• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.4
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• pp.181-189
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• 2003

Because of the gravitation of population toward large cities, a number of masonry buildings have been constructed since 1960. They have been rapidly deteriorated as time passed by. Therefore the purpose of this paper is to present basic data on timeworn masonry buildings which have been managed by metropolitan government and to analyse their deterioration factors. And then, the results of this paper can be used to establish the policy of managing timeworn masonry buildings. According to this study, the crack of masonry wall is the most effective deterioration factor and timeworn masonry buildings have a problem with foundation. The structure grade have an interrelation with occupancy type more than building age. Also, the longer building age becomes, the sooner deterioration speeds. A timeworn masonry building is in urgent need of reinforcement on a thirty-year period of building age.

• Elastomers and Composites
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• v.43 no.1
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• pp.8-17
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• 2008

Styrene-butadiene rubber(SBR) has good abrasion resistance, miscibility, and anti-vibration property. however, it is easily damaged by ozone and swelled by hydrocarbon fluids because of unsaturation part in main chain, that causes loss of visco-elasticity and reduction of product's life cycle. Therefore, object of this study is to cope with this problem. SBR is blended with various proportion of ethylene-propylene-diene terpolymer(EPDM), which has excellent ozone and oxygen resistance, to improve physical properties and ozone resistance, and diverse analytical techniques are used to measure morphology, glass transition temperature$(T_g)$, ozone-resistance, degradation temperature, static spring constant, hardness for considering a suitability for anti-vibration industrial product. We found that the blend consisting of SBR 70% and EPDM 30% showed no crack after ozone test and good miscibility between SBR and EPDM from this study.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.1
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• pp.146-151
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• 2021

Currently, the demand for vehicles from one family is increasing in many countries at home and abroad, reducing the number of people on the vehicle and increasing the number of vehicles on the road. The multi-passenger lane system, which is available to solve the problem of traffic congestion, is being implemented. The system allows police to monitor fast-moving vehicles with their own eyes to crack down on illegal vehicles, which is less accurate and accompanied by the risk of accidents. To address these problems, applying deep learning object recognition techniques using images from road sites will solve the aforementioned problems. Therefore, in this paper, we compare and analyze the performance of existing deep learning models, select a deep learning model that can identify real-time vehicle occupants through video, and propose a vehicle occupancy detection algorithm that complements the object-ident model's problems.

• International Journal of Computer Science & Network Security
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• v.22 no.2
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• pp.123-130
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• 2022

During the past decades, detection of gear defects remains as a major problem, especially when the gears are subject to non-stationary phenomena. The idea of this paper is to mixture a multilevel wavelet transform with a fast EMD decomposition in order to early detect gear defects. The sensitivity of a kurtosis is used as an indicator of gears defect burn. When the gear is damaged, the appearance of a crack on the gear tooth disrupts the signal. This is due to the presence of periodic pulses. Nevertheless, the existence of background noise induced by the random excitation can have an impact on the values of these temporal indicators. The denoising of these signals by multilevel wavelet transform improves the sensitivity of these indicators and increases the reliability of the investigation. Finally, a defect diagnosis result can be obtained after the fast transformation of the EMD. The proposed approach consists in applying a multi-resolution wavelet analysis with variable decomposition levels related to the severity of gear faults, then a fast EMD is used to early detect faults. The proposed mixed methods are evaluated on vibratory signals from the test bench, CETIM. The obtained results have shown the occurrence of a teeth defect on gear on the 5th and 8th day. This result agrees with the report of the appraisal made on this gear system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.120-122
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• 2021

Currently, as demand for cars at home and abroad increases, the number of vehicles is decreasing and the number of vehicles is increasing. This is the main cause of the traffic jam. To solve this problem, it operates a high-ocompancy vehicle (HOV) lane, a multi-passenger vehicle, but many people ignore the conditions of use and use it illegally. Since the police visually judge and crack down on such illegal activities, the accuracy of the crackdown is low and inefficient. In this paper, we propose a system design that enables more efficient detection using imaging techniques using computer vision to solve such problems. By improving the existing vehicle detection method that was studied, the trigger was set in the image so that the detection object can be selected and the image analysis can be conducted intensively on the target. Using the YOLO model, a deep learning object recognition model, we propose a method to utilize the shift amount of the center point rather than judging by the bounding box in the image to obtain real-time object detection and accurate signals.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.125-126
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• 2021

In order to improve the housing culture, construction changes for the utilization of diverse and multifunctional spaces are appearing in response to the increasing diverse needs of consumers. Cellular Light-weight Concrete (CLC) is being developed for use in fire-resistant heat-insulating walls and non-bearing walls. However, manufacturing non-uniformity has become a problem as a drawback due to the use of foamed bubbles and normal temperature curing, and additional research is required. Therefore, in order to suppress cracks due to drying shrinkage, silica sand is mixed with CLC to try to understand its characteristics. In the experiment, the compressive strength from 7 to 28 days of age was measured via a constant temperature and humidity chamber, and the drying shrinkage was analyzed according to each condition using a strain gauge. The compressive strength of matrix tends to decrease as the substitution rate of silica sand increases. This is judged by the result derived from the fact that the specific surface area of silica sand is smaller than that of slag. Based on KS F 2701 (ALC block), the compressive strength of 0.6 products is 4.9 MPa or more as a guide, so the maximum replacement rate of silica sand that satisfies this can be seen at 60%. Looking at the change in drying shrinkage for just 7 days, the shrinkage due to temperature change and drying is 0.7 mm, and the possibility of cracking due to shrinkage can be seen, and it seems that continuous improvement and supplementation are needed in the future.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.4
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• pp.39-46
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• 2017

This paper presents the fabrication of ceramic insulation layer on metallic heat spreading substrate, i.e. an insulated metal substrate, for planar type heater. Aluminum alloy substrate is preferred as a heat spreading panel due to its high thermal conductivity, machinability and the light weight for the planar type heater which is used at the thermal treatment process of semiconductor device and display component manufacturing. An insulating layer made of ceramic dielectric film that is stable at high temperature has to be coated on the metallic substrate to form a heating element circuit. Two technical issues are raised at the forming of ceramic insulation layer on the metallic substrate; one is delamination and crack between metal and ceramic interface due to their large differences in thermal expansion coefficient, and the other is electrical breakdown due to intrinsic weakness in dielectric or structural defects. In this work, to overcome those problem, selected metal oxide buffer layers were introduced between metal and ceramic layer for mechanical matching, enhancing the adhesion strength, and multi-coating method was applied to improve the film quality and the dielectric breakdown property.

• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.763-771
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• 2007

Over the last few decades, many researches have been conducted in order to find solution to the problem of corrosion in steel reinforced concrete. As a result, methods such as the use of stainless steel bars, epoxy coatings, and concrete additives, etc., have been tried. While effective in some situations, such remedies may still be unable to completely eliminate the problems of steel corrosion. Fiber reinforced polymer (FRP) elements are appealing as reinforcement due to some material properties such as high tensile strength, low density, and noncorrosive. However, due to the generally lower modulus of elasticity of FRP in comparison with the steel and the linear behavior of FRP, certain aspects of the structural behavior of RC members reinforced with FRP may be substantially different from similar elements reinforced with steel reinforcement. This paper presents the flexural behavior of one-way concrete slabs reinforced with FRP bars. They were simply supported and tested in the laboratory under static loading conditions to investigate their crack pattern and width, deflections, strains and mode of failure. The experimental results shows that behavior of the FRP reinforced slabs was bilinearly elastic until failure. Also, the results show that the FRP overreinforced concrete beams in this study can be safe for design in terms of deformability.

• Journal of Conservation Science
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• v.26 no.3
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• pp.277-294
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• 2010

The Seosanmaaesamjonbulsang (National Treasure No. 84) consists of light gray and coarse to mediumgrained biotite granite with partly developed pegmatite and quartz vein. The host rock is divided into dozens of rock blocks with various shape along irregular discontinuity plane. The evaluation results of discontinuity systems reveal that the host rock were exposed to instable sloping environments. Results of deterioration diagnosis show that the degree of damage has been made worse by physical weathering and surface discoloration laying stress on part that vertical and horizontal joints are massed. Generally, deterioration rate of the triad Buddha surface cover with 42.7%, however, the rate of physical weathering and surface discoloration are subdivided to 9.6% and 33.1%, respectively. Ultrasonic measurements indicate that the triad Buddha was reached highly weathered grade in general. And the rock material was weaken to show low velocity zone of 1,000m/s along irregular joint systems. Indoor and outdoor mean relative humidity of the shelter was recorded more than 70% during every season, and high frequency appears in high relative humidity range over 95%. Such environments seem to have produced dew condensation on the rock surface with rainfall and supply water, promoted physical, chemical and biological weathering along crack and joint, resulting in high permeation of water and percentage of water content. Therefore, it is judged that for scientific conservation of the triad Buddha it needs environment control through persistent preservation environment monitoring including water problem.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.4
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• pp.323-330
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• 2019

The 500 MW Korean standard coal-fired power plant is the largest standardized power plant in Korea and has played a pivotal role in domestic power generation for over 20 years. In addition to the aging degradation due to long term operation, the probability of failure of power generation facilities is increasing due to frequent startup and stop caused by the lower utilization rate due to air pollution problem caused by coal-fired power plants. Among them, steam piping plays an important role in transferring high-temperature & pressure steam produced in a boiler to turbine for power generation. In recent years, failure of steam piping of large coal-fired power plant has frequently occurred. Therefore, in this study, failure analysis of high pressure piping weld was conducted. We identify the damage caused by high stress due to abnormal supporting structure of the piping and suggest improved supporting structure to eliminate high stress through microstructure analysis and piping stress analysis to prevent the occurrence of the similar failure of other power plant in the case of repetitive damage to the main steam piping system of the 500 MW Korean standard coal-fired power plant.