Enhancing signal-to-noise ratio and resolution in low-field NMR relaxation measurements using post-acquisition digital filters

The traditional way to enhance signal-to-noise ratio (SNR) of nuclear magnetic resonance (NMR) signals is to increase the number of scans. However, this procedure increases the measuring time that can be prohibitive for some applications. Therefore, we have tested the use of several post-acquisition digital filters to enhance SNR up to one order of magnitude in time domain NMR (TD-NMR) relaxation measurements. The procedures were studied using continuous wave free precession (CWFP-T₁) signals, acquired with very low flip angles that contain six times more noise than the Carr–Purcell–Meiboom–Gill (CPMG) signal of the same sample and experimental time. Linear (LI) and logarithmic (LO) data compression, low-pass infinity impulse response (LP), Savitzky–Golay (SG), and wavelet transform (WA) post-acquisition filters enhanced the SNR of the CWFP-T₁ signals by at least six times. The best filters were LO, SG, and WA that have high enhancement in SNR without significant distortions in the ILT relaxation distribution data. Therefore, it was demonstrated that these post-acquisition digital filters could be a useful way to denoise CWFP-T₁, as well as CPMG noisy signals, and consequently reducing the experimental time. It was also demonstrated that filtered CWFP-T₁ method has the potential to be a rapid and nondestructive method to measure fat content in beef and certainly in other meat samples.     

WCDMA系统接口信令消息的描述与实现

WCDMA作为第三代移动通信系统的主流标准，能够提供多种类型的多媒体服务。为了实现各种用户平面数据的传输，系统会提前通过控制平面对所需的无线资源进行分配。由于配置过程是通过接口之间发送控制平面应用协议消息来实现的，因此能否正确有效地对信令消息进行编解码成为保证系统稳定工作的关键因素。3GPP标准中，ASN．1语言被用来描述接口信令消息。首先简要介绍了WCDMA系统结构以及主要接口协议，重点描述了ASN．1存在的意义及其编解码规则，最后给出了基于ASN．1的开发环境下应用层网络协议的开发流程。     

脉冲序列的快速搜索法及可信度分析

对于周期脉冲序列的信号分选识别，可采用序列搜索的时域方法[1，2]。本文将大周期内完全重复的脉冲序列分解为多个“单周期信号”．并把它们均定义为周期性信号．同时，提出了序列搜索的一种软件实现方法及密集视频脉冲信号分选的变步长、信步长快速搜索法．在此基础上，本文针对序列搜索分选法的可信度计算公式进行了推导和分析，证实了这种方法的可行性和有效性．     

A novel compact circuit for 4-PAM energy-efficient high speed interconnect data transmission and reception

Transmission of signals, whether on-chip or off-chip, places severe constraints on timing and extracts a large price in energy. New silicon device technologies, such as back-plane CMOS, provide a programmable and adaptable threshold voltage as an additional tool that can be used for low power design. We show that one particularly desirable use of this freedom is energy-efficient high-speed transmission across long interconnects using multi-valued encoding. Our multi-valued CMOS circuits take advantage of the threshold voltage control of the transistors, by using the signal-voltage-to-threshold-voltage span, in order to make area-efficient implementations of 4-PAM (pulse amplitude modulation) transceivers operating at high speed. In a comparison of a variety of published technologies, for signal transmission with interconnects of 10-15 mm length, we show up to 50% improvement in energy for on-chip signal transmission over binary encoding together with higher limits for operating speeds without a penalty in circuit noise margin.     

计算机远程控制系统的设计与实现

介绍了一个计算机远程控制系统的设计与实现，该系统采用客户机／服务器模式，实现远程屏幕的实时传输，采用LZW压缩算法对图像进行压缩传输，在接受方进行解码并且实现了远程文件创建和删除、显示被控制端的主机信息、发送实时消息等功能。采用鼠标，键盘的模拟方式对计算机进行实时控制。     

爆磁压缩发生器通过脉冲变压器对脉冲形成线充电的理论分析

 将爆磁压缩等效为电流源的方法，对爆磁压缩发生器通过脉冲变压器对脉冲形成线充电进行了理论分析，得出爆磁压缩发生器在负载上产生电流波形（简称负载电流）为直线情况和任意电流波形情况下充电电流和充电电压的表达式。分析表明变压器耦合互感与负载电流随时间变化增长率是脉冲形成线充电的两个重要参数，脉冲形成线第一个充电电压峰值与变压器的耦合互感和负载电流波形斜率成正比，负载电流波形斜率的变化可以改变充电电压峰值的时间，斜率不断增加可以延长第一个充电电压峰值时间，从而可能增加充电电压的幅值，提高爆磁压缩发生器能量的利用效率。     

LZW压缩算法解析及应用设计

ＬＺＷ压缩算法是一种无限压缩算法，它主要是用一种代码来表示数据流中出现的重复串，以达到压缩的目的。     

合成孔径雷达干扰技术的研究

合成孔径雷达（Synthetic Aperture Radar）是一种新型高辨力成像雷达。其在距离上利用发射的线性调频（LFM）的脉冲压缩信号来获取距离上的高分辨力，在方位上利用接收脉冲之间的多普勒信息获得方位上的高分辨力。本文在简单分析合成孔径雷达工作原理基础上，针对合成孔径雷达的特点与弱点，讨论了几种干扰样式。     

基于小波变换的医学图象压缩编码

本文研究了医学图象小波变换系数的统计特征。根据医学图象的特点，提出了基于小波变换的医学图象编码方法。实验表明，这种方法具有较好的压缩编码性能，优于JPEG标准。同时，它支持逐次浮现式传输，从而能满足医学图象存储、通信、检索的需要。