• 한국태양에너지학회 논문집
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• 제37권6호
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• pp.1-12
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• 2017

The DC link of Grid-Connected 3-Phase 3-Level T-type Photovoltaic PCS (PV-PCS) consists of two series connected capacitors for using their neutral voltage. The mismatch between two capacitor characteristics and transient states happened in load change cause the imbalance of neutral voltage. As a result, PV-PCS performance is degraded and the system becomes unstable. In this paper, a mathematical model for analyzing the imbalance of neutral voltage is derived and a compensation method using offset voltage is proposed, where offset voltage adjusts the applying time of P-type and N-type small vectors. The validity of the proposed methods is verified by simulation and experiment.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.629-634
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• 2000

Generally, the accuracy of motion control systems is strongly influenced by both the mechanical characteristics and servo characteristics of feed drive systems. In the fed drive systems of machine tools that consist of mechanical parts and electrical parts, a torsional vibration is often generated because of its elastic elements in torque transmission. Especially, a torsional vibration caused by the elasticity of mechanical elements might deteriorate the quick movement of system and lead to shorten the life time of the mechanical transmission elements. So it is necessary to analyze the electromechanical system mathematically to optimize the dynamic characteristics of the feed drive system. In this paper, based on the simplifies feed drive system model, radius errors due to position gain mismatch and servo response characteristic have been developed and an optimal criterion for tuning the gain of speed controller is discussed. The proportional and integral parameter gain of the feed drive controller are optimal design variables for the gain tuning of PI speed controller. Through the optimization problem formulation, both proportional and integral parameter are optimally tuned so as to compensate the radius errors by using the genetic algorithm. As a result, higher performance on circular profile tests has been achieved than the one with standard parameters.

• 전기학회논문지
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• 제65권12호
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• pp.2008-2013
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• 2016

This paper proposes analysis and suppression method for reactive power vibration of the slave motor caused by back-EMF mismatch between the master and the slave motor and stator resistance during middle-low speed operation. The master and slave motors are parallel connected dual SPMSMs(Surface mounted Permanent Magnet Synchronous Motors) fed by a single inverter. To suppress vibration of reactive power, RPC(Reactive Power Compensator) proposed in this paper analyzes flux-axis current vibration of the slave motor that occurs in middle-low speed operation using a mathematical model of the fan motor. And RPC adds vibration components detected from flux-axis current of the slave motor to flux-axis current of the master motor. The results of experiment conducted verify the efficacy of the proposed method.

• 한국조리학회지
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• 제22권1호
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• pp.141-152
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• 2016

Recently, not only development of curriculum associated directly with job, the development of new education model is in great need. So, the purpose of this study is to develop the instructional design guideline utilizing goal-based scenario(GBS) for college students who major in culinary arts. First, to achieve this goal, we recognized the 7 core elements(learning goal, mission, cover story, role activity, scenario operating, resource, feedback) composing GBS through literature review and case study. Second, we drew a conclusion about the problem and guideline for traditional culinary practice course by conducting inspection about culinary practice environment and needs with professors who are teaching culinary arts. Third, we applied the instructional design guideline for culinary practice to regular classes according to GBS's factors, and then we did formative evaluation with content experts and educational technology expert. Finally, we designed the final instructional design guideline for culinary practice by modifying early model reflected the result of formative evaluation. The results of this study are as following. First, when we applied GBS to culinary practice, professors have to focus on process of materialization by developing easy scenario to students. Also, they have to prepare the class circumstance to feel about sense of realism in advance. Second, to give a conjugally new skill at working, professors's effort is important. culinary practice education at college has responsibility to carry out the vocational training that has competitiveness and difference with labor market's needs. Therefore, it is necessary for us to develop the teaching and learning model for culinary practice which is suitable for major based on the manpower demand for industry without causing job mismatch from demand for industry.

• 기술혁신학회지
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• 제14권1호
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• pp.22-39
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• 2011

본 논문은 대학 졸업생의 숙련 불일치 문제에 대한 분석의 일환으로 임금으로 대표되는 노동시장성과에 대해 전공-직업 일치의 시각에서 접근한 것이다. 실증 분석에 있어서는 선행연구들에서 자주 제기되었던 표본선택편의 문제를 명시적으로 분석 과정에 반영하였고, 분석의 편의상 이항변수로 취급되었던 전공직업일치 변수도 설문조사가 제공한 다항선택변수로 설정하여 분석하였다. 특히 1982년, 1992년, 2002년 세 코호트에 대한 조사 결과를 활용하여 비교적 장기간에 걸친 노동시장의 구조적 변화도 고려하고자 하였다. 실증분석 결과, 전공일치 직업선택에 따른 표본선택편의와 전공직업일치의 임금효과를 확인할 수 있었다. 또 전공직업일치 정도와 비례해 임금프리미엄도 체증하고, 특히 전공계열별 분석을 통해 사회 계열, 공학 계열, 자연 계열에서 전공과 직업이 일치한 경우 상대적으로 높은 임금을 확인할 수 있었다. 그러나 전공 계열별로 선택편의의 영향에 차이가 있음도 볼 수 있었다. 또 1982년, 1992년, 2002년을 비교하면 1992년에 전공직업일치 경향은 급격히 낮아졌고 1992년과 2002년의 차이는 오히려 크지 않아 이 같은 숙련 불일치 현상이 상당히 오래 전부터 진행되어 온 현상임을 확인할 수 있었다.

• 한국멀티미디어학회논문지
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• 제18권9호
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• pp.1027-1038
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• 2015

For last several decades, the color correction methods have been proposed for HDR(high dynamic range) images. However, color distortion problems take place after correcting the colors such as halos, dominant color as well known. Accordingly, this article presents a novel approach in which the method consists of tone-mapping method and cone response function. In the proposed method, the tone mapping method is used to improve the contrast in the given HDR image based on chromatic and achromatic based on the CIEXYZ tristimulus value, expressed in c/m². The cone response function is used to deal with mismatch between corrected image and displayed image as well as to estimate various human visual effects based on the CMCAT2000 color appearance model. The experimental results show that the proposed method yields better performance of color correction over the conventional method in subjective and quantitative quality, and color reproduction.

• 제어로봇시스템학회논문지
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• 제13권8호
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• pp.743-748
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• 2007

Recently, various types of camera mouse are developed using the image processing. The camera mouse showed limited performance compared to the traditional optical mouse in terms of the response time and the usability. These problems are caused by the mismatch between the size of the monitor and that of the active pixel area of the CMOS Image Sensor. To overcome these limitations, we designed a new input device that uses the face recognition as well as the speech recognition simultaneously. In the proposed system, the area of the monitor is partitioned into 'n' zones. The face recognition is performed using the web-camera, so that the mouse pointer follows the movement of the face of the user in a particular zone. The user can switch the zone by speaking the name of the zone. The multimodal mouse is analyzed using the Keystroke Level Model and the initial experiments was performed to evaluate the feasibility and the performance of the proposed system.

• 전기학회논문지
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• 제59권2호
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• pp.242-247
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• 2010

This paper introduces a real-time load flow program for Korean energy management system(EMS). This study is concentrated on the following aspects. First, we propose the model of the real-time database and power system equipment for the real-time load flow. These models are extracted from the needs of load flow functions and are designed to the application common information. Second, several techniques are applied for the efficient convergence and computational speed. The generation/load mismatch is redistributed using generator participation factors which are separated to the reference bus. For the voltage control, the jacobian matrix is composed with the basic Y matrix elements and the voltage control elements. Through the optimally ordering, jacobian row and column for a column is changed. However all jacobian matrix entries have same order with the Y matrix. The proposed program is tested using the Korea Electric Power Corporation(KEPCO) system. Through the test, we verified that the proposed program can be effectively used to accomplish the Korean EMS system.

• 전력전자학회논문지
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• 제6권2호
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• pp.149-157
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• 2001

본 논문에서는 간단한 외란 관측 기법을 이용한 영구자석형 동기 전동기(Permanent Magnet Syncoronous Motor:PMSM)의 비선형 속도 제어 기법이 제안된다. 피드백 선형화(feedback linearization) 기법을 이용함으로써 비선형 요서가 효과적으로 제거되고 출력 오차 동특성을 선형 제어 기법에 기반하여 설정할 수 있다. 그러나 이 방식은 제어기의 파라미터들이 실제 모터의 파라미터들과 일치하지 않으면 만족스러운 성능을 기대할 수 없다. 본 논문에서는 파라미터들이 실제 모터의 파라미터들과 일치하지 않으면 만족스러운 성능을 기대할 수 없다. 본 논문에서는 파라미터 변동에 의한 비선형 외란을 제거하기 위해 외란 관측 기법을 이용한다. 제안한 방식에는 두개의 축소 차수 관측기만 이용되므로 관측기 설계가 상당히 간단하고 파라미터 추정을 위한 제어기의 계산량에 많은 부담을 주지 않는다. 제안한 관측기를 이용한 비선형 속도 제어 알고리즘이 파라미터 변동에 대해 상인한 제어특성을 가짐을 시뮬레이션과 실험 결과로 입증하였다.

• 한국콘텐츠학회논문지
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• 제12권3호
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• pp.34-43
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• 2012

두 문자열 간의 유사도를 계산하는 문제는 정보 검색, 오타 교정, 스팸 필터링 등 다양한 분야에 응용될 수 있다. 동적 계획법 기반의 유사도 계산 방법을 통하여 한글 문자열의 유사도 계산을 위해서는 우선 음소간의 유사도에 대한 정의가 필요하다. 그러나 기존의 방법들은 수동적 설정에 의한 유사도 점수를 사용하고 있다는 한계점이 있다. 본 논문에서는 PAM(Point Accepted Mutation) 행렬과 유사한 확률 모델을 이용하여 변형 단어 집합으로부터 음소 간의 유사도를 자동적으로 계산하는 기법을 제안한다. 제안 기법은 주어진 변형 단어의 집합 내 유사한 단어 쌍을 찾아 문자열 정렬(Text Alignment)을 수행함으로써 음소 변형 규칙을 도출하고, 이로부터 각 음소 쌍의 상호 변형 빈도에 따른 유사도 점수를 계산한다. 실험 결과 특이도(Specificity) 77.2~80.4% 수준에서 불일치 여부에 따른 단순 점수 부여 방식에 비해서는 10.4~14.1%, 수동으로 음소 간 유사도를 직접 설정하는 방식에 비해서는 8.1~11.8%의 민감도(Sensitivity) 향상이 있음을 확인하였다.