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Modeling, Steady-State Analysis of a SEPIC dc-dc Converter Based on Switching Function and Harmonic Balance Technique

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Journal of Power and Energy Engineering 2014年第4期2卷 704-711页

作者： Ajayi Samuel taiwo joseph Yakubu Oricha Electrical and Computer Engineering Department Ahmadu Bello University Zaria Nigeria

The paper presents modeling approach of a Single Ended Primary Inductance Converter (SEPIC) system. The complete model derivation of the SEPIC converter system has been presented in different modes of operation. Steady state and small signal analysis was carried out on the converter dynamic equations using the method of Harmonic balance Technique. The steady state variables and their respective ripple quantities obtained were plotted against duty ratio D. The results obtained for a supply input voltage of 60 volts to the converter at a duty ratio of D = 0.8 , compares well with simulation results.

关键词： SEPIC Converter Switching Function Harmonic Balance Technique

A Solar Energy System Design for Green Hydrogen Production in South-Western Nigeria, Lagos State, Using HOMER & ASPEN

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Open Journal of Optimization 2023年第2期12卷 72-97页

作者： Wilson Fidelis Ekpotu joseph taiwo Akintola Martins Chineme Obialor Philemon Chukwuebuka Udom Department of Chemical & Petroleum Engineering University of Uyo Akwa Ibom Nigeria Department of Research & Development Vitapur Nigeria Limited Lagos Nigeria Department of Chemical Engineering Federal University of Owerri Owerri Nigeria

Solar system design for green hydrogen production has become the most prominent renewable energy research area, and this has also actively fueled the desire to achieve net-zero emissions. Hydrogen is a promising energy carrier because it possesses more energy capacity than fossil fuels and the abundant nature of renewable energy systems can be utilized for green hydrogen production. However, the design of an optimized electrical energy system required for hydrogen production is crucial. Solar energy is indeed beneficial for green hydrogen production and this research designed, discussed, and provided high-level research on HOMER design for green hydrogen production and deployed the energy requirement with ASPEN Plus to optimize the energy system, while also incorporating fuzzy logic and PID control approaches. In addition, a promising technology with a high potential for renewable hydrogen energy is the proton exchange membrane (PEM) electrolyzer. Since its cathode (hydrogen electrode) may be operated over a wide range of pressure, a control process must be added to the system in order for it to work dynamically efficiently. This system can be characterized as an analogous circuit that consists of a resistor, capacitor, and reversible voltage. As a result, this research work also explores the Fuzzy-PID control of the PEM electrolysis system. Both the PID and Fuzzy Logic control systems were simulated using the control simulation program Matlab R2018a, which makes use of Matlab script files and the Simulink environment. Based on the circuit diagram, a transfer function that represents the mathematical model of the plant was created, and the PEM electrolysis control system is determined to be highly significant and applicable to the two control systems. The PI controller, however, has a 30.8% overshoot deficit, but when the fuzzy control system is compared to the PID controller, it is found that the fuzzy control system achieves stability more quickly, demonstrating i

关键词： Homer Solar Design Solar Energy Renewable Energy Green Hydrogen Production Fuzzy Logic HOMER

Variability and Trends of Daily Heavy Rainfall Events over Niger River Basin Development Authority Area in Nigeria

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American Journal of Climate Change 2014年第1期3卷 1-7页

作者： joseph Sunday Babatolu Rufus Temidayo Akinnubi Akintade taiwo Folagimi Omosuyi Oluwayemisi Bukola Department of Agricultural Science Adeyemi College of Education Ondo Nigeria Department of Geography Adeyemi College of Education Ondo Nigeria Department of Physics Adeyemi College of Education Ondo Nigeria

Using 70 years of daily rainfall records in eight stations, an analysis of variability and trends of daily heavy rainfall events over Niger River Basin Development Authority Area was carried out by using Standardized Anomaly Index and Spearman Rank Correlation Coefficient. Significant temporal variability on interannual and decadal time-scales was observed in the frequency of heavy rainfall events and annual heavy rainfall amount. Both the annual heavy rainfall amount and frequency of heavy rainfall events demonstrated no pronounced temporal decreasing or increasing trend. However, more recent data records from 1981 onwards revealed an increasing trend. Thus, evidence of a temporal change is apparent in heavy rainfall events in the last three decades in sympathy with global warming.

关键词： Rainfall Anomalies River Niger Basin Development Authority Area

Cryptococcal Antigenaemia among Treatment-Naïve Adult HIV-Infected Nigerian Patients

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World Journal of AIDS 2016年第1期6卷 1-7页

作者： taiwo Modupe Balogun Mbang Okokon Faleye Dasola Esuola joseph Oyetubosun Adewolu Abimbola Basil Bonaventure Antiretroviral Therapy Clinic Haematology Department Lagos State University Teaching Hospital Lagos Nigeria

Background: There is a high burden of HIV-related cryptococcal meningitis in Sub-Saharan Africa and it is a leading cause of morbidity and early mortality among severely immunocompromised patients. Objectives of the Study: This study was carried out to determine the prevalence of cryptococcal antigen (CrAg) and the relationship of positivity to CD4+ve T cell counts and WHO clinical stage among severely immunocompromised treatment naive adult HIV-infected Nigerian patients. Methods: This was a hospital based cross sectional and prospective study carried out among newly diagnosed and confirmed HIV infected patients. Bio data of consenting consecutive subjects was collected by the attending physician using structured questionnaire. Rapid point of care lateral flow assay kits (IMMY, USA) was used to screen plasma samples from subjects strictly following manufacturer’s instructions. Data were analysed with statistical package for social sciences (spss 15.0) software. Results were presented in simple tables with frequencies and percentages while statistical significance was taken to be p value ≤ 0.05. Results: Of 432 subjects, there were 184 (42.6%) males and 248 (57.4%) females in the study. The median CD4 count of the subjects was 74 (range 6 - 1264) cells/ul. Seven (1.6%) of the subjects were positive for cryptococcal antigen (CrAg) and all were females (100%). Six (85.7%) of CrAg positives had CD4+ T cell count less than 100 cells, while 1 (14.3%) had count above 200cells/ul. The WHO clinical stage of studied patients was;stage I 163 (37.7%), stage II 132 (30.6%) stage III 95 (22.0%) and stage IV 42 (9.7%). Among the CrAg positive subjects, 3 (42.9%) were in WHO clinical stage l while 4 (57.1%) were in stage II disease. Conclusion: The observed overall prevalence of CrAg positivity among studied patients was low but occurred most frequently among the severely immunocompromised subjects. Advancement in WHO clinical stage was not a predicting risk factor for cryptococca

关键词： HIV Cryptococcal Antigen Infected Adults Nigeria

Potentials of Arbuscular Mycorrhiza Fungus in Tolerating Drought in Maize (<i>Zea mays</i>L.)

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American Journal of Plant Sciences 2014年第6期5卷 779-786页

作者： Odunayo joseph Olawuyi Adegboyega Christopher Odebode Busayo Joshua Babalola Ezekiel taiwo Afolayan Chidinma Pauline Onu Biology Department Federal College of Education Abeokuta Abeokuta Nigeria Department of Biosciences and Biotechnology Babcock University Ilisan-Remo Lagos Nigeria Department of Botany University of Ibadan Ibadan Nigeria

Maize is one of the most important cereal crops widely grown for food, feed, and fodder/forage throughout the world in a range of agroecological environments. Drought stress continues to haunt the maize farmers across south western part of Nigeria, thereby leading to low quantity of this essential staple food in the market. Efforts have been made to enhance the growths and yields in maize by investigating the influence of Arbuscular mycorrhizal fungus (Gigaspora gigantea) on the tolerance of maize to drought stress. The experiment was conducted in the teaching and research farm of Babcock University, Ilishan-Remo, Nigeria. The experiment was laid out in a complete randomized design with four replicates. Data were collected on eight morphological drought related characters. The objective of this research work was to evaluate the morpho-agronomic responses and potential of Gigaspora gigantea colonization in maize drought tolerance, and also to select parents in maize breeding for improved yield related components. The combined analysis of variance showed significant (P 0.05) treatment effect on majority of the traits evaluated. The treatments of Arbuscular Mycorrhiza Fungus (AMF) produced significant higher growth related traits suggesting that AMF treated plants had higher potential in influencing the tolerance to drought. Accession 3 was considered best for most of the traits studied and can be selected as parents in maize breeding for yield related components.

关键词： Maize Gigaspora gigantea Drought Stress Tolerance Growth Yields

Application of Geophysical Methods to Building Foundation Studies

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International Journal of Geosciences 2013年第9期4卷 1256-1266页

作者： Folahan Peter Ibitoye Felix Vincent Ipinmoroti Mudasiru Salami Kunle joseph Akinluwade Adeyinka Taofeek taiwo Adelana Rasaki Adetunji 1Department of Applied Geophysics Federal University of Technology Akure Nigeria 2Prototype Engineering Development Institute National Agency for Science and Engineering Infrastructure (NASENI) Ilesa Nigeria 1Prototype Engineering Development Institute National Agency for Science and Engineering Infrastructure (NASENI) Ilesa Nigeria 2Department of Materials Science and Engineering African University of Science and Technology (AUST) Abuja Nigeria 1Prototype Engineering Development Institute National Agency for Science and Engineering Infrastructure (NASENI) Ilesa Nigeria 2Department of Materials Science and Engineering Obafemi Awolowo University Ile-Ife Nigeria Prototype Engineering Development Institute National Agency for Science and Engineering Infrastructure (NASENI) Ilesa Nigeria

A geophysical survey involving the electrical resistivity method utilizing the Vertical Electrical Sounding (VES) and Electrical Imaging Techniques was conducted around the premises of an area within south-western Nigeria with the aim of studying structural defects which may be responsible for future problems and characterizing the soil conditions of the site. A total of 15 VES stations were occupied using Schlumberger Configuration with AB/2 varying from 1 to 65 m. In the electrical imaging, dipole-dipole array was adopted and the two traverses were occupied in the S-N and E-W directions close to where wall cracks and subsurface problems were manifested. Five main geoelectric sequences were delineated within the study area;these include the topsoil (clay and sandy clay), lateritic clay, weathered bedrock (clay, sandy clay and clayey sand), fractured bedrock and fresh basement. A major discontinuity (fracture zone) was discovered along the S-N direction, while a weak zone was also discovered along E-W direction. The result of this research has shown that the causes of the cracks and distress on the walls within the site may have been influenced by the differential settlement resulting from the incompetent subsoil materials and the fractured bedrock on which the foundation of the building was laid.

关键词： Foundation Bedrock Basement Cracks Subsurface Instability

Abnormal Uterine Bleeding due to Retention of Fetal Bones after Abortion: A Case Report

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Open Journal of Obstetrics and Gynecology 2023年第11期13卷 1881-1885页

作者： Okafor Love Chimezirim Ogoke Nwakamma Chisom William Oladiran taiwo Simon joseph Adagadzu Kingsley Iyoko Iseko Aminyene Essien Meraiyebu Department of Obstetrics and Gynaecology The Limi Hospital Abuja Nigeria Department of Anaesthesia The Limi Hospital Abuja Nigeria Department of Radiology The Limi Hospital Abuja Nigeria

Background: Retention of fetal bones is a rare cause of abnormal uterine bleeding. Others may present as subfertility, chronic pelvic pain, abnormal vaginal discharge, menometrorrhagia, dysmenorrhea and spontaneous expulsion of bony fragments. Incidence is 0.26% among patients undergoing hysteroscopy. Aim: To document a pattern of presentation of retained fetal bone and its management. Case Presentation: Our patient is an 18-year old who presented with vaginal bleeding of four weeks duration and managed for abnormal uterine bleeding due to retained fetal bone following second trimester abortion. Conclusion: The use of transvaginal ultrasound in making diagnosis of retained fetal bone is effective. Treatment by removal of bones through evacuation by dilatation and curettage or hysteroscopy brings about resolution of symptoms. Use of pelvic ultrasonography to confirm complete evacuation of the uterus after abortion especially second trimester abortion could aid in early diagnosis and management of incomplete abortion.

关键词： Abnormal Uterine Bleeding Retained Fetal Bones Abortion Transvaginal Ultrasound Dilatation and Curettage Hysteroscopy

Numerical Optimization of Sand Casting Parameters Using the Dantzig’s Simplex Method

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Journal of Minerals and Materials Characterization and Engineering 2013年第5期1卷 250-256页

作者： John Ogheneortega Oji Simon Godenaan Datau Kunle joseph Akinluwade Adeyinka Taofeek taiwo Dayo Adeyemi Isadare Sunday Hendrix Pamtoks Adelana Rasaki Adetunji Department of Materials Science & Engineering Obafemi Awolowo University Ile-Ife Nigeria Department of Materials Science and Engineering African University of Science and Technology Abuja Nigeria Department of Mechanical Engineering Federal Polytechnic Bauchi Nigeria Prototype Engineering Development Institute (PEDI) Ilesa Nigeria

This study adopts the Dantzig’s Simplex method to investigate optimization of sand casting parameters for optimum service performance. Some process variables and mechanical properties were adapted into the Simplex method. Aluminium alloy samples were cast, machined and subjected to a series of mechanical tests. From the body of data collected, linear functions and constraint equations were formulated and employed in the Dantzig’s Simplex method for optimization of process parameters. The results showed that the Simplex method can be adapted for studying performance opti- mization of castings.

关键词： Sand Casting Dantzig’s Simplex Method Optimization Constraint Equations Aluminium Alloy

Light and Electron Microscopy Studies of the Visible Diffusion Zone of Mild Steel Pack Cyanided in Processed Cassava Leaves

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材料科学与工程（中英文B版） 2013年第9期3卷 567-570页

作者： Akinluwade Kunle joseph Adelana Rasaki Adetunji Mosobalaje Adeoye Lasisi Ejibunu Umoru Adeyinka Taofeek taiwo Peter Kalu Azeez Rommly Dayo Adeyemi Isadare Winston Wole Soboyejo Olusegun Oyeleke Adewoye Prototype Engineering Development Institute National Agency for Science and Engineering Infrastructure (NASENI) llesa233036 Nigeria Department of Materials Science and Engineering African University of Science and Technology Abuja 900108 Nigeria Department of Chemical Materials and Biomolecular Engineering University of Connecticut Farmington CT 06032 USA Department of Materials Science and Engineering Obafemi Awolowo University lle-lfe 220282 Nigeria Department of Mechanical Engineering Florida Agricultural and Mechanical Engineering University Florida 34420 USA

This study investigates the microstructure of the visible diffusion zone formed in low carbon steel pack cyanided using processed cassava leaves. Standard parts machined from low carbon steel were pack cyanided by high temperature in-situ diffusion of nascent carbon and nitrogen into austenite. Formation of a visible diffusion zone was confirmed after observation with a Reichert-Jung Polyval optical microscope coupled with Zeiss AxioCam ICc 1 camera. High magnification Scanning Electron Microscope (SEM) imaging of the visible diffusion zone was done with a CamScan Series 2 scanning electron microscope. The zone was found variable in depth as measured from a representative position. The structure of all samples consists of ferrite and pearlite as determined by optical and SEM examination. Resulting products were thus both tough and hard suitable for service environments requiring high resistance to both wear and impact failure.

关键词：扫描电子显微镜光学显微镜木薯叶扩散加工氰化低碳钢包