Avoiding Transient Loops During the Convergence of Link-State Routing Protocols

When using link-state protocols such as OSPF or IS-IS, forwarding loops can occur transiently when the routers adapt their forwarding tables as a response to a topological change. In this paper, we present a mechanism that lets the network converge to its optimal forwarding state without risking any transient loops and the related packet loss. The mechanism is based on an ordering of the updates of the forwarding tables of the routers. Our solution can be used in the case of a planned change in the state of a set of links and in the case of unpredictable changes when combined with a local protection scheme. The supported topology changes are link transitions from up to down, down to up, and updates of link metrics. Finally, we show by simulations that sub-second loop-free convergence is possible on a large Tier-1 ISP network.     

用于敞开式变电站的特高压开关设备

作为1 100 kV的UHV(特高压)输电,面临技术--生态环境的巨大挑战.变电站的UHV开关装置模块,需要的是可靠、成本/效益比好、环境友好、可维护的方案.对于这些所需的参数以及技术规范的验证,采用AIS(空气隔离变电所)技术能完全满足这些需要.介绍由瓷柱式断路器、隔离开关和NCIT(非传统互感器)所组成的UHV模块.这些装置是根据模块原理预先设计好的,其中的设备间的连接肯定允许快速安装.在变电站设备控制和检测方面,模块是预制标准化.加拿大和德国的试验站对断路器、隔离开关等独立的开关元件,在1 100 kV上做BIL、SIL和工频等绝缘试验,性能表现非常优越.因为对于特高压电压等级,IEC标准至今尚未规定,所以将根据外推法和现场数据作合理解释.瓷柱式断路器采用了最新复合绝缘体技术,在安全方面有所改进.AIS方案其他的关键技术,例如环境保护和成本,在可比的功能间,根据市场估计价值,与GIS解决方法作了比较.     

Avoiding Disruptions During Maintenance Operations on BGP Sessions

This paper presents a solution aimed at avoiding losses of connectivity when an eBGP peering link is shut down by an operator for a maintenance. Currently, shutting down an eBGP session can lead to transient losses of connectivity even though alternate path are available at the borders of the network. This is very unfortunate as ISPs face more and more stringent service level agreements, and maintenance operations are predictable operations, so that there is time to adapt to the change and preserve the respect of the service level agreement.     

Low Complexity Antenna Selection Scheme for Multicarrier MIMO Broadcast Communication

A low complexity antenna selection scheme for multicarrier MIMO (Multiple Input Multiple Output) broadcast systems is proposed in this paper. Under special condition of single user in the system or when the number of subcarrier is only one, the system reduces to conventional MIMO-OFDM (Orthogonal Frequency Division Multiplexing) system or MIMO-BC (Broadcast Channel) system respectively. By analysing sub-optimal antenna selection schemes developed earlier for single user MIMO-OFDM systems and single carrier MIMO-BC systems, one can see many similarities which can be extended to multicarrier MIMO broadcast systems. The proposed method exploits these similarities to obtain a low complexity system design with acceptable performance. The performance of the proposed scheme is studied via extensive simulation, and the computational complexity involved is compared to the conventional scheme. A selection gain of approximately 0.5 b/s/Hz is shown to be achievable using only two out of three antennas, and the proposed scheme is able to achieve up to 90% of the gain. This is achieved at a complexity that is significantly lower than the conventional methods, hence the practical implementation of the proposed scheme can be justified.     

Scalp Current Density Mapping: Value and Estimation from Potential Data

Scalp current density (SCD) makes possible the identification of scalp sources and sinks of current. SCD is reference independent and its peaks and troughs are sharper than those of the scalp potential (SP). SCD, by comparison to SP, reflects mainly the activity of cortical generators. SCD mapping appears to be a valuable tool to spatially split smeared SP distribution due to simultaneously active generators. The SCD map may be computed from any sufficiently smooth mathematical SP map. An evaluation of the error of SCD estimation is given for a surface spline method of interpolation of SP. An example of the simultaneous use of SP and SCD in the analysis of somatosensory evoked data is given.     

Evaluation of uncertainties in sewer condition assessment

Closed Circuit Television Inspection is used since decades as industry standard for sewer system inspection and structural performance evaluation. In current practice, inspection data are helpful to support asset management decisions. However, the quality and uncertainty of sewer condition assessment is rarely questioned. This article presents a methodology to determine the probability to underestimate, overestimate or accurately estimate the real condition of a pipe using visual inspection. The approach is based on the analysis of double inspections of the same sewer pipes and has been tested using the extensive data-set of the city of Braunschweig in Germany. Results indicate that the probability to inspect correctly a pipe in poor condition is close to 80%. The probability to overestimate the condition of a pipe in bad condition (false negative) is 20% whereas the probability to underestimate the condition of a pipe in good condition (false positive) is 15%. Finally, sewer condition evaluation can be used to assess the general condition of the network with an excellent accuracy probably because the respective effects of false positive and false negative are buffered.     

Carbon–polymer composites with extreme electrical conductivity

The aim of this study was to develop Carbon–polymer composites with extreme electrical conductivity (100 S/cm) combined with good flexural strength. Despite the many optimization methods described in the literature, no comprehensive optimization procedure was to be found because the formulation did not control by itself the final properties. This study showed the major influence of the processing conditions with these peculiar materials. A detailed study of the influence of the processing conditions on the microstructural and macroscopic properties was performed. We, thereby, proposed a comprehensive way to optimize the properties of the final product. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42274.     

后京都议定书时代的大都市:从手段到目的,从规划到激发

2008年,法国政府发起"后京都议定书时代大都市"和"未来都市巴黎"的研究,l'AUC事务所入选10家国际团队作为大巴黎研究项目的咨询顾问。本文展示了l'AUC事务所的方案及其他4个项目,分别针对当代规划、城市主义和建筑不同方面的主要问题:回收,生态城,紧凑和节点城市。     

Consideration of chiral optical fibres

Circular birefringence is a property of chiral materials. In this work, we consider the use of chiral materials in optical fibres to produce circularly birefringent optical fibres and in fibres where a contrast in circular birefringence contributes to forming the waveguide. (-)-menthyl methacrylate is also investigated as a possible material for the fabrication of such fibres.