• Journal of Korean Association for Spatial Structures
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• v.18 no.4
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• pp.89-96
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• 2018

The paper presents the damage estimation of bridge structures in Daegu city based on the scenario-based earthquakes. Since the fragility curves for domestic bridge strucures are limited, the Hazus methodology is employed to derive the fragility curves and estimate the damage. A total of four earthuquake scenarios near Daegu city are assumed and structure damage is investigated for 81 bridge structures. The seismic fragility function and damage level of each bridge had adopted from the analytical method in HAZUS and then, the damage probability using seismic fragility function for each bridge was evaluated. It was concluded that the seismic damage to bridges was higher when the magnitude of the earthquake was large or nearer to the epicenter.

• Journal of Korean Society of Disaster and Security
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• v.13 no.4
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• pp.13-24
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• 2020

Abnormal weather conditions have lately been occurring frequently due to the rapid economic development and global warming. Natural disasters classified as storm and flood damages such as heavy rain, typhoon, strong wind, high seas and heavy snow arouse large-scale human and material damages. To minimize damages, it is important to estimate the scale of damage before disasters occur. This study is intended to develop a strong wind damage estimation function to prepare for strong wind damage among various storm and flood disasters. The developed function reflects weather factors and regional characteristics based on the strong wind damage history found in the Natural Disaster Yearbook. When the function is applied to a system that collects real-time weather information, it can estimate the scale of damage in a short time. In addition, this function can be used as the grounds for disaster control policies of the national and local governments to minimize damages from strong wind.

• Nuclear Engineering and Technology
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• v.48 no.5
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• pp.1280-1290
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• 2016

This paper presents an advanced estimation method for obtaining the probability density functions of a damage parameter for valve leakage detection in a reciprocating pump. The estimation method is based on a comparison of model data which are simulated by using a mathematical model, and experimental data which are measured on the inside and outside of the reciprocating pump in operation. The mathematical model, which is simplified and extended on the basis of previous models, describes not only the normal state of the pump, but also its abnormal state caused by valve leakage. The pressure in the cylinder is expressed as a function of the crankshaft angle, and an additional volume flow rate due to the valve leakage is quantified by a damage parameter in the mathematical model. The change in the cylinder pressure profiles due to the suction valve leakage is noticeable in the compression and expansion modes of the pump. The damage parameter value over 300 cycles is calculated in two ways, considering advance or delay in the opening and closing angles of the discharge valves. The probability density functions of the damage parameter are compared for diagnosis and prognosis on the basis of the probabilistic features of valve leakage.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.297-302
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• 2005

In this paper, an estimating damage on external surface of container using Capsize-Gaussian-Function (be called CGF) is presented. The estimation of the damage size can be get directly from two parameters of CGF, these are the depth and the flexure, also the direction of damage. The performance of the present method has been illustrated using an image of damage container, which had been taken from Hanjin Busan Port, after using image processing techniques to do preprocessing of the image, especially, the main used technique is Canny edge detecting that is widely used in computer vision to locate sharp intensity and to find object boundaries in the image, then correlation between the edge image from the preprocessing step and the CGF with three parameters (direction, depth, flexure), as a result, we get an image that perform damage information, and these parameters is an estimator directly to the damage.

• Journal of the Society of Disaster Information
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• v.16 no.2
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• pp.223-236
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• 2020

Purpose: In this study, a strong wind damage prediction function was developed in order to be used as a contingency during disaster management (preventive-preventive-response-recovery). Method: The predicted strong wind damage function proposed in this study took into account the re-enactment boy power, weather data and local characteristics at the time of damage. The meteorological data utilized the wind speed, temperature, and damage history observed by the Korea Meteorological Administration, the disaster year, and the recovery costs, population, vinyl house area, and farm water contained in the disaster report as factors to reflect the regional characteristics. Result: The function developed in this study reflected the predicted weather factors and local characteristics based on the history of strong wind damage in the past, and the extent of damage can be predicted in a short time. Conclusion: Strong wind damage prediction functions developed in this study are believed to be available for effective disaster management, such as decision making by policy-makers, deployment of emergency personnel and disaster prevention resources.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.307-312
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• 2003

The object of this study is to investigate a damage estimation of single edge cracked tensile specimens ($2_a$/W) as a function of acoustic emission (AE) according to the unidirectionally oriented carbon/epoxy composites, CFRP AE signals were analyzed and classified 3 regions by event counts, energy and amplitude for coressponding applied load. On tensile loading and using the results of the AE analysis, it was found that the event counts, cumulative counts or energy, and amplitude distributions useful for the prediction of damage failure.

• Journal of Wetlands Research
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• v.5 no.1
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• pp.41-52
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• 2003

The flood damage reduction studies have been performed by the channel improvement plan and the levee has mainly constructed with the freeboard concept. However, the freeboard concept might be an inappropriate choice as a safety factor of the levee because many uncertainties are involved in the procedure of the channel improvement plan studies. So, we considered the uncertainties In the discharge-probability, stage-discharge, and stage-damage functions and estimate the expected annual damage. The Monte Carlo technique for uncertainty analysis is used. As our results, the expected annual damage with uncertainty shows the larger value than without uncertainty. Since the expected annual damage with uncertainty already considers the safety factor it is the proper result. However, the expected annual damage without uncertainty does not consider the safety factor yet. Thus, if the expected annual damage without uncertainty considers the freeboard concept, it could be compared with the expected annual damage with uncertainty for the evaluation of the overestimation or underestimation of the levee construction.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1995.04a
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• pp.136-143
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• 1995

The problem of the structural identification becomes important, particularly with relation to the rapid increase of the number of the damaged or deteriorated structures, such as highway bridges, buildings, and industrial facilities. This paper summarizes the recent studies related to those problems by the present authors. The system identfication methods are generally classified as the time domain and the frequency domain methods. As time doamin methods, the sequential algorithms such as the extended Kalman filter and the sequential prediction error method are studied. Several techniques for improving the convergences are incorporated. As frequency domain methods, a new frequency response function estimator is introduced. For damage estimation of existing structures, the modal perturbation and the sensitivity matrix methods are studied. From the example analysis, it has been found that the combined utilization of the measurement data for the static response and the dynamic (modal) properties are very effictive for the damage estimation.

• The Journal of the Korea Contents Association
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• v.18 no.1
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• pp.154-163
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• 2018

Not only South Korea but also Global world show that the frequency and damages of large-scale natural disaster due to the rise of heavy rain event and typhoon or hurricane intensity are increasing. Natural disasters such as typhoon, flood, heavy rain, strong wind, wind wave, tidal wave, tide, heavy snow, drought, earthquake, yellow dust and so on, are difficult to estimate the scale of damage and spot. Also, there are many difficulties to take action because natural disasters don't appear precursor phenomena However, if scale of damage can be estimated, damages would be mitigated through the initial damage action. In the present study, therefore, wind wave damage estimation functions for the western coastal zone are developed based on annual disaster reports which were published by the Ministry of Public Safety and Security. The wind wave damage estimation functions were distinguished by regional groups and facilities and NRMSE (Normalized Root Mean Square Error) was analyzed from 1.94% to 26.07%. The damage could be mitigated if scale of damage can be estimated through developed functions and the proper response is taken.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.455-463
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• 2000

In order to develop nondestructive techniques for the quantitative estimation of creep damage a series of crept copper samples were prepared and their ultrasonic velocities were measured. Velocities measured in three directions with respect to the loading axis decreased nonlinearly and their anisotropy increased as a function of creep-induced porosity. A progressive damage model was described to explain the void-velocity relationship, including the anisotropy. The comparison of modeling study showed that the creep voids evolved from sphere toward flat oblate spheroid with its minor axis aligned along the stress direction. This model allowed us to determine the average aspect ratio of voids for a given porosity content. A novel technique, the back propagation neural network (BPNN), was applied for estimating the porosity content due to the creep damage. The measured velocities were used to train the BP classifier, and its accuracy was tested on another set of creep samples containing 0 to 0.7 % void content. When the void aspect ratio was used as input parameter together with the velocity data, the NN algorithm provided much better estimation of void content.