SRAT-Distribution Voltage Sags and Reliability Assessment Tool

Interruptions to supply and sags of distribution system voltage are the main aspects causing customer complaints. There is a need for analysis of supply reliability and voltage sag to relate system performance with network structure and equipment design parameters. This analysis can also give prediction of voltage dips, as well as relating traditional reliability and momentary outage measures to the properties of protection systems and to network impedances. Existing reliability analysis software often requires substantial training, lacks automated facilities, and suffers from data availability. Thus it requires time-consuming manual intervention for the study of large networks. A user-friendly sag and reliability assessment tool (SRAT) has been developed based on existing impedance data, protection characteristics, and a model of failure probability. The new features included in SRAT are a) efficient reliability and sag assessments for a radial network with limited loops, b) reliability evaluation associated with realistic protection and restoration schemes, c) inclusion of momentary outages in the same model as permanent outage evaluation, d) evaluation of the sag transfer through meshed subtransmission network, and e) simplified probability distribution model determined from available faults records. Examples of the application of the tools to an Australian distribution network are used to illustrate the application of this model

Plasmonic eigenmodes in individual and bow-tie graphene nanotriangles

Serving as a new two-dimensional plasmonic material, graphene has stimulated an intensive study of its optical properties which benefit from the unique electronic band structure of the underlying honeycomb lattice of carbon atoms. In classical electrodynamics, nanostructured graphene is commonly modeled by the computationally demanding problem of a three-dimensional conducting film of atomic-scale thickness. Here, we propose an efficient alternative two-dimensional electrostatic approach where all the calculation procedures are restricted to the plane of the graphene sheet. To explore possible quantum effects, we perform tight-binding calculations, adopting a random-phase approximation. We investigate the multiple plasmon modes in triangles of graphene, treating the optical response classically as well as quantum mechanically in the case of both armchair and zigzag edge termination of the underlying atomic lattice. Compared to the classical plasmonic spectrum which is "blind" to the edge termination, we find that the quantum plasmon frequencies exhibit blueshifts in the case of armchair edge termination, while redshifts are found for zigzag edges. Furthermore, we find spectral features in the zigzag case which are associated with electronic edge states not present for armchair termination. Merging pairs of such triangles into dimers, the plasmon hybridization leads to energy splitting in accordance with plasmon-hybridization theory, with a lower energy for the antisymmetric modes and a smaller splitting for modes with less confinement to the gap region. The hybridization appears strongest in classical calculations while the splitting is lower for armchair edges and even more reduced for zigzag edges. Our various results illustrate a surprising phenomenon: Even 20 nm large graphene structures clearly exhibit quantum plasmonic features due to atomic-scale details in the edge termination.Comment: 27 pages including 7 figures. Supplementary information available upon request to author

An investigation of messy genetic algorithms

Genetic algorithms (GAs) are search procedures based on the mechanics of natural selection and natural genetics. They combine the use of string codings or artificial chromosomes and populations with the selective and juxtapositional power of reproduction and recombination to motivate a surprisingly powerful search heuristic in many problems. Despite their empirical success, there has been a long standing objection to the use of GAs in arbitrarily difficult problems. A new approach was launched. Results to a 30-bit, order-three-deception problem were obtained using a new type of genetic algorithm called a messy genetic algorithm (mGAs). Messy genetic algorithms combine the use of variable-length strings, a two-phase selection scheme, and messy genetic operators to effect a solution to the fixed-coding problem of standard simple GAs. The results of the study of mGAs in problems with nonuniform subfunction scale and size are presented. The mGA approach is summarized, both its operation and the theory of its use. Experiments on problems of varying scale, varying building-block size, and combined varying scale and size are presented

Collective narratives and politics in the contemporary study of work : the new management practices debate

In this article we explore the question of how as sociologists of work we might research those who constitute the substance of our labour process. We approach this question through an examination of the New Management Practices debate, principally in the labour movement where a distinctive and critical view of NMP developed in the late 1980s. Second, we argue that there is a link between this debate and the wider politics of labour process discussion both within and beyond the labour movement which has witnessed a shift away from an earlier engagement with worker interventions. In response we suggest the need to re-evaluate the nature of academic engagement with labour thus reanimating a closer engagement with labour-in-work and collective worker narratives

Bounded Delay Scheduling with Packet Dependencies

A common situation occurring when dealing with multimedia traffic is having large data frames fragmented into smaller IP packets, and having these packets sent independently through the network. For real-time multimedia traffic, dropping even few packets of a frame may render the entire frame useless. Such traffic is usually modeled as having {\em inter-packet dependencies}. We study the problem of scheduling traffic with such dependencies, where each packet has a deadline by which it should arrive at its destination. Such deadlines are common for real-time multimedia applications, and are derived from stringent delay constraints posed by the application. The figure of merit in such environments is maximizing the system's {\em goodput}, namely, the number of frames successfully delivered. We study online algorithms for the problem of maximizing goodput of delay-bounded traffic with inter-packet dependencies, and use competitive analysis to evaluate their performance. We present competitive algorithms for the problem, as well as matching lower bounds that are tight up to a constant factor. We further present the results of a simulation study which further validates our algorithmic approach and shows that insights arising from our analysis are indeed manifested in practice

"The Strategic Effects of Firm Sizes and Dynamic Capabilities on Overseas Operations: A Case-based Comparison of Toyota and Mitsubishi in Thailand and Australia"

In international business, much attention has been directed to the international expansion of firms based on their use of resources and competitive capabilities that have been built up in a home country to create a competitive advantage over host-country firms. More recently, the organizational capabilities and competitive advantages of Japanese manufacturing firms in general (in autos, electronics, etc.) have been analyzed as important factors in the establishment of overseas transplants. The theoretical framework of the overseas application of home-country management resources has been effective as a basic tool in analyzing the fundamental issue of international operations of the firm. However, the existing models, which tend to emphasize application of country-specific resources, does not sufficiently explain the frequently encountered question of why multinational enterprises (following, MNEs) from the same home country pursue different strategic paths and actions when managing overseas operations. The present paper attempts to incorporate a dynamic and firm-specific perspective and empirically analyze how differences in the financial resources and organizational capabilities of MNEs from the same home country affect the strategy and competitive behavior of their operations in the same local country. The analysis will center on the two Japanese auto assemblers, specifically Toyota Motor Corporation and Mitsubishi Motors Corporation, which have local production facilities in both Australia and Thailand. These two countries provide interesting case studies because in both the local operations experienced a serious crisis in recent years. The crisis for local auto producers in Australia began in the 1980s with the removal of protectionist policies and the rapid liberalization of the auto market. In Thailand, exceedingly severe conditions for local auto assemblers were caused by the 1997 Asian economic crisis. The present paper will focus its attention on the differences in the responses by Toyota and Mitsubishi to these crises, which we characterize as "larger competent firm" and "smaller competent firm" respectively. The two firms in question have both maintained international competitiveness in production in their common home country of Japan, in addition to building top-level local competitiveness in their Australian and Thai operations. However, when faced with a growth opportunity and a subsequent crisis, the responses of the local operations of the firms were markedly different. It is anticipated that behind these differences in firm conduct lie interfirm differences in firm scale (i.e. financial power) and dynamic organizational capabilities (e.g., capability-building capability) in their home country. The present paper will attempt to delineate these interfirm differences and their effects on firm conduct to explain why two firms from the same home country would show such different patterns of conduct even though they face the same local opportunities and crises.