一种基于预编码的CPM正交扩频系统

针对传统CPM正交扩频系统实现复杂度高的问题,提出了一种基于预编码的CPM正交扩频系统。利用所提的预编码和可变星座映射技术,保证了CPM扩频信号的正交性;接收端采用码片校正技术,同步实现CPM解调和解扩,降低传统CPM扩频系统分步实现的复杂度。理论分析和仿真结果均表明,在AWGN和Rayleigh衰落信道下系统具有良好的误比特率性能。最后针对超短波通信进行应用设计和测试评估,结果表明,本系统优于美军SINCGARS系统约6dB。     

奥氏体不锈钢温加工新技术的研究

奥氏体不锈钢 1Cr18NigTi 的温加工温度范围以 200—400℃为宜。在此温度范围内加工时,钢具有较低的变形抗力、较高的工艺塑性,加工后具有良好的力学性能。当变形速率一定时,真应力的大小取决于变形温度和变形程度。当 T=200—400℃ 时,σ=Kε~n;当 T=400—600℃ 时,σ=K_1ε~ne~(B/T_K)。钢的变形抗力、塑性和加工后室温力学性能的变化主要是由钢组织中的双晶界间距和位错密度的变化所决定。     

基于进化神经网络的入侵检测方法

将神经网络与遗传算法结合,提出入侵检测的进化神经网络方法,它是个高效并行非线性动态处理系统,可以满足实时处理要求·首先用遗传算法优化神经网络结构,然后用优化的神经网络进行入侵检测预测、预警·用进化神经网络方法不断演化,寻找最优的网络结构·当进化神经网络学会系统正常工作模式后,能够对偏离系统正常工作的事件做出反应,进而可以发现一些新的攻击模式·实验表明预警率是很高的     

无粘结预应力砼框架梁施工工艺的保证和改进措施

以贵阳龙洞堡机场航站楼等工程为例，讨论后张法无粘结钢绞线预应力砼框架梁施工中的钢绞线，钢丝束、锚夹具等材质检验，以及准确控制张拉力，施工中伸长值，摩阻、变形等参数的定量监测。工程实践表明，自行组装的实验装置及专用机具使用方便可靠，施工中改进措施简便可行，各项指标符合（JGJ／T92－93）《无粘结预应力砼结构技术规程》及设计要求。     

The 1997-1998 warm event in the South China Sea

A strong warm event happens during spring 1997 to spring 1999 in the South China Sea. Its intensity and duration show that it is the strongest event on the record over the past decades. It also corresponds with the severe flood over the valley of the Yangtze River and a couple of marine environmental events. This note addressed the evolution process by using several data sets, such as sea surface temperature, height and wind stress in addition to subsurface temperature. The onset of the warm event almost teleconnects with the El Ni?o event in the tropical Pacific Ocean. Summer monsoon is stronger and winter monsoon is weaker in 1997 so that there are persistent westerly anomalies in the South China Sea. During the development phase, the warm advection caused by southerly anomalies is the major factor while the adjustment of the thermocline is not obvious. Subsequently, the southerly anomalies decay and even northerly anomalies appear in the summer of 1998 resulting from the weaker than normal summer monsoon in 1998 in the South China Sea. The thermocline develops deeper than normal, which causes the downwelling pattern and the start of the maintaining phase of the warm event. Temperature anomalies in the southern South China Sea begin to decay in the winter of 1998-1999 and this warm event ends in the May of 1999.     

师范院校高级英语教学策略分析

师范院校的高级英语课的教学,一直面临一个师生两难的教学状况.为提高教学质量,应更新教学理念,改进教学方法.同时,还要体现师范特色,增加职训力度.     

WC/45钢复合材料的温压烧结工艺及其磨损性能

选取尺寸为0．076～0．100mm的WC颗粒为增强相，45钢为基体，系统地研究了粉末冶金真空烧结法制备颗粒增强钢基复合材料的温压烧结工艺，考察了常温压制烧结和温压烧结两种工艺条件下材料的滑动摩擦磨损性能．结果表明：对于509／6WC 50E钢(质量分数)粉末，采用硬脂酸锌作润滑剂，在压制温度为140℃、压力为320kN时，得到了较为理想的压坯密度(9．4362g／cm^3)，其相对密度达到91．6％，比常温压制的压坯密度(9．1292g／cm^3)提高了3．4％．销盘磨损试验结果表明：温压试样的耐磨性分别是15Cr高铬铸铁的2．9倍，20Cr高铬铸铁的2．6倍，同样工艺条件下常温压制试样的2．8倍，通过扫描电镜分析了复合材料的磨损机理。     

2002： The extra-strong warm winter event in North Asia and its accompanying anomalous atmospheric circulation

Features of an extra-strong warm winter event in North Asia in 2002 and its accompanying anomalous atmospheric circulation were studied through diagnosis on the atmospheric reanalysis data set. Results show that the winter of 2002 is of the warmest in the recent 54 years in North Asia, which was caused by both decadal scale and interannual scale variability. The interannual variability is proved to be as the main cause for the event, and it is related to the global scale atmospheric circulation anomalies, with the strongest of them in the Eastern Hemisphere and in the middle and high latitude region of the Southern Hemisphere.     

L波段数字微波本振源设计

叙述了集成锁相本振源的原理、关键技术及设计过程 ,并应用Motorola大规模集成电路 ,采用“脉冲吞食”可变分频技术设计L波段锁相本振源 ,达到了很好的指标     

基于小波变换的ECG信号消噪

以小波变换的多分辨率分析为理论基础 ,依据信噪在小波分析下的分离性 ,对体表心电信号 (ECG信号 )进行了消噪算法的设计与实现 ,并着重强调了其中双尺度预处理算法的重要性 .实验表明 ,本消噪算法不仅能实时有效地降噪 ,还能对原信号突变点进行定位