22 resultados para Electricity in mining.
em Aston University Research Archive
Resumo:
Coleridge, looking back at the end of the ‘long eighteenth century’, remarked that the whole of natural philosophy had been ‘electrified’ by advances in the understanding of electrical phenomena. In this paper I trace the way in which these advances affected contemporary ‘neurophysiology.’ At the beginning of the long eighteenth century, neurophysiology (in spite of Swammerdam’s and Glisson’s demonstrations to the contrary) was still understood largely in terms of hollow nerves and animal spirits. At the end of that period the researches of microscopists and electricians had convinced most medical men that the old understanding had to be replaced. Walsh, Patterson, John Hunter and others had described the electric organs of electric fish. Gray and Nollet had demonstrated that electricity was not merely static, but flowed. Franklin had alerted the world to atmospheric electricity. Galvani’s frog experiments were widely known. Volta had invented his ‘pile.’ But did ‘animal electricity’ exist and was it identical to the electricity physicists studied in the inanimate world? Was the brain a gland, as Malpighi’s researches seemed to confirm., and did it secrete electricity into the nervous system? The Monros (primus and secundus), William Cullen, Luigi Galvani, Alessandro Volta, Erasmus Darwin, Luigi Rolando and François Baillarger all had their own ideas. This paper reviews these ‘long-eighteenth century’ controversies with special reference to the Edinburgh medical school and the interaction between neurophysiology and physics.
Resumo:
Greenhouse cultivation is an energy intensive process therefore it is worthwhile to introduce energy saving measures and alternative energy sources. Here we show that there is scope for energy saving in fan ventilated greenhouses. Measurements of electricity usage as a function of fan speed have been performed for two models of 1.25 m diameter greenhouse fans and compared to theoretical values. Reducing the speed can cut the energy usage per volume of air moved by more than 70%. To minimize the capital cost of low-speed operation, a cooled greenhouse has been built in which the fan speed responds to sunlight such that full speed is reached only around noon. The energy saving is about 40% compared to constant speed operation. Direct operation of fans from solar-photovoltaic modules is also viable as shown from experiments with a fan driven by a brushless DC motor. On comparing the Net Present Value costs of the different systems over a 10 year amortization period (with and without a carbon tax to represent environmental costs) we find that sunlight-controlled system saves money under all assumptions about taxation and discount rates. The solar-powered system, however, is only profitable for very low discount rates, due to the high initial capital costs. Nonetheless this system could be of interest for its reliability in developing countries where mains electricity is intermittent. We recommend that greenhouse fan manufacturers improve the availability of energy-saving designs such as those described here.
Resumo:
Purpose – The purpose of this paper is to contribute to the ongoing debate on governance, accountability, transparency and corporate social responsibility (CSR) in the mining sector of a developing country context. It examines the reporting practices of the two largest transnational gold-mining companies in Tanzania in order to draw attention to the role played by local government regulations and advocacy and campaigning by nationally organised non-governmental organisations (NGOs) with respect to promoting corporate social reporting practices. Design/methodology/approach – The paper takes a political economy perspective to consider the serious implications of the neo-liberal ideologies of the global capitalist economy, as manifested in Tanzania’s regulatory framework and in NGO activism, for the corporate disclosure, accountability and responsibility of transnational companies (TNCs). A qualitative field case study methodology is adopted to locate the largely unfamiliar issues of CSR in the Tanzanian mining sector within a more familiar literature on social accounting. Data for the case study were obtained from interviews and from analysis of documents such as annual reports, social responsibility reports, newspapers, NGO reports and other publicly available documents. Findings – Analysis of interviews, press clips and NGO reports draws attention to social and environmental problems in the Tanzanian mining sector, which are arguably linked to the manifestation of the broader crisis of neo-liberal agendas. While these issues have serious impacts on local populations in the mining areas, they often remain invisible in mining companies’ social disclosures. Increasing evidence of social and environmental ills raises serious questions about the effectiveness of the regulatory frameworks, as well as the roles played by NGOs and other pressure groups in Tanzania. Practical implications – By empowering local NGOs through educational, capacity building, technological and other support, NGOs’ advocacy, campaigning and networking with other civil society groups can play a pivotal role in encouraging corporations, especially TNCs, to adopt more socially and environmentally responsible business practices and to adhere to international and local standards, which in turn may help to improve the lives of many poor people living in developing countries in general, and Tanzania in particular. Originality/value – This paper contributes insights from gold-mining activities in Tanzania to the existing literature on CSR in the mining sector. It also contributes to political economy theory by locating CSR reporting within the socio-political and regulatory context in which mining operations take place in Tanzania. It is argued that, for CSR reporting to be effective, robust regulations and enforcement and stronger political pressure must be put in place.
Resumo:
Perturbations in the bismuth market resulted in Mining and Chemical Products Ltd., seeking further outlets in the market. Together with Manchem Ltd. they were anxious to evaluate the possibility of using bismuth compounds as a replacement for lead/calcium soaps in paint driers. A range of new organobismuth compounds were synthesised of the type RBiX2 and R3BiX2 (X= halogen, OOCR, dithiocarbamate). A variety of synthetic techniques were explored, including the use of mathematical reactions, phase-transfer catalysis and microwave energy. The preparation of a range of trivalent and pentavalent organobismuth carboxylates is reported and their infra-red , 13C, lH nmr spectra. The compounds were evaluated as paint driers and in cases found to enhance paint drying to a greater degree than the standard driers, to which they were being compared. The drying times of paint films containing the organobismuth compounds are reported, together with a comparison of the drying times with the addition of bismuth tris-diethyldithiocarbamate, which may promote the cross-linking reaction that occur in paint films during the drying process. Examples are reported to illustrate the great reductions in reaction times possible when using microwave energy. Reactions such as metallation of aromatic rings, ligand redistribution and synthesis were carried out in PTFE containers in a conventional domestic microwave oven. An X-ray diffraction study of (phenylazophenyl-C,N')mercury(II) chloride has shown it to be dimeric via long Hg-Cl bridging interactions of 3.367A. Its crystal structure is reported, together with its 13C nmr spectra and mass spectrum. The Lewis acidity of compounds of the type RBiX2 was investigated. The donor group being anchored to the organo group (R). The dithiocarbamates bis- (diethyldithiobarbamato)phenylbismuth(Ill) and [2-2-pyridyl)phenylbismuth(III) were synthesised, and their crystal structures, 14N, 13C nmr ar1d infra-red spectra are reported. Both compounds are pseudo-pentagonal bipyramidal in geometry, with two long Bi-S bonds and two short Bi-S bonds. The reaction of RBiBr2 (R= 2-(pyridyl) with various ligands is reported. The infra-red evidence suggesting that the coordination of extra ligands is accompanied by a reduction of the strength of the Bi-interaction.
Resumo:
This paper provides a preliminary comparative longitudinal analysis of the impact on workers made redundant due to the closure of the Mitsubishi plant in Adelaide and the MG Rover plant in Birmingham. Longitudinal surveys of ex-workers from both firms were undertaken over a 12-month period in order to assess the process of labour market adjustment. In the Mitsubishi case, given the skills shortage the state of Adelaide was facing, together with the considerable growth in mining and defence industries, it would have been more appropriate if policy intervention had been redirected to further training or re-skilling opportunities for redundant workers. This opportunity was effectively missed and as a result more workers left the workforce, most notably for retirement, than could have otherwise been the case. The MG Rover case was seen as a more successful example of policy intervention, with greater funding assistance available and targeted support available, and with more emphasis on re-training needs to assist adjustment. However, despite the assistance offered and the rhetoric of successful adjustment in both cases, the majority of workers have nevertheless experienced deterioration in their circumstances particularly in the Australian case where casual and part-time work were often the only work that could be obtained. Even in the UK case, where more funding assistance was offered, a majority of workers reported a decline in earnings and a rise in job insecurity. This suggests that a reliance on the flexible labour market is insufficient to promote adjustment, and that more active policy intervention is needed especially in regard to further up-skilling.
Resumo:
Conventional DEA models assume deterministic, precise and non-negative data for input and output observations. However, real applications may be characterized by observations that are given in form of intervals and include negative numbers. For instance, the consumption of electricity in decentralized energy resources may be either negative or positive, depending on the heat consumption. Likewise, the heat losses in distribution networks may be within a certain range, depending on e.g. external temperature and real-time outtake. Complementing earlier work separately addressing the two problems; interval data and negative data; we propose a comprehensive evaluation process for measuring the relative efficiencies of a set of DMUs in DEA. In our general formulation, the intervals may contain upper or lower bounds with different signs. The proposed method determines upper and lower bounds for the technical efficiency through the limits of the intervals after decomposition. Based on the interval scores, DMUs are then classified into three classes, namely, the strictly efficient, weakly efficient and inefficient. An intuitive ranking approach is presented for the respective classes. The approach is demonstrated through an application to the evaluation of bank branches. © 2013.
Resumo:
The objective of the thesis was to analyse several process configurations for the production of electricity from biomass. Process simulation models using AspenPlus aimed at calculating the industrial performance of power plant concepts were built, tested, and used for analysis. The criteria used in analysis were performance and cost. All of the advanced systems appear to have higher efficiencies than the commercial reference, the Rankine cycle. However, advanced systems typically have a higher cost of electricity (COE) than the Rankine power plant. High efficiencies do not reduce fuel costs enough to compensate for the high capital costs of advanced concepts. The successful reduction of capital costs would appear to be the key to the introduction of the new systems. Capital costs account for a considerable, often dominant, part of the cost of electricity in these concepts. All of the systems have higher specific investment costs than the conventional industrial alternative, i.e. the Rankine power plant; Combined beat and power production (CUP) is currently the only industrial area of application in which bio-power costs can be considerably reduced to make them competitive. Based on the results of this work, AsperiPlus is an appropriate simulation platform. How-ever, the usefulness of the models could be improved if a number of unit operations were modelled in greater detail. The dryer, gasifier, fast pyrolysis, gas engine and gas turbine models could be improved.
Resumo:
Retrospective clinical data presents many challenges for data mining and machine learning. The transcription of patient records from paper charts and subsequent manipulation of data often results in high volumes of noise as well as a loss of other important information. In addition, such datasets often fail to represent expert medical knowledge and reasoning in any explicit manner. In this research we describe applying data mining methods to retrospective clinical data to build a prediction model for asthma exacerbation severity for pediatric patients in the emergency department. Difficulties in building such a model forced us to investigate alternative strategies for analyzing and processing retrospective data. This paper describes this process together with an approach to mining retrospective clinical data by incorporating formalized external expert knowledge (secondary knowledge sources) into the classification task. This knowledge is used to partition the data into a number of coherent sets, where each set is explicitly described in terms of the secondary knowledge source. Instances from each set are then classified in a manner appropriate for the characteristics of the particular set. We present our methodology and outline a set of experiential results that demonstrate some advantages and some limitations of our approach. © 2008 Springer-Verlag Berlin Heidelberg.
Resumo:
The fatigue-crack propagation and threshold behaviour of a C-Mn steel containing boron has been investigated at a range of strength levels suitable for mining chain applications. The heat-treatment variables examined include two austenitizing temperatures (900 degree C and 1250 degree C) and a range of tempering treatments from the as-quenched condition to tempering at 400 degree C. In mining applications the haulage chains undergo a 'calibration' process which has the effect of imposing a tensile prestrain on the chain links before they go into service. Prestrain is shown to reduce threshold values in these steels and this behaviour is related to its effects on the residual stress distribution in the test specimens.
Resumo:
This paper is located within the corporate social reporting and stakeholder management literature. It is concerned with the use of the Internet as a way of communicating with stakeholders and the extent to which this communication is or is not two-way. The evidence from the electricity industry in the UK is that the Internet is used but this use is selective and there is little true dialogue. It appears that the Internet provides an opportunity for greater corporate accountability in the future but whether this potential will be fulfilled is as yet unclear. Further research of a longitudinal nature is required to see how the Internet and more specifically corporate social or stakeholder reporting develops over time.
Resumo:
This thesis proposes to explore the potential for stakeholder based accounting as a means to explain the social performance of organisations. It argues that organisations have a contract with society and as a consequence they must be accountable to that society for their actions. Further, it is suggested that as part of this accountability there is a broader need in the public interest for social accounting. Due to the pluralistic nature of modern societies it is argued that a stakeholder framework is one way in which this accountability can be achieved. In order to consider the nature of such social accounting a case study of the electricity industry in England and Wales is undertaken. This industry is very important to modern society, has significant environment implications and has a recent history of remarkable change. These factors make it an interesting and unique case within which to consider accountability. From the performance measurement and accounting literature and a series of interviews with both stakeholders and privatised companies a model of stakeholder performance is developed. This is then used to analyse the electricity industry in England and Wales since privatisation. The objective is to demonstrate how certain stakeholders have fared, whether they have won or lost. Further, institutional and resource dependency theories are used to consider what factors determine the relative success or failure of the different stakeholder groups. Finally the possible implications of recent developments in Social Accounting Standards, such as the Global Reporting Initiative (GRI), AccountAbility 1000 (AA1000) and Social Accountability 8000 (SA8000), and the potential for Internet reporting are considered.
Resumo:
This thesis is concerned with certain aspects of the Public Inquiry into the accident at Houghton Main Colliery in June 1975. It examines whether prior to the accident there existed at the Colliery a situation in which too much reliance was being placed upon state regulation and too Iittle upon personal responsibility. I study the phenomenon of state regulation. This is done (a) by analysis of selected writings on state regulation/intervention/interference/bureaucracy (the words are used synonymously) over the last two hundred years, specifically those of Marx on the 1866 Committee on Mines, and (b) by studying Chadwick and Tremenheere, leading and contrasting "bureaucrats" of the mid-nineteenth century. The bureaucratisation of the mining industry over the period 1835-1954 is described, and it is demonstrated that the industry obtained and now possesses those characteristics outlined by Max Weber in his model of bureaucracy. I analyse criticisms of the model and find them to be relevant, in that they facilitate understanding both of the circumstances of the accident and of the Inquiry . Further understanding of the circumstances and causes of the accident was gained by attendance at the lnquiry and by interviewing many of those involved in the Inquiry. I analyse many aspects of the Inquiry - its objectives. structure, procedure and conflicting interests - and find that, although the Inquiry had many of the symbols of bureaucracy, it suffered not from " too much" outside interference. but rather from the coal mining industry's shared belief in its ability to solve its own problems. I found nothing to suggest that, prior to the accident, colliery personnel relied. or were encouraged to rely, "too much" upon state regulation.
Resumo:
This thesis analyses the impact of deregulation on the theory and practice of investment decision making in the electricity sector and appraises the likely effects on its long term future inefficiency. Part I describes the market and its shortcomings in promoting an optimal generation margin and plant mix and in reducing prices through competition. A full size operational model is developed to simulate hour by hour operation of the market and analyse its features. A relationship is established between the SMP and plant mix and between the LOLP and plant margin and it is shown bow a theoretical optimum can be derived when the combined LOLP payments and the capital costs of additional generation reach a minimum. A comparison of prices against an idealised bulk supply tariff is used to show how energy prices have risen some 12% in excess of what might have occurred under the CEGB regime. This part concludes with proposals to improve the marl
Resumo:
This thesis investigates the cost of electricity generation using bio-oil produced by the fast pyrolysis of UK energy crops. The study covers cost from the farm to the generator’s terminals. The use of short rotation coppice willow and miscanthus as feedstocks was investigated. All costs and performance data have been taken from published papers, reports or web sites. Generation technologies are compared at scales where they have proved economic burning other fuels, rather than at a given size. A pyrolysis yield model was developed for a bubbling fluidised bed fast pyrolysis reactor from published data to predict bio-oil yields and pyrolysis plant energy demands. Generation using diesel engines, gas turbines in open and combined cycle (CCGT) operation and steam cycle plants was considered. The use of bio-oil storage to allow the pyrolysis and generation plants to operate independently of each other was investigated. The option of using diesel generators and open cycle gas turbines for combined heat and power was examined. The possible cost reductions that could be expected through learning if the technology is widely implemented were considered. It was found that none of the systems analysed would be viable without subsidy, but with the current Renewable Obligation Scheme CCGT plants in the 200 to 350 MWe range, super-critical coal fired boilers co-fired with bio-oil, and groups of diesel engine based CHP schemes supplied by a central pyrolysis plant would be viable. It was found that the cost would reduce with implementation and the planting of more energy crops but some subsidy would still be needed to make the plants viable.