一种CDMA—时隙ALOHA系统及其性能分析

本文提出了一种CDMA-时隙ALOHA系统。其中,所有用户使用相同的伪随机序列,但发送时加入不同的随机时延,接收端利用伪随机序列的自相关特性捕获并接收各用户的信号,文中分析了当基站中采用的接收机数不同时,系统的信道吞吐率,并进行了计算仿真。分析和仿真结果表明系统的最大吞吐率比一般时隙ALOHA系统大大提高。     

模态分析中的机床稳定性指标

本文探讨了模态分析中的机床稳定性指标,导出了影响稳定模态的表达式;提出了提高机床稳定性的措施。     

ATM网络中的小波语音变速率编码

针对未来的通信网络为基于ＡＴＭ的ＢＩＳＤＮ网,讨论语音信号的编码技术。提出根据信源熵构造变速率、恒定质量的编码系统的方案,而利用小波包进行信号的多分辨率分解是合理分配比特的有效途径。     

ADSL调制/解调中FFT设计及实现

阐述了ＡＤＳＬ（非对称数字用户线）的调制／解调技术,并给出一种用可擦可编程逻辑器件来实现其中ＦＦＴ（快速傅立叶变换）的具体方案。     

Trace metals in soil, dust, and tree leaves of the urban environment, Guangzhou, China

Metals have been constantly introduced to urban environments via various point and non-point sources of pollution,and have contaminated different urban compartments(sample types).However,most research projects have focused on a single environmental compartment to characterize urban metal contamination.In the present study,an integrated sampling program that includes surface soils,different size fractions of soil and road dust(<50 μm,50-100 μm,100-250 μm,and 250-1000 μm),tree leaves,and grasses,was conducted in a typical urban area of Guangzhou,China.The aim of the study was to investigate the interrelationships among the metal pollutants in these samples.The concentrations of trace metals varied greatly among different sample types,and their distribution was generally in the following order:road dust > soil dust ≥ surface soils ≈ top soils > grasses ≥ tree leaves.As for the relationships among the trace metals,different combinations were seen among the sample types,indicating different loadings of trace metals in the sampling medium.Significant correlations of metal concentrations were found between tree leaves and the smallest(<50 μm) fraction of road dust,and between soil dust(50-100 μm) and surface soils,suggesting that trace metals in these samples may influence each other.     

A parallel algorithm for statistical-fairness-based spectrum allocation of cognitive radios

A parallel algorithm for statistical-fairness-based spectrum allocation of cognitive radios is proposed in this paper. The key idea of the algorithm is to pursue the maximum total spectrum utilization of the system by adopting a parallel technique in every spectrum allocation, and to ensure the statistical fairness rule by deploying a particular scheme during a series of allocations. The simulation results show that the proposed algorithm not only achieves a fairer and more efficient allocation of spectrum resources, but also has much shorter allocation duration than the color sensitive graph coloring (CSGC) algorithm.     

如何推进企业信息化的建设和发展

阐述了信息化的概念和意义,分析了山西省企业信息系统开发水平落后的原因,主要从管理、投资、人员培训与组织管理、网络建设等几方面提出企业MIS总体开发的一些实施策略.     

下一代超媒体文件传输协议（HTTP—NG）的结构分析与研究

对当前ＨＴＴＰ存在的问题和Ｗｅｂ应用的需求进行了分析，并给出了一下代超媒体传输协议ＨＴＴＰ－ＮＧ的结构模式及其各层的功能，昔在改善目前ＨＴＴＰ／１．ｘ的性能，以适应Ｗｅｂ应用迅速发展的需要。     

KSHT-I型三辊穿轧机快速回退控制仪的研制

本文主要介绍了“ＫＳＨＴ－Ｉ型三辊穿轧机快速回退控制仪”，这个简单而实用单片机系统的基本组成、软件设计、研制过程和现场实际中产生的问题以及针对这些问题所采用的有效措施。实践证明快速回退控制仪和所采用的压力传感器及其信号放大装置实用可行。     

迭加原理的数学基础及其在物理学中的应用

迭加原理是线性系统具有的一个重要性质，在物理学中有着广泛的应用，为人们在许多领域的研究提供了简便的方法，但它不是普遍成立的原理。本文从数学物理的角度讨论了迭加原理的数学基础，概述了迭加原理在物理学中的应用，并指出迭加原理的适用范围。