Is commercial livestock farming environmentally viable within the Orange and Fish River catchment area (OFCA) of Southern Namibia?

Includes bibliographical references.There are neither historical nor current baseline information relating to the productivity of the OFCA veld and a definite link between the current crisis and the possibly that it is suffering from the effects of having farmed the OFCA veld into a state of durable suboptimal productivity remains to be conclusively established. This current study has been undertaken in order to investigate such a possible link, and to reach a more definite conclusion with regards to the contribution of negative environmental feedback which may have arisen from commercial farming. Specifically, the study investigates the relationship between commercial livestock grazing regimes, possible associated resource degradation (losses in veld productivity and adverse structuring of botanical communities due to livestock grazing effects), and the current productive crisis within the sector

The use of stereolithography and related technologies to produce short run tooling

ThesisWhere material properties are critical to a polymer part, rapid prototype (RP) models are inappropriate for evaluation purposes and actual parts moulded in a range of materials are required for evaluation. Conventional tool making processes have extremely long lead times considering that numerous iterations may be required. The aim of this project was to generate polymer parts, utilising various approaches to Rapid Tooling (RT) , including Stereolithography or related technologies, as part of the process. The objective was to establish decision-making criteria for deciding on the appropriateness of various processes and the risks involved to assist prospective users of these technologies. The first phase of the project focused on the process validation of utilising Stereolithography as a direct means to generate injection mould tooling inserts, which were fitted into an injection mould designed for the trial purposes. The objective was to obtain process information with regard to insert generation for Stereolithography. A three dimensional model of the part was generated with CAD and the associated mould was generated around the part. The insert halves were processed and solid epoxy inserts were generated with the 3D Systems SLA500 Stereolithography machine. These inserts were post-finished and fitted to the injection mould . Additional features were added to the inserts to test cooling and gating and wear resistance of the cavity material. The author attended the basic injection tool setting course of the Plastics Federation to enable him to contribute more directly to this process. This also highlighted some of the design issues to facilitate ease of production . Initial difficulties were experienced in finding optimal process parameters. A total of 70 parts were produced, with measurable insert degradation. During the author's training at 3D Systems in the USA, he obtained additional insight in current methods of insert modelling and insert generation. If these process problems could be overcome, it would be possible to produce in excess of a 100 parts with one set of inserts, assuming a tolerance specification of 0.2mm. The cost of producing the inserts was approximately 50% that of conventional tooling fabrication . The time lapse between growing of the inserts and production of parts was one week compared to 6 to 8 weeks tool manufacture time with conventional methods. The second phase of the project focused on methods to enhance the cavity surface. Electroplating of inserts and inserts generated from Aluminium filled epoxy were tested , to investigate the effects that plating has on tool life, dimensional accuracy, temperature distribution, and the cost implications for these subsequent process steps. Stereolithography inserts were generated, taking into account the design considerations. Aluminium filled epoxy inserts were subsequently cast from silicone moulds drawn off the Stereolithography master patterns. Two sets of Stereolithography inserts were plated with 20 ~m of electrolytic nickel plating. One set of aluminium filled epoxy inserts were plated with electrolytic copper followed by electroless nickel. The mould sets were subjected to the same injection moulding trials using Polypropylene. The third phase of the project evaluated the use of Stereolithography investment casting masters to produce tool steel inserts, through the QuickCast process. Porosity was evident, with substantial machining required to fit the inserts. Not all the detail was retained during the casting process. Thin rib features on the part were thus lost. Due to the porosity the cooling was changed to copper tubes fitted into the rear of the tool and back-filled with aluminium epoxy. As the Stereolithography patterns were not polished the metal inserts had to be hand finished. This was a time consuming process and skill is required to obtain a good finish. A cost comparison indicated that machining aluminium inserts would be more cost effective. The tool manufacture time and eventual cost is not significantly less than conventional machining . In fact, trials with aluminium High speed CNC machining proved to be more time, finish and cost effective. This is discussed as part of the trial examples. Wax injection into AIM tooling was investigated on behalf of a client, with good results . As ceramic and polymer injection are very similar, apart from the ceramic being far more abrasive, it is the author's opinion that AIM tooling would be applicable, taking into account that fewer parts may be achieved. The KelTool process was also investigated during the author's USA visit. The licensing fees and additional equipment are extremely costly due to the Rand IDollar exchange rate. Issues related to this process are documented in this report. Clearly the deciding factors remain the quantity of parts required and the complexity of form. Each manufacturing process has a certain level of risk involved. Accumulative risk not only sets manufactured parts at risk but could jeopardise project time scales and iterations of a process have significant impact on a project budget

An evaluation of appreciative inquiry as an alternative organisation development approach

The research provides an insight into the main challenges of previous Organisation Development processes, and Appreciative Inquiry is explored to establish the value it can offer as an alternative which minimises these challenges in today’s organisations. Organisation Development originated during the early 1950s and has evolved, adapted and changed dramatically since then. Two classical Organisation Development processes, Lewin’s 3-Step model and the Action Research spiral, are described, and typical challenges of applying them in today’s organisations are outlined. To remain competitive, organisations need to identify, adjust, and adapt to changing circumstances. These changing circumstances are constant and are due to increasingly complex demands from technological, economic, managerial, and cultural needs. Appreciative Inquiry as an approach is explored as an alternative Organisation Development process: it shifts the question from ‘what is going wrong’ to ‘what is going right in the organisation’. Appreciative Inquiry consists of the Discovery, Dream, Design and Destiny stages, and searches for the best in people and their organisations. In accordance with the constructionist paradigm, the research offers conclusions through the confirmation of past practices, conversations and relationships combined with creative new methods or experimentation of a positive intended future. The One- Group Pretest-Posttest, as a design, was selected to explore the effect of the variable (the Appreciative Inquiry intervention) in relation to the pre- and post-experimental evaluation. The design consists of an initial engagement (Pretest), the influencing variable (an Appreciative Inquiry intervention) and final engagement (Posttest) with the same group. The research was supported by a mixed method approach, with qualitative data supported by quantitative data. The quantitative data provided a general understanding of how participants experienced the change interventions. The qualitative data provided the information on how respondents experienced Organisation Development before an Appreciative Inquiry intervention and their views after an Appreciative Inquiry intervention. A South African secondary school was selected as a research site. Limited research is available regarding the application of Organisation Development and especially Appreciative Inquiry as a process in schools in general, and in South African schools in particular. A survey questionnaire was the instrument for collecting the quantitative data regarding the participants’ biographical information and change process perceptions. For the collection of qualitative data, interview questionnaires were used. The findings indicate that whereas previous change processes appear to have regarded the various staff levels of the school as separate entities, during the Appreciative Inquiry approach all staff were included as being an integral part of the organisation. The main finding after completion of the Appreciative Inquiry intervention was that collectively discussing and defining issues in a positive light instead of a problem to be solved changes the perspective of participants. Through the application of the Appreciative Inquiry’s four stages, participants were invited to think in a new way by applying innovation, enhancing participation, maintaining a positive core, and providing practical solutions through provocative statements. Conclusions reached from the research are that Appreciative Inquiry is a viable alternative for minimising Organisation Development challenges in contemporary organisations. The conclusions are based on factors such as understanding the reason for change; strong leadership; defining what is a successful intervention; understanding the Appreciative Inquiry process, the value of provocative statements; and the sustainability of change

A MEMS based valveless micropump for biomedical applications

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: The valveless micropump holds great potential for the biomedical community in applications such as drug delivery systems, blood glucose monitoring and many others. It is also a critical component in many a lab-on-a-chip device, which in turn promises to improve our treatment and diagnosis capabilities for diseases such as diabetes, tuberculosis, and HIV/AIDS. The valveless micropump has attracted attention from researchers on the grounds of its simple design, easy manufacturability and sensitive fluid handling characteristics, which are all important in biomedical applications. The pump consists of a pump chamber with a diffuser and nozzle on opposing sides of the pump chamber. The flow into the diffuser and nozzle is induced by an oscillating piezoelectric disc located on top of the pump chamber. The nozzle and diffuser rectify the flow in one direction, due to different pressure loss coefficients. The design process however is complex. In this study, we investigate the characteristics of a diffuser / nozzle based micropump using detailed computational fluid dynamic (CFD) analyses. Significant parameters are derived using the Buckingham-Pi theorem. In part based on this, the respective shapes of the diffuser and of the nozzle of the micropump are selected for numerical investigation. Hence the influence of the selected parameters on the flow rate of the micropump is studied using three-dimensional transient CFD analyses. Velocity profiles from the CFD simulations are also compared to the Jeffery-Hamel solution for flow in a wedge shaped channel. Significant similarities exist between the data and the predicted Jeffery-Hamel velocity profiles near the exit of the diffuser. Three different diffuser geometries were simulated at three frequencies. The flow rate and direction of flow are shown to be highly sensitive to inlet and outlet diffuser shapes, with the absolute flow rate varying by as much as 200% for the geometrical perturbations studied. Entrance losses at both the diffuser inlet and nozzle inlet appear to dominate the flow resistance at extremely laminar flow conditions with the average Reynolds number of Reave ≈ 500.AFRIKAANSE OPSOMMING: Die kleplosemikropomp hou groot potensiaal in vir die biomediese gemeenskap in toepassings soos medisyne dosering sisteme, bloed glukose monitering en baie ander. Dit is ook ’n kritiese komponent in “lab-on-chip” sisteme, wat beloof om die behandeling en diagnose van siektes soos suikersiekte, tuberkulose enMIV/VIGS te verbeter. Die kleplose mikropomp het tot dusver die aandag van navorsers geniet as gevolg van sy eenvoudige ontwerp, maklike vervaardiging en sensitiewe vloeistof hantering. Hierdie kenmerke is krities inmenige biomediese toepassings. Die pomp bestaan uit ’n pompkamer met ’n diffusor en ’n mondstuk aan teenoorstaande kante van die pompkamer. Vloei in die diffusor en mondstuk in word geinduseer deur ’n ossillerende piëso-elektiese skyf wat bo-op die pompkamer geleë is. Weens verskillende druk verlies koëffisinëte van die diffusor en diemondstuk word die vloei in een rigting gerig. Die ontwerp-proses is egter kompleks. In hierdie studie word die eienskappe van die diffusor /mondstuk ondersoek deur gebruik temaak van gedetailleerde numeriese vloei-dinamiese analises. Belangrike parameters word afgelei deur gebruik te maak van die Buckingham-Pi teorema. Gedeeltelik gebaseer hierop word die onderskeidelike vorms van die diffusor en die mondstuk van die mikropomp geselekteer vir numeriese ondersoek. Gevlolglik word die invloed van die geselekteerde parameters op die vloei tempo van diemikropomp ondersoek deur gebruik temaak van drie-dimensionele tyd afhanklike numeriese vloei-dinamiese analises. Snelheids profiele van hierdie simulasiesword vergelykmet die Jeffrey-Hamel oplossing vir die vloei in ’n wigvormige kanaal. Daar is oorwegende ooreenkomstighede tussen hierdie data en die voorspelde Jeffrey-Hamel snelheids profiele veral by die uitgang van die diffusor. Drie verskillende diffusor vorms is by drie frekwensies gesimuleer. Daar is bewys dat die vloei tempo en vloeirigting baie sensitief is vir inlaat- en uitlaat diffusor vorms en dat die absolute vloei tempo kan varieermet soveel as 200%vir die geometriese versteuringswat ondersoek is. Inlaat verliese by beide die diffusor inlaat en die mondstuk inlaat, blyk om die vloei weerstand te domineer waar die vloei uiters laminêr ismet ’n gemiddelde Reynolds getal van Regem ≈ 50

Rehabilitate body, nature and architecture : sports rehabilitation centre Groenkloof campus

Man and nature...captured within a relational existence. Theoretically this document disputes the man-nature-relationship with the emphasis on architectural participation, in an at tempt to redefine their interdependency.Dissertation (MArch(Prof))--University of Pretoria, 2010.Architectureunrestricte

Comparative study into occupant support concepts with respect to crash response

It is argued that together with improved protection structures and energy dissipation systems, a favourable pilot position with sufficient support and restraint could reduce fatalities in aviation accidents. In this document the crash response of three different pilot positions are compared to justify the proposal of supporting a pilot in the rather unusual prone position. The normal seated and supine pilot positions have already been adopted and implemented in various aircraft. The occupant’s response to specified crash scenarios in these two positions was compared to that of a pilot in the prone position. To obtain the best prone pilot support configuration, different concepts were considered during the analysis. A dynamic event simulation program called ADAMS was used to perform the analysis and existing injury criteria and a study of common causes of aviation fatalities and human body tolerance limits were used to compare the results. Additionally, methods to improve survivability of a pilot in the prone position during likely accidents were investigated with ADAMS. Concepts for the Exulans fuselage layout and energy absorption systems were proposed and recommendations for the pilot support system were derived from the results.Dissertation (MEng (Aeronautical Engineering))--University of Pretoria, 2006.Mechanical and Aeronautical Engineeringunrestricte

MODELLING AND VALIDATION OF A TESTING TRAILER FOR ABS AND TYRE INTERACTION ON ROUGH TERRAIN

The main purpose of a vehicle anti-lock braking system (ABS) is to prevent the tyres from locking-up in order to brake efficiently whilst maintaining steering control and stability. Sport utility vehicles (SUV) are designed to drive on various roads under different driving conditions, making it challenging to identify optimal operating conditions for ABS algorithms to be implemented. This paper describes the development and modelling of a testing trailer that is designed to benefit the research of a SUV tyre operating in ABS braking modes on non-deformable rough terrain. The test trailer can be to investigate the variation of tyre contact forces and vibration characteristics influenced by ABS braking and rough terrain excitation. Undesirable fluctuations of wheel speed, normal force and braking moments make measurements more complicated and limits the performance of active safety systems. A trailer made from a Land Rover Defender chassis is used with standard ABS components and is implemented with a Bosch ABS algorithm for experimental tests. In addition to the ABS system the necessary measuring equipment such as Wheel Force Transducers (WFT), accelerometers, brake pressure transducers, GPS and vehicle speed measurement instrumentation is used. An Adams model of the trailer in co-simulation with ABS and test control in MATLAB/Simulink is created to validate the model. The centre of gravity position and inertia characteristics of the trailer are determined through experimental testing. A validated FTire tyre model, suitable for off-road conditions, is incorporated to accurately resemble the specific tyre used during tests. The validated Adams model and test trailer will enable further development of ABS algorithms including the identification of key parameters through which ABS braking can be optimised for various roads as well as optimizing interaction with semi-active suspension systems

Systemic inflammation and acute-on-chronic liver failure: too much, not enough

ACLF is a specific, but complex and multifactorial form of acute decompensation of cirrhosis and is characterized by an extraordinary dynamic natural course, rapidly evolving organ failure, and high short-term mortality. Dysbalanced immune function is central to its pathogenesis and outcome with an initial excessive systemic inflammatory response that drives organ failure and mortality. Later in its course, immuno-exhaustion/immunoparalysis prevails predisposing the patient to secondary infectious events and reescalation in end-organ dysfunction and mortality. The management of patients with ACLF is still poorly defined. However, as its pathophysiology is gradually being unravelled, potential therapeutic targets emerge that warrant further study such as restoring or substituting albumin via plasma exchange or via albumin dialysis and evaluating usefulness of TLR4 antagonists, modulators of gut dysbiosis (pre- or probiotics), and FXR-agonists