基于气动参数之间关系的桥梁断面气动导纳识别

气动导纳的准确估计对大跨桥梁抖振分析具有重要意义.目前在识别方法、试验技术等方面均有诸多进展,但尚未建立识别全部气动导纳函数的方法.针对这一问题,基于气动导数与气动导纳之间的关系,结合根据紊流风场中的抖振响应同时识别桥梁结构气动导数和气动导纳这一思路,首先采用随机子空间法识别得到紊流风场中桥梁结构的气动导数,然后利用气动导数与气动导纳之间的近似关系获取与竖向脉动风分量对应的气动导纳函数,最后根据抖振力谱和脉动风速谱来确定与水平向脉动风分量对应的气动导纳函数.实例研究表明,本文方法对流线型断面气动导纳的识别是可行的.     

含弹簧-质量系统的多段杆的撞击响应

 杆截面形状和质量以某些特定函数（如多项式函数、指数函数及三角函数等）变化时,给出了其弹性撞击问题的闭合解。使用直接模态叠加法（DMSM）研究了不等截面杆及含附加弹簧 质量系统杆的弹性撞击问题。把撞击物和被撞击物作为一个整体系统振动,从而把撞击问题转化为振动问题。基于各段杆上纵向位移的闭合解,得到撞击系统的频率方程、广义质量,并由Duhamel积分得到动力响应。与常规有限元法比较,所提方法能够减少划分单元的总数和CPU运行时间。算例验证了本文方法的有效性。     

MODAL PARAMETERS EXTRACTION WITH CROSS CORRELATION FUNCTION AND CROSS POWER SPECTRUM UNDER UNKNOWN EXCITATION

Artificial excitation is the most employedtype,but it is not suitable for some large- scalestructures such as platforms,bridges and build-ings,because a sufficient amount of excitation en-ergy can be needed to vibrate these structures,andthat impliesthe dangerofdamaging them locally orglobally.So natural excitation ( such as wind,wave,and traffic excitation) can be used in thesecases.However,a measure of the input force be-ing applied to the systems is not available and onlythe response can be…     

Frequency hop multiple access codes based upon the theory of cubiccongruences

The need for families of frequency-hop codes which have mutually small auto-ambiguity and cross-ambiguity functions is discussed. Current coding methods are reviewed. A new family of frequency-hop codes based upon the number-theoretic concept of cubic congruences is introduced. It is shown that for about 50% of the prime numbers, families of full codes exist which have at most two coincidences for any time-frequency shift in their auto-ambiguity functions and at most three coincidences in the set of mutual cross-ambiguity functions     

Probability Densities and Characteristic Functions for Fluctuating Targets

Probability density functions and characteristic functions for the projected area of a tumbling target object are derived together with the densities and characteristic functions for the corresponding signal-plus-noise voltage output of an infrared sensor. Several cases are considered in which the signal pulse arrival time is either known or unknown, a matched filter or a suboptimum filter is used; the signal pulse shape is either Gaussian or is unspecified; and the target orientation angles are either uniformly or nonuniformly distributed.     

Concepts of user centered automation

The accident statistics of large technical systems have been steadily improved during the last decades. Also the number of fatal accidents in air and surface transportation is decreasing in spite off increased traffic. However, the relative share of so called human errors is increasing across application areas. Hence, for further improved reliability, the functional integration of humans in such systems must be reconsidered. Since the user, in the long run, will not and should not be eliminated by computers this paper reviews basic requirements of a human centered automation. Following an analysis of generic system functions, human factors requirements for automated functions are defined. It is shown how manual functions can be supported by assistance functions, for which a general system architecture and a classification scheme are presented.     

Comparison of variants of the triangular discrete element shape functions for the vector method of shell displacement interpolation

Different variants of finding shape functions in a triangular finite element are considered. The efficiency of the vector method proposed by the authors for obtaining approximating functions is proved by specific examples.     

浅析FAA和CAAC制造检查领域委任代表的授权职能

基于民用航空器制造的实践经验和美国联邦航空局（Federal Aviation Administration,以下简称FAA）与中国民用航空局（Civil Aviation Administration of China,以下简称 CAAC）适航规章的研究,重点分析了FAA与CAAC制造符合性检查领域对委任代表的授权职能。从适航规章要求、制造符合性检查领域委任代表的分类、具体的授权职能及产生这些差异的原因进行了阐述。虽然两个民航局在制造符合性检查的授权职能上存在差异,但是只有与航空工业水平相适应的适航管理,才能更好地促进航空业的发展。     

Design of Weighting Functions Under Peak Amplitude and Effective Radiated Voltage Constraints

The problem of designing optimum weighting functions subject to peak amplitude and effective radiated voltage constraints occurs in the design of active phased arrays and in spectrum control of high-pulse-repetition frequency (PRF) pulsed Doppler transmitters. Algorithms for generating such weighting functions are developed using a least-squares technique. Numerical results are presented which show that these algorithms yield substantial performance improvement over textbook weighting functions in favorable circumstances.     

可压缩湍流边界层壁面函数方法综述

以建立工程实用的高超声速湍流边界层模拟方法为目标,从湍流壁面函数是湍流边界层方程近似解的角度,梳理了相关文献的研究工作,得到如下认识:1)壁面函数与所求定解问题数值解的相容程度决定了壁面第一层网格允许放粗的程度,在流动分离点和再附点附近区域,目前壁面函数尚需进一步完善,而"子网格"壁面函数从理论上解决了相容性问题,尽管...     

阶梯函数逼近阶与若干函数类的特征

利用阶梯函数逼近给出了连续函数类的特征,并在此基础上分别导出阶梯函数逼近李普希兹函数类和狄尼-李普希兹函数类的逼近阶。     

基于自适应多点约束逼近的二级结构优化方法研究

 本文对结构优化设计提出了一种二级逼近方法。基于优化过程中所得到的若干点上临界约束函数值及其一阶导数,构造出显式近似函数逼近原约束函数。该近似函数的非线性程度由自适应方法控制,使之在其展开域内接近真实约束函数;由此建立逼近原结构优化问题的第一级显式非线性序列近似问题。为处理其中每个子问题,建立逼近它的第二级序列近似问题,然后采用对偶方法对其求解。算例表明本文方法具有收敛迅速稳定的特点。     

论政府经济职能与非经济职能的关系

政府职能是由政府经济职能与政府非经济职能(包括政治职能和社会职能)构成的职能体系.政府经济职能与非经济职能是政府应该履行的不同职能,两者之间存在着相同之处,也存在着不同之处;两者相互依存,相互制约.政府经济职能目标与非经济职能目标既存在协调的一面,也存在相冲突的一面.在政府要实现的职能目标中,政府优先选择的顺序是不同的,政府经济职能与非经济职能之间相互依存、相互制约的关系决定了政府职能机构体系的复杂性,也决定了政府要有效地履行其职能,就必须使政府各职能部门相互配合和协调.     

教学计划管理MIS的设计与实现

本文详细介绍了沈阳航空工业学院教学计划管理信息系统的开发过程、功能及实现技术。此系统基于校园网环境，实现了教务管理中的教学培养计划管理、学分计算、部门管理、课程管理及各项统计。     

民用飞机刹车系统接地保护、锁轮保护和滑水保护研究

介绍了民用飞机刹车系统的三个保护功能,即接地保护、锁轮保护和滑水保护功能,这三者虽然是刹车防滑功能的辅助功能,却对飞机的安全性和操作性有着重要影响。针对三个保护功能,分别分析了其设置目的、工作阶段、作用原理和控制逻辑,并给出了控制逻辑的建议值。鉴于其重要的安全性作用,进行了定性的安全性FHA需求分析。同时,对于控制逻辑相对复杂的锁轮保护功能,对比分析了两种不同控制方案,并给出了结论。     

A method for representing the thermodynamic and thermophysical functions in simulation of powerplant processes

A method for representing thermodynamic and thermophysical functions is presented; the functions make it possible to simulate thermal and gasodynamic processes in powerplants that use different individual substances or their mixtures as a working fluid. The method also involves consideration of real gas properties.     

四阶常微分方程两点边值问题解的存在性

利用上下解的方法,讨论了非线性四阶常微分方程y(4)=f(t,y,y',y″,y)满足条件g0(y(a),y'(a))=0,g1(y'(a),y″(a))=0,g2(y″(a),y(a))=0h(y(c),y'(c),y″(c),y(c))=0的非线性两点边值问题解的存在性,其中函数f,gi和h是具有一定单调性质的连续函数。     

地形提示和警告系统研究

地形提示和警告系统(TAWS)能够有效地避免可控撞地事故(CFIT)的发生,极大地提高了民用飞机飞行的安全性。目前,国外对TAWS的研究和应用比较成熟,而国内仍处于起步阶段。结合作者在设计中积累的经验,首先介绍了近地警告系统(GPWS)的功能特点,通过分析GPWS的应用局限性,给出了TAWS系统的发展历程。对TAWS的主要功能和应用进行了深入研究,重点分析了TAWS的前视功能。并在此基础上,给出了TAWS系统在实际应用过程中的优点和尚待解决的问题。最后,提出了适应民航系统未来发展的新一代TAWS系统的发展趋势。     

矩阵变量超几何函数的一种有效计算方法

计算矩阵变量超几何函数的关键在于带状多项式的计算。利用带状多项式的定义和对称函数的性质,提出一种有效计算带状多项式的递推方法,详细讨论了带状多项式中系数和单项式对称函数的递推过程,并通过实例证明了所提算法的有效性和正确性。     

Optimum Signals for High-Resolution Radio Transmission Systems

This paper reports on progress in signal design that has led to improvedresolution capability in radar and communication systems without theuse of complicated signal-processing techniques.Two approaches to the problem of improving resolution capabilityare made. The first approach emphasizes the need to produce sharplypeaked autocorrelation functions. The optimum signal amplitude infrequency is specified to accomplish this, and the spectral density ofthe deterministic signal is shown to satisfy a homogeneous Wiener-Hopfequation. The second approach emphasizes the need to producelow and flattened cross-correlation functions, in order to distinguishthem (since they correspond to error outputs) from the sharply peakedautocorrelation functions. With the use of stationary phase integration,a detailed method for producing any desired cross-correlationamplitude is presented. In particular, the techniques necessary to producesinusoidally modulated cross-correlation functions are discussed.These tools are applied to a realistic N-signal processing system,and the resulting optimum signals are shown to be amplitude-modulatedchirped sinusoids. Detailed examples for physically justifiablesystem parameters are included.