• Computational Structural Engineering
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• v.9 no.4
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• pp.127-134
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• 1996

This paper is about a progressive fracture analysis of concrete by boundary element method. From both displacement boundary integral equation and traction boundary integral equation of solids with cracks, a boundary integral equation for crack problem is derived. For the analysis of progressive fracture of concrete, fracture process zone is modelled based on Dugdale-Barenblatt model with linear tension-softening curve. By using the boundary element modeling, the progressive fractures of concrete beam and compact-tension specimens with various loading conditions are analyzed and compared with experiments. The analysis results show that the technique in this paper can predict the maximum strength and the nonlinear behavior of concrete including post-peak behavior.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.340-345
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• 2000

진동하는 구조물의 음향 방사 예측에는 키르히호프-헬름홀쯔 적분 방정식에 근본을 둔 경계 요소 해석이 널리 사용된다. 이 경계 요소 해석은 익히 알고 있듯이 구조물의 동적 거동이 정량적으로 표현될 수 있는 경우는 매우 높은 정확도의 예측 결과를 제공한다. 그러나 실제 현상에서 접할 수 있는 복잡한 구조물의 음향 방사 예측에는 많은 변수들로 인해 예측의 정확도가 감소됨은 확실하다. 다른 방법으로는 실험을 통한 임의의 음장 예측 방법인 근음장 음향 홀로그래피(nearfield acoustical holography) 방법을 들 수 있다. 이 방법은 실제로 발생되는 음향 방사로부터 마이크로폰을 이용하여 홀로그램면의 음압 또는 속도를 측정하고 키르히호프-헬름홀쯔 적분 방정식에 적용하여 임의의 홀로그램면에 투사(mapping)시켜 음장을 예측하는 방법이다. 근음장 음향 홀로그래피는 탁월한 정확성을 갖고 있으나, 측정의 복잡성과 홀로그램면을 형성하기 위한 많은 이산점(절점)의 필요성 등의 단점을 갖고 있다. 본 논문에서는 또 다른 음장 예측 방법인 실험의 장점과 유한 요소 해석의 장정을 복합시킨 모드 확장 방법(modal expansion method)을 사용하여 단순 구조물인 평판의 진동에 의한 음장을 예측해 보았다. 모드 확장 방법은 구조물의 동적 거동은 모드의 선형 조합으로 표현될 수 있다는 것에 그 원리를 둔다. 본 논문은 단순 평판을 대상으로 유한 요소 해석으로 구한 모드 정보와 실험에 의해 얻은 입의 가진 주파수에 대한 진동 표면의 속도 분포를 조합하여 속도 경계 조건을 구성, 경계 요소 해석으로 음장 예측을 수행하였으며 모드 확장 방법을 사용함에 있어 고려해야할 몇 가지 사항에 대해 다루었다.

• The Korean Journal of Applied Statistics
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• v.27 no.5
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• pp.797-808
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• 2014

It is increasingly interested in investigating the relationships and the dynamic characteristics of variations among high class corporate values. This study formulates a statistical model of simultaneous equation system to examine the relationships among variations of stock returns for each class of corporate governance structure and to analyze the dynamic patterns of their long-run adjustment processes. Changes in stock returns for each class of corporate governance by an exogenous shock are found to have common structural features of slow adjustments to the long-run equilibriums.

• Korean Journal of Childcare and Education
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• v.6 no.3
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• pp.45-63
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• 2010

The purpose of this investigation was to examine the mediating effects of delinquent peers between attachment to parents, low self-control and adolescent deviant behaviors. After specifying a research model based on Gottfredson and Hirschi's general theory of crime and Hirschi's control theory of delinquency, the study analysed the model using structural equation modeling. The data for this investigation came from a sample of 2,448 Korean adolescents. The results showed the both measurement model and structural model had a good fit to the data and all paths of structural model were statistically significant. The main findings were the attachment to parents and low self-control had direct and indirect effects on adolescent deviant behaviors through delinquent peers. The implications for practical intervention and further research in the field of delinquency were discussed.

• Computational Structural Engineering
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• v.10 no.2
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• pp.149-160
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• 1997

Mechanical structures are composed of substructures connected by joints and boundary elements. While the finite element representation of plain substructures is well developed and reliable, joints have a lot of uncertainties in being accurately modelled and affect dynamic behavior of a total system. In order to improve the accuracy of a finite element model, a new method is proposed, in which reduced finite element model is combined with a system identification technique. After substructures except joints are modelled with finite element method and joint properties are represented by parameter states, non-linear state equation is derived in which parameter states are multiplied by physical states such as displacements and velocities. So the joint parameter identification is transformed into non-linear state estimation problem. The methods are tested and discussed numerically and the feasibility for physical application has been demonstrated through two example structures.

• Communications of the Korean Mathematical Society
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• v.15 no.3
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• pp.391-434
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• 2000

심플렉틱 구조는 국소적으로는 모두 같기 때문에 심플렉틱 다양체 연구는 대역적으로 연구해야한다. 그로모브가 복소해석학적 곡선을 원소를 하는 모률라이 공간의 연구가 심플렉틱 다양체를 연구하는 물고를 텃다. 특이점이 없는 복소곡선의 개수를 세는 그로모브 불변량은 도넬슨의 비선형 게이지 이론의 간략화라 할 수 있는 아벨리안게이지 이론에서 사이버그-위튼 불변량과 같음을 타우브스가 발견하였다. 또한 사이버그-위튼 불변량은 심플렉틱 다양체의 불변량으로 심플렉틱 구조연구에 큰 이바지하고 있다. 그로모브의 모듈라이 공간의 컴펙트하는 과정에서 자연스럽게 마크점과 특이점을 갖는 곡선의 그로모브-위튼 모듈라이 공간이 켐펙트가 되고 여기소 그로모브-위튼 불변량이 얻어진다. 이 그로모브-위튼 불변량은 대수기하와 이론 물리학의 끈이론에서 찾는 대수곡선의 개수를 나타내고, 코호몰로지의 컵곱의 일반화라 할 수 있는 퀸텀곱을 유도하고, 그로모브-위튼 포텐셜함수의 계수를 결정한다. 퀸텀곱의 결합법칙은 포텐셜함수의 WDVV-방정식과 동치를 나타나며 이는 프로베니우스 구조가 평탄함을 나타낸다. 그로모브-위튼 불변량은 앞으로 활발히 연구되고 수학에 광범하게 이바지 할 것이다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.6
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• pp.583-590
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• 2016

This paper presents a dynamic crack propagation algorithm with Rayleigh damping effect based on the MLS(Moving Least Squares) Difference Method. Dynamic equilibrium equation and constitutive equation are derived by considering Rayliegh damping and governing equations are discretized by the MLS derivative approximation; the proportional damping, which has not been properly treated in the conventional strong formulations, was implemented in both the equilibrium equation and constitutive equation. Dynamic equilibrium equation including time relevant terms is integrated by the Central Difference Method and the discrete equations are simplified by lagging the velocity one step behind. A geometrical feature of crack is modeled by imposing the traction-free condition onto the nodes placed at crack surfaces and the effect of movement and addition of the nodes at every time step due to crack growth is appropriately reflected on the construction of total system. The robustness of the proposed numerical algorithm was proved by simulating single and multiple crack growth problems and the effect of proportional damping on the dynamic crack propagation analysis was effectively demonstrated.

• Standardization Trend in Telecommunications
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• s.23
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• pp.56-70
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• 1992

본 보고서는 주로 통신망 및 방송국과 같은 정보제공 기관을 상호 연겨라는 정보구조의 전반적인 개념적 구조를 소개하고 설명합니다. 그리고 사용자의 관점에서 제공된 정보처리 서비스와 사업의 제휴관계가 2차원의 맵 형태로 표현되며, 그 맵과 연관된 맥스웰의 전자기 방정식과 방송서비스 등을 사용하여 통신 서비스에 적용하였습니다. 전자정보전송의 합법적 통합구조와 ''국지적이나 공공의 정보망''의 전개를 위한 연구대상을 제안하고 설명하였습니다. 그리고, 현재 통신과 방송에 관련된 법규들을 간략하게 조사하였습니다.(일본의 경우를 중심으로)

• Journal of Korean Society of Transportation
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• v.26 no.2
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• pp.17-24
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• 2008

Traffic accident forecasting model has been developed steadily to understand factors affecting traffic accidents and to reduce them. In Korea, the length of highways is over 3,000km, and it is within the top ten in the world. However, the number of accidents-per-one kilometer highway is higher than any other countries. The rapid increase of travel demand and transportation infrastructures since 1980's may influence on the high rates of traffic accident. Accident severity is one of the important indices as well as the rate of accident and factors such as road geometric conditions, driver characteristics and type of vehicles may be related to traffic accident severity. However, since all these factors are interacted complicatedly, the interactions are not easily identified. A structural equations model is adopted to capture the complex relationships among variables. In the model estimation, we use 2,880 accident data on highways in Korea. The SEM with several factors mentioned above as endogenous and exogenous variables shows that they have complex and strong relationships.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2819-2830
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• 2009

Load bearing structural members in a wide variety of applications accumulate damage over their service life. During experiment much effort and cost is needed for measuring structural safety assessment. The sparseness and errors of measured data have to be considered during the safety estimation of structures. This paper introduces parameter estimation and damage identification algorithm by a system identification using static and dynamic response. The equation error estimator and response error widely used in system identification are based on the minimization of least squared error between measured and calculated responses by a mathematical model of a structure. Since each estimator has a specific form of application in noisy environment and proposes different definitions for these forms. To study the behaviour of the estimators in noisy environment Using Monte Carlo simulation, and a data measured pertubation scheme is adopted to investigate the influence of measurement errors on identification results. The assessment result by static and dynamic response were compared, and the efficiency and applicabilities of the proposed algorithm are demonstrated through simulated static and dynamic responses of a dimensional truss type structures.