• Journal of the Korean Institute of Gas
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• v.22 no.2
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• pp.72-77
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• 2018

This paper presents the FEM analysis results on the strength safety of LPG fuelling nozzle, which is composed of ball valve and long cylinder tube. For the strength safety analysis of LPG fuelling Nozzle, the gas pressure of 0.5~3.5MPa has been supplied to the ball valve and long cylinder tube bodies with the wall thickness of 1.7~3.5mm. The maximum von Mises stress of the ball valve with 1.7mm wall thickness is 25.4MPa for the supply gas pressure of 3.5MPa, which is 25.9% compared with that of the yield stress of the brass. And the maximum von Mises stress was 23.7MPa when a 3.5MPa gas pressure was applied to a long cylinder tube with a wall thickness of 1.7mm, which was 6.7% more safe than the ball valve which was analyzed under the same conditions. For the increased wall thickness, 2.0mm of the long cylinder tube, the maximum von Mises stress of 20.2MPa is 14.8% more safe compared with that of 1.7mm wall thickness of the same cylinder tube. Thus, the wall thickness of the ball valve and cylinder tube is recommended as an optimized thickness of 1.7~2.0mm for the strength safety of the LPG fuelling nozzle.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4066-4076
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• 2023

Pressure resistance welding is usually used to seal the connection between the cladding tube and the end plug made of zirconium alloy. The seal welded joint has a direct effect on the service performance of the fuel rod cladding structure. In this paper, the pressure resistance welded joints of zirconium alloy tube-plug structure were obtained by thermal-mechanical simulation experiments. The microstructure and microhardness of the joints were both analyzed. The effect of processing parameters on the microstructure was studied in detail. The results showed that there was no β-Zr phase observed in the joint, and no obvious element segregation. There were different types of Widmanstätten structure in the thermo-mechanically affected zone (TMAZ) and heat affected zone (HAZ) of the cladding tube and the end plug joint because of the low cooling rate. Some part of the grains in the joint grew up due to overheating. Its size was about 2.8 times that of the base metal grains. Due to the high dislocation density and texture evolution, the microhardnesses of TMAZ and HAZ were both significantly higher than that of the base metal, and the microhardness of the TMAZ was the highest. With the increasing of welding temperature, the proportion of recrystallization in TMAZ decreased, which was caused by the increasing of strain rate and dislocation annihilation.

• Structural Engineering and Mechanics
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• v.37 no.3
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• pp.321-330
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• 2011

Long-term properties of concrete affect structures in many respects, not excepting dynamic behaviors. This paper investigates the influence of concrete creep on the dynamic behaviors of concrete filled steel tube (CFT) arch bridges, by means of combining the analytical method for the creep of axially compressed CFT members, which is based on Model B3 for concrete creep, with the finite element model of CFT arch bridges. By this approach, the changes of the stress and strain of each element in the bridge with time can be obtained and then transformed into damping and stiffness matrices in the dynamic equation involved in the finite element model at different times. A numerical example of a long-span half-through CFT arch bridge shows that creep influences the natural vibration characteristics and seismic responses of the bridge considerably, especially in the early age. In addition, parameter analysis demonstrates that concrete composition, compressive strength and steel ratio have an obvious effect on the seismic response of the CFT arch bridge.

• Journal of Power System Engineering
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• v.16 no.1
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• pp.58-64
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• 2012

Power plant boiler is one of the most important utilities providing steam to turbine in thermal power plant. It is composed of thousands of boiler tubes for high efficient heat transfer. Boiler tube material is used in such high temperature and pressure as $540^{\circ}C$, $170kg/mm^2$. The boiler tube material is needed to resist corrosion damage, creep damage and fatigue damage. 2.25%Cr-1Mo steel is used for conventional boiler tubes. In these days steam temperature and pressure of the power plant became higher for high plant efficiency. So, the material property of boiler tube must be upgraded to meet the plant property. Several boiler tube material was developed to meet such condition. X20CrMoV12.1 steel is also developed in early 1980's and used for superheater and reheater tubes in supercritical boilers. The material has martensitic structure, which is difficult to evaluate the material degradation. Boiler tube material at severe condition was tested to evaluate long term and short term degradation and creep. Through long term and high temperature degradation test, lath structure was decreased and recrystallization has been proceeded by sub-crystal. And in this research the effect of temperature and stress on boiler tube characteristic,for example, deformation by creep was changed rapidly at relatively high temperature and stress because creep was affected easily by temperature and stress.

• Advances in pediatric surgery
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• v.10 no.2
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• pp.92-98
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• 2004

The history of esophageal replacement in infants or children is the history of development of various kinds of alternative conduits such as stomach, colon, and small bowel. The gastric tube has been the most widely used conduit. From January 1988 to May 2003, 23 esophageal replacements with gastric tube were performed at the Department of Pediatric Surgery, Seoul National University Childrens Hospital. Statistical analysis was performed using Windows SPSS11.0 Pearson exact test. There were Gross type A(n=10), type B(n=1), type C(n=11), type D(n=1). Ten patients who had long gap esophageal atresia (type A-8, type B-1, type C-1) and 13 patients (type A 2, type C-10, type D-1) who had stenosis, leakage, recurred tracheoesophageal fistula, and esophagocutaneous fistula after previous corrective operations, had esophageal replacement with gastric tube. Mean follow-up periods were 4 year 2 months (7 months-15 year 1 month). There were postoperative complications including GERD in 16 (69.6 %), leakages in 7 (30.4 %), diverticulum at anastomosis in 2 (8.7 %), anastomosis site stenosis in 4 (17.3 %), and distal stenosis of the gastric tube in 1 (4.3 %). There was no statistical significance between operation types and postoperative leakage and gastroesophageal reflux. In conclusion, esophageal replacement with gastric tube may be a useful surgical option in esophageal atresia with long gap and esophageal atresia complicated by previous corrective operation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.8
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• pp.701-706
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• 2008

A continuous 3D tube bending machine has been developed for industrial boiler panel production. The machine consists of a main bender, a sub bender, a side bender, tube feeding rollers and control system that includes data management system. Tube position is controlled by a numerical control system. The bending former can be easily replaced according to the shape of bending form. Reduction of working time and improvement of production capacity from the practice have been achieved by bending a long tube in the machine developed.

• Structural Monitoring and Maintenance
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• v.5 no.2
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• pp.189-204
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• 2018

This paper examines the seismic responses of a reinforced concrete (RC) frame core-tube building with pre-pressed spring self-centering energy dissipation (PS-SCED) braces. The PS-SCED brace system consists of friction devices for energy dissipation, pre-pressed combination disc springs for self-centering and tube members as guiding elements. A constitutive model of self-centering flag-shaped hysteresis for PS-SCED brace is developed to better simulate the seismic responses of the RC frame core-tube building with PS-SCED braces, which is also verified by the tests of two braces under low cyclic reversed loading. Results indicate that the self-centering and energy dissipation capabilities are well predicted by the proposed constitutive model of the PS-SCED brace. The structure with PS-SCED braces presents similar peak story drift ratio, smaller peak acceleration, smaller base shear force and much smaller residual deformations as compared to the RC frame core-tube building with bucking-restrained braces (BRBs).

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2047-2052
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• 2004

Inconel-600 alloy has been used as steam generator tube material for current pressurized water reactors (PWRs). The long-term operation of steam generators showed that the use of this material induced localized corrosion damages and increased tube wear of steam generator. To protect these problems, steam generator tube material is being changed to Inconel-690 alloy. Based on the current trend, we have chosen Inconel 690 as the Advanced Power Reactor 1400 (APR1400) steam generator(SG) tube material and performed the design optimization of preventive measure against tube fretting wear for the APR1400 steam generator. In this paper, we examined the technical consideration in this modification : the selection of material, wear characteristics, effect of the Egg-crate Flow Distribution Plate installation, and effect analysis of vertical strip installation.

• Journal of the speleological society of Korea
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• no.4
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• pp.33-39
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• 1996

Secondary mineral deposits of gypsum, mirabilite, thenardite, crisobolite have long been known and, in fact, are quite common in lava tubes of southwest Idaho. Until recently, calcium carbonate were found in a few tubes in very small amounts and were thought to be qu are. The recent ‘rediscovery’ of Helen's Hidden Hide - Away lava tube h significantly changed this thinking. The deposits in this lava tube are only quite extensive but extremely varied in structure. As this is a v recent discovery, only basic preliminary work will be presented in t paper. It is hoped this will stimulate intrest for further and more inte study of the lava tubes of southwestern Idaho.

• Journal of the speleological society of Korea
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• no.5
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• pp.70-78
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• 1997

Secondary mineral deposits of gypsum, mirabilite, thenardite, and cristpbolite have long been known and, in fact, are quite common in the lava deposits tubes of southwest idaho. Until recently, calcium carbonate were only found in a few tubes in very small amounts and were though to be quite rare. The recent ‘rediscovery’ of Henlen's Hidden Hide -A way lava tube has significantly changed this thinking. The deposits in the lava tube are not only quite extensive but extremely varied in structure. As this is a very recent discovery, only basic preliminary work will be presented in this paper. It is hoped this will stimulate interest for further and more intensive study of the lava tubes of southwestern idaho.