• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.11
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• pp.2471-2477
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• 2010

lately, vehicle blackbox increasing importance and usability Is needed accuracy and variety of information. because, blackbox help to analyze the exact cause of the accident and use as objective evidence in vehicle-related crime. In the paper, to overcome the limitations of the existing black box, use various sensors and vehicle information blackbox store current state of the vehicle with OBD-II protocol using vehicle state information and store exact current location and direction information of the vehicle with Gyro sensor and GPS and use global time of GPS for synchronization of information. In addition, blackbox back the information up with wifi. because, when blackbox damaged, dirvers were able to verify the information.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.76-79
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• 2010

lately, vehicle blackbox increasing importance and usability Is needed accuracy and variety of information. because, blackbox help to analyze the exact cause of the accident and use as objective evidence in vehicle-related crime. In the paper, to overcome the limitations of the existing black box, use various sensors and vehicle information blackbox store current state of the vehicle with OBD-II protocol using vehicle state information and store exact current location and direction information of the vehicle with Gyro sensor and GPS and use global time of GPS for synchronization of information. In addition, blackbox back the information up with wifi. because, when blackbox damaged, dirvers were able to verify the information.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.1
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• pp.135-146
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• 2019

In this paper, the preventive maintenance strategy in operation stage of a bridge using Bayesian inference is proposed. The proposed technique can be used to predict the variation in the performance (or condition) of the bridge with higher accuracy, considering the uncertainty of monitoring. The applicability of the proposed method to the existing bridges is verified and analyzed that have an advantage in terms of maintenance cost efficiency compared to the conventional periodic maintenance system, which establishes maintenance after damage. It is expected that the proposed preventive maintenance method can be used to overcome the limitation of the conventional periodic maintenance method and to make practical bridge maintenance decision.

• Composites Research
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• v.33 no.6
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• pp.415-420
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• 2020

The interfacial properties in carbon fiber composites, which control the overall mechanical properties of the composites, are very important. Effective interface enhancement work is conducted on the modification of the carbon fiber surface with carbon nanotubes (CNTs). Nonetheless, most surface modifications methods do have their own drawbacks such as high temperatures with a range of 600~1000℃, which should be implemented for CNT growth on carbon fibers that can cause carbon fiber damages affecting deterioration of composites properties. This study includes the use of in-situ interfacial polymerization of polyamide 610/CNT to fabricate the carbon fiber composites. The process is very fast and continuous and can disperse CNTs with random orientation in the interface resulting in enhanced interfacial properties. Scanning electron microscopy was conducted to investigate the CNT dispersion and composites morphology, and the thermal stability of the composites was analyzed via thermogravimetric analysis. In addition, fiber pull-out tests were used to assess interfacial strength between fiber and matrix.

• Korean Journal of Construction Engineering and Management
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• v.25 no.2
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• pp.36-44
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• 2024

This paper presents the application of Convolutional Neural Networks (CNNs) and Region of Interest (ROI) techniques for concrete crack analysis. Surfaces of concrete structures, such as beams, etc., are exposed to fatigue stress and cyclic loads, typically resulting in the initiation of cracks at a microscopic level on the structure's surface. Early detection enables preventative measures to mitigate potential damage and failures. Conventional manual inspections often yield subpar results, especially for large-scale infrastructure where access is challenging and detecting cracks can be difficult. This paper presents data collection, edge segmentation and ROI techniques application, and analysis of concrete cracks using Convolutional Neural Networks. This paper aims to achieve the following objectives: Firstly, achieving improved accuracy in crack detection using image-based technology compared to traditional manual inspection methods. Secondly, developing an algorithm that utilizes enhanced Sobel edge segmentation and ROI techniques. The algorithm provides automated crack detection capabilities for non-destructive testing.

• Journal of Korean Society of Steel Construction
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• v.20 no.6
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• pp.723-730
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• 2008

Due to the higher ratio of live load to total loads of railway bridges, the accumulated damage by cyclic fatigue is significant. Moreover, it is highly possible that the initiated crack grows faster than that of highway bridges. Therefore, it is strongly needed to assess the safety for the accumulated damage analytically. The initiation and growth of fatigue-crack are related with the stress range, number of cycles, and the stiffness of the structural system. The stiffness of the structural system includes uncertainties of the planning, design, construction and maintenance, which varies as time goes. In this study, the authors developed the design and risk assessment techniques based on the reliability theories considering the uncertainties in load and resistance. For the probabilistic risk assessment of crack growth and the remaining life of the structures by the cyclic load of railway and subway bridges, response surface method (RSM) combined with first order second moment method were used. For composing limit state function, the stress range, stress intensity factor and the remaining life were selected as input important random variables to the RSM program. The probabilities of failure and the reliability indices of fatigue life for the considered specimen under cyclic loads were evaluated and discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.718-725
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• 2017

A liquid storage tank is one of the most important structures in industrial complexes dealing with chemicals, and its structural damage due to an earthquake may cause a disastrous event such as the leakage of hazardous materials, fire, and explosion. It is thus essential to assess the seismic fragility of liquid storage tanks and prepare for seismic events in advance. When a liquid storage tank is oscillated by a seismic load, the hydrodynamic pressure caused by the liquid-structure interaction increases the stress and causes structural damage to the tank. Meanwhile, the seismic fragility of the structure can be estimated by considering the various sources of uncertainty and calculating the failure probabilities in a given limiting state. To accurately evaluate the seismic fragility of liquid storage tanks, a sophisticated finite element analysis is required during their reliability analysis. Therefore, in this study, FERUM-ABAQUS, a recently-developed computational platform integrated with commercial finite element and reliability analysis software packages, is introduced to perform the finite element reliability analysis and calculate the failure probability of a liquid storage tank subjected to a seismic load. FERUM-ABAUS allows for automatic data exchange between these two software packages and for the efficient seismic fragility assessment of a structure. Using this computational platform, the seismic fragility curve of a liquid storage tank is successfully obtained.

• Clinical and Experimental Pediatrics
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• v.52 no.1
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• pp.44-49
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• 2009

Purpose : Early surfactant treatment and minimal ventilation, bronchopulmonary dysplasia needed prolonged oxygen supplement is a problem. This study aimed to report the effects of early surfactant treatment and minimal ventilation on the prevention of bronchopulmonary dysplasia in respiratory distress syndrome. Methods : We retrospectively studied 139 premature newborn infants (gestational age, 36 weeks; birth weight, 1,500 gm) admitted to the neonatal intensive care unit of Daegu Fatima Hospital between January 2001 and December 2006. We analyzed the occurrence of bronchopulmonary dysplasia with respect to ventilator care and surfactant treatment. Results : The incidence of bronchopulmonary dysplasia was significantly higher with prolonged ventilator care, moderate to severe respiratory distress syndrome, and low Apgar score (P<0.001). Despite early surfactant treatment and minimal ventilation, mild bronchopulmonary dysplasia occurs in a considerable number of patients with mild respiratory distress syndrome. The patient group with low Apgar scores required ventilator care for a prolonged period (P=0.020). Conclusion : Early surfactant treatment and minimal ventilation shortens the duration of ventilator care; however, the preventive effects on bronchopulmonary dysplasia are limited. Therefore, not only early surfactant treatment and minimal ventilation but also appropriate management in the delivery room is essential.

• Journal of the Korean Geosynthetics Society
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• v.22 no.4
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• pp.17-26
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• 2023

To consider the risk of damage and fracture of P.C strands, the existing post-maintenance system alone has the limitations, hence it is necessary to quantitatively evaluate and predict the deterioration, durability and safety of facilities and establish a reasonable maintenance system considering the asset value of facilities. Therefore, it is worth considering a preventive maintenance plan that allows proactive measures to be taken before a major defect occurs in the temporary anchor. This study devised a preventive over tension method, reviewed its effectiveness through design and field tests, by calculating the resistance factors by performing a reliability-based optimization design. At this time, the over tension anchor method was evaluated using the ratio of the residual tension force after the fracture of P.C strands to the effective tension force before the fracture of P.C strand, followed by the resistance factor calculated by the optimal solution for each random variables using Excel solver and applying it to the limit state equations. As a result of the study, if the over tension ratio is 125% to 130%, the remaining strands showed a high resistance effect even after the fracture of P.C strand. As a result of the optimization design, it was found that it is appropriate to apply the load factor (γ) of 1.25, and the resistance factors of Φ₁, Φ₂, Φ₃ as 0.7, 0.5, 0.6.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.3
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• pp.103-110
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• 2016

Recently, structural health monitoring system(SHMS) has been appled cable bridges as the effective maintenance tool and the management threshold is considered to assess the status of the bridge in SHMS. The threshold is generally determined by the allowable limit based on design specification because there is no method and standard for threshold calculation. In case of the conventional thresholds, it is difficult to recognize the event, abnormal behavior and gradual damage within the threshold. Therefore, this study reviewed the problem of previous methods and proposed the advanced methodologies based on probabilistic approach for threshold calculation which can be applied to practice work. Gumbel distribution is adopted in order to calculate the threshold for caution and warning states considering the expectations for return periods of 50 and 100 years. The thresholds were individually determined for measurement data and data variation to detect the various abnormal behaviors within allowable range. Finally, it has confirmed that the thresholds by the proposed method is detectable the abnormal behavior of real-time measuring data from SHMS.