• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.4 s.235
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• pp.606-613
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• 2005

Effects of circumferentially local wall thinning on the fracture behavior of pipes were investigated by monotonic four-point bending. Local wall thinning was machined on the pipes in order to simulate erosion/corrosion metal loss. The configurations of the eroded area included an eroded ratio of d/t= 0.2, 0.5, 0.6, and 0.8, and an eroded length of ${\ell}\;=10mm,$ 25mm, and 120mm. Fracture type could be classified into ovalization, local buckling, and crack initiation depending on the eroded length and eroded ratio. Three-dimensional elasto-plastic analyses were also carried out using the finite element method, which is able to accurately simulate fracture behaviors excepting failure due to cracking. It was possible to predict the crack initiation point by estimating true fracture ductility under multi-axial stress conditions at the center of the thinned area.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.617-621
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• 2003

The purpose of this paper is to analyze piping failure trend of safety pipings In domestic nuclear power plants. First, database for the piping failure was constructed with 105 data fields. The database includes plant population data, event data, and service history data. 7 kinds of piping failures in domestic NPPs were investigated. Among the 7 cases, detailed root causes were investigated for 3 cases. The first one is pipe wall thinning in main feedwater pipings of Westinghouse 3 loop type plants. The root cause of the wall thinning was flow accelerated corrosion near welding area. The next one is leak event in chemical and volume control system(CVCS) due to vibration. Some cracks occurred in socket welding area. The events showed that the integrity or socket weld is very vulnerable to vibration. The last one is also a leak event in primary sampling line in Korean standard reactor due to thermal fatigue. Although the structural integrity was not maintained by the events, there was no effect on nuclear safety in the above 3 piping failure eases.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.3
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• pp.287-291
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• 2006

This paper describes mechanical and electric properties of ACSR $410\;mm^2$ conductor from many of older overhead conductor. Samples of conductors itemized two division according to operation sector, green area, salt and pollution area. Samples of conductors operated various environment conditions have undergone laboratory metallurigical investigation and tensile strength torsional ductility and electrical performance. The steel core were found to have retained their original properties to a large degree in both tensile strength and the number of turns to failure. On the other hand the aluminum conductor showed reductions in tensile strength. To determine the remaining useful life of aged conductor, an unacceptable deterioration level has to established for each diagnostic procedure.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.265-268
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• 2005

This paper discusses a strategy and status for development and operation of durability mock-up test facilities for offshore structures. The strategy is examplified and facilitated using an offshore transmission tower crossing the West sea and the Shihwha lake, which was designed and constructed 345kV T/L lines transmitting power from Yeong-Heung fossil power plant to Seoul metropolitan area. Various data for corrosion protection, aging, life-prediction of concrete and steel offshore structures can be obtained using the proposed mock-up test facility. Acquired data will be used for further research on durability, life-prediction, and retrofit of structures. It is important to maintain the safety of 345 kV Yeong-Heung transmission line crossing the Shihwha lake because the offshore structure is one of the critical electric facilities transmitting large power to the metropolitan area. Operation of the offshore transmission tower mock-up is expected to make a significant contribution to stable power supply.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.18 no.2
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• pp.61-68
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• 2022

Accurate evaluation of residual stress is important for stress corrosion cracking assessment. In this paper, electron beam welding experiment is simulated via finite element analysis and the sensitivity of the parameters related to the combined heat source model is investigated. Predicted residual stresses arecompared with measured residual stresses. It is found that the welding efficiency affects the size of the tensile residual stress area and the magnitude of maximum longitudinal residual stress. It is also found that the parameter related to the ratio of energy distributed to the two-dimensional heat source has little effect on the size of tthe tensile residual stress area, but affects the size of the longitudinal residual stress in the center of the weld.

• Journal of the Speleological Society of Korea
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• v.56
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• pp.15-38
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• 1998

Biomass and soil properties of plant communites was investigated in the limestone ares, Tanyang, Ch'ungbuk Province in Korea. Plants was classified in calcicoles and calcifuges within plant communities occurring in the limestone area. Biomass of plant populatins in the limestone area was measured that Stellaria aquatica was the lowest(0.58g/plant), Chrysanthemum boreale was the highest(8.87g/plant) and that Pennisetum alopecuroides, Miscanthus sinensis was 6.67g/plant, 5.76g/plant, respectively. Diameter of breast height among the tree layer communities was investigated that Pinus densiflora was the widest(20cm), Juniperus rigida was the narrowest(6cm) and that Quercus aliena, Populus ${\times}$ tomentiglandulosa was 10cm, 12cm, respectively. The high of density in the tree layer was found out Populus ${\times}$ tomentiglandulosa, Juniperus rigida, Quercus aliena, Pinus densiflora in this order. Dominant species in the study area were Pinus densiflora, Quercus aliena, Juniperus rigida, Quercus dentata in the tree layer, Lespedeza bicolor, Buxus microphylla, Rhus chinensis in the shrub layer, Humulus Japonicus, Erigeron canadensis, Xanthium strumarium, Oenothera odorata Persicaria hypropiper on the riverside, Pennisetum alopecuroides, Vicia amoena, Chrysanthemum boreale on the roadside. Soil properties of the limestone area was investigated around the protrusion of rock in the upper region, around the cave and underlayer accumulated by corrosion in the study area. Lime-chlorosis was observed in the upper region, underlayer and around the cave. It was observed that biota of kum-gul and dungbong-gul was Rhinolophus ferrumequinum korai, Epanerchodus kimi, Antrokoreana gracilipes, Diestrammena japonical. Dominant species were Humulus japonicus, Stellaria aquatica, Hydrocotyle maritima, Phragmites communis, Miscanthus sinensis around the inlet of a kum-gul. It was classified that plants in the study area was 34 order, 53 family, 135 species in all. Calcicoles were 11 order, 16 family, 18 species and calcufuges were 6 order, 8 family, 11 species of them all.

• Journal of environmental and Sanitary engineering
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• v.9 no.1
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• pp.17-28
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• 1994

There are many possibilities that may lead to low quality of drinking water Recently, some unknown deposits in tap water raised a lot of public concern regarding the safety of drinking water in Seoul. We analyzed the quality of tap water from several areas of Seoul, including the area where public complaints about tap water were high. The results shows that the quality of tap water in Seoul was good, well below the environmental standards. Only the tap water from the area with high public complaints showed turbidity higher than that of other area. Also, result shows that component of deposit in tap water was Al, Fe, Mn, and Zn. Based on the research result we propose several measures that might help to reduce the amount of deposit in tap water as follows : 1 Using coagulant aid when coagulating or adjusting pH when filtering. 2. Replacing old water pipeline with new corrosive- resistant one. 3. Increasing water treatment efficiency by enhancing water treatment system such as automation of water treatment system adjusting production capacity, and improving operational condition of filler basin. 4. Chlorine disinfection at the distribution reservoir would help maintaining the same pH level and chlorine concentration throughout the water pipeline and reduce corrosion of pipe.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.1
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• pp.81-88
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• 2001

This study proposed an analytical method to evaluate a local allowable wall thickness (LAWT) for locally thinned pipe subjected to internal pressure and bending moment. In this method, the stresses in the thinned region were calculated by finite element analysis and plastic collapse was applied as a failure criterion of thinned pipe. Using this method, LAWT for a simplified thinned pipe was evaluated with variation in axial extent of thinned area, and it was compared with allowable wall thickness provided by previous pipe wall thickness criteria. The results showed that the LAWT was lower, about 50%, than that calculated by construction code or ASME Code N-597, and it was higher, about 2 times, than that estimated by evaluation model based on pipe experiments. In addition, LAWT was decreased with increasing axial extent of thinned area and saturated with further increase in axial extent. And, the variation in LAWT with axial extent of thinned area depended on type of load, especially a magnitude of bending moment, considering in the evaluation.

• Journal of Wind Energy
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• v.15 no.1
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• pp.82-90
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• 2024

Bio-fouling has positive aspects that are used as a fish resource, but there are also negative aspects such as corrosion of the surface of the support structure, aesthetics and work safety problems. A specimen was produced using a polyurea material with excellent anti-fouling and methodology, and contact angle, high water pressure, adhesion, and real sea area tests were performed. As a result of measuring the contact angle of the specimen with a 10 cm x 10 cm area of polyurea, There was found to be an average of 124.4 ° at nine points. No surface damage was found even above 5 Mpa when high water pressure was sprayed, and adhesive strength of 300LSE adhesives was confirmed between 22.84 and 23.04 Mpa with an adhesion test. During the 6-month real sea area test, it was confirmed that about 17.24 % of the polyurea film was less generated than the comparison group.

• Journal of Conservation Science
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• v.25 no.4
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• pp.373-381
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• 2009

To preserve steel cultural properties on display outdoors, the surface of these relics is processed with a covering treatment, which is a typical anti-corrosion method. Since the registered cultural heritage of Korea No. 78 Locomotive at Jangdan Station of Gyeongui Line will be treated by preservation process and displayed in the open outdoor area, effective surface covering agents were selected through testing to prevent the corrosion of the locomotive. The mixed wax are based on two types of microcrystalline wax which is one of regular surface covering agents for locomotives and bee‘s wax. For the weather resistance test, 3 types of wax were applied to each specimen of the locomotive and the specimens were tested in the Xenon-Arc Accelerated Weathering Tester for 1000 hours in accordance with the ISO 4892-1981 criteria and the test results were compared. As a result, on the surface of the specimen coated with the bee's wax, a whitening event appears after 400 hours which causes aging, and the specimens coated by the microcrystalline wax showed signs of a whitening event after 800 hours. The moisture contact angle with the microcrystalline wax coating was also less than with the bee's wax. Therefore, it was found that the high temperature microcrystalline wax is the most effective coating agent in terms of weather resistance and moisture blocking capability and the high temperature microcrystalline wax was adopted for coating the surface of the locomotive.