• 한국정밀공학회지
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• 제7권1호
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• pp.37-52
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• 1990

In this study, the characteristics of cooling and rolling during strip casting process is obtained in comparison with the experimental and analytical results. The prupose of this study is to effectively analyze the thermal and mechanical deformation of roller applying the results of the heat transfer and the pressure distribution to boundary conditions. And then the relation between strip thickness and roll deformation is shown. The second purpose is to obtain the proper condition of the continuous casting for stainless steel. The summary and conclusions can be made on the basis of the results obtained by the theories and experiments. a) The strip casting condition for the fine surface quality of tin-alloy as-cast material was obtained in accordance with the velocity of roll rotation and initial roll gap. b) The experimental condition that the dimension of the cast strip thickness coincide with that of the initial roll gap was according to the experimental result of continuous casting by twin-roll type. c) The thermoelastic finite element model to calculate the roll deformation is represented. Thermoelastic model prediction for the roll deformation are in good agreement with the experimental results considering the thermal expansion of the roll. d) The higher cooling rates were obtained by a twin-roller quenching technique. Also quenched microstructure of the rapidly solidified shell was verified. e) The magnitude of roll deformation due to the thermal expansion and roll separating force is quantit- atively represented in the analysis of continuous casting for stainless steel.

• 설비공학논문집
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• 제19권12호
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• pp.842-849
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• 2007

For a $CO_2$ two-stage twin rotary compressor used for heat pump water heater system, changes of $CO_2$ solubility in PAG oil were investigated along the gas passages from the first stage suction to final discharge. Only slight changes in solubility took place in suction chambers for both of the first and second stages, but for compression chambers, solubility variation ranged from 0.115 to 0.136, and from 0.133 to 0.182, respectively for the first and second stages. Calculation of gas flashing in parts of leakage oil flows and of oil contained in control volumes due to solubility changes was conducted and included in gas pressure calculation. For the second stage, gas flashing amounts to around $5%\sim6%$ for most leakage flows. Cooling capacity, compressor input, and COP obtained by calculation were well compared to the experimental results. Effects of operation speed on the compressor performance was also studied: as the shaft speed increased, adiabatic efficiency decreased rapidly due to increased over-compression loss.

• 복식문화연구
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• 제19권5호
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• pp.1009-1018
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• 2011

The purpose of this study was to develop slacks patterns for middle-aged abdomen-obese adult males by using the 3D virtual-twin and virtual-garment simulation system. The criteria for subjects in this study were males who had over $25kg/m^2$ of BMI, over 90cm of waist, and over 0.90 of WHR. A total of 211 adult males who met these criteria were enrolled. The results were as follows: first, a new slacks pattern considerate of abdomen-obese men was development. The basic numerical formula were as follows: front and back hip girth H/4+3.5, front waist girth W/4+1+0.5, back waist girth W/4+1-0.5, front crotch extension H/16, back crotch extension H/8-0.5, front pleats amount 2.7, and back dart amount 1.5. Second, according to the results of the new slacks patterns appearance evaluation, the new slacks pattern scored more highly than the existing pattern in silhouette and ease amount, confirming that the new slacks pattern is appropriate for the abdomen-obese men. Also, the new slacks pattern was evaluated allowing proper space length of waist, abdomen and hip. Virtual models of production through data from a 3D body scan, pattern draft and virtual garment digital program were applied to a prototypic design method in order to enhance the fitness of ready-made garments. The use of the virtual twin made it impossible to comprehend the appearances and ease correspondent to motions. In order to evaluate wearing fitness, therefore, the system should be improved so as to change arm positions and perform various motions.

• 설비공학논문집
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• 제19권1호
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• pp.19-27
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• 2007

Analytical investigation on the performance of a two stage twin rotary compressor for $CO_2$ heat pump water heater system has been carried out. A computer simulation program was made based on analytical models for gas compression in control volumes, leakages among neighboring volumes, and dynamics of moving elements of the compressor. Calculated cooling capacity, compressor input, and COP were well compared to those of experiments over the compressor speeds tested. For the operating condition of suction pressure of 3 MPa, and discharge pressure of 9 MPa, and compressor inlet temperature of $35^{\circ}C$, the compressor efficiency was calculated to be 80.2%: volumetric, adiabatic, and mechanical efficiencies were 88.3%, 93.2%, and 92.7%, respectively. For the present compressor model, volumetric and adiabatic efficiencies of the second stage cylinder were lower by about $6{\sim}7%$ than those of the first stage mainly due to the smaller discharge port at the second stage. Parametric study on the discharge port size showed that the compressor performance could be improved by 3.5% just by increasing the discharge port diameter by 20%.

• 한국의류산업학회지
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• 제21권1호
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• pp.59-66
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• 2019

The purpose of this study was to develop slacks pattern of elderly women aged over 60s by using the virtual twin and 3D virtual garment simulation system. The results were as follows; first, By using 3D Virtual Garment Simulation, new slacks pattern considered elderly women was development. The basic numerical formula were as follows, front waist girth W/4+2+1.5, back waist girth W/4+1.5+0.5, front hip girth H/4+0.75, back hip girth H/4+1.5, front crotch extension H/16-0.5, back crotch extension H/8-1.3, front dart amount 2 and back dart amount 1.5. Second, according to the results of the new slacks pattern's appearance evaluation, it estimated more highly than existing pattern in silhouette and ease amount, confirming that new slacks pattern is appropriate for the elderly women. Also, new slacks pattern was evaluated to allow proper space length of waist, abdomen and hip. Virtual models production through 3D body scan data, pattern draft and virtual garment digital program were applied to prototypic design method so as to enhance the fitness of ready-made garments. The use of the virtual twin made it impossible to comprehend the appearances and ease correspondent to motions. In order to evaluate wearing fitness, therefore, the system should be improved so as to change arm positions and perform various motions.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 제5회 압연심포지엄 신 시장 개척을 위한 압연기술
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• pp.72-82
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• 2004

The deformation mechanism of hexagonal close-packed materials is quite complicate including slips and twins. A deformation mechanism, which accounts for both slip and twinning, was investigated for polycrystalline hop materials. The model was developed in a finite element polycrystal model formulated with initial strain method where the stiffness matrix in FEM is based on the elastic modulus. We predicted numerically the texture of Mg alloy(AZ31B) sheet by using FEM based on crystal plasticity theory. Also, we introduced the recrystallized texture employed the maximum energy release theory after rolling. From the numerical study, it was clarified that the shrink twin could not be the main mechanism for shortening of c-axis, because the lattice rotation due to twin rejects fur c-axis to become parallel to ND(normal direction of plate). It was showed that the deformation texture with the pyramidal slip gives the ring type pole figure having hole in the center.

• 한국융합학회논문지
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• 제9권9호
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• pp.199-207
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• 2018

본 연구는 4차 산업혁명으로 불리는 생산 패러다임 변화에 선도적으로 대응하기 위해 차세대 생산혁신 기술을 증거기반 키워드 네트워크를 통해 분석하는 것을 목적으로 한다. 분석을 위해 차세대 생산혁신 기술과 관련한 총 441건의 논문데이터를 추출하였고, 이 논문들의 저자 키워드 동시 등장 관계를 기반으로 차세대 생산혁신 기술 네트워크를 구축하였다. 구축된 기술 네트워크를 바탕으로 중심성 및 키워드 그룹 분석을 통해 주요 기술을 탐색하였다. 그 결과 'digital twin', 'modeling and simulation' 등 가상세계와 물리세계를 실시간으로 완벽하게 연결하여 인사이트를 발견하고, 이를 설계 및 공정에 반영하는 기술들이 주요 기술로 분석되었다. 이러한 결과는 관련 산업 내에서 4차 산업혁명으로 인한 변화를 대비하는 기업들에게 의미 있는 정보를 줄 수 있을 것으로 기대된다.

• 디지털융복합연구
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• 제16권7호
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• pp.55-62
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• 2018

미국의 차터스쿨은 규제로부터 자유로우나 결과에 대해 책임지는 선택권 기반의 독립적 공립학교이다. 차터스쿨은 2017년에 출범 25주년을 맞았고 미국 공교육 지평의 하나로 그 위상이 자리를 잡았다. 그러나 단위 차터스쿨에 대한 연구는 아직 미흡한 실정이다. 이 연구의 목적은 성공적인 차터스쿨의 주요 성공요인을 분석하는데 있었다. 이러한 연구 목적을 달성하기 위해 질적연구 접근방법을 선택하여 7차례의 심층면담을 실시하였다. 4명의 교사가 참여하였으며 반구조화된 질문지를 활용하였다. 중요한 연구결과는 다음과 같다. 첫째, 데이튼 차터스쿨의 주요 성공요인으로는 구조적인 요인과 문화적인 요인의 조화를 꼽을 수 있었다. 둘째, 게이트웨이와 어드바이저리는 구조적인 요인의 쌍둥이 시스템으로 작동하였다. 이러한 연구결과는 한국의 교육적 상황에 시사하는 바가 크며, 교육정책적 발전을 위해 활용될 수 있을 것이다.

• 방송공학회논문지
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• 제26권4호
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• pp.390-397
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• 2021

디지털 트윈 기술을 다양한 산업 분야에 응용함에 따라 대용량 데이터를 효과적으로 처리하기 위한 기술들이 필요하다. 본 논문에서는 지하 공동구 관리를 위한 대용량 데이터를 고속 검색하고 효과적인 전달을 위한 맞춤형 서비스 방안에 대해 논한다. 제안하는 방안은 크게 두 가지로 방대한 데이터를 효율적으로 검색하고 축약해서 보여주기 위한 고속 검색 데이터 생성 방법과 맞춤형 정보 서비스 분할 방법에 대해 제안한다. 고속 검색 데이터 생성에서는 지하 공동구 내 센서들에 의해 수집되는 시계열 분석을 위한 동기화 과정에 대해 구성과 데이터 축약에 따른 부가정보 방안에 대해서 논한다. 사용자 맞춤형 서비스 방법에서는 평상시와 재난 시의 사용자 유형을 정의하고 그에 따른 서비스하는 방법에 대해 논한다. 본 연구를 통해 재난 상황에서 대용량 데이터를 효과적으로 검색하고 서비스 받을 수 있는 지하 공동구 관리를 위한 데이터 생성과 서비스 모델에 대한 체계성을 갖출 수 있을 것으로 예상된다.

• 한국산업정보학회논문지
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• 제27권6호
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• pp.127-140
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• 2022

최근 정보통신기술(ICT)의 발달로 산업혁명은 3차 산업에서 4차 산업으로 옮겨가고 있다. 기업이 미래에 생존하기 위해서는 이러한 기술을 채택해야 한다는 것에는 의심의 여지가 없다. 본 연구의 목적은 제4차 산업혁명을 위한 사물인터넷(IoT) 연구 문헌의 지적 구조를 분석하여 해당 분야에 대한 더 나은 통찰력을 제시하는 것이다. 연구 데이터는 Web of Science 데이터베이스에서 추출되었으며, CiteSpace를 사용하여 총 1,631개의 문서와 72,754개의 참고 문헌을 분석하였다. 저자동시인용분석을 이용하여 제4차 산업혁명을 위한 사물인터넷 연구 분야의 지적 구조를 분석하기 위해 군집분석, 타임라인 분석, 연구전환점 분석을 수행하여 'Supply Chain', 'Digital Twin', 'Smart Manufacturing System' 등 12개의 하위 영역을 식별하였다. 타임라인 분석을 통해 연구가 확대되고 있는 분야와 축소되고 있는 분야를 분석하였으며, 연구의 한계점과 향후 연구방향을 결론과 함께 제시하였다.