• Magazine of the Korea Concrete Institute
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• v.9 no.3
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• pp.137-147
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• 1997

Interface shear strength of' concrete under static loading and deterioratiion of interface strength by fatigue loading in shear were experimentally investigated using composite beam test specimens. Thirteen beams were constructed. Five composite beams were tested statically until interface delaminations were observed in the static tests. Seven composite beam and one monolithically cast beam were subjected to two to three million cycles of fatigue load. Test variables were interface roughness, interface shear reinforcement, and presence of interface bond. The average interface shear strength of the composite beams with bonded-rough interface was 6, 060 kPa. No interface delamination was observed after cycling for the composite beams with bonded - rough interface and interface bond was not influenced by repeated application of the shear stress of 2.000 kPa(about 1/3 of the static interface shear strength). Smooth interface and unbonded-rough interface with shear reinforcement deteriorated under repeated shear loading.

• 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 Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.160-168
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• 2003

In Korea, a large portion of aerial power-transmission cables is installed in the mountains. In the case of a fire in the mountains, steel wires coated with zinc and aluminum wires of those power cables exposed to the fire or near around will be deteriorated by the blaze and the high temperature. Deterioration proceeds by interactions of a variety of factors like quality, manufacturing process, the condition of installation and exposure environment of a wire, and so on. Generally, the characteristic of a conductor affect by a forest fire can not be analyzed without the effect through simulating a forest fire. However, there are little research accomplishments of that kind of simulation about it, and there's been no analysis of a sample exposed to an actual forest fire. This thesis shows the experimental results that apply to a new wire by an artificial flame-maker because it's difficult to directly analyze the characteristic of deterioration by a forest fire. Those results include the intensity of extension and wrench for a conductor. In addition, there's been an experiment and analysis about the mechanical characteristics of the wire of ACSR 480[$\textrm{mm}^2$] which was removed from Pohang area by a forest fire. Then, the database will be made to predict the state of deteriorated wires by a forest fire using those two data, and data necessary to diagnose the life state of an ACSR wire affected by a forest fire will be given.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.6
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• pp.85-92
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• 2000

This paper has developed the system that can monitor the distribution transformers(pole and pad) using simplified deterioration detecting sensor in oil and wireless data communication. This system is made up by deterioration detecting sensor, oil level measuring system, deterioration measuring system and communication unit. To prove the usefulness of the system, the paper compared and analyzed the system with the existed system, and after studying the correlation of the both, the result proved goodness of the new system. The proposed monitoring system, when it is used on the pole and pad transformer, would make the reliable diagnoses possible with less rate.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.1
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• pp.10-14
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• 2009

Heat generation mechanism of ultrasound infrared thermography is still not well understood, yet and there are two reliable assumptions of heat generation, friction and thermo-mechanical effect. This paper investigates the principal cause of heat generation at fatigue crack with experimental and numerical approach. Our results show most of heat generation is contributed by friction between crack interface and thermo-mechanical effect is a negligible quantity.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.569-569
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• 2012

탄소나노튜브(carbon nanotubes)의 우수한 전기적, 물리적 특성으로 인해 트랜지스터, 태양전지, 고감도 센서, 나노 섬유, 고분자-탄소나노튜브 고기능 복합체 등 다양한 분야에서 이를 응용하려는 노력이 활발히 진행되고 있다. 흥미롭게도 탄소나노튜브는 구조적인 특성 (직경, 밀도, 벽의 수)에 따라 각기 다른 비표면적, 열 전도성, 전기 전도성, 접촉각, 전계방출 특성을 지닌다고 보고되고 있다. 따라서 다양한 분야의 응용을 위해서는 구조적인 특성 제어가 핵심적인 요소라고 할 수 있다. 본 연구에서는 열화학기상증착법(thermal chemical vapor deposition)을 이용하여 수직 정렬된 탄소나노튜브를 합성 하였다. 합성과정에서 압력의 변화가 탄소나노튜브의 밀도와 길이에 큰 영향을 미친다는 것을 확인하였고, 이러한 현상을 이해하기 위해 두 가지의 가능성을 고려하였다. 첫째는 압력의 변화에 따른 촉매의 형성 변화 가능성이며, 둘째는 탄화수소가스의 유입양의 변화에 따른 영향이다. 분석 결과, 동일한 압력에서 탄화수소가스의 부분압을 변화시켜 실험한 결과로부터 탄화수소의 유입양의 변화가 합성된 탄소나노튜브의 밀도에 큰 영향을 미치고 밀도가 높은 경우 길이가 긴 탄소나노튜브가 합성되는 것을 확인할 수 있었다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.6
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• pp.152-158
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• 2007

Chloride attach is one of the main factors which cause the deterioration of structures. In the case highway bridges, de-ice salts very significantly increase the surface scaling due to frost action. The deteriorated concrete is subject to experience degrading of durability under chloride attach environment. In this study, diagnosis report of 147 bridges is investigated and core sample of 21 bridge decks is examined and analyzed. The results show that the cover of decks concrete is required more than 8cm for retaining bridge lifetime over 30 years.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.849-852
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• 2008

In the wheel tracking test to evaluate abrasion resistance for concrete surface coating materials applied parking lot, weight of the wheel, test temperature, scattered sand amount, wheel speed, etc. various test condition is used for reliable evaluating the abrasion resistance performance of surface coating materials and the results depends on the test condition. In this paper, we carried experimental study as following on abrasion resistance with 2kinds of different environmental conditions. - Commons : real car tire with 300kg of load, 5km/h of speed, 80,000 cycle. - Control A : no other deterioration condition - Control B : scattering 1.0g of sand per every 30rounds from 1m height.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.6
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• pp.136-144
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• 2004

Dissolved gas in oil analysis has been used for fault diagnosis of oil immersed insulation. In this paper to improve the reliability in deciding the degradation causes of the oil immersed insulation, we carried out electrical and thermal degradations for the insulations, and analyzed the characteristics of dissolved gases distribution on each situation. As a result more reliable faults discrimination is possible if we use the interrelation of factors like key gases and gas compositions of hydrocarbon gases and ratios of CO/$CO_2$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.2
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• pp.102-105
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• 2009

The accelerated life time test of the MLCCs with different $BaTiO_3$ particle sizes were conducted at $150^{\circ}C$, 75 V condition and the effect of $BaTiO_3$ particle size on the breakdown voltage and degradation characteristics of MLCCs was investigated. The MLCCs were prepared by using the $BaTiO_3$ particles having the size of $0.525{\mu}m$, $0.555{\mu}m$, $0.580{\mu}m$ and Ni-electrode, respectively. The MLCCs which have the particle size of $0.525{\mu}m$, $0.555{\mu}m$, and $0.580{\mu}m$, respectively were confirmed to meet the standard requirements of X5R(change capacitance within ${\pm}15%$ at $-55{\sim}85^{\circ}C$) by TCC(Temperature Coefficient of Capacitance). The effect of the $BaTiO_3$ particle size on the insulation resistance behavior of MLCCs was confirmed by BDV(Breakdown Voltage) measurements and the cause and degree of degradation of MLCCs were characterized by XPS analysis after the accelerated life test. The MLCCs with $0.525{\mu}m-BaTiO_3$ showed better insulation resistance and BDV characteristics compare to other MLCCs and XPS analysis revealed that the MLCCs degradation is caused by the NiO peak and $BaTiO_3$ peak decrease.