• Nuclear Engineering and Technology
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• v.43 no.4
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• pp.343-354
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• 2011

It is critically important to identify unexpected loose parts in a nuclear reactor pressure vessel, since they may collide with and cause damage to internal structures. Mass estimation can provide key information regarding the kind as well as the location of loose parts. This study proposes a mass estimation method based on an artificial neural network (ANN), which can overcome several unresolved issues involved in other conventional methods. In the ANN model, input parameters are the discrete cosine transform (DCT) coefficients of the auto-power spectrum density (APSD) of the measured impact acceleration signal. The performance of the proposed method is then evaluated through application to a large-sized plate and a 1/8-scaled mockup of a reactor pressure vessel. The results are compared with those obtained using a conventional method, the frequency ratio (FR) method. It is shown that the proposed method is capable of estimating the impact mass with 30% lower relative error than the FR method, thus improving the estimation performance.

• Journal of Nuclear Fuel Cycle and Waste Technology
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• v.1 no.1
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• pp.83-92
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• 2013

A novel methodology to evaluate remote dismantling equipment for a reactor pressure vessel (RPV) in a decommissioning project is presented in this paper. The remote dismantling equipment, mainly composed of cutting tools and positioning equipment, is absolutely required to cut and handle highly radioactive and large components in nuclear power plants (NPPs); this equipment has a great effect on the overall success of the decommissioning project. Conventional evaluation methods have only focused on cutting technologies or positioning equipment, although remote dismantling equipment cannot achieve its goal without organic interaction between the cutting tools and the positioning equipment. In this paper, the cutting tools and the positioning equipment are evaluated by performance parameters according to their original characteristics, the relationship between the two systems, and common factors. Finally, the remote dismantling equipment used in recent decommissioning projects has been evaluated based on the proposed methodology. The results of this paper are expected to be useful for future decommissioning projects.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.5
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• pp.76-82
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• 2010

In this study, we carried out to evaluate the shock-proof of a large scale motor for the naval vessel using dynamic design analysis method (DDAM) and full transient dynamic analysis. Analytical models for main assemblies (motor frame, rotor and stator assembly) were consisted of the tetrahedral solid elements and the equipments which installed in the upper side of the motor were substituted the mass elements. And we also modelled resilient mounts of a motor using the beam elements with appropriate directional stiffness. The DDAM was conducted according to NRL memorandum report 1396 and the full transient dynamic analysis was performed applying directional triple half triangle shock wave to the motor using ANSYS 12. As a result, we could compare of the results according to each analytic method and find the motor to satisfy the design criteria of the maximum stress and deformation.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.5
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• pp.64-73
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• 1995

A numerical simulation of heat and fluid flow for predicting the effect of passage arrangement in automotive heat battery has been performed. The system is assumed to be a two-dimensional laminar flow and isothermal boundary is applied to the surface of the latent heat storage vessel. In the case of ideal heat battery the flow rate into each flow passage is evenly distributed. The various models are considered in the view of pressure drop and bulk temperature. The effects on the efficiency of the heat battery are examined by varying geometrical factors such as flow passage clearance, length of a inlet and outlet tank and the length of a latent heat storage vessel. The flow clearance is a very important -factor on the efficiency of a heat battery. As the flow passage clearance becomes narrow, the flow distribution becomes uniform and the bulk temperature increases, however the pressure drop is large. Therefore, optimal flow passage clearance has to be chosen. The present work can be used in optimizing heat battery efficiency.

• Archives of Plastic Surgery
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• v.47 no.1
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• pp.88-91
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• 2020

Cutaneous squamous cell carcinoma (SCC) is the second most common skin malignancy. This report describes the case of an unusual extensive SCC involving the whole hemiface, which required reconstruction with a combination of a dual vascular free transverse rectus abdominis muscle (TRAM) flap and a skin graft. A 79-year-old woman visited our hospital with multiple large ulcerated erythematous patches on her right hemiface, including the parieto-temporal scalp, bulbar and palpebral conjunctiva, cheek, and lip. A preliminary multifocal biopsy was performed in order to determine the resection margin, and the lesion was resected en bloc. Orbital exenteration was also performed. A free TRAM flap was harvested with preserved bilateral pedicles and was anastomosed with a single superior thyroidal vessel. The entire TRAM flap survived. The final pathological examination of the resected specimen confirmed that there was no regional nodal metastasis, perineural invasion, or lymphovascular involvement. The patient was observed for 6 months, and there was no evidence of local recurrence. Usage of a TRAM flap is appropriate for hemifacial reconstruction because the skin of the abdomen matches the color and pliability of the face. Furthermore, we found that the independent attachment of two extra-flap anastomoses to a single recipient vessel can safely result in survival of the flap.

• Nuclear Engineering and Technology
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• v.39 no.4
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• pp.257-272
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• 2007

Supercritical water-cooled reactors (SCWRs) are recognized as a Generation IV reactor concept. The Super LWR is a pressure-vessel type thermal spectrum SCWR with downward-flow water rods and is currently under study at the University of Tokyo. This paper reviews Super LWR safety. The fundamental requirement for the Super LWR, which has a once-through coolant cycle, is the core coolant flow rate rather than the coolant inventory. Key safety characteristics of the Super LWR inhere in the design features and have been identified through a series of safety analyses. Although loss-of-flow is the most important abnormality, fuel rod heat-up is mitigated by the "heat sink" and "water source" effects of the water rods. Response of the reactor power against pressurization events is mild due to a small change in the average coolant density and flow stagnation of the once-through coolant cycle. These mild responses against transients and also reactivity feedbacks provide good inherent safety against anticipated-transient-without-scram (ATWS) events without alternative actions. Initiation of an automatic depressurization system provides effective heat removal from the fuel rods. An "in-vessel accumulator" effect of the reactor vessel top dome enhances the fuel rod cooling. This effect enlarges the safety margin for large LOCA.

• Progress in Superconductivity and Cryogenics
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• v.23 no.1
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• pp.7-11
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• 2021

Cryogenic vessels are special equipment that requires periodic evaluation of their thermal insulation performance. At the current standard, the test is considered as the loss product or heat leakage of cryogenic vessel, which takes over 72 h to evaluate; consequently, a large amount of working medium is discharged to the environment in the process. However, hydrogen is flammable and explosive, and the discharged gas may be dangerous. If liquid hydrogen is replaced with liquid nitrogen before testing, the operation then becomes complicated, and the loss product or heat leakage cannot respond to the thermal insulation performance of cryogenic vessels for liquid hydrogen. Therefore, a novel method is proposed to evaluate the heat leakage of cryogenic vessels for liquid hydrogen in self-pressurization. In contrast to the current testing methods, the method proposed in this study does not require discharge or exchange of working medium in all test processes. The proposed method is based on one-dimensional heat transfer analysis of cryogenic vessels, which is verified by experiment. When this method is used to predict the heat leakage, the comparison with the experimental data of the standard method shows that the maximum error of heat leakage is less than 5.0%.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.3088-3101
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• 2023

A pressurized vessel-pipe-safety valve (PVPSV) combination is a commonly used configuration in nuclear power plants, and a good numerical model is essential for the system design, sizing and performance optimization. However, owing to the large-scale and cross-scale features, it is still a challenge to build a system level numerical model with both high accuracy and efficiency. To overcome this, a novel system level modeling method which can synthesize the advantages of various models is proposed in this paper. For system modeling, the analytical approach, the method of characteristics (MOC) and the surrogate model approach are respectively adopted to predict the dynamics of the pressure vessel, the connecting pipe and the safety valve, and different models are connected through data interfaces. With this system model, dynamic simulations were carried out and both the stable and the unstable system responses were obtained. For the model verification purpose, the simulation results were compared with those obtained from experiments and full CFD simulations. A good agreement and a better efficiency were obtained, verifying the ability of the model and the feasibility of the modeling method proposed in this paper.

• Archives of Reconstructive Microsurgery
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• v.9 no.1
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• pp.80-87
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• 2000

Acute high speed accidents that results in full thickness skin defect and exposure of tendon, nerve, vessel and periosteum over denuded bone demands soft tissue coverage. Exposed bone often ensues chronic infection and requires free flap transplantation which surely covers defects in one stage operation and enhances transport of oxygen-rich blood and converts a non-osteogenic or partially osteogenic site into a highly osteogenic site, but exposed bone which had performed free flap transplantation sometimes necroses and needs secondary bone procedure. Scar contracture limits joint motion should be excised and covered with normal soft tissue to restore normal range of motion. Authors have performed the large latissimus dorsi myocutaneous free flap in 8 cases of extensive soft tissue defect and exposed bone lesion in the leg and 1 case of the flap was failed. The secondary ilizarov bone procedure was performed in 3 of 8 cases. 2 cases of large burn scar contracture and 1 case of posttraumatic scar contracture in lower extremity were restored with the large latissimus dorsi myocutaneous free flap. Authors concluded that large latissimus dorsi myocutaneous free flap is the most acceptable microvascular procedure in large soft tissue defect combined with exposed periosteum and bone requiring secondary bone procedure and in large burn scar contracture limiting knee joint motion.

• Journal of Korean Neurosurgical Society
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• v.30 no.6
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• pp.805-812
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• 2001

Objectives : The goal of the surgical management of large and giant aneurysm is complete extirpation of the aneurysms with preservation or reconstruction of the parent artery. To improve the surgical management results of those aneurysms in the future, we review our experience and discuss technical maneuvers and strategies used to avoid potential complications of those aneurysm surgery. Material and Methods : During the past 12 years, thirty six cases of large and giant aneurysms(diameter>19mm) were managed by surgery. The clinical characteristics, treatment methods, surgical complications and outcome of those cases were analyzed and, based on the review of the literatures, the preventive methods of surgical complication related to the clipping of those aneurysms were discussed. Results : The locations of those aneurysms were anterior circulation in 34 cases and posterior circulation in 2 cases. The most frequent site of aneurysmal location was a paraclinoidal region of the anterior circulation. The aneurysms were managed surgically by direct clipping of aneurysmal neck in 31 cases, aneurysmal trapping followed by extracranial-intracranial bypass in 2 cases, proximal clipping of parent artery, aneurysmorrhaphy, and excision of aneurysm followed by end to end anastomosis of parent artery in each one case. Surgical complications occurred in 13 cases. A parent vessel occlusion by thrombus formation and parent vessel stenosis after clipping of aneurysm were the main complications. We obtained good outcome in 27, fair 5, poor 1 and dead in 3 case(s). Conclusion : We conclude that selection of suitable management method for each case, high quality of surgical technique and prevention of complication during operation are important key points for the successful treatment of large and giant aneurysm. The heparinization prior to application of temporary clip on parent vessels, aneurysmal decompression during dissection and clipping of aneurysm, complete closing of the aneurysmal neck and avoiding the narrowing of parent vessel after clipping of aneurysm were the main technical maneuvers used to avoid complications of those aneurysm surgery.