• Journal of Korean Society on Water Environment
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• v.30 no.3
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• pp.298-303
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• 2014

We measured by electrochemical method for TRC (total residual chlorine) in ocean. From the results of Au electrode used for working electrode through cyclic voltammetry test, we obtained charge in voltage ranged from 0.0V-1.0V, and analyzed correlations of charge for TRC. Reduction peak TRC was investigated to be approximately 0.65 V vs. Ag/AgCl, and in the case that salt concentrations and temperatures in ocean appeared different, charge was analyzed for being different in the same TRC. However, in the case that each condition was constant, charge was measured at highly correlations for TRC.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.8
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• pp.661-666
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• 2003

Constant area expansion devices such as capillary tubes, short tube orifices are being gradually replaced with electronic expansion valves (EEVs) because of increasing focus on comfort and energy conservation. In this study, the performance of a water-to-water heat pump as a function of refrigerant charge is investigated in steady state, cooling mode operation with expansion devices of a capillary tube and an EEV. The performance of the capillary tube system varies drastically according to the change of refrigerant charge amount and inlet temperature of the secondary fluid in the condenser. Cooling capacity and COP of the EEV system show little dependence on the refrigerant charge, while those are strongly dependent on the secondary fluid temperature at the condenser inlet. In general, for a wide range of operating conditions the EEV system shows much higher performance as compared with the capillary tube system. The performance of the EEV system can be optimized by adjusting EEV opening to maintain a constant superheat at all test conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.207-210
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• 1998

Electrical properties such as space charge distribution and electrical conduction of XLPE/VLDPE blends were studied. When the VLDPE is blended, residual charge inside XLPE increases. In case of electrical conduction characteristics, there were no changes in electrical conduction mechanism, space charge limited conduction. XLPE/VLDPE blend including crosslinking coagent showed relatively small current density. It might be due to the carbonyl group in crosslinking coagent.

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.71-74
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• 2002

The apparent barrier height for charge transfer through an interfacial water layer between a Pt/Ir tip and a gold surface has been measured using STM technique. The average thickness of the interfacial water layer inside an STM junction was controlled by the amount of moisture. A thin water layer on the surface was formed when relative humidity was in the range of 10 to 80%. In such a case, electron tunneling through the thin water layer became the majority of charge transfers. The value of the barrier height for the electron tunneling was determined to be 0.95 eV from the current vs. distance curve, which was independent of the tip-sample distance. On the other hand, the apparent barrier height for charge transfer showed a dependence on tip-sample distance in the bias range of 0.1-0.5 V at a relative humidity of approximately 96%. The non-exponentiality for current decay under these conditions has been explained in terms of electron tunneling and electrochemical processes. In addition, the plateau current was observed at a large tip-sample distance, which was caused by electrochemical processes and was dependent on the applied voltage.

• Proceedings of the KIEE Conference
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• 2000.07e
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• pp.9-12
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• 2000

A new type electrolyzing cell with slits on parallel plate electrodes and wire-to-cylinder type electrode system has been proposed instead of the conventional parallel plate type. An investigation was carried out on the effect of the number and size of slits on ion precipitation and oxidant generation characteristics, evidenced by eliminated space charge limiting action and by elevated electric fields in active interelectrode spacing. And it is also studied on the effect of the diameter of wire electrode to ion precipitation and oxidant generation characteristics. With electrode with 48 slits, very oxidants generation water of 3.1 [ppmm] and 19.0 [ppmm] in positive electrode side were obtained with tap water and 0.1 [wt%] NaCl dissolved tap waterfed. In addition, with wire-to-cylinder type electrode system, it is found that oxidant contained water of 0.48 [ppmm] and 5.46 [ppmm] in positive electrode side were obtained with tap water and 0.1 [wt%] NaCl dissolved tap water fed for the case of discharge electrode diameter of 0.5 [$mm{\phi}$]. Consequently, very high ion precipitation and dense oxidant generation characteristics can be realized by having slits on the electrodes of conventional cell as these slits increase the electric fields and decrease the space charge limiting actions in interelectrode spacing.

• Safety and Health at Work
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• v.8 no.3
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• pp.296-305
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• 2017

Background: Surfactant-containing water sprays are commonly used in coal mines to collect dust. This study investigates the dust collection performance of different surfactant types for a range of coal dust particle sizes and charges. Methods: Bituminous coal dust aerosol was generated in a wind tunnel. The charge of the aerosol was either left unaltered, charge-neutralized with a neutralizer, or positively- or negatively-charged using a diffusion charger after the particles were neutralized. An anionic, cationic, or nonionic surfactant spray or a plain water spray was used to remove the particles from the air flow. Some particles were captured while passing through spray section, whereas remaining particles were charge-separated using an electrostatic classifier. Particle size and concentration of the charge-separated particles were measured using an aerodynamic particle sizer. Measurements were made with the spray on and off to calculate overall collection efficiencies (integrated across all charge levels) and efficiencies of particles with specific charge levels. Results: The diameter of the tested coal dust aerosol was $0.89{\mu}m{\pm}1.45$ [geometric $mean{\pm}geometric$ standard deviations (SD)]. Respirable particle mass was collected with $75.5{\pm}5.9%$ ($mean{\pm}SD$) efficiency overall. Collection efficiency was correlated with particle size. Surfactant type significantly impacted collection efficiency: charged particle collection by nonionic surfactant sprays was greater than or equal to collection by other sprays, especially for weakly-charged aerosols. Particle charge strength was significantly correlated with collection efficiency. Conclusion: Surfactant type affects charged particle spray collection efficiency. Nonionic surfactant sprays performed well in coal dust capture in many of the tested conditions.

• Journal of Environmental Health Sciences
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• v.35 no.1
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• pp.64-70
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• 2009

The aims of this study is to examine the effects of the changes in HRT(Hydraulic Retention Time) and media charge in a water-mill, among other operation factors, on the nitrogen and phosphorus removal in order to use up-flow anaerobic reactors, anoxic reactors and water-mill aerobic reactors for sewage treatment. The extension of HRT improved the nitrogen removal efficiency, however the removal pattern was constant regardless of HRT. The removal of phosphorus was constant (80%-90%) regardless of the change in HRT. The removal rate with change in influx load varied such that at the OLR (Organic Load Rate) of 1-3 kg/d, the T-N removal efficiency was 80.7%-88.9% and the T-P removal efficiency was 82.9%-89.3% while at the NLR (Nitrogen Loading Rate) of 0.108-0.156 kg/d the removal efficiencies were 80.7-88.9% (T-N) and 82.9-89.3% (T-P). The analyses of the nitrogen and phosphorous removal characteristics with the C/N and C/P ratio showed that the mean T-N removal rate was 88% at the C/N ratio of 1.2-2.6, and that the mean T-P removal rate was 86% at the C/P ratio of 7.2-14.1. Also, the analysis of nitrogen and phosphorous removal characteristics were analyzed in relation to media charge. The comparison between with and without media charge in the water-mill showed that while the nitrogen removal efficiencies were 86-94% and 85-89% respectively, the difference of phosphorous removal efficiencies were between the two conditions was not significant, thus it suggested that the media charge has less effect on the removal efficiency of phosphorous compared to that of nitrogen.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.95-98
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• 2006

Filtration by fibrous filter is one of the Principle methods used for removing pollutant particles in the liquid. Because of the increasing need to protect both human health and valuable devices from exposure to fine particles, filtration has become more important. Filters have been developed with modified surface charge characteristics to capture and adsorb particles by electrokinetic interaction between the filter surface and particles contained in water. The main purposes of this study are to develop and evaluate the performance evaluation of the apparatus for making a positively charged porous filter media and to analyze the surface characteristics of the filter media for capturing negavitely charged contaminants mainly bacteria and virus from water. The experimental apparatus consists of a mixing tank, a vacuum pumping system, a injection nozzle, a roller press and a controller. The filter media is composed of glass fiber(50-750 nm), cellulose($10-20{\mu}m$) and colloidal charge modifier. The characteristics of filter media is analyzed by SEM(Scanning Electron Microscopy), AFM(Atomic Force Microscopy) and quantified by measuring the zeta potential values.

• Journal of Ocean Engineering and Technology
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• v.33 no.4
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• pp.364-376
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• 2019

When underwater blasting is conducted, both shock waves and water waves have an effect on adjacent coastal areas. In this study, an empirical formula for estimating the details of water waves caused by underwater blasting was applied to a non-reflected wave generation system, and a 3D numerical wave tank (NWT) was improved to reproduce the generation and propagation of such water waves. The maximum elevations of the propagated water waves were comparatively analyzed to determine the validity and effectiveness of the NWT. Good agreement was demonstrated between the empirical and simulation results. The generation and propagation of water waves were also simulated under each underwater blasting scenario for the removal of the Todo islet at the Busan Newport International Terminal (PNIT). It was determined that the water waves generated by the underwater blasting scenario examined in this study did not have a significant impact on the PNIT. In addition, multiple-charge blasting caused higher wave heights than single-charge blasting. As the amount of firing charge increased, the wave height also increased. Finally, larger water waves were generated during the later blasting conducted at a deeper depth as compared with an earlier blasting conducted at a relatively shallow depth.

• Journal of Korean Society on Water Environment
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• v.26 no.1
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• pp.89-95
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• 2010

The electrokinetic potential of $CaCO_3$, which takes an important part in aquatic system, has been measured and the variation of total energy between $CaCO_3$ particles with the distance of particles was estimated based on DLVO theory. The electrokinetic potential of particles was observed to increase to positive direction as the charge valence of cations which was added to suspension was increased. Also, the total interaction energy between particles was estimated to be more negative as the charge valence of cation was higher and its concentrations was raised. When a mixture of cations with different charge valences was added, the influence of cation with a higher charge valence was more significant on the total interaction energy between particles. When anion was added to the suspension of $CaCO_3$, the total energy estimated by DLVO theory was examined to move to positive direction and the electrokinetic potential of particles became more negative. Likewise cations, the effect of anions on the electrokinetic potential of particles and total interaction energy between them was observed to be proportional to their charge valence and the influence of the mixture of anions with different charge valence became more remarkable as the mixing ratio of the anion with a higher charge valence was increased.