Vertical axis wind turbines (VAWTs) extract energy through reduction of the kinetic and turbulent kinetic energies, and the vertical momentum flux. Detailed turbulence profiling and energy balance analysis were attempted through direct turbulence quantification using the Eddy Covariance method. A high-frequency sonic anemometer was employed to measure flow and turbulence upwind and downwind of a Darrieus-type VAWT at different positions that cover the entire windswept area. The data was processed and analysed using a custom Matlab script. Energy balance analysis showed that there was a significant drop in kinetic energy before and after the VAWT (72% to 42%) but a small increase in turbulent kinetic energy (28% to 31%). The results also showed that the rotational direction of VAWT contributed to a higher value of longitudinal turbulence at the windward edge of the VAWT. The VAWT affected the flow field upwind by generating reverse flows. The largest vertical momentum flux transfer occurred downwind of the windward side of the VAWT. Spectral analysis shows that the VAWT produced smaller but faster momentum flux vortices due to the rotating rotors in the 1 Hz to 5 Hz range. This data and results have important applications to accurately model complex flows around VAWTs.
{"title":"Energy Balance Analysis and Turbulence Profile of a Darrieus-type Vertical Axis Wind Turbine","authors":"Y. H’ng, Y. Yusup, S. A. Zaki","doi":"10.21315/JPS2019.30.1.5","DOIUrl":"https://doi.org/10.21315/JPS2019.30.1.5","url":null,"abstract":"Vertical axis wind turbines (VAWTs) extract energy through reduction of the kinetic and turbulent kinetic energies, and the vertical momentum flux. Detailed turbulence profiling and energy balance analysis were attempted through direct turbulence quantification using the Eddy Covariance method. A high-frequency sonic anemometer was employed to measure flow and turbulence upwind and downwind of a Darrieus-type VAWT at different positions that cover the entire windswept area. The data was processed and analysed using a custom Matlab script. Energy balance analysis showed that there was a significant drop in kinetic energy before and after the VAWT (72% to 42%) but a small increase in turbulent kinetic energy (28% to 31%). The results also showed that the rotational direction of VAWT contributed to a higher value of longitudinal turbulence at the windward edge of the VAWT. The VAWT affected the flow field upwind by generating reverse flows. The largest vertical momentum flux transfer occurred downwind of the windward side of the VAWT. Spectral analysis shows that the VAWT produced smaller but faster momentum flux vortices due to the rotating rotors in the 1 Hz to 5 Hz range. This data and results have important applications to accurately model complex flows around VAWTs.","PeriodicalId":16757,"journal":{"name":"Journal of Physical Science","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80341209","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. Alnakhlani, Belqees Hassan, M. Ahlam, Muhammad Abdulhafiz
Samples of superconducting compounds were prepared by a solid-state reaction technique in a sealed quartz tube under normal pressure. The impact of the compound on the electrical properties has been studied using the electrical resistance measurements of the samples as a function of temperature. The obtained results appear that an enhancement in the phase formation, and the superconducting transition temperature Tc were improved. It may be due to the decreasing of the magnetic impurities or the delocalisation of carriers which resulted in the enhancement of the density of mobile carriers in the conducting CuO2 planes.
{"title":"Effect of Preparation and Annealing Temperature on the Properties of (Hg,Tl)-2223 Superconductor","authors":"A. Alnakhlani, Belqees Hassan, M. Ahlam, Muhammad Abdulhafiz","doi":"10.21315/JPS2019.30.1.6","DOIUrl":"https://doi.org/10.21315/JPS2019.30.1.6","url":null,"abstract":"Samples of superconducting compounds were prepared by a solid-state reaction technique in a sealed quartz tube under normal pressure. The impact of the compound on the electrical properties has been studied using the electrical resistance measurements of the samples as a function of temperature. The obtained results appear that an enhancement in the phase formation, and the superconducting transition temperature Tc were improved. It may be due to the decreasing of the magnetic impurities or the delocalisation of carriers which resulted in the enhancement of the density of mobile carriers in the conducting CuO2 planes.","PeriodicalId":16757,"journal":{"name":"Journal of Physical Science","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77618834","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}
Good stratigraphy mapping of a site is essential in archaeological explorations but Guar Kepah, Penang, Malaysia had no detailed subsurface mapping done previously up till now. As many archaeological remnants in the vicinity have an affiliation with shell middens, better understanding on Guar Kepah’s strata will increase the efficiency of uncovering the shell middens while also saving a huge amount of energy in excavating. This research aims to distinguish Guar Kepah’s buried shell midden from the surrounding strata using electrical resistivity method. The study area is composed of three shallow strata of unconsolidated soil with low resistivity values. The sandy-clay layer has the lowest resistivity (< 40 Ωm), followed by densely packed shell layer (40–70 Ωm) and sandy layer (> 70 Ωm). The presence of shells indicates that the uppermost strata is of marine origin, which automatically makes Gula Formation the youngest formation in Guar Kepah due to the absence of terrestrial deposits (Beruas Formation) on top of the layer. The shell layer from the resistivity profiles suggests that the layer has relatively uniform thickness throughout the site. The layer also becomes undulating and shallow towards the south (dipping), making the top sandy-clay soil become thinner or absent in the south. The dipping feature of the shell layer acts as an indicator that Guar Kepah used to be a beach ridge during sea transgression, and further proves that the area was once a marine environment. However, the shell layer at the southern zone poses an anomaly where it suddenly dips toward the centre. As a result, two zones were marked as potential shell middens at the south-western zone (only exhibits one side of the midden that is dipping towards centre) and south-eastern zone (shell midden elongated to the east). Subsequent excavation based on this study had successfully exposed the south-eastern midden and Shell Midden at Guar Kepah 100 proved that resistivity method could be used not only in stratigraphy identification, but also in characterising shell layer and detecting shell midden.
{"title":"Resistivity Characterisation of Shallow Stratigraphy in Delineating Shell Midden at Guar Kepah, Penang, Malaysia","authors":"N. Rosli, N. Ismail, H. Mansor, M. Saidin","doi":"10.21315/JPS2019.30.1.8","DOIUrl":"https://doi.org/10.21315/JPS2019.30.1.8","url":null,"abstract":"Good stratigraphy mapping of a site is essential in archaeological explorations but Guar Kepah, Penang, Malaysia had no detailed subsurface mapping done previously up till now. As many archaeological remnants in the vicinity have an affiliation with shell middens, better understanding on Guar Kepah’s strata will increase the efficiency of uncovering the shell middens while also saving a huge amount of energy in excavating. This research aims to distinguish Guar Kepah’s buried shell midden from the surrounding strata using electrical resistivity method. The study area is composed of three shallow strata of unconsolidated soil with low resistivity values. The sandy-clay layer has the lowest resistivity (< 40 Ωm), followed by densely packed shell layer (40–70 Ωm) and sandy layer (> 70 Ωm). The presence of shells indicates that the uppermost strata is of marine origin, which automatically makes Gula Formation the youngest formation in Guar Kepah due to the absence of terrestrial deposits (Beruas Formation) on top of the layer. The shell layer from the resistivity profiles suggests that the layer has relatively uniform thickness throughout the site. The layer also becomes undulating and shallow towards the south (dipping), making the top sandy-clay soil become thinner or absent in the south. The dipping feature of the shell layer acts as an indicator that Guar Kepah used to be a beach ridge during sea transgression, and further proves that the area was once a marine environment. However, the shell layer at the southern zone poses an anomaly where it suddenly dips toward the centre. As a result, two zones were marked as potential shell middens at the south-western zone (only exhibits one side of the midden that is dipping towards centre) and south-eastern zone (shell midden elongated to the east). Subsequent excavation based on this study had successfully exposed the south-eastern midden and Shell Midden at Guar Kepah 100 proved that resistivity method could be used not only in stratigraphy identification, but also in characterising shell layer and detecting shell midden.","PeriodicalId":16757,"journal":{"name":"Journal of Physical Science","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80580570","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}
Pub Date : 2019-05-15DOI: 10.21315/JPS2019.30.1.13
U. Reuben, A. F. Ismail, A. Ahmad, H. Maina, Aziah Daud
Indoor air quality refers to the air quality in and around laboratory buildings and facilities, which directly affects the health and comfort of workers. Poor air quality poses numerous health challenges to the laboratory workers and environment, and causes sick building syndrome (SBS) among workers. The objective of this study is to determine associations of SBS related to indoor air concentration in a dose-dependent manner among Nigerian laboratory university workers. This was a cross-sectional study on a population-based sample of Nigerian university laboratories and the workers. Data were collected using an indoor air quality control meter, dosimeter tubes gases of interest, and a set of questionnaires (MM-40). The results showed that the mean indoor air concentrations in a dose-dependent manner for chemical parameters range from 473.0 ppm to753.0 ppm, 17.9 ppm to 27.3 ppm, 5.7 ppm to 8.5 ppm, and 6.3 ppm to 9.1 ppm for CO2 , CO, NO2, H2S and SO2 , respectively. The prevalence of SBS, i.e., skin-related syndrome (SRS) is 38.5%, general-related symptom (GRS) is 28.3%, mucosal-related symptom (MRS) is 19.2% and at least one score was a respiratory-related symptom (RRS), which is 13.9%. The significant associated factors of SBS revealed by multinomial logistic regression in this study were NO2 [SRS (P = 0.022), GRS (P = 0.023), MRS (P = 0.032)], H2 S [SRS (P = 0.031), GRS (P < 0.001), MRS (P = 0.021)], and SO2 [SRS (P = 0.001), GRS (P < 0.001), MRS (P = 0.022)]. On the other hand, office laboratory temperature and relative humidity were shown to be negatively statistically associated with prevalence symptoms relative to RRS. In this study, SBS was found to be high. Indoor air concentration Air Quality and SBS Syndrome 180 in a dose-dependent manner and environmental parameters could increase the prevalence and incidence of SBS-related symptoms. Therefore, it is important to educate the workers on occupational and environmental health at a workplace to minimise SBS in the future.
{"title":"Indoor Air Quality and Sick Building Syndrome Among Nigerian Laboratory University Workers","authors":"U. Reuben, A. F. Ismail, A. Ahmad, H. Maina, Aziah Daud","doi":"10.21315/JPS2019.30.1.13","DOIUrl":"https://doi.org/10.21315/JPS2019.30.1.13","url":null,"abstract":"Indoor air quality refers to the air quality in and around laboratory buildings and facilities, which directly affects the health and comfort of workers. Poor air quality poses numerous health challenges to the laboratory workers and environment, and causes sick building syndrome (SBS) among workers. The objective of this study is to determine associations of SBS related to indoor air concentration in a dose-dependent manner among Nigerian laboratory university workers. This was a cross-sectional study on a population-based sample of Nigerian university laboratories and the workers. Data were collected using an indoor air quality control meter, dosimeter tubes gases of interest, and a set of questionnaires (MM-40). The results showed that the mean indoor air concentrations in a dose-dependent manner for chemical parameters range from 473.0 ppm to753.0 ppm, 17.9 ppm to 27.3 ppm, 5.7 ppm to 8.5 ppm, and 6.3 ppm to 9.1 ppm for CO2 , CO, NO2, H2S and SO2 , respectively. The prevalence of SBS, i.e., skin-related syndrome (SRS) is 38.5%, general-related symptom (GRS) is 28.3%, mucosal-related symptom (MRS) is 19.2% and at least one score was a respiratory-related symptom (RRS), which is 13.9%. The significant associated factors of SBS revealed by multinomial logistic regression in this study were NO2 [SRS (P = 0.022), GRS (P = 0.023), MRS (P = 0.032)], H2 S [SRS (P = 0.031), GRS (P < 0.001), MRS (P = 0.021)], and SO2 [SRS (P = 0.001), GRS (P < 0.001), MRS (P = 0.022)]. On the other hand, office laboratory temperature and relative humidity were shown to be negatively statistically associated with prevalence symptoms relative to RRS. In this study, SBS was found to be high. Indoor air concentration Air Quality and SBS Syndrome 180 in a dose-dependent manner and environmental parameters could increase the prevalence and incidence of SBS-related symptoms. Therefore, it is important to educate the workers on occupational and environmental health at a workplace to minimise SBS in the future.","PeriodicalId":16757,"journal":{"name":"Journal of Physical Science","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82435409","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}
Pub Date : 2019-05-15DOI: 10.21315/JPS2019.30.1.11
N. A. Mokri, Oh Pei Ching, H. Mukhtar, C. Leng
Mobil Composition of Matter no. 48 (MCM-48) is a promising inorganic particle due to its unique crystal structure and 3-dimensional porous network. Incorporating a discrete amount of nanosized MCM-48 for material development would give significant impact to the material’s performance and mechanical robustness. Thus far, the synthesis of MCM-48 in the nanoscale regime has been achieved via chemical modification techniques. However, they are often not reproducible due to limited understanding of surfactant behaviour. On the other hand, physical modification technique is more stable, thereby can reduce the possibility of producing other undesired mesophase. Nevertheless, this technique has not been adapted for nanosized MCM-48 synthesis. In this work, the physical modification technique was adapted to tailor MCM-48 particle size by varying stirring speed (i.e., 1000 rpm, 3000 rpm and 5000 rpm) and using different types of washing medium. Particle size distribution (PSD) studies showed mean particle size of 250 ± 50 nm. XRD analysis displayed several crystalline peaks indexed to cubic crystal mesophase. Transmission electron microscopy (TEM) and Brunauer-Emmett Teller (BET) analyses also showed a unique 3D cubic interconnecting porous network with specific surface area of 1030 m2 g–1. It was revealed that the degree of agglomeration increased as relative polarity of alcohol increased, CH3OH > CH3CH2OH. Therefore, particle size and agglomeration state of MCM-48 can be tailored by varying the physical modification techniques while maintaining its intrinsic pore morphology.
{"title":"Tailoring Particle Size and Agglomeration State of Mesoporous MCM-48 via Optimisation of Sol-gel Silica Process","authors":"N. A. Mokri, Oh Pei Ching, H. Mukhtar, C. Leng","doi":"10.21315/JPS2019.30.1.11","DOIUrl":"https://doi.org/10.21315/JPS2019.30.1.11","url":null,"abstract":"Mobil Composition of Matter no. 48 (MCM-48) is a promising inorganic particle due to its unique crystal structure and 3-dimensional porous network. Incorporating a discrete amount of nanosized MCM-48 for material development would give significant impact to the material’s performance and mechanical robustness. Thus far, the synthesis of MCM-48 in the nanoscale regime has been achieved via chemical modification techniques. However, they are often not reproducible due to limited understanding of surfactant behaviour. On the other hand, physical modification technique is more stable, thereby can reduce the possibility of producing other undesired mesophase. Nevertheless, this technique has not been adapted for nanosized MCM-48 synthesis. In this work, the physical modification technique was adapted to tailor MCM-48 particle size by varying stirring speed (i.e., 1000 rpm, 3000 rpm and 5000 rpm) and using different types of washing medium. Particle size distribution (PSD) studies showed mean particle size of 250 ± 50 nm. XRD analysis displayed several crystalline peaks indexed to cubic crystal mesophase. Transmission electron microscopy (TEM) and Brunauer-Emmett Teller (BET) analyses also showed a unique 3D cubic interconnecting porous network with specific surface area of 1030 m2 g–1. It was revealed that the degree of agglomeration increased as relative polarity of alcohol increased, CH3OH > CH3CH2OH. Therefore, particle size and agglomeration state of MCM-48 can be tailored by varying the physical modification techniques while maintaining its intrinsic pore morphology.","PeriodicalId":16757,"journal":{"name":"Journal of Physical Science","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84420337","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}
Recent finding of “Penang Woman” skeleton in Guar Kepah, Penang, Malaysia has triggered researchers to discover more archaeological remains inside the area. Some part has been excavated, exposing some shell mound where the skeleton was found. It is believed that the shell mound remarks the burial place of people in early age civilisation. More excavation processes need to be conducted in the area to see if any more skeleton, monument and pottery could be found. 2-D resistivity method was carried out in the study area to determine resistivity value of shell mound and locate another possible shell mound. Pole-dipole array was used along four survey lines where one of the survey lines is conducted on the existing shell mound while the rest are on undisturbed ground in the study area. The data were processed by using Res2Dinv software. The results show that the resistivity value of the exposed shell mound is within the range of 100 Ωm to 200 Ωm. This value was used as the reference in predicting possible shell mound on the other survey lines. Some part of the other survey lines shows the same resistivity value as the existing mound. Therefore, it can be predicted as shell mound.
{"title":"Shell Mound Investigation at Guar Kepah (Penang, Malaysia) Using 2-D Resistivity Imaging for Archaeological Study","authors":"Nazrin Rahman, N. Ismail, M. Saidin","doi":"10.21315/JPS2019.30.1.2","DOIUrl":"https://doi.org/10.21315/JPS2019.30.1.2","url":null,"abstract":"Recent finding of “Penang Woman” skeleton in Guar Kepah, Penang, Malaysia has triggered researchers to discover more archaeological remains inside the area. Some part has been excavated, exposing some shell mound where the skeleton was found. It is believed that the shell mound remarks the burial place of people in early age civilisation. More excavation processes need to be conducted in the area to see if any more skeleton, monument and pottery could be found. 2-D resistivity method was carried out in the study area to determine resistivity value of shell mound and locate another possible shell mound. Pole-dipole array was used along four survey lines where one of the survey lines is conducted on the existing shell mound while the rest are on undisturbed ground in the study area. The data were processed by using Res2Dinv software. The results show that the resistivity value of the exposed shell mound is within the range of 100 Ωm to 200 Ωm. This value was used as the reference in predicting possible shell mound on the other survey lines. Some part of the other survey lines shows the same resistivity value as the existing mound. Therefore, it can be predicted as shell mound.","PeriodicalId":16757,"journal":{"name":"Journal of Physical Science","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87306003","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}
Munasir, Triwikantoro, M. Zainuri, R. Bäßler, Darminto
The fabrication and characteristics of amorphous silica reinforced Al matrix composites are studied in this paper. The major starting materials were commercial Al powder and extracted nanoparticle SiO2 (NPS) powder from Indonesian silica sands. Two different active solutions,namely N-butanol and tetramethylammonium hydroxide (TMAH), were introduced during synthesis. Characterisations in terms of physical, mechanical, microstructural and corrosion rate examinations were also employed. Introducing the SiO2 nanoparticles into the Al matrix has decreased the density and increased the porosity of the composites. The addition of N-butanol into Al/SiO2(Al/SiO2(B)) led to broader and lower X-ray diffraction profiles than the addition of TMAH (Al/SiO2(T)). From the microstructural analysis, we found that the SiO2 particles enter and agglomerate into the opening gap of the Al sheets. Furthermore, yield strength, ultimate compression strength and modulus of elasticity tended to reduce the addition of SiO2. The corrosion rate of Al/SiO2(T) was lower than that of Al/SiO2(B) composites.
{"title":"Mechanical Strength and Corrosion Rate of Aluminium Composites (Al/SiO2): Nanoparticle Silica (NPS) as Reinforcement","authors":"Munasir, Triwikantoro, M. Zainuri, R. Bäßler, Darminto","doi":"10.21315/JPS2019.30.1.7","DOIUrl":"https://doi.org/10.21315/JPS2019.30.1.7","url":null,"abstract":"The fabrication and characteristics of amorphous silica reinforced Al matrix composites are studied in this paper. The major starting materials were commercial Al powder and extracted nanoparticle SiO2 (NPS) powder from Indonesian silica sands. Two different active solutions,namely N-butanol and tetramethylammonium hydroxide (TMAH), were introduced during synthesis. Characterisations in terms of physical, mechanical, microstructural and corrosion rate examinations were also employed. Introducing the SiO2 nanoparticles into the Al matrix has decreased the density and increased the porosity of the composites. The addition of N-butanol into Al/SiO2(Al/SiO2(B)) led to broader and lower X-ray diffraction profiles than the addition of TMAH (Al/SiO2(T)). From the microstructural analysis, we found that the SiO2 particles enter and agglomerate into the opening gap of the Al sheets. Furthermore, yield strength, ultimate compression strength and modulus of elasticity tended to reduce the addition of SiO2. The corrosion rate of Al/SiO2(T) was lower than that of Al/SiO2(B) composites.","PeriodicalId":16757,"journal":{"name":"Journal of Physical Science","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82309481","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}
M. J. Rashid, A. Mamun, Md. Samiul Islam Sadek, T. Hossain, S. Hasan
This study describes the characteristics of GaN/Al1-xGaxN quantum well (QW) operating in the UV region by varying different parameters. It is well known that the spontaneous and piezoelectric polarisations in wurtzite nitride heterostructures give rise to large built-in electric fields, which leads to an important consequence in the optical properties of GaN/Al1-xGaxN quantum wells. We first modelled the effect of electric field on the calculated electronic band structure. The increase in electric field affected the band structure for a fixed QW and barrier thickness. Then we investigated the effect of QW thickness on the bandgap energy for different electric fields. Afterwards, the Al composition (1-x) and Al1-xGaxN barrier thickness are varied for different well thickness with a fixed electric field.
{"title":"Simulation Study of GaN/Al1-xGaxN Quantum Well (QW) Operating in the UV Region","authors":"M. J. Rashid, A. Mamun, Md. Samiul Islam Sadek, T. Hossain, S. Hasan","doi":"10.21315/JPS2019.30.1.3","DOIUrl":"https://doi.org/10.21315/JPS2019.30.1.3","url":null,"abstract":"This study describes the characteristics of GaN/Al1-xGaxN quantum well (QW) operating in the UV region by varying different parameters. It is well known that the spontaneous and piezoelectric polarisations in wurtzite nitride heterostructures give rise to large built-in electric fields, which leads to an important consequence in the optical properties of GaN/Al1-xGaxN quantum wells. We first modelled the effect of electric field on the calculated electronic band structure. The increase in electric field affected the band structure for a fixed QW and barrier thickness. Then we investigated the effect of QW thickness on the bandgap energy for different electric fields. Afterwards, the Al composition (1-x) and Al1-xGaxN barrier thickness are varied for different well thickness with a fixed electric field.","PeriodicalId":16757,"journal":{"name":"Journal of Physical Science","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76856321","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}
Pub Date : 2019-04-25DOI: 10.21315/JPS2019.30.1.10
Vicinisvarri Inderan, M. arafat, A. Haseeb, K. Sudesh, H. Lee
A comparative study of structural and ethanol gas sensing properties of pure, nickel and palladium doped SnO 2 nanorods synthesised by the hydrothermal method. J. Phys. Sci. , 30(1), 127–143, ABSTRACT: SnO 2 nanostructures are usually modified with some metal dopants in order to improve its gas sensing properties. In this work, pure tin oxide (SnO 2 ), nickel (Ni) doped SnO 2 (Ni:SnO 2 ) and palladium (Pd) doped SnO 2 (Pd:SnO 2 ) nanorods were successfully synthesised via hydrothermal method at low temperature (180°C) without templates or further calcination. All the samples were systematically analysed using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The sensor response (R = R 0 /R g ) towards 1000 ppm ethanol gas was investigated using nitrogen gas as a carrier gas. XRD results confirmed that all samples consisted of rutile tetragonal-shaped SnO 2 . It was found that the average diameter of nanorods formed in Ni:SnO 2 and Pd:SnO 2 were decreased to ~6 nm and ~10 nm, compared with nanorods formed in pure SnO 2 (~25 nm). The gas sensing results indicated that the sensor properties of SnO 2 were enhanced after the doping process. At 450°C, the Pd:SnO 2 nanorod sensor recorded the highest response value towards 1000 ppm ethanol gas which is 15 times higher than pure SnO 2 nanorods. Interestingly, all samples showed similar response time, ~ 40 s. However, pure SnO 2 and Ni:SnO 2 nanorods sensors exhibited longer recovery time compared to Pd:SnO 2 nanorods. Pd:SnO 2 nanorods recorded only 12 min of almost 100% recovery. It is proposed that Pd:SnO 2 sensor could be a promising candidate for the detection of ethanol gas.
{"title":"A Comparative Study of Structural and Ethanol Gas Sensing Properties of Pure, Nickel and Palladium Doped SnO2 Nanorods Synthesised by the Hydrothermal Method","authors":"Vicinisvarri Inderan, M. arafat, A. Haseeb, K. Sudesh, H. Lee","doi":"10.21315/JPS2019.30.1.10","DOIUrl":"https://doi.org/10.21315/JPS2019.30.1.10","url":null,"abstract":"A comparative study of structural and ethanol gas sensing properties of pure, nickel and palladium doped SnO 2 nanorods synthesised by the hydrothermal method. J. Phys. Sci. , 30(1), 127–143, ABSTRACT: SnO 2 nanostructures are usually modified with some metal dopants in order to improve its gas sensing properties. In this work, pure tin oxide (SnO 2 ), nickel (Ni) doped SnO 2 (Ni:SnO 2 ) and palladium (Pd) doped SnO 2 (Pd:SnO 2 ) nanorods were successfully synthesised via hydrothermal method at low temperature (180°C) without templates or further calcination. All the samples were systematically analysed using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The sensor response (R = R 0 /R g ) towards 1000 ppm ethanol gas was investigated using nitrogen gas as a carrier gas. XRD results confirmed that all samples consisted of rutile tetragonal-shaped SnO 2 . It was found that the average diameter of nanorods formed in Ni:SnO 2 and Pd:SnO 2 were decreased to ~6 nm and ~10 nm, compared with nanorods formed in pure SnO 2 (~25 nm). The gas sensing results indicated that the sensor properties of SnO 2 were enhanced after the doping process. At 450°C, the Pd:SnO 2 nanorod sensor recorded the highest response value towards 1000 ppm ethanol gas which is 15 times higher than pure SnO 2 nanorods. Interestingly, all samples showed similar response time, ~ 40 s. However, pure SnO 2 and Ni:SnO 2 nanorods sensors exhibited longer recovery time compared to Pd:SnO 2 nanorods. Pd:SnO 2 nanorods recorded only 12 min of almost 100% recovery. It is proposed that Pd:SnO 2 sensor could be a promising candidate for the detection of ethanol gas.","PeriodicalId":16757,"journal":{"name":"Journal of Physical Science","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82202250","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}
Pub Date : 2019-02-15DOI: 10.21315/JPS2019.30.S1.5
N. F. Zaaba, H. Ismail
Plastics have many benefits due to their light weight, cost effectiveness, durability and other advantages. They are used as agricultural films, packaging, disposal consumer items, health, construction, etc. However, most plastics are not degradable which cause serious environmental problem. Addition of natural fillers into thermoplastics not only reduce the cost of the thermoplastic/natural filler composites but also help in reducing the waste of non-degradable plastic composite materials in the environment. Present short review deals with the issue of non-degradable plastic materials and the application of various natural fillers in thermoplastic composites. The chemical modifications including compatibilisation and radiation are reviewed and discussed.
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