分支限界算法的研究与实现

分支限界算法是一种在问题的解空间树上搜索问题的解的方法,主要采用广度优先或最小耗费优先的方法搜索解空间树,其核心思想就是＂剪枝＂。首先提出了分支限界算法的一般策略与实施步骤,然后以电路板布线问题为实例,设计并实现该问题的算法,经过实验数据验证了其性能,进而反映了分支限界算法的高效性。     

基于VC和Matlab的短波电台通信仿真设计

文中结合VC与Matlab在程序设计上的优势,设计并仿真了一种常见短波电台,实现了自检、信道选择、存储和调用等基本功能。完成了短波电台可视化界面的软件开发,并基于Watterson短波信道模型实现了电台间的点对点通信,用仿真流程图描述了整个系统程序运行的过程。     

多波长OCDMA与WDMA系统的性能分析和比较

分析了色散效应对多波长光码分多址(MWOCDMA)系统的归一化吞吐量性能的影响.光脉冲信号的切普宽度越小,色散效应就越大,MWOCDMA系统的归一化吞吐量性能也就下降得越严重.在考虑色散效应和多用户干扰的情况下,比较了MWOCDMA系统与波分多址(WDMA)系统的归一化吞吐量性能.结果表明:当负载较小时,MWOCDMA系统的性能不如WDMA系统;当负载较大时,MWOCDMA系统的性能优于WDMA系统.     

Supergain antennas and the Yagi and circular arrays

The characteristics of endfire, Yagi, and circular arrays of dipoles are reviewed with special reference to their directional properties and the possibility of supergain. The quantum-mechanical analog that suggested the investigation is described. The critical newly emphasized feature is the high-Q property of a correctly designed closed loop of coplanar dipoles when only one element is driven and all dimensions (the length of the elements, their cross-sectional size and shape, the number of elements, and the circumference of the closed loop array) are correctly chosen so that the entire array is adjusted to resonance. An immediate application to beam scanning is described     

Galvanomagnetic and thermoelectric properties of BiTeBr and BiTeI single crystals and their electronic structure

BiTeI and BiTeBr single crystals are synthesized by the Bridgman method, and their galvanomagnetic and thermoelectrical properties are investigated. Both semiconductors have n-type conductivity. The thermoelectric efficiency of BiTeBr is much higher than that of BiTeI, which is related mainly to a larger See-beck coefficient for the former compound. For both crystals, the band structure is calculated from the density-functional theory. It is shown that both compounds are semiconductors with an indirect energy band gap.     

Two- and four-wave mixing with saturable absorption and gain

An exact solution to a model of two- and four-wave mixing in photorefractive media with saturable gain and absorption is presented. Pump depletion effects are accounted for, and the procedure for matching two-point boundary conditions is given. Possibilities of multistable solutions are investigated, and procedures on how to deal with such situations are outlined. It is found that the energy transfer between waves is less effective in the nonsaturated regime as compared to the saturated regime. It is also established that the nonsaturated system is more stable than the saturated under the same conditions     

红外光学系统中心偏差及装调方法研究分析

光学系统的装调是决定光学系统成像性能的关键因素,所以对于光学系统装调技术的要求日益增加。在红外光学系统中,中心偏差是光学系统成像质量决定性因素。为了保证镜头组件为共轴光学系统,倾斜偏心与水平偏心应调至最小。本文简述了红外中心偏差出现的原因及几种测量方法,并分析了中波无热化镜头的权重因子,重新设计了中波无热化镜头的机械结构。最后介绍了一种基于红外中心偏测量仪的中波无热化镜头的装调方法。     

Wavelets and filter banks: theory and design

The wavelet transform is compared with the more classical short-time Fourier transform approach to signal analysis. Then the relations between wavelets, filter banks, and multiresolution signal processing are explored. A brief review is given of perfect reconstruction filter banks, which can be used both for computing the discrete wavelet transform, and for deriving continuous wavelet bases, provided that the filters meet a constraint known as regularity. Given a low-pass filter, necessary and sufficient conditions for the existence of a complementary high-pass filter that will permit perfect reconstruction are derived. The perfect reconstruction condition is posed as a Bezout identity, and it is shown how it is possible to find all higher-degree complementary filters based on an analogy with the theory of Diophantine equations. An alternative approach based on the theory of continued fractions is also given. These results are used to design highly regular filter banks, which generate biorthogonal continuous wavelet bases with symmetries     

VCD,DVD技术与发展

本文介绍了ＶＣＤ，ＤＶＤ的有关技术及规格，并将之作了比较，据此，分析了ＶＣＤ，ＤＶＤ产品在我国市场的发展前景。     

Component and agent-based FMS modeling and controller synthesis

In order to reduce manufacturing control software design cycle and costs, it is imperative to reuse off-the-shelf software components, ensure system properties at design time, and automate software design process. To this end, a component and an agent-based plant modeling of three structures and systematic controller synthesis approaches are proposed under a hierarchical flexible manufacturing system (FMS) architecture. That is, the static structure is modeled using class diagrams of Unified Modeling Language (UML); the dynamic structure is modeled using Petri net (PN); the functional logic is modeled using rule sets. A plant PN controller can be derived systematically with the approach proposed in this article while the desirable system behaviors (e.g., liveness and cyclicness) will be obtained.     

裸板测试与PCBA性能测试及使用功能分析探究

裸板测试-bare board test,又称"通断测试"。此检测工序是在整个电路板制程后质量检验中尤为重要关键的一个生产环节,因为它是保证客户原始设计网络关系、基本性能使用的电检测试工序。然而"通断测试"使用电检测试设备进行手动或自动测试过程中,由于在测试中测试治具与PCB形成接触,又因各种治具制作和PCB制成的因素导致最终成品板焊接盘形成接触式损伤,存在客户使用功能的性能隐患,所以为了达到客户焊盘的使用要求,在"通断测试"中采用一些特殊的测试设备、工具或物料进行测试、以此最大程度减少甚至杜绝焊盘接触式损伤,并对产品设计和通断测试这些可能产生隐患的方面进行有效的审核识别和生产控制,才可以使得成品板焊盘质量得到有效的保证。     

透射与反射式云纹挠度术及其应用

给出了透射与反射式云纹挠度术,并且应用于测试物体的斜率及曲率。     

射频识别技术及在药品库存与安全中的应用

介绍RFID技术的基本原理,针对日益严峻的药品安全形势,详细分析射频识别技术（RFID）在药品库存与安全方面应用的有效性和可行性、药品安全中RFID技术的国内外研究现状、关键技术和原理,设计了软件系统。RFID在药品安全方面的应用有很大优势,但标准和成本问题有待进一步改进。     

一种高速、宽动态范围检波器的研制

微波检波器具有结构简单、使用方便的特点,是射频微波领域的一种常用器件。基于微带混合电路技术,研制了一种高速、宽灵敏度动态范围的脉冲检波器。仿真设计了带宽为5.6~13.8 GHz的宽带带通滤波器和3 GHz的宽阻带低通滤波器作为检波器的输入输出电路。该检波器可以对6~12 GHz频段内、功率为-8~16 dBm的脉冲调制信号进行检波,灵敏度动态范围约25 dB,响应时间小于3~4 ns。     

Engineering education and industrial research and development-thepromise and the reality

The author observes that the social fabric of engineering, the support infrastructure of the profession, and the political and economic systems of the world are undergoing shifts that affect what engineering is, how it is accomplished, and what it should do. He asks what these changes mean in terms of the educational system and explores a few of these issues that lie between academia and the industrial environment beyond. He discusses the engineering curriculum as seen from industry, the role of continuing education, research in academia     

Vector-based signal processing and quantization for image and videocompression

Image and video compression has become an increasingly important and active area. Many techniques have been developed in this area. Any compression technique can be modeled as a three-stage process. The first stage can be generally called a signal processing stage where an image or video signal is converted into a different domain. Usually, there is no or little loss of information in this stage. The second stage is quantization where loss of information occurs. The third stage is lossless coding that generates the compressed bit stream. The purpose of the signal processing stage is to convert an image or video signal into such a form that quantization can achieve better performance than without the signal processing stage. Because the quantization stage is the place where most of compression is achieved and loss of information occurs, it is naturally the central stage of any compression technique. Since scalar quantization or vector quantization may be used in the second stage, the operation in the first stage should be scalar-based or vector-based respectively in order to match the second stage so that the compression performance can be optimized. In this paper, we summarize the most recent research results on vector-based signal processing and quantization techniques that have shown high compression performance     

Blocking and desensitization in bipolar and MOSFET differentialamplifiers

Blocking and desensitization are among the nonlinear effects that result when bipolar and MOSFET differential amplifiers are operating in a multisignal electromagnetic interference (EMI) environment. When a weak desired signal is processed along with a strong undesired interferer signal, the weak signal may experience a reduced gain; that is, desensitization. If the amplitude of the undesired signal is sufficiently large, the gain of the desired signal may drop to zero; that is, blocking. Using a Fourier-series model for the differential input-voltage/output-current characteristics, closed-form expressions for predicting the desensitization in bipolar and MOSFET differential amplifiers are presented. These expressions are valid over a wide range of desired and blocking interfering signals amplitudes     

干扰与雷达一体化系统及信号共享

分析了新型预警机对我国防空安全的威胁,介绍了早期的E-2T/E-2C预警机噪声干扰站的组成和性能特点,并分析了其在对抗美台新型预警机雷达时的不足,提出了新一代P波段噪声干扰与雷达一体化系统的设想,阐述了噪声干扰与雷达一体化系统的性能和优势,简要介绍了一体化系统组成方案和工作方式。文中着重介绍了F-22的隐身性能以及在不同频段的雷达截面积,并据此评估了一体化系统对F-22的探测性能。     

轻小型推扫视频一体化相机设计与验证

介绍了一种轻小型推扫视频一体化微纳遥感相机的综合优化设计思路。系统设计时综合考虑星地一体化处理,采用大F数RC系统降低产品光机体积重量;电子学采用商用货架产品加固技术实现高性能同时降低成本,星上数据处理采用数字TDI技术实现面阵相机推扫视频一体化成像,大幅提升成像效能。采用该方法设计的微纳遥感相机具备视频、推扫、条带等多种工作模式,满足不同应用场景需求。该技术在欧比特视频相机等微纳遥感载荷的设计及研制中进行了应用,在轨获取了高品质的视频及遥感图像,在商业遥感载荷市场具有广阔的应用前景。     

Nonradiating and minimum energy sources and their fields:generalized source inversion theory and applications

A new general framework for characterizing scalar and electromagnetic (EM) nonradiating (NR) and minimum energy (ME) sources and their fields is developed that is of interest for both radiation and source reconstruction problems. NR sources are characterized in connection with the concept of reciprocity as nonreceptors. Localized ME sources are shown to be free fields truncated within the source's support. A new source analysis tool is developed that is based on the decomposition of a source and its field into their radiating and NR components. The individual radiating and reactive energy roles of the radiating and NR parts of a source are characterized. The general theory is illustrated with a time-harmonic EM example