• 한국압력기기공학회 논문집
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• 제8권1호
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• pp.1-7
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• 2012

A PHE (Process Heat Exchanger) is a key component required to transfer heat energy of $950^{\circ}C$ generated in a VHTR (Very High Temperature Reactor) to the chemical reaction that yields a large quantity of hydrogen. A small-scale PHE prototype made of Hastelloy-X is being tested in a small-scale gas loop at Korea Atomic Energy Research Institute. In order to properly evaluate the high-temperature structural integrity of the small-scale PHE prototype, it is very important to impose a proper constraint condition on its structural analysis model. For this effort, we tried to impose several constraint conditions on the structural analysis model and consequently fixed a proper and effective displacement constraints.

• 대한가정학회지
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• 제43권4호
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• pp.203-223
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• 2005

This study investigated the leisure constraints and leisure life satisfaction of the institutional elderly. The respondents were 302 elderly people residing in 5 free institutionalized elderly homes in Seoul. The data were analyzed by frequency analysis, factor analysis, One-way ANOVA, Duncan's post hoc test and regression analysis using SPSS WIN 12.0 program. Exploratory factor analysis revealed that the 10 items in the proposed scale could be grouped into four factors of constraint on leisure:'physical constraint','psychological constraint','interpersonal constraint', and 'structural constraint 'There were differences in leisure constraints according to sex, age, education degree, interaction with facility colleagues, and interaction with facility staff. There were differences in leisure life satisfaction according to sex, age, having religion or not, interaction with facility colleagues, interaction with facility staff and leisure constraints. Regression analysis results indicated that the main effective factors of leisure life satisfaction were leisure constraints.

• 경영과정보연구
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• 제38권2호
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• pp.209-223
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• 2019

본 연구는 소셜네트워크에서 SNS 광고에 대한 구전 제약요인의 개념과 측정도구 개발을 통하여 온라인 구전을 활성화하는데 그 목적이 있다. 이런 연구 목적을 달성하기 위해 3단계의 연구를 수행하였다. 첫째, 문헌고찰과 정성적 조사방법을 통하여 구전 제약에 대한 개념과 범위에 대하여 탐색적 조사(표적 집단 면접과 심층면접, 전문가 면접)를 실시하였다. 둘째, 개발된 측정항목은 정제작업을 위해 설문 조사를 실시하여 측정문항에 대한 신뢰성과 타당성 검증을 하였다. 셋째, 개발된 측정문항과 다른 주요 구성개념과 관계를 살펴봄으로써 측정항목의 예측타당성을 검증하였다. 연구결과 6개의 구성요인과 이에 대한 총 23개의 측정문항이 도출되었으며, 각각 내재적 및 대인적 제약(심리적 민감성, 보상적 민감성, 타인평가 민감성), 구조적 제약(신뢰성, 정보성, 오락성)으로 명명하였다. 정성적 연구와 정량적 연구를 통해 구전 제약의 측정문항을 개발하였으며, SNS 성과 및 평가 측면에서 SNS 광고 구전의 제약요인으로 작용하고 있는 사회적, 심리적, 환경적인 방해 요인들을 구전 제약의 관점에서 통합적으로 살펴보았다. 본 연구를 통해 온라인 구전 제약에 대한 체계적이고 실증적인 연구수행을 위한 기본 틀과 효과적인 SNS 구전을 이끌어 낼 수 있을 것이다.

• Structural Engineering and Mechanics
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• 제50권2호
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• pp.215-229
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• 2014

Due to the lack of effective longitudinal constraint for center tower, structural stiffness of three-tower suspension bridge becomes less than that of two-tower suspension bridge, and therefore it becomes more susceptible to the seismic action. By taking a three-tower suspension bridge-the Taizhou Highway Bridge over the Yangtze River with two main spans of 1080 m as example, structural dynamic characteristics and seismic performance of the bridge is investigated, and the effects of cable's sag to span ratio, structural stiffness of the center tower, and longitudinal constraint of the girder on seismic response of the bridge are also investigated, and the favorable structural system is discussed with respect to seismic performance. The results show that structural response under lateral seismic action is more remarkable, especially for the side towers, and therefore more attentions should be paid to the lateral seismic performance and also the side towers. Large cable's sag, flexible center tower and the longitudinal elastic cable between the center tower and the girder are favorable to improve structural seismic performance of long-span three-tower suspension bridges.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 봄 학술발표회논문집
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• pp.253-259
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• 2000

This thesis investigated the behavior of super structure by varying the factors such as the change of pile rigidity, the characteristics of soil and the constraint condition of support. The results of this study are as follows; 1. The pile rigidity in the Fig 3.3 computed by the rotating deformed plane method becomes the elastic range at approximately about 5.1 m (D : 1.0 m) below the ground level. This result is consistent with the previous study that the pile deformation occurs approximately 3 to 6 times pile diameter from the pile head. 2. The values of forces and deformations for the structure-pile system in Y-direction appeared larger than that in X-direction, since the pile rigidity and constraint condition of support were changed as shown Fig.3.5 to 3.8. 3. The current practice for the analysis of structure-pile system has not considered the variation of pile rigidity and the constraint condition of support. So, the analysis of structure-pile system with large difference in super-structure rigidity must includes these factors in both X and Y directions.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.93-98
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• 2002

This study presents a new method to derive the constraint coefficient from the degree of angular deformation caused by welding, as measured experimentally by varying the shape of welded joints and the magnitude of constraints and from analysis results given by the elastic FEM method. The equivalent load was then calculated with this constraint coefficient. The validity of the numerical analysis involved in this new method was confirmed by its agreement with the experimental results. As for the effects of the constraints based on the shape of the welded joints in the case of Butt welding when the constraint coefficients are not considered, the deformed quantity produced by analysis is larger that produced by experiment and consequently is largely affected by the constraints.

• Structural Engineering and Mechanics
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• 제5권5호
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• pp.565-576
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• 1997

The material-based homogenization design method generates arbitrary topologies of initial structural design as well as reinforcement structural design by controlling the amount of material available. However, if a small volume constraint is specified in the design of Lightweight structures, thin and slender structures are usually obtained. For these structures stability becomes one of the most important requirements. Thus, to prevent overall buckling (that is, to increase stability), the objective of the design is to maximize the buckling load of a structure. In this paper, the buckling analysis is restricted to the linear buckling behavior of a structure. The global stability requirement is defined as a stiffness constraint, and determined by solving the eigenvalue problem. The optimality conditions to update the design variables are derived based on the sequential convex approximation method and the dual method. Illustrated examples are presented to validate the feasibility of this method in the design of structures.

• Smart Structures and Systems
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• 제18권4호
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• pp.733-754
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• 2016

Structural optimization involves a large number of structural analyses. When optimizing large structures, these analyses require a considerable amount of computational time and effort. However, there are specific types of structure for which the results of the analysis can be achieved in a much simpler and quicker way thanks to their special repetitive patterns. In this paper, frequency constraint optimization of cyclically repeated space trusses is considered. An efficient technique is used to decompose the large initial eigenproblem into several smaller ones and thus to decrease the required computational time significantly. Some examples are presented in order to illustrate the efficiency of the presented method.

• Steel and Composite Structures
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• 제46권1호
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• pp.33-51
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• 2023

This research presents a multi-material topology optimization for functionally graded material (FGM) and nonFGM with elastic buckling criteria. The elastic buckling based multi-material topology optimization of functionally graded steels (FGSs) uses a Jacobi scheme and a Method of Moving Asymptotes (MMA) as an expansion to revise the design variables shown first. Moreover, mathematical expressions for modified interpolation materials in the buckling framework are also described in detail. A Solid Isotropic Material with Penalization (SIMP) as well as a modified penalizing material model is utilized. Based on this investigation on the buckling constraint with homogenization material properties, this method for determining optimal shape is presented under buckling constraint parameters with non-homogenization material properties. For optimal problems, minimizing structural compliance like as an objective function is related to a given material volume and a buckling load factor. In this study, conflicts between structural stiffness and stability which cause an unfavorable effect on the performance of existing optimization procedures are reduced. A few structural design features illustrate the effectiveness and adjustability of an approach and provide some ideas for further expansions.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.1-6
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• 2000

FFP(Fitness For Purpose) type defect assessment methodologies based on ECA(Engineering Critical Analysis) have been established and are in use for the structural integrity evaluation of gas pipelines. ECA usually includes the fracture mechanics analysis, and it assumes that J-integral uniquely characterizes crack-tip stress-strain fields. However, it has been shown that it is not sufficient to characterize the crack-tip field under low levels of constraint with a single parameter. Since pipeline structures are made of ductile material, locally loaded in tension, cracks may experience low level of constraint, and therefore, J-dominance will be lost. For this reason, the level of constraint must be quantified to establish a precise assessment procedure for pipeline defects. The objective of this paper is to Investigate the fracture behavior of a crack in gas pipeline by quantifying the level of constraint. For this purpose, tensile tests and CTOD tests were performed at room temperature$(24^{\circ}C)$ and low temperature$(-40^{\circ}C)$ to obtain the material properties. J-Q analyses were performed for SENB and SENT specimens based on 2-D finite element analyses, in order to investigate the in-plane constraint effects on pipeline defects.