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Sub-Saharan Africa is a treasure chest of natural materials remaining to be explored for commercial applications and as alternative foods to diversify and improve food sustainability. The Marula tree is available in abundance in South Africa and bears a fruit with a highly nutritious kernel containing high oil and protein content. The oil from the kernels has various applications from food to cosmetics. The accepted oil processing practice is required to be a green technology, producing no effluent or using toxic solvents. Therefore, the oil is extracted using an expeller. However, with average 55 wt. % oil in the kernel the extracted oil yield is far from optimal, typically ranging from as low as 7 wt. % to 47 wt. %. The latter is obtained only with proprietary modified expellers. Therefore, an alternative green technology which retains the native characteristics of the Marula oil is needed. Communication with local producers, South African and Namibian, confirmed the need for investigation of an alternative means of extraction of Marula oil from the seed kernels which can improve the yield and potentially the quality of the oilcake. The latter of which is typically adversely affected by the expelling process. A review of various processing technologies available for oil extraction was completed and supercritical fluid extraction utilizing carbon dioxide as the extraction solvent was identified as a potential solution. An overview on supercritical fluid extraction using carbon dioxide (SFE-CO2) of similar materials to the Marula kernels, such as hazelnuts, walnuts and pine kernels indicates that yields similar to that of solvent extraction and of the quality of the oils obtained by cold pressing can be obtained with the technique. The theory, practical applications, and how one can use the system to improve yield from various natural materials were reviewed. It was determined that the two main parameters one can manipulate on supercritical extraction systems to optimize the yield, were pressure and temperature. Subsequently kernels of the Sclerocarya birrea tree, common name Marula, cultivated in South Africa, were obtained for extraction with supercritical carbon dioxide. The effects of pressure and temperature on extraction yield were investigated. The total maximum yield of Marula kernel oil obtained was found to be 54 wt. %, compared to a solvent extracted yield of 52 wt. %, such that a 100 % oil recovery was obtained with SFE-CO2. The optimal conditions were found to be 450 bar and 60 °C as the yield per kg solvent initially was 41 g kg-1 CO2. Following the extractions, the oils were characterized for fatty acid composition using gas chromatography. Quality parameters of a cold pressed sample and a sample obtained at the optimal extraction conditions were determined and compared; and the results indicate that the two oils are of similar composition and quality. Supercritical fluid extraction using carbon dioxide was successfully verified as a potential processing method for the extraction of Marula oil from the kernels. The SFE-CO2 provided an improved yield compared to cold pressing and a quality of oil similar to cold pressed Marula oil. Additionally, after SFE-CO2 processing, the defatted Marula kernels contain high protein content, 69 wt. %, in the form of a pure white powder. Due to the favourable nutritional content the residue may be used for human consumption to create new products such as meat analogues, porridges, and shakes, or can be sold as a high protein powder. / MSc (Engineering Sciences in Chemical Engineering), North-West University, Potchefstroom Campus, 2015

Sub-Saharan Africa is a treasure chest of natural materials remaining to be explored for commercial applications and as alternative foods to diversify and improve food sustainability. The Marula tree is available in abundance in South Africa and bears a fruit with a highly nutritious kernel containing high oil and protein content. The oil from the kernels has various applications from food to cosmetics. The accepted oil processing practice is required to be a green technology, producing no effluent or using toxic solvents. Therefore, the oil is extracted using an expeller. However, with average 55 wt. % oil in the kernel the extracted oil yield is far from optimal, typically ranging from as low as 7 wt. % to 47 wt. %. The latter is obtained only with proprietary modified expellers. Therefore, an alternative green technology which retains the native characteristics of the Marula oil is needed. Communication with local producers, South African and Namibian, confirmed the need for investigation of an alternative means of extraction of Marula oil from the seed kernels which can improve the yield and potentially the quality of the oilcake. The latter of which is typically adversely affected by the expelling process. A review of various processing technologies available for oil extraction was completed and supercritical fluid extraction utilizing carbon dioxide as the extraction solvent was identified as a potential solution. An overview on supercritical fluid extraction using carbon dioxide (SFE-CO2) of similar materials to the Marula kernels, such as hazelnuts, walnuts and pine kernels indicates that yields similar to that of solvent extraction and of the quality of the oils obtained by cold pressing can be obtained with the technique. The theory, practical applications, and how one can use the system to improve yield from various natural materials were reviewed. It was determined that the two main parameters one can manipulate on supercritical extraction systems to optimize the yield, were pressure and temperature. Subsequently kernels of the Sclerocarya birrea tree, common name Marula, cultivated in South Africa, were obtained for extraction with supercritical carbon dioxide. The effects of pressure and temperature on extraction yield were investigated. The total maximum yield of Marula kernel oil obtained was found to be 54 wt. %, compared to a solvent extracted yield of 52 wt. %, such that a 100 % oil recovery was obtained with SFE-CO2. The optimal conditions were found to be 450 bar and 60 °C as the yield per kg solvent initially was 41 g kg-1 CO2. Following the extractions, the oils were characterized for fatty acid composition using gas chromatography. Quality parameters of a cold pressed sample and a sample obtained at the optimal extraction conditions were determined and compared; and the results indicate that the two oils are of similar composition and quality. Supercritical fluid extraction using carbon dioxide was successfully verified as a potential processing method for the extraction of Marula oil from the kernels. The SFE-CO2 provided an improved yield compared to cold pressing and a quality of oil similar to cold pressed Marula oil. Additionally, after SFE-CO2 processing, the defatted Marula kernels contain high protein content, 69 wt. %, in the form of a pure white powder. Due to the favourable nutritional content the residue may be used for human consumption to create new products such as meat analogues, porridges, and shakes, or can be sold as a high protein powder. / MSc (Engineering Sciences in Chemical Engineering), North-West University, Potchefstroom Campus, 2015

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Quantitation of the amount of finish applied during fiber manufacturing is an important industrial quality control process. Finish levels that are too low result in excessive fiber and mechanical wear. On the other hand, overly high finish levels may cause residue buildup on the processing equipment. Removal of the finish has traditionally been done with solvents such as chloroform or Freon followed by gravimetric or spectroscopic analysis of the removed material. Quantitation of low molecular weight oligomeric material is another important quality control practice for the fiber industry in that the presence of these species and their concentration affect the physical properties of the polymer. Also, excessively high concentrations of oligomers may result in residue deposits on processing equipment. Typical conventional methods for determining the concentration of oligomers present in fibers involve large quantities of organic solvent for removal of the oligomers followed by chromatographic analysis. Increased government regulation of chlorinated and other solvents has led to investigations of alternate methods of extraction. Several studies have shown that supercritical fluid extraction (SFE) using carbon dioxide as the extraction fluid is an important alternative to conventional organic solvent extraction for the removal of both textile finishes and oligomeric material. This research seeks to extend the previous studies regarding the application of SFE for the quantitation of finish and oligomers from nylon 6,6 fibers. The effects of pressure, extraction temperature, modifier percentage, static extraction time, and dynamic extraction time on the supercritical fluid extraction efficiency of nylon 6,6 oligomers were examined. Results from the SFE methods for both finish and oligomer extractions were compared to results from conventional solvent extraction. The extracted oligomers were identified by HPLC with coupled on-line atmospheric pressure chemical ionization mass spectrometry (APCI-MS) and HPLC fractionation coupled with off-line Liquid Secondary Ion Mass Spectrometry (LSIMS). / Master of Science

High-performance variable-speed drives, such as PMSM and BLDC, rely on instantaneous torque control. Over the years, several strategies have been investigated in this domain, with the prominent strategies being field-oriented control and direct torque control. Regardless of the strategy employed, a precise rotor position during operation is an essential requirement. While a wide range of sensing technologies to monitor the rotor position have been employed, industries at large presently focus on Hall effect sensors for this application because they are highly cost-effective, low maintenance, noninvasive, and occupy very little space compared to its alternatives. However, the downside of using Hall effect sensors is their low accuracy. In particular, in the application of handheld battery-powered tools, output signals are affected by vibrations and harmonics from the electromagnetic field. Approaches that are being investigated to reduce or eliminate this noise from the signals can be broadly categorized into 1) installation position optimization, 2) filter methods, and 3) measurement model methods. As they are widely cited and easy to implement in the application of handheld battery-powered tools, four filter structures, namely, ANF with PLL, only PLL, SFE, and SFE with PLL, have been investigated in this thesis. This thesis evaluated the filter’s performance when applied to a real-world application of battery-powered tools. The filters were evaluated for their ability to preserve fundamental frequency components and reject harmonic content up to the 5th order. Visual inspections of Lissajous curves, rotor angle curves and generated reference signals provided insights into peculiarities during operation. Operations were categorized into four scenarios to facilitate the examination of filter response during acceleration and steady state in forward and reverse directions. Only performances of ANFPLL and SFE-PLL proved to be satisfactory with some limitations. The SFE filter yielded insignificant results which could be attributed to a lack of feedback mechanism. While the findings presented in this thesis contribute to the understanding of the viability of filter applications in batterypowered tools, additional testing is imperative. This entails the conversion of filter structures into algorithms suitable  for integration within software frameworks, ensuring their practical applicability and efficacy in real-world scenarios. / Högpresterande frekvensomriktare, såsom Permanent Magnet Synchronous Motor (PMSM) och Brushless DC Electric Motor (BLDC), förlitar sig på momentan vridmomentkontroll. Under årens lopp har flera strategier undersökts inom detta område, där de framträdande strategierna är fältorienterad kontroll och direkt vridmomentkontroll. Oavsett vilken strategi som används är en exakt rotorposition under drift ett väsentligt krav. Medan ett brett utbud av avkänningstekniker för att övervaka rotorns position har använts, fokuserar industrier i stort på Hall-effektsensorer för denna applikation eftersom de är mycket kostnadseffektiva, låga underhållskostnader, ickeinvasiva och upptar mycket lite utrymme jämfört med dess alternativ. Men nackdelen med att använda Hall-effektsensorer är deras låga noggrannhet. I synnerhet vid tillämpning av handhållna batteridrivna verktyg påverkas utsignalerna av vibrationer och övertoner från det elektromagnetiska fältet. Tillvägagångssätt som undersöks för att minska eller eliminera detta brus från signalerna kan brett kategoriseras i 1) installationspositionsoptimering, 2) filtermetoder och 3) mätmodellmetoder. Eftersom de är allmänt citerade och lätta att implementera i tillämpningen av handhållna batteridrivna verktyg, fyra filterstrukturer, nämligen Adaptive Notch Filter (ANF) med Phase Locked Loop (PLL), endast PLL, Synchronous Frequency Extractor (SFE) och SFE med PLL, har undersökts i denna avhandling. Denna avhandling utvärderade filtrets prestanda när det tillämpades på en verklig tillämpning av batteridrivna verktyg. Filtren utvärderades med avseende på förmågan att bevara grundfrekvenskomponenten och avvisa övertonsinnehåll upp till 5:e ordningen. Visuella inspektioner av Lissajous-kurvor, rotorvinkelkurvor och genererade referenssignaler gav insikter om egenheter under drift. Operationer kategoriserades i fyra scenarier för att underlätta undersökning av filterrespons under acceleration och stationärt tillstånd i framåt- och bakåtriktning. Endast prestanda av ANF-PLL och SFE-PLL visade sig vara tillfredsställande med vissa begränsningar. SFE-filtret gav obetydliga resultat som kunde tillskrivas bristen på återkopplingsmekanism. Även om resultaten som presenteras i denna avhandling bidrar till förståelsen av användbarheten av filtertillämpningar  i batteridrivna verktyg, är ytterligare tester absolut nödvändiga. Detta innebär omvandling av filterstrukturer till algoritmer lämpliga för integration inom mjukvaruramverk, vilket säkerställer deras praktiska tillämpbarhet och effektivitet i verkliga scenarier.

In this thesis current questions regarding the functionality of liberalized electricity markets are studied addressing different topics of interest in two main directions: market power and competition policy on electricity wholesale markets, and network investments and incentive regulation. The former is studied based on the case of the German electricity market with respect to ex-post market power analysis and ex-ante remedy development. First an optimization model is designed to obtain the competitive benchmark which can be compared to the observed market outcomes between 2004 and 2006. In a second step the horizontal breaking up of dominant firms (divestiture) is simulated applying equilibrium techniques (the classical Cournot approach and the Supply Function Equilibrium approach). The later issue of transmission capacity investment is addressed by highlighting the complexity of network investments in electricity markets and by analyzing a regulatory mechanism with a two part tariff approach. The technical characteristics of power flows are combined with economic criteria and tested for different network settings.

À l’heure où l’intégration des enjeux environnementaux dans le développement de procédés éco-efficients joue un rôle essentiel dans le moteur de l’innovation responsable, la chimie verte est devenue l’un des sujets de préoccupation majeure. Ainsi, le développement de nouveaux procédés éco-respectueux pour la production d’ingrédients naturels issus de matières premières végétales renouvelables est devenu une démarche incontournable dans le modèle de recherche. L’objectif de cette thèse a consisté au développement d’une stratégie d’éco-valorisation innovante employant les fluides sub/supercritiques pour l’extraction, la caractérisation, la production et l’imprégnation sur support cosmétique de produits naturels d’origine végétale. Pour cela, nous avons utilisé comme modèle végétal : les graines oléagineuses de la plante Kniphofia uvaria, sélectionnée pour des applications cosmétiques grâce à ses propriétés bioactives antioxydantes et anti-âge. Dans un premier temps, le développement de méthodes complémentaires en SFC ainsi que le développement du couplage SFC-MS a été réalisé à l’aide de la source APCI afin d’identifier les molécules responsables des activités bioactives des graines de Kniphofia uvaria. Ainsi, le développement d’un système hybride (U)HPLC/SFC-HRMS a été réalisé afin de mettre en place ce couplage. Des optimisations en termes de proportion et nature de solvant make-up ainsi qu’un travail au niveau des paramètres SFC et MS ont été faits afin de d’améliorer la sensibilité et la spécificité des analyses lipidiques. Dans un second temps, nous nous sommes attachés au développement d’une stratégie d’enrichissement en composés bioactifs à l’aide des méthodes : SFE et CPC. Ainsi, en SFE, des optimisations en termes de température, pression, nature/proportions de co-solvant dans le fluide ont été réalisées alors qu’en CPC, des optimisations au niveau de l’injection ont été faites. Des conditions optimales pour le fractionnement sélectif des anthraquinones et des triglycérides ont été déterminées en SFE et CPC. Dans un dernier temps, ce travail a consisté à développer un couplage en-ligne pour extraire et imprégner sélectivement sur silice cosmétique : les anthraquinones. Le développement et l’optimisation de ce procédé en-ligne ont été réalisés à l’échelle du laboratoire et ont démontré la faisabilité de ce couplage ainsi qu’un intérêt certain pour l’obtention de produits naturels sous une première forme galénique, destinée à une future incorporation dans la formulation de cosmétiques. / Nowadays, green chemistry is a great challenge. It seeks innovation in the development of eco-efficient processes. The production of natural products from renewable materials by these new environmentally friendly processes is more and more used. The aim of this Ph.D thesis is to develop an eco-valuation strategy to extract, characterize, produce and impregnate natural products onto a cosmetic support using sub/supercritical fluids. Consequently, we used oleaginous plant seeds from Kniphofia uvaria as a plant model, which was selected for its interesting cosmetic properties such as antioxidant or anti-ageing. Firstly, the SFC-MS hyphenation with the APCI as an ionization source was developed to screen bioactive molecules; responsible of cosmetic properties. This coupling was performed by the hybrid combination of (U)HPLC/SFC-HRMS. Various optimizations in terms of the solvent make-up (nature and proportion), modulation with SFC and MS parameters were carried out in order to improve sensitivity and selectivity of lipid analysis. Secondly, an enrichment strategy to concentrate bioactive compounds in the final extract was developed by SFE and CPC. Thus, in SFE, experimental parameters (temperature, pressure, nature/proportion of the modifier in the CO2 fluid) were optimized while in CPC, the injection optimization was realized. Methods for the selective fractionation of anthraquinones and triglycerides were obtained in CPC and SFE. Finally, an on-line sub/supercritical extraction-impregnation process was developed to extract and for simultaneously impregnating anthraquinones onto a cosmetic silica. Development and optimization of this process was realized on a laboratory scale. Consequently, this study demonstrated the feasibility of this concept and it presents a great interest to provide natural products as a galenic form, which could be used in the cosmetic formulation.

The following work describes the instrumentation and application of hyphenated FT-IR techniques specifically involving supercritical fluid extraction (SFE), supercritical fluid chromatography (SFC), and liquid chromatography (LC). Three studies are presented. The first involves the application of SFE/FT-IR towards the extraction of finishes from textile fibers. SFE has previously been applied to less complex finish systems. The proposed method making use of intermediate trapping is viable for more complex systems that show limited solubility in a supercritical fluid. Quantification of the percent finish on yarn was performed and results were favorable when compared with plant data. The range of applications was expanded to on-line SFE/SFC in the extraction and analysis of components from the polymer matrix itself. SFE/SFC/FT-IR was used to identify extractable components from a variety of Nylons. Following identification of one of the primary extractables, caprolactam, SFE/SFC was used to quantitate the amount of residual starting material in a Nylon copolymer. The second study involves the extractables in polystyrene which is a softer polymer with respect to solubility of components in supercritical CO ₂. Dimers and trimers as well as processing agents were identified via FT-IR with relatively mild supercritical extraction conditions. Following these two studies was the expansion of hyphenated FT -IR to mobile phase elimination. A system optimization was carried out using polymer additive standards. The effects of nebulizer flow, sheath flow, and sheath temperature were shown. The data were analyzed at in terms of library matches as well as GramSchmidt reconstruction peak heights. Peak intensities were the primary source for choosing optimum conditions. Under optimized conditions, approximately 200 ng of analyte were analyzed and found to be above the limit of detection. The applicability of the interface was demonstrated by the identification/analysis of triclosan, an antibacterial agent, in Colgate toothpaste. Aside from the identification of the analyte this study was used to show the effect of deposition parameters such as disk rotation rate as well as the effectiveness of FT-IR spectral library searches. The analysis of triglycerides was also carried out to show the effectiveness of using LC/FTIR for viscous liquids which are difficult analytes to deposit onto a solid substrate. Using this FT-IR technique allowed one to look at the degree of saturation/unsaturation in an olive oil sample. The linearity of the method was shown using a set of triglyceride standards. Lastly, the feasibility of using the commercially manufactured mobile phase elimination interface for SFC was demonstrated. Additive standard was deposited using both pure and methanol modified CO₂. No effluent split mechanism was used for decompressed flows up to 150 mL/min. Detection limits are proposed to fall in the low (10 - 25) ng range. The infrared spectra are enhanced over those acquired with a flow cell interface because CO₂ absorbance bands no longer obscure a portion of the analyte absorption spectrum. / Ph. D.