• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.24-27
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• 2001

Nowadays, increasing demand of the customized products has led to an increased usage of rapid prototyping in the product development. However, the acquisition price of a rapid prototyping equipment is still too high that not every body can afford to buy one. To offer a wide access to the users who need physical prototypes, a connection of the rapid prototyping equipment to the Internet is a viable step. It would allow a large group of customers all over the world to use the manufacturing capability of a service provider offering this kind of manufacturing service. To realize how such an e-manufacturing concept can look like, a LOM-type 3D printer developed at KIST has been used as test site and connected to the Internet. A possible user can log on to the server of the equipment and view his STL file and start the building operation from a remote place. To see whether the operation runs properly, a CCD camera is used to transmit the actual state of operation online. The result so far proves the feasibility of rapid prototyping on the Internet as well as an order-adaptive manufacturing system via web.

• Journal of Advanced Marine Engineering and Technology
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• 제31권2호
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• pp.138-144
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• 2007

The variation of the crankshaft speed in a multi-cylinder engine is determined by the resultant gas pressure torque and the torsional deformation of the crankshaft. Under steady state operation, the crankshaft speed has a quasi-periodic variation. For the diagnosis the engine instantaneous speed versus crankshaft angle is utilized. This paper describes a simple measurement method of the engine instantaneous speed versus crankshaft angle using the teeth on the flywheel of the crankshaft. Two non-contacting magnetic pickup combinations detect the crank angle and TDC position for the data acquisition. The results from experiments on a 6 cylinder marine diesel engine demonstrate that the crankshaft speed variation are detected with good resolution. And the crankshaft speed variation is investigated according to the operation conditions. Also, it is confirmed that the engine output measured by EMS can be evaluated larger than the actual value due to TDC position error caused by instantaneous speed variation.

• 한국소음진동공학회논문집
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• 제13권6호
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• pp.474-483
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• 2003

In this study, the dynamic characteristics of a catenary system and pantograph supplying electrical power to high-speed trains are investigated. One of the most important issues accompanied by increasing the speed of high-speed rail is stabilization of current collection. To stabilize current collection, it is necessary the contact force between the catenary and the pantograph to be kept continuous without loss of contact. The analytical model of a catenary and a pantograph is constructed to simulate the behavior of an actual system. The analysis of the catenary based on the Finite Element Method (FEM) is performed to develop a catenary model suitable for high speed operation. The reliability of the models is verified by the comparison of the excitation test with Fast Fourier Transform (FFT) data of the actual system. The static deflection of the catenary, stiffness variation in contact lines, dynamic response of the catenary undergoing constant moving load, contact force, and each state of the pantograph model were calculated. It is confirmed that a catenary and pantograph model are necessary for studying the dynamic behavior of the pantograph system.

• 한국산업융합학회 논문집
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• 제8권1호
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• pp.11-17
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• 2005

This study was performed to analysis the operation process when fabric pattern design was done by the use of CAD system compared with the manual work in order to determine the operation efficiency with the application of fabric design CAD system. The results of the study were as follows: 1. since 160,000 colors were supported by CAD system, color proposed by consumer was able to match exactly according to the its design. However, exact color matching was not possible by manual work. 2. Woven state of back of pattern design could be identified simultaneously with face of it for CAD system, while face and back of the fabrics should be designed separatedly in case of manual work. 3. Since the combination of warp and filling yarn was compatible with the fabric density in one repeat unit in CAD system, exact size of pattern design to be woven was able to expressed. 4. Only simple graphical expression by manual work was seen, while with the CAD system, texture and shade effect as well as graphical expression could be expressed and so fault could be reduced in advance with the simulation of actual feeling of fabrics in the screen. In conclusion, when CAD system will be introduced to the textile industry, operation time of designing pattern can be reduced. Since the operation is easy and simple, a beginner can operate CAD system easily. Thus, production and wage costs can be saved and this can be related directly with the improvement of productivity which is the main purpose of introducing CAD system.

• 한국도서관정보학회지
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• 제53권1호
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• pp.31-54
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• 2022

본 연구는 2021년도 여름방학 중에 사서교사(1급) 자격연수를 운영한 K대학교 교육연수원의 사례를 바탕으로, 자격연수가 어떻게 구성 및 운영되는지 교육과정에 대한 실태를 살펴보는데 목적이 있었다. 연구 결과 사서교사(1급) 자격연수에는 초등학교에서 50명(남성 4명, 여성 46명), 중학교에서 24명(남성 4명, 여성 20명), 고등학교에서 37명(남성 5명, 여성 32명), 총 111명의 사서교사들이 참여했다. 또한 자격연수의 교육과정은 '학습자 힘 기르기'의 영역 및 '사서교사 역할 성명서'의 직무 범위에 부합되는 핵심역량과 교과목들로 구성되어 있었으며, 자격연수에 참여했던 사서교사 111명의 만족도는 평균 5점 만점에 4.76점으로 나타났다. 따라서 전반적으로 만족도가 높은 편이이었으나, 가장 낮거나 평균보다 낮았던 부분에 대해 제언하였다.

• 한국정보통신학회논문지
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• 제1권2호
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• pp.209-220
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• 1997

직접위성방송(DBS)은 해상에까지 광범위한 방송서비스를 제공할 수 있는 매우 유용한 매체이다. 그러나 해상에서의 DBS 수신장치는 선박의 운항이나 동요의 상태에 관계없이 안테나가 위성을 계속 추적해야 하는 복잡한 제어장치를 필요로 한다. 본 연구는 한반도 연 근해를 항해하는 선박에서 Koreasat의 DBS를 수신할 수 있는 장치의 개발이 목표였으며, 특히 소형선박에 쉽게 탑재하고 사용할 수 있도록 다른 항법장비와 연계됨이 없이 장치의 독립적인 운용형태로 설계하였고 소형, 경량, 저가격화에 중점을 두었다. 그러므로 한반도 연·근해에서 koreasat의 탐색과 추적조건을 분석하고 이에 적합한 Az/El 2축 마운트를 설계하여 제작하였으며, 스텝트랙(step track) 방식에 의한 추적과 각속도 센서를 이용한 마운트의 동요보정 기능을 연구하였다. 실험을 위하여 장치를 탑재할 수 있는 선박운동 시뮬레이터를 제작하여 목표치의 동요를 구현하고, 추적과 동요보정에 따른 수신상태를 측정, 분석하면서 실험적으로 최적의 알고리즘을 구현하였다.

• Journal of Power Electronics
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• 제3권4호
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• pp.249-258
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• 2003

This paper presents a high-efficient and cost effective three-phase AC/DC-DC/AC power conversion system with a single two-switch type active Auxiliary Resonant DC Link (ARDCL) snubber circuit, which can minimize the total power dissipation. The active ARDCL snubber circuit is proposed in this paper and its unique features are described. Its operation principle in steady-state is discussed for the three phase AC/DC-DC/AC converter, which is composed of PWM rectifier as power factor correction (PFC) converter, sinewave PWM inverter. In the presented power converter system not only three-phase AC/DC PWM rectifier but also three-phase DC/AC inverter can achieve the stable ZVS commutation for all the power semiconductor devices. It is proved that the proposed three-phase AC/DC-DC/AC converter system is more effective and acceptable than the previous from the cost viewpoint and high efficient consideration. In addition, the proposed two-switch type active auxiliary ARDCL snubber circuit can reduce the peak value of the resonant inductor injection current in order to maximize total system actual efficiency by using the improved DSP based control scheme. Moreover the proposed active auxiliary two-switch ARDCL snubber circuit has the merit so that there is no need to use any sensing devices to detect the voltage and current in the ARDCL sunbber circuit for realizing soft-switching operation. This three-phase AC/DC-DC/AC converter system developed for UPS can achieve the 1.8% higher efficiency and 20dB lower conduction noise than those of the conventional three-phase hard-switching PWM AC/DC-DC/AC converter system. It is proved that actual efficiency of the proposed three-phase AC/DC-DC/AC converter system operating under a condition of soft switching is 88.7% under 10kw output power.

• 한국화재소방학회논문지
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• 제26권5호
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• pp.54-60
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• 2012

이 연구는 소방 119구급대에서 근무하는 1급 응급구조사의 병원임상수련 실태를 조사한 연구이다. 조사대상은 소방에 근무하는 1급 응급구조사 42명으로 하였으며, 2012년 5월 11일부터 2012년 5월 12일까지 구조화된 무기명 자기기입식 설문지를 이용한 설문조사에 의하였다. 연구결과 1급 응급구조사의 업무범위를 한 번 이상 직접 경험한 경우는 56.5 %였고, 이들 중 기관내삽관 66.9 %, 후두마스크 8.4 %, 정맥로확보 76.6 %, 니트로글리세린 설하투여 61.2 %, 기관지확장제 흡입 50.0 %, 수액투여 73.8 %, 인공호흡기 사용 57.6 %, 포도당 주입 57.6 %를 경험하였으며, 1급 응급구조사 업무범위를 16개 의료기관별로 살펴본 결과 58.0 %가 한 번 이상 직접 경험하였다. 향후 1급 응급구조사의 교육 요구도에 대한 지속적 연구가 필요하며, 병원임상수련의 문제점 분석, 임상실습지침서의 보완과 실무중심의 교육프로그램 운영 및 관리에 대한 규정과 지속적인 평가가 필요하다.

• Journal of Power Electronics
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• 제16권2호
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• pp.685-694
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• 2016

This paper presents a reliability assessment model for the power semiconductors used in wind turbine power converters. In this study, the thermal loadings at different timescales of wind speed are considered. First, in order to address the influence of long-term thermal cycling caused by variations in wind speed, the power converter operation state is partitioned into different phases in terms of average wind speed and wind turbulence. Therefore, the contributions can be considered separately. Then, in regards to the reliability assessment caused by short-term thermal cycling, the wind profile is converted to a wind speed distribution, and the contribution of different wind speeds to the final failure rate is accumulated. Finally, the reliability of an actual power converter semiconductor for a 2.5 MW wind turbine is assessed, and the failure rates induced by different timescale thermal behavior patterns are compared. The effects of various parameters such as cut-in, rated, cut-out wind speed on the failure rate of power devices are also analyzed based on the proposed model.

• 한국문헌정보학회지
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• 제44권1호
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• pp.137-155
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• 2010

본 연구는 초 중등학교의 학교도서관 관련 학교정보공시 실태를 분석하고 문제점을 파악하여 개선방안을 제안하기 위해 수행되었다. 이를 위해 미국의 학교성과보고서에서 도서관/미디어센터에 대한 정보공개 사례를 살펴보았고 우리나라의 학교정보공시제도 의미와 내용을 정리하였다. 그리고 학교도서관 관련 13개 공시범위를 대상으로 정보공시 실태와 문제점을 파악하고 비교를 통해 개선점을 분석하였다. 연구 결과, 교육주체들에게 학교정보공시를 통해 학교도서관 현황과 가치를 종합적으로 이해하기 쉽게 알리는 데는 공시양식 및 지침서와 학교알리미 서비스 수준이 미흡한 것으로 분석되었다. 이를 토대로, 학교도서관의 공시내용 추가, 공시정보의 가독성 및 활용성, 이용자 편리성, 공시업무 효율성 등에 초점을 두고 몇 가지의 개선방안을 제안하였다.