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Long-term mine plans are based on forecast future metal prices. By the time the development is put in place, the forecasts may have been proved wrong and the production plan might not meet the company's financial objectives. At that point, the common reaction to this situation is to create a new revised long-term plan and spend more capital, only to find out at a later time that the metal prices have changed again. This results in an inefficient use of capital with low returns to the investors. The objective of this thesis is to develop a methodology to determine the cut-off grade and production rate of a narrow-vein underground mine such that the long-term strategic plan is robust. As a requirement to do so, it is necessary to have a good understanding of the resources, revenues, capital and operating costs as a function of the design parameters. Also, the operational limits of the mine must be determined so that the solution is practical. Afterwards, annual metal prices are randomly generated with a Monte Carlo process on stochastic metal price models, and the combination of production rate and cut-off grade yielding the highest net present value is identified and recorded. This process is repeated many times, and the probabilities of the solutions occurring at any given design combination are calculated. The results are plotted on a bubble graph, where the size of a bubble is directly proportional to the probability a solution occurs at that point. Finally, the combination with the largest bubble is the solution, as this point has the highest probability of yielding the highest net present value in most circumstances. The model was first tested on an actual gold-copper orebody where very detailed resource and cost information was available. The methodology was applied with success and the solution reflected the important impact of the copper milling and roasting process on revenues. Other tests were then done on a hypothetical gold orebody and the results showed a great degree of sensitivity to the average grade of the deposit. / Thesis (Ph.D, Mining Engineering) -- Queen's University, 2008-04-25 12:42:24.623

This work evaluates SiteManager, the construction documentation system used by VDOT, as a tool for collecting the daily installed quantity and active crew days necessary to populate the operations level of the database. This evaluation first sought to determine if SiteManager was a feasible option for collecting performance data. This was done by establishing data collection methods to enable SiteManager to have the ability to collect performance data, implementing the methods on select projects, resolving issues, and developing recommendations to cause SiteManager to be a more practical option. Secondly, a statistical analysis was performed to determine if the data collected from SiteManager was reasonably accurate. Thirdly, the technical issues of transferring performance data from SiteManager into the performance time database were resolved. It was found SiteManager could not be used in its current format to collect performance data and some modifications are required. / Master of Science

abstract: In this research, a new cutting edge wear estimator for micro-endmilling is developed and the reliabillity of the estimator is evaluated. The main concept of this estimator is the minimum chip thickness effect. This estimator predicts the cutting edge radius by detecting the drop in the chip production rate as the cutting edge of a micro- endmill slips over the workpiece when the minimum chip thickness becomes larger than the uncut chip thickness, thus transitioning from the shearing to the ploughing dominant regime. The chip production rate is investigated through simulation and experiment. The simulation and the experiment show that the chip production rate decreases when the minimum chip thickness becomes larger than the uncut chip thickness. Also, the reliability of this estimator is evaluated. The probability of correct estimation of the cutting edge radius is more than 80%. This cutting edge wear estimator could be applied to an online tool wear estimation system. Then, a large number of cutting edge wear data could be obtained. From the data, a cutting edge wear model could be developed in terms of the machine control parameters so that the optimum control parameters could be applied to increase the tool life and the machining quality as well by minimizing the cutting edge wear rate. In addition, in order to find the stable condition of the machining, the stabillity lobe of the system is created by measuring the dynamic parameters. This process is needed prior to the cutting edge wear estimation since the chatter would affect the cutting edge wear and the chip production rate. In this research, a new experimental set-up for measuring the dynamic parameters is developed by using a high speed camera with microscope lens and a loadcell. The loadcell is used to measure the stiffness of the tool-holder assembly of the machine and the high speed camera is used to measure the natural frequency and the damping ratio. From the measured data, a stability lobe is created. Even though this new method needs further research, it could be more cost-effective than the conventional methods in the future. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2019

Re-entrant lines are widely used in many manufacturing systems, such as semiconductor, electronics, etc. However, the performance analysis of re-entrant lines is largely unexplored due to its complexity. In this thesis, we present iterative procedures to approximate the production rate of re-entrant lines with Bernoulli reliability of machines. The convergence of the algorithms, uniqueness of the solution, and structural properties, have been proved analytically. The accuracy of the procedures is investigated numerically. It is shown that the approaches developed can either provide a lower bound or a closed estimate of the system production rate. Finally, a case study of automotive ignition component line with re-entrant washing operations is introduced to illustrate the applicability of the method. The results of this study suggest a possible route for modeling and analysis of re-entrant systems.

Many production systems have split and merge operations to increase production capac- ity and variety, improve product quality, and implement product control and scheduling policies. This thesis presents analytical methods to model and analyze split and merge production systems with Bernoulli and exponential reliability machines under circulate, priority and percentage policies. The recursive procedures for performance analysis are de- rived, and the convergence of the procedures and uniqueness of the solutions, along with the structural properties, are proved analytically, and the accuracy of the estimation is justi¯ed numerically with high precision. In addition, comparisons among the e®ects of di®erent policies in system performance are carried out.

Concerning management of smoke following an accidental fire within a building it is desirable to be able to estimate, within some understood, acceptable magnitude of error, the volume of smoke resulting from the combustion process of a predefined design fire scenario. Traditionally a range of first principle-based and empirically derived correlations are used to estimate the mass flow of smoke at a height of interest within the fire plume and are based upon the understanding that the mass flow of smoke at that height is a function only of the gravitational vector within the fire system, that is to say, that induced by the pressure differential between the naturally occurring hot plume gases and the surrounding quiescent bulk fluid. The statement that the fire plume is surrounded by a quiescent bulk fluid is in itself a significant simplification and is a key assumption required to facilitate the relative simplicity of the Froude-based entrainment correlations. It is of course quite intuitive to imagine that in real accidental fire scenarios in the built environment and across an array modern infrastructure, rarely does a fire exist submerged in a passive, quiescent atmosphere. This disconnect between the natural mechanics of the buoyant fire mechanism and the surrounding fluid in which it exists was necessary when the problem of entrainment by the fire plume was first described in the mainstream engineering literature around the middle of the twentieth century. Some 25 years later as ideal entrainment mechanics were beginning to be discussed specifically for application by a field of engineering in its infancy, a few researchers in the field of fire safety engineering published data that suggested that the addition of a relatively weak cross flow to the fire plume could have a significant impact upon the rate of air entrained by the plume, and by extension, the resultant smoke mass flow rate. The data published appeared more as a brief comment on an observation made during testing. It would be easily missed, nuzzled away in the middle of a lengthy doctoral thesis. Said thesis however happens to be one of the primary pieces of work that may be cited in reference to the formulation of perhaps the best known form of the axis-symmetric fire plume entrainment correlation, that of the so-called Zukoski correlation. It is perhaps curious then that the mention of a 3-fold increase in entrainment measurements following “small disturbances” in the atmosphere during the experimental work has seemingly been ignored by researchers, probably never-learned by students, and apparently forgotten by an industry. In a fire situation smoke can limit way-finding ability, severely irritate critical soft tissue like the eyes, trachea and oesophagus, impair cognitive function, contribute to significant property damage, facilitate the transfer of heat and carcinogens to locations remote to the fire source and it is well understood that most deaths due to fire are caused by asphyxiation following smoke inhalation. Significant portions of project budgets may be spent on designing, validating, installing and maintaining smoke management systems including the use of active systems such as extraction and pressurisation, passive curtains/reservoirs and detection such aspirating, video and beam detectors. Turbulent atmospheres may arise in any manner of situations such as modern buildings with large open spaces (airports, museums), hotel foyers and those with atriums spanning many floors, hangars and storage facilities/warehouses. Strong winds are normal on offshore oil platforms, outside the window on most floors of super-tall buildings or quite simply, anywhere on a blustery day. In specific cases the extraction systems designed to remove smoke and even normal HVAC systems can cause substantial air flow over large areas. In fact, a simple compartment with an uneven distribution of ventilation points (windows/doorways) has been shown to result in a directional fire flow that results in a significantly tilted flame, essentially inducing a cross flow scenario using the natural fire alone. With the coming-of-age of computational fluid dynamics models which are now a standard tool in all commercial fire engineering design offices, and probably in every smoke modelling report, it might be argued that there is little need to revisit the hand calculations from the ground up. Accepting, however, that a cross flow may increase the rate of entrainment of a fire plume and that this challenges the fundamental principles that all previous entrainment correlation knowledge is based on, and demonstrating the outcome (in terms of plume mass flow rate) with the use of a computational model, is an entirely different thing to understanding why this happens. Smoke management is one of the core design criteria, or questions at least, in practically all fire engineering design projects. In the literature there appears to be; no work quantitatively investigating cross flow fire plume entrainment rates; no work qualitatively describing the behaviour of the flame / fire plume under the influence of a cross flow (with respect to entrainment); and certainly no work framing this paradigm in the theoretical or practical context of the impact upon modern smoke control systems. This work aims to venture into these areas in the hope of beginning to piece together the overarching story of entrainment in the cross flow fire plume. The fundamental paradigm here is the addition of cross flow inertia (a horizontal pressure differential) to the axis-symmetric case where buoyancy (a zero initial momentum, vertical pressure differential) is the sole driver of the fluid flow system. How these flows then interact in a mixed convection sequence is investigated and described in terms that are useful for practical consideration by fire safety engineers. It is hoped that the concepts postulated and the questions raised will inspire further investigation into this poorly understood, but fundamental fire safety problem.

This work involved an investigation into the mechanisms governing the reduction of material in the solids bed of the Ifcon® process. Thermo gravimetric analyses were done to investigate the influence of various operational parameters on the rate of solid state reduction. The experiments were modeled, and model predictions were compared to experimental results. Kinetic data was analised and the reduction rate constants were calculated. The rate constants were used as inputs to a model, which describes the reduction behaviour and temperature profile in a composite solids bed (similar to that in the Ifcon® process). High temperature reduction- and melting tests were done in an 150 kW induction furnace, to simulate final reduction in a solids bed. The temperature profile through the solids bed was measured and results were compared to model predictions. Finally the extent to which solid state reduction occurs in the solids bed was estimated as a function of production rate. / Dissertation (MEng (Metallurgical Engineering))--University of Pretoria, 2008. / Materials Science and Metallurgical Engineering / unrestricted

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22264号 / 理博第4578号 / 新制||理||1657(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)准教授 松四 雄騎, 教授 千木良 雅弘, 教授 岩田 知孝 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM