• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 춘계학술대회
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• pp.625-626
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• 2015

그룹 속도 분산과 비선형 효과의 상호 작용에 의해 왜곡되는 WDM 신호의 보상을 위해 전체 전송로 중간에 광 위상 공액기 (optical phase conjugator)가 적용되고 중계 구간의 단일 모드 광섬유(SMF; single mode fiber) 길이와 RDPS(residual dispersion per span)를 인위적으로 분포하는 $80km{\times}50spans$의 광전송 링크의 최적 분포 패턴을 도출하였다.

• 한국생산제조학회지
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• 제22권2호
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• pp.324-330
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• 2013

The dispersion of acoustic noise during the turn-on and turn-off switching of HEV(hybrid electric vehicle) relay was experimentally analyzed to identify the reason for the dispersion of noise level. An effective method was proposed to reduce the dispersion of noise level. First, a method to wrap the side of moving core with a tape was adopted to reduce the transverse vibration. It enabled the moving core to make a consistent motion and reduce the dispersion of noise level from switching operation of relay. Second, the dispersion of noise level from vibration transmission of parts such as the outer frame and yoke caulking part of relay were tested to find out main sources. From this result, it was identified that the yoke caulking part made inconsistent transient vibration and noise dispersion.

• 한국자동차공학회논문집
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• 제9권6호
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• pp.16-23
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• 2001

Spray dispersion in high pressure diesel engines have been simulated experimentally with a special emphasis on the effect of swirl by using a liquid injection technique. A constant volume chamber was designed to be rotatable in order to generate a continuous swirl and to have the flow field closely resembling a solid body rotation. Emulsified fuel was injected into the chamber and the developing process of fuel sprays was visualized. The effect of swirl on the spray dispersion was quantified by calculating non-dimensionalized dispersion area according to the spray tip penetration length. The results show that the effect of swirl on the spray dispersion is different between short and long spray penetrations. For short range of spray tip penetration, the effect of swirl on spray dispersion is quite small. However, as the spray tip is penetrated into longer distance in spray chamber, the effect of swirl on spray dispersion becomes larger. These results can be used as a basic data for designing combustion chamber and injection system of direct injection diesel engine.

• Journal of the Optical Society of Korea
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• 제13권3호
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• pp.367-372
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• 2009

In this paper we propose an electronic domain timing phase selection scheme for the optical communication systems suffering from inter-symbol-interference (ISI) distortion due to chromatic dispersion (CD) or polarization mode dispersion (PMD). In the presence of CD/PMD a proper timing phase selection is important for discrete time domain equalizers, since different timing phases produce different nonlinear ISI channels of different severity. The proposed timing phase recovery scheme based on dispersion minimization (DM) practically approximates the optimal minimum mean squared error (MMSE) timing phase without training signals which reduces overall throughput substantially, especially in time-varying channels such as PMD. The simulation results show that the proposed DM timing agrees with MMSE timing phase, under proper normalization of the received signals, for various dispersion and OSNR.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 추계학술대회
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• pp.967-970
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• 2014

광전송 링크의 유연한 구성을 위해 중계 구간의 RDPS(residual dispersion per span)가 램덤하게 분포하는 광전송 링크에서 RDPS 편차에 따른 분산 특성과 시스템 성능을 살펴보았다. 전송 링크를 구성하는 중계 구간의 RDPS 편차가 적을수록 최적 전체 잉여 분산 (NRD; net residual dispersion)에서 유효 입사 전력의 크기가 신장되는 것을 확인하였다. 또한 RDPS 편차가 적을수록 WDM 채널의 입사 전력에 따른 유효 NRD 범위도 넓어지는 것을 확인하였다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2019년도 춘계학술대회
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• pp.579-581
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• 2019

본 연구에서는 분산 제어와 광 위상 공액이 적용된 링크에서 누적 분산이 지속적으로 증가/감소하는 광전송 링크를 제안하고자 한다. 본 연구에서 제안한 광전송 링크에서 전체 잉여 분산이 -15 ps/nm나 15 ps/nm로 설정된 경우 왜곡된 파장 분할 다중 채널의 보상이 최상으로 이루어지는 것을 확인하였다.

• 한국입자에어로졸학회지
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• 제13권3호
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• pp.133-139
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• 2017

In this paper, we proposed an emulsification method without using an emulsifier and investigated the effects of particle size distribution in fluids on dispersion stability. Surfactant-free oil in water emulsion was prepared with 1 % (w/w) of olive oil by using high speed agitation, high pressure and ultrasonic dispersion methods. The particle size, microscopic observation, and dispersion stability of each sample were evaluated and dispersion stability according to various dispersion methods was compared. As a result, the emulsion dispersed by the ultrasonic dispersion method showed the smallest particle size and uniform distribution of $0.07{\sim} 0.3{\mu}m$ and was the most stable in a 7 days stability evaluation. In the above experiment, four olive oil emulsions having different particle sizes were prepared using ultrasonic dispersion technology that was capable of producing stable emulsions. The dispersion stability of each samples with oil droplet sizes of (A) 0.1 to $0.5{\mu}m$, (B) 0.3 to $4{\mu}m$, (C) 1 to $10.5{\mu}m$ and (D) 2 to $120{\mu}m$, was observed for 7 days, and the relationship between the stability and performance was studied. Emulsion (A) with particle size less than $0.5{\mu}m$ displayed the dispersion stability showing below 5 % change in a 7 days stability evaluation. In the case of (B), (C), and (D) that had larger particle than $0.5{\mu}m$, the changes of dispersion stability were 10 %, 13 % and 35 % respectively. From these results, it was proved that dispersion stability of emulsion with uniform particle size of $0.5{\mu}m$ or less was confirmed to be very stable.

• Journal of Pharmaceutical Investigation
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• 제41권3호
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• pp.179-184
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• 2011

This study aimed to confirm the effect of molecular weight (MW) in solid dispersion of carvedilol with poly-vinylpyrrolidone (PVP) of various MW. Solid dispersion of carvedilol with PVP was prepared by spray-drying method. Scanning electron microscopy (SEM) was used to analyze the surface of solid dispersion samples. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were used to analyze the crystalline of solid dispersion. Fourier transform infrared spectroscopy (FT-IR) was used to analyze the change of chemical structure characteristic of solid dispersion. DSC and XRD show that drug crystalline was changed. FT-IR revealed that chemical structure of solid dispersion comparing the chemical structure of drug was changed. The dissolution studies of solid dispersion presented at simulated gastric juice (pH 1.2). The dissolution rate of solid dispersion was dramatically enhanced than pure drug and the MW of PVP has an effect on the release property of carvedilol in solid dispersion. In conclusion, the present study has confirmed the effect of MW of PVP on release property of solid dispersion formulation of carvedilol with PVP.

• 한국통신학회논문지
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• 제33권1A호
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• pp.7-15
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• 2008

본 논문에서는 광섬유에서 발생하는 그룹 속도 분산과 비선형 효과에 의한 왜곡을 보상하기 위해 적용하는 MSSI(Mid-Span Spectral Inversion)에서 광 위상 공액기(OPC; optical phase conjugator)를 중심으로 광 전력의 비대칭화 때문에 나타나는 기술적 한계를 부가적으로 집중형 분산 제어(DM; dispersion management) 기술을 결합시켜 극복할 수 있다는 것을 고찰하였다. 본 연구에서 고려한 집중형 DM은 송신단 바로 다음과 수신단 바로 앞에만 분산 보상 광섬유(DCF; dispersion compensating fiber)를 두는 구조(구조 A)와 전체 전송 링크 중간에 위치한 OPC의 바로 전후에 DCF를 두는 구조(구조 B)로 나누어 각 경우에 대해 전송 성능 개선 정도를 비교하였다. 분석 결과 MSSI에 구조 A의 집중형 DM이 결합된 경우가 구조 B가 결합된 경우에 비해 전송 성능을 크게 개선하는 것을 확인하였다. 본 논문에서 고려한 2가지 구조 모두 비선형 현상 중 자기 위상 변조(SPM; self phase modulation)에 의해 성능이 제한되는 WDM 시스템에서 총 전송 링크의 전체 잉여 분산량(NRD; net residual dispersion)이 양의 값으로 결정되어야 모든 채널에 대해 최상의 성능을 얻을 수 있다는 것을 확인하였다.

• 한국항행학회논문지
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• 제26권6호
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• pp.474-480
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• 2022

광 위상 공액은 파장 분할 다중 (WDM; wavelength division multiplexed) 신호의 장거리 전송을 위해 필수적인 색 분산과 비선형성에 의한 왜곡을 보상할 수 있는 기술 중 하나이다. 이 기술이 그동안 가지고 있었던 한계를 주기적 분산 프로파일을 갖는 분산 맵을 통해 해소하는 방안을 제안하고 분석해 보았다. 제안하는 시스템에서 광 위상 공액기 (OPC; optical phase conjugator)는 전체 링크의 1:2 또는 2:1의 위치에 배치되고, 분산 맵의 프로파일은 사인파 또는 반전된 사인파 모양의 주기적 형태를 갖는다. OPC가 전체 링크의 2:1 지점이 아닌 1:2 지점에 위치할 때 제안된 주기적 형태의 분산 맵을 통해 왜곡된 960 Gb/s WDM 신호의 보상이 더욱 개선되는 것을 확인하였다. 또한 제안된 주기적 분산 맵을 갖는 분산 제어 링크의 설계 융통성을 늘리기 위해서는 중계 구간에 할당되는 최대 RDPS (residual dispersion per span)가 1,800 ps/nm 이상이 되어야 하는 것도 알 수 있었다.