College of Art and Built Environment
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- ItemConstruction of a novel convolution based fractional derivative mask for image edge analysis(KNUST, 2016-08) Appati Justice KwameThis thesis presents a new approach in constructing a more efficient fractional derivative mask for image edge analysis based on the definition and properties of convolution. By the definition of convolution, the generalised Strivastiva-Owa’s operator was rewritten with its order restricted to the Riemann-Liouville fractional derivative. Applying linearity, commutative and derivative properties of convolution to the resultant expression, a new mask with higher efficiency, memory effect and computational equivalence to the classical edge detector is developed as per the experimental results obtained. From the experimental results, it is observed that, the new mask has the potency to find edges in details quite significantly as well as hidden edges which is a deficiency of the classical edge detectors. It can also be used on a region growing algorithm during region segmentation acting as an edge function in its termination process. The experiments conducted on the mask were done using some selected well known synthetic and medical images with realistic geometry. Using visual perception and performing both mean square error and peak signal-to noise ratios analysis, the method demonstrated significant advantages over other known methods
- ItemDivergence regularization method for solving ill-posed Helmholtz equation(KNUST, 2016-06) Barnes,Benedictn this work, we introduce Divergence Regularization Method (DRM) for regularizing the Cauchy problem of the Helmholtz equation where the boundary deflection is not equal to zero in Hilbert space H. The DRM incorporates a positive integer scaler which homogenizes inhomogeneous boundary deflection in Cauchy problem of the Helmholtz equation to ensure the existence and uniqueness of solution for the equation. The DRM employs its regualarization term (1 + α2m)em to restore the stability of the regularized Helmholtz equation, and guarantees the uniqueness of solution of Helmholtz equation when it is imposed by Neumann boundary conditions in the upper half-plane. The DRM gives better stability approximation when compared with other methods of regularization for solving Cauchy problem of the Helmholtz equation where the boundary deflection is zero. In the process, we introduce Adaptive Wavelet Spectral Finite Difference (AWSFD) method to obtain the approximated solutions of the regularized Helmholtz equation with regularized Cauchy boundary conditions, regularized Neumann boundary conditions in the upper half-plane, and finally with regularized both Dirichlet and Cauchy boundary conditions where the boundary deflection is equal to zero. The AWSFD method captures the boundary points to obtain approximated solution of Helmholtz equation. This method reduces the Helmholtz equation in two dimensions to one dimension which is then solve spectrally using a suitable wavelet basis. The solutions by AWSFD method confirms the analytic solutions of regularized Helmholtz equation by DRM. The norm of relative error between the analytic solution by DRM and the approximated solution by AWSFD method is minimal. Moreover, we introduce interpolation scheme in the AWSFD method to obtain the approximated solutions of the regularized Helmholtz equation with above boundary conditions.
- ItemTensile properties, water absorption and enzymatic degradation studies of polyethylene/starch filled hydroxyapatite blend for orthopaedic applications(KNUST, 2016-06) Bernard Owusu Asimeng,Linear low-density polyethylene (LLDPE)/starch blends filled with hydroxyapatite have been synthesized by injection moulding. The aim was to control the rate of biodegradation of LLDPE/starch blends for bone screw fixation using hydroxyapatite (HA). Hydroxyapatite contents were varied from 1.0% to 3.0% in intervals of 0.5% by parts and the blend phases were characterised using X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Biodegradation was studied by performing water absorption and enzymatic tests. Water uptakes by the samples were carried out according to ASTM D570 and enzymatic test was carried out on samples in phosphate buffered saline (PBS) containing α-amylase. Tensile properties of the samples before and after enzymatic degradation were determined using Titan and Testometric’s universal testing machine while the surface changes were determined with Meiji Techno optical microscope. Seven different samples were formed for the study, two of the samples; one composed of LLDPE only and the other of 60% LLDPE, 40% starch and 0% hydroxyapatite, were used as controls. The results obtained show that the incorporation of starch granules into the LLDPE reduces the tensile strength but almost doubles the tensile modulus and this was attributed to starch granules expanding the amorphous tie chain of LLDPE. Addition of hydroxyapatite into the blend gave an increase in the tensile strength. The increase in strength with increasing HA content was statistically significant at a p-value of 0.0008 and the improvement slowed the rate at which the blend degraded. Hydroxyapatite is suspected to have affected the intermediate phase of the LLDPE by the hydroxyl group through hydrogen bonding. The water absorption by the blends showed that as hydroxyapatite content increased, the moisture uptake of the blends increased and enzymatic degradation rate increased, giving rise to high percentage loss in tensile strength and v | P a g e modulus. Conversely there was a high gain in percentage elongation. Optical micrographs of the surfaces of the degraded samples showed surface erosion and agglomerates. The samples that showed higher erosion and more agglomerates had the highest water uptake and highest percentage loss in tensile strength and those with less erosion and fewer agglomerates had less water uptake and less percentage loss in tensile strengt
- ItemCarbohydrate composition and amylase activity of sweet potato (ipomoea batatas) root(KNUST, 2016-08) Eric Owusu MensahSelection of sweetpotato clone(s) for production and utilisation depends on its quality attributes especially sugars, dry matter, starch content and amylase activity. The levels of these attributes are however influenced by factors such as the diversified production environments, cooking treatments, and genotypic compositions. The aim of the study is to determine the range of variation and factors of significant influence on concentrations of these attributes during growth and processing of sweetpotatoes. Development of an efficient and accurate technique for rapid assessment of these quality attributes was also relevant to the study. In order to achieve the overall aim, two main approaches were adopted; varying the levels of identified factors that alter the concentration of the attributes, and using near-infrared reflectance spectroscopy technique to develop a prediction model for their assessment. Sugars (sucrose, glucose, fructose and maltose), starch, dry matter content, amylase activity and sweetness were evaluated at harvest, during heating and after cooking. Adaptive Main Effects and Multiplicative Interaction (AMMI) model was employed to ascertain the magnitude of interactions between the factors tested. It was established that concentrations of the quality attributes were significantly affected by all the factors examined. Genotype contributed the highest variability during the growth stage while cooking treatment produced the highest effect during processing. Effect of interaction was more pronounced on amylase activity compared to sugars, dry matter and starch content. Sucrose was the predominant sugar in the raw form while levels of maltose increased substantially during cooking. High precision calibration was also developed for evaluating sugars and starch content in cooked sweetpotato roots. Sweetpotato varieties in Ghana have a wide range of quality attributes, making it a versatile crop for many food applications. Nonetheless recommendation for specific application should consider choice of production environment and processing conditions, which have significant impact on the final quality of the processed product
- ItemInvestigation of Superluminal Motion of Free Spin-half Particles in Spacetime(KNUST, 2016-07) azoya, Emmanuel Komi DokodjoThe possibility of free spin-1/2 particles (also called Dirac particles) superluminal motion in spacetime, is investigated. The universal cover of the entire Lorentz group L consists of SL(2, C) and the spinor map so that to obtain a relativistically invariant description of the state of an electron, one looks to the representations of SL(2,C), that is, to the 2-valued representation of L, known as spinors. We restrict our approach to realistic one-particle systems along with the “positive energy” and utilize the free Dirac waves propagating in the z−direction. The Dirac wave function ψ (x,t) is considered as a “classical field” and the corresponding wave equation is derived from a symmetrized Lagrange function. It is observed that variation in spin angular momentum (in the light cone) leads to causality violation, whereas variation in orbital angular momentum does not. Consequently, it is shown that the expectation value of the generalized translational relative velocity component of a free spin-half field indeed exceeds the speed of light. This result is also feasible in a fiber bundle formalism.