• 한국기계가공학회지
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• 제9권5호
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• pp.50-56
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• 2010

Meshfree methods show many advantages over finite element method(FEM) in the class of problems for which the remeshing process is inevitable when the conventional FEM used, such as propagating crack problems, large deformation and so on. One of the promising applications of meshfree methods is the adaptive refinement for problems having multi-scale nature. In this study, an adaptive node generation procedure is proposed and several numerical examples are also presented to illustrate the efficiency of proposed method.

• 대한금속재료학회지
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• 제49권8호
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• pp.649-656
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• 2011

The present study evaluated the microstructures and mechanical properties of severely deformed Ni-30Cr alloys. Cross-roll rolling (CRR) process was introduced as a severe plastic deformation (SPD), and Ni-30Cr alloy sheets were cold rolled to 90% thickness reduction and subsequently annealed at $700^{\circ}C$ for 30 min to obtain the recrystallized microstructure. Electron back-scattering diffraction (EBSD) was introduced to analyze grain boundary character distributions (GBCDs). The application of CRR to the Ni-30Cr alloy was effective in enhancing the grain refinement through heat treatment; consequently, the average grain size was significantly refined from $33{\mu}m$ in the initial material to $0.6{\mu}m$. This grain refinement directly improved the mechanical properties, in which yield and tensile strengths significantly increased relative to those of the initial material. We systematically discuss the grain refinement and accompanying improvement of the mechanical properties, in terms of the effective strain imposed by CRR relative to conventional rolling (CR).

• 자원리싸이클링
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• 제30권1호
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• pp.14-25
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• 2021

고품질 철강의 수요가 증가함에 따라 2차 정련 공정의 중요성이 높아지고 있다. 하지만 공정 시간에 따라 변화하는 용강, 슬래그 및 비금속 개재물의 조성은 정련 공정이 평형 상태가 아님을 의미하며, 정련 공정에서는 용강, 슬래그, 비금속 개재물, 내화물 및 합금 원소 간의 동시 다발적 반응이 일어난다. 다양한 상들의 비평형 상태에서 복잡한 반응을 고려하기 위해, 이전 연구자들은 실험을 통해 도출된 반응 속도 수식들을 기반으로 kinetic 기반의 고급강 제조 정련 시뮬레이션 모델을 발표하였다. 정밀한 시뮬레이션 모델의 개발을 위해 보고된 2차 정련 모델들의 분석 및 검토가 필요하다. 본 연구에서는 국내외로 발표된 정련 공정 관련 종합 모델들 및 단일 반응 모델들에 대하여 검토하고 소개하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 Ⅳ
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• pp.2044-2047
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• 2003

In this paper, we propose efficient motion vector refinement algorithm for frame-rate reduction transcoding. The proposed algorithm is to set the search range for motion refinement based on the incoming motion vector. The algorithm calculates the importance of motion vector of the skipped frame and then selects two motion vector to set search range. Through this process, we determine the accuracy of incoming motion vector and set the search range lot refinement adaptively by means of the accuracy. In experiments, we show efficiency of our algorithm to reduce the search points for refinement.

• 한국컴퓨터정보학회논문지
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• 제21권12호
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• pp.97-105
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• 2016

Network-Centric Operational Environment(NCOE) service becomes critical in today's military environment network because reusability of service and interaction are being increasingly important as well in business process. However, the refinement of service by semantic similarity and functional similarity at the business process was not detailed yet. In order to enhance accuracy of refining of business service, in this study, the authors introduce a method for refining service by semantic similarity and functional similarity in BPMN model. The business process are designed in a BPMN model. In this model, candidated services are refined through binding related activities by the analysis result of semantic similarity based on word-net and functional similarity based on properties specification between activities. Then, the services are identified through refining the candidated service. The proposed method is expected to enhance the service identification with accuracy and modularity. It also can accelerate more standardized service refinement developments by the proposed method.

• 대한수학교육학회지:학교수학
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• 제9권4호
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• pp.467-486
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• 2007

이 논문은 스프레드시트를 활용한 수학적 모델링에서 스프레드시트 환경이 수학적 모델의 정교화과정에 어떤 영향을 미치는 지를 고찰한 것이다. 좀 더 자세히 살피면 수학적 모델링에서 스프레드시트 모델의 활용은 학생이 분석 불가능한 수학적모델도 분석할 수 있도록 해줌으로써 모델을 단순화하지 않고, 대신 모델을 정교화 할 수 있는 기회를 제공하고 수학적 개념을 확장해 나갈 수 있음을 보였다. 또한 수학적 모델을 스프레드시트 모델로 변환하여, 수학적 모델로부터 수학적 결론을 얻는 단계를 거치지 않고도 실세계 상황을 해석하고 설명할 수 있는 기회를 제공할 수 있음을 보였다.

• 시스템엔지니어링학술지
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• 제13권1호
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• pp.41-50
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• 2017

Systems engineering is being applied to various fields of industry such as national defense, aerospace, transportation, railway, and information technology industries. But in Korea, systems engineering has been selectively applied to government-driven projects such as space rocket development projects and unmanned flight development projects. And systems engineering processes introduced from international systems engineering standards has been directly applied to those projects. Unfortunately, this application method is not recommended as it requires highly experienced systems engineers. From our previous paper, we have proposed that domain specific engineering standards should be developed to be used as references for development of organizational engineering guide, so that more successful engineering performances can be achieved. And in this paper we have proposed a refinement of systems engineering processes from international systems engineering standards as they are bases of domain specific engineering standards.

• 한국주조공학회지
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• 제17권3호
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• pp.302-308
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• 1997

In spite of the fact that magnesium has low density and good machinability, its applications are restricted as a structural engineering material because of the poor strength, ductility, and corrosion resistance of the conventional ingot metallurgy alloys. Such properties can be improved by microstructural refinement via rapid solidification processing. In this study, Mg-5wt%Zn alloys have been produced as continuous strips by the melt overflow technique. In order to evaluate the influence of the cooling rate on the grain refinement and mechanical properties, seven different thickness strips were produced by means of controlling the speed of the cooling wheel. Then the microstructual observations were undertaken with the objective of evaluating the grain refinement as function of the cooling rate. The tremendous increase in hardness of Mg-Zn alloy was mainly due to the refinement of the grain structure by the effect of rapid solidification. The formation of intermetallic phases on the grain boundaries may have a positive effect on the corroion resistance. Therefore, despite competition from many other developments, the rapid solidification process emerges as a valuable method to develop superior and commercially acceptable magnesium alloys.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.111.1-111.1
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• 2011

The solar energy is dramatically increasing as the alternative energy source and the silicon(Si) solar cell are used the most. In this study, the improved process and equipment for the metallurgical refinement of multicrystalline Si were evaluated for the inexpensive solar cell. The planar plane and columnar dendrite aheadof the liquid-solid interface position caused the superior segregation of impurities from the Si. The solidification rate and thermal gradient determined the shape of dendrite in solidified Si matrix solidified by the directional solidification(DS) method. To simulate this equipment, the commercial software, PROCAST, was used to solve the solidification rate and thermal gradient. Si was vertically solidified by the DS system with Stober process and up-graded metallurgical grade or metallurgical grade Si was used as the feedstock. The inductively coupled plasma mass spectrometry (ICP) was used to measure the concentration of impurities in the refined Si ingot. According to the result of ICP and simulation, the high thermal gradient between the two phases wasable to increase the solidification rate under the identical level of refinement. Also, the separating heating zone equipped with the melting and solidification zone was effective to maintain the high thermal gradient during the solidification.

• 소성∙가공
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• 제8권3호
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• pp.284-293
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• 1999

The rigid-plastic finite element analysis requires a large amount of computation time due to its non-linearity. For economic computation, mismatching refinement, and efficient domain decomposition method with different mesh density for each sub domain, is developed. A modified velocity alternating scheme for the interface treatment is proposed in order to obtain good convergence and accuracy. As a numerical example, the axisymmetric extrusion process is analyzed. The results are discussed for the various velocity update schemes form the viewpoint of convergence and accuracy. The three-dimen-sional extrusion process with rectangular section is analyzed in order to verify the effectiveness of the proposed method. Comparing the results with those of the conventional method of full region analysis, the accuracy and the computational efficiency of the proposed method are then discussed.