<p> Thirty cross-bred steers (initial BW 375 &plusmn;37.2, replicate 1; and 535.0 &plusmn; 39.4 kg, replicate 2) were utilized to investigate the effects of Mo water concentration on performance, carcass characteristics, and mineral status of feedlot steers fed a growing and finishing diet for 151 and 112 d for replicate 1 and replicate 2, respectively. The experimental design was a randomized complete block design. Steers were blocked by weight and then divided into 2 weight block replicates each consisting of 15 steers. Steers were randomly assigned within block to one of 5 treatments (3 pens/treatment; 1 steer/ pen; 2 replicates/treatment). Water treatments consisted of: 1) 0.0 &mu;g, 2) 160 &mu;g, 3) 320 &mu;g 4) 480 &mu;g Mo/L, and 5) 960 &mu;g of supplemental Mo/L added as Na₂MoO₄ to the drinking water. Steers were housed in individual pens that contained individual 265 L water tanks for monitoring water intake. Daily water intake was recorded for each steer. Steers were individually weighed on 2 consecutive days at the beginning and end of the experiment and interim weights and jugular blood samples were obtained every 28 d. Liver biopsies were obtained on d0 and 84 from each steers. Steers were transported to a commercial abattoir, slaughtered, and individual carcass data and liver samples were collected. Initial BW was used as a covariate for statistical analysis of the data and significance was determined at <i>P</i> &le; 0.05. No differences were observed for final BW (<i>P</i> &le; 0.98). Overall ADG, DMI, feed efficiency and water intake were similar across treatments. Hot carcass weight, dressing percentage, yield grade, LMA, adjusted fat thickness, KPH, and marbling scores were similar across treatments. Liver and plasma Cu, Mo, and Zn concentrations were similar across treatments. These data indicate that water Mo concentration had no impact on performance, mineral status, water intake, and carcass characteristics in feedlot steers fed a high concentrate diet.</p>

Additive manufacturing of aluminium alloys using selective laser melting (SLM) is of research interest nowadays because of its potential benefits in industry sectors such as aerospace and automotive. However, in order to demonstrate the credibility of aluminium SLM for industrial needs, a comprehensive understanding of the interrelation between the process parameters, produced microstructure, and mechanical behaviour is still needed. This thesis aims at contributing to developing this comprehensive understanding through studying the various aspects of the process, with investigation of the powder raw material to the near fully dense samples, focussing on the alloy AlSi10Mg. The primary building blocks in the SLM process are the single tracks. Their formation is affected by the physical properties of the material that control the laser-material interactions. Keyhole mode melting was found to be dominant when processing AlSi10Mg, producing conical-shaped melt pools. Porosity was not evident in single tracks and individual layers. Satellites and balling defects, however, were observed on top of the tracks and layers at higher scan speeds, which contribute to porosity formation with layer progression. The combination of process parameters controls the amount of porosity formed, with the scan speed controlling the type of pore; metallurgical or keyhole pore. A pre-melt scan strategy significantly reduced porosity and successfully produced 99.8% dense samples. Furthermore, the pre-melt scan strategy was seen to effectively reduce the number of pores developed when using powder that does not fully comply with the process standards. The gas flow rate within the process chamber controlled laser spatter and condensate removal during processing, which in its turn affected the degree of porosity in the samples. The SLM process resulted in an AlSi10Mg alloy with a characteristically fine microstructure, with fine equiaxed grains at the melt pool core and coarser elongated grains at the boundary. The material showed a strong texture, owing to directional solidification. Cellular dendritic Al with inter-dendritic Si was observed. The material was subjected to a T6 heat treatment that transformed the microstructure into spheroids of Si in the Al matrix. This study investigated, for the first time, the local mechanical properties within the SLM material using nanoindentation. This showed a uniform nano-hardness profile that was attributed to the fine microstructure and good dispersion of the alloying elements. Spatial variation within the material was recorded after the T6 heat treatment due to phase transformation. This study is also the first to report on the compressive behaviour of solid SLM material, which is important for developing prediction and simulation models. The heat treatment softened the material and provided it with an increased ductility under indentation, tensile, and compressive types of loading. In addition, the material showed good fatigue performance, which was further improved by heat treatment and machining to obtain a smoother surface roughness. This investigation has, therefore, developed an understanding of the various aspects of the SLM process yielding near fully dense parts and defined the microstructure-mechanical property interrelation promoting the process for Al alloys in a number of industrial sectors.

Fluidised bed combustion (FBC) has been identified as one of the best technologies available for lump coal combustion. A major drawback during prolonged operation of FBC systems particularly bubbling fluidised bed (BFB) systems is sintering and agglomerate formation of bed material that affects performance efficiency and reliability in industrial applications as exemplified at Associated British Sugar (AB Sugar). The mechanisms responsible for sintering and agglomerate formation in this type of system need to be understood, to promote continual use of this technology for efficient coal utilisation. The first set of investigations focused on agglomeration properties of bed material (Garside 14/25 sand) used in Industrial FBC at AB Sugar. Bed material was calcinated between 800 and 1200°C in a high temperature furnace in the absence and presence of coal (three types of bituminous coals) or coal ash. Results showed sintering and agglomerate formation of bed material can occur in the absence of coal or coal ash at a calcination temperature near 1200°C. Addition of coal or coal ash further promotes sintering and agglomerate formation at 1000°C. Combustion stages appears to influence surface morphology, chemistry and mechanisms of agglomerated bed material based on similarities observed in the agglomerated bed material formed from calcination of Garside 14/25 sand bed material mixed with coal, and those formed in industrial scale FBC during combustion of lump coal. The second set of investigations used two different lump bituminous coals classified as washed (undergone washing process to remove mud/shale stone) or unwashed (still containing the mud/shale) from the same mine (Blyth, typically referred to as Blyth coals) as those used in the AB Sugar industrial FBC. Combustion of washed and unwashed Blyth lump coals (9 to 19 mm particle size) was investigated in a 30 kW pilot scale bubbling fluidised bed combustor (PSBFBC) during normal combustion and crash stop combustion runs. This simulated conditions in the AB Sugar Industrial FBC system with a thermal rating of approximately 30 MW, which uses larger coal particle size of 12 to 25 mm. Results reveal unwashed Blyth lump coal in the PSBFBC and industrial FBC causes some sintering and agglomerate formation of the bed material over short operation periods of 52 and 240 hours respectively, which was not observed in the washed Blyth coal system over a similar operating period. Observed sintering and agglomeration formation in unwashed Blyth coal is mainly attributed to accumulation of mud/shale stones in the bed, which would have been mostly removed by the washing process. The crash stop combustion run, done to simulate the fan trip scenario in the industrial FBC system, promoted sintering and agglomerate formation in the PSBFBC, possibly due to the 30 to 50°C temperature rise in the bed when fluidised air was stopped. Continuous deposition and increasing concentration of mud/shale stones in the bed affects the localised temperature as well as the fluidising properties and quality, eventually promoting sintering and agglomerate formation. PSBFBC bed height, bed material particle size and measured pressure drop also increase with increasing operating time and mud/shale stones deposition in the bed. Deposition of coal ash to the surface of the bed material (sand) in the PSBFBC was analysed by the use of SEM-EDX and XRF. The deposition of ash to the surface of PSBFBC bed material sand increases as the operation times increases, as identified by increasing concentration of Al, K and Ca on fluidised bed sand particle surfaces in their stable oxide forms of Al2O3, K2O and CaO respectively.

Design criteria of the Longitudinal Sub-Level Caving method of mining, as it would particularly apply to Granduc Mines, has been studied by means of geometrically scaled mine models. Principles of similarity and their use in the model test work with due consideration to the simplifying assumptions have been analysed. Gravity flow theories of granular material as applicable to the bin design work have been used where possible in the stope design. A total of thirty-seven tests on a 1:30 scale model were conducted involving various orebody configurations. Qualitative observations are reported and the effects that will have to be dealt with by theoretical treatment are described. Within reasonable experimental accuracy, the draw figures of the flow of broken ore material in the model are determined. Based on these figures, mine layout patterns which would ensure maximum ore recovery with minimum waste dilution from the stopes have been presented for the mine development work. Quantitative design of ‘blast retreat distance’ depending on change in natural conditions of the stope, such as moisture content and confining pressures, etc. have been determined by measuring the flow properties of the ore material with Triaxial compression testing equipment. A remarkable change in the flow properties and hence the draw configuration is predicted. Recommendations on further and advanced work are included on the quantitative design of stoping layouts for the modern sub-level caving methods / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

A project report submitted to the faculty of Engineering, University of the Witwatersrand, in partial fulfilment of requirement of Master of Science in Engineering Johannesburg, 1992 / The optimal depletion of a mineral deposit involves the optimisation of all the proccesses involved in the mining operation. [Abbreviated Abstract. Open document to view full version] / MT2017

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<p> This study analyzed intercultural communication and cross-cultural hurdles between a multinational mining company, &ldquo;the Company,&rdquo; and the indigenous Western Shoshone community in Northern Nevada. Standpoint theory, as presented by Wood (2004), was the framework used to analyze the engagement methods utilized by the Company and the local tribal organizations to identify communication barriers between the two groups. This study explored an external perception of the Company and the general mining industry from tribal employees, as well as the unique perspective of those participants who bring a Native American standpoint to their position of employment within the Company. Research data was derived from focus groups of the Company employees of Native American descent and targeted interviews with external Native American stakeholders. The focus group participants varied by departmental function, tenure, and standing across multiple geographic operations, while the interview participants were employed by two different tribal organizations. Focus group and interview data each highlighted a discernable gap in the Company&rsquo;s current outreach with the local Native American communities and indicated key areas for improvement. Both internal and external participants recommended improvements to the Company&rsquo;s communications strategy and provided specific examples of culturally effective outreach methods and topics. These disparities originated from differing cultural perspectives and standpoints between the Company and the Native American communities. Through improved dialogue practices and communication outreach, this intercultural relationship can progress.</p>

<p> This research shows that worst-case methane-air detonation loading on coal mine seals could be more severe than the design loads required by federal regulations, and therefore mine seals should be designed with sufficient ductility beyond the elastic regime. For this study, reinforced concrete mine seals were designed according to traditional protective structural design methods to meet the federal regulation requirements, and then the response to worst-case loads was analyzed in a single-degree- of-freedom model. Coal mine seals designed to resist the regulation loads elastically experienced support rotations up to 4.27 deg when analyzed with the worst-case loads. The analysis showed that coal mine seals designed to satisfy the federal regulations can survive worst-case methane-air detonations if they have sufficient ductility, but will undergo permanent, inelastic deformation.</p>

<p>In order to better inform and train industry professionals, as well as engineering students and new users, an electronic user's manual and comprehensive online training course for LaModel has been developed in an open online learning environment. The online user?s manual provides widespread access to detailed information on the installation, proper use, and troubleshooting procedures through a combination of: written documentation, voiced-over and captioned software simulations and slide presentations, and relevant academic articles. Some of the online LaModel material has also been organized into a set of progressive, self-paced training modules using a number of the slide presentations and software demonstrations, with the addition of pedagogically designed learning activities and proficiency quizzes. These training modules are designed such that a new user can complete the sequence of three learning tracks (novice, intermediate, and advanced) to become a proficient user of the LaModel program. This thesis reports on the development and implementation of the new LaModel user's manual and training course. Currently, the on-line material includes 84 pages of technical notes and 6 hours of slides and hands-on learning activities. In this thesis, the overall layout and format of the user's manual, training modules, and proficiency quizzes are presented along with samples from specific manual sections and classroom lessons. With an increase in operational difficulties, geologic intricacies, and regulatory review, this generation of mining engineers require complex analyzes to determine the integrity of underground mine works. Through access to the new online user's manual and training modules, novice LaModel users can be effectively trained on the correct operation and analysis techniques for using the LaModel program, while experienced users can quickly access detailed information on the newer and/or more complex LaModel functions. The development of both the user's manual and online training course will ultimately increase the effectiveness of mining engineers within the industry, leading to more productive and safer mine designs.