• The KSFM Journal of Fluid Machinery
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• v.17 no.2
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• pp.41-47
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• 2014

Experimental results are given for the vertical motion of water in the water chambers for wave energy converter aligned along the wave propagation direction in order to avoid the impulsive wave forces. This paper mainly focuses on the property of the amplitude of the vertical motion of the water surface in the chambers. The amplification has been investigated by dimensionless parameters of wave period to resonance period ratio of the U-shaped oscillation, $T/T_r$, chamber size to wave length ratio, l/L, water depth to wave length ratio, h/L, amplitude of up-down motion of water particles to draft of the front wall ratio, ${\zeta}/D$. It has been shown that l/L should be less than 0.1 and as $T/T_r$ approaches unity the up-down of the water in the chambers is amplified. Also, the structure of the walls which form th water chambers has been examined roughly. It is deduced that the chambers set on both sides of the hull of a single-point moored floating vessel is preferable to those set along a fixed structure such as breakwaters.

• Journal of Ocean Engineering and Technology
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• v.36 no.1
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• pp.21-31
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• 2022

In recent years, various studies have been conducted on oscillating-water-column-type wave energy converters (OWC-WECs) with multiple chambers with the objective of efficiently utilizing the limited space of offshore/onshore structures. In this study, a numerical investigation based on a numerical wave tank was conducted on single, dual, and triple OWC chambers to examine the hydrodynamic performances and the energy conversion characteristics of the multiple water columns. The boundary value problem with the Laplace equation was solved by using a numerical wave tank based on a finite element method. The validity of the current numerical method was confirmed by comparing it with the measured data in the previous experimental research. We undertook a series of numerical simulations and observed that the water column motion of sloshing mode in a single chamber can be changed into the piston motion of different phases in multiple OWC chambers. Therefore, the piston motion in the multiple chambers can generate considerable airflow at a specific resonant frequency. In addition, the division of the OWC chamber results in a reduction of the time-dependent variability of the final output power from the device. As a result, the application of the multiple chambers leads to an increase of the energy conversion performance as well as a decrease of the variability of the wave energy converter.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.1
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• pp.37-44
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• 1996

Water hammer pressure waves were measured in a simplified water piping system with and without arresters and air chambers by the operations of the solenoid valve. Experiments were performed to investigate the effects of the location of the arresters and the effects of the volume of the air chambers on maximum and minimum water hammer pressures and wave frequency for various flow rates.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.3
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• pp.239-245
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• 2017

As a new technical approach, wave energy converter by using vertical motion of water in the multiple water chambers were developed to realize actual wave power generation as eco-environmental renewable energy. And practical use of wave energy converter was actually to require the following conditions: (1) setting up of the relevant device and its application to wave power generation in case that severe wave loading is avoided; (2) workability in installation and maintenance operations; (3) high energy conversion potential; and (4) low cost. In this system, neither the wall(s) of the chambers nor the energy conversion device(s) are exposed to the impulsive load due to water wave. Also since this system is profitable when set along the jetty or along a long floating body, installation and maintenance are done without difficulty and the cost is reduced. In this paper, we describe the system which consists of a float, a shaft connected with another shaft, a rack and pinion arrangement, a ratchet mechanism, and rotary type generator(s). Then, we present the dynamics model for evaluating the output electric power, and the results of numerical calculation including the effect of the phase shift of up/down motion of the water in the array of water chambers aligned along the direction of wave propagation.

• Journal of People, Plants, and Environment
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• v.23 no.1
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• pp.15-21
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• 2020

In this study, we compared efficiency of different aquatic plants in removing indoor pollutants and examined their potential to purify indoor air. Two liter of water in chamber was used as the control, while the other chambers containing water lettuce (Pistia stratiotes), water hyacinth (Eichhornia crassipes), and water coin (Hydrocotyle umbellata) were used as treatment groups. Temperatures inside all the chambers were maintained between 20 ℃ and 23 ℃. Humidity in the chambers with aquatic plants increased by 30% and 50% control respectively. The removal of formaldehyde per unit leaf area was examined in each aquatic plant. It turned out that water hyacinth removed the highest amount of formaldehyde, followed by water lettuce and water coin. Both water hyacinth and water lettuce increased the amount of removal of formaldehyde until the end of the experiment. In the case of airborne dust (PM 10) and fine dust (PM 2.5), water coin, which had the highest number of leaves, removed more PM 10 and PM 2.5 than the other aquatic plants, with statistically significant difference. In addition, both water coin and water hyacinth smoothly opened and closed stomata before and after the experiment. Consequently, as the aquatic plants were effective in controlling humidity and removing pollutants, they can be used as air purifying plants.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5B
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• pp.459-467
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• 2006

In this study, hydraulic and numerical model experiments were performed to analyze and improve the effects of flow-rate increase in the intake canal of Boryeong Thermal Power Plants on the flow condition in the circulation water pump (CWP) chambers. Based on the numerical simulation results, when the flow-rate increased in the circulation water intake canal, the velocity in the canal and vertical vorticities in the circulation water pump chambers increased and hence the vortex occurrence potential would be greatly increased. It was found by performing hydraulic model experiments that the velocity distribution near the bottom in the inlet of the circulation water pump chambers was highly non-uniform while the velocity distribution near the water surface was nearly uniform. To reduce the non-uniformity in the velocity distribution, triangular flow deflectors were devised. The installation of the flow deflectors in the inlet of circulation water pump chambers was successfully to reduce velocity non-uniformities and to remove flow reversal problems.

• Journal of Korea Water Resources Association
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• v.38 no.8 s.157
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• pp.631-643
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• 2005

The objective of this study is to perform hydraulic and numerical model experiments of the flows in circulation-water-pump(CWP) chambers of combined cycle power plants (CCPP) to be built and to suggest improvement plans if the flows might cause a serious problem on the operation of CWPs. Hydraulic model was constructed in a scale of 1 to 20 using acrylic sheets and a two dimensional numerical model used was RMA2. To evaluate results of Hydraulic and numerical model experiments, evaluation criteria of flow conditions in the intake canal and CWP chambers were determined. Vertical vorticities obtained from numerical simulations for the initial plan of CCPPs were qualitatively compared with results of hydraulic model experiments and the formation possibility of a large scale vortex, one of the flow evaluation criteria, was evaluated. The initial plan was found not to satisfy the flow evaluation. Nine improvement plans were devised and numerically simulated. Four alternative plans among nine improvement plans were selected and hydraulically experimented. On the ground of the results of hydraulic model experiments, a final improvement plan, one of four improvement plants, was suggested. When CWP chambers and intake canals were designed with spatial constraints, flow separating wall and guide walls were found to improve flow conditions in CWP chambers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.1-5
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• 2000

As the semiconductor devices are miniaturized, the number of the unit cleaning processes increases. In order to processes by conventional RCA cleaning process, the consumption of volume of liquid chemical and DI water became huge. Therefore, the problem of environmental issues are evolved by the increased consumption of chemicals. To resolve this matter, an advanced cleaning process by Electrolyzed Water was studied in this work. The electrolyzed water was made by an electrolysis equipment which was composed of three chambers of anode, cathode, and middle chambers. In the case of electrolyzed water with electrolytes in the middle chamber, oxidatively acidic water of anode and reductively alkaline water of cathode were obtained. The oxidation/reduction potentials and pH of anode water and cathode water were measured to be +l000mV and 4.8, and -530mV and 6.3, respectively. The Si-wafers contaminated with metallic impurities were cleaning with the electrolyzed water. To analysis the amounts of metallic impurities on Si-water surfaces, ICP-MS(Inductively Coupled Plasma-Mass spectrometer) was introduced. From results of ICP-MS measurements, it was concluded that the ability of electrolyzed water was equivalent to that of the conventional RCA cleaning.

• Proceedings of the KAIS Fall Conference
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• 2001.05a
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• pp.124-128
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• 2001

A present semiconductor cleaning technology is based upon RCA cleaning technology which consumes vast amounts of chemicals and ultra pure water(UPW) and is the high temperature Process. Therefore, this technology gives rise to the many environmental issues, and some alternatives such as functional water cleaning are being studied. The electrolyzed water was generated by an electrolysis system which consists of anode, cathode, and middle chambers. Oxidative water and reductive water were obtained in anode and cathode chambers, respectively. In case of NH$_4$Cl electrolyte, the oxidation-reduction potential and pH for anode water(AW) and cathode water(CW) were measured to be +1050mV and 4.8, and -750mV and 10.0, respectively. AW and CW were deteriorated after electrolyzed, but maintained their characteristics for more than 40 minutes sufficiently enough for cleaning. Their deterioration was correlated with CO$_2$ concentration changes dissolved from air. It was known that AW was effective for Cu removal, while CW was more effective for Fe removal. The particle distributions after various particle removal processes maintained the same pattern. In this work, RCA consumed about 9$\ell$chemicals, while EW did only 400$m\ell$ HCI electrolyte or 600$m\ell$ NH$_4$Cl electrolyte. It was hence concluded that EW cleaning technology would be very effective for eliminating environment, safety, and health(ESH) issues in the next generation semiconductor manufacturing.

• Journal of Aquaculture
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• v.16 no.4
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• pp.252-256
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• 2003

Effluent from farm trefish contained high concentrations of nitrogen and phosphorus, such kinds of nutrients were released to the environment without proper treatment and thses increased the pollution of the environment. We evaluated the conventional treatment system with cost effective ecotechnologies for the removal of nutrients. Water lettuce chambers were investigated under the various experimental conditions to improve the efficiency of N&P removal and the treatment of from aquaculture effluent. In this research, six water lettuce chambers (80 liter each) received combination of aquaculture wastewater effluent at hydraulic retention times (HRTs) of 1, 2, 4 and 8days. The water lettuce chambers operated at a 8 day HRT investigated for aquaculture effluent (1'st) showed average removal efficiency, BOD, T-N, T-P of 92.8, 79.0 and 93.6% on average respectively.