• 한국도로학회논문집
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• 제15권5호
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• pp.31-45
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• 2013

PURPOSES : Determination of particle packing model variables that can be used for formulation of new DEM based particle packing model by examining existing particle packing models METHODS : Existing particle packing models are thoroughly examined by analytical reformulation and sensitivity analysis in order to set up DEM based new particle packing model and to determine its variables. All model equations considered in this examination are represented with consistent expressions and are compared to each others to find mathematical and conceptual similarity in expressions. RESULTS : From the examination of existing models, it is observed that the models are very similar in their shapes although the derivation of the models may be different. As well, it is observed that variables used in some existing models are comprehensive enough to estimate particle packing but not applicable to DEM simulation. CONCLUSIONS : A set of variables that can be used in DEM based particle packing model is determined.

• Geomechanics and Engineering
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• 제16권5호
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• pp.471-482
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• 2018

A flat-jointed bonded-particle model (BPM) has been proved to be an effective tool for simulating mechanical behaviours of intact rocks. However, the tedious and time-consuming calibration procedure imposes restrictions on its widespread application. In this study, a systematic approach is proposed for simplifying the calibration procedure. The initial relationships between the microscopic, constitutive parameters and macro-mechanical rock properties are firstly determined through dimensionless analysis. Then, sensitivity analyses and regression analyses are conducted to quantify the relationships, using results from numerical simulations. Finally, four examples are used to demonstrate the effectiveness and robustness of the proposed systematic approach for the calibration procedure of BPMs.

• 대한토목학회논문집
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• 제12권4호
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• pp.33-47
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• 1992

본 논문에서는 케이블로 지지된 프리스트레스트 콘크리트(PC) 뼈대의 시공중의 각 단계를 고려하고 콘크리트와 PC 강재, 케이블 재료의 시간의존적 특성 및 재료의 비선형성과 케이블의 색 및 구조물의 처짐에 의한 기하학적 비선형성도 고려하는 해석방법을 제시했다. 구조물의 비선형거동을 해석하기 위한 운동방정식은 Updated Lagrangian 방식을 이용하여 유도하고 시간의존적인 거동올 해석하기 위해서 시간영역을 시간단계로 나누어 순차적으로 적분했다. 시공중의 각 단계를 표현하기 위해 계속적인 구조계의 변화를 고려했다. 본 논문에서 제시한 해석방법에 근거하여 컴퓨터 프로그램 CFRAME을 개발하고 예제들을 통하여 해석방법의 정당성을 보였다.

• Interaction and multiscale mechanics
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• 제2권2호
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• pp.129-151
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• 2009

This paper presents a meshfree procedure using a convex generalized meshfree (GMF) approximation for the large deformation analysis of particle-reinforced rubber compounds on microscopic level. The convex GMF approximation possesses the weak-Kronecker-delta property that guarantees the continuity of displacement across the material interface in the rubber compounds. The convex approximation also ensures the positive mass in the discrete system and is less sensitive to the meshfree nodal support size and integration order effects. In this study, the convex approximation is generated in the GMF method by choosing the positive and monotonic increasing basis function. In order to impose the periodic boundary condition in the unit cell method for the microscopic analysis, a singular kernel is introduced on the periodic boundary nodes in the construction of GMF approximation. The periodic boundary condition is solved by the transformation method in both explicit and implicit analyses. To simulate the interface de-bonding phenomena in the rubber compound, the cohesive interface element method is employed in corporation with meshfree method in this study. Several numerical examples are presented to demonstrate the effectiveness of the proposed numerical procedure in the large deformation analysis.

• 한국실내디자인학회논문집
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• 제29호
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• pp.273-280
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• 2001

In architecture, each project participant must maintain organic relationship with others. However, current practices are rather procedural and discrete than organic, which result in considerable inefficiencies. The cool-downs of Korean construction market also force the architects to be familiar with the new construction methods and systems. This research mainly focuses on the pre-development stage of such systems, analysing relationships between the information of architectural design and other parts of construction information like structure, construction, environment, and so forth. The result of analysis can be organized into attributes of members in a physical building, which can be modeled in a 3D system. The resulting model can be used for automated generation of drawing, Bill of Materials, finite element meshes for structural analysis and energy analysis, etc. by extracting meaningful information from it. Hence, the purpose of this research is to analysis the relationship among domain-specific information (e.g. structural engineering, construction detail, energy evaluation) that are represented in drawings, and to represent the attributes of the information relevantly so that they can be applied to each unit task that forms the whole project. Therefore, an object oriented methodology is introduced to compose design informations in three dimension, and expressing properties of building factors and materials, and to construct a database for computers to recognize architecture informations.

• Nuclear Engineering and Technology
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• 제25권1호
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• pp.51-62
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• 1993

입자수송방정식의 각분할해석법에서 입자흐름방향을 묘사하는 각방향에 대한 각분할집합이 고정된 값이 아니고 각입자속으로 조종되는 각요소법에 근거하여 방사선차폐해석 목적의 전산프로그램(TDET)를 2차원직각좌표계에 대해서 개발하였다. 산란선원항의 각의존성은 Spherical Harmonics Series Expansion으로 해석하였고 입자의 에너지 의존성은 다중에너지군으로 처리하였다. 3 종류의 Benchmark 시험을 통해서 TDET 프로그램을 검증하였다. 평판형 등방적 선원을 가진 사방흡수체에 대한 해석에서 TDET 해석결과가 MORSE-CG 해석결과에 잘 일치하고. 각분할법으로 해석할때 나타나는 Ray effect를 DOT 4.3 보다 잘 치 유하고 있다. 차폐체 내에 좁은 Vacuum duct가 있는 문제의 해석에서 TDET는 MORSE-CG와 마찬가지로 duct를 통한 streaming leak-age에 대해서 분명하고 현저한, 그리고 DOT 4.3보다 매우 훌륭한 해석결과를 보여주고 있다. 원자로차폐구조물 규모에 대해, 2 에너지군, 등방적 산란 및 선형 비등방 산란의 경우에 대해서 해석한 결과 각분할법으로 계산하여 제시하고 있는 기준치에서는 여러 mesh들에 걸쳐 넓은 규모의 Ray effect를 나타내고 있는데, TDET에 의한 해석결과에서는 이웃 mesh들 간에 미세한 Ray effect를 나타내고 있다.

• 한국도로학회논문집
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• 제17권4호
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• pp.25-31
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• 2015

PURPOSES: Implementation and verification of the simple linear cohesive viscoelastic contact model that can be used to simulate dynamic behavior of sticky aggregates. METHODS: The differential equations were derived and the initial conditions were determined to simulate a free falling ball with a sticky surface from a ground. To describe this behavior, a combination of linear contact model and a cohesive contact model was used. The general solution for the differential equation was used to verify the implemented linear cohesive viscoelastic API model in the DEM. Sensitivity analysis was also performed using the derived analytical solutions for several combinations of damping coefficients and cohesive coefficients. RESULTS : The numerical solution obtained using the DEM showed good agreement with the analytical solution for two extreme conditions. It was observed that the linear cohesive model can be successfully implemented with a linear spring in the DEM API for dynamic analysis of the aggregates. CONCLUSIONS: It can be concluded that the derived closed form solutions are applicable for the analysis of the rebounding behavior of sticky particles, and for verification of the implemented API model in the DEM. The assumption of underdamped condition for the viscous behavior of the particles seems to be reasonable. Several factors have to be additionally identified in order to develop an enhanced contact model for an asphalt mixture.

• Structural Engineering and Mechanics
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• 제35권1호
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• pp.19-35
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• 2010

This paper proposes a hybrid heuristic and criteria-based method of optimum design which combines the advantages of both the iterated simulated annealing (SA) algorithm and the rigorously derived optimality criteria (OC) for structural optimum design of reinforced concrete (RC) buildings under multi-load cases based on the current Chinese design codes. The entire optimum design procedure is divided into two parts: strength optimum design and stiffness optimum design. A modified SA with the strategy of adaptive feasible region is proposed to perform the discrete optimization of RC frame structures under the strength constraints. The optimum stiffness design is conducted using OC method with the optimum results of strength optimum design as the lower bounds of member size. The proposed method is integrated into the commercial software packages for building structural design, SATWE, and for finite element analysis, ANSYS, for practical applications. Finally, two practical frame-shear-wall structures (15-story and 30-story) are optimized to illustrate the effectiveness and practicality of the proposed optimum design method.

• 대한기계학회논문집A
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• 제29권9호
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• pp.1262-1269
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• 2005

Thrust of linear motor is one of the important factor to specify motor performance. Maximum thrust can be obtained by increasing the current in conductor and is relative to the sizes of conductor and magnet. But, the current and the size of conductor have an effect on temperature of linear motor. Therefore, it is practically important to find design results that can effectively maximize the thrust of linear motor within limited range of temperature. Finite element analysis was applied to calculate thrust and the temperature of the conductor was calculated by the thermal resistance. The diameter of copper wire among design variables has discrete value and number of turns must be integer. Considering these facts, special techinque for optimum design is presented. To reduce excessive computation time of thrust in optimization, the design variables was redefined by analysis of variance and second order regression model for thrust was determined by response surface metheodology. As a result, it is shown that the proposed method has an advantage in optimum design of linear motor.

• Current Optics and Photonics
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• 제7권5호
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• pp.529-536
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• 2023

The Morlet wavelet transform method is proposed to analyze a single interferogram with spatial carrier frequency that is captured by an optical interferometer. The method can retain low frequency components that contain the phase information of a measured optical surface, and remove high frequency disturbances by wavelet decomposition and reconstruction. The key to retrieving the phases from the low-frequency wavelet components is to extract wavelet ridges by calculating the maximum value of the wavelet transform amplitude. Afterwards, the wrapped phases can be accurately solved by multiple iterative calculations on wavelet ridges. Finally, we can reconstruct the wave-front of the measured optical element by applying two-dimensional discrete cosine transform to those wrapped phases. Morlet wavelet transform does not need to remove the spatial carrier frequency components manually in the processing of interferogram analysis, but the step is necessary in the Fourier transform algorithm. So, the Morlet wavelet simplifies the process of the analysis of interference fringe patterns compared to Fourier transform. Consequently, wavelet transform is more suitable for automated programming analysis of interference fringes and avoiding the introduction of additional errors compared with Fourier transform.