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A regional GNSS-VTEC model over Nigeria using neural networks： A novel approach

Geodesy and Geodynamics 2016年第1期7卷 19-31页

作者： Daniel Okoh oluwafisavo owolabi Christovher Ekechukwu Olanike Folarin Gila Arhiwo Joseph Agbo Segun Bolaji Babatunde Rabiu NASRDA Center for Atmospheric Research Kogi State University Anyigba Campus Nigeria Ionospheric & Space Physics Laboratory Department of Physics University of Lagos Nigeria Department of Physics University of Calabar Nigeria Department of Physics Federal University of Agriculture Makurdi Nigeria Department of Surveying & Geo-informatics Nnamdi Azikiwe University Awka Nigeria

A neural network model of the Global Navigation Satellite System - vertical total electron content （GNSS-VTEC） over Nigeria is developed. A new approach that has been utilized in this work is the consideration of the International Reference Ionosphere＇s （IRI＇s） critical plasma frequency （foF2） parameter as an additional neuron for the network＇s input layer. The work also explores the effects of using various other input layer neurons like distur- bance storm time （DST） and sunspot number. All available GNSS data from the Nigerian Permanent GNSS Network （NIGNET） were used, and these cover the period from 2011 to 2015, for 14 stations. Asides increasing the learning accuracy of the networks, the inclusion of the IRI＇s foF2 parameter as an input neuron is ideal for making the networks to learn long-term solar cycle variations. This is important especially for regions, like in this work, where the GNSS data is available for less than the period of a solar cycle. The neural network model developed in this work has been tested for time-varying and spatial per- formances. The latest 10% of the GNSS observations from each of the stations were used to test the forecasting ability of the networks, while data from 2 of the stations were entirely used for spatial performance testing. The results show that root-mean-squared-errors were generally less than 8.5 TEC units for all modes of testing performed using the optimal network. When compared to other models, the model developed in this work was observed to reduce the prediction errors to about half those of the NeQuick and the IRI model.

关键词： Global Navigation Satellite System(GNSS) ionosphereTotal electron content (TEC)Nigerian permanent GNSS network(NIGNET)Neural networkInternational reference ionosphere(IRI)

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Pavement sustainability index for highway infrastructures： A case study of Maryland

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Frontiers of Structural and Civil Engineering 2018年第2期12卷 192-200页

作者： Stella O. OBAZEE-IGBINEDION Oludare owolabi Montgomery County Department of Transportation 100 Edison Park Drive Gaithersburg MD 20878 USA Department of Civil Engineering Morgan State University 1700 East Cold Spring Lane Baltimore MD 21251 USA

Pavement deterioration creates conditions that undermine their performances, which gives rise to the need for maintenance and rehabilitation. This paper develops a mathematical multi-linear regression analysis （MLRA） model to determine a pavement sustainability index （PSTI） as dependent variable for flexible pavements in Maryland. Four categories of pavement performance evaluation indicators are subdivided into seven pavement condition indices and analyzed as independent variables for each section of pavement. Data are collected from five different roadways using field evaluations and existing database. Results indicate that coefficient of determination （R^2） is correlated and significant, R^2 = 0.959. Of the seven independent variables, present serviceability index （PSI） is the most significant with a coefficient value of 0.032, present serviceability rating （PSR） coefficient value=0.028, and international roughness index （IRI） coefficient value = -0.001. Increasing each unit value of coefficients for PSI and PSR would increase the value of PSTI; thereby providing a more sustainable pavement infrastructure; which explains the significance of the model and why IR/ will most likely impact environmental, economic and social values.

关键词： pavement indices sustainability pavement performance flexible pavements

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Modeling and Simulation of Microstructurally Small Crack Formation and Growth in Notched Nickel-base Superalloy Component

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Journal of Materials Science & Technology 2014年第3期30卷 203-212页

作者： G.M.owolabi H.A.Whitworth Department of Mechanical Engineering Howard University

Studies on microstructurally small fatigue cracks have illustrated that heterogeneous microstructural features such as inclusions, pores, grain size distribution as well as precipitate size distribution and volume fraction create stochasticity in their behavior under cyclic loads. Therefore, to enhance safe-life and damage-tolerance approaches, accurate modeling of the influence of these heterogeneous microstructural features on microstructurally small crack formation and growth from stress raisers is necessary. In this work, computational micromechanics was used to predict the high cycle fatigue of microstructurally small crack formation and growth in notched polycrystalline nickel-base superalloys and to quantify the variability in the driving force for formation and growth of microstructurally small crack from notch root in the matrix with non-metallic inclusions. The framework involves computational modeling to obtain three-dimensional perspectives of microstructural features influencing fatigue crack growth in notched nickel-base superalloys, which accounts for the effects of nonlocal notch root plasticity, loading, microstructural variability, and extrinsic defects on local cyclic plasticity at the microstructure-scale level. This approach can be used to explore sensitivity of minimum fatigue lifetime to microstructures. The simulation results obtained from this framework were calibrated to existing experimental results for polycrystalline nickel-base superalloys.

关键词： Microstructuraliy small crack Crystal plasticity Nickel-base superalloy Fatigue life

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Shear Band Formation in AISI 4340 Steel Under Dynamic Impact Loads:Modeling and Experiment

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Acta Metallurgica Sinica(English Letters) 2013年第4期26卷 378-384页

作者： Daniel Odoh Gbadebo owolabi Akindele Odeshi Horace Whitworth Department of Mechanical Engineering Howard University Department of Mechanical Engineering University of Saskatchewan57 Campus DriveSaskatoonSKS7N 5A9Canada

In this study, the occurrence of the adiabatic shear bands in AISI 4340 steel under high velocity impact loading was investigated using finite element analysis and experimental tests. The cylindrical specimen subjected to the impact load was divided into different regions separated by nodes using finite element method in ABAQUS environment with boundary conditions specified. The material properties were assumed to be lower in the region where the probability of strain localization is high based on prior experimental results in order to initialize the formation of the adiabatic shear bands. The finite element model was used to determine the maximum flow stress, the strain hardening, the thermal softening, and the time to reach the critical strain for the formation of adiabatic shear bands. Experimental results show that deformed bands were formed at low strain rates and there was a minimum strain rate required for the formation of the transformed band in the alloy and the cracks were initiated and propagated along the transformed bands leading to fragmentation under the impact loading. The susceptibility of the adiabatic shear bands to cracking was markedly influenced by the strain-rates and the initial material microstructure. The simulation results obtained were compared with the experimental results obtained from the AISI 4340 steel under high strain-rate loading in compression using split impact Hopkinson bars. A good agreement between the experimental and simulation results was obtained.

关键词： Adiabatic shear bands Finite element model Strain hardening Thermal softening Johnson-Cook model AISI 4340 steel

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Analysis of Mathematics and Numerical Pattern Formation in Superdiffusive Fractional Multicomponent System

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Advances in Applied Mathematics and Mechanics 2017年第6期9卷 1438-1460页

作者： Kolade M.owolabi Abdon Atangana Institute for Groundwater Studies Faculty of Natural and Agricultural SciencesUniversity of the Free StateBloemfontein 9300South Africa

In this work,we examine the mathematical analysis and numerical simulation of pattern formation in a subdiffusive multicomponents fractional-reactiondiffusion system that models the spatial interrelationship between two preys and predator *** major result is centered on the analysis of the system for linear *** of the main model reflects that the dynamical system is locally and globally asymptotically *** propose some useful theorems based on the existence and permanence of the species to validate our theoretical *** and efficient methods in space and time are formulated to handle any space fractional reaction-diffusion *** numerically present the complexity of the dynamics that are theoretically *** simulation results in one,two and three dimensions show some amazing scenarios.

关键词： Asymptotically stable coexistence Fourier spectral method numerical simulations predator-prey fractional multi-species system

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Analysis and Dynamics of Illicit Drug Use Described by Fractional Derivative with Mittag-Leffler Kernel

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Computers, Materials & Continua 2020年第12期65卷 1905-1924页

作者： Berat Karaagac Kolade Matthew owolabi Kottakkaran Sooppy Nisar Faculty of Mathematics and Statistics Ton Duc Thang UniversityHo Chi Minh CityVietnam Department of Mathematics Education Faculty of EducationAdıyaman UniversityAdıyamanTurkey Department of Mathematical Sciences Federal University of TechnologyAkureNigeria Department of Mathematics College of Arts and SciencesWadi AldawaserPrince Sattam Bin Abdulaziz UniversityAl KharjSaudi Arabia

Illicit drug use is a significant problem that causes great material and moral losses and threatens the future of the *** this reason,illicit drug use and related crimes are the most significant criminal cases examined by *** paper aims at modeling the illegal drug use using the Atangana-Baleanu fractional derivative with Mittag-Leffler ***,in this work,the existence and uniqueness of solutions of the fractional-order Illicit drug use model are discussed via Picard-Lindelöf theorem which provides successive approximations using a convergent *** the stability analysis for both disease-free and endemic equilibrium states is conducted.A numerical scheme based on the known Adams-Bashforth method is designed in fractional form to approximate the novel Atangana-Baleanu fractional operator of order 0

关键词： Atangana-Baleanu fractional operator illicit drug use existence and uniqueness of solutions stability analysis

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Effects of regenerative mechanical vibration on the mechanical integrity of ceramic diesel particulate filters

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Journal of Advanced Ceramics 2018年第1期7卷 5-16页

作者： Gbadebo owolabi Akindele ODESHI Paul RAGALLER AlexANDer SAPPOK Department of Mechanical Engineering Howard University Department of Mechanical Engineering University of Saskatchewan CTS Corporation Boston Innovation Office

In this study, the effects of mechanical vibration on the mechanical properties of ceramic diesel particulate filters(DPFs) were investigated. The goal is to determine how the mechanical vibration used in the regenerative ash cleaning process for these filters affects their mechanical integrity during subsequent reuse. Both virgin and vibrated DPF samples were subjected to compressive and 3-point flexural loading at three different loading rates along axial and tangential directions. Statistical analysis was conducted to determine the significance of variation in the compressive and flexural strengths of the DPFs as a result of exposure to mechanical vibration. The results show that there is no statistically significant difference in both compressive and flexural strengths of the virgin DPFs and the DPFs subjected to the same level of mechanical vibration typically used in ash cleaning of DPFs. When the intensity of vibration was doubled, the drop in compressive strength became statistically significant, but less than 10% under axial loading. However, no drop in flexural strength was observed for DPFs subjected to this high intensity of mechanical vibration. The safe threshold for mechanical vibration of ceramic filters is considered to be much higher than that currently used in vibration-based ash cleaning process.

关键词： diesel particulate filter(DPF) cordierite mechanical testing filter regeneration vibration based ash cleaning technology

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Small Hydropower in Nigeria

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Small Hydro Power News 2002年第67期19卷 2-4页

作者： P.EOKRANEFE S.owolabi MinistryofPower＆SteelNigeria

Nigeria is the most populaous black nation in the world. It has an area of 913,072 square kilometres. The country population is about 120 million. There are three major languages, Hausa, Yoruba and Igbo, although there is still more than 380 dialects in local languages. There are large number of household on the African continent that are *** Nigeria about 70 million people remain literally in the dark without access to electricity. The majority of these numbers are in the rural areas. This workshop is apt in a number of ways. It is a joint effort between government, private sector, the academic and other practitioners in small hydro power station, it is also a promotion of business and industrial activities as well as development of renewable energy resources. I wish to commend the organizers of this workshop. The focus of the workshop is relevant to the agenda of the Federal Ministry of Power and Steel and aspirations of the Federal Government of Nigeria to provide regular and steady electricity to majority of Nigerians before the end of year 2001.

关键词：尼日利亚水力发电能源工业能源供应水电站

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Effect of pineapple peel extract on total phospholipids and lipid peroxidation in brain tissues of rats

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Asian Pacific Journal of Tropical Medicine 2011年第3期4卷 182-184页

作者： Erukainure OL Ajiboye JA Adejobi RO Okafor OY Kosoko SB owolabi FO Food Technology Division Federal Institute of Industrial ResearchOshodiNigeria College of Natural and Applied Sciences Bells University of TechnologyOtaNigeria

Objective:To investigate the ability of the methanolic extract of pineapple peel to attenuate alcohol-induced changes in total phospholipids and lipid peroxidation in brain tissues. Methods:Oxidative stress was induced by oral administration of ethanol(20%w/v) at a dosage of 5 mL/kg bw in *** 28 days of treatment,the rats were fasted overnight and sacrificed by cervical *** tissues were assayed for total phospholipid(TP) content and malondialdehyde(MDA).Results:Administration of alcohol significantly caused a reduction in TP *** with pineapple peel extract significantly increased the TP content. Significant high levels of MDA was observed in alcohol-fed rats,treatment with pineapple peel extract significantly reduced the MDA ***:Results obtained from this study indicates that pineapple peel extract protects against alcohol-induced changes in total phospholipids and lipid peroxidation in brain tissues.

关键词： Brain Malondialdehyde Total phospholipids Alcohol

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An application of artificial intelligence for investigating the effect of COVID-19 lockdown on three-dimensional temperature variation in equatorial Africa

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Geoscience Frontiers 2022年第2期13卷 52-61页

作者： Daniel Okoh Loretta Onuorah Babatunde Rabiu Aderonke Obafaye Dauda Audu Najib Yusuf Oluwafisayo owolabi Centre for Atmospheric Research National Space Research and Development AgencyAnyigbaNigeria Department of Physical and Geosciences Godfrey Okoye UniversityEnuguNigeria Institute for Space Science and Engineering African University of Science and TechnologyAbujaNigeria

We present interesting application of artificial intelligence for investigating effect of the COVID-19 lockdown on 3-dimensional temperature variation across Nigeria(2°-15°E,4°-14°N),in equatorial *** neural networks were trained to learn time-series temperature variation patterns using radio occultation measurements of atmospheric temperature from the Constellation Observing System for Meteorology,Ionosphere,and Climate(COSMIC).Data used for training,validation and testing of the neural networks covered period prior to the *** was also an investigation into the viability of solar activity indicator(represented by the sunspot number)as an input for the *** results indicated that including the sunspot number as an input for the training did not improve the network prediction *** trained network was then used to predict values for the lockdown *** the network was trained using pre-lockdown dataset,predictions from the network are regarded as expected temperatures,should there have been no *** comparing with the actual COSMIC measurements during the lockdown period,effects of the lockdown on atmospheric temperatures were *** overall,the mean altitudinal temperatures rose by about 1.1℃ above expected values during the *** altitudinal breakdown,at 1 km resolution,reveals that the values were typically below0.5℃ at most of the altitudes,but exceeded 1℃ at 28 and 29 km *** temperatures were also observed to drop below expected values at altitudes of 0-2 km,and 17-20 km.

关键词： Temperature Neural network Equatorial Africa COVID-19 lockdown Time-series Sunspot number

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