902 resultados para Supervisory Control and Data Acquisition (SCADA)


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We present the first experimental implementation of a recently designed quasi-lossless fibre span with strongly reduced signal power excursion. The resulting fibre waveguide medium can be advantageously used both in lightwave communications and in all-optical nonlinear data processing.

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The need for an adequate information system for the Highways Departments in the United Kingdom has been recognised by the report of a committee presented to the Minister of Transport in 1970, (The Marshall Report). This research aims to present a comprehensive information system on a sound theoretical basis which should enable the different levels of management to execute their work adequately. The suggested system presented in this research covers the different functions of the Highways Department, and presents a suggested solution for problems which may occur during the planning and controlling of work in the different locations of the Highways Department. The information system consists of:- 1. A coding system covering the cost units, cost centres and cost elements. 2. Cost accounting records for the cost units and cost centres. 3. A budgeting and budgetary control system covering, the different planning methods and procedures which are required for preparing the capital expenditure budget, the improvement and maintenance operation flexible budgets and programme of work, the plant budget, the administration budget, and the purchasing budget. 4. A reporting system which ensures that the different levels of management are receiving relevant and timely information. 5. The flow of documents which covers the relationship between the prime documents, the cost accounting records, budgets, reports and their relation to the different sections and offices within the department. A comprehensive cost units, cost centres, and cost elements codes together with a number of examples demonstrating the results of the survey, and examples of the application and procedures of the suggested information system have been illustrated separately as appendices. The emphasis is on the information required for internal control by management personnel within the County Council.

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A novel architecture for microwave/millimeter-wave signal generation and data modulation using a fiber-grating-based distributed feedback laser has been proposed in this letter. For demonstration, a 155.52-Mb/s data stream on a 16.9-GHz subcarrier has been transmitted and recovered successfully. It has been proved that this technology would be of benefit to future microwave data transmission systems. © 2006 IEEE.

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Contrast sensitivity improves with the area of a sine-wave grating, but why? Here we assess this phenomenon against contemporary models involving spatial summation, probability summation, uncertainty, and stochastic noise. Using a two-interval forced-choice procedure we measured contrast sensitivity for circular patches of sine-wave gratings with various diameters that were blocked or interleaved across trials to produce low and high extrinsic uncertainty, respectively. Summation curves were steep initially, becoming shallower thereafter. For the smaller stimuli, sensitivity was slightly worse for the interleaved design than for the blocked design. Neither area nor blocking affected the slope of the psychometric function. We derived model predictions for noisy mechanisms and extrinsic uncertainty that was either low or high. The contrast transducer was either linear (c1.0) or nonlinear (c2.0), and pooling was either linear or a MAX operation. There was either no intrinsic uncertainty, or it was fixed or proportional to stimulus size. Of these 10 canonical models, only the nonlinear transducer with linear pooling (the noisy energy model) described the main forms of the data for both experimental designs. We also show how a cross-correlator can be modified to fit our results and provide a contemporary presentation of the relation between summation and the slope of the psychometric function.

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Building on the ‘law and economics’ literature, this paper analyses corporate governance implications of debt financing in an environment where a dominant owner is able to extract ex ante ‘private benefits of control’. Ownership concentration may result in lower efficiency, measured as a ratio of a firm’s debt to investment, and this effect depends on the identity of the largest shareholder. Moreover, entrenched dominant shareholder(s) may be colluding with fixed-claim holders in extracting ‘control premium’. One of possible outcomes is a ‘crowding out’ of entrepreneurial firms from the debt market, and this is supported by evidence from the transition economies.

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Large prospective trials designed to assess the relationship between metabolic control and CV outcomes in type 2 diabetes have entered a new phase of scrutiny due to strict requirements imposed by the FDA to assess new anti-diabetic agents. So what have we learned from recently completed trials and what do we expect to learn from on-going trials?

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The open content creation process has proven itself to be a powerful and influential way of developing text-based content, as demonstrated by the success of Wikipedia and related sites. Distributed individuals independently edit, revise, or refine content, thereby creating knowledge artifacts of considerable breadth and quality. Our study explores the mechanisms that control and guide the content creation process and develops an understanding of open content governance. The repertory grid method is employed to systematically capture the experiences of individuals involved in the open content creation process and to determine the relative importance of the diverse control and guiding mechanisms. Our findings illustrate the important control and guiding mechanisms and highlight the multifaceted nature of open content governance. A range of governance mechanisms is discussed with regard to the varied levels of formality, the different loci of authority, and the diverse interaction environments involved. Limitations and opportunities for future research are provided.

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We present the first experimental implementation of a recently designed quasi-lossless fiber span with strongly reduced signal power excursion. The resulting fiber waveguide medium can be advantageously used both in lightwave communications and in all-optical nonlinear data processing. © 2005 IEEE.

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High-speed optical clock recovery, demultiplexing and data regeneration will be integral parts of any future photonic network based on high bit-rate OTDM. Much research has been conducted on devices that perform these functions, however to date each process has been demonstrated independently. A very promising method of all-optical switching is that of a semiconductor optical amplifier-based nonlinear optical loop mirror (SOA-NOLM). This has various advantages compared with the standard fiber NOLM, most notably low switching power, compact size and stability. We use the SOA-NOLM as an all-optical mixer in a classical phase-locked loop arrangement to achieve optical clock recovery, while at the same time achieving data regeneration in a single compact device

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We present the first experimental implementation of a recently designed quasi-lossless fibre span with strongly reduced signal power excursion. The resulting fibre waveguide medium can be advantageously used both in lightwave communications and in all-optical nonlinear data processing.

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Purpose – This paper aims to consider how climate change performance is measured and accounted for within the performance framework for local authority areas in England adopted in 2008. It critically evaluates the design of two mitigation and one adaptation indicators that are most relevant to climate change. Further, the potential for these performance indicators to contribute to climate change mitigation and adaptation is discussed. Design/methodology/approach – The authors begin by examining the importance of the performance framework and the related Local Area Agreements (LAAs), which were negotiated for all local areas in England between central government and Local Strategic Partnerships (LSPs). This development is located within the broader literature relating to new public management. The potential for this framework to assist in delivering the UK's climate change policy objectives is researched in a two-stage process. First, government publications and all 150 LAAs were analysed to identify the level of priority given to the climate change indicators. Second, interviews were conducted in spring 2009 with civil servants and local authority officials from the English West Midlands who were engaged in negotiating the climate change content of the LAAs. Findings – Nationally, the authors find that 97 per cent of LAAs included at least one climate change indicator as a priority. The indicators themselves, however, are perceived to be problematic – in terms of appropriateness, accuracy and timeliness. In addition, concerns were identified about the level of local control over the drivers of climate change performance and, therefore, a question is raised as to how LSPs can be held accountable for this. On a more positive note, for those concerned about climate change, the authors do find evidence that the inclusion of these indicators within the performance framework has helped to move climate change up the agenda for local authorities and their partners. However, actions by the UK's new coalition government to abolish the national performance framework and substantially reduce public expenditure potentially threaten this advance. Originality/value – This paper offers an insight into a new development for measuring climate change performance at a local level, which is relatively under-researched. It also contributes to knowledge of accountability within a local government setting and provides a reference point for further research into the potential role of local actions to address the issue of climate change.

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Purpose – The purpose of this paper is to consider hierarchical control as a mode of governance, and analyses the extent of control exhibited by central government over local government through the best value (BV) and comprehensive performance assessment (CPA) performance regimes. Design/methodology/approach – This paper utilises Ouchi's framework and, specifically, his articulation of bureaucratic or hierarchical control in the move towards achievement of organisational objectives. Hierarchical control may be inferred from the extent of “command and control” by Central Government, use of rewards and sanctions, and alignment to government priorities and discrimination of performance. Findings – CPA represents a more sophisticated performance regime than BV in the governance of local authorities by central government. In comparison to BV, CPA involved less scope for dialogue with local government prior to introduction, closer inspection of and direction of support toward poorer performing authorities, and more alignment to government priorities in the weightings attached to service blocks. Originality/value - The paper focuses upon the hierarchic/bureaucratic mode of governance as articulated by Ouchi and expands on this mode in order to analyse shifts in performance regimes in the public sector.