Thesis (M.A.)--University of Wyoming, 2008. / Title from PDF title page (viewed on Dec. 7, 2009). Includes bibliographical references (p. 148-162).

Commodity markets are fundamentally cyclical, exposing mining companies to large swings in profitability during periods of economic boom and bust. Although this is well documented, companies continue to produce mine plans based on present market conditions that fail to acknowledge long-term metal price variability. The purpose of this thesis is to adapt McIsaac’s (2008) mathematical model for determining the most robust underground mining plan under conditions of metal price uncertainty for application in an open pit environment. An overview of conventional open pit algorithms is given to demonstrate that a circular analysis precludes the determination of an optimal solution when metal prices are uncertain. Under the proposed methodology, the optimal solution is achieved by selecting the cutoff grade and production rate under stochastic metal prices such that the net present value and probability of a positive net present value are maximized. The mathematical model was formulated with costs represented as a function of the level of production, rate of production or both. Revenues are achieved from either a mill, heap leach or stockpile process dependent on the level of production and metal price in the year of consideration. Metal prices are generated annually according to a stochastic model that balances short-term volatility with long-term trends. The compiled cash flow model determines the optimal net present value for a given production profile under input metal prices. The feasible area of production is established based on mine life, resource and financing constraints. Net present values are generated for a broad search grid, which converges towards a unimodal solution according to a golden search algorithm. The process is then repeated many times in order to identify the production profile at which the optimal solution is repeatedly reached. As a visual representation, the solutions are plotted on a bubble graph where the size of the bubble corresponds to the frequency of the solution; the largest bubble is associated with the optimal solution. The methodology is tested on two massive copper porphyry deposits, contained within a single claim, for which a Preliminary Economic Assessment has been completed. / Thesis (Master, Mining Engineering) -- Queen's University, 2010-02-08 22:07:52.331

Thesis (M.D.S.)--University of Adelaide, Dept. of Dentistry, 1987. / Bibliography: p. 110.

Thesis (M.S.)--School of Dentistry. University of Missouri--Kansas City, 2008. / "A thesis in dental hygiene education." Advisor: Bonnie Branson. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Aug. 07, 2008. Includes bibliographical references (leaves 53-58). Online version of the print edition.

Magíster en Minería. Ingeniero Civil de Minas / Hoy en día, las minas a cielo abierto están siendo cada vez más profundas, lo que hace cada vez más atractivo el recuperar las reservas restantes mediante métodos subterráneos, tanto en las partes más profundas del pit como en sus zonas circundantes. Por lo tanto, estas operaciones han empezado a desarrollar nuevas estrategias para extraer el mineral mediante operaciones subterráneas. Para cuerpos masivos, los métodos más rentables son los que consideran el hundimiento de la roca, en particular, los métodos de block/panel caving, debido a sus bajos costos operacionales y alta productividad con respecto a otros métodos subterráneos de extracción. Las metodologías aplicadas para definir el periodo óptimo de transición desde la mina a cielo abierto a la subterránea son casi siempre limitados o sesgados, debido a que tienden a darle prioridad a la primera, que no necesariamente resulta en el VAN óptimo. En este trabajo, se propone una nueva metodología para maximizar el VAN basado en la secuencia de agendamiento para el caso conjunto cielo abierto a panel caving. Primero, se calculan las envolventes económicas para la mina a cielo abierto y la mina de panel caving, considerando potenciales pilares coronas entre ellos a modo de estabilidad. Después, se realiza el secuenciamiento de bloques y la maximización del VAN, considerando restricciones operacionales y geomecánicas para estudiar su influencia en el agendamiento. Este modelo de optimización ha sido aplicada tanto a modelos de bloques sintéticos y aquellos de escala minera. Los planes de producción, cambios en el periodo óptimo de transición, el secuenciamiento de los bloques, la alimentación a planta y las variaciones del VAN se analizan basados en los diferentes grupos de parámetros y variantes de extracción para suplir el ramp-up de la mina subterránea. Dichas variaciones en el caso de estudio tienen un impacto importante en el periodo óptimo de transición (pasando desde el año 31 hasta el año 50), enfrentando bajas importantes en la alimentación a planta en los planes de carácter secuencial durante la transición. El VAN, por su parte, no difiere de manera importante al analizar el proyecto desde su inicio (variación cercana al 1.2\% entre el peor y el mejor caso). Sin embargo, si se toma el año inicial para el análisis del VAN en un periodo posterior, como lo es el año 30 de la extracción, las diferencias son de mayor importancia (cercano al 93\% entre el peor y el mejor caso). Esta metodología es una herramienta que puede ayudar al planificador a observar diferentes casos durante la transición. Sin embargo, se recomienda incluir más componentes al modelo, como es la incorporación de un modelo geomecánico extenso tanto para la mina a cielo abierto como la subterránea, además de la integración de fases e interacción entre ellas en este primer método, y la integración de sectores o paneles en el segundo. / Este trabajo ha sido parcialmente financiado por CSIRO y AMTC

The effect of sand mining on model groups of organisms (vascluar plants, beetles, amphibians and birds) was studied in South Bohemia. The studies were made in the next biotopes by model area sand pit Roudná II southern from Planá nad Lužnicí: unforested area (after mining), forest (on recultivated plots and seminatural forest) and water biotopes (depressions after mining). The next characteristics of biodiversity were determined: the diversity of communites, the frequency of protected, rare and vulnerable species. The protected species occur mainly in amphibians and birds. The suitable recultivation measures were proposed on the base of biodiversity studies.

D.Sc. (Botany) / Please refer to full text to view abstract

Modern large-scale open pit mines move hundreds of thousands of tonnes of material daily, from the loading sources to the destination zones, whether these are massive mine dumps or, to a lesser extent, to the grinding mills. Mine dumps can be classified as leach or waste dumps, depending upon their economic viability to be processed in-place, a condition that has experienced great progress in the last decades and has reconfigured the open pit haulage network with an increase in the number of dumps. Therefore, new methods for dump design optimization are of the highest priority in mine planning management. This paper presents a methodology to model and optimize the design of a dump by minimizing the total haulage costs. The location and design of these dumps will be given mainly by the geological characteristics of the mineral, tonnage delivered, topographical conditions, infrastructure capital and transportation costs. Spatial and physical design possibilities, in addition, provide a set of parameters of mathematical and economic relationship that creates opportunities for modelling and thus facilitates the measurement and optimization of ultimate dump designs. The proposed methodology consists of: (1) Formulation of a dump model based on a system of equations relying on multiple relevant parameters; (2) Solves by minimizing the total cost using linear programming and determines a "preliminary" dump design; (3) Through a series of iterations, changes the "preliminary" footprint by projecting it to the topography and creates the ultimate dump design. Finally, an application for a waste rock dump illustrates this methodology.

Surface mining is the most common mining method worldwide, and open pit mining accounts for more than 60% of all surface output. Haulage costs account for as much as 60% of the total operating cost for these types of mines, so it is desirable to maintain an efficient haulage system. As the size of the haulage fleet being used increases, shovel productivity increases and truck productivity decreases, so an effective fleet size must be chosen that will effectively utilize all pieces of equipment. One method of fleet selection involves the application of queuing theory to the haul cycle. Queuing theory was developed to model systems that provide service for randomly arising demands and predict the behavior of such systems. A queuing system is one in which customers arrive for service, wait for service if it is not immediately available, and move on to the next server or exit the system once they have been serviced. Most mining haul routes consist of four main components: loading, loaded hauling, dumping, and unloaded hauling to return to the loader. These components can be modeled together as servers in one cyclic queuing network, or independently as individual service channels. Data from a large open pit gold mine are analyzed and applied to a multichannel queuing model representative of the loading process of the haul cycle.  The outputs of the model are compared against the actual truck data to evaluate the validity of the queuing model developed. / Master of Science

Indiana University-Purdue University Indianapolis (IUPUI) / BACKGROUND The efficacy of sealants to aid in the prevention of pit and fissure caries is well documented. In order for the sealants to be effective, they must be placed properly and retained for as long as possible. Clinicians must be aware that the proper placement of sealants is technique-sensitive and must be well controlled in order to achieve the best results. This study aims to determine if certain variables have an effect on curing of the sealant material to a degree that would compromise its integrity, strength, and longevity. METHODS AND MATERIALS Two commonly used sealant materials Ultraseal XT (Ultradent Products Inc., South Jordan, UT) and Delton (Dentsply International, Woodbridge, Ontario, Canada) were chosen and tested for microhardness and abrasion resistance after they were polymerized. This study did not focus on the materials themselves, but rather the technique by which they were polymerized and what effect this had on the materials. Three separate light sources, a traditional halogen light (QHL 75, Dentsply International, Woodbridge, Ontario, Canada), and two newer LED lights (Ultralume LED, Ultradent Products Inc., South Jordan, UT; and 3M Freelight LED, 3M Corp, St Paul, MN) were used in this study. The materials were then cured with each light at each of three different distances: contact (0.5 mm), 2 mm, and 10 mm. The effects of light source variation and distance from the material at the time of polymerization was then evaluated for any significance to sealant placement technique. Specimens were tested for each variable combination of sealant material, light source, and distance between the two while curing. Six samples were tested for each variable grouping for abrasion resistance, and four separate san1ples were tested fron1 the san1e grouping for Knoop hardness. The results were analyzed for significance to determine if certain techniques are or could be beneficial or damaging to the quality of care provided by today's practitioners. RESULTS It was found that materials and light sources varied in combination and with different techniques (e.g., distance). In general, the top surface polymerized best when cured at a distance of 2 mm to 10 mm, while the bottom surface polymerized best at a distance of 0.5 mm. The halogen light consistently outperformed the two LED lights, with the 3M LED consistently producing the worst results. CONCLUSIONS The halogen curing light used in this study outperformed the LED lights in almost every category, despite the LED light manufacturer's claims of equality. For more reliable polymerization, the halogen light should be used. SIGNIFICANCE The practitioner must be aware of the material that he/she is using and how the chosen light source polymerizes that material. Manufacturers' claims and recommendations cannot be trusted to accurately produce the best results with every product on the market today, sometimes not even with the manufacturers' own products. It is crucial for practitioners to be well versed and knowledgeable about the products that they use, based on current research and not manufacturers' claims.