Resource management in the next-generation DS-CDMA cellular networks

Direct sequence code-division multiple access has been shown as the predominant access technology to provide high-speed multimedia services in next-generation wireless cellular networks. The DS-CDMA cellular network significantly differentiates itself from the traditional narrowband TDMA/FDMA system, in which great capacity gain can be explored by taking advantage of its unique characteristics. This article addresses resource management in DS-CDMA cellular networks. We first provide an overview of the DS-CDMA network and discuss the main challenges in the design of resource management schemes. We then examine several critical issues within the scope of resource management, including congestion control, rate and power control, and cell planning, with the emphasis on call admission control. Finally, we offer some insights and discussions on the performance aspects, strengths, and weaknesses of existing proposals.     

阻燃沥青的研究进展与建议

介绍了对沥青进行阻燃处理的必要性、沥青的阻燃机理、常用阻燃剂的特性及其作用模式;参照塑料材料阻燃性能的测试手段介绍了常用的沥青材料阻燃性能的测试方法;最后分析了我国沥青阻燃的研究现状,指出了该领域存在的主要问题,并给出了相应的建议。     

GIS中矢量图形的结构分析与VC++中的实现

简要讨论了GIS各类矢量图形元素间的空间拓朴结构及基位置关系 ,并用VC 6 . 0及MFC具体分析了圆弧与多边形区域的相交关系及实现。为利用VC开发专用图形软件提供了有用帮助。     

In situ polymerization and characterization of polyester‐based polyurethane/nano‐silica composites

Polyester‐based polyurethane/nano‐silica composites were obtained via in situ polymerization and investigated by Fourier‐transform infrared spectroscopy (FTIR), or FTIR coupled with attenuated total reflectance (FTIR‐ATR), Transmission electron microscopy (TEM), atomic force microscopy (AFM), an Instron testing machine, dynamic mechanical analysis (DMA) and ultraviolet‐visible spectrophotometry (UV‐vis). FTIR analysis showed that in situ polymerization provoked some chemical reactions between polyester molecules and nano‐silica particles. FTIR‐ATR, TEM and AFM analyses showed that both surface and interface contained nano‐silica particles. Instron testing and DMA data showed that introducing nano‐silica particles into polyurethane enhanced the hardness, glass temperature and adhesion strength of polyurethane to the substrate, but also increased the resin viscosity. UV‐vis spectrophotometry showed that nano‐silica obtained by the fumed method did not shield UV radiation in polyurethane films. Copyright © 2003 Society of Chemical Industry     

Aroused problems in the deposition of diamond-like carbon films by using the liquid phase electrodeposition technique

Hydrogenated diamond-like carbon (DLC) films were prepared by using liquid phase electrodeposition technique. The effects of the applied potential and the carbon sources on the deposition process and film structures were studied. It has been found that the organic liquids with high dielectric constants, small viscosities and the methyl group bonding to the polar group are appropriate carbon sources. The increasing of potential improves the formation of sp³ carbon during the deposition process. In a high electric field, organic molecules are polarized and reacted on the surface of the electrode, turning out DLC and other products. It is believed that the reaction follows a polarization-reaction mechanism.     

柘树青青

柘树是中华大地上最古老的树种之一,柘木是制弓的良材,汁能染赤黄色,叶可以饲蚕,皮、茎、叶、果实均可入药.早在远古时代,柘与人民的生活就有着密切的关系.历史上,柘就被用来命名后宫,柘枝还被用作曲调、歌舞之名.     

Rheology in Processing of in Situ Composites of Polypropylene and Low Melting Poing Metals

The low melting point metallic tin powder or alloy of tin and lead was blended with polypropy-lene. A kind of in situ composite has been prepared. The variations of torque were studied when the composites were mixed in Haake torque rheogeniometer. By way of capillary extrusion, effects upon rheology of the in situ com-posites of the low melting point metals (LMPM) and coupling agent for their different variety and content, were investigated. From flow curves, the results indicate that in situ composites mixed with the LMPM are a kind of pseudoplastic fluid. If the LMPM were melted, the higher the content of the LMPM , the lower apparent viscosity of composites. Meanwhile, when the coupling agent is added into composites, the viscosity of composite will go up first and drop then. This shows that the LMPM have a promoter flow action on the polypropylene.     

单晶高温合金DD3亚结构超细化定向凝固工艺研究EI

利用ＺＭ定向凝固装置研究了镍基单晶高温合金ＤＤ３在高温度梯度（７００～１２００Ｋ／ｃｍ）定向凝固条件下的微观组织演化特征及其对工艺参数的响应函数，结果表明：该合金在高界面温度梯度条件下，柱晶生长速度范围向高速区扩展，从而使单晶亚结构细化成为可能。所得单晶棒中亚结构一次间距可比传统ＨＲＳ法定向凝固籽晶中相应尺度减小５～１０倍。本文还对其组织演化机制进行了分析。     

SiH4激光等离子体内H谱线的线型研究

本文利用OMA-Ⅲ系统测量了脉冲TEA CO_2激光诱发的SiH_4等离子体发光谱内H巴耳末系的H_α、H_β和H_γ线的线型及线宽。通过理论及实验分析,认为这些谱线的主要加宽机制为Stark加宽。由实验线型和理论线型的拟合得到等离子体的电子温度T≈40000K和电子密度N≈10~(17)cm~(-3)。     

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本文针对天然气井提高钻井速度问题,总结分析了盆地中部井身结构,水力、机械参数,聚合物钻井液,正注反挤固井等工艺技术对该地区钻速的影响。指出提高天然气井钻井速度,必须搞好系统工程,形成配套技术。