Comments, with reply, on 'convergence properties of Gram-Schmidt and SMI adaptive algorithms' by K. Gerlach and F.F. Kretschmer, Jr

The commenter summarizes Q-R decomposition techniques for solving the least squares (LS) problem and comments on associated aspects of the work presented by K. Gerlach and F.F. Kretschmer, Jr. (ibid., vol.267, no.1, Jan.90). In response to the commenter's statement that the statistical properties of the LS that determine the convergence performance are well known. Gerlach and Kretschmer assert that this is true only under the assumptions that have been used in the past to analyze the convergence performance of the canceler and for only a limited number of convergence performance measures. Gerlach and Kretschmer also address the commenter's points on overmatching degrees of freedom.<>     

Use of Nonquadratic Regularization in Fourier Imaging

In many Fourier imaging applications, the presence of unaccounted for amplitude or phase errors in the Fourier domain data can lead to a degraded system impulse response and high sidelobes in the image domain. Historically, many methods for data-driven correction of these effects have been proposed, and numerical optimization of nonquadratic, p-norm image quality metrics has recently emerged as a robust solution. This paper presents a tutorial examination of the sources of image sidelobes in Fourier imaging applications, and studies the effectiveness of p-norm regularization algorithms under various experimental conditions. Several observations are made, including comments on robustness to noise and methods for tapered window design and energy-constrained sparse aperture imaging. Image examples are presented as experimental validation.     

飞机风挡透明件的鸟撞分析

 本文研究了风挡透明件鸟撞动力响应的分析模型和方法。考虑了撞击载荷与风挡透明件动力响应的耦合作用和非线性效应。为了能方便地使用现有的非线性有限元分析程序并避免数值解的振荡现象,在研究中不采用常用的拉格朗日法和罚函数法,而是采用动量平衡法。同时,为了避免不断调整撞击接触点和修改网格,本文采用超弹性的橡皮材料来模拟鸟体,而不是象国外那样采用流体柱。研究和比较了衍生动载荷响应解,并提出相应的看法。     

Transfer element method with application to acoustic design of aeroengine nacelle

In the present survey, various methods for the acoustic design of aeroengine nacelle are first briefly introduced along with the comments on their advantages and disadvantages for practical application, and then detailed analysis and discussion focus on a kind of new method which is called ‘‘transfer element method'(TEM) with emphasis on its application in the following three problems: turbomachinery noise generations, sound transmission in ducts and radiation from the inlet and outlet of ducts, as well as the interaction between them. In the theoretical frame of the TEM, the solution of acoustic field in an infinite duct with stator sound source or liner is extended to that in a finite domain with all knows and unknowns on the interface plane, and the relevant acoustic field is solved by setting up matching equation. In addition, based on combining the TEM with the boundary element method(BEM) by establishing the pressure and its derivative continuum conditions on the inlet and outlet surface, the sound radiation from the inlet and outlet of ducts can also be investigated. Finally, the effects of various interactions between the sound source and acoustic treatment have been discussed in this survey. The numerical examples indicate that it is quite important to consider the effect of such interactions on sound attenuation during the acoustic design of aeroengine nacelle.     

Xs-MET-a reduced complexity fabrication process using complementaryheterostructure field effect transistors for analog, low power, spaceapplications

The requirements for space-based integrated circuit applications are defined with an emphasis on being radiation tolerant and low power consuming. Flexible analog signal processors (FASPs) are outlined as a means by which effective circuit designs can be utilized to perform a multitude of tasks. The development of complementary III-V technologies have been proven to meet the demands of the space environment, and have demonstrated the potential for frequency operation beyond 1 GHz using power supply voltages at or below 1.5 Volts. The novel fabrication process known as Xs-MET (pronounced kismet, which uses the Creek letter chi, X, and stands for Complementary Heterostructure Integrated Single Metal Transistor), is introduced as a manufacturing technique to be used in FASP design. The Xs-MET fabrication process is outlined with preliminary device results presented. An example of a FASP circuit design using Xs-MET is provided. Conclusions regarding the utilization of the Xs-MET process for FASPs are outlined with comments focusing on a space-based demonstration     

GEOS-1 observations of electrostatic waves,and their relationship with plasma parameters

In this paper we describe and discuss the occurrence of natural wave emissions detected by GEOS-1 at frequencies above the electron gyrofrequency. The bulk of the data presented comes from the first six months of satellite operation and thus concerns mainly dayside phenomena. The paper is arranged as follows:After some general remarks, a classification of the wave phenomena is developed in Section 2, and experimental evidence and morphological information relevant to this classification are contained in Section 3. Section 4 includes some preliminary comments on nightside observations. The results are discussed in Section 5, where it is argued that they can be understood as manifestations of electron cyclotron harmonic (Bernstein) wave emission in a plasma parameter range which has only very recently received any theoretical examinations. This theme is further developed in a comparison paper (Ronnmark et al., 1978).     

A Comparison of Techniques for Solving the Poisson Equation in CFD

CFD is a ubiquitous technique central to much of computational simulation such as that required by aircraft design. Solving of the Poisson equation occurs frequently in CFD and there are a number of possible approaches one may leverage. The dynamical core of the MONC atmospheric model is one example of CFD which requires the solving of the Poisson equation to determine pressure terms. Traditionally this aspect of the model has been very time consuming and so it is important to consider how we might reduce the runtime cost. In this paper we survey the different approaches implemented in MONC to perform the pressure solve. Designed to take advantage of large scale, modern, HPC machines, we are concerned with the computation and communication behaviour of the available techniques and in this text we focus on direct FFT and indirect iterative methods. In addition to describing the implementation of these techniques we illustrate on up to 32768 processor cores of a Cray XC30 both the performance and scalability of our approaches. Raw runtime is not the only measure so we also make some comments around the stability and accuracy of solution. The result of this work are a number of techniques, optimised for large scale HPC systems, and an understanding of which is most appropriate in different situations.     

Remarks on ?Comments on 'Signal Resolution via Digital Inverse Filtering'?

Published comments on a recent paper criticized the use of inverse filtering as applied to resolution of overlapping radar signal returns. It is shown that an inadequate model of the inverse filter was assumed by the critic, which lead him to predict excessive time sidelobes at the filter output. It is demonstrated, by computer simulation, that the time sidelobes at the output of the true inverse filter are down 30 dB or more.     

国际反倾销制度评析

论述了WTO下的国际反倾销制度概念，对各国反倾销制度进行了比较研究，并对当前国际反倾销制度的扩大化和成为贸易保护手段的趋势及对中国的影响进行了探讨。     

BW—1变稳飞机飞行品质试验研究

本文论述利用BW-1变稳飞机对人感特性与短周期特性及其组合进行的大量的地面模拟试验和空中飞行试验。由驾驶员操纵飞机完成特定的任务,通过大量的客观试验数据和驾驶员的主观评定(评定等级和建议),研究纵向操纵品质特性,使中国驾驶员对库珀—哈珀评定标准有了进一步的认识,给出了一些结论和建议。     

桨扇的气动弹性力学和气动声学

在桨扇技术发展过程中,桨扇的气动弹性力学与气动声学是主要技术关键中的两个很受重视的问题。本文对于上述二问题的历史发展过程,处理方法及己取得的主要成果作了阐述,对于其现状和发展趋势提出了一些看法。      

多部件模型在全尺寸小型双函道涡扇发动机气流数值模拟中的应用

利用高阶单调Ｇｏｄｕｎｏｖ显／隐格式求解全尺寸小涡扇发动机Ｓ２流面上带粘性力项的非定常Ｅｕｌｅｒ方程组,获得了令人满意的稳定收敛解。对多部件模型方法在双函道小涡扇发动机气流数值模拟应用中存在的问题提出了建议。     

一维、稳态、非热平衡发汗冷却的解析解研究

为了研究热平衡假设给求解发汗冷却问题带来的误差,同时避免非热平衡能量方程求解中边界条件提法上的争议,对一维、稳态、非热平衡发汗冷却数学模型进行了简化。通过忽略冷却介质流体在微孔流动中的热传导作用,得到了发汗冷却问题的解析解。利用解析解,讨论了热平衡与非热平衡的变化趋势以及影响热平衡的关键参数,并在此基础上,提出一个定量的热平衡假设使用准则。通过分析多孔材料骨架温度的变化趋势,研究了影响发汗冷却效率的因素。      

鸟撞飞机的一般规律和防撞措施

 1.按月份统计的事故次数 不同月份鸟撞事故的次数有明显的差别。图1中实线是中国空军1957年～1982年50例的统计情况;虚线是美国空军1966年～1972年2492例的统计情况。资料表明,每年4月、5月、9月、10月为事故多发期,约占60％。日本一家民航公司1981年～1983年的统计表明约有60％的事故发生在7月～10月中。究其原因,一是春秋两季为候鸟迁徙期;二是此     

浅析朱敦儒隐逸词

朱敦儒隐逸词题材广泛，内容丰富，反映了作者曲折的生活经历和出尘脱俗的精神世界。其恬淡、豁达的心境，既是诗人的人生个性，也创造了南宋隐逸词晶莹明净的优美意境。     

绍剧:乌篷船里看一夜好戏

那夜似的好戏,是让江南的百姓兴奋千年,至今痴迷追逐的绍剧。这个评价里除了对戏剧本身的赞叹,也夹着文学巨匠对家乡绍兴的浓厚感情。"大敲,大叫,大跳……很不适于剧场,但若在野外散漫的所在,远远地看起来,也自有它的风致。"绍剧,质朴而高昂,一年四季天天有人演,场场观众人山人海,尤其是进入腊月后的数月里,常常因观众"拥挤不堪"而临时取消演出。它从来不以复杂的技巧或者华丽的装扮取舍,却传承数千年的根本是那浓烈的人情味,至今仍紧紧地与地气相接的地方剧种已经少而又少。     

海南航空公司偿债能力评价

航空公司具有高投入、高风险、低利润的特征，航空公司偿债能力分析对航空公司的管理者、投资者和债权人都具有十分重要的意义，客观评价其偿债能力状况显得尤为重要。通过对国内四家上市航空公司2003年年报资料(母公司)进行对比分析，对海南航空股份有限公司的偿债能力状况提出自己的看法。     

略论民航术语的统一和规范化

首先介绍了民航术语及其典籍出版现况,其次根据近期发表的科技术语规范原则在比较和对照的基础上,提出了作者的见解,最后以中国民航总局适航司和安全技术中心编译的《民用航空术语汇编》作为例样,择其某些欠妥词语,参照术语规范原则加以比较和剖析。     

Comments on "Receiver antenna scan rate requirements needed to implement pulse chasing in a bistatic radar receiver"

For original paper see D.S.Purdy, ibid., vol.37, no.1, pp.285-7 (2001). It is shown that by selecting a different time variable, the approximations the author claims to be in error are indeed accurate. A reply by D.S.Purdy to these comments is included.