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Exploring Engineering Students' Understanding Of Techniques Of Integration
No full textPublished ArticleThis study explored engineering students' understanding of the techniques of
integration in calculus. There were 30 first year engineering students who
participated in the project. The concepts were covered as part of a
mathematics course at a university of technology in KwaZulu-Natal, South
Africa. Activity sheets, constructed with tasks based on integration were
administered to the participants. Their written responses, which were used to
identify the mental constructions of these concepts, were analysed using the
three worlds of mathematics framework and interviews were carried out to
clarify the written responses. The discussions and written work indicated that
students seemed to be operating in the conceptual-embodied world of
cognitive development and students displayed the ability to manipulate
symbols and embedded procedures. The findings raised some didactical
implications for higher education and also provided applications of the three
worlds of mathematics framework
Green Synthesis of Pyran Derivatives Using Lemon Peel Powder as a Natural Catalyst and their Antimicrobial Activity
No full textPubbbbished ArticleA simple and green one pot protocol for the synthesis of bioactive pyran annulated heterocyclic
compounds at room temperature in ethanol has been developed using lemon peel powder as a
catalyst. This method provides operational simplicity and environmentally benign green approach.
All the synthesized compounds were evaluated for antimicrobial activity against
E. coli
,
Welsiella
sp
.
and
fusarium moniliforme
Yb(OTf)3 Catalyzed Synthesis, Antimicrobial and Insecticidal activity of some Biscoumarins
Get PDFPublished ArticleIn the present study, we report Yb(OTf)3 catalyzed synthesis of biscoumarins by pseudo
three-component reaction of aldehyde and 4-hydroxycoumarin. The synthesized biscoumarins were evaluated
for antimicrobial and insecticidal activity. Results of antimicrobial activity were found to be moderate
to good in terms of zones of inhibition and MIC values against E. coli, P. vulgaris and S. aureus. The compounds
were inactive against the used fungal strains except B4 in case of Penicillium. Insecticidal activity
of the biscoumarins B-1, B-3, B-5 and B-11 was found to be good exhibiting 70-75% mortality effect on
Callosobruchus maculatus
Root-enhancing properties of rhizospheric bacteria on Eucalyptus hybrid cuttings
Get PDFPublished ThesisWorldwide, the demand for hardwood from commercial plantations is rising as the consumption of forest products increases. In Eucalyptus plantation forestry the formation of interspecific hybrids has driven the commercial forestry industry to produce a variety of different hybrids that are often deployed in marginal areas. Superior hybrid genotypes are deployed through the application of vegetative propagation and the rooting of cuttings. However, the cuttings of some hybrid genotypes demonstrate relatively low rooting percentages, which results in financial losses experienced by many commercial forestry nurseries. This study was thus undertaken to assess the potential of rhizospheric bacteria to improve the rooting capacity of two hybrids clones of E. grandis × E. nitens (GN 018B and GN 010).
Methods: Firstly, the rhizospheric bacterial composition of Eucalyptus rhizospheric soils of different ages were characterised using fatty acid methyl ester (FAMEs) analyses. Thereafter, rhizospheric bacteria were isolated from Eucalyptus rhizospheres and characterised by sequencing the ≈1,300 base pair fragment of the 16S rRNA gene, after which the sequences were submitted to BLAST searches to identify the bacterial strains. Thereafter, the identified bacterial strains were tested for two important root promoting characteristics; the ability to produce indole-3-acetic acid and to solubilise phosphates. Bacterial inoculums were prepared and tested on cuttings of the two hybrids in the nursery. Four treatments were applied to the cuttings; the nursery standard, which acted as the control, two treatments prepared from the isolated rhizospheric bacteria and a commercial treatment containing a live fungus. Cutting survival, rooting, rooting architecture and growth were measured after eight weeks of growth.
Results: This study revealed that rhizospheric microbial communities’ diversity evolved over time. Younger rhizospheres displayed significantly greater diversity when compared to the older rhizospheres. The presence of higher concentrations of saturated fatty acids in younger rhizospheres than in the older rhizospheres was indicative of aerobic conditions, while increased proportions of polyunsaturated fatty acids in the older rhizospheres indicated anaerobic conditions. The greater proportion of polyunsaturated fatty acids in the older rhizospheric soil samples, especially linoleic (C18:2ω6c), α-linolenic (C18:3ω3c), γ-linolenic (C18:3ω3c) fatty acids, as well as the unique γ-linolenic fatty acids, suggest growing establishment of fungi as a rhizosphere ages. Both Shannon and Simpson’s indexes confirmed that younger soils were more diverse. Thirty two rhizospheric bacterial strains were isolated and identified. These strains belonged to 12 unique species of eight different genera. Of the 12 rhizospheric bacterial species, seven demonstrated the ability to produce indole-3-acetic acid and to solubilise phosphates. These seven strains were used to prepare the inoculums to treat the cuttings of the two hybrids. Bacillus aryabhattai, Pseudomonas fluorescens, P. koreensis and P. putida were mixed into one rooting treatment, while Brevibacterium frigoritolerans, Burkholderia phytofirmans and Chryseobacterium rhizosphaerae were mixed into another treatment. Cuttings of both hybrid clones demonstrated relatively high survival rates and rooting percentages for all treatments, although the nursery standard treatment (indole-3-butyric acid) marginally outperformed all other treatments. The cutting growth responses of the two hybrids showed highly significant differences amongst the treatments (P < 0.0001). The rhizospheric rooting treatment comprising of the non-Pseudomonas-Bacillus bacteria, as well as fungus treatment, were closest in performance to the nursery standard, while the Pseudomonas-Bacillus treatment often showed lower values when compared to the other treatments. However, Pseudomonas-Bacillus bacterial treatment appeared to improve fibrosity of the rooting architecture of cuttings of one of the hybrid genotypes, which could be of value when rooted cuttings are planted out in plantations. A noteworthy outcome of this study was the finding that extensive genotypic differences existed between the two hybrid clones.
Conclusions: The aim of this study was to test the application of rhizospheric bacteria as root stimulating agents in the cuttings of two Eucalyptus hybrid genotypes. The rhizospheric bacterial preparations used in this study did not enhance the number of rooted cuttings when compared to the nursery standard in a significant way, however, there were strong indications that the rhizospheric bacterial inoculums did promote fibrosity. These findings suggest further investigation into the formulation and application of potential rhizospheric bacterial preparations for rooting enhancement of Eucalyptus cuttings
Vegetation gradients, soil microbial pools and carbon sequestration in cactus-invaded semi-arid rangelands of western Free State
Get PDFThesis (D. Tech. Health and Environmental Sciences: Agriculture) - Central University of Technology, Free State, 2019This study was done in the Xhariep district, western Free State region. The western Free State rangeland is classified as Nama Karoo biome, and is characterized by dwarf Karoo shrubs mixed with grasses. Eriocephalus eriocoides, Eriocephalus spinescens, Pentzia spp., Pteronia spp., Euryops asparagoides, Lycium spp. and Asparagus spp. are dominant shrubs. The grass stands are dominated by Aristida spp., Eragrostis spp. and Stipagrostis spp. However, cacti (Opuntia humifusa) and companion invaders are overrunning the rangelands. The study therefore assessed the effects of invasive creeping prickly pear on the composition of forage grasses and shrubs in rangelands continuously grazed by sheep and cattle herds. The objective of study 1 was to characterize the vegetation profiles in sheep- and cattle-grazed areas. The rangeland was stratified based on utilization and density of cacti. The newly invaded zone (NI) resembled the typical western Upper Karoo vegetation type, where disturbance indicator (DI) grasses constituted 86%, intermediate grasses (Aristida adscensionis and Aristida congesta) constituted 10%, and shrubs were 4% of the vegetation. The dominance of DI grasses suggests that grazing management, climate and competition for nutrient resources exerted by cactus (O. humifusa) invasions were affecting vegetation characteristics.
The objective of study 2 was to (a) determine the relationship between vegetation cover type on soil carbon, microbial populations and minerals in degraded rangelands, and (b) to characterize above-ground forage quality in the degraded rangelands. Four cover types were defined as cactus cover (CC), shrub cover (SC), grass cover (GC) and bare area (BA). The soil in bare area (BA) had the highest N content as nitrate (NO3-) and ammonium (NH4+) forms. Bacterial and fungal populations were the lowest in the BA. The bacterial count was 30%; and the fungal count 15% less than in areas covered by invasive species are critical in validation of global vegetation models that predict the response of fragile rangelands to climate change.
In study 3, interactions of rainfall and invasive species on rangeland grazing capacity were assessed. Semi-structured questionnaires were administered on 40 cattle and sheep farms within the Eastern Parkland vegetation type and the Transitional Zone. There was an increase in the grass component in both zones; however, the former had a higher proportion of DI. Shrub density increased by 16% over the past 30 years. Subclimax grass increased by 15.4%, and by 7.1% in the Eastern Parkland and Transitional Zone, respectively. There were no differences in change of palatable species in both zones. However, a small increment of 5.1% was noted with unpalatable shrubs in the Transitional Zone, and 1.7% in the Eastern Parkland. The Eastern Parkland’s vegetation type was generally more stable and less sensitive to annual rainfall changes, compared to the Transitional Zone. It is uncertain whether vegetation patterns in the Koffiefontein rangeland (Eastern Parklands, Eragrostis-Karoo shrub and Transitional stage between Eastern Parkland and Eragrostis karoo shrub vegetation type) represent short-term cycles or permanent retrogression. There is a need for further analysis of the interactions of moisture, invasive and carrying capacity, which most likely will shape Karoo vegetation and utilization patterns in the next half century. It is also critical to assess the soil organic matter changes and carbon sequestration attributable to cacti invasion, and to ascertain if improvements in carbon accumulation would provide ecosystem services that compensate for losses in palatable forages in the next half century
Development of a rhino anti-poaching model for game farms and nature reserves in the Free State Province of South Africa
Get PDFThesis (Doctor of Technology in Agriculture) -- Central University of Technology, Free State, 2018During the last ten years, the rhino populations of South Africa have suffered under an intense poaching onslaught. This onslaught has moved to the Free State Province of South Africa and there is a justified concern that its rhino populations are at risk. To protect the rhinos in the Province a need exists to manage the risk of poaching through a practical rhino anti-poaching model, which can assist to protect them effectively. This Rhino Anti-Poaching Model can determine and predict a poaching risk, can identify weaknesses, can assist to address problem areas, and will enable efficient monitoring.
It is imperative to know which rhino species occurred in the Free State Province in historical times, to ensure that the correct rhino species is protected against the risk of poaching and that they be kept in a suitable habitat. Nine farms in the Free Sate have rhino as a prefix in their names, which may be an indication that rhino did occur in the Province. Various historical photos and literature give a retrospective view, and show that there was insufficient browsing vegetation for black rhinos to survive. The occurrence of open grassland however suggests that white rhinos did occur in those specific areas during the time of the first pioneers. During this study period a count of rhinos was done, and currently there are 669 white rhinos and 11 black rhinos in the Province, thus a total of 680 rhinos in the Free State Province.
The South African Constitution mandated the State to enforce measures that will ensure adequate environmental protection for the benefit of future generations. The South African government promulgated a myriad of new environmental legislation. Several international agreements were also introduced as enforcement tools to regulate rhinos. The enforcement measures are noble, but out of balance, with many inspectors, but too few law enforcement officials. It also over-regulates and ensnare officials in minor issues.
A brief discussion on the latest technological innovations gives insight to the purpose of its development and effectiveness in combating rhino poaching. There are currently no technical or strategic solutions to save rhinos from poaching, therefore a combination of techniques is needed. Although self-manufactured unconventional devices seem to be more efficient to deceive poachers, a combination with the latest technological equipment and conventional strategies might be the best solution to counter rhino poaching.
Free State rhino farmers own 90% of the Province’s rhinos. However, these rhino farmers lack the appropriate security measures required to adequately protect their rhinos. A questionnaire was developed and data were collected, providing statistics on the current stance of security measures on rhino sites in the Province. It showed that 80% of rhino poaching occurs in rhino camps bordering public roads, 69% of the rhino sites located within 20km from the nearest town reported poaching, and 77% of large rhino camps are prone to poaching incidents. 57% of the respondents experienced rhino poaching on their sites. Through the questionnaire, it was gathered that rhino farmers in the Province are not vested in the concept of using trained rhino security.
A Production Loss Formula was constructed that calculates the production loss of a poached rhino. This formula reflects the reality experienced by the breeder. It indicated that the Province lost almost R300 million due to the poaching of 60 rhinos and that a poached breeding bull scores a higher production loss than all other gender groups. The Production Loss Formula also indicated that the State had a larger mean amount of loss compared to the rhino farmers, despite the lower bull per cow ratio owned by the State.
As part of the Rhino Anti-Poaching Model, a spreadsheet Formula was developed to calculate the total poaching risk percentage of each rhino site in the Province. Subsequently, an average rhino-poaching risk of almost 65% was obtained. After a rectification of the risks, the average poaching risk was reduced to nine percent and 10 sites scored below 50% (versus the current four). The statistical analysis indicates that the most important predictors for number of rhinos poached in the Free State Province were the Rhino Camp and Rhino Population categories
Investigation of the high strain rate behaviour and impact toughness of Ti6Al4V (ELI) parts built by the EOS M280 DMLS System with standard process parameters : as-built and stress relieved
Get PDFThesis (Master of Engineering in Mechanical Engineering) -- Central University of Technology, Free State, 2018The high strain rate behaviour and the impact toughness of Direct Metal Laser Sintering (DMLS) produced Ti6Al4V (ELI) parts were investigated. The as-built (AB) specimens were also taken through stress-relieving heat treatment and are hereinafter referred to as SR samples or specimens.
The high strain rate deformation of the two forms of the alloy (AB and SR) was studied using the Split Hopkinson Pressure Bar (SHPB) test, in compression and tension. Two high strain rates of 400 s-1 and 700 s-1 in compression and 250 s-1 and 360 s-1 in tension were used in these tests. The test results were used to investigate the relative strain rate dependence of flow stresses and fracture strain. Microstructural analysis was carried out to study the dominant fracture mechanisms on the deformed surfaces of the compression and tensile test samples using optical and scanning electron microscopy. Measurements of Vickers microhardness for the test samples were taken before and after the compression and tensile tests. The results of the high rate tensile and compression tests showed significant strain rate sensitivity in both compression and tension. Moreover, the rate sensitivity was seen to be relatively higher in the SR samples than in the AB samples. Microstructural analysis of the tested specimens showed that adiabatic shear bands dominated the deformed surfaces in the compression test samples. Multiple cracks that were more pronounced on the surfaces of the tested specimens were seen to initiate randomly on the deformed surfaces of the tensile test samples. The Vickers microhardness of the tested samples were observed to be higher for loaded specimens than for the unloaded specimens.
The impact properties of the AB and SR DMLS Ti6Al4V (ELI) specimens were studied using an instrumented Charpy impact tester. The transition curves for the absorbed energy and lateral expansion were obtained by performing the experiments in the temperature range 130 ºC to 250 ºC. The effect of the orientation of the v-notch on the standard test specimen with relation to the base plate of the DMLS machine was investigated. Furthermore, the effects of stress-relieving heat treatment on the notch toughness of DMLS Ti6Al4V (ELI) specimens was also studied. The analysis of the fracture surfaces resulting from the tests at various temperatures was done using a scanning electron microscope (SEM). The values of absorbed energy and the lateral expansion of the specimens that were determined from this series of tests indicated that specimens built with the v-notch facing the base plate of the DMLS machine had better impact toughness and notch ductility in comparison to those built with the v-notch facing away from the base plate over most of the temperature range of testing. Besides improving toughness, stress-relieving heat treatment gave rise to a shift of the ductile-to-brittle transition temperatures (DBTT) to lower values. The study further established that the DMLS Ti6Al4V (ELI) retains appreciable notch toughness even at sub-zero temperatures
Establishment of a wireless charging system for a battery-operated automatic guided vehicle
No full textThesis (Masters of Engineering in Electrical Engineering) -- Central University of Technology, Free State, 2018Modern technology provided a requirement that more power systems are being replaced with automated systems. Automatic Guided Vehicles (AGV) are Electric Vehicles (EV) that make use of re-chargeable batteries as a power module in the automation process. The increase in use of an AGV requires an essential method that is safe, quick and convenient to recharge the system. Wireless transfer technology has become an effective and reliable option to replace the conventional wire transfer technology. The topology involves a power transmitter assembled to the grid, and a power receiver assembled to the battery. A wireless power transfer system should satisfy three conditions, namely high efficiency, large air gaps and high power. Recent studies have provided wireless mid-range charging technology to transfer power through resonant inductive coupling.
The theory of resonant inductive coupling will therefore be used as the main technology in the design and implementation of a wireless charging system that can be successfully implemented with AGVs. The intention is to be able to wirelessly transform and transfer an alternating oscillating waveform into a DC voltage, to demonstrate instantaneous power transfer. To improve the comprehension on the theories related to “Magnetic Resonant Coupling”, quality factor and optimisation techniques of wireless power transfer systems, a design will be presented, along with the working principles and constructions of various components
An Analysis of Master Dissertations: A Case Study of Central University of Technology, South Africa
Get PDFPublished ArticleKnowledge is built on the foundation of information which may be gathered from various
sources, including from dissertations. Gathering information from postgraduate dissertations can highlight the differences between, and in, disciplines, with regard to specific variables. Moreover, it has been reported that African postgraduate students struggle to complete their dissertations, as they do not know how to structure them correctly, which may include not knowing how many words, pages, images and
tables to include in their dissertations. The purpose of this article is to analyse 157 Master
dissertations spanning a 10-year period in order to identify the average number of supervisors, words, pages, images and tables that have been used in successful research studies in order to highlight the differences between disciplines and to provide a guideline regarding the average length of a standard dissertation. An ex-post facto study is employed where informetric analysis is used to obtain quantitative data. Results reveal that the five variables vary dramatically per faculty. Management Sciences produced the highest number of average words (40 467), the highest number of average pages (194) and the highest number of average tables (28), while Engineering produced the highest
number of average images (53) per dissertation. Health and Environmental Sciences had the highest average number of supervisors (2.2) per dissertation. An important implication of this research is that it may help postgraduate students to better understand how to structure their dissertations when considering their length. A key recommendation is to include the results of this study in brochures which are distributed to postgraduate students at the start of their studies, giving them a better idea of the differences between, and in, disciplines with regard to the number of supervisors and the length of a standard dissertation
Computer Anxiety, Computer Self-efficacy and Attitudes towards the Internet of First Year Students at a South African University of Technology
Get PDFPublished ArticleNotwithstanding the benefits that information and communications technology (ICT) offers to
learning processes, the majority of learners in rural and township areas in South Africa either
do not have access to computers and the internet, or they lack sufficient skills to exploit the
benefits of ICT. This lack of skills and access to computers may lead to computer anxiety and
low computer self-efficacy among undergraduates entering higher education. Low computer
anxiety and high computer self-efficacy levels are important factors in assisting students to
be academically successful in the present technological era. This article reports on a study
that assessed the computer anxiety, computer self-efficacy and attitude towards the internet
among first year students at a South African university of technology. Data collection was
done through a five section survey. The research revealed that students suffer from moderate
computer anxiety; they have a moderate compute self-efficacy; and their attitude towards the
internet is positive. The results, research contributions, and limitations are discussed, and
implications for future studies are suggested