School of Engineering and the Built Environment

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Dialogical system design across cultural boundaries
(2001) Winschiers, Heike; ; ;
Engineered kinetics about photocatalytic degradation of textile wastewater
(2006) Shigwedha Nditange
Capacity for public-private sectors to implement e-governance (CP-PSIe): Enhancing information and service delivery in Namibia.
(2014) Funda, Semba
e-Governance is being used by many governments around the world to improve information and service delivery to their citizens. This is achieved mainly through the use of Information and Communication Technology (ICT) solutions. As a result, the capacity for Public and Private Sectors to implement e-Governance plays a pivotal role in making e-Governance a success. Through the use of qualitative and quantitative research methods, this study took an in-depth look at the current levels of capacity in Namibia. The study found that the lack of available capacity in the country is a critical barrier in many e-Government initiatives in Namibia causing them to move at a very slow pace. Furthermore, it was also found that the majority of the Namibian citizens do not know what e-Governance is and are not aware of any e-Government projects that are already underway. It is evident that the development of capacity in the country would impact positively on e-Government projects and would also reduce Namibia’s dependence on foreign and usually expensive consultants to pilot them. In this vein, the study proposed ways in which the available capacities could be utilised. It further made suggestions on how the missing capacities could be acquired and also suggested how the Public and Private Sectors could collaborate with each other for the efficient delivery of e-Governance in Namibia. Lastly, but not the least, the study concludes by emphasizing that the Namibian Government urgently needs to prioritise the development of e-Government capacity to ensure that e-Governance implementation becomes a success.
A comparison of the performance of Namibia-specific conservation and conventional tillage technologies as used for pearl millet production in northern Namibia
(University of Namibia, 2017) Mudamburi, Bertha
Studies were conducted over a period of three years (2011 to 2013) at the Ogongo Campus of the University of Namibia (UNAM), to compare the differences between tractors and animal-drawn implements both using conventional and Namibia Specific Conservation Tillage (NSCT) technologies. Two conventional tillage (CV) treatments (i.e. tractor-drawn disc harrow (TDH) and animal-drawn mouldboard plough (AMP) were compared to two NSCT treatments (tractor-drawn ripper furrower (TRF) and animal-drawn ripper furrower (ARF). There were four specific objectives. The first objective is to compare the field performances compare the field performances of the two technologies each for the NSCT and CV on (i) depth of cut, (ii) width of cut, (iii) draught of the power source (iv) efficiency and v) effective field capacity under Ogongo conditions. NSCT technologies (TRF and ARF) performed better than CV technologies (TDH and AMP) on depth of cut in all the three years. Though the NSCT technologies also resulted in higher draught forces than the CV technologies, however, the specific draught of NSCT technologies were better across the three seasons showing that they were more energy efficient than CV technologies. Tractor drawn tillage methods resulted in lower specific draught than animal-drawn tillage methods across the three years. ARF performed better than AMP in the last two years. None of the tractor-drawn implements in the study met the ASAE Standards of Efficiency (70-90%). The on-station field efficiencies fell short by 16% for TDH and by 8% for TRF. Across the three years, the effective field capacities for tractor-drawn tillage methods were: TDH = 0.68 ha hr-1, TRF = 0.74 ha hr-1. For animal-drawn tillage methods, the effective field capacities for AMP = 0.03 ha hr-1 and for ARF = 0.15 ha hr-1, 80% better than AMP.
Echo state network approach for radio signal strength prediction applied to cellular communication frequency bands in northen Namibia
(University of Namibia, 2018) Gideon, Kenneth
Reliance on mobile connectivity has led to demands for wireless spectrum capacity to grow on a daily basis resulting to congested networks. Ensuring acceptable levels of Quality of Service (QoS) for users in wireless communication systems, through continuous wireless network analysis using simulation tools based on radio propagation models has become increasingly prominent. To provide automated analytical model building, the use of machine learning methods has been considered to predict characteristics of the wireless channel. Thus, in this work, a method for predicting radio signal strength using Echo State Networks (ESNs) is proposed and applied to three different locations in Northern Namibia. This method aims at providing a better approach for radio signal strength prediction, which leads to improvements in wireless communication planning, design and analysis. Its performance is compared with the Support Vector Regression (SVR) method optimized for radio propagation modeling. Simulations are conducted in Python using propagation data measured from the three locations based on the following four performance metrics: goodness of fit criteria; error measures; computation complexities; and F-Test for statistical model comparison. Simulation results show that the ESN gives a better prediction accuracy in terms of the goodness of fit criteria and the error measures (i.e. average R2 = 0.82 and average mean absolute error (MAE) = 0.0312 for ESN compared to 0.648 and 0.0624 for SVR), but it is inferior to the SVR in terms of computation complexities (i.e. average training complexity of 410 ms and average testing complexity of 79.0 ms for ESN compared to 8.19 ms and 1.04 ms for SVR). In addition, results from the F-Test also indicates that the ESN provides a significantly better fit than the SVR.
Performance evaluation and redesign of waste stabilization ponds for the treatment of wastewater in Ongwediva
(University of Namibia, 2018) Rukoro, Oriri
The existing Ongwediva Waste Stabilization Ponds have had several problems in their operations over the past years. Thus, the treatment performance of the waste stabilization ponds was assessed in terms of the reduction efficiency of some physical, chemical and biological pollutants of importance. Data were collected daily from May to June 2017 and analyzed for both raw and treated wastewater. Results of these investigation showed that the average effluent concentrations of BOD, DO, TSS FC, nitrate, nitrite, ammonia, pH, EC and turbidity taken at the secondary facultative pond were 22.07mg/l, 1.91 mg/l, 21.73 mg/l, 2×105 counts/100 ml, 2.33 mg/l, 0.39 mg/l, 0.74 mg/l, 7.64, 16.67 NTU and 98.52 mS/m respectively. The results also indicated that the average effluent concentrations of BOD, nitrate, nitrite, ammonia, TSS and pH complied with the Namibian treated wastewater standards for disposal. However, FC, EC, TDS and turbidity exceeded their maximum permissible limits. The lowest overall efficiencies were for EC, TDS and FC of 5.05%, 5.12% and 20% respectively. Hence the addition of two maturation ponds of size 5408m2 as a final stage of OWSPs. The design of facultative ponds can also be modified by adding additional entrances of wastewater to the ponds to make complete mix in the ponds.
Water resources governance in the upper Swakop basin of Namibia
(University of Namibia, 2018) Pazvakawambwa, Godfrey T.
This dissertation examined and presented adaptive water governance analysis and tools for the Upper Swakop Basin (USB) in Namibia where integrated river basin management is still in its infancy. The water governance concerns in the basin include pollution monitoring and control challenges that are further threatening the security and adequacy of the developed drinking water sources. By applying and triangulating different methods (models, statistical analysis, quantitative and qualitative measures etc.), this study uniquely analysed the water governance issues in the Upper Swakop Basin. The objectives of the study were to assess the water quality at potential pollution sources and at major receiving waters in the Upper Swakop Basin based on secondary data obtained from key stakeholders; to evaluate the adequacy and availability of drinking water sources in the USB; to assess the ethical, social and acceptability perceptions of water reuse for potable purposes based on primary data obtained from a purposive stakeholder survey; to qualitatively assess water governance structures and participation as well as to evaluate overall water governance processes and outcomes in the USB. Water quality parameters were assessed using descriptive statistics, extreme value analysis, spatial analysis and some of the parameters were compared to those given in the water quality regulations and standards of Namibia using ANOVA. The adequacy and availability of water was assessed using the simple water balance method, the Box-Jenkins ARIMA time series forecasting models, and the WEAP model. The ethical, social and health acceptability views and perceptions on water reuse for potable purposes were assessed using frequency tables, charts, and graphs. Stakeholder participation was analysed using scenario workshops, mediated modelling and social multi-criteria evaluation methods and was based on the ADVISOR framework. The researcher developed the 7”I”s water governance tool which was used to map stakeholders and to assess the overall water governance performance of the USB. The study found that water pollution parameters values were extremely high for agro-industries. Moreover it was found that the developed water resources supplying the USB are inadequate especially in Windhoek where additional drinking water sources outside the USB are required to augment its demand of 26.7 Mm3 per annum in 2015 to a projected amount of 52.93 Mm3 per annum in 2050. Acceptability levels of water reuse for potable purposes were found to be moderate. Stakeholder participation in water governance needs to be more inclusive. The existing legal and institutional framework for water governance was found to be inadequate due to lack of implementing technical capacity (in terms of personnel, technical skills, database management and information sharing). One of the unique contribution of the study to new knowledge is the development of the 7”I”s evaluation tool for overall water governance performance which can also be used in other similar basins. The pollution extreme parameter values assessment is proposed as a quick and initial evaluation of any problematic river catchment and to take remedial measures on would be polluters. Proper water pollution control and compliance strategies should be stepped up for agro-based industrial landuses. Landuse based water governance policy interventions may be required to prevent water pollution on the Swakoppoort Dam. The study proposed a new concept of utilizing the smaller already polluted Goreangab Dam, which receives polluted water from Windhoek and is situated upstream of Swakoppoort Dam, as a pollution detention and check dam as well as a clean-up dam for the downstream dam. A study on the feasibility of this new concept should be carried out. If the concept proves to be successful, it could be used to solve the problem of polluted dams downstream of “city river catchments” elsewhere. The time series of the rainfall in Windhoek area was stationary. This could mean climate change might have had little effect on Windhoek rainfall for the past 121 years. Therefore the study recommended more adaptive water resource planning, multi-source optimization and water governance initiatives of exploring the available secondary sources for the sustainable development of the USB. Water security in the USB can be enhanced by optimizing the Windhoek Rechargeable Aquifer Storage capacity. Institutions that supply bulk water to Windhoek can be unified into a single water governance institution to optimize and integrate these multiple sources. Based on adaptive water governance resource planning and multi-source optimization, the study further proposed a basin management strategy to ensure suitable water quality and quantity and to build adequate technical capacity.
Failure of pump systems operating in highly corrosive mine water at Otjihase mine
(2018) Hango, Silas Ithete
In the Namibian Otjihase underground mine, water is pumped from natural underground reservoirs to the surface using mild steel pumps that have cast iron valves and shaft sleeves coated with a Ni-Cr-Fe alloy. As these components failed very frequently in the highly corrosive mine water environment, it became necessary to provide recommendations for alternative pump materials. The Ni-Cr-Fe coated, carbon steel shaft sleeves were mechanically worn by abrasion in contact with debris trapped in packing glands. The highly corrosive mine water contained solid soil particles, which contributed to internal erosion-corrosion of the pump components. Once the protective coating was breached, the exposed steel corroded rapidly when reacting with the corrosive mine water, resulting in leakages. The main objective of this work was therefore to characterise the steel and cast iron components used in the pump system, determine methods to improve the tribocorrosion resistance of the pump components and recommend a hardfacing material with improved performance in the tribocorrosive mine environment. To simulate and study the synergistic effect of electrochemical and mechanical interaction between the pump components and highly corrosive mine water, the hardness and electrochemical response in synthetic mine water of the following proposed bulk materials were tested: Hastelloy G30, ULTIMET, Stellite 6B and ToughMet 3. Hastelloy G30 demonstrated good corrosion resistance, but had low hardness and poor abrasion resistance. ToughMet 3 had high hardness, but low corrosion resistance. As ULTIMET and Stellite 6B both had high hardness and good corrosion resistance, they were selected for further investigation to assess sliding abrasive wear and tribocorrosion behaviour in synthetic mine water. The possibility of enhancing the corrosion resistance of ULTIMET and Stellite 6 (not 6B) alloys as protective coatings by adding minor amounts of ruthenium was investigated. ULTIMET and Stellite 6 powders were each mixed with nominal 0.3 wt% Ru and nominal 0.6 wt% Ru additions. The powders with no Ru, nominal 0.3 wt% Ru and nominal 0.6 wt% Ru were then thermally sprayed by the high velocity oxy-fuel flame (HVOF) process onto a carbon steel substrate, and compared to a Cr2O3 coated steel as a benchmark. The powders and the coatings were characterised using optical and scanning electron microscopy with energy dispersive X-ray spectroscopy, and X-ray diffraction. Hardness, sliding abrasive wear, and corrosion and tribocorrosion behaviour of the coatings and the substrate in synthetic mine water were then determined. Comparison of the hardness showed that the nominal 0.3 wt% Ru ULTIMET coating had higher hardness than the same coatings with no Ru and nominal 0.6 wt% Ru, the nominal 0.6 wt% Ru Stellite 6 coating had the highest hardness and overall, the Stellite 6 coatings had higher hardness values than both ULTIMET and Cr2O3 coatings. At pH 6, the ULTIMET and Stellite 6 coatings with and without Ru additions had low corrosion current densities and consequently low corrosion rates in synthetic mine water. For the ULTIMET coatings, the corrosion rates decreased as the Ru content increased. The Stellite 6 coating had slightly lower corrosion current densities and corrosion rates than ULTIMET under all tested conditions. Stellite 6 coatings had lower abrasive wear rates at the tested loads than the other materials. The lowest abrasive wear rates were recorded with additions of nominal 0.3 wt% Ru (5 N), and nominal 0.6 wt% Ru (10 N). As expected, tribocorrosive wear rates increased with increasing load for all alloys. Ruthenium additions to ULTIMET and Stellite 6 coatings decreased the tribocorrosive wear rate. The best tribocorrosion resistance was achieved by the Stellite 6 coatings. Stellite 6B bulk samples and Stellite 6 coatings with Ru had higher hardnesses, lower corrosion rates, lower wear rates and lower tribocorrosion rates than the carbon steel substrate, Cr2O3 coating, and ULTIMET bulk material and coatings. Stellite 6 coating with nominal 0.6 wt% Ru exhibited lower corrosion rates at pH 6 and 3 than the ULTIMET coating. Therefore, the Stellite 6 coating were recommended for use in pump shaft sleeves and the Stellite 6B bulk alloy in valves at Otjihase Underground Mine. The cost saving for using the proposed alternative materials was calculated as US$ 8 546.68 (R 128 200.20) per year. This is a major economic incentive for Otjihase Underground Mine
Assistive technology for students with dyslexia at Eros Girls School
(University of Namibia, 2019) Veiko, Veiko
Assistive Technology for Children with Learning Disabilities (ATCLD) was developed in response to the language and arithmetic challenges faced by learners with dyslexia of Eros Girls School (EGS). This development followed from requirement elicitation and is intended for grades 5 - 7. Having discussed the above, Assistive Technology (AT) is any item, piece of equipment or product system, whether acquired commercially off the shelf, modified, or customised, that is used to increase, maintain, or improve the functional capabilities of children with disabilities (“Assistive Technology Device”, 2004). As a counterexample to numerous schools in Namibia, EGS enrols and educates pupils diagnosed with learning difficulties in regular teaching and learning environment. Equally, the Ministry of Education (2009) states that Namibian classes have a wideband mixed ability range of learners, and learners with special educational needs are often included in mainstream school. In response to the dilemma outlined, this study developed ATCLD which is characterised with text to speech features to enable compensatory learning that emphasises repetition. The endeavour of ATCLD pursued the following methods; the Initial and final stage utilised qualitative; case study and quantitative; experimental techniques respectively. Mixed methods state the blend of these approaches. The inferential statistics of the ATCLD, a part of the text – speech assistive technologies of Namibia now, associate younger children with most improved mark. This implies that younger children have the capacity to create new schemas for information. It is reasonable to acquaint them with basic knowledge, since doing this at a later stage may implicate. Furthermore, the widespread input and output text to speech and speech to text assistive technology would expand this research in the future.
Assessment of hydraulic performance of the Eastern National Water Carrier, Namibia: Flumes three to four
(University of Namibia, 2019) Mutelo, Mukendoyi A.
In response to drought impacts, water augmentation by developing more boreholes in the Grootfontein-Otavi karst area and increase the use of the Eastern National Water Carrier (ENWC) was prioritised. Hence, plans to increase water transportation should be based a sound understanding of the hydraulic behaviour of the ENWC. Thus, this study sought to utilise the HECRAS model for the primary objective of assessing the hydraulic performance of the section between flumes 3 and 4 i.e. evaluating the hydraulic behaviour of the ENWC and determining its maximum water transportation capacity using HEC-RAS as well as perform a rough estimate of leakage and evaporation losses. The results show that the mean Manning's roughness coefficients n = 0.099, 0.124, 0.028 and 0.038 were respectively found in Canal! and 2, and Siphon land 2. An assessment of observed and the predicted water depth exhibited a very good agreement, that yielded an R2 = 0.997. The estimated maximum capacity of the canal system between flumes 3 and 4 was found to be discharge Q = 0.3 m3/s while the flows accommodated in different sections of the canal ranged from Q = 0.3 to 1 m3 /s. A variation of the roughness coefficients did not seem to noticeably alter the estimated maximum capacity or influence the water levels of the normal flow regimes. With respect to leakage losses, the majority of canal sections i.e. Canal 1, Siphon 1 and Siphon 2, bad leakage losses of the order of20% or more of mean discharge in those respective sections. Therefore, it can be deducted that the hydraulic state of the aqueduct is undesirable when compared to the roughness condition n = 0. 015 of concrete-lined aqueducts. Hence robust strategies for operation and maintenance of the aqueduct are required.
Cryptosporidium screening of selected water resources of the Cuvelai-Etosha basin and Kunene basins and implications for water management
(University of Namibia, 2019) Muhenje, Swanu
In the Cuvelai-Etosha and Kunene Basins, a remarkable percentage of the population depends on a variety of unprotected water resources for both domestic and livestock purposes, which includes Earth dams, wells, boreholes and streams. Waterborne transmission of Cryptosporidium could be prevalent in water basins were water resources have no protection against direct-microbial contamination. However, little is known about the influence of management of water resources on Cryptosporidium prevalence. The main objective of this study was to assess the prevalence of Cryptosporidium in selected water resources of the Cuvelai-Etosha and Kunene basins and assess the implications of findings on water management. On-site parameters of conductivity, dissolved oxygen, temperature and pH were measured from a total of 47 water samples from 47 sampling sites were screened for Cryptosporidium at the end of the rainy season by quantitative polymerase chain reaction (qPCR). The results showed a prevalence of 4.3 %, all from unprotected water resources which suggest that management (protection) of water resources from direct access to animals and direct-runoff is essential to lower the risk of waterborne infection of cryptosporidiosis. We recommend source protection of water resources in the basins to lower the risk of Cryptosporidium contamination. Further longitudinal studies screening for Cryptosporidium should be conducted to assess prevalence.
The use of life cycle cost analysis in determining the cost effectiveness of railway lines' design and maintenance options for railway lines through windblown sandy desert in Namibia: Case study of the Aus - Luderitz railway line
(University of Namibia, 2019) Hamalwa, Jonas
Railway transport in Namibia is one of the most important mode of transport with great importance to the economy of the country. Currently, road networks are the most important because of the low population density of the nation. However, railway lines have been reported to be the most economical, efficient, environmentally friendly, and the safe solution for long distance transportation of heavy goods [1]. The Namibian Railway Network lines linking to the coastal towns and ports, i.e. Swakopmund-Walvis Bay and Aus-Lüderitz Railway Line, are passing through the Namib Desert. Deposit of wind-blown sand onto the railway lines poses a great challenge to the maintenance and operations of this lines. The challenge for decision-makers is which solution is cost-effective to implement in the Namibia context to solve the problem. It has been reported widely [2, 3, 5, 7] that the best way to evaluate the cost effectiveness of different solution is by using the Life Cycle Cost Analysis (LCCA) approach. The main objective of this study is to use LCCA, as an engineering economic tool, to determine the cost-effectiveness of the options to the challenging wind-blown sand on the railway lines passing through the desert. Specific objectives are: 1) Identify the best infrastructure design options and technical maintenance solutions for mitigating the sand problem onto the tracks. 2) Use the LCCA to evaluate the cost-effectiveness of the different solutions in order to recommend the best strategy. The study has exploded the knowledge of the LCCA of railway infrastructure in Namibia for both the analysts and decision-makers. This study has presented a good insight of the LCCA as one of the best systematic approach to use to guarantee the best performance of the railway system. Ultimately the LCCA was successfully employed in the study to determine the cost-effectiveness of the solution(s) to combat the challenge of sand ingress onto the railway line. In the LCCA process, different alternatives were identified, discussed and analysed; which includes both railway infrastructure design solutions and technical mitigation measures. The LCCA results presented the Humped Slab Track to be the cost-effective solution compared to all other alternatives. However, it was further discussed that this option is only ideal for the sections where dynamic dunes are not crossing. This has proven that in as much as LCCA is a good engineering economic tool, it needs to be coupled with viability criterion/criteria in order to determine the cost-effectiveness of the design and maintenance solutions to combat the challenging problem of wind-blown sand on the railway line passing through desert areas. The study further proved that Tubular Track system was cost-effective compared to the Conventional Track system. The study provides a good insight of analysis to prove that Tubular Track system covered in the Tunnel System is the most viable and cost-effective solution to the sand problem along the dune belt. A number of recommendations for future improvement(s) and further researches were also proposed.
Assessment of the impact of urban development on flood peaks in the Acacia surburb, Arebbusch sub-catchment Windhoek, Namibia
(University of Namibia, 2019) Coetzee, Dirk Jones
Climate change is affecting global weather patterns, more so by exacerbating the sporadic nature of Namibia’s rainfall patterns. This has negative consequences on urbanization as increased rainfall in certain rainy seasons coupled with increased urban development could lead to dangerous flooding in low-lying areas, as was the case with Acacia residential, Windhoek, in 2004. Increased urban development has the potential to increase runoff and flood peaks by 20% to 50% of those under natural conditions. This study investigated the urban development in the greater Arebbusch catchment, and its impact on the Acacia suburb. Employed methods and techniques comprised remote sensing, GIS, SANRAL Drainage manual and hydraulic modelling software (HEC-RAS). Landsat and Sentinel images were used to produce and determine land cover changes in the study area between 1989 and 2018, respectively. Furthermore, computer models of the Acacia River section, the steady and unsteady flow simulations and flood inundation area were carried out in the Acacia residential area and compared with the existing, regulatory 1:50-year flood line that the City of Windhoek uses as reference for urban development. Results indicate that the flood peaks in the study area increased by 13% over the past 30 years. This suggests that urban development influenced flood peaks in the study area, whilst the 1:50-year flood line remains static. It is therefore recommended that more assessment be done on the hydraulic flow of all constructions in close proximity to the 1:50-year flood line, whilst taking into greater consideration the accumulative effects of urban development on urban flood peaks.
Assessment of the impact of Namibian rural road characteristics on crash incidence
(2020) Ambunda, Robert; Johannes, Petrina
Road user perceptions and roadway design elements play a vital role in determining the crash risk level on the roads. The study investigated factors that play a prominent role in causing road traffic crashes on rural roads on the Namibian road network. The study found that animals and pedestrians were the highest cause of road traffic crashes on the study sections. The high volume of vehicles traversing the roads section combined with the lack of appropriate barriers to separate traffic from the high presence of animals and pedestrians along the study section contributed to the hazardous safety situation on the road. The study identified that drivers losing control of vehicles on the study sections was one of the highest cause of traffic crashes. Speeding combined with negative design of various road elements directly impacts driver perceptions of the road environment and misleads road users, thereby leading to human errors that influence the frequency and severity of road crashes on the study section. The study identified under-reporting and misinformation on road crashes as some of the factors impeding the development of a vivid picture on the actual scale of the road safety problem on Namibian rural roads. The analysis of the road crashes will assist and enable road safety stakeholders in identifying, developing and implementing appropriate safety measures to sustainably address the road safety issue on Namibian roads. In addition to the road safety assessment, a road design audit carried out on the study section found that the shoulder grade and lane widths did not comply with the Technical Recommendations for Highways 17 on the Geometric Design of Rural Roads in Namibia. The study therefore developed multivariate road crash models using Negative Binomial Regression to investigate the extent of the link between road crash rates of various severity and the road design elements. The models identified several interactive relationships between lane widths, shoulders widths, 85th operating speed and horizontal curve radii on the section that significantly influenced crash rates on the roads.
An intrusion detection system using recurrent neural network with a real-world dataset
(University of Namibia, 2020) Aludhilu, Hilma Ndapewa
Computer network technologies have grown speedily in the last decade and they are susceptible to numerous intrusions. Recently, Deep Leaming methodologies for example Recurrent Neural Networks have been the new trend for building Intrusion Detection System (IDS). However, Recurrent Neural Network (RNN) IDS can be biased, as datasets from real-world production networks are mostly not used during the training of IDSs. The purpose of this study is to develop an IDS using RNN with two datasets from real-world networks and one synthetic dataset. The study aims to create a dataset from real-world network traffic, train an RNN model and test the corresponding IDS using several datasets: from real-world networks (Kyoto and UNAM datasets) and also synthetic (NLS-KDD dataset). Finally, the performance of the RNN-IDS is evaluated. A quantitative research design, with the experimental approach, is used for this study. An experiment is carried out to compare several RNN architectures: basic RNN, LSTM and GRU, offering insight into how the RNN architectures perform when trained and tested with real-world and synthetic datasets. The results of the study show that the GRU model outperformed other RNN architectures with an accuracy score of 95% using the real-world datasets and 97% using the synthetic dataset. The study concludes that the GRU model performs well with real-world datasets. Furthermore, the study recommends finding methods to solve the imbalance of classes in real-world datasets, without turning the data into synthetic data. It is also recommended to consider the environment in which the IDS will work in, before choosing the best model to be used.
Assessment of copper recovery from leaching of microwave pre-treated tailing from the Otjihase mine
(University of Namibia, 2020) Amuthenu, Victoria L
Copper forms one of the world 's most important metals, with vital properties such as high malleability, toughness, and is an excellent conductor of heat and electricity. These properties make copper su itable for a vast range of industrial applications, and predominantly electrical applications. Currently, Namibia has a limited number of active copper mines, and hence a means to recover copper from secondary sources would positively impact Namibia's copper production and would also be beneficial to the Namibian economy. In this study, the assessment of copper dissolution efficiency by microwave-assisted leaching is considered. XRD analysis of the as-received mine tailings revealed that copper is present in the tailings material in the form of sulphide minerals only, covellite (CuS) and chalcopyrite (CuFeS2). Dry mine tailings of particle size -75μm were subjected to microwave pre-heating for 6 minutes in a domestic microwave oven for varying microwave intensities. This was followed by leaching with 0.5M Sulphuric Acid at varying temperatures and leaching times, in a water bath at atmospheric pressure. Results of the effect of leaching time, leaching temperature and microwave irradiation intensity are provided in this work. The results suggest that increasing leaching time and leaching temperature has a slight positive impact on copper leaching efficiency, with the highest recovery of 36.13% obtained at a leaching time of 50 minutes, leaching temperature of 80°C and microwave pre-treatment power of 700W. It was also observed that increasing microwave power from 100 to 700W had no significant impact on the efficiency of copper dissolution. Shrinking core models revealed that diffusion through the product layer, as governed by the equation kdt = 1 - 2x8 - (1 - X8 ) 2!3 was found to 3 be the rate-determining step, and hence the dissolution reaction mechanism. Arrhenius plots were used to determine the activation energy, which was calculated to be in the range of 7.7- 22.69kJ/mol. Multiple linear regression revealed that microwave power, leaching time and leaching temperature were related to percentage copper recovery by the following equation: Rcu = 4.8525 * 10-4 i + 4.8325 * 10-2 t + 1.11565 * 10-1r + 23.92999
Factors affecting the adoption of sustainable water conservation practices in smallholder farming systems: A case study of smallholder farmers in Omusati region, Namibia
(University of Namibia, 2020) Amukuhu, Bernadette N.
Namibia is the driest country in Sub-Saharan Africa and water shortage remains a serious challenge in agricultural productivity. Smallholder farmers in rural areas are often advised to adopt sustainable water conservation practices aimed to counter these challenges. However, the adoption of such practices among smallholder farmers is far below the expectations. Hence, this study was conducted to examine the current sustainable water conservation practices used by smallholders and what influential factors affect adoption of the introduced water conservation practices. A random sample of 30 smallholder farmers from six constituencies in Omusati Region was used. Field observation and a two-part questionnaire were used to collect data used in examining the level of water conservation adoption and to profile smallholder farmers. Descriptive and analytical statistics were used to analyse the collected data. The study showed that some sustainable water conservation practices such as ripping, planting basins, compost and drip irrigation were being adopted. ANOVA test results indicated that education status and farming experience of household heads have a significant impact on adoption rate of the introduced sustainable water conservation practices. Conversely, family size per household, farm size or cultivated land and the age of household heads have no significant effects on the adoption of sustainable water conservation practices. The challenges affecting smallholder’s adoption of sustainable water conservation practices include lack of farm implements, lack of water conservation awareness, climate characteristics, lack of funds, shortage of farm labour, lack of water conservation knowledge, limited farmland for cultivation and lack of extension services and institutional supports. Based on the study findings its thus recommended that the Ministry of Agriculture, Water and Forestry and other concerned bodies should consider the identified influential factors and challenges to improve the situation and enhance the adoption of introduced water conservation practices.
Assessment of floodwater harvesting infrastructures in the Namibian Cuvelai-Etosha basin
(University of Namibia, 2020) Niipare, Emeritha
The Cuvelai-Etosha Basin lies in north-central Namibia and due to the prevailing climatic situation, the basin is dominated by strong seasonal and annual variations of either very dry conditions with drought or heavy flooding in certain years. A growing population in the Cuvelai-Etosha Basin has resulted in increased demand for water for daily use and agricultural activities. Floodwater Harvesting Infrastructures are considered to be a more effective way to solve those problems. Hence the current status of the initiatives taken to harvest floodwater for use in the dry seasons needs to be determined by means of remote sensing, secondary data and field validation. The main objective of the study was to assess the condition and performance of Floodwater Harvesting Infrastructures in the Cuvelai-Etosha Basin. The Ministry of Agriculture, Water and Forestry constructed 34 earth dams in this Basin from 2008 to 2011. Out of these newly constructed earth dams, 18 were randomly selected for the study. The research design was based on using both qualitative and quantitative data on a completely randomised basis. Sentinel data was used to identify the water bodies by means of remote sensing. Information was gathered by means of structured interviews from the locals or people acquainted with the sites. The results from the interviews taken among 96% of the participants showed that the highest usage of earth dams is livestock watering while few people use them for irrigation purposes. Due to sedimentation in the earth dams, depth has reduced and surficial area has increased; hence the dams can no longer retain the quality and quantity of water they were designed for. In conclusion, the method developed from GIS successfully identified 94% of the existing earth dams.
Mineral processing technology II: Student manual
(2021) Ilunga, Odilon K.
Mineral processing equipment performance depends on the behaviour of each particle that is processed. It is however impossible, though necessary, to design equipment (base Computational procedures) that considers each of the particles due to their bigger number and their difference. Useful models cannot be based on average properties of particles either. Individual particles differ from each other by: - Properties that influence their behaviours in equipment, the two most important of these properties are the size and mineralogical composition. - Other properties such as shape, specific gravity, fracture energy, surface area, surface energy. In addition to the particle size and mineral composition, comminution, classification and concentration are dependent also on specific gravity, brittleness which influences the behaviour of particles. Examples: Gravity concentration makes use of differences in specific gravity between particles to separate them. Particles properties are not totally independent of each other. For example the specific gravity is related to the mineralogical composition. Surface energy of a particle is related to mineral composition on the surface of the particle. Some aspects of the particle’s properties in a population are needed with more details for models to be sufficiently sensitive to individual particle properties although these properties cannot be defined for each individual particle. Such aspects or scheme are provided by a description using distribution functions.
Modelling of conventional and microchannel delugeable tube bundle for a direct air-cooled steam condenser
(University of Namibia, 2023) Angula, Ester
This study presents the thermal performance modelling of conventional and microchannel delugeable tube bundle which incorporated into a second stage of the induced Hybrid (Dry/Wet)) Dephlegmator (HDWD). Hybrid dry/wet dephlegmator was proposed to replace a Conventional Dephlegmator (CD) of a direct Air-Cooled Condenser (ACC) system, coupled to 30 MW steam turbine of a generating unit. The Conventional Delugeable Tube Bundle (CDTB) thermal performance was modelled and configured using one- and two - dimensional models by employing heat and mass transfer approach. The geometric parameters for both first and second stages tube bundles of HDWD were derived from that of CD of ACC system of the considered generation unit. Therefore, the thermal performance of CDTB was optimised to ensure highest performance, and appropriate geometric parameters that are corresponding to that of CD and available space for installation. The best CDTB configuration’s performance was compared to similar existing Delugeable Round Tube Bundle (DRTB) in literatures. When the tube pitch varied from 25 mm to 38 mm, the DRTB’s heat transfer rate and air-side pressure drop were found to be in the range of 1.4 to 2 times and 1.3 to 2.2 times that of CDTB, respectively. The Microchannel Delugeable Tube Bundle (MDTB) thermal performance was analysed using semi-empirical model, which comprises of microchannel heat transfer and flow correlations. The size and geometric parameters of MDTB was equivalent to that of CDTB, and the only difference was that, the MDTB has microchannel/ ports on the steam-side. The MDTB thermal performance was found to increase as the hydraulic diameter of the channels decreased. The thermal performance comparison of the CDTB and MDTB at bundle, component and system levels was carried out. At all the levels, the MDTB performance was higher than that of CDTB. However, this higher performance came at expense of higher steam-side pressure drop. As the ambient air temperature increased from 32 ℃ to 44 ℃, the MDTB’s heat transfer rate for 140 𝜇𝑚 hydraulic diameter was found to be 9 to 6 % higher than that of CDTB. The air-side pressure drop variations between the two bundles were insignificant. Furthermore, the thermal performance of HDWD incorporated with either CDTB or MDTB was compared to that ii of CD at component and system levels. At system level, and as the ambient air temperature increased from 32 ℃ to 44 ℃, the heat transfer rate of the CD was found to be 27 % to 31 % less than that of HDWD incorporated with either CDTB or MDTB. The Air-side pressure drop for HDWD was found to be about 41 % higher than that of CD. Additionally, the steam turbine output and net powers were found to be higher when the ACC was incorporated with HDWD than when CD was incorporated into ACC

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