Abstract The present article investigates whether the drag coefficient of low density objects can be determined by free fall experiments with sufficient accuracy. Among other things, the drag coefficient depends on the flow velocity, which can be controlled in wind channels experiments. Free fall experiments do not offer an experimental environment with constant flow velocity. Especially the later part of the movement gets relevantly influenced by air drag deceleration. We theoretically estimate an average sphere drag coefficient for the relevant part of the movement of falling spheres. The results are verified by examining the drag coefficient from experimental data. Finally, we determine the drag coefficient of a model rocket, which is compared to the result of the corresponding wind channel experiment.
{"title":"Drag Coefficient Estimation of Low Density Objects by Free Fall Experiments","authors":"T. Günther, K. A. Hoang","doi":"10.2478/awutp-2023-0005","DOIUrl":"https://doi.org/10.2478/awutp-2023-0005","url":null,"abstract":"Abstract The present article investigates whether the drag coefficient of low density objects can be determined by free fall experiments with sufficient accuracy. Among other things, the drag coefficient depends on the flow velocity, which can be controlled in wind channels experiments. Free fall experiments do not offer an experimental environment with constant flow velocity. Especially the later part of the movement gets relevantly influenced by air drag deceleration. We theoretically estimate an average sphere drag coefficient for the relevant part of the movement of falling spheres. The results are verified by examining the drag coefficient from experimental data. Finally, we determine the drag coefficient of a model rocket, which is compared to the result of the corresponding wind channel experiment.","PeriodicalId":31012,"journal":{"name":"Annals of West University of Timisoara Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73431939","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}
Mohammed Nadir Bousahla, Mohammed Alaa Bousahla, A. Chahed, Z. Bousahla, H. Rozale, H. Bendjilali
Abstract This research explored the crystal structure, mechanical and elastic, electronic, magnetic, and optical properties of spinel compoundsATi2S4 (A=Ca, Sr and Ba). The ferromagnetic phase of the compounds was found to be stable, and FP-LAPW method within density functional theory (DFT) was used to calculate and compare the lattice constant a, bulk modulus B0, and its pressure derivative B'. The exchange-correlation potential was also treated with both the GGA and TB-mBJ potential approximation. The results of the study showed that the examined spinels exhibit half-metallic behavior, which makes them a potential material for use in spintronic and optoelectronic devices.
{"title":"Structural, Mechanical, Elastic, Electronic, Magnetic and Optical Properties of Spinel Compounds ATi2S4 (A=Ca, Sr and Ba): AB Initio Study","authors":"Mohammed Nadir Bousahla, Mohammed Alaa Bousahla, A. Chahed, Z. Bousahla, H. Rozale, H. Bendjilali","doi":"10.2478/awutp-2023-0003","DOIUrl":"https://doi.org/10.2478/awutp-2023-0003","url":null,"abstract":"Abstract This research explored the crystal structure, mechanical and elastic, electronic, magnetic, and optical properties of spinel compoundsATi2S4 (A=Ca, Sr and Ba). The ferromagnetic phase of the compounds was found to be stable, and FP-LAPW method within density functional theory (DFT) was used to calculate and compare the lattice constant a, bulk modulus B0, and its pressure derivative B'. The exchange-correlation potential was also treated with both the GGA and TB-mBJ potential approximation. The results of the study showed that the examined spinels exhibit half-metallic behavior, which makes them a potential material for use in spintronic and optoelectronic devices.","PeriodicalId":31012,"journal":{"name":"Annals of West University of Timisoara Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72491076","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}
Abstract In the recent years, great progress has been made in developing terrestrial and satellite-based networks for the measurement of atmospheric parameters, which serve as inputs in clear sky parametric models. However, some parameters may still be missing from the model input due to small temporal sampling or lack of in situ data. This paper presents a case study on the accuracy of the clear-sky solar irradiance estimation by a parametric model, when the availability of inputs is limited. The study was conducted with high-quality radiometric and atmospheric data recorded by the INOE-Magurele station, Romania. Seven different scenarios were studied. In each scenario the clear-sky solar irradiance model was run assuming that certain parameters are missing from the input. The results quantitatively confirm the dominant role of aerosols in establishing the accuracy of solar irradiance estimation under clear sky conditions. The unavailability of the measured Ångström turbidity coefficient may lead to a twofold/threefold increase in the uncertainty of direct-normal/diffuse solar irradiance estimation.
{"title":"Uncertainties in Clear-Sky Solar Irradiance Modeling Induced by the Limited Availability of the Atmospheric Parameters","authors":"E. Carstea, M. Paulescu","doi":"10.2478/awutp-2023-0004","DOIUrl":"https://doi.org/10.2478/awutp-2023-0004","url":null,"abstract":"Abstract In the recent years, great progress has been made in developing terrestrial and satellite-based networks for the measurement of atmospheric parameters, which serve as inputs in clear sky parametric models. However, some parameters may still be missing from the model input due to small temporal sampling or lack of in situ data. This paper presents a case study on the accuracy of the clear-sky solar irradiance estimation by a parametric model, when the availability of inputs is limited. The study was conducted with high-quality radiometric and atmospheric data recorded by the INOE-Magurele station, Romania. Seven different scenarios were studied. In each scenario the clear-sky solar irradiance model was run assuming that certain parameters are missing from the input. The results quantitatively confirm the dominant role of aerosols in establishing the accuracy of solar irradiance estimation under clear sky conditions. The unavailability of the measured Ångström turbidity coefficient may lead to a twofold/threefold increase in the uncertainty of direct-normal/diffuse solar irradiance estimation.","PeriodicalId":31012,"journal":{"name":"Annals of West University of Timisoara Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89415503","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}
V. Ordodi, I. Borlea, D. A. Vereș, C. Stănese, B. F. Mercè
Abstract Identifying possibilities to increase the performance of photovoltaic cells is a priority for the energy field. This article presents preliminary results obtained in natural environment conditions with an experimental device that allows the cooling of photovoltaic cells and additionally the partial transformation of the heat transferred to the cold source (natural flowing water) by coupling with a thermoelectric generator based on the Seebeck effect. The structure of the experimental device is a sandwich type with the following main elements: the polycrystalline silicon photovoltaic cell, the Bi-Te thermoelectric generator and an aluminum radiator in contact with the cold water of the river. In this way, an increase in the electrical output power of approximately 28% is obtained, compared to the same photovoltaic cell alone.
{"title":"The Performance of a Photovoltaic Cell Coupled with a Thermoelectric Generator","authors":"V. Ordodi, I. Borlea, D. A. Vereș, C. Stănese, B. F. Mercè","doi":"10.2478/awutp-2023-0002","DOIUrl":"https://doi.org/10.2478/awutp-2023-0002","url":null,"abstract":"Abstract Identifying possibilities to increase the performance of photovoltaic cells is a priority for the energy field. This article presents preliminary results obtained in natural environment conditions with an experimental device that allows the cooling of photovoltaic cells and additionally the partial transformation of the heat transferred to the cold source (natural flowing water) by coupling with a thermoelectric generator based on the Seebeck effect. The structure of the experimental device is a sandwich type with the following main elements: the polycrystalline silicon photovoltaic cell, the Bi-Te thermoelectric generator and an aluminum radiator in contact with the cold water of the river. In this way, an increase in the electrical output power of approximately 28% is obtained, compared to the same photovoltaic cell alone.","PeriodicalId":31012,"journal":{"name":"Annals of West University of Timisoara Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75381722","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}
Abstract The Pythagoras Tree Fractal patch is considered on a SiO2 substrate thickness of 1.5 µm to radiate at four frequencies of 4.975THz, 5.38THz, 6.73THz, and 7.61THz with Voltage Standing Wave Ratio (VSWR) ≤ 2. This is a very creative fractal design of a multiband THz antenna, based on a very thin graphene layer, the study proved a value in terms of high radiation efficiency and high gain, at the level of current research we made a comparison study where the design has evidently huge potential regarding applicability for telecommunication technology in the terahertz regime. The demand for high-performance terahertz (THz) antennas has increased significantly in recent years due to their potential applications in various fields such as medical imaging, security screening, and wireless communications. In this paper, the authors present an analysis of a graphene Pythagoras Tree Fractal (GPTF) antenna with a thin SiO2 substrate for THz regime. The GPTF antenna is designed using a fractal geometry approach, which provides multiple resonant frequencies and enhances the overall radiation efficiency. The thin SiO2 substrate is used to reduce the substrate losses and improve the radiation performance of the antenna. The authors use the Finite-Difference Time-Domain (FDTD) software to simulate the performance of the proposed antenna. The results show that the proposed antenna exhibits high gain, low return loss, and wide bandwidth, making it a promising candidate for THz applications.
{"title":"Analysis of Graphene Pythagoras Tree Fractal Antenna with Thin SiO2 Substrate in Terahertz Regime","authors":"Zakarya Hafdi, Zinelabiddine Mezache, Jun-Lei Tao, Ghada Guergour","doi":"10.2478/awutp-2023-0001","DOIUrl":"https://doi.org/10.2478/awutp-2023-0001","url":null,"abstract":"Abstract The Pythagoras Tree Fractal patch is considered on a SiO2 substrate thickness of 1.5 µm to radiate at four frequencies of 4.975THz, 5.38THz, 6.73THz, and 7.61THz with Voltage Standing Wave Ratio (VSWR) ≤ 2. This is a very creative fractal design of a multiband THz antenna, based on a very thin graphene layer, the study proved a value in terms of high radiation efficiency and high gain, at the level of current research we made a comparison study where the design has evidently huge potential regarding applicability for telecommunication technology in the terahertz regime. The demand for high-performance terahertz (THz) antennas has increased significantly in recent years due to their potential applications in various fields such as medical imaging, security screening, and wireless communications. In this paper, the authors present an analysis of a graphene Pythagoras Tree Fractal (GPTF) antenna with a thin SiO2 substrate for THz regime. The GPTF antenna is designed using a fractal geometry approach, which provides multiple resonant frequencies and enhances the overall radiation efficiency. The thin SiO2 substrate is used to reduce the substrate losses and improve the radiation performance of the antenna. The authors use the Finite-Difference Time-Domain (FDTD) software to simulate the performance of the proposed antenna. The results show that the proposed antenna exhibits high gain, low return loss, and wide bandwidth, making it a promising candidate for THz applications.","PeriodicalId":31012,"journal":{"name":"Annals of West University of Timisoara Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88823942","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}
Hichem Necib, D. Belatrache, Hafnaoui Goutar, Nesrine Sahraoui
Abstract This study aims to improve the thermal efficiency of concrete slabs by introducing a plant material. This can contribute to the improvement of internal thermal comfort for buildings and this by lower energy consumption. For this, several experiments were carried out at the laboratory, to find the thermal properties of a new innovative building material produced by inserting ALFA (STIPA TENACISSIMA) into a concrete slab. Several mass percentages of ALFA relative to the total mass of the concrete slab (0%, 0.4%, 0.8%, 1.2% and 1.6%) were studied to see the effect of the introduced quantity of this plant on the thermal conductivity of concrete. It was concluded that the insertion of ALFA in the concrete, decreases considerably the thermal conductivity. The best results are noticed for 1.2% of ALFA, whose thermal conductivity of the concrete is reduced up to 50.61%. As a result, heat gains and losses, through wall or slab, are significantly reduced, which reduces the energy consumed by cooling and heating of homes. In addition, the degree-day method was used to calculate the costs of cooling and heating energy for 58 regions in Algeria. The lowest total energy cost is noticed in the TENES region, while the highest energy cost is noticed in the BORDJ B. MOKHTAR region.
摘要本研究旨在通过引入植物材料来提高混凝土板的热效率。这有助于改善建筑物的内部热舒适性，从而降低能耗。为此，在实验室进行了几项实验，以发现将ALFA (STIPA TENACISSIMA)插入混凝土板中产生的新型创新建筑材料的热性能。研究了ALFA相对于混凝土板总质量的几个质量百分比(0%，0.4%，0.8%，1.2%和1.6%)，以观察该植物的引入量对混凝土导热性的影响。结果表明，ALFA在混凝土中的掺入，显著降低了混凝土的导热系数。当ALFA添加量为1.2%时，效果最好，混凝土导热系数降低50.61%。因此，通过墙壁或板的热量增益和损失大大减少，从而减少了家庭制冷和供暖所消耗的能量。此外，还利用度日法计算了阿尔及利亚58个地区的冷热能源成本。总能源成本最低的是TENES区域，最高的是BORDJ B. MOKHTAR区域。
{"title":"Experimental Study of Thermal Conductivity of Concrete with Biosourced Material for Saved Energy in Buildings","authors":"Hichem Necib, D. Belatrache, Hafnaoui Goutar, Nesrine Sahraoui","doi":"10.2478/awutp-2022-0011","DOIUrl":"https://doi.org/10.2478/awutp-2022-0011","url":null,"abstract":"Abstract This study aims to improve the thermal efficiency of concrete slabs by introducing a plant material. This can contribute to the improvement of internal thermal comfort for buildings and this by lower energy consumption. For this, several experiments were carried out at the laboratory, to find the thermal properties of a new innovative building material produced by inserting ALFA (STIPA TENACISSIMA) into a concrete slab. Several mass percentages of ALFA relative to the total mass of the concrete slab (0%, 0.4%, 0.8%, 1.2% and 1.6%) were studied to see the effect of the introduced quantity of this plant on the thermal conductivity of concrete. It was concluded that the insertion of ALFA in the concrete, decreases considerably the thermal conductivity. The best results are noticed for 1.2% of ALFA, whose thermal conductivity of the concrete is reduced up to 50.61%. As a result, heat gains and losses, through wall or slab, are significantly reduced, which reduces the energy consumed by cooling and heating of homes. In addition, the degree-day method was used to calculate the costs of cooling and heating energy for 58 regions in Algeria. The lowest total energy cost is noticed in the TENES region, while the highest energy cost is noticed in the BORDJ B. MOKHTAR region.","PeriodicalId":31012,"journal":{"name":"Annals of West University of Timisoara Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90538829","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}
Robert Blaga, C. Dughir, Andreea Săbăduş, N. Stefu, M. Paulescu
Abstract This study deals with the performance of PV2-state model in intra-hour forecasting of photovoltaic (PV) power. The PV2-state model links an empirical model for estimating the PV power delivered by a PV system under clear-sky with a model for forecasting the relative position of the Sun and clouds. Sunshine number (SSN), a binary quantifier showing if the Sun shines or not, is used as a measure for the Sun position with respect to clouds. A physics-based approach to intra-hour forecasting, processing cloud field information from an all-sky imager, is applied to predict SSN. The quality of SSN prediction conditions the overall quality of PV2-state forecasts. The PV2-state performance was evaluated against a challenging database (high variability in the state-of-the-sky, thin cloud cover, broken cloud field, isolated passing clouds) comprising radiometric data and sky-images collected on the Solar Platform of the West University of Timisoara, Romania. The investigation was performed from two perspectives: general model accuracy and, as a novelty, identification of characteristic elements in the state-of-the-sky which fault the SSN prediction. The outcome of such analysis represents the basis of further research aiming to increase the performance in PV power forecasting.
{"title":"Short-Term PV Power Forecasting Based on Sky Imagery. A Case Study at the West University of Timisoara","authors":"Robert Blaga, C. Dughir, Andreea Săbăduş, N. Stefu, M. Paulescu","doi":"10.2478/awutp-2022-0010","DOIUrl":"https://doi.org/10.2478/awutp-2022-0010","url":null,"abstract":"Abstract This study deals with the performance of PV2-state model in intra-hour forecasting of photovoltaic (PV) power. The PV2-state model links an empirical model for estimating the PV power delivered by a PV system under clear-sky with a model for forecasting the relative position of the Sun and clouds. Sunshine number (SSN), a binary quantifier showing if the Sun shines or not, is used as a measure for the Sun position with respect to clouds. A physics-based approach to intra-hour forecasting, processing cloud field information from an all-sky imager, is applied to predict SSN. The quality of SSN prediction conditions the overall quality of PV2-state forecasts. The PV2-state performance was evaluated against a challenging database (high variability in the state-of-the-sky, thin cloud cover, broken cloud field, isolated passing clouds) comprising radiometric data and sky-images collected on the Solar Platform of the West University of Timisoara, Romania. The investigation was performed from two perspectives: general model accuracy and, as a novelty, identification of characteristic elements in the state-of-the-sky which fault the SSN prediction. The outcome of such analysis represents the basis of further research aiming to increase the performance in PV power forecasting.","PeriodicalId":31012,"journal":{"name":"Annals of West University of Timisoara Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88558478","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}
Abstract Structural stability, electronic, optical, and photovoltaic properties of pure and doped InP were evaluated by using first principles calculations via the density functional theory (DFT). The exchange-correlation potential is treated with generalized gradient approximation (GGA-PBE). Additionally, the Tran Blaha modified Becke-Johnson exchange potential (TB-mBJ) is employed, because it gives very accurate results of the band gap in solids. Our results reveal that all compounds are energetically and mechanically stable. It is found that for Y concentrations less than 30%, the favored structure is a Zinc blende-like one, while for Y concentrations greater than 30%, the favored structure is a NaCl-like structure. The substitution of In by Y is found to be able to enlarge the direct bandgap of about 34% (from 1.43 eV to 2.17 eV) and confirms the semiconductor behavior for zinc blende stable structures. The absorption coefficient is reasonably exceeding 105 cm−1 for YxIn1-xP alloys in the case (x=0 and x=25%). The reflectivity shows less than 30% around the energy value of 2 eV and an efficiency of solar cell of 18% can be achieved for Y0.25In0.75P. Also, a thickness of L = 1μm is enough to confirm the experimental data. Regarding to the matching of lattice parameters (a mismatch < 4%) of InP and Y0.25In0.75P and the band gap energy difference made Y0.25In0.75P suitable for optoelectronic and photovoltaic devices in particularity as Tandem solar cells (Y0.25In0.75P/InP) and quantum well (Y0.25In0.75P/InP/Y0.25In0.75P) applications. In the absence of experimental works, our results can be useful for further studies.
{"title":"Investigation of the Optoelectronic and Photovoltaic Properties of YxIN1-xP Alloys using First Principles Calculations","authors":"K. Talbi, Youcef Cherchab, A. Mir, B. Bouhadef","doi":"10.2478/awutp-2022-0009","DOIUrl":"https://doi.org/10.2478/awutp-2022-0009","url":null,"abstract":"Abstract Structural stability, electronic, optical, and photovoltaic properties of pure and doped InP were evaluated by using first principles calculations via the density functional theory (DFT). The exchange-correlation potential is treated with generalized gradient approximation (GGA-PBE). Additionally, the Tran Blaha modified Becke-Johnson exchange potential (TB-mBJ) is employed, because it gives very accurate results of the band gap in solids. Our results reveal that all compounds are energetically and mechanically stable. It is found that for Y concentrations less than 30%, the favored structure is a Zinc blende-like one, while for Y concentrations greater than 30%, the favored structure is a NaCl-like structure. The substitution of In by Y is found to be able to enlarge the direct bandgap of about 34% (from 1.43 eV to 2.17 eV) and confirms the semiconductor behavior for zinc blende stable structures. The absorption coefficient is reasonably exceeding 105 cm−1 for YxIn1-xP alloys in the case (x=0 and x=25%). The reflectivity shows less than 30% around the energy value of 2 eV and an efficiency of solar cell of 18% can be achieved for Y0.25In0.75P. Also, a thickness of L = 1μm is enough to confirm the experimental data. Regarding to the matching of lattice parameters (a mismatch < 4%) of InP and Y0.25In0.75P and the band gap energy difference made Y0.25In0.75P suitable for optoelectronic and photovoltaic devices in particularity as Tandem solar cells (Y0.25In0.75P/InP) and quantum well (Y0.25In0.75P/InP/Y0.25In0.75P) applications. In the absence of experimental works, our results can be useful for further studies.","PeriodicalId":31012,"journal":{"name":"Annals of West University of Timisoara Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74270429","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}
Abstract UV radiation at ground level undergoes many variations in the present, due to the ozone column, aerosols, clouds, surface reflectivity, both positive and negative variations, depending on latitude. This work reports on the updating of the semi-empirical equation proposed by Madronich in 2007 for estimating the UV index, by updating its coefficients, as they encapsulate the state of the atmosphere. Data for Bucharest in 2019-2021 was used for fitting the equation. It was found that the new equation improves the accuracy of the estimation of the UVI in Bucharest five times for 2021 (from nRMSE = 17.3% to nRMSE=3.3%). The validity of the obtained equation was assessed in various locations, showing a great improvement of the estimation accuracy in most of them (in 12 of the 14 chosen locations), regardless of latitude. The equation produces a negative bias for locations having Koppen climate types A and B, a positive bias for the investigated locations situated in climate type D and no definite bias for temperate climates (type C). More studies are needed for drawing a definite conclusion and further improving the applicability of the equation.
{"title":"Actualization of Semi-Empirical Equation for UV Index","authors":"Adriana Vasi, N. Stefu","doi":"10.2478/awutp-2022-0008","DOIUrl":"https://doi.org/10.2478/awutp-2022-0008","url":null,"abstract":"Abstract UV radiation at ground level undergoes many variations in the present, due to the ozone column, aerosols, clouds, surface reflectivity, both positive and negative variations, depending on latitude. This work reports on the updating of the semi-empirical equation proposed by Madronich in 2007 for estimating the UV index, by updating its coefficients, as they encapsulate the state of the atmosphere. Data for Bucharest in 2019-2021 was used for fitting the equation. It was found that the new equation improves the accuracy of the estimation of the UVI in Bucharest five times for 2021 (from nRMSE = 17.3% to nRMSE=3.3%). The validity of the obtained equation was assessed in various locations, showing a great improvement of the estimation accuracy in most of them (in 12 of the 14 chosen locations), regardless of latitude. The equation produces a negative bias for locations having Koppen climate types A and B, a positive bias for the investigated locations situated in climate type D and no definite bias for temperate climates (type C). More studies are needed for drawing a definite conclusion and further improving the applicability of the equation.","PeriodicalId":31012,"journal":{"name":"Annals of West University of Timisoara Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88182294","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. Ouledali, B. Amrani, S. Daoud, S. Louhibi-Fasla, H. Rekab-Djabri, N. Beloufa, S. Bekheira, I. Ouadha
Abstract The structural, electronic, and optical properties of ZnSnP2 compound were determined using the first principles calculations. We applied the full-potential enhanced plane wave method (FP-LAPW) within the framework of density functional theory (DFT) as implemented in the Wien2k package. The exchange-correlation potential term was treated using the local density approximation (LDA), the generalized gradient approximation (GGA), the Engel–Vosko generalized gradient approximation (EV–GGA) and GGA plus modified Becke– Johnson (mBJ). The lattice parameters of the ZnSnP2 obtained by minimizing the total energy are consistent well with the existing theoretical and experimental results. The Dugdale and MacDonald Grüneisen parameter was found to be 1.43 from the GGA and 1.44 from the LDA, respectively. According to the electronic properties, the band structure analysis of ZnSnP2 shows that it has a direct band gap in the (Γ-Γ) direction with a value of 1.43 eV. We have investigated the optical properties of ZnSnP2 semiconducting compound. The data of the dielectric functions shown that the peaks are positioned at around 2.41, 3.21, 3.83 and 4.09 eV, respectively.
利用第一性原理计算确定了ZnSnP2化合物的结构、电子和光学性质。我们在密度泛函理论(DFT)框架内应用了Wien2k软件包中实现的全势增强平面波方法(FP-LAPW)。采用局部密度近似(LDA)、广义梯度近似(GGA)、Engel-Vosko广义梯度近似(EV-GGA)和GGA加修正Becke - Johnson (mBJ)处理交换相关势项。通过最小化总能量得到的ZnSnP2晶格参数与已有的理论和实验结果吻合较好。GGA的Dugdale和MacDonald grisen参数分别为1.43和1.44。根据电子性质，对ZnSnP2的能带结构分析表明，ZnSnP2在(Γ-Γ)方向上具有直接带隙，带隙值为1.43 eV。我们研究了ZnSnP2半导体化合物的光学性质。介电函数数据表明，峰值分别位于2.41、3.21、3.83和4.09 eV附近。
{"title":"Theoretical Investigation of Structural, Electronic, and Optical Properties of ZnSnP2 Semiconductor","authors":"M. Ouledali, B. Amrani, S. Daoud, S. Louhibi-Fasla, H. Rekab-Djabri, N. Beloufa, S. Bekheira, I. Ouadha","doi":"10.2478/awutp-2022-0006","DOIUrl":"https://doi.org/10.2478/awutp-2022-0006","url":null,"abstract":"Abstract The structural, electronic, and optical properties of ZnSnP2 compound were determined using the first principles calculations. We applied the full-potential enhanced plane wave method (FP-LAPW) within the framework of density functional theory (DFT) as implemented in the Wien2k package. The exchange-correlation potential term was treated using the local density approximation (LDA), the generalized gradient approximation (GGA), the Engel–Vosko generalized gradient approximation (EV–GGA) and GGA plus modified Becke– Johnson (mBJ). The lattice parameters of the ZnSnP2 obtained by minimizing the total energy are consistent well with the existing theoretical and experimental results. The Dugdale and MacDonald Grüneisen parameter was found to be 1.43 from the GGA and 1.44 from the LDA, respectively. According to the electronic properties, the band structure analysis of ZnSnP2 shows that it has a direct band gap in the (Γ-Γ) direction with a value of 1.43 eV. We have investigated the optical properties of ZnSnP2 semiconducting compound. The data of the dielectric functions shown that the peaks are positioned at around 2.41, 3.21, 3.83 and 4.09 eV, respectively.","PeriodicalId":31012,"journal":{"name":"Annals of West University of Timisoara Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89037059","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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