• 대한치과보철학회지
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• 제43권6호
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• pp.727-735
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• 2005

Statement of problem. Platform switching in implant prosthesis has been used for esthetic and biological purpose. But there are few reports for this concept. Purpose. The purpose of this study is evaluation of platform switching in wide implant by three dimensional finite element analysis. Materials and Methods. The single implant and prosthesis was modeled in accordance with the geometric designs for Osstem implant system. Three-dimensional finite element models were developed for (1) a wide diameter 3i type titanium implant 5 mm in diameter, 13 mm in length with wide cemented abutment, titanium alloy abutment screw, and prosthesis (2) a wide diameter 3i type titanium implant 5 mm in diameter, 13 mm in length with regular cemented abutment, titanium alloy abutment screw and prosthesis(platform switching) was made for finite element analysis. The abutment screws were subjected to a tightening torque of 30 Ncm. The amount of preload was hypothesized to 650N, and round and flat type prostheses were loaded to 200 N. Four loading offset point (0, 2, 4, 6 mm from the center of the implants) were evaluated. Models were processed by the software programs HyperMesh and ANSA. The PAM-CRASH 2G simulation software was used for analysis of stress. The PAM-VIEW and HyperView were used for post processing. Results. The results from experiment were as follows; 1. von Mises stress value is increased in order of bone, abutment, implant and abutment screw. 2. von Mises stress of abutment screw is lower when platform switching. 3. von Mises stress of implant is lower when platform switching until loading offset 4 mm. 4. von Mises stress of abutment is similar between each other. 5. von Mises stress of bone is slightly higher when platform switching. Conclusion. The von Mises stress pattern of implant components is favor when platform switch ing but slightly higher in bone stress distribution than use of wide abutment. The research about stress distribution is essential for investigation of the cortical bone loss.

• 소성∙가공
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• 제15권6호
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• pp.445-452
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• 2006

In most of automobile body panel manufacturing, trimming process is generally performed before flanging. To find feasible trimming line is crucial in obtaining accurate edge profile after flanging. Section-based method develops blank along manually chosen section planes and find trimming line by generating loop of end points. This method suffers from inaccurate results of edge profile. On the other hand, simulation-based method can produce more accurate trimming line by iterative strategy. In this study, new fast simulation-based method to find feasible trimming line is proposed. Finite element inverse method is used to analyze the flanging process because final shape after flanging can be explicitly defined and most of strain paths are simple in flanging. In utilizing finite element inverse method, the main obstacle is the initial guess generation for general mesh. Robust initial guess generation method is developed to handle genera] mesh with very different size and undercut. The new method develops final triangular mesh incrementally onto the drawing tool surface. Also in order to remedy mesh distortion during development, energy minimization technique is utilized. Trimming line is extracted from the outer boundary after finite element inverse method simulation. This method has many advantages since trimming line can be obtained in the early design stage. The developed method is verified by shrink/stretch flange forming and successfully applied to the complex industrial applications such as door outer flanging process.

• 한국산학기술학회논문지
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• 제16권10호
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• pp.6673-6678
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• 2015

최근 빈번히 건설되고 있는 비정형 건축물들은, 개별부재의 수직/수평적 연결방식 에서 벗어나, 외관 및 내부 구성요소들의 단면이 자유롭게 변화되는 곡선의 형태를 띠고 있다. 이러한 구조물의 안정성 평가를 위해서 고전적 방식의 유한요소 해석기법이 적용된 상용프로그램이 사용되고 있으나, 과도한 절점분할 방식 또는 유한요소망(Finite Element Mesh)의 도입으로 인하여 해석시간이 길어지고 사용성 및 해석 정밀도가 낮은 문제점을 안고 있다. 따라서 본 연구에서는, 전술된 문제점을 개선하기 위하여, 임의의 곡률을 가진 단위 부재 및 단위요소에 대한 수학적 해석모형을 활용하여 비정형구조물에 대한 구조안정성 평가를 효과적으로 수행할 수 있는 전후처리 모듈을 개발하였다. 본 연구에서 개발된 전후처리 모듈은 곡선형 부재의 곡률을 NURBS 제어점을 이용하여 제어할 수 있도록 개발되었으며, 그로 인해 상용프로그램보다 빠른 형상 모델링이 가능하였다. 또한, 자유로운 형상에 대한 시각적 확인이 가능하여 비정형 건축물의 형상과 거동양상의 현실적인 묘사가 가능하였다.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제32권4호
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• pp.477-493
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• 2018

교과서 저자들은 여러 나라의 교과서 및 교수 학습 자료들을 참고하여 2015 개정 교육과정에서 강조하고 있는 역량들을 담아내고자 하였다. 문제해결, 추론, 의사소통 역량은 2009 개정 교육과정에서 수학적 과정 요소로 이미 강조되어 왔으며, 정보 처리 역량의 경우에는 이전 교육과정부터 계산기와 컴퓨터 사용이 교수 학습 방법 부문에 명시되어 있다(교육부, 2009). 또, 태도 및 실천은 다른 역량과 달리 정의적 영역의 특성을 갖는바, 문제 해결 과정에서 이 역량을 판단하는 것은 쉽지 않다. 그렇다면, 2015 개정 교육과정에 좀 더 관심을 기울이고 새롭게 반영해야 할 역량으로 창의 융합을 들 수 있다. 한편, 2015 개정 수학과 교육과정의 중학교 1학년에 '다양한 상황을 그래프로 나타내고, 주어진 그래프를 해석할 수 있다'는 성취기준이 도입되었다. 교과서마다 주어지는 문제 상황도 다양할 것이고 주어지는 그래프의 유형도 다를 것이다. 본 연구에서는 총 10종의 중학교 1학년 수학 교과서의 그래프 단원을 대상으로 수학 교과서에서의 창의 융합 역량 요소의 반영 현황을 살펴보고자 하였으며, 이를 위하여 선행 연구를 토대로 창의 융합 역량의 하위 요소로 생산적 사고, 독창적 사고, 여러 가지 방법으로 해결, 수학 내적 연결, 수학 외적 연결의 5가지 요소를 선정하여 적용하였다.

• The Korean Journal of Physiology and Pharmacology
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• 제23권3호
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• pp.161-169
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• 2019

Fumigaclavine C (FC), an active indole alkaloid, is obtained from endophytic Aspergillus terreus (strain No. FC118) by the root of Rhizophora stylosa (Rhizophoraceae). This study is designed to evaluate whether FC has anti-adipogenic effects in 3T3-L1 adipocytes and whether it ameliorates lipid accumulation in high-fat diet (HFD)-induced obese mice. FC notably increased the levels of glycerol in the culture supernatants and markedly reduced lipid accumulation in 3T3-L1 adipocytes. FC differentially inhibited the expressions of adipogenesis-related genes, including the peroxisome proliferator-activated receptor proteins, CCAAT/enhancer-binding proteins, and sterol regulatory element-binding proteins. FC markedly reduced the expressions of lipid synthesis-related genes, such as the fatty acid binding protein, lipoprotein lipase, and fatty acid synthase. Furthermore, FC significantly increased the expressions of lipolysis-related genes, such as the hormone-sensitive lipase, Aquaporin-7, and adipose triglyceride lipase. In HFD-induced obese mice, intraperitoneal injections of FC decreased both the body weight and visceral adipose tissue weight. FC administration significantly reduced lipid accumulation. Moreover, FC could dose-dependently and differentially regulate the expressions of lipid metabolism-related transcription factors. All these data indicated that FC exhibited anti-obesity effects through modulating adipogenesis and lipolysis.

• 한국주조공학회지
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• 제30권4호
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• pp.130-136
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• 2010

Sulfide segregation behavior, characteristics of solidification microstructure and compositional distribution in the riser/castings junction of heavy-section main bearing support (MBS) steel castings were investigated; Sulfide streaks of A segregation were formed in the transitional region from columnar grain to coarse equiaxed grain and floated with aggregation of the dendritic free crystal. Solute segregation behaviors of elements Si, P and S were V shape negative segregation from the bottom of the castings to upper part of the riser with the reference of vertical center-line of the specimen block. Those of elements C and Mn were V shape negative segregation in the main body and A shape positive segregation in the riser of the casting. Just beneath the pipe shrinkage in the riser segregation ratio of each element was the highest, and that of S was 3.6 times higher, C 3.3 times, P 2.1 times, Si 1.6 times and Mn 1.0 times respectively. [Mn/S] ratio of the specimen block was distributed in the wide range of 20~275.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.274-278
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• 2002

Surface finishing is still indispensable for most rapid prototyping (RP) processes because of the inherent stair-stepped surface and shrinkage of the parts. These problems can be minimized in the $VLM-_ST$ Process, because it uses expandable polystyrene foam sheets, each of which has a thickness of3.9 mm and a linear-interpolated side slope. The use of thick layers, however, limits the process capability of constructing fine details. This study focuses on the design of post-processing tool for fine details of $VLM-_ST$ parts and investigation of thermal characteristics during EPS foam cutting using the post-processing tool. To calculate the heat flux from the tool into the foam sheet, the tool was modeled as a heat source of radiation for finite element analysis. Results of the analysis agreed well with those of the experiment.

• 대한토목학회논문집
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• 제32권6B호
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• pp.379-385
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• 2012

최근의 컴퓨터 연산 성능의 향상과 전산유체역학 분야의 이론적 발전은 완전한 Navier-Stokes 방정식을 이용한 파랑의 수치모의를 가능하게 하였다. 본 연구에서는 질량원천함수를 이용한 내부조파 기법을 레블셋 유한요소법과 결합하였다. 수치모형은 먼저 2차원 파랑 조파와 전파에 적용되었다. 다음에 같은 문제의 3차원 파랑 모의에 적용되었다. 컴퓨터 자원의 효율적 활용과 연산속도 향상을 위하여 3차원 문제에는 병렬 계산 알고리즘이 고안되어 적용되었다. 수치모의에 의한 계산 결과를 이론적인 값과 비교하였으며, 잘 일치함을 확인할 수 있었다.

• Structural Engineering and Mechanics
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• 제14권6호
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• pp.625-647
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• 2002

Parallel execution of computational mechanics codes requires efficient mesh-partitioning techniques. These mesh-partitioning techniques divide the mesh into specified number of submeshes of approximately the same size and at the same time, minimise the interface nodes of the submeshes. This paper describes a new mesh partitioning technique, employing Genetic Algorithms. The proposed algorithm operates on the deduced graph (dual or nodal graph) of the given finite element mesh rather than directly on the mesh itself. The algorithm works by first constructing a coarse graph approximation using an automatic graph coarsening method. The coarse graph is partitioned and the results are interpolated onto the original graph to initialise an optimisation of the graph partition problem. In practice, hierarchy of (usually more than two) graphs are used to obtain the final graph partition. The proposed partitioning algorithm is applied to graphs derived from unstructured finite element meshes describing practical engineering problems and also several example graphs related to finite element meshes given in the literature. The test results indicate that the proposed GA based graph partitioning algorithm generates high quality partitions and are superior to spectral and multilevel graph partitioning algorithms.

• 소성∙가공
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• 제22권5호
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• pp.250-257
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• 2013

A series of finite element analyses of the rolling process were performed and a neural network algorithm was employed to calculate the amount of ski-effect for an arbitrary thickness of incoming material in the roll gap. Pilot hot plate rolling tests were also conducted to verify the usefulness of the finite element analyzes conducted in this study. In these experiments, plates with thicknesses varying from 25 to 65 mm were tested. In addition, a number of rolling reductions of up to 31% were examined. Finally, a number of circumferential upper and lower rolls were investigated. Experimental validations demonstrated that the neural network algorithm predicted the proper amount of ski when rolling conditions(material thickness, reduction ratio, roll velocity differential) changed arbitrarily.