• The Journal of Korean Academy of Prosthodontics
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• v.29 no.2
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• pp.195-209
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• 1991

When the porcelain fused to metal restorations were fractured at the metal interface, various techniques and materials for intraoral porcelain repair have been suggested. The purpose of this study was to investigate the effect of metal surface treatment method and water storage on the shear bond strength of four porcelain repair systems. : Clearfil(Kuraray), All-bond(Bisco), Superbond C & B(Sun Medical), Panavia OP(Kuraray). After the metal surfaces of the specimens were sandblasted by aluminum oxide or roughened by diamond point, they were stored in double deionized water(24 Hr., $37^{\circ}C$) and thermocycling was performed(24 Hr., 1024 cycles), and again half of specimes were stored in water bath(2 Months, $37^{\circ}C$). Mean shear bond strength and mode of failure were recorded. The results of this study were obtained as follows : 1. Differences were observed between the sandblasted and diamond - treated specimens in Clearfil, All-bond, and Superbond. No statistically significant differences were observed in Panavia. 2. The 2-month storage time significantly affected the bond strength of All-bond and Superbond. No statistically significant differences were observed in Clearfil and Panavia. 3. The failures were observed at the interface between opaque resin and the metal in Clearfil and All-bond. 4. The failures were observed at the interface between opaque resin and veneered resin in Panavia. The failures were observed at the interface between opaque resin and veneered resin in Superbond, but 40% of them were fractured at the interface between the metal and opaque resin after 2-month storage time.

• Current Optics and Photonics
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• v.7 no.4
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• pp.387-397
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• 2023

Tooth surface shape error is an important parameter in gear accuracy evaluation. When tooth surface shape error is measured by laser interferometry, the gear interferogram is highly distorted and the gray level distribution is not uniform. Therefore, it is important for gear interferometry to extract the foreground region from the gear interference fringe image directly and accurately. This paper presents an approach for foreground extraction in gear interference images by leveraging the sinusoidal variation characteristics shown by the interference fringes. A gray level mask with an adaptive threshold is established to capture the relevant features, while a local variance evaluation function is employed to analyze the fluctuation state of the interference image and derive a repair mask. By combining these masks, the foreground region is directly extracted. Comparative evaluations using qualitative and quantitative assessment methods are performed to compare the proposed algorithm with both reference results and traditional approaches. The experimental findings reveal a remarkable degree of matching between the algorithm and the reference results. As a result, this method shows great potential for widespread application in the foreground extraction of gear interference images.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1D
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• pp.73-80
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• 2009

To repair the deteriorated concrete structures, the deteriorated parts should be removed by using surface treatment methods and replaced by new construction materials. Hydrodemolition is one of the most effective methods for chipping off the deteriorated concrete and treating the remaining concrete. The water jet can remove the deteriorated concrete without damaging the reinforcement steel and surrounding aggregates. Using the water jet system improves surface texture, which ensures to improve adhesive strength between new and old concretes. In this study, three different concrete slab strengths and two water jet machine sets were investigated. Experimental results showed the relationship between concrete strength and water jet condition and this would enable to provide the information of the domestic water jet system and specification, which would contribute to automatization and efficiency of concrete repairing and rehabilitation works.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1626-1630
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• 2007

This dissertation finds out trouble types and occurrence regions using the faulty statistics of nondestructive test items in rolling stock parts of the Seoul Metro and using mechanical test about defective and broken parts with broken surface observation, cutting examination about trouble region, hardness experiment and tensile test. Also this dissertation finds out cause of trouble and damage through observation of microscopic formation using metallurgical microscope and scanning electron microscope, residual stress measurement about welding parts and damage diagnosis about defective and broken parts. Moreover it will present the improved plan of nondestructive method about trouble and the removal method of defect and repair welding and find solutions of reliability in parts and preventive maintenance.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.234-239
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• 2004

Recently, the tunnel structures are increasing. And the tunnels are to be large diameter tunnel and long. Therefore, inspection, repair, and maintenance of tunnels are an extremely important part of infrastructure management, with particular technical and safety considerations arising from the very nature of underground construction. To inspect surface state of tunnels, concrete structures, it must generally use method of conventional visual inspection, but this method is very not objective. To measure the width, length, position, direction of a crack, it is very difficult, when the tunnel is long span and high rise. Thus, to make up for this demerits, in this paper is proposed the Tunnel Scanning System that we can check conditions of the tunnel structures quickly, detect the detailed data objectively, count automatically the width of a crack by the original software and follow the trend of long tenn changes in the condition of a tunnel.

• Corrosion Science and Technology
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• v.14 no.2
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• pp.54-58
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• 2015

A heavy oil of low quality has been mainly used in the diesel engine of the merchant ship as the oil price has been significantly jumped for several years. Thus, a combustion chamber of the engine has been often exposed to severely corrosive environment more and more because temperature of the exhaust gas of the combustion chamber has been getting higher and higher with increasing of using the heavy oil of low quality. As a result, wear and corrosion of the engine parts such as exhaust valve, piston crown and cylinder head surrounded with combustion chamber are more serious compared to the other parts of the engine. Therefore, an optimum repair welding for these engine parts is very important to prolong their lifetime in a economical point of view. In this study, 1.25Cr-0.5Mo filler metal was welded with SMAW method in the forged steel which would be generally used with piston crown material. And the corrosion properties of weld metal, heat affected and base metal zones were investigated using electrochemical methods such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% $H_2SO_4$ solution. The weld metal and base metal zones exhibited the highest and lowest values of hardness respectively. And, the corrosion resistance of the heat affected and weld metal zones was also increased than that of the base metal zone. Furthermore, it appeared that the corrosive products with red color and local corrosion like as a pitting corrosion were more frequently observed on the surface of the base metal zone compared to the heat affected and weld metal zones. Consequently, it is suggested that the mechanical and corrosion characteristics of the piston crown can be predominantly improved by repair welding method using the 1.25Cr-0.5Mo electrode.

• Journal of Veterinary Clinics
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• v.23 no.1
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• pp.81-85
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• 2006

Complete ruptures of the Achilles tendon were repaired in two hunting dogs of a 3-year-old, 20 kg and a 4-year-old, 14 kg with non weight bearing lameness. Both dogs were injured by wild animals and the skin defect was showed on the caudal surface of the right limb. Surgical repair involved the attachment of the ruptured tendon with a three-loop pulley method, using nonabsorbable suture materials. After surgical procedure, a bivalved cast was applied and maintained for 6 weeks. Exercise was restricted for 2 weeks more before gradually returned to normal. Gait and standing posture of dogs were returned to normal during the follow-up of 10 weeks.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.7
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• pp.1575-1581
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• 2005

Recently, further study is being done on the affect of crack on concrete structure and many people have made every endeavor not to leave it unsettled but to minimize it by repair works. In this paper we propose the image processing method that do not remain manual but automatically process the length, the direction and e width of cracks on concrete surface. First, we calibrate light's affect from image by using closing operation, one of morphology methods that can extract the feature of oracle and we extract the edge of crack image by sobel mask. After it, crack image is binarized by iteration binarization. And we extract the edge of cracks using noise elimination method that use an average of adjacent pixels by 3${\times}$3 mask and Glassfire Labeling algorithm. on, in this paper we propose an image processing method which can automatically measure the length, the direction and the width of cracks using the extracted edges of cracks. The results of experiment showed that the proposed method works better on the extraction of concrete cracks. Also our method showed the possibility that inspector's decision is unnecessary.

• Composites Research
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• v.29 no.3
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• pp.117-124
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• 2016

The failure strength of composite single-lap joint repaired using scarf patch was investigated by test and finite element method. A total of 45 specimens were tested changing scarf ratio, stacking pattern, and defect size to study the failure strength and mode. Except for one case, all repaired specimens showed the equal or higher strength than the sound specimens and the effect of considered repair parameters was not remarkable. It was found through the failure mode inspection that the surface treatment for bonding was not enough in the case which failed at the lower load than the sound specimen. Three-dimensional finite element analysis was conducted to verify the test results. It was confirmed that the considered repair parameters do not significantly affect the stress distribution of the specimens. It was also observed that the applied tensile load is relieved passing through the overlapped region thickness of which is almost double. From this study, it is concluded that if the bonding procedure for adherends and patch including surface treatment for fabric layer is thoroughly followed, the strength of repaired single-lap joint can be restored up to the strength of sound one.

• Economic and Environmental Geology
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• v.39 no.3 s.178
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• pp.285-299
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• 2006

The Mireuksaji stone pagoda in Iksan is the largest stone pagoda existing in Eastern Asia. It was assumed that originally it had been established in the shape of nine-storied pagoda but as time went by only six-storied pagoda remained partially due to collapsing, repair and reconstruction. According to the reference, we can't make sure when its modification happened. The form that the pagoda is having now, was modified with concrete by the Japanese during the 1910s. The materials mixed in concrete were mixture of Portland cement, all sorts of stone, sand, and a little bit of new building stone, additive and compound. And also these materials were applied to cultural assets without any experiment at the time of 1910s as maintenance, which are still used recently. To prevent the change of its shape, the west side, south side and the north side which is partially destructed was rebuilt and reinforced with concrete and some of the deformed parts were also filled. The amounts of concrete used were about 200 tons. Such method had prevented the pagoda from destructing, however, by choosing a wrong repair method, its surface of the stone has secondary contaminants and precipitation caused by concrete. This kind of contamination speeds up the weathering which accelerates the aging mechanism of the stone to make it even harder to revive the absence of historical nature. Therefore, we are to find the best cleaning method to remove the secondary hazard contaminants.