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  Subjects -> SCIENCES: COMPREHENSIVE WORKS (Total: 426 journals)
Showing 1 - 200 of 265 Journals sorted alphabetically
AAS Open Research     Open Access   (Followers: 1)
ABC Journal of Advanced Research     Open Access  
Accountability in Research: Policies and Quality Assurance     Hybrid Journal   (Followers: 22)
Acta Materialia Transilvanica     Open Access  
Acta Nova     Open Access   (Followers: 1)
Acta Scientifica Malaysia     Open Access  
Acta Scientifica Naturalis     Open Access   (Followers: 3)
Adıyaman University Journal of Science     Open Access  
Advanced Science     Open Access   (Followers: 13)
Advanced Science, Engineering and Medicine     Partially Free   (Followers: 11)
Advanced Theory and Simulations     Hybrid Journal   (Followers: 5)
Advances in Research     Open Access  
Advances in Science and Technology     Full-text available via subscription   (Followers: 17)
African Journal of Science, Technology, Innovation and Development     Hybrid Journal   (Followers: 8)
Afrique Science : Revue Internationale des Sciences et Technologie     Open Access   (Followers: 2)
AFRREV STECH : An International Journal of Science and Technology     Open Access   (Followers: 4)
American Academic & Scholarly Research Journal     Open Access   (Followers: 6)
American Journal of Applied Sciences     Open Access   (Followers: 27)
American Journal of Humanities and Social Sciences     Open Access   (Followers: 17)
ANALES de la Universidad Central del Ecuador     Open Access   (Followers: 4)
Anales del Instituto de la Patagonia     Open Access  
Applied Mathematics and Nonlinear Sciences     Open Access   (Followers: 1)
Apuntes de Ciencia & Sociedad     Open Access  
Arab Journal of Basic and Applied Sciences     Open Access  
Arabian Journal for Science and Engineering     Hybrid Journal   (Followers: 5)
Archives Internationales d'Histoire des Sciences     Partially Free   (Followers: 7)
Archives of Current Research International     Open Access  
ARO. The Scientific Journal of Koya University     Open Access  
ARPHA Conference Abstracts     Open Access   (Followers: 6)
ARPHA Proceedings     Open Access   (Followers: 5)
ArtefaCToS : Revista de estudios sobre la ciencia y la tecnología     Open Access   (Followers: 1)
Asia-Pacific Journal of Science and Technology     Open Access  
Asian Journal of Advanced Research and Reports     Open Access   (Followers: 2)
Asian Journal of Applied Science and Engineering     Open Access   (Followers: 2)
Asian Journal of Scientific Research     Open Access   (Followers: 3)
Asian Journal of Technology Innovation     Hybrid Journal   (Followers: 7)
Australian Field Ornithology     Full-text available via subscription   (Followers: 4)
Australian Journal of Social Issues     Hybrid Journal   (Followers: 7)
AZimuth     Full-text available via subscription   (Followers: 2)
Bangladesh Journal of Scientific Research     Open Access   (Followers: 1)
Beni-Suef University Journal of Basic and Applied Sciences     Open Access   (Followers: 3)
Berichte Zur Wissenschaftsgeschichte     Hybrid Journal   (Followers: 10)
Berkeley Scientific Journal     Full-text available via subscription  
BIBECHANA     Open Access   (Followers: 2)
BibNum     Open Access  
Bilge International Journal of Science and Technology Research     Open Access   (Followers: 1)
Bioethics Research Notes     Full-text available via subscription   (Followers: 16)
Bistua : Revista de la Facultad de Ciencias Básicas     Open Access  
BJHS Themes     Open Access   (Followers: 1)
Black Sea Journal of Engineering and Science     Open Access  
Borneo Journal of Resource Science and Technology     Open Access  
Brazilian Journal of Science and Technology     Open Access   (Followers: 2)
Bulletin de la Société Royale des Sciences de Liège     Open Access  
Bulletin of the National Research Centre     Open Access  
Butlletí de la Institució Catalana d'Història Natural     Open Access  
Central European Journal of Clinical Research     Open Access  
Chain Reaction     Full-text available via subscription  
Ciencia & Natura     Open Access   (Followers: 1)
Ciencia Amazónica (Iquitos)     Open Access   (Followers: 1)
Ciencia en Desarrollo     Open Access   (Followers: 3)
Ciencia en su PC     Open Access   (Followers: 1)
Ciencia Ergo Sum     Open Access  
Ciência ET Praxis     Open Access  
Ciencia y Tecnología     Open Access  
Ciencia, Docencia y Tecnología     Open Access  
Ciencias Holguin     Open Access   (Followers: 2)
CienciaUAT     Open Access   (Followers: 1)
Citizen Science : Theory and Practice     Open Access   (Followers: 2)
Communications Faculty of Sciences University of Ankara Series A2-A3 Physical Sciences and Engineering     Open Access  
Communications in Applied Sciences     Open Access  
Comprehensive Therapy     Hybrid Journal   (Followers: 3)
Comunicata Scientiae     Open Access   (Followers: 1)
ConCiencia     Open Access  
Conference Papers in Science     Open Access   (Followers: 2)
Configurations     Full-text available via subscription   (Followers: 10)
COSMOS     Hybrid Journal   (Followers: 1)
Crea Ciencia Revista Científica     Open Access   (Followers: 2)
Cuadernos de Investigación UNED     Open Access  
Current Issues in Criminal Justice     Hybrid Journal   (Followers: 15)
Current Research in Geoscience     Open Access   (Followers: 8)
Dalat University Journal of Science     Open Access  
Data     Open Access   (Followers: 5)
Data Curation Profiles Directory     Open Access   (Followers: 5)
Dhaka University Journal of Science     Open Access  
Dharmakarya     Open Access  
Diálogos Interdisciplinares     Open Access  
Digithum     Open Access   (Followers: 2)
Discover Sustainability     Open Access   (Followers: 3)
Einstein (São Paulo)     Open Access  
Ekaia : EHUko Zientzia eta Teknologia aldizkaria     Open Access  
Elkawnie : Journal of Islamic Science and Technology     Open Access  
Emergent Scientist     Open Access  
Enhancing Learning in the Social Sciences     Open Access   (Followers: 9)
Enseñanza de las Ciencias : Revista de Investigación y Experiencias Didácticas     Open Access  
Entramado     Open Access  
Entre Ciencia e Ingeniería     Open Access   (Followers: 1)
Epiphany     Open Access   (Followers: 4)
Ergo     Open Access  
Estação Científica (UNIFAP)     Open Access   (Followers: 1)
Ethiopian Journal of Education and Sciences     Open Access   (Followers: 6)
Ethiopian Journal of Science and Technology     Open Access  
Ethiopian Journal of Sciences and Sustainable Development     Open Access   (Followers: 5)
European Online Journal of Natural and Social Sciences     Open Access   (Followers: 12)
European Scientific Journal     Open Access   (Followers: 10)
Evidência - Ciência e Biotecnologia - Interdisciplinar     Open Access  
Exchanges : the Warwick Research Journal     Open Access   (Followers: 2)
Experimental Results     Open Access   (Followers: 1)
Extensionismo, Innovación y Transferencia Tecnológica     Open Access   (Followers: 3)
Facets     Open Access  
Fides et Ratio : Revista de Difusión Cultural y Científica     Open Access   (Followers: 1)
Fırat University Turkish Journal of Science & Technology     Open Access  
Fontanus     Open Access  
Forensic Science Policy & Management: An International Journal     Hybrid Journal   (Followers: 378)
Frontiers for Young Minds     Open Access  
Frontiers in Climate     Open Access   (Followers: 3)
Frontiers in Science     Open Access   (Followers: 1)
Fundamental Research     Open Access  
Futures & Foresight Science     Hybrid Journal   (Followers: 4)
Gaudium Sciendi     Open Access   (Followers: 1)
Gazi University Journal of Science     Open Access  
Ghana Studies     Full-text available via subscription   (Followers: 15)
Global Journal of Pure and Applied Sciences     Full-text available via subscription  
Global Journal of Science Frontier Research     Open Access   (Followers: 2)
Globe, The     Full-text available via subscription   (Followers: 4)
HardwareX     Open Access  
Heidelberger Jahrbücher Online     Open Access  
Heliyon     Open Access  
Himalayan Journal of Science and Technology     Open Access   (Followers: 1)
History of Science and Technology     Open Access   (Followers: 1)
Hoosier Science Teacher     Open Access  
Iberoamerican Journal of Science Measurement and Communication     Open Access  
Impact     Open Access   (Followers: 2)
Indian Journal of History of Science     Hybrid Journal   (Followers: 2)
Indonesian Journal of Fundamental Sciences     Open Access  
Indonesian Journal of Science and Mathematics Education     Open Access   (Followers: 4)
Indonesian Journal of Science and Technology     Open Access  
Ingenieria y Ciencia     Open Access   (Followers: 1)
Innovare : Revista de ciencia y tecnología     Open Access  
Instruments     Open Access  
Integrated Research Advances     Open Access  
Interciencia     Open Access   (Followers: 1)
Interface Focus     Full-text available via subscription  
International Annals of Science     Open Access  
International Archives of Science and Technology     Open Access  
International Journal of Academic Research in Business, Arts & Science     Open Access   (Followers: 2)
International Journal of Advanced Multidisciplinary Research and Review     Open Access  
International Journal of Applied Science     Open Access  
International Journal of Basic and Applied Sciences     Open Access   (Followers: 4)
International Journal of Computational and Experimental Science and Engineering (IJCESEN)     Open Access  
International Journal of Culture and Modernity     Open Access   (Followers: 3)
International Journal of Engineering, Science and Technology     Open Access  
International Journal of Innovation and Applied Studies     Open Access   (Followers: 12)
International Journal of Innovative Research and Scientific Studies     Open Access   (Followers: 6)
International Journal of Network Science     Hybrid Journal   (Followers: 3)
International Journal of Recent Contributions from Engineering, Science & IT     Open Access   (Followers: 1)
International Journal of Research in Science     Open Access   (Followers: 2)
International Journal of Science & Emerging Technologies     Open Access   (Followers: 1)
International Journal of Social Sciences and Management     Open Access   (Followers: 3)
International Journal of Technology Policy and Law     Hybrid Journal   (Followers: 7)
International Letters of Social and Humanistic Sciences     Open Access   (Followers: 1)
International Review of Applied Sciences     Open Access  
InterSciencePlace     Open Access   (Followers: 1)
Investiga : TEC     Open Access  
Investigación Joven     Open Access  
Investigación Valdizana     Open Access  
Investigacion y Ciencia     Open Access   (Followers: 1)
Iranian Journal of Science and Technology, Transactions A : Science     Hybrid Journal  
iScience     Open Access   (Followers: 2)
Issues in Science & Technology     Free   (Followers: 7)
Ithaca : Viaggio nella Scienza     Open Access  
J : Multidisciplinary Scientific Journal     Open Access  
Jaunujų mokslininkų darbai     Open Access   (Followers: 1)
Journal de la Recherche Scientifique de l'Universite de Lome     Full-text available via subscription   (Followers: 2)
Journal of Chromatography & Separation Techniques     Open Access   (Followers: 12)
Journal of Advanced Research     Open Access   (Followers: 3)
Journal of Al-Qadisiyah for Pure Science     Open Access   (Followers: 1)
Journal of Alasmarya University     Open Access   (Followers: 3)
Journal of Analytical Science & Technology     Open Access   (Followers: 6)
Journal of Applied Science and Technology     Full-text available via subscription   (Followers: 1)
Journal of Applied Sciences and Environmental Management     Open Access   (Followers: 3)
Journal of Big History     Open Access   (Followers: 3)
Journal of Composites Science     Open Access   (Followers: 3)
Journal of Critical Thought and Praxis     Open Access   (Followers: 2)
Journal of Deliberative Mechanisms in Science     Open Access  
Journal of Diversity Management     Open Access   (Followers: 6)
Journal of Indian Council of Philosophical Research     Hybrid Journal  
Journal of Institute of Science and Technology     Open Access  
Journal of Integrated Science and Technology     Open Access  
Journal of Interaction Science     Open Access   (Followers: 1)
Journal of Kerbala University     Open Access   (Followers: 1)
Journal of King Saud University - Science     Open Access   (Followers: 1)
Journal of Mathematical and Fundamental Sciences     Open Access  
Journal of Natural Sciences and Mathematics Research     Open Access  
Journal of Natural Sciences Research     Open Access   (Followers: 4)
Journal of Negative and No Positive Results     Open Access  
Journal of Responsible Technology     Open Access   (Followers: 1)
Journal of Science (JSc)     Open Access  
Journal of Science and Engineering     Open Access  
Journal of Science and Technology     Open Access   (Followers: 2)
Journal of Science and Technology     Open Access   (Followers: 1)

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Journal of Applied Science and Technology
Number of Followers: 1  
 
  Full-text available via subscription Subscription journal
ISSN (Print) 0855-2215
Published by African Journals Online Homepage  [262 journals]
  • Computer simulation of optimal tilt angles of photovoltaic module for
           maximum solar irradiation at locations in southern Nigeria

    • Free pre-print version: Loading...

      Authors: Y.N. Udoakah, U.S. Ikafia
      Pages: 1 - 12
      Abstract: Numerical algorithm was developed to simulate optimal tilt angles at which maximum solar radiation was incident on south-facing photovoltaic (PV) module. A MATLAB Code was implemented to examine the relationship bet-ween solar irradiation and module tilt angles for four locations in Southern Nigeria, and the results were validated with data from Meteorological Agency of Nigeria. The Code facilitated faster computation of the optimal tilt angles, rather than manual and time consuming calculations; and ensured accurate installation of PV systems for imp-roved efficiency and performance; thereby enhancing the prospects of solar energy utilization. The simulation algorithm was based on mathematical formulation of global solar intensity as a function of solar declination angle, hour angle, irradiation on horizontal and tilted surfaces, clearness index and diffused radiation at the location. The optimum tilt angles were determined for each month by selecting the corresponding values of angles for which the highest radiation intensities were received. The computer simulation confirmed that Calabar, Uyo, Warri and Owerri on nearly same latitudes had identical optimum monthly tilt angles; and for best performance, fixed solar PV module must be oriented to face south at optimal tilt angle equivalent to the latitude (°) of the location.Keywords: Optimum Tilt Angle, Photovoltaic Module, Solar Angles, Albedo, Hour Angle, Global Irradiation
      PubDate: 2020-01-29
      DOI: 10.4314/jast.v23i1-2.
      Issue No: Vol. 23, No. 1-2 (2020)
       
  • Predicting molar composition of biogas by reaction kinetics and
           temperature dependence on anaerobic digestion

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      Authors: A.L. Fagbemi, D.G.F. Adamon, S Bouraima
      Pages: 13 - 22
      Abstract: Mathematical model was developed and simulated to predict the molar composition of biogas produced by anaero-bic digestion. Several models have been developed for anaerobic processes with reduced number of parameters, but requiring data resolution, thus posing problem of data precision. The prediction model was based on reaction kinetics of anaerobic digestion, while Ratkowsky's formulation was used to examine the dependence of temperatu-re on methanogenic process. The reaction kinetics model was simulated using SciLab coding of fourth order Ru-nge Kutta numerical algorithm. Comparison of numerical experimentation results with published experimental data gave satisfactory agreement. The cumulative volume of methane was predicted in the temperature range of 20 - 40 °C, and the maximum volume of methane generated was 26.39 L at 35 °C for mesophilic bacteria.Keywords: Anaerobic Digestion, Hydrolysis, Acidogenesis, Acetogenesis, Methanogenesis, Mesophilic Bacteria
      PubDate: 2020-01-29
      DOI: 10.4314/jast.v23i1-2.
      Issue No: Vol. 23, No. 1-2 (2020)
       
  • Profiles of amino acids and volatile organic compounds from dawadawa
           produced by defatting and fermentation of locust bean (P. biglobosa), soy
           bean (G. max) and roselle (H. sabdariffa) seeds

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      Authors: A.A. Shahidah, A.A. Farouq, M.A. Magashi, A.D. Ibrahim
      Pages: 22 - 31
      Abstract: Free amino acids and volatile organic compounds generated in dawadawa produced by defatting and fermentation of locust bean (P. biglobosa), soy bean (G. max) and roselle (H. sabdariffa) seeds were profiled. The amino acids were determined using amino acid analyser, while the volatile organic compounds were analysed using Gas Chro-matography-Mass Spectrometry. The ground, defatted and fermented P. biglobosa and G. max seeds only showed slight increase in contents of essential amino acids and non-essential amino acids (arginine and glutamic acids). Serine and glutamic acids were the major amino acids in the ground, defatted and fermented seeds of P. biglobosa and G. max. The ground, defatted and fermented H. sabdariffa seeds showed minor differences in threonine, valiine, isoleucine, leucine and glutamic acids, compared with the full fat, ground and fermented seeds. Diverse volat-ile organic flavour compounds identified in dawadawa produced from P. biglobosa, G. max and H. sabdariffa seeds were acid-class flavour volatiles, alcohols, aldehydes, ketones, amides, carbonyl, esters, hydrocarbons and phenol. The ground, defatted seeds of G. max showed presence of various volatile organic compounds with n-He-xadecanoic acid, 9, 12- Octadecadienoic acid (Z, Z)- and 9-Octadec-enamide (Z)- of varying degree of abundance. For ground full fat and defatted seeds of H. sabdariffa, seven volatile organic compounds were detected, where six were unique to the H. sabdariffa seeds; and were detected irrespective of the seeds being defatted, or not, or fermented. Of the volatiles, hexadecanoic acid, ethyl ester and eicosane increased in quantity for defatted and fermented dawadawa produced from H. sabdariffa seeds. Defatting of all three seeds generated amino acids and volatile organic compounds in dawdawa produced.Keywords: Amino acids, Volatile Organic Compounds, Dawadawa, Condiment, Fermentation, Defatting
      PubDate: 2020-01-29
      DOI: 10.4314/jast.v23i1-2.
      Issue No: Vol. 23, No. 1-2 (2020)
       
  • Numerical computation of efficiency of beta polynomial kernel using
           product approach

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      Authors: I.U. Siloko, O Ikpotokin, F.O. Oyegue, E.A. Siloko, C.C. Ishiekwene
      Pages: 32 - 38
      Abstract: The efficiency values of beta polynomial kernel functions were computed using bivariate product approach, which involved multiplication of two univariate beta kernel functions. The statistical properties of bivariate beta kernel functions, in terms of roughness and variance, were evaluated to compute the efficiency values. The efficiency values of univariate form of beta polynomial kernels were also determined, and compared with values of bivariate beta kernel functions, since most applications of kernel estimators are in the bivariate form. The kernel estimator is a non-parametric density estimator with direct applications in data analysis and visualization. The computations showed that efficiency values tended to be smaller for bivariate beta polynomial kernel functions than for univari-ate kernel functions, due to effects of dimensionality associated with non-parametric statistics.Keywords: Bivariate Kernel, Kernel Estimator, Product Approach, Efficiency of Beta Polynomial
      PubDate: 2020-01-29
      DOI: 10.4314/jast.v23i1-2.
      Issue No: Vol. 23, No. 1-2 (2020)
       
  • Characterization of crystallinity and molecular functional groups of
           silver nanoparticle-Piptadeniastrum africanum (Dahoma) sawdust composites
           synthesized in-situ

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      Authors: D Gyasi-Antwi, A.O. Boansi, D Quansah
      Pages: 39 - 45
      Abstract: Silver nanoparticles prepared by Turkevich method of reacting trisodium citrate as reducing agent with silver nitr-ate were incorporated in-situ with P. africanum (Dahoma) sawdust to produce nano-composite. Conventional X-ray powder diffraction of the nano-composite showed complex diffraction pattern, with line peak broadening in the crystalline phase and particle size widening in the amorphous region. The Miller indices of the four main peaks identified were (111), (200), (220) and (311); which confirmed the permitted reflections attributed to the presce-nce of crystalline silver. The mean lattice parameter calculated by Bragg’s law was 4.0903 Å, corresponding to face centred cubic Bravais lattice of silver. Using Scherrer formula, the crystallite sizes ranging from 4.95 – 15.25 nm were calculated for the broadened line peaks. The particle sizes in the amorphous phase were determined from the distorted peak or widening of the non-reflecting diffraction angles, and ranged from 1.35 - 4.10 nm. Fourier transform infrared (FTIR) spectroscopy of the nano-composite showed spectra lines of absorption peaks attributed to molecular functional group C-H-O at 1422.24 cm-1 (major component of sodium citrate), while a band centred at 3450 cm-1 was assigned to O-H bending or stretching of the interlayer water molecules (of H-bound and OH group vibrations), and the spectra line at 515.14 cm-1 indicated the presence of Ag-O stretching modes. The crystalline characteristics of the nano-composites could be indicative of potential applications in industry.Keywords: Nano-composite, X-ray Powder Diffraction, Crystallites, Lattice Parameter, Infrared Spectroscopy, Molecular Functional Groups
      PubDate: 2020-01-29
      DOI: 10.4314/jast.v23i1-2.
      Issue No: Vol. 23, No. 1-2 (2020)
       
  • Impact resistance and electrical conductivity of copper
           nanoparticle-Milicia excels sawdust composites

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      Authors: D Gyasi-Antwi, A.O. Boansi, P.K. Mensah
      Pages: 46 - 50
      Abstract: Copper nanoparticles (Cu(NPs)) prepared by chemical reduction of cupper (II) sulphate pentahydrate using ascorbic acid were blended with Milicia excels (Odum) sawdust and Polyvinyl Formal/Calcium Carbonate wood adhesive as matrix to produce rectangular slabs of nano-composites with potential applications for industrial pack-aging or building panelling. The nano-composites were characterized by Fourier Transform Infrared (FTIR) Spec-troscopy, and hydroxyl (OH) groups -CH2- (Alkane groups), C=C (Alkene or Aromatic groups), C-O (Carbonyl) groups of lignin, cellulose or hemicelluloses or C-O-C Ester groups of cellulose and hemicelluloses were identifi-ed. The mechanical toughness of the nano-composites were tested to determine the impact resistance, using Tinius Olsen IT 406 High Energy Pendulum Impact Machine. The impact energy of 26.89 ± 0.02 J exceeded values for individual constituents of the composites, was comparable to natural fibre reinforced composites, and the nano-composites could serve as panelling or packaging materials. The electrical characteristics of the nano-composites were examined by determining the electrical conductivity, resistivity and electric field strength, using simple dire-ct current Ohms bridge, and the values were respectively, (1.73 ± 0.05) x 10-2 ohm-1 m-1, 57.8 ± 0.5 Ω m, and 186.3 ± 0.5 V m-1. The low value of electrical conductivity was suggestive that the Cu(NP)-sawdust composite could be likened to intrinsic semiconductor, but the process for transition into extrinsic semiconductor was not in-vestigated. The imposed voltage increased with percentage moisture content, presumably due to hydrolyzed bon-ds on the surfaces of the nano-composite. The nano-composites could be used as insulating and packaging materi-als for sensitive electronic equipment.Keywords: Cu(NPs), Ascorbic Acid, FTIR Spectroscopy, Polyvinyl Formal, Impact Test, Electrical Resistivity
      PubDate: 2020-01-29
      DOI: 10.4314/jast.v23i1-2.
      Issue No: Vol. 23, No. 1-2 (2020)
       
  • Occupational dose assessment for radiation staff at nuclear reactor
           research centre, 2011 – 2015 (prior to core conversion)

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      Authors: M.A. Addo, P Davor, J.S. Lomotey, F Ameyaw, K Gyamfi, E.O. Amponsah-Abu
      Pages: 51 - 57
      Abstract: Radiation absorbed dose data of staff at the Nuclear Reactor Research Centre (NRCC) of Ghana Atomic Energy Commission, from 2011 to 2015, was analyzed to evaluate the performance of personnel monitoring program prior to the reactor core conversion, and to set baseline criteria for compliance after the core conversion. Personnel radiological deep dose data Hp (10) and surface dose data Hp (0.07) of three radiation workgroups, each of 4 wor-kers were extracted from Thermolumiscent Dosimeters (TLDs). The reactor dose rate data from coolant water was used as control factor influencing radiation absorbed by the staff. The mean dose rate values were respectively, 0.56 mSv and 0.48 mSv for Hp(10) and Hp (0.07), which were very low compared to the annual occupational limit of 20 mSv/year averaged over any 5-year period set by the International Commission on Radiological Protection. Statistical analyses were performed using Repeated Measure Analysis of Variance, Multivariate Analysis and Mauchly test. Significant differences were found in both Hp (10) (F(11, 36) = 7.45, p < 0.05) and Hp (0.07) (F(11, 36) = 4.51, p < 0.05) per year, however, no significant differences were found among the three workgroups. The dose data showed reduction in personnel radiological dosage over the five-year period, indicating either effec-tiveness of radiological protection program, reduction in reactor power due to burn out of nuclear fuel after 20 years of operation or reduced staff workload.Keywords: Occupational Dose, Thermolumiscent Dosimeter, Effective Dose, Personnel Monitoring, Analysis of Variance
      PubDate: 2020-01-29
      DOI: 10.4314/jast.v23i1-2.
      Issue No: Vol. 23, No. 1-2 (2020)
       
  • Regulatory framework for nuclear power plant fire safety and risk
           assessments from global perspective

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      Authors: M Asamoah, P Díaz, J Dies, A de Blas
      Pages: 58 - 68
      Abstract: The evolution of regulatory framework for fire safety and risk assessments at Nuclear Power Plants (NPPs) is on-going globally. The first generation commercial NPPs were designed and operated with minimal radiological risk posed by fire, as evidenced by the Brown Ferry (Alabama) NPP station cable tray accident in 1975. The present-ation provides global perspective of insights and integration of fire safety in the planning, design, construction, and operation of NPPs, with the aim for setting up safety regulations, particularly for countries embarking to oper-ate NPPs. Prescriptive fire safety regulations were instituted for commercial NPPs already in operation before 1979, leading to significant modification. The implementation challenges and cost of modifications provided sch-emes for voluntary risk-informed regulations. Since then, the regulatory framework has evolved from prescriptive to risk-informed performance-based assessments, with integrated system of combining deterministic and probabil-istic approaches, and other requirements in risk-informed decision making at the nuclear facility. From global per-spectives and experiences, such system-wide regulatory framework would identify generic issues of fire safety which could be resolved through design, construction and operation of NPPs by applications of risk-informed methodologies.Keywords: Prescriptive Regulation, Risk-informed Decision, Performance-based Assessment, Deterministic Approach, Defense-in-Depth, Probabilistic Safety and Risk Assessments, Suppressants
      PubDate: 2020-01-29
      DOI: 10.4314/jast.v23i1-2.
      Issue No: Vol. 23, No. 1-2 (2020)
       
  • Nucleation and growth of spherical water bubbles in hydrothermal grown
           quartz (A Review)

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      Authors: A Ayensu Gyeabour I.
      Pages: 69 - 92
      Abstract: Formation of water bubbles by precipitation of supersaturated water vapour and interactions of the bubbl-es with dislocations are fundamental for understanding the phenomenon of hydrolytic weakening of quartz during high temperature deformation. Annealing deformed synthetic quartz crystals at temperature in excess of 500 °C leads to phase-separation of grown-in water into hydroxyl (OH) species and molecular water (H2Om). By homoge-neous inter-conversion hydroxyl reaction of H2Om and O (anhydrous oxygen), the excess OH groups agglomerate into clusters to form embryos. Embryonic-nuclei of radii less than Gibbs critical size dissolve, while embryos of larger sizes grow to form stable nuclei in equilibrium with the supersaturated vapour. Ostwald ripening dissoluti-on-diffusion growth of nuclei at near critical state is limited by OH diffusion and surface vacancy kinetics. Chemi-cal potential difference of OH at the nucleus-bulk interface leads to changes in interfacial energy and higher OH concentration for growth of larger nucleus, as described by Gibbs-Thompson equation. For size evolution of nuclei, concentration gradients provide additional driving force for growth of larger nuclei at expense of smaller nuclei. La Mer model accounts for separation of nucleation and growth. Irreversible aggregation of stable nuclei form macrobubbles at the supercritical stage, which coalesce into spherical water bubbles of equilibrium sizes.Hydroxyl groups of low solubility in quartz are considered as interstitial defects, which are primarily tra-pped by vacancies. The spherical bubbles consisting of OH-vacancy complexes grow by absorbing OH monomers and coalescing with other bubbles under annealing conditions. The rate-controlling steps for bubble growth are migration by volume, surface diffusion, and interaction with lattice defects. By coalescence events of random co-llisions and OH capture, the bubbles gain energy for growth due to reduction of surface energy, limited by vacancy relaxation of strain fields produced by excess pressure in the bubble.The review examines mechanisms of nucleation and growth of water bubbles in quartz and presents com-prehensive models describing the processes occurring during bubble formation from evolution of clusters, embryonic-nuclei dissolution and growth, stable nuclei aggregation into nanobubbles, and coalescence to form macro-bubbles, which grow into equilibrium bubbles. The mathematical formulations governing clustering, dissolution-diffusion growth, coalescence events, interfacial hydroxyl mass diffusion, and surface adsorption kinetics for the physical processes of nucleation and growth of water-filled bubbles in quartz crystals are also presented.Keywords: Embryonic-Nucleus, La Mer Model, Ostwald Ripening, Interfacial Energy, Chemical Potential, Coale-scence Event, Rate Theory
      PubDate: 2020-01-29
      DOI: 10.4314/jast.v23i1-2.
      Issue No: Vol. 23, No. 1-2 (2020)
       
 
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