Modulation and Equalisation Considerations for High Performance Radio LANs

The European Telecommunications Standards Institute (ETSI) has recently defined a European standard for a high performance radio LAN (known as HIPERLAN). To operate as wired LAN replacements, these systems will operate at 5.2 GHz and support instantaneous bit rates of just under 24 Mb/s. To counteract the time dispersive nature of the indoor radio channel, the use of adaptive equalisation is suggested. In this paper a number of possible modulation and equalisation techniques are presented and, in particular, the Bit Error Rate (BER) performance of quasi-coherent GMSK combined with Decision Feedback Equalisation is explored through computer simulation. The trade off between symbol spaced and fractionally spaced equalisation is considered together with the importance of feedfoward and feedback synchronisation to the channel's power delay profile. The paper also includes a comparison of the RLS and LMS based training algorithms and compares the modem developed under the ESPRIT III LAURA project with that specified in HIPERLAN.The application of dual antenna diversity is investigated and its impact on the number of received error free data packets obtained as a function of signal leval and rms delay spread. The use of such diversity is shown to greatly improve the BER performance of a HIPERLAN modem. The problem of frequency offset is considered and modifications are proposed to the HIPERLAN frame structure to improve the receiver's tolerance to such errors. Important practical issues such as frame and symbol synchronisation, frequency offset correction and hardware implementation are discussed from both the LAURA and HIPERLAN viewpoint.     

大型现浇钢筋混凝土U型渡槽施工技术

禹门口提水工程干渠上的十几座大型钢筋混凝土渡槽采用现浇混凝土施工方案。经过十几座渡槽的施工及通水检验，证明现浇施工技术与工艺已经成熟。本文就施工中遇到的高大排架外形与垂直度控制、槽身模板制做与固定、模具的空中支撑、运输与入仓办法等做以简单介绍。     

冶金过程中复杂夹杂物和钢液化学平衡计算

本文提出一个同温冶炼过程中预测非金属夹杂物沉淀的计算机程序。本研究中，多元硅酸盐溶体的Ｇｉｂｂｓ自由能由基于统计热力学的晶胞模型来计算，该晶胞模型按照氧与周围的阳离子构成的对称和非对称晶胞来描述硅酸盐熔体结构，假定高温冶炼时认与非金属夹杂物平衡，钢液中氧化物元素的活度由Ｗａｇｎｅｒ交互作用系数来计算，利用本程序可以估计炼钢时沉淀的非金属氧化物的成分，为调整冶炼工艺和提高产品质量提供指导，进一步可计     

小型过程控制器中编程功能的实现

根据中小规模生产设备过程控制的特点,提出了生产工艺程序在过程控制器中应具有的一般形式,并详细分析如何使小型过程控制器具有编辑这种工艺程序的功能。     

以网格曲线为连续条件的光滑曲面

本文提出一种以网格边界曲线定义曲面的方法。曲面的计算式唯一地由网格的四条边界线的参数而定，各网格间连接的光滑度完全由网格间的边界线的光滑度来决定。当网格间的边界线具有Ｃ~１连续以上的光滑度时，网络曲面间将自动保证是Ｃ~１连续的，否则将是Ｃ~０连续。利用这个方法，可以方便地从线框模型（ｗｉｒｅ－ｆｒａｍｅｍｏｄｅｌ）建立面模型（ｓｕｒｆａｃｅｍｏｄｅｌ）。     

实体造型中的几何约束

实体造型是一个基于约束的过程，完成从功能约束到几何约束、再到代数约束的转化而得到实体模型。本文讨论了几何约束的层次性及其表示，并且对几何约束同设计意图的关系进行了研究，提出了基于ＣＳＧ／ＧＣＧ／Ｂ－ｒｅｐ的模型表示。     

强度反射型光纤温度传感器

本文提出并研究了一种新型的强度反射型光纤温度传感器.根据定容气体温度与压力的线性关系,通过简单的测温元调制光纤中的反射光强,从而得知待测温度.这种传感器结构紧凑,造价低廉.在30~50℃范围内,灵敏度可以达到30mV/℃以上.     

BP算法的改进及用模拟电路实现的神经网络分类器

基于用模拟电路实现神经网络分类器的目的，对多层静态前馈神经网络的ＢＰ算法做了改进，采用线性限幅函数代替Ｓｉｇｍｏｉｄ函数作为神经元的激活函数，给出了改进的ＢＰ算法。对该算法性能的实验研究表明：这种改进算法不但方便了用线性模拟集成运算放大电路实现神经网络，而且具有学习速度快，映射能力强等优点。根据本文算法设计的神经网络分类器，无论是计算机仿真，还是模拟电路实现，都得到了比较高的识别率。     

Suppressive effect of corticosteroids on the gene expression of interleukin-5 and eosinophil activation in asthmatics

Although cortico steroids are effective anti-inflammatory agents in ameliorating asthma symptoms and bronchial hperreactivity, their mechanism of action is unknown. Interleukin (IL)-5 is known to play a key role in regulating eosinophil proliferation and activation. Therefore, we examined the changes of IL-5 mRNA expressions in PBMC semi-quantitatively with RT-PCR as well as serum ECP levels and MCH-PC20 values in asthmatics before and after being treated with corticosteroids. The results revealed that there were significant decrease in the level of IL-5 mRNA and serum ECP concentration after therapy (P < 0.05) and there was remarkable improvement in the values of MCH-PC20 and FEV1% (P < 0.05). It was also found that the changes of serum ECP levels or MCH-PC20 values were accompanied by a reduction in IL-5 mRNA expression (r = 0.5426 or 0.4857, P < 0.05). These results suggested that the therapeutic effects of corticosteroids in asthma may result from modulation of IL-5 gene expression with consequent inhibition of eosinophil activation.