• Fire Science and Engineering
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• v.18 no.3
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• pp.51-56
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• 2004

A fire outbreak in a reinforcement concrete structure looses the organism by the different contraction and expansion of hardened cement pastes and aggregate, and causes cracks by thermal stress, leading to the deterioration of the durability. So concrete reinforcement structure is damaged partial or whole structure system. Therefore diagnosis of deterioration is needed based on mechanism of fire deterioration in general concrete structures. Fundamental information and data on the properties of concrete exposed to high temperature are necessary for accurate diagnosis of deterioration. In this study, it was presented data for the accurate diagnosis and selection of repair and reinforcement system for the deteriorated concrete heated highly, various concrete such as standard design compressive strength, fine aggregate and admixture were exposed to a high temperature environment. And fundamental data were measured engineering properties such as explosive spatting, ultrasonic pulse velocity and compressive strength.

• Elastomers and Composites
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• v.40 no.3
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• pp.196-203
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• 2005

In this work, the engine oil resistant evaluation and breakdown analysis of room temperature vulcanizing silicone adhesives were performed through the surface properties, thermal stabilities, adhesive strength, and morphology measurements. As a result, the permeation of engine oil into adhesive specimens was carried out from surface to center in the specimens. And the oil content in the adhesive specimens was increased and the Si-O-Si bond of the adhesives was decomposed with increasing the aging time. The TGA results indicated that the thermal degradation was mainly occurred at under and surfaces of the specimens. The tensile strength, elongation, and adhesive strength of the adhesives were significantly decreased after the engine oil resistant tests, which could be attributed to the initial lose of adhesive properties resulting from the engine oil absorption and thermal aging. And the failure mode of the adhesive specimens was changed from cohesive failure to interfacial failure.

• Resources Recycling
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• v.17 no.3
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• pp.35-41
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• 2008

The study of coking technology to upgrade oil sand bitumen which is considered as alternative fuel was performed by using thermogravity analyzer and delayed coking reactor(600ml). To analyzed and compared coking characteristics of oil sand bitumen, the reactivities of oil sand bitumen were measured in the TGA. At the temperature conditions of $400{\sim}550^{\circ}C$ and the temperature rising velocity of $50^{\circ}C/min$. the termination time of coking reaction and conversion efficiencies increased with an increase of bed temperature. However the increase rate decreased over $450^{\circ}C$. So the coking reaction with oil sand bitumen might be over $450^{\circ}C$. Also the termination time decreased with increasing the temperature rising velocity. But the content of coke increased with increasing temperature rising velocity. At the experiments in the delayed coker, the temperature condition at maximum oil yield was $475^{\circ}C$ and the fuel properties of oil from coking reaction was almost equal with conventional diesel. It was verified that the coking process might be useful process to upgrade the oil sand bitumem by using API and SIMDAS.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.4
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• pp.793-801
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• 2000

This paper presents the effect of lightning impulse current on ZnO varistors(390[V], 6.5[kA]) used in low-voltage AC mains as a protective device against transient overvoltages. The electrical characteristics of ZnO varistors are deteriorated by overtime impulse current, and a deteriorated ZnO varistor is brought to a thermal runaway and finally destroyed even in normal operating voltage. Therefore, it is important to estimate the changes of the electrical characteristics of ZnO varistors. A lightning impulse current standardized in IEC 61000-4-5 is applied to the varistors to accelerate deterioration, and the energy applied to the varistor at each time is about 12 [J]. In the experiment, various parameters such as leakage current, reference voltage are measured with the number of applied impulse current. Also, micro-structure changes of the varistors after applying the lightning impulse current of 200 times are compared. The electrical characteristics of the varistors are degraded by overtime impulse current, showing increase in leakage current and decrease in reference voltage.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.103-110
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• 2021

Elastomeric bearings composed of flexible rubber materials and steel reinforcement plates are widely used for seismic retrofit of bridges due to their excellent vertical stiffness and flexible lateral stiffness. Especially, it has the advantages of simple construction and low cost. Chloroprene rubber, a type of rubber material, has greater resistance to aging than natural rubber, but its performance is also degraded due to various deterioration factors. Although these aging characteristics are not reflected in the seismic design standards and seismic performance evaluation guidelines, it is reasonable to reflect this when related studies are accumulated. For chloroprene rubber, accelerated heat aging test was performed with variables of heating temperatures and exposure time to analyze shear characteristics. As aging progresses the maximum shear stress and shear strain decrease. Also, the shear stiffness is greatly increased at the same shear strain.

• The Journal of the Convergence on Culture Technology
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• v.8 no.2
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• pp.329-336
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• 2022

Unreadable Khitan scripts of ancient documents written by indian ink on parchment(sheepskin) are visualized by active infrared thermography without contacting and damaging the document which are deteriorated and aged presumably over many years. Sinusoidal infrared thermal wave using Halogen lamp is applied to the surface of the document in order to selectively magnify and record the thermal response of indian ink. The infrared image of the document captured in real time by infrared camera under the active external excitation shows the better sharpness and readability of Khitan characters than the optical image, from which many Khitan letters like ' ' and ' ' sounding as 'd' and 'ri' in English alphabet are detected and deciphered. It is concluded from the experiment that the active infrared thermography can be used as a promising method for digital reconstruction and preservation of ancient documents in the future.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.3
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• pp.127-133
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• 2013

As an essential part of current industrial society, electric power energy is contantaly increasing in pace with the development of science and technology. In order to meet the demand of electric power, power facilities which take care of the higher voltage and bigger capacity is required. To produce and supply electric power on a sound basis the electric facilities should operate with reliability. To prevent disasters in advance, the high quality facilities should be manufactured, and a constant management should be done. When the power facilities cause accidents, the result is huge national deficits. Since the power facilities play a pivotal role in the key industry of national infrastructures of they should operate for a long time in maintaining a stable state, and the accidents can be prevented in advance. The lifetime of a power cable is considered to be 30 years at the time of manufacture, but in real fields, accidents of cable occur 8-12 years from the start of operation, resulting in a heavy loss of properties. In this paper, we will show that we have found out the cause and process of the deterioration of 22kV cable systems in operation. The result is that the process of deterioration does not follow the Weibull distribution only ; but rather, after the heat deterioration the Weibull distributed deterioration comes, then the cable is destroyed due to the partial discharge resulting from the Weibull distributed deterioration.

• Journal of the Korean Wood Science and Technology
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• v.44 no.5
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• pp.785-808
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• 2016

The objective of this study was to investigate the effect of the short-term weathering on the flame retardant performance of wood coated with Dancheong. Flame retardants were applied on the Dancheong coated Korean red pine. Flame retardants applied panels were layed at the two conditions of outdoor exposure and artificial aging to assess the reliability of artificial aging. Flame retardants used were commercial products developed for historical wooden buildings. Scanning electron micrographs revealed the forming of carbonized membrane by melting of flame retardant on wood surface. These carbonized membranes may help delay the further combustion of wood. Flame retardant performance was assessed by measuring heat release rate (HRR) and total heat release (THR) by cone calorimetry. There was no difference in flame retardant performance between before and after 6-month outdoor exposure tests. And also no difference in flame retardant performance between before and after 2-week artificial aging which corresponds to 6-month outdoor exposure. Both tests showed the similar results of combustion characteristics.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.3
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• pp.267-274
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• 2002

This research is described on the applicability of a electrochemical techniques for evaluating nondestructive material degradation with various polarization characteristics for Cr-Mo-V steel. The applied electrochemical technique is anodic polarization test which are widely used to evaluate the corrosion rate and/or sensitization at depleted zone of strengthening elements mainly caused by thermal experience for stainless steels. The evaluation of material degradation is performed by small punch test which has been well known as micromechanics test method using specimen size of $10{\times}10{\times}0.5mm$. The 1,000hrs aged material at $630^{\circ}C$ shows the highest material degradation$({\Delta}[DBTT]_{SP})$, but the 2,000hrs and 3,000hrs aged materials show the decrease of ${\Delta}[DBTT]_{SP}$ as aging time increases. It is observed that the difference of current density $({\Delta}I_{FP}\;and\;{\Delta}I_{SP})$.

• Journal of Korean Society for Geospatial Information Science
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• v.21 no.1
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• pp.27-37
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• 2013

A roof surface temperature monitoring, utilizing remotely sensed thermal infrared image has been specifically proposed to explore evidential data for heating load in winter by cool roof. The remotely sensed thermal infrared image made it possible to identify area-wide patterns of changing trends of surface temperature according to rooftop color (white, black, blue, green) which cannot be acquired by traditional field sampling. The temperature difference of cool roof having a higher solar reflectance were ranged from $3^{\circ}C$ up to $9^{\circ}C$, compared to the general roofs. It is confirmed that there is a significant potential to the energy saving by introducing the cool roof in a Korean climate since up to $18.46^{\circ}C$ difference in cool roof, compared to the general roofs in summer were already identified in Seoul, South Korea. It is anticipated that this research output could be used as a valuable reference in identifying heating load in winter by cool roof since an objective monitoring has been proposed based on the area-wide measured, fully quantitative performance of remotely sensed thermal infrared image.