• 대한기계학회논문집B
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• 제29권10호
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• pp.1075-1082
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• 2005

The characteristics of longitudinal dispersion enhancement by the flow oscillation are numerically studied according to various groove geometries in a 2-D channel in the present study. The length of expanded section l$_{1}$/h$_{1}$ is varied from 0 to 8.75. The oscillating flow condition is given at both side ends, i.e., u = Asin ($2{\pi}ft$) The non-dimensional temperatures at both side ends are set to zero. The bottom and top walls are adiabatic. The local heat sources are located at the middle of the groove wall. In order to solve the governing equations, the SIMPIER algorithm is employed. The present results indicate that maximum longitudinal thermal dispersion can be achieved when the area ratio of the expanded section to the contracted section in the grooved channel becomes 1.

• IEIE Transactions on Smart Processing and Computing
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• 제5권6호
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• pp.418-429
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• 2016

In this paper, we propose a hybrid Wyner-Ziv video coding structure that combines conventional motion predictive video coding and Wyner-Ziv video coding to eliminate the feedback channel, which is a major practical problem in applications using the Wyner-Ziv video coding approach. The proposed method divides a hybrid frame into two regions. One is coded by a motion predictive video coder, and the other by the Wyner-Ziv coding method. The proposed encoder estimates side information with low computational complexity, using the coding information of the motion predictive coded region, and estimates the number of syndrome bits required to decode the region. The decoder generates side information using the same method as the encoder, which also reduces the computational complexity in the decoder. Experimental results show that the proposed method can eliminate the feedback channel without incurring a significant rate-distortion performance loss.

• 대한기계학회논문집B
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• 제21권8호
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• pp.1046-1055
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• 1997

An anisotropic k-.epsilon. turbulence model for predicting the rotating flows is proposed with the simple inclusion of a new parameter dealing with the extra straining effects in the .epsilon.-equation. This model is employed to compute the effects of Coriolis forces on fully-developed flow in a rotating channel. The predicted results indicate that the present model captures fairly well the striking rotational-induced effects on the Reynolds stresses and the mean flow distributions, including the argumentation of turbulent transport on the unstable side (pressure surface) of the channel and its damping on the stable side (suction surface).

• 한국통신학회논문지
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• 제33권4A호
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• pp.467-472
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• 2008

One of the maindisadvantages of Orthogonal Frequency Division Multiplexing (OFDM) is the Peak to Average Power Ratio (PAPR) problem. To reduce PAPR and improve the error performance of the OFDM signal over a fading channel, an OFDM system combining an Adaptive Symbol Selection Scheme (ASSS) and channel estimation can be used. Because of the side information of ASSS, however, the data rate decreases in the conventional ASSS OFDM system. In this letter, to overcome this impairment, we propose a technique to transmit side information by using pilot tones, and demonstrate that the proposed technique can give reasonable bit error rate (BER) performance.

• 한국수자원학회논문집
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• 제45권5호
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• pp.495-503
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• 2012

하천에 설치되는 강변저류지의 효율적 설계를 위해서는 정확한 부정류 흐름 해석이 반드시 필요하다. 일반적으로 하천의 부정류 수치모의는 1차원 부정류 수치모형인 HEC-RAS를 많이 사용하고 있다. 하지만 강변저류지가 있는 하도에서의 부정류 흐름에 대한 수리실험과 현장 모니터링 자료가 거의 없기 때문에 HEC-RAS를 이용한 부정류 수치모의 결과의 신뢰도를 확신하기가 어렵다. 따라서 본 연구에서는 부정류 수리실험을 수행하여 강변저류지가 있는 하도에서의 HECRAS를 이용한 부정류 수치모의 적용성을 검토하였다. HEC-RAS 적용성 검토는 직선수로에 강변저류지가 설치되어 있거나 그렇지 않은 경우에 대해 부정류 수리실험을 실시하여 측정된 결과와 비교하여 평가하였다. 특히, 강변저류지가 설치되어 있는 경우는 강변저류지의 저류용량이 충분하여 하도에서 강변저류지로 통하는 위어에 완전 횡월류 흐름만 발생하는 경우에 대해 실험을 수행하였다. 강변저류지가 설치되지 않은 직선수로에 대한 HEC-RAS의 수위 계산 결과는 최대 3% 오차를 유량은 최대 1% 오차를 보였으며, 강변저류지가 설치된 경우의 HEC-RAS 수위 계산 결과는 최대 4% 오차를 유량은 최대 2% 오차를 나타냈다.

• 한국인터넷방송통신학회논문지
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• 제10권3호
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• pp.1-10
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• 2010

IR (impulse radio)를 사용하는 IR-UWB 방식은 짧은 펄스를 전송하기 때문에 송수신기를 간단히 구현할 수 있고, 저 전력으로 구현 가능하며, 다중 경로 지연과 같은 외부 환경에 강한 특성을 가진다. 더불어, 짧은 펄스를 사용하므로 데이터 수신시 채널의 특징을 파악하기 위해 정확한 채널 추정 방법이 요구 된다. 채널 추정한 후 추정된 채널 이득과 지연 값은 레이크 수신기의 경로 선택에 이용되고, 데이터 수신시 파라메타를 정확히 찾는 정도에 따라서 성능이 좌우된다. 본 문서에서는 수신된 프리엠블 등의 신호를 이용하여 채널의 특성을 파악하여 관련 파라메터를 추출하는 채널 추정 알고리즘 및 다양한 관련 기술에 대하여 소개한다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.39-44
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• 2008

In this paper, heat transfer coefficients were measured in a channel with one side dimpled surface. The sphere type dimples were fabricated and the diameter and depth of dimple was 16mm and 4mm, respectively. Two channel heights of about 0.6 and 1.2 time of the dimple diameter, two dimple configuration were tested. The Reynolds numbers based on the channel hydraulic diameter was varied from 30000 to 50000. The improved hue detection based transient liquid crystal technique was used in the heat transfer measurement. Heat transfer measurement results showed that high heat transfer was induced downstream of dimples due to flow reattachment. Due to the flow recirculation on the upstream side in the dimple, the heat transfer coefficient was very low. As the Reynolds increased, the overall heat transfer coefficients also increased. With same dimple arrangement, the heat transfer coefficients and the thermal performance factor were higher for the lower channel height. As the distance between dimples became smaller, the overall heat transfer coefficient and the thermal performance factor were increased.

• The Korean Journal of Physiology and Pharmacology
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• 제7권1호
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• pp.15-23
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• 2003

Cellular redox state is known to be perturbed during ischemia and that $Ca^{2+}$ and $K^2$ channels have been shown to have functional thiol groups. In this study, the properties of thiol redox modulation of the ATP-sensitive $K^2$ ($K_{ATP}$) channel were examined in rabbit ventricular myocytes. Rabbit ventricular myocytes were isolated using a Langendorff column for coronary perfusion and collagenase. Single-channel currents were measured in excised membrane patch configuration of patch-clamp technique. The thiol oxidizing agent 5,5'-dithio-bis-(2-nitro-benzoic acid) (DTNB) inhibited the channel activity, and the inhibitory effect of DTNB was reversed by dithiothreitol (disulfide reducing agent; DTT). DTT itself did not have any effect on the channel activity. However, in the patches excised from the metabolically compromised cells, DTT increased the channel activity. DTT had no effect on the inhibitory action by ATP, showing that thiol oxidation was not involved in the blocking mechanism of ATP. There were no statistical difference in the single channel conductance for the oxidized and reduced states of the channel. Analysis of the open and closed time distributions showed that DTNB had no effect on open and closed time distributions shorter than 4 ms. On the other hand, DTNB decreased the life time of bursts and increased the interburst interval. N-ethylmaleimide (NEM), a substance that reacts with thiol groups of cystein residues in proteins, induced irreversible closure of the channel. The thiol oxidizing agents (DTNB, NEM) inhibited of the $K_{ATP}$ channel only, when added to the cytoplasmic side. The results suggested that metabolism-induced changes in the thiol redox can also modulate $K_{ATP}$ channel activity and that a modulatory site of thiol redox may be located on the cytoplasmic side of the $K_{ATP}$ channel in rabbit ventricular myocytes.

• 물과 미래
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• 제25권3호
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• pp.87-96
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• 1992

측류취소로와 만곡부가 있는 원형수로를 1:20으로 축척한 모형수로에 대해 수리모형실험을 수행하여 만곡부에서의 유속, 수위와 유황과 같은 수리학적 특성을 살펴보고, 측류취소로가 만곡부에 미치는 영향을 살펴보고자 한다. 또한 모형수로에 대해 ADI방법으로 천수방정식을 수치해석하여 얻은 만곡부에서의 수리학적 특성을 실험에 의한 것과 비교하여 사용된 수치기법을 검증하였다. 대상이 된 전영역에 대하여 수리모형실험에서 얻어진 유속, 수위와 유황은 수치해석한 결과와 잘 일치한다. 그러나 직각좌표계를 사용함으로서 상대적으로 만곡부에서 단면축소 효과가 발생하므로 수치해석으로 얻어진 유속은 만곡부에서 실험치보다 약간 크게 나타나는데, 이것은 격자간격을 줄이면 개선되리라 판단된다. 수리모형실험과 수치해석 모두 만곡부 외측의 수위가 상승하고 내측의 유속이 빨라지는 만곡부의 특성을 잘 모사하고 있다. 만곡부 직전에 측류취수로가 있을 경우 측류취수로의 영향이 만곡수로내까지 미침을 알 수 있었다.

• 한국환경과학회지
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• 제9권5호
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• pp.375-384
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• 2000

It is very important to interprete and simulate the variation of phytoplankton maximum region for the prediction and control of red tide. This study was composed of two parts first the hydrodynamic simulation such as residual current and salinity diffusion and second the ecological simulation such as phytoplankton distribution according to freshwater discharge and pollutant loads. Without the Nakdong river discharge residual current was stagnated in inner side of this estuary and surface distribution of salinity was over 25psu. On the contrary with summer mean discharge freshwater stretched very far outward and some waters flowed into Chinhae Bay through the Kadok channel and low salinity extended over coastal sea and salinity front occurred. From the result of contributed physical process to phytioplankton biomass the accumulation was occurred at the west part of this estuary and the Kadok channel with the Nakdong river discharge. When more increased input discharge the accumulation band was transported to outer side of this estuary. The frequently outbreak of red tide in this area is caused by accumulation of physical processes. The phytoplankton maximum region located inner side of this estuary without the Nakdong river discharge and with mean discharge of winter but it was moved to outer side when mean discharge of the Nakdong river was increased. The variation of input concentration from the land loads was not largely influenced on phytoplankton biomass and location of maximum region. When discharge was increased phytoplankton maximum region was transferred to inner side of the Kadok channel. ON the other hand when discharge was decreased phytoplankton maximum region was transferred to inner side of this estuary and chlorophyll a contents increased to over 20$\mu\textrm{g}$/L Therefore if any other conditions are favorable for growth of phytoplankton. decreas of discharge causes to increase of possibility of red tide outbreak.