• 한국환경과학회지
• /
• 제11권3호
• /
• pp.191-199
• /
• 2002

In this study, water protection reservoir is selected as the target which is located at the estuary of Taehwa river to analyze and examine the effects of hydraulic structure on river environment. This study aims at the definition of factors which cause the change of ecological environment of river due to the effects of the sediment protection reservoir, and the proposal of the direction of environmental friendly river space development through the analysis and examination of stream variation conditions and riverbed variation characteristics among many effects of hydraulic structure on river environment before and after removal of the sediment protection reservoir when design flow is yielded. Firstly, in case of removal the existing sediment protection reservoir, the hydraulic variation characteristics like depth drop due to removal of the sediment protection reservoir are thought of little because it is examined that depths drop with about 0.01m and 0.01~0.56m when low flow is yielded and design flood yielded, respectively. Nextly, as the examination result of the variation characteristics of flow velocity in case of removal the existing sediment protection reservoir, it is thought that the concern about riverbed erosion is not serious according to the analyzed result as the mean velocity of the channel section where the velocity varies in case of removal the sediment protection reservoir is about 0.07~1.36m/s when low flow is yielded, and is about 1.02~2.41m/s when design flood is yielded despite riverbed erosion is concerned as it is examined that flow velocity is getting increase as about 0.01m/s when low flow is yielded and about 0.01~0.44m/s when design flood is yielded. Lastly, from the prediction result of riverbed variation for each flow amount condition before and after removal the sediment protection reservoir, it is known that the variation range of riverbed is nearly constant when flow amount of the channel exceeds a specific limit as it is analyzed that the more flow amount, the more erosion and sediment in the channel section of down stream part of the sediment protection reservoir and the sediment protection reservoir~Samho-gyo, and the variation ranges according to flow amount between flood condition and design flood condition have little difference in the channel section of the upstream of Samho-gyo.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
• /
• pp.323-324
• /
• 2012

Flammability limits of opposed flow diffusion flame in a narrow channel was investigated experimentally and theoretically. There were three different extinction modes corresponding to high strain rate (HSR), low strain rate (LSR) and dilution ratio (DR) limits. To investigate these limits, a theoretical study was followed by focusing on flow and heat transfer characteristics. Consequently, a dead space concept that has been used for premixed flames was important to reveal the heat loss mechanism in a narrow channel especially for LSR conditions even in the case of diffusion flames.

• 한국통신학회논문지
• /
• 제29권2A호
• /
• pp.140-146
• /
• 2004

본 논문은 다중사용자를 위한 OFDMA/FDD(Orthogonal Frequency Division Multiple Access/Frequency Division Duplex) 시스템에서 가변적인 전송율로 전송하기위한 무선 채널의 피드백 정보를 감소하는 방안을 제시한다. 제한된 상향링크 제어채널을 통해 기지국으로 무선 채널 정보를 전송하기 위해서, 제안된 알고리즘은 인근 클러스터간의 무선 채널의 유사 정도를 나타내는 정보로 채널 변화 수준(channel variation level)을 사용하며, 모든 클러스터에 대해서 하나의 MCS(Modulation & Coding Scheme)을 사용한다. 시뮬레이션은 하나의 셀 내에서 수행되었으며, 기존의 알고리즘의 피드백 정보와 유사한 오버헤드로 대역 효율 및 outage probability에서 더 좋은 성능을 나타내었다.

• 한국어류학회지
• /
• 제26권2호
• /
• pp.125-132
• /
• 2014

한강 하구역에서 출현하는 자치어의 시공간적 분포 특성을 파악하고 해양환경요인과 자치어의 분포 및 출현양상과의 연관성을 평가하기 위해 한강 하구역을 대표하는 염하수로, 석모수로, 장봉수로에서 2007년 5월에서 2008년 8월 사이 계절별로 자료를 수집하여 분석하였다. 연구기간 동안 자치어는 총 13개 분류군 총 3,642개체가 출현하였고, 웅어속이 48.8%로 우점하였다. 장봉수로에서 총 11개 분류군이 출현하여 가장 많았다. 석모수로에서는 웅어속이 대량 채집되어 채집량이 2,428개체로 가장 높았다. 춘계와 하계에 출현량이 증가하였으며, 동계에는 흰베도라치만이 출현하였다. 염하수로 및 석모수로에서는 기수종이 주를 이루었고 장봉수로에서는 연안성 어종, 연안 회유성 어종, 연안정착성 어종 등 다양하게 출현하였다. 정준대응분석(CCA) 결과 자치어는 수온 및 염분과 유의한 상관관계를 보였다. 한강 담수유입에 따른 염분에 따라 주요 자치어는 2개의 그룹(염하 석모수로, 장봉수로)으로 구분되었다.

• 설비공학논문집
• /
• 제27권11호
• /
• pp.559-566
• /
• 2015

The main objective of this work is to experimentally investigate the effect of angle variation on the distribution of two-phase flow at header-channel junctions. The cross-sections of the header and the channels were fixed at $16mm{\times}16mm$ and $12mm{\times}1.8mm$, respectively. Air and water were used as the test fluids. Four different header-channel positions were tested : Vertical header with Horizontal channels (case VM-HC), Horizontal header with Horizontal channels (case HM-HC), Horizontal header with Vertical Downward channels (case HM-VDC), and Horizontal header with Vertical Upward channels (case HM-VUC). In all cases, liquid flow distribution tended to decrease gradually in the upstream header region. However, in the downstream region, different trends could be seen. The reason for these different tendencies were identified by flow visualization in each case. The standard deviations for the liquid and gas flow distribution in each case were calculated, and the case of VM-HC had the lowest values compared to other cases because of the symmetrically distributed liquid film and strong flow recirculation near the end plate.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2002년도 학술대회지
• /
• pp.255-258
• /
• 2002

Liquid rocket engines using liquefied natural gas (LNG) or methane as a fuel is known to have several good characteristics, such as high specific impulse compared to other hydrocarbon fuels, environment-friendly exhaust gas, low production cost, and re-usability with low soot generation in the cooling channel. In this study, experimental combustion chambers capable of using LNC and $CH_{4}$ are being researched through experimental firing tests, and within easy range of eyes' inspection, there are the periodical existence of soot or discoloration in the chamber wall surface. This result means that mixture ratio of oxidizer and fuel fluctuates periodically between outer-row injectors in the mixing head in the circumferential direction. Therefore, based on this phenomenon, the variation of mixture ratio near the chamber wall caused by the spill pattern of a shear coaxial injector was analyzed quantitatively and the thermal heat flux Into the cooling channel is modified. Then, the calculated and modified results are compared with the measured ones.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2003년도 하계종합학술대회 논문집 V
• /
• pp.2745-2748
• /
• 2003

In this paper, we implement the photoplethysmo-graphy system that have three channel pulse wave detects and one channel ECG amplifier. In order to detect the artery state, we measured the pulse waves at different positions, simultaneously. In general, arterial vascular system suffers the decrease of compliance, increase of resistance, and decrease of distensibility through aging. Therefore, we compared and analyzed variation of tile Pulse waves parameter both in time and frequency domains that is concerned with the changes of arterial characteries. And then evaluated the correlation coefficients between the parameters variation and the age group. As the result of experiment, we found that the Parameters have a significant correlation about aging.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2006년도 학술발표회 논문집
• /
• pp.1328-1332
• /
• 2006

As the city is developed, Sewerage outlet is installed for the discharge of rainfall special at new town or modified the existed sewerage network. But the sewerage outlet is influenced to the cannel flow. In this paper, for analyzing variation of flow properties by installing sewerage outlet, it was experimented a with $120^{\circ}$ channel junction. The water depth is rapidly increasing at the just before sewerage installed position, but the velocity is represented increasing at the just after sewerage installed position. In addition, the biggest increment of water depth and velocity is represented $3.0m^3/hr{\sim}4.0.m^3/hr$. At the position of the sewerage outlet installation, separate install at up and downstream is rather than only one position at up or down stream. If it was not install both installation, the upstream installation is better than downstream installation.

• 한국산업융합학회 논문집
• /
• 제10권4호
• /
• pp.275-283
• /
• 2007

This study aims at the calculation of a variation of flow characteristics of main channel for tributary inflow in river junction. So this study was analyzed the variation of flow depth and velocity in main channel for a change of inflow degree. For this purpose, FLDWAV model are carried out for variations of $30^{\circ}$, $60^{\circ}$ and $90^{\circ}$ tributary inflow at junction. Results show that velocity ratio(V1/V3) increases and flow depth ratio(H1/H3) decreases for discharge ratio(Q1/Q3) of upstream and downstream when degree increases in junction. And FLDWAV model was applied at a real river junctions. Selected area is a junction of Gumho river and Sin stream. Results show that pattern is similar to a virtual channel.

• 한국가시화정보학회지
• /
• 제10권1호
• /
• pp.9-14
• /
• 2012

In this study, a piezoelectric inkjet nozzle with a rectangular shaped channel has been developed, and the characteristics of droplet formation have been investigated according to the variation of pulse widths in bipolar waveform. The channel of the nozzle was fabricated transparently by a precision machining technique. A tantalum membrane which was attached to a piezoelectric material covers the channel. By applying two types of bipolar waveforms to the piezoelectric actuators, droplet formation through the nozzle was monitored by a CCD camera. For the variety of the first and second pulse widths in the bipolar waveforms, the regimes of single and double droplet formations are presented. The change of droplet velocity which depends on the pulse width and the type of waveform is also discussed.