• KEPCO Journal on Electric Power and Energy
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• 제4권2호
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• pp.89-99
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• 2018

Downtime and malfunction of industrial rotor machines represents a crucial cost burden and productivity loss. Fault diagnosis of this equipment has recently been carried out to detect their fault(s) and cause(s) by using fault classification methods. However, these methods are of limited use in detecting rotor faults because of their hypersensitivity to unexpected and different equipment conditions individually. These limitations tend to affect the accuracy of fault classification since fault-related features calculated from vibration signal are moved to other regions or changed. To improve the limited diagnosis accuracy of existing methods, we propose a new approach for fault diagnosis of rotor machines based on the model generated by supervised learning. Our work is based on feature residual values from vibration signals as fault indices. Our diagnostic model is a robust and flexible process that, once learned from historical data only one time, allows it to apply to different target systems without optimization of algorithms. The performance of the proposed method was evaluated by comparing its results with conventional methods for fault diagnosis of rotor machines. The experimental results show that the proposed method can be used to achieve better fault diagnosis, even when applied to systems with different normal-state signals, scales, and structures, without tuning or the use of a complementary algorithm. The effectiveness of the method was assessed by simulation using various rotor machine models.

• Structural Engineering and Mechanics
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• 제88권5호
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• pp.463-480
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• 2023

The buckling-restrained braced frames with eccentric configurations (BRBF-Es) exhibit stable cyclic behavior and possess a high energy absorption capacity. Additionally, they offer architectural advantages for incorporating openings, much like Eccentrically Braced Frames (EBFs). However, studies have indicated that significant residual drifts occur in this system when subjected to earthquakes at the Maximum Considered Earthquake (MCE) hazard level. Consequently, in order to mitigate these residual drifts, it is recommended to employ self-centering systems alongside the BRBF-E system. In our current research, we propose the utilization of the Direct Displacement-Based Seismic Design method to determine the design base shear for a hybrid system that combines BRBF with an eccentric configuration and a self-centering frame. Furthermore, we present a methodology for designing the individual components of this composite system. To assess the effectiveness of this design approach, we designed 3-, 6-, and 9-story buildings equipped with the BRBF-E-SCF system and developed finite element models. These models were subjected to two sets of ground motions representing the Maximum Considered Earthquake (MCE) and Design Basis Earthquake (DBE) seismic hazard levels. The results of our study reveal that although the combined system requires a higher amount of steel material compared to the BRBF-E system, it substantially reduces residual drift. Furthermore, the combined system demonstrates satisfactory performance in terms of story drift and ductility demand.

• 한국CDE학회논문집
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• 제12권1호
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• pp.27-38
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• 2007

This paper describes a multiresidual approximation method for scattered volumetric data modeling. The approximation method employs a volumetric NURBS or VNURBS as a data interpolating function and proposes two multiresidual methods as a data modeling algorithm. One is called as the residual series method that constructs a sequence of VNURBS functions and their algebraic summation produces the desired approximation. The other is the residual merging method that merges all the VNURBS functions mentioned above into one equivalent function. The first one is designed to construct wavelet-type multiresolution models and also to achieve more accurate approximation. And the second is focused on its improvement of computational performance with the save fitting accuracy for more practical applications. The performance results of numerical examples demonstrate the usefulness of VNURBS approximation and the effectiveness of multiresidual methods. In addition, several graphical examples suggest that the VNURBS approximation is applicable to various applications such as surface modeling and fitting problems.

• 대한기계학회논문집
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• 제19권6호
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• pp.1402-1410
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• 1995

An influence coefficient method with an optimal correction balancing algorithm is developed for balancing a high-speed flexible rotor system. Conventional flexible balancing algorithms such as least square and weighted least square algorithms may not satisfy allowable residual vibration levels in certain speed ranges, while the optimal correction balancing method can be more effective in controlling vibration levels in a target speed. Related analyses were reviewed and applied to a test rig to show the effectiveness of the optimal correction balancing method.

• Journal of Welding and Joining
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• 제14권5호
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• pp.69-77
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• 1996

This study aims to analyze the S. I. F. K value upon Mode I cracks in a finite-width plate of varying thickness, which is expressed in terms of width ratio ($\omega$), thickness ratio ($\beta$) and non-dimensional crack length (λ) by using the 2-dimensional finite element method. Then, by comparing the effectiveness of the results obtained by the two finite element methods, it is seen that the 2-dimensional finite element method can be used in order to analyse the S. I. F. K values upon a various thickness model. A model is developed in order to analyze the effects of initial residual stress upon the fatigue crack growth behavior in various thickness welded specimens. In this model, crack growth rate da/dN appears to be come small as the thickness ratio with the same ΔK is increased. Also, in the initial step, as ΔK is increased with crack growth rate is decreased and then increased because the repeated compressive residual stress retards crack growth rate.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.594-597
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• 2006

Image co-registration is the process of overlaying two images of the same scene. One of which is a reference image, while the other (sensed image) is geometrically transformed to the one. Numerous methods were developed for the automated image co-registration and it is known as a time-consuming and/or computation-intensive procedure. In order to improve efficiency and effectiveness of the co-registration of satellite imagery, this paper proposes a pre-qualified area matching, which is composed of feature extraction with Laplacian filter and area matching algorithm using correlation coefficient. Moreover, to improve the accuracy of co-registration, the outliers in the initial matching point should be removed. For this, two outlier detection techniques of studentized residual and modified RANSAC algorithm are used in this study. Three pairs of Landsat images were used for performance test, and the results were compared and evaluated in terms of robustness and efficiency.

• Steel and Composite Structures
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• 제9권3호
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• pp.209-221
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• 2009

Heating correction, through heating and flattening a structure with a pressing machine, is the in-situ method used to repair buckled steel structures. The primary purpose of this investigation is to develop an FEM model which can predict the mechanical response of heat-corrected plates accurately. Our model clarifies several unsolved problems. In previous research, the location of the imperfection was limited to the center of the specimen although the mechanical behavior is strongly affected by the location of the imperfection. Our research clarifies the relationship between the location of the imperfection and the mechanical behavior. In addition, we propose further reinforcement methods and validate their effectiveness. Our research concludes that the strength of a buckled specimen can be recovered by heating correction and the use of an adequate stiffener.

• 한국소음진동공학회논문집
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• 제15권7호
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• pp.871-877
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• 2005

This paper proposes a new modeling scheme to describe the hysteresis between input voltage and displacement of piezoelectric actuators in the inchworm. From the experimental analysis of Piezoelectric actuator behaviors. the hysteresis characteristics including residual displacement can be modeled by second order functions of a maximum Input voltage and preload. Various experiments are performed to demonstrate the effectiveness and validation of the proposed modeling scheme.

• Structural Monitoring and Maintenance
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• 제1권3호
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• pp.309-322
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• 2014

Detection of fatigue cracks at an early stage of their development is important in structural health monitoring. The breathing of cracks in a structure generates higher harmonic components of the exciting frequency in the frequency spectrum. Previously, the residual operational deflection shape (R-ODS) method was successfully applied to beams with a single crack. The method is based on the ODSs at the exciting frequency and its higher harmonic components which consider both amplitude and phase information of responses to map the deflection pattern of structures. Although the R-ODS method shows the location of a single crack clearly, its identification for the location of multiple cracks in a structure is not always obvious. Therefore, an improvement to the R-ODS method is presented here to make the identification process distinct for the beams with multiple cracks. Numerical and experimental examples are utilised to investigate the effectiveness of the improved method.

• 로봇학회논문지
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• 제13권1호
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• pp.1-7
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• 2018

The image-to-image translation is one of the deep learning applications using image data. In this paper, we aim at improving the performance of object transfiguration which transforms a specific object in an image into another specific object. For object transfiguration, it is required to transform only the target object and maintain background images. In the existing results, however, it is observed that other parts in the image are also transformed. In this paper, we have focused on the structure of artificial neural networks that are frequently used in the existing methods and have improved the performance by adding constraints to the exiting structure. We also propose the advanced structure that combines the existing structures to maintain their advantages and complement their drawbacks. The effectiveness of the proposed methods are shown in experimental results.