations, and throughout the entire computational domain of those carried out in two‐dimensions. The structures beyond the post‐transition region of the three‐dimensional simulations appear to behave in a much different manner to their pre‐transition cousins, with no pairing‐type interactions observed in the turbulent flow. In order to accurately simulate spatially developing mixing layers, it is postulated that the inflow conditions must closely correspond to the conditions present in the reference experiment. Copyright © 2007 John Wiley & Sons, Ltd.     

一种脉冲多普勒天气雷达接收机

介绍了一种C波段脉冲多普勒天气雷达接收机。该接收机采用了大动态接收、低相噪频率合成、频率稳定性在机测试、系统实时标定和先进BITE等技术 ,取得了十分满意的效果。目前该雷达已成为我国气象组网骨干雷达     

大平面二极管虚阴极振荡器的宽脉冲微波辐射

给出了产生宽脉冲微波辐射的大平面天鹅绒二极管虚阴极振荡器的结构和测试装置，测得了二极管中阴－阳极等离子体的闭合速率为３０～４３ｋｍ／ｓ，获得了微波辐射的最大脉宽为１．５μｓ，产生的微波峰值功率约为１５ＭＷ，频率为０．５ＧＨＺ，指出这种平面二极管型虚阴极振荡器在辐射脉宽，辐射频率和辐射功率三者之间存在着物理上的制约关系，认为同轴型虚阴极振荡器是突破这种制约关系的一个新途径．