• 한국환경과학회지
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• 제20권8호
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• pp.997-1009
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• 2011

In order to estimate volume transport by upwelling for single artificial seamount, same shape and size of artificial seamount already deployed was applied to numerical experiment. The result showed that strong upwelling appeared at front while took place downwelling at rear. The strongest upwelling existed at the top of the artificial seamount. Volume transport by upwelling was computed as 785 m3/s. Column arrangement was applied to two artificial seamount in three cases; case 1) no clearance, case 2) sixty-five meters of clearance as half of artificial seamount's length, and case 3) hundred-thirty meters of clearance as an artificial seamount's length. All cases of column arrangements showed more upwelling volume transport than that of single seamount. Particularly, the case of no clearance calculated as 106% and appeared the most upwelling effect comparing to two other cases. Row arrangement was also applied to two artificial seamount in three cases; case 4) no clearance, case 5) forty meters of clearance as an artificial seamount's width, and case 6) eighty meters of clearance as twice of artificial seamount's width. Upwelling volume transport in case 4 increased 48% than the case of single seamount. Other two cases of 5 and 6 were estimated as 97% increased and more effective than case 4. According to the case experiments, column arrangements show more upwelling volume transport than that of row arrangements. In cases of column arrangements, with decreasing clearance between two seamount, the effect increases while showing maximum value at clearance zero. In cases of row arrangements, on the contrary, with decreasing clearance between two seamount, the effect decreases while showing minimum value at clearance zero. Since simple barotropic condition was considered for this study, further study is necessary by considering baroclinic condition to get close to reality. In conclusion, in deploying artificial seamount, optimal arrangement should be well designed to enhance primary and secondary productivity and to increase the diversity of species as well as reducing time and space.

• 전기화학회지
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• 제11권1호
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• pp.51-58
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• 2008

고분자 전해질 연료전지의 성능향상을 위한 방법으로 유동채널의 형상을 변경한 많은 연구가 진행되어 왔으나 동일한 유동채널 형상에서 유동방향 변경에 따른 연구는 많이 진행되지 못하였다. 본 연구에서는 동일한 반응면적과 동일한 유동채널의 고분자 전해질 연료전지의 수소와 산소의 유동방향을 Co-flow에서 Counter-flow로 변경될 경우의 연료전지의 성능변화를 분석하기 위하여 연료극과 공기극이 포함된 3차원 수치해석모델을 개발하였다. 개발된 수치해석모델을 활용하여 Co-flow와 Counter-flow의 유동채널 내부의 압력손실, 반응물질의 농도분포, 고분자 전해질 막을 통한 Water Transport, 고분자 전해질 막의 이온전도도 및 I-V 성능곡선을 비교하였다. 그 결과 반응물질의 농도분포, Water Transport, 고분자 전해질 막의 이온전도도가 우수한 Counter-flow 유동조건에서의 성능이 Co-flow 유동조건에 비하여 더욱 우수하였다.

• 약학회지
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• 제49권4호
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• pp.275-283
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• 2005

The purpose of the present study was to kinetically investigate the carrier-mediated uptake in the hepatic transport of organic anions, and to simulate the 'in vivo counter-transport' phenomena, using kinetic model which was developed in this study. The condition that the mobility of carrier-ligand complex is greater than that of free carrier is not essential for the occurrence of 'counter-transport' phenomenon. To examine the inhibitory effects on the initial uptake of organic anions by the liver, it is necessary to judge whether the true counter-transport mechanism (trans-stimulation) is working or not. Effects of bromophenol blue (BPB) or bromosulfophthalein (BSP) on the plasma disappearance curves of a 1-anilino-8-naphthalene sulfonate (ANS) were then kinetically analyzed based on a flow model, in which the ligand is eliminated only from the peripheral compartment (liver compartment). Moreover, 'in vivo counter-transport' phenomena were simulated based on the perfusion model which incorporated the carrier-mediated transport and the saturable intracellular binding. The 'in vivo counter-transport' phenomena in the hepatic transport of a organic anions were well demonstrated by incorporating the carrier-mediated process. However, the 'in vivo counter-transport' phenomena may be also explained by the enhancement of back diffusion due to the displacement of intracellular binding. In conclusion, one should be more cautious in interpreting data obtained from so-called 'in vivo counter-transport' experiments.

• 대한교통학회지
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• 제34권5호
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• pp.394-408
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• 2016

본 연구는 효율적인 공공자전거 도입과 운영을 위하여 기상조건과 스테이션 입지특성이 공공자전거 수요 및 이용패턴에 영향을 파악하고자 고양시 공공자전거 대여자료를 가지고 선형회귀분석방법을 통해 시간대별 대여량 모형을 구축하였다. 기상조건에 따른 영향은 평균 기온이 상승할수록 대여량이 늘어나는 것으로 분석되었으며, 강수량이 10mm 이상 되거나, 평균기온이 29도 이상으로 높아지는 경우, 풍속이 7m/s 이상 되는 경우에 대여량이 떨어지는 것으로 분석되었다. 입지특성에 따른 영향은 새벽시간대는 유흥가가 위치한 중심상업지역이, 낮 시간대에는 공원지역과 중심 및 일반상업 지역의 대여량이 높은 것으로 나타났다. 하교시간대는 학교인근 스테이션의 대여량이 증가하고, 퇴근시간대는 지하철역 인근의 대여량이 두드러지게 높아진다. 심야시간대에는 공원지역에서의 대여량이 두드러졌다.

• Journal of Pharmaceutical Investigation
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• 제22권4호
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• pp.289-300
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• 1992

The counter-transport phenomena in the hepatic transport of 1-anilino-8-naphthalene sulfonate (ANS) were kinetically investigated by analyzing the plasma disappearance-time profiles and the transport into the isolated hepatocytes. In vivo "counter transport phenomena" were simulated based on the perfusion model which incorporated the carrier-mediated transport and the saturable intracellular binding. The condition that the mobility of carrier-ligand complex is greater than that of free carrier is not essential for the occurrence of counter-transport phenomenon. To examine the inhibitory effects on the initial uptake of a ligand by the liver, it is necessary to judge whether the true counter-transport mechanism (trans-stimulation) is working or not. The initial plasma disappearance curves of ANS were then kinetically analyzed based on a two-compartment model, in which the ligand is eliminated only from the peripheral compartment (liver compartment). No effects on the initial plasma disappearance rates of ANS were observed after preloading of bromophenol blue (BPB) or rose bengal (RB) in the liver. Inhibitory effect of BPB or RB on the initial uptake (or efflux) rates of ANS by the isolated hepatocytes were not observed, suggesting that the true counter transport mechanism is not working. In conclusion, checking the preloading effects of transstimulation on the initial uptake of a ligand by the liver could be a useful criterion for carrier cycling and common use of the same carrier between two ligands. However, one cannot exclude those possibilities even if the preloading effects cannot be observed.

• 한국통신학회논문지
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• 제30권3B호
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• pp.85-94
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• 2005

본 논문은 적응형 오류제어 기법을 바탕으로 신뢰성 있는 UDP 기반의 미디어 고속 전송을 제안한다. 제안된 적응형 전송기법은 대역폭의 변화에 효과적으로 대처하기 위해서 네트워크 모니터링을 기반으로 잉여 데이터의 양을 제어한다. 수신측 피드백은 패킷 손실의 유형, 전송률 등의 수신 상황을 송신측이 인지하도록 하여 앞으로 발생될 네트워크 상황을 예측하고 이를 바탕으로 전송률과 적응형 FEC 코드 조합을 적응적으로 제어함으로써 신뢰성 있는 전송을 가능하게 한다. 제안된 시스템의 성능을 측정하기 위한 고속 네트워크에서의 전송 실험은 수백 Mbps의 전송 속도를 보이며 향상된 신뢰성을 보여준다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권11호
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• pp.3711-3730
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• 2014

Cognitive radio networks (CRNs) have emerged as a promising solution to enhance spectrum utilization by using unused or less used spectrum in radio environments. The basic idea of CRNs is to allow secondary users (SUs) access to licensed spectrum, under the condition that the interference perceived by the primary users (PUs) is minimal. In CRNs, the channel availability is uncertainty due to the existence of PUs, resulting in intermittent communication. Transmission control protocol (TCP) performance may significantly degrade in such conditions. To address the challenges, some transport protocols have been proposed for reliable transmission in CRNs. In this paper we survey the state-of-the-art transport protocols for CRNs. We firstly highlight the unique aspects of CRNs, and describe the challenges of transport protocols in terms of PU behavior, spectrum sensing, spectrum changing and TCP mechanism itself over CRNs. Then, we provide a summary and comparison of existing transport protocols for CRNs. Finally, we discuss several open issues and research challenges. To the best of our knowledge, our work is the first survey on transport protocols for CRNs.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 1998년도 추계연구발표회 논문개요집
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• pp.8-9
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• 1998

• 한국ITS학회:학술대회논문집
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• 한국ITS학회 2007년도 제6회 추계학술대회 및 정기총회
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• pp.192-195
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• 2007

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2018년도 학술발표회
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• pp.149-149
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• 2018

Prediction on initial motion of sediment is crucial to evaluate sediment transport and channel stability. The condition of incipient movement of sediment is characterized by bed shear stress, which is generated from force of moving water against the bed of the channel, and by critical shear stress, which depends on force resisting motion of sediment due to the submerged weight of the grains. When the bed shear stress exceeds the critical shear stress, sediment particles begin rolling and sliding at isolated and random locations. In Mountain River, debris flow frequently occurs due to heavy rainfall and can lead some natural stones from mountain slope into the bed river. This phenomenon could add additional forces to sediment transport system in the bed of river and also affect or change direction and magnitude of sediment movement. In this paper, evaluations on incipient motion of uniform coarse gravel under falling spheres impacts using small scale flume channel were conducted. The drag force of falling spheres due to water flow and length movement of falling spheres were investigated. The experiments were carried out in flume channel made by glass wall and steel floor with 12 m long, 0.6 m wide, and 0.6 m deep. The bed slopes were selected with the range from 0.7% to 1.5%. The thickness of granular layer was at least 3 times of diameter of granular particle to meet grain placement condition. The sphere diameters were chosen to be 4cm, 6 cm, 8 cm, 10 cm. The spheres were fallen in to the bed channel for critical condition and under critical condition of motion particle. Based on the experimental results, the Shields curve of particles Reynold number and dimensionless critical shear stress were plotted. The relationship between with drag force and the length movement of spheres were plotted. The pathways of the bed material Under the impact of spheres falling were analyzed.