非均匀损耗介质体电磁逆散射的非相关照射法

本文提出一种恢复非均匀损耗介质体复介电常数的新方法。它基于这样一个原则,即当介质体被一组非相关入射波照射。可以从其散射场中获得充分的有关介质体的信息。本文给出了有关的公式和数值模拟结果。准确的恢复数据说明这种方法在电磁逆散射和微波成象的研究中很有潜力。     

Hybrid methods for airframe noise numerical prediction

This paper describes some significant steps made towards the numerical simulation of the noise radiated by the high-lift devices of a plane. Since the full numerical simulation of such configuration is still out of reach for present supercomputers, some hybrid strategies have been developed to reduce the overall cost of such simulations. The proposed strategy relies on the coupling of an unsteady nearfield CFD with an acoustic propagation solver based on the resolution of the Euler equations for midfield propagation in an inhomogeneous field, and the use of an integral solver for farfield acoustic predictions.In the first part of this paper, this CFD/CAA coupling strategy is presented. In particular, the numerical method used in the propagation solver is detailed, and two applications of this coupling method to the numerical prediction of the aerodynamic noise of an airfoil are presented.Then, a hybrid RANS/LES method is proposed in order to perform some unsteady simulations of complex noise sources. This method allows for significant reduction of the cost of such a simulation by considerably reducing the extent of the LES zone. This method is described and some results of the numerical simulation of the three-dimensional unsteady flow in the slat cove of a high-lift profile are presented. While these results remain very difficult to validate with experiments on similar configurations, they represent up to now the first 3D computations of this kind of flow.     

一种解介质体散射问题的新方法

本文提出一种解非均匀介质体电磁散射问题的新方法。由测量到的介质体外的散射场,按照递推关系,可以求出全部介质体内的场分布。文章详细地推导了介质体内场分布的递推关系,并给出了计算机模拟计算的结果。     

用PSPICE实现电子电路的分析与设计

本文就一个有源低通滤波器的设计及其群时延均衡的过程,具体说明了PSPICE在电子电路分析和设计中所起的作用。     

Application de méthodes intégrales au calcul du bruit de cavitéComputation of cavity noise using integral methods

A direct numerical simulation of the sound radiated by a flow over a 2-D subsonic cavity is performed using Computational AeroAcoustics tools. The simulation is consistent with Karamcheti's experiments. The numerical results are used as a reference to study two integral formulations: the Ffowcs Williams and Hawkings acoustic analogy and a wave extrapolation method based on FW-H equation. These hybrid approaches agree with the direct computation by DNS data and provide powerful tools to compute far-field noise. To cite this article: X. Gloerfelt et al., C. R. Mecanique 330 (2002) 13–20     

Recent advances of computational aeroacoustics

Computational aeroacoustics (CAA) is an interdiscipline of aeroacoustics and computational fluid dynamics (CFD) for the investigation of sound generation and propagation from various aeroacoustics problems. In this review, the foundation and research scope of CAA are introduced firstly. A review of the early advances and applications of CAA is then briefly surveyed, focusing on two key issues, namely, high order finite difference scheme and non-reflecting boundary condition. Furthermore, the advances of CAA during the past five years are highlighted. Finally, the future prospective of CAA is briefly discussed.     

光学系统计算机辅助装调分析与应用

光学系统的计算机辅助装调（CAA）技术自20世纪80年代提出,从90年代开始在各个国家得到发展并逐渐运用到各个领域。在此简要介绍了计算机辅助装调技术及其装调过程,并推导了CAA的数学模型。通过广泛调研国内外计算机辅助装调的发展与应用,比较了各国成功应用CAA技术完成的装调。分析了目前国内CAA技术的发展状况,对传统装调方法和CAA方法的适用情况做了比较,为我国计算机辅助装调提供借鉴。     

A NUMERICAL METHOD OF DIRECT SEARCH OPTIMIZATION FOR PARAMETERS OF RECIPROCAL LOSSLESS TWO-PORT NETWORK

A numerical method of direct search optimization is presented for calculating param-eters of a reciprocal lossless two-port network(RLTPN).Some examples are given.It is pointedout that the results obtained by different methods agree with one another.     

AN IMPROVEMENT TO THE HARMONIC-BALANCE TECHNIQUE FOR ANALYZING NONLINEAR CIRCUITS

In this paper,an improved method,which is based on the harmonic-balance tech-nique,for speeding up the convergence iteration procedure is presented.As an example,it isapplied to the nonlinear analysis of microwave mixer,in which a simple time domain to fre-quency domain transformation technique for the mixer diode is firstly introduced.The use of thistechnique saves computing time dramatically.And the analyzed results are in good agreementwith the results published.The improved method can also be extended to the CAA of nonlinearcircuits with multi-devices.     

一个新的电路设计程序：TADS—C4

TADS-C4是以SPICE2GS&2G6为核心开发的电路模拟与设计程序。TADS-C4保持了SPICE的全部功能,并成功地加入了5种新的分析功能和8种新元器件。本文介绍新的分析功能和新元器件加入SPICE的原则、措施,最后给出计算实例。