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- 摘要
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- 实验方案
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Coupling sky images with radiative transfer models: a new method to estimate cloud optical depth
摘要： A method for retrieving cloud optical depth (τc) using a UCSD developed ground-based sky imager (USI) is presented. The radiance red–blue ratio (RRBR) method is motivated from the analysis of simulated images of various τc produced by a radiative transfer model (RTM). From these images the basic parameters affecting the radiance and red–blue ratio (RBR) of a pixel are identified as the solar zenith angle (θ0), τc, solar pixel angle/scattering angle (?s), and pixel zenith angle/view angle (?z). The effects of these parameters are described and the functions for radiance, Iλ (τc, θ0, ?s, ?z), and RBR(τc, θ0, ?s, ?z) are retrieved from the RTM results. RBR, which is commonly used for cloud detection in sky images, provides non-unique solutions for τc, where RBR increases with τc up to about τc = 1 (depending on other parameters) and then decreases. Therefore, the RRBR algorithm uses the measured I meas (?s, ?z), in addition to RBRmeas (?s, ?z), to obtain a unique solution for τc. The RRBR method is applied to images of liquid water clouds taken by a USI at the Oklahoma Atmospheric Radiation Measurement (ARM) program site over the course of 220 days and compared against measurements from a microwave radiometer (MWR) and output from the Min et al. (2003) method for overcast skies. τc values ranged from 0 to 80 with values over 80, being capped and registered as 80. A τc RMSE of 2.5 between the Min et al. (2003) method and the USI are observed. The MWR and USI have an RMSE of 2.2, which is well within the uncertainty of the MWR. The procedure developed here provides a foundation to test and develop other cloud detection algorithms.
关键词： sky imager,cloud optical depth,solar forecasting,radiative transfer model,red–blue ratio
更新于2025-09-04 15:30:14
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An enhanced Bouc-Wen model for characterizing rate-dependent hysteresis of piezoelectric actuators
摘要： A classical Bouc-Wen model is widely applied in hysteresis modeling and compensation for piezoelectric ceramic actuators. However, the classical Bouc-Wen model cannot characterize rate-dependent hysteresis under excitations at high frequencies precisely. In this paper, an enhanced Bouc-Wen model is developed by introducing the frequency of input voltage based on the classical Bouc-Wen model. A number of experiments were conducted to characterize the rate-dependent hysteresis of piezoelectric ceramic actuators under sinusoidal excitations at a range of 1–150 Hz. The measured data were used to demonstrate the validity of the developed model. A method of parameter estimation based on the Matlab/Simulink parameter estimation tool is adopted to identify the parameters of models. The comparisons of experiments and simulations show that the developed model can describe rate-dependent hysteresis more accurately than the classical Bouc-Wen model. The modeling errors of the developed model were decreased by nearly 75% compared with that of the classical Bouc-Wen model. The root-mean-square error of the developed model is controlled in 0.1719 μm.
关键词： parameter estimation,Bouc-Wen model,rate-dependent hysteresis,piezoelectric actuators
更新于2025-09-04 15:30:14
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Collisional - radiative model of xenon plasma with calculated electron impact fine-structure excitation cross sections
摘要： Detailed electron impact excitation cross section results for xenon in the wide range of incident energy from threshold to 1000eV are calculated using relativistic distorted wave (RDW) theory. Various transitions from the ground 5p6 state to the excited 5p56s, 5p56p, 5p55d, 5p57s and 5p57p as well as among these excited states are considered. The relativistic Dirac-Fock multi-configuration wave functions for the ground and excited states of the xenon are obtained and used in the calculations. Where available our cross section results are compared with previously reported measurements and calculations. We have also fitted the calculated cross sections through analytical formulae for plasma modeling purposes. As an application, using the obtained cross sections, a collisional Radiative (C-R) model coupled with an optical emission measurement from the inductively coupled Xe plasma is developed and the extracted plasma parameters are reported.
关键词： relativistic distorted wave theory,Electron impact excitation,cross-sections,collisional radiative model
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Chengdu (2018.3.26-2018.3.28)] 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Terahertz Wave Scattering by Skin Cancer Tissues
摘要： This paper presents an approximate method for analysis of scattering by skin cancer tissues at Terahertz. The complex dielectric parameters of skin tissues are based on the double Debye model. The cancer tissue is taken to be a weak disturbance to the bulk skin organ. Born approximation is used to calculate the scattering field by the equivalent volume currents of cancer tissues in a layered configuration. Discrete complex image method is employed to evaluate the Sommerfeld-type integral. Numerical results show that the proposed approach is efficient and viable.
关键词： Born approximation,Terahertz scattering,skin cancer tissues,double Debye model
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Frequency-Selective Rasorber with a Transparent Window Between Absorption Bands
摘要： In this paper, a novel frequency-selective rasorber (FSR) which has a transmission band between two absorption bands is proposed. The FSR is composed of curved metal sheets with lumped resistors printed on a dielectric substrate and a frequency selective surface (FSS) used as the ground plane of the absorber. An equivalent circuit model of the structure is given for analyzing its operation mechanism. A good stability of the transmission and two-band absorption under the incident angle o30 for TE and TM polarizations has been obtained.
关键词： equivalent circuit model,transmission band,frequency-selective rasorber,absorption bands,FSR
更新于2025-09-04 15:30:14
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[IEEE 2018 7th International Conference on Renewable Energy Research and Applications (ICRERA) - Paris, France (2018.10.14-2018.10.17)] 2018 7th International Conference on Renewable Energy Research and Applications (ICRERA) - Energy Consumption Optimization through Dynamic Simulations for an Intelligent Energy Management of a BIPV Building
摘要： Having 6500 integrated sensors and a wide network of embedded systems, the ADREAM building can be categorized as one of the prototype smart buildings of France. As needs for intelligent management of energy are growing, the associated project provides a multidisciplinary platform of experimentation, developing solutions for efficient Energy Networks, HVAC Systems, Photovoltaics, and Smart Grids. This paper provides the overview of the project along with three different modeling techniques, simulating the thermal behavior of the building and the functioning of the different energy systems. A thermal model of the building was developed and calibrated for energy consumption analysis and prediction, using the software Pleiades+Comfie. A “black box” model was developed using artificial neural networks for the simulation of energy system parameters and the exploration of efficient control strategies. The last method provides the overview of developing an all-inclusive physical model with equivalent Matlab/Simulink for simulating the global functioning of the building and its HVAC systems. The conclusion addresses the utility of exploring and combining different types of models for optimizing the energy management of Smart Buildings.
关键词： Simulink,Energy Optimization,Model Calibration,Building Simulation,Smart Building,Pleiades + Comfie,Energy Management
更新于2025-09-04 15:30:14
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PT symmetry protected non-Hermitian topological systems
摘要： We study PT symmetry protected topological phase in non-Hermitian 1D and 2D systems. We show that topological phase exist in non-Hermitian PT symmetric systems for both gapped and gapless systems and discuss appearance of exceptional points. We apply our formalism to a complex extension of the SSH model, topological semimetals and nodal superconductors.
关键词： SSH model,nodal superconductors,non-Hermitian systems,topological semimetals,PT symmetry,topological phase
更新于2025-09-04 15:30:14
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Combined sphere-spheroid particle model for the retrieval of the microphysical aerosol parameters via regularized inversion of lidar data
摘要： In this work we propose a two-step advancement of the Mie spherical-particle model accounting for particle non-sphericity. First, a naturally two-dimensional (2D) generalized model (GM) is made, which further triggers analogous 2D re-definitions of microphysical parameters. We consider a spheroidal-particle approach where the size distribution is additionally dependent on aspect ratio. Second, we incorporate the notion of a sphere-spheroid particle mixture (PM) weighted by a non-sphericity percentage. The efficiency of these two models is investigated running synthetic data retrievals with two different regularization methods to account for the inherent instability of the inversion procedure. Our preliminary studies show that a retrieval with the PM model improves the fitting errors and the microphysical parameter retrieval and it has at least the same efficiency as the GM. While the general trend of the initial size distributions is captured in our numerical experiments, the reconstructions are subject to artifacts. Finally, our approach is applied to a measurement case yielding acceptable results.
关键词： regularization,microphysical parameters,aerosol,lidar,spheroidal-particle model
更新于2025-09-04 15:30:14
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SAR Ground Moving Target Imaging Based on a New Range Model Using a Modified Keystone Transform
摘要： Imaging of a ground moving target (GMT) with synthetic aperture radar (SAR) is a challenging task, particularly when the Doppler ambiguity happens. This paper proposes a novel GMT range model and a novel Doppler ambiguity-tolerated GMT imaging algorithm based on modified keystone transform. In the proposed GMT range model, the range from radar antenna to the scattering center on the target is divided into two parts: the range from radar antenna to the target centroid and the projection length on the light of sight from the target centroid to the scattering center. Based on the new range model, a Doppler ambiguity-tolerated range cell migration correction (RCMC) method is proposed, in which keystone transform is modified to realize the differential RCMC by interpolation with nonzero phase sinc kernel. Finally, the GMT image is obtained in the range-Doppler domain by matched filtering in the slow-time domain and is restored into the 2-D space domain. The effectiveness of our proposed model and imaging method is demonstrated by both simulated and real airborne SAR data.
关键词： Ground moving target imaging (GMTIm),keystone transform,range cell migration correction (RCMC),range model,synthetic aperture radar (SAR)
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Atlanta, GA, USA (2018.10.31-2018.11.2)] 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Investigation of Performance Degradation in Enhancement-Mode GaN HEMTs under Accelerated Aging
摘要： In this paper, the performance degradation of enhancement-mode (E-mode) GaN HEMFs under accelerated aging is presented in detail. A real-time degradation monitoring tool is essential to prevent costly shutdowns and minimize safety concerns. Specifically, a DC power cycling setup is first designed which operates within the safe operating area (SOA) of the device to mimic the field operation and accelerate the aging process. The E-mode GaN devices are mounted on a custom designed PCB adaptor to accommodate the curve tracer where all the parasitics are carefully controlled to minimize the measurement errors. Using the curve tracer, the parameter shifts are periodically monitored at certain aging cycles. From the experimental results, it is observed that the on-state resistance and the threshold voltage are gradually increasing over the aging cycles, which makes potential failure precursors. Meanwhile, a variation in the transfer characteristics is observed, and the transconductance decreases as the device is aged. Finally, a detailed theoretical analysis is provided to explain this parameter shift in experiments.
关键词： Power cycling,Cascode GaN device,Failure model,Aging precursor
更新于2025-09-04 15:30:14