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A long essay or dissertation or thesis involving personal research, written by postgraduates of University of Ghana for a university degree.
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Item Institutions and African Economic Development(Working Paper, 2022) Fosu, A.K.In light of the increasing importance of institutions in economic development and Africa’s desire to catch up, the present paper provides an account of this crucial subject, ‘Institutions and African Economic Development. First, adopting the usual definition of ‘institutions’ as ‘rules of the game’, the paper shows that improvements in economic institutions, such as economic freedom, had begun by the early 1990s, and accelerated about the mid-1990s, consistent with observed improvements in economic and development outcomes. Also improved are measures of political institutions: an index of electoral competitiveness, constraint on the executive branch of government, and polity 2 as an indicator of the level of democracy, beginning in the late 1980s or early 1990s. Second, based primarily on a review of the extant literature, the paper observes that these improvements in the measures of economic and political institutions are positively associated with the increasing economic development in Africa. Third, indicators of institutional instability, measured by the frequency of civil wars and the incidence of coups d’etat, have been diminishing since the early 1990s, with implications for improved growth and human development. Fourth, some evidence is provided in support of the notion that African countries with better performance on institutional quality during the period of growth resurgence have also exhibited greater progress in poverty reduction. Finally, the paper concludes by flagging the potential risk of African countries backtracking on their respective trajectories toward achieving the democratic consolidation required to sustain the gains in growth and development.Item Ensemble learning prediction of transmittance at different wavenumbers in natural hydroxyapatite(Scientific African, 2020) Okafor, E.; Dodoo-Arhin, D.; Obada, D.O.Material engineering-based research has often relied so much on tedious human exper iments for generating specific engineering properties with a major draw-back of high time demand that can span between an hour and days. Hence to deviate from the usual paradigm, we provide an alternative approach which employs artificial intelligence (AI) based ensemble learning methods for predicting the degree of transmittance for a range of wavenumbers of infrared radiation through hydroxyapatite (HAp) samples. The effective samples (transmittance and wavenumber) were passed as input to the predictive systems. For this, we trained two ensemble learning methods: Extreme Gradient Boosting (XGBoost) and Random Forest on variants of HAp (density and time variations), while considering a fixed amount of 10,000 base estimators. The results show that Random Forest marginally outperforms the XGBoost in the testing phase but requires a much longer computing time. However, XGBoost is much faster than the Random Forest. Furthermore, the examined en semble learning models yielded a coefficient of determination (R2 > 0.997): which are in close agreement with experimental data, depicting an excellent generalization capacity. Additionally, the examined ensemble learning models showed a significant ≥ 99.83% de crease in computational complexity relative to the time spent when generating the exper imental data. Overall, the use of ensemble learning models is very important for validating material engineering propertiesItem Photocatalytic degradation of Rhodamine dyes using zinc oxide nanoparticles(Materials Today: Proceedings, 2020) Dodoo-Arhin, D.; Asiedu, T.; Agyei-Tuffour, B.; et al.This paper presents the synthesis of nanocrystalline zinc oxide (ZnO) particles via the sol-gel method using zinc acetate as a precursor. The calcination temperature of the ZnO was varied to determine its effect on particle size. The resultant samples were characterized using X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), UltraViolet–visible Spectroscopy (UV–Vis) and Scanning Electron Microscopy (SEM). Nanocrystalline wurtzite ZnO particles with crystallite sizes ranging from 16 nm to 30 nm were produced. The Energy Band gap of the synthesized zinc oxide nanoparticles decreased with increasing calcination temperature and crystallite size. SEM Micrographs showed rice-like microstructure morphology of ZnO nanoparticles. The usage of the ZnO nanoparticles as a photocatalyst was also explored in the degradation of Rhodamine B dye using UV light, with particular attention paid to the effect of particle size and catalyst load on the degradation efficiency of the dyes. The nanoparticles calcined at 400 C with a crystallite size of 16 nm resulted in the highest degradation efficiency of 95.41% when 0.2 g catalyst loading was applied. 2019 Elsevier Ltd. All rights reserved. Selection and peer review under the responsibility of the scientific committee of the International Symposium on Nanostructured, Nanoengineered, and Advanced MaterialsItem The physico-mechanical influence of dehydroxylized activated local kaolin: A supplementary cementitious material for construction applications(Case Studies in Construction Materials, 2019) Marfo, K.K.; Dodoo-Arhin, D.; Agyei-Tuffou, B.; et al.This work presents the effect of partially replacing metakaolin with Portland limestone cement to produce mortars for construction. Teleku Bokazo kaolin was explored as an SCM for the production of mortars. The hydration product between Portland limestone and metakaolin was studied. The kaolin was heat treated to form metakaolin and partially used to replace Portland limestone cement (PLC) in mortars to explore the optimum replacement and its mechanical and durability effect. The samples were characterized using X-ray diffraction (XRD) for phases and crystallinity of the kaolin. Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) gave information on the functional groups formed during the hydration and structure and surface morphology respectively. The pastes and mortars produced were subjected to setting time, water absorption, flexure, and compression strength tests. The mechanical properties were observed to increase with increasing metakaolin replacements. Therefore, from the results obtained, it is suggested that a 20 % replacement of Portland limestone cement with Teleku Bokazzo metakaolin can be very suitable for construction applications.Item Hydroxyapatite ceramics prepared from two natural sources by direct thermal conversion: From material processing to mechanical measurements(Materials Today: Proceedings, 2020) Akpan, E.S.; Dodoo-Arhin, D.; Dauda, M.; et al.In this study, hydroxyapatite (HAp) was extracted from catfish bones (CB) and non-separated animal bones (NB). The bioceramic samples were prepared by a facile synthesis route and the representative scaffolds were prepared by cold compaction and sintered at 900 C, 1000 C, and 1100 C. To evaluate the properties of the produced HAp, X-ray diffraction (XRD) and Fourier Transform Spectroscopy (FT IR) analyses were carried out. The evaluation of the hardness of the representative bio-derived scaffolds was experimentally conducted while the fracture toughness and brittleness index were obtained by calculation using the hardness test parameters. The experimental data showed that as temperature increased up to 1000 C for CB, there was a consequential increase in hardness, while for NB, hardness values reduced throughout the sintering regimes. These gradients in mechanical measurements are ascribed to phase changes during heat treatment. 2020 The Authors. Published by Elsevier Ltd. This is an open-access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by nc-nd/4.0). Selection and Review under the responsibility of the scientific committee of the International Conference & Exposition on Mechanical, Material and Manufacturing TechnologyItem Modified nanostructured titania photocatalysts for aquatic disinfection applications(Materials Today: Proceedings, 2020) Dodoo-Arhin, D.; Bowen-Dodoo, E.; Agyei-Tuffour, B.; et al.According to SDG 6, everyone on earth should have access to safe and affordable drinking water. In sharing water-treatment technologies that lead to accomplishing this goal, it is imperative to devise ways of removing microbial contaminants such as E. coli from drinking water, especially in resource-limited settings that lack centralized water supply systems. One of the approaches is bacterial disinfection of water at the point of use. In this study, the bactericidal effects of the photocatalysis of titanium dioxide-based nanoparticles under UV and visible light are explored. Pristine and silver doped nanostructured mesoporous titanium dioxide (Ag-TiO2, TiO2) particles with high specific surface area and average crystallite domain size of 7.0–7.5 nm were prepared using the simple and cost-effective sol-gel technique followed by thermal treatment. The addition of Ag+ ions during the hydrolysis/condensation of the Ti(IV) molecular precursor led to the homogeneous dispersion of the Ag+ cations on the titania matrix. The As-prepared nanoparticles were characterized using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), thermogravimetry, Fourier Transform Infra-Red (FTIR), and Raman Spectroscopy. X-ray diffraction, FTIR, and Raman spectroscopy confirmed that the crystalline structure of the TiO2 matrix corresponds to the anatase polymorph; however, the presence of the dopant led to an increase in the system disorder due to the rise in the concentration of oxygen vacancies. The As-prepared nanoparticles were used for Escherichia coli (E. coli) inactivation under dark and UV–visible light conditions. Under dark conditions, Ag-doped titania and pristine titania resulted in 95% and 64% E. coli population inactivity while under light conditions, 99% and 97% degradation respectively were observed. Taken together, these results demonstrate that, the synthesized TiO2 nanoparticles have promising applications in the light-mediated point-of-use inactivation of bacterial contaminants in water. 2019 Elsevier Ltd. All rights reserved. Selection and peer review under the responsibility of the scientific committee of the International Symposium on Nanostructured, Nanoengineered, and Advanced Materials.Item Synthesis andApplication of Fe-Doped TiO2-Halloysite Nanotubes Composite and Their Potential Application in Water Treatment(Advances in Materials Science and Engineering, 2019) Nyankson, E.; Agyei-Tuffour, B.; Adjasoo, J.; et al.In this work, the potential application of TiO2-Fe-HNT photocatalyst-adsorbent composite in water treatment technologies was confirmed. ,e photocatalyst-adsorbent composite (TiO2-Fe-HNTs) was synthesized by the hydrothermal method and characterized by X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron mi croscopy-energy dispersive X-ray spectroscopy, and diffuse reflectance spectroscopy. ,e adsorption and photocatalysis mechanism by the TiO2-Fe-HNT composite were examined on methylene blue dye, rhodamine blue dye, naproxen sodium (pharmaceutical drug waste), and imidacloprid (pesticide). ,e TiO2-Fe-HNT composite was active in UV and visible regions of the electromagnetic spectrum. ,e adsorption and photocatalytic efficiency increased with increasing amounts of HNTs. ,e photocatalyst-adsorbent composite exhibited excellent removal efficiency for pharmaceutical waste (naproxen sodium) and pesticides (imidacloprid). An adsorption equilibrium data fitted well with the pseudo-second-order kinetics for both methylene blue and rhodamine blue dyes with the intraparticle model describing its rate-controlling steps. ,e Langmuir and Freundlich isotherm models further described the adsorption of methylene blue and rhodamine blue molecules, respectively.Item Effects of substrates on the performance of optoelectronic devices: A review(Cogent Engineering, 2020) Asare, J.; Agyei-Tuffour, B.; Dodoo-Arhin, D.; et al.This review discusses the effects of substrates on devices fabricated for optoelectronic applications. It includes the types and characteristics of substrates, synthesis, and fabrication of substrates, and the influence of substrates on the optical properties, surface morphology, and current-voltage behavior of optoelectronic devices. The study showed that two main types of substrates: planar and textured are commonly used in the industry. Flexibility, semi-rigidity, and rigidity are characteristics of the substrates and they vary in modulus, transparency, and texture. Whereas glass and metal substrates can be produced via melt casting, polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), etc are produced by crosslinking polymer base materials with curing agents. The mechanical and current-voltage characteristics are also shown for planar and textured substrate-based devices. The textured substrates showed ridges, wrinkles, and buckled surface morphology whereas the planar showed uniform and largely flat morphology. Textured substrates also recorded higher optical absorbance and improved device efficiencies than planar substrates. The molecular configuration of the polymer chains is edged-on for planar substrates and edge-on and face-on for textured substrates. The findings and their implications have been discussed to highlight the importance of substrates in the fabrication and performance of optoelectronic devices.Item Effects of Purity on the Mechanical Properties of Single-Walled Carbon Nanotubes-Polymer Nanocomposites(British Journal of Applied Science & Technology, 2013) Yaya, A.; Dodoo-Arhin, D.; Onwona-Agyeman, B.; et al.This study investigated the superior mechanical properties of single-walled carbon nanotubes (SWCNTs), and its polymer nanocomposites using 0.5% and 1% loading of raw and purified SWCNTs in an epoxy matrix and the degree of dispersion. The extent of load transfer between the nanotubes and the matrix was studied by analyzing the second order G’-band ( 2550 cm-1) of Raman Spectroscopy. The samples have been characterized by structural (Raman spectroscopy), mechanical (tensile test), physical, and microstructural (SEM) point of view. Purified SWCNTs give a better-reinforcing potential compared to raw SWCNTs. We found an increase in Young’s Modulus (3780 MPa-4263 MPa) and toughness (62 MPa-68.8 MPa) for the nanocomposites prepared from purified SWCNTs.Item Fabrication and Characterisation of Ghanaian Bauxite Red Mud-Clay Composite Bricks for Construction Applications(American Journal of Materials Science, 2013) Dodoo-Arhin, D.; Konadu, D.S.; Annan, E.; et al.The behavior of Ghanaian-based bauxite red mud-Tetegbu clay composites has been investigated for their applicability in the ceramic brick construction industry as a means of recycling bauxite waste. The initial raw samples were characterized by X-ray diffraction (XRD), X-ray Fluorescence spectroscopy (XRF), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (Tg-DTA). The red mud-clay composites have been formulated as 80%-20%, 70%-30%, 60%-40%, 50%-50% and fired at sintering temperatures of 800ºC, 900ºC and 1100ºC. Generally, mechanical strengths (modulus of rupture) increased with higher sintering temperatures. The results obtained for various characterization analyses such as bulk densities of 1.59 g/cm3 and 1.51 g/cm3 compare very well with literature and hold potential in bauxite residue eco-friendly application for low-cost recyclable constructional materials.