• 대한기계학회논문집
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• 제19권3호
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• pp.771-783
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• 1995

A simplified model for the so-called ACRT(accelerated crucible rotation technique) Bridgman crystal growth was considered in order to investigate the principal effects of the periodic variation of angular velocity. Numerical solutions were obtained for Ro=0.5, Ra=4.236*10$_{6}$ and E=2.176*10$^{-3}$ . The effects of spin-up process combined with natural convection was investigated as a preliminary study. The spin-up time scale for the present problem was a little larger than that observed for homogeneous spin-up problems. Numerical results reveal that over a time scale of (H$^{2}$/.nu..omega.$_{f}$)$^{1}$2/ the forced convection due to the formation of Ekman layer predominates. When the state of rigid body rotation is attained, natural convection due to buoyancy emerges as the main driving force and them the steady-state is approached asymptotically. Based on our preliminary results with simple spin-up, several fundamental features associated with variation of rotation speed are successfully identified. When a periodic variation of angular velocity was imposed, the system response was also periodic. Due to effect of mixing, the heat transfer was enlarged. From the analysis of time-averaged Nusselt number along the bottom surface the effect of a periodic variation of angular velocity on the interface location could be indirectly identified.d.

• 대한토목학회논문집
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• 제3권2호
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• pp.97-107
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• 1983

비선형(非線型) 2차원조석(次元潮汐)모델의 경기만남부해역(京畿灣南部海域)에의 적용(適用)이 서술(敍述)되었다. 모델을 이용(利用)하여 만체계(灣體系)의 조류유동현상(潮流流動現像), 해저마찰력(海底摩擦力) 및 에너지소산(消散)에 대(對)한 초기평가(初期評價)를 할 수 있었다. 또한 모델에 의(依)한 수치실험(數値實驗)을 통(通)해 아산만접근수로(牙山灣接近水路)를 준설(浚渫)할 경우(境遇) 주태음반일주조(主太陰半日週潮)($M_2$)의 영향(影響) 및 해면(海面)에 작용(作用)하는 $10dyne/cm^2$의 균일정상풍(均一定常風)에 의(依)한 유동현상(流動現像)의 변화(變化)를 평가(評價)하였다. 초기결과(初期結果)들이 제시(提示)되었으며 토의(討議)되었다.

• Coupled systems mechanics
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• 제7권2호
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• pp.233-254
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• 2018

In order to reduce the dependency on fossil fuels, a policy to increase the production capacity of wind turbine is set up. This can be achieved with increasing the dimensions of offshore wind turbine blades. However, this increase in size implies serious problems of stability and durability. Considering the cost of large turbines and financial consequences of their premature failure, it is imperative to carry out numerical simulations over long periods. Here, an energy-conserving time-stepping scheme is proposed in order to ensure the satisfying computation of long-term response. The proposed scheme is implemented for three-dimensional solid based on Biot strain measures, which is used for modeling flexible blades. The simulations are performed at full spatial scale. For reliable design process, the wind loads should be represented as realistically as possible, including the fluid-structure interaction (FSI) dynamic effects on wind turbine blades. However, full-scale 3D FSI simulations for long-term wind loading remain of prohibitive computation cost. Thus, the model to quantify the wind loads proposed here is a simple, but not too simple to be representative for preliminary design studies.

• Journal of Photoscience
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• 제9권3호
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• pp.41-43
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• 2002

PDT-mediated cyototoxicity basically depends on the penetrated light-dose into the tumor tissue. This limits the efficiency of PDT to the superficial tumor region typically less than 1 cm. The localized photochemical generation of reactive oxygen species, including singlet oxygen is known to increase expression of assortment of early response genes including heat shock protein. In order to increase PDT cytotoxicity in the treatment of solid tumor, it is desirable to combine PDT with other therapeutic effects. In this preliminary study we evaluated enhanced cytotoxicity from the PDT-mediated expression of thymidine kinase in a transfected tumor cell line. Two types of photo sensitizers, a hematoporphyrin derivative(Photogem, Russia) and aluminium sulphonated phthalocyanine(Photosense, Russia) were used to evaluate the overexpression of hsp-70 in PDT-treated cell. Transient increase of hsp-70 was observed at 6-8 hrs later following irradiation in the photosense-treated cell whereas it was not observed in Photogem-treated cell. In the presence of ganciclovia, transfected cell showed a 17％ increase in the cytotoxicity compared to the PDT only cell.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1454-1462
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• 2008

This paper is focused on the analysis of the noise and vibration measured near the wheelset of the high-speed trains using a time-varying frequency transform as a preliminary research of running monitoring. Due to the non-stationary characteristics, it is necessary to examine noise and vibration of the train with time-varying frequency transforms. In this paper, the short-time Fourier transform method is utilized - the stored data is localized by modulating with a window function, and Fourier transform is taken to each localized data. For the examination, the non-stationary noise and vibration of the high-speed train's wheelset are measured by using some microphones and accelerometers, and those signals are stored in a on-board data acquisition system. The non-stationary random signal analyses with the short-time Fourier transform are performed, and the result are classified as follows; auto-spectral density, cross-spectral density, frequency response, and coherence functions. From those functions, it is possible to observe the frequency characteristics of sleepers, switchers, tunnels, and steel bridges. Also, some distinct peaks, which are not dependent upon the train's speed, are identified from the results.

• 한국기계가공학회지
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• 제18권1호
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• pp.65-71
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• 2019

The development of adsorbed natural gas (ANG) has emerged as one of potential solutions. It is desirable to reduce the weight of vessel by applying light-weighed a composite carbon fiber in order to response to a egulation of $CO_2$ emission. Through understanding of a composite carbon fiber, and material characteristic of a composite carbon fiber is required in order for better application of a reduction of weight and an analysis of material characteristic. Herein, this study suggest the composite carbon fiber vessel applied to the characteristic of carbon fiber, and it decides the preliminary shape based on the test of material characteristic for ANG vessel applied to a composite carbon fiber, and its basic shape calculate through on the netting theory. Moreover, the detail shape design is analyzed by a finite element analysis, and in the stage of detail sahp design and analysis of stress was performed on the typical shape using a finite element analysis, and the result of preliminary design was verified.

• 산업경영시스템학회지
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• 제44권2호
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• pp.66-77
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• 2021

Companies widely use survey to identify customer requirements, but the survey has some problems. First of all, the response is passive due to pre-designed questionnaire by companies which are the surveyor. Second, the surveyor needs to have good preliminary knowledge to improve the quality of the survey. On the other hand, text mining is an excellent way to compensate for the limitations of surveys. Recently, the importance of online review is steadily grown, and the enormous amount of text data has increased as Internet usage higher. Also, a technique to extract high-quality information from text data called Text Mining is improving. However, previous studies tend to focus on improving the accuracy of individual analytics techniques. This study proposes the methodology by combining several text mining techniques and has mainly three contributions. Firstly, able to extract information from text data without a preliminary design of the surveyor. Secondly, no need for prior knowledge to extract information. Lastly, this method provides quantitative sentiment score that can be used in decision-making.

• 대한지역사회영양학회지
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• 제14권3호
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• pp.316-326
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• 2009

The purposes of this study were to identify the significance of a nutrition teacher, to analyze the importance of competence as a nutrition teacher and to evaluate the importance and difficulty for duties of nutrition teachers. The questionnaire was distributed to 554 preliminary teachers and a total of 468 usable data were collected with 84.5% of response rate from August to October 2006. The statistical data analysis was completed by using SPSS Win (ver. 10.0) for descriptive analysis, t-test, ANOVA and ${\chi}^2-test$. The results were as follows: Preliminary nutrition teachers expected that conversion of a school dietitian into a nutrition teacher could lead to systematic and constant nutrition education and come into synergic effect by doing meal service with nutrition education. For a teacher's competence, all three paradigms were perceived as important. It was evaluated to be high for a knowledge factor in the empirical analytic paradigm, a personality factor in the practical interpretive paradigm and an attitude factor in the critical emancipatory paradigm. And 'a knowledge for nutrition and sanitation (4.59)' and 'an ability to raise a self-management capacity for right food habit and dietary life (4.59)' were showed as most important in a nutrition teacher. It appeared that both important and difficult duties of nutrition teachers were nutrition education, nutrition counseling and sanitation quality of nutrition education; the most necessary solution was to develop a reference and program for nutrition education (37.4%). In conclusion, the systematic supports of district offices of education and associated institutions as well as sustained efforts of preliminary nutrition teachers for themselves should lead to establish a successful system of nutrition teachers.

• 한국전산구조공학회논문집
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• 제17권4호
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• pp.389-403
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• 2004

이 연구에서는 교량의 모드자료를 이용한 구조해석모델의 개선에 관하여 연구하였다. 교량의 초기해석모델은 도면 및 현장조사결과를 바탕으로 작성되므로, 시간에 따라 손실된 강성의 영향 및 경계조건 등을 합리적으로 반영하기 어려우며, 따라서 구조물에 대한 정적 혹은 동적실험을 수행하고, 그 결과를 반영하여 해석모델을 개선하는 것이 바람직하다. 이 연구에서는 구조물의 고유주파수 및 모드형상 등의 모드특성을 바탕으로 추계론적 최적화 기법인 유전자 알고리즘을 이용하여 해석모델을 개선하고자 하였다. 임진강교 및 행주대교에 대한 동적실험 자료를 이용하여 교량의 모드특성을 추정하였으며, 추정된 모드특성을 바탕으로 유전자 알고리즘을 이용하여 수치해석모델을 개선하였다. 개선된 모델을 사용하여 해석한 결과, 초기해석모델에 의한 해석결과보다 실험으로 추정한 모드특성에 가까움을 확인하였고, 이로부터 개선모델의 합리성을 검증하였다.

• 한국기록관리학회지
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• 제22권1호
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• pp.159-176
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• 2022

본 연구에서는 코로나19를 비롯한 각종 감염병 재난에 대한 대학의 대응체계를 마련하기 위해 대학기록관의 코로나19 도큐멘테이션 전략을 수립하였다. 이를 위해 '코로나19 시기 대학'을 주제로 헤크만의 도큐멘테이션 전략을 적용하여 '도큐멘테이션 영역 정의 및 예비분석'과 '전략 설계'를 수행하였다. 먼저, 예비분석 단계에서는 해외 대학의 코로나19 도큐멘테이션 사례조사와 이해관계자 면담조사를 실시하였으며, 다음으로 전략 설계 단계에서는 기록관리 전문요원을 대상으로 면담조사를 실시하였다. 이를 토대로 도큐멘테이션 전략안을 작성하였으며, 기록관리 전문요원으로부터 의견을 수렴한 후, 전략안을 확정하였다. 전략안에는 도큐멘테이션 목적과 영역, 그룹을 비롯한 참고정보, 주요 고려사항 등이 포함되었다. 이 연구는 코로나19 사례를 중심으로 대학기록관의 도큐멘테이션 전략을 개발한 것으로 추후 감염병 재난에 대비한 기록 확보 가이드라인으로 활용될 수 있을 것이다.