线路装耦合地线后耐雷水平计算与过电压分析

鉴于在导线下方架设耦合地线 (CGW )既可增加地线对导线的耦合程度 ,降低绝缘子串上的电压 ,又可对雷电流起分流作用 ,提高输电线路的耐雷水平 ,介绍了装设CGW后输电线路耐雷水平计算的方法 ;并结合实际线路 ,利用EMTP软件对线路雷电过电压进行电磁暂态仿真。计算结果表明CGW可有效提高线路耐雷水平     

Ten years of transport of vitrified high level waste (HLW) from Areva La Hague

Abstract

Areva has extensive experience in reprocessing irradiated fuel from both gas cooled and water cooled reactors and has legal obligations to return residues to respective foreign owners, usually in the form of vitrified waste. Such returns are subject to appropriate quality assurance controls. Appropriate transport flasks have been designed and certified. Transport operations are routinely conducted to Belgium, Germany, Japan, Switzerland and the Netherlands. The present paper reviews the experiences over a ten year period from 1995 to 2005.     

Microstructure characteristics in non-modified and Sr modified Al–Si–Cu–Mg 319 type alloys

Abstract

This study was carried out on 319 alloys containing low and high levels of Mg, in the non-modified and Sr modified conditions (150 ppm Sr addition). Single step, two step and triple step heat treatments were applied to identify the optimum solution heat treatment to minimise incipient melting of the copper phases Al₂Cu and Al₅Mg₈Cu₂Si₆ in these alloys in relation to the alloy properties. In Mg free alloys, no incipient melting of Al₂ Cu was observed even in samples heat treated at 520°C. Addition of Sr leads to modification of Si particles but also to an increase in area per cent porosity and pore length, especially when the solution temperature reaches 520°C. Addition of Mg results in a decrease in the Si particle aspect ratio but an increase in particle size. Magnesium was also found to increase the possibility of incipient melting resulting from the formation of the insoluble Al₅Mg₈Cu₂Si₆ phase. To some degree, Sr decreases the effect that Mg has in increasing the area per cent porosity and pore length, while Mg impairs the effects that Sr has on modifying Si particles, even though the lowest Al–Si eutectic temperature is obtained for the 319 alloy containing both Mg and Sr.     

A Developable Photographic System Based on Arsenic

The allotropic change of metastable yellow arsenic into metallie arsenic has been shown to be a developable photographic reaction: conceptually, if not practically, the simplest that can be constructed.     

Experiences with Cooperating Register Allocation and Instruction Scheduling

Compile-time reordering of low level instructions is successful in achieving large increases in performance of programs on fine grain parallel machines. However, because of the interdependences between instruction scheduling and register allocation, a lack of cooperation between the scheduler and register allocator can result in generating code that contains excess register spills and/or a lower degree of parallelism than actually achievable. This paper describes a strategy for providing cooperation between register allocation and both global and local instruction scheduling. We experimentally compare this strategy with other cooperative and uncooperative scenarios.     

TINA Network Resource Information Model

The TINA (Telecommunications InformationNetworking Architecture) Network Resource InformationModel (NRIM) is a technology-independent network levelresource model that provides the foundation for the management and control of networks envisionedin the TINA architecture. Such networks are capable ofsupporting multimedia and multipoint communicationsessions and may consist of network elements based on different technologies. Different portionsof such networks will be under the control of differentnetwork administrations. NRIM describes such a networkabstractly in terms of network elements, aggregations of network elements, the topologicalrelationship between the elements, transport entities,and endpoints of transport entities. In addition, NRIMdefines management support objects for alarmsurveillance, resource configuration, and accounting. NRIM isindependent of the architecture of the individualmanagement functions. Further, the model is describedabstractly in terms of objects and relationships and it is independent of the protocols used forcommunication between management functions. Informationmodels for the management of specific networktechnologies can be derived from the generic modeldefined by the NRIM. This paper presents an overview ofthe NRIM emphasizing the recent advances made in theNRIM specification.     

Level sets and stable manifold approximations for perceptually driven non-holonomically constrained navigation

This paper addresses problems of robot navigation in the presence of non-holonomic motion constraints arising from kinematics as well as holonomic constraints arising from perception. We consider the theoretical problem of visually registering a unicycle with respect to camera images of a known, persistent landmark. We propose a general hybrid procedure that adapts to this constrained motion setting the standard feedback controller arising from a navigation function in the fully actuated case. The algorithm switches back and forth between moving down and across the associated gradient field toward the stable manifold it induces in the constrained dynamics. Guaranteed to avoid obstacles in all cases, after the introduction of some technical (and not easily verified) additional assumptions, the algorithm can be readily shown to converge to an arbitrarily small neighborhood of the goal. We then introduce a more realistic, 'relaxed' version of the algorithm that appears to result in asymptotic convergence to the goal. Illustrative simulations are provided for two different perceptual models appropriate to environments with visual beacons.     

Speculative Memory Cloaking and Bypassing

We revisit memory hierarchy design viewing memory as an inter-operation communication mechanism. We show how dynamically collected information about inter-operation memory communication can be used to improve memory latency. We propose two techniques: (1) Speculative Memory Cloaking, and (2) Speculative Memory Bypassing. In the first technique, we use memory dependence prediction to speculatively identify dependent loads and stores early in the pipeline. These instructions may then communicate prior to address calculation and disambiguation via a fast communication mechanism. In the second technique, we use memory dependence prediction to speculatively transform DEF-store-load-USE dependence chains within the instruction window into DEF-USE ones. As a result, dependent stores and loads are taken off the communication path resulting in further reduction in communication latency. Experimental analysis shows that our methods, on the average, correctly handle 40% (integer) and 19% (floating point) of all memory loads. Moreover, our techniques result in performance improvements of 4.28% (integer) and 3.20% (floating point) over a highly aggressive, dynamically scheduled processor implementing naive memory dependence speculation. We also study the value and address locality characteristics of the values our methods correctly handle. We demonstrate that our methods are orthogonal to both address and value prediction.     

Stress corrosion cracking of oil and gas pipelines in near neutral pH environment: review of recent research

Abstract

Since the discovery of transgranular stress corrosion cracking (SCC) on a Canadian gas transmission line in 1985, much research has been conducted in the past 20 years. Findings of the effects of operating conditions, metallurgical and the environmental factors have been useful in preventing and mitigating failures. Several overviews of this problem can be found in the literature and the purpose of this update is to review the research results produced since the turn of the century. The recent report of SCC under static stressing conditions confirms that the cracking is indeed a true SCC process, although the rate of which is low without dynamic loading. In contrast to the high pH pipeline stress corrosion cracking in the carbonate–bicarbonate solution, this forms of cracking in dilute near neutral environment takes much longer time to initiate. Once initiated, the crack growth rate is highly sensitive to the loading rate of the applied mechanical force.