School of Engineering
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Item Efficient Modelling of a PCB Transmission Line for High Speed Digital Systems(2018) Acakpovi, A.; Sowah, R.; Asabere, N.Y.; et al.This paper proposes a model of PCB traces for high-speed digital systems. The adopted approach involves predetermined geometry using direct discretization of transmission lines. Initially, the proposed methodology involves computing the line propagation delay by employing its geometry with associated empirical equations. The initial procedure paves the way to design a Lattice diagram which depicts multiple reflections that the signal underwent due to impedance mismatches between transmission lines and loads. Subsequent computations of electrical model parameters were further done. Simulation results using Multisim software illustrated a favorable performance with a time delay of 1.42 ns and an equivalent electrical model of 10 lumped LC cells. The time delay between the input and output signal obtained from the simulation was approximately 15.152 ns corresponding to the time it took for a transmitted signal to reach a steady state which further signifies the good performance of our proposed method.Item Investigation Of The Cytotoxicity Of Cassava Microfiber-Gelatin Composite Scaffold(University of Ghana, 2022-06) Plange, P.N.ACellulose fiber-reinforced composite scaffolds have recently become an interesting target for Biomedical Engineers and Biomaterials Researchers for Tissue Engineering (TE) applications. This has led to the exploration of cellulose from diverse sources such as tunicates, bacteria and especially from plants. Cassava bagasse, which is a fibrous solid residue obtained after the extraction of cassava and soluble sugars, has recently been explored as a potential source of cellulose, and has been successfully used to enhance the mechanical properties of gelatin scaffold for TE purposes. However, there is lack of knowledge on the biocompatibility of this fabricated scaffold, limiting its potential to be considered at the research level as a biomaterial for TE purposes. This study provided knowledge on the cytotoxicity of the scaffold by using HEK 293 and MDA MB 231 cell lines. The tests performed were according to ISO standards for checking in vitro cytotoxicity of medical devices- extraction and direct contact tests. Scaffold prepared with gelatin only, and cells cultured on well plates with no scaffold were used as the controls. Extracts obtained from the samples were exposed to the cells and analyzed after 24 h and 48 h of incubation, using optical and fluorescence microscopy. Additionally, cells were seeded directly on the samples and analyzed after day 1, 3 and 5 using tetrazolium-based colorimetric assay. Results obtained for HEK 293 cells demonstrated enhanced cell viability and little/no changes in cell morphology. However, there was a decline in cell viability and changes in cell morphology for MDA MB 231 cells. These results suggest that the presence of the fiber in gelatin is not cytotoxic to HEK 293 cells and can be considered for TE purposes when using normal cells. On the contrary, the presence of the fiber in gelatin is cytotoxic to MDA MB 231 cells and may not be considered for TE purposes such as 3D tumor cell studies that require the growth of cancer cells. However, further studies are required to explore the use of the cassava bagasse for its anti-cancer cell properties as demonstrated in this study.Item Self-Reporting System For Incidents Detection In Automated Teller Machine (Atm) Using Machine Learning Techniques(University Of Ghana, 2021-09) Payne, I.N.Automated Teller Machines (ATMs) have increased over the past decade due to their advantages in the banking sector. ATMs provide convenience to customers, optimizes banking operations, and minimizes transaction cost. However, undesirable security incidents such as tempering, skimming, physical attacks, robbery, and transaction reversal fraud may occur on ATM systems and negatively affect the user experience and banking institutions. ATM incidents occur either by system defect or through a deliberate act of physical attack by an intruder. In most security incidents, financial losses are imminent, and the customers' confidence in banking reduces. Developing a Self-Reporting System for ATM Incident Detection (SRSAID) is needed to avert the threats posed by security incidents on ATM systems. This research uses a machine-learning approach to solve this problem. Regional Convolutional Neural Network (R-CNN) and Support Vector Machine (SVM) algorithms are used to develop a detection model that detects occurrences of security incidents on an ATM system. Datasets used in the machine learning model development were obtained from NCR Ghana and the online repository. Experimental results showed that two CNN architecture models, ALEXNET and ssdlite_mobilenet_V2, obtained an accuracy score of 80% and 96%, respectively. SVM classifiers were developed using the linear, polynomial, and radial basis kernels, getting accuracy scores of 70.6%, 72.56%, and 81.21%, respectively. The initial results necessitated hyperparameter optimization to improve the performance of the classifiers. This resulted in improved accuracy scores of 76%, 77%, and 86% for linear, polynomial, and radial basis kernels, respectively, for the SVM models. The machine learning model was later deployed on a Raspberry Pi system which connected to a web application that provided a graphical user interface for user interactivity and viewing of reports.Item Fabrication And Characterization Of Crosslinked Cellulose Nanocrystals Re-Enforced Bipolymeric Films For Preservation Of Leafy Vegetables(University Of Ghana, 2021-07) Lartey, C.S.N.L.Biodegradable polymer films are increasingly being used as alternate packaging material due to the less environmental and health burden compared to synthetic plastics. Biobased films are also attractive candidates for packaging fresh food such as vegetables and fruits as they possess high moisture retention capacity and maintain desirable sufficient moist surface around the fresh food. Due to the high hydrophilicity of biobased or biodegradable polymers, the practical application of biobased polymer films in food packaging is challenging as their large hydrophilic groups on surface and in between polymer chains can absorb excess moisture which may lead to polymer chain disentanglement and dissolution as excess water can disrupt the weak physical forces (intermolecular hydrogen bonding) holding the individual polymer chains together in the film. The objective of the work is to perform film post treatment techniques in reducing the number of free hydrophilic groups on the surface of the film as well as dehydrate the film using chemical crosslinking and thermal treatment respectively. In this work, a simple packaging film was fabricated by solution casting method using polyvinyl alcohol (PVA), chitosan, citric acid as cross linker and cellulose nanocrystals (CNC) in varied amounts, as fillers to enhance mechanical strength. The films were characterized using tensile machine, Fourier Transformed Infra-red spectroscopy, thermal analysis, moisture absorption studies, film dissolution, film permeability studies and X-ray diffraction analysis. Varying the amount of CNC affected the thermal stability of the films, wherein increased amounts improved thermal properties. TGA studies showed that T max (temperature where highest mass loss occurs) in E3 (398°C) increased to 404 °C in E12 with increased amounts of CNC. Acylation with acetic anhydride, heat treatment of films at 100°C and a combination of both treatments improved film stability in water. Swelling degree observed after 15 minutes of immersion of films in distilled water were at their barest minimum in all films subjected to any of the treatments. The films significantly decreased the rate of browning of fresh lettuce, keeping its fresh green colour for approximately eleven days before signs of browning set in. This was in contrast to fresh lettuce packaged with poly ethylene films which turn brown after three to four days. The fabricated films may serve as active packaging system for extending the shelf life of fresh lettuce, and potentially other vegetables and fruits in the food distribution chain.Item Decision Support System For Sustainable Siting And Management Of National Food Buffet Stock Systems In Ghana(University Of Ghana, 2022-02) Buah, I.E.National Food Buffer Stock Company of Ghana (NAFCO), being the government’s emergency food reserve and source of raw materials for agro-processing factories, is established to reduce post-harvest losses, and stabilize food supply and price. These stated aims are very broad, conflicting, and non-profit-oriented, making the buffer stock systems economically unsustainable. This research, therefore, develops a decision support system where decision-makers can stimulate various scenarios to allow them to design a sustainable national food buffer stock system that is fit for its purpose. The decision support system comprises a risk assessment conducted on the operations of NAFCO, pseudo-p-median model, goal programming model and inventory model. The efficacy of the decision support system was illustrated through a series of simulations, where six predicted optimal locations for siting NAFCO warehouses were identified with an average transportation cost of GHS 1.7924E+6. The optimal network design of NAFCO warehouses was to reduce the cost of transportation incurred by the respective stakeholders. The research also investigated the number of grains to be purchased during every quarter, if NAFCO was to stock their warehouses with 100,000 tonnes of grain in the year to reduce the cost of operation. An integrated approach coupled with readily available data was used in stimulating the models developed. Furthermore, the research provides NAFCO with the necessary actions to take to reduce the risk associated with the unit operation of transporting grains from the farm to the warehouses and from the warehouses to the markets and harbour since this operation had a risk profile number of 648. In conclusion, decisions must be taken to revamp the operations of NAFCO with the mindset of reducing cost by adopting decision support systems in sustainably siting and managing their operations.Item Decision Support System For Sizing Drying Bins, Fan Selection And Drying Parameters Determination For Selected Grains(University Of Ghana, 2022-01) Parker – Allotey, C.K.Grain drying is a very important step in the storage and handling of grains. Computer models have been created over the past years to optimise and ease the amount of work and calculations that are invested into the planning, economics building, operation and management of drying systems and facilities. Although there have been advancements in computerised systems and programmes, decision making when it comes to planning, costing, construction, management, and operation of drying systems can still prove to be a strenuous task to undertake. Also, most computerised systems require in-depth knowledge in drying to operate. Most of these systems do not also provide features which allow for economic decision making. There is therefore still the need to develop a new programme which is relatively easier to use and can further optimise the decision-making process. A computer programme was developed using python that calculates the bin diameter, grain depth, airflow and airflow rate, and fan horsepower using the specific grain to be dried, the desired volume, drying method, and budget type as inputs. Various formulas and assumptions were used to perform calculations for each parameter. The programme was created to provide realistic estimates for each drying parameter depending on the inputs provided by the user. The programme also provides a database that allows users to select fans based on the calculated fan horsepower. The programme created was successful in performing calculations for all the parameters listed above. This programme simplified certain calculations that must be made during the decision-making process, thereby allowing for its use by people with shallow knowledge in drying systems decision making with respect to budgeting.Item Determination Of Engineering Properties Of Two Soils At Fohrec (Kade) And Sirec (Kpong)(University of Ghana, 2019-07) Danso-Acquah, E.Agriculture, its operations, and soils properties are inter-related. Cultivation of crops; tillage, irrigation and farm operations, commuting to and from farm plot and building of structures are greatly influenced by the soil specifically its properties. Shear stress, cohesion and angle of friction are parameters that play major roles in influencing how soils are used or worked on. It is, therefore, important to determine the shear stress, cohesion and angle of friction of the soils in Kade and Kpong. As a result, a study was conducted on two soils from Forest and Horticulture Research Centre (FOHREC), Kade, and Soil and Irrigation Research Centre (SIREC), Kpong, at depth ranges of 0-15cm and 15-30cm under saturated and unsaturated conditions to determine the shear stress, cohesion and angle of friction to ascertain how they will affect tillage, traction and trafficability, irrigation and structures such as dams and foundations. Normal stress ranging from 1kg/cm2 to 5kg/cm2 was used as an independent variable to determine the stated properties. The results showed that the Kpong soil had a higher shear stress under all conditions than that of Kade soil. An interesting observation was made concerning the soil under unsaturated condition where at 3kg/cm2 it behaved as if it is is under saturation. The normal stress had a significant effect (p < 0.05) on shear stress, cohesion and angle of friction, where increase in normal stress reflected an increase in shear stress and cohesion but a decrease in angle of friction. The research provided ample data on shear stress required for failure to occur normal to the shear plane, cohesion and coefficient of internal friction. These measurements are relevant and important for the design of farm equipment, farm structures such as dam wall, storage buildings, etc. Kpong soil (Akuse series) had a higher shear stress under all conditions than that of the Kade soil (Kokofu series). Keywords: Shear Strength, Cohesion, Angle of friction, Trafficability, Tillage, Moisture contentItem A Comparative Study of Phosgene Sensing Using Carbon and Boron Nitride Nano Materials – A DFT Approach(University of Ghana, 2021-04) Kweitsu, E.O.Phosgene (COCl2), a valuable industrial compound, maybe a public safety and health risk due to potential abuse and possible accidental spillage. Conventional techniques suffer from issues related to procedural complexity and sensitivity. Therefore, there is a need for the development of simple and highly sensitive techniques that overcome these challenges. Recent advances in nanomaterials science offer the opportunity for the development of such techniques by exploiting the unique properties of the nanostructures. In this study, we investigated the potential of six types of nanomaterials: three carbon-based ([5,0] CNT, C60, C70) and three boron nitride-based (BNNT, BN60, BN70) for the detection of COCl2. The local density approximation (LDA) approach of the density functional theory (DFT) was used to estimate the adsorption characteristics and conductivities of these materials. The results show that the COCl2 molecule adsorbed spontaneously on the Fullerene or nanocages and endothermically on the pristine zigzag nanotubes. Using the magnitude of the bandgap modulation, the order of suitability of the different nanomaterials was established as follows: PBN60 (0.19%) < PC70 (1.39%) < PC60 (1.77%) < PBNNT (27.64%) < PCNT (65.29%) < PBN70 (134.12%). Since the desired criterion for the design of an electronic device is increased conductivity after adsorption due to the resulting low power consumption, PC60 was found most suitable because of its power consumption as it had the largest decrease of 1.77% of the bandgap.Item Evaluation of Irrigation and Mulching on the Establishment of Transplanted Cocoa(University Of Ghana, 2019-07) Kpakpo-Sraha, M.A.Field experiment was conducted at the University of Ghana Forest and Horticultural Crop Research Centre (FOHCREC) in Kade from October 2017 to March 2018 to evaluate the effect of deficit irrigation on the establishment of transplanted cocoa. The experimental design used was the split plot design and was made up of 3 irrigation levels namely no irrigation (NI), deficit irrigation (DI) and full irrigation (FI) and 2 mulch levels namely mulch (M) and no mulch (NM). The Kc at the end of the experiment was 0.76, 0.78 and 0.96 for NI, DI and FI respectively under no mulch treatment. The Kc for mulch treatment at the end of the experiment was 0.64, 0.71 and 0.80 for NI, DI and FI respectively. The cumulative ETc at the end of the experiment under no mulch was 376.77 mm, 378.29 mm and 409.83 mm for NI, DI and FI respectively. The cumulative ETc for mulch treatment at the end of the experiment was 369.16 mm, 389.06 mm and 392.62 mm for NI, DI and FI respectively. High vigour scores translated to high seedling establishment with NI, DI and FI having an establishment percentage of 92%, 96% and 100% respectively under no much. The percentage establishment of cocoa for NI, DI and FI was 96%, 96% and 100% respectively under mulch. Irrigation and mulch did not have any significant difference in the plant vigour and percentage establishment of cocoa at P ≤0.05. It can be concluded that the effect of Irrigation and mulch could not be seen on seedling survival because of the high rainfall amount and short dry season during the experiment period.Item Noni Juice Extraction: Process Evaluation and Design for Efficiency(University Of Ghana, 2020-10) Nartey, N.A study examined factors affecting the time of drip extraction of noni (Morinda citrifolia) juice. The factors studied were the presence of noni fruit peels, temperature of extraction, extraction time, water addition during extraction and the quantity of fruits used for extraction. Morinda citrifolia juice was dripped extracted from the noni fruit to determine the influence of temperature, time and mass of fruit on the drip extraction process separately before combining these factors to design a CCRD experiment. The effect of each factor was assessed with a factorial experiment followed with analysis of variance. Temperature and mass of fruit extracted were found to affect the time of drip extraction and the quality of juice produced in terms of yield and physio-chemical characteristics of the juice of which pH and total soluble solids were considered. Using the CCRD, different combinations of fruit mass (0.5, 0.8, 1.25, 1.7 and 2 kg), temperature of extraction (30, 36.08, 45, 53.92 and 60oC) and extraction time (3, 6.65, 12, 17.35 and 21days) were used to drip juice from the noni fruit. Total soluble solids content, pH and juice recovered in terms of yield were measured after each extraction. CCRD results showed that the responses of pH, total soluble solids and yield were in good agreement with the theoretically predicted values of the model. Total soluble solids content and pH were significantly affected by temperature of extraction and the extraction duration (time) whiles noni juice yield was significantly affected by the mass of fruit drip extracted.