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- 摘要
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- 实验方案
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[IEEE 2018 UKSim-AMSS 20th International Conference on Computer Modelling and Simulation (UKSim) - Cambridge, United Kingdom (2018.3.27-2018.3.29)] 2018 UKSim-AMSS 20th International Conference on Computer Modelling and Simulation (UKSim) - A Multiple Quantum Well Structure Simulator
摘要： A simulator was developed for modeling and designing multiple quantum wells structures such as quantum well infrared photodetectors and quantum cascade laser, based on a single-electron effective mass Schr?dinger equation. It employs box integration finite differences and transfer matrix approaches to find energies of bound and scattering states in the structures. The graphical user interface allows the user to vary easily design parameters including effective mass, layer thickness and number of layers as well as simulation parameters in order to optimize the structure for different device applications and functionality. Three simulation examples were performed on: three coupled quantum wells infrared two-color asymmetric quantum well structure, photodetector structure and on a quantum cascade laser design. The results show an accuracy which is comparable to more complicated simulations.
关键词： Effective mass approximation,TMM,Multiple Quantum Wells Structures,FDM
更新于2025-09-23 15:22:29
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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) - MLFMA-ACA Based Method for Efficient Calculation of Scattering from Underground Targets
摘要： Electromagnetic (EM) non-destructive evaluation (NDE) of underground targets is of great significance for the safety of urban construction. Succesful detection of underground targets during construction depends on the accurate and efficient simulation of wave propagation. Among the most popular numerical methods in electromagnetics, surface integral equation (SIE) based method of moments (MoM) is used to simulate the scattering from underground targets in this paper. While MoM has high computational complexity O(N^2) and memory cost O(N^2) if iterative solver is applied, where N is the number of unknowns. As one of the most efficient fast algorithms, multi-level fast multi-pole algorithm (MLFMA) is used to reduce the computational complexity and memory cost. However, MLFMA is more difficult to calculate in this case because of the coupling action between rough surface and target has its limitations. So, adaptive cross approximation (ACA) is used to solve this problem. In this paper, a hybrid method combining MLFMA and ACA (MLFMA-ACA) is proposed to compute the scattering from underground targets. While MLFMA is used to compress the coupling matrix between rough surface and target, ACA is added to compress the coupling matrix between different media targets. The combination between them can build a more efficient method to compute scattering from underground targets.
关键词： method of moment,multi-level fast multi-pole algorithm,Adaptive cross approximation,electromagnetic scattering,underground target
更新于2025-09-23 15:22:29
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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 - A Study of Cross-Polarized Sea Clutter Using the SSA2 High Frequency Approximation and the Two-Scale Model
摘要： Cross-polarized backscatter normalized radar cross section (NRCS) measurements have been of increasing interest due to their potential to improve wind speed retrievals at high wind speeds. The development of physics-based forward models for cross-polarized backscatter has been challenging due to the higher-order scattering mechanisms that contribute to this quantity. In this paper, predictions of the two-scale model (TSM) and the small slope approximation (SSA2) for cross polarized backscatter are examined to obtain insight into their relative merits. A recently introduced high frequency (HF) approximation for cross polarized backscatter under the SSA2 is also examined and compared to a similar approximation based on the TSM. The results provide guidance for the continued development of forward models for sea surface remote sensing using cross polarized backscatter.
关键词： Cross-polarized,high frequency approximation,Sea clutter,Two scale model
更新于2025-09-23 15:21:21
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Geometrical Theory of Diffraction Formulation for On-Body Propagation
摘要： A Geometrical Theory of Diffraction model for on-body propagation is developed in the article. The exact solution to the canonical problem of a plane wave incident on an in?nitely long cylinder, with arbitrary constitutive parameters, is found. The same is done for a magnetic and an electric in?nitesimal dipole source of any orientation, located on the surface of the cylinder. The exact solutions are transformed with the Watson transformation to yield asymptotic expressions that are valid in the deep shadow region. These asymptotic expressions are validated by comparison to the numerically evaluated exact solution. It is found that the expressions are valid as long as the object is opaque, with a geometry down to the size κ2+τ 2 > λ0/2, and the rays not too torsional τ /κ < 2, where κ and τ are the curvature and torsion of the local geometry, respectively. The asymptotic expressions are found to approximate the exact solution signi?cantly better than the asymptotic expression of an equivalent perfect electric conductor geometry. The same is the case for the impedance boundary condition asymptotic approximation for low dielectric constant materials. Finally, the asymptotic expressions are generalized so they can be applied to any convex geometry of the human body or an opaque lossy dielectric of electrically large size.
关键词： asymptotic approximation,WBAN,lossy dielectric cylinder,Geometrical Theory of Diffraction,on-body communication
更新于2025-09-23 15:21:21
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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Time Domain Modelling of Pulse Wave Scattering on Small Metal Spheres
摘要： We consider a short pulse plane wave incident on a small metal sphere. The scattered field from the sphere can be presented as a multipole expansion over spherical harmonics. For small spheres (compared to the signal duration) the scattered field will be mainly presented by the dipole component. So we find in a closed form and analyze the convolution operator that relates the induced dipole moment (both electric and magnetic dipoles are considered) to the incident electric field waveform. The numerical approach to calculate scattering from several such spheres is described.
关键词： transient electric dipole,discrete dipole approximation,induced dipole moment,closed-form solution,transient diffraction
更新于2025-09-23 15:21:21
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Adaptability analysis of radiative transport diffusion approximation in planar-graded-index media
摘要： To study the applicability of diffusion approximation method, the influence of the optical thickness, scattering albedo, and wall emissivity of the examined medium on the accuracy of the diffusion approximation is analyzed. The accuracy is determined by comparison with results obtained by using the Monte Carlo method. By calculating the dimensionless radiation heat flux distributions at the bottom of the medium for various parameter combinations, the influence of each optical parameter is analyzed. In addition, the adaptability of the diffusion approximation method to the case of a gradient-index medium is examined. The results show that in the homogeneous-refractive-index medium and the gradient-index medium, the accuracy of diffusion approximation method is improved by an increase in the optical thickness or the scattering albedo and by a decrease in the wall emissivity. Moreover, the maximum relative errors are primarily distributed at the medium boundary and center. In the case of increased optical thickness or decreased wall emissivity, the error of the diffusion approximation method becomes stable and remains at a small value.
关键词： numerical analysis,relative error,diffusion approximation,gradient index,Radiative transfer
更新于2025-09-23 15:21:21
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[IEEE 2019 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Zhenjiang, China (2019.8.4-2019.8.8)] 2019 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Modification of Wettability Property of NITI Alloy by Laser Texturing and Carbon Ion Implantation
摘要： Nonlocal self-similarity of images has attracted considerable interest in the field of image processing and has led to several state-of-the-art image denoising algorithms, such as block matching and 3-D, principal component analysis with local pixel grouping, patch-based locally optimal wiener, and spatially adaptive iterative singular-value thresholding. In this paper, we propose a computationally simple denoising algorithm using the nonlocal self-similarity and the low-rank approximation (LRA). The proposed method consists of three basic steps. First, our method classifies similar image patches by the block-matching technique to form the similar patch groups, which results in the similar patch groups to be low rank. Next, each group of similar patches is factorized by singular value decomposition (SVD) and estimated by taking only a few largest singular values and corresponding singular vectors. Finally, an initial denoised image is generated by aggregating all processed patches. For low-rank matrices, SVD can provide the optimal energy compaction in the least square sense. The proposed method exploits the optimal energy compaction property of SVD to lead an LRA of similar patch groups. Unlike other SVD-based methods, the LRA in SVD domain avoids learning the local basis for representing image patches, which usually is computationally expensive. The experimental results demonstrate that the proposed method can effectively reduce noise and be competitive with the current state-of-the-art denoising algorithms in terms of both quantitative metrics and subjective visual quality.
关键词： self-similarity,Back projection,patch grouping,image denoising,low-rank approximation (LRA),singular value decomposition (SVD)
更新于2025-09-23 15:21:01
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Convection Dynamics Forced by Optical Trapping with a Focused Laser Beam
摘要： Optical trapping dynamics of colloidal particles in solution is essential for understanding laser-induced assembling of molecules and nanomaterials, which contributes to nanofabrication, bioengineering, and microfluidics. In this paper, the importance of the surrounding fluid motion in optical trapping is investigated; that is, we reveal convection fluid dynamics forced by optical trapping with a focused laser beam. The fluid flow in optical trapping is evaluated by both experiments using the particle-image-velocimetry of fluorescent particles in solutions and theoretical consideration based on numerical analysis. A theoretical model consists of Navier?Stokes equations with the Boussinesq approximation that considers the temperature elevation induced by a photothermal effect. Furthermore, the effect of the particle motion induced by the optical force on fluid flow is also included in the analysis by developing a simple one-way homogeneous-type multiphase flow model. From both experimental and theoretical results, it turns out that the fluid flow in optical trapping is caused not only by thermal convection due to the temperature elevation but also by the collective particle motion induced by optical forces. Therefore, the optical forces can induce the large-scale fluid convection, which supports accumulating the target particles to the focal spot.
关键词： thermal convection,fluid dynamics,colloidal particles,photothermal effect,Boussinesq approximation,optical trapping,multiphase flow model,Navier?Stokes equations,particle-image-velocimetry
更新于2025-09-23 15:21:01
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On the imprecisions that may be induced when applying the Blaugrund approximation for the analysis of Doppler-shift attenuation lifetime measurements
摘要： It is shown that the Blaugrund approximation could have led to some imprecise lifetime determinations in the past which used the Doppler-shift attenuation method (DSAM). Comparison with Monte Carlo simulations of the slowing-down process show that there is not an easy way to judge using them on the reliability of old data.
关键词： Lineshapes analysis in DSAM measurements,Monte Carlo simulations,Lifetime determination,Blaugrund approximation
更新于2025-09-23 15:21:01
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[IEEE 2019 XXIX International Scientific Symposium "Metrology and Metrology Assurance" (MMA) - Sozopol, Bulgaria (2019.9.6-2019.9.9)] 2019 XXIX International Scientific Symposium "Metrology and Metrology Assurance" (MMA) - The metod of reducing measurement error of the propagation delays in optical elements and optical fibers
摘要： The paper presents a method of reducing the measurement error propagation delays of signals in optical elements and optical fibers, based on the approximation of the recorded form of optical pulses and determining the time intervals between pulses, using the values of the parameters of the approximating functions. The scheme of the installation implementing the proposed method is presented, as well as the results of experimental approbation of the method.
关键词： optical element,optical fiber,signal propagation delay,approximation
更新于2025-09-23 15:21:01