• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2007년도 학술대회
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• pp.323-326
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• 2007

Mobility Anchor Points are used for the mobility management in HMIPv6 networks. Currently a mobile node selects the MAP farthest away from itself as a new MAP among available candidates when it undertakes a macro handoff. With this technique, however, the traffic tends to be concentrated at a MAP with the largest domain size and the communication cost increases due to the distance between the mobile node and the MAP. In this work, we proposed a cost effective MAP selection scheme. When leaving the current MAP domain. the mobile node calculates the optimum MAP domain size to minimize the local mobility cost at the new MAP domain considering mobile node's velocity and packet transmission rate. The mobile node then selects a MAP domain of size close to the optimum domain size calculated among the candidate MAP domains. In this way, it is possible for the mobile node to select an optimal MAP adaptively taking the network and node states into account, thus reducing the communication cost.

• 한국정보과학회논문지:정보통신
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• 제32권5호
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• pp.625-632
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• 2005

최근 실시간성이 요구되는 서비스나 이동 단말기의 폭증으로 인하여 노드 이동 시에 발생하는 핸드오프나 시그널링 비용을 줄이기 위해 제안된 프로토콜이 HMIPv6이다. HMIPv6에서 이동 노드가 동일한 MAP도메인 영역내외 서브넷들을 이동할 시에는 대응 노드나 흠 에이전트에 위치 등록을 수행할 필요가 없으며, 단지 MAP에게만 그 위치를 등록하게 된다 그러나, HMIPv6에서 선택한 거리기반 MAP 선택 방법에서는 이동 노드 패턴에 관계없이 이동 노드에서 거리가 가장 먼 MAP을 선택하여 큰 크기의 MAP 도메인이 형성되도록 하는데 이러한 경우, MAP 선택을 위한 오버헤드와 그 사이의 핸드오프 딜레이가 발생하며 비효율적으로 항상 큰 크기의 MAP 도메인이 형성된다. 따라서, 본 논문에서는 이동 노드의 한 서브넷 내의 상주시간에 따라 이동 노드의 이동 패턴을 고려하여 노드마다 다른 크기의 MAP 도메인이 형성되도록 하는 방법을 제안한다.

• 산업기술연구
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• 제26권B호
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• pp.207-213
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• 2006

Mobility Anchor points are used for the mobility management in HMIPv6 networks. Currently a mobile node selects the MAP farthest away from itself as a new MAP among available candidates when it undertakes a macro hand off. With this technique, however, the traffic tends to be concentrated at a MAP with the largest domain size and the communication cost increases due to the distance between the mobile node and the MAP. In this work, we propose a novel scheme to select a MAP to minimize the communication cost, taking the mobile node's moving speed and data rate into account. To come up with the scheme we analyses the communication analyses the communication cost into the binding update cost and the data packet delivery cost, and derive an equation representing the optimal MAP domain size to minimize the total cost.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.31-34
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• 2007

In this study, optimum processing condition of AZ31 Mg alloy was investigated utilizing processing map and constitutive equation considering microstructure evolution (dynamic recrystallization) during hot-working. A series of mechanical tests were conducted at various temperatures and strain rates to construct a processing map and to formulate the recrystallization kinetics and grain size relation. Dynamic recrystallization (DRX) was observed to occur revealing maximum intensity at a domain of $250^{\circ}C$ and 1/s. The effect of DRX kinetics on microstructure evolution was implemented in a commercial FEM code followed by remapping of the state variables. The volume fraction and grain size of deformed part were predicted using a modified FEM code and compared with those of actual hot forged one. A good agreement was observed between the experimental results and predicted ones.

• 소성∙가공
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• 제17권2호
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• pp.117-123
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• 2008

In this study, optimum processing condition of rolled AZ31 Mg alloy was investigated by utilizing processing map and constitutive equation considering microstructure evolution(dynamic recrystallization) occurring during hot-working. A series of mechanical tests were conducted at various temperatures and strain rates to construct a processing map and to formulate the recrystallization kinetics in terms of grain size. Dynamic recrystallization(DRX) was observed to occur at a domain of $250^{\circ}C$ and 1/s(maximum dissipation-efficiency region). The effect of DRX kinetics on microstructure evolution was implemented in a commercial FEM code followed by remapping of the state variables. The volume fraction and grain size of deformed part were predicted using a modified FEM code and were compared with those of actual hot forged part. A good agreement was observed between the experimented results and predicted ones.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.159-162
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• 2003

The remeshing algorithm using the constrained Delaunay method adapted to the mesh density map is developed. In the finite element simulation of forging process, the numerical error increases as the process goes on. However, it is not desirable to use a uniformly fine mesh in the whole domain. Therefore, it is necessary to reduce the analysis error by constructing locally fine mesh at the region where the error is concentrated such as die corner. In this paper, the point insertion algorithm is used and mesh size is controlled by using a mesh density map constructed with a posteriori error estimation. And an optimized smoothing technique is adapted to have smooth distribution and improve the quality of the mesh.

• 소성∙가공
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• 제13권4호
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• pp.334-341
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• 2004

In this study, a remeshing algorithm adapted to the mesh density map using the Delaunay mesh generation method is developed. In the finite element simulation of forging process, the numerical error increases as the process goes on because of discrete property of the finite elements and distortion of elements. Especially, in the region where stresses and strains are concentrated, the numerical error will be highly increased. However, it is not desirable to use a uniformly fine mesh in the whole domain. Therefore, it is necessary to reduce the analysis error by constructing locally refined mesh at the region where the error is concentrated such as at the die corner. In this paper, the point insertion algorithm is used and the mesh size is controlled by using a mesh density map constructed with a posteriori error estimation. An optimized smoothing technique is adopted to have smooth distribution of the mesh and improve the mesh element quality.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.35-37
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• 2007

Super resolution using stochastic approach which based on the Bayesian approach is to easy modeling for a priori knowledge. Generally, the Bayesian estimation is used when the posterior probability density function of the original image can be established. In this paper, we introduced the improved MAP algorithm based on Bayesian which is stochastic approach in spatial domain. And we presented the observation model between the HR images and LR images applied with MAP reconstruction method which is one of the major in the SR grid construction. Its test results, which are operation speed, chip size and output high resolution image Quality. are significantly improved.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권1호
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• pp.242-259
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• 2015

Three-dimensional video coding is one of the main challenges restricting the widespread applications of 3D video and free viewpoint video. In this paper, a novel fractal coding algorithm with motion-vector-field-based motion estimation for depth map sequence is proposed. We firstly add pre-search restriction to rule the improper domain blocks out of the matching search process so that the number of blocks involved in the search process can be restricted to a smaller size. Some improvements for motion estimation including initial search point prediction, threshold transition condition and early termination condition are made based on the feature of fractal coding. The motion-vector-field-based adaptive hexagon search algorithm on the basis of center-biased distribution characteristics of depth motion vector is proposed to accelerate the search. Experimental results show that the proposed algorithm can reach optimum levels of quality and save the coding time. The PSNR of synthesized view is increased by 0.56 dB with 36.97% bit rate decrease on average compared with H.264 Full Search. And the depth encoding time is saved by up to 66.47%. Moreover, the proposed fractal depth map sequence codec outperforms the recent alternative codecs by improving the H.264/AVC, especially in much bitrate saving and encoding time reduction.

• 한국통신학회논문지
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• 제28권8C호
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• pp.795-802
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• 2003

영상 잡음의 제거를 위해서는 영상에 대한 통계적 모델을 설정하고, 잡음이 섞인 영상에서 원 영상의 분산을 정확하게 추정하는 것이 매우 중요하다. 분산을 추정하기 위해서는 일반적으로 유한한 크기의 주변 영역 정보를 이용한다. 주변 영역의 크기는 평탄 영역 및 에지 영역과 같이 영상의 영역에 따라 달라진다. 즉, 에지 영역인 경우는 주변 영역의 크기를 작게 설정할수록 추정 분산이 보다 정확하며, 평탄 영역의 경우는 주변 영역의 크기가 크면 분산의 추정이 정확해 진다. 이와 같이 추정된 원 영상의 분산을 이용하여 잡음 영상에 Wiener 필터를 적용함으로써 영상의 잡음을 제거하는 것이 일반적이다. 본 논문에서는 영상의 잡음을 제거하기 위해 웨이블릿 영역의 부모-자식 관계를 이용하여 중요도를 작성하고, 이를 이용하여 분산을 구하기 위한 이웃 영역의 범위를 결정하는 방법을 제안한다. 먼저 웨이블릿 계수의 중요한 특성을 획득할 수 있는 중요도를 작성하기 위해 간단한 분류 방법을 사용한다. 중요한 웨이블릿 계수의 수에 근거하여 웨이블릿 계수의 범위를 결정한 뒤 ML 방법을 이용하여 원 신호의 분산을 추정한다. 실험 결과를 통하여 제안 방법이 기존의 방법보다 나은 결과를 보여줌을 알 수 있다.