Novel Rat-race Hybrid Coupler for RF Front-end Module

In this paper, a novel compact rat-race hybrid coupler incorporating an improved beeline compact microstrip resonant cell(IB-CMRC) is presented firstly. The size of the coupler is reduced by 46.5% than conventional one due to IB-CMRC’s excellent slow-wave effect. The novel coupler possesses strong ability of high-order harmonic suppression (above 30 dB) in addition. The measured insertion loss is comparable to that of a conventional microstrip hybrid coupler. Great potential applications of this IB-CMRC can be explored in MICs and MMICs to reduce the circuits size, suppress harmonics and improve the overall performance of the RF front-end module.     

RELATIVELY WEAKLY COMPACT SETS IN THE DEN JOY SPACE

Some topological Properties of the completion H of the Denjoy space are studied. In particular sufficient conditions for a subsets of H be relatively compact and characterizations for a subsets of H be restively weakly compact are given.     

Dispersion and stability analyses of the linearized two‐dimensional shallow water equations in boundary‐fitted co‐ordinates

In the present investigation, a Fourier analysis is used to study the phase and group speeds of a linearized, two‐dimensional shallow water equations, in a non‐orthogonal boundary‐fitted co‐ordinate system. The phase and group speeds for the spatially discretized equations, using the second‐order scheme in an Arakawa C grid, are calculated for grids with varying degrees of non‐orthogonality and compared with those obtained from the continuous case. The spatially discrete system is seen to be slightly dispersive, with the degree of dispersivity increasing with an decrease in the grid non‐orthogonality angle or decrease in grid resolution and this is in agreement with the conclusions reached by Sankaranarayanan and Spaulding (J. Comput. Phys., 2003; 184 : 299–320). The stability condition for the non‐orthogonal case is satisfied even when the grid non‐orthogonality angle, is as low as 30° for the Crank Nicolson and three‐time level schemes. A two‐dimensional wave deformation analysis, based on complex propagation factor developed by Leendertse (Report RM‐5294‐PR, The Rand Corp., Santa Monica, CA, 1967), is used to estimate the amplitude and phase errors of the two‐time level Crank–Nicolson scheme. There is no dissipation in the amplitude of the solution. However, the phase error is found to increase, as the grid angle decreases for a constant Courant number, and increases as Courant number increases. Copyright © 2003 John Wiley & Sons, Ltd.     

Criterion for uniform invertibility of families of strong approximations to one-dimensional singular integral operators with continuous coefficients

A criterion is obtained for the applicability of the approximation method based on strongly approximating operator families converging to a one-dimensional singular integral operator with coefficients continuous in the circle. Some special cases are considered. Translated fromMatematischeskie Zametki, Vol. 62, No. 3, pp. 430–439, September, 1997. Translated by A. M. Chebotarev     

On certain spectral properties of a quadratic self-adjoint matrix pencil with dominating main diagonals

Sufficient conditions for the “separation of the spectrum” of a quadratic matrix pencil with self-adjoint coefficients are found. A criterion for the representability of a positive operator in a finite-dimensional space in the form of a matrix with dominating main diagonal in each orthonormal basis is obtained. Translated fromMatematicheskie Zametki, Vol. 61, No. 3, pp. 381–390, March, 1997. Translated by A. I. Shtern     

微分流形上的变换群

本文主要讨论如何把仿射Ｋｉｌｌｉｎｇ向量场、共形Ｋｉｌｌｉｎｇ向量场和射影Ｋｉｌｌｉｎｇ向量场推广成为四种张量场．我们得到了仿射Ｋｉｌｌｉｎｇｐ（≥１）形式和射影Ｋｉｌｌｉｎｇｐ（≥１）形式的多种定义，文献［１］中的定义仅是其中之一．     

Partial decay on simple manifolds

Existence, uniqueness and weighted regularity of solutions of linear and nonlinear second-order uniformly elliptic differential equations on complete punctured compact N-manifolds, N > 2. Application to prescribed curvature problems: scalar curvature in a quasi-isometry class (including a contribution to the Lichnérowicz-York equation of General Relativity); Ricci curvature in a weighted Kähler class (with a related result in equiaffine geometry). A new asymptonic behaviour is allowed throughout, called partial decay, which requires its own maximum principle.Current support: CNRS; partial support; CEE contract GADGET # SC1-0105-C.     

Eberlein mulian定理在局部凸空间中的推广

设（Ｅ，Ｔ）是一个分离的局部凸空间．本文主要结果是：（１）如果（Ｅ，Ｔ）是次可分的，那么ＡＥ是相对弱紧集Ａ是相对弱可数紧集Ａ是相对弱序列紧集．（２）如果（Ｅ，Ｔ）是强次可分且（Ｅ，β（Ｅ，Ｅ））是桶型空间，那么ＡＥ是相对弱紧集Ａ是相对弱可数紧集Ａ是相对弱序列紧集．     

一个新型电子直线加速器的预制研究

文中给出了对一个新型紧凑的电子直线加速器(linac)证明原理的研究结果.在该linac中,通过偏转磁场选择特定能量和相位的大功率速调管用毕束流,然后将它们注入到加速节中,同时使速调管工作在自激振荡状态,使传统linac上的许多部件都可以省去.据此建成的linac的结构简单、维护容易、性能良好、造价经济.因此实现这种具有众多优点的新型linac将有助于linac应用的推广.要实现这样的linac有许多关键的问题需要解决.电子束团的性能参量,如能量、电流、发射度,以及速调管自激振荡的频率稳定度等都必须符合加速的要求.文中给出的计算机模拟和实验结果都表明了实现这种新型的linac的可行性