Matrix Conditioning Effects on Implicit Time-Domain Maxwell Solvers

Abstract Purpose: Non-proliferative diabetic retinopathy (NPDR) is the earliest stage of diabetic eye disease. Microscopic changes occur in the blood vessels of the eye in NPDR. The changes typically do not produce symptoms and are not visible to the naked eye. This paper aims to investigate a method for distinguishing NPDR based on Electroretinogram (ERG).Method: The ERG responses were recorded in 20 eyes from 14 patients with NPDR and 20 eyes from 20 healthy subjects as the control group. The responses of three standard stimuli were collected for both groups. Time-domain parameters, including amplitudes and implicit time, and a nonlinear criterion, were used to differentiate the groups. Results: This study showed that implicit time and amplitude of b-wave in dark-adapted 10.0 ERG and amplitude and implicit time of light-adapted flicker 30 Hz could distinguish between controls and NPDR groups. Theta values obtained for dark-adapted 10.0 ERG (p=0.0019), light-adapted 3.0 ERG (p=0.0021), and light-adapted flicker 30 Hz (p=0.0023) had significant differences between the groups. Conclusion: The proposed features have made it possible to distinguish between healthy and NPDR eyes. Choosing an appropriate method can effectively evaluate inner retinal dysfunction, especially in diabetic retinopathy.

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An Optimized Explicit–Implicit Time-Marching Formulation for Dynamic Analysis

International Journal of Computational Methods ◽

10.1142/s0219876220500450 ◽

2020 ◽

pp. 2050045

Author(s):

Delfim Soares ◽

Matheus M. Rodrigues

Keyword(s):

Dynamic Analysis ◽

Time Domain ◽

Optimization Algorithm ◽

Computational Efficiency ◽

Implicit Time ◽

Excellent Performance ◽

Time Step ◽

Time Marching ◽

Adaptive Time

In this paper, an optimized approach is proposed to enhance the performance of combined explicit–implicit time-domain analyses. In this context, an entirely automated explicit-implicit adaptive time-marching procedure is discussed as well as an optimization algorithm is introduced to compute the adopted time-step value of the analysis, so that the amount of explicit and implicit elements occurring along the model may be optimally provided, in terms of computational efficiency. The proposed formulation is very effective, allowing evaluating highly accurate responses considering much reduced computational efforts. At the end of the manuscript, numerical applications are presented, illustrating the excellent performance of the proposed formulation.

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Transient analysis of electromagnetic scattering from wire structures utilizing an implicit time-domain integral-equation technique

Microwave and Optical Technology Letters ◽

10.1002/(sici)1098-2760(199801)17:1<66::aid-mop18>3.0.co;2-9 ◽

1998 ◽

Vol 17 (1) ◽

pp. 66-69 ◽

Cited By ~ 25

Author(s):

Sadasiva M. Rao ◽

Tapan K. Sarkar

Keyword(s):

Integral Equation ◽

Time Domain ◽

Electromagnetic Scattering ◽

Transient Analysis ◽

Implicit Time ◽

Domain Integral ◽

Time Domain Integral Equation

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Exact nonreflecting boundary conditions for exterior wave equation problems

Publications de l Institut Mathematique ◽

10.2298/pim1410103f ◽

2014 ◽

Vol 96 (110) ◽

pp. 103-123 ◽

Cited By ~ 4

Author(s):

Silvia Falletta ◽

Giovanni Monegato

Keyword(s):

Boundary Condition ◽

Wave Equation ◽

Time Domain ◽

Region Of Interest ◽

Boundary Integral ◽

Implicit Time ◽

Artificial Boundary ◽

Equation Problem ◽

Classical Wave Equation ◽

The Time Domain

We consider the classical wave equation problem defined on the exterior of a bounded 2D space domain, possibly having far field sources. We consider this problem in the time domain, but also in the frequency domain. For its solution we propose to associate with it a boundary integral equation (BIE) defined on an artificial boundary surrounding the region of interest. This boundary condition is nonreflecting (or transparent) for both outgoing and incoming waves and it does not have to include necessarily the problem datum supports. The problem physical domain can even be a multi-domain, defined by the union of several disjoint domains. These domains can be convex or nonconvex. This transparent boundary condition is imposed pointwise on the chosen artificial boundary; therefore, its (space collocation) discretization can be coupled with a (space) finite difference or finite element method for the associated PDE problem. In the time-domain case, a classical (explicit or implicit) time integrator is also used. We present a consistency result for the BIE discretization and a sample of the intensive numerical testing we have performed.

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