A. Macamo, Jardel Lourenço Macu acua, Lina Rafael Langa Macamo
Plant oil extracted from Kanyu almonds offers the potential to be an alternative to fossil fuel resources. This study aims to characterize the physico-chemical properties of kanyu almond oil, as safe indicators of the use of this biofuel for energy generators. Samples of the oils examined were density, kinematic viscosity, acid value, and oxidation stability. The experimental results showed that the oils had different sensitivities from the properties and indicate a clear deterioration of the kinematic viscosity and oxidation stability. These results were not in a condition to be used directly, such as fuels in diesel engines. Also, oil cannot be used immediately for feeding because it contains a high acid value. However, with the refining process, its kinematic viscosity and acid value can be improved, and can thus be used as biofuel and for other purposes. Key words: Kinematic viscosity, Induction time, Acid value, and Kanyu (Marula).
{"title":"Physical-chemical characterization of kanyu almond oil (Sclerocarya birrea) for use as biofuel","authors":"A. Macamo, Jardel Lourenço Macu acua, Lina Rafael Langa Macamo","doi":"10.5897/IJPS2021.4948","DOIUrl":"https://doi.org/10.5897/IJPS2021.4948","url":null,"abstract":"Plant oil extracted from Kanyu almonds offers the potential to be an alternative to fossil fuel resources. This study aims to characterize the physico-chemical properties of kanyu almond oil, as safe indicators of the use of this biofuel for energy generators. Samples of the oils examined were density, kinematic viscosity, acid value, and oxidation stability. The experimental results showed that the oils had different sensitivities from the properties and indicate a clear deterioration of the kinematic viscosity and oxidation stability. These results were not in a condition to be used directly, such as fuels in diesel engines. Also, oil cannot be used immediately for feeding because it contains a high acid value. However, with the refining process, its kinematic viscosity and acid value can be improved, and can thus be used as biofuel and for other purposes. \u0000 \u0000 Key words: Kinematic viscosity, Induction time, Acid value, and Kanyu (Marula).","PeriodicalId":14294,"journal":{"name":"International Journal of Physical Sciences","volume":"22 1","pages":"110-114"},"PeriodicalIF":0.0,"publicationDate":"2021-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85431809","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}
S. Dalhatu, K. A. Modu, Auwal Adamu Mahmoud, H. Adamu, Ridwanu Murtala
Purpose: Many researchers reported the use of chitosan in various applications due to its desirable properties, but then its application in a certain condition is limited due to its lower mechanical stability, lower solubility in certain solvents, and crystallinity of the polymer. Numerous report has been published by many researchers across the world modifying chitosan to enhanced its properties thereby improving its application in various field Methodology: Poly (2-dimethylaminoethyl methacrylate) (Cs-g-PDMAEMA) were successfully synthesized by Ultrasonic methods for the first time. The synthetic method was optimized by varying various reaction parameters and reaction conditions. The grafting was confirmed by characterizing the copolymer with FTIR, XRD, XPS, SEM, TGA, DTG, and DTA. Findings: The results show a good percent grafting and percent yield up to 132%G and 94.7%Y at optimum condition, and also shows a decrease of thermal stability and crystallinity of chitosan, there was improved in porosity of the surface, and complexity of the surface functional group making it a good candidate for metal chelating. Observing various changes in the spectrum of these derivatives and that of pure chitosan in addition to the change in properties of these polymers such as surface morphology, thermal stability, and crystallinity. Uniqe Contribution to Theory, Practice and Policy: It was suggested that this modification may improve the application of these polymers. KeyWords: Chitosan, Cs-g-PDMAEMA, Ultrasonication, Grafting
{"title":"ULTRASONIC ASSISTED SYNTHESIS AND CHARACTERIZATION OF CHITOSAN GRAF WITH 2-(DIMETHYLAMINOETHYLMETHACRYLATE) (DMAEMA) Cs-g-PDMAEMA","authors":"S. Dalhatu, K. A. Modu, Auwal Adamu Mahmoud, H. Adamu, Ridwanu Murtala","doi":"10.47941/jps.650","DOIUrl":"https://doi.org/10.47941/jps.650","url":null,"abstract":"Purpose: Many researchers reported the use of chitosan in various applications due to its desirable properties, but then its application in a certain condition is limited due to its lower mechanical stability, lower solubility in certain solvents, and crystallinity of the polymer. Numerous report has been published by many researchers across the world modifying chitosan to enhanced its properties thereby improving its application in various field\u0000Methodology: Poly (2-dimethylaminoethyl methacrylate) (Cs-g-PDMAEMA) were successfully synthesized by Ultrasonic methods for the first time. The synthetic method was optimized by varying various reaction parameters and reaction conditions. The grafting was confirmed by characterizing the copolymer with FTIR, XRD, XPS, SEM, TGA, DTG, and DTA. \u0000Findings: The results show a good percent grafting and percent yield up to 132%G and 94.7%Y at optimum condition, and also shows a decrease of thermal stability and crystallinity of chitosan, there was improved in porosity of the surface, and complexity of the surface functional group making it a good candidate for metal chelating. Observing various changes in the spectrum of these derivatives and that of pure chitosan in addition to the change in properties of these polymers such as surface morphology, thermal stability, and crystallinity. \u0000Uniqe Contribution to Theory, Practice and Policy: It was suggested that this modification may improve the application of these polymers. \u0000KeyWords: Chitosan, Cs-g-PDMAEMA, Ultrasonication, Grafting","PeriodicalId":14294,"journal":{"name":"International Journal of Physical Sciences","volume":"137 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80264538","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}
The corrosion inhibition of Aluminium alloy AA8011 in 0.25 M hydrochloric acid solution by Rosmarinus officinalis L. (rosemary) leaves extract was studied using the gravimetric technique at 303, 313, 323 and 333K, and in the presence of an external magnetic field. The study reveals that the methanolic extract of rosemary leaves inhibits corrosion of Al in 0.25 M HCl. The inhibition efficiency was found to increase with increase in concentration of the extract, but decreased with increase in temperature. Thermodynamic activation parameters like the activation energy (Ea), ranged from 15.29 to 35.06 kJ/mol, thereby suggesting the mix mechanism of physichemisorption; calculated values of the standard adsorption enthalpieswere positive indicating an endothermic process, while negative values of entropiesimplied an associative interaction between the inhibitor molecules and the Al surface. The corrosion data was found to be a good fit for the Langmuir (R2 > 0.98) and Villamil (R2 > 0.99) isotherm models. Values of the adsorption free energy obtained were negative, thereby describing a spontaneous adsorption process. The effect of an external magnetic field was found to have a mixed behaviour in the presence of the R. offinalis L. extract at room temperature. Nonetheless, the corrosion rate was generally found to decrease with increase in strength of the magnetic field. Key words: Acid corrosion, rosemary, aluminium, langmuir model, magnetic field.
{"title":"Adsorption and thermodynamic studies of the corrosion inhibition effect of Rosmarinus officinalis L. leaves on aluminium alloy in 0.25 M HCl and effect of an external magnetic field","authors":"Paul A. Andoor, K. Okeoma, U. Mbamara","doi":"10.5897/IJPS2021.4945","DOIUrl":"https://doi.org/10.5897/IJPS2021.4945","url":null,"abstract":"The corrosion inhibition of Aluminium alloy AA8011 in 0.25 M hydrochloric acid solution by Rosmarinus officinalis L. (rosemary) leaves extract was studied using the gravimetric technique at 303, 313, 323 and 333K, and in the presence of an external magnetic field. The study reveals that the methanolic extract of rosemary leaves inhibits corrosion of Al in 0.25 M HCl. The inhibition efficiency was found to increase with increase in concentration of the extract, but decreased with increase in temperature. Thermodynamic activation parameters like the activation energy (Ea), ranged from 15.29 to 35.06 kJ/mol, thereby suggesting the mix mechanism of physichemisorption; calculated values of the standard adsorption enthalpieswere positive indicating an endothermic process, while negative values of entropiesimplied an associative interaction between the inhibitor molecules and the Al surface. The corrosion data was found to be a good fit for the Langmuir (R2 > 0.98) and Villamil (R2 > 0.99) isotherm models. Values of the adsorption free energy obtained were negative, thereby describing a spontaneous adsorption process. The effect of an external magnetic field was found to have a mixed behaviour in the presence of the R. offinalis L. extract at room temperature. Nonetheless, the corrosion rate was generally found to decrease with increase in strength of the magnetic field. \u0000 \u0000 Key words: Acid corrosion, rosemary, aluminium, langmuir model, magnetic field.","PeriodicalId":14294,"journal":{"name":"International Journal of Physical Sciences","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76972493","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}
Many authors in the literature have worked on models for producing PV module performance, but the question of a climate-specific model is problematic. Some studies have shown more appropriate models for any PV module technology, while others have highlighted models that are more appropriate for a given climate. The aim of this work is to evaluate our model which is based on the I-V characteristic and their accuracy was assessed versus one-year of ground measurement from a system of PV module at different time resolutions. To predict the performance of PV modules in crystalline silicon in a sahelian climate in Senegal, the results obtained experimentally and those of the model were compared. The monthly nRMSE is 17.33% during the rainy season and 17.46% in dry season. There was a good correlation of the model, with a coefficient of 0.88 in January and 0.94 in September. Key words: PV module, short-circuit current, open circuit-voltage, maximum power output, I-V curve.
{"title":"Evaluation of PV performance prediction model in tropical environment in Senegal","authors":"Issa Faye, Ababacar Ndiaye, D. Kobor, M. Thiame","doi":"10.5897/IJPS2019.4836","DOIUrl":"https://doi.org/10.5897/IJPS2019.4836","url":null,"abstract":"Many authors in the literature have worked on models for producing PV module performance, but the question of a climate-specific model is problematic. Some studies have shown more appropriate models for any PV module technology, while others have highlighted models that are more appropriate for a given climate. The aim of this work is to evaluate our model which is based on the I-V characteristic and their accuracy was assessed versus one-year of ground measurement from a system of PV module at different time resolutions. To predict the performance of PV modules in crystalline silicon in a sahelian climate in Senegal, the results obtained experimentally and those of the model were compared. The monthly nRMSE is 17.33% during the rainy season and 17.46% in dry season. There was a good correlation of the model, with a coefficient of 0.88 in January and 0.94 in September. \u0000 \u0000 Key words: PV module, short-circuit current, open circuit-voltage, maximum power output, I-V curve.","PeriodicalId":14294,"journal":{"name":"International Journal of Physical Sciences","volume":"14 1","pages":"68-78"},"PeriodicalIF":0.0,"publicationDate":"2021-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89620475","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}
H. N. Sabaly, J. Basse, I. Diba, A. Sarr, M. Camara
This work uses the Weibull distribution for assessing the wind potential in Senegal; a country located in West Africa. In this study, data from the ERA5 reanalysis and the Ziguinchor station were used to characterize the spatio-temporal variability of wind and its available power density at 10 m and 100 m of altitude. The results showed that the wind potential was stronger on the coast and the north-western part of the country. A case study was carried out in the Basse Casamance on five (5) different sites located on the coast and inland (Kafountine, Diembering, Kabrousse, Bignona, and Ziguinhor). The results show good wind potentials in the coastal areas: Kabrousse, Kafountine, and Diembering. The most favourable period for wind power production is the winter. The ERA5 data and those of the Ziguinchor weather station were also compared. The results showed that the annual average wind power density calculated with the ERA5 reanalysis was slightly higher than that of the data from the station. The wind rose’s analysis, an essential parameter of the turbine's orientation, shows that the dominant wind direction in the Basse Casamance is northwest. In the last part of the study, an analysis of the choice of wind turbines adapted to the Ziguinchor site was carried out. Finally, this study provides the basic knowledge necessary for better planning of wind power projects in Senegal, especially in the Basse Casamance area. Key words: Wind potential, power density, Weibull distribution, ERA5 reanalysis, Senegal.
{"title":"Analysis of wind distribution and potential wind energy in Senegal with a focus on Basse Casamance","authors":"H. N. Sabaly, J. Basse, I. Diba, A. Sarr, M. Camara","doi":"10.5897/IJPS2020.4918","DOIUrl":"https://doi.org/10.5897/IJPS2020.4918","url":null,"abstract":"This work uses the Weibull distribution for assessing the wind potential in Senegal; a country located in West Africa. In this study, data from the ERA5 reanalysis and the Ziguinchor station were used to characterize the spatio-temporal variability of wind and its available power density at 10 m and 100 m of altitude. The results showed that the wind potential was stronger on the coast and the north-western part of the country. A case study was carried out in the Basse Casamance on five (5) different sites located on the coast and inland (Kafountine, Diembering, Kabrousse, Bignona, and Ziguinhor). The results show good wind potentials in the coastal areas: Kabrousse, Kafountine, and Diembering. The most favourable period for wind power production is the winter. The ERA5 data and those of the Ziguinchor weather station were also compared. The results showed that the annual average wind power density calculated with the ERA5 reanalysis was slightly higher than that of the data from the station. The wind rose’s analysis, an essential parameter of the turbine's orientation, shows that the dominant wind direction in the Basse Casamance is northwest. In the last part of the study, an analysis of the choice of wind turbines adapted to the Ziguinchor site was carried out. Finally, this study provides the basic knowledge necessary for better planning of wind power projects in Senegal, especially in the Basse Casamance area. \u0000 \u0000 Key words: Wind potential, power density, Weibull distribution, ERA5 reanalysis, Senegal.","PeriodicalId":14294,"journal":{"name":"International Journal of Physical Sciences","volume":"7 1","pages":"52-67"},"PeriodicalIF":0.0,"publicationDate":"2021-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89465200","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}
The anti-microbial efficiency of a composite material formulated from a scrap metal-based (iron (III) sulphate) coagulant and indigenous salt (NaCl) activated biomaterials (coconut shell carbon and counter wood) were evaluated by using the composite materials as coagulant and disinfectant adsorbent by treating borehole water and river samples at point-of-use. The results of the microbial analysis of the untreated and treated ABW, FBW, ERWA, and EBRW samples revealed a 75, 75, 80, and 66.6% bacteria genera removal was obtained during rainy season while there was 100, 66.6, 80, and 100% bacteria genera removal during rainy and dry seasons, respectively. Over 500 isolates of Escherichia coli, Pseudomonas species, Salmonella species and Vibrio cholera; Pseudomonas spp., E. coli, Bacillus species and Salmonella spp.; Shigella species, E. coli, Pseudomonas spp., Salmonella spp. and Staphylococcus species; E. coli, Salmonella spp. and Pseudomonas spp. bacteria genera were identified each in the untreated ABW, FBW, ERWA and EBRW samples during the rainy season, while Bacillus spp. and Citrobacter freundi; Klebsiella pneumoniae, E. coli and Pseudomonas spp.; E. coli, Salmonella spp., Shigella spp., K. pneumonia and Staphylococcus spp.; E. coli and E. faecium bacteria genera were identified during the dry season, respectively. After treatment, 3 and 2 genera of bacteria each were present in 48 and 9 isolates during rainy and dry seasons, respectively. The means of the aerobic bacteria count (ABC) during the two seasons showed no significant variations at p Eƒ 0.05 confidence limit. Key words: Anti-microbial activity, disinfection, coagulant, activated biomaterials.
{"title":"Evaluation of the anti-microbial efficiency of scrap metal-based coagulant and local salt modified-biomaterials for point-of-use water treatment","authors":"D. Igwe, J. Afiukwa, F. Nwabue","doi":"10.5897/IJPS2020.4926","DOIUrl":"https://doi.org/10.5897/IJPS2020.4926","url":null,"abstract":"The anti-microbial efficiency of a composite material formulated from a scrap metal-based (iron (III) sulphate) coagulant and indigenous salt (NaCl) activated biomaterials (coconut shell carbon and counter wood) were evaluated by using the composite materials as coagulant and disinfectant adsorbent by treating borehole water and river samples at point-of-use. The results of the microbial analysis of the untreated and treated ABW, FBW, ERWA, and EBRW samples revealed a 75, 75, 80, and 66.6% bacteria genera removal was obtained during rainy season while there was 100, 66.6, 80, and 100% bacteria genera removal during rainy and dry seasons, respectively. Over 500 isolates of Escherichia coli, Pseudomonas species, Salmonella species and Vibrio cholera; Pseudomonas spp., E. coli, Bacillus species and Salmonella spp.; Shigella species, E. coli, Pseudomonas spp., Salmonella spp. and Staphylococcus species; E. coli, Salmonella spp. and Pseudomonas spp. bacteria genera were identified each in the untreated ABW, FBW, ERWA and EBRW samples during the rainy season, while Bacillus spp. and Citrobacter freundi; Klebsiella pneumoniae, E. coli and Pseudomonas spp.; E. coli, Salmonella spp., Shigella spp., K. pneumonia and Staphylococcus spp.; E. coli and E. faecium bacteria genera were identified during the dry season, respectively. After treatment, 3 and 2 genera of bacteria each were present in 48 and 9 isolates during rainy and dry seasons, respectively. The means of the aerobic bacteria count (ABC) during the two seasons showed no significant variations at p Eƒ 0.05 confidence limit. \u0000 \u0000 Key words: Anti-microbial activity, disinfection, coagulant, activated biomaterials.","PeriodicalId":14294,"journal":{"name":"International Journal of Physical Sciences","volume":"42 1","pages":"36-51"},"PeriodicalIF":0.0,"publicationDate":"2021-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81493993","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}
A. Husin, B. Muslim, J. Efendi, D. R. Martiningrum
The Global Navigation Satellite System (GNSS) technologies have made significant contribution to seismology studies. Some processing strategies are well known, like real time PPP and DGPS techniques. These two methods have been widely used for GNSS based seismic activities monitoring. The first method requires accurate models of GNSS measurement errors to achieve accuracy in centimeter (cm) and need convergence time in order of minutes to hours. The second method need relative short distance of reference stations to reduce significantly measurement errors. To overcome disadvantages of such two methods, the variometric method was used to attain accuracy, but the method needs to be tested in the high ionospheric disturbance of equatorial region. During occurrences of plasma bubble, the radio signals from satellite passing through the ionosphere sometimes show rapid amplitude and phase variations called ionospheric scintillation. The occurrences of ionospheric scintillation could degrade the performance of systems and generate errors in received messages. In this study, variometric measurements are performed during the equinoctial month (March 2012) when the occurrence of scintillation was more intense. Results showed degradation of measurement accuracy during strong scintillation occurrences. The errors reached more than 1 m/s, especially for up-down measurement. Key words: Equinox, GISTM, ionospheric scintillation, variometric.
{"title":"Test of velocity-displacement estimation using variometric method under the condition of ionospheric scintillation during equinoctial months of solar maximum period 2012","authors":"A. Husin, B. Muslim, J. Efendi, D. R. Martiningrum","doi":"10.5897/IJPS2020.4921","DOIUrl":"https://doi.org/10.5897/IJPS2020.4921","url":null,"abstract":"The Global Navigation Satellite System (GNSS) technologies have made significant contribution to seismology studies. Some processing strategies are well known, like real time PPP and DGPS techniques. These two methods have been widely used for GNSS based seismic activities monitoring. The first method requires accurate models of GNSS measurement errors to achieve accuracy in centimeter (cm) and need convergence time in order of minutes to hours. The second method need relative short distance of reference stations to reduce significantly measurement errors. To overcome disadvantages of such two methods, the variometric method was used to attain accuracy, but the method needs to be tested in the high ionospheric disturbance of equatorial region. During occurrences of plasma bubble, the radio signals from satellite passing through the ionosphere sometimes show rapid amplitude and phase variations called ionospheric scintillation. The occurrences of ionospheric scintillation could degrade the performance of systems and generate errors in received messages. In this study, variometric measurements are performed during the equinoctial month (March 2012) when the occurrence of scintillation was more intense. Results showed degradation of measurement accuracy during strong scintillation occurrences. The errors reached more than 1 m/s, especially for up-down measurement. \u0000 \u0000 Key words: Equinox, GISTM, ionospheric scintillation, variometric.","PeriodicalId":14294,"journal":{"name":"International Journal of Physical Sciences","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76166569","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}
A number of potentially super-hard materials were examined using ab-initio methods. Low Gibbs free energy polymorphs of diamond-like materials for y = 0 to 7 in the stoichiometric type C8-y By, were identified at absolute zero of temperature. These were proposed as possible super-hard materials with useful applications. The materials with y = 0 to 3, that is, diamond (C), cubic C7B (c-C7B), rhombohedral C3B (r-C3B) and orthorhombic C5B3 (o-C5B3) were found to be dynamically and mechanically stable. A diamond standard was used as a stable comparison. Results of their bulk modulus calculations suggest that these materials were potentially super-hard in character. Systematic trends were established, the hardness was observed to reduce with increasing boron content. The materials under study were all determined as being brittle with diamond being the most brittle, C3B and C5B3 are the least brittle with B/G values of 1.32. Of the materials studied, diamond was determined to have the lowest degree of elastic anisotropy with a Universal Elastic Anisotropy Index of only 0.041 while C5B3 had the highest anisotropy of 1.160, making it the most susceptible to micro-cracks. Our electronic band structure studies of c-C7B, which was predicted to be the hardest in the C8-y By system after diamond, showed that the top of the valence band was about 1.7 eV above the Fermi level with a band gap between the valence and conduction bands, making c-C7B a hole-type conductor having a likely increase in conductivity with increased applied hydrostatic pressure. Key words: Phase stability, elastic anisotropy, ultra-hard material.
{"title":"Stability and elastic anisotropy of diamond related C8-yBy materials","authors":"G. Samukonga, A. Habanyama, N. K. Mumba","doi":"10.5897/IJPS2020.4920","DOIUrl":"https://doi.org/10.5897/IJPS2020.4920","url":null,"abstract":"A number of potentially super-hard materials were examined using ab-initio methods. Low Gibbs free energy polymorphs of diamond-like materials for y = 0 to 7 in the stoichiometric type C8-y By, were identified at absolute zero of temperature. These were proposed as possible super-hard materials with useful applications. The materials with y = 0 to 3, that is, diamond (C), cubic C7B (c-C7B), rhombohedral C3B (r-C3B) and orthorhombic C5B3 (o-C5B3) were found to be dynamically and mechanically stable. A diamond standard was used as a stable comparison. Results of their bulk modulus calculations suggest that these materials were potentially super-hard in character. Systematic trends were established, the hardness was observed to reduce with increasing boron content. The materials under study were all determined as being brittle with diamond being the most brittle, C3B and C5B3 are the least brittle with B/G values of 1.32. Of the materials studied, diamond was determined to have the lowest degree of elastic anisotropy with a Universal Elastic Anisotropy Index of only 0.041 while C5B3 had the highest anisotropy of 1.160, making it the most susceptible to micro-cracks. Our electronic band structure studies of c-C7B, which was predicted to be the hardest in the C8-y By system after diamond, showed that the top of the valence band was about 1.7 eV above the Fermi level with a band gap between the valence and conduction bands, making c-C7B a hole-type conductor having a likely increase in conductivity with increased applied hydrostatic pressure. \u0000 \u0000 Key words: Phase stability, elastic anisotropy, ultra-hard material.","PeriodicalId":14294,"journal":{"name":"International Journal of Physical Sciences","volume":"436 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76667275","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}
Rain-based attenuation (RBA) is a major deteriorating factor affecting radio wave signals operating at microwave and millimetre wave bands for a typical Earth-Space Communication Link (ESCL). Although the international telecommunication union (ITU) recommended a standard model for predicting RBA along the terrestrial and ESCL, the technique underperforms in tropical environments. However, the model can be supported by appropriate modulation to enhance link performance. The present study assesses the performance of selected RBA models, namely the ITU, Moupfouma, and Garcἱa-Lὁpez models based on rain types for K-V frequency bands over some selected locations in Southwestern Nigeria. Link performance was further tested based on different modulation scaling to minimize signal degradation. The result shows that Garcίa-Lόpez and ITU models performed well at low rain rate R ≤2 mm/h but underestimated at higher rain rates (except thunderstorms rain type) at the high-frequency band. However, the Moupfouma model performed well for all the rain types irrespective of the selected frequency band, while the ITU model underestimated attenuation for R 30 mm/h (thunderstorm) rain type from the K-V band frequency, Garcia Lopez underestimates the RBA value for R 5 mm/h up to the Ka frequency band. Considering the modulation scaling on link performance shows that the bit-error-rate (BER) will severely degrade with a high rain rate compared to the low rain rate across different frequencies. The BER for 8-PPM outperforms the other types of modulation schemes that were used in this study. Overall results revealed that modulation technique DPSK with selective combining diversity gave a marginal improvement with the increase in link distance and operating frequency. Key words: ESCL, rain attenuation models, modulation techniques, K-V frequency bands.
在典型的地空通信链路(ESCL)中，雨基衰减是影响微波和毫米波波段无线电波信号恶化的主要因素。尽管国际电信联盟(ITU)推荐了一种标准模型来预测沿陆地和ESCL的RBA，但该技术在热带环境中表现不佳。然而，该模型可以通过适当的调制来支持，以提高链路性能。本研究根据尼日利亚西南部一些选定地点K-V频段的降雨类型，评估了选定的RBA模型的性能，即ITU、Moupfouma和Garc ο a-L ο pez模型。进一步测试了基于不同调制比例的链路性能，以最小化信号退化。结果表明，garc - lpez和ITU模型在低雨率R≤2 mm/h时表现良好，但在高频高雨率(雷暴雨类型除外)时表现较差。然而，Moupfouma模型在所有降雨类型中都表现良好，而ITU模型低估了r30mm /h(雷暴)降雨类型从K-V频段频率的衰减，Garcia Lopez低估了r5mm /h至Ka频段的RBA值。考虑调制尺度对链路性能的影响表明，在不同频率下，高降雨率比低降雨率会严重降低误码率。8-PPM的误码率优于本研究中使用的其他类型的调制方案。结果表明，采用选择性组合分集的DPSK调制技术，随着链路距离和工作频率的增加，其性能有一定的提高。关键词:ESCL，雨衰减模型，调制技术，K-V频段。
{"title":"Evaluation of simulated rain-based attenuation techniques at k-v frequency bands for satellite services under different modulation techniques over Southwestern Nigeria","authors":"J. Ojo, K. Adedayo, A. N. Uchegbu","doi":"10.5897/IJPS2020.4902","DOIUrl":"https://doi.org/10.5897/IJPS2020.4902","url":null,"abstract":"Rain-based attenuation (RBA) is a major deteriorating factor affecting radio wave signals operating at microwave and millimetre wave bands for a typical Earth-Space Communication Link (ESCL). Although the international telecommunication union (ITU) recommended a standard model for predicting RBA along the terrestrial and ESCL, the technique underperforms in tropical environments. However, the model can be supported by appropriate modulation to enhance link performance. The present study assesses the performance of selected RBA models, namely the ITU, Moupfouma, and Garcἱa-Lὁpez models based on rain types for K-V frequency bands over some selected locations in Southwestern Nigeria. Link performance was further tested based on different modulation scaling to minimize signal degradation. The result shows that Garcίa-Lόpez and ITU models performed well at low rain rate R ≤2 mm/h but underestimated at higher rain rates (except thunderstorms rain type) at the high-frequency band. However, the Moupfouma model performed well for all the rain types irrespective of the selected frequency band, while the ITU model underestimated attenuation for R 30 mm/h (thunderstorm) rain type from the K-V band frequency, Garcia Lopez underestimates the RBA value for R 5 mm/h up to the Ka frequency band. Considering the modulation scaling on link performance shows that the bit-error-rate (BER) will severely degrade with a high rain rate compared to the low rain rate across different frequencies. The BER for 8-PPM outperforms the other types of modulation schemes that were used in this study. Overall results revealed that modulation technique DPSK with selective combining diversity gave a marginal improvement with the increase in link distance and operating frequency. \u0000 \u0000 Key words: ESCL, rain attenuation models, modulation techniques, K-V frequency bands.","PeriodicalId":14294,"journal":{"name":"International Journal of Physical Sciences","volume":"12 1","pages":"1-15"},"PeriodicalIF":0.0,"publicationDate":"2021-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83016064","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}
The coherent perfect absorption (CPA) for a planar resonator of silver has been elaborated here in numerical and analytical approaches. It is investigated numerically in different geometrical shapes and spectral regimes. The CPA mode is observed to be spectrally sensitive to the geometry of the resonator. The scattering matrix method is employed in theoretical analysis. The CPA conditions and output irradiance expressions are extracted. The mode is studied by the relative phase between two counter inputs of the resonator. The appearance of this mode is attributable to the dipole resonance effect. The way light is controlled in the required regime in perfect subwavelength structural geometry is obtained in this study. The nanostructure is functional in optical switching, modulation and terahertz sensor of photonics devices. Key words: Sensor, modulation, resonator, scattering and finite-difference time-domain (FDTD).
{"title":"Coherent perfect absorption in plasmonic planar metasurface","authors":"Alamgir Badsha","doi":"10.5897/IJPS2020.4924","DOIUrl":"https://doi.org/10.5897/IJPS2020.4924","url":null,"abstract":"The coherent perfect absorption (CPA) for a planar resonator of silver has been elaborated here in numerical and analytical approaches. It is investigated numerically in different geometrical shapes and spectral regimes. The CPA mode is observed to be spectrally sensitive to the geometry of the resonator. The scattering matrix method is employed in theoretical analysis. The CPA conditions and output irradiance expressions are extracted. The mode is studied by the relative phase between two counter inputs of the resonator. The appearance of this mode is attributable to the dipole resonance effect. The way light is controlled in the required regime in perfect subwavelength structural geometry is obtained in this study. The nanostructure is functional in optical switching, modulation and terahertz sensor of photonics devices. \u0000 \u0000 Key words: Sensor, modulation, resonator, scattering and finite-difference time-domain (FDTD).","PeriodicalId":14294,"journal":{"name":"International Journal of Physical Sciences","volume":"9 1","pages":"213-220"},"PeriodicalIF":0.0,"publicationDate":"2020-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81313392","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}
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