967 resultados para Asymptotically optimal policy
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XVIII IUFRO World Congress, Ljubljana 1986.
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XVIII IUFRO World Congress, Ljubljana 1986.
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XVIII IUFRO World Congress, Ljubljana 1986.
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XVIII IUFRO World Congress, Ljubljana 1986.
Resumo:
XVIII IUFRO World Congress, Ljubljana 1986.
Resumo:
XVIII IUFRO World Congress, Ljubljana 1986.
Resumo:
XVIII IUFRO World Congress, Ljubljana 1986.
Resumo:
XVIII IUFRO World Congress, Ljubljana 1986.
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XVIII IUFRO World Congress, Ljubljana 1986.
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The tourism development nexus in southern Africa involves highly topical issues related to tourism planning, power relations, community participation, and natural resources. Namibia offers a particularly interesting context for the study of these issues due to its colonial legacy, vast tourism potential, recently adopted tourism policy and community-based approaches to tourism and natural resource management. This study is an interdisciplinary endeavour to analyse the role of tourism in Namibia s post-apartheid transformation process by focusing on Namibian tourism policy and local tourism enterprises' policy knowledge. Major attention is paid to how the tourism policy's national development objectives are understood and conceptualised by the representatives of different tourism enterprises and the ways in which they relate to the practical needs of the enterprises. Through such local policy knowledge the study explores various opportunities, challenges and constraints related to the promotion of tourism as a development strategy. The study utilises a political economy approach to tourism and development through three current and interrelated discourses which are relevant in the Namibian context. These are tourism, power and inequality, tourism and sustainable development, and tourism and poverty reduction. The qualitative research material was gathered in Namibia in 2006-2007 and 2008. This material consists of 34 semi-structured interviews in 16 tourism enterprises, including private trophy hunting farms and private lodges, small tour operators and community-based tourism enterprises. In addition, the research material consists of observations in the enterprises, and 37 informal and 23 expert interviews. The findings indicate that in the light of local tourism enterprises the tourism policy objectives appear more complex and ambiguous. Furthermore, they involve multiple meanings and interpretations which reflect the socio-economic stratification of the informants and Namibian society, together with the professional stratification of the tourism enterprises and restrictions on the capacity of tourism to address the development objectives. In the light of such findings it is obvious that aspects of power and inequality affect the tourism development nexus in Namibia. The study concludes that, as in the case of other southern African countries, in order to promote sustainable development and reduce poverty, Namibia should not only target tourism growth but pay attention to who benefits from that growth and how. From a political economy point of view, it is important that prevailing structural challenges are addressed equally in the planning of tourism, development and natural resource management. Such approach would help the Namibian majority to enjoy the benefits of increasing tourism in the country.
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In the recent years. India has emerged as one of the fast growing economies of the world necessitating equally rapid increase in modern energy consumption. With an imminent global climate change threat, India will have difficulties in continuing with this rising energy use levels towards achieving high economic growth. It will have to follow an energy-efficient pathway in attaining this goal. In this context, an attempt is made to present India's achievements on the energy efficiency front by tracing the evolution of policies and their impacts. The results indicate that India has made substantial progress in improving energy efficiency which is evident from the reductions achieved in energy intensities of GDP to the tune of 88% during 1980-2007. Similar reductions have been observed both with respect to overall Indian economy and the major sectors of the economy. In terms of energy intensity of GDP, India occupies a relatively high position of nine among the top 30 energy consuming countries of the world. (C) 2009 Elsevier Ltd. All rights reserved.
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In a max-min LP, the objective is to maximise ω subject to Ax ≤ 1, Cx ≥ ω1, and x ≥ 0 for nonnegative matrices A and C. We present a local algorithm (constant-time distributed algorithm) for approximating max-min LPs. The approximation ratio of our algorithm is the best possible for any local algorithm; there is a matching unconditional lower bound.
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Soft tissue sarcomas are malignant tumours of mesenchymal origin. Because of infiltrative growth pattern, simple enucleation of the tumour causes a high rate of local recurrence. Instead, these tumours should be resected with a rim of normal tissue around the tumour. Data on the adequate margin width are scarce. At Helsinki University Central Hospital (HUCH) a multidisciplinary treatment group started in 1987. Surgical resection with a wide margin (2.5 cm) is the primary aim. In case of narrower margin radiation therapy is necessary. The role of adjuvant chemotherapy remains unclear. Our aims were to study local control by the surgical margin and to develop a new prognostic tool to aid decision-making on which patients should receive adjuvant chemotherapy. Patients with soft tissue sarcoma of the extremity or the trunk wall referred to HUCH during 1987-2002 form material in Studies I and II. External validation material comes from the Lund university sarcoma registry. The smallest surgical margin of at least 2.5 centimetres yielded local control of 89 per cent at five years. Amputation rate was 9 per cent. The proposed prognostic model with necrosis, vascular invasion, size on a continuous scale, depth, location and grade worked well both in Helsinki material and in the validation material, and it also showed good calibration. Based on the present study, we recommend the smallest surgical margin of 2-3 centimetres in soft tissue sarcoma irrespective of grade. Improvement in local control was present but modest in margins wider than 1 centimetre. In cases where gaining a wider margin would lead to a considerable loss of function, smaller margin is to be considered combined to radiation therapy. Patients treated with inadequate margins should be offered radiation therapy irrespective of tumour grade. Our new prognostic model to estimate 10-year survival probability in patients with soft tissue sarcoma of the extremities or trunk wall showed good dicscrimination and calibration. For time being the prognostic model is available for scientific use and further validations. In the future, the model may aid in clinical decision-making. For operable osteosarcoma, neoadjuvant multidrug chemotherapy followed by delayed surgery and multidrug adjuvant chemotherapy is the treatment of choice. Overall survival rates at five years are approximately 75 per cent in modern trials with classical osteosarcoma. All patients diagnosed and reported to the Finnish Cancer Registry with osteosarcoma in Finland during 1971-2005 form the material in Studies III and IV. Limb-salvage rate increased from 23 per cent to 78 per cent during 1971-2005. The 10-year sarcoma-specific survival for the whole study population improved from 32 per cent to 62 per cent. It was 75 per cent for patients with a local high-grade osteosarcoma of the extremity diagnosed during 1991-2005. This study outlines the improved prognosis of osteosarcoma patients in Finland with modern chemotherapy. The 10-year survival rates are good also in an international scale. Nonetheless, their limb-salvage rate remains inferior to those seen for highly selected patient series. Overall, the centralisation of osteosarcoma treatment would most likely improve both survival and limb-salvage rates even further.
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The aim of the thesis is to assess the fishery of Baltic cod, herring and sprat by simulation over 50 years time period. We form a bioeconomic multispecies model for the species. We include species interactions into the model because especially cod and sprat stocks have significant effects on each other. We model the development of population dynamics, catches and profits of the fishery with current fishing mortalities, as well as with the optimal profit maximizing fishing mortalities. Thus, we see how the fishery would develop with current mortalities, and how the fishery should be developed in order to yield maximal profits. Especially cod stock has been quite low recently and by optimizing the fishing mortality it could get recovered. In addition, we assess what would happen to the fisheries of the species if more favourable environmental conditions for cod recruitment dominate in the Baltic Sea. The results may yield new information for the fisheries management. According to the results the fishery of Baltic cod, herring and sprat are not at the most profitable level. The fishing mortalities of each species should be lower in order to maximize the profits. By fishing mortality optimizing the net present value would be almost three times higher in the simulation period. The lower fishing mortality of cod would result in a cod stock recovery. If the environmental conditions in the Baltic Sea improved, cod stock would recover even without a decrease in the fishing mortality. Then the increased cod stock would restrict herring and sprat stock remarkably, and harvesting of these species would not be as profitable anymore.
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A model comprising several servers, each equipped with its own queue and with possibly different service speeds, is considered. Each server receives a dedicated arrival stream of jobs; there is also a stream of generic jobs that arrive to a job scheduler and can be individually allocated to any of the servers. It is shown that if the arrival streams are all Poisson and all jobs have the same exponentially distributed service requirements, the probabilistic splitting of the generic stream that minimizes the average job response time is such that it balances the server idle times in a weighted least-squares sense, where the weighting coefficients are related to the service speeds of the servers. The corresponding result holds for nonexponentially distributed service times if the service speeds are all equal. This result is used to develop adaptive quasi-static algorithms for allocating jobs in the generic arrival stream when the load parameters are unknown. The algorithms utilize server idle-time measurements which are sent periodically to the central job scheduler. A model is developed for these measurements, and the result mentioned is used to cast the problem into one of finding a projection of the root of an affine function, when only noisy values of the function can be observed