• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.528-532
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• 1987

Closed-loop fiber-optic gyroscope with linear scale factor for a wide dynamic range is demonstrated using a gating process and two-harmonic phase modulation, of which the second harmonic is obtained by a frequency doubler. Also the effects of the second harmonic and duty cycle of gating signal on the linearity of scale factor are estimated theoretically and compared with the measured data. The experimental results show the best linearity of scale factor is about 0.5% within the rotation rate 90.deg./sec. The closed-loop fiber-optic gyroscope with gated two-harmonic phase modulation can be used in the application demanding less sensitive performance and modest scale factor linearity.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.242-245
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• 1995

In this paper the multiple three rectifiers for the power factor correction are proposed, analyzed and designed. The multiple three phase rectifiers draw sinusoidal ac currents from the ac voltage sources with nearly unity input power factor and operate with PWM making the control circuit simple and system cost low. Outstandingly it reduces the rated power capacity of devices and the input filter size by reducing input current ripples. Moreover design rules can be obtained from input and output current equations. With the proposed rules, input power factor and output power capacity are determined approximately. Finally these design rules are verified with computer simulations.

• The Journal of Asian Finance, Economics and Business
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• 제7권10호
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• pp.555-569
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• 2020

This study examines the impact of corporate tax, a fiscal measure along with trade liberalization and research and development on total factor productivity for a panel of 153 industrial firms listed on the Pakistan Stock Exchange over the period 1997-2017. For empirical analysis, we employ the system generalized method of moment estimator. In the first step, we estimate industrial production function and the results reveal that raw material, industrial labour force and energy play vital role in enhancing industrial production. Whereas, industrial capital exerts negative impact on industrial output. We also measured total factor productivity using the production elasticities. In the second step, we examine the impact of corporate tax, trade liberalization and research and development on total factor productivity. The results indicate that higher level of corporate tax exerts negative impact on total factor productivity. The findings reveal that higher corporate taxation discourages industrial firms to undertake research and development thereby exerting adverse impact on total factor productivity of firms. The impact of trade liberalization proxied by average tariff is positive while customs duty and sales tax negatively impact firm-level total factor productivity. These findings provide useful insights for managers, investors and policy makers in Pakistan.

• 디지털융복합연구
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• 제11권1호
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• pp.1-11
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• 2013

최근 사회복지사들에 대한 클라이언트의 폭력문제는 사회복지서비스에 대한 클라이언트의 권리의식 강화와 더불어 사회복지사들이 대상자들이 생활하는 환경에 노출되면서 폭력문제에 쉽게 노출되어 그 심각성이 커지고 있으나 대다수의 사회복지사들이 클라이언트 폭력에 소극적으로 대응하여 이를 예방할 수 있는 방안에 대한 모색이 제대로 이루어지지 않고 있다. 따라서 본 연구에서는 청소년쉼터 종사자들의 개인적 특성과 기관의 특성이 클라이언트 폭력에 어느 정도로 영향을 미치고 있으며 이 가운데 어떤 요인이 클라이언트 폭력에 영향을 미치는지에 대해 알아보고자 한다. 이를 위해 본 연구에서는 가출청소년 쉼터에서 근무하는 종사자들을 대상으로 설문조사를 실시한 결과 개인적 특성과 기관의 특성에 따른 폭력 경험정도를 비교하기 위해 T검증과 분산분석을 실시한 결과 개인적 특성으로는 연령, 기관의 특성으로는 주당 근무시간과 쉼터유형이 유의미한 차이를 가지는 것으로 나타났다. 다음으로 클라이언트 폭력에 영향을 미치는 관련 요인을 분석하기 위해 다중회귀분석을 실시한 결과 개인적 특성 중 연령이 신체적 폭력, 현 기관 근무연수가 기타 피해와 관련이 있는 것으로 나타났고, 기관의 특성 중 주당 근무시간은 신체적, 재산상, 정서적, 기타 피해 등 폭력의 4가지 유형과 모두 관련이 있는 것으로 나타났으며, 쉼터유형은 재산상 피해, 정서적 폭력 그리고 기타 피해와 관련 있는 것으로 밝혀졌고, 상담시간이 신체적 폭력과 관련이 있는 것으로 나타났다.

• 전기학회논문지
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• 제61권2호
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• pp.199-208
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• 2012

This paper proposes a quasi Z-source DVR(Dynamic Voltage Restorer) system with a series connection of the output terminals, to compensate the voltage variations in the 6.6[kV]/60[Hz] power distribution system. The conventional DVR using one quasi Z-source AC-AC converter has the advantage which it can compensate the voltage variations without the need for the additional energy storage device such as a battery, but it is impossible to compensate for the 50[%] under voltage sags. To solve this problem, a DVR system using two quasi Z-source AC-AC converters with the series connection of the output terminals is proposed. By controlling the duty ratio D in the buck-boost mode, the proposed system can control the compensation voltage. For case verification of the proposed system, PSIM simulation is achieved. As a result, in case that the voltage sags-swells occur 10[%], 20[%], 60[%] in power distribution system, and, in case that the 50[%] under voltage sags-swells continuously occur, all case could compensate by the proposed system. Especially, the compensated voltage THD was examined under the condition of the 10[%]~50[%] voltage sags and the 20[${\Omega}$]~100[${\Omega}$] load changes. The compensated voltage THD was worse for the higher load resistances and more severe voltage sags. Finally, In case of the voltage swells compensation, the compensation factor has approached nearly 1 regardless of the load resistance changes, while the compensation factor of voltage sags was related to the load variations.

• 대한지역사회영양학회지
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• 제14권3호
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• pp.316-326
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• 2009

The purposes of this study were to identify the significance of a nutrition teacher, to analyze the importance of competence as a nutrition teacher and to evaluate the importance and difficulty for duties of nutrition teachers. The questionnaire was distributed to 554 preliminary teachers and a total of 468 usable data were collected with 84.5% of response rate from August to October 2006. The statistical data analysis was completed by using SPSS Win (ver. 10.0) for descriptive analysis, t-test, ANOVA and ${\chi}^2-test$. The results were as follows: Preliminary nutrition teachers expected that conversion of a school dietitian into a nutrition teacher could lead to systematic and constant nutrition education and come into synergic effect by doing meal service with nutrition education. For a teacher's competence, all three paradigms were perceived as important. It was evaluated to be high for a knowledge factor in the empirical analytic paradigm, a personality factor in the practical interpretive paradigm and an attitude factor in the critical emancipatory paradigm. And 'a knowledge for nutrition and sanitation (4.59)' and 'an ability to raise a self-management capacity for right food habit and dietary life (4.59)' were showed as most important in a nutrition teacher. It appeared that both important and difficult duties of nutrition teachers were nutrition education, nutrition counseling and sanitation quality of nutrition education; the most necessary solution was to develop a reference and program for nutrition education (37.4%). In conclusion, the systematic supports of district offices of education and associated institutions as well as sustained efforts of preliminary nutrition teachers for themselves should lead to establish a successful system of nutrition teachers.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.318-320
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• 2003

This paper presents a novel single-stage high frequency resonant DC-DC converter using zero voltage switching with high input power factor. The proposed high frequency resonant converter integrates half-bridge boost rectifier as power factor corrector (PFC) and half-bridge resonant converter into a single stage. The input stage of the half-bridge boost rectifier is working in discontinuous conduction mode(DCM) with constant duty cycle and variable switching frequency. So that a high power factor is achieved naturally. Simulation results through the Pspice have demonstrated the feasibility of the Proposed DC-DC converter. This proposed converter will be able to be practically used as a power supply in various fields as induction heating applications, DC-DC converter etc.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.1030-1033
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• 2002

This paper, a new simple controller operates in continuous conduction mode (CCM) for Boost power factor collection converter is introduced. The duty ratios are obtained by comparisons of a sensed signal from inductor current and a negative ramp carrier waveform in each switching period. By using the proposed controller, input voltage sensing, error amplifier in the current feedback loop, and analog multiplier／divider are not required, then, the control circuit implementation is very simple. To verify the proposed controller, the circuit simulation for Boost power factor correction converter was applied. For the results, the input current waveform was shaped to be closely sinusoidal, implying low THD.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.264-269
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• 1998

A proposed soft-switching buck-boost PWM converter has a lot of advantages, Viz., electric isolation, a high power factor, low switching losses, low EMI noise, reduction of the voltage and current stresses, etc. In a new PFC converter, the switching device is replaced by the loss-less snubber circuit to achieve the zero voltage switching (ZVS) at the maximum current. However, the charging current of the capacitor in the loss-less snubber circuit distorts the input current waveforms. To improve the input current waveform, a new duty factor control method is proposed in this paper.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.635-636
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• 2006

A pulse with modulation(PWM) that keeps a constant angle of dwell and adjust duty ratio is a good method to control a speed of SRM. And a method of one pulse control is proper a operation on range of high speed in SRM for a good energy efficiency. Because PWM method is more safety than one pulse method, conversion of those is best choice according the speed range. So, some algorithm is need for smooth conversion of the mode of control. This paper presents a factor of conversion that proper the conversion of control mode between PWM and one pulse method This factor is from estimation of torque and proper at the variable range of conversion and show the better conversion characteristic than constant factor of conversion.