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Development of a novel noninvasive system for measurement and imaging of the arterial phase oxygen density ratio in the retinal microcirculation
摘要： Purpose This study was conducted in order to develop a novel noninvasive system for measurement and imaging of the arterial oxygen density ratio (ODR) in the retinal microcirculation. Methods We developed a system composed of two digital cameras with two different filters, which were attached to a fundus camera capable of simultaneously obtaining two images. Actual measurements were performed on healthy volunteer eyes (n = 61). A new algorithm for ODR measurement and pixel-level imaging of erythrocytes was constructed from these data. The algorithm was based on the morphological closing operation and the line convergence index filter. For system calibration, we compared and verified the ODR values in arterioles and venules that were specified in advance for 56 eyes with reproducibility. In 10 additional volunteers, ODR measurements and imaging of the arterial phase in the retinal microcirculation corresponding to changes in oxygen saturation of the peripheral arteries at normal breathing and breath holding were performed. Results Estimation of incident light to erythrocytes and pixel-level ODR calculation were achieved using the algorithm. The mean ODR values of arterioles and venules were 0.77 ± 0.060 and 1.02 ± 0.067, respectively. It was possible to separate these regions, calibrate at the pixel level, and estimate the arterial phase. In each of the 10 volunteers, changes in the arterial phase ODR corresponding to changes in oxygen saturation of the peripheral arteries were observed before and after breath holding on ODR images. The mean ODR in 10 volunteers was increased by breath holding (p < 0.05). Conclusions We developed a basic system for arterial phase ODR measurement and imaging of the retinal microcirculation. With further validation and development, this may provide a useful tool for evaluating retinal oxygen metabolism in the retinal microcirculation.
关键词： Retinal microcirculation region,Arterial phase,Line convergence index filter,Oxygen density ratio,Morphological closing operation
更新于2025-09-23 15:23:52
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Fast 6D object pose refinement in depth images
摘要： Recovering 6D object pose has gained much focus, because of its application in robotic intelligent manipulation to name but a few. This paper presents an approach for 6D object pose refinement from noisy depth images obtained from a consumer depth sensor. Compared to the state of the art aimed at the same goal, the proposed method has high precision, high robustness to partial occlusions and noise, low computation cost and fast convergence. This is achieved by using an iterative scheme that only employs Random Forest to minimize a cost function of object pose which can quantify the misalignment between the ground truth and the estimated one. The random forest in our algorithm is learnt only using synthetic depth images rendered from 3D model of the object. Several experimental results show the superior performance of the proposed approach compared to ICP-based algorithm and optimization-based algorithm, which are generally used for 6D pose refinement in depth images. Moreover, the iterative process of our algorithm can be much faster than the state of the art by only using one CPU core.
关键词： Object pose refinement,Random forest,Depth images,6D pose estimation,Fast convergence
更新于2025-09-23 15:22:29
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Variational source condition for ill-posed backward nonlinear Maxwell's equations
摘要： This paper examines the mathematical analysis of an electromagnetic inverse problem governed by nonlinear evolutionary Maxwell’s equations. The aim of the inverse problem is to recover electromagnetic ?elds at the past time by noisy measurement data at the present time. We consider the Tikhonov regularization method to cope with the ill-posedness of the governing backward nonlinear Maxwell’s equations. By means of the semigroup theory, we study its convergence analysis and derive optimality conditions through a rigorous ?rst-order analysis and adjoint calculus. The ?nal part of the paper is focused on the convergence rate analysis of the Tikhonov regularization method under a variational source condition (VSC), which leads to power-type convergence rates. Employing the spectral theory, the complex interpolation theory and fractional Sobolev spaces, we validate the proposed VSC on account of an appropriate regularity assumption on the exact initial data and the material parameters.
关键词： convergence rate analysis,electromagnetic inverse problem,variational source condition,nonlinear Maxwell’s equations,Tikhonov regularization
更新于2025-09-23 15:21:21
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Bidirectional SMF and PF-POF transmission of 400 Gbps Nyquist shaped on DP-QPSK systems
摘要： This work experimentally shows a transmission path based on standard single-mode optical fiber and perfluorinated graded-index plastic optical fiber with the connections between distinct optical fibers being made by fiber collimators using free-space optical transmission. The data stream consists of a bidirectional 400 Gbps optical transmission using four wavelength channels with quadrature phase-shift keying modulation format, combined with dual-polarization and Nyquist pulse-shaped. The results obtained seeks to study the use of short-distance cables in plastic optical fiber as a flexible means of interconnection, when inserted between single-mode optical fibers or as a coupling medium between devices with single-mode optical inputs/outputs located in data centers/video headends.
关键词： bidirectional transmission,optical network convergence,free-space optical connection,Perfluorinated polymer optical fibers
更新于2025-09-23 15:21:21
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Homogenization of time-harmonic Maxwella??s equations in nonhomogeneous plasmonic structures
摘要： We carry out the homogenization of time-harmonic Maxwell’s equations in a periodic, layered structure made of two-dimensional (2D) metallic sheets immersed in a heterogeneous and in principle anisotropic dielectric medium. In this setting, the tangential magnetic field exhibits a jump across each sheet. Our goal is the rigorous derivation of the effective dielectric permittivity of the system from the solution of a local cell problem via suitable averages. Each sheet has a fine-scale, inhomogeneous and possibly anisotropic surface conductivity that scales linearly with the microstructure scale, d. Starting with the weak formulation of the requisite boundary value problem, we prove the convergence of its solution to a homogenization limit as d approaches zero. The effective permittivity and cell problem express a bulk average from the host dielectric and a surface average germane to the 2D material (metallic layer). We discuss implications of this analysis in the modeling of plasmonic crystals.
关键词： Jump condition on hypersurface,Time-harmonic Maxwell’s equations,Layered structures,Two-scale convergence,Homogenization
更新于2025-09-23 15:21:01
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Visual Servoing With Photometric Gaussian Mixtures as Dense Feature
摘要： The direct use of the entire photometric image information as dense feature for visual servoing brings several advantages. First, it does not require any feature detection, matching, or tracking process. Thanks to the redundancy of visual information, the precision at convergence is really accurate. However, the corresponding highly nonlinear cost function reduces the convergence domain. In this paper, we propose a visual servoing based on the analytical formulation of Gaussian mixtures to enlarge the convergence domain. Pixels are represented by two-dimensional Gaussian functions that denotes a “power of attraction.” In addition to the control of the camera velocities during the servoing, we also optimize the Gaussian spreads allowing the camera to precisely converge to a desired pose even from a far initial one. Simulations show that our approach outperforms the state of the art and real experiments show the effectiveness, robustness, and accuracy of our approach.
关键词： photometric Gaussian mixture,Large convergence domain,visual servoing
更新于2025-09-23 15:21:01
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DOUBLY-PERIODIC PHOTONIC CRYSTALS: SPECTRAL PROBLEMS ANALYSIS
摘要： The present work is devoted to the clari?cation of the conditions necessary for step-by-step justification of the possibility of reduction of the homogeneous system of linear algebraic equations for the spectral problems of 2-D photonic crystals by the plane waves method. The issues related to the algorithms and the numerical solutions of these spectral problems are analyzed. The possibility of analytical regularization is investigated, and the ways to improve the convergence of the obtained results are identi?ed.
关键词： spectral problems,plane waves method,photonic crystals,convergence,analytical regularization
更新于2025-09-23 15:21:01
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Unconditional La?? convergence of a compact ADI scheme for coupled nonlinear Schr??dinger system
摘要： In this paper, a three-level compact alternating direction implicit (ADI) scheme is formulated for the two-dimensional coupled nonlinear Schr¨odinger system. By using an important new lemma and a mathematical induction method, it is proved that the compact ADI scheme is unconditionally convergent in L∞ norm with the convergence order of two in time and four in space. Numerical experiments have been conducted to support the theoretical results and show the e?ciency of the new method.
关键词： Coupled nonlinear Schr¨odinger system,Compact ADI scheme,Convergence in L∞ norm
更新于2025-09-23 15:19:57
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Sensor Malfunction Detection and Mitigation Strategy for a Multilevel Photovoltaic Converter
摘要： This paper presents the design of a state convergence (SC)-based bilateral controller for a nonlinear teleoperation system, which has been approximated by a Takagi–Sugeno (TS) fuzzy model. The selection of SC is made due to the advantages offered by this scheme both in the modeling and control design stages. The modeling stage considers master/slave systems, which can be represented by the nth order differential equations, while the control design stage offers an easy way to determine the control gains required for assigning desired closed loop dynamics to teleoperation system. After the master/slave systems are represented by TS fuzzy models, a stabilizing fuzzy law is adopted which allows deploying the SC scheme with all its bene?ts to design the fuzzy bilateral controller. In this way, not only the simplicity of the design scheme is ensured but also the existing SC scheme is able to control a nonlinear teleoperation system based on its TS fuzzy model description. As an additional advantage, the SC-based existing linear bilateral controller can be easily derived from the SC-based proposed fuzzy bilateral controller. Various cases of master/slave systems originally reported in terms of their linear model representation and communication in the absence/presence of time delay are all discussed in the corresponding fuzzy framework. The MATLAB simulations, considering a one-degree-of-freedom teleoperation system, are performed to validate the proposed methodology for controlling a nonlinear teleoperation system.
关键词： Teleoperation systems,TS fuzzy models,bilateral control,state convergence,MATLAB
更新于2025-09-23 15:19:57
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[IEEE 2019 8th International Conference on Renewable Energy Research and Applications (ICRERA) - Brasov, Romania (2019.11.3-2019.11.6)] 2019 8th International Conference on Renewable Energy Research and Applications (ICRERA) - Enhancing the Performance of Photovoltaic Systems under Partial Shading Conditions Using Cuttlefish Algorithm
摘要： This paper presents the design of a state convergence (SC)-based bilateral controller for a nonlinear teleoperation system, which has been approximated by a Takagi–Sugeno (TS) fuzzy model. The selection of SC is made due to the advantages offered by this scheme both in the modeling and control design stages. The modeling stage considers master/slave systems, which can be represented by the nth order differential equations, while the control design stage offers an easy way to determine the control gains required for assigning desired closed loop dynamics to teleoperation system. After the master/slave systems are represented by TS fuzzy models, a stabilizing fuzzy law is adopted which allows deploying the SC scheme with all its bene?ts to design the fuzzy bilateral controller. In this way, not only the simplicity of the design scheme is ensured but also the existing SC scheme is able to control a nonlinear teleoperation system based on its TS fuzzy model description. As an additional advantage, the SC-based existing linear bilateral controller can be easily derived from the SC-based proposed fuzzy bilateral controller. Various cases of master/slave systems originally reported in terms of their linear model representation and communication in the absence/presence of time delay are all discussed in the corresponding fuzzy framework. The MATLAB simulations, considering a one-degree-of-freedom teleoperation system, are performed to validate the proposed methodology for controlling a nonlinear teleoperation system.
关键词： Teleoperation systems,TS fuzzy models,bilateral control,state convergence,MATLAB
更新于2025-09-23 15:19:57