• 한국소음진동공학회논문집
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• 제23권6호
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• pp.546-552
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• 2013

A cantilevered piezoelectric energy harvester(PEH) and an auxiliary mass-spring unit can be integrated into a novel two-degrees-of-freedom PEH where its lowest eigenmode is not an in-phase modes but an out-of-phase mode. This typical behavior was shown to enhance output power considerably compared with its stand-alone counterpart. The objective of this study is to newly develop a continuum-based mathematical model suitable for efficient analysis of the mode-sequence reversed PEH. Once such a mathematical model is available, various physical behaviors can be analytically investigated for better designs. After a new mathematical model is developed, its validity is checked by using ANSYS results, in terms of resonant frequency, open-circuit voltage, and output power with a specified external resistance.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.708-712
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• 2001

A new phase-shifted parallel-input/series-output (PI SO) dual inductor-fed push-pull converter for high-power step­up applications is proposed. This converter is operated at a constant duty cycle and employs an auxiliary circuit to control the output voltage with a phase-shift between the two modules. It features a voltage conversion characteristic which is linear to changes in the control input, and high step-up ratio with a greatly reduced switch turn-off stress resulting in a significant increase in the converter efficiency. It also shows a low ripple content and low root-mean-square (RMS) current in the output capacitor. The operational principle is analyzed and a comparative analysis with the conventional pulse-width-modulated (PWM) PISO dual inductor-fed push-pull converter is presented. A 50kHz, 800W, 350Vdc prototype with an input of 20-32Vdc has also been constructed to validate the proposed converter. The proposed converter compares favorably with the conventional counterpart and is considered well suited to high-power step-up applications.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.231-234
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• 2003

This paper presents a novel high frequency transformer linked full-bridge type soft-switching phase-shift PWM control scheme DC-DC power converter, which can be used as power conditioner fur small-scale fuel cell power generation system. Using full-bridge soft-switching DC-DC converter topology makes possible to use low voltage high performance MOSFETs to achieve high efficiency of the power conditioner. A tapped inductor filter is implemented in the proposed soft-switching converter topology to achieve soft-switching PWM constant high frequency operation for a wide load variation range. to minimize circulating and idling currents without using additional resonant circuit and auxiliary power switching devices. The practical effectiveness of the proposed soft-switching DC-DC converter is verified in laboratory level experiment with 1 kW 100kHz breadboard setup using power MOSFETs. Actual efficiency of 94-96$\%$ is obtained for the wide load range

• 전력전자학회논문지
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• 제17권3호
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• pp.191-197
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• 2012

This paper proposes a new synthetic test circuit (STC) to confirm the switching operation of thyristor valve in HVDC converter. The proposed STC uses a 6-pulse thyristor converter with 2-phase chopper as a high-current source to provide turn-on current to the test valve. The operation of proposed STC was verified through theoretical analysis and computer simulations. Based on computer simulations, a hardware scaled model was built and tested to confirm the feasibility of implementing a real-size test facility. The proposed system has an advantage of simple structure and operation over the existing system.

• 한국과학교육학회지
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• 제32권3호
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• pp.486-501
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• 2012

The aims of this study are to investigate two main problems for the hypothetico-deduction method and to develop a scientific inquiry model to resolve these problems. The structure of this scientific inquiry model consists of accounts of the context of discovery and justification that the hypothetico-deduction holds as two main problems : 1) the heuristic flaw in the hypothetico-deduction method is that there is no limit to creating hypotheses to explain natural phenomena; 2) Logically, this brings into question affirming the consequent and modus tollens. The features of the model are as follows: first, the generation of hypotheses using an analogical abduction and the selection of hypotheses using consilience and simplicity; second, the expansion phase as resolution for the fallacy of affirming the consequent and the recycle phase as resolution for modus tollens involving auxiliary hypotheses. Finally, we examine the establishment process of Copernicus's Heliocentric Hypothesis and the main role of the history of science for the historical invalidity of this scientific inquiry model based on three examples of If/and/then type of explanation testing suggested by Lawson (International journal of science and Mathematics Education, 2005a, 3(1): 1-5) We claim that this hypotheticho-deduction process involving abduction approach produced favorable in scientific literacy rising for science teacher as well as students.

• Journal of Electrical Engineering and Technology
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• 제8권1호
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• pp.137-143
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• 2013

This paper presents development of variable speed generation (VSG) system with energy saving function. The rubber tyred gantry crane (RTGC) requires the power from diesel-engine. Significant fuel savings by reducing the engine speed can be achieved, because all of operation modes except hoisting are required lower power than rated value of engine. When low speed operation output voltage of generator is decrease until acceptable range of motor driver inverters and auxiliary load supplier. According to power demand engine speed is varying from 20 to 60Hz, and voltage is varying between 210Vac and 480Vac. When idle mode or low power operation dc/dc converter operates by constant output voltage control and inverters dc site voltage is compensated by it. This paper proposed 3-phase interleaved boost converter which has the same structure as the commercially available 3-phase inverter and current sharing capability. 400kW interleaved converter is designed and a performance of converter is evaluated through several experiments with a RTGC system. Energy saving VSG system can cut down fuel consumption by 36% and 21.3% at idle and unidirectional load operations.

• 환경영향평가
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• 제11권2호
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• pp.67-77
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• 2002

Air traffic increased 12% annually in Korea since 1988 after the Olympics, this rate is two times than the rate of the world average. In order to accommodate fast growing aviation demand, Incheon International Airport is operated at Yongjong Island since March, 2001. The Incheon airport project will continue till 2020. After the final phase in 2020, Incheon International Airport will handle 100 million passengers, 530,000 flights and 7 million tons of cargo annually. In this study, air pollution from aircraft and other sources are calculated and assessed in Incheon International Airport area by EDMS(Emission and Dispersion Modeling System), which is a combined emission and dispersion model for airport. EDMS could also be considered power plant, incinerator and aircraft support equipment such as ground support equipment, aerospace ground equipment, auxiliary power units. And EDMS is recommended as preferred model for air quality assessment of the airport area by U.S. EP A. The result of this study shows that NOx emission from aircraft and support utility is estimated as 27,000 - 35,000 ton/yr and Namdong-Gu area in Incheon city is affected as 30-60 ppb by the NOx emission from these sources in 2020, the final phase of Incheon international airport construction.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권7호
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• pp.418-423
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• 2000

The fiber Fabry-Perot interferometric(FFPI) sensor is well known in the field of industrial diagnosis due to its outstanding properties such as tiny size, simple and rugged structure, and easy interrogation. As other fiber interferometric sensors, it also suffers from ambiguous output caused by highly periodic feature in its optical transfer function. In most cases, the ambiguity leads to relatively short dynamic operating range and long processing time during power-on reset, which limits its application to some specific fields requiring very high resolution. In this paper a method based on double sensing scheme was proposed to overcome the above difficulty. By employing a fringe selection auxiliary FFPI sensor the original FFPI sensor can identify its true position on the phase domain. The performance test with 10mm FFPI sensor and a thermocouple temperature sensor for reference shows wide dynamic range 0-900$\ell$ keeping a reasonable resolution of 0.1$\ell$ over the entire range.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.959-961
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• 2004

A multi pole SRM(switched reluctance motor) is applied by the regulated current in regular sequence. So, it can be started by itself. But a single phase SRM can not be started by itself because the positive torque is only generated in the limited zone which the inductance is increased. Therefore, it is required auxiliary device for self starting which place the rotor in start position. The prototype was designed and fabricated in the previous research. It has the permanent magnet, which is installed in the bottom of the rotor, for self starting. But the permanent magnet affect the prototype during operation and cause the decrease of the torque and speed. The influence of the permanent magnet on the average torque and speed was already confirmed. On this paper, the instant torque of the prototype was calculated from the experiment results which is the inductance and current according to installed permanent magnet or not.

• 전기학회논문지
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• 제66권1호
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• pp.211-215
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• 2017

The APF (All Pass Filter) method that utilizes the computational power of the controller is most commonly used. However, since the calculation of the filter coefficient is complicated, the calculation is carried out in advance. It is difficult to apply it to the frequency fluctuation environment because the coefficient value is fixed. In this paper, a new control method of single phase PLL that can be usefully used in PWM converter device for electric railway was explained. Comparison and examination of similarities and differences between the conventional APF method PLL controller method and the newly proposed modified MA filter method PLL technique were performed. The possibility of implementation of the modified MA filter method through computer simulation was analyzed. In conclusion, the method proposed as the conclusion was applied to the APU(Auxiliary Power System) of 8200 Series Electric Locomotive and its usefulness was confirmed.