- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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A regularized approach evaluating origin intensity factor of singular boundary method for Helmholtz equation with high wavenumbers
摘要： Evaluation of the origin intensity factor of the singular boundary method for Helmholtz equation with high wavenumbers has been a difficult task for a long time. In this study, a regularized approach is provided to bypass this limitation. The core idea of the subtraction and adding-back technique is to substitute an artificially constructed general solution of the Helmholtz equation into the boundary integral equation or the hyper boundary integral equation to evaluate the non-singular expressions of the fundamental solutions at origin. The core difficulty is to derive the appropriate artificially constructed general solution. The regularized approach avoids the unstable inverse interpolation and has strict mathematical derivation process. Therefore, it is easy-to-program and free of mesh dependency. Numerical experiments show that the proposed technique can be used successfully to avoid singularity and hyper singularity difficulties encountered in the boundary element method and the singular boundary method.
关键词： Three-dimensional Helmholtz equation,Singularity and hyper singularity,Boundary element method,Origin intensity factor,Singular boundary method
更新于2025-09-23 15:22:29
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Light scattering by a homogeneous sphere near a plane boundary II
摘要： The problem of light scattering by a homogeneous sphere above a plane boundary is considered in this paper. Hankel transformation and Erdélyi’s formula are used to satisfy the boundary conditions on the plane and the determination of the unknown coefficients in the scattered field is achieved by matching the electromagnetic boundary conditions on the surface of the sphere. Existence and uniqueness of the solution involving these unknown coefficients are shown and the extinction efficiency factor is presented.
关键词： plane boundary,Light scattering,homogeneous sphere,extinction efficiency factor
更新于2025-09-23 15:22:29
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All Passive Realization of Lossy Coupling Matrices Using Resistive Decomposition Technique
摘要： A complex coupling matrix has been extensively used in lossy filters and negative group delay devices. For the realization, conventional technique decomposes the complex coupling matrix into lossy resonators and complex inverters. Since the complex inverter does not follow the passivity in some cases, the resultant realization may be globally passive but locally active. This paper proposes a new decomposition technique to ensure the passivity everywhere. It decomposes the complex coupling matrix into a resistive connection matrix and a conventional real coupling matrix, which are both passively realizable. This technique provides a passive realization of the complex coupling matrix. Furthermore, a loss equalization technique is also proposed, to further achieve a uniform quality factor (Q) distribution among all the lossy resonators. Several illustrative examples and an experimental validation are finally provided.
关键词： Lossy filter,resistive connection,quality factor,decomposition,complex coupling matrix,complex inverter
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) - Monostatic GTD Model for Double Scattering due to Specular Reflections or Edge Diffractions
摘要： GTD model is a good candidate to extract the features of radar targets, which describes the frequency dependence of scattering centers for many geometries or mechanisms and can represent the attribute information of the geometrical structures. The mechanisms associated with this model have been proven to include single reflection, single diffraction and multiple reflections from dihedral and trihedral corner reflectors. However, multi-scattering mechanisms from more complex structures are not studied adequately. In this paper, we expand the GTD model to any double scattering due to specular reflections or edge diffractions, and derive the related frequency-dependence factor. Finally, a simulation validates the theory.
关键词： specular reflection,multiple scattering mechanism,frequency-dependence factor,flat surface,straight edge,doubly-curved surface,GTD model,curved edge,edge diffraction,singly-curved surface
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE 3rd International Conference on Signal and Image Processing (ICSIP) - Shenzhen, China (2018.7.13-2018.7.15)] 2018 IEEE 3rd International Conference on Signal and Image Processing (ICSIP) - An Analytical Imaging Algorithm for Parallel Invariant SAR
摘要： This paper discusses the processing method for parallel invariant SAR, and an analytical imaging algorithm based on GLBF is proposed. The bulk focusing is performed by reference function multiplication (RFM), then the range scaling factor is derived and further corrected by Chirp-z transform (CZT). The algorithm can be applied to wide scene imaging with the derived data blocking rules. The proposed imaging algorithm is verified by simulations.
关键词： chirp-z transform (CZT),parallel invariant SAR,range scaling factor
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Electronics, Control, Optimization and Computer Science (ICECOCS) - Kenitra, Morocco (2018.12.5-2018.12.6)] 2018 International Conference on Electronics, Control, Optimization and Computer Science (ICECOCS) - Backstepping Control for Three Phase Single Stage Grid Connected PV System with Improved Power Quality
摘要： The development of PV-systems has increased due to the high demand for clean energy. Used worldwide in the distributed power generation markets, the photovoltaic energy must not only be maximized, but also adapted to the global standards on harmonic emissions towards the power utility. Hence, the tracking of the maximum power point and the harmonic filtering becomes necessary. A three-phase single stage grid-connected Photovoltaic system consisting of a photovoltaic array and a three-phase PWM inverter coupled through the LCL-filter to the electrical grid is studied in this paper. A new control design is developed to maximize power in the side of PV panels and to ensure a unit power factor at the grid side. Grid synchronization is provided by a three-phase PLL (Phase-Locked Loop) and the closed-loop stability is demonstrated using Lyapunov analysis. Simulation results clearly illustrate that the proposed controller has achieved all of its objectives. In order to demonstrate the performance of the LCL-filter in minimizing the harmonics produced by the photovoltaic inverter, the frequency response of the injected currents was compared to that obtained using a simple L-filter.
关键词： backstepping controller,PV systems,maximum power point tracking,three-phase inverter,LCL-filter,unity power factor,grid connection
更新于2025-09-23 15:22:29
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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Through glass via technology for ultra-high Q factor inductors
摘要： Increasing demand for more advanced electronic products has driven semiconductor industry to develop more innovative and emerging advanced packaging technologies. Integrated Passive Devices have been proved to be an effective solution for fabricating products with better performance. In order to form higher Q factor inductors, the 3D integration inductors are designed and fabricated based on through glass via (TGV) method. Effect of substrate material and structure of 3D integration inductors was investigated by the simulation of HFSS and the test result. The results show that the ultra-high Q factor 3D integration inductors can be achieved by choosing glass substrate as long as selecting through glass via method. 3D integration inductors were achieved by reducing losses caused by MOS parasitic capacitor in the 3D integration inductors.
关键词： TGV,inductors,IPD,3D integration,Q factor
更新于2025-09-23 15:22:29
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High-voltage regrown nonpolar m-plane vertical p-n diodes: A step toward future selective-area-doped power switches
摘要： We report high-voltage regrown nonpolar m-plane p-n diodes on freestanding GaN substrates. Secondary-ion mass spectroscopy (SIMS) measurements indicate O and Si spikes at the regrowth interfaces with maximum concentration ~ 5×1017 cm-3, which is similar to previously published c-plane studies. A high blocking voltage of 540 V at ~ 1 mA/cm2 (corresponding to an electric field of E ~ 3.35 MV/cm), turn-on voltages between 2.9-3.1 V, specific on-resistance of 1.7 mΩ.cm2 at 300 A/cm2, and a minimum ideality factor of 1.7 were obtained for the regrown diodes. Our results suggest that Si, O and C interfacial impurity levels up to 2×1017 cm-3, 8×1017 cm-3, and 1×1019 cm-3, respectively, at the metallurgical junction of m-plane p-n diodes do not result in very early breakdown in the reverse bias, although the off-state leakage current in forward bias is affected. The impact of growth interruption/regrowth on diode performance is also investigated.
关键词： Selective-area doping,GaN,Specific on-resistance,Impurity incorporation,Avalanche breakdown,Leakage currents,Ideality factor,Nonpolar,SIMS,Vertical p-n diodes
更新于2025-09-23 15:22:29
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Uncertainty Analysis and Experimental Design in the Monte Carlo Ray-Trace Environment
摘要： Despite the dominant role of the Monte Carlo ray-trace (MCRT) method in modern radiation heat transfer analysis, the contemporary literature remains surprisingly reticent on the uncertainty of results obtained using it. After first identifying the radiation distribution factor as a population proportion, standard statistical procedures are used to estimate its mean uncertainty, to a stated level of confidence, as a function of the number of surface elements making up the enclosure and the number of rays traced per surface element. This a priori statistical uncertainty is then shown to compare favorably with the observed variability in the distribution factors obtained in an actual MCRT-based analysis. Finally, a formal approach is demonstrated for estimating, to a prescribed level of confidence, the uncertainty in predicted heat transfer. This approach provides a basis for determining the minimum number of rays per surface element required to obtain the desired accuracy.
关键词： Monte Carlo ray-trace,uncertainty analysis,experimental design,radiation heat transfer,distribution factor
更新于2025-09-23 15:22:29
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Longitudinal Changes in Spherical Equivalent Refractive Error Among Children With Preschool Myopia
摘要： PURPOSE. Preschool myopia generally indicated a high risk of progression to high myopia. However, no previous study has reported its longitudinal evolution. This study aimed to investigate the longitudinal changes in preschool myopia and explore the associated key determinants. METHODS. Medical records of patients seeking refractions at Zhongshan Ophthalmic Center between 2009 and 2017 were retrospectively reviewed. Mean rates of change in spherical equivalent (SE) refractive errors were evaluated in patients with preschool myopia. Association between the rate of change in SE and patient characteristics at the initial visit were examined using linear mixed-effect regression models. RESULTS. A total of 495 cases (median initial age: 5.12 years, interquartile range [IQR], 4.12–5.76 years) were assessed with at least 2-year follow-up. The initial median SE was (cid:2)3.00 D (IQR, (cid:2)5.25 to (cid:2)1.75 D) and the median duration of follow-up was 3.69 years (IQR, 2.89–4.99 years). On average, myopia progressed by (cid:2)0.59 6 0.47 D/year. A total of 312 (63.0%) children demonstrated myopia progression (mean rate of change in SE (cid:3) (cid:2)0.50 D/year in either eye) and 177 (35.8%) children demonstrated refraction stability (mean rate of change < 60.50 D/year in both eyes). Older age (b ? (cid:2)0.06, P ? 0.003), female sex (b ? (cid:2)0.09, P ? 0.035), and initial lower myopic SE (b ? (cid:2)0.07, P < 0.001) were associated with faster myopia progression. CONCLUSIONS. Preschool myopia on average progresses, although considerable proportion of subjects demonstrates longitudinal refraction stability. The rate of myopia progression is associated with initial patient characteristics.
关键词： preschool myopia,risk factor,progression
更新于2025-09-23 15:22:29