新的无向双环网络G(N;±1,±s)直径求解方法

提出新的无向双环网络G(N;±1,±s)的直径求解法——分步法,并得到一种新的直观图——螺旋环,研究了螺旋环的性质,给出无向双环网络的直径d(N;±1,±s)的显式公式,给出N,s都固定的直径算法。给出N固定,2≤s≤N?1这样一族无向双环网络的直径算法。利用VB6.0和SQL Server 2000来仿真2≤s≤N?1,找出了该族无向双环网络直径的分布特点:具有最大值、最小值和中间对称性;对任意N,有不少s使得G(N;±1,±s)紧优或几乎紧优。验证了Boesch和Wang等提出的无向双环网络G(N;±1,±S)的直径下界,给出了一个新的直径上界公式。     

新的无向双环网络G(N;±1,±s)直径求解方法

提出新的无向双环网络G（N；±1，±s）的直径求解法——分步法，并得到一种新的直观图——螺旋环，研究了螺旋环的性质，给出无向双环网络的直径d（N；±1，±s）的显式公式，给出N,s都固定的直径算法。给出N固定，2≤s≤N-1这样一族无向双环网络的直径算法。利用VB6．0和SQL Server2000来仿真2≤s≤N-1，找出了该族无向双环网络直径的分布特点：具有最大值、最小值和中间对称性：对任意N，有不少s使得G（N；±1，±s）紧优或几乎紧优。验证了Boesch和Wang等提出的无向双环网络G（N；±1，±S）的直径下界，给出了一个新的直径上界公式。     

双环网络并行最优寻径策略及宽直径的研究

将双环网络拓扑结构映射到平面直角坐标系,基于直角坐标系研究双环网络的并行最优寻径方法。首先研究坐标轴上节点及其等价节点的分布规律,建立等价节点分布模型,得出基于等价节点的并行最优寻径策略及双环网络宽直径求解方法。在双环网络最小路径图（MDD）的基础上拓展,提出并行路径图（PDD）的设计思路并予以仿真实现,基于PDD图,设计两点间2条内点不交的并行最短路径的快速求解方法。仿真实验表明,宽直径分布随步长的变化呈现一定波动性,相对于传统的寻径方式,并行最优寻径明显提高了网络传输效率。     

关于有向环网平均直径的研究

根据有向双环网络平均直径与其最小路径图(L-型瓦)4个几何参数(a、b、p和q)之间的关系,提供了平均直径的计算公式,并提供了快速计算平均直径的算法。提供了构造有向三环网络的最小路径图(等价树)的新方法,研究了三环网络的任意2点之间的最短路径与等价树的层之间的关系,给出了三环网络平均直径的计算公式和算法。实验结果表明:同一网络的平均直径约为直径的一半;在一个无限族中,直径达到最小值时平均直径不一定为最小值,但平均直径为最小值时直径一定为最小值。研究表明平均直径比直径更能准确地反映环网的传输效率,所以平均直径应成为设计最优网络重要的依据之一。     

有向双环网络G(N;h)的容错路由算法

针对有向双环网络G(N;h)的容错问题,研究了有向双环网络G(N;h)容错节点所对应的等价节点的分布规律,给出一种有向双环网络G(N;h)的容错路由算法. 给出了当有向双环网络任意两个节点之间的最短路径出现故障时,找出另一条最短路径的方法. 此算法的时间复杂度为O(d).     

试论±1100kV特高压直流换流站过电压保护和绝缘配合

本文就±1100kV特高压直流换流站过电压保护和绝缘配合进行了具体研究,希望这一研究能够在一定程度上推动我国电力事业的相关发展.     

一类可靠性双环网络的容错分析

本文简述了双环网络的最新发展,分析了跳跃距离为[N~(1/2)]的前向环后向跳双环网络在多条弧中断的情况下网络出现故障的概率,建立了网络可靠性、平均故障时间以及在1～3个节点故障后网络通信率的数学模型.     

±800kV换流变压器现场安装技术

±800kV特高压直流输电工程是我国电力工程建设的重要组成部分,而换流变压器是特高压直流输电工程的关键设备,是交、直流输电系统中换流、逆变两端接口的核心设备.本文首先对换流变压器进行简要阐述,然后总结了±800kV换流变压器现场安装技术,最后提出了现场安装控制要点.     

模2~n±1乘法的可重构设计与实现

论文提出了一种可同时实现模2~n±1乘法的算法及其VLSI结构。通过对常规并行前缀加法器和乘法器的改造,在实现普通加法和乘法的基础上增加少量逻辑,实现了模2~n±1乘法(n=8、16、32)。较之同类设计,该设计实现了对常规加法器和乘法器资源的高度重用,而且性能较高。     

双环网络G(N;1,s)的直径求解算法和实现

提出了双环网络G(N,1,S)的直径求解算法,利用VB6.0作为编程语言、SQL Server2000作为数据库来实现这一算法,对任意给定N,而2≤S≤N-1的这样一族双环网络的直径都可以计算出来,结果存入数据库,并且利用VB6.0的控件MSChart来模拟显示计算结果.找出了该族双环网络直径的分布特点:具有最大值、最小值和中间对称性;对任意N,有不少s使得G(N;1,s)紧优或几乎紧优.     

双环网络G(N;1,s)直径的改进求解算法与实现

目前实现的双环网络G(N;1,s)直径求解算法的不足之处是利用数据库存取中间结果,严重影响了计算速度,当N值很大时需要计算的时间过长。针对这一不足,提出利用数组取代数据库来存取中间结果,实验结果表明,改进的算法极大地提高了计算速度;给出两例大值N直径分布图,并对直径分布特点作了进一步的分析。     

Effect of a magnetic field on the energy levels of donor impurities in the ZnO parabolic quantum well

Energy levels of a donor impurity in the ZnO parabolic quantum well under the magnetic field are investigated using the variational method.The binding energy of the ground state,the energies of 2p±state and 1 s→2p±transition energies of a hydrogenic donor in the ZnO parabolic quantum well are numerically calculated as a function of the strength of magnetic field for different parabolic potential fields.The results show that the external magnetic field has an obvious influence on the binding energies and the 1 s→2p±transition energies of a hydrogenic donor.The Is to 2p±transition energy increases linearly with the strength of magnetic field,but the Is to 2p_ transition energy decreases when the strength of magnetic field increases for the small field strength. Compared to the GaAs parabolic well,the donors are more tightly bound to the ZnO parabolic well and the influence of external magnetic field on the binding energy of a donor is much stronger in the ZnO parabolic well.     

Quantifying the benefit of configurability in circuit-switched WDMring networks with limited ports per node

In a reconfigurable network, lightpath connections can be dynamically changed to reflect changes in traffic conditions. This paper characterizes the gain in traffic capacity that a reconfigurable wavelength division multiplexed (WDM) network offers over a fixed topology network where lightpath connections are fixed and cannot be changed. We define the gain as the ratio of the maximum offered loads that the two systems can support for a given blocking probability. We develop a system model to approximate the blocking probability for both the fixed and reconfigurable systems. This model is different from previous models developed to analyze the blocking probability in WDM networks in that it accounts for a port limitation at the nodes. We validate our model via simulation and find that it agrees strongly with simulation results. We study high-bandwidth calls, where each call requires an entire wavelength and find that reconfigurability offers a substantial performance improvement, particularly when the number of available wavelengths significantly exceeds the number of ports per node. In this case, in a ring with N nodes, the gain approaches a factor of N/2 over a fixed topology unidirectional ring, and N/4 over a fixed topology bidirectional ring. Hence, a reconfigurable unidirectional (bidirectional) ring can support N/2(N/4) times the load of a fixed topology unidirectional (bidirectional) ring. We also show that for a given traffic load, a configurable system requires far fewer ports per node than a fixed topology system. These port savings can potentially result in a significant reduction in overall system costs     

Efficient routing and wavelength assignment for reconfigurable WDMnetworks

Through the use of configurable wavelength-division-multiplexing (WDM) technology including tunable optical transceivers and frequency selective switches, next-generation WDM networks will allow multiple virtual topologies to be dynamically established on a given physical topology. For N node P port networks, we determine the number of wavelengths required to support all possible virtual topologies (PN lightpaths) on a bidirectional ring physical topology. We show that if shortest path routing is used, approximately N wavelengths are needed to map N lightpaths. We then present novel adaptive lightpath routing and wavelength assignment strategies that reduce the wavelength requirements to [(N/2)] working wavelengths per port for protected networks and [(N/3)] wavelengths in each direction per port for unprotected networks. We show that this reduced wavelength requirement is optimal in the sense that it is the minimum required to support the worst case logical topology. Furthermore, we prove that a significant number of logical topologies require this minimum number of wavelengths. We also develop joint routing and wavelength assignment strategies that not only minimize the number of wavelengths required to implement the worst case logical topologies but also reduce average wavelength requirements. Finally, methods for extending these routing and wavelength assignment results to general two-connected and three-connected physical topologies are presented     

Scalability of a Metropolitan Bidirectional Multifiber WDM-Ring Network

We analyze the scalability of a metropolitan bidirectional multifiber wavelength-division-multiplexed (WDM) ring network. The analysis is carried out by using a bidirectional transmission model for optical networks and by building an experimental network. The model includes major limiting factors in WDM-ring networks such as relative intensity noise (RIN) due to multiple Rayleigh backscattering, amplified spontaneous emission (ASE) accumulation in a cascade of bidirectional erbium-doped fiber amplifiers (EDFA), tilting of the EDFA gain spectrum and input saturation power of the EDFA. We found that in metropolitan areas the scalability of a WDM-ring network using bidirectional transmission is not mainly limited by the RIN arising from the Rayleigh backscattering. The result was verified experimentally. The maximum size of the demonstrated network is 33–43 nodes with a spacing of 5–10 km between nodes. With this spacing, which is typical in metropolitan areas, the scalability of the network is mainly limited by the gain tilt and the input saturation power of the EDFA.     

Additional Insight on SAGE-based Carrier and Residual Frequency Offset Estimations in OFDM Systems

Insight on estimations of the space-alternating generalized expectation-maximization (SAGE)-based carrier ω and residual e{\epsilon} frequency offset with the inclusion of inter-carrier interference (ICI) power using Cramer-Rao’s lower bound (CRLB) theorem and a linear model method is given. Additional simulation results are given. Detailed discussions are presented.     

交互式有线电视系统树形同轴电缆网络双向通信控制分析

本文首先说明光纤／同轴电缆混合（ＨＦＣ）有线电视网络在宽带综合信息网络和信息高速公路发展中的重要地位，同时指出同轴电缆网络双向通信问题是ＨＦＣ宽带接入网的核心问题之一。