• Journal of Korean Society on Water Environment
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• v.29 no.6
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• pp.762-776
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• 2013

Load duration curve was applied to determine important water quality parameter control term for improvement of Paldang lake water quality. Load duration curve was analyzed with long term data from 1985 to 2012 including water quality, flow rate and climate state of Paldang water environment. From the result of flow rate patterns of paldang lake, differences between high and low flow rate of each year showed tendency of increase because rainfall characteristics of paldang lake watershed were changed by climate exchange. Both of land use state of upper Paldang lake watershed and number of limit excess from load duration curve indicated that seasonal action related with land use such as agricultural fertilizer distribution in upper watershed affected Paldang lake water quality. So focused BOD (biological oxygen demand) management during spring season from march to June is required to control organic materials in Paldand lake. The main affecting factor of TOC (total organic carbon) increase in Paldang lake was initial rainfall after march. T-N (total nitrogen) kept increasing during research period, so enhancement of T-N standard is needed to T-N control. Initial rainfall and increase of temperature during spring season from March to June showed a positive correlation with TP (total phosphorus) and Chl-a, respectively.

• Journal of Korean Society on Water Environment
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• v.34 no.4
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• pp.391-398
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• 2018

The main purpose of this study is to suggest and recommend the more reliable flow direction methods within the framework of DEM and power law distribution, by investigating the existing methodologies. To this end SFD (single flow direction method), MFD (multiple flow direction method) and IFD (Infinite flow direction method) are applied to analyze the determination of a flow direction for the water particles as seen in the Jeonjeokbigyo basin, and then assessed with respect to the variation of flow accumulation in that region. As the main results revealed, the study showed the different patterns of flow accumulation are found out from each applications of flow direction methods utilized in this study. This brings us to understand that as the flow dispersion on DEM increases, in this case the contributing areas to the outlet grow in sequence of SFD, IFD, MFD, but it is noted that the contribution of individual pixels into outlet decreases at that time. In what follows, especially with the MFD and IFD, the result tends to make additional hydrologic abstraction from rainfall excess, as noted due to the flow dispersion within flow paths on DEM. Based on the parameter estimation for a power law distribution, which is frequently used for identify the aggregation structure of complex system, by maximum likelihood flow accumulation can be thought of as a scale invariance factor. In this regard, the combination of flow direction methods could give rise to the more realistic water flow on DEM, as revealed through the separate flow direction methods as utilized for dispersion and aggregation effects of water flow within the available different topographies.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.660-667
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• 2017

Equilibrium data of the mixture is essential in the design and operation of separation equipment such as distillation or extraction in chemical processes. These equilibrium data can be obtained through experiments or by calculations using the known binary parameters and the thermodynamic models. Generally, to obtain these parameters, phase equilibrium experimental data such as gas-liquid and liquid-liquid are used. In this study, the excess enthalpy of the mixture was measured using the flow type microcalorimeter which is a simpler method than phase equilibria experiments, and the parameters of various theories were obtained by using this data. In order to investigate the relationship between carbon chain length, enthalpy and binary parameters in the alkane system, excess enthalpies for the n-hexane + alkane (n-pentane, n-heptane, n-octane and n-dodecane) were measured at 298.15 K and the banary interaction parameters of Wilson, NRTL, and UNIQUAC were obtained from the experimental data. In addition, we wanted to obtain basic information on the interaction and association phenomena of the system including electrolyte applicable to various fields by using the excess enthalpy experimental data and the existing theory. First, we investigated the excess enthalpy for the NaOH / Water / Ethanol system as a basic experiment and examined the applicability using the electrolyte-NRTL (eNRTL) theory.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.489-495
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• 2006

Proton exchange membrane (PEM) should be sufficiently hydrated with a careful consideration of heat and water management. Water management has been a critical operation issue for better understanding the operation and optimizing the performance of a PEM fuel cell. The flooding on cathode side resulting from excess water can limit the fuel cell performance. In this study, the visual cell was designed and fabricated fur the visualization of liquid water droplet dynamics related to cathode flooding in flow channels. The experiment was carried out to observe the formation, growth and removal of water droplets using CCD imaging system. Effects of operating conditions such as cell temperature, air flow rate and air relative humidity on cathode flooding characteristics were mainly investigated. Based on this study, we can get the basic insight into flooding phenomena and its two-phase flow nature. It is expected that data obtained can be effectively used fur the setup and validation of two-phase PEM fuel cell models considering cathode flooding.

• Journal of The Korean Society of Agricultural Engineers
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• v.63 no.2
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• pp.85-96
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• 2021

Irrigation return flow is defined as the excess of irrigation water that is not evapotranspirated by direct surface drainage, and which returns to an aquifer. It is important to quantitatively estimate the irrigation return flow of the water cycle in an agricultural watershed. However, the previous studies on irrigation return flow rates are limitations in quantifying the return flow rate by region. Therefore, simulating irrigation return flow by accounting for various water loss rates derived from agricultural practices is necessary while the hydrologic and hydraulic modeling of cultivated canal-irrigated watersheds. In this study, the irrigation return flow rate of agricultural water, especially for the entire agricultural watershed, was estimated using the SWMM (Storm Water Management Model) module from 2010 to 2019 for the Madun reservoir located in Anseong, Gyeonggi-do. The results of SWMM simulation and water balance analysis estimated irrigation return flow rate. The estimated average annual irrigation return flow ratio during the period from 2010 to 2019 was approximately 55.3% of the annual irrigation amounts of which 35.9% was rapid return flow and 19.4% was delayed return flow. Based on these results, the hydrologic and hydraulic modeling approach can provide a valuable approach for estimating the irrigation return flow under different hydrological and water management conditions.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.04a
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• pp.204-209
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• 1997

This paper reports on the theoretical study of the vane motions in a positive displacement vane pump. Vane detachment cause the pressure fluctuation, noise, wear in cam ring, and decrease the volumetric efficiency. Dynamic equation of vane motion and flow continuity equation have been modeled and solved simultaneously using 4th order Runge-Kutta method. As results of analysis, vane detachment occurs due to pressure overshoot by excess compression in the pumping chamber. Amount of vane detachment has been reduced by decreasing the pressure overshoot.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.292-296
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• 1992

There are lots of disturbance in the super heater temperature control system of power plant boiler as follows. 1.Burner light off. 2.Excess Air. 3.Burner tilt. 4.G.R fan flow. Temperature control system of super heater in the power plant has delay time about 5 min. So it is difficult to control the super heater temperature in the power plant. This paper show us the application of domestic development DCS to control the super heater temperature in seoul #5 thermal power plant unit.

• Journal of Digital Convergence
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• v.11 no.8
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• pp.199-204
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• 2013

Computational fluid dynamics (CFD) is used to reduce number of experiments. The CFD tools are widely used for engine design and flow pattern analysis to reduce experiments. In this study the performance of a PEMFC single cell was analyzed by using STAR-CD, product of CD-ADAPCO. The effect of cell design and flow pattern on the performance of a PEMFC was analyzed with the 3-D simulation. As a result the performance of rectangular cell was the higher than that of square cell, while the flow direction scarcely affected on the performance of a PEMFC. Also the current density according to different excess ratio of air flow rate was compared and analyzed. The difference between maximum and minimum current density of flip-flow was lower than that of co-flow.

• Journal of Korean Society on Water Environment
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• v.34 no.1
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• pp.33-45
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• 2018

In this study, we discussed the application of Watershed model and Load Duration Curves (LDC) in Total Water Load Management System. The Flow Duration Curves (FDC) and the LDC were generated using the results of the daily HSPF model and analyzed on monthly or yearly flow duration variability, and non-point pollutant discharge loads by entire flow conditions. As a result of the calibration and verification of the HSPF model, both the flow and the water quality were appropriately simulated. The simulated values were used to generate the Flow Duration Curve and the Load Duration Curve, and then the excess rate by entire flow conditions was analyzed. The point and non-point pollutant discharge loads for entire flow conditions were calculated. It is possible to evaluate the variability of water quality in specific flow duration through the curves reflecting the flow duration variability and to confirm the characteristics of the pollutant source. For a more scientific Total Water Load Management System, it is necessary to switch from a current system to a system that can take into account the entire flow conditions. For this, the application of the watershed model and load duration curve is considered to be the best alternative.

• Journal of Korean Society on Water Environment
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• v.28 no.6
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• pp.933-942
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• 2012

The purpose of this study is to evaluate the degree of waterbody impairment according to the flow conditions and present to the appropriate water quality improvement alternatives using observed water quality and flow for Total Maximum Daily Load (TMDL) implementation at 39 unit watersheds the nakdong river basin. Observed water quality data for 7 years are divided into five cumulative flow frequency group and comparing the each observed water quality data and TMDL Target water quality (TWQ) the last evaluate the water quality is impaired group. We found that the cumulative flow frequency group-specific the average excess rate of V group was the highest (32.86%), followed by the IV group (26.04%), group III (23.36%), II group (22.67%), I group (20.70%), the degree of impaired waterbody tended to be inversely proportional to the flow rate. Resulted from cumulative flow frequency group of impaired water quality assessment, 13 unit watersheds are impaired from a group IV and group V affected by point sources. Therefore, improvement of sewage discharge and the initial composition of the riparian buffer zone are needed. Nakbon F, Namkang D and Namkang E within 13 unit watersheds are impaired from group II and III affected by non-point sources. Therefore, application of Best Management Practices (BMPs) is needed for these watersheds. Evaluation of impaired waterbody using Cumulative flow frequency group is able to determine the extent of the judgment to TWQ exceeded by the flow conditions and helps proper setting Standard flow and planning pollutant reduction for TMDL.