• Journal of Mechanical Science and Technology
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• 제20권5호
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• pp.621-633
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• 2006

To reflect the size effect of material $(1\sim15{\mu}m)$ during plastic deformation of polycrystalline copper, a constitutive equation which includes the strain gradient plasticity theory and intrinsic material length model is coupled with the finite element analysis and applied to plane strain deformation problem. The method of least square has been used to calculate the strain gradient at each element during deformation and the effect of distributed force on the strain gradient is investigated as well. It shows when material size is less than the intrinsic material length $(1.54{\mu}m)$, its deformation behavior is quite different compared with that computed from the conventional plasticity. The generation of strain gradient is greatly suppressed, but it appears again as the material size increases. Results also reveal that the strain gradient leads to deformation hardening. The distributed force plays a role to amplify the strain gradient distribution.

• Smart Structures and Systems
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• 제9권5호
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• pp.411-426
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• 2012

Thin-walled adaptive structures render a large and important group of adaptive structures. Typical material system used for them is a composite laminate that includes piezoelectric material based sensors and actuators. The piezoelectric active elements are in the form of thin patches bonded onto or embedded into the structure. Among different types of patches, the paper considers those polarized in the thickness direction. The finite element method (FEM) imposed itself as an essential technical support for the needs of structural design. This paper gives a brief description of a developed shell type finite element for active/adaptive thin-walled structures and the element is, furthermore, used as a tool to consider the aspect of mesh distortion over the surface of actuators and sensors. The aspect is of significance for simulation of behavior of adaptive structures and implementation of control algorithms.

• 한국전기전자재료학회논문지
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• 제13권3호
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• pp.265-272
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• 2000

In this paper the corona discharge in SF$_{6}$ gas used as insulating material in lots o high voltage equipment, is simulated by finite element method with Flux-Corrected Transport(FCT) method. By application of proposed method the negative corona discharge characteristics in needle to plane electrode is analyzed with time step. For the accuracy of analysis the secondary electron emission by photon and ion are also considered as well as the accuracy of analysis the secondary electron emission by photon and ion are also considered as well as townsend first ionization and electron attachment. The calculated results show that the electric field intensity between anode and ion group is decreased as times go-by according to field distortion by those space charge. Accordingly the electron density is decreased strongly by the attatchment effect of SF6 gas so that the corona discharge becomes extinguished abruptly.y.

• 소성∙가공
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• 제28권5호
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• pp.275-280
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• 2019

The aim of this study is to fabricate an ultra-fine pure rhodium wire using multi-pass wire drawing process. To manufacture $30{\mu}m$ ultra-fine rhodium wire from the initial $50{\mu}m$ wire, a multi-pass wire drawing process was designed based on the uniform reduction ratio theory. The elastic-plastic finite element analysis was then conducted to validate the efficacy of the designed process. The drawing load, drawing stress, and the distribution of the effective strain were evaluated using the finite element analysis. Finally, the wire drawing experiment was performed to validate the designed wire drawing process. From the results of the experiment, the diameter of the final drawn wire was found to be $29.85{\mu}m$.

• 대한수학회보
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• 제52권2호
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• pp.363-366
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• 2015

In this note, we prove Gluck's conjecture and Isaacs-Navarro-Wolf Conjecture are true for the solvable groups with disconnected graphs by using Lewis' group structure theorem with respect to the disconnected character degree graphs.

• East Asian mathematical journal
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• 제21권2호
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• pp.205-217
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• 2005

In this paper we consider the fuzzy ideals of N-group G where N is a near-ring. We introduce the concepts: minimal elements, fuzzy linearly independent elements, and fuzzy basis of an N-group G and obtained fundamental related results.

• Kyungpook Mathematical Journal
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• 제56권3호
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• pp.927-938
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• 2016

In this note, we study a monodromy map of a fibered 2-bridge knot. We show the monodromy map of a fibered 2-bridge knot as an element in the automorphism group of a free group.

• 대한수학회보
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• 제51권4호
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• pp.923-931
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• 2014

Let x be an element of a group G and be an automorphism of G. Then for a positive integer n, the autocommutator $[x,_n{\alpha}]$ is defined inductively by $[x,{\alpha}]=x^{-1}x^{\alpha}=x^{-1}{\alpha}(x)$ and $[x,_{n+1}{\alpha}]=[[x,_n{\alpha}],{\alpha}]$. We call the group G to be n-auto-Engel if $[x,_n{\alpha}]=[{\alpha},_nx]=1$ for all $x{\in}G$ and every ${\alpha}{\in}Aut(G)$, where $[{\alpha},x]=[x,{\alpha}]^{-1}$. Also, for any integer $n{\neq}0$, 1, a group G is called an n-auto-Bell group when $[x^n,{\alpha}]=[x,{\alpha}^n]$ for every $x{\in}G$ and each ${\alpha}{\in}Aut(G)$. In this paper, we investigate the properties of such groups and show that if G is an n-auto-Bell group, then the factor group $G/L_3(G)$ has finite exponent dividing 2n(n-1), where $L_3(G)$ is the third term of the upper autocentral series of G. Also, we give some examples and results about n-auto-Bell abelian groups.

• 대한치과교정학회지
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• 제26권2호
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• pp.219-232
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• 1996

본 연구의 목적은 II급 1류 부정교합에서 bionator를 사용한 환자의 치료 전후 두부방사선계측사진에 유한요소법을 적용하여 나타난 변화를 각 요소별로 나타내며, 이러한 변화와 치료에 영향을 미치는 인자들 간의 연관성을 살펴보는데 있다. 앵글 II급 1류 부정 교합을 가진 73명을 치료결과가 양호한 군(1군)과 치료결과가 불량한 군(2군)으로 나눈 후 각각의 치료효과에 대한 유한요소분석을 실시한 후 성별간, 치료결과군간 및 치료시작시기와의 유의성을 검증하였으며 (SAS ANOVA, p<0.05), 치료기간과의 상관관계를 살펴보았다. 또한 치료결과가 다르게 나오는 이유를 보고자 두개저의 길이(Ba-N)를 기준으로 1군에서 2군으로 유한요소분석을 실시하여 다음의 결과를 얻을 수 있었다. 1. 치료효과와 성별간, 치료결과군간 사이에 유의한 차이가 없었다 (p>0.05). 2. 치료시작 연령과 치료효과 사이에 유의한 차이가 없었다(p>0.05). 3. 치료효과와 치료기간 사이에서는 상악체, 상악절치, 하악절치, 전안면, 전상안면, 전하안면, 하악지 등을 대표하는 유한요소에서 유의한 차이(p<0.05)가 있었으나, 상관관계는 높지 않았다. 4. 유한요소 분석 결과 골격보다는 치아를 대표하는 요소의 변화가 더 컸다. 특히 상악절치의 위치, 하악절치의 위치, overbite 등을 나타내는 요소의 변화를 뚜렷하게 관찰할 수 있었다. 5. 치료결과가 다르게 나타나는 이유를 두개저 (Ba-N)의 길이를 중심으로 유한요소로 분석 한 결과 두군사이에 골격 및 치아의 위치에서 상당한 차이가 있음을 관찰할 수 있었다. 치료결과가 나쁜 군에서 상악의 후하방 회전, 하악의 후방위치, 상악전치의 상대적인 설측경사, 하악절치의 상대적인 순측경사 등을 관찰할 수 있었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.394-401
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• 2006

This study developed two dimensional finite element program(FE-SCP) for the analysis of a composite ground reinforced by sand compaction piles with a low area replacement ratio based on the Mohr-Coulomb elastic perfectly plastic constitutive model. Program FE-SCP give some conveniences to users such as automatic mesh generation according to the replacement ratio and the effective sand pile diameter in the post processor. Also, it contains optimum processor in calculation of In-situ stress equilibrium considering different coefficient of earth pressure between sand pile and surrounding clay. Estimated stress-strain behavior using FE-SCP and the measured one from a centrifuge test showed good agreement comparing to the result from a general finite element program.