- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - ZnTe Back Buffer Layer to Enhance the Efficiency of CdS/CdTe Solar Cells
摘要： Doppler velocity can be derived by calculating Doppler shift anomalies between predicted and estimated Doppler centroids. The predicted Doppler centroid is calculated based on a geometric model of satellite assuming that the target is not moving. The estimated Doppler centroid can be directly extracted from the raw SAR signal data by applying the average cross-correlation coefficient method. It is known that wind-generated ocean waves can significantly contribute to Doppler velocity due to the correlation between orbital motions of the waves and (tilt and hydrodynamic) modulated radar cross sections, in addition to what sea surface current contributes. In this study, the characteristics of Doppler velocities under hurricane conditions were investigated using RADARSAT-1 ScanSAR raw data. Five different hurricanes (Hurricane Dean, Hurricane Ivan, Hurricane Kyle, Hurricane Lili, and Typhoon Xangsane) and sequential acquisitions of two hurricanes (Hurricane Kyle and Hurricane Lili) were selected to study the contribution of wind-induced waves to Doppler velocities and compared with in situ measurements of drifting buoys. The results show that hurricane-generated seas and associated winds and waves appear to be different from ordinary sea state. This leads to lower estimates of Doppler velocities than expected and much closer to sea surface current velocities.
关键词： wind-induced waves,drift current,Doppler velocity,hurricane,RADARSAT
更新于2025-09-23 15:19:57
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Design for A Highly Stable Laser Source Based on the Error Model of High-Speed High-Resolution Heterodyne Interferometers
摘要： Heterodyne interferometers with two opposite Doppler shift interference signals have been proposed for high-resolution measurement with high measurement speed, which can be used in the background of high-speed high-resolution measurement. However, a measurement error model for high-speed high-resolution heterodyne interferometers (HSHR-HIs) has not yet been proposed. We established a HSHR-HI measurement error model, analyzed the influence of beat frequency stability with a simplified optical structure, and then designed an offset-locked dual-frequency laser source with a digital control system to reduce the impact of beat frequency drift. Experiments were used to verify the correction of the measurement error model and the validity of the laser source. The results show that the new laser source has a maximum beat frequency range of 45 MHz, which shows the improvements in the measuring speed and resolution.
关键词： heterodyne interferometer,drift,error model,beat frequency
更新于2025-09-23 15:19:57
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Modeling and Experimental Validation of a Low-Cost Radiation Sensor Based on the Photovoltaic Effect for Building Applications
摘要： The energy consumed to cool buildings is very elevated and solar gains represent a high percentage of these cooling loads. To minimize the thermal load it is necessary to control external shading systems. This control requires continuous measurement of solar radiation in different locations of the building. However, for such applications the use of conventional irradiance sensors increases the cost and reduces the profitability of the installation. This paper is focused on the development, modeling, and experimental validation of low cost irradiation sensors based on photovoltaic effect in order to reduce the costs of dynamic external shading devices and to improve the profitability of the system. With this proposal, firstly, small commercial photovoltaic cells have been adapted for use as an irradiation measurement device. Subsequently, quasi-stationary and continuous experimental measurements of these silicon cells, facing south and installed horizontally, have been carried out in Jaén (Spain) in 2009 and 2010. Finally, a nonlinear multiparameter function has been developed to evaluate the irradiance using the electric current generated by the cell, cell temperature, ambient temperature, and absolute humidity. A favorable agreement between the model predictions and experimental data has been observed with a coefficient of determination around 0.996 for all cells.
关键词： thermal drift,solar radiation,photovoltaic,building,solar cells,irradiance estimation
更新于2025-09-23 15:19:57
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A Method of Interstory Drift Monitoring Using a Smartphone and a Laser Device
摘要： Interstory drift is an important engineering parameter in building design and building structural health monitoring. However, many problems exist in current interstory drift monitoring methods. The traditional method is imprecise—double numerical integration of acceleration data—and other direct monitoring methods need professional equipment. This paper proposes a method to solve these problems by monitoring the interstory drift with a smartphone and a laser device. In this method, a laser device is installed on the ceiling while a smartphone is ?xed on a steel projection plate on the ?oor. Compared with a reference sensor, the method designed in this study shows that a smartphone is competent in monitoring the interstory drift. This method utilizes a smartphone application (APP) named D-Viewer to implement monitoring and data storage just in one place, which is also inexpensive. The results showed that this method has an average percent error of 3.37%, with a standard deviation of 2.67%. With the popularization of the smartphone, this method is promising in acquiring large amounts of data, which will be signi?cant for building assessment after an earthquake.
关键词： structural health monitoring,laser device,interstory drift,smartphone,seismic monitoring
更新于2025-09-23 15:19:57
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Improved chemical exchange saturation transfer imaging with real-time frequency drift correction
摘要： Purpose: To investigate the effects of frequency drift on chemical exchange saturation transfer (CEST) imaging at 3T, and to propose a new sequence for correcting artifacts attributed to B0 drift in real time. Theory and Methods: A frequency‐stabilized CEST (FS‐CEST) imaging sequence was proposed by adding a frequency stabilization module to the conventional non‐frequency‐stabilized CEST (NFS‐CEST) sequence, which consisted of a small tip angle radiofrequency excitation pulse and readout of three non‐phase‐encoded k‐space lines. Experiments were performed on an egg white phantom and 26 human subjects on a heavy‐duty clinical scanner, in order to compare the difference of FS‐CEST and NFS‐CEST sequences for generating the z‐spectrum, magnetization transfer ratio asymmetry (MTRasym) spectrum, and amide proton transfer weighted (APTw) image. Results: The B0 drift in CEST imaging, if not corrected, would cause APTw images and MTRasym spectra from both the phantom and volunteers to be either significantly higher or lower than the true values, depending on the status of the scanner. The FS‐CEST sequence generated substantially more stable MTRasym spectra and APTw images than the conventional NFS‐CEST sequence. Quantitatively, the compartmental‐average APTw signals (mean ± standard deviation) from frontal white matter regions of all 26 human subjects were –0.32% ± 2.32% for the NFS‐CEST sequence and –0.14% ± 0.37% for the FS‐CEST sequence. Conclusions: The proposed FS‐CEST sequence provides an effective approach for B0 drift correction without additional scan time and should be adopted on heavy‐duty MRI scanners.
关键词： amide proton transfer (APT),chemical exchange saturation transfer (CEST),frequency drift,frequency stabilized CEST (FS‐CEST)
更新于2025-09-19 17:15:36
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Electrical Properties of Metal-Porous GaAs Structure at Water Adsorption
摘要： This paper reports the morphological, optical, luminescent and electrical properties of electrochemically made porous GaAs in order to evaluate their humidity sensing performance. The obtained porous GaAs exhibits non-homogenous surface morphology, which consists of pyramid-shaped crystallites and micropores. Photoluminescent and FTIR study shows that the surface of such material is covered by an oxide of As and Ga. The impedance spectroscopy was applied to analyze the influence of water vapor on electrical properties of metal-porous GaAs. It was shown that water adsorption results in the Nyquist plots shift to the region of higher frequencies. In humid atmosphere resistance Rv and characteristic time of charge accumulation s are decreased by 1.4 times and 5 times, respectively; resistance Rb and capacity Cb decreased by 1.4 times and 4.4 times, respectively. The response of the metal-porous GaAs structure to the adsorption of water is attributed to the decreasing of the bulk resistivity and potential barrier height. The formed oxide layer on the surface of porous GaAs plays a dual role—it increases the ability to adsorb water molecules and prevents the surface from receiving structural degradation.
关键词： SEM,DRIFT spectrum,impedance spectroscopy,Nyquist plot,Porous GaAs,humidity sensor
更新于2025-09-19 17:15:36
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Effect of the Accidental Impurities onto the Absorption Spectrum of NaGd(WO <sub/>4</sub> ) <sub/>2</sub> Laser Crystal
摘要： Doppler velocity can be derived by calculating Doppler shift anomalies between predicted and estimated Doppler centroids. The predicted Doppler centroid is calculated based on a geometric model of satellite assuming that the target is not moving. The estimated Doppler centroid can be directly extracted from the raw SAR signal data by applying the average cross-correlation coefficient method. It is known that wind-generated ocean waves can significantly contribute to Doppler velocity due to the correlation between orbital motions of the waves and (tilt and hydrodynamic) modulated radar cross sections, in addition to what sea surface current contributes. In this study, the characteristics of Doppler velocities under hurricane conditions were investigated using RADARSAT-1 ScanSAR raw data. Five different hurricanes (Hurricane Dean, Hurricane Ivan, Hurricane Kyle, Hurricane Lili, and Typhoon Xangsane) and sequential acquisitions of two hurricanes (Hurricane Kyle and Hurricane Lili) were selected to study the contribution of wind-induced waves to Doppler velocities and compared with in situ measurements of drifting buoys. The results show that hurricane-generated seas and associated winds and waves appear to be different from ordinary sea state. This leads to lower estimates of Doppler velocities than expected and much closer to sea surface current velocities.
关键词： RADARSAT,Doppler velocity,hurricane,drift current,wind-induced waves
更新于2025-09-19 17:13:59
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Time-delay encoded image recognition in a network of resistively-coupled VO2 on Si oscillators
摘要： Doppler velocity can be derived by calculating Doppler shift anomalies between predicted and estimated Doppler centroids. The predicted Doppler centroid is calculated based on a geometric model of satellite assuming that the target is not moving. The estimated Doppler centroid can be directly extracted from the raw SAR signal data by applying the average cross-correlation coefficient method. It is known that wind-generated ocean waves can significantly contribute to Doppler velocity due to the correlation between orbital motions of the waves and (tilt and hydrodynamic) modulated radar cross sections, in addition to what sea surface current contributes. In this study, the characteristics of Doppler velocities under hurricane conditions were investigated using RADARSAT-1 ScanSAR raw data. Five different hurricanes (Hurricane Dean, Hurricane Ivan, Hurricane Kyle, Hurricane Lili, and Typhoon Xangsane) and sequential acquisitions of two hurricanes (Hurricane Kyle and Hurricane Lili) were selected to study the contribution of wind-induced waves to Doppler velocities and compared with in situ measurements of drifting buoys. The results show that hurricane-generated seas and associated winds and waves appear to be different from ordinary sea state. This leads to lower estimates of Doppler velocities than expected and much closer to sea surface current velocities.
关键词： wind-induced waves,drift current,Doppler velocity,hurricane,RADARSAT
更新于2025-09-19 17:13:59
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Two different types of S-shaped J-V characteristics in organic solar cells
摘要： In this paper, S-shaped characteristics of organic solar cells (OSCs) are analyzed by a drift–diffusion model which includes charge carrier surface recombination and thermal injection on the anode and cathode through boundary conditions. By varying surface recombination velocities (SRVs) for electrons and holes on both contacts and the injection barrier heights for majority carriers, two different S-shaped deviations in OSCs J-V characteristics were observed. The first type of S-shaped J-V characteristic manifests the S-shape bending in the vicinity of the voltage axis, after which it rises almost exponentially. This kind of S-shape deformation was found to arise from the finite SRVs. The second type of the S-shaped J-V characteristic also makes a kink near the voltage axis but proceeds to grow monotonically, having only one saddle point. The S-shaped J-V curve of this kind turned out to be the consequence of the electron injection barrier height larger than 0.2 eV. The validity of our model is confirmed by comparing the simulated J-V curves with the experimentally obtained data. The model has been applied to the ITO/PEDOT:PSS/P3HT:PCBM/Al and ITO/PEDOT:PSS/P3HT:ICBA/Al solar cells. For the P3HT:PCBM based solar cells, the regular J-shaped J-V curves were measured, while for the P3HT:ICBA solar cells, the J-V curves with anomalous S-shape behavior were recorded. All experimentally obtained J-V curves were reproduced very well with our model. It seems that the ITO/PEDOT:PSS/ P3HT:ICBA/Al solar cell S-shaped J-V curve originates from the electron barrier height on the cathode contact, rather than from the low surface recombination on the electrodes.
关键词： Solar cells,Drift–diffusion model,Organic materials,S-shaped J-V curve
更新于2025-09-19 17:13:59
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PVRD-FASP: A Unified Solver for Modeling Carrier and Defect Transport in Photovoltaic Devices
摘要： In this article, we present a simulator for modeling transport of charge carriers and electrically active defect centers in solar cells by treating them on an equal footing, which allows us to address metastability and reliability issues. The exact nonlinear differential equations set solved by our solver is presented. The formulation of such differential equations, namely the continuity equations, drift-diffusion equation, and Poisson equation, for studying charge and defect transport is explained. The parameters needed for forming the differential equations are taken from first principle calculations. The solver is verified with test cases built on PN heterojunctions, Cu diffusion in single crystal CdTe and comparing Silvaco simulations with our numerical results.
关键词： drift-diffusion,PN heterojunction,transient solutions for continuity equation,Defect reaction solver,implicit Euler with Newton iteration,chemical reactions
更新于2025-09-16 10:30:52