• 대한전기학회논문지
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• 제45권4호
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• pp.474-483
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• 1996

In this paper, as a part of the method improving stability, the load-flow calculation in D.C. power system and the models for stability analysis are studied with A.C-D.C. interconnected power systems transmission performed. Moreover, the theory is established in relation to each control method of D.C. power systems. Then the stability of A.C-D.C.interconnected power systems is compared and considered by the way of dividing the operating control method of the rectifier inverter converter into ACR-AVR, APR-A.gamma.R, A.alpha.R-ACR. The dynamics characteristic of terminal voltage, frequency, active-reactive power and rotor angle of the generator with disturbances and load fluctuations is considered. In addition, the characteristic of direct voltage, direct current, power and control systems. From this the comparative analysis of the direct current control method, the possibility of the stability analysis of A.C.-D.C. interconnected power system is considered. (author). refs., figs., tabs.

• 전기학회논문지
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• 제60권4호
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• pp.711-716
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• 2011

This paper defines a generator reactive reserve considering power system network. Conventional generator reserve is calculated by the difference between the maximum reactive power output of generator and the current reactive power of generator. However, all generators could not affect on the whole power system. Thus, the effective generators should be selected by sensitivity analysis. The sensitivity depends on network configuration is the relation between generator reactive power outputs and reactive power loads. Using the sensitivity, the effective generator reactive reserve can be calculated.

• 한국산학기술학회논문지
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• 제14권6호
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• pp.2839-2843
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• 2013

본 연구에서는 각막굴절력에 따른 누액층 파괴시간(TBUT)의 연관성을 분석하여 콘택트렌즈의 선택 및 착용을 위한 참고자료로 활용하고자 한다. 각막손상 및 안질환이 없는 만 21세부터 27세 이하(평균 $22.87{\pm}1.48$세) 대학생들의 각막곡률반경을 각막곡률계로 측정하였다. 각막굴절력은 곡률반경을 이용하여 계산하였고 TBUT는 각막곡률계의 마이어(mire) 상이 처음으로 왜곡되는 시간으로 측정하였다. 각막굴절력과 TBUT의 관계에서 우안의 경우, 'y=37.921-0.610x'의 관계를 가지며 각막굴절력이 클수록 누액층이 파괴되는 시간이 단축되는 음의 연관성을 나타냈다(r=-0.462, p=0.010). 좌안은 'y=41.894-0.695x'의 관계로서 음의 연관성(r=-0.509, p=0.004)으로 측정되어 좌 우안 모두 각막근시도가 높으면 TBUT는 짧아지는 음의 상관관계가 있는 것으로 분석되었다. 이 결과는 피검자의 각막곡률반경 측정으로 콘택트렌즈 착용여부를 결정하는데 필요한 TBUT의 기본적인 예측이 가능하다.

• 조명전기설비학회논문지
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• 제21권5호
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• pp.99-105
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• 2007

본 논문에서는 초 중 고등학교 전기시설물을 대상으로 전기안전에 대한 현장조사를 하였다. 현장조사는 수전설비, 교실, 과학실 및 음악실 등을 대상으로 연구원, 경력 15년 이상의 전기기술자 및 기타 관련 전문가에 의해 전국적으로 수행하였다. 41개 학교를 대상으로 현장조사를 실시한 결과, 수전설비의 접지방식은 공통접지방식이 지배적이었다. 위험요소로는 선풍기 조절기함의 부재, 실험대 전원의 인체보호용 누전차단기의 미설치, 비접지 콘센트의 사용 등으로 나타났다.

• 전기학회논문지
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• 제58권3호
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• pp.437-443
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• 2009

In recent years, electric power systems have been experiencing a rapid change due to the increasing electricity market. For the effective use of power system under the deregulated environment, it is important to make a fast and accurate calculation of the maximum available transfer capability (ATC) from a supply point to a demand point. In this paper, the purpose of this research is to calculate ATC fast and accurately for securing the stability of system and raising the efficiency as a result of anticipating transmission congestion according to transmission open access progressed in the future under the regulated environment of electricity market. In this paper, a study utilized a relation of the potential energy and energy function by which calculated CCT and then utilized a relation of PEBS for transient stability ATC calculation. In this paper, ATC was calculated as RPF and Energy Function method and calculation results of each method was compared. Contingence ranking method decided the weak bus by the Eigenvalues of Jacobian matrix and overloading branches by PI-index. As a result, a study proved the fast and accurate ATC calculation method considering transient stability suggested in this paper. Through the case study using New England 39 bus system, it is confirmed that the proposed method can be used for real time operation and the planning of electric market.

• 한국유체기계학회 논문집
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• 제17권6호
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• pp.64-68
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• 2014

This paper is intended to provide experimental data for the design of the small VAWT(vertical axis wind turbine). Three types(lift, drag, and hybrid) of the blade of VAWT are tested with digital wind tunnel in this study. From the test, the relation of power coefficient and tip speed ratio for the blades are evaluated and compared each other depending on the blade type. Especially, the characteristics of hybrid blade which is shown to be expanded in the market without any logical data is proposed in the relation of power coefficient and tip speed ratio. It is shown that the hybrid blade can be used to make higher starting torque with trade off of degradation of power coefficient.

• 한국강구조학회 논문집
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• 제11권2호통권39호
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• pp.143-151
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• 1999

본 논문에서는 냉간성형 profiled steel sheeting과 보통강도의 콘크리트로 이루어진 합성보의 휨거동에 관한 연구를 통하여 새로운 형식의 보부재의 사용가능성을 검토하였다. 합성보의 비선형거동을 추적하기 위하여 profiled steel sheeting, 철근 및 콘크리트의 재료비선형을 포함할 수 있는 해석적 방법을 개발하였으며, 합성보의 비선형 모멘트-곡률 관계를 나타낼 수 있는 Power Model식을 제시하였다. Power Model은 원래 보-기둥 접합부의 모멘트-회전각과의 관계를 예측하기 위해 제안된 것이나 합성보에 맞게 수정하였다. 합성보의 하중-처짐 거동은 Power Model에 의한 모멘트-곡률 관계를 이용하여 변위조절법인 단계별 수치적분법을 적용하여 계산하였으며, 실험결과와 비교하였다.

• 전자공학회논문지A
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• 제30A권8호
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• pp.57-62
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• 1993

In this paper, both feasible power gain and power added efficiency at the operating center frequency of 12 GHz are stressed to design a power FET with double-heterjunction structure. The variable parameters or the design are the unit gate width, the gate length, the doping density of AlGaAs, the AlGaAs thickness, the spacer thickness, the Al mole fraction, and the GaAs well thickness. The results of simulation for the FET with 1.mu.m gate length show that the power gain and the power added efficiency are 10.2 dB and 36.3% at 12GHz, respectively. An extrapolation of the relation between current gain and unilateral gain yields a 17 GHz cutoff frequency and 43GHz maximum frequency of oscillation. The calculation of the current versus voltage characteristics show that the output power of the device is about 0.62W.

• International Journal of Precision Engineering and Manufacturing
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• 제3권3호
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• pp.28-36
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• 2002

The continuously variable transmission (CVT) mechanism considered here is the output coupled type which combines the functions of a 2K-H I type differential gear unit and a V-belt type continuously variable unit (CVU). One shaft of the CVU is connected directly to the output shaft and another shaft of it is linked to the differential gear unit. It is shown that some fundamental relations (speed ratios, power flows and efficiencies) for twelve mechanisms previously described are valid by various experimental studies, six of them produce a power circulation and the others produce a power split. Parametric analysis is carried out in relation to the efficiency, speed ratio and power ratios in order to assist in the design of an optimum configuration. Some useful properties associated with power flow modes also are discussed in the output coupled type continuously variable transmission.

• 대한안전경영과학회지
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• 제24권3호
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• pp.47-53
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• 2022

In order to conduct a study on the importance of the wrist joint, which causes a lot of pain among middle-aged people, in relation to work related to musculoskeletal disorders, the effect of stretching on grasping power was studied. In order to compare the grasping power of the wrist for middle-aged people in their 50s, the experiment was conducted by comparing before and after the wrist joint motion stretching. According to the experimental results of wrist gripping power for the control group and the experiment group on wrist gripping power, it was investigated that stretching did not change much in increasing wrist gripping power, but stretching application had an effect on wrist gripping power. In terms of preventing musculoskeletal accidents, reducing pain due to degenerative diseases, and preventing accidents, stretching seems to have an effect when approaching, so it is considered that continuous stretching before and after work is necessary. Therefore, it is suggested that stretching time secured quantitatively through safety and health education before work is necessary.