• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.3
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• pp.257-265
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• 2000

Brushless DC(BLDC) motors are widely used as AC servo motors in factory automation fields because of their quick instantaneous mobility, good energy saving efficiency and easiness of design for control system comparing with induction motors. Recently, a Two-Degree-of-Freedom(2DOF) PI control law has been adopted to some application parts to accomplish an advanced speed control of BLDC motors. The method can treat the two conflicting performances, minimum tracking errors versus reference inputs without large overshoot and rejection of some disturbances including modeling errors, independently. However, the method can not design the optimal system which is able to minimize tracking errors and energy consumption simultaneously. In this paper, a 2DOF integral type optimal servo control method is investigated to promote the speed control performances of BLDC motors considering energy consumption. In order to applicate the method to the speed servo system of the BLDC motor, the motor is modeled in the state space using the vector control and decoupling technique. To verify the validity of the suggested method, some simulations and experiments are performed.

• Journal of the Korean association of regional geographers
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• v.21 no.3
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• pp.461-473
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• 2015

The aim of this paper is to explore limits to the institutional formation and operation for network city as a case study of Daegu-Gyeongbuk Free Economic Zone (DGFEZ) in the introductory context. The legal and institutional framework of FEZ in Korea can be characterized by multi-dimensional, vertical or horizontal governance. However, in terms of its implementation process of DGFEZ, the density of the public-private network becomes relatively week, and consequently, the level of participation by local people was not institutionalized in a more collaborative way. With respect to the network city for DGFEZ, while at the initial stage its plan was highly focused upon the conceptual framework of the city, the process of its implementation was based upon a polarization strategy of individual unit and a performance-oriented type. Other evidence for it is that administrative organization in DGFEZ changed from development-based throughout investment attraction-focused up to region-based department. Therefore, there are limits to the institutional formation and operation for the network city in the context of DGFEZ.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.1
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• pp.35-42
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• 2001

본 연구는 변화곡률 수평 곡선보의 면외 자유진동에 관한 연구이다. 뒴과 회전관성을 고려한 변화곡률 수평 곡선보의 자유진동을 지배하는 상미분방정식이 유도되었고, 이 지배미분방정식을 수치해석하여 곡선보의 고유진동수를 산출하였다. 지배미분방정식을 수치적분하기 위하여 Runge-Kutta method를 이용하였고, 고유진동수를 산출하기 위하여 Regula-Falsi method와 결합한 행렬값 탐사법을 이용하였다. 본 연구의 이론적 타당성을 검증하기 위하여 타문헌의 고유진동수와 비교하였고, 실험실 규모의 모형실험을 실시하여 이론값과 실험값의 고유진동수를 비교하였다. 수치해석의 결과로 무차원 재변수들의 변화에 따른 무차원 고유진동수를 제 3모드까지 산출하였고, 그 결과들을 고찰하였다. 본 연구의 결과는 곡선형 교량 등과 같이 곡선부재로 이루어진 구조물의 설계시에 유용하게 이용될 수 있을 것으로 기대된다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.9
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• pp.849-855
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• 2010

This paper investigated the roll lock-in phenomena of a canard-controlled missile with freely spinning tailfins by applying Falanga's roll-rate equation. To confirm and validate the accuracy of the results of the roll-rate and roll lock-in prediction for freely spinning tailfins, the results were compared with Blair's wind tunnel test data. For calculation of the roll-rate of freely spinning tailfins, rolling moment coefficients of the tailfins were obtained from the wind tunnel test data and roll-damping coefficients were calculated by missile DATCOM. The roll-rate and roll lock-in of the freely spinning tailfins were calculated by applying these values to the roll-rate equation for freely spinning tailfins. The calculation results showed good agreement with the wind tunnel test data, and the roll lock-in could be anticipated as well.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.931-936
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• 1995

서울시 중심부 300m 상공에서 약 22kT의 플루토늄 원폭이 폭발했을 때를 가정하고 폭발시 나오는 초기 방사선에 의한 선량을 계산하였다. 계산을 위하여 몬테칼로 코드인 MCNP4A를 이용하였으며 방사선의 위해도를 알아보기 위하여 선량당량으로 환산 하였다. 계산 결과 가까운 거리에서는 평균자유행로가 짧은 중성자에 의한 선량이 높게 나왔으나 거리가 멀어질수록 감마선에 의한 영향이 더 큰 것으로 나타났다.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.3
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• pp.1-9
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• 2011

The purpose of this study is to examine the dynamic characteristics of low, medium and high speed Maglev trains and guideways through dynamic interaction analysis. The coupled dynamic equations of motion for a vehicle of 10-dof and the associated guideway girders are developed by superposing vibration modes of the girder itself. The controller used in the UTM-01 Maglev vehicle is adopted to control the air gap between the bogie and guideway in this study. The effect of roughness, the guideway deflection-ratio and vehicle speed on the dynamic response of the maglev vehicle and guideway are then investigated using the 4th Runge-Kutta method. From the numerical simulation, it is found that the air gap increases with an increase of vehicle speed and the roughness condition. In particular, the dynamic magnification factor of the guideway girder is small at low and medium speeds, but the factor is noticeable at super-high speeds.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.3
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• pp.509-518
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• 1999

교량거동의 동적 특성과 인접거덩간의 충돌의 영향을 파악하기 위하여 여러 단순보로 이루어진 교량시스템의 교축방향에 대한 거동을 분석하였다. 충돌은 물론 교각의 비선형, 그리고 기초의 병진 및 회전운동을 고려할 수 있는 단순화된 다자유도시스템을 소개하고 이에 상응하는 운동방정식을 유도하여 교량거동을 예측하는 방법을 개발하였다. 개발된 다자유도시스템은 지진하중을 받는 교량시스템의 거동분석에 대한 적절한 정보를 제공할 수 있는 것을 밝혔다. 충돌의 주 영향은 강진시 인접거더간의 상대변위를 감소시키며, 미진 시에는 상대적으로 증가시킴을 밝혔다. 따라서, 강진이 아닌 지진하중을 받는 교량의 거동분석 시에도 이러한 충돌로 인한 영향에 대하여 각별한 주의가 필요하다는 것을 제안한다.

• Journal of The Korean Association For Science Education
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• v.31 no.2
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• pp.143-152
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• 2011

The purpose of this study is to investigate the contents of open inquiry activities of the newly revised 2007 National curriculum for each grade level and to teach open inquiry activities and selection of rational inquiry activities. For this study, 470 elementary students in Seoul, ranging from 3rd to 6th grades were surveyed. The experiment plans written by students were analyzed based on the analysis criteria. These criteria consisted of the reason for the selection, type, and suitability of open inquiry activities. The reason for selecting open inquiry activities were analyzed according to the reason why they want to conduct the activity, degree of getting help and the object of getting help. The types of the open inquiry activities were analyzed according to the field of inquiry, the inquiry method and the period of inquiry. Suitability of the open inquiry activities were analyzed according to the reason of suitability or unsuitability.

• The Journal of Bigdata
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• v.5 no.1
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• pp.65-75
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• 2020

This study intends to propose a policy plan for the activation of the Busan Blockchain Regulation-Free Zone, which is selected by the government's comprehensive negative regulation policy. Unlike Europe and the United States, Korea is based on a positive regulation and aims at suppression, not activation. The Korean government proposed a transition to "comprehensive negative regulation" as a groundbreaking regulatory innovation policy to solve the problems of positive regulation. For this implementation plan, seven regulation-free zones were selected. Busan was selected as the Blockchain Regulation-Free Zone, and secured an opportunity to revitalize the stagnant regional economy based on the blockchain. This study is a policy study for the activation of the Busan Blockchain Regulation-Free Zone, and aimed to propose a method to create an industrial ecosystem with the discovery of a Busan-specific Blockchain service that can be commercialized in the Regulation-Free Zone.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.167-174
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• 2021

This study examined the influences of participation in the free semester on school life satisfaction and interest in classes and whether the effect persisted longitudinally. The participants were students from middle schools located in large cities: 451 students in the experimental group and 466 students in the control group. Only the students of the experimental group participated in the free semester. The data were collected at the end of the free semester for three years, and the results are as follows. First, the school life satisfaction of students in the experimental group was significantly higher than those in the control group until the second year but not in the third year. Second, there was no difference in interest in the main subject classes between the experimental and control groups until the third year. Third, students' interest in art and sports classes in the experimental group was significantly higher than those in the control group until the second year but not in the third year. These findings suggest that long-term planning and management of the institution rather than short-term introduction is required for the continuous effects of the free semester.