• 한국전자통신학회논문지
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• 제5권1호
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• pp.17-22
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• 2010

일반적으로 카오스 회로에는 Chua's 회로, Lorenz 회로, Duffing 회로 등이 있다. 이들 카오스 회로 중에서 Chua's 회로가 전자부품을 이용하여 가장 쉽게 구성할 수 있는 회로로 알려져 있다. Chua's 회로는 일반적으로 저항성분인 R, 인턱터 성분인 L, 캐패시터 성분인 C로 구성하는 선형요소와 비선형 저항으로 구성하는 비선형 요소로 구성된다. 그러나 L 요소는 포화특성으로 인하여 시중에서 구입한 부품으로는 실제 하드웨어를 구현하기 어려운 문제점이 있다. 본 연구에서는 Chua 회로의 선형 요소인 R,L,C 성분의 요소 중에서 포화 특성을 자지고 있어 상용화된 제품으로는 제작 구현이 어려운 L 성분을 C 성분으로 대체하는 간략화한 Chua's 회로 제작 기법을 PSpice로 해석하고, 그 결과를 확인한다.

• 대한조선학회논문집
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• 제39권2호
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• pp.61-68
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• 2002

K-a 관계가 동일하면, 선형파괴역학적 견지에서 균열개구 거동이 같다고 가정할 수 있다. 본 연구에서는 실제 구조물과 같은 K-a 관계를 주는 무한판 관통균열의 응력분포를 등가분포응력으로 정의한다. 실제 구조물과 동일한 K-a 관계가 구현되는 응력분포를 간단한 시험편에 작용시켜, 피로균열전파 해석을 수행하면 실제 구조요소의 피로전파수명 추정이 가능하다. 구조물에 대한 K-a 관계는 유한요소법 등의 이산화 수법 혹은 간이 추정법 등에 의하여 추정이 가능하다. 등가분포응력을 이용하여 유효 균열진전 음력을 구하는 방법의 타당성을 검토한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.281-286
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• 2008

Wall thinning defect due to flow accelerated corrosion is one of major aging phenomena in most power plant industries, and it results in reducing load carrying capacity of the piping systems. A failure testing system was set up for real scale elbows containing various simulated wall thinning defects, and monotonic in-plane bending tests were performed under internal pressure to find out the failure behavior of thinned elbows. Various finite element models were generated and analysed to figure out and simulate the behavior for other thinning shapes and loading conditions. This paper presents the decreasing trends of load carrying capacity according to the thinning dimensions which were revealed from the investigation of finite element analysis results. A mechanical integrity evaluation model for thinned elbows was proposed, also. This model can be used to calculate the TES plastic load of thinned elbows for general internal pressure, thinning location, and in-plane bending direction.

• 한국구조물진단유지관리공학회 논문집
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• 제2권4호
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• pp.137-147
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• 1998

The neural net application was tried to develop the technique for monitoring the health status of a steel truss bridge which was scaled down to 1/15 of the real bridge for the laboratory experiments. The damage scenarios were chosen as 7 cases. The dynamic behavior, which was changed due to the breakage of the members, of the bridge was investigated by finite element analysis. The bridge consists of single spam, and eight (8) main structural subsystems. The loading vehicle, which weighs as 100 kgf, was operated by the servo-motor controller. The accelerometers were bonded on the surface of 7 cross-beams to measure the dynamic behavior induced by the abnormal structural condition. Artificial neural network technique was used to determine the severity of the damage. At first, the neural net was learnt by the results of finite element analysis, and also, the maximum detection error was 3.65 percents. Another neural net was also learnt, and verified by the experimental results, and in this case, the maximum detection error was 1.05 percents. In future study, neural net is necessary to be learnt and verified by various data from the real bridge.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.935-937
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• 1993

This paper presents a three dimensional automatic mesh generation scheme for the boundary element method, and this scheme can be applicable to practical problems of complex shape. The geometry of the problem is expressed as an assemblage of linear Coon's surfaces, and each surface is made up of four edge curves which are defined in the form of a parametric function. Curves are automatically segmented according to their characteristics. With these segments of curves, interior points and triangular mesh elements are generated in the parametric plane using Lindholm's method, and then their projection on the real surface forms the initial mesh. The refinement of initial mesh is performed so that the discrete triangular planes are close to the real continuous surfaces. The bisection method is used for the refinement. Finally, interior points in the refined mesh are rearranged so as to make each element be close with an equilateral triangle. An attempt has been made to apply the proposed method to a DY(Deflection Yoke) model.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.181-183
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• 2002

The accurate permeability for preform is critical to model and design the impregnation of fluid resin in the composite manufacturing process. In this study, the in-plane and transverse permeability for a woven fabric are predicted numerically through the coupled flow model which combines microscopic with macroscopic flow. The microscopic and macroscopic flow which are flows within the micro-unit and macro-unit cell, respectively, are calculated by using 3-D CVFEM(control volume finite element method). To avoid checker-board pressure field and improve the efficiency on numerical computation, A new interpolation function for velocity is proposed on the basis of analytic solutions. The permeability of plain woven fabric is measured through unidirectional flow experiment and compared with the permeability calculated numerically. Based on the good agreement of the results, the relationships between the permeability and the structures of preform such as the fiber volume fraction and stacking effect can be understood. The reverse and the simple stacking are taken in account. Unlike past literatures, this study is based on more realistic unit cell and the improved prediction of permeability can be achieved. It is observed that in-plane flow is more dominant than transverse flow in the real flow through preform and the stacking effect of multi-layered preform is negligible. Consequently, the proposed coupled flow model can be applied to modeling of real composite materials processing.

• 한국수학교육학회지시리즈A:수학교육
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• 제45권1호
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• pp.61-74
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• 2006

The ability of understanding the number and number systems, grasping the properties of number systems, and manipulating number systems is the foundation to understand algebra. It is useful to deepen students' mathematical understanding of number systems and operations. The authentic understanding of numbers and operations can make it possible for the students to manipulate algebraic symbols, to represent relationship among sets of numbers, and to use variables to investigate the properties of sets of numbers. The high school students need to understand the number systems from more abstract perspective. The purpose of this study is to study on understanding and application ability of eleventh graders of basic properties of operations with real numbers.

• 복합신소재구조학회 논문집
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• 제5권2호
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• pp.15-20
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• 2014

This study carried out passenger safety assessment by real car crash simulation of composite post structures for road facilities. The effects of different material properties of composites for various parameters are studied using the LS-DYNA finite element program for this study. In this study, the existing finite element analysis of steel post structures using the LS-DYNA program is further extended to study dynamic behaviors of the structures made of various composite materials. The numerical results for various parameters are verified by comparing different models with displacements and stress distribution occurred in the post and car.

• 한국대기환경학회지
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• 제9권3호
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• pp.242-246
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• 1993

Theoretically, spectral method has the highest accuracy among present numerical methods, but it is generally difficult to apply to complex terrains because of complex boundary conditions. Recently, spectral-element method, basically divide the domain into a set of rectangular subdomain and solve the equation at each subdomain, has been introduced. However, boundary conditions become more complex and requires more computing time, thus spectral-element method is not powerful for all complex terrain problems. In this paper, potential flow theory was intorduced to solve the air flows and diffusion phenomenon in the presence of terrain obstacles. Using the velocity potential-stream line orthogonal coordinate space, the diffusion problems of hilly terrain by pseudospectral method were solved and compared those with no terrain real scale solutions.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.587-592
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• 2000

As the residential spaces become high-rised and high-density, Multi-story buildings were constructed with transfer girders, Deep beams, wall foundations, floor diaphragms an shear walls which may have column offsets. Especially, In the analysis and design of Multi-story buildings, the lateral loads must be taken into account. But, there have been no appropriate theory and national design code for predicting ultimate shear strength of reinforced concrete Deep beams with web opening. Only empirical and semi-empirical formulas for predicting their ultimate load bearing capacities due to the complexities of the structural non-linearity and material heterogeneity. So this study analyze tow-dimensional finite element model that represents exactly the behavior of real structures with SBETA which are general nonlinear finite element analysis program, and compare the results with that from the real reinforced Concrete Deep beams with web opening tests. From the comparison, and parametric study, The Study presents the elementary data of the earthquake resistance for the reinforced concrete Deep beams with web opening.