• 한국가스학회지
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• 제15권1호
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• pp.46-53
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• 2011

최근에 정보기술 패러다임은 유비쿼터스 기술이 도입되면서 스마트 서비스 환경으로 변화하고 있다. 도로, 상하수도, 가스 등과 산업 시설물에 유비쿼터스 기술이 접목되어 비용 감소 및 사고 예방성 향상이 높아지면서 관련된 연구 및 기술이 가속화되고 있다. 그러나 현재까지 공통환경 IT기술 위주로 개발되어 산업 도메인 특성이 고려되지 않았기 때문에 유비쿼터스 기술이 생활환경 및 산업시설에 활발하게 도입되지 못하고 있다. 본 논문은 도시가스 주요시설에 유비쿼터스 기술을 도입하기 위하여 현장지향형 무선 데이터 전송 인프라를 구축하고 효율적인 서비스를 제공하는 무선기반 도시가스 안전관리 시스템을 목적으로 한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.345-350
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• 2000

Adaptive finite element analysis, which its solution error meets with the user defined allowable error, is recently used far improving reliability of finite element analysis results. This adaptive analysis is composed of two procedures; one is the error estimation of an analysis result and another is the reconstruction of finite elements. In the rp-method, an element size is controlled by relocating of nodal positions(r-method) and the order of an element shape function is determined by the hierarchical polynomial(p-method) corresponding to the element solution error. In order to show the effectiveness and accuracy of the suggested rp-method, various numerical examples were analyzed and these analysis results were examined by comparing with those obtained by the existed methods. As a result of this study, following conclusions are obtained. (1) rp-method is more accurate and effective than the r- and p-method. (2) The solution convergency of the rp-method is controlled by means of the iterative calculation numbers of the r- and p- method each other.

• 한국멀티미디어학회논문지
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• 제8권8호
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• pp.1051-1056
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• 2005

적응신호처리 분야에서 LMS 알고리즘은 수식이 간단하고, 적은 계산량으로 인해 널리 사용되고 있지만, 시간영역의 적응 알고리즘은 입력신호의 고유치 분포폭이 넓게 분포할 때는 수렴속도가 느려지는 단점이 있다. 또한 알고리즘의 성능을 좌우하는 고정된 적응상수를 적절하게 선택해야만 알고리즘이 수렴할 수 있다. 이런 문제점을 개선하기 위하여 본 논문에서는 시간영역의 적응알고리즘을 변환영역인 웨이블렛 변환에서 적응알고리즘을 적용한다. 그리고 안정되고 빠른 수렴을 위해 고정된 적응상수를 오차신호의 순시치 절대값에 비례하여 각 반복구간마다 변화시키는 가변스텝사이즈를 갖는 웨이블렛 기반 적응알고리즘을 제안, 적응 잡음제거기에 적용하여 기존의 알고리즘과 비교하여 그 성능이 우수함을 입증하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.877-882
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• 2001

A finite element analysis of end-to-end artery/PTFE anastomosis has been presented in this study to evaluate the distribution of compliance and stresses in the vicinity of the anastomosis due to any mismatch in compliance characteristics. The artery wall was assumed to be made of linear isotropic material in this simplified model and a nonlinear analysis and convergency study with respect to increasing meshed element numbers were performed with a mean artery pressure loading of the artery-PTFE model. Also, sub-modeling method was introduced to progress the accuracy of the finite element analysis. The results are as follow : 1. A hypercompliant zone on the artery side was observed around 4.0mm from the anastomosis and a high hoop stresses in the wall of artery and PTFE was dominent. 2. An artery displays large deformation so that nonlinear analysis and sub-modeling method was used. 3. An anastomosis with the thinner thickness and larger diameter PTFE (C type) could reduce the compliance disagreement.

• 대한기계학회논문집A
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• 제27권4호
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• pp.551-558
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• 2003

An efficient and reliable subspace iteration algorithm using the block algorithm is proposed. The block algorithm is the method dividing eigenpairs into several blocks when a lot of eigenpairs are required. One of the key for the faster convergence is carefully selected initial vectors. As the initial vectors, the proposed method uses the modified Ritz vectors for guaranteering all the required eigenpairs and the quasi-static Ritz vectors for accelerating convergency of high frequency eigenvectors. Applying the quasi-static Ritz vectors, a shift is always required, and the proper shift based on the geometric average is proposed. To maximize efficiency, this paper estimates the proper number of blocks based on the theoretical amount of calculation in the subspace iteration. And it also considers the problems generated in the process of combining various algorithms and the solutions to the problems. Several numerical experiments show that the proposed subspace iteration algorithm is very efficient, reliable ,and accurate.

• 복합신소재구조학회 논문집
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• 제2권2호
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• pp.13-19
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• 2011

본 연구에서는 강재가 맞대기 이음으로 연결될 경우 CFRP(Carbon Fiber Reinforced Plastic) 쉬트(sheet)를 맞대기 이음부에 접착할 경우 강재 및 CFRP 쉬트에 발생하는 응력을 해석하였다. CFRP 쉬트로 보강한 경우 접착제의 두께, 강재와의 접착 길이, CFRP 강도 변화를 매개변수로 사용하여 이 매개변수에 변화에 따른 이음부의 응력분포를 분석하였다. 또한 CFRP를 여러 층으로 접착할 경우 각 층의 강도를 다르게 변화시켜 맞대기 이음부에 유리한 응력분포를 나타내는 CFRP의 강도를 제시하였다. 본 연구를 위해 빠른 수렴성을 가지며 왜곡된 요소형상에서도 정확한 응력결과를 보이는 강화변형률장(Enhanced Assumed Strain Field)을 사용한 평면변형률 유한요소에 대한 프로그램을 작성하였다.

• 대한기계학회논문집A
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• 제27권1호
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• pp.34-41
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• 2003

Finite element analysis of end-to-end artery/PTFE anastomosis recently have been researched. But, these studies were carried out without the compensation for the error of finite element analysis and assumed the artery and PTFE as the simple cylindrical shape in spite of being the fatty tissue which covers the heart. Therefore, we performed the convergency study with respect to increasing the element numbers and considered the fatty tissue as the elastic foundation in the finite element analysis. The results are as fallow ： 1. An anastomosis with the thinner thickness and larger diameter PTFE than artery could reduce the compliance disagreement. 2. A fatty tissue was affected to reduce the compliance mismatch in the vicinity of anastomosis of different material. Therefore a hypercompliant zone become narrorw and a compliance discrepancy decrease between the artery and the PTFE about 70%. And radial displacement with respect to longitudinal direction of an artery and the PTFE anastomosis was similar to a sectional compliance.

• 한국수산과학회지
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• 제18권1호
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• pp.15-22
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• 1985

The study on computation time, accuracy, and convergency characteristic of the implicit finite difference method is presented with the variation of the space increment and time step in a two-dimensional transient heat conduction problem with a dirichlet boundary condition. Numerical analysis were conducted by the model having the conditions of the solution domain from 0 to 3m, thermal diffusivity of 1.26 $m^2/h$, initial condition of 272 K, and boundary condition of 255.4 K. The results obtained are summarized as follows : 1) The degree of influence with respect to the accuracy of the time step and space increment in the alternating-direction implicit method and Crank-Nicholson implicit method were relatively small, but in case of the fully implicit method showed opposite tendency. 2) To prescribe near the zero for the space increment and tine step in a two dimensional transient problem were good in a accuracy aspect but unreasonable in a computational time aspect. 3) The reasonable condition of the space increment and the time step considering accuracy and computation time could be generalized with the Fourier modulus increment, F, ana dimensionless space increment, X, irrespective of the solution domain.

• 한국주거학회논문집
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• 제21권4호
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• pp.89-97
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• 2010

Digital convergence era has been already started and is rapidly developed. Recently, convergency technology became an essential issue in all industries, and is expected to accelerate. This means that we can experience growth and change of architecture using new technology and approaching method. The AR (Augmented Reality) technology, among these convergence technology, is a kind of virtual reality technology that user can see a scene of real world which is overlapped by virtual world with additional information. It has been used in manufacturing and management in the whole industry fields including medical, mechanical, military field and so on because it can provide higher sense of reality. Thus, in this paper, we suggest the utilization of AR technology for organically connecting the roads, facilities, green area, landscape and others in the layout planning of housing complex. Users can see real world with virtual object by overlap computer graphic on the real world. This method provides users with various information about territoriality and openness. As the result of this study it is expected that this technology will help the layout planning of housing complex to become more reasonable in the aspect of design, time and cost.

• 한국정보시스템학회지:정보시스템연구
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• 제29권2호
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• pp.51-69
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• 2020

Purpose Today, the increasing of internet use and the expansion of internet range provide us with many opportunities. Therefore, this study examine relation of perceived ease of use, perceived playfulness, perceived risk, perceived usefulness based on previous studies. And we examine the effect of O2O service satisfaction on continuous use intention. Also, we studied the relationship between perceived ease of use, perceived playfulness, perceived risk, perceived usefulness according to user innovation. Design/Methodology A Structural Equation Model(SEM) method was used to test the theoretical framework based on a sample of 451 respondents who have experienced the O2O service. Factor analysis and confirmation factor analysis was conducted to check the reliability, convergency validity and discriminant validity. To test moderating effect of the user innovation, multi group analysis was conducted. Findings First, perceived ease of use, perceived playfulness, perceived risk have significant effects on perceived usefulness. Second, perceived usefulness of O2O service have a positive effect on satisfaction. Third, satisfaction of O2O service have a positive effect on continuous use intention. The relationship that perceived ease of use, perceived playfulness, perceived risk affect perceived usefulness is differ depending on user innovation. Based on these findings, this study suggested to marketing practitioners the need for different approach by a user innovation.