光电对抗与军用光电技术研究进展

本文对光电对抗与军用光电技术研究的内容和组成进行了阐述,介绍了光电对抗与军用光电技术研究现状,系统地论述了光电对抗技术研究的趋势,综合介绍了光电对抗技术现有技术研究及成型的武器装备,并对今后光电对抗技术研究的重点技术进展进行了详尽的讨论。     

OFDM系统无线资源分配综述

简要介绍OFDM系统无线资源分配的概念及研究模型,阐述了OFDM资源分配技术的国内外研究现状,并讨论分析了OFDM资源分配技术研究中存在的问题,展望了OFDM资源分配技术的研究趋势。     

蠕虫建模仿真及检测技术研究进展

计算机网络蠕虫作为当前互联网所面临的最为严重的安全威胁之一,对其进行细致的研究显得尤为重要。为了体现网络蠕虫技术研究方面的最新成果,针对当前网络蠕虫技术研究领域的热门方向,整理并分析了蠕虫传播模型和蠕虫软件仿真技术等方面的研究思路和成果,并对多种新型的网络蠕虫检测技术进行了分析和评估。最后根据研究结果,对网络蠕虫技术研究的新方向进行了总结与展望。     

数据库技术的发展述评

回顾了数据库技术的发展 ,指出数据库技术目前的研究状态 ,并在此基础上 ,分析了数据库应用所面临的挑战 ,指出数据库技术的研究热点。     

深空通信特点与关键技术分析

在讨论深空通信相关基本概念的基础上,对深空通信的特点进行了分析,并对适应于这些特点所涉及的关键技术进行了研究。着重阐述了阵列天线技术、高效调制解调技术、信道编码和传输层协议技术、信源编码和数据压缩技术、通信协议等技术的相关内容。研究认为,深空通信对我国航天事业的发展有着关键作用,将是今后通信技术的一个热点研究领域,并有可能带来新的技术上的突破。     

SMT焊点质量自动检测与智能鉴别技术

在分析SMT焊点组装质量常用检测技术的基础上,提出并介绍了基于SMT焊点虚拟成形技术的SMT焊点质量自动检测与智能鉴别技术的基本原理和方法,并对该技术的研究意义、主要研究内容和研究思路等进行了探讨。     

基于MIMO系统的联合传输(JT)技术

近年来,诸多学者提出并研究了一种新的下行链路传输技术——联合传输(JT)技术。这里着重研究了MIMO系统下的JT技术,给出了该系统下的系统数据模型,并研究了用户终端调制矩阵M的求解方式。     

网格技术研究与发展趋势综述

简要介绍了网格以及网格计算的概念,阐述了网格技术的国内外研究现状及其应用,并讨论分析了网格技术研究中存在的问题,展望了网格技术的发展趋势.     

偏振探测技术在空间目标识别中的应用

介绍了目前偏振探测技术识别目标的几种方法,分析了国内外偏振探测技术的研究概况、水平和发展趋势,并指出目前国内外偏振探测技术的研究方向.     

基于物联网技术的存储载体智能管理系统研究

对物联网技术在移动存储载体管理方面进行了研究。通过分析研究物联网技术,结合移动存储载体的使用特点,设计了基于物联网技术的移动存储载体智能管理系统总体技术架构,对该架构中的关键技术进行了研究,设计并实现了原型验证系统。     

Smart antenna techniques and their application to wireless ad hoc networks

In this article the use of smart antennas in mobile ad hoc and mesh networks is discussed. We first give a brief overview of smart antenna techniques and describe the issues that arise when applying these techniques in ad hoc networks. We consider ad hoc/mesh networks with directional antennas, beamforming/adaptive antennas, and/or multiple-input-multiple-output (MIMO) techniques. We then show how the MAC/routing techniques can be modified to get the maximum benefit with smart antennas, while also showing examples of degradation in system performance, rather than improvement, when smart antenna techniques are added to networks with standard MAC/routing techniques.     

Random modulation techniques with fixed switching frequency forthree-phase power converters

This paper proposes a new family of random modulation techniques for three-phase power converters which operate with a fixed switching frequency. The techniques are based on adjusting the duration of the zero-vectors or adjusting the three pulse positions in a switching period. Three methods are selected for experimental tests because they preserve the fixed switching frequency known from standard PWM techniques. The new methods are also compared with random switching frequency modulation and with fixed switching frequency modulation. Voltage, current and acoustic noise spectra are used for comparison and it is concluded that two of the techniques are especially useful at lower fundamental frequencies. The techniques can substitute classic random modulation techniques with variable switching frequency in some applications     

Super-resolution TOA estimation with diversity for indoor geolocation

This paper presents an in-depth investigation of frequency-domain super-resolution time-of-arrival (TOA) estimation with diversity techniques for indoor geolocation applications. A methodology for performance evaluation of super-resolution techniques based on the measurements of indoor radio propagation channels is presented. The performance of super-resolution techniques is compared with the performance of conventional TOA estimation techniques. The effects of diversity techniques on the performance of super-resolution techniques are evaluated. The measurement and simulation methods presented in this paper can be used to establish empirical performance bounds for real implementation of super-resolution indoor geolocation systems.     

A review on MR vascular image processing: skeleton versus nonskeleton approaches: part II

Vascular segmentation has recently been given much attention. This review paper has two parts. Part I of this review focused on the physics of magnetic resonance angiography (MRA) and prefiltering techniques applied to MRA. Part II of this review presents the state-of-the-art overview, status, and new achievements in vessel segmentation algorithms from MRA. The first part of this review paper is focused on the nonskeleton or direct-based techniques. Here, we present eight different techniques along with their mathematical foundations, algorithms and their pros and cons. We will also focus on the skeleton or indirect-based techniques. We will discuss three different techniques along with their mathematical foundations, algorithms and their pros and cons. This paper also includes a clinical discussion on skeleton versus nonskeleton-based segmentation techniques. Finally, we shall conclude this paper with the possible challenges, the future, and a brief summary on vascular segmentation techniques.     

窄禁带碲镉汞调制光谱的近期进展和前景

简要介绍了红外光调制反射谱和调制光致发光谱的最新进展,并重点比较了相对于传统实验方法在信噪比,谱分辨率和实验耗时等方面所取得的显著进展.给出了在MBE生长HsCdTe薄膜样品研究中的应用实例,显示了该技术在光谱研究窄禁带半导体带间和低维结构带内跃迁方面的应用前景.     

链路自适应技术在MIMO系统中的应用

MIMO技术和链路自适应技术都是未来无线通信系统的关键技术，二者的结合将会更好地发挥它们的优势，讨论了链路自适应技术的基本原理。其在MIMO系统中的应用方式、相关算法以及必须考虑的若干问题问题。     

The influence of electromagnetic environment on operation of activearray antennas: analysis and simulation techniques

This paper presents an overview of active array antennas, system-level nonlinear effects in such antennas, and their modeling and simulation techniques. Advantages of active array antennas, in comparison with passive array antennas, are discussed. The influence of nonlinear distortions and interference in active antennas on the overall system performance is considered. Modeling and simulation techniques that can be applied to active array antennas are substantially different from those used for circuits and systems. Analytical and numerical techniques are used for the analysis of active antennas, with the prevailing use of numerical techniques at the present time. Electromagnetic-level and circuit-level simulation techniques are discussed. System-level simulation techniques are considered in detail, with special emphasis on their application to active array antennas. The “instantaneous” quadrature technique is proposed as an effective tool for numerical simulation of active arrays over wide frequency and dynamic ranges in a computationally-effective way     

Review and Development of Reception Reliability Estimation Techniques for Mobile Radio System Planning

There are two general types of reception reliability estimation techniques presented in the literature, namely bit detection techniques and statistical channel techniques. This paper presents a review of these techniques and assesses their usefulness as tools for system planners. In the planning of wideband systems the effects of power delay spread need to be considered. A new statistical channel technique incorporating delay spread, noise and cochannel interference is presented in this paper. The results from this technique are consistent with those derived from more specialised and computationally expensive bit detection techniques.     

Error resilience in video and multiplexing layers for very lowbit-rate video coding systems

The transmission of audio-visual services on low-bit-rate, wireless telecommunications systems requires the use of coding techniques that are both efficient in their use of bits and robust against errors introduced in transmission. In this paper, we present efficient techniques for improving the error resilience of audio-visual services. These techniques are based on coding simultaneously for synchronization and error protection or detection. We apply the techniques to improve the performance of the multiplexing protocol (which combines the video and audio streams so that they can be transmitted on a single circuit), and also to improve the robustness of the coded video. We show through simulations that the techniques are efficient in their use of bits and effective against bursty errors common in wireless channels. For a simulation of the DECT channel at a bit-error rate of 10^-3, the techniques give an order of magnitude improvement in the probability of lost packets in the multiplexer layer over more conventional techniques. In the video layer, the techniques give an improvement of between 1-2 dB over ITU-T Recommendation H.263. The techniques proposed for the video layer also have the advantage of permitting simple transcoding with bit streams complying with H.263     

Advanced bus-clamping PWM TechniquesBased on space vector approach

Conventional space vector pulsewidth modulation (CSVPWM) employs conventional switching sequence, which divides the zero vector time equally between the two zero states in every subcycle. Existing bus-clamping PWM (BCPWM) techniques employ clamping sequences, which use only one zero state in a subcycle. This paper deals with a special type of switching sequences, termed here as "double-switching clamping sequences," which use only one zero state and apply an active vector twice in a subcycle. The present work brings out a class of bus-clamping PWM techniques, which employ such sequences. It is shown analytically as well as experimentally that the proposed BCPWM techniques result in reduced harmonic distortion in the line currents over CSVPWM as well as existing BCPWM techniques at high modulation indices for a given average switching frequency of F/sub SW/. At high modulation indices, the dominant harmonic components in the line voltages are around 2F/sub SW/ with the proposed BCPWM techniques, while the dominant components are around F/sub SW/ and 1.5F/sub SW/, respectively, with CSVPWM and existing BCPWM techniques. The proposed techniques also reduce the inverter switching losses at high power factors over CSVPWM and existing BCPWM techniques.