Study of the electric capacitance spectra on symmetric quantum-dot pattern

We have calculated the ground-state energy of the symmetric quantum-dot pattern by the ab initio calculation method, i.e. unrestricted Hartree-Fock-Roothaan (UHFR) method based on the Gaussian basis, and studied their electric capacitance spectra, assuming each quantum dot of quantum-dot pattern to be confined in a three-dimensional spherical potential well of finite depth. For the systems in question, our results show that our method and theoretical model not only give the electric capacitance peaks similar to s-shell and p-shell atom-like quantum dot, but also show some new fine-structure of electric capacitance in the symmetric quantum-dot pattern system. This method might be a feasible tool to study few-electron problems on the symmetric quantum-dot pattern system.     

IMS的技术发展分析和运营商思路建议

通过对IMS技术发展情况以及全球各大运营商IMS试验和部署情况的研究，提出核心网络向IMS演进的建议。     

WiMAX 业务定位与运营考虑

近年来，随着电信市场的开放和通信与信息技术的快速发展，各种高速率的宽带接入不断涌现，而宽带无线接入系统凭借其建设速度快，运营成本低，投资成本回收快等特点，受到多方关注，在高速Internet接入，信息家电联网，移动办公，军事，救灾，空间探险等领域具有广阔的应用空间。[编者按]     

井下作业数据中心建设及其应用

按照中国石化集团公司主辅分离、改制分流的总体工作部署和规划，2004年6月胜利油田将各采油厂所辖的作业大队、准备大队、特车大队重新组建成三个井下作业公司，和已有的一家井下作业公司一起，成为胜利油田的四支专业化井下作业施工队伍，共同为胜利油田有限公司提供井下作业服务，并进一步开拓油田外部市场。     

Contrast Adaptation Decreases Complexity in Retinal Ganglion Cell Spike Train

The difference in temporal structures of retinal ganglion cell spike trains between spontaneous activity and firing activity after contrast adaptation is investigated. The Lempel-Ziv complexity analysis reveals that the complexity of the neural spike train decreases after contrast adaptation. This implies that the behaviour of the neuron becomes ordered, which may carry relevant information about the external stimulus. Thus, during the neuron activity after contrast adaptation, external information could be encoded in forms of some certain patterns in the temporal structure of spike train that is significantly different, compared to that of the spike train during spontaneous activity, although the firing rates in spontaneous activity and firing activity after contrast adaptation are sometime similar.     

Experimental Study on Electrostatic with Two Guiding of Supersonic D20 Molecular Beam Charged Wires

We demonstrate the guiding of a supersonic heavy-water （D2O） molecular beam using a hollow electrostatic field generated by the combination of two parallel charged-wires and two grounded metal-plates, and report some new and preliminary experimental results. In the experiment, we detect the guiding signals by using the method of time-of-flight mass spectrum and study the dependence of the relative transmission of the beam guide on the guiding voltage. Our study shows that the relative transmission of the beam guide is increased linearly with increasing guiding voltage Vguid, and the number of the guided D20 molecules is at least increased by 89.4% when the guiding voltage is ＋20.0k V. Finally, some potential applications of our guiding scheme in the molecule optics are briefly discussed.     

双离子(40Ar+,C2H6+)辐照合成金刚石纳米晶颗粒

用双离子(40Ar+,C1H6+)辐照实验完成了从多壁碳纳米管向金刚石纳米晶颗粒的转变.对转变机理进行了初步探讨.这一探索有望能成为一种金刚石纳米晶合成的新途径.由此可知,多重荷能离子辐照用于其他材料纳米结构的制备也不是凭空设想.     

固定移动融合发展趋势

面对新的竞争压力，国外电信运营商纷纷提出了转型计划，通过整合不同的业务和网络，发挥全业务运营的优势，其中FMC的实施是主要环节。本文分析了固定／移动融合的总体发展趋势、业务融合发展趋势、终端融合发展趋势和网络融合发展趋势等。     

中国运营商对下一代传送网的发展考虑

目前，光传送网的带宽不再是光网络发展的主要矛盾，设备的稳定性、多业务性，组网的灵活性，网络的智能性成为当前关注的焦点。未来WDM系统将主要围绕超大容量和超长距离传输展开，而OXC和OADM主要用于实现灵活、可靠的波长路由配置以及有效的网络管理。[编者按]     

PON应用及运营考虑

一、xPON接入技术介绍 无源光网络（PON）技术是一种点到多点的光纤接入技术，它由局侧的OLT（光线路终端）、用户侧的ONU（光网络单元）以及ODN（光分配网络）组成。一般，其下行采用TDM广播方式、上行采用TDMA方式，而且可以灵活组成树型、星型、总线型等拓扑结构。所谓“无源”指ODN中不含有任何有源电子器件。因此，采用H＆N技术具有高速率，可实现多业务接入、节省光纤、易于升级扩容、便于维护管理等优点，它是较为理想的宽带接入技术。PON技术可以分为两大类，一类是由ITU定义的APON（G.983）、GPON（G．984）标准，另外一类是由IEEE定义的EPON、（IEEE802．3ah）标准。APON基于ATM技术，支持上下行对称的155Mbit／S速率和非对称的155／622Mbit／s速率，最大传输距离为20km。APON利用了ATM的多业务支持能力和QoS机制，可提供语音、数据、图像等多种业务接入，具有完善的OAM功能。随着互联网的快速发展和以太网技术的广泛使用，基于ATM技术的APON由于标准复杂，设备成本较高，传送IP业务效率较低，致使其推广应用受阻，新出现的EPON和GPON技术将成为PON接入领域的主流技术。