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6TH INAUGURAL LECTURE RADIATION RAIN, RUIN BUT REIGN, -MAN IN THE RING
(Federal University of Petroleum Resources, Effurun, 2024-09-05) Agbalagba,E.O
Physics is a branch of science concerned with the nature and properties of matter and energy. It has several branches. It is declined as the science that deals with the structure of matter and the interactions between the fundamental constituents of the observable universe (Einstein's 1926 Britannica essay on space-time). It dwells more in the course of this lecture on Radiation Physics, as it affects and relates to the environment, human health, and radiation protection. The term "radiation" can be defined as the energy that is emitted as electromagnetic waves or particles and travels through the atmosphere or a material medium. Radiation is felt when we work in the field on a sunlit day, or when we stay by the fireside. Radiation is energy that moves from one place to another in a form that can be described as waves or particles. The word "radiation" arises from the phenomenon of waves radiating (i.e., traveling outward in all directions) from a source. This aspect leads to a system of measurements and physical units that apply to all types of radiation. Radiation is a natural phenomenon of emission of energy in the form of electromagnetic that obeys Pauli's exclusive principle, travels through space or medium, and impacts man and the environment. Radiation is always around us all the time, and as such, man is constantly exposed to it. This exposure has influenced our survival, reproduction, and evolution.
A Comparative Analysis Performance of Data Augmentation on Age-Invariant Face Recognition Using Pretrained Residual Neural Network
(Journal of Theoretical and Applied Information Technology, 2021) ABERE, REUBEN; OKOKPUJIE, KENNEDY; OFOCHE, JOYCE C.; BIOBELEMOYE, BASUO J.; OKOKPUJIE, IMHADE PRINCESS
There has been an immense improvement in face recognition research. Unfortunately, the accuracy of face recognition systems recognizing the same person over time due to ageing is open research. Minor geometric changes in the face that occur due to ageing contribute to face recognition systems' inaccuracy. Researchers, over subsequent years, have come up with methods to improve the performance of Age Invariant Face Recognition (AIFR) systems, the most recent one being the use of Convolutional Neural Network (CNN) to create face recognition models. The pre-trained residual network (ResNet) is trained and tested using a heterogeneous database to actualize this improvement. The heterogeneous database consists of images from 82 Caucasian subjects in the FG-Net database and 11 African subjects. These obtained images were augmented using geometric transformation and Noise to increase the amount of data for training. Afterwards, a model robust is developed. The Sliding Window framework was used to detect the faces fed into CNN for training and testing. After getting the results from our classification model, an analysis was carried out on the classification models of both the original dataset and augmented datasets. It was observed that the model performed remarkably with the noise-injected dataset and performed worst with the geometric transformation database.
A Contingent Claim Approach to Bank Valuation
(Scientific Research Publishing, 2014) Okedoye, Michael Akindele; Owoloko, Enahoro Alfred; Omoregbe, Nicholas Amienwan
In this paper, the model formulated incorporated stochastic variables such as bank loans and deposits as well as some deterministic variables: cash available, depreciation, capital expenditure, tax and costs, comprising variable costs and fixed costs. This paper assumes that the dynamics of bank loans and deposits at time t follow a geometric Brownian motion, therefore, it satisfies certain stochastic differential equations (SDEs) formulated on some probability space. On the other hand, the growth rate μL(t) in loan at time t, growth rate μD(t) in deposit at time t, and the variable cost η(t) at time t are assumed to be driven by mean-reverting Ornstein-Uhlenbeck processes. The SDEs of the dynamics of bank loans, growth rate in loans, bank deposits, growth rate in deposits and variable cost arising from the model were solved by means of the ItÔ Lemma. Discrete time approximations of the exact solutions of the SDEs were derived and used in a Monte Carlos simulation software.
An Assessment of the Contribution of Municipal Solid Waste Dump Sites Fire to Atmospheric Pollution
(Scientific Research Publishing(SCIRP), 2014) Rim-Rukeh Akpofure
Municipal solid waste open dump site operation is an important element of waste management in Nigeria, both today and in the future. Dump site fires are common occurrences in the study area. The contribution of municipal solid waste dump site fires to atmospheric pollution in the Niger Delta, Nigeria has been assessed experimentally. Five (5) municipal solid waste dump sites where fire incidence is a frequent and regular occurrence were chosen for the study. At each of the identified municipal solid waste dump site, eight (8) air quality monitoring parameters, suspended particulate matter (SPM10), nitrogen dioxide (NO2), carbon dioxide (CO2), carbon monoxide (CO), sulphur dioxide (SO2), methane (CH4), ammonia (NH3) and Hydrogen sulphide (H2S) were determined using a series of hand held air quality monitoring equipment. Results indicate the levels of SPM ranged between 773 and 801 µg/m3 and the levels of CO ranged between 133.7 and 141.6 ppm. The levels of CO2 ranged between 401 ppm and 404.5 ppm while that of NO2 ranged between 21.0 ppm and 27.3 ppm. The levels of SO2 ranged between 27.7 ppm and 37.1 ppm while that of NH3 ranged from 14.7 to 19.5 ppm. The levels of methane in the study area ranged between 2310 ppm and 2771 ppm and within the vicinity of dump site fires H2S concentration ranges from 3.4 to 7.7 ppm. Levels of SPM, CO, CO2, and CH4 within the vicinity of the dump site fires were above regulatory limits. Dump site fires in the study area could threaten the health of anyone especially the dump site workers that are regularly exposed to the thick smoke and can be implicated in climate change debate. There is a need to develop better practices with regard to municipal solid waste open dump site operation and emission control.
Analyzing the Impact of Heat and Mass Transfer on Unsteady MHD Flow with Thermal Radiation and Binary Chemical Reaction
(European Journal of Theoretical and Applied Science, 2024) Okedoye, Akindele M.; Ometan, Sunday O.; Alabi, Mathew O.
In this paper, we investigate the combined effects of heat and mass transfer on unsteady oscillatory magnetohydrodynamic (MHD) flow with thermal radiation and binary chemical reaction. The governing equations of the flow field, energy equation, and species concentration equation are derived under the assumptions of incompressible flow, uniform magnetic field, and small amplitude oscillations. The influence of thermal radiation and chemical reaction is incorporated through appropriate boundary conditions. Mathematical formulations are presented for the coupled system of equations, and numerical simulations are conducted to analyze the heat and mass transfer characteristics of the flow. Sensitivity analysis of the governing parameters were conducted and presented through graphs and discussed. The results provide insights into the complex interplay between fluid dynamics, thermal radiation, and chemical reaction in MHD systems and their implications for engineering applications.
Application of the Taylor Series Technique to the Solution of Bratu Problems
(FNAS Journal of Mathematical Modeling and Numerical Simulation, 2025) Otaide, I.J; Ugbene I.J.
This study presents a numerical solution of the Bratu differential equations (BDE) using Taylor’s series technique. The effectiveness and reliability of the proposed method were further demonstrated by two numerical examples. The outcomes were also compared to other previously published research. Our suggested approach outperforms the Salem and Thanoon (2022) method in terms of approximating the exact solution. The Maple 18 software was used to perform the computations
Assessment of Asymmetric Mangrove Restoration Trials in Ogoniland, Niger Delta, Nigeria: Lessons for Future Intervention
(Ecological Restoration, 2016) Nenibarini Zabbey; Franklin B.G. Tanee
Mangrove restoration has been undertaken with varying degrees of success in many tropical and subtropical marine shorelines around the globe. However, mangrove reforestation in the Niger Delta, Africa’s largest delta and mangrove belt is, at best, rudimentary. Here, we present floristic results on two opportunistic artificial mangrove regeneration case studies aimed at restoring mangrove swamps damaged by oil pollution (Bodo Creek) and colonized by invasive Nypa fruticans (nypa palm) (Kono Creek) in Ogoniland, eastern Niger Delta, Nigeria. Nursery raised seedlings of the delta’s dominant Rhizophora racemosa were planted 1 m apart in zigzag fashion at both locations. Planting at the oil-polluted site was preceded by soil quality investigation and bio-stimulation with fertilizer, whereas at Kono Creek, there was no addition of fertilizer before and after planting. A 3-year post planting evaluation of survival rate, growth, and girth parameters showed better performance of mangroves at the Bodo Creek restoration than at the Kono Creek restoration, with survival rates of 72% and 12%, respectively. In sharp contrast to the Bodo Creek restoration, few stands of the planted mangroves at the Kono Creek restoration had started producing propagules. Investigations of soil quality, and where necessary, followed by remedial treatment, particularly augmenting key nutrients, are critical precursors of successful artificial mangrove regeneration.
Assessment of Rainwater Quality in Warri and Environ, Southern Nigeria for Domestic Purposes
(Journal of Geoscience and Environment Protection,12, 2024-06-28) Agbozu,I.E, Maminor,T.R and Bassey,U (2024)
The study aimed to assess the physiochemical characteristics of rainwater in Warri and its environment was investigated. Pb, Zn, Cd, Cu, and Cr concentrations in rainwater from the roof and non-roof sources were determined using Atomic Absorption Spectrophotometry. Three geospatial locations comprising Jakpa, Udu, and Ubeji were selected based on prevailing anthropogenic activities. The rainwater samples were systematically collected from the (aluminum) roof and non-roof sources for the months of April, June, August, and October 2022, treated and analyzed in the laboratory for sixteen physicochemical parameters. Results were statistically analyzed using ANOVA, and T-test for the determination of the level of relationships and variations across geospatial locations. Significant correlations (r = 0.72) exist between Cr in rainwater from the roof and non-roof sources. Implying point-source contaminations and may be emanating from the influence of roof materials. Furthermore, high concentrations of Cd and Pb in roof source above WHO standards were mostly in Jakpa and Ubeji. The calculated Health Risk Index (HRI) for children and adults is greater than 1. The results showed that most samples from the locations are considered not safe (HRI > 1) especially for Cd, which means that there are potential health risks in consuming rainwater from Jakpa, Udu and Ubeji. Therefore, there is a need for a prompt sensitization program to dissuade people from directly drinking rainwater from these locations.
Assessment of rainwater quality in Warri and environ, Southern Nigeria for domestic purposes
(Journal of Geoscience and Environment Protection, 2024-06-28) Agbozu, I.E, Maminor, T.R & Bassey, U.
The study aimed to assess the physicochemical characteristics of rainwater in Warri and its environment. Pb, Zn, Cd, Cu, and Cr concentrations in rainwater from the roof and non-roof sources were determined using Atomic Absorption Spectrophotometry. Three geospatial locations comprising Jakpa, Udu, and Ubeji were selected based on prevailing anthropogenic activities. The rainwater samples were systematically collected from (aluminum) roof and non-roof sources for the months of April, June, August, and October 2022, treated and analyzed in the laboratory for sixteen physicochemical parameters. Results were statistically analyzed using ANOVA, and T-test for the determination of the level of relationships and variations across geospatial locations. Significant correlations (r = 0.72) exist between Cr in rainwater from the roof and non-roof sources. Implying point-source contaminations and may be emanating from the influence of roof materials. Furthermore, high concentrations of Cd and Pb in roof sources above WHO standards were mostly in Jakpa and Ubeji. Calculated Health Risk Index (HRI) for children and adults is greater than 1. The results showed that most samples from the locations are considered not safe (HRI > 1) especially for Cd, which means that there are potential health risks consuming rainwater from Jakpa, Udu and Ubeji. Therefore, there is a need for prompt sensitization program to dissuade people from directly drinking rainwater from these locations
Assessment of Solid Mineral to Soil Radioactivity Contamination Index in selected Mining Sites and their Radiological Risk Indices to the Public
(International Journal of Environmental Analytical Chemistry ·, 2021-06-11) Agbalagba,E.O; Chaanda,M.S.; Egarievwe,S.U
This study examined the radioactivity levels of soil samples within selected solid mining sites in Nigeria using high purity germanium (HpGe) detector. Sixty soil samples in all were collected from the ten solid mineral mining sites investigated and six samples were collected as control samples from non-mining environment for analyses. The results of the activity concentration values obtained for 40K, 226Ra and 232Th are 100.22 Bq kg-1, 33.15 Bq kg- 1 and 77.31 Bq kg-1 respectively. The 226Ra and 40K activities were found to be within the United Nation Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) acceptable permissible limit, but the 232 Th mean value was above the permissible limit of 30 Bq kg-1 for the public. In comparison, 40K, 226Ra and 232 Th soil samples 20 mean activity concentrations were higher than the control soil samples values by 48.6%, 43.7% and 62.3% respectively. The results of estimated radiation hazard indices indicate average values of 150.72 Bq kg-1 68.40η
BEHeDaS: A Blockchain Electronic Health Data System for Secure Medical Records Exchange
(Journal of Computing Theories and Application, 2024) Abere, Reuben Akporube et. al.
Blockchain platforms propagate into every facet, including managing medical services with professional and patient-centered applications. With its sensitive nature, record privacy has become imminent with medical services for patient diagnosis and treatments. The nature of medical records has continued to necessitate their availability, reachability, accessibility, security, mobility, and confidentiality. Challenges to these include authorized transfer of patient records on referral, security across platforms, content diversity, platform interoperability, etc. These, are today – demystified with blockchain-based apps, which proffers platform/application services to achieve data features associated with the nature of the records. We use a permissioned-blockchain for healthcare record management. Our choice of permission mode with a hyper-fabric ledger that uses a world-state on a peer-to-peer chain – is that its smart contracts do not require a complex algorithm to yield controlled transparency for users. Its actors include patients, practitioners, and health-related officers as users to create, retrieve, and store patient medical records and aid interoperability. With a population of 500, the system yields a transaction (query and https) response time of 0.56 seconds and 0.42 seconds, respectively. To cater to platform scalability and accessibility, the system yielded 0.78 seconds and 063 seconds, respectively, for 2500 users.
Biodegradation Potential of Oil-based Drill Cuttings Encapsulated with Cement in the Soil Environment
(Journal of Applied Sciences and Environmental Management (JASEM), 2011-12) Rim-Rukeh Akpofure
Biodegradation potential of slabs made from oil-based drill cuttings encapsulated with cement in a soil environment has been experimentally investigated. Results of soil analyses show that physico-chemical and biological characteristics of the soil environment as; pH (5.6 – 3.9), temperature (27.7 – 39.5 oC), redox potential (-114mV – (-80mV), total organic carbon (12.7% - 7.3%), sulphate (0.7 – 0.2mg/l), nitrate (6.7 – 2.2mg/l), moisture content (82-89%) and total microbial count (105 – 1013 cfu/g). Experimental results shows a mass loss of oil base drill cuttings encapsulated with cement slab during the period of the study, indicating approximate linear relationship between mass loss and time. When the log of mass-loss is plotted against time, an approximate linear relationship is obtained confirming a first-order chemical reaction for the biodegradation process. Results of the analyses of the soil sample indicate an environment that has the potential to degrade cement encapsulated oil based drill cuttings.
Consideration of phthalates distribution in underground water in some selected regions in Delta State, Southern Nigeria
(Sciendo, 2020) EDJERE, Oghenekohwiroro; OGWUCHE, Ene Christina; BASSEY, Uwem; RIM-RUKEH, Akpofure
The choice of phthalates as plasticizers have been on the increase especially in household products. They are ubiquitous environmental pollutants due to their physical attribute. This study was carried out to determine the occurrence and level of phthalates in the groundwater in some regions of Delta State. Groundwater samples were collected from fourteen sampling points and analyzed using standard procedures. The obtained results showed that the concentration(µg/l) of six phthalate ester compounds present in the water samples was of the order: < 0.05 - 0.05 BBP, < 0.05 - 3.71BEHP, < 0.05 - 0.54 DBP, < 0.05 - 0.55 DEP, < 0.05 - 0.13 DMP, and < 0.05 - 0.48 DnOP. BEHP was observed to be the major compound of the phthalate acid esters present in most sampling stations, whilst others, especially BBP, were found to be in low concentration and does not pose any immediate threat to human health. The presence of BEHP in most samples from different locations suggests an inflow of the phthalate to underground water, hence it becomes imperative for continuous monitoring and a call to various governments and environmental regulatory agencies to establish standards for phthalate esters in order to monitor its presence in the environment.
DE-RISKING "SEARCH" FOR THE BLACK GOLD: GEOPHYSICS, ANSWER TO QUESTIONS UNKNOWN
(Federal University of Petroleum Resources, Effurun, 2024-11-20) OGAGARUE, D.O.E
"Black Gold" is another word for petroleum. Petroleum is derived from the words petra (rock in Greek) and oleum (oil in Latin). Hence, petroleum is simply rock oil and is more often called crude oil. The word “crude oil” is, however, limiting because crude oil has some natural gas in it when it is produced. For example, a single barrel of crude oil extracted from the earth may contain enough natural gas that can fill our homes. Therefore, in general terms, petroleum refers to crude oil and natural gas. Perhaps the realization of this fact was the reason for the change of name from the Nigerian National Oil Corporation to the Nigerian National Petroleum Corporation in 1977. Petroleum is often called black gold because when crude oil is extracted from the ground, it is mostly black in colour, and because of the oil and gas in it and due to their value, it is often described as gold.
Determination and Risk Associated with Phthalic Esters Distribution from the Ekpan River, Effurun, Delta State, Nigeria
(European Journal of Environment and Earth Sciences (EJ-GEO), 2022-07-28) Oghenekohwiroro Edjere; Daniel Igiegie; Rim-Rukeh Akpofure
Phthalates are additives or plasticizers added to make plastics soft. However, they could leach into the environment and cause harm to human health when contacted. Sites along the Ekpan river have been used for open dumping of refuse. The river also serves as a point source for the disposal of effluents from the Warri Refinery and Petrochemical Company Limited (WRPC). Hence, the need for a preliminary study of phthalates across the river system. Surface water samples were collected from six points along the Ekpan river. Phthalates were extracted using USEPA standard method 3535 and EPA method 8061. Gas Chromatography-Mass Spectrometer (GC-MS) was used for the analysis of six PAEs including di-n-butyl phthalate (DnBP or DPX), butyl benzyl phthalate (BBP), di(2-Ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (D-n-OP)), Dimethyl phthalate (DMP), and Diethyl phthalate (DEP) in the river system. Analysis of phthalates in the Ekpan river system showed that DEP across the Effurun river system ranged from 4.22 – 13.81 μg/L, DPX; 3.03 – 11.5 μg/L, BBP; 0.11–1.39 μg/L, DEHP; 0.12 – 3.33 μg/L. D-n-OP and DMP were below the limit of detection of the analytical instrument used (0.1 μg/L). The distribution of PAEs along the network of the river revealed that the sampling sites in the urban region were more contaminated with PAEs due to urbanization and an increase in population across the river network. Human health risk assessment revealed that the hazard quotient (HQ) for DEP, DPX, DEHP, and D-i-NP were below 1, indicating an acceptable risk of PAEs via ingestion or bathing of the river water. In addition, the Hazard Index (HI) via ingestion and bathing of the river water was less than 1 indicating acceptable risks. According to this study, these PAEs congeners are safe for toddlers, adolescents, and adults to eat and bathe in tap water. Even DEHP, the only PAEs congener designated as a carcinogenic agent by WHO, was shown to have a tolerable cancer risk. These findings indicate that there is no harm to children, adolescents, and adults from DEHP in the river water studied.
Dissipative Non-Slip MHD Nanofluid Flow with Variable Viscousity and Thermal Conductivity in the Presence of Arrhenius Chemical Reaction
(European Journal of Theoretical and Applied Science, 2024) Ogboru, Kelvin O.; Lawal, Muhammad M.; Okedoye, Akindele M.
This research investigates the intricate dynamics of dissipative nonslip magnetohydrodynamic (MHD) nanofluid flow, characterized by variable viscosity and thermal conductivity, under the influence of an Arrhenius chemical reaction. The inclusion of the Arrhenius chemical reaction adds complexity through heat generation or absorption, impacting temperature and concentration gradients. The study is motivated by the extensive applications of nanofluids in engineering and industrial processes, where precise control of heat and mass transfer is critical. We develop a comprehensive mathematical model that incorporates the variable properties of the nanofluid, the effects of the Lorentz force due to the applied magnetic field, and the temperature-dependent reaction rates dictated by the Arrhenius equation. The formulated governing equations were non-dimensionalised to identify the flow governing parameters. Finite Element Method (FEM), grid generation, solution algorithms, and post-processing to analyse velocity, temperature, and concentration distributions were used to obtain the numerical methods to solve fluid flow problems based on the Navier-Stokes equations, involving concepts of discretization. pdsolve subpackage in Maple 2023 was used to numerically solve PDEs with specific initial and boundary conditions, incorporating the plot and display commands for graphical analysis, and the results are presented and discussed. The findings reveal that the interplay between parameters like Hartmann number, Darcy parameter, and heat generation or absorption profoundly influences flow behaviour and thermal characteristics. The reactivity parameter is crucial, dictating the rate of chemical reactions and affecting system dynamics. This research enhances understanding of the interdependencies among fluid properties, chemical reactions, and external parameters in nanofluid flows.
Ecological effects of oil spill on water and sediment from two riverine communities in Warri, Nigeria
(Interantional Journal of Biological & Chemical Sciences., 2017-02-01) OGELEKA, Doris Fovwe; TUDARARO-AHEROBO, Laurelta Esivweneta; OKIEIMEN, Felix Ebodaghe
The ecological effects of oil spill in the environment were studied in Warri riverine areas of Ubeji and Jeddo, Delta State, where an oil spill occurred and cleanup or remediation was not carried out for over a year prior to this evaluation. The American Public Health Association (APHA) and the American Society for Testing and Materials (ASTM) methods were employed for the laboratory test for organics [polyaromatic hydrocarbon; total petroleum hydrocarbon (TPH)] and heavy metals in the water and sediment. The results indicated that there were still significant concentrations (P <0.05) of organics indicating hydrocarbon pollution. Mean concentrations recorded for TPH in Ubeji and Jeddo waters were 23.60 ± 1.18 mg/L and 29.96 ± 0.14 mg/L respectively while total PAHs was 0.009 ± 0.002 mg/L and 0.008 ± 0.001 mg/L. Mean concentrations of TPH in the sediment was 48.83 ± 1.49 ppm and 1093 ± 74 ppm respectively while total PAHs was 0.012 ± 0.002 ppm and 0.026 ± 0.004 ppm. Low concentrations were recorded for most of the heavy metals in the water and sediment. Hydrocarbon degrading bacteria (HDB) recorded mean values of 3.86E + 03 and 3.44E + 02 for Ubeji and Jeddo waters, while Hydrocarbon degrading fungi (HDF) recorded mean values of 2.86E + 03 and 2.46E + 02 respectively. The observed concentrations of hydrocarbons in the study areas should provide the impetus for regulatory surveillance of oil discharged intentionally/unintentionally into the Warri riverine waters and sediment since hydrocarbon released into the environment sorb to the sediment particles where they cause harm to organisms in the sediment and overlying waters.
Ecological effects of oil spill on water and sediment from two riverine communities in Warri, Nigeria
(African Journals Online, 2017-05-29) Ogeleka, Doris Fovwe; Tudararo-Aherobo, Laurelta Esivweneta; Okieimen, Felix Ebodaghe
The ecological effects of oil spill in the environment were studied in Warri riverine areas of Ubeji and Jeddo, Delta State, where an oil spill occurred and cleanup or remediation was not carried out for over a year prior to this evaluation. The American Public Health Association (APHA) and the American Society for Testing and Materials (ASTM) methods were employed for the laboratory test for organics [polyaromatic hydrocarbon; total petroleum hydrocarbon (TPH)] and heavy metals in the water and sediment. The results indicated that there were still significant concentrations (P <0.05) of organics indicating hydrocarbon pollution. Mean concentrations recorded for TPH in Ubeji and Jeddo waters were 23.60 ± 1.18 mg/L and 29.96 ± 0.14 mg/L respectively while total PAHs was 0.009 ± 0.002 mg/L and 0.008 ± 0.001 mg/L. Mean concentrations of TPH in the sediment was 48.83 ± 1.49 ppm and 1093 ± 74 ppm respectively while total PAHs was 0.012 ± 0.002 ppm and 0.026 ± 0.004 ppm. Low concentrations were recorded for most of the heavy metals in the water and sediment. Hydrocarbon degrading bacteria (HDB) recorded mean values of 3.86E + 03 and 3.44E + 02 for Ubeji and Jeddo waters, while Hydrocarbon degrading fungi (HDF) recorded mean values of 2.86E + 03 and 2.46E + 02 respectively. The observed concentrations of hydrocarbons in the study areas should provide the impetus for regulatory surveillance of oil discharged intentionally/unintentionally into the Warri riverine waters and sediment since hydrocarbon released into the environment sorb to the sediment particles where they cause harm to organisms in the sediment and overlying waters
Effect Of Nonlinear Radiative Heat And Mass Transfer On Mhd Flow Over A Stretching Surface With Variable Conductivity And Viscosity
(Journal of the Serbian Society for Computational Mechanics, 2019) Akindele M. Okedoye; Sulyman O. Salawu
A theoretical investigation on the flow of nonlinear magnetohydrodynamic (MHD), laminar, viscous, incompressible boundary layer fluid with thermal radiative heat transfer and variable properties past a stretching plate was carried out. The liquid is taken to be gray, absorbing, emitting but with non-scattering medium. The main nonlinear equations governing the flow are reduced to ordinary differential equations by using appropriate similarity variables and quantities. The obtained nonlinear equations are computationally solved by applying shooting techniques coupled with Nachtsheim-Swigert method for asymptotic satisfaction of boundary conditions by fourth order Runge Kutta scheme. The computational results for momentum and heat distribution are obtained for various values of the emerging parameters. The results for the coefficient of skin friction and dimensionless heat gradient are likewise obtained for different physical parameters values. From the study, it was observed that the parameters which enhanced the heat source terms decreased the fluid viscosity and caused increase in the flow rate. Also, parameter that reduced heat source terms encouraged viscosity which resulted in retardation of the fluid velocity.
Effects of Data Resampling on Predicting Customer Churn via a Comparative Tree-based Random Forest and XGBoost
(Journal of Computing Theories and Applications, 2024) Abere, Reuben Akporube et. al.
Customer attrition has become the focus of many businesses today – since the online market space has continued to proffer customers, various choices and alternatives to goods, services, and products for their monies. Businesses must seek to improve value, meet customers' teething demands/needs, enhance their strategies toward customer retention, and better monetize. The study compares the effects of data resampling schemes on predicting customer churn for both Random Forest (RF) and XGBoost ensembles. Data resampling schemes used include: (a) default mode, (b) random-under-sampling RUS, (c) synthetic minority oversampling technique (SMOTE), and (d) SMOTE-edited nearest neighbor (SMOTEEN). Both tree-based ensembles were constructed and trained to assess how well they performed with the chi-square feature selection mode. The result shows that RF achieved F1 0.9898, Accuracy 0.9973, Precision 0.9457, and Recall 0.9698 for the default, RUS, SMOTE, and SMOTEEN resampling, respectively. Xgboost outperformed Random Forest with F1 0.9945, Accuracy 0.9984, Precision 0.9616, and Recall 0.9890 for the default, RUS, SMOTE, and SMOTEEN, respectively. Studies support that the use of SMOTEEN resampling outperforms other schemes; while, it attributed XGBoost enhanced performance to hyper-parameter tuning of its decision trees. Retention strategies of recency-frequency-monetization were used and have been found to curb churn and improve monetization policies that will place business managers ahead of the curve of churning by customers.

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