• 한국수자원학회논문집
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• 제42권10호
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• pp.867-876
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• 2009

본 연구에서는 하상이 경년별로 변화함에 따라 발생되는 수위-유량 관계곡선의 오차를 보완하기 위해 최근(2006 년)의 수위-유량 관계곡선을 기준으로 채택하여 일원화시키고, 과거의 하상상태와 경년별로 작성되어 왔던 수위-유량 관계곡선들과의 관계 및 수위, 단면적, 유속 등에 대한 수리기하학적 특성을 분석하였다. 연구 대상지점으로는 낙동강의 주요지점인 적포교와 진동 지점을 택하였으며, 과거의 실측 유량값을 최근(2006년)하에서의 유량으로 환산하였을 때 얻어지는 수위(환산수위)와 과거수위와의 관계 및 환산유속과 과거유속간의 관계 그리고 수위-통수단면적 관계, 수위-유속 관계 등의 상관식을 도출하여 기왕의 많은 자료들을 활용할 수 있도록 상관해석을 실시하였다.

• 한국농공학회논문집
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• 제47권5호
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• pp.75-86
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• 2005

Recently since urbanization has brought about a dried stream and a worse water quality, Anyang city discharged the third treated sewage into the upper stream of Anyancheon and Hakuicheon. As the result, Hakuicheon had the water level and velocity enough for a living thing in the water to live in but water quality was worse than it had been. Therefore in case of meeting the water level and velocity of the second grade water-quality which living things in the water can live in, the discharge and water quality to secure in-stream flow must be at least 0.350 $m^3/s$ and $BOD_5\;3.2 mg/{\iota}$ respectively. In Anyancheon the water level was increased a little higher than it had been but the velocity was almost unchanged in comparison with it before. On the other hand the water quality was a little better than it had been. Therefore in case of meeting the water level and velocity of the third grade water-quality that people can do water-friendly activity, the discharge and water quality to secure in-stream flow must be at least 0.688 $m^3/s$ and $BOD_5\;4.8 mg/{\iota}$ respectively. The water-quality prediction on the suggested eight scenarios was simulated in all satisfying the third grade water-quality.

• Ocean Systems Engineering
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• 제10권4호
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• pp.359-371
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• 2020

The performance of a multi-level overtopping wave energy converter (OWEC) has been numerically and experimentally investigated in a two-dimensional wave tank in order to study the effects of opening width of additional reservoirs. The device is a fixed OWEC consisting of an inclined ramp together with several reservoirs at different levels. A particle-based numerical simulation utilizing the Lattice Boltzmann Method (LBM) is used to simulate the flow behavior around the OWEC. Additionally, an experimental model is also built and tested in a small wave flume in order to validate the numerical results. A comparison in energy captured performance between single-level and multi-level devices has been proposed using the hydraulic efficiency. The enhancement of power capture performance is accomplished by increasing an overtopping flow rate captured by the extra reservoirs. However, a noticeably large opening of the extra reservoirs can result in a reduction in the power efficiency. The overtopping flow behavior into the reservoirs is also presented and discussed. Moreover, the results of hydrodynamic performance are compared with a similar study, of which a similar tendency is achieved. Nevertheless, the LBM simulations consume less computational time in both pre-processing and calculating phases.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.296-307
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• 2020

Permanent magnet sodium flowmeter (PMSF) have been used to measure the sodium flow in fast breeder reactors. Due to the effects of irradiation, thermal cycling, time lapse, etc., the magnetic flux density of the PMSF will decrease after being used in the reactor for a period of time. Therefore, it must be calibrated regularly. But some flowmeters that immersed in sodium cannot be removed for an off-line calibration, so the on-line calibration is required. However, the best online calibration accuracy of PMSF using cross-correlation analysis method was 2.0-level without considering the repeatability. In order to further improve this work, the operational principle of the transducer in PMSF is analyzed and the design principle of the transducer is proposed. The transducers were tested on the sodium flow loop to collect the experimental data. The signal characteristics are analyzed from the time and frequency domains, respectively. The cross-correlation analysis method based on biased estimation is adopted to obtain the flow rate. The verification experimental results showed that the measurement accuracy is 1.0-level when the flow velocity is above 0.5 m/s, and the measurement accuracy is 3.0-level when the flow velocity is in the range of 0.2 m/s to 0.5 m/s.

• 대한환경공학회지
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• 제22권1호
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• pp.149-157
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• 2000

깅릉 남대천 수계에서 처음으로 용존 비소(As)의 분포와 거동에 관한 연구가 수행되었다. 풍수기인 1997년 8월 28일(최종 방류량; $1.97{\times}10^6$ 톤/일)과 갈수기인 동년 11월 21일(최종 방류량; $0.13{\times}10^6$ 톤/0일). 두 차례에 걸쳐 조사된 As의 농도 분포는 같은 시기에 조사된 다른 중금속들과 다소 차이를 보인다. 도암댐 보다 오봉댐 유출수의 농도가 미소하게 높았고, 갈수기인 11월 하류부의 농도 급증현상도 나타나지 않았을 뿐 아니라 풍수기인 8월 하류부의 농도보다도 낮았다. 그리고 두 조사기간사이의 농도차가 미비하며, 원시적인 강들과 세계평균치에 비해서도 비교적 낮은 농도로서 남대천 수계에서는 As의 인위적인 오염원이 없고, 자연적인 배경농도(background level) 수준임을 알 수 있다. 하구에서 담수와 해수가 혼합되는 과정에서는 외부 유입이나 제거 기작없이 염분과 함께 직선적으로 증가하는 보존적인 분포를 보이며, 남대천을 통하여 동해로 유출되는 As의 양은 연간 65.12kg 정도이다.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.3902-3909
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• 2021

SACOS series of subchannel analysis codes have been developed by XJTU-NuTheL for many years and are being used for the thermal-hydraulic safety analysis of various reactor cores. To achieve fine whole core pin-level analysis, the input preprocessing and parallel capabilities of the code have been developed in this study. Preprocessing is suitable for modeling rectangular and hexagonal assemblies with less error-prone input; parallelization is established based on the domain decomposition method with the hybrid of MPI and OpenMP. For domain decomposition, a more flexible method has been proposed which can determine the appropriate task division of the core domain according to the number of processors of the server. By performing the calculation time evaluation for the several PWR assembly problems, the code parallelization has been successfully verified with different number of processors. Subsequent analysis results for rectangular- and hexagonal-assembly core imply that the code can be used to model and perform pin-level core safety analysis with acceptable computational efficiency.

• International Journal of Vascular Biomedical Engineering
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• 제1권2호
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• pp.13-19
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• 2003

Endothelial release of nitric oxide (NO) contributes to the regulation of vascular tone by inducing vascular relaxation. To estimate the blood flow-dependent nitric oxide level and half-life (T1/2) of nitric oxide in vivo state, we investigated the change of aortic NO currents during the change of aortic blood flow rate using NO-selective electrode system and electromagnetic flowmeter in the aorta of anesthetized rats. Resting mean aortic blood flow rate was $49.6{\pm}5.6ml/min$ in the anesthetized rats. NO currents in the aorta were increased by the elevation of blood pressure and/or blood flow rate. When the aortic blood flow was occluded by the clamping, aortic NO currents were decreased. The difference of NO concentration between resting state and occluded state was $1.34{\pm}0.26{\mu}M$ (n=7). This NO concentration was estimated as blood flow-dependent nitric oxide concentration in the rats. Also, while the aortic blood flow was occluded, NO currents were decreased with exponential pattern with $12.84{\pm}2.15$ seconds of time constant and $7.70{\pm}1.07$ seconds of half-life. To summarize, this study suggested that blood flow-dependent NO concentration and half-life of nitric oxide were about $1.3{\mu}M$ and 7.7 seconds, respectively, in the aorta of anesthetized rats. The nitric oxide-selective electrode system is useful for the direct and continuous measurement of NO in vivo state.

• 한국도로학회논문집
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• 제14권6호
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• pp.131-138
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• 2012

PURPOSES : Two-lane highways have one lane in each direction, and lane changing and passing maneuvers take place in the opposing lane depending on the availability of passing sight distance. 2001 Korea Highway Capacity Manual (KHCM) is classified into two classes of two-lane highways (Type I, II), and average travel speed and time-delayed rate are used as measures of effectiveness (MOEs). However, since existing two-lane highways have both uninterrupted and interrupted traffic flow-system elements, a variety of free-flow speeds exhibits in two-lane highways. In addition, it is necessary to check if the linear-relationship between volumes and time-delayed rate is appropriate. Then, this study is to reestablish the relationship between average travel speed, time-delayed rate, and flow. METHODS : TWOPAS model was selected to conduct this study, and the free-flow speeds of passenger cars and the percentage of following vehicles observed in two-lane highways were applied to the model as the input. The revised relationships were developed from the computer simulation. RESULTS : In the revised average travel speed vs. flow relationship, the free-flow speed of 90km/h and 70km/h were added. It shows that the relationship between time delayed-rate and flow appeared to be appropriate with the log-function form and that there was no difference in time-delayed rate between the free flow speeds. In addition to revise the relationships, the speed prediction model and the time-delayed rate prediction model were also developed. CONCLUSIONS : The revised relationships between average travel speed, time-delayed rate, and flow would be useful in estimating the Level of Service(LOS) of a two-lane highway.

• 한국물환경학회지
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• 제34권5호
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• pp.462-469
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• 2018

There are differences in method and cycle of flow rate survey depending on purpose of the operating department. To verify and use results of flow data according to the purpose, flow data of the directly measured and tele monitoring system were compared to verify validity. Flow measurement in the Ministry of Environment is aimed at setting up a standard flow of target water quality for water quality management and securing flow data of low and normal water level seasons for water quality evaluation. In this study, correlation analysis result ($R^2$) of same time zone data by direct measurement and tele monitoring system (TMS) at Seombon D point, a unit watershed of Seomjin river, for six years ('10 ~ '15) according to implementation of Total Daily Maximum Load (TDML) was wading 0.716, boating 0.962 and on bridge 0.943, and effectiveness of measurement method was verified by characteristics of flow duration as a season of dry and low-water; normal and high water are appropriate for wading, boating, and on bridge respectively. Results revealed it is reasonable to use directly measured results using the wading and boating method for low water level and dry seasons, and TMS data for rainy seasons. It can be used important data for future policy decisions.

• 한국응용과학기술학회지
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• 제40권5호
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• pp.1001-1009
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• 2023

몰입은 내적동기와 관련성이 큰 개념으로 스포츠심리학에서 스포츠 수행에 있어 긍정적인 요소로 여겨진다. 몰입과 중독의 상관관계에 대한 연구들이 선행되었지만, Flow와 Commitment의 개념이 혼동돼 사용되었다. 또한 몰입이 장기적으로 미치는 영향에 대해서는 충분한 연구가 이루어지지 않았다. 따라서 본 연구는 선행연구들을 통해 몰입의 중독성을 확인하였으며, 기존의 연구들과 다르게 장기적으로 몰입이 내적동기를 저하시킬 수 있다는 새로운 가설을 제시하고자 한다. 적응수준 이론과 한계효용체감의 법칙의 관점에서는 몰입을 통해 얻는 만족감이 지속적으로 감소하게 된다. 어느 시점에서 이러한 개인의 발전은 한계를 느끼게 되며, 몰입을 경험하지 못하는 시점에 도달하게 된다. 하지만 개인은 몰입을 다시 경험하고자 하는 욕구가 존재하므로 지속적으로 노력할 것이다. 그러나 몰입 경험의 실패로 이어질 때 반복적인 실패는 슬픔으로 작용하여 내적동기를 약화시키게 된다. 따라서, 본 연구를 통해서 몰입의 부정적인 요소와 장기적인 관점에서 미치는 영향에 대한 연구들이 필요하다고 사료된다.