Journal of Nigerian Society of Physical Sciences最新文献

{"title":"Improving forecasting accuracy using quantile regression neural network combined with unrestricted mixed data sampling","authors":"Umaru Hassan, Mohd Tahir Ismail","doi":"10.46481/jnsps.2023.1394","DOIUrl":"https://doi.org/10.46481/jnsps.2023.1394","url":null,"abstract":"A traditional regression method involving time series variables is often observed at the same frequencies. In a situation where the frequencies differ, the higher ones are averaged or aggregated to the lower frequency. A Mixed Data Sampling (MIDAS) regression model was introduced to address such problems. In any country, stakeholders are interested in monitoring and forecasting accurately the Gross Domestic Product (GDP) using the dynamics of macroeconomic variables. We applied the hybrid QRNN-U-MIDAS model to forecast quarterly GDP using monthly and weekly data. The Quantile Regression Neural Network (QRNN) is designed to model nonlinear relationships amongst data sampled at the same frequency. Therefore, we take advantage of QRNN skills using the optimization techniques of gradient descent-based algorithms to optimise the estimated loss function Ea (tau), and introduce them into the U-MIDAS framework, which can handle mixed data frequencies, and construct a QRNN-U-MIDAS model. The suggested hybrid QRNN-U-MIDAS model was implemented in an R-package that we created to perform both simulation and real-time data applications. The findings indicate that the QRNN-U-MIDAS regression model outperforms competing models in terms of its capacity for prediction across the conditional distribution of a response variable with a comprehensive view of the information contained in the variables, which is lacking in other competing models like U-MIDAS, ANN-U-MIDAS etc. More so, this novel model will add to the existing works of literature on robust forecasting models.","PeriodicalId":34011,"journal":{"name":"Journal of Nigerian Society of Physical Sciences","volume":"37 18","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136282574","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}

{"title":"Synthesis and characterization of silica xerogel and aerogel from rice husk ash and pulverized beach sand via sol-gel route","authors":"K. M. Omatolaa, A. D. Onojah, A. N. Amah, I. Ahemen","doi":"10.46481/jnsps.2023.1609","DOIUrl":"https://doi.org/10.46481/jnsps.2023.1609","url":null,"abstract":"The high cost and toxicity associated with the use of orthosilicates as silica precursors drive growing interest in an environmentally friendly and cost - efficient natural silica source. Rice husk (a biomass) and beach sand are both natural and non - toxic and the extraction of silica from each using sodium hydroxide makes the process green for the production of nanosilica gels (xerogel and aerogel) via the sol – gel route. The gels from the ash of rice husk and pulverized beach sand were dried by the use of a laboratory oven and supercritical extraction methods. The structures of the gels were studied through X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), X - ray fluorescence (XRF) spectroscopy and Fourier transform infrared (FTIR) spectroscopic analyses. XRF spectroscopy revealed silicon in its oxide form as the prominent element with low levels of trace elements concentrations. XRD results showed the crystalline nature of the prepared silica. TEM images confirmed the crystalline and nanometric structures of the streak - free xerogel and aerogel. SAED confirmed that the gels were polycrystalline with no streaks. SEM monographs showed varied globes of fine surfaces indicating the high level of purity of the gels. FTIR showed the absorption peaks of the silanol-OH bond and Si-O-Si vibration, confirming the gels as nanometric structures. The high yield, crystalline nature, purity and crystallographic features of the produced silica suggest rice husk ash and pulverized beach sand as alternative silica sources for the production of silica gels nanoparticles with potential applications in biomedical field, nanofiltration and as additive for improving the strength of materials.","PeriodicalId":34011,"journal":{"name":"Journal of Nigerian Society of Physical Sciences","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136352171","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}

{"title":"On sentinel method of one-phase Stefan problem","authors":"Merabti Nesrine Lamya, Iqbal M. Batiha, Imad Rezzoug, Adel Ouannas, Taki-Eddine Ouassaeif","doi":"10.46481/jnsps.2023.1772","DOIUrl":"https://doi.org/10.46481/jnsps.2023.1772","url":null,"abstract":"This paper is interested in studying the one-phase Stefan problem. For this purpose, we use the nonlinear sentinel method, which relies typically on the approximate controllability and the Fanchel-Rockafellar duality of the minimization problem, to prove the existence and uniqueness of a solution to this problem. In particular, our research focuses on the application of the nonlinear sentinel method to the single-phase Stefan problem. This approach aids in identifying an unspecified boundary section within the domain undergoing a liquid-solid phase transition. We track the evolution of the temperature profile in the liquid-solid material and the corresponding movement of its interface over time. Eventually, the local convergence used for the iterative numerical scheme is demonstrated.","PeriodicalId":34011,"journal":{"name":"Journal of Nigerian Society of Physical Sciences","volume":"16 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135341472","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}

{"title":"Identification and Quantification of Bioactive Compounds in Different Extracts of Morinda lucida Benth (Rubiaceae) Root Using GC–MS Analysis","authors":"David Adekunle, Esther Faboro, Labunmi Lajide","doi":"10.46481/jnsps.2023.1534","DOIUrl":"https://doi.org/10.46481/jnsps.2023.1534","url":null,"abstract":"This study aims to analyze and describe the chemical constituents of various crude extracts derived from the root of Morinda lucida Benth (Rubiaceae), an ethnomedicinal plant commonly found in Nigeria. The root of Morinda lucida was dried at room temperature and pulverized into powder. The soxhlet extraction technique was used with solvents of different polarities, namely hexane, chloroform, and methanol, to obtain three distinct extracts. Subsequently, gas chromatography-mass spectrometry analysis was carried out on the extracts. A total of 69 compounds were identified from the different extracts of M. lucida root. The hexane extract had 3 major compounds and 8 minor ones, with diethyl phthalate being the most prominent with 87.10% peak area. The chloroform extract had 24 compounds, with phthalic acid, 2-Ethylhexyl isohexyl ester being the highest with 16.61% peak area. Six of these compounds had more than 5%, while the remaining 18 ranged from 2.50% to 1.00%. The ethanol extract contained 36 compounds, with 6 compounds being greater than 5% and the remaining 30 less than 5%. The highest percentage in the ethanol extract was 2-Pyrrolidinone, 1-methyl-, at 16.05%. In terms of the biological and pharmacology benefits, these chemicals are regarded as crucial. Also, each of the three extracts has a few similarities in their physicochemical properties that can be related to the natural substances that are abundantly found in M. lucida root. The GC-MS analysis of different extracts of M. lucida revealed the presence of several bioactive compounds that have potential therapeutic properties.","PeriodicalId":34011,"journal":{"name":"Journal of Nigerian Society of Physical Sciences","volume":"14 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135876116","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}

{"title":"Analysis of a fractional order climate model due to excessive emission and accumulation of carbon dioxide in the atmosphere","authors":"Peter Urane Achimugwu, Mathew Ngugi Kinyanjui, David Mumo Malonza","doi":"10.46481/jnsps.2023.1749","DOIUrl":"https://doi.org/10.46481/jnsps.2023.1749","url":null,"abstract":"The devastating consequences of climate change on our planet cannot be taken lightly. Greenhouse gas emissions due to the various activities of the increasing human population are solely responsible for this change. The chief and most significant of these gases is carbon dioxide. A fractional-order model of five compartments is considered. The uniqueness and existence, the positivity, and the boundedness of the model solution are established. The equilibrium points of the model are given. By formulating different Lyapunov functions, the global stability of the four equilibrium points was determined. The numerical simulation of the model was done using the Predict-Evaluate-Correct-Evaluate method of Adam-Bashforth-Moulton by considering four different orders of 0.7, 0.8, 0.9, and 1.0. According to the results, excessive concentrations of carbon dioxide in the atmosphere can be reduced by the joint employment of mitigation measures.","PeriodicalId":34011,"journal":{"name":"Journal of Nigerian Society of Physical Sciences","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135825475","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}

{"title":"Effects of different electrolytes on the structure and yield ofgraphene oxide produced via electrochemical exfoliation","authors":"Oluwole Adigun, Lasisi Egibunu Umoru, Temidayo Nancy Iwatan","doi":"10.46481/jnsps.2023.1183","DOIUrl":"https://doi.org/10.46481/jnsps.2023.1183","url":null,"abstract":"The most suitable electrolyte for graphene oxide synthesis, in terms of both production efficiency and quality, using the electrochemical exfoliation technique has been investigated and reported in this study. Simultaneous anodic and cathodic graphene oxide production using ten (10) different electrolytes, including acids (H2SO4, HCl, HNO3), bases (KOH, Ca(OH)2, Mg(OH)2, NaOH), and salts (NaCl, (NH4)2SO4, K2SO4), was studied under the same experimental conditions of bias voltage, graphite nature, exfoliation time, electrolyte molarity, and post-exfoliation treatments. Assessment of the graphene oxide structures and production rates was supported using Raman spectroscopy, high-resolution scanning electron microscopy (HRSEM), and EDS (energy dispersive x-ray spectroscopy), attached to the scanning electron microscope. Analysis of the results obtained reveals that H2SO4 showed the highest graphene oxide yield (86%) but with comparably low graphene oxide quality in terms of defect concentration, presence of oxygen functional group contamination, and crystallite properties. The aqueous NaCl, Ca(OH)2 and Mg(OH)2 electrolytes did not show any graphene oxide exfoliation effect. However, from the series of electrolytes examined, aqueous (NH4)2SO4 exhibited an excellent combination of efficient graphene oxide yield and high-quality characteristics due to its relatively high yield of 74% and superior quality of the produced graphene oxide with the comparatively lowest defect density, ?D, and highest C/O (carbon-to-oxygen) ratio. The tortuous, agglomerated, and planar layers of the distinct 2D graphene oxide sheets were also clearly revealed by the SEM images. In essence, the roles played by dissociated sulfate (SO42?), nitrate (NO32?), chlorides (Cl?), and hydroxides (OH?) ions in the series of complex electrochemical reactions toward the intercalation, exfoliation, yield, and properties of graphene oxide produced are discussed. From the series of electrolytes tested, aqueous (NH4)2SO4 emerged as the most relatively suitable electrolyte for the synthesis of graphene oxide because it combines both high yield and fine quality.","PeriodicalId":34011,"journal":{"name":"Journal of Nigerian Society of Physical Sciences","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135967705","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}

{"title":"Unsteady Prandtl nanofluidic flow through stretching sheet due to mixed convection, first-order slip, and chemical reaction","authors":"V. Ramanjini, G. Gopi Krishna, Mani Ramanuja, Hari Kamala Sree, S. R. Mishra","doi":"10.46481/jnsps.2023.1140","DOIUrl":"https://doi.org/10.46481/jnsps.2023.1140","url":null,"abstract":"This article explores the unsteady flow, heat, and mass transport of a Prandtl nanofluid flow over a stretching sheet due to the existence of mixed convection, first-order slip, and chemical reaction. The flow characteristics are analysed for the interaction of thermal and solutal Biot numbers. The system of coupled non-linear leading partial differential equations (PDEs) is converted into non-linear ordinary differential equations (ODEs) with the facilitation of given similarity transformations. Furthermore, these equations are solved by applying a semi-analytical method termed the “Optimal Homotopy Analysis Method” (OHAM) using the computational software MATHEMATICA. The tables and Figures present the numerical computations of the pertinent parameters of the flow problems. The essential findings of this study are for the growing values of the Prandtl parameter, the velocity profile is enhanced, and the temperature profiles show the opposite behaviour. Unsteady parameters reduced the thickness of the heat and moving boundary layers. The temperature profiles are enhanced as the thermal Biot number grows, and similar characteristics can be observed in the solutal Biot number on concentration profiles.","PeriodicalId":34011,"journal":{"name":"Journal of Nigerian Society of Physical Sciences","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135197883","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}

{"title":"Experimental and computational studies of the corrosion inhibitive effects of Zingiber officinale rhizomes on mild steel corrosion in acidic solutions","authors":"Chinonso Adindu, Simeon Nwanonenyi, Chinyere Ikpa","doi":"10.46481/jnsps.2023.1386","DOIUrl":"https://doi.org/10.46481/jnsps.2023.1386","url":null,"abstract":"The study investigates the anticorrosion potentials of Zingiber officinale (ZO) on mild steel induced in 1.0 M HCl and 0.5 M H2SO4 acid solution respectively using structural characterization (gas chromatography-mass spectroscopy, GC-MS and Fourier transform infrared spectroscopy, FTIR) and electrochemical (electrochemical impedance spectroscopy, EIS and potentiodynamic polarization, PDP) techniques respectively and theoretical simulations. The structural characterization was performed to identify chemical constituents and functional groups present in the plant extract whereas electrochemical techniques and theoretical computations were used to examine the anticorrosion potentials of the extract and validate the experimental results. The GC-MS result revealed the presence of twenty-three (23) compounds within the extract and out of which three (1-(1,5-dimethyl-4-hexenyl)-4-methyl-, dodecanoic acid and 9-Octadecenoic acid (Z)-2-hydroxy-1-(hydroxymethyl)ethyl ester) were selected for computational simulation and the results of FTIR revealed the presence of the following functional groups (O-H, C=C, C=O, C-C and C-H) in the ZO extract. The results of EIS revealed that extract of ZO exhibited corrosion inhibition efficieny of 82.7% and 93.6 % for mild steel in 1 M HCl and 0.5 M H2SO4 solution respectively at maximum inhibitor concentration of 1000 mg/L for mild steel. Also, PDP results revealed that ZO extract functioned as mixed inhibitor because both the anodic and cathodic reaction process was altered. The quantum chemical calculation results revealed that 9- Octadecenoic acid (Z)-2-hydroxy-1-(hydroxymethyl) ethyl ester had a good energy gap (Delta E) compared to other two compounds, indicating its better adsorption interaction with the metal surface in sulfuric acid environment. This was further confirmed by its good adsorption energy of -355.55 Kcal/mol with mild steel surface in H2SO4 environment compared with -167.81Kcal/mol in HCl environment from the molecular dynamic simulation.","PeriodicalId":34011,"journal":{"name":"Journal of Nigerian Society of Physical Sciences","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135354452","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}