• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.357-373
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• 2022

The high-temperature gas-cooled reactor pebble-bed module project is the first commercial Generation-IV NPP(Nuclear Power Plant) in China. A new joint is used for the vertical support of RPV(Reactor Pressure Vessel). The steel corbel is integrally embedded into the reactor-cabin wall through eight asymmetrically arranged pre-stressed high-strength bolts, achieving the different path transmission of shear force and moment. The vertical monotonic loading test of two specimens is conducted. The results show that the failure mode of the joint is bolt fracture. There is no prominent yield stage in the whole loading process. The stress of bolts is linearly distributed along the height of corbel at initial loading. As the load increases, the height of neutral axis of bolts gradually decreases. The upper and lower edges of the wall opening contact the corbel plate to restrict the rotation of the corbel. During the loading, the pre-stress of some bolts decreases. The increase of the pre-stress strength ratio of bolts has no noticeable effect on the structure stiffness, but it reduces the ultimate bearing capacity of the joint. A simplified calculation model for the elastic stage of the joint is established, and the estimation results are in good agreement with the experimental results.

• Composites Research
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• v.23 no.6
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• pp.61-66
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• 2010

In this paper, the variation of mechanical properties of T800 carbon/epoxy composites according to the forming pressure, which was referred to previous studies on a filament winding process, were investigated. The specimens of all the tests were fabricated by an autoclave de-gassing molding process controlling forming pressure (absolute pressures of 0.1MPa, 0.3MPa, 0.7MPa including vacuum) and water jet cutting after fabricating composite laminates. Various tensile tests were performed for in-plane properties and interlaminar properties were also measured by using Iosipescu test jig. Fiber volume fraction was measured to correlate the property variation and the forming pressure. This properties are expected to be utilized in the design of Type III pressure vessel for hydrogen vehicles which uses the same carbon fiber (T800 carbon fiber) for the filament winding process.

• Journal of the Korean Society of Safety
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• v.33 no.6
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• pp.15-21
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• 2018

Ships may collide with reefs or other objects during operation, when arriving or departing ports. The hull plate may be damaged due to the contact with other ships. The total number of domestic powered fishing vessels has decreased, but that of FRP fishing vessels has increased by 0.7% and the ratio of FRP fishing vessels to the total fishing vessels increased to 96%. Recently, fishing vessels has been used as fishing boats for income of non-fishermen as well as fishermen. Therefore, safety management for repair and maintenance is necessary. The penetration of moisture and moisture in the composite material such as FRP may deteriorate the mechanical properties and the salt (NaCl) component of the damaged portion may cause a relatively high deterioration in material strength. The gel coat painting is the final stage of repairs ans maintenance of FRP fishing vessels. The thickness criteria in the domestic and foreign gel coat is 0.3~0.762 mm. The joint specimens, which was immersed in seawater for 120 days, were compared with those without seawater immersion. As a result, the tensile strength was 83 ~ 121.8% and the flexural strength was 83 ~ 113% compared with the specimens without seawater immersion. According to the previous study the tensile strength decreased by more than 29% and the flexural strength decreased by more than 50% when the composite material was immersed in seawater for 1,083 hours without coating. As a result, it was found that the gel coat with 0.5 mm thickness is very effective in preventing the strength decrease of the composite material.

• Journal of Chest Surgery
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• v.53 no.6
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• pp.339-345
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• 2020

Background: Iliac artery aneurysm is frequently found in patients undergoing surgical repair of an abdominal aortic aneurysm. The use of commercial bifurcated grafts is insufficient for aorto-biiliac replacement with complete iliac artery aneurysm resection. We evaluated the effectiveness of handmade composite grafts for this purpose. Methods: A total of 233 patients underwent open surgery for abdominal aortic aneurysm between 2003 and 2019, including 155 patients (67%) treated with commercial grafts and 78 patients (33%) treated with handmade composite grafts. Their operative characteristics, postoperative outcomes, and late outcomes were retrospectively reviewed. Results: The early mortality rate did not differ significantly between the groups. On average, the handmade composite graft technique took approximately 15 minutes longer than the commercial graft technique (p=0.037). Among patients who underwent elective surgery, no significant differences between the conventional and composite groups were observed in the major outcomes, including red blood cell transfusion volume (2.8±4.7 units vs. 3.1±4.7 units, respectively; p=0.680), reoperation for bleeding (2.7% vs. 3.1%, respectively; p>0.999), bowel ischemia (0% vs. 1.6%, respectively; p=0.364), and intensive care unit stay duration (1.9±6.6 days vs. 1.6±2.4 days, respectively; p=0.680). The incidence of target vessel occlusion also did not differ significantly between groups. Conclusion: The increased technical demand involved with handmade composite grafting did not negatively impact the outcomes. This technique may be a viable option because it overcomes problems associated with commercial grafts.

• Journal of Forest and Environmental Science
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• v.14 no.1
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• pp.1-13
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• 1998

In this paper, it has been discussed on the relation between the anatomical features of woods and the penetration of methyl methacrylate monomer system into major Korean tree species, especially the Pinus koraiensis, Larix leptolepis, Quercus mongolica and Tilia amurensis. 1. There was some differences in penetration of polymers among different tree species, but generally the penetration of ring porous woods seems to be larger than that of diffuse porous woods and it was very difficult to penetrate to Larix leptolepis, especially to the that of heart wood. 2. The penetration on transeverse surface was relatively easy but radial and tangential impregnation were somewhat hard and differences between them were negligible. 3. The penetration of sapwood was larger than that of heartwood and its differences varied according to the existence of tyloses or contents in vessel. 4. Generally the polymer penetration of earlywood was larger than that of latewood in ring porous woods, but on the contrary, penetration of earlywood was small than that of latewood on diffuse porous woods. 5. Vessel diameter of wood had nearly no relation to polymers penetration. This seems to come from the reason that effective vessel diameter varies with the existence of tyloses or contents in vessel. 6. The penetration of ray tracheids was larger than that of ray parenchyma cells in softwoods, but penetration of hardwood rays seems to be small in comparison with softwood ray parenchyma cells. 7. Specific gravity and annual ring width had no relation to the penetration of polymer.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.193-196
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• 2007

We developed and tested the high pressure hydrogen gas cylinder(type4) for fuel cell vehicle. The working pressure is 350bar. We conducted material tests, production tests and design qualification tests on the developed cylinders according to modified NGV2-2000(hydrogen). The high pressure hydrogen gas cylinder met all the design qualification requirements of ANSI/CSA NGV2-2000 and acquired NGV2 certification from independent inspection agency.

• Steel and Composite Structures
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• v.23 no.1
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• pp.131-142
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• 2017

Determining limit load for a pressure bearing structure using elastic-plastic finite element analysis was computationally very expensive. A series of robust methods using elastic modulus adjustment techniques (EMAP) to identify the limit load directly were proposed. The numerical implementation of the robust method had the potential to be an attractive alternative to elastic-plastic finite element analysis since it was simple, and required less computational effort and computer storage space. Another attractive feature was that the method provided a go/no go criterion for the limit load, whereas the results of an elastic-plastic analysis were often difficult to interpret near the limit load since it came from human sources. To explore the performance of the method further, it was applied to a number of configurations that include two-dimensional and three-dimensional effects. In this study, limit load of cylinder with nozzle was determined by the robust methods.

• Steel and Composite Structures
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• v.22 no.6
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• pp.1391-1415
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• 2016

Limit load of pressure bearing structures was reviewed in this article. By means of the finite element analysis, limit load of pressurized cylinder with nozzle was taken as an example. Stress classification method and Elastic-plastic finite element analysis combining with limit load determination methods were used to determine limit load of cylinder with nozzle. Comparison of limit load determined by different methods, the results indicated that limit load determined by linearization method was the smallest. Limit load determined by twice elastic slope criterion was the nearest than experimental results. Elastic-plastic finite element analysis had comparably computational precision, but required time consuming. And then the requirements of computer processing and storage capacity by power system became higher and higher. Most of criteria for limit load estimation included any human factors based on a certain substantive characteristics of experimental results. The reasonable criterion should be objective and operational.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.9
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• pp.938-945
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• 2012

To design and estimate material failures of Type III pressure vessels, which have excellent stability and performance, various modeling techniques have been introduced. This paper provided a hybrid modeling technique composed of ply-based modeling for a cylinder part and laminate-base modeling technique for a dome part for enhancing modeling efficiency. The ply-based modeling technique provided accurate ply stresses directly for predicting material failure, on the other hand, additional manipulations in stress calculations, which may cause some errors, were needed for the case of the laminate-based modeling technique. The ply stresses in fiber, transverse and in-plane shear directions were compared with the corresponding material strengths to predict material failure.

• Archives of Plastic Surgery
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• v.32 no.3
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• pp.327-334
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• 2005

This study was designed to investigate the effect of the surgical delay in the prefabricated cutaneous flap. Abdominal skin flaps (n=40), $4.5{\times}6.0cm$ in size, were created by the subcutaneous implantation of a saphenous vascular tissue in the male Sprague-Dawley rats. In the groups 1 and 2, the pedicle was skeletonized. In the groups 3 and 4, perivascular muscle cuff or gracilis fascia was retained, respectively. Six weeks later, each flap was elevated as an island flap and reposed in place. All flaps of the group 2 had a 72-hours of delay period. Five days after the flap repositioning, estimation of flap viability, microangiographies, and histological evaluation of vessel development were performed. The groups 2 and 3 showed higher viability in flap survival. The dilated choke vessels and fully developed vascular network were observed in the flap of the group 2, but not typically seen in the other groups. New vessels around the implanted pedicle were more developed in the group 2. Amount of the vessels in the mid-portion of the flap was significantly increased in the groups 2 and 4. In conclusion, the delay procedure enhanced the viability, and its effect was dependent on the new vessel formation around the implanted pedicle.