Search

The global requirement for sustainable energy provision will become increasingly important over the next fifty years as the environmental effects of fossil fuel use become apparent. Therefore, the issues surrounding integration of renewable energy supplies need to be considered carefully. The focus of this work was the development of an innovative computer aided design of a 3 Dimensional renewable energy platform for Togo’s smart grid power system infrastructure. It demonstrates its validation for industrial, commercial and domestic applications. The Wind, Hydro, and PV system forming our 3 Dimensional renewable energy power generation systems introduces a new path for hybrid systems which extends the system capacities to include, a stable and constant clean energy supply, a reduced harmonic distortion, and an improved power system efficiency. Issues requiring consideration in high percentage renewable energy systems therefore includes the reliability of the supply when intermittent sources of electricity are being used, and the subsequent necessity for storage and back-up generation The adoption of Genetic algorithms in this case was much suited in minimizing the THD as the adoption of the CHB-MLI was ideal for connecting renewable energy sources with an AC grid. Cascaded inverters have also been proposed for use as the main traction drive in electric vehicles, where several batteries or ultra-capacitors are well suited to serve as separate DC sources. The simulation done in various non-linear load conditions showed the proportionality of an integral control based compensating cascaded passive filter thereby balancing the system even in non-linear load conditions. The measured total harmonic distortion of the source currents was found to be 2.36% thereby in compliance with IEEE 519-1992 and IEC 61000-3 standards for harmonics This work has succeeded in developing a more complete tool for analysing the feasibility of integrated renewable energy systems. This will allow informed decisions to be made about the technical feasibility of supply mix and control strategies, plant type, sizing and storage sizing, for any given area and range of supply options. The developed 3D renewable energy platform was examined and evaluated using CAD software analysis and a laboratory base mini test. The initial results showed improvements compared to other hybrid systems and their existing control systems. There was a notable improvement in the dynamic load demand and response, stability of the system with a reduced harmonic distortion. The derivatives of this research therefore proposes an innovative solution and a path for Togo and its intention of switching to renewable energy especially for its smart grid power system infrastructure. It demonstrates its validation for industrial, commercial and domestic applications.

For sprint events longer than 100 m, more than half the race is run on the bend, yet bend sprinting has received little attention in biomechanics literature. The aim of this thesis was to understand the effect of the bend on maximal effort sprint performance and technique, using bend radii and surfaces typical of outdoor competition. Three empirical studies were undertaken with experienced bend sprinters. Initial 3D kinematics investigations revealed an approximately 5% velocity decrease on the bend compared to the straight. However, step characteristic changes contributing to this reduction were different for the left and right steps. For the left step there were significant decreases in step frequency (p < 0.05), due to increased ground contact time, which agreed with previously proposed theoretical models. For the right step, however, a significantly reduced flight time resulted in a significant reduction in step length (p < 0.05). Maintaining step length and an ‘active touchdown’ were closely related to an athlete’s ability to better maintain straight line velocity on the bend. Generally, velocity decreased as bend radius decreased, with mean differences of up to 2.3% between lanes 8 and 2. However, changes to athletes’ technique due to different lanes were not conclusive. Ground reaction forces revealed between-limb differences during bend sprinting. Furthermore, frontal plane forces were up to 2.6 times larger on the bend than on the straight. Overall, asymmetries were identified between left and right steps for several performance, technique and force variables, suggesting that bend sprinting induces different functional roles between left and right legs, with the left step contributing more to turning to remain on the bend trajectory. The differences in kinematic and kinetic characteristics between the bend and straight, and between-limb asymmetries mean that athletes should apply the principle of specificity to bend sprinting training and conditioning, without sacrificing straight line technique.

This study describes the development of a novel method of three dimensional perfused cell culture for in vitro toxicity testing. Multiple parallel perfused microbioreactors (TissueFlexTM) were adopted to provide a well-controlled cell culture environment. Alginate and collagen type I, commonly used as hydrogel scaffolds to support cell culture, were tested as the scaffolding materials for this application. Alginate supports cell proliferation, but does not support cell attachment. Collagen gel (type I), good for cell attachment but with poor mechanical strength, could be used at the high concentration of 5mg/ml to prevent the degradation of the gel. Improvement of collagen biomechanical property by a purpose-designed compressor to physically induce cross-linking showed promising results and merits further study. The suitability of alamarBlue® assay, a common non-toxic non-destructive viability assay method, was confirmed for this study and the protocol was optimised. To demonstrate the effectiveness of three dimensional perfused cell culture, human mesenchymal stem cells (MSC) seeded in collagen type I were employed to test the cell inhibition of two antibiotics, trimethoprim and pyrimethamine. The results displayed the perfusion system has greater advantage and sensitivity than the static system, as does these of 3D scaffolds, compared with 2D. Such differences are related to the continuous supply of fresh culture medium to keep cells at a stable pH, temperature, oxygen, and a more physiological like environment. The cytotoxicity of two stereoisomer compounds, obtained confidentially from Pfizer. Ltd., was assessed using the developed method and compared to conventional 2D static and perfused culture by using rat adipose mesenchymal stem cells. The results successfully distinguished toxic and non-toxic compounds and also demonstrated that the 3D perfused system improved the prediction of drug toxicity over 2D culture. 3D perfused bioreactors were applied to hepatotoxicity study using freshly isolated rat hepatocytes. Only algimatrixTM supported hepatocyte spheroid formation among those tested including collagen type I, alginate beads, poly lactic acid fibres, and AlgimatrixTM. A new variation of TissueFlexTM bioreactor with micro-patterned surface, designed specifically for hepatocyte self-assembly culture without use of any scaffold, was tested. The results demonstrated that, compared with the standard sandwich culture, the self-assembly culture in the micro-patterned bioreactors showed high cell viability, biomarkers expression, as well as more physiological immunocytochemistry. Moreover, the differential gene expression indicated that self-assembly culture could provide more relevant information regarding metabolising processes than the 2D sandwich culture, which would potentially improve hepatotoxicity prediction. In conclusion, 3D perfused cell culture for in vitro toxicity testing improved the predictivity, reliability and physiological relevance of drug toxicity compared to traditional 2D culture.

The aims of this study were to form uncompressed thermobonded 3D wool nonwoven shell structures in one continuous process, and to study the controlling factors that govern this process. Lack of bonding between wool fibres and between wool and thermoplastic fibres was attributed to the wool fibre's low surface energy because of the lipids on the outer surface of wool fibres (epicuticle). To overcome this problem, three different surface treatments were investigated; chlorination, Hercosett and plasma. The purpose of these treatments was to raise the surface energy of wool fibres by bond scission and the introduction of new functional polar groups and ablation of the outer lipid layer or membrane. For thermobonding with wool fibres, low melting nylon fibres were chosen because of their high polarity and chemical compatibility with wool fibres. SEM, BSM and ESEM imaging techniques as well as tensile strength testing for single fibres, pair bonded samples and 3D nonwoven shells were used to assess the samples. Results have shown that it is possible to thermobond wool and nylon fibres as 3D shell structures, given that wool fibres are treated appropriately and the bonding temperature is controlled properly. Moreover, it has been found that, for pair bonded samples, the wrapping angle and the bonding angle have significant effects on the tensile strength and number of bonding points. Hercosett treated wool fibres yielded the strongest bonds with nylon fibres followed by plasma, chlorinated and untreated fibres.

The Large-scale Semi-Geostrophic Equations (LSGE, Salmon[73]) are three-dimensional equations valid for an ocean with a rigid lid and length scales much greater than the internal deformation radius (about 40km). In this thesis I reduce the LSGE to a pair of two-dimensional equations via the ansatz that the temperature is independent of the vertical co-ordinate. I refer to these as the Depth-Independent-Temperature (DIT) equations. Whilst this is regarded as a paradigm for the entire ocean, the reduction is similar in spirit to that utilised by many authors for modelling the mixed layer of the ocean. The equations of this thesis differ from the work of such mixed layer models because they involve no ad hoc vertical averaging and so solutions to these equations are also solutions to the full three-dimensional LSGE. The DIT are arguably the simplest equations for ocean circulation to include the effects of inertia, topography and baroclinicity. The DIT are studied both analytically and numerically. It is shown that the model exhibits baroclinic instabilities and analogies are drawn with classical Rayleigh-Benard convection. It is shown that both viscosity and thermal diffusivity are required to avert an ultra-violet catastrophe. Numerical simulations of turbulence demonstrate that the long-time behaviour resembles barotropic flow and that the temperature is reduced to the role of a passive tracer unless large-scale thermal structure is imposed externally on the flow. One of the advantages of the current model over the more widely used quasi-geostrophic models is that there is no restriction on the vertical extent of the bottom topography. This allows the simulation of idealised oceanic basin circulations in which the depth of the ocean vanishes smoothly at boundaries. These ocean simulations are used to study the sensitivity of the model to the Rossby Number, Ekman Number and forcing parameters. Comparison of a barotropic and a DIT ocean reveals the influence of baroclinicity in the latter model. Characteristic features of the Gulf Stream such as meandering, recirculation gyres and the shedding of warm and cold core rings are reproduced by the DIT model and the simple nature of the equations permits an interpretation of these features.