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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Experimental Validation of Compact Tomosar for Vegetation Characterization
摘要： The study aims to explore the potentials of compact TomoSAR for vegetation characterization. The compact mode transmits either in linear or circular polarized waves and receives at horizontal and vertical polarization providing a different perspective to the understanding of the target. The goal of this study is to assess and evaluate the performance of compact polarimetric SAR modes to reconstruct the 3D reflectivity of forest volume and estimate the vertical structure in comparison with FP modes. Preliminary investigation of compact TomoSAR is conducted using L-band BIOSAR 2008 dataset consisting of six flight tracks acquired over Krycklan in northern Sweden.
关键词： SAR Tomography,Reflectivity,Vegetation Structure,Compact Polarimetry,PolInSAR
更新于2025-09-09 09:28:46
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FIRST PRINCIPLES STUDY OF STRUCTURAL, ELECTRONIC AND OPTICAL PROPERTIES OF HALF-HEUSLER ALLOYS LIMGN, NaMGN AND KMGN
摘要： In this study, we performed our calculations using the full-potential linearized-augmented plane wave (FP-LAPW) method as implemented in the WIEN2k code based on DFT. The generalized gradient functional with the Wu-Cohen (WC) parameterization was used to evaluate the structural, electronic, optical and thermoelectric properties of the materials under this study. We have calculated the structural parameters and our obtained results are in good agreement with available experimental and previous theory calculations. The density of states and band structure figures have been calculated and analyzed. The optical properties that covered by dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity and energy-loss function have been calculated and analyzed in a range energy from 0eV to 30eV.
关键词： generalized gradient functional,dielectric function,reflectivity,absorption,half-Heusler,Density functional theory
更新于2025-09-09 09:28:46
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First-principles investigation of the electronic band structures and optical properties of quaternary <i>A</i> Ba <i>MQ</i> <sub/>4</sub> ( <i>A</i> = Rb, Cs; <i>M</i> = P, V; and <i>Q</i> = S) metal chalcogenides
摘要： In this paper, we study the optoelectronic properties of quaternary metal chalcogenide semiconductor ABaM Q4 (A = Rb, Cs; M = P, V; and Q = S) compounds using state-of-the-art density functional theory (DFT) with TB-mBJ approximation for the treatment of exchange-correlation energy. In particular, the electronic and optical properties of the relaxed geometries of these compounds are investigated. Our first-principles ab-initio calculations show that the CsBaPS4 and RbBaPS4 compounds have direct bandgaps whereas the CsBaVS4 compound exhibits indirect bandgap nature. Importantly, the theoretically calculated values of the bandgaps of the compounds are consistent with experiment. Furthermore, our analysis of the electronic charge densities of these compounds indicates that the above quaternary chalcogenides have mixed covalent and ionic bonding characters. The effective masses of these compounds are also calculated which provide very useful information about the band structure and transport characteristics of the investigated compounds. Similarly, high absorptivity in the visible and ultraviolet regions of the electromagnetic spectrum possibly predicts and indicates the importance of these materials for potential optoelectronic applications in this range.
关键词： energy band structure,electronic charge densities,optical conductivity,Chalcogenides,refractive index,dielectric constants,optical reflectivity
更新于2025-09-09 09:28:46
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Ultrafast electron and spin dynamics of strongly correlated NdNiO <sub/>3</sub>
摘要： Electron and spin dynamics of strongly correlated NdNiO3 are investigated across the metal–insulator transition with ultrafast optical spectroscopy at different temperatures, pump laser fluences, and laser polarizations. Transient differential reflectivity measurements on the insulating phase NdNiO3 show two characteristic electronic decay processes. The slow decay process, strongly dependent on coherent phonon excitation, is attributed to the electron–phonon interaction, while the fast decay process, to the electron-spin interaction. The temporal evolution of Kerr rotation reveals that net spin polarization can be induced by circularly polarized light in insulating NdNiO3 via electron excitation from the Ni t?2g to e?g orbital, and two net spin polarizations with opposite directions are observed given the antiferromagnetic ordering in insulating NdNiO3. At the insulator-to-metal transition, the transient differential reflectivity reverses its sign; the metallic phase NdNiO3 also shows two characteristic electronic decay processes, a typical metallic decay processes and a slow decay process; the slow decay process is attributed to the interaction between electrons and the low frequency coherent phonons (～2.45 THz). Our experiments demonstrate that the phase transition involves several processes upon continuous heating: the electron-spin interaction disappears at 9 K below the transition temperature; at the transition temperature, NdNiO3 transitions into the metallic phase and the antiferromagnetic ordering transitions into the paramagnetic ordering; at the transition temperature, the structure of NdNiO3 changes from a monoclinic structure ( P21/n) to a high temperature orthorhombic ( Pbmn) structure. Such a structure change results in the change in phonon vibrations, and subsequently, leads to the disappearance of the electron–phonon interactions due to the insulating phase NdNiO3 and the emergence of other types of electron–phonon interactions due to the metallic phase.
关键词： time-resolved Kerr rotation measurements,electron and spin dynamics,femtosecond transient reflectivity measurement,polymer-assisted deposition,strongly correlated oxide NdNiO3
更新于2025-09-09 09:28:46
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45.1: <i>Invited Paper:</i> Formulation of Jones matrix for the general reflective birefringent medium
摘要： We have formulated the Jones matrix for the general reflective birefringent medium and derived an expression of the intensity reflectivity for the general reflective birefringent medium with a single polarizer. Two examples are illustrated to show how one can use them in real cases.
关键词： liquid crystal,Jones matrix,liquid crystal display,reflective TN cell,intensity reflectivity,optics,reflective display,birefringent,polarization
更新于2025-09-04 15:30:14
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Reflectivity and thickness analysis of epiretinal membranes using spectral-domain optical coherence tomography
摘要： · AIM: To compare thickness and reflectivity spectral domain optical coherence tomography (SD-OCT) findings in patients with idiopathic epiretinal membranes (ERMs), before and after ERM peeling surgery, with normal controls. · METHODS: A retrospective study analyzing SD-OCTs of eyes with ERMs undergoing ERM peeling surgery by one surgeon from 2008 to 2010 and normal control eyes. SD-OCTs were analyzed using a customized algorithm to measure reflectivity and thickness. The relationship between the SD-OCT findings and best corrected visual acuity (BCVA) outcomes was also studied. · RESULTS: Thirty-four ERM eyes and 12 normal eyes were identified. Preoperative eyes had high reflectivity and thickness of the group of layers from the internal limiting membrane (ILM) to the retinal pigment epithelium (RPE) and the group of layers from the ILM to the external limiting membrane (ELM). The reflectivity of these two groups of layers decreased postoperatively, but were still higher than normal eyes. In contrast, preoperative eyes had lower reflectivity of two 10 × 15 pixel regions of interest (ROIs) incorporating: 1) ELM + outer nuclear layer (ONL) and 2) photoreceptor layer (PRL) + RPE, compared to controls. The values of reflectivity of these ROIs increased postoperatively, but were still lower than normal. A larger improvement in BCVA postoperatively was correlated with a greater degree of abnormal preoperative reflectivity and thickness findings. · CONCLUSION: Quantitative differences in reflectivity and thickness between preoperative, postoperative, and normal SD-OCTs allow assessment of changes in the retina secondary to ERM. Our study identified hyperreflective inner retinal changes and hyporeflective outer retinal changes in patients with ERMs. SD-OCT quantitative measures of reflectivity and/or thickness of specific groups of retinal layers and/or ROIs correlate with improvement in BCVA.
关键词： epiretinal membranes,retina,imaging,reflectivity,optical coherence tomography,vitrectomy
更新于2025-09-04 15:30:14
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Nanoparticles at Biomimetic Interfaces: A Combined Experimental and Simulation Study on Charged Gold Nanoparticles/Lipid Bilayers Interfaces
摘要： The poor understanding of the interaction of nanomaterials with biologically relevant interfaces is recognized as one of the major issues currently limiting the development of nanomedicine. The central purpose of this study is to compare experimental (Confocal Microscopy, Fluorescence Correlation Spectroscopy, X-ray Reflectivity) and computational (Molecular Dynamics simulations) results to thoroughly describe the interaction of cationic gold nanoparticles (AuNP) with mixed zwitterionic/anionic lipid membranes. The adhesion of AuNPs to the lipid membrane is investigated on different length scales from a structural and dynamical point of view; with this approach, a series of complex phenomena, spanning from lipid extraction, localized membrane disruption, lateral phase separation and slaved diffusion, are characterized and interpreted from a molecular level to macroscopic observations.
关键词： Nanoparticles,Gold Nanoparticles,Molecular Dynamics,X-ray Reflectivity,Fluorescence Correlation Spectroscopy,Lipid Bilayers,Biomimetic Interfaces,Confocal Microscopy
更新于2025-09-04 15:30:14
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Synthetic Aperture Radar Target Feature Modulation Using Active Frequency Selective Surface
摘要： Target feature control on the synthetic aperture radar (SAR) image using the passive way is a challenging task in the field of SAR jamming. The conventional passive jamming devices such as corner reflectors and chaffs cannot achieve the flexible modulation of SAR target feature duo to their fixed scattering cross section. As a passive material, active frequency selective surface (AFSS) can dynamically control their electromagnetic characteristics and has been widely applied in the radar target stealth field. In this paper, a target feature modulation method based on AFSS is proposed against SAR. The method intermittently switches the scattering intensity of AFSS material and imposes periodic or random code amplitude modulation onto the radar signal. As a consequence, multi-false targets with verisimilar characteristics or cross-shaped areas are formed when modulated signal is received and processed by the victim SAR. Thus the protected target is difficult to detect and identify by SAR system. Microwave anechoic chamber experiments and measured SAR data simulations with different modulating parameters are separately conducted to demonstrate the effectiveness of the proposed method.
关键词： Synthetic aperture radar (SAR),reflectivity,target feature,periodic modulation,random code modulation,active frequency selective surface (AFSS)
更新于2025-09-04 15:30:14
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Unruh-DeWitt detectors as mirrors: Dynamical reflectivity and Casimir effect
摘要： We demonstrate that the Unruh-DeWitt harmonic-oscillator detectors in (1 t 1) dimensions derivative-coupled with a massless scalar field can mimic the atom mirrors in free space. Without introducing the Dirichlet boundary condition to the field, the reflectivity of our detector or atom mirror is dynamically determined by the interaction of the detector’s internal oscillator and the field. When the oscillator-field coupling is strong, a broad frequency range of the quantum field can be mostly reflected by the detector mirror at late times. Constructing a cavity model with two such detector mirrors, we can see how the quantum field inside the cavity evolves from a continuous to a quasidiscrete spectrum which gives a negative Casimir energy density at late times. In our numerical calculations, the Casimir energy density in the cavity does not converge until the UV cutoff is sufficiently large, with which the two internal oscillators are always separable.
关键词： Unruh-DeWitt detectors,atom mirrors,Casimir effect,reflectivity,quantum field theory
更新于2025-09-04 15:30:14
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Quasi-Distributed Fabry-Perot Optical Fibre Sensor for Temperature Measurements
摘要： This paper presents a simulation and an experimental quasi-distributed Fabry–Perot optical fibre sensor for temperature measurements implemented on a serial array using a combined frequency division multiplexing and wavelength division multiplexing arrangement. Quasi-distributed fibre sensors have been of great interest in the industry for the monitoring of power transformers, jet engines, and furnaces. This paper is aimed at providing theoretical results for a quasi-distributed sensor system made of 25 local sensors imprinted on a serial array of the single mode fibre whereby the local sensors are of weak reflectivity. In addition, a sensor system of nine quasi-distributed local sensors is experimentally tested and a sensitivity of 10 pm/oC and a resolution of 0.125°C are obtained. Its higher resolution, higher spatial distribution, and ability to measure temperature at different points simultaneously make it a very attractive temperature sensor.
关键词： Fabry-Perot,resolution,weak reflectivity,sensitivity
更新于2025-09-04 15:30:14