• Maxillofacial Plastic and Reconstructive Surgery
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• 제30권4호
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• pp.323-332
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• 2008

Aim of the study: Scaffolds are crucial to tissue engineering/regeneration. Biodegradable polymer/ceramic composite scaffolds can overcome the limitations of conventional ceramic bone substitutes such as brittleness and difficulty in shaping. In this study, poly(L-lactide)/hydroxyapatite(PLLA/HA) composite scaffolds were fabricated for in vivo bone tissue engineering. Material & methods: In this study, PLLA/HA composite microspheres were prepared by double emulsion-solvent evaporation method, and were evaluated in vivo bone tissue engineering. Bone marrow mesenchymal stem cell from rat iliac crest was differentiated to osteoblast by adding osteogenic medium, and was mixed with PLLA/HA composite scaffold in fibrin gel and was injected immediately into rat cranial bone critical size defect(CSD:8mm in diameter). At 1. 2, 4, 8 weeks after implantation, histological analysis by H-E staining, histomorphometric analysis and radiolographic analysis were done. Results: BMP-2 loaded PLLA/HA composite scaffolds in fibrin gel delivered with osteoblasts differentiated from bone marrow mesenchymal stem cells showed rapid and much more bone regeneration in rat cranial bone defects than control group. Conclusion: This results suggest the feasibility and usefulness of this type of scaffold in bone tissue engineering.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제30권4호
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• pp.353-358
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• 2008

Purpose: The purpose of this clinical retrospective study was to evaluate our experience of radial forearm free flap for reconstruction of the oral cavity. Material and methods: From 1997 to 2006, 50 radial forearm free flaps were employed for head and neck reconstruction in 50 patients at department of oral and maxillofacial surgery, Yonsei University, Korea. Data were obtained from chart review, and clinical follow-up. Results: Patients' age ranged from 26 to 82 years (mean 53.2). There were 39 men and 11 women. 43 of the 50(86%) patients had squamous cell carcinoma. The total flap survival were 47(94%), complication rate were revealed for 15(30%). Conclusion: In the reconstruction of soft tissue within the oral cavity, several free flaps have been used. Because of its constant anatomy, long pedicle allows a hypothetic vascular anastomosis in the contralateral neck, contourability for various type of oral defects, pliability and can be used simultaneous reconstruction in intraoral and extra oral defects, the radial forearm free flap constitutes one of the best choice of intraoral soft tissue reconstruction.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제30권6호
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• pp.513-517
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• 2008

Purpose: This study aimed to evaluate distribution and maximal value of mechanical stresses on the reconstruction plate, bridging mandibular symphysis defect, and to optimize the most appropriate locations of the plate to distribute the stress causing the fracture of the plate. Materials and methods: Four types of reconstruction were constructed by different number and location of the reconstruction plates on the 3 D finite element model (FEM) of a human edentulous mandible; Type I: one plate on the inferior border of the anterior mandible, Type II: one plate on the middle of the anterior mandible, Type III: one plate on the superior border of the anterior mandible, and Type IV: two plates on the inferior and superior border of the anterior mandible. Results: The results showed that the maximal stress of type I (234.29 Mpa) was lower than that of type II (260.91 Mpa) and type III (247.37 Mpa), but higher than that of type IV (186.64 Mpa). We could also observe that the stresses are tending to focus on the inner side and inferior part of the plate which connected proximal segment from the vertical load. Conclusions: On the basis of the findings, it was concluded that using a plate on the inferior border of mandible or two plates on the inferior and superior border of mandible are more favorable to distribute mechanical stresses, which could reduce the fracture of the plate.

• Archives of Reconstructive Microsurgery
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• 제7권1호
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• pp.15-19
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• 1998

Microsurgical free-tissue transfer has allowed surgeons to salvage injured limbs but choosing appropriate healthy recipient vessels has proved to be a difficult problem. Retrograde flow flaps are established in island flaps. Retrograde flow anastomosis could prevent the possible kinking and twisting of the arterial anastomosis. By not interrupting the proximal blood flow to the fracture or soft tissue defect site, the compromise of fracture or wound healing might be prevented. We wished to estabilish an animal model in rat for a retrograde arterial flow based free flap. Nembutal-anesthetized male rats; weighing 250 to 300 gm, were used. The femoral artery and common carotid artery were exposed and divided. The systemic and retrograde arterial pressure were quantified by utilizing a parallel tubing system connected with peripheral arterial line. In this study, the retrograde flow was not pulsatile and the retrograde arterial pressure was 64-65mmHg, with a mean arterial pressure of 106-109mmHg. An epigastiic skin flap, measuring $3{\times}3cm$, was raised with its vascular pedicle. The epigastric free flap was transfered in the same rat from femoral vessels to carotid vessels in end to end fashion. We anastomosed the donor arteries to the distal parts of the divided recipient arteries and the donor veins to the proximal parts of the recipient veins. Twelve experiments were performed and the transplantations succeeded in 75 percent of them. In the remaining 25 percent, the experiments failed due to thrombosis at the site of anastpmosis, or other causes. This animal model represents an excellent example of retrograde arterial flow free flap transfer that is reliable.

• Tribology and Lubricants
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• 제40권5호
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• pp.157-162
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• 2024

This study evaluates the structural stability of the drive system of a monorail and investigates the causes of derailment accidents using finite element analysis. We assume a scenario where the gear pitch decreases by 1 mm owing to construction defects and perform dynamic analysis as the pinion gear traverses the abnormal pitch interval of the rack gear. The contact analysis between the rack and pinion gears reveals that the pinion gear collides in the abnormal pitch range due to the construction defect at the rack gear connection. The collision generates stresses exceeding the yield strength of the gear and rail materials, leading to plastic deformation. This study additionally investigates the bearings where the actual damage occurs utilizing the load data derived from the analysis. Findings indicate that plastic deformation and fatigue damage occurs in the bearing retainer and balls owing to the impact load, leading to ball detachment and retainer failure. Moreover, repetitive impact loads can rapidly degrade bearing durability, directly contributing to accidents. The findings of this study should be considered during the design, manufacturing, assembly, and maintenance processes of monorail system components, enhancing the safety through precise manufacturing and assembly practices.

• Journal of the Korea Institute of Building Construction
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• 제1권2호
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• pp.185-190
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• 2001

The purpose of this study is the development of practical Dry floor tile unit method that settle the defect of a wet method and designed for resin mat. With use of PE resin which is confirmed the basic property, it is developed that resin mat, joint-sealing compound with fixed form and space management to Dry floor tile unit method. The result of this study is below. 1) To acquire above the 4kgf/$\textrm{cm}^2$ - construction specification criterion, the bonding space that between resin mat and tile has to occupy the 50% of resin mat module space(10,000$\textrm{cm}^2$). 2) Criteria of bonding part plane is below. simpleness of metal form. productivity, uniform quality after injection molding cooling, easy cutting for remain space management, adhesive property, construction ability, transformation of a severed piece under pressure and so on. 3) To get the shape that could protect the interfacial breakdown, it is designed that resin mat and tile are unified after the bond input. 4) Adapted joint-sealing compound is the material of urethane kinds wedge form. Resin mat has the water passageway that could drain the water. 5) To manage the severed piece of tile, the resin mat is likely to divide the half and the quarter and the plastic drainage is developed in the severed piece.

• Journal of Genetic Medicine
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• 제9권2호
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• pp.89-92
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• 2012

Campomelic dysplasia (CMD) is a rare, often lethal, genetic disorder characterized by multiple congenital anomalies and abnormal development of the reproductive organs in males. Mutations in the SOX9 gene are known to cause CMD. We present a Korean CMD girl with a normal 46,XX karyotype and a female reproductive organ phenotype. She was born at 2.35 kg at 38 weeks of gestation and showed characteristic phenotypes, including cleft palate, micrognathia, hypertelorism, flat nasal bridge, congenital bowing of limbs, hypoplastic scapulae, deformed pelvis, and 11 pairs of ribs. She also had an atrioseptal defect of the heart and marked laryngotracheomalacia requiring tracheostomy and tracheopexy. SOX9 mutation analysis revealed the presence of a novel nonsense mutation, $p.Gln369^*$, and the patient was genetically confirmed to have CMD. Although she showed marked failure to thrive and neurodevelopmental delay, she is now 40 months of age and is the only surviving patient with CMD in Korea.

• Steel and Composite Structures
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• 제18권4호
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• pp.1045-1062
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• 2015

Concrete-filled circular t steel tubular joints (CFSTJs) in practice are frequently subjected to fluctuated loadings caused by wind, earthquake and so on. As fatigue crack is sensitive to such cyclic loadings, assessment on performance of CFSTJs with crack-like defect attracts more concerns because both high stress concentration at the brace/chord intersection and welding residual stresses along weld toe cause the materials in the region around the intersection to be more brittle. Once crack initiates and propagates along the weld toe, tri-axial stresses in high gradient around the crack front exist, which may bring brittle fracture failure. Additionally, the stiffness and the load carrying capacity of the CFSTJs with crack may decrease due to the weakened connection at the intersection. To study the behaviour of CFSTJs with initial crack, experimental tests have been carried out on three full-scale CFCST T-joints with same configuration. The three specimens include one uncracked joint and two corresponding cracked joints. Load-displacement and load-deformation curves, failure mode and crack propagation are obtained from the experiment measurement. According to the experimental results, it can be found that he load carrying capacity of the cracked joints is decreased by more than 10% compared with the uncracked joint. The effect of crack depth on the load carrying capacity of CFCST T-joints seems to be slight. The failure mode of the cracked CFCST T-joints represents as plastic yielding rather than brittle fracture through experimental observation.

• Journal of Welding and Joining
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• 제35권1호
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• pp.55-60
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• 2017

There are many Industry Code and Standard (ICS) for Structural Integrity Assessment (SIA) on welded structure with defect. The general ICSs, such as R6, BS 7910 and API 579-1/ASME FFS-1, provide equations to determine the upper bound residual stress profiles based on collections from many literatures. However, these residual stress profiles used in the SIA cause the conservative design for welded structures. In this study, the structural integrity assessment for girth weld in pipeline has been conducted based on fracture mechanics. In addition, thermo-elastic plastic FE analysis was performed for evaluating the residual stress of girth weld in pipeline. The weight function solution is used to determine the stress intensity factor using the residual stress profile obtained by the FE analysis. This approach can account for redistribution and relaxation of residual stress as the defects grow. In order to the evaluate quantitative comparison between BS 7910 and weight function solution, structural integrity assessment determining allowable crack size on cracked pipe was performed with failure assessment diagram.

• Journal of the Korean Society for Precision Engineering
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• 제22권3호
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• pp.68-77
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• 2005

The set-up of an injection molding process is a ye complicated and time-consuming job because it is required to well determine a lot of variables closely related to products. Thus, the productivity of the set-up process mainly depends on operators' expertise and know-how. To solve the problem mentioned before, this research constructs a support system which helps operators determining the condition of the injection molding easily and systematically. The construction of the support system consists of the following four steps: 1) to determine the control variables which affect the target defect types, 2) to design and implement UI(user interface) using a scenario of set-up process, 3) to design and implement the search algorithms for the initial and optima] condition, and 4) to construct the embedded system which integrates the support system with the operating system of a plastic injection molding machine. The test experiments of some typical products are performed using the embedded system to verify the validity of the support system.