Um processo alternativo à solda por arco para aplicação em materiais de difícil junção ou em ambientes submersos é a solda por fricção. Neste trabalho foi desenvolvido um equipamento de solda por fricção para pesquisas e determinação de parâmetros ótimos de soldagem em diferentes meios. Para verificar o desempenho do equipamento foi utilizado o processo de solda por fricção de pinos consumíveis. Os registros das variáveis de soldagem permite avaliar o comportamento do sistema para a faixa de operação utilizada. Diferentes uniões de aço de baixo carbono e aço de baixa liga foram obtidas. Mediante análises macrográficas da junta foi avaliada a zona afetada pelo calor e a presença de regiões com possível falta de preenchimento. O controle servohidráulico desenvolvido apresenta uma resposta dinâmica adequada para esta aplicação, no entanto são apresentadas algumas propostas de melhorias. / An alternative process to the conventional arc welding for mating difficult-to-join materials or in underwater environment is friction welding. During this work a friction welding equipment was developed for research and determination of optimum welding parameters under different environments. To evaluate the equipment performance the friction hydro pillar processing method was used. Data acquisition of the welding parameters allows assessing the system behavior within the operational range. Joints of low carbon and low alloy steels have been obtained. Macrographic analyses of the weld joint were performed to evaluate the heat affected zone and the presence of unfilled regions. The servohydraulic control developed have shown an adequate dynamic response for this application, nevertheless some improvements are proposed.

O método de lavra câmaras e pilares é muito utilizado em minas de carvão subterrâneo, principalmente nos estados de Santa Catarina e Paraná, onde todas as minas subterrâneas utilizam este método. Vale ressaltar, porém, que o método apresenta recuperações de lavra abaixo de 50%, dependendo do tamanho dos pilares, e a produtividade é altamente dependente de uma boa concatenação das operações unitárias. Entre os aspectos relacionados à eficiência produtiva, a distância de transporte é um item preponderante no desempenho do sistema. Devido à profundidade da lavra, há um aumento do tamanho dos pilares de sustentação da mina, e assim, surgem problemas relacionados ao incremento no tempo de ciclo de transporte dos equipamentos. O aumento da distância de transporte entre uma frente de lavra com material desmontado e o alimentador/britador primário, reduz o resultado da produção de um conjunto de equipamentos. Em mineração a céu aberto, este tipo de problema é resolvido com o aumento da frota de transporte, todavia, na mineração de carvão subterrânea, não é possível aumentar de forma irrestrita a quantia de máquinas em subsolo, pois impactaria diretamente na necessidade de incremento da vazão de ar, assim como, limitação de espaço para o tráfego de equipamentos. A aproximação da distância do ponto de descarga para um local adjacente às frentes de serviço é uma alternativa para solucionar a necessidade de incremento da frota de produção. No entanto, o ponto de mudança deve ser avaliado de forma consistente para determinar o momento mais adequado para que essa reaproximação proporcione um resultado ótimo. Este estudo buscou compreender esta etapa necessária ao processo produtivo, utilizando técnicas de regressão para analisar o impacto da distância de transporte na capacidade produtiva. O problema foi modelado e foram propostas alternativas que forneçam um sequenciamento de lavra capaz de amenizar os problemas decorrentes do aumento da distância de transporte das frentes de lavra aos respectivos pontos de descarga. Os resultados demonstraram que a distância de transporte tem influência direta na produção, mas não somente a distância máxima, mas também, uma distância mínima que deve ser respeitada para obter maior produtividade quando se tem a associação de equipamentos de produção. É possível concluir com este estudo que a distância de transporte tem impacto relevante e deve ser considerada, não tão somente no sequenciamento, mas também no dimensionamento da frota e consequente capacidade produtiva. / The room and pillar mining method is widely used in underground coal mines. Santa Catarina and Paraná where all underground mines use this method. Indeed, the method has mining recoveries below 50% and the productivity is highly dependent on a good concatenation of unit operations. Among the aspects related to production efficiency, the transport distance is an important item on system performance. Due to the depth of the mine, there is an increment in the size of the underground supporting pillars, and consequently, problems related to the increase in equipment cycle times. The increase of the transportation distance between mining faces and the primary crusher reduces the result of a set of production equipment. In open pit mining, this problem is solved by increasing the haulage fleet, however, in the underground coal mining, the number of machines cannot be increased indefinitely because it would impact directly on the need of increased air flow. Therefore, the approximation of the distance from the discharge point to an adjacent location from the mining faces is an alternative to address the need of increased production fleet. However, the relocation point must be evaluated consistently to determine the most appropriate time to get the most from this approach. The goal of the study was to understand this imperative step for the production process, using regression techniques to analyze the impact of transport distance in productive capacity. Based on the experimental design used in this study, alternative proposals provide a mining sequence able to mitigate the problems from increasing transportation distance from mining faces to their discharge points. The results show that the transport distance has directly influence on the production, and it is not limited to the maximum distance. Likewise, a minimum distance must be respected for higher productivity when you have the combination of production equipment. So, it is possible to conclude that the transport distance has a significant impact and must be considered not only during the sequencing, but also when determining the fleet size and consequent production capacity.

This thesis studies airflow patterns in the face area of a typical room-and-pillar mining area, using Computational Fluid Dynamics (CFD) modeling. This research is designed to develop a scientific understanding of airflow distribution in room-and-pillar mining areas that is fundamental to developing engineering controls. The overall goal of the study is to develop improved engineering controls to minimize dust exposure of mine workers in the face area. Dust exposure can be a health hazard in underground coal mining industry based on historical data of coal workers' pneumoconiosis among underground mine workers. Current regulatory dust exposure standards of 1.5 mg/m3, averaged over an 8-hour period, have been recently revised with approval of new MSHA standards in April of 2014. Mining companies are currently seeking new technologies in order to comply with the new dust standards. Since mining geometries are complex and do not lend themselves to closed-form analytical solutions, CFD numerical modeling approach was used to develop an understanding of airflow distribution in the face areas. Since previous studies had focused on some cuts in mining heights of less than 2.4 m (8-ft), this study was performed for high mining areas of 4.2 m (14-ft). Such mining heights are very common in longwall mine development areas, particularly in the State of Illinois. The primary goal was to identify major differences in airflow between the two mining heights and how they affect development of engineering controls for minimizing dust exposure. Simulations were done using ANSYS software such as DesignModeler for modeling and meshing and FLUENT for calculations. Recirculation (RC) and low air velocity (LAV) zones were located for straight deep cut, straight deepest cut, cross-cut right, cross-cut right mine through, left turn cross-cut, and left turn cross-cut mine through for low mining height (LMH) and high mining height (HMH) with varying air quantity at the end of the line curtain (ELC). Air at the ELC was adjusted to achieve a ratio of 0.85, 1.00 and 1.15 over the wet scrubber fan (WSF) discharge capacity. Results show that the air velocity in HMH case is much lower than for the LMH. In addition, the location of RC and LAV zones differ based on mining height and air quantity at the ELC. Furthermore, lower air quantity at the ELC causes the air exhausted by the WSF to recirculate back to the face area in order to satisfy the WSF requirement. Recommendations to deal with these differences are formulated.

This thesis has developed wetting characteristics of coal dust from Herrin coal seam in Illinois for improved respirable coal and quartz dust (< 10µm) control. Wetting characteristics were assessed by a wettability technique called Fixed Time Wettability (FTW) method which simulates the actual underground wetting environment. Immediate roof and immediate floor materials bulk samples were found to be 100% wettable by water alone, whereas coal seam samples were 55-90% wettable. Two variables: contact time between water droplets and dust particles and, the temperature of the water were found to affect the degree of wettability. FTW was carried out at as a function of water temperature (7.2oC to 40.5oC) and contact time (10 to 25 seconds) which increased wettability 2-18% and 8-32%, respectively. In addition, the wetted and un-wetted samples collected from wettability experiments were subjected to Scanning Electron Microscopy (SEM) and particle size distribution analyses. It was found that particles are irregular in shape in both wetted and un-wetted fractions and some agglomeration of fine particles was observed in a few un-wetted fraction samples. The concept of increased contact time was incorporated in engineering controls by increasing the wet scrubber filter screen inclination (which is a function of the screen surface area). The filter screen inclination was minimizing the pressure drop across it using Computational Fluid Dynamics (CFD) analysis. It was found that 60 degree (with respect to the vertical) would provide minimal pressure drop and should be considered for implementation. Additional research should be conducted on assessing selective wetting of different particle sizes of coal and quartz in airborne dust, developing data on wettability as a function of particle size and implementing the developed concepts such as contact time and temperature in the field for improved dust control.

Um processo alternativo à solda por arco para aplicação em materiais de difícil junção ou em ambientes submersos é a solda por fricção. Neste trabalho foi desenvolvido um equipamento de solda por fricção para pesquisas e determinação de parâmetros ótimos de soldagem em diferentes meios. Para verificar o desempenho do equipamento foi utilizado o processo de solda por fricção de pinos consumíveis. Os registros das variáveis de soldagem permite avaliar o comportamento do sistema para a faixa de operação utilizada. Diferentes uniões de aço de baixo carbono e aço de baixa liga foram obtidas. Mediante análises macrográficas da junta foi avaliada a zona afetada pelo calor e a presença de regiões com possível falta de preenchimento. O controle servohidráulico desenvolvido apresenta uma resposta dinâmica adequada para esta aplicação, no entanto são apresentadas algumas propostas de melhorias. / An alternative process to the conventional arc welding for mating difficult-to-join materials or in underwater environment is friction welding. During this work a friction welding equipment was developed for research and determination of optimum welding parameters under different environments. To evaluate the equipment performance the friction hydro pillar processing method was used. Data acquisition of the welding parameters allows assessing the system behavior within the operational range. Joints of low carbon and low alloy steels have been obtained. Macrographic analyses of the weld joint were performed to evaluate the heat affected zone and the presence of unfilled regions. The servohydraulic control developed have shown an adequate dynamic response for this application, nevertheless some improvements are proposed.

O método de lavra câmaras e pilares é muito utilizado em minas de carvão subterrâneo, principalmente nos estados de Santa Catarina e Paraná, onde todas as minas subterrâneas utilizam este método. Vale ressaltar, porém, que o método apresenta recuperações de lavra abaixo de 50%, dependendo do tamanho dos pilares, e a produtividade é altamente dependente de uma boa concatenação das operações unitárias. Entre os aspectos relacionados à eficiência produtiva, a distância de transporte é um item preponderante no desempenho do sistema. Devido à profundidade da lavra, há um aumento do tamanho dos pilares de sustentação da mina, e assim, surgem problemas relacionados ao incremento no tempo de ciclo de transporte dos equipamentos. O aumento da distância de transporte entre uma frente de lavra com material desmontado e o alimentador/britador primário, reduz o resultado da produção de um conjunto de equipamentos. Em mineração a céu aberto, este tipo de problema é resolvido com o aumento da frota de transporte, todavia, na mineração de carvão subterrânea, não é possível aumentar de forma irrestrita a quantia de máquinas em subsolo, pois impactaria diretamente na necessidade de incremento da vazão de ar, assim como, limitação de espaço para o tráfego de equipamentos. A aproximação da distância do ponto de descarga para um local adjacente às frentes de serviço é uma alternativa para solucionar a necessidade de incremento da frota de produção. No entanto, o ponto de mudança deve ser avaliado de forma consistente para determinar o momento mais adequado para que essa reaproximação proporcione um resultado ótimo. Este estudo buscou compreender esta etapa necessária ao processo produtivo, utilizando técnicas de regressão para analisar o impacto da distância de transporte na capacidade produtiva. O problema foi modelado e foram propostas alternativas que forneçam um sequenciamento de lavra capaz de amenizar os problemas decorrentes do aumento da distância de transporte das frentes de lavra aos respectivos pontos de descarga. Os resultados demonstraram que a distância de transporte tem influência direta na produção, mas não somente a distância máxima, mas também, uma distância mínima que deve ser respeitada para obter maior produtividade quando se tem a associação de equipamentos de produção. É possível concluir com este estudo que a distância de transporte tem impacto relevante e deve ser considerada, não tão somente no sequenciamento, mas também no dimensionamento da frota e consequente capacidade produtiva. / The room and pillar mining method is widely used in underground coal mines. Santa Catarina and Paraná where all underground mines use this method. Indeed, the method has mining recoveries below 50% and the productivity is highly dependent on a good concatenation of unit operations. Among the aspects related to production efficiency, the transport distance is an important item on system performance. Due to the depth of the mine, there is an increment in the size of the underground supporting pillars, and consequently, problems related to the increase in equipment cycle times. The increase of the transportation distance between mining faces and the primary crusher reduces the result of a set of production equipment. In open pit mining, this problem is solved by increasing the haulage fleet, however, in the underground coal mining, the number of machines cannot be increased indefinitely because it would impact directly on the need of increased air flow. Therefore, the approximation of the distance from the discharge point to an adjacent location from the mining faces is an alternative to address the need of increased production fleet. However, the relocation point must be evaluated consistently to determine the most appropriate time to get the most from this approach. The goal of the study was to understand this imperative step for the production process, using regression techniques to analyze the impact of transport distance in productive capacity. Based on the experimental design used in this study, alternative proposals provide a mining sequence able to mitigate the problems from increasing transportation distance from mining faces to their discharge points. The results show that the transport distance has directly influence on the production, and it is not limited to the maximum distance. Likewise, a minimum distance must be respected for higher productivity when you have the combination of production equipment. So, it is possible to conclude that the transport distance has a significant impact and must be considered not only during the sequencing, but also when determining the fleet size and consequent production capacity.

Um processo alternativo à solda por arco para aplicação em materiais de difícil junção ou em ambientes submersos é a solda por fricção. Neste trabalho foi desenvolvido um equipamento de solda por fricção para pesquisas e determinação de parâmetros ótimos de soldagem em diferentes meios. Para verificar o desempenho do equipamento foi utilizado o processo de solda por fricção de pinos consumíveis. Os registros das variáveis de soldagem permite avaliar o comportamento do sistema para a faixa de operação utilizada. Diferentes uniões de aço de baixo carbono e aço de baixa liga foram obtidas. Mediante análises macrográficas da junta foi avaliada a zona afetada pelo calor e a presença de regiões com possível falta de preenchimento. O controle servohidráulico desenvolvido apresenta uma resposta dinâmica adequada para esta aplicação, no entanto são apresentadas algumas propostas de melhorias. / An alternative process to the conventional arc welding for mating difficult-to-join materials or in underwater environment is friction welding. During this work a friction welding equipment was developed for research and determination of optimum welding parameters under different environments. To evaluate the equipment performance the friction hydro pillar processing method was used. Data acquisition of the welding parameters allows assessing the system behavior within the operational range. Joints of low carbon and low alloy steels have been obtained. Macrographic analyses of the weld joint were performed to evaluate the heat affected zone and the presence of unfilled regions. The servohydraulic control developed have shown an adequate dynamic response for this application, nevertheless some improvements are proposed.

This deals with the pension system reform in the Czech Republic with a focus on the second pension pillar. The aim of the thesis is to evaluate the already canceled second pillar, to identify the causes of the failure and to outline in which aspects it could be learned from the experiences of other countries. The thesis describes the development of the reform, its main parameters and the attitudes of individual actors. The main cause of the fall was the low interest of citizens in participation in the second pillar, which was caused mainly by political factors, inappropriate settings and poor citizens' awareness. For future reforms, it would be advisable to take lessons from reforms implemented by other states. This paper describes the reforms in Hungary, the Netherlands and Sweden.

Oil shale industry in Estonia is looking at other mining technologies as alternative to strip mining and room and pillar mining methods. One such alternative to the room and pillar method is the punch-longwall mining method. Enefit Kaevandused AS, one of the major oil shale companies in Estonia, plans to employ this technology in exploiting some of its resources in the near future. This thesis examines the different stability problems related to the planned punch-longwall mining project in Narva oil shale mine. Determining optimal chain pillar dimensions and stability of the punch-longwall highwall slope are the main objectives of this project. Rock mechanical analyses have been done and recommendations are made based on the rock mechanical aspect of the mining process. Taavi Lõhmuste is responsible for the chain pillar stability analysis and Ott Oisalu for the punch-longwall highwall slope stability analysis. It is essential to understand the geology of a certain area in order to make accurate stability assessments. Because of the previously stated requirements, the geology of Estonian oil shale deposit is examined in the first part of the thesis in order to determine the geological and rock mechanical conditions to set the foundation for further analyses. In conclusion, for the part of the highwall slope, a properly designed barrier pillar plays a key role in the stability of the slope. After reviewing and analyzing the results of both highwall slope numerical models, it can be stated that the minimum length for the barrier pillar that still will yield in stable highwall slope is 65 meters. For the part of the chain pillars, in conclusion, it can be determined that optimal chain pillar dimensions that should be suitable, from the stability standpoint, are 6x6 meters for 3-entry system and 7x7 meters for 2-entry system (length x width).

The main goal of this diploma thesis is to map the development of China's competitiveness in the period from 1970's to the present and to outline the development of the economy in the next 2 decades. The simplified view of the Chinese competitiveness is used in the thesis, which means that we can identify 2 strategies aimed at the development of the Chinese competitiveness. The first chapter contains a definition of term competitiveness and introduces the way of its measurement. The first strategy was applied in China in the period 1978-2005 and is described in the 2nd, 3rd and the 4th chapter. The main goal of these 3 chapters is to describe the reforms adopted by the government and to evaluate the impacts of these reform measures on pillars of the Chinese competitiveness. The latest strategy is described in the last chapter and a special attention is paid to the reform measures aimed at boosting China's innovation performance.