Evaluating the business improvement strategies, practices and challenges in the platinum mining industry

The purpose of this study was to evaluate the strategies, practices and challenges relating to business performance and the implementation of business improvement to align production and maintenance strategies to the corporate strategy in Anglo American Platinum, a mining operation in South Africa. A set of questions were used in a qualitative research design through interview questions to collect data from corporate strategic management and the operational management involved in business improvement initiatives in the production and maintenance processes. Globally, mining companies are faced with many challenges, including safety, system integration and standardisation, caring for the environment, cost controlling and reliability of machinery and equipment. The mining industry is both labour and capital-intensive. While the South African labour force has unlimited demands on wages and salaries, most machinery runs at its maximum capacity and requires more capital for the operations to continue production, ensuring value creation for all stakeholders and hence sustainability of the operations. The situation was aggravated when market forces determining the commodity prices became volatile, causing the slump in the commodity prices. As a result, profit margins were eroded by the higher costs of production and higher wages costs. To create a sustainable, cost-effective operation and improve recovery and grades, mining companies such as Anglo American Platinum implemented a business improvement initiative. This study aims to evaluate the strategies, practices and challenges in relation to business improvement at Anglo American Platinum. Observations are that the impact of misalignment between corporate strategy, together with business improvement production and maintenance strategies, contribute minimally to the performance of production at Anglo American Platinum

Operation of induction machines in the presence of unbalanced supplies

Includes bibliographical references.Three-phase induction machines are widely used in South Africa for industrial, commercial and residential applications because of their simple construction and low maintenance. The manufacturers design these motors to provide their nameplate ratings when supplied with balanced sinusoidal voltages. However, the power system experiences unbalanced voltages, overvoltages, undervoltages, etc, which are seen at the motor terminals. The South African Electricity Supply Utility (Eskom) supplies the commercial and industrial systems with a line voltage range of 400V +- 10%. An Induction motor rated at 380V or 400V will therefore experience overvoltages or undervoltages depending on the location of the motor from the supply. Besides overvoltages and undervoltages, unbalanced voltages exist on the power system. The tolerable level of voltage unbalance on the South African three-phase networks is 2%, and may be up to 3% in the rural areas. In practice, induction motors experience a combination of overvoltages or undervoltages with unbalanced voltages. This affects motor life. NEMA has done research on induction motors operating under unbalanced voltages. They defined voltage unbalance and produced a derating curve, assuming the average voltage applied to the motor is equal to the rated voltage. The EEC has another definition of voltage unbalance based on the positive and negative sequence voltages. The IEC definition is referred to as the true definition. Two formulas that approximate the true definition also exist. An analysis was done in order to understand the implications of using these definitions of voltage unbalance in the South African power system. It was found that the NEMA definition and the true definition do not differ significantly below a 5% unbalance. in order to estimate motor life when a motor is supplied with unbalanced voltages, in combination with over or undervoltages, electrical and thermal models were developed to predict the temperature. The electrical model was based on the positive and negative sequence equivalent circuits. The thermal model used, separated stator and rotor thermal circuits. The thermal parameters were obtained from simple tests rather than from motor design data. The predicted temperature values agree closely to the measured values. The interaction between the electrical model, thermal model and the thermal ageing equation were used to estimate motor life when the motor is supplied with unbalanced voltages, in combination with over or undervoltages. Motor life is reduced when the operating temperature exceeds the rated. In order to restore motor life, new derating curves were developed since the NEMA derating curve is limited to rated average voltage. Motor life can be restored by applying the new derating curves developed here

Crude incidence in two-phase designs in the presence of competing risks.

BackgroundIn many studies, some information might not be available for the whole cohort, some covariates, or even the outcome, might be ascertained in selected subsamples. These studies are part of a broad category termed two-phase studies. Common examples include the nested case-control and the case-cohort designs. For two-phase studies, appropriate weighted survival estimates have been derived; however, no estimator of cumulative incidence accounting for competing events has been proposed. This is relevant in the presence of multiple types of events, where estimation of event type specific quantities are needed for evaluating outcome.MethodsWe develop a non parametric estimator of the cumulative incidence function of events accounting for possible competing events. It handles a general sampling design by weights derived from the sampling probabilities. The variance is derived from the influence function of the subdistribution hazard.ResultsThe proposed method shows good performance in simulations. It is applied to estimate the crude incidence of relapse in childhood acute lymphoblastic leukemia in groups defined by a genotype not available for everyone in a cohort of nearly 2000 patients, where death due to toxicity acted as a competing event. In a second example the aim was to estimate engagement in care of a cohort of HIV patients in resource limited setting, where for some patients the outcome itself was missing due to lost to follow-up. A sampling based approach was used to identify outcome in a subsample of lost patients and to obtain a valid estimate of connection to care.ConclusionsA valid estimator for cumulative incidence of events accounting for competing risks under a general sampling design from an infinite target population is derived

Detecting outliers and/or leverage points: a robust two-stage procedure with bootstrap cut-off points

This paper presents a robust two-stage procedure for identification of outlying observations in regression analysis. The exploratory stage identifies leverage points and vertical outliers through a robust distance estimator based on Minimum Covariance Determinant (MCD). After deletion of these points, the confirmatory stage carries out an Ordinary Least Squares (OLS) analysis on the remaining subset of data and investigates the effect of adding back in the previously deleted observations. Cut-off points pertinent to different diagnostics are generated by bootstrapping and the cases are definitely labelled as good-leverage, bad-leverage, vertical outliers and typical cases. The procedure is applied to four examples

Climate change promotes parasitism in a coral symbiosis.

Coastal oceans are increasingly eutrophic, warm and acidic through the addition of anthropogenic nitrogen and carbon, respectively. Among the most sensitive taxa to these changes are scleractinian corals, which engineer the most biodiverse ecosystems on Earth. Corals' sensitivity is a consequence of their evolutionary investment in symbiosis with the dinoflagellate alga, Symbiodinium. Together, the coral holobiont has dominated oligotrophic tropical marine habitats. However, warming destabilizes this association and reduces coral fitness. It has been theorized that, when reefs become warm and eutrophic, mutualistic Symbiodinium sequester more resources for their own growth, thus parasitizing their hosts of nutrition. Here, we tested the hypothesis that sub-bleaching temperature and excess nitrogen promotes symbiont parasitism by measuring respiration (costs) and the assimilation and translocation of both carbon (energy) and nitrogen (growth; both benefits) within Orbicella faveolata hosting one of two Symbiodinium phylotypes using a dual stable isotope tracer incubation at ambient (26 °C) and sub-bleaching (31 °C) temperatures under elevated nitrate. Warming to 31 °C reduced holobiont net primary productivity (NPP) by 60% due to increased respiration which decreased host %carbon by 15% with no apparent cost to the symbiont. Concurrently, Symbiodinium carbon and nitrogen assimilation increased by 14 and 32%, respectively while increasing their mitotic index by 15%, whereas hosts did not gain a proportional increase in translocated photosynthates. We conclude that the disparity in benefits and costs to both partners is evidence of symbiont parasitism in the coral symbiosis and has major implications for the resilience of coral reefs under threat of global change

Long-term effects of nutrient and CO2 enrichment on the temperate coral Astrangia poculata (Ellis and Solander, 1786)

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Experimental Marine Biology and Ecology 386 (2010): 27-33, doi:10.1016/j.jembe.2010.02.007.Zooxanthellate colonies of the scleractinian coral Astrangia poculata were grown under combinations of ambient and elevated nutrients (5 μM NO3 -, 0.3 μM PO4 -3, and 2 nM Fe+2) and CO2 (~780 ppmv) treatments for a period of 6 months. Coral calcification rates, estimated from buoyant weights, were not significantly affected by moderately elevated nutrients at ambient CO2 and were negatively affected by elevated CO2 at ambient nutrient levels. However, calcification by corals reared under elevated nutrients combined with elevated CO2 was not significantly different from that of corals reared under ambient conditions, suggesting that CO2 enrichment can lead to nutrient limitation in zooxanthellate corals. A conceptual model is proposed to explain how nutrients and CO2 interact to control zooxanthellate coral calcification. Nutrient limited corals are unable to utilize an increase in dissolved inorganic carbon (DIC) as nutrients are already limiting growth, thus the effect of elevated CO2 on saturation state drives the calcification response. Under nutrient replete conditions, corals may have the ability to utilize more DIC, thus the calcification response to CO2 becomes the product of a negative effect on saturation state and a positive effect on gross carbon fixation, depending upon which dominates, the calcification response can be either positive or negative. This may help explain how the range of coral responses found in different studies of ocean acidification can be obtained.Funding for this work was provided by the Ocean Life Institute, NSF OCE-0648157, and an International Society for Reef Studies / Ocean Conservancy Fellowship. This material is based upon work supported under a National Science Foundation Graduate Research Fellowship

A multi-wavelength study of powerful high redshift radio galaxies

Philosophiae Doctor - PhDWe present a new sample of distant powerful radio galaxies, in order to study their host-galaxy properties and provide targets for future observations of Hi absorption with new radio telescopes. We cross-match the Sydney University Molonglo Sky Survey radio catalogue at 843 MHz with the VISTA Hemisphere Survey near-infrared catalogue using the Likelihood Ratio technique, producing contour plots as a way to inspect by eye a subset of bright sources to validate the automated technique. We then use the Dark Energy Survey optical and near-infrared wavelength data to obtain photometric redshifts of the radio sources. We find a total of 249 radio sources with photometric redshifts over a 148 square degree region. By fitting the optical and near-infrared photometry with spectral synthesis models, we determine the stellar masses and star-formation rates of the radio sources. We find typical stellar masses of 1011−1012 M for the powerful high-redshift radio galaxies. We also find a population of low-mass blue galaxies. We then report results from the first search for associated Hi 21 cm line absorption with the new MeerKAT radio telescope (shared-risk early science programme). We used a 16-antenna sub-array of MeerKAT to carry out a survey for Hi absorption in the host galaxies of nine powerful (L1.4 GHz > 1026 W Hz−1 ) radio galaxies at cosmological distances (z = 0.29 to 0.54). We found no evidence of absorption with 5σ optical depth detection limits. We only obtain a tentative absorption towards a radio source 3C 262 at z = 0.44 with significant ongoing star formation at a rate of 10.5 M yr−1 . The source consists of two radio lobes separated by 28.5 kpc with no evidence of a compact core. If the absorption arises from neutral gas from an extended disc, the line is redshifted by 79(21) km s−1 with respect to the nucleus and has an average Hi column density across the source of NHI ∼ 7 × 1019−20 cm−2 , which is consistent with the rate of star formation. But after further tests, we find that the Hi detection towards 3C 262 is likely to be an artefact. We conclude that the new correlator with 32 k channel resolution will be needed before searching for its associated absorption in MIGHTEE data

The effect of climate change on the farming business in Nwanedi Irrigation Scheme in Musina Local Municipality, Limpopo Province

Thesis(MBA.) -- University of Limpopo, 2018Nwanedi Irrigation Scheme (NIS) is situated at the far north of Limpopo. It is comprised of both livestock and crop farmers. Currently, the total number of farmers in the scheme is 160. Noteworthy is that the majority of farmers grow and harvest crops. The dominant crop produced in the area is jam tomato with a few of people who cultivate table tomato and other vegetables such as cabbage and eggplant (Mashala, 2013). The irrigation scheme covered an area of about 2000 hectares land, which belongs to the state and part of it belongs to the Communal Property Association (CPA). Moreover, agriculture is considered as one of the most sensitive to weather and climate variables, which include temperature, precipitation, light and weather extremes such as droughts, floods and severe storms. The aim of the study was to evaluate the impact brought about by climate change on farming business. Moreover, to evaluate the problems that were associated with climate change that affected farming, crop production and eventually the profit generation at NIS. Considering greenhouse gas emissions, it is believed that they are one of the causes of the change in global climate. Again, most food production means rely on inputs to some or all tillage, seeds, fertilisers, irrigation, feed for animals, pest and disease control. Henceforth, the study has collected primary data. The study employed both qualitative and quantitative paradigms. The 160 crop farmers, as a sample size of 32 (20% of the population) respondents, were randomly selected and interviewed. The study found out that drought was real and had been experienced in NIS. Meanwhile, in crop farming, water is more important just as a growth media such as fertilised soil. Without water, no farming activity could take place. The drought experienced had led farmers not to plant anything on their farms, which meant that no income was generated in the entire drought period. Furthermore, most of the farmers in the area had no alternative means of acquiring water to irrigate their crops. Few farmers who managed to plant had used a very small scale than usual because there was not enough water. Drought affected job loss in the farming business where many employees had to be ceased from coming to work. The study also found that NIS had experienced high temperature, which were never experienced before. Musina is best known for its excessive heat, but the recent heat wave that has been experienced in the area of the study was extreme to a point that crop farming was very difficult because the little moisture in the soil had quickly depleted. Crops could no longer absorb it as it dried up rapidly. Usually, when it is extremely hot, the condition favours pests and diseases. Later, it was found that a new pest referred to as Eelworm (Tuta Tundra), which was not found in the area before had been discovered. Consequently, the introduction of the new pests in the area was a challenge because farmers did not know which insecticides to apply in order to control the manifestation and prevent the damage it caused on the crops, tomato in particular. Eelworm has affected the tomato crop as it damaged the leaves of their plants. That had negatively affected the fruit production. Most farmers who have experienced Eelworm in their tomato fields, had their fruits severely attacked to be unusable

The physiological response of hermatypic corals to nutrient enrichment

Nutrient enrichment of tropical waters constitutes an increasing threat to the health and biodiversity of coral reefs. In order to manage these ecosystems effectively, the onset of nutrient pollution has to be closely monitored. This thesis examined the possibility of using some physiological responses of hermatypic corals as an early-warning bio-assay, to detect nutrient enrichment before reef deterioration has taken place. To this aim, the physiology of the common branching coral Porites porites and the massive coral Montastrea annularis was studied both in the laboratory and on the reef under different nutrient conditions. By measuring the organic and inorganic productivity of corals and by constructing carbon budgets, it was hoped to relate differences in the fixation, allocation and utilisation of carbon to differences in nutrient regimes. Nubbins of Porites porites and explants of Montastrea annularis were chosen as the experimental units. Nubbins were obtained by cutting coral tips (approx. 20 mm), grounding their cut surface flat, and gluing them onto a perspex tile with cyanoacrylate glue. To obtain explants, a coral head was cored under a drill press fitted with a hole saw. Cores were then cut to fit, and sealed into polyethylene cups with underwater epoxy putty. A new culturing system was developed to grow corals successfully in the laboratory under completely controlled and repeatable conditions. This system (the 'photostat') consisted of glass aquaria (30x21x18 cm) placed in a constant temperature water-bath under metal halide lamps. The aquaria were fitted with specially designed air lines and coral trays to maintain a strong water motion around the corals, independent of the rate of water-flow. A peristaltic pump ensured a daily water turn-over. A new improved carbon budget methodology was developed by comparing the well established methods of Davies (1984) and Muscatine et al (1984) on Porites porites. These methodologies differed in the measurement of zooxanthellae respiration rate (Rz) and zoozanthellae growth rate (). Rz,DAVIES was found to be twice as small as Rz,MUSCATINE (RZ, MUSCATINE (RZ, DAVIES = 18.1 gC cm-2d-1 vs. Rz,MUSCATINE = 33.1 gC cm-2d-1), but this accounted for a difference of only 3% when Rz was expressed as a percentage of the total daily carbon input. By comparison, a 25-fold difference between methods occurred in the component of carbon required for the daily growth of the zooxanthellae. Davies' method measured the net rate of zooxanthellae growth (NET) from the increase in surface area, assuming a constant zooxanthellae population density. In this case NET was only 1.65 gC cm-2d-1. (DXN008,321

A new sample of southern radio galaxies: Host-galaxy masses and star-formation rates

In this study we define a new sample of distant powerful radio galaxies in order to study their host galaxy properties and provide targets for future observations of H I absorption with new radio telescopes and to understand the fuelling and feedback from such sources. We have cross-matched the Sydney University Molonglo Sky Survey (SUMSS) radio catalogue at 843 MHz with the VISTA Hemisphere Survey (VHS) near-infrared catalogue using the likelihood ratio technique. Photometric redshifts from the Dark Energy Survey are then used to assign redshifts to the radio source counterparts. We found a total of 249 radio sources with photometric redshifts over a 148 deg2 region. By fitting the optical and near-infrared photometry with spectral synthesis models we determine the stellar mass and star formation rates of the radio sources, finding typical stellar masses of 1011–1012 M⊙ for the powerful high-redshift radio galaxies