• KIEE International Transactions on Electrophysics and Applications
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• 제5C권3호
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• pp.102-110
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• 2005

Piezoelectric transformers(PT) are expected to be small, thin and highly efficient, and which are attractive as a transformer with high power density for step down voltage. For these reasons, we have attempted to develop a step-down PT for the miniaturized adaptor. We propose a PT, operating in thickness extensional vibration mode for step-down voltage. This PT consists of a multi-layered construction in the thickness direction. In order to develop the step-down PT of 10 W class and turn ratio of 0.1 with high efficiency and miniaturization, the piezoelectric ceramics and PT designs are estimated with a variety of characteristics. The basic composition of piezoelectric ceramics consists of ternary yPb(Zr$_{x}$Ti$_{1-x}$)O$_{3}$-(1-y)Pb(Mn$_{1/3}$Nb1$_{1/3}$Sb$_{1/3}$)O$_{3}$. In the piezoelectric characteristics evaluations, at y=0.95 and x=0.505, the electromechanical coupling factor(K$_{p}$) is 58$\%$, piezoelectric strain constant(d$_{33}$) is 270 pC/N, mechanical quality factor(Qr$_{m}$) is 1520, permittivity($\varepsilon$/ 0) is 1500, and Curie temperature is 350 $^{\circ}C$. At y = 0.90 and x = 0.500, kp is 56$\%$, d33 is 250 pC/N, Q$_{m}$ is 1820, $\varepsilon$$_{33}$$^{T}$/$\varepsilon$$_{0}$ is 1120, and Curie temperature is 290 $^{\circ}C$. It shows the excellent properties at morphotropic phase boundary regions. PZT-PMNS ceramic may be available for high power piezoelectric devices such as PTs. The design of step-down PTs for adaptor proposes a multi-layer structure to overcome some structural defects of conventional PTs. In order to design PTs and analyze their performances, the finite element analysis and equivalent circuit analysis method are applied. The maximum peak of gain G as a first mode for thickness extensional vibration occurs near 0.85 MHz at load resistance of 10 .The peak of second mode at 1.7 MHz is 0.12 and the efficiency is 92$\%$.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1991년도 추계학술대회 논문집
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• pp.171-179
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• 1991

This paper refers to the results of a study on the usefulness of simulation techniques based on both modeling and experiments of KICK DOWN pressure control circuit using an duty solenoid valve controlled by pulse width modulation for an automatic transmission. In this study, dynamic characteristics of solenoid valve plunger and first pressure are verified. Besides, this paper shows the design data for improvement of feeling in changing of gear by means of simulation according to varying the size of jet orifice and temperature of automatic transmission fluid, which are the important variables of the first pressure.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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• pp.273-274
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• 2021

This paper proposes a process to calculate the amount of construction and demolition (C&D) of underground vertical extension methods through considering the characteristics of used construction and demolished materials. The underground vertical extension methods analyzed in this paper were the bottom-up, normal top-down, and top-down methods with multi-post downward (MPD). In order to check the applicability of the proposed process, 24 illustrative examples were generated. The amount of C&D waste of the illustrative examples were calculated and compared. As the results, the top-down method with MPD was the most efficient method to reduce the amount of C&D waste.

• 교육녹색환경연구
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• 제11권2호
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• pp.1-8
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• 2012

Due to the fact that there are low birth rate and longer life longevity, schools have been shutting down and converted into welfare facilities. However, most of researches about utilizing closed down school are focused on case researches or architectural planning and design. Moreover, majority of existing welfare centers for the aged are not designed with the flow of human traffic in mind, which means there is no consideration of physical or psychological characteristics of elderly people. That fact leads to increasing number of shutting down welfare facilities. Therefore, this thesis will present the necessity of effective space allocation, extension and reconstruction for residents in aged care by analyzing space using index of space syntax with depth-map software.

• Journal of Advanced Marine Engineering and Technology
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• 제32권2호
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• pp.256-261
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• 2008

The purpose of this study is to propose practicable configurations against Rapid Load Down like propeller racing of ships which have been using SOFC/GT hybrid system on board. This paper suggests four kinds of countermeasures against propeller racing. The types A and B keep a fixed load of SOFC and save a surplus electric power to a storage system. In types of C and D, the load of SOFC is changed with the propeller racing. The best desirable countermeasure for Rapid Load Down depends upon the size of the ship, the propulsion power, and the characteristics of the engine system.

• 전기전자학회논문지
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• 제12권1호
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• pp.34-42
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• 2008

This paper proposes a new on-chip voltage down converter(VDC), which employs a new reference voltage generator(RVG). The converter adopts a temperature-independence reference voltage generator, and a voltage-up converter. The architecture of the proposed VDC has a high-precision, and it was verified based on a 0.25${\mu}m$ 1P5M standard CMOS technology. For 2.5V to 1.0V conversion, the RVG circuit has a good characteristics such as temperature dependency of only 0.2mV/$^{\circ}C$, and the voltage-up circuit has a good voltage deviation within ${\pm}$0.12% for ${\pm}$5% variation of supply voltage VDD. The output voltage is stabilized with ${\pm}$1mV for load current varying from 0 to 100mA.

• 한국전기전자재료학회논문지
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• 제19권2호
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• pp.130-138
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• 2006

We have investigated pattern scaling down of silicon stamps through the oxidation technique, During oxidizing the silicon stamps, silicon dioxide that has 300 nm and 500 nm thickness was grown, and critical deformations were not observed in the patterns. There was positive effect to reduce size of patterns because vertical and horizontal patterns have different orientation. We achieved pattern reduction rate of $26\%$. In addition, the formation of polymer patterns had been investigated with varied temperature and pressure conditions to improve the filling characteristics of polymers during nanoimprint lithography when pattern sizes were few micrometers. In these varied conditions, polymers had been affected by free space compensation and elastic stress relaxation for filling the cavities. Based on the results, defect control which is an important issue in the nanoimprint lithography were facilitated.

• IEIE Transactions on Smart Processing and Computing
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• 제3권6호
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• pp.372-381
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• 2014

This study examined a radar signal active cancelation technique, which is a theoretical way of achieving stealth by employing a baseband process that involves sampling the incoming hostile radar signal, analyzing its characteristics, and generating countermeasure signals to cancel out the linear-FM signal of the hostile radar signal reflected from the airborne target. To successfully perform an active cancelation, the effects of errors in the countermeasure signal were first analyzed. To generate the countermeasure signal that requires very fast and accurate processing, the down-sampling technique with the suboptimal maximum likelihood estimation (sMLE) scheme was proposed to improve the speed of the estimation process while preserving the estimation accuracy. The simulation results showed that the proposed down-sampling technique using a 2048 FFT size yields substantial power reduction despite its small FFT size and exhibits similar performance to the sMLE scheme using the 32768 FFT size.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권12호
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• pp.560-564
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• 2006

ZnO thin films were prepared by RF magnetron sputter deposition on p-Si(100) wafer with various cooling rates of substrate temperature such as the substrates were pre-heated to $400^{\circ}C$ before the deposition and then cooled down naturally or slowly to $300^{\circ}C,\;200^{\circ}C,\;100^{\circ}C$, and R.T. by the temperature controller during the deposition. Crystalline and micro-structural characteristics of the films were investigated by XRD and SEM. ZnO films which cooled down naturally or slowly by the temperature controller during the deposition, especially the film were deposited with cooling down from $400^{\circ}C\;to\;200^{\circ}C$ slowly. showed the most outstanding c-axis preferred orientation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기물성,응용부문
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• pp.39-41
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• 2003

본 논문은 TPMS(Tire Pressure Monitoring System) 개발을 목적으로 압력센서를 무전원/무선 표면탄성파 센서를 이용하여 측정할 수 있는 방법을 연구한 것이다. Touch mode 방식의 압력센서의 경우 Touch down 되었을 때 정전용량은 큰 변화를 가지며 이후 압력의 증가에 대해 선형적으로 증가한다는 것을 이론적인 계산을 통해서 확인하였다. 또한 이와 같은 특성은 표면탄성파 센서의 응답 주파수의 변화를 통해 측정이 가능하다는 이론적인 모델링을 제시하였다.