SUNScholar - Browsing by browse.metadata.type "Thesis"

Browsing by browse.metadata.type "Thesis"

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1.3 Ghz Kamlyn banddeurlaatfilter
(Stellenbosch : Stellenbosch University, 1990) Le Roux, S. J.(Stefanus Johannes); Stellenbosch University. Faculty of . Dept. of .
A 10 GHz oversampling delta modulating analogue-to-digital converter implemented with hybrid superconducting digital logic
(Stellenbosch : Stellenbosch University, 2001-03) Fourie, Coenrad Johann; Perold, W. J.; De Swardt, J. B.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
ENGLISH ABSTRACT: Rapid Single Flux Quantum (RSFQ) logic cells are discussed, and new cells developed. The expected yield of every cell is computed through a Monte Carlo analysis, and where necessary these cells are optimized for use in a complex system. A mathematical study of the Josephson junction and SQUIDs (Superconducting Quantum Interference devices) as switching elements precede a discussion on the operation of RSFQ and COSL (Complementary Output Switching Logic.) These logic families are implemented in low temperature niobium technology, and require liquid helium cooling. A 10 GHz oversampling delta modulating analogue-to-digital converter is then designed and constructed using RSFQ and COSL building blocks in a hybrid configuration. The design emphasis is on devising ways to test the operation of RSFQ with limited equipment. Yield analysis procedures on the complex system are discussed, followed by a detailed discussion on the circuit layout and layout problems. Software routines are developed to calculate the required dimensions of layout structures.
10 kW L-Band planar power combiner
(Stellenbosch : University of Stellenbosch, 2006-12) Fourie, Gerhardus Johannes; Van Niekerk, C.; Van der Walt, P. W.; University of Stellenbosch. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
This thesis relates to the design and characterization of a 10 kW L-band power combiner consisting of 8 input ports. The design is implemented in a non-radial planar transmission line architecture and operates between 1.2 and 1.4 GHz. Because of the ultra high power requirements for the combiner, special attention is given to the power handling capabilities of the transmission lines and the other components involved. Simulated S-parameter models of connector to stripline transitions and a one to four-way junction, as well as measured S-parameter models of high power terminations are incorporated in the final design. A 10 kW combiner was built and measured at low power only due to time constraints and the limited availability of high power sources. Satisfactory results were obtained in terms of the graceful degradation of unit amplifiers, port mismatches and power combining efficiency.
A 195Pt Nuclear magnetic resonance and molecular dynamics computer simulation study of the solvation of simple platinum (IV) chlorido complex anions in water and water-miscible solvent mixtures
(2017-03) Engelbrecht, Leon de Villiers; Koch, Klaus R.; Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science.
ENGLISH ABSTRACT: A combined 195Pt NMR spectroscopy and Molecular Dynamics (MD) computer simulation study of the solvation of the octahedral Pt(IV) complex [PtCl6]2‒ in binary mixtures of water and the fully water-miscible organic solvents methanol, 2-methoxyethanol and 1,2-dimethoxyethane has been carried out. A recent 195Pt NMR chemical shift-trends study indicated a preferential solvation of the aforementioned platinum complex by the organic solvent component in such solvent mixtures. The solvent dependence of the intrinsic 1Δ195Pt(37/35Cl) NMR isotope shifts of [PtCl6]2‒ in pure solvents indicate a slight increase in magnitude ~7 ppb in the order water < methanol < 2-methoxyethanol < 1,2-dimethoxyethane. In selected equimolar binary mixtures of water and organic solvents, 1Δ195Pt(37/35Cl) is found to be similar in magnitude to that in the pure organic solvents, supporting the proposed preferential solvation of the platinum complex. 195Pt NMR T1 spin relaxation times and pulsed gradient spin echo (PGSE) translational diffusion measurements were performed for [PtCl6]2‒ in selected solvents and binary mixtures. The results were interpreted in the context of hydrodynamic continuum models of molecular diffusion; while these were found to be not strictly appropriate, the rotational and translational dynamics results appear to be notionally consistent with the preferential solvation phenomenon as indicated. A series of classical MD computer simulations were performed for [PtCl6]2‒ in these equimolar binary solvent mixtures, using a recently revised force field developed by Naidoo et al. The results using the standard force field indicate a strong preference for water in the primary solvation shell region of the complex in all solvent mixtures studied. A similar result is obtained for [PtCl4]2‒ in an equimolar water‒methanol mixture. Simulations were repeated with ionic charges scaled according to the recently developed Molecular Dynamics in Electronic Continuum (MDEC) theory, which is intended to account for the dielectric screening of charges in condensed phases. In these MDEC simulations, a significant reduction in the contribution of water to the primary solvation shells of both complexes is observed; this is particularly evident in the solvation shell of [PtCl6]2‒ in mixtures of water with 2-methoxyethanol and 1,2-dimethoxyethane, for which a strong preferential solvation by the organic components has been indicated. Dynamic properties were also computed from MD trajectories, and are qualitatively consistent with experimental trends, but deviate due to the solvent model combination. Finally, an interpretation of the fascinating 35/37Cl and 16/18O isotope-induced fine structure in the 195Pt NMR spectra of complexes of the type [PtCln(OH)6‒n]2‒, n = 0‒5, is presented, based on the expected trans-influence series of ligands for Pt(IV) OH‒ > Cl‒ > H2O in aqueous solution.
Die 2 1/2 eeu van Genadendal : 'n kultuurhistoriese ondersoek
(Stellenbosch : Stellenbosch University, 1986) Balie, Isaac Henry Theodore,1948-; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Afrikaans and Dutch.
No Abstract Available
2-D and 3-D proximal remote sensing for yield estimation in a Shiraz vineyard
(Stellenbosch : Stellenbosch University, 2020-03) Hacking, Christopher James; Poblete-Echeverria, Carlos; Poona, Nitesh; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Geography and Environmental Studies.
ENGLISH ABSTRACT: Precision viticulture aims to minimise production input expenses through the efficient management of vineyards, yielding the desired quantity and quality, while reducing the environmental footprint associated with modern farming. Precision viticulture practices aim to manage the inherent spatial variability in vineyards. Estimating vineyard yield provides insight into this process, enabling informed managerial decisions regarding production inputs. At the same time, yield information is important to the winery, as it facilitates logistical planning for harvest. Traditional yield estimation methods are destructive by nature and require in-situ sampling, which is labour-intensive and time-consuming. Proximal remote sensing (PRS) presents a suitable alternative for estimating yielding a non-destructive manner. PRS employs terrestrial proximal sensors for data acquisition that can be combined with computer vision (CV) techniques to process and analyse the data, generating the estimated yield for the vineyard. This research intends to investigate 2-dimensional (2-D) and 3-dimensional (3-D) PRS and related CV techniques for estimating yield in a vertically shoot position (VSP) trellised Shiraz vineyard. This research is presented as two components. The first component evaluates 2-D and 3-D methodologies for estimating yielding a vineyard. Three experiments are presented at bunch-and plant-level, incorporating both laboratory and in-situ experimental conditions. Under laboratory conditions (bunch-level only), the 2-D methodology achieved an r2 of 0.889, while the 3-D methodology achieved a higher r2 of 0.950. Both methodologies demonstrate the potential of PRS and associated CV techniques for estimating yield. The in-situ plant-level results favoured the 2-D methodology (fullcanopy (FC): r2= 0.779; leaf removal (LR): r2= 0.877) over the 3-D methodology (FC: r2= 0.487; LR: r2= 0.623). The general performance of the 2-D methodology was superior, and thus implemented in the subsequent component. The two set out to determine the ideal phenological stage for estimating yield. The 2-D methodology was employed with slight improvements and multitemporal digital imagery were acquired on a weekly basis for 12 weeks; culminating in a final acquisition two days prior to harvest. This component also successfully implemented image segmentation using an unsupervised k-means clustering (KMC) technique, an improvement to the colour thresholding (CT) technique implemented in component one. The ideal phenological stage was approximately two weeks prior to harvest (final stages of berry ripening), which achieved a global (bunch-level: 50 bunches) r2of 0.790 for estimating yield. This research successfully implements 2-D and 3-D PRS and CV techniques for estimating yield in a Shiraz vineyard, and thereby accomplishes the aim of this research. The research demonstrates the suitability of the methodologies–specifically the 2-D methodology, which demonstrated superior performance (simple data acquisition and analysis with competitive results). Future research could refine the presented methodologies for operational use.
The 2003 Cricket World Cup : implications for identity formation and democratization prospects for Zimbabwe
(Stellenbosch : Stellenbosch University, 2004-03) Van der Merwe, Justin Daniel Sean; Van der Westhuizen, Janis; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Political Science.
ENGLISH ABSTRACT: There can be little doubt about the ability of major international sporting events to capture the aspirations and hopes of nations. These events have an uncanny ability of seemingly effortlessly doing what a hundred speeches and mass rallies by politicians could only hope to achieve. Therefore, it is no surprise that they are commonly understood to be able to bring nations and people together and provide a focus for national identity and unity. The 1995 Rugby World Cup in South Africa is an obvious proponent of such a claim, whereby South Africa was emerging from a long and arduous political transition and needed something more than going to the polling booths to unite the nation. Major international sporting events are also said to be able to provide a catalyst or incentive for democratization and human rights enhancement in authoritarian or semi-authoritarian regimes. The 1988 Olympics in South Korea is a landmark of such claims whereby the South Korean government was said to bow to the democratizing pressures exerted on it due to its hosting of the event. Many have argued that China’s hosting of the Olympics in 2008 will have a similar effect. However, equally potent, major international sporting events can have various unintended consequences in terms of identity formation, democratization prospects and human rights for the host nations. An analysis of South Africa and Zimbabwe’s co-hosting of the 2003 Cricket World Cup demonstrates this point. The outcomes of the study suggest that whilst it is normally the intention for the host nations to use the games to bring nations and people together, the Cricket World Cup opened up a rift between races, both within the race contours of the cricket playing Commonwealth world and within South Africa's domestic politics. It was also established that much like the 1995 Rugby World Cup had sought to reconcile blacks and whites domestically under the “Rainbow Nation” during Mandela's presidency, the 2003 Cricket World Cup, with its more regional focus and under Mbeki’s presidency, presented an excellent opportunity for transnational reconciliation between Africa and the Anglo-Saxon world. However, the 2003 Cricket World Cup, as a project in racial reconciliation, was essentially a failure. This was predominantly due to the choice by South Africa of Zimbabwe as co-host and due to the shift of South Africa's national identity from that of the “Rainbow Nation” under Mandela, to that of “Africanism” under Mbeki. President Mbeki’s drive towards “Africanism” proved divisive both transnationally and domestically. Symbolically, the Cricket World Cup, when compared with the 1995 Rugby World Cup, had served to highlight the decline of the “Rainbow Nation”. Zimbabwe's co-hosting of the event had served to further entrench the authoritarian regime. Instead of the regime opening up due to its co-hosting of the event, a broad clampdown on civil and political liberties was experienced. The Zimbabwean government felt the need to tighten its grip during the lead up to the event and throughout the tournament itself. The aim was to project a sanitized view of Zimbabwe to the rest of the world. Thus, the event presented an opportunity for the government to shore up its credibility and produce political propaganda. South Africa’s stance of “quiet diplomacy” also indirectly helped to further entrench the regime through the World Cup. Zimbabwe's co-hosting also impacted negatively on the opposition, the MDC. In addition to this, the various pressures which major events are said to exert on a host nation to reform politically and which result from boycott campaigns, pressure from the media, stimulation of civil society and protests, were not very effective in enhancing democratization prospects and human rights in Zimbabwe. This study reaches the overall conclusion that the claims that major events bring nations and people together and provide a catalyst or incentive for democratization and human rights enhancement in authoritarian regimes, need further revision. South Africa and Zimbabwe's co-hosting of the event did indeed have unintended consequences. Policy implications are also assessed. Future areas for research are also identified.
2015-12-31 Effective public leadership to drive organisational change in the public health sector in order to improve service delivery : the case of the Western Cape Department of Health
(Stellenbosch : Stellenbosch University, 2015-04) Isaacs, Rafeeqah; Schwella, Lyzette; Stellenbosch University. Faculty of Economic and Management Sciences. School of Public Leadership.
ENGLISH ABSTRACT: The goal of this research was to investigate effective leadership that drives organisational change in the public health sector to meet the changing environmental needs to improve service delivery within the Western Cape Department of Health. Organisational change in the public health sector must lead to improved public health service delivery. The role of leadership is to deal with incompetent personnel as they are the cause of problems regarding inadequate service delivery. Leadership must contribute to the main areas where competency development needs to take place. Healthcare 2030 requires transformational leadership from the ranks of managers and clinicians for collective and distributed leadership across all levels of organisations. The research methodology used in this study was a combination of qualitative and quantitative research methodologies. The methodology included an empirical investigation in the form of a literature review and a preliminary semi-structured interview as well as a nonempirical investigation. The empirical investigation was conducted by using semi-structured interviews as well as a survey questionnaire which was designed to gather information focussing on leader personality traits, task-related traits and understanding the organisation. This study specifically focussed on effective public leadership to drive organisational change in the health sector and to improve service delivery. The results provide support for a cohesive trait-behavioural model of leadership effectiveness. In general, leadership traits associated with task competence are related to task-oriented leadership behaviours, which improve performance-related leadership outcomes. Effective leadership in the public health sector that drives organisational change is based on the general personality traits of a leader, task-related traits and understanding the organisation. These are the elements that are important for effective public leadership to improve service delivery.
2020-12-11 Global transcriptomic investigation of the human macrophage response towards pathogenic/non-pathogenic mycobacteria
(Stellenbosch : Stellenbosch University, 2019-12) Mishra, Abhilasha Madhvi; Baker, Bienyameen; Leisching, Gina; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences: Molecular Biology and Human Genetics
Background:Tuberculosis (TB) is a major cause of infection-related mortalityworldwide. In 2017 an estimated 1.3 million people who were HIV-negative died of TB. An estimated 5-10% of infected individual develop active TB during their lifetime, while the remaining90% (of infected population) successfully control the bacteria. Also, some of the close household contacts of TB patients remain uninfected and healthy. Studying host immune response towards Mycobacterium tuberculosis(M. tb) can unfold the reason behind this enigma. Methods:We conducted a detailed investigation of in vitrohost response from human monocyte derived macrophages(hMDMs)towards different strains of mycobacteria(grown in detergent-freemedia), i.e. pathogenic (M. tbR179) andnon-pathogenic (M. smegmatisand M. bovisBCG). The host response was measured post-infection (at mRNA and protein levels) using AmpliSeq, quantitative real time polymerase chain reaction (qRT-PCR), multiplex ELISA (Luminex), intracellular mycobacterial survivaland cytotoxicity assay. Biological network analysis (ingenuity pathway analysis IPA) was performed to understand the gene regulatory networkinvolved in the pathophysiology associated with the host-immune system.Based on false discovery rate (FDR) and biological functions, we selected an inter-related gene family of interferon induced protein with tetratricopeptides (IFIT1, IFIT2 andIFIT3) from the list of 19 potential differentially expressed genes(DEGs)for knock-up (vector-based over-expression)/down experiments. This gene family is known to form a protein complex during viral infection to act against the antigen. Studyencompassing their role against bacteria is not well established.Therefore, we performed knocking-up of IFITsvia vector-based transfection and knocking-down via small interferingRNA (siRNA) approach to investigate their effect upon mycobacteria inside the host macrophages. Results:AmpliSeqanalysis found 19 DEGs at 12 hours post-infection across all three strains. We observed lower number of mycobacterial CFUs and higher host response (at both RNA and protein level) in hMDMs infected with M. smegmatisas compared to other two strains. Biological network analysis revealed interferon-interleukin associated signalling pathways as most prominent among the 19 differentially expressed genes.We found a differed host response towardsall three strains, which mayattributeto their pathogenicity. Messenger RNA and protein level comparisons at different time points, depicted strong role of interferon and interleukin associated gene network. This network was able to successfully counter M. smegmatisbut succumb to M. bovisBCG andM. tbR179. Most importantly, across all three strains, intra-cellular bacterial growth and survival measured through colony forming units (CFUs)decreased significantly upon knocking up of IFITs(IFIT1, IFIT2 andIFIT3),while we recordedan increase in CFUs upon knocking down ofIFITsin the host macrophages. Using multiplex ELISA, we found higher expression of key pro-inflammatory cytokines (i.e. IDO1, IFN-γ, IL-6, and IL-23) during knock-up (vector-based over-expression)of IFITsresulting in reduction of mycobacteria. Conclusion:Differentially expressed IFITs showed a strong effect against mycobacteria, which can be used as a promising therapeutic targetadjunct to anti-TB therapy. This knowledge will broaden the scope of host drug targets for resistance free bacteriostatic immuno-therapy.
2020-12-31 The role of student feedback in university teaching at a research-led university
(Stellenbosch : Stellenbosch University, 2016-12) Petersen, Melanie; Bitzer, Eli; Stellenbosch University. Faculty of Education. Dept. Educational Psychology
ENGLISH ABSTRACT : Student feedback is widely accepted as a useful source of information about the quality of teaching and as a potential professional learning tool to enhance university teachers’ teaching. A review of the literature, however, revealed a shortage of systematic research about how student feedback influences university teachers’ teaching practices. A similar gap in knowledge was identified at Stellenbosch University. Preliminary studies at this institution indicated dissonance between university teachers’ perceptions of the potential value of student feedback and how they actually made use of student feedback in their teaching. In researchled university contexts, teaching is often perceived to have lower status than research. This study therefore set out to explore how university teachers at this particular research-led institution experienced the role of student feedback in their teaching. A case-study research design was followed, with the potential relationship between student feedback and university teaching practice at a research-led university constituting the unit of analysis. Qualitative data was generated by way of semistructured interviews with 16 purposely selected university teachers. Institutional policies relating to student feedback, teaching and learning and human resource management were also included as secondary sources of data to ascertain how university teachers’ experiences of student feedback related to institutional policy directives. Activity theory was used as analytical framework to interrogate the data. The findings of the study indicate that the research-led context at Stellenbosch University plays a significant role in how university teachers experience and respond to student feedback. The perceptions of research being more valued than teaching in terms of recognition and rewards, limits the optimal use of student feedback for the purpose of improving teaching. Raising the stature of teaching would thus be a necessary requirement for promoting the use of student feedback to improve teaching. Furthermore, the potential role of student feedback in university teaching practice at Stellenbosch is influenced by other subsystems, in particular the performance appraisal system. A concerted effort should be made at institutional level to come to a common understanding of what good teaching is considered to be. In the absence of such a common understanding, the growing culture of performativity has led to student feedback being reduced to a mere quantitative measure of the quality of teaching in many cases. Since mid-level university management carries the biggest responsibility for managing the performance appraisal processes in academic departments, they also exert a significant influence on how university teachers would use student feedback for professional learning and the enhancement of their teaching. The diverse practices followed by mid-level managers in the various academic departments represented in this study further pointed to the possible need for a guiding framework to support an ethics of practice approach to the use of student feedback. Based on its findings, this study is considered to have made a contribution to the body of knowledge regarding the contextual and relational nature of student feedback, particularly within a research-led university context.
A 22.2 GHz Antenna for water vapour radiometry
(Stellenbosch : Stellenbosch University, 2019-04) Cerfonteyn, William; De Villiers, D. I. L.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
ENGLISH ABSTRACT: For this thesis a low-cost antenna solution for a low-cost water vapour radiometry system is designed. The most important specifications for the antenna is that it has to have a -20 dB sidelobe level, a 3° -3 dB beamwidth and have to be electronically steerable. It also has to be low-cost. The first design that is considered is the phased array solution as it can be electronically steered. Since components can be etched onto the design the manufacturing cost is also reduced. The number of elements required for this design to reach the specifications is determined to be more than 16x16 elements, and thus proves to be cost impractical. The analysis is tested by designing a 1x4 and 2x2 multilayered aperture coupled patch antenna array with a corporate feed network, to both test if a better antenna element design can improve the results, and if the analysis is accurate in determining the impracticality of an array design. This also proves that the array design is infeasible. A reflector solution is then considered. The reflector system is designed to statically observe in a few specified directions, removing the need for electronic steering. Two parabolic reflectors and a conical horn is designed. The reflectors are combined through interpolation into one larger reflector. After the horn design proves to be ineffective, a new horn is considered that almost allows the reflector system to meet the specifications. Finally the system is measured, but unfortunately the measured result proves that the physical system does not meet all the specifications. The sidelobe level is around -16 dB, however, the -3 dB beamwidth is well below 3°.
2D Edge-based finite elements for guided and scattered wave problems
(Stellenbosch : Stellenbosch University, 1999-03) Hansmann, Riana Helena; Davidson, D. B.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
ENGLISH ABSTRACT: This thesis may be divided into two parts: the first describes the Finite Element Method (FEM) and its application to guided wave problems. The second part is devoted to scattering configurations, specifically the use of the Boundary Element Method (BEM) and the hybrid Finite Element Method-Boundary Element Method (FEM-BEM) to obtain solutions for scattering problems. The formulations are restricted to two dimensions throughout the thesis. A variational formulation is introduced and the implementation of boundary conditions is described. The use of vector approximation functions for the Finite Element Method is explained and the advantages highlighted. The properties of these functions are derived and graphical representations are given. A comparison between a lower order and higher order approximation is made. This is applied to problems which demonstrate the capabilities of the Finite Element Method such as ridged waveguides and circular waveguides containing eccentric dielectric rods. Results obtained compare well to analytic solutions, in the cases where these are available. An integral equation for scattering problems is derived. This relates the tangential field components on a contour enclosing a scattering object to the scattered fields and enables a solution to be obtained when the tangential components on the contour are known. It is shown how the interior region enclosed by the contour is discretised and how the Finite Element Method can be coupled with the Boundary Element Method by imposing continuity conditions on the enclosing contour. The resulting system of equations obtained may be solved. Solutions for scattering from perfectly conducting cylinders are obtained and compare well to analytic results.
2D irregular strip packing at Kohler signs
(Stellenbosch : Stellenbosch University, 2014-12) Bossenger, Wayne; Nieuwoudt, Isabelle; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Economics.
ENGLISH ABSTRACT: Kohler Signs (PTY) Ltd is a sign production company located in Cape Town, South Africa. They manufacture and install signs for the City of Cape Town and private companies as well as manufacture advertisement signs to be placed on vehicles. Road signs consist of steel sheets that are cut and bent to the appropriate size and frame, and an image design, which is cut from re ective vinyl, are applied to the bent steel sheet. The image design consists of various letters, numbers and symbols which are categorised as irregular items. When these irregular items are combined in a distinctive way, with the use of di erent coloured vinyl, they convey a message to the road user which may be to yield for pedestrians crossing the street, or indicate to the road user the various highway exits that exist on the interchange ahead. These irregular items are placed upon re ective vinyl for cutting which results in vinyl o cuts that are wasted. The focus of this thesis is to minimise the waste incurred by placing these irregular items upon the vinyl in an optimal and timely manner for industry use. The vinyl printer, which cuts the irregular items out of the vinyl, consists of a xed width and is only limited in height by the vinyl itself. Thus, this problem may be described as a Two Dimensional Irregular Strip Packing Problem. These irregular items have only a few possible heights for each type of irregular item packed, which allows these irregular items to be packed as a level packing problem. The items are packed within levels as though they are regular items with the assistance of a prede ned rule-set. In this thesis various packing algorithms and image processing methodologies from the literature are researched and used to develop a new packing algorithm for this speci c problem. The newly developed algorithm is put through various benchmarks to test its performance. Some of these benchmarks are procured from Kohler Signs themselves, whereas others are randomly generated under certain conditions. These benchmarks reveal that the newly developed algorithm performs better for both the minimisation of waste and the minimisation of algorithm running time than the tried and trusted techniques utilised in industry by Kohler Signs.
2D Modelling of turbulant transport of cohesive sediments in shallow reservoirs
(Stellenbosch : University of Stellenbosch, 2006-12) De Villiers, J. W. L.; Basson, G. R.; University of Stellenbosch. Faculty of Engineering. Dept. of Civil Engineering.
Modelling of the transport of fine cohesive sediments, as found in most South African reservoirs, has not been well developed. This is because the transport processes that are involved are complex and the theories not as implicit as the traditional equilibrium transport theories for coarse non-cohesive sediment. Advection and dispersion are found to be the processes that best describe the transport of fine sediments in turbulent flow conditions. A two-dimensional modelling tool, MIKE 21C, which simulates reservoir hydrodynamics and cohesive sediment transport processes with an advection-dispersion model, was evaluated in this thesis. The creation of such a numerical model involves the setting up of a suitable curvilinear grid and requires data on the bathymetry, recorded inflows as well as water levels. It also requires sediment characteristic parameters and transport parameters. These parameters have to be specified by the user based on previous studies and field measurement data. MIKE 21C was applied to laboratory flume tests and reservoir case studies in the field in order to determine the effects that these parameters have on the sediment transport in a series of sensitivity studies. Ranges were determined within which these parameter values should fall. A procedure was also developed through which reservoir sedimentation models can be calibrated.
A 3-axis attitude control system hardware design for a CubeSat
(Stellenbosch : Stellenbosch University, 2014-12) Gerber, Jako; Steyn, W. H.; Stellenbosch University. Faculty of Engineering. Department of Electrical and Electronic Engineering.
ENGLISH ABSTRACT: With CubeSats becoming popular as a cheap alternative to larger satellites, the need for advanced miniature attitude determination and control systems (ADCS) arises to meet the pointing requirements of satellite operations such as earth imaging and orbit maintenance. This thesis describes the design of a complete ADCS for use on CubeSats. A previously designed CubeSat on-board-computer, CubeComputer, and ne sun and nadir sensor, CubeSense, is incorporated in the design. The remaining requirements with regard to sensors and actuators were met by CubeControl, an additional module, the design, manufacturing and testing of which are described. CubeControl can implement magnetic control with the use of a magnetometer and three magnetorquers. It is also capable of driving three reaction wheels for accurate active 3-axis stabilization.
3-Axis geomagnetic magnetometer system design using superconducting quantum interference devices
(Stellenbosch : Stellenbosch University, 2014-04) Kilian, Anton Theo; Fourie, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
ENGLISH ABSTRACT: This work discusses the design of a 3-axis Geomagnetometer SQUID System (GSS), in which HTS SQUIDs are used unshielded. The initial GSS installed at SANSA was fully operable, however the LN2 evaporation rate and SQUID orientation required improving. Magnetic shields were also developed in case the SQUIDs would not operate unshielded and to test the system noise with geomagnetic variations removed. To enable removing the double layer shield from the probes while the SQUIDs remain submerged in LN2, the shield was designed to disassemble. The shields proved to be effective, however due to icing the shields could not be removed without removing the SQUIDs from the LN2.
3-D face recognition
(Stellenbosch : Stellenbosch University, 1999-12) Eriksson, Anders; Weber, D.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical & Electronic Engineering.
ENGLISH ABSTRACT: In recent years face recognition has been a focus of intensive research but has still not achieved its full potential, mainly due to the limited abilities of existing systems to cope with varying pose and illumination. The most popular techniques to overcome this problem are the use of 3-D models or stereo information as this provides a system with the necessary information about the human face to ensure good recognition performance on faces with largely varying poses. In this thesis we present a novel approach to view-invariant face recognition that utilizes stereo information extracted from calibrated stereo image pairs. The method is invariant of scaling, rotation and variations in illumination. For each of the training image pairs a number of facial feature points are located in both images using Gabor wavelets. From this, along with the camera calibration information, a sparse 3-D mesh of the face can be constructed. This mesh is then stored along with the Gabor wavelet coefficients at each feature point, resulting in a model that contains both the geometric information of the face as well as its texture, described by the wavelet coefficients. The recognition is then conducted by filtering the test image pair with a Gabor filter bank, projecting the stored models feature points onto the image pairs and comparing the Gabor coefficients from the filtered image pairs with the ones stored in the model. The fit is optimised by rotating and translating the 3-D mesh. With this method reliable recognition results were obtained on a database with large variations in pose and illumination.
31 Eskader en 34 Eskader Suid-Afrikaanse Lugmag se aandeel aan die Warskou-operasies gedurende Augustus en September 1944 : 'n histories-analitiese beskrywing
(Stellenbosch : Stellenbosch University, 1985) Möller, Pieter Lodewikus; Stellenbosch University. Faculty of . Dept. of .
36 Chlorine isotope systematics in saline groundwater in the Buffels River Valley
(Stellenbosch : Stellenbosch University, 2018-03) Van Gend, Jani; Miller, Jodie A.; Clarke, Catherine E.; Stellenbosch University. Faculty of Science. Dept. of Earth Sciences.
ENGLISH ABSTRACT: It is typical for coastal aquifers in arid regions to be affected by salinisation, populations in these areas that rely upon groundwater resources are often directly afflicted by this phenomenon. Large parts of the western coast of South Africa are affected by variably saline groundwater as a result of varying degrees of salinisation, primarily driven by evaporative processes. Initial stable δ2H and δ18O isotopic investigations suggest rainfall and groundwaters carry evaporative signatures, further investigation has suggested that there are other significant salt contributors in the region, although these sources and pathways are poorly constrained. One such alternate salt source may arise from paleo-termite mounds, called heuweltjies, that are found in areas along the west coast. These structures typically consist of salt- and nutrient-rich sediments and the recorded sediment EC values for these structures are an order of magnitude higher than that of the adjacent interheuweltjies. Furthermore, sediment EC values of heuweltjies increase with depth and the difference between deep and shallow EC values in heuweltjies are between 1000 and 3000 μS/cm, with the deeper samples having the higher EC value. The possibility of heuweltjie salts entering the groundwater system and contributing to groundwater salinisation in this area has not been investigated as yet. The town of Buffels Rivier in the western region of the Northern Cape has limited surface water resources and is dependent on local groundwater for subsistence. For this reason, it is an ideal site to investigate these atypical salinisation drivers. In order to effectively isolate the additional salt sources, several geochemical, isotopic and geophysical methods were implemented. Highly variable soil and groundwater EC values were observed in the field area. Furthermore, 36Cl isotope ratios together with noble gas data provides some evidence that aquifer mixing occurs. This is further evidenced by the spatial discontinuity in groundwater 87Sr/86Sr ratios. The geology of this area consist of basement granite gneisses and the contribution of rock salt to the groundwater cannot be excluded. 87Sr/86Sr ratios in groundwater in the Buffels River Valley are elevated, ranging between 0.73030 and 0.78240, which is typically associated with the water-rock interaction granitic rocks. The extent of the salt contribution from the various systems in the Buffels River Valley is still not fully understood but it is evident that conventional, semi-arid salinisation through evaporation is not the only driver in this regional system.
3D concrete printing technology: enhancing productivity in the South African construction industry – exploring the benefits, barriers, and improvement strategies
(Stellenbosch : Stellenbosch University, 2023-11) Mogale, Setekoane Phillemon ; Van Zijl, Gideon P. A. G.; Van Rooyen, Algurnon Steve Tata ; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: Provided its multitude of benefits, 3D Concrete Printing (3DCP) technology has the potential to transform the South African construction industry, with specific reference to the building sector, by revolutionizing the current traditional construction techniques. However, to fully realize the full potential of this innovative technology, it is of utmost importance to have a comprehensive awareness of its benefits, an understanding of the potential barriers associated with its adoption, and strategic measures tailored to smoothly integrate it into the construction industry. Therefore, this research study aims to comprehensively explore the benefits, barriers, and strategic measures associated with the adoption and implementation of 3DCP technology within the South African construction industry. The research process began by conducting a comprehensive literature study, which delved deep into assessing the current state of 3DCP technology and its application in the construction industry. To fully comprehend the complex dynamics of this technology, a strong foundation was established through the literature study by synthesizing and consolidating information and conceptual frameworks. This assessment process provided insights into the unique potential opportunities and challenges that could be faced by the South African construction industry as it navigates its way into adopting and implementing 3DCP technology as one of the mainstream construction techniques. In addition to this, a survey questionnaire was distributed to various professionals working in the South African construction industry to collect detailed primary data. The survey questionnaire was well designed to probe their perceptions regarding this technology within the South African construction industry given its unique context. The collected data was subjected to a thorough and systematic analysis by applying both descriptive and inferential statistical techniques to determine how the industry perceives the benefits, barriers, and improvement strategies associated with the adoption of 3DCP technology. This systematic analysis yielded a wealth of information that highlighted common trends and main themes that shape the landscape of 3DCP technology adoption within the South African construction industry. The findings of this research highlighted that the South African construction industry is fraught with substantial barriers despite being ripe and well-positioned to embrace the transformative potential of 3DCP technology. The high initial investment was consistently highlighted as the most prevalent barrier, followed by the absence of 3DCP technology experts and the lack of government incentives and support. However, the strategic measures formulated to mitigate these barriers were highly appraised by the professionals, further highlighting the readiness of the industry to leverage this innovative construction technology. Ultimately, these research findings have implications that go beyond mere academic research as they are of significant value for stakeholders with a vested interest in the adoption and successful implementation of 3DCP technology in the South African construction industry. The research study promotes the application of sustainable and efficient innovative construction techniques, tailored to enhance productivity, and encourage environmentally friendly practices, thereby guiding the industry towards a future driven by innovation, competitiveness, and steady growth.

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