• 설비공학논문집
• /
• 제20권3호
• /
• pp.213-219
• /
• 2008

Microscale heat transfer and microfluidics have become increasingly important to overcome some very complex engineering challenges. The use of very small passages to gain heat transfer enhancement is a well documented method for achieving high heat flux dissipation. In this study, the performance evaluation of micro-channel plated heat exchangers with straight, V-shaped and Y-shaped channels has been experimentally carried out under the counterflow condition. It is found that the mixing effect in V-shaped and Y-shaped channels enhances the heat transfer but pressure drop does not increase seriously in the range of low Reynolds number.

• 한국광학회:학술대회논문집
• /
• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
• /
• pp.72-73
• /
• 2000

Optical fiber gratings have been intensively studied for applications in optical fiber communications and sensor systems due to their all-fiber configuration, low insertion loss, low cost, and high flexibility. Especially, cladding mode coupling fiber devices such as long period gratings (LPG) and acousto-optic tunable filters (AOTF) have been developed as a gain equalization filter in erbium doped fiber amplifier (EDFA) for wavelength division multiplexing (WDM) systems$^{(1-2)}$ . (omitted)

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2015년도 제46회 하계학술대회
• /
• pp.1599-1600
• /
• 2015

본논문은 철도의 무선통신의 링크거리 확보를 위하여 아테나의 이득을 높이는 방법을 제시한다. 안테나의 이득을 높이기 위한 방법으로 안테나 상면에 유전체층을 사용하며 유전체 상면에서 전계의 위상이 동일하도록 거리에 따른 유효유전율이 다른 구조를 사용하였다. 원하는 유효유전율을 얻기 위하여 유전체에 구멍을 뚫은 구조를 사용하였으며, 시뮬레이션 결과 안테나의 이득이 향상되는 것을 확인하였다. 동작주파수 5.8GHz에 대해서 유전체층이 없는 패치안테나의 경우 이득이 4.66dB이며 제안한 유전체층이 있는 경우 이득이 9.36으로 기존의 안테나보다 4.5dB 개선을 하였다.

• 한국공작기계학회논문집
• /
• 제11권3호
• /
• pp.51-56
• /
• 2002

In order to achieve high precision machine tools, Performance enhancement of feed drive systems is required. One of the important technical issues is how to decrease thermal expansion of ball screw in proportion to the increase of machining speed. When measuring force of stretch of ball screw, since not only actual expansion and the value of bending have to be considered, it is impossible to define the exact value of expansion. In addition, support bearings of ball screw gain considerable force in axial direction. It also generates thermal expansion on the ball screw, and deteriorates the performances of the hearings. In conclusion, it is impossible to give the pretension enough to absorb all the elongation due to thermal expansion generated during machine is running. If given bed column and saddle are all bent to chance machine accuracy, and the support bearings of ball screw is damaged.

• 한국방송∙미디어공학회:학술대회논문집
• /
• 한국방송공학회 2009년도 IWAIT
• /
• pp.23-27
• /
• 2009

A scalable video coding (SVC) extension to the H.264/AVC standard has been developed by the Joint Video Team (JVT). SVC provides spatial, temporal and quality scalability with high coding efficiency and low complexity. SVC is now developing the extension of the first version including color format scalability. The paper proposes to remove some luminance related header and luminance coefficients when an enhancement layer adds only additional color information to its lower layer. Experimental results shows 0.6 dB PSNR gain on average in coding efficiency compared with an approach using the existing SVC standard.

• Nuclear Engineering and Technology
• /
• 제30권5호
• /
• pp.396-402
• /
• 1998

Experiments on the steamside corrosion and hydrogen pick-up of Zircaloy-4 under high pressure up to 10.3MPa are carried out to estimate the pressure effects on the kinetics. Temperature and reaction time are determined to be 37$0^{\circ}C$ and 72hours for the pre-transition test and $700^{\circ}C$ and 210minutes for the post-transition test, respectively. Results show that under 10.3MPa pressure the oxidation reaction is 50% and 100% enhanced in the pre-and the post-transition regime, respectively. Total amount of hydrogen uptake in the reaction is proportionally increased as corrosion weight gain is elevated. However, pick-up fraction is not affected by the high pressure. The fraction is almost twice greater than that in the waterside corrosion. Edges in the specimens play a certain role in the enhancement, especially in the post-transition regime. To identify physical property changes of oxide film such as micro-cracks or micro-pores, careful and thorough examination must be needed with some special techniques.

• Journal of the Optical Society of Korea
• /
• 제1권1호
• /
• pp.1-4
• /
• 1997

The theoretical limit of the noise correlation between the signal and idler outputs of a nondegenerate optical parametric amplifier (NOPA) with a coherent state signal and vacuum state idler input can be enhanced if a non-vacuum coherent state idler input is employed. By choosing a balanced signal and idler input, the noise correlation is $1/{({\root}g + {\root}{g-1})}^2$, where g is the intensity gain of the NOPA, and that is superior to the prediced outputs with single signal input by approximately 3dB. The result is applicable to all the schemes that use the NOPA to produce a sub-shot noise light generation such as feed-back or feed-forward control.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2003년도 통신소사이어티 추계학술대회논문집
• /
• pp.113-116
• /
• 2003

In this paper, we propose a dynamic parallel channel allocation mechanism that dynamically controls total number of allocation channels of each subscriber to effectively service user bandwidth demands while high utilization and fairness are guaranteed in WDM based optical access networks. The logical performance gain of statistical multiplexing by dynamic channel allocation is validated with analytic method as well as simulations. We also introduce the adaptive padding scheme in order to efficiently distribute forwarded frames to aggregated multi-link channels which are formed by parallel channel allocation mechanism. The proposed scheme shows the performance enhancement by minimizing unnecessary padding size and the processing time.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2003년도 통신소사이어티 추계학술대회논문집
• /
• pp.149-152
• /
• 2003

In this paper, we propose a scheme that applies to the VoIP application based on H.323 protocol to enhance the bandwidth efficiency. We multiplex the audio and video stream. In this scheme, audio frame is carried with video stream. And we applies not only multiplexing but also (in header compressing to the real audio/video stream to increase the bandwidth efficiency. With the multiplexing and RTP header compressing, we gain the bandwidth efficiency. In the finite network environment, We can assign bandwidth to other users who want to use other service. and other VoIP users. If we can apply the real time network situation to the our VoIP application, we can get more efficient performance.

• 한국정보전자통신기술학회논문지
• /
• 제4권2호
• /
• pp.77-82
• /
• 2011

본 논문에서는 패닝 기법을 이용하여 믹싱된 스테레오 음원에서 음원을 분리하는 방법에 대하여 고찰한다. 음원 분리 알고리즘은 다채널 포맷 변환을 위한 업믹스나 음질 개선, 고품질 음원 분리 등 다양한 응용분야에 사용될 수 있다. 본 논문에서 사용하는 음원 분리 알고리즘은 믹싱된 스테레오 채널을 시간-주파수 별로 PCA(Principal Component Analysis) 분석 방법을 이용하여 각각의 음원들이 패닝된 방향을 추정하며, 추정된 방향의 성분만을 추출하는 방향 필터링 과정을 거쳐 음원들을 독립적으로 분리 해 낸다. 실험을 통해 각 음원 분리 알고리즘의 성능을 평가하였다.