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Defected waveguide structure designs and characteristics
摘要： This article presented defected waveguide structure (DWS) designs and characteristics with microstrip-fed circular monopole antenna for ultrawideband applications. Typically, waveguide is often designed and employed as antenna and filter application in its rigid dimension. The reconfigurable design toward the waveguide in terms of structural alteration with DWS was found less concerned among researchers although defected ground structure and defected microstrip structure have been applied widely. The motivation of this article was to propose the different DWS designs and characteristics in terms of the S-parameters result. DWS in basic square geometry with different configurations of straight lines were introduced and compared with FR4 substrate waveguide. Simulated S-parameters results were modeled in terms of equivalent circuit and measured for validation. For practical measurement, waveguide ports at both open-ended surface of waveguide were replaced by the monopole antenna. For the modeled S-parameters results, the square DWS design and square DWS with horizontal straight lines showed quite similar characteristics with higher S11 and lower S21 above frequency 9 GHz. Whereas square DWS with vertical straight lines and square DWS with both horizontal vertical straight lines showed higher S11 and lower S21 below frequency 3.5 GHz. Square DWS with vertical straight lines achieved the lowest S21 around ?70 dB below 3.5 GHz and lower S21 around ?50 dB at frequency 10.3 GHz. Thus, DWS is proposed for the future smart antenna technology as it can be further modified to meet the different requirements without changing the antenna configuration.
关键词： characteristics,monopole antenna,reconfigurable,equivalent circuit modeled,defected waveguide structure
更新于2025-09-11 14:15:04
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An Efficient and Simple Method for Modelling Solar Cells
摘要： Accurate and reliable PV device modelling is a fundamental tool to optimize system performance. The regular operation of the PV system in an outdoor condition implies the need for a model that relate the environmental effects. This paper presents a new, simple, and efficient method for constructing the I-V characteristics for a PV cell incorporating the environmental conditions. The proposed model is based on the idea of dividing the voltage axis of the solar cell I-V characteristics using a fixed time interval. For each voltage interval point, a two-dimensional current matrix is calculated, corresponding different irradiance conditions and temperatures. Polynomial surface fitting is used to build sub-models for each voltage interval. The current two-dimensional matrix, for each point, is calculated by two different methods. The first method is based on linear interpolation of the measured I-V curves. The second method uses pre-extracted five parameters for the well known single diode model at a wide range of environmental conditions. The developed modelling technique provides accurate results compared with the measured data for a mono-crystalline solar cell.
关键词： solar cell,I-V characteristics,single diode model
更新于2025-09-11 14:15:04
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Self-assembled chiral nanoribbons studied by terahertz time-domain spectroscopy and other biological methods
摘要： Massive Multiple Input Multiple Output (MIMO) has been widely considered as one of the most promising technologies for the fifth-generation (5G) wireless communication. In massive MIMO system, the research on channel characteristics is important. In this paper, the characteristics for massive MIMO channels at both 2 GHz and 6 GHz are investigated. Based on the real-world measurements, the channel parameters in the delay and frequency domains are extracted to show the non-stationary phenomenon over the large-scale antenna array. Furthermore, the characteristics of the angular parameters extracted by space-alternating generalized expectation-maximization (SAGE) algorithm are investigated and the fluctuations are modeled. The results for different frequencies are useful for deep understanding of massive MIMO channels in the future.
关键词： Massive MIMO,Channel characteristics,Angular parameter
更新于2025-09-11 14:15:04
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The role of NaF post-deposition treatment on the photovoltaic characteristics of semitransparent ultrathin Cu(In,Ga)Se <sub/>2</sub> solar cells prepared on indium-tin-oxide back contacts: a comparative study
摘要： Cu(In,Ga)Se2 (CIGSe) solar cells with absorber thicknesses of <500 nm are important for lowering the cost of photovoltaic (PV)-generated electricity. Moreover, ultrathin bifacial CIGSe solar cells can be prepared on indium-tin-oxide (ITO) back contacts (BCs). In contrast to Mo BCs, ITO BCs suppress the di?usion of Na from soda-lime glass (SLG) to the CIGSe absorber. Na present in the absorber is supposed to ameliorate the PV properties of CIGSe solar cells, but in the absence of Na or when the Na concentration is extremely low, the PV performance is expected to be poor. In this study, a NaF post-deposition treatment (PDT) was applied to a <500 nm thick semitrasparent CIGS absorber prepared by a 1-stage co-evaporation process. A detailed comparison is made between the CIGSe solar cell that underwent the NaF PDT (C–Na) and a reference CIGSe solar cell in which no Na was supplied from an external source (C0). All the PV parameters (i.e., the open-circuit voltage, short-circuit current density, ?ll factor, and e?ciency) of C–Na considerably improved compared with those of C0. To understand the factors that led to this improvement, the solar cells are analyzed by various characterization techniques, including JV measurements, external quantum e?ciency measurements, temperature-dependent measurements of the open-circuit voltage, capacitance–voltage measurements, drive level capacitance pro?lometry, and admittance spectroscopy. Furthermore, the reaction occurring at the CIGSe/ITO interface is investigated with transmission electron microscopy, and the implications of this reaction on the device performance are discussed.
关键词： ultrathin,solar cells,semitransparent,indium-tin-oxide back contacts,NaF post-deposition treatment,Cu(In,Ga)Se2,photovoltaic characteristics
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Waikoloa Village, HI (2018.6.10-2018.6.15)] 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - 10.3% Efficient CuIn(S,Se)<inf>2</inf> Solar Cells from DMF Molecular Solution with the Absorber Selenized under High Argon Pressure
摘要： Owing to the transformation of the biomedical model of health, more and more professionals pay close attention to the occupational social psychological factors, such as occupational stress. Due to the socioeconomic impact of occupational stress and the petroleum workers stationed in the unique environment in Xinjiang, a cross-sectional study was carried out between May and December 2016 to investigate the relationship between occupational stress and demographic characteristics. A total of 1480 workers were selected. Occupational stress was evaluated with the Occupational Stress Inventory-Revised Edition. The findings of the present study revealed that the values of the Occupational Roles Questionnaire results (t = 9.266, P < .001) and Personal Strain Questionnaire results (t = 21.381, P < .001) were found to be higher than the national normal. Personal Resources Questionnaire values (t = (cid:1)17.575, P < .001) were found to be lower than the national normal in petroleum workers stationed in the arid desert, and suggested a strong correlation between occupational stress and demographic characteristics. These data provide evidence that different demographic characteristics are associated with different occupational stress levels in petroleum workers stationed in the arid desert.
关键词： occupational stress,petroleum workers,arid desert,demographic characteristics
更新于2025-09-11 14:15:04
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Mixed Gaussian Models for Modeling Fluctuation Process Characteristics of Photovoltaic Outputs
摘要： In order to model ?uctuation process characteristics of photovoltaic (PV) outputs, this paper proposes a novel mixed Gaussian model with the expectation maximization (EM) algorithm. Firstly, random components of PV outputs are obtained through computing the difference between the measured data of PV output and its theoretical outputs. Secondly, the EM algorithm is used to determine the weight of different Gaussian distribution functions. Finally, the mixed Gaussian model is obtained by linearly superimposing these Gaussian functions with the weight. Based on the simulation results on the measured data in Xichang City, China, the effectiveness of the proposed model is veri?ed. Furthermore, this model has proven to be signi?cantly better than other traditional models including t location-scale (TLS) distribution model.
关键词： expectation maximization algorithm,PV output modeling,?uctuation characteristics,mixed Gaussian models,probability density distribution
更新于2025-09-11 14:15:04
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[IEEE 2019 International Conference on Electromechanical and Energy Systems (SIELMEN) - Craiova, Romania (2019.10.9-2019.10.11)] 2019 International Conference on Electromechanical and Energy Systems (SIELMEN) - Analysis of the Aspects of Increasing the Efficiency of Electricity Generation by Photovoltaic Power Plants
摘要： The increase in the share of energy produced from renewable sources in the energy balance presents itself as a strategic problem for world energy sector. The use of solar energy to produce electricity is possible everywhere. The purpose of this work is to analyze the factors that affect the efficiency of electricity production, as well as the development of theoretical aspects of increasing the efficiency of the operation of photovoltaic power plants. The research methodology is based on the complex analysis of the particularities of the conversion of solar radiation into electricity by photovoltaic cells, which are presented through ideal equivalent schemes and equivalent schemes that take into account the impact of temperature, the intensity of solar radiation and the partial shading factor of the photovoltaic cells. As a research tool it is proposed to perform the modeling of the characteristics of current- voltage and voltage - power of the solar panels and platforms with PV panels mounted. It presents the methodological aspects of the analysis of the energy production of the PV plants for different operating conditions, the results of the analysis of the electricity production of the PV plants in the world and the estimation of the influence of the main factors (temperature, the intensity of the solar radiation, the degree of shading) on the deviation of the characteristics of the photovoltaic cells. It has been proposed the concept and the general theoretical aspects regarding the elaboration of the mathematical model of the PV power station, which takes into account the influencing factors on the efficiency of electricity production. It has been shown that in the mathematical model the influence of the sun's motion on the celestial vault can be modeled by varying the intensity of the solar radiation depending on the positioning of the sun.
关键词： characteristics of temperature,share of production,power,influence factors,intensity of solar radiation,electricity,current and voltage
更新于2025-09-11 14:15:04
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Predictive Value of Corneal Donor Demographics on Endothelial Cell Density
摘要： Corneal endothelial cell density (ECD) is an important measure for determining suitability for transplantation. Although age has been correlated with ECD, the impact of sex and ethnicity is unclear. Methods: Corneal donor information from SightLife Eye Bank was collected between 2012 and 2016. Tests of association were adjusted for covariates using linear regression including age, race, and sex. “Unsuitable for transplantation” was a label assigned to specimens with extensive cell dropout, ECD ,2000 cells/mm2, and poor cell morphology. Repeated-measures analysis was used to account for the within-individual correlation between left and right eyes. Results: A total of 39,679 donor corneas were analyzed, with a mean ECD 2743.5 cells/mm2 and mean age of 58. Simple linear regression demonstrated an association between ECD and age (P , 0.001). Multiple regression showed no association between sex and ECD. Compared with whites, African American, and Asian ethnicities were predictors of increased ECD (mean +45.7 cells/mm2 (P , 0.001) and +90.3 cells/mm2 (P , 0.001), respectively); Hispanic ethnicity was a predictor of decreased ECD [mean 236.9 cells/mm2 (P = 0.002)]. A total of 233 (0.59%) corneas were unsuitable for transplantation, which was associated with age (P , 0.001) but not sex or ethnicity. Conclusions: Analysis of a large sample of donor corneas continues to show age but not sex as a predictor of decreased ECD. African American and Asian ethnicities tend to have slightly higher ECD than that of white donors, whereas Hispanic donors have slightly lower ECD; however, ethnicity was not a predictor of suitability for transplantation. Clinical signi?cance of these ?ndings is yet to be determined.
关键词： corneal endothelium,corneal transplantation,corneal donor characteristics
更新于2025-09-11 14:15:04
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A comparative study of surface characterization and corrosion performance properties of laser surface modified biomedical grade nitinol
摘要： Laser melting and quick solidification of shape memory alloy surfaces promise to explore the multifunctional capabilities required for enhanced biocompatibility of different implantable medical devices. Before subsequent bio-trial, understanding of the effect of cooling rate vis-à-vis laser fluence on surface characteristics and corrosion protection performance is essential before designing a tailor-made biocompatible surface for various implantable devices. The current study systematically investigates the effect of laser fluence on physical, mechanical and chemical surface characteristics along with corrosion protection performance of the modified surface as compared to bare Nitinol surface. Various phases were prominent on the top surface, namely nickel and titanium-rich phase along with different nickel-titanium intermetallics and nano-structure of titanium oxide, based on varying melting pool recirculation time and cooling rate with laser fluence energy. At low laser fluence up to 4 J/mm2, no significant melting pool were formed and only transformation to the martensitic phase of Nitinol took place on the top surface, which seemed to be highly too much corrosion-prone under simulated body fluid. At moderate laser fluence of 6–8 J/mm2, mostly titanium-rich phases are prominent on the surfaces on account of optimum recirculation of melting pool and subsequent surfacing out of comparably light phase of titanium. Titanium-rich phases on top surface exhibit superior corrosion resistance as compared to all other samples including bare nitinol. However, titanium oxide nano-particles-reinforced martensitic structure is formed under high laser fluence due to over recirculation of molten pool. The modulus of elasticity also varied from 10 to 110 GPa based on top surface formation under different fluence levels, and thus this process can act as a tailor-made controllable pre-treatment process over the traditional coating processes.
关键词： Corrosion protection performance,Laser melting and re-solidification,Surface characteristics,Nitinol surface modification
更新于2025-09-11 14:15:04
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A Novel CMUTs-based Resonant Biochemical Sensor Using Electrospinning Technology
摘要： A novel CMUTs-based resonant biochemical sensor was presented to detect SO2 with a sensitive polymer electrospinning technology. The electrospinning technology was proposed as an innovative functionalization method to fabricate nano reticular polymer fibers with the diameters of 50 nm~500 nm on the movable plates of the CMUTs. The surface topography of electrospun nanofibers and the impedance properties of functionalized CMUTs were characterized. The CMUTs-based resonant biochemical sensor was packaged to detect SO2 in the experiments. Its resonant frequency shifts varied against the variation of SO2 concentration. The influences of the mixed gas flow rate were also analyzed. These showed the proposed sensor had good volume sensitivity and frequency stability.
关键词： volume sensitivity,electrospinning technology,impedance characteristics,CMUTs-based resonant biochemical sensor,frequency shift
更新于2025-09-11 14:15:04