• Proceedings of the Korean Information Science Society Conference
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• 2007.06c
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• pp.43-48
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• 2007

데이터 스트림 관리 시스템에서 조인 연산자는 질의가 내포하는 여러 연산자들 가운데 상대적인 계산비용이 높은 연산자로, 센서 네트워크와 같이 한정적 정보들이 개별적으로 입력되는 환경에서는 필연적으로 요구된다. 데이터 스트림은 잠재적으로 무한한 크기를 가지므로 조인 연산자는 슬라이딩 윈도우 제약사항을 가져야 하며, 종합적인 결과를 얻기 위해 조인 연산자가 여러 입력을 취할 수 있어야 한다. 이를 가능하게 하는 것이 바로 슬라이딩 윈도우를 가지는 MJoin 연산자이다. 본 논문에서는 이러한 여러 MJoin 연산자가 시스템에 등록되어 있는 환경을 가정하고, 슬라이딩 윈도우 제약사항과 MJoin의 특성을 반영하여 전역적으로 공유된 질의 실행 계획 수립 및 처리에 관한 문제를 다룬다. 이러한 다중 MJoin에 대한 전역 공유 질의 실행 계획 수립 문제가 NP-Hard임을 증명하고, 근사화 접근 방법을 제안한다. 또한 전역적으로 공유된 질의 실행 계획을 올바르게 수행할 수 있는 처리 기법을 제안한다. 이러한 연구의 노력은 데이터 스트림 환경에서 효율적인 다중 질의 최적화 및 처리기법의 기초 연구로 활용될 수 있다.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.2
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• pp.82-89
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• 2000

Edge detection is the first step and very important step in image analysis. In this paper, proposed edge detection operators based on informations of edge types and it is different from other classical edge detection operators such as gradient and surface fitting operators. The first, we defined characteristics of edge types such as localization, thinness, length. The second, we defined valid edge types and ideal edge pixel positions in $3\times3$window based on edge characteristics of edge types. And we proposed edge detection algorithm and twelve windows based on valid edge types. In specially, proposed algorithm was shown better performence of edge detection than other operators such as gradient operator and the LoG(Laplacian of Gaussian) operator of zero crossings.

• The Journal of the Korea Contents Association
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• v.8 no.4
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• pp.48-54
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• 2008

This paper analyzes cost tradeoffs between memory usage and computation for window-based operators in data stream environments. It identifies generic operator network constructs, and sets up a cost model for the estimation of the expected memory reduction and the computation overheads when window memory relocations are applied to each operator network construct. This cost model helps to identify the utility of window memory relocations. It also helps to apply window memory relocation to improve a query execution plan to save memory usage. The proposed approach contributes to expand the scope of query processing and optimization in data stream environments. It also provides a basis to develop a cost estimation model for the query optimization using window memory relocations.

• Journal of KIISE:Databases
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• v.35 no.1
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• pp.1-16
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• 2008

Join queries having heavy cost are necessary to Data Stream Management System in Sensor Network where plural short information is generated. It is reasonable that each join operator has a sliding-window constraint for preventing DISK I/O because the data stream represents the infinite size of data. In addition, the join operator should be able to take multiple inputs for overall results. It is possible for the MJoin operator with sliding-windows to do so. In this paper, we consider the data stream environment where multiple MJoin operators are registered and propose MMJoin which deals with issues of building and processing a globally shared query considering characteristics of the MJoin operator with sliding-windows. First, we propose a solution of building the global shared query execution plan. Second, we solved the problems of updating a window size and routing for a join result. Our study can be utilized as a fundamental research for an optimization technique for multiple continuous joins in the data stream environment.

• Journal of Software Assessment and Valuation
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• v.16 no.2
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• pp.153-162
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• 2020

Digital image forgery detection is one of very important fields in the field of digital forensics. As the forged images change naturally through the advancement of technology, it has made it difficult to detect forged images. In this paper, we use passive forgery detection for copy paste forgery in digital images. In addition, it detects copy-paste forgery using the L₀ Norm-based LE operator, and compares the detection accuracy with the forgery detection using the existing L₂, L₁ Norm-based LE operator. In comparison of detection rates, the proposed lower triangular(Ayalneh and Choi) window was more robust to BAG mismatch detection than the conventional window filter. In addition, in the case of using the lower triangular window, the performance of image forgery detection was measured increasingly higher as the L₂, L₁ and L₀ Norm LE operator was performed.

• The Transactions of the Korea Information Processing Society
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• v.3 no.5
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• pp.1337-1345
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• 1996

Edge detection is the first step and very important step in image nalyisi. In this paper, proposed edge detection algorithm based on informations of edge structures and it is different from other classical edge detection operators such asgradient and surface fitting algorithm. The firs, we defined characteristics of edge structures such as continuity, thinness, localization, length. The second, we defined valid edge structures and ideal edge pixel positions in $3\times3$ window based on edge characteristics of edge structures. And we proposed twelve windows for enhance dissimilarity regions based on valid edge structures and ideal edge pixel positions. In specially, proposed algorithm was shown better performance of edge detection than other operators such as gradient operator and the LoG(Laplacian of gradient) operator of zero crossings in noisy test image with $\sigma=30$.

• Journal of the Korea Society of Computer and Information
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• v.10 no.5 s.37
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• pp.179-186
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• 2005

This paper describes a genetic algorithm and compares three crossover operators for Rural Postman Problem with Time Windows (RPPTW). The RPPTW which is a multiobjective optimization problem, is an extension of Rural Postman Problem(RPP) in which some service places (located at edge) require service time windows that consist of earliest time and latest time. Hence, RPM is a m띤tieect optimization Problem that has minimal routing cost being serviced within the given time at each service Place. To solve the RPPTW which is a multiobjective optimization problem, we obtain a Pareto-optimal set that the superiority of each objective can not be compared. This Paper performs experiments using three crossovers for 12 randomly generated test problems and compares the results. The crossovers using in this Paper are Partially Matched Exchange(PMX) Order Exchange(OX), and Modified Order Exchange(MOX) which is proposed in this paper. For each test problem, the results show the efficacy of MOX method for RPPTW.

• KIPS Transactions on Software and Data Engineering
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• v.2 no.5
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• pp.347-352
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• 2013

In impulse noise filtering techniques window size play an important role. Usually, an appropriate window is determined according to the noise density. A small window may not be able to suppress noise properly whereas a large window may remove edges and fine image details. Moreover, the value of the central pixel is estimated by considering all pixels within the window. In this work, contrary to the previous approaches, we propose an iterative impulse noise removal scheme that emphasizes on noise-free pixels within a small neighborhood. The iterative process continues until all noisy pixels are replaced with the estimated pixels. In order to estimate the optimal value for a noisy pixel, a genetic programming (GP) based estimator is evolved that takes few noise-free pixels as input. The estimator is constituent of noise-free pixels, arithmetic operators and random constants. Experimental results show that theproposed scheme is capable of removing impulse noise effectively while preserving the fine image details. Especially, our approach has shown effectiveness against high impulse noise density.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.5 s.305
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• pp.19-26
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• 2005

In this paper, a new method for obtaining three-dimensional shape of an object by measuring relative blur between images using wavelet analysis has been described. Most of the previous methods use inverse filtering to determine the measure of defocus. These methods suffer from some fundamental problems like inaccuracies in finding the frequency domain representation, windowing effects, and border effects. Besides these deficiencies, a filter, such as Laplacian of Gaussian, that produces an aggregate estimate of defocus for an unknown texture, can not lead to accurate depth estimates because of the non-stationary nature of images. We propose a new depth from defocus (DFD) method using wavelet analysis that is capable of performing both the local analysis and the windowing technique with variable-sized regions for non-stationary images with complex textural properties. We show that normalized image ratio of wavelet power by Parseval's theorem is closely related to blur parameter and depth. Experimental results have been presented demonstrating that our DFD method is faster in speed and gives more precise shape estimates than previous DFD techniques for both synthetic and real scenes.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.451-453
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• 2011

본 논문에서는 챔퍼 디스턴스 매칭(chamfer distance matching)를 이용하여 위성 영상 상의 북한군 자주포진지(self-propellent artillery position)를 매칭하는 기법을 제안한다. 먼저 입력되는 위성 영상을 잡음환경에 강인한 가우시안-라플라시안 연산자를 이용하여 에지(edge)를 추출한다. 추출된 에지 영상의 각 픽셀에 대해 가장 가까운 에지까지의 거리를 나타내는 거리 변환(distance transform) 영상을 생성한다. 템플릿 영상은 다양한 자주포진지 영상에서 샘플링된 영상으로 에지를 추출한 후 거리 변환을 거친다. 마지막으로 템플릿 영상을 입력된 거리 변환 영상에 윈도우 슬라이딩(window sliding)하여 최소값의 가지는 위치를 구한다. 제안 기법은 잡음에 강인한 가우시안-라플라시안 연산자를 사용하여 기상조건에 의한 입력 영상의 편차에도 효율적인 매칭이 가능하다. 또한 에지 기반의 챔퍼 매칭을 이용하기 때문에 비 균일 조명 환경에서도 강인한 매칭이 이루어진다. 전산 모의 실험에서 제안 알고리즘은 입력 위성 영상 상의 자주포진지를 적은 계산량으도 신뢰있게 매칭함을 보여준다.