• Smart Structures and Systems
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• v.10 no.4_5
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• pp.471-483
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• 2012

In this paper, the structural health monitoring (SHM) benchmark problem of the Canton tower is studied. Based on the field monitoring data from the 20 accelerometers deployed on the tower, some modal frequencies and mode shapes at measured degrees of freedom of the tower are identified. Then, these identified incomplete modal data are used to update the reduced finite element (FE) model of the tower by a novel algorithm. The proposed algorithm avoids the problem of subjective selection of updated parameters and directly updates model stiffness matrix without model reduction or modal expansion approach. Only the eigenvalues and eigenvectors of the normal finite element models corresponding to the measured modes are needed in the computation procedures. The updated model not only possesses the measured modal frequencies and mode shapes but also preserves the modal frequencies and modes shapes in their normal values for the unobserved modes. Updating results including the natural frequencies and mode shapes are compared with the experimental ones to evaluate the proposed algorithm. Also, dynamic responses estimated from the updated FE model using remote senor locations are compared with the measurement ones to validate the convergence of the updated model.

• Structural Monitoring and Maintenance
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• v.4 no.1
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• pp.33-52
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• 2017

A cantilever beam with a breathing crack is studied to improve the breathing crack identification sensitivity by the parametric optimization of sample entropy and wavelet transformation. Crack breathing is a special bi-linear phenomenon experienced by fatigue cracks which are under dynamic loadings. Entropy is a measure, which can quantify the complexity or irregularity in system dynamics, and hence employed to quantify the bi-linearity/irregularity of the vibration response, which is induced by the breathing phenomenon of a fatigue crack. To improve the sensitivity of entropy measurement for crack identification, wavelet transformation is merged with entropy. The crack identification is studied under different sinusoidal excitation frequencies of the cantilever beam. It is found that, for the excitation frequencies close to the first modal frequency of the beam structure, the method is capable of detecting only 22% of the crack depth percentage ratio with respect to the thickness of the beam. Using parametric optimization of sample entropy and wavelet transformation, this crack identification sensitivity is improved up to 8%. The experimental studies are carried out, and experimental results successfully validate the numerical parametric optimization process.

• Nuclear Engineering and Technology
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• v.53 no.6
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• pp.2038-2045
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• 2021

The main objective of this work is to propose a reliable routine standard operation procedures (SOP) for structural health monitoring and diagnosis of nuclear power plants (NPPs). At present, NPPs have monitoring systems that can be used to obtain the quantitative health record of containment (CTMT) buildings through system identification technology. However, because the measurement signals are often interfered with by noise, the identification results may introduce erroneous conclusions if the measured data is directly adopted. Therefore, this paper recommends the SOP for signal screening and the required identification procedures to identify the dynamic characteristics of the CTMT of NPPs. In the SOP, three recommend methods are proposed including the Recursive Least Squares (RLS), the Observer Kalman Filter Identification/Eigensystem Realization Algorithm (OKID/ERA), and the Frequency Response Function (FRF). The identification results can be verified by comparing the results of different methods. Finally, a preliminary CTMT healthy record can be established based on the limited number of earthquake records. It can be served as the quantitative reference to expedite the restart procedure. If the fundamental frequency of the CTMT drops significantly after the Operating Basis Earthquake and Safe Shutdown Earthquake (OBE/SSE), it means that the restart actions suggested by the regulatory guide should be taken in place immediately.

• Geomechanics and Engineering
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• v.31 no.5
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• pp.489-503
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• 2022

A 1257-m-long irregular deep foundation pit located in the central of Nanjing, China was constructed using the combined full-width and half-width top-down method. Based on the long-term field monitoring data, this study analyzed the evolution characteristics of the vertical movement of the columns, internal force of the struts, and axial force of the structural beam and slab. The relevance of the three mentioned above and their relationship with the excavation process, structural system, and geological conditions were also investigated. The results showed that the column uplift was within the range of 0.08% to 0.22% of the excavation depth, and the embedded depth ratio of the diaphragm wall and the bottom heave affected significantly on the column uplift. The differential settlement between the column and diaphragm wall remained unchanged after the base slab was cast. The final settlement of the diaphragm wall was twice the column uplift. The internal force of the struts did not varied monotonically but was related to numerous factors such as the excavation depth, number of struts, and environmental conditions. Additionally, the dynamic force and deformation of the columns, beams, and slabs were analyzed to investigate the inherent relationship and variation patterns of the responses of different parts of the structure.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.3226-3236
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• 2011

In this paper, with the background features on which measuring the transverse left-right and up -down vibration of wheel, bogie and body by wireless measurement system, performance evaluation systems which can assess the running behavior of high speed trains based on UIC code 518-OR and evaluate the ride comfort of them based on ISO code 2631 and UIC code 513 were developed. The characteristics of dynamic vibration are generally analyzed by an acceleration of a car body of high speed train and the acceleration can be applied to evaluation of running safety. In this paper, also matching system of distance from tachometer and vibration from accelerometer was programmed in development software, and the SD card embedded system which prevent to loss of data in wireless measurement was mounted on this system. Finally the software perform to analysis with filtering and statistical post-process in the unit sections and zones and focus on developing the capability monitoring in the main control center. For the verification of this system, the running behavior and safety factor were analyzed based on field measured data of the Cheonjun-gunnum-sun turn out point in the new KTX railway.

• Journal of the Korea Society of Computer and Information
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• v.21 no.6
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• pp.63-69
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• 2016

In this paper, we proposed the location tracking system based on MS-Based/Assisted(Mobile Station-Based and Assisted) location trigger service model with context-awareness for the intelligent location tracking of moving objects. It provides the proper resulting value that matches the context of users through the analysis about the situation of the user, physical environment, computing resource and the existing information on user input. In order to provide real-time data, we proposed the location tracking system which realizes the intelligent information such as the expecting arrival time and passing the specific area of the moving object by adopting the location trigger. So, it derives to minimize the costs of communication for the mobile object tracking applications. The proposed location tracking system based on context-awareness can be used for realtime monitoring, intelligent alarm/action, setting up of the optimized moving path, dynamic adjustment of strategies and policies. So it has the advantage to develop the application system which is aimed at optimization of the object tracking and movement.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2705-2707
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• 2003

Over the past several years, the application extent of the real-time systems is being expanded with the progress of civilization. An effort to minimize power consumption at the system is being accomplished in several fields from the design of an analog/digital circuit up to the device level. Things of this effort have included the power optimum-technique to minimize power consumption at the digital logic circuit and the dynamic managed skill by means of the decision of the operating system. In this paper, we designed of low power system by using power-optimized method. As an effective low-power design, we designed the low power system which it has a monitoring system within the main board and a personal computer.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.5
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• pp.432-437
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• 2001

This paper describes a new developed 3.3KV/4MW class three-level Voltage Source Inverter(VSI), which is equipped with IIMS(Inverter Information Management System) based on the world wide web and with the Virtual operation simulator. The algorithm for motor control is the stator oriented Direct Torque Control(DTC), which works without speed sensor and gives the physically fastest dynamic response. The IIMS have the functions of operation monitoring and data managements. Virtual operation simulator can analyze and tune the system characteristics without main power. Now, this system is under the field test to verify the confidence.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2453-2466
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• 2022

Nuclear power plant operators in the main control room are exposed to stressful conditions in emergency situations as immediate and appropriate mitigations are required. While emergency operating procedures (EOPs) provide operators with the appropriate tasks and diagnostic guidelines, EOPs have static properties that make it difficult to reflect the dynamic changes of the plant. Due to this static nature, operator workloads increase because unrelated information must be screened out and numerous displays must be checked to obtain the plant status. Generally, excessive workloads should be reduced because they can lead to human errors that may adversely affect nuclear power plant safety. This paper presents a framework for an operator support system that can substitute the initial responses of the EOPs, or in other words the immediate actions and diagnostic procedures, in the early stages of an emergency. The system assists operators in emergency operations as follows: performing the monitoring tasks in parallel, identifying current risk and latent risk causality, diagnosing the accident, and displaying all information intuitively with a master logic diagram. The risk causalities are analyzed with a functional modeling methodology called multilevel flow modeling. This system is expected to reduce workloads and the time for performing initial emergency response procedures.

• Journal of IKEEE
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• v.26 no.3
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• pp.389-395
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• 2022

With the evolution of technology, cyber physical systems (CPSs) are being upgraded, and new types of cyber attacks are being discovered accordingly. There are many forms of cyber attack, and all cyber attacks are made to manipulate the target systems. A representative system among cyber physical systems is a cyber physical power system (CPPS), that is, a smart grid. Smart grid is a new type of power system that provides reliable, safe, and efficient energy transmission and distribution. In this paper, specific types of cyber attacks well known as false data injection attacks targeting state estimation and energy distribution of smart grid, and protection strategies for defense of these attacks and dynamic monitoring for detection are described.