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High-pressure operation of a xenon-GPSC/MSGC hybrid detector for hard X-ray spectrometry

Coelho, L. C. C.; Veloso, J. F. C. A.; Covita, D. S.; Ferreira, L. F. Requicha; Santos, J. M. F. dos
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
Português
Relevância na Pesquisa
35.92%
The performance of a high-pressure xenon gas proportional scintillation counter/microstrip gas chamber (GPSC/MSGC) hybrid detector has been investigated for filling pressures from 1 up to 10 bar, for 22-, 30- and 60-keV photons. GPSC/MSGC hybrid detectors are based on a xenon-GPSC instrumented with a CsI-coated microstrip plate photosensor placed directly within the xenon envelope, as a substitute for the photomultiplier tube. This design avoids the constraints due to the use of a quartz scintillation window for GPSC-photosensor coupling, which absorbs a significant amount of scintillation and is a drawback for applications where large detection areas and high filling pressures are needed. The lowest energy resolutions are achieved for 2 bar (5.5% and 3.4%, FWHM, for 22- and 60-keV photons, respectively). Increasing the pressure to the 5-6 bar range, competitive energy resolutions of 7% and 4.5% are still achieved for 22- and 60-keV photons, respectively. This detector could be a compelling alternative in applications where compactness, large detection area, insensitivity to strong magnetic fields, room temperature operation, large signal-to-noise ratio and good energy resolution are important requirements.; http://www.sciencedirect.com/science/article/B6TJM-4M3B6DG-8/1/04ba8b77386c4c69025c7ca19342f792

Design of pressure vessels using shape optimization: An integrated approach

Carbonari, Ronny Calixto; MUNOZ-ROJAS, P. A.; ANDRADE, E. Q.; Paulino, Gláucio Hermógenes; Nishimoto, Kazuo; Silva, Emilio Carlos Nelli
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.99%
Previous papers related to the optimization of pressure vessels have considered the optimization of the nozzle independently from the dished end. This approach generates problems such as thickness variation from nozzle to dished end (coupling cylindrical region) and, as a consequence, it reduces the optimality of the final result which may also be influenced by the boundary conditions. Thus, this work discusses shape optimization of axisymmetric pressure vessels considering an integrated approach in which the entire pressure vessel model is used in conjunction with a multi-objective function that aims to minimize the von-Mises mechanical stress from nozzle to head. Representative examples are examined and solutions obtained for the entire vessel considering temperature and pressure loading. It is noteworthy that different shapes from the usual ones are obtained. Even though such different shapes may not be profitable considering present manufacturing processes, they may be competitive for future manufacturing technologies, and contribute to a better understanding of the actual influence of shape in the behavior of pressure vessels. (C) 2011 Elsevier Ltd. All rights reserved.; PETROBRAS[0050.0042368.08.4]; CNPq[303689/2009-9]

Adaptações autonômicas e cardiovasculares em atletas de alto rendimento: influência da modalidade e periodização do treinamento físico; Autonomic and cardiovascular adaptations in high performance athletes: influence of sport modality and physical training periodization

Azevedo, Luciene Ferreira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 11/08/2011 Português
Relevância na Pesquisa
26.14%
INTRODUÇÃO: O treinamento físico provoca adaptações cardiovasculares, sendo que maiores adaptações estruturais cardíacas são observadas em atletas de elite, que realizam treinamento físico de alta intensidade com o objetivo de aumento no rendimento. Além disto, atletas apresentam diminuição da frequência cardíaca de repouso, embora os mecanismos que explicam a bradicardia em atletas ainda são controversos. O nível das adaptações pode variar e fatores como o tipo de modalidade esportiva, tempo e nível de treinamento físico podem contribuir para tal variação. Desta forma, o objetivo deste estudo foi investigar a influência de modalidades esportivas (ciclismo, corrida de longa distância e remo) e da periodização do treinamento físico nas adaptações estruturais e funcionais, autonômicas e não autonômicas cardíacas e vasculares em atletas de elite no repouso, na inclinação ortostática e nas 24 horas. MÉTODOS: Neste estudo experimental longitudinal prospectivo foram avaliados 13 ciclistas, 13 corredores e 11 remadores de elite, saudáveis (entre 20 e 36 anos; masculino), engajados em treinamento físico competitivo, em 2 períodos de treinamento: período básico-PB e período competitivo-PC. Avaliação da capacidade funcional máxima foi feita por teste cardiorrespiratório. Adaptações estruturais cardíacas foram avaliadas por meio do ecocardiograma bidimensional com doppler. Frequência cardíaca intrínseca foi estudada por meio do duplo bloqueio farmacológico (atropina 0...

Efeitos da carga e duração do exercício sobre o conforto e os parâmetros biomecânicos de contato com o selim em ciclistas; Effects of load and duration exercise on comfort and biomechanics parameters of saddle related contact in cyclists

Dagnese, Frederico
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
Português
Relevância na Pesquisa
26.16%
O objetivo deste estudo foi analisar os efeitos da carga de trabalho e do tempo de pedalada sobre a área, força, pressão de contato e o conforto no selim e as relações dos hábitos de vida e características da prática esportiva com a função erétil em ciclistas. Quinze ciclistas recreacionais (CR) e 15 amadores competitivos (CC) do sexo masculino foram avaliados antropometricamente e responderam a questionários relacionados à prática esportiva, aos hábitos de vida e ao índice internacional da função erétil (IIEF). Eles completaram os protocolos de ciclismo que consistiram (1) no ajuste do posicionamento corporal sobre a bicicleta (PAP), (2) protocolo de carga incremental (PCI) para determinação da potência máxima (PM), (3) protocolo de carga variável (PCV) e (4) protocolo de carga constante (PCC). Durante o PCV e PCC foi monitorada a área, força e pressão de contato no selim. No PCC, além destas, foi monitorado o grau de desconforto no selim. Os dados foram descritos na forma de média e desvio padrão considerando nível de significância de a=0,05. Os resultados demonstraram que as diferenças antropométricas e de desempenho entre os grupos foram diferentes, corroborando os diferentes níveis de condicionamento procurados. Foi observada correlação positiva e moderada entre o perímetro de quadril com a área de contato com o selim. Não houve diferença entre os grupos quando comparadas a área...

Estudo da distribuição da pressão plantar e do equilibrio corporal em corredores de longa distancia; Study of plantar pressure distribution and body balance in long distance runners

Ademir Schmidt
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 17/10/2006 Português
Relevância na Pesquisa
35.99%
As corridas de longa distância, sejam de caráter competitivo ou de promoção da saúde, geram cargas compressivas consideráveis no sistema locomotor. Essas cargas, se não adequadamente distribuídas, predispõem os praticantes a lesões crônicas e agudas. Nesse sentido, o objetivo desta pesquisa foi estudar a distribuição da pressão plantar e do equilíbrio corporal em corredores de longa distância. Participaram do estudo 17 corredores de longa distância do sexo masculino com idade X = 28,5 :t 9,5 anos, peso X = 63,6 :t 6,9 Kg e altura X = 173,5 :t 7,0 cm. A seleção dos sujeitos foi feita segundo critérios de acessibilidade. Para o estudo da distribuição da pressão plantar e do equiHbrio corporal, foi utilizado um baropodômetro eletrônico para realizar uma análise estática, dinâmica (andando e correndo) e uma análise estabilométrica. Os três testes foram realizados com os corredores inicialmente descalços e posteriormente utilizando seu tênis de corrida. Além da análise baropodométrica, os sujeitos responderam um questionário contendo 23 perguntas sobre sua rotina de treino, índice de lesões sofridas, distância percorrida semanalmente, dentre outras. Na análise estatística utilizou-se o teste paramétrico t-Student para grupos independentes. Os resultados da análise baropodométrica estática dos corredores demonstraram distribuição assimétrica da carga entre os membros inferiores...

Strategic management in the Telecom industry to create competitive advantage

Zuhdi, Muneer
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.1%
O presente trabalho teve por objetivos a identificação de uma estratégia e o desenvolvimento de um modelo que permita às operadoras de telecomunicações a sua sustentabilidade, bem como a identificação de caminhos para a adaptação a uma realidade sempre em mudança como é a da indústria das telecomunicações. Numa primeira parte do trabalho elaborou-se uma revisão de literatura do atual estado da arte das principais estratégias relevantes e com aplicação à indústria de telecomunicações. A pesquisa realizada investigou a estrutura atual da indústria de telecomunicações e o estado da competitividade das operadoras de telecomunicações. Dos resultados desta foi possível constatar uma evolução constante da tecnologia e dos modelos de negócio neste ecossistema, assim como a presença de uma pressão concorrencial significativa exercida sobre as operadoras, quer por parte das empresas já existentes no mercado quer por parte das emergentes. As operadoras têm de transformar o seu modelo de rede e de negócios para se adaptarem às mudanças e às tendências da indústria e do mercado. Com base na revisão de literatura, elegeu-se a metodologia baseada num inquérito de pesquisa empírica para aferir o estado da indústria e derivar as estratégias possíveis. Este inquérito foi efetuado a especialistas da área de telecomunicações de diferentes subsectores e países para abordar todos os elementos estratégicos do modelo de negócio futuro. Os resultados da pesquisa revelaram que as empresas que operam no mercado da Internet (Over The Top - OTT) representam a maior ameaça sobre o futuro dos operadores de telecomunicações. Os operadores só vão conseguir responder através da modernização de sua rede...

A importância da competitive intelligence no processo de tomada de decisão

Jorge, João Pedro Godinho Alves
Fonte: Instituto Superior de Economia e Gestão Publicador: Instituto Superior de Economia e Gestão
Tipo: Dissertação de Mestrado
Publicado em /10/2009 Português
Relevância na Pesquisa
36.1%
Mestrado em Marketing; A Competitive Intelligence está a tornar-se numa prática mundial e numa importante ferramenta estratégica de suporte à decisão, conferindo às organizações maior ênfase analítica e orientação para a acção. Mais do que recolher ou arquivar o máximo de informação, muitas vezes só passível de análise posterior, as organizações necessitam saber o que fazer com ela, devendo reconhecer valor apenas à informação tratada e concentrar-se na colocação de boas perguntas e na definição das suas necessidades, deixando para segundo plano a existência ou não da informação. Este estudo investiga a aplicabilidade dos conceitos de Competitive Intelligence, ao nível das organizações portuguesas, avaliando a sua influência no processo de tomada de decisão, gestão estratégica e táctica, tentando responder à questão: “Quais os antecedentes que promovem uma resposta célere a acções competitivas da concorrência?”, Utiliza-se uma metodologia de pesquisa quantitativa, assente em técnicas multivariadas, resultante dum questionário on-line e numa amostra não probabilística, abarcando funções de topo das 1.000 maiores empresas nacionais por volume de facturação. Concluiu-se a existência de uma relação positiva entre a variável “Estrutura...

Quantitative assay for totipotent reconstituting hematopoietic stem cells by a competitive repopulation strategy.

Szilvassy, S J; Humphries, R K; Lansdorp, P M; Eaves, A C; Eaves, C J
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1990 Português
Relevância na Pesquisa
35.98%
Although hematopoiesis is known to originate in a population of very primitive cells with both lymphopoietic and myelopoietic potential, a procedure for enumerating such cells has to date not been available. We now describe a quantitative assay for long-term repopulating stem cells with the potential for reconstituting all hematopoietic lineages. This assay has two key features. The first is the use of competitive repopulation conditions that ensure not only the detection of a very primitive class of hematopoietic stem cells but also the survival of lethally irradiated mice transplanted with very low numbers of such cells. The second is the use of a limiting-dilution experimental design to allow stem cell quantitation. The assay involves transplanting limiting numbers of male "test" cells into lethally irradiated syngeneic female recipients together with 1-2 x 10(5) syngeneic female marrow cells whose long-term repopulating ability has been compromised by two previous cycles of marrow transplantation. The proportion of assay recipients whose regenerated hematopoietic tissues are determined to contain greater than or equal to 5% cells of test cell origin (male) greater than or equal to 5 weeks later is then used to calculate the frequency of competitive repopulating units (CRU) in the original male test cell suspension (based on Poisson statistics). Investigation of this assay system has shown that all three potential sources of stem cells (test cells...

Quiet Eye Training Facilitates Competitive Putting Performance in Elite Golfers

Vine, Samuel J.; Moore, Lee J.; Wilson, Mark R.
Fonte: Frontiers Research Foundation Publicador: Frontiers Research Foundation
Tipo: Artigo de Revista Científica
Publicado em 28/01/2011 Português
Relevância na Pesquisa
26.15%
The aim of this study was to examine the effectiveness of a brief quiet eye (QE) training intervention aimed at optimizing visuomotor control and putting performance of elite golfers under pressure, and in real competition. Twenty-two elite golfers (mean handicap 2.7) recorded putting statistics over 10 rounds of competitive golf before attending training individually. Having been randomly assigned to either a QE training or Control group, participants were fitted with an Applied Science Laboratories Mobile Eye tracker and performed 20 baseline (pre-test) putts from 10 ft. Training consisted of video feedback of their gaze behavior while they completed 20 putts; however the QE-trained group received additional instructions related to maintaining a longer QE period. Participants then recorded their putting statistics over a further 10 competitive rounds and re-visited the laboratory for retention and pressure tests of their visuomotor control and putting performance. Overall, the results were supportive of the efficacy of the QE training intervention. QE duration predicted 43% of the variance in putting performance, underlying its critical role in the visuomotor control of putting. The QE-trained group maintained their optimal QE under pressure conditions...

Competitive Outcome of Daphnia-Simocephalus Experimental Microcosms: Salinity versus Priority Effects

Loureiro, Cláudia; Pereira, Joana L.; Pedrosa, M. Arminda; Gonçalves, Fernando; Castro, Bruno B.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 05/08/2013 Português
Relevância na Pesquisa
36.04%
Competition is a major driving force in freshwaters, especially given the cyclic nature and dynamics of pelagic food webs. Competition is especially important in the initial species assortment during colonization and re-colonization events, which depends strongly on the environmental context. Subtle changes, such as saline intrusion, may disrupt competitive relationships and, thus, influence community composition. Bearing this in mind, our objective was to assess whether low salinity levels (using NaCl as a proxy) alter the competitive outcome (measured as the rate of population biomass increase) of Daphnia-Simocephalus experimental microcosms, taking into account interactions with priority effects (sequential species arrival order). With this approach, we aimed to experimentally demonstrate a putative mechanism of differential species sorting in brackish environments or in freshwaters facing secondary salinization. Experiments considered three salinity levels, regarding NaCl added (0.00, 0.75 and 1.50 g L−1), crossed with three competition scenarios (no priority, priority of Daphnia over Simocephalus, and vice-versa). At lower NaCl concentrations (0.00 and 0.75 g L−1), Daphnia was a significantly superior competitor, irrespective of the species inoculation order...

Does Tougher Import Competition Foster Product Quality Upgrading?

Fernandes, Ana M.; Paunov, Caroline
Fonte: Banco Mundial Publicador: Banco Mundial
Português
Relevância na Pesquisa
36.05%
Over the past two decades, globalization, and more specifically the increased exposure to competition from low-price producers in China and India, has created a new economic environment for other emerging economies. The most advantageous way for manufacturing firms in those economies to position themselves in domestic and international markets is to offer upgraded and differentiated rather than "mundane" labor-intensive products. This paper investigates whether increased competitive pressure from imports forces firms to improve the quality of their products. The econometric analysis relies on a rich dataset of Chilean manufacturing plants and their products. Product quality is measured with unit values (average prices) and industry-level transport costs are used as an exogenous measure of import competition. The authors find a positive and robust effect of import competition on product quality. This effect is found to be particularly strong for non-exporting plants. The results also show that increased import competition from less advanced economies is the major cause for the positive impact on quality upgrading. The overall evidence points to the benefits of trade openness for product innovation but demonstrates at the same time that competitive pressure alone will not enable local plants to catch up with leading world producers.

Exchange Rates during the Crisis

Weber, Sebastian; Wyplosz, Charles
Fonte: Banco Mundial Publicador: Banco Mundial
Português
Relevância na Pesquisa
26.13%
Nearly two years after the onset of the financial crises, many central banks have brought their policy interest rates down to, or close to zero. Various governments have seen their budget deficits soar. Both policies have affected exchange rates, partly through market expectations. With a majority of exchange rates officially floating, exchange rate movements do not necessarily reflect official decisions as was the case in the 1930s. Yet, also in the 2008 crisis, authorities have directly intervened in the foreign exchange market, sometimes in order to defend a falling currency but in other instances with the aim to limit appreciation pressure, akin of competitive devaluations. This paper documents the exchange rate interventions during the height of the 2008/09 financial crisis and identifies the countries which have particular high incentives to intervene in the foreign exchange market to competitively devalue their currency. While various countries had increased incentives to devalue, we find that direct exchange rate interventions have been rather limited and contagion of devaluation has been restricted to one regionally contained case. However...

Rising Income Inequality in China : A Race to the Top

Luo, Xubei; Zhu, Nong
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Português
Relevância na Pesquisa
35.82%
Income inequality in China has risen rapidly in the past decades across regions, between rural and urban sectors, and within provinces. The dynamics of divergence across these sub-national areas have taken the form of a "race to the top" - meaning that all segments of the population, including the poor with low education in lagging inland rural areas, have experienced gains in average income. The largest gains have been registered by those with higher income and education in leading coastal urban areas. Using the China Economic, Population, Nutrition and Health Survey data of 1989 and 2004, we show that the most important factors explaining overall inequality are differential returns to schooling and sector of employment. A decomposition analysis based on household income determination shows that the increase in returns to education explains two-thirds of income changes in urban areas and one-sixth in rural areas. The widening income gaps are the consequence of higher growth in leading urban and coastal areas and that the skilled population has benefited more from the economic reforms carried out during the last 25 years. The authors argue that rising income inequality can be part of a normal process of development at a certain stage...

Productivity and the Investment Climate: What Matters Most?

Bastos, Fabiano; Nasir, John
Fonte: World Bank, Washington, D.C. Publicador: World Bank, Washington, D.C.
Português
Relevância na Pesquisa
46.13%
The authors explore the links between the investment climate and firm-level productivity and attempt to identify which dimensions of the investment climate matter most for productivity. Their analysis is based on data collected in a recent investment climate survey of garment and food processing firms in five countries in Eastern Europe and Central Asia. The authors use the first principal components of a series of indicators to summarize broad aspects of the investment climate and identify those most important in determining productivity. Their results indicate that competitive pressure is the most critical factor in the investment climate, accounting for more variation in firm-level productivity than infrastructure provision or issues related to government rent seeking and bureaucratic burden. This suggests that to improve productivity, increase output, and reduce poverty, policymakers should focus reform efforts on removing barriers to entry and creating open, highly competitive markets.

Revisiting Policy Options on the Market Structure in the Power Sector

World Bank
Fonte: Washington, DC Publicador: Washington, DC
Português
Relevância na Pesquisa
35.98%
The objectives of this study are to develop a taxonomy of the existing power market structures, as shown by the extent of vertical and horizontal unbundling found among restructured power systems, across developing countries; to design an analytical framework for assessing the desirability of unbundling under the variety of economic conditions found among developing countries; and To propose insights for operational guidance on alternative market structures based on relevant criteria, in particular on the initial conditions of a country and its power sector. The study specifically examines whether power system size and country per capita income can be reliable indicators of initial conditions for guiding policy on power market structure. This guidance is needed to address issues such as whether there are solid foundations for recommending vertical unbundling for small power systems in low-income countries, particularly in the absence of short term privatization prospects. The policy recommendations therefore have to be tailored to the specific taxonomy of market structures that characterize the electricity sector in developing countries. The study reports the evidence from econometric analysis and case studies on the (relative) success of achieving the objectives of unbundling. These objectives may be to enhance transparency and governance...

On the Discrepancies between Macro and Micro Level Identification of Competitive Strategies

HERRMANN, Andrea
Fonte: Instituto Universitário Europeu Publicador: Instituto Universitário Europeu
Tipo: Trabalho em Andamento Formato: application/pdf; digital
Português
Relevância na Pesquisa
35.93%
As economic internationalization advances, the question of how firms cope with increasing pressure for competitiveness gains momentum. While scholars agree that firms need a competitive advantage, they debate whether firms exploit the comparative advantage of their economy and specialize in that strategy facilitated by national institutions. ‘No’, argue strategic management proponents of the resource-based view. ‘Yes’, claim contributors to the competitiveness literature. My micro-level studies of these opposing views show that firms within one economy do not specialize in the institutionally supported strategy. The discrepancies between these findings and the analyses of the competitiveness literature are attributed to differences in the indicators employed to measure corporate strategies. Whenever macro-level indicators are used, the related loss of information on micro-level variety entails that specialization effects are pronounced - possibly exaggerated.

Career concerns and competitive pressure

Feriozzi, Fabio
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: Trabalho em Andamento Formato: application/pdf
Publicado em /11/2005 Português
Relevância na Pesquisa
45.97%
In a duopoly model I study the effects of increased competitive pressure on the implicit incentives provided by career concerns. By building a good reputation, managers are able to capture on the labor market part of the profits that they produce in excess with respect to less talented managers. Increased competition, then, has an ambiguous effect: it raises the reputational concern to the extent that it makes to hire a good manager more valuable. The threat of a hostile takeover is then introduced and it is shown to reduce managerial salary while having a potentially negative effect on ex ante incentives. In particular, it is argued that if alternative governance systems are already available, the threat of a hostile takeover can be harmful.

Foreign direct investment, competitive pressure and spillovers, an empirical analysis of spanish firm level data

Sembenelli, Alessandro; Siotis, Georges
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: Trabalho em Andamento Formato: application/pdf
Publicado em /02/2005 Português
Relevância na Pesquisa
45.97%
A short review of the theoretical and empirical evidence indicates that foreign direct investment (FDI) has the potential to increase the intensity of competition as well as to act as a channel for technology transfers. One would expect, all else equal, an increase in average firm performance following a wave of FDI, as multinational corporations (MNCs) enjoy higher levels of efficiency and have the potential to generate positive spillovers. At the same time, the entry of foreign firms has also been associated with an increase in competitive pressure on the domestic market. Using a large firm level dataset covering all sectors of Spanish manufacturing during the period 1983-96, we disentangle these three effects by estimating a dynamic model of firm level performance, which we proxy by profitability. We find that FDI has a positive long-run effect on the profitability of target firms, but this is limited to firms belonging to R&D intensive sectors. In addition, the results indicate that foreign presence dampens margins. However, this effect appears to be more than compensated by positive spillovers in the case of knowledge intensive industries.

Retrospective on the Experience of Parental Pressure and Support by Male Participants that Withdrew from Competitive Youth Hockey: A Phenomenological Investigation

Schonewille, Daniel
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
Português
Relevância na Pesquisa
36.16%
The purpose of this study was to gain an in-depth understanding of the lived experiences of parental pressure and support for males who withdrew from competitive youth hockey. A phenomenological approach was used to explore this phenomenon and develop meaning from the participants' experiences. Data for this study was collected by conducting one in-depth interview with each of the seven participants. Fourteen themes emerged as a result of the data analysis. These themes were grouped into three clusters: (1) Description of parental involvement: “I want them to be there and help me”; (2) Perceived impacts of parental involvement: “I felt like he actually cared”; and (3) Impact of parental involvement on commitment: “I kind of miss hockey now”. The descriptions provided by the participants in this study, and the themes that emerged, offer insight into what it is like for young males to experience parental involvement in competitive youth hockey.

A progress report on ultra-high-pressure waterjet cutting underground: the future of narrow reef gold and PGE mining

Gauert,C.D.K.; van der Westhuizen,W.A.; Claasen,J.O.; Viljoen,S.; Grobler,J.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2013 Português
Relevância na Pesquisa
35.92%
High-pressure waterjet technology is proposed as an alternative tool for selective underground mining of high-grade ore sections in stratiform orebodies showing a preferred 'bottom' or 'top' enrichment such as the Witwatersrand reefs and the Bushveld Complex platiniferous reefs. This technique, utilizing known mining technology together with more advanced machinery and additives as used in industrial and cleaning applications, may lead to an increased life-of-mine (LOM) for mining operations. A series of experiments was successfully carried out in a laboratory on Witwatersrand quartzite material, indicating acceptable cutting performance. Mining volumes by selectively cutting of reef portions are considered to be comparable to traditional drilling and blasting. Economic advantages of waterjet mining include energy savings due to the lower quantity of gangue rock to be hoisted to surface, as well as savings by a decrease in the usage of blasting materials. Capital expenditure of waterjet cutting, if applied on a broad scale, could be lower in the long term than that of conventional drilling and blasting methods. Mining by the application of high-pressure waterjet technology could become a competitive 'green technology' improving the economics and safety of labour-intensive mining operations. This paper suggests that waterjet cutting at an industrial scale can become a routine hard-rock mining technique in the future.