• 한국CDE학회논문집
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• 제12권3호
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• pp.220-232
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• 2007

Current geometric modeling and analysis are commonly based on B-Rep modeling and a finite elements method respectively. Furthermore, it is difficult to represent an object whose material property is heterogeneous using the B-Rep method because the B-Rep is basically used for homogeneous models. In addition, meshes are required to analyze a property of a model when the finite elements method is applied. However, the process of generating meshes from B-Rep is cumbersome and sometimes difficult especially when the model is deformed as time goes by because the topology of deforming meshes are changed. To overcome those problems in modeling and analysis including homogeneous and heterogeneous materials, we suggest a unified modeling and analysis method based on implicit representation of the model using R-function which is suggested by Rvachev. For implicit modeling of an object a distance field is approximated and blended for a complex object. Using the implicit function mesh-free analysis is possible where meshes are not necessary. Generally mesh-free analysis requires heavy computational cost compared to a finite elements method. To improve the computing time of function evaluation, we utilize GPU programming. Finally, we give an example of a simple pipe design problem and show modeling and analysis process using our unified modeling and analysis method.

• Advances in concrete construction
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• 제5권3호
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• pp.221-240
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• 2017

The modeling of the mechanical behavior of quasi-brittle materials is still a challenge task, mainly in failure processes when fracture and plasticity phenomena become important actors in dissipative processes which occur in materials like concrete, as instance. Many homogenization-based approaches have been proposed to deal with heterogeneous materials in the last years. In this context, a computational homogenization modeling for concrete is presented in this work using the concept of Representative Volume Element (RVE). The material is considered as a three-phase material consisting of interface zone (ITZ), matrix and inclusions-each constituent modeled by an independent constitutive model. The Representative Volume Element (RVE) consists of inclusions idealized as circular shapes symmetrically and nonsymmetrically placed into the specimen. The interface zone is modeled by means of cohesive contact finite elements. The inclusion is modeled as linear elastic and matrix region is considered as elastoplastic material. A set of examples is presented in order to show the potentialities and limitations of the proposed modeling. The consideration of the fracture processes in the ITZ is fundamental to capture complex macroscopic characteristics of the material using simple constitutive models at mesoscopic level.

• 한국방재학회 논문집
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• 제7권5호
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• pp.99-110
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• 2007

A single slab concrete pavement has been modeled and analyzed by ABAQUS program. The stress and displacement of the JCP slab under traffic load with frictionless contact interaction between slab and base calculated by ABAQUS program have been compared with the results obtained by KENSLABS program. The results of the stresses of the two modeling show similar tendency and the difference of the two modeling is very small however the results of the displacement of the two modeling show some dissimilarity. In order to analyze the effects of material and geometric properties on the responses of slab, some varying parameters were chosen as input for the modeling. The changing parameters include the thickness and elastic modulus of the concrete slab, the thickness and elastic modulus of base and the elastic modulus of the subgrade. The contact interaction between the slab and base layer had been also studied and different friction coefficient 0, 2.5, 6.6, 7.5, 8.9 had been used to simulate the different friction interface condition. The results of the analysis showed that the responses of the concrete slab vary with the material and geometric properties of the pavement structure and the slab-base friction condition.

• Computers and Concrete
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• 제6권2호
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• pp.133-153
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• 2009

Discrete element modeling (DEM) in concrete technology is concerned with design and use of models that constitute a schematization of reality with operational potentials. This paper discusses the material science principles governing the design of DEM systems and evaluates the consequences for their operational potentials. It surveys the two families in physical discrete element modeling in concrete technology, only touching upon probabilistic DEM concepts as alternatives. Many common DEM systems are based on random sequential addition (RSA) procedures; their operational potentials are limited to low configuration-sensitivity features of material structure, underlying material performance characteristics of low structure-sensitivity. The second family of DEM systems employs concurrent algorithms, involving particle interaction mechanisms. Static and dynamic solutions are realized to solve particle overlap. This second family offers a far more realistic schematization of reality as to particle configuration. The operational potentials of this family involve valid approaches to structure-sensitive mechanical or durability properties. Illustrative 2D examples of fresh cement particle packing and pore formation during maturation are elaborated to demonstrate this. Mainstream fields of present day and expected application of DEM are sketched. Violation of the scientific knowledge of to day underlying these operational potentials will give rise to unreliable solutions.

• Advances in biomechanics and applications
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• 제1권4호
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• pp.253-267
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• 2014

The human head is identified as the body region most frequently involved in life-threatening injuries. Extensive research based on experimental, analytical and numerical methods has sought to quantify the response of the human head to blunt impact in an attempt to explain the likely injury process. Blunt head impact arising from vehicular collisions, sporting injuries, and falls leads to relative motion between the brain and skull and an increase in contact and shear stresses in the meningeal region, thereby leading to traumatic brain injuries. In this paper the properties and material modeling of the subarachnoid space (SAS) as it relates to Traumatic Brain Injuries (TBI) is investigated. This was accomplished using a simplified local model and a validated 3D finite element model. First the material modeling of the trabeculae in the Subarachnoid Space (SAS) was investigated and validated, then the validated material property was used in a 3D head model. In addition, the strain in the brain due to an impact was investigated. From this work it was determined that the material property of the SAS is approximately E = 1150 Pa and that the strain in the brain, and thus the severity of TBI, is proportional to the applied impact velocity and is approximately a quadratic function. This study reveals that the choice of material behavior and properties of the SAS are significant factors in determining the strain in the brain and therefore the understanding of different types of head/brain injuries.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.579-580
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• 2014

In this research, modeling and analysis of an ultrasonic transducer composed of single crystal piezoelectric material(PMN-28PT) are conducted with FEM in reference with that composed of piezoelectric ceramic(PZT-4). Acoustic performances of the ultrasonic transducer are compared with magnitude, phase of impedance and trasmitting voltage response according to the type of piezoelectric materials.

• 한국CDE학회논문집
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• 제11권4호
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• pp.235-245
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• 2006

This paper proposes a CSG-based representation scheme for heterogeneous objects including multi-material objects and Functionally Graded Materials (FGMs). In particular, this scheme focuses on the construction of complicated heterogeneous objects guaranteeing desired material continuities at all the interfaces. In order to create various types of heterogeneous primitives, we first describe methods for specifying material composition functions such as geometry-independent, geometry-dependent functions. Constructive Material Composition (CMC) and corresponding heterogeneous Boolean Operators (e.g. material union, difference, intersection. and partition) are then proposed to illustrate how material continuities are dealt with. Finally, we describe the model hierarchy and data structure for computer representation. Even though the proposed scheme alone is sufficient for modeling all sorts of heterogeneous objects, the proposed scheme adopts a hybrid representation between CSG and decomposition. That is because hybrid representation can avoid the unnecessary growth of binary trees.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.100-103
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• 2008

Recently Development of construction system that subjective operators share and control information efficiently based on the three-dimensional space and design information throughout life cycle of construction project is progressing dynamically. In case of civil structures which are infrastructure, Demand for structure of complex system which has multi-functions such as super and smart bridges and express rails is increasing and system development which computerizes and integrates process of structure design is in need. For that, research about link way between three dimensional modeling data and structure analysis programs should be preceded. In this research, therefore, research about interface design between three dimensional virtual modeling data to automate efficient civil-structure-design and nonlinear finite element analysis program which is made up of reinforced concrete material model that express material's character clearly.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.135-138
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• 2005

HDL(Hardware Description Language) is the most important modem tools used to describe hardware, and becomes important as we move to higher levels of abstraction. The HDL has been made brisk use of in analog design, MEMS device[1-2], process related field as well as digital design. The most important characteristics of HDL is Abstraction which is the strongest tool that extend greatly designer's design ability. In this paper by the Modelling Continuum with hierarchical structure of abstraction, we apply UML(Unified Modeling Language) to SoC Design with HDL UML makes an easy and visual description of the various levels of abstraction, and gives designers good flexible modeling capabilty for SoC Design.

• 대한공업교육학회지
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• 제43권1호
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• pp.1-19
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• 2018

최근 건설 분야에서 BIM 설계 기술이 의무 적용됨에 따라 실무 현장이나 대학의 건축설계 교육은 3D 모델링 중심으로 크게 변화하고 있다. 그러나 건설 분야 특성화 고등학교에서의 건축설계 교육은 수제도와 2D CAD 중심으로 구성되어 그 변화에 적절하게 대응하지 못하고 있다. 학생들에게는 새로운 건축 설계 흐름에 부합하는 3D 모델링 설계능력을 필수적으로 갖추어야 함에도 불구하고 이를 충족할 수 있는 3D 주택설계 수업자료가 매우 부족한 실정이다. 이 연구는 특성화 고등학교 전문제도 과목을 위한 BIM 기반의 3D 주택설계 수업 자료를 개발하고, 특성화고 학생들에게 적용하여 학생들의 흥미도와 주택설계 과제수행능력이 얼마나 향상되는지를 분석하기 위한 연구이다. 이 연구에 사용되는 3D 주택설계 수업자료는 PDIE 모형 절차에 따라 준비, 개발, 실행, 평가의 4단계를 거쳐 개발하였으며, 가설 검증을 위한 실험설계 모형은 이질통제집단 전후검사설계를 사용하였다. 실험설계 모형에 따라 실험 집단에는 BIM 기반의 3D 주택설계 수업자료를 적용하여 수업을 실시하였으며, 통제 집단에는 2D CAD 기반의 일반적인 주택설계 수업자료로 수업을 실시하였다. 실험 처치는 건설 분야 특성화 고등학교 학생들을 대상으로 실시하였고, 총 12차시의 전문제도 교과 수업에 적용하였다. 실험 처치의 전과 후에는 각각 흥미도와 주택설계 과제수행능력에 대한 검사를 실시하였으며, 검사결과를 바탕으로 독립표본 t-검정을 통해 3D 주택설계 수업자료에 대한 효과를 분석하였다. 이 연구에서 개발된 BIM 기반의 3D 주택설계 수업자료는 학생들의 수업 흥미도를 향상시키는데 효과적이었으며, 기존 2D 기반의 주택설계 수업보다 과제수행능력을 향상시키는 것으로 나타났다.