Restoration approach in WDM optical networks

Critical applications require proactive-based survivability strategy which provides 100% degree of survivability, low blocking probability and very low restoration time. In this paper, we have proposed an efficient proactive restoration approach for WDM optical network that efficiently utilizes the resources and reduces blocking probability as compared to existing proactive restoration approach. It gives priority to primary lightpath as compared to backup lightpath because primary lightpath should not share resources with other lightpaths in critical applications but backup lightpaths can share the resources, i.e. backup multiplexing.     

Multicast protection algorithms based on aggregated logical topology in survivable multi-domain optical networks

Since the optical network carries a lot of traffic, the survivability is an important issue to ensure the service continuity. At the same time, with the network scale increasing, the optical network has been divided into multi-domains each of which is managed by a unique network provider. Therefore, the survivability in multi-domain optical networks has got more attention in recent years. However, current works mostly addressed the unicast survivability and few or no solved the multicast survivability in multi-domain optical networks. Therefore, in this paper we propose two heuristic algorithms called Multicast Multi-domain Dedicated Protection (MMDP) and Multicast Multi-domain Shared Protection (MMSP) to provide the survivability in multicast multi-domain optical networks. In MMDP and MMSP, to provide the intra-domain protection, we use the modified Minimal-cost Path Heuristic (MPH) algorithm to compute the intra-domain survivable multicast tree. To provide the inter-domain protection, based on multi-domain logical topology, we firstly use the MPH algorithm to compute the inter-domain logical multicast tree and then use the Dijkstra algorithm to compute the inter-domain logical backup sub-path for each inter-link on this logical multicast tree. Simulation results show that MMSP has better resource utilization efficiency and lower blocking probability.     

A new green multicast grooming protection algorithm in WDM optical networks

Since optical network carries a lot of traffic, survivability is very important to ensure the service continuity against network failures. Recently, multicast services become more popular to meet the huge multimedia demand in network, so that multicast survivability in optical network has got more attention. However, multicast survivability may lead to more energy consumption due to more redundant backup resources allocated. Since greening network is particularly important with the energy crisis keeping growing, green multicast survivability in optical network is a challenging issue. This paper focuses on the green multicast grooming protection problem in optical network and designs two auxiliary graphs that includes a virtual topology graph and an integrated graph to address the survivable multicast grooming, routing and wavelength assignment. Based on the auxiliary graphs, this paper proposes an efficient heuristic called green multicast grooming algorithm based on spanning path dedicated protection (GMG-SPDP), in which the network reliability and the energy efficiency are jointly taken into account. Simulation results show that, compared to other algorithms, the proposed GMG-SPDP not only has lower blocking probability and higher bandwidth utilization ratio, but also saves more energy.     

基于SRLG不相关的共享保护算法的研究

通过对共享保护算法的深入分析,使用K条最短路和迭代思想的方法,提出了两种共享风险链路组不相关的共享保护算法,并在仿真平台上对两种算法的性能进行了仿真.KWFF算法借鉴了传统的K条最短路策略,并且在每一个波长平面上,都对新到业务进行了K条工作路由的计算,极大挖掘了网络中潜在的波长资源.而IFF算法由于引入了迭代的思想,避免了共享风险链路组问题中,所特别有“陷阱”问题的出现,并且利用两套权重计算公式,在计算工作路由和保护路由的时候,充分考虑了网络资源的实时变化情况.通过仿真数据可以看到,与以往算法相比,KWFF和IFF算法大大降低了网络阻塞率,并且提高了网络资源的使用效率.     

Feed forward rings

Military and other critical (life-threatening/life-saving) systems require performance evaluations from a survivability, reliability, maintainability, and availability (SRMA) perspective. Applying SRMA concepts to commercial token passing ring local area networks (LANs) (e.g., IEEE-802.5, FDDI, SAE-9B) has uncovered several design issues that could impact the utility of these networks in a critical system. This article discloses a new architecture for token passing rings, called “feed forward rings” (FFR), which provides a significant improvement in system survivability, can eliminate “jabber mode” induced ring failures, and provides for passive optical bridging between rings.

The basic “feed forward” concept is that LANs, based on token passing protocols and utilizing multiple, physically separated, fiber optic rings, should have the serial data stream on each ring flowing in the same direction of rotation. This article provides qualitative observations on the performance of current commercial rings and discusses the advantages of several FFR topologies. Implementation issues related to FFRs are also discussed. It is recommended that FFR alternatives to counterrotating rings (CRR) with separated cables be considered for inclusion in LAN standards.     

Provisioning for restorable WDM optical networks

Restoration is a very critical issue in WDM optical networks. Provisioning also plays a great role in the networks because it deals with resource allocation. In this paper, we have presented two provisioning strategies for restorable networks: unity link weight strategy and varying link weight strategy. The strategies are implemented for critical applications which require 100% degree of survivability. The simulation is done using different proportionate of resources for working and restoration lightpaths. The simulated results show that the performance of the unity link weight strategy is much better than the varying link weight strategy in terms of resource requirement and blocking probability.     

Feed forward rings

Military and other critical (life-threatening/life-saving) systems require performance evaluations from a survivability, reliability, maintainability, and availability (SRMA) perspective. Applying SRMA concepts to commercial token passing ring local area networks (LANs) (e.g., IEEE-802.5, FDDI, SAE-9B) has uncovered several design issues that could impact the utility of these networks in a critical system. This article discloses a new architecture for token passing rings, called “feed forward rings” (FFR), which provides a significant improvement in system survivability, can eliminate “jabber mode” induced ring failures, and provides for passive optical bridging between rings.

The basic “feed forward” concept is that LANs, based on token passing protocols and utilizing multiple, physically separated, fiber optic rings, should have the serial data stream on each ring flowing in the same direction of rotation. This article provides qualitative observations on the performance of current commercial rings and discusses the advantages of several FFR topologies. Implementation issues related to FFRs are also discussed. It is recommended that FFR alternatives to counterrotating rings (CRR) with separated cables be considered for inclusion in LAN standards.     

Detailed ball bearing model for magnetic suspension auxiliary service

Catcher bearings (CBs) provide backup protection for rotating machines with active magnetic bearings (AMBs). The CBs are required in the event of an AMB failure or high transient loads. Numerical simulations of a rotor drop on CBs in flywheel energy storage system are conducted with a detailed CB model which includes a Hertzian load–deflection relationship between mechanical contacts, speed-and-preload-dependent bearing stiffness due to centrifugal force, and a Palmgren's drag friction torque. The transient simulation results show the rotor shaft response variations with the design parameters: shaft/bearing friction coefficients, axial preload, support damping of damper liner, and side loads from magnetic bearings. The results reveal that friction coefficients, support damping, and side loads are critical parameters to satisfy CB design objectives and prevent backward (super) whirl.     

Dynamic diffraction moiré: Theory and applications

As advanced structural materials such as graphite epoxy, metal matrix and ceramic matrix composites or optical mirror substrate materials such as beryllium and silicon carbide are increasingly used in high performance systems, their ability to withstand environments that will cause loss of system survivability must be taken into account. The concept of survivability includes cases where the system is not destroyed, but is inoperable because of subtle effects on the system. These effects can be delamination from weak shock events, critical platform misalignment from large slew motions, or even mirror coating and substrate deformations of as little as a fraction of a micron from their specifications. All the effects listed above, in the system survivability realm, are very subtle and are due to transient deformations at a local or micromechanical level. This paper describes recent work at the Idaho National Engineering Laboratory, under the Office of Naval Research funding, to understand the transient mechanisms in composite interfaces that lead to impact delamination. The principal tool of investigation was dynamic moiré interferometry coupled with continuum analysis. Results for two configurations under impact loading are presented. The first result shows dynamic interfacial shears in a AS4/3501-6 [0/90]_s composite. The second result shows similar effects in a [0₂/90₂]_s configuration of the same material. Similarities and dissimilarities will be discussed, as will future work.     

有噪量子信道生存函数研究及其仿真

为了构建高生存性的量子信令网, 基于保真度概念, 提出量子信道生存函数和信令网生存性的概念. 分析光纤和自由空间生存系数, 计算三种消相干机理下有噪量子信道保真度, 给出生存函数测试模型. 仿真分析表明, 通过降低量子态跃迁率, 控制光纤衰减损耗和大气衰减系数, 减小量子态演化时间, 设置量子中继, 可以建立高生存性量子信道, 为量子纠缠信令网标准的制定提供理论基础. 关键词： 量子通信 量子信令网 保真度 生存函数     

CNG发动机火核形成和发展的三维数值模拟研究

本文利用三维燃烧模型对CNG发动机的燃烧过程进行数值模拟,研究过量空气系数的循环变动对CNG发动机火核形成和发展及燃烧各阶段的影响。研究结果显示,过量空气系数的变动对初始火核参数的影响非常小,对燃烧过程三个阶段的影响程度也不同。主燃烧阶段受过量空气系数的变动的影响最大,火核形成和发展阶段受过量空气系数的变动的影响很小。过量空气系数的变动不是火核形成和发展产生变动的主要原因。     

Evidence of marked glycogen variations in the characteristic Raman signatures of human embryonic stem cells

Human embryonic stem cells (hESCs) have typical Raman signatures, but specific factors that contribute to variations in these signatures have not been reported to date. Furthermore, variations due to the passaging that is necessary for hESC culture maintenance could potentially distort these signatures. It is therefore important to characterize the impact of these culture manipulations on the Raman spectra to gain a better understanding of the origins and nature of their variations. Here we report on the Raman microspectroscopy of hESCs samples from maintenance cultures, complemented with periodic acid Schiff (PAS, carbohydrates) and 4′‐6‐diamidino‐2‐phenlyindol (DAPI, nuclei) staining. The component predominantly responsible for variations between spectra was spectrally identified as glycogen. Variations in the Raman map of the 480 cm⁻¹ glycogen marker band corresponded with those of a PAS stain of the same sample area. The 785‐nm Raman microspectra of hESC cultures examined daily after passaging showed that the same nonrandom spectral variances occurred at all time points after passaging. The pattern of these variances was identified as being due to glycogen spectral components. Our results help validate the previously observed spectral signatures of hESCs and further delineate and characterize the variations that can be expected in these signatures under normal maintenance culture conditions, and aid distinguishing them from those corresponding to differentiation, thus providing a benchmark for future studies. Copyright © 2010 John Wiley & Sons, Ltd.     

IP/GMPLS/Optical多层网络生存性机制的协调

通过对多层网络生存性问题、独立的网络生存性配置方案和多层网络生存性配置方案的研究分析,基于快速发展的GMPLS技术提出了IP/GMPLS/Optical多层网络结构,明确了多层网络生存性方案存在的问题,并利用GMPLS的统一控制平面进一步提出了基于层间协调机制的集成多层网络生存性方案,获得了优化的多层网络故障恢复能力.     

Magnetic hysteresis in the microwave surface resistance of Nb samples in the critical state

We discuss the hysteretic behavior of the field-induced variations of the microwave surface resistance in superconductors in the critical state. Measurements have been performed in a bulk sample of Nb and a powdered one at different values of the temperature. We discuss a model, based on the Coffey and Clem theory, in which we take into account the flux distribution inside the sample, due to the critical state. The experimental results are quite well justified in the framework of our model. We show that by fitting the experimental data it is possible to determine the value of the critical current density and its field dependence.     

量子纠缠信令网Poisson生存模型及保真度分析

量子信令态在传输过程中,由于环境影响产生退相干,造成信令损伤,从而会对构建高生存性的量子纠缠信令网产生影响. 为分析所造成的影响,建立了自然灾害下的量子信令网Poisson损伤模型. 首先,根据信令保真度定义了灾害级数;其次,提出信令态平均损伤量子比特数,并给出信令网生存函数;最后,研究了信令损伤的修复策略并进行仿真. 仿真结果表明,灾害级数的增加会大大降低信令网生存性,而增加信令转接点数和控制信令损伤上限可改善生存性,且该修复策略循环次数少,并可将信令态的保真度由0.6快速提高到0.9,信令网的生存函数由0.4提高到0.9. 关键词： 量子通信 量子信令网 保真度 生存函数     

熔体初始温度对液态金属Na凝固过程中微观结构影响的模拟研究

采用分子动力学方法对熔体初始温度热历史条件对液态金属Na凝固过程中微观结构的影响，进行了模拟研究，并采用双体分布函数g(r)曲线、键型指数法和原子团类型指数法对凝固过程中的微观结构进行了分析.结果表明：液态金属Na在不同熔体初始温度条件下以1×10¹¹K/s冷速凝固时，均形成晶化结构，其中1661和1441键型或体心立方基本原子团(14 6 0 8)在凝固过程中对微观结构的转变起决定性作用.同时发现：熔体初始温度对凝固微结构有显著影响，而对液态和过冷态的微观结构影响并不明显，只有在晶化起始温度T_c附近才充分地展现出来.不同熔体初始温度对凝固结构的晶化程度有不同的影响，虽其影响程度是随着熔体初始温度的下降呈非线性变化关系的，但仍表明是可以通过改变熔体初始温度来加以控制的.原子团类型指数法(比键型指数法)更进一步表征了晶化体系中原子团的结构特征，将有利于对液态金属凝固过程中微观结构的转变机理进行更为深入的研究.     

The impact of model detail on power grid resilience measures

Extreme events are a challenge to natural as well as man-made systems. For critical infrastructure like power grids, we need to understand their resilience against large disturbances. Recently, new measures of the resilience of dynamical systems have been developed in the complex system literature. Basin stability and survivability respectively assess the asymptotic and transient behavior of a system when subjected to arbitrary, localized but large perturbations in frequency and phase. To employ these methods that assess power grid resilience, we need to choose a certain model detail of the power grid. For the grid topology we considered the Scandinavian grid and an ensemble of power grids generated with a random growth model. So far the most popular model that has been studied is the classical swing equation model for the frequency response of generators and motors. In this paper we study a more sophisticated model of synchronous machines that also takes voltage dynamics into account, and compare it to the previously studied model. This model has been found to give an accurate picture of the long term evolution of synchronous machines in the engineering literature for post fault studies. We find evidence that some stable fix points of the swing equation become unstable when we add voltage dynamics. If this occurs the asymptotic behavior of the system can be dramatically altered, and basin stability estimates obtained with the swing equation can be dramatically wrong. We also find that the survivability does not change significantly when taking the voltage dynamics into account. Further, the limit cycle type asymptotic behaviour is strongly correlated with transient voltages that violate typical operational voltage bounds. Thus, transient voltage bounds are dominated by transient frequency bounds and play no large role for realistic parameters.     

Quality assurance and quality control in light stable isotope laboratories: A case study of Rio Grande,Texas, water samples†

New isotope laboratories can achieve the goal of reporting the same isotopic composition within analytical uncertainty for the same material analysed decades apart by (1) writing their own acceptance testing procedures and putting them into their mass spectrometric or laser-based isotope-ratio equipment procurement contract, (2) requiring a manufacturer to demonstrate acceptable performance using all sample ports provided with the instrumentation, (3) for each medium to be analysed, prepare two local reference materials substantially different in isotopic composition to encompass the range in isotopic composition expected in the laboratory and calibrated them with isotopic reference materials available from the International Atomic Energy Agency (IAEA) or the US National Institute of Standards and Technology (NIST), (4) using the optimum storage containers (for water samples, sealing in glass ampoules that are sterilised after sealing is satisfactory), (5) interspersing among sample unknowns local laboratory isotopic reference materials daily (internationally distributed isotopic reference materials can be ordered at three-year intervals, and can be used for elemental analyser analyses and other analyses that consume less than 1 mg of material) – this process applies to H, C, N, O, and S isotope ratios, (6) calculating isotopic compositions of unknowns by normalising isotopic data to that of local reference materials, which have been calibrated to internationally distributed isotopic reference materials, (7) reporting results on scales normalised to internationally distributed isotopic reference materials (where they are available) and providing to sample submitters the isotopic compositions of internationally distributed isotopic reference materials of the same substance had they been analysed with unknowns, (8) providing an audit trail in the laboratory for analytical results – this trail commonly will be in electronic format and might include a laboratory information management system, (9) making at regular intervals a complete backup of laboratory analytical data (both of samples logged into the laboratory and of mass spectrometric analyses), being sure to store one copy of this backup offsite, and (10) participating in interlaboratory comparison exercises sponsored by the IAEA and other agencies at regular intervals.     

Analysis of Connection Availability in an All-Optical Mesh Network

This paper presents the method of an availability performance analysis that can be used for all-optical networks. We compare different schemes of protection and restoration in a fully connected mesh network based on optical cross-connects, optical fibers, and fiber amplifiers. Specifically treated is an optical mesh network physically mapped onto a Scandinavian backbone. In order to compare different survivability strategies, we selected two nodes located roughly 420 km apart. The goal of this work is to point out possible ways to improve connection availability. A number of survivability schemes are compared, for which the availability model of logical connection is derived and a calculation procedure is described. Our results show that unprotected schemes cannot ascertain reasonably high requirements on connection availability in the backbone network. Thus, if a redundant structure of logical connection is considered, the particular survivability scheme should be evaluated in order to maximize connection availability.