School for Science and Technology
Permanent URI for this community
Browse
Browsing School for Science and Technology by Title
Now showing 1 - 20 of 39
Results Per Page
Sort Options
- ItemAnalysis of heat transfer in Berman flow of nanofluids with Navier slip, viscous dissipation, and convective cooling(Hindawi Publishing Corporation, 2014-03-31) Makinde, O. D.; Khamis, S.; Tshehla, M. S.; Franks, O.Heat transfer characteristics of a Berman flow of water based nanofluids containing copper (Cu) and alumina (Al2O3) as nanoparticles in a porous channel with Navier slip, viscous dissipation, and convective cooling are investigated. It is assumed that the exchange of heat with the ambient surrounding takes place at the channel walls following Newtonās law of cooling. The governing partial differential equations and boundary conditions are converted into a set of nonlinear ordinary differential equations using appropriate similarity transformations. These equations are solved analytically by regular perturbation methods with series improvement technique and numerically using an efficient Runge-Kutta Fehlberg integration technique coupled with shooting scheme.The effects of the governing parameters on the dimensionless velocity, temperature, skin friction, pressure drop, and Nusselt numbers are presented graphically and discussed quantitatively.
- ItemAnalysis of thermal stability in a convecting and radiating two-step reactive slab(Hindawi, 2013) Makinde, O. D.; Tshehla, M. S.This paper investigates the combined effects of convective and radiative heat loss on thermal stability of a rectangular slab of combustible materials with internal heat generation due to a two-step exothermic chemical reaction, taking the diffusion of the reactant into account and assuming a variable (temperature dependent) preexponential factor. The nonlinear differential equation governing the transient reaction-diffusion problem is obtained and tackled numerically using a semidiscretization finite difference technique. A special type of Hermite-Pade approximants coupled with perturbation technique are employed to analyze the effects of Ā“ various embedded thermophysical parameters on the steady state problem. Important properties of the temperature field including thermal stability conditions are presented graphically and discussed quantitatively.
- ItemApplication of successive linearisation method to squeezing flow with bifurcation(Hindawi Publishing Corporation, 2014-01-02) Motsa, S. S.; Makinde, O. D.; Shateyi, S.This paper employs the computational approach known as successive linearization method (SLM) to tackle a fourth order nonlinear differential equation modelling the transient flow of an incompressible viscous fluid between two parallel plates produced by a simple wall motion. Numerical and graphical results obtained show excellent agreement with the earlier results reported in the literature. We obtain solution branches as well as a turning point in the flow field accurately. A comparison with numerical results generated using the inbuilt MATLAB boundary value solver, bvp4c, demonstrates that the SLM approach is a very efficient technique for tackling highly nonlinear differential equations of the type discussed in this paper.
- ItemAssessing public participation strategies in peopleās housing process in Wallacedene(Stellenbosch : Stellenbosch University, 2020-12) Sandile, Unathi; Theron, Francois; Stellenbosch University. Faculty of Military Science. Dept. of Science and Technology.ENGLISH ABSTRACT: Public participation is important in housing development. Since the start of democratic government in South Africa, local governments have been encouraged to promote and use public participation to empower its citizens to influence, direct, control and own their development initiatives. In this study the researcher assessed public participation strategies in Nomzabalazo Peopleās Housing Process in Wallacedene (NPHPW). The study assesses the public participation process applied and relevant strategies used in a housing development programme in the community, and to establish whether public participation in housing development in this area is practiced as local governance legislation suggests. The study also aims to establish how the selected public participation strategies used affect housing development, in particular assess if housing beneficiaries can actually āinfluence, direct, control and ownā the housing project. In addition, the study aims to establish whether the COCT creates an enabling environment for authentic and empowering public participation for housing beneficiaries on matters that affect their lives. Furthermore, the study evaluates public participation by the members of the public particularly beneficiaries in housing development by assessing the public participation strategies used during the housing planning and delivery in Wallacedene, using the International Association for Public Participation (AIP2) Spectrum model and Arnsteinās (1969) ladder typologies.
- ItemThe background radiation and exposure levels at various South African west coast military units(Stellenbosch University. Faculty of Military Science (Military Academy), 2014) Bezuidenhout, JacquesThe West Coast of South Africa between St Helena Bay to the north and Langebaan Lagoon to the south is characterised by numerous granite protrusions. These outcrops are elements of the underlying Cape Granite Suite, which forms the bedrock of a large part of the Western Cape. Granite contains high levels of natural radionuclides, which results in high levels of natural background radiation in the surrounding area. The impacts of these high levels of radiation exposure on military personal are of concern. There are four military units located in this part of the West Coast, namely SAS Saldanha, 4 Special Forces Regiment, Langebaan Road Air Force Base and the Military Academy. Different sites in and around these military units were selected and soil samples were taken. Laboratory gamma ray measurements were done to determine the levels of natural radioactive nuclides in the soil samples. The radioactive nuclide concentrations were interpolated and then mapped with the help of geographic information systems (also known as geospatial information systems or GIS) software. An evaluation of the annual dose rate of military personnel at the units on the West Coast was made and found to range between 0,017 mSv/y and 0,163 mSv/y. These values were mapped and compared to the average global annual dose rate of 0,070 mSv/y. This article reports on an investigation of these results and the overall exposure levels of personnel from the various military units on the West Coast of South Africa.
- ItemChemically reacting on MHD boundary-layer flow of nanofluids over a non-linear stretching sheet with heat source/sink and thermal radiation(Thermal Science, 2018) Makinde, Oluwole Daniel; Mabood, Fazle; Ibrahim, Mohammed S.In this paper, steady 2-D MHD free convective boundary-layer flows of an electrically conducting nanofluid over a non-linear stretching sheet taking into account the chemical reaction and heat source/sink are investigated. The governing equations are transformed into a system of non-linear ODE using suitable similarity transformations. Analytical solution for the dimensionless velocity, temperature, concentration, skin friction coefficient, heat and mass transfer rates are obtained by using homotopy analysis method. The obtained results show that the flow field is substantially influenced by the presence of chemical reaction, radiation, and magnetic field.
- ItemComputational dynamics of arterial blood flow in the presence of magnetic field and thermal radiation therapy(Hindawi Publishing Corporation, 2014-04-22) Chinyoka, T.; Makinde, O. D.We conduct a numerical study to determine the influence of magnetic field and thermal radiation on both velocity and temperature distributions in a single blood vessel. The model here assumes that blood is a Newtonian incompressible conducting fluid with radially varying viscosity due to hematocrit variation. The transient equations of momentum and energy transport governing the flow in an axisymmetric configuration are solved numerically using a semi-implicit finite difference method. Results are presented graphically and discussed both qualitatively and quantitatively from the physiological point of view. The results of this work may enhance current understanding of the factors that determine the effects of hyperthermia treatment on tumor tissues.
- ItemEffect of the elemental content of shells of the bivalve mollusks (Mytilus galloprovincialis) from Saldanha Bay (South Africa) on their crystallographic texture(MDPI, 2021) Nekhoroshkov, Pavel; Zinicovscaia, Inga; Nikolayev, Dmitry; Lychagina, Tatiana; Pakhnevich, Alexey; Yushin, Nikita; Bezuidenhout, JacquesA both wild and farmed mussels in natural conditions, anthropogenic inputs are usually reflected in the increase of the content of specific elements. To determine the possible effect of the elemental patterns of farmed and wild mussels (Mytilus galloprovincialis) collected in the Saldanha Bay area (South Africa) on the crystallographic texture of the shells, the content of 20 elements in shells and 24 in the soft tissue of mussels was determined by neutron activation analysis. The crystallographic texture of mussel shells was analyzed using time-of-flight neutron diffraction. The wild mussels from open ocean site live in stressful natural conditions and contain higher amounts of the majority of determined elements in comparison with mussels farmed in closed water areas with anthropogenic loadings. The changes between the maximums of the same pole figures of the three samples are in the range of variability identified for the genus Mytilus. The content of Cl, Sr, and I was the highest in mussels from the open ocean site, which is reflected by the lowest mass/length ratio. The determined crystallographic textures of mussels are relatively stable as shown in the analyzed pole figures despite the concentrations of Na, Mg, Cl, Br, Sr, and I in shells, which significantly differ for wild and farmed mussels. The stability of the crystallographic texture that we observed suggests that it can be used as a reference model, where if a very different texture is determined, increased attention to the ecological situation should be paid.
- ItemEffects of thermal radiation on MHD peristaltic motion of walters-B fluid with heat source and slip conditions(Regional Information Center for Science and Technology, 2017) Makinde, O. D.; Reddy, M. Gnaneswara; Reddy, K. VenugopalIn this paper, we examine the combined effects of magnetic field, thermal radiation, heat source, velocity slip and thermal jump on peristaltic transport of an electrically conducting Walters-B fluid through a compliant walled channel. Using small wave number approach, the nonlinear model differential equations are obtained and tackled analytically by regular perturbation method. Expressions for the stream function, velocity, temperature, skin-friction coefficient and heat transfer coefficient are constructed. Pertinent results are presented graphically and discussed quantitatively. It is found that the velocity distribution depresses while the fluid temperature rises with an increase in Hartmann number. The trapping phenomenon is observed and the size of trapped bolus increases with an increase in Hartmann number.
- ItemEstimation of radon potential through measurement of uranium concentrations in granite geology(Academy of Science of South Africa, 2019) Bezuidenhout, JacquesThe geology of an area can be used as a predictor for radon potential. Granite rock typically contains a high concentration of uranium and subsequent elevated emanation of radon gas. The geology of the western part of the Western Cape Province in South Africa is dominated by granite bedrock but very few studies on radon have been conducted in this area. Uranium concentrations were consequently measured on a large granite hill in the Saldanha Bay area of the Western Cape and a relationship between indoor radon and uranium concentrations was used to model radon potential on the outcrop. Results from granite rich environments in India were modelled in order to extract a relationship between indoor radon concentrations, radon exhalation rates and uranium concentrations. Radon exhalation rates greater than 0.35 Bq/m2h were predicted and estimated indoor radon concentrations in excess of 400 Bq/m3 were also predicted for the hill. The modelled results were compared with indoor radon measurements taken in the town of Paarl in the Western Cape, which sits on the same granite bedrock formation. The predicted radon potential correlated well with the physical measurements.
- ItemThe flow of a variable viscosity fluid down an inclined plane with a free surface(Hindawi, 2013) Tshehla, M. S.The effect of a temperature dependent variable viscosity fluid flow down an inclined plane with a free surface is investigated.The fluid film is thin, so that lubrication approximation may be applied. Convective heating effects are included, and the fluid viscosity decreases exponentially with temperature. In general, the flow equations resulting from the variable viscosity model must be solved numerically. However, when the viscosity variation is small, then an asymptotic approximation is possible. The full solutions for the temperature and velocity profiles are derived using the Runge-Kutta numerical method.The flow controlling parameters such as the nondimensional viscosity variation parameter, the Biot and the Brinkman numbers, are found to have a profound effect on the resulting flow profiles.
- ItemHeat and mass transfer analysis of MHD peristaltic flow through a complaint porous channel with variable thermal conductivity(IOP Science, 2020-02-18) Vaidya, H.; Rajashekhar, C.; Manjunatha, G.; Prasad, K. V.; Makinde, O. D.; Vajravelu, K.The MHD peristaltic motion of Bingham fluid through a uniform channel is examined under the influence of long wavelength and small Reynolds number. The impact of variable thermal conductivity, convective heat transfer, porous boundaries, and wall properties are considered. The semi-analytical technique is utilized to solve the governing nonlinear temperature equation. The effects of different parameters on the physiological quantities of interest are captured with the assistance of MATLAB programming. The assessment reveals that an ascent in a magnetic parameter reduces the velocity field. Further, an increment in the estimation of variable thermal conductivity upgrades the temperature profiles. Besides, the trapped bolus is a function of a porous parameter, and an increase in porous parameter will have the proportional increment in the other parameter.
- ItemICP-MS analysis of trace metals in pacific oysters (Crassostrea gigas) within the port of Saldanha, South Africa(Stellenbosch : Stellenbosch University, 2022-12) Dhlalani, Nomcebo Marry; Bezuidenhout, J.; Stellenbosch University. Faculty of Military Sciences. School of Science and Technology. Dept. of Physics.ENGLISH ABSTRACT: The aim of the study was to monitor the accumulation of the trace metals, Manganese(Mn), Cadnium (Cd), Zinc (Zn), Copper (Cu) and Mercury (Hg) in oysters that were cultivated in Saldanha Bay over the period 2018 until 2020. Eight strategic positions were selected in Saldanha Bay for biomonitoring; three at the oyster growers lease areas in Small Bay, one at the oyster growers lease areas in Big Bay and four close to the Multi-purpose Terminal. At each monitoring station a cohort tower was deployed which contained the oysters used for biomonitoring. At most, ten of these oyster spat were selected and assessed for trace metal content to establish a baseline condition to measure trace metal accumulation. The oysters were analysed for trace metal content over long- and short-term intervals. Long-term monitoring entailed deploying the long-term oyster cohort for a total period of 24 months. After every three months of deployment, the oyster towers were retrieved and a sample of five oysters was selected from the long-term cohort, placed in a labelled plastic bag, and sent for analysis. The short-term monitoring, on the other hand, entailed deploying a fresh oyster cohort every three months over a period of 24 months. After three months of deployment, the oyster tower was retrieved and a fresh batch of oyster tower was replaced in the same sampling point for both long-term and short-term intervals. The samples of both long-term and short-term monitoring were sent to the ICP-MS laboratory, University of Stellenbosch, where tissue was extracted from the oysters, frozen and submitted for trace metal analysis using an Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). It was found that the average concentration of Mn ranges between 1.14 mg/kg and 1.80 mg/kg and Zn ranges between 55.45 mg/kg and 97.90 mg/kg. It was assumed that the anti-fouling products used in the Small Bay influenced the concentration of Cu, which gave high values ranging from 2.18 mg/kg up to 4.49 mg/kg. Concentration of Cd range from 0.75 mg/kg to 1.20 mg/kg and Hg was between 0.00 mg/kg and 0.01 mg/kg. When looking at short-term trends, generally after deployment, oysters recorded an increase in concentrations for the following metals, Mn, and Zn, while Hg, Cu, and Cd recorded a general decrease in concentrations over the same short-term deployments. Not all general trends were omnipresent as spatial and temporal specific variations were observed during the study. This suggested that in some cases trace metal supply intake coupled with seasonal variation could influence the amount of trace metal present in the oyster at any time. The average trace metal concentrations in oysters presented were in a decreasing trend of Zn > Cu > Mn> Cd > Hg. The oyster proved to be good biomonitors due to its ability to accumulate trace metals over time. There were however, oyster mortalities over the period of the study, but these mortalities were related to parasitic infections.
- ItemThe impact of saccharomyces cerevisiae on a wine yeast consortium in natural and inoculated fermentations(Frontiers Media, 2017) Bagheri, Bahareh; Bauer, Florian; Setati, Mathabatha E.Natural, also referred to as spontaneous wine fermentations, are carried out by the native microbiota of the grape juice, without inoculation of selected, industrially produced yeast or bacterial strains. Such fermentations are commonly initiated by non-Saccharomyces yeast species that numerically dominate the must. Community composition and numerical dominance of species vary significantly between individual musts, but Saccharomyces cerevisiae will in most cases dominate the late stages of the fermentation and complete the process. Nevertheless, non-Saccharomyces species contribute significantly, positively or negatively, to the character and quality of the final product. The contribution is species and strain dependent and will depend on each species or strainās absolute and relative contribution to total metabolically active biomass, and will therefore, be a function of its relative fitness within the microbial ecosystem. However, the population dynamics of multispecies fermentations are not well understood. Consequently, the oenological potential of the microbiome in any given grape must, can currently not be evaluated or predicted. To better characterize the rules that govern the complex wine microbial ecosystem, a model yeast consortium comprising eight species commonly encountered in South African grape musts and an ARISA based method to monitor their dynamics were developed and validated. The dynamics of these species were evaluated in synthetic must in the presence or absence of S. cerevisiae using direct viable counts and ARISA. The data show that S. cerevisiae specifically suppresses certain species while appearing to favor the persistence of other species. Growth dynamics in Chenin blanc grape must fermentation was monitored only through viable counts. The interactions observed in the synthetic must, were upheld in the natural must fermentations, suggesting the broad applicability of the observed ecosystem dynamics. Importantly, the presence of indigenous yeast populations did not appear to affect the broad interaction patterns between the consortium species. The data show that the wine ecosystem is characterized by both mutually supportive and inhibitory species. The current study presents a first step in the development of a model to predict the oenological potential of any given wine mycobiome.
- ItemImpact of second order slip and non-uniform suction on non-linear stagnation point flow of alumina-water nanofluid over electromagnetic sheet(International Information and Engineering Technology Association, 2019) Nayak, Manoj Kumar; Zeeshan, Ahmad; Pervaiz, Zeshan; Makinde, Oluwole DanielThe purpose of the present article is to study the influence of second order slip and variable suction on non-linear stagnation point flow of Alumina-water nanofluid past an electromagnetic sheet embedded in a porous medium. A simulation model was established through hybrid Homotopy Analysis Method (HAM) and Genetic Algorithm Method (GAM). Through this it was found that favorable pressure gradient and modified Hartmann number yield accelerated fluid motion while porous matrix and first order slip result in decelerated flow over stationary/moving electromagnetic sheet. The finding of this research may serve as greater cooling agent due to more heat transfer rate from the electromagnetic sheet subject to favorable pressure gradient.
- ItemImpact of thermophoretic transport of AlāOā nanoparticles on viscoelastic flow of oil-based nanofluid over a porous exponentially stretching surface with activation energy(Institute of Fundamental Technological Research, 2019) Etwire, Christian John; Seini, Ibrahim Yakubu; Rabiu, Musah; Makinde, Oluwole DanielThe influence of thermophoretic transport of AlāOā nanoparticles on heat and mass trans- fer in viscoelastic flow of oil-based nanofluid past porous exponentially stretching surface with activation energy has been examined. Similarity technique was employed to transform the gov- erning partial differential equations into a coupled fourth-order ordinary differential equations which were reduced to a system of first-order ordinary differential equations and then solved numerically using the fourth-order Runge-Kutta algorithm with a shooting method. The re- sults for various controlling parameters were tabulated and graphically illustrated. It was found that the thermophoretic transport of AlāOā nanoparticles did not affect the rate of flow and heat transfer at the surface but it affected the rate of mass transfer of the nanofluid which decayed the solutal boundary layer thickness. This study also revealed that activation energy retards the rate of mass transfer which causes a thickening of the solutal boundary layer.
- ItemInfluence of rotation on transversely isotropic piezoelectric rod coated with a thin film(Polish Academy of Sciences, 2018) Selvamani, Rajendran; Makinde, Oluwole DanielIn this paper, the influence of rotation on axisymmetric waves of a piezoelectric rod coated with a thin film is studied using constitutive form linear theory elasticity and piezo-electric equations. Potential functions are introduced to uncouple the equations of motion in radial and axial directions. The surface area of the rod is coated by a perfectly conducting material. The frequency equations are obtained for longitudinal and flexural modes of vibration and are studied numerically for PZT-4 ceramics. The computed non-dimensional frequency, phase velocity, relative frequency shift, electromechanical coupling and electric displacement are presented in the form of dispersion curves. This type of study is important in the construction of rotating sensors and gyroscope.
- ItemInvestigating e-commerce adoption in the procurement processes of the Botswana Defence Force : a qualitative study(Stellenbosch : Stellenbosch University, 2007) Moswetsi, William; Botha, D.; Stellenbosch University. Faculty of Military Science. Dept. of Science and Technology.ENGLISH ABSTRACT: This study sets out to explore the factors that affect e-commerce adoption in the Botswana Defence Force (BDF) procurement process. The factors that were identified as affecting e-commerce adoption emerged from studies conducted mainly in the context of the developed world, particularly the Western world. Discussions in the academic literature therefore appear to be based on assumptions that do not necessarily apply to the developing world. This study explores these factors in an organisation in a developing country. The purpose of the study was to develop a rich picture of the factors that affect ecommerce adoption in the BDF procurement process. The study aimed to identify issues, factors, and problems critically involved in IT adoption in the BDF procurement process and to develop a theory that could help to understand these factors. Grounded theory methodology was the chosen method of qualitative data collection and analysis. This methodology was chosen because it facilitates inductive theory generation from an interpretive perspective. This approach was suitable for the study as the aim was to develop a theory that was grounded in the data and likely to resemble reality. The data was gathered through semistructured interviews with procurement officers, IT officers, and BDF senior officers. The research findings identified the benefits, limitations, drivers and barriers of ecommerce adoption in the BDF procurement process. The technological capabilities of the BDF were identified and it was concluded that the BDF is prepared in terms of IT infrastructure for e-commerce adoption. A theory of the factors affecting e-commerce adoption was developed using grounded theory methodology and a model of the factors affecting e-commerce adoption in the procurement process was developed. To strengthen the theory that was 'built', it was compared to previous e-commerce adoption literature. Overall, this research provided a stepping stone for new research into ecommerce adoption in the Botswana Defence Force. It has facilitated better understanding of how participants view e-commerce adoption in the BDF. The study also contributes to the literature on e-commerce adoption, which is currently under-researched, particularly in developing countries such as Botswana.
- ItemThe investigation of radionuclides distributions in beach sand by means of GIS techniques(CONSAS Conference, 2015-11) Bezuidenhout, JacquesA transportable and robust gamma ray detection system (GISPI) was employed to determine the concentrations of naturally occurring radionuclides on various beaches in and around Saldanha Bay, located on the West Coast of South Africa. Several mathematical techniques were applied to obtain GIS overlay that could be used to investigate various geophysical phenomenon. The results demonstrated direct relationships between radionuclide concentrations, grain size of beach sediment and the intensity of wave action. The element concentrations were used to make deductions on the origin of some of the beach sand. The article finally draws conclusions on coastal and beach formation processes, based on the results of the distribution of various radionuclides.
- ItemIrreversibility analysis of hydromagnetic flow of couple stress fluid with radiative heat in a channel filled with a porous medium(Elsevier, 2017) Eegunjobi, A. S.; Makinde, O. D.Numerical analysis of the intrinsic irreversibility of a mixed convection hydromagnetic flow of an electrically conducting couple stress fluid through upright channel filled with a saturated porous medium and radiative heat transfer was carried out. The thermodynamics first and second laws were employed to examine the problem. We obtained the dimensionless nonlinear differential equations and solves numerically with shooting procedure joined with a fourth order Runge-Kutta-Fehlberg integration scheme. The temperature and velocity obtained, used to analyse the entropy generation rate together with some various physical parameters of the flow. Our results are presented graphically and talk over.