SUNScholar - Browsing by Author "Bezuidenhout, Jacques"

Browsing by Author "Bezuidenhout, Jacques"

Now showing 1 - 12 of 12

Analysing the changes in the bathymetry of Saldanha Bay between the years 1977 and 2021
(CONSAS Conference, 2022-12) Du Toit, Louis; Henrico, Ivan; Bezuidenhout, Jacques; Mtshawu, Babalwa
The construction of the Saldanha Port has been the reason for the major changes in the bathymetry and sediment dynamics observed in Saldanha Bay in the last decades. In this paper, newly acquired soundings from the National Hydrographer were used to analyse the changes between 1977 and 2021 - over a 44-year period - in the bathymetry of Saldanha Bay. The Ordinary Kriging (OK) interpolation method, available through the Geostatistical Wizard in ArcGIS Pro, was used for creating surface models to conduct comparisons with the bathymetry of Saldanha Bay. The results indicate a general increase in depth since 1977 of between 0.395 and 3.203 m, and an average increase in depth within the Big Bay of 1.799 m. Between 1977 and 2021, a total volume loss of 49 364 560.0 m3 in sediment was calculated - an indication of how the sedimentation process in Saldanha Bay has changed subsequent to the construction of the harbour.
The background radiation and exposure levels at various South African west coast military units
(Stellenbosch University. Faculty of Military Science (Military Academy), 2014) Bezuidenhout, Jacques
The 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.
Cross sections and analysing power energy-sharing distributions of valence (p,2p)-knockout from 208Pb with a projectile of 200MeV
(Stellenbosch : Stellenbosch University, 2000-12) Bezuidenhout, Jacques; Cowley, A. A.; Arendse, G. J.; Stellenbosch University. Faculty of Science. Dept. of Physics.
ENGLISH ABSTRACT: The aim of this work was to study the 208Pb(p,2p)207Tl quasi-free knockout process. The experimental data were measured at the National Accelerator Centre using incident polarised protons of 200 MeV. The two scattered particles, from the knockout reaction, were detected in coincidence and their energies were determined using a magnetic spectrometer and a solid state detector telescope. Cross section and analysing power energy distributions were extracted from the experimental measurements and these were compared with theoretical values for the Distorted Wave Impulse Approximation. The theoretical cross-section calculations predict the experimental cross-section distribution well for all combinations of distorting potentials and bound states that were investigated, both with regard to shape, as well as absolute magnitude. However the theoretical analysing power distributions did not agree with the experimental quantities. Therefore it is not clear whether the analysing power is a useful tool to extract information on the specifics of the quasi-free reaction mechanism. The spectroscopic factors were found to be consistent with the results obtained in previous studies, thereby inspiring confidence that the problem with the analysing power distribution is not ascribable to a possible deficiency in the experimental techniques exploited in this work.
Determining the change in the bathymetry of Saldanha Bay due to the harbour construction in the seventies
(2020-09) Henrico, Ivan; Bezuidenhout, Jacques
ENGLISH ABSTRACT: Bathymetry is the science to study and measure the depths of the ocean floor. The differences in water depth, underwater slope and ocean floor structure were investigated using a geographic information system (GIS). This article investigates changes to the hydrodynamic sedimentation processes in Saldanha Bay as a result of the harbour constructions that took place in the early 1970s. The construction of the harbour included the massive dredging operations and resultant relocation of 30 million m3 of soil. Bathymetric data from Saldanha Bay before (1957) and after (1977) the construction of the harbour in the early seventies were analysed and compared in ArcGIS. It was found that the overall depth of the inner part of Saldanha Bay increased with about 1.4 m and that the bottom and slopes were smoothed. The physical structure that was constructed for the harbour had a serious impact on the hydrodynamic sedimentation processes. It was found that these interventions altered the depth profile of the Bay and the article finally draws conclusions on coastal and beach formation, based on the change in the hydrodynamic sedimentation processes of Saldanha Bay.
Effect 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, Jacques
A 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.
Estimation of radon potential through measurement of uranium concentrations in granite geology
(Academy of Science of South Africa, 2019) Bezuidenhout, Jacques
The 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.
The investigation of radionuclides distributions in beach sand by means of GIS techniques
(CONSAS Conference, 2015-11) Bezuidenhout, Jacques
A 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.
The mapping and investigation of radionuclide pollution in the processing plant of a spent phosphate mine by using GIS techniques
(CONSAS, 2018) Bezuidenhout, Jacques
The mining and refinement of phosphate is characterised by high levels of uranium. An in situ gamma ray survey was done at the processing plant of a spent phosphate mine near Vredenburg on the west coast of South Africa in order to assess radionuclide concentrations. The concentrations of potassium, thorium and radioactive progeny of uranium were measured and plotted with the help of QGIS software. The results demonstrated high concentrations in specific areas of the plant. The highest concentrations were found to be 898 Bq/kg for potassium, 162 Bq/kg for 232Th and 639 Bq/kg for 226Ra. It was demonstrated that the refinement process technologically enhanced the naturally occurring radioactive nuclides and contaminated sections of the processing plant. The causes of the contamination were also investigated. The effective dose for the various parts of the processing plant was also estimated and the highest level was found to be 0.45 mSv/y. The article finally draws conclusions as to the environmental impact of the radiation and possible future preventative measures that could be followed in order to minimize pollution.
Mapping of historical human activities in the Saldanha Bay military area by using in situ gamma ray measurements
(Faculty of Military Science, Stellenbosch University, 2012) Bezuidenhout, Jacques
Saldanha Bay on the west coast of South Africa is surrounded by various nature reserves, military units and training sites. Over a long period of time, large parts of this semi-arid area were exposed to human activities, including military training and the preparation of forces for war. This article investigates the prospect of identifying areas where human activities took place via mapping of the variation in primordial radioactive isotopes. For this purpose, in situ gamma-ray data were obtained from selected locations around Saldanha Bay. The data were used to extract concentrations of primordial radioactive isotopes in these locations. The radioactive primordial isotope concentrations were then mapped and compared to historical evidence of human activities in these areas. The concentrations of potassium isotope showed a relationship to the height above mean sea level. Historical human activities were mainly confined to flatter regions of the area around Saldanha Bay and therefore also relate to the height above mean sea level. The potassium concentrations and the areas where human activities took place were compared and a significant relationship was found.
Nature of military geography
(Stellenbosch University, Faculty of Military Science (Military Academy), 2012) Bezuidenhout, Jacques; Galgano, Francis A.; Palka, Eugene J.
The author presents a review of the book " Modern Military Geography" edited by Francis A. Galgano and Eugene J. Palka (2011), about the relationship between geography and military conflict.
Pre-equilibrium helion emission induced by protons
(Stellenbosch : University of Stellenbosch, 2006-12) Bezuidenhout, Jacques; Cowley, A. A.; University of Stellenbosch. Faculty of Science. Dept. of Physics.
This thesis is devoted to a study of the 93Nb( p r ,3He) and 59Co( p r ,3He) reactions at incident energies of 100 MeV, 130 MeV and 160 MeV. Double differential cross sections and analysing power distributions were measured from a threshold of ~30 MeV up to the kinematic maximum and at scattering angles between 15º and 120º. The experimental data were compared with theoretical calculations done by combining a statistical multistep theory with a deuteron pickup mechanism in the final stage. The contribution of the first three steps towards the total double differential cross section and analysing power was assessed. The theory described the experimental double differential cross section and analysing power data reasonably well over all incident and scattered energies and for both target nuclei. As the incident energy was increased, the characteristics of the reaction mechanism also remained consistent. Thus the results supported the underlying multistep-pickup theory. The two target nuclei demonstrated similar responses, suggesting these two share the same basic reaction mechanism. The total double differential cross section for the reaction dropped with an increase in incident energy. At a fixed emission energy, near the maximum allowed value, the slope of the double differential cross section increased with an increase in incident energy, resulting in the dominance of forward peaked reactions at higher incident energies. The sensitivity of analysing power to the multistep part of the reaction was valuable to the study. Forward-peaked contributions that were associated with single step direct reactions resulted in large analysing power values at small scattering angles, and values dropped to around zero at large angles. The analysing power also appeared to decrease to values approximating zero as the incident energy was increased to 160 MeV. Furthermore, this study also confirmed the dominance of higher step mechanisms at high excitation energies, irrespective of incident energy. In general the results were in agreement with the predicted properties of the assumed reaction mechanism at all incident and emission energies, which inspires confidence that the theoretical interpretation is likely to be correct.
Testing and implementation of a transportable and robust radio-element mapping system
(Academy of Science of South Africa, 2015-09-25) Bezuidenhout, Jacques; Military Science
Gamma ray spectroscopy has been successfully applied as a survey tool in the fields of morphology, geology and mineral exploration. Gamma ray surveys are regularly done at ground level, which frequently requires transecting remote and unforgiving environments. Thus a need for the development of a transportable, robust and portable gamma ray detection system was identified. In addition to collecting radiation data, such a system was required to also provide the geographic position of the data and allow for various analyses tools to be utilised in the field. These functions were achieved by integrating a USB-driven scintillation detector with a field tablet and creating software to control acquisition and analyses of radiation data, as well as logging position. The system was tested in different geographical locations under different modes of transport. The instrument was tested by employing several different methods of data analysis in order to extract natural nuclide condensations. The consistency in the obtained data demonstrated the reliability of the instrument in the different environments. The system also successfully replicated previous radio-element survey findings and provided information on several geographical phenomena, including information on the geology, paved road structure and beach sediment characteristics.

Browsing by Author "Bezuidenhout, Jacques"

Results Per Page

Sort Options