Prediction of fusion zone in numerical modelling of welds using a modified heat transfer model requires experimental results for validation. Primarily, the modified heat transfer models are developed from the point and disc source heat models which can be assumed to be a semi-circle or spherical shape. In this study, a simple relationship between melt areas, the depth of penetration and weld width was proposed for point and disc source profiles to represent the actual weld profile. The results obtained for focused and defocused laser beams indicate that the actual weld profile is closer to a point source than the disc source. The transition between the conduction and keyhole regimes was achieved when the actual weld depth of penetration is below that of the point source.
{"title":"Comparison of Theoretical Disc and Point Source Profiles with Actual-Melt Source Profile in Conduction Welding","authors":"W. Ayoola, W. Suder, S. Williams","doi":"10.4314/njtd.v19i3.8","DOIUrl":"https://doi.org/10.4314/njtd.v19i3.8","url":null,"abstract":"Prediction of fusion zone in numerical modelling of welds using a modified heat transfer model requires experimental results for validation. Primarily, the modified heat transfer models are developed from the point and disc source heat models which can be assumed to be a semi-circle or spherical shape. In this study, a simple relationship between melt areas, the depth of penetration and weld width was proposed for point and disc source profiles to represent the actual weld profile. The results obtained for focused and defocused laser beams indicate that the actual weld profile is closer to a point source than the disc source. The transition between the conduction and keyhole regimes was achieved when the actual weld depth of penetration is below that of the point source.","PeriodicalId":31273,"journal":{"name":"Nigerian Journal of Technological Development","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41749768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
combination of seismic data and petrophysical logs from five wells acquired in ‘J’ Field, Niger Delta, Nigeria, have been analyzed to assess the carbon dioxide (CO2) storage potential of some saline aquifers in ‘J’ field. The study aims to evaluate the volume of CO2 that can be potentially stored in the aquifers and the risk of CO2 leakages in the storage. The sand aquifers were correlated across the five wells to evaluate their thicknesses and lateral extent. Porosity, permeability, formation water resistivity, and net sand thickness were estimated in the different wells. The Horizons corresponding to the top of the aquifers was mapped, and time and depth structured maps were generated for structural analysis and volumetric estimations. The risk of CO2 leakages through sealing layers (cap rocks) was evaluated in terms of caprock integrity and pore pressure sealing mechanism. Results of the study showed that four aquifers, namely, L20, N30, M40, and P50, are laterally extensive across the five wells and have thicknesses that range from 14 to 352 m. The individual CO2 storage capacity of L20, M30, N40, and P50 was estimated to be 6.97×1010, 1.48×1010, 7.78×109 and 1.49×1010 tons, respectively. The combined aquifer storage capacity was estimated to be 1.07×1011 tons. The sealing layers have low risk of CO2 leakages. The study concluded that the aquifers have good potential for CO2 storage and low risk of leakages. The study ranked L20 as the best among the four aquifers.
{"title":"Assessment of Carbon Dioxide Storage Capacity of Selected Aquifers in ‘J’ Field, West Africa","authors":"W. Raji, S. Bello, T. O. Adeoye","doi":"10.4314/njtd.v19i3.4","DOIUrl":"https://doi.org/10.4314/njtd.v19i3.4","url":null,"abstract":"combination of seismic data and petrophysical logs from five wells acquired in ‘J’ Field, Niger Delta, Nigeria, have been analyzed to assess the carbon dioxide (CO2) storage potential of some saline aquifers in ‘J’ field. The study aims to evaluate the volume of CO2 that can be potentially stored in the aquifers and the risk of CO2 leakages in the storage. The sand aquifers were correlated across the five wells to evaluate their thicknesses and lateral extent. Porosity, permeability, formation water resistivity, and net sand thickness were estimated in the different wells. The Horizons corresponding to the top of the aquifers was mapped, and time and depth structured maps were generated for structural analysis and volumetric estimations. The risk of CO2 leakages through sealing layers (cap rocks) was evaluated in terms of caprock integrity and pore pressure sealing mechanism. Results of the study showed that four aquifers, namely, L20, N30, M40, and P50, are laterally extensive across the five wells and have thicknesses that range from 14 to 352 m. The individual CO2 storage capacity of L20, M30, N40, and P50 was estimated to be 6.97×1010, 1.48×1010, 7.78×109 and 1.49×1010 tons, respectively. The combined aquifer storage capacity was estimated to be 1.07×1011 tons. The sealing layers have low risk of CO2 leakages. The study concluded that the aquifers have good potential for CO2 storage and low risk of leakages. The study ranked L20 as the best among the four aquifers.","PeriodicalId":31273,"journal":{"name":"Nigerian Journal of Technological Development","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41482013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sign language is used by people who have hearing and speaking difficulties, but not understood by many without these difficulties. Therefore, sign language recognition systems are developed to aid communication between hearing impaired people and others. This paper developed a static American Sign Language Recognition (ASLR) system using canny-edge and histogram of oriented gradient (HOG) for feature extraction with K-Nearest Neighbour (K-NN) as classifier. The sign language image datasets used consist of English alphabets from both Massey University and Kaggle, and numbers (0-9) from Massey University. Median filter was used to remove noise after images were converted to grayscale. Otsu algorithm was used for segmentation while edges in the images were preserved using canny edge detection technique with HOG parameters tuning to obtain feature vectors. The extracted features were used by K-NN for classification. An average recognition accuracy and computational testing time of 97.6% and 0.39s respectively were obtained based on experiments with the Massey University dataset. Similarly, an average recognition accuracy and computational testing time of 99.0% and 0.43s respectively were obtained based on experiments with the Kaggle dataset. The developed system successfully recognized static English alphabets and numbers and outperformed some existing systems.
{"title":"Development of an American Sign Language Recognition System using Canny Edge and Histogram of Oriented Gradient","authors":"I. Adeyanju, O. O. Bello, M. A. Azeez","doi":"10.4314/njtd.v19i3.2","DOIUrl":"https://doi.org/10.4314/njtd.v19i3.2","url":null,"abstract":"Sign language is used by people who have hearing and speaking difficulties, but not understood by many without these difficulties. Therefore, sign language recognition systems are developed to aid communication between hearing impaired people and others. This paper developed a static American Sign Language Recognition (ASLR) system using canny-edge and histogram of oriented gradient (HOG) for feature extraction with K-Nearest Neighbour (K-NN) as classifier. The sign language image datasets used consist of English alphabets from both Massey University and Kaggle, and numbers (0-9) from Massey University. Median filter was used to remove noise after images were converted to grayscale. Otsu algorithm was used for segmentation while edges in the images were preserved using canny edge detection technique with HOG parameters tuning to obtain feature vectors. The extracted features were used by K-NN for classification. An average recognition accuracy and computational testing time of 97.6% and 0.39s respectively were obtained based on experiments with the Massey University dataset. Similarly, an average recognition accuracy and computational testing time of 99.0% and 0.43s respectively were obtained based on experiments with the Kaggle dataset. The developed system successfully recognized static English alphabets and numbers and outperformed some existing systems.","PeriodicalId":31273,"journal":{"name":"Nigerian Journal of Technological Development","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43333752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. D. Akpenpuun, Q. O. Ogunlowo, A. Rabiu, M. A. Adesanya, W. Na, M. Omobowale, Y. Mijinyawa, H. W. Lee
This review documents the present knowledge and knowledge gap in applying building energy simulation (BES) dynamic models to greenhouses. The focus of this review is to compile the literature on the BES dynamic model of greenhouse microclimate, covering materials, energy requirements and thermal blankets using the Transient System Simulation version 18 (TRNSYS 18) software. Fifty-two journal articles, mostly Science Citation Index (SCI) and Scopus index journals, on BES development and simulation of greenhouse microclimate, greenhouse energy requirement, covering materials and thermal blankets were reviewed. These researchers sought to optimise greenhouse crop production. The main features of the TRNSYS 18 software for BES development are outlined; each research consulted for this review successfully developed, simulated and validated its BES. However, none of these developed models included the vapour pressure deficit (VPD) as a greenhouse microclimate factor, an essential climate parameter. In conclusion, this study demonstrates that applying a BES developed using TRNSYS has excellent potential to optimise greenhouse crop production and help adapt appropriate climate control strategies and energy-saving techniques. However, it is recommended to include VPD in future BES model development.
{"title":"Building Energy Simulation Model Application to Greenhouse Microclimate, Covering Material and Thermal Blanket Modelling: A Review","authors":"T. D. Akpenpuun, Q. O. Ogunlowo, A. Rabiu, M. A. Adesanya, W. Na, M. Omobowale, Y. Mijinyawa, H. W. Lee","doi":"10.4314/njtd.v19i3.10","DOIUrl":"https://doi.org/10.4314/njtd.v19i3.10","url":null,"abstract":"This review documents the present knowledge and knowledge gap in applying building energy simulation (BES) dynamic models to greenhouses. The focus of this review is to compile the literature on the BES dynamic model of greenhouse microclimate, covering materials, energy requirements and thermal blankets using the Transient System Simulation version 18 (TRNSYS 18) software. Fifty-two journal articles, mostly Science Citation Index (SCI) and Scopus index journals, on BES development and simulation of greenhouse microclimate, greenhouse energy requirement, covering materials and thermal blankets were reviewed. These researchers sought to optimise greenhouse crop production. The main features of the TRNSYS 18 software for BES development are outlined; each research consulted for this review successfully developed, simulated and validated its BES. However, none of these developed models included the vapour pressure deficit (VPD) as a greenhouse microclimate factor, an essential climate parameter. In conclusion, this study demonstrates that applying a BES developed using TRNSYS has excellent potential to optimise greenhouse crop production and help adapt appropriate climate control strategies and energy-saving techniques. However, it is recommended to include VPD in future BES model development.","PeriodicalId":31273,"journal":{"name":"Nigerian Journal of Technological Development","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49121221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Arinkoola, S. Alagbe, K. Salam, B. M. Ajagbe, I. Akinwole
This study assessed the rheological and mechanical properties of Nigerian Ewu-Obi Calcium Bentonite (ECaB) as cement partial replacement for shallow depth cementing operations using experimental design and response surface methodology. Rheological properties, Thickening Time (TT), and Compressive Strength (CS) were measured using a 12-speed rotational viscometer, High-Pressure High Temperature (HPHT) Consistometer, and Ultrasonic Cement Analyzer, respectively. The effect of the increase in the concentration of bentonite clay as well as its interaction with other cement additives (accelerator and antifoam) on plastic viscosity (PV), yield point (Yp), fluid loss (FL), TT, and CS were investigated. The result shows that the optimum replaceable percentage of ECaB in class G cement, accelerator, and antifoam is 23.5, 7.5, and 0.95 wt %, respectively. At optimum conditions, the PV (17.5±1.35 cp), FL (20 ml/30 min/100 psi), TT (228±16.4 min), and CS24 (614±0.57 psi) obtained agreed with the API standard and compared favorably with literature.
{"title":"Assessment of Nigerian Calcium Bentonite as Cement Replacement for Shallow depth Oil Well Cementing Operation","authors":"A. Arinkoola, S. Alagbe, K. Salam, B. M. Ajagbe, I. Akinwole","doi":"10.4314/njtd.v19i3.7","DOIUrl":"https://doi.org/10.4314/njtd.v19i3.7","url":null,"abstract":"This study assessed the rheological and mechanical properties of Nigerian Ewu-Obi Calcium Bentonite (ECaB) as cement partial replacement for shallow depth cementing operations using experimental design and response surface methodology. Rheological properties, Thickening Time (TT), and Compressive Strength (CS) were measured using a 12-speed rotational viscometer, High-Pressure High Temperature (HPHT) Consistometer, and Ultrasonic Cement Analyzer, respectively. The effect of the increase in the concentration of bentonite clay as well as its interaction with other cement additives (accelerator and antifoam) on plastic viscosity (PV), yield point (Yp), fluid loss (FL), TT, and CS were investigated. The result shows that the optimum replaceable percentage of ECaB in class G cement, accelerator, and antifoam is 23.5, 7.5, and 0.95 wt %, respectively. At optimum conditions, the PV (17.5±1.35 cp), FL (20 ml/30 min/100 psi), TT (228±16.4 min), and CS24 (614±0.57 psi) obtained agreed with the API standard and compared favorably with literature.","PeriodicalId":31273,"journal":{"name":"Nigerian Journal of Technological Development","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42339162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Ishaq, M. I. M. Said, S. Azman, M. Abdulwahab, M. Alfa
Landfills and solid waste disposal facilities have historically been the most common point sources of pollution with the potential to release contamination leachate plumes into the environment. Waste disposal is one of the biggest problems that the world is facing. In man’s everyday life, he produces waste materials which, if not properly managed, can affect health and environment. The seepage of landfill leachate into groundwater tables and aquifer systems significantly creates a possible danger and threat to human health and environment at large and remains a subject of concern in Nigeria and other parts of the world. This paper provides a review of existing approaches to leachate treatment in Nigeria and current practices across the globe, depicts the impact on environmental implications, documented previous findings, challenges and mitigation measures, and future perspectives of landfill leachate management in Nigeria, and compares with global practice of leachate management. In Nigeria, there are only a few standard techniques of landfill leachate treatment. This resulted in severe environmental impacts that threaten human life, especially in the north-eastern part of the country. Vector-borne and water-related illnesses such as cholera, Dengue, Diarrhoea, Trachoma, typhoid, malaria etc, have become a major source of concern resulting from the leaching effect from landfills. Advanced treatment methods, including membrane filtration, trickling filters, and Batch and Sequencing-Batch Reactors (SBR) are used in some of the cities and private organizations in Nigeria. Most researchers in Nigeria have stressed the necessity to utilise efficient, cost-effective technology in landfill wastewater treatment. Despite this, landfill leachate has continued to have severe effects in Nigeria and the situation seems to be escalating, requiring further study.
{"title":"Impact, Mitigation Strategies, and Future Possibilities of Nigerian Municipal Solid Waste Leachate Management Practices: A Review","authors":"A. Ishaq, M. I. M. Said, S. Azman, M. Abdulwahab, M. Alfa","doi":"10.4314/njtd.v19i3.1","DOIUrl":"https://doi.org/10.4314/njtd.v19i3.1","url":null,"abstract":"Landfills and solid waste disposal facilities have historically been the most common point sources of pollution with the potential to release contamination leachate plumes into the environment. Waste disposal is one of the biggest problems that the world is facing. In man’s everyday life, he produces waste materials which, if not properly managed, can affect health and environment. The seepage of landfill leachate into groundwater tables and aquifer systems significantly creates a possible danger and threat to human health and environment at large and remains a subject of concern in Nigeria and other parts of the world. This paper provides a review of existing approaches to leachate treatment in Nigeria and current practices across the globe, depicts the impact on environmental implications, documented previous findings, challenges and mitigation measures, and future perspectives of landfill leachate management in Nigeria, and compares with global practice of leachate management. In Nigeria, there are only a few standard techniques of landfill leachate treatment. This resulted in severe environmental impacts that threaten human life, especially in the north-eastern part of the country. Vector-borne and water-related illnesses such as cholera, Dengue, Diarrhoea, Trachoma, typhoid, malaria etc, have become a major source of concern resulting from the leaching effect from landfills. Advanced treatment methods, including membrane filtration, trickling filters, and Batch and Sequencing-Batch Reactors (SBR) are used in some of the cities and private organizations in Nigeria. Most researchers in Nigeria have stressed the necessity to utilise efficient, cost-effective technology in landfill wastewater treatment. Despite this, landfill leachate has continued to have severe effects in Nigeria and the situation seems to be escalating, requiring further study.","PeriodicalId":31273,"journal":{"name":"Nigerian Journal of Technological Development","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45782853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An attempt has been made to develop a new enhanced electrical conductor nanocomposites using green synthesis silver nanoparticles (GAgNPs) modified carbon nanotubes (CNTs) reinforced aluminum nanocomposites. High-intensity ball milling and spark plasma sintering (SPS) were used to produce the composites. The nanocomposite' microstructure, strength, model, and electrical conductivity were all determined. 2%GAg.NPs in Al-4-percent CNTs helps to refine the grain structure of the Al-4-percent CNTs. More dislocation density was generated by the creation of sub-grain in the Al-4 percent CNTs+2 percent GAgNPs composite. Tensile strength and electrical conductivity were increased by 82.14 and 106.88% using Al-4-percent CNTs +2%GAg.NPs nanocomposite. The ductility mode of fracture associated with the tiny sub-grain produced at the surface was greatly improved when 2% GAgNPs were added to Al-4% CNTs. It was established that the GAgNPS can been used to coat CNTs enhance the strength and electrical conductivity of Al-4 percent CNTs nanocomposites.
{"title":"Improved Electrical Conductivity and Strength of α-Al-Carbon Nanotubes Blended with Silver Nanoparticles Composites","authors":"V. Aigbodion","doi":"10.4314/njtd.v19i3.9","DOIUrl":"https://doi.org/10.4314/njtd.v19i3.9","url":null,"abstract":"An attempt has been made to develop a new enhanced electrical conductor nanocomposites using green synthesis silver nanoparticles (GAgNPs) modified carbon nanotubes (CNTs) reinforced aluminum nanocomposites. High-intensity ball milling and spark plasma sintering (SPS) were used to produce the composites. The nanocomposite' microstructure, strength, model, and electrical conductivity were all determined. 2%GAg.NPs in Al-4-percent CNTs helps to refine the grain structure of the Al-4-percent CNTs. More dislocation density was generated by the creation of sub-grain in the Al-4 percent CNTs+2 percent GAgNPs composite. Tensile strength and electrical conductivity were increased by 82.14 and 106.88% using Al-4-percent CNTs +2%GAg.NPs nanocomposite. The ductility mode of fracture associated with the tiny sub-grain produced at the surface was greatly improved when 2% GAgNPs were added to Al-4% CNTs. It was established that the GAgNPS can been used to coat CNTs enhance the strength and electrical conductivity of Al-4 percent CNTs nanocomposites.","PeriodicalId":31273,"journal":{"name":"Nigerian Journal of Technological Development","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45960199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Heat treated steels that are quenched rapidly show an increase in hardness and toughness but also show an increase in brittleness which could lead to a higher surface roughness and low material removal rate while machining. Hence, the choice of quenchants has a significant effect on the hardness of low carbon steels. In this research work, the effect of some selected quenchants on the mechanical properties of heat treated and machined mild steel was investigated. Four samples of the carbon steel rods were furnace heated at 8500C and quenched with water, molten salt, potash alum and used engine oil. Central Composite Designs of Design Expert version 12 was used to plan the experiment. Machining factors used were, speed (100-450 rpm), feed rate (0.01-0.03 mm/rev), depth of cut (1-2mm). Surface roughness and material removal rate as well as the results of quenchant characterization were the responses studied. The favored quenchant was oil with the lowest surface roughness, hardness and material removal rate of 0.33μm and 187.78BHN and 0.020133mm3/min respectively. This is because the use of oil resulted in the highest reduction in surface roughness and enhanced material removal rate.
{"title":"Study of the Effect of Quenchants on the Machinability of Heat Treated Mild-Steel","authors":"T. Ogedengbe, T. Adeyi, O. Ajao, O. A. Ileoye","doi":"10.4314/njtd.v19i3.5","DOIUrl":"https://doi.org/10.4314/njtd.v19i3.5","url":null,"abstract":"Heat treated steels that are quenched rapidly show an increase in hardness and toughness but also show an increase in brittleness which could lead to a higher surface roughness and low material removal rate while machining. Hence, the choice of quenchants has a significant effect on the hardness of low carbon steels. In this research work, the effect of some selected quenchants on the mechanical properties of heat treated and machined mild steel was investigated. Four samples of the carbon steel rods were furnace heated at 8500C and quenched with water, molten salt, potash alum and used engine oil. Central Composite Designs of Design Expert version 12 was used to plan the experiment. Machining factors used were, speed (100-450 rpm), feed rate (0.01-0.03 mm/rev), depth of cut (1-2mm). Surface roughness and material removal rate as well as the results of quenchant characterization were the responses studied. The favored quenchant was oil with the lowest surface roughness, hardness and material removal rate of 0.33μm and 187.78BHN and 0.020133mm3/min respectively. This is because the use of oil resulted in the highest reduction in surface roughness and enhanced material removal rate.","PeriodicalId":31273,"journal":{"name":"Nigerian Journal of Technological Development","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45826155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Trends and sources of air pollution at twenty-five traffic Intersections (TIs) before and during covid-19 lockdown were investigated in Ibadan, Nigeria. The relationships among climatic parameters, vehicular counts and ten air pollutants which includes particulate matter (PM1, PM2.5, PM10 & Total Suspended Particles-TSP) and gaseous pollutants (CO, NO2, SO2, NH3, total volatile organic compounds-TVOCs, and ground level O3) measured simultaneously at TIs were analysed. Results indicated significant decrease in mean concentrations of all pollutants studied except NO2 with 212% increase during the study period. Concentrations of gaseous pollutants CO, SO2, NH3, TVOCs and ground level O3 reduced by 7.92%, 24.80%, 1.58%, 44.08% and 4.28%, respectively while particulates concentrations of PM1, PM2.5, PM10 and TSP concentrations decreased by 49.64%, 60.79%, 81.21% and 84.17%, respectively during lockdown. An integrated source apportionment approach using Pearson’s correlation, Airflow backward trajectories arriving in the study area and Principal component analysis (PCA) identified vehicular emission as the primary source of studied air pollutants at TIs before and during lockdown in Ibadan. Emission from residences, roadside fuel combustion and local air transport of pollutants from nearby upwind areas with industries and farming activities were identified as secondary sources of air pollution affecting the study area.
{"title":"Impacts of Covid-19 Lockdown on Concentration Levels of Traffic-Related Air Pollutants in Ibadan -a West African City","authors":"E. Odedi̇ran, O. Yusuf, A. Adeniran","doi":"10.4314/njtd.v19i3.3","DOIUrl":"https://doi.org/10.4314/njtd.v19i3.3","url":null,"abstract":"Trends and sources of air pollution at twenty-five traffic Intersections (TIs) before and during covid-19 lockdown were investigated in Ibadan, Nigeria. The relationships among climatic parameters, vehicular counts and ten air pollutants which includes particulate matter (PM1, PM2.5, PM10 & Total Suspended Particles-TSP) and gaseous pollutants (CO, NO2, SO2, NH3, total volatile organic compounds-TVOCs, and ground level O3) measured simultaneously at TIs were analysed. Results indicated significant decrease in mean concentrations of all pollutants studied except NO2 with 212% increase during the study period. Concentrations of gaseous pollutants CO, SO2, NH3, TVOCs and ground level O3 reduced by 7.92%, 24.80%, 1.58%, 44.08% and 4.28%, respectively while particulates concentrations of PM1, PM2.5, PM10 and TSP concentrations decreased by 49.64%, 60.79%, 81.21% and 84.17%, respectively during lockdown. An integrated source apportionment approach using Pearson’s correlation, Airflow backward trajectories arriving in the study area and Principal component analysis (PCA) identified vehicular emission as the primary source of studied air pollutants at TIs before and during lockdown in Ibadan. Emission from residences, roadside fuel combustion and local air transport of pollutants from nearby upwind areas with industries and farming activities were identified as secondary sources of air pollution affecting the study area.","PeriodicalId":31273,"journal":{"name":"Nigerian Journal of Technological Development","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45678079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a study of high impedance fault (HIF) arc analysis on 6 km 11 kV distribution network from New Haven to New NNPC, Enugu State. These HIF currents have low fault current ratings and are not readily detected by the distribution sub-station relays and protective equipment. This was realized with the aid of MATLAB. Firstly, the HIF was modelled based on the electric arc theory method for single line-to-ground and double line-to-ground faults, when the 11 kV New-haven to New NNPC Enugu distribution line interfaces with a dry asphalt ground surface. The HIF was incident on the midpoint of the distribution line between the switching times of the circuit breaker from 0.02 to 0.05 seconds. The results showed that for single line-to-ground and double line-to-ground faults, a peak current magnitude of 12.4 A and 2280 A were seen respectively and initial spikes due to arcing in the system voltages at the initial switching times of 0.02 seconds. The corresponding residual currents Ib and Ic are very small with a peak spike of 0.3 A and 1.9 A for double line-to-ground fault (BC-G). These spikes are because of the impact of the initial transients caused by the arc flames as its quenches and re-ignites.
本文研究了从纽黑文到埃努古州新NNPC的6km 11kV配电网的高阻抗故障（HIF）电弧分析。这些HIF电流具有低故障电流额定值，并且配电变电站继电器和保护设备不容易检测到。这是在MATLAB的帮助下实现的。首先，基于电弧理论方法对11 kV New haven至New NNPC Enugu配电线路与干燥沥青地面接触时的单线对地和双线对地故障进行了HIF建模。HIF在断路器的开关时间从0.02秒到0.05秒之间入射在配电线路的中点上。结果表明，对于单线接地和双线接地故障，分别看到12.4A和2280A的峰值电流大小，并且在0.02秒的初始切换时间处，由于系统电压中的电弧而产生初始尖峰。对于双线接地故障（BC-G），相应的剩余电流Ib和Ic非常小，峰值尖峰为0.3A和1.9A。这些尖峰是由于电弧火焰在熄灭和重新点燃时产生的初始瞬态的影响。
{"title":"High impedance fault arc analysis on 11 kV distribution networks","authors":"P. Obi, E. Amako, C. S. Ezeonye","doi":"10.4314/njtd.v19i2.6","DOIUrl":"https://doi.org/10.4314/njtd.v19i2.6","url":null,"abstract":"This paper presents a study of high impedance fault (HIF) arc analysis on 6 km 11 kV distribution network from New Haven to New NNPC, Enugu State. These HIF currents have low fault current ratings and are not readily detected by the distribution sub-station relays and protective equipment. This was realized with the aid of MATLAB. Firstly, the HIF was modelled based on the electric arc theory method for single line-to-ground and double line-to-ground faults, when the 11 kV New-haven to New NNPC Enugu distribution line interfaces with a dry asphalt ground surface. The HIF was incident on the midpoint of the distribution line between the switching times of the circuit breaker from 0.02 to 0.05 seconds. The results showed that for single line-to-ground and double line-to-ground faults, a peak current magnitude of 12.4 A and 2280 A were seen respectively and initial spikes due to arcing in the system voltages at the initial switching times of 0.02 seconds. The corresponding residual currents Ib and Ic are very small with a peak spike of 0.3 A and 1.9 A for double line-to-ground fault (BC-G). These spikes are because of the impact of the initial transients caused by the arc flames as its quenches and re-ignites.","PeriodicalId":31273,"journal":{"name":"Nigerian Journal of Technological Development","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43704145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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