As part of a strategic research initiative at UBC to design and evaluate integrated underground mining and mineral processing systems, work has been done to determine how to utilize the coarse rejects of pre-concentration in the underground environment. An amenability study for nine orebodies from four of Xstrata Nickel’s Ontario operations evaluated both processing and waste disposal methods. Metallurgically the orebodies showed amenability to dense media separation and conductivity sorting. The dense media results showed high mass rejections and high metal recoveries for all nine orebodies. Conductivity sorter results were not as consistent, but still showed good results. Dense media rejects were examined to determine the applicability of their use in rockfills and composite minefills. The geotechnical properties indicated that the rejects would provide a competent material for minefills. The mix designs were examined for both strength and rheological properties and showed that fills utilizing rejects were comparable to fills currently used by industry. Composite fills containing rejects had significantly lower void ratios, decreasing cement requirements for a given strength requirement. Conceptual designs for pre-concentration systems based on the metallurgical, reject characterization, and mix design were developed for each of the four mines in the study. The designs took into consideration the current mining plans.

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A central result in price theory is the law of one price: prices of a homogeneous good sold at different locations should be equal. Empirical studies of the law of one price find that it is often violated. In my dissertation I explore the allocation problem that suppliers face when supplying multiple markets. I use the experimental method to examine the effect of an increase in the number of suppliers in a market, ceteris paribus, has on the allocation decisions of market participants. I also use the experimental method to investigate suppliers that are strategic and show that market concentration and transportation costs restrict the supplier’s ability to coordinate on an efficient equilibrium. A strategic supplier takes account his own effect on prices. Strategic supplies face a difficult strategy coordination problem. If they cannot solve it, then an inefficient outcome may result. Coordination failure may result in price dispersion across the markets. Resulting price signals do not inform suppliers who should respond and by how much. Price signals are not sufficient for suppliers to solve the strategy coordination problem. In the experiments, I observe that increasing the quantity of suppliers, that is the Herfindahl index of concentration, in the market will decrease the frequency of the equilibrium strategy to be played, holding other things constant. Increasing the number of firms in a market, ceteris paribus, increases price dispersion and coordination on an efficient market allocation is decreased. The experiments reveal that the ability of suppliers to coordinate is directly correlated with the optimization premium: the expected payoff difference between best responding to an opponents strategy and the payoff to an inferior response. The incentive is greater to best respond when the optimization premium is larger. Coordination at the equilibrium allocation is quicker.

Ultra-deepwater reservoirs are important unconventional reservoirs that hold the potential to produce billions of barrels of hydrocarbons, but also present major challenges. This type of reservoir is usually high pressure and high temperature (HPHT) and has a relatively high permeability. Hydraulic fracturing high permeability reservoirs are different from the hydraulic fracturing technology used in low permeability formations. The main purpose of hydraulic fracturing in low permeability reservoirs is to create a long, highly conductive path, whereas in high permeability formations hydraulic fracturing is used predominantly to bypass near wellbore formation damage, control sand production and reduce near wellbore pressure drop. Hydraulically fracturing these types of wells requires short fractures packed with high proppant concentrations. In addition, fracturing in high permeability reservoirs aims at achieving enough fracture length to increase productivity, especially when the viscosity of the reservoir fluid is high. In order to pump such a job and ensure long term productivity from the fracture, understanding the behavior of the fracture fluid and proppant is critical. A series of laboratory experiments have been conducted to study conductivity and fracture width with high proppant loading, high temperature and high pressure. Proppant was manually placed in the fracture and fracture fluid was pumped through the pack. Conductivity was measured by pumping oil to simulate reservoir conditions. Proppant performance and fracture fluids, which carry the proppant into the fracture, and their subsequent clean-up during production, were studied. High strength proppant is ideal for deep fracture stimulations and in this study different proppant loadings at different stresses were tested to see the impact of crushing and fracture width reduction on fracture conductivity. The preliminary test results indicated that oil at reservoir conditions improves clean-up of fracture fluid left in the proppant pack compared with using water at ambient temperature. Increasing the proppant concentration in the fracture showed higher conductivity values in some cases even at high closure stress. The increase in effective closure stress with high temperature resulted in a significant loss in conductivity. Additionally, the fracture width decreased with time and increased effective closure stress. Tests were also run to study the effect of cyclic loading which is expected to further decrease conductivity.

Heterogeneous nucleation of bubbles on an advancing solidification front during freezing of water containing a dissolved gas has been experimentally and analytically studied. The formation of bubbles resulting from supersaturation of liquids is commonly encountered in different fields such as heat transfer, manufacturing, and bioscience.In this work, sizes of nucleating bubbles and concentration profiles of dissolved oxygen and carbon dioxide gases in water ahead of the solidification front have been measured.From successful comparisons between the measured and predicted critical radii of nucleating bubbles and distributions of dissolved gas content, phenomena of heterogeneous nuc leation in a binary weak solution during the freezing process are quantitatively confirmed.

This paper numerically simulates flow and concentration fields in a supersaturated liquid in front of the solidification front during freezing. The supersaturated liquid usually produces bubbles. This phenomenon often occurs in different fields, for example, heat transfer, manufacture, biochemistry , etc. The research is based on micro theory to analyze different phenomena of a single bubble, which involve the unsteady interactions between flow and concentration fields, and rising and resistance forces etc. The results contribute to an improved understanding of bubble dynamics generally encountered in technological industries.

Advertising has been one of marketing tools for companies for decades. The question of how advertising affects company¡¦s financial performance had also been answered by marketing literatures. But most of the literatures focus on advertising¡¦s direct effect. How the other factors influence advertising¡¦s effect had been researched rarely. The purpose of this article is to understand how the industry concentration influences the contribution of changes in advertising expenditures. The result shows: (1) the effect of advertising on net sales persist five years or more in manufacture, at the same time, six years or more in retail and service industries (2) in manufacture, the industry concentration has positive effect on the contribution of changes in advertising expenditures, the more industry concentration, the more contribution of changes in advertising expenditures.

Time of concentration parameter is defined very loosely in literature and it is calculated rather subjectively in practice (Akan 1986). The situation becomes adverse as the terrain slope approaches zero; because the slope generally appears in the denominator of any formula for time of concentration, this time goes to infinity as the slope goes to zero. The variables affecting this time parameter on flat terrains have been studied through plot scale field experiments. It has been found that the antecedent moisture and rainfall rate control this parameter. Some of the existing time of concentration methods have been compared, and it is found that all the empirical models compared under predict this time parameter. This under prediction can be attributed first to the differing concepts of time of concentration previous researchers have modeled, secondly to the absence of any accounting for the initial moisture content in their respective equations and thirdly to the watersheds where these models have been calibrated. At lower time of concentrations, Izzard-based model predictions show some results close to the observed values. A methodology to determine the plot scale surface undulations has been developed to estimate the depression storage. Regression equations have been derived based upon the experiments to determine the overland flow times on a flat plot of 30 feet length with uniform rainfall intensity. The application of these equations on other lengths cannot be ascertained. Equations for the hydrograph slope on flat terrains have been determined for bare clay and grass plots.

Texte remanié de: Dissertation--Gemeinsame Fakultät für Geistes- und Sozialwissenschaften--Hanovre, 2001. Titre de soutenance : Der Lagerkomplex des KZ Ravensbrück : Studien über Terror, Zwangsarbeit und Vernichtung. / Bibliogr. p. 687-724. Notes bibliogr. Index.

Texte remanié de: Diss.--Fakultät für Geistes- und Sozialwissenschaften--Universität Hannover, 2001. Titre de soutenance : Der Lagerkomplex des KZ Ravensbrück. Studien über Terror, Zwangsarbeit und Vernichtung. / Bibliogr. p. 575-598. Index.