• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
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• pp.268-273
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• 1998

This study applies an on-line system, which employes an adaptive reconstruction technique to monitor and forecast ocean surface changes. The system adaptively generates an appropriate synthetic time series with recovering missing measurements for sequential images. The reconstruction method incorporates temporal variation according to physical properties of targets and anisotropic spatial optical properties into image processing techniques. This adaptive approach allows successive refinement of the structure of objects that are barely detectable in the observed series. The system sequentially collects the estimated results from the adaptive reconstruction and then statistically analyzes them to monitor and forecast the change in surface characteristics.

• Structural Engineering and Mechanics
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• 제15권5호
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• pp.579-608
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• 2003

This paper deals with adaptive finite element analysis of linearly elastic structures using different error estimators based on flux projection (or best guess stress values) and residual methods. Presentations are given on a typical h-type adaptive analysis, a mesh refinement scheme and the coupling of adaptive finite element analysis with automatic mesh generation. Details about different error estimators are provided and their performance, reliability and convergence are studied using six node quadratic triangular elements. Several examples are presented to demonstrate the reliability of different error estimators.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 가을 학술발표회 논문집
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• pp.1-8
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• 1994

A variable-node-flat shell element designated as CLS which has variable mid-side nodes with drilling freedom has been presented in this paper. The shell element to be applied in finite element analysis has been developed by combining a membrane element named as CLM with drilling rotation d.o.f. and plate bending element. The combined shell element possess six degrees of freedom per node. By introducing the variable-node elements which have physical midside nodes, some difficulties associated with imposing displacement constraints on irregular nodes to enforce interelement compatibility in common adaptive h-refinement on quadrilateral mesh are easily overcome. Detailed numerical studies show the excellent performance of the new shell elements developed in this study.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권6호
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• pp.306-313
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• 2006

A three dimensional adaptive finite element refinement algorithm is developed for non-linear magnetostatic field problems. In the method, the edge elements are used for finite element formulation, and the local error in each element is estimated from the fact that the tangential components of magnetic field intensity and the normal components of magnetic flux density should be continuous at the interface of the two adjacent elements. Based on the estimated error, the elements which have big error are divided into several elements using bisection method. The effectiveness of the developed algorithm is proved through numerical examples.

• Structural Engineering and Mechanics
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• 제1권1호
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• pp.61-74
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• 1993

A new three-dimensional transition solid element was presented for the automated three-dimensional adaptive h-refinement or the local mesh refinement where the steep stress gradient exists. The proposed transition element was established by adding variable nodes(element nodes) to basic 8-node for an effective connection between the refined region and the coarse region with minimum degrees of freedom possible. To be consistent in accuracy with 8-node solid element with nonconforming modes, this transition element was also improved through the addition of the modified nonconforming modes. Numerical examples show that the performance of the element and the applicability to 3D adaptations are satisfactory.

• International journal of advanced smart convergence
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• 제9권3호
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• pp.118-126
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• 2020

In this paper, we present an effective single image fog removal by using the Joint Bright and Dark Channel (JBDC) and pixel-based transmission estimation to enhance the visibility of outdoor images susceptible to degradation due to weather and environmental conditions. The conventional methods include refinement process of coarse transmission with heavy computational complexity. The proposed transmission estimation reveals excellent edge-preserving performance and does not require the refinement process. We estimate the atmospheric light in pixel-based fashion, which can improve the transmission estimation performance and visual quality of the restored image. Moreover, we propose an adaptive transmission estimation to enhance the visual quality specifically in sky regions. Comprehensive experiments on various fog images show that the proposed method exhibits reduced computational complexity and excellent fog removal performance, compared with the existing methods; thus, it can be applied to various fields including real-time devices.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 가을 학술발표회 논문집
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• pp.168-175
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• 1996

This paper deals with the variable-node element for fluid flow and the adaptive h-version mesh refinement algorithm. The transient element has been formulated by the Galerkin approach in which the pressure term is replaced with the penalty function. The present element having variable mid-side node and is suitable for constructing a locally refined mesh avoiding the use of the highly distorted elements. A modified Gauss quadrature is needed to integrate the element matrices to solve the trouble associated with the discontinuity of derivatives of shape functions. Several numerical examples show that the proposed element can be effectively used in the h-version adapt ive mesh refinement

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.57-70
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• 2008

A high-order accurate Euler flow solver based on a discontinuous Galerkin finite-element method has been developed for the numerical simulations of blade-vortex interaction phenomena on unstructured meshes. A free vortex in freestream was investigated to assess the vortex-preserving property and the accuracy of the present flow solver. Blade-vortex interaction problems in subsonic and transonic freestreams were simulated by adopting a multi-level solution-adaptive dynamic mesh refinement/coarsening technique. The results were compared with those of other numerical and experimental methods. It was shown that the present discontinuous Galerkin flow solver can preserve the vortex structure for significantly longer vortex convection time and can accurately capture the complex unsteady blade-vortex interaction flows, including generation and propagation of acoustic waves.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년 추계학술대회논문집
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• pp.57-70
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• 2008

A high-order accurate Euler flow solver based on a discontinuous Galerkin finite-element method has been developed for the numerical simulations of blade-vortex interaction phenomena on unstructured meshes. A free vortex in freestream was investigated to assess the vortex-preserving property and the accuracy of the present flow solver. Blade-vortex interaction problems in subsonic and transonic freestreams were simulated by adopting a multi-level solution-adaptive dynamic mesh refinement/coarsening technique. The results were compared with those of other numerical and experimental methods. It was shown that the present discontinuous Galerkin flow solver can preserve the vortex structure for significantly longer vortex convection time and can accurately capture the complex unsteady blade-vortex interaction flows, including generation and propagation of acoustic waves.

• International Journal of Aeronautical and Space Sciences
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• 제11권1호
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• pp.41-48
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• 2010

In the present study, the turbulent flow fields around a circular cylinder at $Re=3.6{\times}10^6$ were investigated based on an unstructured mesh technique, and the comparisons between URANS(S-A, SST) and hybrid RANS/LES(DES, SAS) methods for the simulation of high Reynolds number flow have been conducted. For this purpose, unsteady characteristics of vortex shedding and time-averaged quantities were compared. A quasi-steady solution-adaptive mesh refinement was also made for the URANS and hybrid RANS/LES approaches. The results showed that the simple changes in the turbulent length scale or source term of turbulent models made the flow fields less dissipative and more realistic in hybrid RANS/LES methods than the URANS approaches.