• 산업경영시스템학회지
• /
• 제44권2호
• /
• pp.140-152
• /
• 2021

During the shift from gasoline vehicles to electric ones, auto parts manufacturing companies have realized the importance of improvement in the manufacturing process that does not require any layout changes nor extra investments, while maintaining their current production rate. Due to these reasons, for the auto part manufacturing company, I-company, this study has developed the simulation model of the PUSH system to conduct a process analysis in terms of production rate, WIP level, and logistics work's utilization rate. In addition, this study compares the PUSH system with other three manufacturing systems -KANBAN, DBR, and CONWIP- to compare the performance of these production systems, while satisfying the company's target production rate. With respect to lead-time, the simulation results show that the improvement of 77.90% for the KANBAN system, 40.39% for the CONWIP system, and 69.81% for the DBR system compared to the PUSH system. In addition, with respect to WIP level, the experimental results demonstrate that the improvement of 77.91% for the KANBAN system, 40.41% for the CONWIP system, and 69.82% for the DBR system compared to the PUSH system. Since the KANBAN system has the largest impacts on the reduction of the lead-time and WIP level compared to other production systems, this study recommends the KANBAN system as the proper manufacturing system of the target company. This study also shows that the proper size of moving units is four and the priority allocation of bottleneck process methods improves the target company's WIP and lead-time. Based on the results of this study, the adoption of the KANBAN system will significantly improve the production process of the target company in terms of lead-time and WIP level.

• 교육녹색환경연구
• /
• 제20권1호
• /
• pp.29-42
• /
• 2021

본 연구는 학생수가 급격히 감소하고 있는 구시가지역의 중장기 학생수 증감 추이, 통학구역 내 학교위치, 통학거리 등을 조사·분석하여 학교 재배치에 도움이 되는 실질적 방안을 제공하고자 하였다. 이를 위하여 선행연구 조사, 사례지역 분석 등을 실시하여 구시가 지역 학교 재배치 모형을 도출하였다. 구시가지역 학교 재배치 모형 도출은 먼저 대상지역과 학교별 학생수의 중장기적 변화추이를 분석하고, 학교별 학생들의 통학거리를 실측하여 통학구역 내의 학교 위치를 본 연구에서 제시한 지역 맞춤형 학교 배치 격자도 모형을 통해 학교를 배치한다. 그리고 학교 재배치 계획은 인근의 도시정비사업과 연계 등을 통해 학교용지를 확보하고 지역 소생활권 계획과 연계한 중장기적 학교 재배치 계획을 수립하여 시행할 필요가 있다.

• 한국환경복원기술학회지
• /
• 제24권4호
• /
• pp.61-75
• /
• 2021

Roadside greenery in the city is not only a means of reducing fine dust, but also an indispensable element of the city in various aspects such as improvement of urban thermal environment, noise reduction, ecosystem connectivity, and aesthetics. However, in studies dealing with the effect of reducing fine dust through trees in existing urban spaces, microscopic aspects such as the adsorption effect of plants were dealt with, structural changes such as the width of urban buildings and streets, and the presence or absence of trees, Impact studies that reflect the actual form of In this study, the effect of greenery composition applicable to urban space on PM2.5 was simulated through the microclimate epidemiologic model ENVI-met, and field measurements were performed in parallel to verify the results. In addition, by analyzing the results of fine dust background concentration, wind speed, and leaf area index, the sensitivity to major influencing variables was tested. As a result of the study, it was confirmed that the fine dust reduction effect was the highest in the case with a high planting amount, and the reduction effect was the greatest at a low background concentration. Based on this, the cost of planting street green areas and the effect of reducing PM2.5 were compared. The results of this study can contribute as a basis for considering the effect of pedestrian space on air quality when planning and designing street green spaces.

• 한국콘텐츠학회논문지
• /
• 제21권5호
• /
• pp.477-487
• /
• 2021

본 연구는 발달장애인을 위한 읽기쉬운자료 개발 교육 시 활용할 수 있는 교재를 개발하는 것을 목적으로 하였다. 교재는 국내외 읽기 쉬운 자료 제작 지침서 분석, 차시 확인 및 교재 내용 개발, 타당도 검증의 단계를 거쳐 개발하였다. 최종 개발된 자료는 독자 구분, 어휘, 상징, 레이아웃, 제작 실습을 포함하여 총 7차시의 교재로 개발하였다. 본 연구에서 개발된 교재의 중요한 특성은 첫째, 국내 최초로 읽기 쉬운 자료를 읽는 독자를 분류하여 보통 읽기(Plain Language) 독자, 읽기 쉬운(Easy to Read) 독자로 소개하였다. 둘째, 읽기 쉬운 자료를 개발하면서 참고할 수 있는 지침을 체크리스트로 개발하여 스스로 점검할 수 있도록 구성하였다. 셋째, 주제별 활동지와 워크북을 개발하여 활동 중심 교재로 활용할 수 있도록 구성하였다.

• 한국융합학회논문지
• /
• 제12권11호
• /
• pp.291-299
• /
• 2021

최근 도시 지역의 고밀도화 및 고층화에 의한 환경 문제로 인해 도심 지역의 공기 유동에 대한 관심이 높아지고 있으며, 이에 따라 건축물의 적절한 형상 및 배치 설계가 요구되고 있다. 본 연구에서는 온도에 따른 색 변화 특성을 갖는 열변색성 염료를 이용하여 건물 주위의 공기 유동 경향을 관찰할 수 있는 실험 방법을 제안하고자 한다. 열변색성 염료는 특정 온도에 대해서만 색이 변하는 특성 때문에 온도 변화를 정밀하게 관찰하기에는 한계가 있지만 실험 모델 및 장비 구성이 용이하고 실험에 소요되는 시간이 짧다는 장점을 가지고 있다. 따라서 본 연구에서는 단순 형상 모델에 대한 CFD 해석을 통하여 건물 주위의 바람에 의한 공기 유동 경향을 분석한 후 열변색 실험 결과와 비교함으로써 제안된 실험 방법의 유용성을 검토하였다. 이러한 실험의 결과로서 열변색성 염료의 특성을 이용하여 도심 건물에 의해 발생되는 박리풍과 와류의 형성 영역을 관찰할 수 있었으며 제안된 방법이 건축물 설계 및 도시 계획에 유용하게 활용될 수 있다는 것을 확인하였다.

• 터널과지하공간
• /
• 제32권3호
• /
• pp.173-193
• /
• 2022

본 연구에서는 GMG (Global Mining Guidelines Group)에서 개발한 광업 분야 가이드라인을 중심으로 스마트 마이닝 기술 국제 표준화 동향을 분석하였다. GMG는 글로벌 광업 커뮤니티를 하나로 묶는 비영리 단체이며, 광업의 안전과 혁신, 지속가능성을 제고시키기 위한 목적으로 설립되었다. 현재 GMG의 실무그룹은 인공지능, 자산관리, 자율 채광, 사이버 보안, 데이터 접근 및 사용/상호 운용성, 전기화, 광물 처리, 지하 채광, 지속가능성 실무그룹으로 구성되어 있다. 스마트 마이닝 기술과 관련한 가이드라인 개발 프로젝트는 인공지능, 자율 채광, 사이버 보안, 데이터 접근 및 사용/상호운용성, 지하 채광 실무그룹에서 진행되고 있다. 2022년 4월 현재 8종의 스마트 마이닝 관련 가이드라인은 사전 착수, 착수, 가이드라인 정의, 콘텐츠 생성, 기술 수정, 레이아웃 및 최종 검토, 투표 과정을 거쳐 출판되었다. GMG에서 출판한 가이드라인은 국내 스마트 마이닝 기술 표준 개발에 있어 중요한 참고 자료가 될 수 있을 것이라 판단된다.

• Nuclear Engineering and Technology
• /
• 제52권12호
• /
• pp.2789-2802
• /
• 2020

Small Modular Reactors (SMRs) are attracting wide attention due to their outstanding performance, extensive studies have been carried out for lead-based fast reactors (LFRs) that cooled with Lead or Lead-bismuth (LBE), and small modular natural circulation LFR is one of the promising candidates for SMRs and LFRs development. One of the challenges for the design small modular natural circulation LFR is to master the natural circulation thermal-hydraulic performance in the reactor primary circuit, while the natural circulation characteristics is a coupled thermal-hydraulic problem of the core thermal power, the primary loop layout and the operating state of secondary cooling system etc. Thus, accurate predicting the natural circulation LFRs thermal-hydraulic features are highly required for conducting reactor operating condition evaluate and Thermal hydraulic design optimization. In this study, a thermal-hydraulic analysis code is developed for small modular natural circulation LFRs, which is based on several mathematical models for natural circulation originally. A small modular natural circulation LBE cooled fast reactor named URANUS developed by Korea is chosen to assess the code's capability. Comparisons are performed to demonstrate the accuracy of the code by the calculation results of MARS, and the key thermal-hydraulic parameters agree fairly well with the MARS ones. As a typical application case, steady-state analyses were conducted to have an assessment of thermal-hydraulic behavior under nominal condition, and several parameters affecting natural circulation were evaluated. What's more, two characteristics parameters that used to analyze natural circulation LFRs natural circulation capacity were established. The analyses show that the core thermal power, thermal center difference and flow resistance is the main factors affecting the reactor natural circulation. Improving the core thermal power, increasing the thermal center difference and decreasing the flow resistance can significantly increase the reactor mass flow rate. Characteristics parameters can be used to quickly evaluate the natural circulation capacity of natural circulation LFR under normal operating conditions.

• 드라이브 ㆍ 컨트롤
• /
• 제19권1호
• /
• pp.43-50
• /
• 2022

The aim of this study was to conduct basic research on the development of a dual-clutch transmission(DCT) and automatic transmission for agricultural tractors. The DCT layout and the DCT simulation model were developed using commercial software. Power transmission efficiency of the DCT and component power loss were analyzed to verify the developed simulation model. Power loss analysis of the components was conducted according to previous studies and ISO(International Organization for Standardization) standards. The power transmission efficiency of the DCT simulation model was 68.4-91.5% according to the gear range. The power loss in the gear, bearing, and clutch DCT system components was 0.75-1.49 kW, 0.77-2.99 kW, and 5.24-10.52 kW, respectively. The developed simulation model not include the rear axle, differential gear, final reduction gear. Therefore actual power transmission efficiency of DCT will be decreased. In a future study, an actual DCT can be developed through the simulation model in this study, and optimization design of DCT can be possible by comparing simulation results and actual vehicle test.

• Structural Engineering and Mechanics
• /
• 제85권1호
• /
• pp.65-80
• /
• 2023

To explore the effect of Engineered Cementitious Composite (ECC) on improving the progressive collapse resistance of reinforced concrete frames under a middle column removal scenario, six beam-column substructures were tested by quasistatic vertical loading. Among the six specimens, four were ECC-concrete composite specimens consisting of different depth of ECC at the bottom or top of the beam and concrete in the rest of the beam, while the other two are ordinary reinforced concrete specimens with different concrete strength grades for comparison. The experimental results demonstrated that ECC-concrete composite specimens can improve the bearing capacity of a beam-column substructure at the stages of compressive arch action (CAA) and catenary action in comparison with ordinary concrete specimen. Under the same depth of ECC, the progressive collapse resistance of a specimen with ECC at the beam bottom was superior to that at the beam top. With the increase of the proportion of ECC arranged at the beam bottom, the bearing capacity of a composite substructure was increased, but the increase rate slows down with the proportion. Meanwhile, the nonlinear numerical analysis software MSC Marc was used to simulate the whole loading process of the six specimens. Theoretical formulas to calculate the capacities of ECC-concrete composite specimens at the stages of flexural action, CAA and catenary action are proposed. Based on the research results, this study suggests that ECC should be laid out at the beam bottom and the layout depth should be within 25% of the total beam depth.

• ETRI Journal
• /
• 제45권1호
• /
• pp.171-179
• /
• 2023

We have developed an InAlAs/InGaAs metamorphic high electron mobility transistor device fabrication process where the gate length can be tuned within the range of 0.13㎛-0.16㎛ to suit the intended application. The core processes are a two-step electron-beam lithography process using a three-layer resist and gate recess etching process using citric acid. An electron-beam lithography process was developed to fabricate a T-shaped gate electrode with a fine gate foot and a relatively large gate head. This was realized through the use of three-layered resist and two-step electron beam exposure and development. Citric acid-based gate recess etching is a wet etching, so it is very important to secure etching uniformity and process reproducibility. The device layout was designed by considering the electrochemical reaction involved in recess etching, and a reproducible gate recess etching process was developed by finding optimized etching conditions. Using the developed gate electrode process technology, we were able to successfully manufacture various monolithic microwave integrated circuits, including low noise amplifiers that can be used in the 28 GHz to 94 GHz frequency range.