• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1741-1751
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• 2004

It is commonly requested that the steam generator tubes wall-thinned in excess of 40% should be plugged. However, the plugging criterion is known to be too conservative for some locations and types of defects and its application is limited to a single crack in spite of the fact that the occurrence of multiple through-wall cracks is more common in general. The objective of this research is to propose the optimum failure prediction models for two adjacent through-wall cracks in steam generator tubes. The conservatism of the present plugging criteria was reviewed using the existing failure prediction models for a single crack, and six new failure prediction models for multiple through-wall cracks have been introduced. Then, in order to determine the optimum ones among these new local or global failure prediction models, a series of plastic collapse tests and corresponding finite element analyses for two adjacent through-wall cracks in thin plate were carried out. Thereby, the reaction force model, plastic zone contact model and COD (Crack-Opening Displacement) base model were selected as the optimum ones for assessment of steam generator tubes with multiple through-wall cracks. The selected optimum failure prediction models, finally, were used to estimate the coalescence pressure of two adjacent through-wall cracks in steam generator tubes.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.1-11
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• 2006

This paper presents a seismic fragility analysis method for a cable-stayed bridge with energy dissipation devices. Model uncertainties represented by random variables include input ground motions, characteristics of energy dissipation devices and the stiffness of cable-stayed bridge. Using linear regression, we established demand models for the fragility analysis from the relationship between maximum responses and the intensity of input ground motions. For capacity models, we considered the moment and shear force of the main tower, longitudinal displacement of the girder, deviation of the stay cables tension and the local buckling of the main steel tower as the limit states for cable-stayed bridge. As a numerical example, fragility analysis results for the 2nd Jindo bridge are presented. The effect of energy dissipation devices is also briefly discussed.

• Magazine of the Korea Concrete Institute
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• v.8 no.6
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• pp.183-193
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• 1996

The objective of this study is to investigate the characteristics of elastic and inelastic bekavior of ductile momenting-resisting reinforced concrete frame subjected to reversed lateral loading such as earthquake excitations. For this purpose, a 2-bay 2-story reinforced concrete plane frame with seismic detail was designed and one 1/2.5-scale subassemblage was manufactured according to the required similitude law. Then, the reversed load test under the displacement control was performed statically to this subassemblage. Finally, the results of this test were analysed regarding to (1) the design load vs actual strength, (2) degradation in stiffness and strength. (3) failure mode or energy dissipation. (4) local deformations.

• Journal of the Korea Convergence Society
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• v.8 no.4
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• pp.189-197
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• 2017

In the design of an automotive structural component, one of the more important tasks for a design engineer is to determine the life of the component and to ensure that the component will not fail prematurely. In order to accomplish this, a design engineer will first use simple section analysis to come up with a section shape in the concept design stage and use more advanced analysis for stress level. At this stage, the analysis should focus on understanding overall behavior in terms of load paths and gross stress levels. A model that is adequate for a stiffness analysis of the structure will usually provide an adequate level of stress information in the design process. To perform a detailed stress analysis, the structure models must have the detailed local areas such as stress concentrations or force(or displacement) distributions. This paper is to present the design considerations for the stress analysis of automotive structure.

• Journal of Sensor Science and Technology
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• v.24 no.6
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• pp.373-378
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• 2015

The structure of the human ear is divided into the outer ear, the middle ear, and the inner ear. The inner ear includes the cochlea that plays a very important role in hearing. Recently, the development of an artificial cochlear device for the hearing impaired with cochlear damage has been actively researched. Research has been carried out on the biomimetic piezoelectric thin film ABM (Artificial Basilar Membrane) in particular. In an effort to improve the frequency separation performance of the existing piezoelectric thin film ABM, this paper presents the design, fabrication, and characterization of the production and performance of a partially etched-type ABM material. $O_2$ plasma etching equipment was used to partially etch a piezoelectric thin film ABM to make it more flexible. The mechanical-behavior characterization of the manufactured partially etched-type ABM showed that the overall separation frequency range shifted to a lower frequency range more suitable for audible frequency bandwidths and it displayed an improved frequency separation performance. In addition, the maximum magnitude of the vibration displacement at the first local resonant frequency was enhanced by three times from 38 nm to 112 nm. It is expected that the newly designed, partially etched-type ABM will improve the issue of cross-talk between nearby electrodes and that the manufactured partially etched-type ABM will be utilized for next-generation ABM research.

• Structural Engineering and Mechanics
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• v.67 no.2
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• pp.207-217
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• 2018

In past years, numerous problems have vexed engineers with regard to buckling, corrosion, bending, and overloading in damaged steel structures. This article sets out to investigate the possible effects of carbon fiber reinforced polymer (CFRP) and steel plates for retrofitting deficient steel square hollow section (SHS) columns. The effects of axial loading, stiffness, axial displacement, the position and shape of deficient region on the length of steel SHS columns, and slenderness ratio are examined through a detailed parametric study. A total of 14 specimens was tested for failure under axial compression in a laboratory and simulated using finite element (FE) analysis based on a numerical approach. The results indicate that the application of CFRP sheets and steel plates also caused a reduction in stress in the damaged region and prevented or retarded local deformation around the deficiency. The findings showed that a deficiency leads to reduced load-carrying capacity of steel SHS columns and the retrofitting method is responsible for the increase in the load-bearing capacity of the steel columns. Finally, this research showed that the CFRP performed better than steel plates in compensating the axial force caused by the cross-section reduction due to the problems associated with the use of steel plates, such as in welding, increased weight, thermal stress around the welding location, and the possibility of creating another deficiency by welding.

• Korean Journal of Metals and Materials
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• v.50 no.5
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• pp.345-351
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• 2012

A three-point bending test was performed on roll-bonded Mg/Al/STS clad-metal plates under two different testing conditions (Mg layer in tension, or STS in tension) and their mechanical response and fracture behavior were investigated. Bending strength was found to be greater under the condition of Mg layer in tension. Heat treatment at $200^{\circ}C$ increased the bending formability, suggesting the interfacial strength increased at $200^{\circ}C$. Under the condition of Mg in tension, the clad heat-treated at $300^{\circ}C$ and $400^{\circ}C$ fractured in two steps, with the first step associated with the interfacial fracture between Mg and Al, and the second the fracture of the Mg layer. STS/Al layers were found to be bent without complete fracture. Under the condition of STS in tension, the clad heat-treated at $300^{\circ}C$ and $400^{\circ}C$ exhibited a very small load drop at the displacement, which is similar to that of the first load drop associated with the interfacial fracture under the condition of Mg in tension. In this case, no interfacial cracks were found and the complete cut-through fracture of clad was observed at low temperature heat treatment conditions, suggesting excellent interfacial strength. When the heat treatment temperature was higher than $300^{\circ}C$, interfacial cracks were observed. The local stress condition and the position of the interface with respect to the surface were found to have a great influence on the fracture behaviors of clad metals.

• Structural Engineering and Mechanics
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• v.71 no.1
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• pp.1-12
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• 2019

This study investigates optimum designs of steel space truss towers under seismic loading by using Jaya optimization algorithm. Turkish Earthquake Code (2007) specifications are applied on optimum designs of steel space truss towers under the seismic loading for different local site classes depending on different soil groups. The proposed novel algorithm does not have any algorithm-specific control parameters and depends only a simple revision equation. Therefore, it provides a practical solution for structural optimization problems. Optimum solutions of the different steel truss examples are carried out by selecting suitable W sections taken from American Institute of Steel Construction (AISC). In order to obtain optimum solutions, a computer program is coded in MATLAB in corporated with SAP2000-OAPI (Open Application Programming Interface). The stress and displacement constraints are applied on the design problems according to AISC-ASD (Allowable Stress Design) specifications. Firstly, a benchmark truss problem is examined to see the efficiency of Jaya optimization algorithm. Then, two different multi-element truss towers previously solved with other methods without seismic loading in literature are designed by the proposed algorithm. The first space tower is a 582-member space truss with the height of 80 m and the second space tower is a 942-member space truss of about 95 m height. The minimum optimum designs obtained with this novel algorithm for the case without seismic loading are lighter than the ones previously attained in the literature studies. The results obtained in the study show that Jaya algorithm is a practical and robust optimization method for structural optimization problems. Moreover, incorporation of the seismic loading causes significant increase in the minimum design weight.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.1
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• pp.371-384
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• 2019

Motion perception has been tremendously improved in neuroscience and computer vision. The baseline motion perception model is mediated by the dorsal visual pathway involving the cortex areas the primary visual cortex (V1) and the middle temporal (V5 or MT) visual area. However, few works have been done on the extension of neural models to improve the efficacy and robustness of motion perception of real sequences. To overcome shortcomings in situations, such as varying illumination and large displacement, an adaptive V1-MT motion perception (Ad-V1MTMP) algorithm enriched to deal with real sequences is proposed and analyzed. First, the total variation semi-norm model based on Gabor functions (TV-Gabor) for structure-texture decomposition is performed to manage the illumination and color changes. And then, we study the impact of image local context, which is processed in extra-striate visual areas II (V2), on spatial motion integration by MT neurons, and propose a V1-V2 method to extract the image contrast information at a given location. Furthermore, we take feedback inputs from V2 into account during the polling stage. To use the algorithm on natural scenes, finally, multi-scale approach has been used to handle the frequency range, and adaptive pyramidal decomposition and decomposed spatio-temporal filters have been used to diminish computational cost. Theoretical analysis and experimental results suggest the new Ad-V1MTMP algorithm which mimics human primary motion pathway has universal, effective and robust performance.

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.15 no.1
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• pp.89-93
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• 2019

Preterm infants have higher possibility of undergoing endotracheal intubation after birth than normal children due to medical conditions. Developmental disturbances of primary incisors following intubation can occur as crown malformation, enamel defects, delayed eruption, displacement of dental follicle in crypt, groove formation of palate or alveolar ridge, acquired cleft palate, and dental arch distortion. This clinical report presents the effect of intubation on primary dentition of preterm infants. A 2-year-old girl with cerebral palsy and premature birth history visited our clinic with chief complaint of unerupted primary upper incisor. A 1-year-old boy with cerebral palsy, status epilepticus and premature birth history visited our clinic due to crown malformation. Developmental disturbances of primary incisors in these cases were not related to the patients' systemic disease, and there were no history of dental trauma. A long term endotracheal intubation prior to tooth eruption might have caused local trauma on alveolar ridge. It is very important to monitor dental problems of preterm infants who had experienced endotracheal intubation during neonatal period. Due to influences on both primary and permanent teeth, periodic re-evaluation of affected areas and establishment of comprehensive treatment plans are necessary.