• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.12 no.1
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• pp.41-48
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• 2016

To investigate the effect of long-term thermal aging on the microstructural and mechanical characteristics of weldment made of nickel base alloy and its weld metal, an accelerated heat treatment was applied to simulate the process of long-term thermal aging in the operating condition of nuclear power plant. A representative nickel-based weldment with Alloy 600 and Alloy 182 was fabricated and heat-treated at $400^{\circ}C$ for 1,713 h and 3,427 h to simulate the thermal aging for the period equivalent to 15 and 30 years in operating pressurized water reactors, respectively. The microstructural and mechanical characteristics were analyzed by using optical microscopy, scanning electron microscopy and Vickers microhardness measurement. Changes were observed in precipitation behavior and microhardness of each specimen, and these changes were mainly attributed to the change in precipitated morphology and residual stress across the weld during the thermal aging process.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.16 no.1
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• pp.22-29
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• 2020

In nuclear power plants, there is a risk of thermal fatigue in equipment and piping affecting system soundness because the temperature change of the system accompanies in every operation and shutdown. Therefore, in order to prevent the excess of the fatigue limit during the lifetime of plants, the fatigue limit of each piping material is determined in the designing stage. However, there are many cases where equipment or piping is locally subjected to thermal fatigue that is not considered in the design, resulting in damage to the equipment and piping, and failure during operation. Currently, local thermal fatigue generation mechanisms that are not taken into account in the design stage are gradually being identified. In this paper, the effects of the fluid temperature fluctuations on the piping soundness due to the mixing of hot and cold water, one of the local thermal fatigue generating mechanisms, were evaluated.

• Journal of Chest Surgery
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• v.14 no.3
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• pp.254-259
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• 1981

This is a case of successfully surgically treated RVOT obstruction caused by projection of the herniated aortic cusp through subpulmonic supracristal VSD at Department of Thoracic and Cardiovascular Sugery, Hanyang University Hospital. The patient was a 17 year old boy. Congenital heart anomaly was suspected at 2 years of his age. He had palpitation, dyspnea on exertion and epistaxis for 2 years prior to admission to our hospital. On examination, the blood pressure was 170/0mmHg. And the pulse rate was 100/rain. Widening of pulse pressure, water hammer pulse [bounding pulse]. To and fro murmur and head nodding were noted. Cardiomegaly was seen in chest x-ray. EKG, Echocardiography, Cardiac catheterization and angiocardiography were performed. On April 27, 81. Open heart surgery was performed under the impression of VSD combined with AI. On Rt. ventriculotomy, we noticed RVOT obstruction caused by prolapsed rt coronary cusp through a VSD. The subpulmonic supracristal VSD measuring 2.5 x 3 Cm in diameter was closed with Teflon patch graft and then the prolapsed aortic leaflet was plicated by placing three 8-figure suture between the free edge and the base of the leaflet through transverse aortotomy. After operation, excellent result was obtained: B.P, was 110/50mmHg and any sign of AI or residual shunt was not found at discharge.

• Corrosion Science and Technology
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• v.20 no.6
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• pp.466-474
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• 2021

A wet type scrubber for merchant vessel uses super austenitic stainless steels with pitting resistance equivalent number (PREN) of 40 or higher for operation in a harsh corrosive environment. However, it is expensive due to a high nickel content. Thus, electrochemical behavior and cavitation erosion characteristics of UNS S32750 as an alternative material were investigated. Microstructure analysis revealed fractions of ferritic and austenitic phases of 48% and 52%, respectively, confirming the existence of ferritic matrix and austenitic island. Potentiodynamic polarization test revealed damage at the interface of the two phases because of galvanic corrosion due to different chemical compositions of ferritic and austenitic phases. After a cavitation test, a compressive residual stress was formed on the material surface due to impact pressure of cavity. Surface hardness was improved by water cavitation peening effect. Hardness value was the highest at 30 ㎛ amplitude. Scanning electron microscopy revealed wave patterns due to plastic deformation caused by impact pressure of the cavity. The depth of surface damage increased with amplitude. Cavitation test revealed larger damage caused by erosion in the ferritic phase due to brittle fracture derived from different strain rate sensitivity index of FCC and BCC structures.

• Journal of Korean Society on Water Environment
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• v.23 no.2
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• pp.193-200
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• 2007

The AOPs research defined by creating a sufficient amount of OH radicals from the dissolution of organic materials through photoxidation and research for a complete elimination of residual organic materials by membrane are actively ongoing. This research focuses on the hybrid processing of AOPs and M/F membrane to dissolve and eliminate organic chemicals in drinking water which are suspected of carcinogens. For this purpose, underground water was used as a source of drinking water for the hybrid processing of AOPs oxidation and M/F membrane, and a pilot plant test device was installed indoor. Carcinogenic chemicals of VOCs and pesticide were artificially mixed with the drinking water, which was then diluted close to natural water in order to examine treatment efficiency and draw optimal operation conditions. The samples used for this experiment include four chemicals phenol, chloroform, in VOCs and parathion, carbaryl in pesticide. As a result of the experiments conducted with simple, and compound solutions, the conditions to sufficiently dissolve and eliminate carcinogenic chemicals from the hybrid processing of where carcinogens were artificially added are : (hydrogen peroxide) prescribed solution 100 mg/L under pH 5.5~6.0, and the temperature $12{\sim}16^{\circ}C$, at the normal temperature and pressure. $d-O_3$ volume of 5.0 ppm and above and 30-40 minutes of reaction time are most appropriate and using MF/UF for membrane was ideal.

• Journal of the Korean Wood Science and Technology
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• v.34 no.2
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• pp.83-87
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• 2006

The leaves of Paulownia coreana Uyeki were extracted with acetone-$H_2O$ (7:3, v/v), concentrated under reduced pressure and fractionated successively with n-hexane, methylene chloride and ethyl acetate, leaving residual water soluble fraction. A portion of the resulting aqueous soluble powder was chromatographed on a Sephadex LH-20 column using aqueous methanol and ethanol-hexane as washing solvents. Three apigenin derivatives were isolated and identified as apigenin-7-O-${\beta}$-D-glucpyranoside, apigenin-7-O-${\beta}$-D-glucuronopyranoside and apigenin-7-O-[${\beta}$-D-glucuronopyranosyl($1{\rightarrow}2$)-O-${\beta}$-D-glucuronopyranoside] by spectroscopic methods including NMR and FAB-MS.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.416-419
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• 2006

Numerical analysis is carried out to identify the wall thinning effect inside the feed water valve. The finite volume method is applied to make analysis for the viscous flows. The commercial cock FLUENT is used for the simulation and the GAMBIT for the grid generation. The RNG $\kappa-\varepsilon$ model is used for the turbulence and the tet-hybrid grid is applied for the modeling. The velocity vector, the pressure contour, the change of residual along the iteration number, and the dynamic head are predicted for the hydrodynamic investigation.

• Membrane and Water Treatment
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• v.7 no.6
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• pp.477-493
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• 2016

Immediate use of activated carbon incorporated polysulfone membrane application for dye separation was reported in this work. Dimethylformamide (DMF) was used as the solvent for the membrane preparation. The membrane thus prepared were characterized in terms of surface morphology, ATR-FTIR, AFM, experimental results as membrane performance. The resultant nanofiltration (NF) membranes were tested with Congo red dye concentration 200 mg/L. The water permeability was found to be considerably higher than that reported in literature. Experimental results show that the real rejection of the Congo red is 99.57% over the transmembrane pressure 100 psi using 30% activated carbon incorporated membrane. Prepared NF membranes shows the corresponding permeates fluxes were $40Lm^{-2}h^{-1}$ to $82Lm^{-2}h^{-1}$ with different activated carbon percentage incorporated in polysulfone membrane. The present study demonstrated that dye rejection enhanced NF may be a feasible method for the dye wastewater treatment. The overall observations thus indicated that toxic residual dyes can be appreciably separated from the membrane technology, provided that the accompanying polymeric membrane, activated carbon as binding agents and the process parameter levels are astutely selected.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.5
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• pp.598-607
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• 2004

In this study, the effects of two pre-treatment processes were observed prior to membrane filtration: pre-coagulation and pre-ozonation. To compare the effect of two above-mentioned pre-treatments, we adopted the four schemes: first one is direct membrane filtration of river surface water, second one is membrane filtration after pre-coagulation, third one is membrane filtration after pre-ozonation and fourth one is membrane filtration after pre-coagulation and pre-ozonation. There are two exceptional characteristics in applied processes. One is the usage of the MF membrane which has high ozone resisting characteristic. Therefore, ozone resides in membrane module during filtration. The other is adoption of Jet Mixed Separator (JMS) as coagulation-sedimentation process. The change in transmembrane pressure and permeate water quality were also examined. As a result, considering the filtration performance efficiency and permeate water quality, the process composed of filtration with combination of both pre-coagulation and pre-ozonation was proved most effective. The improved efficiency was due to the reduction of loading rate of fouling inducing materials to membrane module by coagulation process as well as variable reactions, such as degradation, particle destabilization and coagulation, occurred by residual ozone in membrane module. The additional effect of pre-coagulation before pre-ozonation is suppression of AOC, one of the by-products induced by ozonation. Therefore, combination of pre-coagulation and pre-ozonation is the effective process to overcome the major de-merit of ozonation i.e. by-products formation.

• Journal of Environmental Science International
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• v.17 no.8
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• pp.899-905
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• 2008

Quality test for activated carbon(AC) filter used for drinking water purifier is now an obligatory test and the standard material for valid purifying amount in water purifier performance test has been changed from residual chlorine to chloroform according to the notice of Ministry of Environment in 2006. Therefore, this study aimed to compare the ingredients of AC filters by confirming chloroform removal rate of AC filter and conducting 4 adsorption tests (Iodine, methylene blue decolorization, phenol value, ADS value) for AC filters provided by manufacturers. With water pressure of $1kgf/cm^2$, 1,500 liters of prepared inflow went through to check chloroform removal rate. As a result, product with removal rate of below 60% from all products. On the other hand, 4 adsorption tests were conducted for filters in the market and filters from manufacturers. None of the products satisfied all 4 tests. In particular, they showed great shortage to the standard in phenol value and ADS value test. However, manufacturers' filter showed much better performance than filters in the market. Also, the result of valid purifying amount test for each of five products of appropriate product and inappropriate product based on filter quality test showed average 4,440 liters for appropriate product and average 2,620 liters for inappropriate product. According to the result, it is shown that the filter with good adsorption also had good chloroform removal efficiency and adsorption efficiency. Therefore, it is expected that customers can screen good quality product through obligatory conduct of filter quality test. However, it is considered that complementation in system is required for future inspection.