Musa Mohammed - Academia.edu (original) (raw)

Papers by Musa Mohammed

Computational Fluid Dynamics (CFD) is increasingly being used as a tool for the analysis of outdo... more Computational Fluid Dynamics (CFD) is increasingly being used as a tool for the analysis of outdoor and indoor air flow and thermal conditions. With over half of the world's population living in cities, rapid population growth and dense urban development has increasingly led to the phenomenon of urban heat islands, which in turn contribute to the deteriorating air quality and thermal discomfort in outdoor urban public spaces. In hot arid countries, changes in the characteristics of the urban microclimate are observed due to dense urbanization, high-rise buildings, and industrialization of the building processes and materials, leading to a reduction in thermal comfort in outdoor and indoor spaces. This research highlights the potential of adopting Computational Fluid Dynamics (CFD) as a simulation technique to investigate the complex fluid flow patterns in urban thermal environments, and investigates methods intended to prolong thermal comfort in public places. It discusses the advantages and limitations of CFD tools and the procedural guidelines for conducting CFD simulation. This paper also gives examples of case studies of CFD assessment for indoor and outdoor urban environments, and the practical use of RANS solver in comparison with LES, DES, and DNS models. Finally the paper highlights a case study of a CFD simulation using a RANS turbulence model of an urban street in the hot arid city of Madinah, Saudi Arabia.

Journal of Applied Materials and Technology

Modern Power Distribution Networks (MPDNs) are no longer passive because Distributed Generations ... more Modern Power Distribution Networks (MPDNs) are no longer passive because Distributed Generations (DGs) are integrated with them to enhance system reliability and power quality. For this reason, load modeling has to be updated to capture the new dynamics of active DNs. This paper presents a composite load modeling for a grid-connected photovoltaic (PV) distribution network using the Levenberg-Marquardt algorithm in the deep learning feed-forward neural network approach. Load modeling is constructing a relationship between input excitation(s) and output response(s); it can be used for simulation studies, stability analysis, and control/protection design. A grid-connected PV distribution network was modeled in Matlab/Simulink and generates data for training and model estimation. The estimated model was tested and validated using a laboratory experimental test bed. Results of the model exhibit a good fitness of 99.8% and 97.2% in active and reactive power models respectively during tra...

Emerging Advances in Integrated Technology, 2020

Load modeling plays a significant impact in assessing power system stability margin, control, and... more Load modeling plays a significant impact in assessing power system stability margin, control, and protection. Frequency in the power system is desired to be kept constant, but in a real sense, it is not constant as loads continually change with time. In much literature, frequency dynamics are ignored in the formulation of load models for the basic assumption that it does not affect the models. In this paper, the composite load model was formulated with Voltage-Frequency Dependency (V-FD) on real and reactive powers and applied to estimate the load model. 2- Area network 4- machines Kundur test network was used for testing the developed model. The model was trained with measurements from a low voltage distribution network supplying the Electrical Engineering department at Ahmadu Bello University, Zaria. Both training and testing data were captured under normal system operation (dynamics). To evaluate the V-FD model performance, Voltage-Dependent (VD) model was examined on the same me...

Journal of Applied Materials and Technology, 2020

Power system operation and control required models of generators, lines and loads to be accuratel... more Power system operation and control required models of generators, lines and loads to be accurately estimated, this is to enable operators make a reliable decision on the system. Generators and lines models are so far considered accurate, while load models are considered perplexing due to invention of new types of loads, distribution system are transforming from passive to active. Future distribution systems are desired to be smart and for a network to be smart the system as to be fully and accurately represented. Penetration of renewable energy and application of power electronic devices as well as participation of active customers in distribution systems make traditional methods of load modeling absolute. Accurate load modeling is required to address the new challenges evolving in the task of power system operation, control and stability studies. It is also an interest of power system researchers globally to realize Smart Networks (SNs), in which accurate load models are required....

Asian Journal of Advanced Research and Reports, 2019

Background: Tobacco smoking is one source of heavy metals exposure in the general population. Tob... more Background: Tobacco smoking is one source of heavy metals exposure in the general population. Tobacco smoke has toxic, genotoxic, and carcinogenic properties and has been linked to fatal pregnancy outcomes. Aim: This research was carried out to investigate the concentration of Copper (Cu), lead (Pb) and Zinc (Zn) in different cigarette brands sold in Keffi main market of Nasarawa state and compare with recommended standard. Study Design: To determine the presence of heavy metals in different brands of cigarette sold in Keffi main Market, Nasarawa State, Nigeria and compare them with relevant authorities’ standard. Place and Duration: The study was carried out in the department of physics, Nasarawa State University, Keffi, Nasarawa State, Nigeria between March 2018 and November, 2018. Materials and Methods: Ten brands of cigarette were purchased from Keffi main central market using random sampling. The cigarettes were expose to sun light for 3 hours until they became dry. The filters...

International Conference on Emerging Applications and Technologies for Industry 4.0 (EATI’2020), 2021

Unmanned Aerial vehicle (UAV) systems have an insufficient amount of onboard energy which is bein... more Unmanned Aerial vehicle (UAV) systems have an insufficient amount of onboard energy which is being shared for mobility, transmission, data processing, control and payload related applications. Different energy sources have been investigated and applied to solve unmanned aerial vehicle energy limitations. These energy sources were either used as single sources or hybrid for the reason of UAV weight budget or miniaturization. To achieve the aforementioned designed criteria, researchers around the globe are continuously investigating different energy sources and hybridization techniques while others focus on the Energy Management System (EMS) such to achieve optimal energy sources utilization. Such energy sources and supplying techniques are battery swapping, wireless Power Transfer (WPT), tethering methods, Fuel Cells (FC), and SuperCapacitors (SC). While, the hybridization technique is based on the combination of single energy source with either renewable energy sources, Internal Combustion Engine (ICE) to save fuel or WPT. Example of such hybridization techniques are solar and battery storage, Fuel Cell (FC) and Battery Storage (BS) etc. This article presents an in-depth review of UAV energy sources, hybridization techniques and EMS. Their challenges and methods adopted by researchers to mitigate such UAV energy challenges.

Journal of Applied Materials and Technology, 2020

Solid-State Transformer (SST), a power electronics based transformer is an emerging technology in... more Solid-State Transformer (SST), a power electronics based transformer is an emerging technology in electric power system. The transformer is being investigated to completely replace existing Line/Low Frequency Transformer (LFT). SST is composed of either of the two topologies: AC-DC-AC, two steps approach; or AC-AC, single-step approach. The two steps approach consists of three stages: AC-DC; DC-DC; and DC-AC stages. The DC-DC stage is made up of a boost DC-DC converter, a DC-AC inverter and a High Frequency Transformer, HFT. Therefore, SST performs the tasks of LFT by means of power electronic converters and HFT. The main essence of SST is to provide solution to the problem of bulkiness and heaviness of the LFT in the power distribution network. This is with the view to providing reduction in construction cost, cost of maintenance and transportation. The power electronics transformer provides numerous advantages which are grouped into: The transformer has high power density; it fun...

Asian Journal of Research and Reviews in Physics, 2019

In this study, an investigation of radiofrequency power density distribution around GSM mast in K... more In this study, an investigation of radiofrequency power density distribution around GSM mast in Keffi town, Nigeria was determined. Radiofrequency meter (Electrosmog ED- 155A) was used to measure the EM radiation at 50, 70, 90,110, 130, 150, 170, and 190 m away from mobile base stations. A total of fifteen mobile base stations were randomly selected in Keffi town covering about four network providers (MTN, Globacom, Etisalat, and Airtel), according to their proximity to buildings, number of antennas mounted on their masts, how close they are to other base stations and the population density around them.The result reveal that MBS5 was found to have the highest value of average power density compared to that of the remainder, with a contribution of about 16% (2908.38 µW/m2). The least contribution was recorded in MBS3 with only about 1% (173.71 μW/m2). The other MBS with significant contribution are MBS6 (15%), MBS11 (15%), MBS10 (13%), MBS8 (13%) and MBS13 (11%) with average power de...

Immunology, 2019

Mature T helper (Th) effector cells originate following antigen recognition by naive T precursors... more Mature T helper (Th) effector cells originate following antigen recognition by naive T precursors. The maturation process is accompanied by the acquisition of specific effector functions that distinguish at least three different T helper subsets: Th1, Th2 and Th17. In general, maturation of somatic cells is accompanied by terminal differentiation. However, accumulating evidence shows that effector T cells retain a certain degree of plasticity. This is especially true for Th17 cells, which have been shown to converge towards other phenotypes in response to specific microenvironmental pressure. In this review we will discuss the experimental evidence that supports the hypothesis of Th17 plasticity, with particular emphasis on the generation of Th17-derived 'non-classic' Th1 cells, and the molecular networks that control it. Moreover, we will consider why Th17 plasticity is important for host protection, but also why it can have pathogenic functions during chronic inflammation. Regarding the last point, we will discuss a possible role for biological drugs in the control of Th17 plasticity and disease course.

Computational Fluid Dynamics (CFD) is increasingly being used as a tool for the analysis of outdo... more Computational Fluid Dynamics (CFD) is increasingly being used as a tool for the analysis of outdoor and indoor air flow and thermal conditions. With over half of the world's population living in cities, rapid population growth and dense urban development has increasingly led to the phenomenon of urban heat islands, which in turn contribute to the deteriorating air quality and thermal discomfort in outdoor urban public spaces. In hot arid countries, changes in the characteristics of the urban microclimate are observed due to dense urbanization, high-rise buildings, and industrialization of the building processes and materials, leading to a reduction in thermal comfort in outdoor and indoor spaces. This research highlights the potential of adopting Computational Fluid Dynamics (CFD) as a simulation technique to investigate the complex fluid flow patterns in urban thermal environments, and investigates methods intended to prolong thermal comfort in public places. It discusses the advantages and limitations of CFD tools and the procedural guidelines for conducting CFD simulation. This paper also gives examples of case studies of CFD assessment for indoor and outdoor urban environments, and the practical use of RANS solver in comparison with LES, DES, and DNS models. Finally the paper highlights a case study of a CFD simulation using a RANS turbulence model of an urban street in the hot arid city of Madinah, Saudi Arabia.

Journal of Applied Materials and Technology

Modern Power Distribution Networks (MPDNs) are no longer passive because Distributed Generations ... more Modern Power Distribution Networks (MPDNs) are no longer passive because Distributed Generations (DGs) are integrated with them to enhance system reliability and power quality. For this reason, load modeling has to be updated to capture the new dynamics of active DNs. This paper presents a composite load modeling for a grid-connected photovoltaic (PV) distribution network using the Levenberg-Marquardt algorithm in the deep learning feed-forward neural network approach. Load modeling is constructing a relationship between input excitation(s) and output response(s); it can be used for simulation studies, stability analysis, and control/protection design. A grid-connected PV distribution network was modeled in Matlab/Simulink and generates data for training and model estimation. The estimated model was tested and validated using a laboratory experimental test bed. Results of the model exhibit a good fitness of 99.8% and 97.2% in active and reactive power models respectively during tra...

Emerging Advances in Integrated Technology, 2020

Load modeling plays a significant impact in assessing power system stability margin, control, and... more Load modeling plays a significant impact in assessing power system stability margin, control, and protection. Frequency in the power system is desired to be kept constant, but in a real sense, it is not constant as loads continually change with time. In much literature, frequency dynamics are ignored in the formulation of load models for the basic assumption that it does not affect the models. In this paper, the composite load model was formulated with Voltage-Frequency Dependency (V-FD) on real and reactive powers and applied to estimate the load model. 2- Area network 4- machines Kundur test network was used for testing the developed model. The model was trained with measurements from a low voltage distribution network supplying the Electrical Engineering department at Ahmadu Bello University, Zaria. Both training and testing data were captured under normal system operation (dynamics). To evaluate the V-FD model performance, Voltage-Dependent (VD) model was examined on the same me...

Journal of Applied Materials and Technology, 2020

Power system operation and control required models of generators, lines and loads to be accuratel... more Power system operation and control required models of generators, lines and loads to be accurately estimated, this is to enable operators make a reliable decision on the system. Generators and lines models are so far considered accurate, while load models are considered perplexing due to invention of new types of loads, distribution system are transforming from passive to active. Future distribution systems are desired to be smart and for a network to be smart the system as to be fully and accurately represented. Penetration of renewable energy and application of power electronic devices as well as participation of active customers in distribution systems make traditional methods of load modeling absolute. Accurate load modeling is required to address the new challenges evolving in the task of power system operation, control and stability studies. It is also an interest of power system researchers globally to realize Smart Networks (SNs), in which accurate load models are required....

Asian Journal of Advanced Research and Reports, 2019

Background: Tobacco smoking is one source of heavy metals exposure in the general population. Tob... more Background: Tobacco smoking is one source of heavy metals exposure in the general population. Tobacco smoke has toxic, genotoxic, and carcinogenic properties and has been linked to fatal pregnancy outcomes. Aim: This research was carried out to investigate the concentration of Copper (Cu), lead (Pb) and Zinc (Zn) in different cigarette brands sold in Keffi main market of Nasarawa state and compare with recommended standard. Study Design: To determine the presence of heavy metals in different brands of cigarette sold in Keffi main Market, Nasarawa State, Nigeria and compare them with relevant authorities’ standard. Place and Duration: The study was carried out in the department of physics, Nasarawa State University, Keffi, Nasarawa State, Nigeria between March 2018 and November, 2018. Materials and Methods: Ten brands of cigarette were purchased from Keffi main central market using random sampling. The cigarettes were expose to sun light for 3 hours until they became dry. The filters...

International Conference on Emerging Applications and Technologies for Industry 4.0 (EATI’2020), 2021

Unmanned Aerial vehicle (UAV) systems have an insufficient amount of onboard energy which is bein... more Unmanned Aerial vehicle (UAV) systems have an insufficient amount of onboard energy which is being shared for mobility, transmission, data processing, control and payload related applications. Different energy sources have been investigated and applied to solve unmanned aerial vehicle energy limitations. These energy sources were either used as single sources or hybrid for the reason of UAV weight budget or miniaturization. To achieve the aforementioned designed criteria, researchers around the globe are continuously investigating different energy sources and hybridization techniques while others focus on the Energy Management System (EMS) such to achieve optimal energy sources utilization. Such energy sources and supplying techniques are battery swapping, wireless Power Transfer (WPT), tethering methods, Fuel Cells (FC), and SuperCapacitors (SC). While, the hybridization technique is based on the combination of single energy source with either renewable energy sources, Internal Combustion Engine (ICE) to save fuel or WPT. Example of such hybridization techniques are solar and battery storage, Fuel Cell (FC) and Battery Storage (BS) etc. This article presents an in-depth review of UAV energy sources, hybridization techniques and EMS. Their challenges and methods adopted by researchers to mitigate such UAV energy challenges.

Journal of Applied Materials and Technology, 2020

Solid-State Transformer (SST), a power electronics based transformer is an emerging technology in... more Solid-State Transformer (SST), a power electronics based transformer is an emerging technology in electric power system. The transformer is being investigated to completely replace existing Line/Low Frequency Transformer (LFT). SST is composed of either of the two topologies: AC-DC-AC, two steps approach; or AC-AC, single-step approach. The two steps approach consists of three stages: AC-DC; DC-DC; and DC-AC stages. The DC-DC stage is made up of a boost DC-DC converter, a DC-AC inverter and a High Frequency Transformer, HFT. Therefore, SST performs the tasks of LFT by means of power electronic converters and HFT. The main essence of SST is to provide solution to the problem of bulkiness and heaviness of the LFT in the power distribution network. This is with the view to providing reduction in construction cost, cost of maintenance and transportation. The power electronics transformer provides numerous advantages which are grouped into: The transformer has high power density; it fun...

Asian Journal of Research and Reviews in Physics, 2019

In this study, an investigation of radiofrequency power density distribution around GSM mast in K... more In this study, an investigation of radiofrequency power density distribution around GSM mast in Keffi town, Nigeria was determined. Radiofrequency meter (Electrosmog ED- 155A) was used to measure the EM radiation at 50, 70, 90,110, 130, 150, 170, and 190 m away from mobile base stations. A total of fifteen mobile base stations were randomly selected in Keffi town covering about four network providers (MTN, Globacom, Etisalat, and Airtel), according to their proximity to buildings, number of antennas mounted on their masts, how close they are to other base stations and the population density around them.The result reveal that MBS5 was found to have the highest value of average power density compared to that of the remainder, with a contribution of about 16% (2908.38 µW/m2). The least contribution was recorded in MBS3 with only about 1% (173.71 μW/m2). The other MBS with significant contribution are MBS6 (15%), MBS11 (15%), MBS10 (13%), MBS8 (13%) and MBS13 (11%) with average power de...

Immunology, 2019

Mature T helper (Th) effector cells originate following antigen recognition by naive T precursors... more Mature T helper (Th) effector cells originate following antigen recognition by naive T precursors. The maturation process is accompanied by the acquisition of specific effector functions that distinguish at least three different T helper subsets: Th1, Th2 and Th17. In general, maturation of somatic cells is accompanied by terminal differentiation. However, accumulating evidence shows that effector T cells retain a certain degree of plasticity. This is especially true for Th17 cells, which have been shown to converge towards other phenotypes in response to specific microenvironmental pressure. In this review we will discuss the experimental evidence that supports the hypothesis of Th17 plasticity, with particular emphasis on the generation of Th17-derived 'non-classic' Th1 cells, and the molecular networks that control it. Moreover, we will consider why Th17 plasticity is important for host protection, but also why it can have pathogenic functions during chronic inflammation. Regarding the last point, we will discuss a possible role for biological drugs in the control of Th17 plasticity and disease course.