- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Light propagated distance and redshift of a distant star
摘要： According to the formerly reported 4-D spherical model of the time and universe, factors affecting the redshift are discussed. In addition to the factor from the space expansion, two other factors derived from the light speed variation are proposed. One is the energy density factor of the wave medium, which was formerly reported to determine the light speed. The second is a newly proposed factor caused by the electromagnetic interaction of light with substances in the 3-D space. Subsequently the direct correlation of the light propagated distance with the redshift is given. Superimposed graphs of it on the real observed data from the Supernova Cosmology Project exhibited an excellent fit for a case that the current radius (equal to our observed time) of the universe is between 0.7 and 0.8 of its maximum. This could be an important ground for a possibility of the 4-D spherical model, which implies that the universe has been expanding at a constant speed by our observed time.
关键词： 4-D spherical model,light speed,redshift,universe expansion,Supernova Cosmology Project
更新于2025-09-04 15:30:14
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Uncertainties of optical-model parameters for the study of the threshold anomaly
摘要： In the analysis of elastic-scattering experimental data, optical-model parameters (usually, depths of real and imaginary potentials) are (cid:12)tted and conclusions are drawn analyzing their variations at bombardment energies close to the Coulomb barrier (threshold anomaly). The judgement about the shape of this variation (related to the physical processes producing this anomaly) depends on these (cid:12)tted values but the robustness of the conclusions strongly depends on the uncertainties with which these parameters are derived. We will show that previous published studies have not used a common criterium for the evaluation of the parameter uncertainties. In this work, a study of these uncertainties is presented, using conventional statistic tools as well as bootstrapping techniques. As case studies, these procedures are applied to re-analyze detailed elastic-scattering data for the 12C + 208Pb and the 6Li + 80Se systems.
关键词： elastic-scattering,optical-model parameters,12C + 208Pb,6Li + 80Se,bootstrap techniques,threshold anomaly
更新于2025-09-04 15:30:14
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Blocked populations in ring-shaped optical lattices
摘要： We study a special dynamical regime of a Bose-Einstein condensate in a ring-shaped lattice where the populations in each site remain constant during the time evolution. The states in this regime are characterized by equal occupation numbers in alternate wells and nontrivial phases, while the phase differences between neighboring sites evolve in time yielding persistent currents that oscillate around the lattice. We show that the velocity circulation around the ring lattice alternates between two values determined by the number of wells and with a specific time period that is only driven by the on-site interaction energy parameter. In contrast to the self-trapping regime present in optical lattices, the occupation number at each site does not show any oscillation and the particle imbalance does not possess a lower bound for the phenomenon to occur. These findings are predicted with a multimode model and confirmed by full three-dimensional Gross-Pitaevskii simulations using an effective on-site interaction energy parameter.
关键词： on-site interaction energy,Bose-Einstein condensate,persistent currents,Gross-Pitaevskii simulations,multimode model,ring-shaped lattice
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) - Analysis of Calculation Models for Device Resonance in Critical Mode Converters
摘要： Critical Mode (CRM) converters, superior for high density applications at high frequencies, rely on precision gating signals for best timing of device resonance. Previously, two calculation models were used, one based on device time related output capacitance, Co(tr), and another on device output charge, Qoss. This work applies them to GaN and Si power devices, and analyzes the differences. Results show that the Qoss model is better for both devices in predicting resonant period. However, for prediction current/voltage waveforms the Co(tr) model is better for GaN while the Qoss model better for Si devices. The Qoss model is then simplified and applied to a 1 MHz and 1.4 kW CRM boost converter built with GaN devices. The prototype achieves >99% efficiency from 60% to 100% load at 240V input and 400V output.
关键词： resonance,GaN,model
更新于2025-09-04 15:30:14
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - The Potential of Sentinel Satellites for Large Area Aboveground Forest Biomass Mapping
摘要： Estimation of aboveground forest biomass is critical for regional carbon policies and sustainable forest management. Both passive optical remote sensing and active microwave remote sensing can play an important role in the monitoring of forest biomass. In this study, the recently launched Sentinel-2 Multi Spectral Instrument satellite and Sentinel-1 SAR satellite systems were evaluated and integrated to investigate the relative strengths of each sensor for mapping aboveground forest biomass at a regional scale. The Australian state of Victoria, with its wide range of forest vegetation was chosen as the study area to demonstrate the scalability and transferability of the approach. In this study aboveground forest biomass (AGB) was defined as the tons of carbon per hectare for the aboveground components (stem, branches, leaves) of all live large trees greater than 10 cm in diameter at breast height (DBHOB). Sentinel-2 and Sentinel-1 data were fused within a machine learning framework using a boosted regression tree model and high-quality ground survey data. Multi-criteria evaluations showed the use of the two independent and fundamentally different Sentinel satellite systems were able to provide robust estimates (R2 of 0.62, RMSE of 32.2 t.C.ha-1) of aboveground forest biomass, with each sensor compensating for the weakness (cloud perturbations and spectral saturation for Sentinel 2, and sensitivity to ground moisture for Sentinel 1) of each other. As archives for Sentinel-2 and Sentinel-1 continue to grow, mapping aboveground forest biomass and dynamics at moderate resolution over large regions should become increasingly feasible.
关键词： Sentinel-2,machine learning,data fusion,Sentinel-1,Victoria,boosted regression tree model,Australia,biomass estimation
更新于2025-09-04 15:30:14
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Spherical Harmonic-Based Spectral Projection Model for Holographic SAR Imaging
摘要： A spectral projection model which is based on spherical harmonics is developed for three-dimensional holographic SAR imaging. The addition theorem for spherical harmonics is used for describing the SAR measurement process as a projection of a source spectral vector onto an observation spectral vector. The source vector for a particular scatterer is determined by the spherical coordinates of that scatterer. The dimension of the source vector is determined by the largest dimension of the SAR viewing area. The observation vectors are similarly defined in terms of the spherical coordinates of each measurement point along the SAR flight path. By separating the source and observation terms in the addition theorem, the contribution from each scatterer to each specific SAR measurement is described as the projection of the source spectral vector onto the observation spectral vector. Simulations are used to investigate the spectral properties of a variety of source distributions and SAR flight paths. Sample holographic images are simulated using this spectral projection model.
关键词： addition theorem,Holographic SAR,spectral projection model,spherical harmonics
更新于2025-09-04 15:30:14
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A new method of measuring aerosol optical properties from digital twilight photographs
摘要： An optimal-estimation algorithm for inferring aerosol optical properties from digital twilight photographs is proposed. The sensitivity of atmospheric components and surface characteristics to brightness and color of twilight sky is investigated, and the results suggest that tropospheric and stratospheric aerosol optical thickness (AOT) are sensitive to condition of the twilight sky. The coarse–fine particle volume ratio is moderately sensitive to the sky condition near the horizon under a clean-atmosphere condition. A radiative transfer model that takes into account a spherical-shell atmosphere, refraction, and multiple scattering is used as a forward model. Error analysis shows that the tropospheric and stratospheric AOT can be retrieved without significant bias. Comparisons with results from other ground-based instruments exhibit reasonable agreement on AOT. A case study suggests that the AOT retrieval method can be applied to atmospheric conditions with varying aerosol vertical profiles and vertically inhomogeneous species in the troposphere.
关键词： tropospheric and stratospheric AOT,aerosol optical properties,digital twilight photographs,coarse–fine particle volume ratio,radiative transfer model
更新于2025-09-04 15:30:14
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Towards a user preference model for interior lighting Part 1: Concept of the user preference model and experimental method
摘要： The objective and subjective factors influencing human-centric lighting design and their effect on the user of the lighting system are analysed with the aim of developing a user preference model. It is discussed how to apply this user preference model in the Internet of Things network structure of luminaires in order to obtain an ‘Internet of Luminaires’ for good user acceptance. The method of a visual experiment intended to elucidate these concepts and contribute to the user preference model is described. In the experiment, subjects assessed scene brightness, visual clarity, colour preference and scene preference in a real room. Modelling equations of these attributes will be shown and discussed in Part 2 of this work.
关键词： human-centric lighting,user preference model,colour preference,scene preference,visual clarity,scene brightness,Internet of Luminaires
更新于2025-09-04 15:30:14
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Multi-resolution Image Fusion in Remote Sensing () || Image Fusion: Model Based Approach with Degradation Estimation
摘要： Recently, many researchers have attempted to solve the problem of multi-resolution image fusion by using model based approaches, with emphasis on improving the fused image quality and reducing color distortion [273, 121]. They model the low resolution (LR) MS image as a blurred and noisy version of its ideal high resolution (HR) fused image. Solving the problem of fusion by the model based approach is desirable since the aliasing present due to undersampling of the MS image can be taken care of while modelling. Fusion using the interpolation of MS images and edge-preserving ?lters as given in Chapter 3 do not consider the effect of aliasing which is due to undersampling of MS images. The aliasing in the acquired image causes distortion and, hence, there exists degradation in the LR MS image. In this chapter, we propose a model based approach in which a learning based method is used to obtain the required degradation matrix that accounts for aliasing. Using the proposed model, the ?nal solution is obtained by considering the model as an inverse problem. The proposed approach uses sub-sampled as well as non sub-sampled contourlet transform based learning and a Markov random ?eld (MRF) prior for regularizing the solution.
关键词： model based approach,multi-resolution image fusion,degradation estimation,contourlet transform,Markov random field
更新于2025-09-04 15:30:14
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Surface velocity model of the flow caused by a DBD plasma actuator; DBDプラズマアクチュエータによる流れの表面速度モデル;
摘要： The surface velocity model is proposed for modelling the flow caused by a DBD plasma actuator. While numerical model presented up to now for the DBD plasma actuator, i.e. Suzen’s model, needs to calibrate the five parameters that must be determined by comparison with the experimental results, the surface velocity model presented here requires calibrating three parameters only. The flow by the surface velocity model is compared with the experimental results and that of Suzen’s model. When DBD plasma actuators are activated on the surface of the flat plate or on that of the circular cylinder, the induced flow appears near the electrode. And then the temporal and spatial development of the flow by the surface velocity model is consistent with the results from the experiment and the Suzen’s model. The surface velocity model is very easy to use compared with the Suzen’s model, and it can well simulate the induced flow caused by the plasma actuator.
关键词： Numerical simulation,DBD plasma actuator,Numerical model,Induced flow,Flow control
更新于2025-09-04 15:30:14