• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.3
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• pp.397-411
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• 2023

The number of deteriorated bridges with a service period of more than 30 years has been rapidly increasing in Korea. Accordingly, the importance of advanced maintenance technologies through the predictions of age-induced deterioration degree, condition, and performance of bridges is more and more noticed. The prediction method of the safety grade of bridges was proposed in this study using the classification models of the Decision Tree and the Random Forest based on machine learning. As a result of analyzing these models for the 8,850 bridges located in national roads with various evaluation indexes such as confusion matrix, balanced accuracy, recall, ROC curve, and AUC, the Random Forest largely showed better predictive performance than that of the Decision Tree. In particular, random under-sampling in the Random Forest showed higher predictive performance than that of other sampling techniques for the C and D grade bridges, with the recall of 83.4%, which need more attention to maintenance because of the significant deterioration degree. The proposed model can be usefully applied to rapidly identify the safety grade and to establish an efficient and economical maintenance plan of bridges that have not recently been inspected.

• Journal of Conservation Science
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• v.32 no.3
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• pp.353-364
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• 2016

The materials of sculptured stone property around the Hyeonleung Royal Tomb in Guri consist mainly of high weathered of granitic rocks with magnetite-series. Deterioration characteristics occurred highly with microorganism, soil inflow and black contaminants at the burial mound zone. As a result of deterioration evaluation, stone surface around the burial mound zone show serious comprehensive damage of soil inflow (50.5%) and lichen coverage (47.6%) which are the major damaging factors, and there are about 8.6% of biological growth noticeably in the north side. Surface contaminants and the discoloration had the complex causes. Gypsum occurred between joints of stones and the major contaminant type, darkening which was analyzed organic bodies caused discoloration. From result of ultrasonic velocity measurements, there are mean value of 2,195 m/s with highly weathered (HW) grade. Most of the stone properties showed 4 to 5 weathered grade. Therefore, it turned out that sculpture stone properties require conservation treatments. To remove soil accelerating damage factors and lichen occupying high percents, the cleaning process is necessary and consolidation, rejoining and filling are needed as well. Also, consideration on removing conservation materials containing Ca and e fflorescence is required and retreatments need to be considered.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1487-1490
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• 2004

In this study, the crash analysis was carried out to evaluate the influence of steel sheet grade and thickness on weight reduction and crash characteristics for front side member which had an important role of absorbing the impact energy during front and side impact. In order to achieve the aim of this study the reverse engineering was applied to obtain 3D model of front side member from BIW for the FE simulation. In the result, the crashworthiness of front side member is considerably improved with steel sheet strength and thickness increase. Also, the weight reduction in automotive parts for the improvement of the fuel efficiency can be easily achieved with applying high strength steel without deterioration of crashworthiness.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.149-155
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• 2006

This paper is concerned with the weight reduction of front side member of a vehicle considering the application of high strength steel sheet. The influence of steel sheet grade and thickness on the energy absorption, impact load and deformed shape of front side member is investigated by using reverse engineering and FE-analysis. The reverse engineering is applied to obtain 3D model of front side member from B.I.W for the FE simulation. FE analysis is carried out with commercial crash analysis SW PAM-CRASH. The crashworthiness of front side member is considerably improved with steel sheet strength and thickness increase. From the result of this study the weight reduction in automotive parts for the improvement of the fuel efficiency can be easily achieved with replacing high strength steel without deterioration of crashworthiness.

• Nuclear Engineering and Technology
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• v.30 no.6
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• pp.609-616
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• 1998

Cast duplex stainless steels are extensively used for primary pressure boundary components. These components are, however, embrittled due to the precipitation of $\alpha$' phase by spinodal decomposition and other processes when exposed to reactor operating temperature for a design lifetime or life extension conditions. This report presents a procedure for estimating the current condition and the residual life of safety-related stainless steel components by using ANL database and correlations. The database of Charpy impact energy suggests that CF-8M grade is the most susceptible to thermal aging and CF-3 grade is the least. Thus, the integrity of CF-8M alleys may be degraded seriously and the degree of deterioration may exceed acceptance limit after several years of service in the nuclear reactors.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.1
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• pp.8-12
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• 2000

The properties variation by deterioration of the 600V grade heat-resistant polyvinyl chloride insulated wire(HIV) was analyzed. The weight variation of the thermal deteriorated HIV was about 42% at 80$0^{\circ}C$ and over. From the analysis result of the metallurgical microscope photographs it shows that the sorface of normal wire showed the elongated structures. However the elongated structures did not appear at $900^{\circ} and over and we could observe that particles were grown. The grown oxidized substances in the thermally deteriorated electric wire were observed by SEM. The CuL, CuK, $CuK_b$, OK and CIK spectra of the thermally deteriorated HIV at $300^{\circ}C$ were uniform regardless of the scanning length, but the spectra of CIK could not found at above $700^{\circ}. At the DTA analysis, the endothermic reactions were occurred around $3006{\circ}C\; and\; 400^{\circ}C$ and the exothermic reactions were occurred around $470^{\circ}, respectively.

• Journal of the Korean Society of Hazard Mitigation
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• v.2 no.4 s.7
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• pp.87-95
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• 2002

Because of the gravitation of population toward large cities, a number of buildings have been constructed since 1970's. They have been rapidly deteriorated as time passed by. Therefore the purpose of this paper is to present basic data on private buildings managed by the Seoul Metropolitan Government and to analyse deterioration factors of them as well as interrelation. And then, the results of this paper can be used to establish the policy of managing timeworn buildings. Through this study timeworn masonry buildings occupy the major part of timeworn buildings, which have almost structural instability, especially individual residence. Both structure type and building type have an interrelation with the deterioration grade. The structure grade have an interrelation with occupancy class more than structure type.

• Advances in pediatric surgery
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• v.19 no.2
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• pp.98-107
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• 2013

Debates exist about the appropriate treatment for pancreatic trauma in children. We intended to examine the safety of the operation of pancreatic trauma in children. This is a retrospective study of 13 patients, younger than 15, who underwent surgery for pancreatic trauma, between 1993 and 2011 in Seoul National University Children's Hospital. Medical records were reviewed for mechanism of trauma, clinical characteristics, radiological findings, operation and outcomes. Organ injury scaling from the AAST (American Association for Surgery of Trauma) was used. All injuries were caused by blunt trauma. Patients with grade III, IV, and those who were difficult to distinguish grade II from IV, underwent surgery due to severe peritonitis. Three patients with grade II were operated for reasons of mesenteric bleeding, tumor rupture of the pancreas, and progression of peritonitis. Distal pancreatectomy was performed in 10 patients and subtotal pancreatectomy and pylorus preserving pancreaticoduodenectomy in 1 patient each. The remaining one underwent surgical debridement because of severe adhesions. The location of injury, before and after operation, coincided in 83.3%. The degree of injury, before and after the operation, was identical in all the patients except for those who were difficult to tell apart grade II from grade IV, and those cannot be graded due to severe adhesion. Postoperative complications occurred in 23.1%, which improved with conservative treatment. Patients were discharged at mean postoperative 12(range 8~42) days. Even though patients with complications took longer in time from diagnosis to operation, time of trauma to operation and hospital stay, this difference was not significant. In conclusion, When pancreatic duct injury is present, or patient shows deterioration of clinical manifestation without evidence of definite duct injury, or trauma is accompanied by other organ injury or tumor rupture, operative management is advisable, and we believe it is a safe and feasible method of treatment.

• Korean Journal of Agricultural Science
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• v.31 no.2
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• pp.87-96
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• 2004

This study concentrates on the trail of the CNU(Chungnam National University) forest. The amount of use and the pattern of damage are considered, as well as the extent of environmental damage. Finally, some managerial strategies are proposed in connection with sustainable maintenance. The trail of the university forest is composed of three sections; one is the neighborhood park and the Institute of Information Technology/Communications, the second is the Institute of Information Technology/Communications and the Dormitory, and the third section is the Dormitory and the Foreign prof's Apt. The total length of the trail is 2.6km. The daily amount of use is 1,269 visitors per day. The amount of using increased three times the amount of that in 1998. This study shows the pattern of damage of the trail in the order of root-exposure, widening, rock-exposure, deepening and the divergence in the frequency of occurrence of all these factors. Environmental damage is also graded thus: grade 3 is 27.4m, grade 4 is 0.8m, grade 5 is 1.5m, and grade 6 is 0.2m. Accordingly, some managerial strategies were proposed in connection with the sustainable trail maintenance.

• Korean Journal of Environment and Ecology
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• v.29 no.4
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• pp.605-614
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• 2015

This study was carried out to maintain, manage and restore the trails by assessing the physical conditions, the patterns of deterioration and the impact rating class of the major trails of Juwangsan National Park. The major trails followed 4 routes including Jubong, Gamaebong, Janggunbong~Geumeungwangi and Woloe. The route length of Jubong was 4.6 km; it was 3.6 km for Gamaebong, 5.6 km for Janggunbong~Geumeungwangi and 5.9 km for Woloe. As for the physical conditions, Jubong was the widest and Janggunbong~Geumeungwangi was the narrowest in trail width. In terms of the bared trail width, Jubong was the widest and Janggunbong~Geumeungwangi was the narrowest. As for the depth of erosion, Gamaebong was the deepest and Woloe was the shallowest. Janggunbong~Geumeungwangi was the steepest and Gamaebong was the gentlest in the slope. Further, Gamaebong showed the highest soil hardness, and Woloe had the lowest hardness. In terms of the times of appearance of deterioration patterns, Jubong recorded 71 times, Gamaebong 62 times, Janggunbong~Geumeungwangi 63 times and Woloe 78 times. In case of the impact rating class, the trail erosion was similar to grades I and II grade; the rest were mostly I grade and hence considered to be in a generally good condition. For the ongoing management of trails, a comprehensive study needs to be conducted in the light of various environmental factors. Also, a restoration plan for damaged trails should be established with consideration for the surrounding environment and ecosystem.