• 수산해양기술연구
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• 제20권1호
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• pp.30-36
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• 1984

대규모의 소성역을 동반하면서 파괴하는 고인성 재료의 탄소성 파괴 반가를 위하여 제안된 바 있는 CPE 모형의 유효성을 입증하고자 소성역의 영향을 보정한 선형 파괴역학과의 이론적 검토와 오오스테나이트계 스테인레스강에 대한 실험적 비교검토를 통하여 얻은 결론은 다음과 같다. 예측한 바와 같이 선형 파괴역학의 적용은 소규모 항복조건이 성립하는 경우에만 가능하며 CPE 모형은 대변형을 형성하면서 파괴하는 경우의 파괴모형으로서 유효하다. 더욱 엄밀한 유효성을 입증하기 위하여 다음의 사항이 필요하다고 본다. 1. 크랙의 길이가 짧은 시험편에 대한 실험이 필요하다. 2. 크랙성장 개시점을 정확하게 찾을 수 있는 방법이 필요하다. 3. 파괴 진행영역에 대한 두께의 영향을 고려해 보아야 할 필요성이 있다.

• International Journal of Concrete Structures and Materials
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• 제6권2호
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• pp.111-121
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• 2012

The research presented in this paper analytically examines the fire performance of flat plate buildings. The modeling parameters for the mechanical and thermal properties of materials are calibrated from relevant test data to minimize the uncertainties involved in analysis. The calibrated models are then adopted to perform a nonlinear finite element simulation on a flat plate building subjected to fire. The analysis examines the characteristics of slab deflection, in-plane deformation, membrane force, bending moment redistribution, and slab rotational deformation near the supporting columns. The numerical simulation enables the understanding of structural performance of flat plate under elevated temperature and, more importantly, identifies the high risk of punching failure at slab-column connections that may trigger large-scale failure in flat plate structures.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 봄 학술발표회 논문집
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• pp.287-294
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• 1999

The tensegrity structure by prestressed cable, which may have large freedom in scale and form and therefore are received much attention from the view points of their light weight and aesthetics, is a very flexible and geometrically unstable structure because the cable material has little initial rigidity. For the stable self-equilibrated state of the usually very deformable structure, the method to find the optimal initial stress by the shape analysis is proposed in this paper. The proposed procedure is to derive the nonlinear finite element formula of cable and truss members considering geometric nonlinearity and used to modified load incremental method adding to Newton-Raphson method with the proposed condition for optimal initial stress. The result of the shape analysis for the tensegrity structure with the radius of 30m is shown the almost approximated shape to architectural shape and the changed procedure of initial stress

• 한국공간구조학회논문집
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• 제5권2호
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• pp.81-87
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• 2005

The Space structures may have large freedom in scale and form. And especially Hybrid structures are received much attention from the view points of their light weight and aesthetics. Hybrid systems are stable structures which are reticulated spatial structures composed of compressive straight members, struts and cables and Membranes. In this paper, The Hybrid Unit System are suggested using the Membrane and Cable elements based on the Tensegrity Unit system. Also, The Hybrid System of double-layered single curvature is presented. We analyze the force density method allowing form-finding for Tensegrity systems. And We analyze the shape analysis by the LARSH which is the program for nonlinear analysis.

• Industrial Engineering and Management Systems
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• 제13권4호
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• pp.454-462
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• 2014

Retention of possible churning customer is one of the most important issues in customer relationship management, so companies try to predict churn customers using their large-scale high-dimensional data. This study focuses on dealing with large data sets by reducing the dimensionality. By using six different dimension reduction methods-Principal Component Analysis (PCA), factor analysis (FA), locally linear embedding (LLE), local tangent space alignment (LTSA), locally preserving projections (LPP), and deep auto-encoder-our experiments apply each dimension reduction method to the training data, build a classification model using the mapped data and then measure the performance using hit rate to compare the dimension reduction methods. In the result, PCA shows good performance despite its simplicity, and the deep auto-encoder gives the best overall performance. These results can be explained by the characteristics of the churn prediction data that is highly correlated and overlapped over the classes. We also proposed a simple out-of-sample extension method for the nonlinear dimension reduction methods, LLE and LTSA, utilizing the characteristic of the data.

• Coupled systems mechanics
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• 제9권2호
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• pp.163-182
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• 2020

Coupled thermo-mechanical analysis of reinforced concrete slab at elevated temperatures from a fire accounting for nonlinear thermal parameters is carried out. The main focus of the paper is put on a one-way continuous reinforced concrete slab exposed to fire from the single (bottom) side as the most typical working condition under fire loading. Although contemporary techniques alongside the fire protection measures are in constant development, in most cases it is not possible to avoid the material deterioration particularly nearby the exposed surface from a fire. Thereby the structural fire resistance of reinforced concrete slabs is mostly influenced by a relative distance between reinforcement and the exposed surface. A parametric study with variable concrete cover ranging from 15 mm to 35 mm is performed. As the first part of a one-way coupled thermo-mechanical analysis, transient nonlinear heat transfer analysis is performed by applying the net heat flux on the exposed surface. The solution of proposed heat analysis is obtained at certain time steps of interest by α-method using the explicit Euler time-integration scheme. Spatial discretization is done by the finite element method using a 1D 2-noded truss element with the temperature nodal values as unknowns. The obtained results in terms of temperature field inside the element are compared with available numerical and experimental results. A high level of agreement can be observed, implying the proposed model capable of describing the temperature field during a fire. Accompanying thermal analysis, mechanical analysis is performed in two ways. Firstly, using the guidelines given in Eurocode 2 - Part 1-2 resulting in the fire resistance rating for the aforementioned concrete cover values. The second way is a fully numerical coupled analysis carried out in general-purpose finite element software DIANA FEA. Both approaches indicate structural fire behavior similar to those observed in large-scale fire tests.

• 한국방재학회 논문집
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• 제6권2호
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• pp.25-35
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• 2006

본 연구에서는 GIS 및 지진취약도 분석기법이 결합된 방법에 의한 교통망 시스템의 방재 시스템 구축방안의 국내 적용성을 검토하였다. 연구대상으로는 경상남도 창원시의 교통망을 선택하였고, 지진취약도 분석을 위해 먼저 창원시에 위치한 교량 8개를 선택하고 기본 외관 조사를 수행하였으며, 이를 바탕으로 교량의 FE 모델을 만들었고, 국내 표준 설계 시방서에 의한 응답스펙트럼에 기준하여 인공지진을 생성하고 비선형 해석을 수행하였다. 또한, 각 결과를 500년, 1000년 및 2400년 재현주기를 가지는 지진위험도 곡선 (Seismic Hazard Curve)과 중첩하여 각 교량의 확률적 위험도 및 교통망의 확률적 위험도를 분석하였다. 본 논문에서는 지진 취약도 분석 기법을 활용하여 교량 구조물의 지진 안전도를 분석하였고 그 결과와 GIS를 이용한 네트워크의 지진에 의한 피해를 예측하였다.

• 한국강구조학회 논문집
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• 제20권3호
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• pp.409-419
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• 2008

율리신-이바노브 항복 조건을 이용하여 4절점 순수변위 준적합 쉘요소의 정식화를 제안하였다. 기하강성 행렬은 그린 변형률 텐서를 이용하여 휨변형률 및 전단변형률도 기하강성행렬에 고려되었다. 그 결과 접선강성행렬의 해석적인 적분으로 비선형 해석시 매우 효율적으로 계산이 되고 있다. 이 정식은 변형률 경화의 이바노브-유리신 항복조건을 이용하여 재료 비선형 해석시에도 쉽게 적분이 된다. 즉 두께 방향의 적층 적분을 하지 않는 율리신-이바노브의 정식은 대규모의 쉘 구조에도 계산상 아주 적합하다. 검증된 수치 예제에서 만족스러운 결과를 보여주고 있다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 봄 학술발표회논문집
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• pp.304-307
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• 2000

This paper presents a numerical simulation study for remote parallel pseudo-dynamic testings using Internet. In this testing method, experimental facilities located at different places can be parallelly used for testing a large-scale structure with many components subjected to severe nonlinear behavior. Example analysis is carried out on a base- isolated bridge for earthquake loading. The results indicate that the time required for data communication between two facilities located 250km apart through Internet for t 000 time steps is about 20 minutes, which is fairly equivalent to the time required for pseudo-dynamic testing. This testing method can be more powerful, as the data transmitting technique through Internet improves.

• 전기학회논문지
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• 제67권4호
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• pp.561-568
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• 2018

Passivity theory is significantly applied to analyze stability of nonlinear dynamic systems and construct its stable control systems. This paper presents a passivity based control design approach for exciters and governors which are employed to regulate the terminal voltage and the rotor velocity of synchronous generator systems in industry fields. We consider the IEEE type 1 exciter and the gas turbine (GT) governor models respectively in this paper. We first carry out a passivity analysis for exciter and governor control systems, which are numerically obtained from its mathematical models. And then its control parameters are selected to assure passivity conditions in a design procedure. Lastly, we investigate numerical simulations to demonstrate reliability of the proposed control approach against large-scale generators with parameter changes.