• The Journal of Engineering Geology
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• v.24 no.1
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• pp.123-135
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• 2014

Earthquakes can cause serious loss of life and significant property damage. Thus, the study of active faults is important in evaluating future fault activity and hazards caused by future earthquake events. Structural mapping and the tracing of active faults are the primary steps in studies of active faults. Until now, active faults in South Korea have been mapped using aerial photography, satellite images, and low-quality DEMs. Lineament analysis as a means of identifying active faults is relatively difficult in Korea due to geological characteristics (weak tectonic activity) and dense vegetation cover. In this paper, we introduce the basic concept of the LiDAR technique (a new prospective remote sensing method) and a data analysis method that can overcome these problems. This paper will contribute to a better understanding of the airborne LiDAR technique and its application to South Korea. Some preliminary results from Korean and USA LiDAR data show the usefulness of this technique for tracing lineaments, active faults, and terraces in South Korea.

• International Journal of Control, Automation, and Systems
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• v.6 no.3
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• pp.339-350
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• 2008

A general active fault-tolerant control framework is proposed for nonlinear systems with sensor faults. According to their identifiability, all sensor faults are divided into two classes: identifiable faults and non-identifiable faults. In the healthy case, the control objective is such that all outputs converge to their given set-points. A fault detection and isolation module is firstly built, which can produce an alarm when there is a fault in the system and also tell us which sensor has a fault. If the fault is identifiable, the control objective remains the same as in the healthy case; while if the fault is non-identifiable, the control objective degenerates to be such that only the healthy outputs converge to the set-points. A numerical example is given to illustrate the effectiveness and feasibility of the proposed method and encouraging results have been obtained.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.6
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• pp.321-329
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• 2002

A protection scheme for series active compensator is presented and analyzed in this paper. The proposed series active compensator operated as a high impedance K($\Omega$) to the fundamentals when short-circuit faults occur in the power distribution system, and two control strategies are proposed in this paper The first is the method by detecting the fundamental source current through the p-q theory, the second is the method by detecting the fundamental component of load current in Synchronous Reference Frame(SRF). When the short-circuit faults occur in the power distribution system, the proposed scheme can protect the series active compensator without additional protection circuits. The validity of the Proposed Protection scheme was investigated through experimental results.

• Nuclear Engineering and Technology
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• v.43 no.5
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• pp.437-446
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• 2011

Siting criteria for nuclear power plants require that faults be characterized as to their potential for generating earthquakes, or that the absence of the potential for these occurrences be demonstrated. Because the definition of active faults in Korea has been applied by the deterministic method, which depends on the numerical age of fault movement, the possibility of inherent uncertainties exists in determining the maximum earthquake from the fault sources for seismic design. In an attempt to overcome these problems this study suggests new criteria and a probabilistic quantitative diagnostic procedure that could estimate whether a fault is capable of generating earthquakes in the near future.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.886-889
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• 2017

An active Fault Tolerant Model Predictive Control (FTMPC) using Fuzzy scheduler is developed. Fault tolerant Control (FTC) system stages are broadly classified into two namely Fault Detection and Isolation (FDI) and fault accommodation. Basically, the faults are identified by means of state estimation techniques. Then using the decision based approach it is isolated. This is usually performed using soft computing techniques. Fuzzy Decision Making (FDM) system classifies the faults. After identification and classification of the faults, the model is selected by using the information obtained from FDI. Then this model is fed into FTC in the form of MPC scheme by Takagi-Sugeno Fuzzy scheduler. The Fault tolerance is performed by switching the appropriate model for each identified faults. Thus by incorporating the fuzzy scheduled based FTC it becomes more efficient. The system will be thereafter able to detect the faults, isolate it and also able to accommodate the faults in the sensors and actuators of the Continuous Stirred Tank Reactor (CSTR) process while the conventional MPC does not have the ability to perform it.

• Journal of The Geomorphological Association of Korea
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• v.25 no.3
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• pp.89-103
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• 2018

This study presents results of analysis on fault-related landforms and the Quaternary fluvial landforms, which are important evidences for active faulting by identifying surface deformation, around the Ulsan Fault Zone. In addition, this study suggests lineament map and inferred active fault-line map based on analyzing linearity and continuity of these landforms and by compiling location information of existing active faults. We convince that quantitative tectonic-geomorphological analysis are an effective method for active faults tracking, in particular, considering the conditions of relatively low seismicity and surface ruptured-events in the Korean Peninsula compared to plate boundary active areas. However, research on active fault in South Korea is just an infant stage since the 1990s and requires accumulation of research achievements on development and application of various fault analysis techniques, analysing and standardizing linear structures.

• Journal of The Geomorphological Association of Korea
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• v.26 no.4
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• pp.107-121
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• 2019

This study documents the distribution of (active) faults around the southern part of the Yangsan Fault and the Moryang Fault and the middle part of the Dongrae Fault. For this objective, we extracted lineaments and fault-related landforms by analyzing aerial photos and digital elevation models and with the result of fieldwork on fault-relating features of the Quaternary landforms. Geomorphological techniques for active fault study are not only preliminary but also essential methods because, in general, an active fault can be defined only with fault-deformed Quaternary sediments when there is no way to detect precise timing of faulting. Therefore, geomorphological interpretation in active fault research is necessary to determine the extent, direction, termination and timing of fault. This study addresses the results of such geomorphological analysis and geomorphic markers for tracing the active faults in the study area. It is plan to investigate with geophysical and geological techniques the sites referred in this study.

• Nuclear Engineering and Technology
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• v.54 no.9
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• pp.3283-3292
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• 2022

Based on the Deep Q-Network(DQN) algorithm of reinforcement learning, an active fault-tolerance method with incremental action is proposed for the control system with sensor faults of the once-through steam generator(OTSG). In this paper, we first establish the OTSG model as the interaction environment for the agent of reinforcement learning. The reinforcement learning agent chooses an action according to the system state obtained by the pressure sensor, the incremental action can gradually approach the optimal strategy for the current fault, and then the agent updates the network by different rewards obtained in the interaction process. In this way, we can transform the active fault tolerant control process of the OTSG to the reinforcement learning agent's decision-making process. The comparison experiments compared with the traditional reinforcement learning algorithm(RL) with fixed strategies show that the active fault-tolerant controller designed in this paper can accurately and rapidly control under sensor faults so that the pressure of the OTSG can be stabilized near the set-point value, and the OTSG can run normally and stably.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.6
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• pp.115-122
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• 2010

The main purpose of centralized monitoring system is to manage factory electrical installation efficiently by on-line data acquisition and supervisory control. The existing centralized system is only able to be managed by operator whenever electrical installation's faults are detected. Therefore, it may be possible for propagating the installation's faults when operator make the unexpected mistakes. To overcome the unexpected mistakes, in this paper, the author presents a centralized monitoring system for factory electrical installation using active database. by using active database production rule, stated system can minimize unexpected mistake and can operate centralized monitoring system efficiently. Test results on the five factory electrical installations show that performance is efficient and robust.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1567-1576
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• 2018

The reliability of grid-connected inverters can be improved by algorithms capable of diagnosing faults in LCL filters. A fault diagnostic method during inverter startup is proposed. The proposed method can accurately generate and monitor information on the peak value and the location of the peak frequency component of the step response of a damped LCL filter. To identify faults, the proposed method compares the evaluated response with the response of a healthy higher-order damped LCL filter. The frequency components in the filter voltage response are first analytically obtained in closed form, which yields the expected trends for the filter faults. In the converter controller, the frequency components in the filter voltage response are computed using an appropriately designed fast Fourier transform and compared with healthy LCL response parameters using a finite state machine, which is used to sequence the proposed startup diagnostics. The performance of the proposed method is validated by comparing analytical results with the simulation and experimental results for a three-phase grid-connected inverter with a damped LCL filter.