• 국토계획
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• 제54권1호
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• pp.40-51
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• 2019

The ultimate aim of this study is to diagnose the process stage and look at the step change of transition process to see how the step changes. Therefore, in this study, cluster analysis was conducted by examining four types of commercial characteristics such as Retail Homogeneity, Share of Neighbourhood store, Share of chain store, and Share of cafe & Western food store. Through the cluster analysis, three types have been identified. Type1 is the first step which can explain the time before gentrification occurs and when the ratio of neighborhood facilities is the highest. Type2 is the second step that can explain boutique stage where the gentrification occurs. At this time, the ratio of Cafes & Western food restaurant increased and the proportion of neighborhood shops decreased. And Type3, third step is when the mature gentrification occurs. In the analysis of the transition period, it is necessary to monitor the change of the industry in the period from the first stage to the second stage. In the transition period from the second stage to the third stage, It is necessary to constantly monitor such factors as the increase of shops.

• 한국초전도ㆍ저온공학회논문지
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• 제25권1호
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• pp.16-20
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• 2023

The International Electrotechnical Commission (IEC) 61788-26:2020 provides guidelines for measuring the critical current of Rare-earth barium copper oxide (REBCO) tapes using two methods: linear ramp and step-hold methods. The critical current measurement criterion, 1 or 0.1 μV/cm of electric field from IEC 61788-26 has been normally applied to REBCO coils or magnets. No-insulation (NI) winding technique has many advantages in aspects of electrical and thermal stability and mechanical integrity. However, the leak current from the NI REBCO coil can cause distortion in critical current measurement due to the characteristic resistance which causes the radial current flow paths. In this paper, we simulated the NI REBCO coil by applying both linear ramp and step-hold methods based on a simplified equivalent circuit model. Using the circuit analysis, we analyzed and evaluated both methods. By using the equivalent circuit model, we can evaluate the critical current of the NI REBCO coil, resulting in an estimation error within 0.1%. We also evaluate the accuracy of critical current measurement using both the linear ramp and step-hold methods. The accuracy of the linear ramp method is influenced by the inductive voltage, whereas the accuracy of the step-hold method depends on the duration of the hold-time. An adequate hold time, typically 5 to 10 times the time constant (τ), makes the step-hold method more accurate than the linear ramp method.

• 한국산학기술학회논문지
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• 제11권12호
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• pp.4735-4741
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• 2010

초음파 금속 용착은 신소재, 도금 구조물 등과 같은 다양한 재료의 용착에 대한 가능성 때문에 광범위한 분야에서 사용되고 있으며 용착 조건도 다양하다. 본 연구에서는, 이종 금속 박판의 초음파 금속 용착을 위해 설계된 단부가형 한파장 혼은 유한요소해석 하였다. 유한유소해석은 초음파 혼의 최적 설계와 초음파 공구혼의 고유 주파수를 예상하기 위해 사용되었다. 그리고 설계된 한파장 스텝 혼은 고유 주파수 분석 시스템을 사용하여 실험적으로 검증하였다.

• KIEAE Journal
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• 제14권4호
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• pp.103-109
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• 2014

The purpose of this study was to evaluate the usability and satisfaction of space to which positive elements in Leed-Certified Office Building are applied. The study was conducted using the three-step approach. The first step was to understand the building and identify the issues which included the analysis of floor plans, documentations, and the interview with designers and facility managers. The second step was FGI(Focus Group Interviews), which were conducted with mixed employees of rank and location of workplace. Finally, a web-based questionnaire survey was conducted on the 319 executives and employees. Methods of analysis used were quantitative analysis of questionnaire, qualitative analysis of open ended free-answer, and FGI in the second step. Satisfaction, preference, and comfort level were studied using cross tab, co-relation, ANOVA for quantitative analysis. The results of this study are as follows: First, lobby and atrium are representative elements that are functioning positively and it is recognized as sustainable spaces being utilized by users. Second, there are several dead spaces like green shaft, roof garden and sunken space although they can contribute to Leed-certification. Third, there are some problematic spaces such as the O.A. room and the urinals even though they contribute to the Leed-certification.

• 대한조선학회논문집
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• 제33권4호
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• pp.48-59
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• 1996

비정상 점성유동 수치해석단계는 연속방정식을 만족시키는 공간해석단계와 시간전진단계로 구분할 수 있다. 본 연구에서는 공간해석단계의 압력 Poisson 방정식의 해를 구하는데 스팩트럴법을 이용하였다. 압력 Poisson 방정식의 최고차미분항을 Fourier 급수로 전개하면 압력 및 압력의 1차미분항의 Fourier 급수의 적분으로 표현되므로 Gibb's 현상을 제거할 수 있어, 비주기성인 경우에도 스팩트럴법을 적용할 수 있다. 수치해법의 검증을 위하여 2차원 원주상체 및 날개주위 비정상 점성유동을 수치해석하였고, 그 결과를 비교하여 보았다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 추계학술대회 논문집
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• pp.555-556
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• 2009

• 대한원격탐사학회지
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• 제39권5_1호
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• pp.621-635
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• 2023

시설물 상태평가는 시설물의 사용성을 평가하고, 진단 주기를 결정하는 중요한 과정이다. 현재 수행되고 있는 인력 기반 방법은 안전, 효율, 객관성에 대한 문제를 안고 있어 이를 개선하기 위해 영상을 이용한 딥러닝(deep learning) 기반의 연구가 수행되고 있다. 그러나 시설물 손상 데이터는 발견하기 어려워 다량의 시설물 손상 학습 데이터를 구축하기 어렵고, 이는 딥러닝 기반 상태평가에 한계로 작용한다. 본 연구에서는 영상 기반 시설물 상태평가의 학습 데이터 부족으로 인한 어려움을 개선하기 위해 파운데이션 모델(foundation model) 기반 2-step 시설물 손상 분석을 제시한다. 시설물 상태평가의 요소를 객체화와 정량화로 세분화하고, 정량화 단계에서 영상 분할(segmentation) 파운데이션 모델을 적용하였다. 본 연구의 방법은 기존 영상 분할 방법 대비 10% 포인트 이상 높은 mean intersection over union을 나타냈고, 특히 철근 노출의 경우에는 40% 포인트 이상의 성능 개선을 보였다. 본 연구의 방법이 학습 데이터 구축이 어려운 도메인에 성능 개선을 가져올 것이라 기대한다.

• 한국안전학회지
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• 제32권1호
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• pp.98-107
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• 2017

This study is aimed to design for qualification structure and develop the subjects for examination of the school safety manager qualifications. For the study purpose, job analysis and meetings with experts were performed for extract contents such as task range, criteria of examination, subjects of examination and examination methods, etc. The first step, duties and tasks of the school safety manager were figured out through revised job analysis data of the school safety manager developed before. On the second step, job model was established and developed job specification including importance, difficulty and frequency of each task. On the third step, task specification was developed, and Knowledge-Skill Matrix was the most important thing on examination were completed. The fourth step was the selection of examination subject using task-subject matrix and 6 subjects such as The Principles of Safety, Understanding of the School Safety Manual, Law Related on the School Safety, Introduction to Education, Understanding and Dealing with Type of the School Safety, Establishment of the School Safety Plan were derived from previous procedure. The fifth step was development of guidelines for design examination of each subject. The last step was development for skills education program.

• 대한산업공학회지
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• 제21권4호
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• pp.593-608
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• 1995

In this study two issues are considered, one is to develop a pneumatic servomechanism using a direct-connected circuit between inlet and outlet, the other is to design two kinds of advanced controllers such as fuzzy and PID controllers for a fingering system. Besides, the application of the advanced controllers to the newly proposed servomechanism is presented. The procedure of this study is composed of following 6 steps : [Step 1] Structuring of a control system; [Step 2] Development of a pneumatic circuit for the servomechanism ; [Step 3] Characteristic analysis of the valve and cylinder systems ; [Step 4] Determination of optimal parameters of the PID controller ; [Step 5] Design of a fuzzy controller and parameter tuning; and, [Step 6] Experimental analysis of fuzzy and PID controllers. Experimental results show that the newly proposed pneumatic servomechanism has good performance and, not only the performance of the fuzzy controller is better than that of the PID controller but also the fuzzy controller fits well to the control of the pneumatic servomechanism.

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3301-3312
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• 2023

This study incorporates a high-fidelity transient analysis solver based on multigroup CMFD in the MOC code STREAM. Transport modeling with heterogeneous geometries of the reactor core increases computational cost in terms of memory and time, whereas the multigroup CMFD reduces the computational cost. The reactor condition does not change at every time step, which is a vital point for the utilization of CMFD. CMFD correction factors are updated from the transport solution whenever the reactor core condition changes, and the simulation continues until the end. The transport solution is adjusted once CMFD achieves the solution. The flux-weighted method is used for rod decusping to update the partially inserted control rod cell material, which maintains the solution's stability. A smaller time-step size is needed to obtain an accurate solution, which increases the computational cost. The adaptive step-size control algorithm is robust for controlling the time step size. This algorithm is based on local errors and has the potential capability to accept or reject the solution. Several numerical problems are selected to analyze the performance and numerical accuracy of parallel computing, rod decusping, and adaptive time step control. Lastly, a typical pressurized LWR was chosen to study the rod-ejection accident.