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Culture-Dependent Diversity Profiling of Spoilage Yeasts Species by PCR-RFLP Comparative Analysis
Get PDFPublished ArticleSpoilage caused by yeasts is a constant, widespread problem in the beverage industry that can result in
major economic losses. Fruit juices provide an environment that allows the proliferation of yeast. Some
factories in South Africa are not equipped with laboratory facilities to identify spoilage yeasts and outsourcing
becomes a prolonged process which obstructs corrective action planning. This study aimed to establish
yeast diversity and apply a rapid method for preliminary identification of spoilage yeasts associated with a
small-scale fruit juice bottling factory. Yeast population in the factory was determined by isolation from the
production environment, process equipment and spoiled products. PCR-RFLP analysis targeting the 5.8S-ITS
region and D1/D2 sequencing was used for identification. A total of 207 yeasts belonging to 10 different
genera (Candida, Lodderomyces, Wickerhamomyces, Yarrowia, Zygosaccharomyces, Zygoascus,
Cryptococcus, Filobasidium, Rhodotorula/Cystobasidium and Trichosporon) were isolated and identified
from the production environment and processing equipment. Candida intermedia, C. parapsilosis and
Lodderomyces elongisporus were widely distributed in the factory. Zygosaccharomyces bailii, Z. bisporus,
Zygoascus hellenicus and Saccharomyces cerevisiae were isolated from the spoiled products. The data
provided a yeast control panel that was used successfully to identify unknown yeasts in spoiled products
from this factory using polymerase chain reaction-restriction length polymorphism (PCR-RFLP) comparative
analysis
Optimising The Production Process Of Wood’S Alloy End-Frames For Electron Field Shaping In Radiotherapy
Get PDFDissertationSkin cancer is commonly treated by means of electron radiation generated by a linear electron accelerator (linac). The radiation applied must be limited or shaped to the size of the cancer-affected area on the patient. This is achieved through applicators that attach to the linac unit, while more precise field shaping is made possible through end-frames that fit into the front end of the applicators.
The end-frames are machined out of high-density metal such as lead or, as in recent years, cast in Wood’s alloy. Commercial jigs used to cast the Wood’s alloy present various shortcomings in terms of dimensional accuracy of the end-frames, density of the castings and high cost of the jigs.
The aim of this study was to develop a Wood’s alloy casting unit that can be made available to local oncology units to produce end-frames that are superior to what can be achieved through commercial jigs. The development and manufacturing of the new casting equipment is described as well as experiments that were performed to evaluate the equipment by comparing end-frames produced to those that were cast in the commercial jig. Results of the experiments show that end-frames cast in the newly developed casting equipment are dimensionally accurate, have consistent high density and can be produced in a short timeframe
Optimal Energy Management In A Smart Home, Based On Photovoltaic Systems Energy Feed-In Tariff: Case Of South Africa
Get PDFDissertationIn recent years, concern over environmental problems, such as the increase of
atmospheric temperatures and destruction of the ozone layer, have amplified on a global
scale. In the future, increased efficiency of energy systems and reduced end-use energy
demand will be significant in attaining the 6% curtailment of greenhouse gases, targeted by
the Kyoto Protocol. Although the energy research and development has been known over
an extended period in large buildings, it has recently been applied at household level.
In South Africa, there are approximately 9 million homes that have access to electricity.
Approximately 27% of the generated energy in South Africa was consumed by the
residential sector in 2015. This making the residential sector the second largest energy
consumer in the economy.
In South Africa, electricity is solely supplied by Eskom, a state-owned enterprise. For
the last decade, Eskom have experienced challenges in meeting the national demand. The
issue of the supply being less than the demand, has led to the requirement of additional
fossil fuel plants, which resulted in financial challenges. These financial challenges have
resulted in harsh tariff increases for consumers. With the aim to reduce the load-demand
of the grid during peak periods, the electricity supply commission (ESKOM), implemented
the time-of-use (TOU) tariff structure, billing consumers at a higher tariff rate during
certain periods of the day. These tariff increases are compelling consumers to search for
alternative ways in meeting their energy demand. Currently, many countries are permitting
residential consumers to install renewable forms of energy sources.
With Eskom contending to meet the load demand, load shedding was introduced, in
order to reduce the load demand during certain periods of the day. If load shedding was
never introduced, the load demand may have resulted in the grid collapsing. As a result of
the electricity challenge in South Africa, a few municipalities have begun revising the
regulations on small scale embedded generators, permitting consumers, under strict
regulations, to feed-back excess energy into the grid. This study used a solar photovoltaic
(PV) system, combined with battery storage. The mathematical modelling of the gridinteractive
PV, with battery storage system, has been developed to allow for optimal energy
storage and sales, while ensuring that the consumer load demand is met at all times, considering variable time-of-use (TOU) tariffs and load demand uncertainties, that may
take place in real-time context.
The aim is to develop a model for optimal operation of a residential grid-interactive PV
system with battery storage, operating under TOU and FIT tariffs. The research will further
assess the potential of energy cost saving and cost effectiveness that the system may
achieve, under the new residential feed-in tariff; along with the impact the battery storage
system will have on the profitability of the grid-interactive solar PV system.
Additionally, the second aim is to maximize the energy sales into the grid, if the system is
grid-interactive. The MATLAB optimization toolbox was used to evaluate the cost
effectiveness of the grid-interactive system, in terms of money spent.
The baseline system was established, consisting solely of energy supplied by the grid. The
optimal operation of the proposed system was simulated and compared to the baseline
system.
A life cycle cost (LCC) analysis was conducted for a period of 20 years, for both the
baseline and the optimally controlled grid-interactive PV with battery storage system
scheme. Results from the analysis indicated that the proposed system would break-even
in 11.5 years, with an approximate saving of 35%, translating into savings of R 270 022.83.
The results clearly illustrated that the consumer could save a significant amount if the
system is implemented correctly, including the parameters of the desired system. The
model showed that it could be used for different operating conditions, as long as the user
incorporates the new environment. The model clearly shows that managing the power flow
in a proposed system could be beneficial for electricity consumers in South Africa and not
merely for residential consumers
Dietary Inclusion Levels Of Ensiled Avocado (Persia Americana) Oil Cake Into Pig Diets And Their Effects On The Growth Performance, Nutrient Digestibility, Carcass Characteristics And Meat Quality
Get PDFThe value of ensiled avocado (Persia Americana) oil cake (AOC) in pig diets was evaluated through three experiments. The first experiment was conducted to evaluate the effects of an enzyme addition on the fermentation characteristics, nutritive value and aerobic stability of ensiled AOC. An amount of 700 g AOC /kg fresh matter (FM) was mixed with 250 g wheat bran/kg FM, and 50 g sugarcane molasses/kg FM. This mixture was treated without i) additive (control), or with enzyme (Axtra® XB enzyme) at ii) 3 % and iii) 5% levels, making three treatments in total. The enzyme contained endo-1, 4-β-xylanase (12.200 U/g) and endo 1,3β-gluconase, (1.520 U/g). The forage mixtures were thoroughly mixed and compacted into 1.5 L anaerobic jars. Jars were kept at 25-28◦C room temperature for 90 days and there were 36 jars with nine jars per treatment. Samples of the pre-ensiled mixtures were collected for the determination of nutritive values, pH and water soluble carbohydrates (WSC). Three jars per treatment were then opened on days 3, 7, 10 and 90 post ensiling to determine pH while those of day 90 were also used to determine nutritive values and fermentation profiles of the treatments. Further, silage samples of day 90 were subjected to an aerobic stability test that lasted for 7 days. It was found that good quality silage can be produced from AOC without (P >0.05) the addition of enzyme. However, the effect of enzyme addition was apparent (P<0.05) on the reduction of NDF and increased WSC of ensiled AOC compared to the untreated silage. Although enzyme addition was applied at two different levels (i.e. 3 and 5 %), increasing enzyme addition to AOC at ensiling was not worthwhile since it did not make any significant contribution. The second experiment was conducted to evaluate the effect of different dietary inclusion levels of AOC silage on the growth performance, nutrient digestibility and carcass characteristics in pigs. In this experiment, AOC silage was produced without enzyme additive and ensiled in 200 L drums for 90 days. Experimental diets that contained different levels of AOC silage (i.e. 0, 3 and 5%) were formulated and fed to twenty-seven Large White x Landrace (LW x LR) pig crosses, weighing approximately 22 kg live weight. The pigs were randomly allocated to the three experimental diets (9 pigs/ treatment) balanced on their live weights. Pigs were individually weighed at the start and weekly until the end of the trial. Data on daily feed intake, average daily gains and feed conversion rates were recorded. A nutrient digestibility study whereby daily feed intake and the outputs of faeces and urine were measured, was done a week after completion of the growth study. At the end of the nutrient digestibility experiment, pigs were fasted for twelve hours and weighed to determine the final weight. The pigs were then slaughtered at an abattoir and carcass samples were collected and analysed.
The growth performance of pigs was not (P >0.05) affected by dietary inclusion levels of AOC silage, irrespective of increased fibre levels in the AOC silage diets. However, dietary addition of 3 % AOC silage improved (P0.05) improving average daily gains (ADG) and feed conversion rates (FCR) in pigs. Further, the carcass characteristics of pigs were not (P>0.05) affected by diets, but the small and large intestines were increased (P0.05) affected by dietary treatments. Increasing the enzyme addition to the pig diets was not worthwhile, and enzyme addition only affected the feed intake and nutrient digestion. It was concluded that the AOC can be ensiled and used at less than 5 % in the diets of growing pigs without any detrimental effects on the growth of pigs
Tooling Through Laser Sintering In Maraging Steel For High-Volume Plastic Injection Moulding
Get PDFExisting techniques to manufacture conventional tool steel inserts for the plastic injection moulding process are expensive and time-consuming. Complex mould inserts, difficult to manufacture with conventional processes, can be produced using Direct Metal Laser Sintering (DMLS). DMLS is an additive manufacturing (AM) process that can produce complex functional metal components directly from computer aided design (CAD) data. Recent advances in materials and laser sintering technologies make it possible to process high-performance metals suitable for production components. Maraging Steel MS1, an AM material made available by EOS GmbH Electro Optical Systems (EOS), is a DMLS metal powder designed for tooling applications. It is an ultra-high-strength alloy that is resistant to corrosion, has good thermal conductivity properties and can be hardened with a thermal age-hardening process. Maraging Steel MS1 can be, and is easily machined and EDM spark-eroded in its ‘as-built’ state. Unlike conventional methods traditionally used in the manufacturing of metal components, DMLS can produce complex inner structures (such as conformal cooling) that can be beneficial for the tooling sector.
This dissertation describes an investigation into the possible heat transfer benefits of conformal cooling channels using Maraging Steel MS1 inserts which could result in a reduction of cycle times, cost per product as well as improving part quality by eliminating defects such as warpage and heat sinks.
Two AM inserts for an interlocking floor tile with different conformal cooling channel designs were compared using ANSYS® CFD and SIGMASOFT® virtual moulding to determine the most efficient cooling channel design. During the simulations, factors such as heat transfer rates and turbulent flow inside the cooling channels were considered and the most efficient design was selected based upon these factors.
A comparison between the most efficient AM insert design and an insert manufactured through conventional manufacturing techniques was conducted. Simulation results showed that an AM insert with conformal cooling channels can remove heat more effectively than conventionally manufactured cooling channels. By considering the increased solidification rate of the part produced through the AM insert, a reduction in cycle time of 10.7% was possible from the simulation results. Actual IM trials were conducted and temperatures inside both the AM and conventionally manufactured inserts were recorded. The temperature results recorded from the trials were within 4% of the simulated values. The outcomes from the experimental trials confirmed the simulated results, indicating that simulation software can successfully be used to analyse different cooling channel designs to identify the most efficient cooling channel layout.
After benchmarking the experimental results with the simulation results, the same simulation principles and methodology were applied to an industrial application. Both an AM and conventional insert design were simulated and compared in a virtual injection moulding situation. From the simulated results it was evident that the AM insert with conformal cooling channels was able to remove heat more efficiently than the insert designed for conventional manufacturing, resulting in a reduction of mould temperature and cycle times.
A manufacturing cost and lead-time comparison was conducted. For both cases considered, it indicated that the conventionally manufactured insert reached its break-even point after fewer IM cycles compared to the AM insert due to its lower manufacturing costs. During high-volume production, the AM insert will be more profitable due to its lower running costs and cycle time. From the research results it was concluded that the AM inserts with conformal cooling channels could result in a benefit for high-volume plastic injection moulding, resulting in shorter production times to produce a product
Factors Influencing Farmers' Fertilizer Practices On Irrigation Schemes In The Central Parts Of South Africa
Get PDFDissertationFertilizer containing macro and micro elements forms the basis of a good yield and should be
applied in correct quantities. Fertilizer should be applied at the correct physiological growth
stage of the plant. Of further importance is the cost associated with fertilizers, since it makes a
meaningful contribution to the total input cost per hectare of crop cultivation. A common
problem is that some farmers do not have sufficient knowledge of the fertilisation requirements
of plants to make an informed decision. This makes the farmer entirely dependent on the
recommendations of fertilizer advisors, who are also the salesmen, regarding the types and
quantities of fertilizers (macro and micro elements) to be applied. As a result of the ignorance
or skepticism of farmers, this may lead to under- or overapplication of inorganic fertilizers.
The overall objective of this study is to determine the fertilisation practices as applied by
farmers in the irrigation areas of the Jacobsdal, Prieska, Vaalharts and Douglas regions in the
central parts of South Africa. The study consist of four main objectives, namely:
1. to study the behavior of the farmers regarding their fertilizer management practices;
2. to study the fertilizer salesmen's behaviour and their influence on the farmers’ fertilizer
practices;
3. To determine the fertilizer companies’ marketing strategies and how they influence the
farmers’ decision making; and
4. To determine the level of variations in soil analyses results and recommendations between
different laboratories.
Various sub-objectives were formulated within each objective. A stratified random sample was
used to select the respondents for the study in order to ensure the representability of all groups.
To satisfy the first three objectives of the study, three questionnaires were constructed and
consequently filled via personal interviews with these farmers, fertilizer agents (salespersons)
and fertilizer companies as respective respondents. Both Excel and SPSS were used to analyse
the data while various statistical tests were used to identify trends and correlations within the
data.
Regarding the farmer’s behaviour concerning fertilizer management (the 1st objective),
significant differences were found between some of the four irrigation (sample) areas for the average nitrogen input cost per hectare for early planting (p = 0.0026) and late planting
(p < 0.0001). As far as differences in nitrogen cost based on the farm size are concerned, no
significant differences could be found between the nitrogen input cost between smaller and
larger farm groups. No significant differences were found in the phosphate and potassium input
costs per hectare between the four sample areas. However, a significant difference was found
between the small and larger farms at Vaalharts (p < 0.0001) vis-à-vis potassium costs per
hectare for early planting. Concerning the average cost for micro elements per hectare,
statistical differences was found for an early plant (p = 0.0226), as opposed to a late plant
(p < 0.0001) between some of the areas. When considering the total input cost of fertilizer per
hectare, the Douglas sample group was significantly higher than Vaalharts and Prieska
respectively. It was found that the size of the farming unit makes no significant difference as
far as the total input cost of fertilizer per hectare is concerned. The only exception was with the
Prieska sample group that showed a significant difference in packaging preference of fertilizer
bags, i.e. the larger farmers prefer to use large bags and bulk fertilizer, while the small farmers
prefer small (50kg) bags that can be moved by hand.
The respondents were divided into three groups according to their highest academic
qualification, as well as according to farming experience. No significant differences were found
between these education and experience groups when considering the various fertilizer
practices and assessment of the fertilizer salesmen. The only exception was the significantly
better (p = 0.0059) ability of the group with tertiary agricultural qualifications to understand
the soil analysis report and verify the fertilizer recommendation made by the fertilizer agent.
None of the other demographics (e.g. age, experience and gender) play any significant role in
farmers’ fertilizer practices.
It is recommended that farmers must apply different strategies to control or manipulate the
price of their inputs without compromising yield, soil fertility and the long-term sustainability
of the farming unit. These strategies will differ between farmers due to every farm’s unique
situation, for example economies of scale and the financial position (liquidity) of the farming
business. Regarding the profile of the fertilizer salesman, it was found that when the financial position
of the farming business (i.e. restricted or surplus funding and target yield) is disclosed to the
fertilizer agent, significant differences were found in the quantities of nitrogen, phosphate and
potassium that were recommended by the sales representative, especially reduced N and P
when funds are limited, while significant higher application rates of N, P and K were made when funding is no limitation and nutrient reserves need to be improved. It is recommended
that a farmer must select the fertilizer salesperson with extreme prudence. This person provides
valuable information that will assist the farmer to make decisions that will have a huge impact
on the financial success of the farming business, while it will also influence soil fertility and
contribute to the long-term sustainability of the farm.
Regarding the 3rd objective, whereby the marketing strategies of the fertilizer companies were
perused, the farmer should always bear in mind that a fertilizer company’s mail goal is
maximum profit and not the welfare of the farmer as individual. They all sell basically the same
product and farmers must keep in mind that the company’s agronomic services (for example
soil sampling and cost of analysis), may be costly as it is then integrated into or added to the
price of the purchased fertilizers. Alternative independent agronomic services are available and
the cost thereof can be offset by purchasing much cheaper fertilizers, resulting in a much lower
total cost.
The 4th objective of the study was to investigated variations in soil analysis reports or results
amongst four different laboratories in South Africa. A large soil sample was taken under
supervision of an independent agronomist, then thoroughly mixed and divided into forty (40)
sub-samples. These were sent to four different soil laboratories one week apart in three
different batches. The laboratories were unaware that the three batches were from the same
source. By using an ANOVA, the results of the soil samples were statistically analysed and
meaningful differences (p < 0,05) were found in the analysed levels of macro-elements (N, P
and K) between laboratories as well as between different batches within each laboratory. Less
variation was found with regard to microelements where significant differences were only
found in the analysed copper (Cu) and boron (B) contents of some labs. The study results
indicated that meaningful variations may occur between different laboratories, although it was
found that some laboratories have less or almost no variation between the different batches that
were analysed. A laboratory with the most consistent results must thus be used in order for the
farmer to create a reliable record of the trends in soil fertility status of the farming unit
Numerical Analysis Of The Bivariate Local Linearization Method (BLLM) For Partial Differential Equations In Casson Fluid Flow
Get PDFPublished ArticleThe double diffusion convection Casson fluid flow along a vertical plate incorporating Soret effect and
viscous heating with thermal and solutal dispersion was studied. A well-known system of non-similar partial
differential equations was solved using the bivariate local linearization method (BLLM). The solution procedure
uses an approximation by a bivariate Lagrange interpolation polynomial. Older methods considered collocations
along the non-dimensional boundary layer axis η only. In this paper collocations in both the (η, ζ) directions are
considered. The numerical method is compared to the results obtained by the quasi-linearization method (QLM)
and those previously published in the literature for the case (ζ = 0). This work also analyse the efficiency and
robustness of the numerical method used as compared to traditional methods such as finite differences widely used
in the literature. The increase in thermal stratification parameter decrease heat transfer coefficient and increase
mass transfer coefficient. The increase in the non-Newtonian parameter result in the increase velocity profiles, skin
friction coefficient and reduce both temperature and concentration profiles. Increasing the Biot number decrease
temperature trends
Motivational Value of Code.org’s Code Studio Tutorials in an Undergraduate Programming Course
Get PDFPublished ArticleAs part of an instructional strategy to improve undergraduate
software development students’ basic understanding of programming
constructs, students completed a selection of Code Studio tutorials during
the first three weeks of their programming course. Block-based environments,
such as the one used by the Code Studio tutorials, typically
make it easier for students to learn programming as they can focus on
concepts instead of syntax. Students are, however, less likely to regard
an instructional strategy as meaningful if it presents no motivational
value for them. In this paper, Keller’s ARCS Model is used to organize
the knowledge gained regarding student motivation and the motivational
strategies supported by the Code Studio tutorials. Results obtained from
analysis of numeric and narrative data collected through a paper-based
self-completion questionnaire confirm the high motivation value of the
Code Studio tutorials. The results provide insights regarding students’
perceptions of Code Studio tutorials as a motivational instructional strategy
in an undergraduate programming course. Since students perceive
the Code Studio tutorials to have some educational value, further investigations
should be conducted to consider more appropriate and effective
ways to integrate Code Studio tutorials with undergraduate programming
curricula
Exploring Perspectives of the Information Technology Industry in a South African City
Get PDFPublished ArticleThe information technology (IT) industry has come to the forefront for economic
development of several cities in developing countries such as India and China. Looking at the
success of the IT industry in these countries, an argument has emerged that development of such
industry in South African cities can revitalize their economy. Therefore, the study examined the
potential of development of the IT industry in a South African city by using the case study of a largely
service-oriented city—Bloemfontein. A survey research method and system dynamics modeling
approach were used. Findings suggest that the city has the potential to emerge as an IT industrial city,
however, there exist challenges with regards to infrastructure such as housing, built up space, energy,
and attracting the knowledge workers to the city. Appropriate policy interventions to reinforce these
infrastructures, which can assist to attract the knowledge workers, will enable enhancement in the
earning from the IT industry. Also, the development of the IT industry will strengthen the housing
and built up infrastructure for the IT industry as well as enhance the number of knowledge workers
in the city
GIS Applications to Investigate the Linkage between Geomorphological Catchment Characteristics and Response Time: A Case Study in Four Climatological Regions, South Africa
Get PDFPublished ArticleIn flood hydrology, geomorphological catchment characteristics serve as fundamental input
to inform decisions related to design flood estimation and regionalization. Typically, site-specific
geomorphological catchment characteristics are used for regionalization, while flood statistics are
used to test the homogeneity of the identified regions. This paper presents the application and
comparison of Geographical Information Systems (GIS) modelling tools for the estimation of catchment
characteristics to provide an enhanced understanding of the linkage between geomorphological
catchment characteristics and response time. It was evident that catchment response variability is
not exclusively related to catchment area, but rather associated with the increasing spatial–temporal
heterogeneity of other catchment characteristics as the catchment scale increases. In general, catchment
and channel geomorphology overruled the impact that catchment variables might have on the response
time and resulting runo . Shorter response times and higher peak flows were evident in similar-sized
catchments characterized by lower shape factors, circularity ratios, and shorter centroid distances
and associated higher elongation ratios, drainage densities and steeper slopes. The GIS applications
not only enabled the inclusion of a more diverse selection of catchment characteristics as opposed to
when manual methods are used, but the high degree of association between the di erent GIS-based
methods also confirmed their preferential use