• Membrane and Water Treatment
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• v.7 no.2
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• pp.115-126
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• 2016

In this study, computational fluid dynamics (CFD) analysis was conducted to investigate the flow pattern and to find the occurrence of dead zones in an existing capacitive deionization (CDI) cell. Newly designed cells-specifically designed to avoid dead zones-were analyzed by CFD in accordance with the flow rates of 15, 25 and 35 ml/min. Next, the separation performances between the existing and newly designed cell were compared by conducting CDI experiments in terms of salt removal efficiency at the same flow rates. Then, the computational and experimental results were compared to each other. The salt removal efficiencies of the hexagon flow channel 1 (HFC1) and hexagon flow channel 2 (HFC2) were increased 88-124% at 15 ml/min and 49-50% at 25 ml/min, respectively. There was no difference between the existing cell and the foursquare flow cell (FFC) at 35 ml/min.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1645-1650
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• 2005

FOPDT(First-Order Plus Dead-Time) and SOPDT(Second-Order Plus Dead-Time) process, which are used as the most useful process in industry, are difficult about process identification because of the long dead-time problem and the model mismatch problem. Thus, the accuracy of process identification is the most important problem in FOPDT and SOPDT process control. In this paper, we proposed the real-coded genetic algorithm for identification of FOPDT and SOPDT processes. The proposed method using real-coding genetic algorithm shows better performance characteristic comparing with the existing an area-based identification method and a directed identification method that use step-test responses. The proposed strategy obtained useful result through a number of simulation examples.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.2
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• pp.162-168
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• 1997

Digital variable structure controller(DVSC) is implemented to control the temperature for the hot water heating circulating pump control system. For the DVSC, a control algorithm is suggested, which using a nonlinear sliding surface and a PID sliding surface outside and inside of steady state error boundary layer, respectively. Smith predictor algorithm is used for the compensation of long dead time. The DVSC of the suggested algorithm yields improved control performance compared with the one of existing algorithm. The system responses with the suggested DVSC shows good responses without overshoot and steady state error inspite of heating load change. By decreasing sampling time, dead time and rise time are increasing, and system output noise by flow dynamics is amplified.

• Water for future
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• v.12 no.1
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• pp.56-59
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• 1979

A prompt subsurface runoff producing mechanism whih creaters a depletion curve of direct runoff hydrograph is simulated by a dead zone dispersion model technique. Runoff processes are carried out by routing of the outflow resulted from previous linear channel and effective rainfall from its corresponding subwatershed through a series of conceptual linear channels representing subwatersheds of a catchment. Working rules are explained for evaluation the model parameters such as translatory velocity, diffusive factor, and parameters concerning the infiltration and relative magnitude of the prompt subsurface flow region.

• The Korean Journal of Ecology
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• v.20 no.5
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• pp.367-373
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• 1997

The effects of salinity on the growth and production of rice were studied at Seosan reclaimed land from July to October, 1995. The plant height, the number of living aleaves, dead leaves and total leaves, the number of the grains and the dry weight of the grains per individual, and the dry weight of above the ground in $25cm{\times}25cm$ quadrat were investigated on 5 plots whers were different salinity. The plant height, the number of living leaves and total leaves and the number of grains and the dry weight of grains per individual, and the dry weight of above the ground decreased as the salinity of water increase and the number of dead leaves of rice increased as the salinity of water decrease. The effect of salinity on the reproductive production is severer than the vegetative production. Because of the salinity, the growth and the production of the rice at Seosan reclaimed land are worse than the normal rice field.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.6
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• pp.717-726
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• 2007

Fully-grown flocs in a mixing tank of membrane filtration with dead-end membrane are ruptured while passing through a pump and the ruptured flocs are aggregated again in a Membrane-Feed-Pipe (MFP). To look at more details, this study tries to relate the reaggregation to a parameter of mixing intensity in MFP, i.e., G-value. The G-value is a function of Reynolds number, pipe diameter, friction factor and average velocity in MFP. To deal with polydispersity condition, we develop a representative particle size called in this study EDPD (Effective Diameter for Polydispersity condition in Dead-end filtration). The experimental results show that as the G-value increases, the EDPD decreases and also the cake resistance increases. Through comparison between EDPD and cake resistance, these results show that cake resistances are controlled by reaggregation phenomenon in MFP. The effect of detention time in MFP, however, does not affect the reaggregation of the broken flocs as G-values are increased.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.1
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• pp.65-75
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• 1996

A pilot plant, which is simplified the hot water heating control system of a large scale residential building, is used to investigate the effects of control methods and operating conditions on the system performance and to compare control characteristics. Digital variable structure controller(DVSC) and digital PI controller are implemented to control the speed of the circulating pump for the pilot plant using PC. For the DVSC, a control algorithm is suggested, which using a nonlinear sliding surface and a PID sliding surface outside and inside of output error boundary layer, respectively. Smith predictor algorithm is used for the compensation of long dead time. The suggested DVSC yields improved control performance compared with existing DVSC using linear sliding surface only. the system responses with the suggested DVSC shows good responses without overshoot for various operating conditions and robust under external disturbances compared with digital PI controller.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.6
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• pp.643-648
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• 2010

Portable fuel cells are commonly operated in the dead-end mode because of such as high fuel utilization. However, the performance of such systems deteriorates continuously with an increase in the amount of by-products such as water vapor and nitrogen. In this study, to verify the effect of water vapor on Proton Exchange Membrane Fuel Cells (PEMFCs), constant-load experiments were carried out for a current density of 600 mA/cm2 and a voltage of 0.4 V, respectively. The performance of the cell was more stable under constant voltage conditions than under constant current density conditions. Condensed water accumulated in the anode channel near the cell outlet. The experimental results show how the relative humidity (RH = 0.15, 0.4 and 0.75) of air at the cathode side affect the performance of PEMFCs with dead-end anode. At RH values higher than 0.15, the mean power density increased by up to 51% and the mean purge duration decreased by up to 25% compared to the corresponding initial values.

• The Korean Journal of Mycology
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• v.12 no.3
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• pp.99-103
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• 1984

Hyphal growth by Fusarium moniliforme was best at -14 bars osmotic water potential. Hyphal growth was prevented at -94 bars. The production of microconidia was best at -14 bars osmotic potential and prevented at -84 bars regardless of Strain. In contrast, this fungus sporulated macroconidia best at -1.4 bars and progressively less with each increment drop in water potential below that of basal media. The rate of spore germination followed a similar pattern with all of the spores; uniformly maximal at about -1.4 bars and progressively slower as the water potential was lowered from -1.4 bars to -42 bars. Under the natural conditions, plants infected by F. moniliforme produce microconidia on the dead tissues instead of producing macroconidia. This phenomenon agrees well with the water potential experiment since the dead plant tissues have a lower water potential than the living plant.

• Journal of Korean Society on Water Environment
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• v.34 no.2
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• pp.173-182
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• 2018

Reservoirs, facilities to store water, are being used in several fields for their ability to hold back a large quantity of water for a long time before the water is actually used. However, at the same time, the reservoirs are considered to have a flaw: the longer they store water, the more the quality of water in these reservoirs deteriorates. Further, when the reservoirs are large, they are more likely to have dead-water regions in out-of-the way spots far from either an in-current or an ex-current canal. This study conducted a Computational Fluid Dynamic (CFD) simulation and tried to figure out the internal flow inside each of the reservoirs with different in-current canals built by the multiple hoe screw nozzle method and the drop in-current method. The drop in-current method is more frequently used. According to the analysis of the internal flow inside each reservoir with the different methods applied, we found that the reservoir with the drop in-current canal would have two rotary currents in the lower region of the reservoir and that the velocity of flow would decrease. For a reservoir with the screw nozzle method, a single rotary current occurred, and inside the reservoir, regardless of height, the current turned out to flow in a regular manner.