• 한국공간정보시스템학회 논문지
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• 제10권4호
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• pp.11-19
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• 2008

최근 모바일 기기 및 무선 통신의 발달로 인하여 다양한 위치 기반 서비스에 대한 연구가 증대되고 있으며, 이러한 위치 기반 서비스의 대표적 질의인 k-최근접 질의를 효율적으로 처리하기 위한 연구가 활발히 수행되어 왔다. 기존 연구들은 질의 처리 성능의 향상을 위해, 공간 네트워크 상의 POI와 노드 사이의 거리를 미리 계산하는 pre-computation 기법을 사용한다. 그러나 이러한 pre-computation 기법들은 검색 대상이 되는 POI의 변경을 효과적으로 처리하지 못하는 단점을 갖는다. 본 논문에서는 기존 pre-computation 기법들의 단점을 극복하고, 대용량 이동객체의 위치정보를 효율적으로 관리하기 위하여 S-GRID를 이용한 분산 그리드 기법을 제안한다. 아울러 제안하는 분산 그리드 기법을 위한 k-최근접 질의 처리 알고리즘을 제시한다. 마지막으로, S-GRID 및 분산 그리드 기법의 k-최근접 질의처리 알고리즘의 성능 평가를 통해, 제안하는 기법의 우수성을 입증한다.

• 한국전산유체공학회지
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• 제6권4호
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• pp.15-25
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• 2001

Numerical prediction of the diffusion controlled transition in a turbine gas pass is important because it can change the local heat transfer rate over a turbine blade as much as three times. In this study, the gas flow over turbine blade is simplified to the flat plate boundary layer, and an adaptive grid scheme redistributing grid points within the computation domain is proposed with a great emphasis on the construction of the grid control function. The function is sensitized to the second invariant of the mean strain tensor, its spatial gradient, and the interaction of pressure gradient and flow deformation. The transition process is assumed to be described with a κ-ε turbulence model. An elliptic solver is employed to integrate governing equations. Numerical results show that the proposed adaptive grid scheme is very effective in obtaining grid independent numerical solution with a very low grid number. It is expected that present scheme is helpful in predicting actual flow within a turbine to improve computation efficiency.

• 품질경영학회지
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• 제49권2호
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• pp.201-211
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• 2021

Purpose: This paper proposes a density adaptive grid algorithm for the k-NN regression model to reduce the computation time for large datasets without significant prediction accuracy loss. Methods: The proposed method utilizes the concept of the grid with centroid to reduce the number of reference data points so that the required computation time is much reduced. Since the grid generation process in this paper is based on quantiles of original variables, the proposed method can fully reflect the density information of the original reference data set. Results: Using five real-life datasets, the proposed k-NN regression model is compared with the original k-NN regression model. The results show that the proposed density adaptive grid-based k-NN regression model is superior to the original k-NN regression in terms of data reduction ratio and time efficiency ratio, and provides a similar prediction error if the appropriate number of grids is selected. Conclusion: The proposed density adaptive grid algorithm for the k-NN regression model is a simple and effective model which can help avoid a large loss of prediction accuracy with faster execution speed and fewer memory requirements during the testing phase.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.194-198
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• 2011

In this study, an efficient algorithm for Delaunay triangulation of a number of points which can be used on a GPU-based parallel computation is studied The developed algorithm is programmed using CUDA library. and the program takes full advantage of parallel computation which are concurrently performed on each of the threads on GPU. The results of partitioned triangulation collected from the GPU computation requires proper stitching between neighboring partitions and calculation of connectivities among triangular cells on CPU In this study, the effect of number of threads on the efficiency and total duration for Delaunay grid generation is studied. And it is also shown that GPU computing using CUDA for Delaunay grid generation is feasible and it saves total time required for the triangulation of the large number points compared to the sequential CPU-based triangulation programs.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.326-334
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• 2010

In this study, we provide a comprehensive review of the CIP(Constrained Interpolation Pro file/Cubic Interpolated Propagation) method with a pressure-based algorithm that is known as a general numerical solver for soled liquid, gas and plasmas. And also we introduce a body-fitted grid system(Soroban grid) for computation of strongly nonlinear marine hydrodynamic problems such as slamming water on deck, wave impact by green water. This grid system can keep the third-order accuracy in time and space with the help of the CIP method. The grid system consists of the straight lines and grid points. In the 2-dimensional grid case, each grid points moving in these lines like abacus - Soroban in Japanese. The length of each line can be different and the number of grid points in each line can be different. Mesh generation and searching of upstream departure point are very simple and possible to mesh-free treatment. To optimize computation of free-surface and multi-fluid flows, We adopt the C-CUP method. In most of the earlier computations, the C-CUP method was used with a staggered-grid approach. Here, because of the mesh free nature of the Soroban grid, we use the C-CUP method with a collocated-grid approach.

• 디지털융복합연구
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• 제11권2호
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• pp.299-307
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• 2013

본 논문은 SIFT-Grid 기반의 얼굴 인식 시스템에서 식별 능력의 향상과 계산량 감소를 목적으로 한다. 첫번째는 한 얼굴 클래스의 다양한 훈련 이미지로부터 비슷한 SIFT 특징점들은 제거하고, 상이한 특징점들은 병합하는 통합템플릿의 구성 방법을 제안한다. 통합템플릿은 SIFT-Grid를 통해 나누어진 훈련 이미지들의 동일 부분영역 내의 특징점들에 대한 유사도 행렬의 계산과 임계치 기반의 히스토그램의 계산을 통해 구성하였다. 두 번째는 구성된 통합템플릿들로부터 테스트 이미지의 효과적인 식별을 위한 유사도 계산 방법을 제안한다. 유사도의 계산은 테스트 이미지와 각 클래스의 통합템플릿간의 일대일 비교로 수행된다. 이때 동일 부분영역 별로 유사도 점수와 임계치 기반의 보팅 점수가 계산된다. 얼굴 인식 작업에 대한 실험 결과 제안된 방법이 SIFT-Grid 기반의 다른 두 방법보다 정확한 것으로 확인 되었고, 또한 계산량도 감소하였다.

• International Journal of Contents
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• 제6권1호
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• pp.47-52
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• 2010

Skyline queries are an important new search capability for multi-dimensional databases. Most of the previous works have focused on processing skyline queries over static data set. However, most of the real applications deal with the dynamic data set. Since dynamic data set constantly changes as time passes, the continuous skyline computation over dynamic data set becomes ever more complicated. In this paper, we propose a multiple layer grids method for continuous skyline computation (MLGCS) that maintains multiple layer grids to manage the dynamic data set. The proposed method divides the work space into multiple layer grids and creates the skyline influence region in the grid of each layer. In the continuous environment, the continuous skyline queries are only handled when the updating data points are in the skyline influence region of each layer grid. Experiments based on various data distributions show that our proposed method outperforms the existing methods.

• 정보보호학회논문지
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• 제18권5호
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• pp.181-188
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• 2008

E-Science Grid is designed to cope with computation-intensive tasks and to manage a huge volume of science data efficiently. However, certain tasks may involve more than one grid can offer in computation capability or incur a long wait time on other tasks. Resource sharing among Grids can solve this problem with proper processing-integrity check via audit. Due to their computing-intensive nature, the processing time of e-Science tasks tends to be long. This potential long wait before an audit failure encourages earlier audit mechanism during execution in order both to prevent resource waste and to detect any problem fast. In this paper, we propose a Light-weight, Adaptive and Reliable Audit, LARA, of processing Integrity for e-Science applications. With the LARA scheme. researchers can verify their processing earlier and fast.

• 한국전자파학회지:전자파기술
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• 제3권2호
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• pp.10-15
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• 1992

The electromagentic characteristics of antennas in the complicated metallic structures were analyzed using the electric field integral equation. The accurancy of computer program was confirmed by comparing the computation result with NELC brass model study. And computation result of antenna characteristics in metallic structures was in good argreement with our measuring result.

• 대한공간정보학회지
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• 제20권1호
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• pp.109-116
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• 2012

본 연구에서는 CCHE2D와 EFDC모형을 이용한 모의를 통하여 격자의 횡단해상도에 따른 물리적 지형의 재현성과 모의결과에 대한 영향을 검토하고자 하였다. 낙동강 금호강 유입구간을 대상으로 2006년 강우사상에 대한 부정류모의를 통하여 면적고도곡선과 대상구간내 수위관측소 지점에서의 실측치와 모의치간의 비교를 통하여 구성격자망의 적정성 및 모의결과에 대한 영향을 각각 검토하였다. 일반적으로 격자 해상도의 증가는 계산시간의 증가를 야기하므로 수행 내용과 목적, 계산의 효율성 측면에서 적절한 격자해상도의 선택이 필요하다. 정밀한 모의를 위해서는 고해상도 격자를 이용한 모의를 수행해야 하나, 빠른 의사결정이 요구되는 홍수기와 같이 모형수행의 효율성을 고려해야 하는 경우에 적용 가능한 물리적 지형의 재현성과 결과에 대한 신뢰성을 보장할 수 있는 적정 격자 해상도가 존재함을 확인할 수 있었다.