Includes bibliographical references. / Compressive sensing (CS) also known as compressive sampling is a technique used to reconstruct or recover the full-length of a signal with only a few non-adaptive measurements. It is a model-based framework for data acquisition and signal recovery that is based on the principles of sparsity and incoherence. Sparsity refers to the fact that a signal of interest is sparse and compressible and can be represented concisely in a given basis. Incoherence refers to the idea that a sparse signal is spread out in the basis in which it is acquired. A prominent area of application of this technique is tomography such as magnetic resonance imaging (MRI), X-ray CT, and in 3D synthetic aperture radar (SAR) imaging for reconstructing the elevation reflectivity profile. This dissertation describes the investigation into three-dimensional (3D) synthetic aperture sonar (SAS) imaging in air using compressive sampling. In the work, a 3D SAS simulator using compressive sampling was implemented in MATLAB. The effect of the number of baselines as well as the super-resolution factor on the final image was also investigated. A real 3D SAS imaging system was designed and the results were compared with the results of the simulated system. In the system, the SAS data was captured in a multiple transducer (baseline), single-pass configuration with 15 ultrasonic receivers and a single ultrasonic transmitter that operate at about 40 kHz. Signal conditioning circuits for the transmit and receive signals were built on pieces of veroboard. A PC which ran a custom designed LabVIEW virtual instrument (VI) was used for the synchronous transmission and reception of ultrasonic signals, and the control of the SAS platform via the NI PCI-6070E data acquisition card. The received 2D SAS signal from each transducer was focused using the accelerated chirp scaling algorithm. Compressive sensing was applied to a stack of focused 2D SAS images to achieve focusing in the elevation direction. 3D scenes containing point targets were successfully reconstructed in 3D SAS images using this technique with 9 baselines and a super-resolution factor of 3. The results confirm that CS is an effective technique in super-resolution tomographic reconstructions provided the baseline span is small compared to the imaging range. Also for reliable reconstructions, the appropriate super-resolution factor and number of acquisitions must be chosen.

Bones macroscopically consist of two major constituents; namely cortical and trabecular (also known as cancellous) bone. Cortical bone is the hard and dense outer layer of bone, which holds majority of the load bearing capacity. Trabecular bone is the porous internal bone, which distributes loads at joints by allowing for a larger bearing surface and acts as an energy absorber. Trabecular bone has a complex, heterogeneous, anisotropic open cell lattice structure with a large variation in mechanical properties across anatomic site, species, sex, age, normal loading direction and disease state. A common attempt to account for this variation is to correlate the structure of the trabecular bone sample to the mechanical response, which requires a means of quantifying the structure. Microstructural indices such as bone volume vs. total volume (BV/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), structural modal index (SMI) and mean intercept length (MIL) have been widely used to find correlations between structure and properties. Early studies only considered densitometric indices, which accounted for much of the variation however cross study correlations did not agree, leading to an interest in capturing non-scalar valued indices to account for features such as the anisotropy of the bone. The structural anisotropy varies from fully equiaxed to highly directional based on where the trabecular bone is located and what the function would be. The mean intercept length has been proposed as a measure of the structural anisotropy, specifically the interfacial anisotropy of the sample, which is commonly used to account for the mechanical anisotropy. This research falls within a longer term goal of investigating and understanding the mechanical anisotropy of trabecular bone. To that end, the anisotropy of regular lattice structures was investigated, with the particular goal that the investigated lattices were simple analogues for the more complex structures seen in trabecular bone. A framework for assessing the structure-property relations of trabecular bone is created, with focus on anisotropy. The mechanical anisotropy of idealised trabecular structures is quantified using well known microstructural indices, which are compared to the numerically determined mechanical response. The modelling methodology initially investigated 2D lattices that have very well known responses, such that the modelled approach could be verified. Three 2D lattices were used to do this, with the aim that the 3D lattices would be their analogues. Specifically a 2D square, hexagonal and triangular lattice were investigated. The square lattice is highly anisotropic as is the cubic lattice. The hexagonal lattice is isotropic with a large constraint effect as is the Kelvin cell, and the triangular lattice is isotropic with a small constraint effect. The octet-truss was the closest analogue to the triangular lattice, having a small constraint effect and being less anisotropic than the cubic lattice. The three 3D lattices were chosen to represent highly directional trabecular bone (using a cubic lattice) and more equiaxed trabecular bone, with the fully isotropic Kelvin cell lattice (also known as a tetrakaidecahedron) and the octet-truss lattice which has a lower degree of anisotropy than the cubic. Two confinement arrangements were also investigated as analogues for the trabecular bone at the free surface and at the cortical surface. To assess the mean intercept length analysis as a measure of mechanical anisotropy, this research performed the analysis on three 3D periodic lattice structures and compared the results to mechanical properties which were numerically determined using finite element analysis. The mean intercept analysis was performed by generating 3D images for the lattices, similar to the output of (mu)CT images, using a combination of open-source software and custom code, and performing the analysis in BoneJ, an open-source software package. The mechanical response was determined using two methods, namely discrete and continuum modelling approaches. The discrete approach characterised the lattice with each strut modelled as a Timoshenko beam element solved in LS-DYNA. To capture the anisotropy, the lattice had to be loaded at arbitrary angles, which was achieved by a rotating the whole lattice and cropping it to a specified test region using custom code. The continuum modelling approach used a homogenisation approach by treating the lattice as a solid material with effective properties, this was solved in a custom implicit solver written in MATLAB using solid elements. The anisotropy was modelled by transforming the elasticity tensor to arbitrary coordinate systems to load the model in arbitrary directions. The discrete modelling approach suffered from high computational costs and difficulty in removing the boundary effects, all of which would be worsened for models of real trabecular bone. However the discrete approach did accurately captured the mechanical behaviour of the lattices tested. The continuum approach accurately captured some of the responses but failed to capture all behaviour caused by confinement. The continuum model could not capture the switch in predominant deformation mode of the 2D hexagonal lattice caused by lateral confinement, and failed to accurately capture the symmetry of the highly anisotropic 3D cubic lattice. The mean intercept length analysis failed to capture the anisotropic response of simple periodic lattices, showing no significant difference between the octet-truss and cubic lattices, despite them having a very large difference in mechanical anisotropy. It also showed that the Kelvin cell lattice had the highest degree of geometric anisotropy, which is compared to having the lowest mechanical anisotropy being the only fully isotropic 3D lattice investigated. The mechanical investigation showed that the lateral confinement has a large effect, significantly scaling the response of isotropic lattices whilst distinctly changing the anisotropic behaviour of the cubic and octet-truss lattice. The mean intercept length analysis cannot capture the mechanical confinement effect from geometry alone, and thus fails to capture the mechanical response due to confinement Overall, the continuum modelling approach showed difficulty in capturing the confinement effect in all lattices and thus a more robust method is required. The mean intercept analysis proved unsuccessful in capturing the mechanical response of three periodic idealised trabecular structures. A new microstructural index that can capture the mechanical anisotropy is required, with the ability to consider the effects of confinement on the structure.

Environmental concerns necessitate the recycling of process water within mining operations. On average, recycled water contains more dissolved solids than fresh water. Since water is used as both a transportation and process medium, it is expected that changes in its quality will affect plant processes. Flotation is a process that is acutely sensitive to the immediate conditions of the system. Literature suggests that the efficiency of flotation separation is driven by the hydrophobicity that can be achieved by the mineral particles meant to be floated. The hydrophobicity is in turn driven by the adsorption of specialised reagents i.e. the collectors. Since collectors are added such that they adsorb at the liquidparticle interface, it stands to reason that changing the chemical composition of the aqueous phase will affect the collector adsorption, and hence the flotation response of target minerals. In this study, a sulphide copper ore from the Zambian Copperbelt was floated in synthetic plant waters of varying ionic strengths, and with different concentrations of the collector sodium isobutyl xanthate (SIBX). The synthetic plant waters were prepared by adding varying concentrations of inorganic salts to distilled water in order to achieve process water compositions that reflect water compositions typically found in mining plants. Additionally, a nickel-copper ore from Lapland Finland was floated in the synthetic plant waters as well actual plant waters. To account for the latter ore’s polymetallic nature, the collectors aerophine and sodium isopropyl xanthate (SIPX) were used sequentially. The objective of the study was therefore to investigate the effect of water quality on collector adsorption in the flotation of sulphide ores. The study showed that water quality has a quantifiable effect on SIBX and SIPX adsorption. The respective effects of water quality and collector adsorption on ore flotation could not be irrefutably decoupled. However, it could be concluded that of the tested waters, the copper thickener overflow was the least conducive to xanthate adsorption and valuable mineral recovery. On the other hand, collector adsorption was favoured by waters such as the raw and standard process. However, increased adsorption did not necessarily result in improved grades and recoveries. The study further showed that in the case that the dissolved ionic species are identical, increasing the ionic strength of water yields a linear decrease in xanthate adsorption, and that recycling SIPX retained in flotation waters resulted in reduced separation selectivity.

Spectrum is a natural resource and should be treated as such. Spectrum has dual use applications that range from short distance communication links such as Bluetooth to health, power systems, transport, smart city applications and space communications and exploration. Next Generation Networks (NGNs) are designed to connect millions of devices seamlessly and with high throughput rates in the aforementioned sectors and others not mentioned. The use of spectrum has to be efficiently utilized and appropriated. Cognitive radio communications serve to improve use of dwindling spectrum availability. Spectrum sensing is the first and critical technology in cognitive radio meant to determine radio parameters. Energy Detection (ED) is a spectrum sensing technology that has a low computational and operational complexity, a relatively fast spectrum sensing technique to other spectrum sensing technologies, and requires no knowledge of the primary user’s transmit signal properties such as modulation or error correction schemes. In its classical case, ED compares the signal energy received with a fixed detection threshold, estimated with an expected noise level. Noise however in practice varies randomly due to thermal variations, non-uniform movement of electrons, imperfections of semiconductor materials and external noise sources to mention a few. This creates a noise uncertainty phenomenon which negatively affects the fixed threshold approach used in classical ED. Development of an out-of-tree module for a variable threshold energy detector using the estimated noise power at each sample point is presented in this dissertation. GNU Radio software and Ettus Universal Software Radio Peripheral (USRP) hardware were used to simulate the performance of the proposed variable threshold energy detector. The Neyman-Pearson theory was adopted in achieving the proposed variable threshold energy detector. The variable threshold energy detector successfully sensed the presence of a primary user signal at 1.25% less the spectrum sensing time of the constant threshold. An ROC curve plot also showed that the proposed variable threshold energy detector had a better performance in general as opposed to the constant threshold energy detector at low signal-to-noise ratio levels.

The induction machine is the most widely used electrical machine in the world, they are used for industrial, commercial and industrial applications. When manufactured they have nameplate ratings that stipulate the voltages and currents at which they may be operated. The quality of supply from power utilities can lead to them being operated under unbalanced voltage conditions. Power utilities experience voltage unbalances and voltage dips when they provide services to end users. In South Africa ESKOM is the primary power utility, it has a license agreement with NERSA stipulating the allowable voltage levels. In most cases the operating levels are within the agreed limits however many consumers are exposed to voltage levels at the fringe of these specified limits. This can be detrimental to electrical equipment if operated under these conditions for considerable lengths of time. NRS048 part 2 provides limits for voltage regulation and voltage unbalance which can exist on the power network at various voltage levels. It is incumbent on each utility to ensure that the quality of power supplied to end users complies with the minimum standards specified in the NRS048. Most customers connected to rural 11/22kV networks are farmers, where a large portion of the load is pumps driven by low voltage AC induction motors. NRS048 dictates the voltage limits as ±10% of the nominal supply voltage of 400V. The voltage unbalance on three phase systems is limited to 2%, and 3% for predominantly single-phase systems. Utilities such as Eskom have standards and operating procedures in place to run the networks optimally within these limits. Variations in the voltage levels on rural networks can be significant during load changes. Voltage unbalance levels can also be high due to the use of single-phase loads on these networks. Normally, utilities have operating procedures in place to allow operation of the supply network within the limits specified in the NRS048. Although these operating levels are within specified limits, a large portion of the customer’s plant can however be exposed to voltage levels well above or below the rated value of the equipment. Operating under these conditions can eventually lead to failure of the customer equipment. The impact of operating AC motors with voltages levels above or below the rated levels has not been fully determined on rural networks in South Africa. Research is therefore required to assess the impact of these operating conditions on customer equipment in rural areas and whether utility operating procedures need to be revised to take into consideration customer equipment. This has consequences for Eskom Distribution that relates to: a) The way in which the network voltages are managed, and b) Claims lodged against the Distribution business resulting from damage to customer’s motors The purpose of this research project is to investigate and quantify the impact of voltage regulation (over and under) and unbalance conditions on a typical rural feeder on the lifespan of induction machines. There are various definitions of voltage unbalance by NEMA, the IEC and the IEEE. The IEC definition is used in this research report, it is known as the true definition and incorporates both magnitude and phase information. To estimate the loss of life in induction machines operating under unbalanced conditions, the positive and negative sequence per phase equivalent circuits must be determined and the thermal model needs to be obtained and quantified as well. The losses obtained from the per phase sequence circuits are inputs to thermal model which in turn is used to predict the induction machine stator windings temperatures. Factors that are considered when analysing the impact of voltage unbalance and regulation on the life expectancy of machines include, the induction machine manufacturer, the size of the induction machine, the voltage rating of the induction machine and the efficiency class of the induction machine. The research presented in this report is primarily focused on the impact of voltage unbalance and regulation on the life expectancy of low voltage induction machines. The operating conditions considered in this report are prevalent on a typical rural feeder. Most customers connected to rural 11/22kV networks are farmers and a large portion of load pumps are driven by low voltage induction machines. This report presents the effect of these operating conditions on the life expectancy of the machines. The thermal model presented is suitable for continuously operated machines (S1). Since the operating conditions considered are primarily prevalent on typical rural feeders, the machines considered were also the machines primarily used in those regions. This has consequence that relates to the way in which the network voltages are managed, and claims lodged against power utilities resulting from damage to end user’s induction machines. The thermal model presented in this report can be incorporated as an algorithm and be implemented in microprocessor devices which enhance the level of accuracy and flexibility. As a practical application of the thermal model real time data can be processed according to the firmware thermal algorithm program and results are compared with the expected values and stored in memory. If a machine protection device is used, it computes an analog value which is then compared with the output of the thermal model algorithm. In practice the MPD usually triggers the digital outputs if the compared analog values exceed the set thermal threshold.

The question ‘what is the cost of electricity interruptions?’ is fraught with lots of complexities as electricity interruption is not a tradable commodity. A closely associated question is ‘from whose perspective should this cost be assessed – the electric utility or its customers?’ Extant research has shown that the primal focus should be on the electricity customer as the electric utility’s revenue loss after an electricity interruption event is significantly less than customers’ interruption cost (CIC). Existing methods of assessing the cost of electricity interruptions are not always consistent, because analysts make different assumptions, primarily in the incorporation of key parameters of electricity interruptions and customer characteristics in their analyses. However, one thing is important: the chosen assessment method should suit the decision-making context in which the cost data will be applied. In this dissertation, both micro- and macro-level approaches were applied to the assessment of the cost of electricity interruptions to commercial and industrial electricity customers. However, the central investigation is the micro-level assessment of the direct financial cost of electricity interruptions to suit value-based reliability planning and power system operations management. The cost assessment was done from the business customer’s viewpoint via a firm-level survey of commercial and manufacturing businesses in Cape Town. Three CIC models were developed from an analysis of the survey data viz. a time-invariant average interruption cost (TIAIC) model, a time-varying average interruption cost (TVAIC) model, and a time-varying probabilistic interruption cost (TVPIC) model. All three models were applied in an assessment of reliability worth indices for a case study distribution system to demonstrate the practical application of the cost data. The results showed that the TVPIC model is more effective for describing CIC as it accounts for the time-dependencies and uncertainty in CIC estimates. The TVPIC allows for an evaluation of the impact of different confidence levels in decision-making. Reliability worth indices like ECOST derived based on the TVPIC can be expressed as Rands@Risk in different season-time windows. This allows for optimal implementation of contingency measures like load shedding or reliability improvement programs like switch/disconnect placement on distribution feeders. An exploratory macroeconomic analysis was also done using an input-output (IO) model that allowed the investigation of the effect of the removal of the electricity sector from intersectoral interactions in South Africa’s economy. Based on the model’s framework and assumptions, the potential economy-wide cost of a day-long blackout was estimated to be approximately R2.2 billion. Compared to estimates of the economic cost of past load shedding events, this figure seemed to be a very optimistic estimate and a potential lower bound of a day-long blackout in South Africa. Also, the relationship between the firm-level survey and the macroeconomic IO approaches to estimating the cost of electricity interruptions was assessed via a case study of the weekly cost of load shedding to South Africa’s trade and manufacturing sectors. The ensuing discussions show that caution must be exercised in quoting blanket figures of the cost of load shedding to the South African economy without appropriate description of the basis for estimation.

This project investigates the delamination dependence of fibre reinforced polymers, of different weave patterns, using an image-based crack measurement method. Glass fibre reinforce polymer (FRP) with three different weave pattern namely Unidirectional, Plain weave and Twill weave patterns were manufactured using the infusion process. Waterjet cutting was used to cut the panels to produce the test specimens. The Double Cantilever Beam (DCB) test was used to measure the Mode I fracture toughness, following the standardised test method ASTM D5528. DCB tests requires two hinge blocks to be bonded to the specimens and is conducted using the Zwick machine which actively measures force and opening displacement. In order to calculate the fracture toughness from a DCB test, the crack length must be measured. An image-based crack measurement method was developed, using still images that were extracted from a digital video of the DCB experiment. The image-base method involved scripting a MATLAB file to detect the specimen surface as edges. The specimen was painted white and the test had a black background. This caused a sharp change in intensity which made the specimen edge easier to detect. The detection algorithm only catered for accuracy and not speed. A series of tests were conducted to verify the detection algorithm, of which included designing an Ultrasound Wedge device. The Wedge device was used to emulate a DCB tests in a static position whereby an Ultrasound Thickness Tester was used to obtain and verify the position of the crack tip obtained by the algorithm. DCB tests showed that the Twill weave specimens had the greatest resistance to delamination, while the Unidirectional weave offered the least resistance to delamination. The Plain weave pattern was inconclusive due to the large variation between the Plain weave specimens.

The need to find biodegradable alternatives for common polymer materials has risen due to the increase in pollution (soil and water) and the effects that it has on the ocean and wildlife. Alternatives can be found by turning to plant-based oils, for example castor oil, to be used in the synthesis of a variety of monomers. Castor oil is suitable as it is non-edible; thus its use does not deplete food sources and it has high chemical reactivity. In this study, medical grade castor oil was maleated by the addition of maleic anhydride to form maleated castor oil (MACO). This reaction was performed at 98 ˚C for five hours. The completion of the reaction was monitored using acid value. The maleated castor oil was reacted with styrene monomer (at 60 ˚C) and thermally cured to form a tough but flexible polymer (MACOPS). Curing took place for two hours at 90 ˚C, two hours at 120 ˚C and 1 hour at 160 ˚C. Additionally, the synthesized polymer matrix was reinforced with alkalized greige fibres (consisting of a hemp and cotton mix) using a hand lay-up process. Mechanical tests - tensile, flexural and impact strength - were performed on the neat and reinforced polymer. Comparison tests (to determine mechanical properties) were also conducted on commercial general purpose polystyrene (GPPS) and high impact polystyrene (HIPS). Scanning electron microscopy (SEM) was performed on the tensile fracture surfaces of the reinforced matrix. The crosslink density, contact angles and density of the synthesized polymer were determined. Differential scanning calorimetry (DSC) was used to determine the glass transition temperature(s) of the synthesized and commercial polymers. Thermogravimetry was performed on the synthesized matrix as well as the commercial polymers to determine operating temperatures. Raman spectroscopy was used to obtain structural information on the synthesized polymer as well as confirm the successful completion of the maleation reaction. To test for the compostability of the maleated castor oil-polystyrene polymer matrix, biodegradability tests were conducted for a period of ten weeks. The degraded samples underwent tensile testing and the contact angles were determined. Transmission electron microscopy (TEM) was used to see the distribution of polystyrene throughout HIPS and the MACOPS matrix. The acid value at the start of the reaction was 80.1/100 mgNaOH and at the end of the reaction the acid value decreased to 74.7/100 mgNaOH. A decrease in acid value indicated that the maleic anhydride stopped reacting at the end of the reaction. An increase in viscosity of the mixture served as an indication that the maleation reaction did take place. ASTM D6110 was used for the Charpy impact test. HIPS performed as expected with the highest impact strength of 58.4 kJ/m2 . The addition of MACO to styrene monomer led to an increase in the toughness of the end product. An increase was observed for both the MACOPS and reinforced MACOPS compared to GPPS. MACOPS and reinforced MACOPS had impact strengths of 41.5 kJ/m2 and 45.0 kJ/m2 respectively. The addition of the reinforcing greige fibres did not significantly improve the impact strength. GPPS had the lowest impact strength of 33.9 kJ/m2 . Tensile tests were conducted according to ASTM D638. For MACOPS an ultimate tensile strength (UTS) of 23.0 MPa and a Young's modulus of 983 MPa were found. GPPS on the other hand had a much higher UTS and Young's modulus of 44.8 MPa and 3.3 GPa respectively. Once again the MACOPS had tensile properties closer to those of HIPS. The UTS and Young's modulus of HIPS was 13.5 MPa and 1.5 GPa respectively. The reinforced MACOPS did not perform very well under tension with a UTS of 13.1 MPa and a Young's modulus of only 283 MPa. The theoretical modulus of the composite was calculated using the Rule of Mixtures and the Halpin-Tsai model to determine the efficiency of the greige fibres as reinforcement. The efficiency was determined to be less than 30%. Flexural tests were conducted according to ASTM D7264. A significant difference in the flexibility of the synthesized polymer was found when compared to GPPS. MACOPS had a maximum flexural strength of 22.1 MPa whereas GPPS had a flexural strength of 74.4 MPa. The MACOPS had flexural properties closer to that of HIPS which had a flexural strength of 27.2 MPa. The reinforced MACOPS had a flexural strength of 12.2 MPa. This was ascribed to the presence of significant delamination. GPPS and HIPS have no crosslinks between the polymer chains. A crosslink density of 2.1 x 10-3 mol/cm3 was determined for the MACOPS matrix. This could point to co-polymer formation between MACO and polystyrene. Raman spectroscopy was used to determine if the maleation of castor oil took place successfully. Maleic anhydride has signature absorption bands at 1850 cm-1 and 1790 cm-1 . These peaks were absent in the MACO spectrum, which suggests complete reaction. Signature peaks of both the MACO and GPPS were present in the spectrum of MACOPS. This also may point to co-polymer formation. A Raman map of MACOPS showed uniform distribution of polystyrene throughout the sample whereas HIPS had numerous gaps where polystyrene was of low intensity. This points to the presence of sections containing polybutadiene. Therefore MACOPS can be characterized as either a co-polymer or an interpenetrating polymer network. MACOPS displayed two glass transition temperatures (Tg) when analyzed with DSC. A small (low intensity) glass transition temperature peak was observed at 93.2 °C and a second of higher intensity at 54.9 ˚C. Two glass transition temperature can point to an interpenetrating polymer network. The Tg of 54.9 ˚C was assigned to a co-polymer. The Tg of 93.2 ˚C is possibly due to a small amount of homo-polymerized polystyrene. Due to the fact that the glass transition temperature is relatively close to ambient temperature, the matrix is relatively flexible but not elastomeric; hard and tough but not very brittle. Thermogravimetry indicated a thermal degradation onset temperature of 336 °C for the MACOPS matrix. The onset temperature for thermal degradation of MACOPS is lower than those of HIPS and GPPS. After biodegradability testing, no significant loss in mechanical properties was observed for the MACOPS matrix and reinforced composite. MACOPS showed the most mass loss (10.4%) in comparison with the other materials. A significant decrease was seen in the contact angle measurements of the degraded reinforced MACOPS. The contact angle decreased from 88˚ (original) to 54.2˚ (degraded). This points to surface changes as a result of degradation that decreases the hydrophobicity of the material. It can be seen that the addition of MACO to styrene monomer most likely results in an IPN with a degree of crosslinking. The properties of this matrix is closer to those of HIPS than GPPS. The matrix is hard, tough and more flexible than GPPS. At room temperature the MACOPS matrix is used just above its glass transition temperature. Reinforcing the matrix with greige fibres led to a decrease in mechanical properties. Thus the fibres acted only as a filler. The synthesized MACOPS matrix is hydrophilic and shows no significant degradation when placed in compost after a period of 10 weeks.

Bibliography: leaves 68-71. / The Kenyan sugar industry continues to face the task of being competitive in a liberalized global economy that has witnessed a trend in declining sugar prices and increasing local production costs. This dissertation attempts to investigate possible options that could assist Kenyan sugar industry to cope with the crisis. One such option is the diversification of the sugar industry's product base. Expanding their business to energy as a co-product to sugar processing, sugar companies could generate additional revenue from surplus electricity sales to the national utility. In Mauritius, gross revenue of USD 50 million, equivalent to 90% of that accruing to the miller for cane processing is generated from bagasse-based energy sales. On the basis of the Mauritian and other experiences the research concludes that Kenya sugar industries have the potential to export 43, 258, and 306 GWh of electricity to the national grid, depending on the mode of operation of the power plant. Thus the potential for revenue expansion through power sales for the Kenyan sugar industry is substantial. Power sector reforms have seen the entry into the electricity market of independent power producers (IPPs), and so this presents a good opportunity for sugar companies to enter into power purchase agreements with the national utility for the supply of power. Anaerobic digestion systems, used in the treatment and management of industrial effluent provide an additional benefit of generating boiler fuel in the form of biogas in sugar industries of Kenya. This technology and its application to the sugarcane industry are reviewed as part of this thesis.

Includes bibliographical references. / As many current applications require microwave solid state sources with output powers greater than that available from a single device a need for combining the power from these devices is required. N-way combiners/dividers may be used to achieve this. For high output powers these combiners/dividers must have a high combining efficiency. This dissertation describes various power combining techniques and essentially a power combiner/divider that is both planar and low loss is required. The planar structure is a requirement if efficient heat dissipation is to be achieved. Cylindrical resonant cavity structures give very high combining efficiencies, however, they are non planar and have narrow bandwidths. N-way planar combiners/dividers fabricated on microstrip provide the desired planar structure but due to the characteristics of microstrip are lossy. As a culmination of this work a low loss 8-way planar stripline combiner/divider was constructed that gave a peak combining efficiency of 94 percent which approaches the combining efficiency of 98 percent that was obtained with the cylindrical resonant cavity combiner. The former offers its broader bandwidth and planar structure as advantages.