• Journal of Advanced Marine Engineering and Technology
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• 제19권3호
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• pp.107-118
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• 1995

The characteristics of the current waveforms and 3$\Phi$ power waveforms of the variable speed 3$\Phi$ AC motor system driven by the single-pulse PWM investigated in this paper. The system is composed of a digital bridge inverter and low pass LC filter. It is confirmed that current waveforms and 3$\Phi$ power waveforms can be improved by utilizing the high order low pass LC filter than that of lower order through computer simulation. Also, we propose the low pass LC filter revised from the conventional LC filter.

• 대한기계학회논문집A
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• 제29권12권
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• pp.1597-1604
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• 2005

The identification of a moving noise source is important in reducing the source power of the transport systems such as airplanes or high speed trains. However, the direct measurement using a microphone running with noise source is usually difficult due to wind noise, white the source motion distorts the frequency characteristics of the pass-by sound measured at a fixed point. In this study the relationship between the spectra of the source and the pass-by sound signal is analyzed for an acoustic source moving at a constant velocity. Spectrum of the sound signal measured at a fixed point has an integral relationship with the source spectrum. Nevertheless direct conversion of the measured spectrum to the source spectrum is ill-posed due to the singularity of the integral kernel. Alternatively a differential equation approach is proposed, where the source characteristics can be recovered by solving a differential equation relating the source signal to the distorted measurement in time domain. The parameters such as the source speed and the time origin, required beforehand, are also determined only from the frequency-phase relationship using an auxiliary measurement. With the help of the regularization method, the source signal is successfully recovered. The effects of the parameter errors to the estimated frequency characteristics of the source are investigated through numerical simulations.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -1
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• pp.207-210
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• 2000

This paper introduces a voltage-mode biquadratic circuit using only Operational Amplifiers (OTAs) and Operational Transconductance Amplifiers (OTAs). The proposed circuit can realize low-pass, band-pass, high-pass, band-stop and all-pass transfer functions by suitably choosing the input and output terminals. And the circuit characteristics can be electronically tuned through adjusting the transconductance gains of OTAs. Some examples are given together with simulated results by PSpice. The circuit configuration is very suitable for implementation in both bipolar and CMOS technologies.

• Journal of the Optical Society of Korea
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• 제17권5호
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• pp.441-446
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• 2013

A split-step time-domain model for the analysis of pulse delay characteristics through ring resonator all-pass filters (APF's) is developed and its accuracy is checked. The dependence of the delay time and pulse distortion on the coupling ratios is investigated using the model. It is observed that the bandwidth of the APF's needs to be wide enough to minimize the pulse distortion.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권1호
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• pp.1-8
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• 2018

As the key equipment in deep ocean mining, the slurry pump suffers from wear and blocking problems. In this paper, high-speed photography technique is applied to track the movement rule of single particle of the coarse particle solid-liquid two-phase flow in a double blade slurry pump. The influences of particle diameter and particle density on the pass-through and collision characteristics of particles are analyzed as well. The results show that the average of the passing pump time first decreases and then increases when the particle diameter increases. The average of the passing pump time decreases by 22.7%, when the particle density increases from $1.09g/cm^3$ to $1.75g/cm^3$. Besides, the particle density has great influence on the location where the particle hits the tongue. Most particles of $1.09g/cm^3$ hit the tongue on the left side, while collision location of particles of $1.75g/cm^3$ is mainly on the top and at the right side of the tongue. The research can provide a basis for the optimization design of slurry pump in deep ocean mining system.

• 한국식품영양과학회지
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• 제33권1호
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• pp.152-157
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• 2004

연삭식 정미기를 이용하여 도정한 쌀의 도정 정도에 따른 수력함량은 12.81∼13.15%로서 연삭 횟수가 증가할수록 약간 증가하는 경향이었으며, 조단백질 및 조지방 함량은 각각 7.81∼8.50% 및 1.07∼l.93%로서 도정 정도가 클수록 감소하였으나 백미보다는 높았고, 조지방의 주요 지방산은 palmitic acid(22.06∼25.76%, peak area %), oleic acid(34.04∼35.62%) 및 linoleic acid(39.58∼42.22%)로 확인되었다. 백도는 현미와 백미의 중간 정도이었으며, 쌀눈 부착률은 연삭 4회 및 연마 1회 시료의 경우에도 39.33%에 이르러 백미(4.00%)보다 매우 높은 비율을 나타냈으며, 천립중은 현미와 유의적 차이(p<0.05)가 없었다. 주사전자현미경 관찰 결과 연삭 4회 및 연마 1회 시료는 표면의 매끄러움이 백미와 비슷한 반면 쌀눈이 일부 부착되어 있었다. 취반 후 관능평가 한 결과 연삭,3회, 연삭 4회, 연삭 4회 및 연마 1회 시료는 백미와 유의적 차이가 없거나(맛) 약간 낮은 선호도(색깔, 냄새, 조직감, 전체적 기호도)를 나타냈으나 현미보다 월등히 높은 선호도를 나타내어 영양가 있는 쌀로서 이용되기에 좋은 것으로 판단된다.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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• pp.238-239
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• 2000

The optical fibers are an interesting medium for effective tunable optical frequency conversion in the spectral range of UV, Visible, and near-IR through the nonlinear processes. A number of papers for developing the wideband and flat-gain amplifier for the WDM system applications through the combination of EDFA or thulium-doped fluoride fiber amplifier and Raman amplifier, are reported$^{(1)}$ . Even though a variety of papers related to Raman amplifications are published, the amplification with the feedback of the residual pump is not investigated yet. Accordingly, in this paper, we report the characteristics of forward Raman amplification by the simple and double-pass fiber Raman configuration through the feedback of residual pump beam. (omitted)

• 한국환경과학회지
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• 제16권1호
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• pp.81-94
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• 2007

The purpose of this work is to investigate the water quality change characteristics of treated water in water distribution systems of Water Treatment Plants (WTPs) of Jeju City. For this, the raw water, treated water and tap water that did not pass (named as not pass-tap water) and passed through the water storage tank (named as pass-tap water) were sampled and analyzed monthly from September 2001 to August 2002, for four (W, S, B and O) WTPs except for D WTP (where treated water is not supplied continuously) among WTPs of Jeju City. The concentrations of $NO_3^-$ and $Cl^-$ of treated water in distribution systems changed little, but changed seasonally, which is considered to be based on the seasonal variation of the quality of raw water. The pH of treated water changed little in distribution systems for S WTP, but for the other WTPs, the pH of not pass-tap water was similar to that of treated water and the pH of pass-tap water was higher than that of treated water. The turbidity of treated water in distribution systems changed little except for W2 of W WTP and S4 and S5 of S WTP, where it was higher than that of each treated water. The residual chlorine concentrations between treated water and not pass-tap water changed little, but those between treated water and pass-tap water changed greatly, based on the its long residence time in water storage tank and so its reaction with organic matter, etc or its evaporation. The concentrations of TTHMs (total trihalomethanes) and $CHCl_3$ that induce cancers in water distribution systems of these WTPs, were much lower than their water quality criteria and those in other cities. The concentrations of TTHMs of treated water and not pass-tap water were similar, but concentrations of pass-tap water were 1.5 to 2.0 times higher than those of treated water and not pass-tap water, due to the reaction of residual chlorine and organic matter, etc, with the result of long residence time in water storage tank.

• 정보관리학회지
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• 제36권1호
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• pp.247-267
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• 2019

공공도서관에서 제공하는 향토정보서비스는 낮은 이용률을 나타내고 있으며, 대부분 열람 및 대출형태의 제한적인 서비스를 제공한다. 본 연구는 이러한 문제점을 해결하고 이용자의 정보 요구를 반영하는 새로운 향토정보서비스를 제안하고자, 모바일 어플리케이션 (이하 앱)인 LibPass (Library와 Pass의 합성어)를 개발하였다. LibPass는 향토자원의 특성들이 LibPass의 콘텐츠로 구성되어 이용자가 모바일 앱을 통해 지역의 문화관광자원에 대한 정보탐색을 한 곳에서 간편하게 할 수 있도록 설계되었다. 즉, 관광자원에 대한 소개는 물론이고, 그 이용을 위한 숙박시설, 체험프로그램, 그리고 특화도서관에 대한 정보를 제공함으로써, 향토자원에 대한 효율적인 정보서비스를 도모하고자 했다. 무엇보다도 이 서비스는 국립중앙도서관에서 발행하는 카드로 일원화되어 제공되므로 전국 어디서나 사용이 편리하고, 공공기관의 다양한 콘텐츠를 활용하여 신뢰성과 최신성을 확보하였다. 선행연구를 바탕으로 모바일 관광정보서비스의 품질 평가 요인들을 도출하였으며, 또한 기존의 관광정보서비스 앱을 분석하여 LibPass 앱의 개체들을 구성하고 논리적 개체 관계 모델을 기반으로 프로토타입을 개발하였다. 이 모델은 도서관의 향토정보서비스 이용률을 증가시키고, 더 나아가 이용자 친화적인 앱을 통해 도서관에 대한 긍정적인 인식을 높이는 데 기여할 수 있다.

• 한국컴퓨터정보학회논문지
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• 제5권3호
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• pp.76-83
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• 2000

CMOS기술의 발전에 의해 연속신호시스템은 상당한 발전을 가져왔다. 이 논문에서는 새로운 CMOS floating저항을 써서 저역통과필터를 설계하고 PSpice Simulation을 통하여 그 특성이 우수함을 입증하였다. 특히, CMOS로 구성되는 새로운 floating저항은 포화영역에서 동작하도록 구현하였다. 이 방법으로 설계된 저역통과필터는 SC필터보다 구조가 더 간단하므로 IC화 할 때 칩 면적을 감소시킬 수 있다.