基于希尔伯特-黄与小波变换的压气机失速信号分析方法

针对多级跨声速压气机失速过程壁面静压测量数据,分别采用希尔伯特-黄变换(HHT)和小波分析方法进行时频分析。相比于小波分析方法,HHT时频图中失速过程的频率特征变化更为明显,且利用HHT图中失速发生后的特征频率可判断出失速团的旋转速度。结合方差分析,进一步探索了获取失速先兆信号的可行性。结果表明,两种方法均可用于压气机失速先兆预测,其中HHT方法能够提供更高层次的分解信号,得到的失速先兆更为提前。     

Bernoulli-Euler梁振动的人工神经元网络控制方法

分析了Bernoulli-Euler梁的振动特性,从控制系统的角度得出梁振动控制系统的传递函数,并采用人工神经元网络的方法对其进行控制,辨识器及控制器均采用非线性神经元网络, 最后用matlab对振动控制系统进行仿真。     

Detection of polyphase pulse compression waveforms using the radon-ambiguity transform

The recently developed Radon-ambiguity transform (RAT) detects unknown linear frequency modulated (LFM) signals by computing line integrals through the origin of the signal's ambiguity function (AF) magnitude. It is shown that this method also detects the step LFM and frequency-derived polyphase pulse compression waveforms with varying performance degradation. Simulations are provided to estimate the detection loss relative to the LFM.     

On the free-vibration of rotating composite beams using a higher-order shear formulation

The free vibration behavior of rotating blades modeled as laminated composite, hollow (single celled) boxed beams is investigated. To this end, geometrically nonlinear structural model incorporating a number of non- classical effects such as anisotropy, heterogeneity, transverse shear flexibility, and warping inhibition is developed. Centrifugal and Coriolis force field effects are also considered in the formulation. However, Coriolis effect is discarded during the solution process. It is assumed that in-plane cross-sectional distortion is negligible. In contrast to the existing structural blade models, the traction free boundary conditions on the external surfaces of the beam are identically satisfied. The linearized dynamical equations and numerical results addressing the problem of the free vibration are supplied. Results obtained for the present higher-order shearable model are compared with those of the existing first-order shearable and the non-shearable structural models. Tailoring studies using the present model reveal an enhancement of eigenfrequency characteristics.     

不确定广义系统的鲁棒稳定性分析

本文通过矩阵测度，范数，以及Lyapunov方法研究了具有仿射型时不变香变不确定广义系统的鲁棒稳定性问题，得到了不确定广义系统具有无脉冲鲁棒容许的充分条件。并给出数值算例。     

The benefits of using ATE systems in the testing of printed circuitboards

An industry-based pragmatic review is provided of the economic and product-quality consequences of automatic test equipment (ATE) usage in printed circuit board testing. The company selection process, the nature of the industrial participants, and the data collection process are described. The benefits obtained by users are identified. It is demonstrated that the use of ATE systems does result in definable economic and quality-level benefits     

Integration of onboard information-control systems using the vertical coordination principle

A principle of onboard information-control system integration on the basis of the coordinating control synthesis is proposed; the synthesis provides for transfer of state variable vector in the specified set of information-computing and control subsystems into the required region in one control step.     

Design of a tunable mass damper for mitigating vibrations in milling of cylindrical parts

Milling the free-end of cylindrical parts, which are vertically fixed on the machine table,often suffers from large chatter vibrations. This kind of phenomenon is harmful to the cutting process. Therefore, it is of great importance to develop means to suppress these undesirable chatters.This paper proposes a new idea for designing a tunable mass damper(TMD) to reduce vibrations in milling of cylindrical parts. Frequency response function(FRF) of the milling system is derived to comprehensively reveal the influence of both the dynamic response of the machine tools and the TMD. Critical axial depth of cut, which is usually used to characterize the process stability, is formulated by considering the FRFs of both the milling system itself and the TMD. Maximization of critical axial depth of cut is taken as objective function, while kernel dynamic parameters of TMD,which are involved in the derived expression of critical axial depth of cut, are extracted as designable variables. Optimization procedure is carried out to adjust the parameters of TMD by using sequential quadratic programming algorithm. A series of experiments with a designed passive TMD validate that the design has a good performance in reducing vibrations and improving stability of milling process.     

Some peculiarities of the wave beams in wireless power transmission

Some wave beam peculiarities which usually are wasted are useful in wireless power transmission systems. These peculiarities-the focusing of the beam, the taper distribution of the radiating field, and the discontinuous antenna-are discussed     

A study of the polar current systems using the IMS meridian chains of magnetometers

Magnetic field data from a meridian chain of observatories and the recently developed computer codes constitute a powerful tool in studying substorm current systems in the polar region. In this paper, we summarize some of the results obtained from the IMS Alaska meridian chain of observatories. The basic data are the average daily magnetic field variations for 50 successive days (March 9–April 27, 28) which represent a moderately disturbed period. With the aid of the two computer codes, we obtained the distribution of the following quantities in the polar ionosphere in invariant-MLT coordinates: (1) the total ionospheric current; (2) the Pedersen current; (3) the Hall current; (4) the field-aligned currents; (5) the Pedersen-associated field-aligned currents; (6) the Hall-associated field-aligned currents; (7) the electric potential; (8) the Joule heat production rate; (9) the auroral particle energy injection rate; (10) the total energy dissipation rate. All these quantities are related to each other self-consistently at every point under the initial assumptions used in the computation. By using a model of the magnetosphere, the following quantities in the polar ionosphere are projected onto the equatorial plane and the Y — Z plane at X = -20 R _E: (11) the Pedersen current counterpart; (12) the Hall current counterpart; (13) the electric potential; (14) the Pedersen-associated field-aligned currents; (15) the Hall-associated field-aligned currents. These distribution patterns serve as an important basis for studying the generation mechanisms of substorm current systems and the magnetosphere-ionosphere coupling process.     

航空电子系统中应用多核处理器的挑战分析

作为嵌入式计算的一种,航空电子系统中的处理器具有强实时性、高确定性、高安全性的特征。因此,同其他嵌入式系统相比,在航空电子系统中应用多核处理器面临更多的挑战。针对多核处理器基本的软硬件架构,对挑战产生的原因进行了简要的分析,指出了在航空电子系统中应用多核处理器需要解决的问题。     

小波包分析在内燃机车静液压齿轮箱故障诊断中的应用

本文简述了小波变换的基本原理及利用小波包对振动信号进行分解的方法。小波分析良好的时频局部化性质，适于检测正常信号中夹带的瞬态反常现象并展示其成分，这在旋转机械状态监侧及早期故障诊断中具有重要意义。本文给出利用小波包分析在内燃机车静液压齿轮箱故障诊断中提取微弱轴承冲击故障特征的实例。     

基于EWB的高Q值陷波滤波器的分析与设计方法

本篇文章介绍了用EWB5．0c来设计和分析高Q值陷波滤波器(亦称为：带阻滤波器-BEF)的方法，介绍如何使用AC扫描、波特图仪、参数扫描等操作方法。     

Analysis of shells of revolution under symmetrical loading using the quadrature method

The application of the quadrature method [1] to analyzing the shells of revolution under symmetrical loading relative to the zero meridian is considered. The method can be treated as a generalization of the method presented in [2] to solve the Volterra integral equation of the second kind.     

Analysis of shells of revolution under axisymmetrical loading using the quadrature method

To complete study [1], the procedure of applying the numerical quadrature method to analyzing the shells of revolution under axisymmetrical loading is presented.     

An environment for the integration and test of the Space Stationdistributed avionics systems

An approach is described to supplying an environment for the integration and test of the Space Station distributed avionics systems. Background is included on the development of this concept including the lessons learned from Space Shuttle experience. The environment's relationship to the process flow of the Space-Station verification, from systems development to on-orbit verification, is presented. The uses of the environment's hardware implementation, called Data Management System (DMS) kits, are covered. It is explained how these DMS kits provide a development version of the Space-Station operational environment and how this environment allows system developers to verify their systems performance, fault detection, and recovery capability. Conclusions on how the use of the DMS kits, in support of this concept, will ensure adequate on-orbit test capability are included     

Analysis of shells of revolution under reversely symmetrical loading using the quadrature method

The application of the numerical quadrature method to analyzing the shells of revolution under reversely symmetrical loading is considered.     

Quality analysis of nonlinear elasticity theory for the stability problems of planar laminated curved beams. Algorithm and results of numerical study

The algorithm of numerical solution for the linearized equations of the neutral equilibrium earlier constructed for the planar laminated curved beams is presented. The equations are based on the relations of the classical nonlinear theory of elasticity and the similar relations previously proposed in the consistent variant. We analyzed the results of numerical quality studies of the mentioned variants of nonlinear equations used when the linearized problems on possible buckling modes under the action of conservative forces and a stationary temperature field are formulated.