• Nuclear Engineering and Technology
• /
• v.55 no.3
• /
• pp.968-980
• /
• 2023

The dynamic structural responses are sensitive to the time-frequency content of seismic waves, and seismic input motions in time-history analysis are usually required to be compatible with design response spectra according to nuclear codes. In order to generate spectra-compatible input motions while maintaining the intrinsic non-stationarity of seismic waves, an improved time-domain approach is proposed in this paper. To maintain the nonstationary characteristics of the given seismic waves, a new time-frequency envelope function is constructed using the Hilbert amplitude spectrum. Based on the intrinsic mode functions (IMFs) obtained from given seismic waves through variational mode decomposition, a new corrective time history is constructed to locally modify the given seismic waves. The proposed corrective time history and time-frequency envelope function are unique for each earthquake records as they are extracted from the given seismic waves. In addition, a dimension reduction iterative technique is presented herein to simultaneously superimpose corrective time histories of all the damping ratios at a specific frequency in the time domain according to optimal weights, which are found by the genetic algorithm (GA). Examples are presented to show the capability of the proposed approach in generating spectra-compatible time histories, especially in maintaining the nonstationary characteristics of seismic records. And numerical results reveal that the modified time histories generated by the proposed method can obtain similar dynamic behaviors of AP1000 nuclear power plant with the natural seismic records. Thus, the proposed method can be efficiently used in the design practices.

• Journal of Korean Society for Atmospheric Environment
• /
• v.32 no.4
• /
• pp.372-383
• /
• 2016

This study aimed at analyzing the sensitivity of ozone simulation in accordance with the meteorological nudging for a high nocturnal ozone episode. To demonstrate the effectiveness of nudging methods (e.g., nudging techniques and application domains), the following six experiments were designed: (1) control without nudging, (2) experiment with application of observation nudging to all domains (domain 1~4), and (3)~(6) experiments with application of grid nudging to domain 1, domain 1~2, domain 1~3 and all domains, respectively. As a result, the meteorological nudging had a direct (improvement of input data) and indirect (estimate natural emission) effect on ozone simulation. Nudging effects during the daytime were greater than those during the nighttime due to low accuracy of wind direction during the nighttime. On comparison of the nudging techniques, the experiments in which grid nudging was applied showed more improved results than the experiments in which observation nudging was applied. At this time point, the simulated concentrations were generally similar to the observed concentrations due to the increase in the nudging effect when grid nudging was applied up to the sub-domain. However, for high nocturnal ozone uptakes, the experiment in which grid nudging was applied do domain 1~3 showed better results than the other experiments. This is because, when grid nudging was applied to the high resolution domain (e.g., domain 4 with 1 km), the local characteristics were removed due to the smoothing effects of meteorological conditions.

• Journal of KIISE:Software and Applications
• /
• v.28 no.10
• /
• pp.743-756
• /
• 2001

Component-based software development (CBSD) is a method for building large software system by integrating previously-existing software components. Software development method using components has several advantages such that reducing time to delivery and development costs, and increasing productivity etc. But integrating components developed from multiple vendors is too difficult As a result it is required the understanding on the context of use to develop reusable components. The context of use for software component of determined by software architecture. Therefore, it is possible to develop an application based on components if is based on software architecture. Also, it is essential to consider domain concepts for CBSD. To increase the reusability of components. we should develop components in a domain which is a set of related systems. In this paper, we proposed a domain architecture development methodology that supports component-based software development. Domain architecture that represents components and their relationship is produced through domain analysis and design process. We believe that component development methodology using proposed domain architecture can efficiently develop highly reusable components as well as easily develop and application using information acquired from domain architecture.

• The Journal of Bigdata
• /
• v.3 no.2
• /
• pp.11-18
• /
• 2018

This study is a study on domain automatic classification for domain - based quality diagnosis which is a key element of big data quality diagnosis. With the increase of the value and utilization of Big Data and the rise of the Fourth Industrial Revolution, the world is making efforts to create new value by utilizing big data in various fields converged with IT such as law, medical, and finance. However, analysis based on low-reliability data results in critical problems in both the process and the result, and it is also difficult to believe that judgments based on the analysis results. Although the need of highly reliable data has also increased, research on the quality of data and its results have been insufficient. The purpose of this study is to shorten the work time to automizing the domain classification work which was performed from manually to using machine learning in the domain - based quality diagnosis, which is a key element of diagnostic evaluation for improving data quality. Extracts information about the characteristics of the data that is stored in the database and identifies the domain, and then featurize it, and automizes the domain classification using machine learning. We will use it for big data quality diagnosis and contribute to quality improvement.

• Journal of Korean Society of Steel Construction
• /
• v.12 no.5 s.48
• /
• pp.581-593
• /
• 2000

In this study, vertical dynamic analyses on the suspension bridges under seismic load are developed. Time domain analysis, random vibration analysis, and spectral analysis are formulated theoretically. The random nitration analysis is checked by numerical integration and the mathematical integration with correlation coefficient which include CQC and SRSS method in the conditions of white noise and filtered white noise. Beam, truss and frame elements are used in order to model the suspension bridge. Geometric stiffness due to dead load is considered for cable and tower.

• Journal of Advanced Marine Engineering and Technology
• /
• v.38 no.2
• /
• pp.195-201
• /
• 2014

Flexible risers have been used extensively in recent years for floating and early production systems. Such risers offer the advantage of having inherent heave compliance in their catenary thereby greatly reducing the complexity of the riser-to-rig and riser-to subsea interfaces. Another advantage with flexible risers is their greater reliability. Concerns about fatigue life, gas permeation and pigging of lines have been overcome by extensive experience with these risers in production applications. In this paper, flexible riser analysis results were compared through coupled and uncoupled dynamic analyses methods. A time domain coupled analysis capability has been developed to model the dynamic responses of an integrated floating system incorporating the interactions between vessel, moorings and risers in a marine environment. For this study, SPM (Single Point Mooring) system for an FSU in shallow water was considered. This optimization model was integrated with a time-domain global motion analysis to assess both stability and design constraints of the flexible riser system.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.1059-1060
• /
• 2007

In this paper analysis of the characteristics in the three phase induction motor for the electric forklift truck is researched. There are two kinds of the Finite element analysis method. First thing is time domain analysis by the time transient method. Second thing is frequency domain analysis by method which assumes applied voltage and current sinusoidal. Especially in case of the characteristic studies, electromagnetic analysis is performed about each prototype motors. The obtained results are compared and the result of the test is examined. We could know characteristics of each prototypes and verify the design program of the motor through FEM. Finally this paper shows the factors of discord results of the analysis.

• Journal of Coastal Disaster Prevention
• /
• v.1 no.4
• /
• pp.149-155
• /
• 2014

Flexible risers have been used extensively in recent years for floating and early production systems. Such risers offer the advantage of having inherent heave compliance in their catenary thereby greatly reducing the complexity of the riser-to-rig and riser-to subsea interfaces. Another advantage with flexible risers is their greater reliability. Concerns about fatigue life, gas permeation and pigging of lines have been overcome by extensive experience with these risers in production applications. In this paper, flexible riser analysis results were compared through coupled and uncoupled dynamic analyses methods. A time domain coupled analysis capability has been developed to model the dynamic responses of an integrated floating system incorporating the interactions between vessel, moorings and risers in a marine environment. For this study, SPM (Single Point Mooring) system for an FSU in shallow water was considered. This optimization model was integrated with a time-domain global motion analysis to assess both stability and design constraints of the flexible riser system.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2000.10a
• /
• pp.132-139
• /
• 2000

This paper presents a new hybrid approach for nonlinear dynamic analysis of the soil-structure interaction system in the time domain. It employs, in a practical manner, a linear SSI program and a general-purpose nonlinear finite element program. In order to demonstrate the validity and applicability of the proposed method, seismic response analyses are carried out for a free-field problem and a 2-D subway station. The results indicate that the proposed methodology gives reasonable solution for the linear/nonlinear SSI problem utilizing a general-purpose finite element program. Some further studies will endorse the applicability of the method to various soil-structure interaction problems.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.6 no.4
• /
• pp.46-53
• /
• 1997

This paper presents a method of detection localized defects on tapered roller bearing in main spindle of machine tool system. The feature vectors, i.e. statistical parameters, in time-domain analysis technique have been calculated to extract useful features from acoustic emission signals. These feature vectors are used as the input feature of an neural network to classify and detect bearing defects. As a results, the detection of bearing defect conditions could be sucessfully performed by using an neural network with statistical parameters of acoustic emission signals.