• 한국환경보건학회지
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• 제9권1호
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• pp.1-13
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• 1983

This study was carried out to investigate nitrification in the main stream of the Naktong river for two times, 12-13 August and 23-26 September 1982. The results of this study were as follows : 1. The increase of nitrogen concentration was due to inflow of Geumho river, which was polluted by the municipal and industrial wastewater of Daegu city. 2. The rate constant of ammonia calculated for three reaches was high according to the stream flow and was eminently low in the reach from Goroung to Gangjung. (0.068-0.116 $day^{-1}$). This phenomena might be attributed to the sublethal or even lethal effect upon aquatic life by relatively low DO concentration and high heavy metal concentration. 3. DO consumption rate by nitrification was highest for the reach from Goroung to Daeam where was affected by Geumho river. (56.7-147.8%). This phenomena might be attributed to low DO concentration and high nitrogen concentration. Especially, the less stream flow was, the higher DO consumption was. And so, nitrification in the station where is low DO concentration, especially under the low flow condition, might cause more serious water quality management problem. Therefore, for the purpose of effective conservation of water quality in the Naktong river, it was suggested that We have more concern about the nitrogen compound, and more study on the nitrification phenomena.

• International Journal of Internet, Broadcasting and Communication
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• 제13권4호
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• pp.135-142
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• 2021

Estimating the locations of workers in a shipyard is beneficial for a variety of applications such as selecting potential forwarders for transferring data in IoT services and quickly rescuing workers in the event of industrial disasters or accidents. In this work, we propose a human movement stream processing system for estimating worker locations in shipyards based on Apache Spark and TensorFlow serving. First, we use Apache Spark to process location data streams. Then, we design a worker location prediction model to estimate the locations of workers. TensorFlow serving manages and executes the worker location prediction model. When there are requirements from clients, Apache Spark extracts input data from the processed data for the prediction model and then sends it to TensorFlow serving for estimating workers' locations. The worker movement data is needed to evaluate the proposed system but there are no available worker movement traces in shipyards. Therefore, we also develop a mobility model for generating the workers' movements in shipyards. Based on synthetic data, the proposed system is evaluated. It obtains a high performance and could be used for a variety of tasksin shipyards.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.11-16
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• 2002

In this paper, we present two successful results from active controls of flows over a circular cylinder and a sphere for drag reduction. The Reynolds number range considered for the flow over a circular cylinder is 40-3900 based on the free-stream velocity and cylinder diameter, whereas for the flow over a sphere it is $10^{5}$ based on the free-stream velocity and sphere diameter. The successful active control methods are a distributed (spatially periodic) forcing and a high-frequency (time periodic) forcing. With these control methods, the mean drag and lift fluctuations decrease and vortical structures are significantly modified. For example, the time-periodic forcing at a high frequency (larger than 20 times the vortex shedding frequency) produces $50{\%}$ drag reduction for the flow over a sphere at $Re=10^{5}$. The distributed forcing applied to the flow over a circular cylinder results in a significant drag reduction at all the Reynolds numbers investigated.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.670-677
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• 2005

In this study, we analyzed the three dimensional unsteady flow field around the motor cooling fan using the unsteady lifting surface theory. We obtained the flow rate for various geometries of fan from the calculated results of velocity field. For the data of design parameter and rotating speed(rpm) of the fan, we can predict the flow rate of the motor cooling fan with thin thickness through numerical analysis without the experimental data of the free stream velocity which is a boundary condition of flow field. the numerical results showed the flow rate within 10% of error in comparison with experimental results. The radial fans, which are often used as internal motor fan were also investigated with the same procedure.

• 대한기계학회논문집B
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• 제20권6호
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• pp.1971-1982
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• 1996

The breakup of liquid jet is the result of competing, unstable hydrodynamic forces acting on the liquid jet as it exit the nozzle. The nozzle geometry and up-stream injection conditions affect the characteristics of flow inside the nozzle, such as turbulence and cavitation bubbles. A set of calculation of the internal flow in a single hole type nozzle were performed using a two dimensional flow simulation under different nozzle geometry and up-stream flow conditions. The calculation showed that the turbulent intensity and discharge coefficient are related to needle position. The diesel nozzle with sharp inlet under actual engine condition has possibility of cavitation, but round inlet nozzle has no possibility of cavitation.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2022년도 학술발표회
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• pp.138-138
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• 2022

Understanding a stream's or river's discharge is essential for a variety of hydrological and geomorphological applications at various sizes. However, depending on the stream environment and flow conditions, it is crucial to use the appropriate techniques and instruments. This will ensure that discharge estimations are as reliable as possible. This study presents developed smart system for continuous measurement of open channel discharge and evaluate streamflow measurement over various techniques. This includes developed smart flow meter as flow point measurements, smart water level sensor (installed on Hydraulic Structure ? Weir) and current meters. Advantages and disadvantages of each equipment are presented to ensure that the most appropriate method can be selected. we found that smart water level sensor is more prominent once used during flood event as compared to smart flow meter and current meters, while current meters seems to show better accuracy once applied for open channel.

• 한국환경복원기술학회지
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• 제7권5호
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• pp.66-74
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• 2004

Since 1960s urban streams in Seoul have been dried and polluted because of urbanization. So, these devastated urban stream environment need to be restored for the better life of residents. Since 1995 stream restoration project which is called Natural-Style Stream Project have begun. However, some projects focused on the restoration of park-style open space rather than restoration of stream environment. As a result there are some stream landscapes to be improved. Therefore, this study aims to investigate the current status of urban stream landscape after Natural Style Stream Project and to propose the alternatives for the urban stream landscape improvement. The study site is Yangjae stream, Seoul.

• 한국인터넷방송통신학회논문지
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• 제17권3호
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• pp.115-120
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• 2017

생체의 움직임을 판별을 예측하는 기술은 흐름판별율과 스트림판별율로 변화의 형태를 구성하여 진행한다. 떨림의 움직이는 형태는 판별율의 조건에 따라 움직임의 유동시스템으로 구성한다. 흐름판별율은 생체 내 물질에서 특별한 부위의 신호를 대상으로 생체의 움직임을 정의하고 그 주변에 형태에 따라 흐름을 판별하여 떨림을 비교하여 신호값으로 선정한다. 스트림판별율은 스트림상태의 기준값을 설정하고 측정된 값과 비교하여 신호값으로 선정한다. 대상조건에 따라 판별은 특정부위의 상-아래-주변-중앙을 대상으로 최대치와 최소치 및 평균값으로 변수를 측정하였다. 떨림의 변화에 따라 상 $(-0.817){\pm}0.15$, 주변 $(-2.53){\pm}(-0.11)$, 아래 $(-0.29){\pm}0.03$, 중앙 $(-0.09){\pm}(-0.01)$ 의 최대치-최소치-평균값이 나타났다. 형태의 변화에 따른 현상을 통하여 생체의 움직임의 범위가 어떠한 형태의 유동현상을 갖고 있는지 예측할 수 있고, 특정부위의 상-아래-주변-중앙의 움직임으로 데이터를 구성하면 앞으로 특정부위의 여러 변화를 주었을 때 신체의 다양한 변화를 판별하는 예측기술이 진행될 것으로 판단된다.

• 한국수자원학회논문집
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• 제52권spc2호
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• pp.777-789
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• 2019

본 연구에서는 SWAT (Soil and Water Assessment Tool)을 이용하여 한강유역 ($34,148km^2$)내 다목적 댐(소양강댐, 횡성댐, 충주댐)의 하천유지유량 추가 방류 모의를 통한 유역의 수질 및 수생태계 건강성 변화를 평가하였다. 추가 방류기간은 수생태계 건강성 조사가 수행되는 봄(4-6월), 가을(8-10월)로 산정하였으며, 방류량은 댐의 기존 방류량에 비례하며 총 방류량이 댐별 고시된 하천유지유량을 초과하지 않도록 산정하였다. 하천 유지유량 방류에 따른 수질(T-N, $NH_4$, $NO_3-N$, T-P, $PO_4-P$) 농도는 봄철에 감소하지만 가을철에는 오히려 증가하는 것으로 모의되었다. 변화한 수질농도 데이터를 기존에 구축한 Random Forest 알고리즘에 적용하여 수생태계 건강성을 평가하였을 때, 유역의 하류에서 모든 수생태계 건강성 지수(FAI, TDI, BMI) 등급이 개선되는 것으로 분석되었다. 가을보다 봄에 하천유지유량 방류에 따른 수생태계 개선의 효과가 큰 것으로 나타났다.

• 한국물환경학회지
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• 제37권3호
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• pp.190-203
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• 2021

Water quality, benthic macroinvertebrate communities, and other factors were investigated to explore the effects of the effluent discharge from a sewage treatment plant into Jwagwang stream in Busan in 2019. During the study period, the flow rate of this stream was in the range of 10,400 m³/day to 52,200 m³/day except for the discharge of about 24,000 m³/day of the effluent. After discharge, the flow velocity increased by about 65% and the water depth increased by about 40%. At sites downstream of the discharge point, BOD, COD, TOC, T-N, T-P, and other water quality values were worse than those of the upstream sites. The periphytic algal chlorophyll-a concentrations in the natural substrata were higher than those of the upstream sites, especially in May and August. However, at sites downstream of the discharge point, the individual numbers of Annelida were decreased and individual numbers of the insecta of arthropoda were increased. Also, species numbers and the diversity and dominance indexes were improved in the sites downstream of the discharge point. The functional feeding groups (FFGs) of collector-filterers were increased and the habitat orientation groups (HOGs) of sprawlers, burrowers, and clingers were especially increased at the sites with additional reclaimed wastewater effluent flow. Regardless of the effluent discharge, BMI, an indicator of ecological stream health using benthic macroinvertebrate species, did not show large gaps between the study points. Although the water quality of the sites downstream of the discharge point was much worse than those upstream, their ecosystem soundness was better than those of the upstream sites from an ecological perspective.