Faculty of Science and Technology

Permanent URI for this community

https://hdl.handle.net/20.500.14155/172

Browse

Now showing 1 - 20 of 182

Open Access
A chemical process design for green hydrogen production through water electrolysis in Lesotho
(National University of Lesotho, 2024) Ramaisa, Tsepiso Angelina; Thamae, Timothy
This research addresses the pressing need for process design models that are specifically adapted to Lesotho's distinct resource profile, particularly its vast hydroelectric capacity. At present, there is a noticeable gap in process models designed for green hydrogen production that take into account the unique energy conditions of Lesotho. To address this shortcoming, the study presents a detailed chemical process design for hydrogen production through water electrolysis, utilizing Lesotho’s renewable energy. The process model developed includes detailed mass balances to ensure precise quantification of material flows. Critical process parameters, including molar and mass fractions as well as stream molar flow rates, are defined to accurately describe the system, providing a solution that is specifically optimized for Lesotho's energy resources. The key unit operations, including separators, mixers and an electrolyser, are carefully modelled. Separators are used for phase separation and component purification, while mixers are designed to efficiently combine process streams. The electrolyser, central to the process, is modelled according to the electrochemical reactions which take place and mass transfer considerations. To ensure accurate phase equilibrium calculations, the Rachford-Rice equations are applied. Additional equations are formulated to characterise equipment performance and to address system constraints, such as product purity requirements. The developed model serves as a tool for enhancing hydrogen production and assessing overall process efficiency. It offers a framework for examining how different operating conditions and design parameters affect system performance. Future research should focus on incorporating renewable energy sources like wind and solar to diversify and enhance the sustainability of hydrogen production in Lesotho. Performing comprehensive energy balances will offer deeper insights into the system's efficiency and potential for optimization. Moreover, including economic and environmental assessments will provide a more thorough evaluation of the commercial feasibility of green hydrogen production in the country. These suggestions not only address current gaps but also lay the groundwork for developing a more integrated and scalable model for green hydrogen production, which could be applied to other regions with similar renewable energy resources, supporting both regional and global efforts towards sustainable energy transitions.
Open Access
ACE one cook stove
(National University of Lesotho, 2021-07) Qoola, Thato; Thamae, Thimothy
The study was conducted to evaluate the performance of ACE One cook stove which is manufactured by African Clean Energy (ACE) in Lesotho by assessing the performance of different solid biomass fuels within the stove. Pellets, pine wood, corn cobs and cow dung provided by ACE were used in this study where cooking time, energy consumption, heat transfer, combustion temperature and particulate matter emissions were assessed. The heating values were determined using Proximate Analysis, the values ranged from 13.43 MJ/kg for cow dung to 17.65 MJ/kg for corn cobs. Measurement of air pollutants were performed using mobile air quality monitor and combustion temperature measurements were performed using infrared thermometer. The temperature was measured for each fuel and the highest temperature was found when using wood, about 460 °C, followed by corn cobs with 370 °C, pellets with 340 °C and cow dung with 290 °C. However, the pellets had the most sustained heat compared to other fuels. Using wood and corn cobs transferred heat faster due to their big flame and raised the temperature of the water quickly. When using wood, water in a pot gained 610 kJ in 9 minutes, with corn cobs, pellets and cow dung, energy gained was 410 kJ, 350 kJ and 240 kJ respectively. Water Boiling Tests (WTB) results showed that the use of cow dung required much more fuel and an extended cooking time compared to other fuels. The second WBT using a different mass to test refuelling showed that refuelling slowed the cooking process. When burning the fuels in a closed room, the PM2.5 emissions for all the fuels were above 425 μg/m3, which was considered as hazardous level. Cow dung emitted more particles than other fuels during combustion which lasted longer in a room. The pellets showed the lowest emissions of them all in both open and closed room. In a closed room, the highest value for the pellets was 800 μg/m3 while other fuels had reached 999.9 μg/m3. The values obtained when burning the fuels in an open room had shown a significant decrease in emissions, 60.3 μg/m3 for pellets, 144.7 μg/m3 for wood, 234.2 μg/m3 for corn cobs and 612.4 μg/m3. The study further assessed the performance of the charging system that comes along with the stove. The power dissipated by the solar panel in this study was less than its rated power. The highest value from 4 experiments done one different days was 8.57 W. Time taken to charge the stove with a wall charger was shorter than using a solar panel. Using the battery of the stove to charge a cell phone has shown high power usage but using it for powering LED lamp has shown to be discharging the battery at a very slow rate.
Open Access
ACE One cookstove
(National University of Lesotho, 2021) Qoola, Thato; Thamae, Timothy; Berg, Dominik
The study was conducted to evaluate the performance of ACE One cook stove which is manufactured by African Clean Energy (ACE) in Lesotho by assessing the performance of different solid biomass fuels within the stove. Pellets, pine wood, corn cobs and cow dung provided by ACE were used in this study where cooking time, energy consumption, heat transfer, combustion temperature and particulate matter emissions were assessed. The heating values were determined using Proximate Analysis, the values ranged from 13.43 MJ/kg for cow dung to 17.65 MJ/kg for corn cobs. Measurement of air pollutants were performed using mobile air quality monitor and combustion temperature measurements were performed using infrared thermometer. The temperature was measured for each fuel and the highest temperature was found when using wood, about 460 °C, followed by corn cobs with 370 °C, pellets with 340 °C and cow dung with 290 °C. However, the pellets had the most sustained heat compared to other fuels. Using wood and corn cobs transferred heat faster due to their big flame and raised the temperature of the water quickly. When using wood, water in a pot gained 610 kJ in 9 minutes, with corn cobs, pellets and cow dung, energy gained was 410 kJ, 350 kJ and 240 kJ respectively. Water Boiling Tests (WTB) results showed that the use of cow dung required much more fuel and an extended cooking time compared to other fuels. The second WBT using a different mass to test refuelling showed that refuelling slowed the cooking process. When burning the fuels in a closed room, the PM2.5 emissions for all the fuels were above 425 µg/m3, which was considered as hazardous level. Cow dung emitted more particles than other fuels during combustion which lasted longer in a room. The pellets showed the lowest emissions of them all in both open and closed room. In a closed room, the highest value for the pellets was 800 µg/m3 while other fuels had reached 999.9 µg/m3. The values obtained when burning the fuels in an open room had shown a significant decrease in emissions, 60.3 µg/m3 for pellets, 144.7 µg/m3 for wood, 234.2 µg/m3 for corn cobs and 612.4 µg/m3. The study further assessed the performance of the charging system that comes along with the stove. The power dissipated by the solar panel in this study was less than its rated power. The highest value from 4 experiments done one different days was 8.57 W. Time taken to charge the stove with a wall charger was shorter than using a solar panel. Using the battery of the stove to charge a cell phone has shown high power usage but using it for powering LED lamp has shown to be discharging the battery at a very slow rate.
Open Access
Adaptive, robust, and fault-tolerant control strategies for grid-connected renewable energy systems
(National University of Lesotho, 2024) Nkhabu, Tsitso; Makhele, Molefe; Mokeke, Sebota
Lesotho is currently facing a power generation-demand imbalance. The 2023/24 annual report by the Lesotho Electricity and Water Authority highlights a peak demand of 222.12 MW, which is nearly three times the country’s installed generation capacity of 74.7 MW. Consequently, the nation relies on costly power imports from Mozambique and South Africa to cover the shortfall. To address this issue, Lesotho plans to integrate renewable energy sources, specifically wind and solar, into its national grid. However, integrating these low-inertia and intermittent renewable power sources introduces grid stability challenges, as they are vulnerable to disturbances like load changes or grid faults. This research focused on designing control strategies capable of not only adjusting system voltage to accommodate uncertainties from power system dynamics, internal changes, and external disturbances but also stabilizing the system under small disturbances. The analysis was conducted on a grid-connected 38 MW wind power plant, using five control strategies: Constant Voltage (Const. V), Constant Reactive Power (Const. Q), Constant Power Factor (Const. cosɸ), Voltage Droop based on Reactive Power (voltage Q-droop), and voltage droop based on reactive power in the q-axis (voltage Iq-droop). These strategies were evaluated for their adaptability, robustness, and fault tolerance under two operational scenarios: variations in wind speed and fluctuations in the Point of Connection (POC) bus voltage. With a three-phase short circuit created and cleared on the high voltage (HV) bus bar, all control strategies are within a 5 % voltage deviation upon service restoration and fault clearance within a period of 0.015 seconds. A Supervisory Control and Data Acquisition (SCADA) system was designed for the monitoring and control of the wind power plant. Determined from the closeness of the HV bus voltage to the POC voltage, the most adaptive control strategy is used for each operation scenario, taking into account the wind speed as well as the POC voltage. It was observed that the evaluation by the SCADA system is consistent with the result obtained from the DIgSILENT PowerFactory software. For further exploration, research is recommended for the implementation of Artificial Neural Networks (ANNs) in machine learning to accommodate any wind speed and POC voltage levels for the control strategies under investigation.
Open Access
Afm, stm and sts studies of grain boundaries And ion-beam induced defects in MGB2
(Nova Science Publishers, 2001-06) Narayan, Himanshu; Narlikar, A. V.; Herrmann, P. S. P.; Samanta, S. B.; Gupta, Anurag; Kanjilal, D.; Muranaka, T.; Akimitsu, J.; Vijayaraghavan, R.
Open Access
An optimization approach for the economic dispatch incorporating renewable energy resources into the LEC power sources portfolio
(National University of Lesotho, 2022) Rateele, Thato Nchakha; Thamae, Leboli Zak
Electricity demand in Lesotho has been constantly rising over the past years and has greatly surpassed the main domestic generation of 72 MW hydropower station in ‘Muela, which only supports a monthly average of 58% of the load and the deficit is imported from South Africa and Mozambique through fixed bilateral contracts. Although these contracts are regarded as uninterruptable as transmission paths are secured in advance, they come with heavy reliability premium costs endured by electricity utility, Lesotho Electricity Company (LEC). With the abundant renewable energy sources in Lesotho, Independent Power Producers (IPPs) could be invited to erect wind farms and solar photovoltaics (PV) plants to increase local energy security and diversify LEC power sources. Because electrical power networks must be secure, reliable, and cost-effective, the study developed a power dispatching approach that includes solar PV and wind generators to aid 'Muela meet demand and be backed by imports. According to the analysis, main grid imports are minimized by 22.3% with the introduction of 50 MW Ha-Ramarothole solar PV and by 40.2% with wind farms (24 MW Masitise and 34 MW Lets'eng) working with 'Muela. A 59.7% minimization is obtained by combining solar PV at 50 MW, wind farms at 58 MW, and 'Muela at 72 MW. Furthermore, the study used the Monte Carlo approach to simulate generation adequacy analysis in order to establish the monthly average expected demand not supplied (EDNS) and loss of load probability (LOLP). The EDNS never drops below 0 MW, while the LOLP only reaches a minimum of 52% for all scenarios evaluated, according to generation adequacy analysis of all local generators. Finally, the study assessed the influence of renewable energy absorption on LEC in terms of costs in procuring power locally and from imports using the South African Power Pool (SAPP) Markets: Day Ahead Market (DAM), Forward Physical Market (FPM) weekly and monthly. Since DAM yearly cost of energy is approximately half that of FPM weekly and monthly, it has been shown to be the most cost-effective market to procure under for renewables penetrations. Additionally, the cost of electricity anticipated to be incurred while purchasing from solar at 50 MW, ‘Muela, and DAM is around LSL 45 million less expensive than the fixed bilateral contracts. As a result, minimization of imports and their cost can be effectively accomplished with DAM because the total cost of energy (local prices plus DAM pricing) significantly reduces the potential expenses.
Open Access
Analysis of Quthing River and Letseng-la-Letsie for hydropower potential
(National University of Lesotho, 2020) Lekhanya, Liteboho; Khaba, L; Makhele, M
This dissertation presents the analysis of Quthing River and Letseng-la-Letsie for hydropower potential in Quthing district in Lesotho. Electrical power deficit in the country is more prominent in rural areas like Quthing District. This calls for assessment of electrical sources in the vicinity of rural area load centers to inform policies for electrical production so as to curb power deficit problem. Mountain Rivers like Quthing River with steep slopes or gradients naturally provide good head which needs to be assessed along with its flow rates. Furthermore elevated dams like Letseng-la-Letsie can also provide a natural good head which needs to be assessed alongside with its discharge rates. The assessment was carried out by employing catchment area method to asses flow rates since the abstraction points of the study areas were ungaged and lacks data. The maps in association with QGIS were used to evaluate heads of the study areas and lastly TURBNPRO was used to determine power outputs from the study areas. The resultant net head for Quthing River was found to be 164.15 m while the net head for Letsengla-Letsie was 159.23 m. The design flow rate of Quthing River was found to be 0.58 m3/s while that of Letseng-la-Letsie was 0.116 m3/s. The results from TURBNPRO showed that the power output for Quthing River turbine was 815 kW while the power output for Letseng-la-Letsie turbine was 221 kW. Using typical hydro-electric generators efficiency of 99% and typical capacity factor for Africa of 0.49, the capacity from Quthing River was found to be 807 kW with annual energy of 3.46 MWh. The capacity for Letseng-la-Letsie was found to be 0.22 MW with annual energy of 0.95 MWh.
Open Access
Analysis of Quthing River and Letseng-laLetsie for Hydropower Potential
(National University of Lesotho, 2020) Lekhanya, Liteboho; Dr Khaba, L.; Dr Makhele, M.
This dissertation presents the analysis of Quthing River and Letseng-la-Letsie for hydropower potential in Quthing district in Lesotho. Electrical power deficit in the country is more prominent in rural areas like Quthing District. This calls for assessment of electrical sources in the vicinity of rural area load centers to inform policies for electrical production so as to curb power deficit problem. Mountain Rivers like Quthing River with steep slopes or gradients naturally provide good head which needs to be assessed along with its flow rates. Furthermore elevated dams like Letseng-la-Letsie can also provide a natural good head which needs to be assessed alongside with its discharge rates. The assessment was carried out by employing catchment area method to asses flow rates since the abstraction points of the study areas were ungaged and lacks data. The maps in association with QGIS were used to evaluate heads of the study areas and lastly TURBNPRO was used to determine power outputs from the study areas. The resultant net head for Quthing River was found to be 164.15 m while the net head for Letsengla-Letsie was 159.23 m. The design flow rate of Quthing River was found to be 0.58 m3/s while that of Letseng-la-Letsie was 0.1 16 m3/s. The results from TURBNPRO showed that the power output for Quthing River turbine was 815 kW while the power output for Letseng-la-Letsie turbine was 221 kW. Using typical hydro-electric generators efficiency of 99% and typical capacity factor for Africa of 0.49, the capacity from Quthing River was found to be 807 kW with annual energy of 3.46 MWh. The capacity for Letseng-la-Letsie was found to be 0.22 MW with annual energy of 0.95 MWh.
Open Access
Analysis of the categories of the sustainability dimensions to achieve sustainable mini-grids
(National University of Lesotho, 2023) Maema, Tanki Alfred; Mpholo, M
Taking into consideration the rise of mini-grids globally, their important contribution in reaching the universal access to energy goal, and the uneconomic costs of national grid extension to certain areas, it is only befitting that mini-grids are studied extensively. This study intends to find the variables of a sustainable mini-grid and what makes a mini-grid sustainable, analysed and identifies the sustainability of the different models of mini-grids and finally finds which mini-grid business model is sustainable and is better suited Lesotho in order to raise the countries electricity access and better the populations livelihoods. The study assesses the categories of four (the community-owned, private, Public-Private Partnership (PPP), and utility business models) sustainability dimensions of mini-grids across selected countries with similar conditions to Lesotho. It shows that for a mini-grid to survive throughout its lifetime it has to adequately satisfy the economic, environmental, institutional, social, and technical sustainability dimensions. The developer-consumer and the multi-tier frameworks developed by James Knuckle (2016) and the World Bank (2015) respectively were used in the assessment of the categories of sustainability dimensions for all four mini-grid business models. With the help of the frameworks, the study findings show that the PPP and private mini-grids proved to be the closest models to sustainability in all the assessed categories and dimensions failing in the cash recovery and affordability categories respectively. They are followed by community mini-grids which fall back on some categories ( cash recovery,tariff coverage of the operations and maintenance and tariff setting) for this reason are not sustainable. The PPP model has similar operations to utility mini-grids, as suggested by the frameworks, but has proven to be slightly better in a few categories. Utility minigrids are the furthest from sustainability of the studied mini-grids. They failed in the cash recovery category, failed to have tariffs covering their O&M cost, have low tariff settings and have limited power supplied to their customers. From the already existing research on mini-grid models in Lesotho, suggestions are provided for Lesotho and its upcoming mini-grids. The study shows that a combination of private and community mini-grids is found to be the best uptake provided there are subsidies to help people afford the cost-reflective tariffs.
Open Access
Analysis of the viability of using solar thermal energy for Maluti Mountain Brewery
(National University of Lesotho, 2021) Lillane, Malillane; Hove, Tawanda; Mpholo, M
It has been established by literature that there is worldly movement towards renewable energy usage because of global warming. Solar energy among many is one form of renewable energy that can be used to reduce conventional energy usage. This study realized an opportunity to reduce the conventional energy (coal) use at Maluti Mountain Brewery (MMB); a brewery in Lesotho by preheating the boiler make up water. The boiler at MMB is serviced by condensate (70°C) and the cold water from the tap. The cold makeup water mixes with the condensate prior to the being carried into the boiler and thus reducing the efficiency of the boiler. This is because the boiler in turn demands a lot of coal to heat up the boiler feed water. A retrofitted solar thermal system into the existing system at MMB was done. This system was aimed at preheating the cold make up water before it mixes with the hot condensate in order to avoid the makeup water from reducing the condensate temperature. An Excel based model was made in order to design a solar thermal system that is cost effective and technically viable. The designed system is an active solar thermal system composed of evacuated tube collector with the EPD of 18 kWh/$), collector area of 80 m2 which was decided upon by the required maximum storage tank temperature of 100 °C. The storage tank size of the system was found to be 2110 Liters. A tank of such size could not be found on the market; therefore, a 2500 Liters storage tank would be ideal for the purpose. The actual collector area decided upon according to the collector aperture area of 2.998 was found to be 81 m2. The system was found to be able to preheat 54% of the makeup water (12 % of the boiler feed water is the makeup water). The amount of coal used by MMB would be reduced by 11% and therefore saving the company as the NPVSS is positive, amounting to $25044 for over 20 years.
Open Access
Analysis of the viability of using thermal energy for Maluti Mountain Brewery
(National University of Lesotho, 2021-04) Lillane, Malillane; Mr. Hove, Tawanda; Dr. Mpholo, Moeketsi
It has been established by literature that there is worldly movement towards renewable energy usage because of global warming. Solar energy among many is one form of renewable energy that can be used to reduce conventional energy usage. This study realized an opportunity to reduce the conventional energy (coal) use at Maluti Mountain Brewery (MMB); a brewery in Lesotho by preheating the boiler make up water. The boiler at MMB is serviced by condensate (70°C) and the cold water from the tap. The cold makeup water mixes with the condensate prior to the being carried into the boiler and thus reducing the efficiency of the boiler. This is because the boiler in turn demands a lot of coal to heat up the boiler feed water. A retrofitted solar thermal system into the existing system at MMB was done. This system was aimed at preheating the cold make up water before it mixes with the hot condensate in order to avoid the makeup water from reducing the condensate temperature. An Excel based model was made in order to design a solar thermal system that is cost effective and technically viable. The designed system is an active solar thermal system composed of evacuated tube collector with the EPD of 18 kWh/$), collector area of 80 m2 which was decided upon by the required maximum storage tank temperature of 100 °C. The storage tank size of the system was found to be 2110 Liters. A tank of such size could not be found on the market; therefore, a 2500 Liters storage tank would be ideal for the purpose. The actual collector area decided upon according to the collector aperture area of 2.998 was found to be 81 m2. The system was found to be able to preheat 54% of the makeup water (12 % of the boiler feed water is the makeup water). The amount of coal used by MMB would be reduced by 11% and therefore saving the company as the NPVSS is positive, amounting to $25044 for over 20 years.
Open Access
Analytical solutions to the arithmetic asian options pricing model using lie symmetry methods
(National University of Lesotho, 2025-07) Kubeletsane, Monts’uoe Edward; Nchejane, Ngaka John
This dissertation explores the use of Lie symmetry methods to find analytical solutions for arithmetic Asian options; path-dependent financial derivatives widely used for risk management in commodity markets. The pricing problem is formulated as a partial differential equation (PDE) involving the asset price, time, and the running average of the asset price. Lie symmetry analysis is applied to the PDE to compute its infinitesimal generators, determine an optimal system of one-dimensional sub-algebras, and perform symmetry reductions. Each reduced PDE obtained through this process also admits further symmetries, allowing for successive reductions and the construction of exact invariant solutions. Techniques such as Riccati reductions and the Frobenius method are employed to solve the resulting ordinary differential equations (ODEs). The study further examines the influence of key financial parameters (volatility, interest rate, and time to maturity) on the structure and behavior of the pricing solutions. The findings contribute to the theoretical understanding of Asian option pricing and provide analytical benchmarks for validating numerical approaches.
Metadata only
Antimicrobial activity of the cyclic peptides, Cyclo(D-Phe-4I-Pro) and Cyclo(L-Phe-4I-Pro).
(2013) Qhola, P. J.; Milne, J.
Open Access
Antimicrobial wound healing properties of indigenous medicinal plants of Lesotho and the pharmacist's role in minor wound care
(2021) Hlokoane, O.K.; Sello, M.
Lesotho has a rich supply of indigenous medicinal plant resources. More than a dozen Lesotho medicinal plants have been used to treat minor wound infections among Basotho for over 100 years. The aim is to provide scientifi validation of their antimicrobial activities against microorganisms relevant to the skin. The anti-infective activities of plants are thought to be due to the presence of active phytochemicals in parts of the plants, especially phenolic compounds, anthraquinones, glycosides, and alkaloids. Although there is limited research that establishes the structure-activity relationship of those phytochemicals, there are reports that attributed the phytochemical constituents with the antimicrobial effcts through a variety of mechanisms ranging from inhibition of cytoplasmic membrane function, inhibition of energy metabolism to inhibition of bacterial nucleic acid synthesis. The role of the pharmacist is to provide medical information on these compounds to promote the safe use of herbal products and in combination with conventional medicines.
Open Access
Application of lie symmetrics to solving fractional black-scholes option pricing model in financial mathematics
(National University of Lesotho, 2022-10-21) Ramoeletsi, Realeboha; Kaibe, Bosiu, Ngaka Nchejane
We perform Lie symmetry analysis to the fractional Black-Scholes option pricing model whose price evolution is described in terms of a partial di erential equation (PDE). As a result, new complete Lie symmetry group and in nitesimal generators of the one-dimensional fractional Black-Scholes pricing model are derived. Furthermore, we compute a family of exact invariant solutions that constitute the pricing models for the Black-Scholes model using the associated in nitesimal generators and the corresponding similarity reduction equations. Using known solutions, more solutions are generated via group point transformations
Open Access
Application of Lie Symmetry method in pricing Arithmetic Asian options
(National University of Lesotho, 2024-06-23) Kubeletsane, Monts'uoe Edward
This research investigates the application of Lie symmetry method to find analytic solutions for arithmetic Asian options, which are crucial financial derivatives for managing risk in various commodity markets. By employing a two state partial differential equation approach, the study uses Lie symmetry method to enhance option pricing models. The research involves finding determining equations, infinitesimal generators, and invariant solutions, as well as examining the influence of parameters such as volatility, interest rates, and time on option prices.
Open Access
Application of solution state NMR to structural problems in chemistry
(Durham University, 2006-09) Khoabane, Ntai Martin; Dr. Sanderson, John; Dr. Grayson, Elizabeth; Dr. Natrajan, Louise; Mr. McKeag, Ian; Mrs. Heffernan, Catherine
First and foremost I would like to thank the Lord almighty for the life he has given me. My stay and study at Durham University was funded and supported by Canon Collins Trust to whom I am very thankful. I would also like to pass my gratitude to the National University of Lesotho for releasing me on staff development leave, my dependants’ allowance, and funding my travel both ways. I would like to thank my supervisory team: Dr. Alan M. Kenwright for his supervision and training and demonstrated kindness and patience. He motivated and encouradme during this period. I am also grateful to him for coming up with original ideas of a project on which I worked. Dr. John Sanderson cannot be forgotten for his co-supervisory role. I am also grateful to Dr. Elizabeth Grayson for the supervision in chemistry and for the protection and deprotection of the mannoside compounds. Dr. Louise Natrajan, I thank you for the lanthanide complexes I worked on. I would also like to thank Mr. Ian McKeag and Mrs Catherine Heffernan who contributed a lot to my training in solution state NMR. Other groups of people who contributed to my training need to be mentioned: all my lectures in the taught modules, the mass spectrometry facility and all the Chemistry Department staff. Last but not least my family members. Most importantly my wife and son who suffered the loneliness of my being thousands of miles away from them without complaint. Nuclear Magnetic Resonance (NMR) spectroscopy is a robust, non invasive technique applicable in structure determination as well as in the study of dynamic behaviour of chemical compounds. This thesis is in two sections, the first dealing mainly with a structure determination application of NMR and the second dealing mainly with a study of dynamic behaviour. Section 1 NMR characterisation of carbohydrates has proved challenging because of the limited chemical shift ranges of both the proton and carbon signals. The broad signals due to the labile hydroxyl protons cause further complications by overlapping proton signals from the ring. Protecting group chemistry is vital in the preparation and manipulation of synthetic carbohydrates and can potentially help with the assignment of the (otherwise extremely complicated) NMR spectra of carbohydrates. However, the widely used benzyl protecting group can make the spectrum more difficult to interpret because the benzyl CH2 proton signals often come in the same region of the spectrum as the anomeric protons, usually used as reporter groups of carbohydrates and the benzyl CH2 carbon signals come in the same region as the carbohydrate ring carbons. This section reports the invetsigation and application of a family of alternative protecting groups, namely various fluorobenzyl groups, which have not been used in carbohydrate chemistry before. With pentafluorobenzyl, the proton chemical shift dispersion is improved, and the CH2 and carbohydrate ring carbon signals are shifted to lower frequency, considerably simplifying the task of assigning the carbon spectrum, facilitating the interpretation of all 1H-13C correlation experiments (HSQC, HMQC, HMBC). Section 2 Cyclen complexes of lanthanide (III) ions have found use in magnetic resonance imaging (MRI), luminescence imaging and assay studies. In particular, europium (III) complexes have potential in anlytical, forensic, and biomedical applications based on their impressive emissive properties. However, the emissive properties are modulated by the thermodynamic stability and kinetic inertness of the complexes. For biomedical applications, chelation is necessary to avoid europium toxicity that may be triggerd by accidental dissociation of the complex and release of the metal in vivo. A new cyclen europium(III) complex with pyridyl pendant ligands instead of the usual acetate groups has been synthesised by a group at Manchester University. The pyridyl ligands confer higher emmisive intensities to the complex, to enable applicability of the complex in time gated measurements. The chemical structure determination of the compound was accomplished by 1H, 13C, COSY, HMQC / HSQC and EXSY NMR experiments. Selective inversion experiments data were evaluated using the CIFIT simulation program, and showed that in aqueous solutions from -0.2º C to 107.6º C the dominant dynamic process is flipping of the pendant (pyridyl) arms, and isomerism is biased towards the twisted square antiprism (TSAP).
Metadata only
Approximate Model for a Merge Configuration of Multiservers With Finite Capacity Intermediate Buffers
(International Journal of Applied Mathematics, 2013) Nikolov, A. V.
We consider a queueing network consisting of multiservers in parallel and connected to a merger queue. All servers have an infinite capacity buffers. The configuration is decomposed into two subsystems: merging multi-servers and merger server and then analyzed in isolation. All times are assumed to be exponentially distributed. First we set and solve the equations for the aggregated merger queue, then express the occupancy probabilities of the original queue through the probabilities of the aggregated one, which reduces significantly the number of equations describing the behavior of the network. Using the fore-mentioned result, we derive expressions for the occupancy probabilities and other parameters of the merging queue.
Open Access
Assessment of the impacts and adaptive capacity of the Machobane farming system to climate change in Lesotho
(African Technology Policy Studies Network, 2012) Mekbib, Sissay Bekele; Olaleye, Adesola; Mokhothu, Motlatsi N.; Tilai, Spirit B.; Wondimu, Taddesse; Johane, Masia
Open Access
Baselining Lesotho's disaggregated energy factors, ratios and intensities for household energy demand forecasting
(National University of Lesotho, 2024) Sekatle, Mosa Patricia; Thamae, Leboli Zak
Abstract The approach that is traditionally employed for household energy demand forecasting in many countries, including Lesotho, has primarily focused on two levels of aggregation which are to disaggregate data into rural and urban settlements. This study introduces an approach which is tailored specifically for Lesotho’s unique context. It adopts a methodology that utilizes Lesotho’s four agro-ecological zones, providing four levels of disaggregation which are the Lowlands, Foothills, Mountains and the Senqu River Valley. Additionally, it incorporates Lesotho’s ten administrative districts which are Botha-Bothe, Leribe, Berea, Maseru, Mafeteng, Mohale’s Hoek, Quthing, Qacha’s Nek, Mokhotlong and Thaba-Tseka. They offer 10 levels of disaggregation in household energy demand consumption patterns. The adopted approach allows a more comprehensive understanding of how the households energy consumption behavior varies across different zones and districts of the country. The approach provides valuable insights into zone or district specific energy needs and challenges; thus, it will enhance the accuracy of energy demand forecasting thereby informing more effective and targeted energy policies and interventions in Lesotho. The method used to baseline the disaggregated data is the exploratory data analysis (EDA) based on the Household Energy Consumption Survey (HECS) which was conducted in 2017. It uses both graphical and non-graphical techniques to uncover the data behavior, to spot anomalies and to check the trends through the visual and statistical summaries. The findings of the study, using absolute values, indicate that during summer months, energy intensities per household in zones demonstrate high average intensity on fuel wood (168.4 kg/HH) and animal waste (148.7 kg/HH), and the low average intensity on LPG (6.8 kg/HH), paraffin (21.4 Ltr/HH), and electricity (69.8 kWh/HH). However, during winter months, fuel wood (165.5 kg/HH) and animal waste (147.0 kg/HH) have high intensities, while paraffin (30.8 Ltr/HH), aloe (39.2 kg/HH) and crop waste (62.9 kg/HH) have the lowest intensities. In the districts during summer months, animal waste (155.6 kg/HH) and fuel wood (144.1kg/HH) have the highest average intensities, while LPG (15.5 kg/HH) and paraffin (38.6 Ltr/HH) have the lowest. In winter months, animal waste (157.2 kg/HH) and fuel wood (152.1 Ltr/HH) show high intensities, while aloe (31.1 kg/HH) and LPG (44.1 kg/HH) take the lower energy intensities. Per capita energy consumption in zones during summer months shows shrubs (75.2 kg/cap) and fuel wood (50.2 kg/cap) with high intensities, while LPG (11.1 kg/cap) and paraffin (10.2 Ltr/cap) have the lowest. In winter months, animal waste and fuel wood have the most intensities of 45.6 kg/cap and 50.2 kg/cap respectively. In the districts, animal waste and fuel wood have high intensities of 44.8 kg/cap and 41.9 kg/cap, with the lowest in LPG (4.6 kg/cap) and paraffin (11.9 Ltr/cap) in summer, while in winter, fuel wood (46.9 kg/cap) has the highest and aloe (10.5 kg/cap) has the lowest intensity on average. Lesotho’s energy consumption patterns in agro-ecological zones and administrative districts are mostly influenced by socio-economic and infrastructure gaps, which are apparent in the variation of energy consumption among districts and the reliance on traditional fuels is less urbanized areas. The Lowland zone and the Maseru district dominate most of the energy consumption statistics due to their large populations, better topography, proximity to infrastructure and stronger economic activities. The data delineates that while there is a growing shift towards modern energy sources, significant portion of the population still remain dependent on traditional fuels, particularly in remote areas. 1 This approach provides critical information for policymakers, enabling them to develop more accurate energy demand forecasts and design targeted interventions. The study’s results can guide strategic energy planning to address Lesotho’s specific energy needs, promoting energy access and efficiency while transitioning towards cleaner energy sources. The insights gained from this research lay the foundation for future studies to build more sophisticated, localized energy models that better reflect the dynamics of Lesotho.

Browse

Browsing Faculty of Science and Technology by Title

Results Per Page

Sort Options