811 resultados para Operation Research


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Presentation given to postgraduates at the School of Social and Policy Research, The Northern Institute, Charles Darwin University, Darwin, Northern Territory, 28 August 2010.

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Geographic information is increasingly being touted for use in research and industrial projects. While the technology is now available and affordable, there is a lack of easy to use software that takes advantage of geographic information. This is an important problem because users are often researchers or scientists who have insufficient software skills, and by providing applications that are easier to use, time and financial resources can be taken from training and be better applied to the actual research and development work. A solution for this problem must cater for the user and research needs. In particular it must allow for mobile operation for fieldwork, flexibility or customisability of data input, sharing of data with other tools and collaborative capabilities for the usual teamwork environment. This thesis has developed a new architecture and data model to achieve the solution. The result is the Mobile Collaborative Annotation framework providing an implementation of the new architecture and data model. Mobile Collaborative Mapping implements the framework as a Web 2.0 mashup rich internet application and has proven to be an effective solution through its positive application to a case study with fieldwork scientists. This thesis has contributed to research into mobile computing, collaborative computing and geospatial systems by creating a simpler entry point to mobile geospatial applications, enabling simplified collaboration and providing tangible time savings.

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The paper discusses the operating principles and control characteristics of a dynamic voltage restorer (DVR). It is assumed that the source voltages contain interharmonic components in addition to fundamental components. The main aim of the DVR is to produce a set of clean balanced sinusoidal voltages across the load terminals irrespective of unbalance, distortion and voltage sag/swell in the supply voltage. An algorithm has been discussed for extracting fundamental phasor sequence components from the samples of three-phase voltages or current waveforms having integer harmonics and interharmonics. The DVR operation based on extracted components is demonstrated. The switching signal is generated using a deadbeat controller. It has been shown that the DVR is able to compensate these interharmonic components such that the load voltages are perfectly regulated. The DVR operation under deep voltage sag is also discussed. The proposed DVR operation is verified through the computer simulation studies using the MATLAB software package.

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This paper is an essay on the state of Australian education that frames new directions for educational research. It outlines three challenges faced by Australian educators: highly spatialised poverty with particularly strong mediating effects on primary school education; the need for intellectual and critical depth in pedagogy, with a focus in the upper primary and middle years; and the need to reinvent senior schooling to address emergent pathways from school to work and civic life. It offers a narrative description of the dynamics of policy making in Australia and North America and argues for an evidence-based approach to social and educational policy – but one quite unlike current test and market-based approaches. Instead, it argues for a multidisciplinary approach to a broad range of empirical and case-based evidence that subjects these to critical, hermeneutic social sciences. Such an approach would join educational policy with educational research, and broader social, community and governmental action with the aim of reorganising and redistributing material, cultural and social resources.

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This paper discusses the effects of thyristor controlled series compensator (TCSC), a series FACTS controller, on the transient stability of a power system. Trajectory sensitivity analysis (TSA) has been used to measure the transient stability condition of the system. The TCSC is modeled by a variable capacitor, the value of which changes with the firing angle. It is shown that TSA can be used in the design of the controller. The optimal locations of the TCSC-controller for different fault conditions can also be identified with the help of TSA. The paper depicts the advantage of the use of TCSC with a suitable controller over fixed capacitor operation.

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This article provides an overview of the concept of vulnerability through the lens of the U.S. federal regulations for the protection of human subjects of research. General issues that emerge for nurse researchers working with regulated vulnerable populations are identified. Points of current controversy in the application of the regulations and current discourse about vulnerable groups are highlighted. Suggestions for negotiating the tension between federally regulated human subject requirements and the realities of research with vulnerable subjects are given. The limitations of the designation of vulnerable as a protection for human subjects will also be discussed.

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The challenges facing the Singapore education system in the new millennium are unique and unprecedented in Asia. Demands for new skills, knowledges, and flexible competencies for globalised economies and cosmopolitan cultures will require system-wide innovation and reform. But there is a dearth of international benchmarks and prototypes for such reforms. This paper describes the current Core Research Program underway at the National Institute of Education in Singapore, a multilevel analysis of Singaporean schooling, pedagogy, youth and educational outcomes. It describes student background, performance, classroom practices, student artefacts and outcomes, and student longitudinal life pathways. The case is made that a systematic focus on teachers' and students' work in everyday classroom contexts is the necessary starting point for pedagogical innovation and change. This, it is argued, can constitute a rich multidisciplinary evidence base for educational policy. (Contains 1 figure, 1 table and 3 notes.)

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Most statistical methods use hypothesis testing. Analysis of variance, regression, discrete choice models, contingency tables, and other analysis methods commonly used in transportation research share hypothesis testing as the means of making inferences about the population of interest. Despite the fact that hypothesis testing has been a cornerstone of empirical research for many years, various aspects of hypothesis tests commonly are incorrectly applied, misinterpreted, and ignored—by novices and expert researchers alike. On initial glance, hypothesis testing appears straightforward: develop the null and alternative hypotheses, compute the test statistic to compare to a standard distribution, estimate the probability of rejecting the null hypothesis, and then make claims about the importance of the finding. This is an oversimplification of the process of hypothesis testing. Hypothesis testing as applied in empirical research is examined here. The reader is assumed to have a basic knowledge of the role of hypothesis testing in various statistical methods. Through the use of an example, the mechanics of hypothesis testing is first reviewed. Then, five precautions surrounding the use and interpretation of hypothesis tests are developed; examples of each are provided to demonstrate how errors are made, and solutions are identified so similar errors can be avoided. Remedies are provided for common errors, and conclusions are drawn on how to use the results of this paper to improve the conduct of empirical research in transportation.

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Construction sector application of Lead Indicators generally and Positive Performance Indicators (PPIs) particularly, are largely seen by the sector as not providing generalizable indicators of safety effectiveness. Similarly, safety culture is often cited as an essential factor in improving safety performance, yet there is no known reliable way of measuring safety culture. This paper proposes that the accurate measurement of safety effectiveness and safety culture is a requirement for assessing safe behaviours, safety knowledge, effective communication and safety performance. Currently there are no standard national or international safety effectiveness indicators (SEIs) that are accepted by the construction industry. The challenge is that quantitative survey instruments developed for measuring safety culture and/ or safety climate are inherently flawed methodologically and do not produce reliable and representative data concerning attitudes to safety. Measures that combine quantitative and qualitative components are needed to provide a clear utility for safety effectiveness indicators.

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As the acceptance and popularity of wireless networking technologies has proliferated, the security of the IEEE 802.11 wireless local area network (WLAN) has advanced in leaps and bounds. From tenuous beginnings, where the only safe way to deploy a WLAN was to assume it was hostile and employ higherlayer information security controls, to the current state of the art, all manner of improvements have been conceived and many implemented. This work investigates some of the remaining issues surrounding IEEE 802.11 WLAN operation. While the inherent issues in WLAN deployments and the problems of the original Wired Equivalent Privacy (WEP) provisions are well known and widely documented, there still exist a number of unresolved security issues. These include the security of management and control frames and the data link layer protocols themselves. This research introduces a novel proposal to enhance security at the link layer of IEEE 802.11 WLANs and then conducts detailed theoretical and empirical investigation and analysis of the eects of such proposals. This thesis �rst de�nes the state of the art in WLAN technology and deployment, including an overview of the current and emerging standards, the various threats, numerous vulnerabilities and current exploits. The IEEE 802.11i MAC security enhancements are discussed in detail, along with the likely outcomes of the IEEE 802.11 Task Group W1, looking into protected management frames. The problems of the remaining unprotected management frames, the unprotected control frames and the unprotected link layer headers are reviewed and a solution is hypothesised, to encrypt the entire MAC Protocol Data Unit (MPDU), including the MAC headers, not just the MAC Service Data Unit (MSDU) commonly performed by existing protocols. The proposal is not just to encrypt a copy of the headers while still using cleartext addresses to deliver the frame, as used by some existing protocols to support the integrity and authenticity of the headers, but to pass the entire MPDU only as ciphertext to also support the con�dentiality of the frame header information. This necessitates the decryption of every received frame using every available key before a station can determine if it is the intended recipient. As such, this raises serious concerns as to the viability of any such proposal due to the likely impact on throughput and scalability. The bulk of the research investigates the impacts of such proposals on the current WLAN protocols. Some possible variations to the proposal are also provided to enhance both utility and speed. The viability this proposal with respect to the eect on network throughput is then tested using a well known and respected network simulation tool, along with a number of analysis tools developed speci�cally for the data generated here. The simulator's operation is �rst validated against recognised test outputs, before a comprehensive set of control data is established, and then the proposal is tested and and compared against the controls. This detailed analysis of the various simulations should be of bene�t to other researchers who need to validate simulation results. The analysis of these tests indicate areas of immediate improvement and so the protocols are adjusted and a further series of experiments conducted. These �nal results are again analysed in detail and �nal appraisals provided.

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Australian privacy law regulates how government agencies and private sector organisations collect, store and use personal information. A coherent conceptual basis of personal information is an integral requirement of information privacy law as it determines what information is regulated. A 2004 report conducted on behalf of the UK’s Information Commissioner (the 'Booth Report') concluded that there was no coherent definition of personal information currently in operation because different data protection authorities throughout the world conceived the concept of personal information in different ways. The authors adopt the models developed by the Booth Report to examine the conceptual basis of statutory definitions of personal information in Australian privacy laws. Research findings indicate that the definition of personal information is not construed uniformly in Australian privacy laws and that different definitions rely upon different classifications of personal information. A similar situation is evident in a review of relevant case law. Despite this, the authors conclude the article by asserting that a greater jurisprudential discourse is required based on a coherent conceptual framework to ensure the consistent development of Australian privacy law.

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This paper presents a critical review of past research in the work-related driving field in light vehicle fleets (e.g., vehicles < 4.5 tonnes) and an intervention framework that provides future direction for practitioners and researchers. Although work-related driving crashes have become the most common cause of death, injury, and absence from work in Australia and overseas, very limited research has progressed in establishing effective strategies to improve safety outcomes. In particular, the majority of past research has been data-driven, and therefore, limited attention has been given to theoretical development in establishing the behavioural mechanism underlying driving behaviour. As such, this paper argues that to move forward in the field of work-related driving safety, practitioners and researchers need to gain a better understanding of the individual and organisational factors influencing safety through adopting relevant theoretical frameworks, which in turn will inform the development of specifically targeted theory-driven interventions. This paper presents an intervention framework that is based on relevant theoretical frameworks and sound methodological design, incorporating interventions that can be directed at the appropriate level, individual and driving target group.