Ingeniero Civil de Minas / Existen en la actualidad diversos estudios empíricos que definen los anchos basales mínimos para inducir el hundimiento de la columna según la calidad del macizo rocoso. Sin embargo, muchos de ellos han perdido validez debido a que se realizaron para bajas alturas, bajo régimen de esfuerzos y mala calidad de roca en comparación a los escenarios en los que se encuentra la minería de hoy, siendo la minería por hundimiento la que se posiciona como el método por excelencia para la extracción de yacimientos cada vez más resistentes, más masivos y de menores leyes. En este nuevo escenario, una de las principales necesidades productivas es la necesidad de hundir mayores alturas de columna, objetivo cada vez más complejo de lograr debido a los mayores confinamientos y calidades de roca de los yacimientos modernos. Para entender mejor esta problemática se usa el modelamiento numérico, herramienta computacional que mejora año a año y ayuda a entender fenómenos geomecánicos sin la necesidad de ensayos reales. En particular, el software Abaqus muestra ser una gran herramienta computacional para modelar casos conceptuales y reales de la minería actual. Utilizando estas dos herramientas (empíricas y numéricas), es que se construyen modelos numéricos conceptuales con el fin de entender el impacto que provoca la geometría de la cavidad: el concepto de radio hidráulico basal y la geometría del cave-back, en el régimen de esfuerzos y la altura de columna máxima posible a hundir. La metodología consiste, para determinados radios hidráulicos, geometrías del cave-back y calidades de roca (MRMR), en construir modelos para diferentes razones de ancho y altura de la cavidad con el fin de entender el comportamiento de los esfuerzos principales y las condiciones de hundimiento para cada caso y luego definir las alturas máximas alcanzadas para los distintos escenarios. El mejor criterio encontrado para establecer estas condiciones fue el de la razón de los esfuerzos principales S1/S3 en función de la razón de altura y ancho h/B de la cavidad. Los resultados muestran, como se esperaba, que a mayores radios hidráulicos y menores valores de MRMR las alturas de columna alcanzadas serán mayores. Sumado a esto, se observa que una geometría más plana de la zona del cave-back provoca una disminución de la magnitud de los esfuerzos principales, en particular del esfuerzo principal menor S3 registrando mayores alturas de columna. Es por esto que, para una cavidad de RH y calidad del macizo fija, un cambio en la geometría del cave-back (y valores de los esfuerzos principales en su superficie para tal condición) provocará un aumento importante en las alturas de roca alcanzadas y por ende una mejora en la producción.

The mining industry can greatly benefit from automation. A great deal of work has been done on this subject and is still ongoing. With automation comes the possibility for optimization, because more information is available, and actions can be repeated with more accuracy. Many factors in an underground environment make mining automation a challenging prospect. These factors include the difficulty and cost of installing the needed infrastructure. The work described in this dissertation focuses on a mining setup where vehicles such as LHDs and trucks are used to collect and transport ore underground. Considerable progress has been made in automating underground vehicles, and successful tests have been done underground. The next obvious step is to find ways of using the increased data to optimize the decisions that are made with regards to the dispatching of the vehicles. Possible solutions to the problem of optimizing the autonomous vehicle dispatch system in an underground mine are investigated. Possible optimization strategies are evaluated using a simulated environment. In the simulated environment a block cave mine is modelled, and the simulation setup is discussed in detail. The operation of a block cave mine as it is operated currently is simulated to obtain a benchmark for the evaluation of further results. The simulation results for the developed strategies are evaluated against specific criteria, and indicate definite improvements on current methods used in mines. Some important things that must be kept in mind for the physical implementation of the dispatching strategies, as well as mining automation in general, are also discussed. / Dissertation (MEng (Electronic Engineering))--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / unrestricted

Circadian clocks are endogenous time keeping mechanisms that are ubiquitous among animals. They enable coordination of many essential biological and metabolic processes in relation to the 24 hour light cycle on earth. However, there are many habitats on earth that are not subject to this light cycle. This study aims to look at the potential genetic drift of the circadian rhythm of a subterranean spider, Meta ovalis, as well as gathering general natural history information on this under-studied spider. This study will fill general gaps in knowledge of this spider and its habitat, highlight the importance of studying organisms within a subterranean environment, and place importance on cave conservation and acquiring knowledge of these specialized, and sensitive species. This study integrates circadian and foraging theory to evaluate species as circadian specialists and generalists based on how narrowly or widely their activity is spread over the 24 h cycle. We suggest that M. ovalis benefits from a generalist strategy, showing small bursts of focused activity widely dispersed across the 24 h cycle, allowing it to capture prey opportunistically whenever it is available. Live spiders were collected from area caves, monitored in an environment controlled for light and temperature, and returned to their cave of origin. The activity of each spider was analyzed for differences in circadian activity among and between populations to determine if there is a significant drift of the circadian strategy between isolated populations of Meta ovalis. We expect to see a different circadian strategy implemented between populations due to drift from the spiders being isolated from other populations.

No description available.

Here, we describe saber-toothed cat remains from the early Early Pleistocene (~2.0Ma) of Yanliang Cave, Fusui County, Guangxi Province, South China. Specimens, including a complete left dentary and right m1, are identified as Megantereon based on mandibular and dental characters. The Yanliang Megantereon is the smallest representative of the genus from Asia. Overall size, p4 and m1 dental proportions, the disposition of the p3, and dentary measurements align it with characters attributed to Megantereon whitei, a taxon not recorded from eastern Asia or China. Megantereon whitei is thought to be the most derived member of the genus. If the remains are M.whitei, or a closely related form, this represents an early occurrence of the group outside Africa. Other Megantereon specimens from China, that are roughly the same geologic age, or even younger, are considered to have a more primitive dentition than M.whitei. The Yanliang Megantereon, and our review, further demonstrates uncertainty in the evolutionary history of the group, the overall need for tighter chronologic control, and a systematic revision of the genus that includes discrete morphological characters.

The role of bison in the prehistoric subsistence in southern Idaho is not fully understood. Bison remains from Baker Cave, a late Holocene archaeological site dating to cal A.D. 1042-1265, however, provide evidence of pre-contact subsistence strategies in the region. This thesis focuses on the paleoecology of bison and their role in prehistoric subsistence on the Snake River Plain (SRP). The ecological study of bison focuses on the hypothesized trans-Holocene diminution in bison body size in southern Idaho, while a second study focuses on how these animals figured into prehistoric responses to seasonal fat scarcity. Although bison diminution and its ecological determinants are well understood on the Great Plains, the history of diminution west of the Rocky Mountains is less clear. Bison morphometrics from Baker Cave present the opportunity to assess bison diminution on the Snake River Plain. Bison morphometrics from Baker Cave are indistinguishable not only from other late Holocene bison on the Snake River Plain but iv also from late Holocene bison from the Great Plains. Further, the Baker Cave bison are smaller than early Holocene bison from the Great Plains and Snake River Plain. These results suggest morphological similarity between Snake River Plain bison and Great Plains bison through the Holocene, pointing to similar bottom up ecological constraints on body size. Although bison are common components of SRP archaeofaunas, their role in prehistoric subsistence is poorly understood. To shed light on this problem, I hypothesize that the Baker Cave bison assemblage resulted from hunters seeking skeletal fat. I test predictions drawn from this hypothesis with assemblage-level patterns in element representation, impact scar distribution, and fragmentation. These assemblage-level patterns track the skeletal fat utility of elements. These patterns, combined with winter procurement evidenced by fetal remains, support the hypothesis that fat-seeking behavior was a response to winter fat scarcity. A comparison with smaller bison assemblages from southern Idaho suggests that this fat-seeking behavior might have persisted as far back as the middle Holocene, although this requires confirmation from future studies.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18804号 / 理博第4062号 / 新制||理||1584(附属図書館) / 31755 / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 田上 高広, 教授 土`山 明, 教授 大沢 信二 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

No description available.

Developed out of a need for a reliable methodology of documenting historic landscapes, the National Park Service uses Cultural Landscape Reports to determine the significance and integrity of historic landscapes. Treatment recommendations developed from an analysis of site history and existing conditions guide the management decisions of cultural landscapes. Russell Cave National Monument, located in Bridgeport, Alabama, contains one of the oldest continuous archeological records in North America. A cultural landscape report for the park had not yet been completed. This research consists of a historical narrative covering the 10,000 years of human occupation in the cave, a documentation of existing conditions, an analysis of historic integrity, and recommendations for management, preservation, and restoration of the landscape.

No description available.