一个指挥通信系统数据库的设计和实现

描述了在ＶＦＰ环境下,一个指挥通信系统数据库的设计和实现方法。介绍了数据库设计中的用户界面设计技术、应用系统工具栏设计技术、多媒体技术、数据交换技术、安全保密措施等关键技术。     

Random switching techniques for inverter control

New techniques which dramatically reduce acoustic noise by randomising the inverter switching frequency for inverter control are presented. It is shown that the proposed techniques combine the advantages of conventional pulsewidth modulation (PWM) techniques based on regular-sampling techniques and random PWM techniques     

网站建设技术分析与展望

从网站建设的总体要求、网络技术、系统技术等３个方面对网站建设的技术进行了全面分析,并提出了有益的建议。同时,对未来的网站建设技术和网页设计技术进行了较全面的描述与展望。     

GNSS接收机基带处理电路低功耗设计综述

通过时GNSS接收机基带处理电路低功耗设计技术进行调研和总结,发现大部分技术可归属于两个层次：电路级优化技术和算法级优化技术。电路级优化技术主要包括低功耗的并行相关器的设计、多通道的时分复用、多普勒补偿后的信号下采样、低功耗累加器的使用等技术;算法级优化技术是指接收机的间歇工作方式（在不需要定位输出时,使接收机运行在低功耗模式）,主要通过接收机的高级电源管理系统、快速首次定位、重新捕获定位等技术实现。本文对这些方法进行了总结和对比,给出了两个层次优化技术的优缺点。     

近距离三维激光扫描技术

首先介绍了近距离三维激光扫描技术的基本概念及其主要应用,接着通过比较被动式立体成像技术与主动式立体成像技术以及几种常见的激光测距技术来加深对它的认识。在此基础上论述了当前常见的基于三角法的近距离三维激光扫描的原理和基本步骤,进而介绍了目前国内外近距离三维激光扫描技术的发展状况,最后分析了近距离三维激光扫描技术的难点及其发展前景。     

有线宽带接入技术分析比较及其发展

介绍了目前宽带接入技术的发展概况,对主要的几种有线宽带接入技术如基于铜线的xDSL技术、基于HFC网的Cable Modem技术、基于五类线的以太网接入技术和基于无源光网络(PON, Passive Optical Network)的接入技术进行概述并作分析比较,最后讨论了有线宽带接入技术的发展.     

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.     

信息高速公路的XDSL接入技术

首先简要介绍xDSL技术的发展情况;然后对HDSL,SDSL,ADSL,VDSL等技术通过分析对比,作简明扼要的阐述;最后简单介绍其使用现状和应用前景。在技术分析的基础上阐明：xDSL技术的发展,将使Internet接入真正跨上信息高速公路。     

单模光纤中偏振模色散测量方法的研究

比较了单模光纤中常见的几种线性偏振模色散(PMD)的测量方法,重点讨论了两种最新提出的非线性PMD测量方法,详细分析并指出了每种测量方法的优缺点、测量中应该注意的问题和它们的适用范围.     

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.     

Error resilient video coding techniques

We review error resilience techniques for real-time video transport over unreliable networks. Topics covered include an introduction to today's protocol and network environments and their characteristics, encoder error resilience tools, decoder error concealment techniques, as well as techniques that require cooperation between encoder, decoder, and the network. We provide a review of general principles of these techniques as well as specific implementations adopted by the H.263 and MPEG-4 video coding standards. The majority of the article is devoted to the techniques developed for block-based hybrid coders using motion-compensated prediction and transform coding. A separate section covers error resilience techniques for shape coding in MPEG-4     

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。     

网络视频编码技术

随着视频信息在网络上的应用需求的日益广泛和迫切,适合网络传输的视频编码技术成为了现在研究的一个热点,文章旨在综述网络视频编码技术的发展历程。详细介绍并对比了目前主要的网络视频编码技术:传统的视频编码技术在传输中的应用,视频的可扩展性编码以及视频的多描述编码,最后进一步阐述了未来网络视频编码技术可能的发展方向,分析了综合运用各种编码技术的可能。     

Path vs. subpath vs. link restoration for fault management in IP-over-WDM networks: performance comparisons using GMPLS control signaling

We investigate three restoration techniques (path, subpath, and link restoration) for fault management in an IP-over-WDM network. We have implemented all of these techniques on the ns-2 simulation platform using generalized multiprotocol label switching (GMPLS) control signaling. These techniques can handle practical situations such as simultaneous multiple fiber failures, which are difficult to design for and recover from by nonrestoration techniques. We then present performance measurement results for the three restoration techniques by applying them to a typical nationwide mesh network running IP over WDM. We investigate interesting trade-offs in the performance of the restoration techniques on restoration success rate, average restoration time, availability, and blocking probability.     

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.     

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     

Digital processing techniques for encoding of graphics

This paper deals with two classes of preprocessing techniques for documents which are essentially black and white. These are bilevel quantization and preprocessing techniques for noisy input documents. The effect of such techniques on the compression ratio and the subjective quality of the output copy are studied. It is shown that for noisy documents, certain preprocessing techniques considerably improve the compression ratio. The improvement is substantially more for two-dimensional coding algorithm such as relative address coding (RAC). Simulation results of the effect of preprocessing techniques for noise reduction for both multilevel and bilevel signals are described The results of a subjective experiment to determine the effect of certain preprocessing techniques on the quality of clean and noisy documents are reported.     

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     

The determination of the energy distribution of interface traps in metal-nitride-oxide-silicon (memory) devices using non-steady-state techniques

New techniques are used to study the emission and generation processes through, and to obtain the energy distribution of, interface traps situated throughout the bandgap of MNOS devices. The techniques are based on thermal and isothermal dielectric relaxation current techniques. The trap distribution is observed to contain two peaks, the maxima of which occur at 0·4 eV and 0·74 eV below the bottom of the conduction band. The results of the two techniques compared extremely well, lending confidence to the techniques. It is demonstrated that the techniques are capable of detecting small changes in the trap density, such as might occur due to ageing or temperature cycling.     

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.