无源光网络标准发展及关键技术研究

无源光网络(Passive Optical Network,PON)作为当今接入网的主要技术解决方案,具有带宽使用效率高、传输距离远、抗干扰能力强等特点.通过研究PON技术的发展动态,本文首先归纳了各种PON技术的产生背景和应用特点,整理出各技术间的连接关系及主要标准;其次介绍了PON技术的帧结构,并对带宽、波长、传输模式等PON技术的主要参数进行了汇总;然后将国内外研究热点进行划分,围绕媒体访问控制协议、帧结构、动态带宽分配算法、节能机制等关键技术,阐述了其研究现状及在PON中的重要作用;最后对PON技术的发展趋势进行了展望.     

论精神损害的国家赔偿责任

国家的侵权行为造成相对人的精神损害应当承担赔偿责任是当今世界国家赔偿制度的发展潮流与趋势.确立精神损害的国家赔偿责任对社会公平正义的实现、人权的保护及促使国家公职人员依法行使职权具有重大的意义,因而应在基于我国国情的基础上,构建我国的精神损害国家赔偿制度.     

Preparation and properties of nano-sized SnO2 powder

1　INTRODUCTIONSnO2isoneofthemainmaterialsusedingassensor.Becauseofthehumidityandgassensingfunction,itattractsmoreandmoreattentions.Butthepresentproblemishowtoimprovethestabilityandsensibilityofgassensor.Researchershavetakenmanymeasurestoresolvethisproble…     

BaFe12O19/SiO2-B2O3微晶玻璃陶瓷的制备和微波性能

采用柠檬酸sol-gel工艺合成了BaFe12O19/SiO2-B2O3微晶玻璃陶瓷，研究了SiO2-B2O3玻璃的含量，Ba/Fe原子比和热处理温度对体系析出晶相的影响，以及介电常数和磁异率在1MHz-6GHz频率范围的变化规律，结果表明，休系中SiO2-B2O3玻璃的含量和Ba/Fe比越高，BaF312O19相的析出越困难，前驱体合适的热处理温度为1000℃，介电常数和磁导率基本上随测试频率的增而加下降；介电损耗的最大值为0．43，磁损耗较小。     

Multiuser detection for DS-CDMA UWB in the home environment

We demonstrate the effectiveness of multiuser detection for an ultra-wideband (UWB) pulse based direct sequence spread spectrum system using code division multiple access. Extensive simulations were run using channel soundings of the 2-8 GHz band collected in a residential setting and characterized by a high level of multipath fragmentation. We show that the adaptive minimum mean square error (MMSE) multiuser detection (MUD) receivers are able to gather multipath energy and reject intersymbol and interchip interference for these channels to a much greater extent than RAKE receivers with 4 and 8 arms. We also demonstrate the adaptive MMSE is able to reject a narrowband IEEE 802.11a OFDM interferer, even for signal-to-interference ratio as severe as -30 dB. We show the adaptive MMSE exhibits only a 6 dB penalty relative to the single user case for the heavy multi-access interference (number of asynchronous users equal to spreading code length). The practical RAKE receivers were incapable of effectively rejecting either the strong narrowband interference or the heavily loaded wideband interference. Even more moderate levels of interference caused significant degradation in the performance of the practical RAKE receivers.     

Preparation of flexible polyhedral particles via concentrated emulsion templating polymerization

This paper presents recent efforts on the preparation of flexible polyhedral particles via concentrated emulsion templating polymerization in which the hydrophilic monomer (acrylamide) and hydrophobic monomer (butyl acrylate) are polymerized simultaneously in the continuous and dispersed phase, respectively. Such templating polymerization has been enhanced in our systems owing to the introduction of acrylamide monomer and their higher polymerization rate in continuous phase as compared with butyl acrylate in dispersed phase. Diffusion between the different phases was also inhibited. Furthermore, the stability of the concentrated emulsion and the molecular weight of the produced poly(butyl acrylate) were found to be significantly affected by the amount of redox initiator. The morphology of the particles could be controlled by varying the volume fraction of the dispersed phase and the polyhedral particles were achieved at higher volume fraction. Copyright © 2005 Society of Chemical Industry     

热平衡流量计研究与应用

依据热平衡方法测流量原理研制的热平衡流量计没有任何可动部件，可靠性大大加强，可以代替常用的浮子流量计和涡轮流量计。该仪器的应用为油水井及注聚合物井的流量测试提供了更为有效的手段和方法。     

籼米淀粉超微粉体的制备及其性质

研究了籼米淀粉超微粉体的一种新的制备方法 ,通过正交实验确定了酶处理淀粉的最佳条件 ,考察了淀粉的溶解度和膨润力。结果表明 ,酶处理淀粉的最佳工艺参数为 :水解温度４５℃ ,时间为２５ｈ ,酶用量为水解淀粉的４５%。随着粒径的减小 ,淀粉的溶解度增大 ,膨润力下降。     

Structure and Properties of Electroless Ni Deposits

The changes in structure and the hardness of two electroless deposited Ni-P alloy coatings (with P content of 1.5 and 9.5 wt pct) with heat treatment have been studied by XRD and TEM. The deposits containing 1.5 wt pct P can be represented as an fcc NiP supersaturated solid solution of 5~10 nm microcrystallites. whereas the deposits containing 9.5 wt pct P are amorphous. The heat treatment process induces crystallization of amorphous Ni to Ni phosphides and fcc Ni.Both of the deposits reach maximum hardness after annealing at 400℃ for 1 h. All coated steel specimens are inferior in fatigue strength to uncoated steel specimens mainly due to the poor fatigue resistance of the coating itself