• 한국멀티미디어학회논문지
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• 제13권6호
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• pp.875-883
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• 2010

In this paper, we present a secure biometric hashing scheme for face recognition by random fusion of global and local features. The Fourier-Mellin transform and Radon transform are adopted respectively to form specialized representation of global and local features, due to their invariance to geometric operations. The final biometric hash is securely generated by random weighting sum of both feature sets. A fourfold key is involved in our algorithm to ensure the security and privacy of biometric templates. The proposed biometric hash can be revocable and replaced by using a new key. Moreover, the attacker cannot obtain any information about the original biometric template without knowing the secret key. The experimental results confirm that our scheme has a satisfactory accuracy performance in terms of EER.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.99-104
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• 2006

A semi-Lagrangian finite element scheme with objective time stepping algorithm for solving viscoelastic flow problem is presented. The convection terms in the momentum and constitutive equations are treated using a quasi-monotone semi-Lagrangian scheme, in which characteristic feet on a regular grid are traced backwards over a single time-step. Concerned with the generalized midpoint rule type of algorithms formulated to exactly preserve objectivity, we use the geometric transformation such as pull-back, push-forward operation. The method is applied to the 4:1 planar contraction problem for an Oldroyd B fluid for both creeping and inertial flow conditions.

• 한국통신학회논문지
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• 제34권5A호
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• pp.331-340
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• 2009

In this paper, we propose a new power loading algorithm for orthogonalized spatial multiplexing(OSM) systems over flat-fading multiple-input multiple-output (MIMO) channels. Compared to SVD-based transmission scheme, the OSM scheme exhibits a good system performance with lower complexity and feedback overhead. To further improve the performance in OSM systems with power loading, we introduce a geometric approach on the Euclidean distance between the constellation points in the effective channel. Using this approach, we show that the optimal power loading parameters in terms of the minimum distance can be obtained. Simulation results demonstrate that our algorithm provides a 5dB gain at a bit error rate (BER) of $10^{-4}$ over that of no power loading case with both QPSK and 16-QAM. Consequently, our power loading algorithm allows us to significantly improve the system performance with one additional feedback value.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.294-301
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• 2011

A two-dimensional hybrid flaw solver has been developed for the accurate and efficient simulation of steady and unsteady flaw fields. The flow solver was cast to accommodate two different topologies of computational meshes. Triangular meshes are adopted in the near-body region such that complex geometric configurations can be easily modeled, while adaptive Cartesian meshes are, utilized in the off-body region to resolve the flaw more accurately with less numerical dissipation by adopting a spatially high-order accurate scheme and solution-adaptive mesh refinement technique. A chimera mesh technique has been employed to link the two flow regimes adopting each mesh topology. Validations were made for the unsteady inviscid vol1ex convection am the unsteady turbulent flaws over an NACA0012 airfoil, and the results were compared with experimental and other computational results.

• Nuclear Engineering and Technology
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• 제36권4호
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• pp.285-294
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• 2004

Pressure wave propagation in the discharge piping with a sparger submerged in a water pool, following the opening of a safety relief valve, is analyzed. To predict the pressure transient behavior, a RELAP5/MOD3 code is used. The applicability of the RELAP5 code and the adequacy of the present modeling scheme are confirmed by simulating the applicable experiment on a water hammer with voiding. As a base case, the modeling scheme was used to calculate the wave propagation inside a vertical pipe with sparger holes and submerged within a water pool. In addition, the effects on wave propagation of geometric factors, such as the loss coefficient, the pipe configuration, and the subdivision of sparger pipe, are investigated. The effects of inflow conditions, such as water slug inflow and the slow opening of a safety relief valve are also examined.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.519-521
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• 2003

Within the paper an approach for the automatic extraction and reconstruction of buildings in urban built-up areas base on fusion of high-resolution satellite image and LIDAR data is presented. The presented data fusion scheme is essentially motivated by the fact that image and range data are quite complementary. Raised urban objects are first segmented from the terrain surface in the LIDAR data by making use of the spectral signature derived from satellite image, afterwards building potential regions are initially detected in a hierarchical scheme. A novel 3D building reconstruction model is also presented based on the assumption that most buildings can be approximately decomposed into polyhedral patches. With the constraints of presented building model, 3D edges are used to generate the hypothesis and follow the verification processes and a subsequent logical processing of the primitive geometric patches leads to 3D reconstruction of buildings with good details of shape. The approach is applied on the test sites and shows a good performance, an evaluation is described as well in the paper.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송∙미디어공학회 2021년도 하계학술대회
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• pp.73-74
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• 2021

This paper presents a scheme to downscale the patches in geometry atlas based upon its contents for MPEG Immersive Video (MIV). In proposed scheme, the geometric contents of a patch is analyzed across the intra period, and a decision is made, whether to downscale a patch or not. The patches containing homogeneous information is downscaled by half, while the patches having salient information about the object such as edges are retained. Experimental results show that the bitrate saving is achieved by incorporating the patch level downscaling.

• 대한수학교육학회지:수학교육학연구
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• 제27권2호
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• pp.191-205
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• 2017

본 연구는 서울의 C중학교 1학년 학생들이 기하 증명 문제를 해결하는 과정에서 보여주는 증명스키마 유형과 그 특징을 조사한 것이다. 자료 분석은 Harel, & Sowder의 증명스키마 유형에 기초하여 이루어졌다. 연구 결과, 학업성취수준에 따라 학생들이 사용하는 증명스키마 유형에 차이가 있었다. 상위권에서 하위권으로 갈수록 변형적 증명스키마를 사용하는 학생의 비율이 감소하였고 귀납적(측정) 증명스키마를 사용하는 학생의 비율은 증가하였다. 또한 증명과정에서 비형식적인 부호 사용하기, 문제에서 주어진 그림 특정 비율로 인식하기 등 각 증명스키마 유형마다 고유한 특징이 나타났다. 이를 바탕으로 4개의 의미 있는 결론을 추출하였고, 이것이 증명 교수 학습에 주는 시사점을 논의하였다.

• 한국수자원학회논문집
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• 제41권8호
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• pp.797-806
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• 2008

본 연구에서는 특정 해상도상에서 정의되는 유역의 모든 배수경로들로 구성되는 배수망을 도시하여 자연유역의 배수구조에 대한 기하학적 특성을 분석하여 보았다. 이를 위하여 Fractal 나무와 Horton의 법칙을 기반으로 분기에 의하여 조직되는 망상구조에 대하여 이론적 고찰을 수행하였다. 배수망의 작도에는 ArcGIS를 적용하였고 작도된 배수망에 대하여 Strahler의 차수기법에 따라 위상구조를 수립하여 차수별 배수구조의 기하학적 특성을 분석하고자 시도하여 보았다. Richardson의 방법에 따라 배수구조의 Fractal 특성을 분석해 본 결과 지표면유동과 하천유동 사이에는 개별적인 거동특성이 존재할 수 있음을 볼 수 있었고 자연유역의 하천망은 공간을 채워가는 Fractal 도형임을 확인할 수 있었다. 본 연구의 결과로부터 지표면유동을 포함한 망상구조에 대한 Fractal 이론을 실제유역에 적용하였을 경우 지금까지의 경험식에 의한 차수법칙과 상이한 결과를 나타냄을 알 수 있었다. 이의 결과들은 추후 망상구조의 결정에 크게 기여될 수 있으리라 판단된다.

• 대한조선학회논문집
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• 제53권5호
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• pp.388-399
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• 2016

A motion analysis of an underwater towed cable is a complex task due to its nonlinear nature of the problem. The major source of the nonlinearity of the underwater cable analysis is that the motion of the cable involves large rigid-body motion. This large rigid-body motion makes difficult to use standard displacement-based finite element method. In this paper, the authors apply recently developed nodal position-based finite element method which can deal with the geometric nonlinearity due to the large rigid-body motion. In order to enhance the stability of the large-scale nonlinear cable motion simulation, an efficient time-integration scheme is proposed, namely predictor/multi-corrector Newmark scheme. Three different predictors are introduced, and the best predictor in terms of stability and robustness for impulsive cable motion analysis is proposed. As a result, the nonlinear motion of underwater cable is predicted in a very efficient manner compared to the classical finite element of finite difference methods. The efficacy of the method is demonstrated with several test cases, involving static and dynamic motion of a single cable element, and also under water towed cable composed of multiple cable elements.