• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.32 no.2
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• pp.117-128
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• 2006

Free flap transplantation with microvascular anastomosis has been successfully performed by development of surgical technique, materials and postoperative monitoring equipments of flap. But success rate of microvascular anastomosis is influenced by various factors, and failure rate is about 5-10%. The most influential factor for success rate is surgical technique and other factors that influence failure of microvascular anastomosis are ischemic time of free flap, thrombus formation of anastomosis region and vascular spasm. Many studies has been published in microvascular anastomosis with histologic effect for irrigating solution. But local irrigation solution has been used clinically in microvascular anastomosis, the comparison with each solution, microhistological study for endothelial cell repair and vascular patency has not been reported. The heparin which is anti-thrombotic agent, and urokinase which is fibrinolytic agent are used for this study. Vascular patency and thrombus formation in experimental micro-arterial anastomosis, and endothelial repair were observed with histologic analysis, scanning electron microscopy, transmission electron microscopic examination. The results were obtained as follows: 1. In vascular patency test in 30 minute and 7 days after micro-arterial anastomosis, equal effects of good vascular patency were obtained in group of local irrigation with heparin and urokinase. 2. In thrombus formation in 7 days after micro-arterial anastomosis, equal effects of minimal thrombus formation were obtained in group of local irrigation with heparin and urokinase. 3. In toluidin blue staining in 7 days after micro-arterial anastomosis, local destruction of endothelial cell and inner elastic lamina were seen and endothelial repair was not seen. 4. In scanning electron microscope examination in 7 days after micro-arterial anastomosis, endothelial cell was not seen in peripheral to suture materials, thrombus associated fibrin network was observed. 5. In transmission electron microscope examination in 7 days after micro-arterial anastomosis, inflammatory cell was seen within smooth muscle cells in site of endothelial cell destruction, smooth muscle cell around suture material were arranged irregularly, some collagenous change were seen. From the results obtained in this study, same results of good vascular patency and anti-thrombotic effect of heparin and urokinase were obtained as a local irrigation solution, and repair of endothelial cell was not seen in 7 days after micro-arterial anastomosis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.140-148
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• 2019

Large cast iron structures are used in casings and pipes in shipsand chemical plants. Broken parts in the casings and pipescan result in failures even when stresses are below the yield strength of the part's materials. Fatigue failure of a large cast iron structure is inevitable due to the design constraints and low reliability of the material strength. A small structure can be repaired by welding, but a large structure cannot because it cannot be preheated slowly and uniformly. This study shows that a large structure can be repaired by a cold joint method using a crack repair screw. Large cast iron structures were manufactured by GC 300, and their design stress is below 3.5 MPa. The tensile strength on notched specimens repaired by crack repair screws was 8.2 MPa. Therefore, the safety factors of structures repaired by crack repair screws have a value above 2.3 and are considered to be high values.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.9
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• pp.2271-2279
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• 1993

In the case of life prediction on the structures and machines after long service, it is natural to consider a degradation problems. Most of degradation data form practical structures are isolated data obtained at the time of periodical inspection or repair. From such data, it may be difficult to obtain the degradation curve available and necessary for life prediction. In this paper, for the purpose of obtaining a degradation curves, developed the simulate degradation method and fatigue test and Charpy impact test were conducted on the degraded, simulate degraded and recovered materials. Fatigue life prediction were conducted by using the relationship between fracture transition temperature (DBTT : vTrs) obtained from the Charpy impact test through the degradation process and fatigue crack growth constants of m and C obtained from the fatigue test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05d
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• pp.38-42
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• 2003

The use of VPI impregnated mica tape as high voltage insulation for large rotating electric machines requires a careful balance of processes and materials to obtain the desired electrical, mechanical and thermal characteristics. The stator insulation systems such as epoxy bonded high voltage mica tape have been produced for many years. One such system employing an epoxy and anhydride impregnating resin developed by Hyundai Heavy Industries, Co. (hereafter, HHI), to satisfy customer requests for an epoxy bonded insulation system. HHI applies the following electrical and thermal evaluations such as dielectric breakdown, voltage endurance, dissipation factor vs. temperature, isothermal weight loss, and so on. A detailed laboratory evaluation can describe specific physical limitations for an insulation system and permit development of long-term operation guidelines that permit full utilization of the proposed system. HHI has found these evaluations very helpful in qualifying insulation system for the repair of both large motors and generators.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.731-736
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• 2001

In this thesis, the study on controlling of cracks of concrete box culvert in early ages is presented. The optimum construction method and economical analysis were proposed also through the experiment of the material and field test. As a result of the experiment of the material, using fly ash, CSA expansive agent and BELITE cement(type IV) showed good result in the control of cracks induced by heat of hydration and shrinkage. As a result of construction test analysis, the maintenance time of form system did not show a big difference in controlling of cracks. Control of distribution of reinforcement, spacing of expansion joint and use of BELITE cement showed big differences in the control of cracks in early ages. As a result of economical analysis, control of construction variables before construction can make it possible to reduce the repair expense.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.7 no.1
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• pp.10-16
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• 2011

Performance of ground-source heat pumps (GSHPs) is mainly affected by ground heat exchangers which makes up more than 40% of construction cost. Exact construction and grout as backfill are important, because it is difficult to repair after being installed. As grout materials, bentonite grout material and cement material are used In this paper, thermal conductivity according to mix proportion of cement grout has been experimentally studied. Some variables were set to evaluate thermal conductivities according to change in cement content, unit water ratio, mass per volume of fresh mortar, and aggregate types. From the experimental analysis, high performance cement grout has been proposed.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.70-73
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• 2001

The layup optimization by genetic algorithm (GA) for the interlaminar strength of laminated composites with free edge is presented. For the calculation of interlaminar stresses of composite laminates with free edges, extended Kantorovich method is applied. In the formulation of GA, repair strategy is adopted for the satisfaction of given constraints. In order to consider the bounded uncertainty of material properties, convex modeling is used. Results of GA optimization with scattered properties are compared with those of optimization with nominal properties. The GA combined with convex modeling can work as a practical tool for maximum interlaminar strength design of laminated composite structures, since uncertainties are always encountered in composite materials and the optimal results can be changed.

• The Journal of the Korean dental association
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• v.48 no.11
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• pp.813-818
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• 2010

Since MTA has many beneficial properties such as biocompatibility, great sealing capacity, antibacterial effects, low cytotoxicity, and stimulation of formation of mineralized tissue, it has been widely used as the material of choice in root-end filling, apexification, pulpotomy, perforation repair and so on. However, despite its favorable characteristics, MTA presents working properties which are less than ideal. The resulting cement from the mixing of powder and water is difficult to manipulate, and its setting time has been reported to be 2 h 45 min whereas the working time is <4 minutes. Additional moisture is also required to activate the setting of the cement. Moreover, according to recent studies, the physical properties of MT A may be hampered by acidic environment or blood contamination. Therefore, practitioners may have surprisingly worse results than they expected when they are not fully acquainted with the characteristics and manipulation method of MTA.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.311-314
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• 2001

This paper describes the simulation study, conducted on the propagation characteristics of AE signal in the connection of GIS. In the high voltage and large power system, the equipment with SF$\sub$6/ gas insulation which consists of the component part enclosed in the compressed gas has less affected by the environment than with air insulation. When the breakdown in the electric installation occurs, it takes much time to repair them though. Therefore it is very important to diagnose the propagation characteristics of AE signal in the GIS. So, in this investigation, we make a plane model of 362 kV GIS and modal and harmonic analysis to observe the vibro-acoustic property. Through the result of the analysis, we can make a further understanding on the vibro-acoustic characteristics of AE singnal in the connection of GIS.

• Journal of the Korea Concrete Institute
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• v.12 no.1
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• pp.69-77
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• 2000

Recently, many strengthening methods are developed to repair damaged structures, when the original structure is under loading, which causes the difference of initial stresses between original member and bonded material. However, current design method or theory, which mostly depends on ultimately strength design, cannot account the difference of initial stresses between members, and it disregards the reduction of nominal strength. In this study, a new strengthening design theory and the amount of strengthening which can account the difference of initial stresses are developed, and applied to the case when a structure in service is repaired. The results show that the amount of strengthening material depends on the status of damages of structure, and the nominal strength is reduced depending on the degree of damages.