• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.50.2-50.2
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• 2010

니켈기 초내열합금 Inconel 617은 수소생산용 초고온 가스 냉각로의 열 교환기와 고온 가스관 등의 고온 배관용 후보재료로써, Cr, Mo, 와 W등의 첨가물이 함유된 고용 강화된 합금으로, 우수한 고온 강도, 크립 저항성, 내부식성 및 내산화성을 가지고 있는 것으로 알려져 있다. 본 연구에서는 결정립 미세화가 고온열화에 의해 입계를 따라 형성되는 internal oxide에 미치는 영향에 대해 평가하였고, 이러한 internal oxide가 인장응력 하에서 크렉 형성 및 전파에 미치는 영향을 평가하기 위하여 3-point bending test를 수행하였다. 미세한 결정립을 가지는 Inconel 617은 냉간압연 후 재결정을 통해 확보하였으며, as-received(AR)과 grain-refined(GR) Inconel 617은 $950^{\circ}C$에서 2000시간 동안 He분위기 하에서 열화시험을 수행하였다. AR과 GR에 형성된 internal oxide은 깊이와 분포 등의 뚜렷한 차이를 보였으며, 이러한 차이로 인해 인장응력 하에서 크렉 전파의 큰 차이를 나타내었다.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1021-1024
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• 2008

Near infrared heating as an alternative to the conventional heating techniques for thermography -NDT is tried in this paper. A concrete specimen containing a defect was heated by the near infrared ray and the thermography-NDT technique was applied. Using a dimensinless temperature, the defects were detected. It was found that the near infrared ray could efficiently heat up the concrete specimen compared to others conventional methods like lamps, heat flow, etc.

• The Journal of Korea Robotics Society
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• v.17 no.3
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• pp.314-321
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• 2022

Depth information used in SLAM and visual odometry is essential in robotics. Depth information often obtained from sensors or learned by networks. While learning-based methods have gained popularity, they are mostly limited to RGB images. However, the limitation of RGB images occurs in visually derailed environments. Thermal cameras are in the spotlight as a way to solve these problems. Unlike RGB images, thermal images reliably perceive the environment regardless of the illumination variance but show lacking contrast and texture. This low contrast in the thermal image prohibits an algorithm from effectively learning the underlying scene details. To tackle these challenges, we propose multi-channel remapping for contrast. Our method allows a learning-based depth prediction model to have an accurate depth prediction even in low light conditions. We validate the feasibility and show that our multi-channel remapping method outperforms the existing methods both visually and quantitatively over our dataset.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.902-912
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• 2003

The most common deteriorating processes of concrete structures are carbonation and chloride ion ingress. Many concrete structures have been suffered from chloride ions diffusion or carbonation induced reinforcement corrosion damage and many studies have been done on it. However, those studies were confined mostly to the single deterioration of carbonation or chloride attack only, although actual environment is rather of combined conditions. In case of many in-situ concrete structures, deterioration happened more for the case of combined attack than the single case of carbonation or chloride attack. In this paper, chloride profiles of carbonated concrete is predicted by considering two layer composite model, which is based on Fick's 2nd law. From the experimental result on combined deterioration of chloride and carbonation, it was examined that high chloride concentration was built up to 3∼5 mm over depth from carbonation depth. The analytical modeling of chloride diffusion was suggested to depict the relative influence of the carbonation depth. The diffusion coefficients of carbonation concrete and uncarbonated concrete with elapsed time were considered in this modeling.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.505-508
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• 2008

Concrete is a type of porous materials and is physically and chemically damaged due to exposure to various environments from the placing to the service life. These reactions affect the corrosionof steel bars applied in concrete and that decreases the durability life and strength of such steel bars. Thus, it is very important to insert rust inhibitors into steel bars in the case of a deterioration element that exceeds the critical amount of corrosion in the location of steel bars. However, it is very difficult to guarantee corrosion resistance at the location of steel bars using conventional technology that applies corrosion inhibitors only on the surface of concrete. This study attempts to develop a method that penetrates corrosion inhibitors up to the location of steel bars and investigate the penetration depth of corrosion inhibitors by verifying moisture migration in concrete under an applied pressure.

• 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.

• Journal of the Korean Society of Hazard Mitigation
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• v.2 no.1 s.4
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• pp.143-152
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• 2002

The objectives of this paper were to obtain the fundamental data to analyze the causes of deterioration of 39 freeway concrete viaducts in Seoul metropolitan area. To investigate the degree of concrete deterioration, carbonation depth, soluble chloride concentration in hardened concrete and half-cell potentials of reinforcement were measured. The number of structures which carbonation depth penetrates to reinforcement was 25% of total. The model of carbonation .ate was induced to 3.92 $\sqrt{t}$, which was 5% faster than 3.727 $\sqrt{t}$ assumed 60% water-cement ratio, R=1 in that of kishitani. After measuring chloride concentration in concrete, it was concluded that about 24% of all readings on samples from concrete exceed the critical content to minimize the risk of chloride-induced corrosion. About 31% of the freeway viaducts structures had a value lower than -350mV(vs. CSE), so it could conclude that the excessive chloride concentration was the major cause of reinforcement corrosion. Among the structures which measured half-cell potentials less than -350mV, about 50% exceeds the maximum acceptable limit of chloride concentration.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.1
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• pp.128-138
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• 2015

Carbonation is one of the most critical deterioration phenomena to concrete structures exposed to high $CO_2$ concentration, sheltered from rain. Lots of researches have been performed on evaluation of carbonation depth and changes in hydrate compositions, however carbonation modeling is limitedly carried out due to complicated carbonic reaction and diffusion coefficient. This study presents a simplified carbonation model considering diffusion coefficient, solubility of $Ca(OH)_2$, porosity reduction, and carbonic reaction rate for low concentration. For verification, accelerated carbonation test with varying temperature and MIP (Mercury Intrusion Porosimetry) test are carried out, and carbonation depths are compared with those from the previous and the proposed model. Field data with low $CO_2$ concentration is compared with those from the proposed model. The proposed model shows very reasonable results like carbonation depth and consuming $Ca(OH)_2$ through reduced diffusion coefficient and porosity compared with the previous model.

• Journal of Broadcast Engineering
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• v.14 no.2
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• pp.197-209
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• 2009

Stereoscopic video delivers depth perception to users contrary to 2D video. Therefore, we need to develop a new video quality assessment model for stereoscopic video. In this paper, we propose a new method for objective assessment of stereoscopic video. The proposed method detects blocking artifacts and degradation in edge regions such as in conventional video quality assessment model. And it detects video quality difference between views using depth information for efficient quality prediction. We performed subjective assessment of stereoscopic video to check the performance of the proposed method, and we confirmed that the proposed algorithm is superior to the existing method in PSNR in respect to correlation with results of the subjective assessment.

• Composites Research
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• v.25 no.6
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• pp.236-240
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• 2012

The purpose of this study was to investigate the feasibility on the detection of dental composite delamination using a lock-in thermography method. Amplitude and phase images of detected thermal signals were analyzed according to the lock-in frequencies. At a lock-in frequency of 0.05 Hz, the ligament thickness of 0.5 mm in the specimen exhibited the highest amplitude contrast between defective area and sound area. For ligament thicknesses of 1 mm and 1.5 mm, delamination detection was possible at 0.025 Hz and 0.01 Hz through the amplitude differences. At lock-in frequencies of 0.006 Hz and 0.01 Hz, ligament thickness 0.5 mm exhibited the highest phase contrast. For ligament thicknesses of 1 mm and 1.5 mm, the phase contrast exhibited possible detection of delamination at 0.006-0.1 Hz.