• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.224-229
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• 2006

Many studies have been done on the application of residual charge measurement in cable degradation diagnosis. In this paper, the behavior of residual charges measured with water-tree degraded XLPE sheets and cable are discussed. At charge injection process, the charge is injected by applying dc voltage as a conventional method, suddenly cut-off ac voltage or impulse voltage. Therefore the residual charge is influenced by the applying process. At charge release process, transient dc current flows when applying ac high voltage and also ac high voltage superimposed to dc low voltage. From the results, new diagnosis method is suggested.

• Journal of Korean Society of Water and Wastewater
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• v.9 no.2
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• pp.77-83
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• 1995

The effluent from conventional nightsoil treatment plants contains nutrients, color and chlorides, in addition to residual organics and suspended solids, and thereby causes substantial pollution problems in receving water resources. In order to verify the usefullness of electrolysis in removing those residual pollutants from such conventional nightsoil treatment plant effluent, a bench scale experiment was conducted using sufficiently dilluted human nightsoil as experiment feeds. The result showed mean removals of 45% of total phosphorus and 85% of color, in addition 87% of residual BOD, 47% of residual COD and 85% of residual SS. The optimum electric current was found to be 15 ampere and the optimum hydraulic residence time 21/2 hour.

• Journal of Korean Society of Water and Wastewater
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• v.33 no.6
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• pp.413-420
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• 2019

Pretreatment system of desalination process using seawater reverse osmosis(SWRO) membrane is the most critical step in order to prevent membrane fouling. One of the methods is coagulation-UF membrane process. Coagulation-UF membrane systems have been shown to be very efficient in removing turbidity and non-soluble and colloidal organics contained in the source water for SWRO pretreatment. Ferric salt coagulants are commonly applied in coagulation-UF process for pretreatment of SWRO process. But aluminum salts have not been applied in coagulation-UF pretreatment of SWRO process due to the SWRO membrane fouling by residual aluminum. This study was carried out to see the effect of residual matal salt on SWRO membrane followed by coagulation-UF pretreatment process. Experimental results showed that increased residual aluminum salts by coagulation-UF pretreatment process by using alum lead to the decreased SWRO membrane salt rejection and flux. As the salt rejection and flux of SWRO membrane decreased, the concentration of silica and residual aluminum decreased. However, when adjusting coagulation pH for coagulation-UF pretreatment process, the residual aluminum salt concentration was decreased and SWRO membrane flux was increased.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.377-384
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• 2000

The characteristics and prediction model of the shear strength for unsaturated residual soils was studied. In order to investigate the influence of the initial water content on the shear strength, unsaturated triaxial tests were carried out varying the initial water content, and the applicability of existing prediction models for the unsaturated shear strength was testified. It was shown that the soil - water characteristic curve and the shear strength of the unsaturated soil varied with the change of the initial water content. A sample compacted in the lower initial water content needs a higher suction to get the same degree of saturation while the shear strength of a sample with the lower initial water content displays a lower value. In order to apply the existing prediction models of the unsaturated shear strength to granite residual soils, a correction coefficient, α, on the internal friction angle, ø'was added.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.6
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• pp.587-597
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• 2017

This study aimed to develop a method to optimize residual chlorine concentrations in the process of providing water supply. To this end, this study developed a model capable of optimizing the chlorine input into the clearwell in the purification plant and the optimal installation location of rechlorination facilities, and chlorine input. This study applied genetic algorithms finding the optimal point with appropriate residual chlorine concentrations and deriving a cost-optimal solution. The developed model was applied to SN purification plant supply area. As a result, it was possible to meet the target residual chlorine concentration with the minimum cost. Also, the optimal operation method in target area according to the water temperature and volume of supply was suggested. On the basis of the results, this study derived the most economical operational method of coping with water pollution in the process of providing water supply and satisfying the service level required by consumers in the aspects of cost effectiveness. It is considered possible to appropriately respond to increasing service level required by consumers in the future and to use the study results to establish an operational management plan in a short-term perspective.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.6
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• pp.453-479
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• 2011

Residual pharmaceutical compounds have been recognized as emerging environmental pollutants and are widely distributed all over the world. These compounds cause bioaccumulation and biomagnification during present for a long time in the environment: thereby after adversely biota and human bodies. It is difficult to remove residual pharmaceutical compounds using conventional water/wastewater treatment because of resistant property to photodegradation, biodegradation and chemical decomposition. Moreover, domestic literature data on the pollution of residual pharmaceutical compounds in rivers and lakes are limited. In this paper, species, sources, fate and risk of residual pharmaceutical compounds as well as behavior properties in freshwater resources are demonstrated to encourage the domestic concern about residual pharmaceutical compounds. An extensive review of existing data in the form of figures and tables, encompassing many therapeutic classes are presented.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.137-148
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• 2012

In pressurized water nuclear reactors, dissimilar metal welds are susceptible to primary water stress corrosion cracking. To access this problem, accurate estimation of welding residual stresses is important. This paper provides general welding residual stress profiles in dissimilar metal nozzle butt welds using finite element analysis. By introducing a simplified shape for dissimilar metal nozzle butt welds, changes in the welding residual stress distribution can be seen using a geometry variable. Based on the results, a welding residual stress profile for dissimilar metal nozzle butt welds is proposed that modifies the existing welding residual stress profile for austenitic pipe butt welds.

• Nuclear Engineering and Technology
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• v.44 no.3
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• pp.343-354
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• 2012

Primary water stress corrosion cracking (PWSCC) is a major safety concern in the nuclear power industry worldwide. PWSCC is known to initiate only in the condition in which sufficiently high tensile stress is applied to alloy 600 tube material or alloy 82/182 weld material in pressurized water reactor operating environments. However, it is still uncertain how much tensile stress is re-quired to generate PWSCC or what causes such high tensile stress. This study was performed to pre-dict the magnitude of weld residual stress and operating stress and compare it with previous experi-mental results for PWSCC initiation. For the study, a pressurizer safety nozzle was selected because it is reported to be vulnerable to PWSCC in overseas plants. The assessment was conducted by nu-merical analysis. Before performing stress analysis for plant conditions, a preliminary mock-up ana-lysis was done. The result of the preliminary analysis was validated by residual stress measurement in the mock-up. After verification of the analysis methodology, an analysis under plant conditions was conducted. The analysis results show that the stress level is not high enough to initiate PWSCC. If a plant is properly welded and operated, PWSCC is not likely to occur in the pressurizer safety nozzle.

• Journal of Korean Port Research
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• v.12 no.1
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• pp.95-104
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• 1998

Water pollution in a semi-enclosed sea area such as a bay due to stagnancy of water has been a serious water environmental problem. Recently, some kinds of new methods to activate the tidal exchange between an inner bay and an outer sea area by control of a tidal residual current have been proposed. However, these methods have several problems, that is, I). deterioration in a natural view due to building of huge structures, II). increase of risk of navigation in case of a submerged structure, III). limition of sea area where a tidal current can be controlled and IV). difficulty in removing those structures in case of occurrence of an unexpected impact on water environment. In this paper, a new method is proposed, which can solve all the above problems, to purify water quality in a semi-enclosed bay by creation and control of a pattern of a tidal residual current. The tidal residual current is controlled by unsymmetric structures, which change the properties of resistance according to the direction of flow, arranged on the sea bottom. In this study, several numerical and hydraulic experiments of tidal current and particle-tracking for various arrangements of bottom roughness in a semi-enclosed model bay were carried out. As a result of experiments, it becomes clear that it is possible to generate a new tidal residual current and to activate a tidal exchange by only operation of bottom roughness arrangement.

• YAKHAK HOEJI
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• v.45 no.5
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• pp.437-441
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• 2001

The quasi-drugs including nonwoven fabric and gauze were sterilized using ethylene oxide (EO) gas. Residual EO in the quasi-drugs was extracted with water (20 mL of water for 1 g of sample) for 24h at 37$^{\circ}C$. Residual EO was determined using GC. The optimal analytical conditions were as follows : column, Carbowax 20M (1.D. 0.2 mm); mobile phase, helium with 30 mL/min; oven temperature 57$^{\circ}C$, injector temperature 18$0^{\circ}C$, detector temperature 20$0^{\circ}C$. The detection limit for EO was 0.10$\mu$g/mL. When the residual EO extracted from nonwoven fabric and gauze was determined, it took more than 9h to get the lower level than 25 ppm which is the limit value of FDA guideline. When the EO residues, ethylene chlorohydrine (ECH) and ethylene glycol (EG) in the 7 commercially available quasi-drugs were determined, no residual EO, ECH, EG were found from the seven commercially available quasi-drugs analyzed by this method.