Rwanda Journal of Engineering, Science, Technology and Environment <p>The <em>Rwanda Journal of Engineering, Science, Technology and Environment</em> (RJESTE) is a peer-reviewed journal published bi-annually by the University of Rwanda - College of Science and Technology. The journal aims at publishing original research articles, review articles, and selected conference articles on the latest developments in the fields of engineering, science, technology, environment and related. The publications should either demonstrate a significant new discovery or other contribution that has been established to fairly rigorous scientific standards. The Journal will publish articles written in standard British English.</p> en-US <span lang="EN-GB">The copyright for articles published in this journal is owned by the journal.</span> (Prof Elias Bizuru) (Clarisse Kagoyire) Wed, 14 Jul 2021 09:07:20 +0000 OJS 60 Solving an optimal control problem of hepatitis B virus dynamics: Efficacy of fuzzy logic strategy <p>This work aims at using fuzzy logic strategy to solve a hepatitis B virus (HBV) optimal control problem. To test the efficacy of this numerical method, we compare numerical results with those obtained using direct method. We consider a patient under treatment during 12 months where the two drugs are taken as controls. The results are rather satisfactory. In particular, the reaction of HBV to drugs can be modeled and a feedback can be approximated by the solution of a linear quadratic problem. The drugs reduce the risk of HBV. Furthermore, results of both numerical methods are in good agreement with experimental data and this justifies the efficacy of fuzzy logic strategy in solving optimal control problems.</p> Marcel Gahamanyi, Wellars Banzi, Jean Marie Ntaganda Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000 Navigating housing affordability in Rwanda: Challenges and facilitation strategies <p>Housing and its affordability have, of recent, been of great concern to various stakeholders, especially in the developing world.&nbsp; Consequently, contributing aspects such as construction/tenancy costs, sustainability, environmental impact, and availability of credit facilities with a host of other factors, have dominated contemporary research. Various studies suggest that addressing affordable housing requires understanding the contextual factors that impact affordability of housing. Such studies have not been known to succinctly treat&nbsp; the context of Rwanda. This paper aimed at exploring the perspectives of housing affordability in Rwanda with a view of eliciting the status, challenges, and prospects. The objectives included description of the current status of housing, identifying the challenges of&nbsp; providing affordable housing, and proposals of strategies to enhance its provision. Data, such as for workers’ salary, costs of house construction, inflationary trends and the number of housing units per income group, were sought for and obtained either from the&nbsp; archives of various stakeholder organizations or by interviewing key officers concerned with housing. Descriptive statistics and thematic&nbsp; analyses were employed in analyzing the data in order to fulfil the objectives of the study. It was found that home ownership and tenure statistics varied, yet housing demand was on the rise. Foremost challenges, among others, were recorded to be scarcity and costly plots of land, compounded with costly building materials. In addition, the purchasing power of the local currency depreciated fast over time, thereby making good quality housing unaffordable for the majority of Rwandans. Localizing policy to enhance public awareness, resolving the issue of high cost of construction materials, and coming up with innovative interventions on land costs, were among the key strategies to facilitate housing affordability. </p> Josephine M. Malonza, Nathan Kibwami, Philip O. Lawal Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000 Docking Studies between the Predicted Model of Mouse Zinc Finger MYND Domain-Containing Protein 19 and Cofactor Product Adohcy; towards Drugs Development against Cancer, Obesity and Cardiovascular Diseases <p>Mouse Zinc finger domain-containing protein19 (ZMYND19) is a zinc-finger protein questioned after recently published data reported its C-terminal domain of 49 residues to be associated with cancer, obesity and cardiovascular diseases. The potent drugs are suggested to come from its interactions with ligands understanding. However, the diseases are becoming worse because the three-dimensional structure of Mouse ZMYND19 is not yet reported. Thus, this study analyzed structural interactions between the predicted 3D structure and cofactor products S-Adenosyl homocysteine (AdoHcy) using the computational approaches. Pairwise sequence alignment was performed in the iterated mode of protein blast against protein data bank (PDB) and CLUSTAL omega server was used to perform multiple sequence alignment. Phylogenetic analysis was performed using the PHYLIP package. Structure prediction was successfully completed with the use of SWISS model by exploring homology modeling. The predicted Model structure was evaluated using both ERRAT and PROCHECK servers. Docking studies were performed with the HEX8 package. The evaluation results of the predicted 3D structure suggest that the model is of good quality. Docking studies revealed a high affinity (– 214.24 KjMol-1) between the predicted 3D model and AdoHcy ligand. The interaction between the bound molecules suggests both compounds to be good candidates for cancer, obesity, cardiovascular diseases, thus these two compounds could be considered at the frontline for a potent drug development.</p> Bertin Mugabo, Rene Iradukunda, Jeanne Marie Gatanganwa, Jean Chrisostome Ufitinema, Dieudonne Mutangana Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000 The Use of Geogrids in Mitigating Pavement Defects on Roads Built over Expansive Soils <p>This study was conducted to investigate the potential benefits of using geogrids in mitigating pavement defects notably roughness and longitudinal cracking on pavements built over expansive soils. The seasonal changes of expansive soils (periodic wetting and drying) cause detrimental effects on the overlying road pavements. Such detrimental behavior of expansive soils was simulated in a controlled laboratory environment through allowing cyclic wetting and drying of an expansive soil underlying a pavement section. The shrink/swell effects of the expansive soil subgrade were examined through monitoring its change in moisture, and measuring deformation of overlying pavement section. The experimental study suggested that a geogrid layer in a reinforced pavement section can reduce surface differential shrinking and swelling deformation resulting from underlying expansive soils by a factor of 2 and 3 respectively in comparison to unreinforced section. Given that an oedometer test which is typically used to predict swelling potential of expansive soils is known to overpredict in-situ soil swell, experimental program also investigated quantitatively the extent to which the oedometer can overestimate swelling behaviour of the real-field scenarios. It was found that oedometer percent swell can overpredict in-situ swelling behaviour of the expansive soil by a factor ranging between 2 and 10 depending upon the period over which the in-situ expansive soil has been in contact with water.</p> Richard Shumbusho, Gurmel S. Ghataora, Michael P.N. Burrow, Digne R. Rwabuhungu Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000 Facile Synthesis, Characterization and <i>in Silico</i> Docking Studies of Novel Thiazolidine-2,4-Dione-Based Mannich Base Bearing Furan/Thiophene Moiety as Promising Anti-Inflammatory Agents <p>Mannich bases are compounds bearing a β-amino carbonyl moiety. They are formed in the Mannich reaction that consists of an amino alkylation of an acidic proton placed next to a carbonyl functional group by formaldehyde and a primary or secondary amine. Mannich base products are known for their curative properties such as anti-inflammatory, antibacterial, anticancer, antifungal, anthelmintic, anticonvulsant, analgesic, anti-HIV, antipsychotic, antiviral, and antimalarial activities. Further, thiazolidinedione derivatives have shown to be efficacious in inflammatory diseases as wide-ranging as psoriasis, ulcerative colitis and non-alcoholic steatohepatitis. In light of the above observations, new series of thiazolidine-2,4-dione based Mannich base derivatives were synthesized via a simple and catalyst-free procedure involving the condensation of thiazolidine-2,4-dione, formaldehyde and secondary amines in DMF solvent. The structures of the newly synthesized compounds were confirmed by their IR, 1H-NMR, and Mass spectra. The synthesized compounds were tested for their in silico anti-inflammatory activity by Docking studies against COX-2 enzyme (PDB: 1CX2). Compounds 4a and 4b showed good <em>in silico</em> anti-inflammatory properties comparable to that of standard drug Diclofenac and may be considered as promising candidates for the development of new anti-inflammatory agents.</p> Jean Baptiste Nkurunziza, Pierre Dukuziyaturemye, Edith Musabwa, Balakrishna Kalluraya Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000 Characterization and Removal of Nickel (II) from Paint Industry Effluent by Rice Husk Adsorbent <p>Rice husk adsorbent was studied to assess its efficiency in adsorption of nickel from paint industry effluent and to derive vital parameters that would assist in making timely decisions in tertiary treatment of wastewater. Standard methods were used in conducting the experiments. Results showed that significant adsorption of 84.77% of nickel was removed by carbonized rice husk (CRH) in 10 minutes and 98.42% in 60 minutes, a difference of 13.65%. Optimum pH of 8 was observed as 98.91% of nickel was adsorbed. Slight change in the adsorption efficiencies was noticed between 0.2 g and 0.4 g doses of CRH adsorbent, but reasonable and insignificant change occurred between 0.4 g and 1.0 g doses. Langmuir isotherm plot showed that separation factor was 0.998 an indication of favorable adsorption and a good fit for the Langmuir isotherm model. Therefore, the adsorption process was better described by the Langmuir equilibrium isotherm model. Adsorption intensity of 2.02 was observed in the Freundlich model, a value greater than 1.0 an indication of unfavorable adsorption. Lagergren pseudo first- and second-order plots showed that R2 = 0.799 for pseudo first-order and R2 = 0.969 for pseudo second-order reactions, an indication that adsorption of nickel by CRH follow Lagergren second-order kinetic. FTIR spectra identified N-H, O-H, C=H, C=O, C=C-C, C-Cl, P-O-C, and cis-C-H out-of-plane bend stretching bands as the functional groups involved in nickel adsorption by CRH adsorbent. It was concluded that rice husk is a good adsorbent in tertiary treatment of wastewater.</p> Jude Iloabuchi Obianyo Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000 Influence of Ammonium Sulphate from anaerobic pasteurization digester latrines (APDLs) effluent on soil pH <p>Improper disposal of human waste is one of the most serious health problems in developing countries due to pollution of the&nbsp; environment. The use of chemical fertilizers for agriculture increase the plant growth to meet the food security of the world, but also causes environmental problems including lowering of soil pH. On the other hand, anaerobic pasteurization digester systems enable the recovery of nutrients from human faces and urine for the benefit of agriculture, thus helping to preserve soil fertility. Therefore, the present work aims to assess the potential of using ammonium sulphate processed from anaerobic pasteurization digesters latrines&nbsp; (APDLS) effluent to stabilize soil pH. The experiment was laid out in a completely randomized design with four treatments replicated four times. The treatments were Ammonium sulphate, Compost manure, Di-ammonium Phosphate (DAP) and control. The results showed that soil pH increased significantly (p&lt;0.05) from 4.7 -4.9 before planting to 5.6 - 5.7 after planting. The organic and inorganic fertilizers as well as the interaction between the fertilizer and time did not have significant effect on soil pH (p &gt; 0.05). The Ammonium sulphate recovered from APDLs final effluent could act as effective as a chemical fertilizer without significant reduction in the yield.<br></p> Edith Musabwa, Pierre Dukuziyaturemye, Jean Baptiste Nkurunziza, Gelas Muse Simiyu, Kipkorir Kiptoo Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000 Recruitment and Selection Practices of Construction Employers in Rwanda <p>Human resources play a key role in the achievement of construction projects. This study investigated the recruitment practices of construction employers in Rwanda. The problem of the study is the lack of empirical evidence to support the recruitment and selection practices of construction employers in Rwanda. Similar studies are abundant in other sectors of the economy but very scarce in the construction industry. The descriptive survey research design was adopted for the study. A closed-ended questionnaire was used for data collection. The population of the study are the construction organisations that employ construction workers in Rwanda. Hence, the population of the study is the 580 construction organisations that are officially working in Rwanda. A sample of 80 firms used for the study were determined with the use of Slovin’s formula. The findings of the study indicated that requests for the curriculum vitae, cover letter, face-to-face interview, submission of applications with key information of education/work experience and knowledge test to measure job specific knowledge are the prevalent strategies of recruiting and selecting staff in the construction industry. The prominent sources of recruitment and selection are internship performance, internal advertisement, and local newspaper advertisement. Based on the findings of the study, it was recommended that construction organizations should study and adopt the recruitment and selection strategies that have given them the most effective results. It was also recommended that the organisation should stick to the most effective sources of recruitment and selection for their organisations<br><br></p> Oluwaseun Sunday Dosumu, Philip Olayemi Lawal, Consolatrice Uwineza, Philippe Mugiraneza, Eric Dushimiyimana, Marius Ruzindana Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000 Control measures of malaria transmission in Rwanda based on SEIR SEI mathematical model <p>This research paper investigated the dynamics of malaria transmission in Rwanda using the nonlinear forces of infections which are included in SEIR-SEI mathematical model for human and mosquito populations. The mathematical modeling of malaria studies the interaction among the human and mosquito populations in controlling malaria transmission and eventually eliminating malaria infection. This work investigates the optimal control strategies for minimizing the rate of malaria transmission by applying three control variables through Caputo fractional derivative. The optimal control problems for malaria model found the control parameters which minimize infection. The numerical simulation showed that the number of exposed and infected people and mosquito population are decreased due to the control strategies. Finally, this work found out that the transmission of malaria in Rwanda can be minimized by using the combination of controls like Insecticide Treated bed Nets (ITNs), Indoor Residual Spray (IRS) and Artemisinin based Combination Therapies (ACTs).</p> Emmanuel Hakizimana, Jean Marie Ntaganda Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000 Evaluating the Trend in Managing Human-Wildlife Conflicts in and around Akagera National Park, Rwanda <p>Human-Wildlife Conflict (HWC) makes wildlife conservation more difficult and threatens the endangered species and human livelihood in adjacent protected areas. While the cases of existing conflicts are often evaluated, their trend vis-à-vis the mitigation measures such as an electric fence has been frequently overlooked. This study aimed at evaluating the trend of human-wildlife conflicts in and around Akagera National Park (ANP) by comparing the situations before and after its electric fencing. This study used both secondary and primary data. Secondary data used exiting literature while primary data has been obtained by using field observation, household questionnaire survey, and Key Informant Interview with park managers and local leaders.<br>The findings revealed that both illegal activities from local population and damages from wild animals have significantly reduced if we compare the situations before and after the establishment of an electric fence around ANP in 2013. In fact, between 2011 and 2020, illegal activities in the park have reduced to 70 %, 80 %, 85 %, and 80 % for captured cows, caught poachers, found traps, and killed animals respectively. However, this electric fence has not yet eradicated all forms of human-wildlife conflicts to the extent of zero case. In this regard, a set of sustainable community-based conservation strategies such as revenue sharing scheme, insurance scheme, compensation measures, etc., is highly encouraged.</p> Celestin Banamwana, Pierre Dukuziyaturemye, Gaspard Rwanyiziri Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000 Protection of Natural Wetlands through Landscape Design in Kigali City <p>The city of Kigali has been experiencing rapid growth in recent years. The city enjoys a variety of natural features such as wetland, valley, hill, and great scenery, however, fast expansion of urban areas and human activities could pose a serious threat to the natural environment, and the ecological sustainability. While wetlands, as nature’s kidneys, bring obvious benefits to both ecology and the socioeconomic environment, they have currently faced several problems in Kigali, such as pollution and the risk of decline in the area. This research is aimed at protection of wetland areas through landscape design, which could have a positive influence on maintaining the natural balance of ecology, as well as citizens’ health and well-being. The site study was Kiyovu wetland as one of large wetlands playing a vital role in the city’s character and spatial structure. The research employed observation, questionnaire, and mapping techniques, and the random sample consisted of 37 residents, workers, passers-by, and young people. Findings revealed that safety, environmental issues, accessibility, recreational activities, and quality of the wetland, were significant factors in order of priority that respondents had stressed over the design of the wetland landscape concept. The proposed concept highlighted recreation areas and the connection with other wetlands and green areas as a whole in the city, and it was derived from survey, mapping the results of questionnaires, and feedback from participants. In conclusion, Kiyovu wetland has an enormous capacity to put the idea of green magnet into effect across the city. However, the protection of wetlands without 1. Site-specific ecological landscape plans representing strategic and design levels in periods of time, 2. Legal requirements, and 3. Public awareness about impacts of wetlands degradation would be far less effective. To set up a campaign and a task force to examine changes can make a huge difference to levels of progress and performance</p> Rahman Tafahomi, Reihaneh Nadi Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000 The Influence of Inflexible Work Schedules and Land Use Design on Traffic Congestion in Kigali City <p>Travel demand is still poorly managed in Kigali city. The other research that was done on traffic congestion in Kigali city aimed to regulate the supply side of the problem. However, this study aims to regulate the demand side of traffic congestion on Kimironko- CBD, Nyanza Kicukiro- CBD, and Gisozi- CBD roads in Kigali city where inflexibility of work schedules and land use design were presented as the main issues leading to traffic congestion. The statistical results of the study did not show any strong correlation between the independent variables and the dependent variables because of the limited number of respondents that undermined the relationships and the questionnaire data collected represented peak-period only hence social-economic variables did not show any relationship with travel time as proved by other empirical studies. However, using the data from interviews, questionnaires, ArcGIS Pro, and secondary data, the study shows that there is a significant relationship between inflexible work schedules, land use design, and traffic congestion where departure time choice, commuting distance, land use mix, and connectivity has influenced significantly travel time and level of service. All the 3 roads under study are congested where Gisozi-CBD road is the most congested and Kicukiro-CBD road is the least congested. This study supports the view that traffic congestion can not only be regulated by focusing on the supply side of traffic congestion but balancing both the demand and supply side of the problem. However, travel demand management that aims to reduce unnecessary trips is the pillar to achieve sustainable mobility which focuses on the movement of people and goods rather than the movement of cars.<br>&nbsp;</p> Lea Bagenzi, Taslim Alade, Sylion Muramira Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000 Depth of tillage and its effect on field watershed size in Ejigbo zone, Osun State, Nigeria <p>The study investigated effects of different depths of tillage on flow of runoff in watersheds on fields tilled and planted with maize (Zea mays) hybrids and open pollinated variety (OPV) of maize. Twelve 1 m × 1 m × 2 m pits were dug and overlaid at all sides and at its bottom with impermeable membrane to accumulate watershed’s runoff from the fields. Twelve compartmental plots of 400 m2 each comprising 2 depths of tillage (0-15 cm and 0-30 cm) and 2 varieties of maize (hybrids and open pollinated) were used. Each of the treatments was replicated thrice to make 2 × 2 × 3 factorial design. Each plot measured 4 m × 10 m at 2 m apart. Among the data collected were the volume of water accumulated in the small earthen pits dug, flow velocity (v m/s) of water in runoff channels/collectors that fed earthen pits, slopes of the collectors, cross-sectional area of collectors and wetted perimeter. Results revealed that average infiltrometer values of 15.00±0.24 mm/h and 16.50±0.40 mm/h respectively in the upper part and the lower part were recorded. The 0-15 cm depth of tillage accumulated more volume of runoff water than the 0-30 cm depth of tillage in the pits and it was 23.33% higher in the lower depth of tillage used on the field than the 0-30 cm depth of tillage. Implying that 0-30 cm tillage depth retained more water from the rainfall compare to the water retained by the 0-15 cm depth. Even though, volume of runoff water of 0-15 cm depth of tillage was higher than that of the 0-30 cm depth of tillage, 0-15 cm depth of tillage had the highest yield of maize (9.30±4.26 t ha<sup>-1</sup>).<br><br></p> Wasiu Agunbiade Lamidi, Wasiu Agunbiade Lamidi, Wasiu Agunbiade Lamidi, Wasiu Agunbiade Lamidi, Adedamola Emmanuel Olawumi, Tunde Amos Oyeranmi Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000 Waste Management Practices of Construction Companies at the Airport Hills and Sakumono Areas in Accra, Ghana <p>Waste generated in the construction industry is a major environmental problem but its research is rather limited. Thus, this research was conducted to assess the waste disposal practices of construction companies at the Airport Hills and Sakumono areas in Accra, Ghana. These areas were chosen because of the increasing and fast development of housing projects there. A convenience sampling technique was used in choosing the companies to achieve the research goal. Questionnaires and field observations were used to gather information about the construction companies and their waste management practices. Forty construction companies were identified in both study areas. Majority of the companies recorded a total of 60-80 cubic meters of material waste per month. Eleven companies stated amounts of between USD 250 - 350 as cost of material waste management per month. Several reusable materials were identified at construction sites. Twenty-six companies practised sorting and recovery of waste before final disposal. It was revealed that there was no statistically significant relationship between the educational levels of waste management teams of the construction companies and their practice of proper waste management methods. A significant relationship however existed between the educational level of waste management teams and their use of waste management plans. It is recommended that waste management training programmes are developed by the Environmental Protection Agency of Ghana for construction companies to curb the problem of poor construction waste management.</p> Donald N. Amuna, Zarouk A. Imoro, Samuel J. Cobbina, Samuel A. Ofori Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000 Organic Geochemistry of Peat Deposits in southwest Rwanda <p>Rwanda hosts million tons of peat deposits and that of western province is of great importance as it close to Kivu Lake. The discovery of methane gas in Kivu Lake has attracted investors in methane gas utilization as source of power supply and Compressed Natural Gas (CNG). Researchers identified Kivu Lake and adjacent area as an area of interest for hydrocarbon exploration. However, organic geochemical prospecting for hydrocarbon and energy content assessment is inadequate for the identified areas. The study aimed at determining the organic geochemistry of peat deposits in southwest, Rwanda. Forty (40) subsurface peat samples (1 to 10 m depth) were collected, air-dried and pulverized and screened. Five (5) samples with high organic matter content were subjected to biomarkers analysis using GC-GCMS. The n-alkanes distribution comprised mainly n-C11 to n-C 37. The Pr/Ph ratios (3.3-10.4, the waxiness index (0.09-0.87), CPI (3.6-7.8), OEP (3.5-6.0), C29 steranes (63.0–100.0%), C28 (0.0–28.0%), C27 (0.0–18.0%) and C27/ C29 sterane ratios (0.0-0.28). The ββ/ (ββ + αα) and 20S/ (20S + 20R) are 0.5 and 0.46 respectively. The C30 -moretane/ C30 -hopane ratios ranged from 1.56 to 2.42, while the oleanane index ranged from 0.07 to 0.26. The Ts/ (Ts + Tm) ratios ranged from 0.13 to 1.05. The dominance of C-29 sterols and C29/C27 sterane ratio which ranged from 3.5 to 100 indicating derivation from terrigenous higher plant material. The Pr/Ph ratio (&gt;3) reflect the oxic to sub-oxic environmental condition during peat deposition. The peat deposits in Western Province, Rwanda are very rich in organic matter of mainly terrestrial precursor deposited in dry and cold climate.</p> Theophile Mugerwa, Francois Hategekimana, Olugbenga A. Ehinola, Ibrahim A. Oladosu, Digne Rwabuhungu, Theophile Bimenyimana, Fils V. Byiringiro, Cedrick Nsengiyumva Copyright (c) Wed, 14 Jul 2021 00:00:00 +0000