• 대한기계학회논문집A
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• 제31권12호
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• pp.1173-1179
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• 2007

In recent years, research to machine large-surface micro-features has become important because of the light guide panel of a large-scale liquid crystal display and the bipolar plate of a high-capacity proton exchange membrane fuel cell. In this study, in order to realize the systematic design technology and performance improvements of an ultra-precision machine for machining the large-surface micro-features, a structural characteristic analysis was performed using its virtual prototype. The prototype consisted of gantry-type frame, hydrostatic feed mechanisms, linear motors, brushless DC servo motor, counterbalance mechanism, and so on. The loop stiffness was estimated from the relative displacement between the tool post and C-axis table, which was caused by a cutting force. Especially, the causes of structural stiffness deterioration were identified through the structural deformation analysis of sub-models.

• Journal of Biosystems Engineering
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• 제31권6호
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• pp.500-505
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• 2006

Jujube is one of korean most favorite fruits. Harvesting operations of the jujube farming, however, completely depend on hand labor. Especially, collecting operation requires about three times of hand labor compared with separate operation by impacting or shaking of twigs in the hand-harvesting system of jujube fruits. Consequently, jujube farmers sincerely demand the mechanization of the collecting operation of jujube fruits in the harvesting operation. A new collecting system was designed and constructed five parts-collecting pad, guide ring system, sorting system, frame with driving system, and handle with operation levers, which performed collecting operation of jujube fruits without missing fruits in five part functions, however, an extra future more deliberate study would need how to handle conveniently the collecting pad of the prototype in the narrow space of row of the jujube farm.

• 한국해양공학회지
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• 제17권2호
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• pp.72-76
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• 2003

This paper presents the design concept and operation results of float-off for FSO (340,000 DWT Class, ELF AMENAM KPONO Project) built on the ground, without dry dock facilities. It was the first attempt to build FSO, completely, on the ground and launch it using DBU (Double Barge Unit, which was connected by rigid frame structure.) The major characteristics of FSO, which are similar to general VLCC type hull, including topside structure, weigh 51,000 metric ton. In order to have sufficient stability during the deck immersion of DBU, while passing through a minimum water plane area zone, proper trim control was completed with LMC (Load Master Computer). The major features of the monitoring system include calculation for transverse bending moment, shear force, local strength check of each connector, based on component stress, and deformation check during the load-out and float-off. Another major concern during the operation was to avoid damages at the bottom and sides of FSO, due to motion & movement after free-floating; therefore, adequate clearances between DBU and FSO were to be provided, and guide posts were installed to prevent side damage of the DBU casings. This paper also presents various measures that indecate the connector bending moment, damage stability analysis, and mooring of DBU during float off.

• 한국실내디자인학회논문집
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• 제15권5호
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• pp.60-67
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• 2006

An architecture is a result from representation of design knowledge by architect's creative thinking, and operated only in his internal organization system. Design knowledge based upon the experience that they have achieved in the past as well as the informations they have accumulated over the time. In this point of view, the Schema that formed by problems settlement and process repetitions for the best conclusion, not only play an important part in the designer's thinking system about a specific problem but also appeared by distinctive features. This research looks to achieve a new design method by finding out how architects express traditionality in the contemporary house through schema. This research analyze contemporary house built in seoul of 1990's. The result are as followings. First, Schema is a 'frame' that already exist in the architect's thinking, will make a good guide about express the traditionality. Second, We found out several distinctive characters in the form and the space. The form is divided in five types. It is an condensed form of roof image, the metamorphosis of form grammar, the change of part details, the representation of design principle and the directly expression. Lastly, In the space, it is the borrow of the connection method of inside and external space, the three parts composition of the space, the adaptation of 'Madang' and the Independent composition of the space due to 'Chae'

• 정보교육학회논문지
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• 제11권3호
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• pp.371-378
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• 2007

21세기 IT 선진국을 꿈꾸면서 우리나라는 2001년도부터 초등학교를 비롯한 각급 학교에서 컴퓨터 교육을 실시해 오고 있다. 그러나 기능 위주의 ICT교육은 학생들의 정보 소양 교육에 적당하지 못하다는 지적을 받아왔다. 이에 2005년도에는 "정보통신기술교육 운영지침 개정안" 이 발표되면서 정보 소양 교육이 보다 체계적인 틀을 갖추게 되었다. 뿐만 아니라 전문가들은 컴퓨터 교육에 수행 평가를 도입할 것을 주장하고 있다. 수행평가는 단순한 기능교육 위주의 컴퓨터 교육을 문제 해결 과정으로서의 본격적인 교육을 가능하게 하지만 좋은 수행평가 척도 없이는 소기의 목적을 달성할 수 없다. 따라서 본 논문에서는 정보통신기술교육의 올바른 교육을 위하여 "발표용 문서 작성" 영역의 수행평가 척도를 개발하였다.

• 컴퓨터교육학회논문지
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• 제10권2호
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• pp.17-26
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• 2007

21세기 IT 선진국을 꿈꾸며 우리나라는 2001년도부터 초등학교를 비롯한 각급 학교에서 컴퓨터 교육을 실시해 오고 있다. 그러나 컴퓨터과학을 도외시한 컴퓨터 기능 위주의 정보 소양 교육은 내용 부실이라는 비판을 받아 왔고, 이에 2005년도에는 "정보통신기술교육 윤영지침 개정안"이 발표되면서 컴퓨터과학의 내용이 추가되어 보다 체계적인 틀을 갖추게 되었다. 그러나 정보 사회에서 가장 중요한 능력 중의 하나인 "문제 해결" 능력 신장을 위한 교육과정은 아직 불완전한 모습을 보이고 있다. 따라서 본 논문에서는 "문제 해결" 영역을 중심으로 각국의 초등학교 수준의 컴퓨터 및 수학 교과에서의 교육과정을 분석하고 초등학교 컴퓨터과학 교육과정에서 이루어져야 할 "문제 해결" 영역의 교육과정 개선안을 제안하였다.

• Journal of Power Electronics
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• 제17권1호
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• pp.262-271
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• 2017

This paper studies the performances of five typical Phase-locked Loops (PLLs) for distorted and unbalanced grid, which are the Decoupled Double Synchronous Reference Frame PLL (DDSRF-PLL), Double Second-Order Generalized Integrator PLL (DSOGI-PLL), Double Second-Order Generalized Integrator Frequency-Lock Loop (DSOGI-FLL), Double Inverse Park Transformation PLL (DIPT-PLL) and Complex Coefficient Filter based PLL (CCF-PLL). Firstly, the principles of each method are meticulously analyzed and their unified small-signal models are proposed to reveal their interior relations and design control parameters. Then the performances are compared by simulations and experiments to investigate their dynamic and steady-state performances under the conditions of a grid voltage with a negative sequence component, a voltage drop and a frequency step. Finally, the merits and drawbacks of each PLL are given. The compared results provide a guide for the application of current control, low voltage ride through (LVRT), and unintentional islanding detection.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1249-1254
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• 2010

중앙 안내방식의 모노레일대차 구조는 세계최초로 인천 월미모노레일에 적용되었으며, 대차프레임 소재 또한 우리나라에서는 최초로 알루미늄 재질을 사용하였다. 대차는 수직하중과 수평하중을 노면과 가이드 레일에 전달하는 중요한 시스템으로서 내구성이 충분한 구조를 가지고 있어야 할 뿐만 아니라, 우수한 주행 성능과 승차감이 확보되어야 한다. 본 논문에서는 중앙 안내방식의 모노레일에 적합한 대차 구조를 비롯하여 대차의 주행성능 및 승차감을 확보할 수 있는 시스템 구성 방법은 물론 대차프레임의 내구성을 향상 시킬 수 있는 방안에 대해 제시하였다.

• 소성∙가공
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• 제16권1호
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• pp.42-47
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• 2007

LCD-BLU is one of kernel parts of LCD and it consists of several optical sheets: LGP, light source and mold frame. The LGP of LCD-BLU is usually manufactured by etching process and forming numerous dots with $50\sim300{\mu}m$ diameter on the surface. But the surface of the etched dots of LGP is very rough due to the characteristics of the etching process during the mold fabrication, so that its light loss is high along with the dispersion of light into the surface. Accordingly, there is a limit in raising the luminance of LCD-BLU. In order to overcome the limit of current etched dot patterned LGP, optical pattern with continuous microlens was designed using optical simulation CAE. Also, a mold with continuous micro-lens was fabricated by UV-LiGA reflow process and applied to 7 inch size of navigator LCD-BLU in the present study.

• 소성∙가공
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• 제16권1호
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• pp.48-53
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• 2007

LCD-BLU(Liquid Crystal Display - Back Light Unit) consists of several optical sheets: LGP(Light Guiding Plate), light source and mold frame. The LGP of LCD-BLU is usually manufactured by etching process and forming numerous dots with $50{\mu}m$ in diameter on the surface. But the surface roughness of LGP with etched dots is very high, so there is much loss of light. In order to overcome the limit of current etched dot patterned LGP, optical pattern design with microlens of $50{\mu}m$ diameter was applied in the present study. The microlens pattern fabricated by modified LiGA with thermal reflow process was applied to the optical design of LGP and optical simulation was carried out to know tendency of microlens patterned LGP simultaneously. The attention was paid to the effects of different aspect ratio(i.e. $0.2\sim0.5$) of optical pattern conditions to the brightness distribution of BLU with microlens patterned LGP. Finally, high aspect ratio microlens patterned LGP showed superior results to the one made by low aspect ratio in average luminance.