Institutional Repository of the Kwame Nkrumah University of Science and Technology

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Recent Submissions

Design of pattern-reconfigurable circularly polarized unidirectional antenna based on quasi-radiator for ISM applications
(Heliyon, 2022-11-21) Arthur, Philip; Ellis, Mubarak Sani; Ahmed, Abdul-Rahman; Kponyo, Jerry John
A pattern-reconfigurable circularly polarized antenna for 2.45 GHz industrial, scientific, and medical (ISM) band applications is designed in this work. The proposed antenna consists of a slotted-stepped monopole connected to a rectangular ground plane via a shorting side-stub. This converts the omnidirectional radiation pattern of the antenna into stable unidirectional radiation. To dynamically steer the realized pattern, two switchable RF PIN diodes are jointly incorporated into the side-stubs to achieve symmetrical radiations in specific operating modes. In this way, the radiation patterns can be simultaneously tuned in the y directions by the simple switching of the PIN diodes ON and OFF. The fabricated prototype achieves an S11 smaller than -10dB within the 3dB axial ratio (AR) bandwidth with stable far-field patterns. The antenna maintains a low-profile and compact size of 0:055λ20 which makes it suitable for body-centric wireless communication (BWC) and personal wireless area networks.
The Role of the Mineralogical Composition on Wettability via Flotation Test and Surface Complexation Modeling (SCM)
(Geosciences, MDPI, 2024-02-06) Erzuah, Samuel; Fjelde, Ingebret; Omekeh, Aruoture Voke
Minerals are the chief constituents of rocks and have varied properties, such as the surface area, surface charge, site density, etc. Hence, numerous interactions are bound to occur in a reservoir during rock–fluid (i.e., rock, crude oil and brine) interactions. This study seeks to assess the role of the mineralogical composition in the wettability of sandstone rocks (SRs) and mineral mixture (MM) using both surface complexation modeling (SCM) and a flotation test. From the considered sandstone rocks, both the experimental results and the simulated counterparts revealed that the SRs were preferentially hydrophilic. For the MM, when the mass fraction of the hydrophobic mineral was increased, the affinity of the MM became slightly hydrophobic, and vice versa. For the dominant sandstone reservoir rock minerals with predominantly negatively charged surfaces, negligible oil adsorption took place due to the interfacial repulsive forces at the oil–brine and mineral–brine interfaces. For the MM with low calcite content, the wetting preference was influenced by the mineral with a prominent surface area. Our developed model portrayed that the main mechanism of oil adhesion onto sandstone minerals was divalent cation bridging. Nonetheless, adhesion of carboxylate (>COO−) onto the illite, montmorillonite and calcite sites also took place, with the latter being more pronounced.
Design of a fully integrated VHF CP-PLL frequency synthesizer with an all-digital defect-oriented built-in self-test
(The Journal of Engineering, 2022-10-28) Kommey, Benjamin; Boateng, Kwame Osei; Yankey, Jephthah; Addo, Ernest Ofosu; Agbemenu, Andrew Selasi; Tchao, Eric Tutu; Akowuah, Bright Yeboah
This paper presents the design of an on-chip charge pump phase-locked loop (CP-PLL) with a fully digital defect-oriented built-in self-test (BIST) for very-high frequency (VHF) applications. The frequency synthesizer has a 40–100 MHz tuning range and uses a ring voltage-controlled oscillator for frequency synthesis. The PLL exhibits a phase noise of −132 dBc/Hz at 1 MHz and consumes 1.8mWon a 3 V supply. The BIST implementation uses fewer external input or output, is capable of efficient fault diagnosis, and is compact, posing a low area overhead. The integrated circuit design was realized in the AMI 0.6μ complementary metal-oxide-semiconductor process.
Gender and leadership positions: understanding women’s experiences and challenges in patriarchal societies in Northern Ghana
(International Journal of Sociology and Social Policy, 2023) Adongo, Awinaba Amoah; Dapaah, Jonathan Mensah; Azumah, Francess Dufie; 0000-0002-0261-3295; 0000-0002-9349-6273; 0000-0001-6023-8000
Purpose – Women are rarely seen in positions of leadership in patriarchal societies, which is unsurprising.Following gender equity policies, few women have been able to break through the gender equity barrier and assume leadership positions in schools. Few research investigations have delved into the experiences and challenges that women encounter in positions of leadership in patriarchal societies in government schools in Northern Ghana. The study seeks to comprehend the experiences and challenges that women confront in positions of leadership in patriarchal societies in Northern Ghana. Design/methodology/approach – The study aimed to gain a better understanding of the experiences and challenges that women encounter in educational leadership roles in patriarchal societies in Northern Ghana. To achieve the study’s objectives, a quantitative research approach and a social survey design were used, as well as descriptive and inferential statistics. Findings – The findings of the study revealed that in patriarchal societies in Northern Ghana, women experience conventional gender roles that conflict with roles, cultural values, gender stereotyping, family responsibilities and cultural beliefs and perceptions of women and attitudes and low expectations of women’s managerial skills discourage women from taking on leadership positions in men-dominated societies.
Building the capacity of students in creative problem-solving and critical thinking skills: Aesthetic narrative of Ayigya Township, Ghana
(Royallite Global, 2023) Kquofi, Steve; Adom, Dickson;;
The study set out to investigate the environmental aesthetics present in habitual areas, specifically in Ayigya Township, Ashanti Region, focusing on picture-making tendencies for optimal skill development. A total of 346 respondents from various structures were specifically chosen to participate in the study using the Narrative Case Study Design under the qualitative research approach. Semi-structured interviews, observation, and photographic documentation were used for the data collection. The data were analysed using photographic documentary and qualitative narrative analysis. The findings demonstrated how dispersed aesthetic elements are in everyday life and how this appreciation would have a positive impact on the Senior High School student’s capacity for creative problem-solving and critical thinking skills. It is suggested that students develop alternative means of expressing their creativity. The study contends that art teachers must help students to use aesthetics in their environments to develop the tools and materials for their artistic productions.
Molecular characterization of interactions between the D614G variant of SARS-CoV-2 S-protein and neutralizing antibodies: A computational approach
(Infection, Genetics and Evolution, 2021) Kwarteng, Alexander; Asiedu, Ebenezer; Sylverken, Augustina Angelina; Larbi, Amma; Sakyi, Samuel Asamoah; Asiedu, Samuel Opoku; 0000-0002-0893-2908; 0000-0003-2867-1984; 0000-0002-7691-914X; 0000-0002-3814-6924; 0000-0001-5168-4762; 0000-0002-0352-3195
The D614G variant of SARS-CoV-2 S-protein emerged in early 2020 and quickly became the dominant circulating strain in Europe and its environs. The variant was characterized by the higher viral load, which is not associated with disease severity, higher incorporation into the virion, and high cell entry via ACE-2 and TMPRSS2. Previous strains of the coronavirus and the current SARS-CoV-2 have demonstrated the selection of mutations as a mechanism of escaping immune responses. In this study, we used molecular dynamics simulation and MM-PBSA binding energy analysis to provide insights into the behaviour of the D614G S-protein at the molecular level and describe the neutralization mechanism of this variant. Our results show that the D614G S-protein adopts distinct conformational dynamics which is skewed towards the open-state conformation more than the closed-state conformation of the wild-type S-protein. Residue-specific variation of amino acid flexibility and domain specific RMSD suggest that the mutation causes an allosteric conformational change in the RBD. Evaluation of the interaction energies between the S-protein and neutralizing antibodies show that the mutation may enhance, reduce or not affect the neutralizing interactions depending on the neutralizing antibody, especially if it targets the RBD. The results of this study have shed insights into the behaviour of the D614G S-protein at the molecular level and provided a glimpse of the neutralization mechanism of this variant.
Testing the pecking order theory of banks listed on the ghana stock exchange
The research examined the pecking order theory practice of banks listed on the Ghana Stock Exchange. The link between leverage and firm specific characteristics such as profitability, loan quality, growth, age and size of firms was ascertained. The research used quantitative approaches and employed the descriptive designs. Secondary data from the annual financial statements of banks listed on the Ghana Stock Exchange from the year 2010 to 2019 were used for the studies. As at the end of the year 2019, eight (8) banks were listed consisting of Ecobank Ghana Ltd, Societe Generale, Standard Chartered Bank, Cal bank, Agricultural Development Bank, Access Bank, Republic Bank, and Ghana Commercial Bank. The data was analyzed using version 25 of Statistical Package for Service Solution. The Augmented Dickey Fuller, Tolerance, Durbin Watson and Variance Inflation Factor tests were used as estimation techniques to ensure accuracy of data. Panel data regression method was used to establish the presence of the pecking order theory. The study found that leverage was negatively related to profitability of listed banks but was statistically insignificant. Leverage was also negatively related to loan quality but statistically insignificant. Leverage showed positive correlation to the size and the age of the firm and was statistically significant, while leverage was positively correlated to growth but insignificant. The study recommends that management of the banks listed put in the necessary measures such as ensuring quality loans and using debt as financing strategies to enhance an increase in the growth levels of firms