利用DCT有效实现正交复用QAM系统

正交复用 QAM(O-QAM)系统是一个相邻载频间隔为波特率的多路系统,可以用数字信号处理技术实现.这种系统在复用路数无限增加时可以达到奈奎斯特速率,并且对传输媒介引超的延迟和幅度失真不灵敏.本文提出用离散余弦变换(DCT)处理器级联一个权重网络实现 O-QAM 系统的新方案.该方案由于充分利用了 FIR 滤波器系数的对称性,使权重网络计算量明显下降.DCT 通过快速卷积算法获得,总计算量明显下降.     

Magnetic characteristics and its environmental implications of core YSJD-86GC sediments from the southern South China Sea

Sediments of core YSJD-86GC （referred to as 86GC） collected from the southern South China Sea were selected for environmental magnetic studies. Combined with the published chronological framework, sediment magnetic properties were revealed for the study area since the MIS3 stage. The rock magnetic results indicate that low-coercivity magnetite is the main magnetic mineral within the sediments. Also, a certain amounts of hematite are present. The King plot and Day plot, which reflect the magnetic particle size, show that fine-grained pseudo-sin- gle-domain phase magnetic particles dominate the magnetic minerals in the sediments. Comparison of magnetic parameters and geochemical indicators show that magnetic properties of core 86GC sediments reflect a terrigenous input. Simultaneously, magnetic characteristics of the stud- ied sediment are influenced by the quantity of terrigenous sediment input, oxidation-reduction conditions of the provenance area, and the transportation environment and distance. Sea level fluctuation caused by global climate change was the main factor for variation in concentration of magnetic minerals and magnetic particle size of thestudied core sediments. Thus, variation of sediment magnetic properties in the study area can be used as an indirect indicator of sea level fluctuation.     

一类非线性反应扩散方程的内层问题

研究了具有非线性反应扩散方程奇摄动内层问题,讨论了在适当的条件下,退化问题具有两个相交解时的外部解,并引入伸长变量,构造了问题的解的形式渐近展开式,利用微分不等式理论,得到了原初始边值问题解的一致有效的渐近解。     

人脐血造血干／祖细胞体外扩增的实验研究

探索脐血造血干／祖细胞体外扩增的最佳条件;初步验证以单个核细胞作为培养起始细胞的可行性,以脐血单个核细胞作为培养起始细胞,在IMDM培养基中加入不同的因子组合培养7d,流式细胞仪测定培养前后的CD34＋细胞百分数、CD34^ CD38^-细胞百分数,分别计算单个核细胞,CD34^ 细胞和CD34^ CD38^-细胞的增长倍数,培养7d后,对照及各组合中脐血单个核细胞总数均比扩增前有十分显著的增加,但各组合相互之间扩增倍数差异不显著,CD34^ 细胞总数均比扩增前有十分显著的增加,加入SCF使扩增倍数增加更明显,未加入SCF组合中的CD34^ CD38^-细胞总数与培养前相比无明显增长,相对于对照扩增倍数也无差异;而加入SCF的组合相对于对照则有明显扩增,以上结果证实以单个核细胞作为培养的起始细胞也能达到较好的扩增效果,在本实验所用的细胞因子组合中,以SCF＋IL01＋IL－3＋IL－6＋GM－CSF＋EPO效果更佳,昆虫细胞基因工程生产的rhSCF及人尿来源的L－TPO对细胞扩增具有刺激作用,两者的协同作用明显。     

一种基于模糊决策表的知识获取方法

本文描述了一种基于模糊逻辑的决策表方法，该方法可用于构造知识库。     

Control system design of hybrid fuel cell city bus

This paper introduced the design of the hybrid powertrain of the Fuel Cell City Bus demonstrated in 2008 Beijing Olympic Games. The configuration of the hybrid fuel cell powertrain was introduced. The safety of hydrogen storage and delivery system, the hydrogen leakage alarm system were developed. The real-time distributed control and diagnosis system based on the Time Trigger Controller Area Network (TTCAN) with 10 ms basic control period was developed. The concept and implementation of processor (or controller) monitor and process (or task) monitor technique based on the TTCAN were applied in this paper. The fault tolerant control algorithm of the fuel cell engine and the battery management system were considered. The demonstration experience verified that the fault tolerant control was very important for the fuel cell city bus.     

稀土族Pm和Tm两元素固溶度的抛物线法预测

本文利用张邦维等提出的键参数函数和尺寸因素方法对稀土族Ｐｍ，Ｔｍ两元素基上的室温下固溶度作抛物线法预测，对２３个过渡族基，１８个简单元素基，１３个稀土族元素基和３个锕系元素基的研究所得结果与实验测定数据很好地符合，因此，预测结果是可信的。     

基于小波域中视觉门限模型的数字水印技术

给出了一种在小波变换域中给图像加水印的方案,本方案利用了小波分析的优良性质,结合人类视觉系统（ＨＶＳ）的特性,基于小波变换域中的视觉门限模型,对小波变换后的图像系数按不同的方向,层次子带分别加水印,使得在每个小波系数所加的水印的幅值不超过此系数所能掩盖的失真,这样可以保证水印在不可视的前提下尽可能提高坚固性,模拟实验结果表明这个方案取得了良好的效果。     

水平集方法及其在柔顺机构拓扑优化中的应用

由于具有跟踪拓扑结构变化、优化边界清晰光滑等优点,水平集方法作为一种新颖的机构拓扑优化方法近来受到了重视.文中首先讨论了水平集方法中Hamilton-Jacobi方程的求解、水平集函数的重新初始化、速度场扩展等出现的问题.在此基础上,给出了应用逆风差分格式求解Hamilton-Jacobi方程的数值方法,并采用改进的符号函数有效解决了数值的不稳定问题,提出的快速扫描法可以对速度场进行有效扩展.最后,建立了基于水平集方法的柔顺机构拓扑优化模型,利用水平集法对反位移柔顺机构进行了拓扑优化设计.