• Structural Engineering and Mechanics
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• v.85 no.2
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• pp.197-206
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• 2023

The deterioration caused by chloride penetration and carbonation plays a significant role in a concrete structure in a marine environment. The chloride corrosion in some marine concrete structures is invisible but can be dangerous in a sudden collapse. Therefore, as a novelty, this research investigates the ability of a non-destructive damage detection method named the Power Spectral Density (PSD) to diagnose damages caused only by chloride ions in concrete structures. Furthermore, the accuracy of this method in estimating the amount of annual damage caused by chloride in various parts and positions exposed to seawater was investigated. For this purpose, the RC Arosa bridge in Spain, which connects the island to the mainland via seawater, was numerically modeled and analyzed. As the first step, each element's bridge position was calculated, along with the chloride corrosion percentage in the reinforcements. The next step predicted the existence, location, and timing of damage to the entire concrete part of the bridge based on the amount of rebar corrosion each year. The PSD method was used to monitor the annual loss of reinforcement cross-section area, changes in dynamic characteristics such as stiffness and mass, and each year of the bridge structure's life using sensitivity equations and the linear least squares algorithm. This study showed that using different approaches to the PSD method based on rebar chloride corrosion and assuming 10% errors in software analysis can help predict the location and almost exact amount of damage zones over time.

• International Journal of Computer Science & Network Security
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• v.22 no.3
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• pp.37-44
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• 2022

Plug-in Hybrid electric vehicles (PHEV) show great potential to reduce gas emission, improve fuel efficiency and offer more driving range flexibility. Moreover, PHEV help to preserve the eco-system, climate changes and reduce the high demand for fossil fuels. To address this; some basic components and energy resources have been used, such as batteries and proton exchange membrane (PEM) fuel cells (FCs). However, the FC remains unsatisfactory in terms of power density and response. In light of the above, an electric storage system (ESS) seems to be a promising solution to resolve this issue, especially when it comes to the transient phase. In addition to the FC, a storage system made-up of an ultra-battery UB is proposed within this paper. The association of the FC and the UB lead to the so-called Fuel Cell Battery Electric Vehicle (FCBEV). The energy consumption model of a FCBEV has been built considering the power losses of the fuel cell, electric motor, the state of charge (SOC) of the battery, and brakes. To do so, the implementing a reinforcement-learning energy management strategy (EMS) has been carried out and the fuel cell efficiency has been optimized while minimizing the hydrogen fuel consummation per 100km. Within this paper the adopted approach over numerous driving cycles of the FCBEV has shown promising results.

• Journal of the Korean Geotechnical Society
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• v.24 no.10
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• pp.71-81
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• 2008

Wall displacements caused by earth pressure, rainfalls, rise in ground water level, inappropriate deep excavation and structural defects of the wall may produce differential settlements to existing buildings, which often result in damages and/or collapses of the building structures. In this case, measures to protect the walls and nearby structures would be required. One of the recent measures to reduce differential settlements and protecting walls is to reinforce the ground using micro-piles. In this study physical model tests were carried out to evaluate the performance of the micro-pile method. It is revealed that reduction of the settlement was maximized when the length of micro-pile is twice of the foundation width, distance between piles is twice of the pile diameter and the distance to wall is one tenth of the foundation width. Based on the test results some design recommendations were made.

• Composites Research
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• v.20 no.4
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• pp.9-17
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• 2007

Powder metallurgy has been employed for the development of SiC particle reinforced aluminum metal matrix composites by means of hot isotropic pressing and vacuum hot pressing. A material model based on micro-mechanical approach then has been presented for the processes. Densification occurs by the inelastic flow of matrix materials during the consolidation, and consequently it depends on many process conditions such as applied pressure, temperature and volume fraction of reinforcement. The model is implemented into finite element software so that the process simulation can be performed enabling the predicted relative density to be compared with experimental data. In order to determine the performance of finished products, further tensile test has been conducted using the developed specimens. The effect of internal void of the materials on mechanical properties therefore can be investigated.

• Structural Engineering and Mechanics
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• v.86 no.4
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• pp.461-472
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• 2023

This paper proposes a novel method for increasing the distortional frame rigidity of off-rail box girder bridges for cranes by reinforcing the diaphragm with staggered truss. The study starts by using the Matrix Displacement Method to determine the shear angle of the staggered truss diaphragm under two assumptions: hinge joint and rigid joint. To obtain closed-form solutions for the transversal and longitudinal deformations and warping stress of the crane girder, the study employs the Initial Parameter Method and considers the compatibility of shear deformation at joints between the diaphragms and the girder. The theoretical solutions are validated through finite element analysis, which also confirms that the hinge-joint assumption accurately represents the shear angle of the staggered truss diaphragm in girder distortion. Additionally, the study conducts extensive parameter analyses to examine the impact of staggered truss dimensions on distortional stress and deformation. Furthermore, the study compares the distortional warping stresses of crane girders reinforced with staggered truss diaphragms and those reinforced with perforated ones, emphasizing the importance of incorporating stagger truss in diaphragms. Overall, this paper provides a thorough evaluation of the proposed approach's effectiveness in enhancing the distortional frame rigidity of off-rail box girder bridges for cranes. The findings offer valuable insights into the design and reinforcement of diaphragms using staggered truss to enhance the structural performance of crane girders.

• Journal of Korean Medicine for Obesity Research
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• v.23 no.1
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• pp.10-17
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• 2023

Objectives: The aim of this study was to compare the total phenolic content of Korean Acanthopanax senticosus stems harvested in different seasons and provide basic data for developing functional reinforcement products based on the optimal harvesting time. Methods: Each sample harvested in different seasons was extracted and concentrated twice for 2 hours using 70% ethyl alcohol. Phenolic compounds were analyzed using high-performance liquid chromatography for simultaneous multi-component analysis of 14 compounds, including syringaresinol and so on. Results: The results showed that the stem of Korean Acanthopanax senticosus harvested in winter (November 29th) (EAS-5) had the highest phenolic content of 1.038%. The stem of Korean Acanthopanax senticosus harvested in autumn (October 1st) (EAS-4) showed the second-highest phenolic content of 0.764%, followed by the stem of Korean Acanthopanax senticosus harvested in spring (February 2nd) (EAS-1) with a content of 0.390%. On the other hand, the stem of Korean Acanthopanax senticosus harvested in the summer (June 2nd) (EAS-3) showed the lowest content at 0.342%. In conclusion, the stem of Korean Acanthopanax senticosus harvested in winter (EAS-5) showed the highest phenolic compound content. Conclusions: Considering the extraction yield and the total phenolic content, as well as the concentrations of key functional components such as eleutheroside B, chlorogenic acid, and syringaresinol in the 70% ethyl alcohol extract of Korean Acanthopanax senticosus, it is suggested that the stems of Korean Acanthopanax senticosus harvested during the winter season are suitable for the development of novel materials with enhanced anti-obesity functionality.

• KIPS Transactions on Software and Data Engineering
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• v.12 no.5
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• pp.237-242
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• 2023

Research on high-performance walking robots is being actively conducted, and quadruped walking robots are receiving a lot of attention due to their excellent mobility and adaptability on uneven terrain, but they are difficult to introduce and utilize due to high cost. In this paper, to increase utilization by applying intelligent functions to a low-cost quadruped robot, we present a method of improving uneven terrain overcoming ability by mounting IMU and reinforcement learning on embedded board and automatically detecting objects using camera and deep learning. The robot consists of the legs of a quadruped mammal, and each leg has three degrees of freedom. We train complex terrain in simulation environments with designed 3D model and apply it to real robot. Through the application of this research method, it was confirmed that there was no significant difference in walking ability between flat and non-flat terrain, and the behavior of performing person detection in real time under limited experimental conditions was confirmed.

• The Journal of the Korea Contents Association
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• v.22 no.5
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• pp.542-552
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• 2022

The importance of the child-care teacher's job has recently been greatly emphasized due to changes in the transitional social environment, but the performance conditions are poor, requiring management of various job factors. For the purpose of providing information for practical application and institutional support related to child-care teachers, this study selected Flourish, Care that Respects the Rights of Child, and Job Crafting to verify the functional impact relationship and effectiveness. Since there are no domestic studies on child-care teachers using these variables, hierarchical regression analysis was performed on 223 child-care teachers to obtain initial information. As a result of the analysis, only the average difference between groups was found in terms of Flourish according to age and Negative Job Demand Reduction according to working hours. And it was found that the Enhancement of Social Job Resources had a moderating effect. Therefore, it is necessary to prepare a new job management strategy based on the information provided by this study and to develop a highly effective reinforcement program for each factor.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.775-785
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• 2006

This study focused on the development of surface deformations of GFRP rebars with a better bond characteristic for reinforcing concrete, and simultaneously, of GFRP rebars with more simple and economic production process. This research paper describes a development and bond performance of GFRP rebar with molded deformations, which is composed of polymer resin and milled glass fiber. To determine proper mix ration of milled fibers, material test of hardened epoxy and pullout tests of GFRP rebar with various mix ratio were conducted. The test results indicate that the new strategy of using a mixture of epoxy resin and milled fiber could be successfully applied to a surface structure of GFRP rebar to enhance bond with concrete. The bearing resistance of the ribs was further enhanced by the milled fibers at mechanical and environmental loading state.

• Computers and Concrete
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• v.32 no.1
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• pp.75-85
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• 2023

This work utilizes simplified higher-order shear deformation beam theory (HSDBT) to investigate the vibration response for functionally graded carbon nanotube-reinforced composite (CNTRC) beam. Novel to this work, single-walled carbon nanotubes (SWCNTs) are distributed and aligned in a matrix of polymer throughout the beam, resting on a viscoelastic foundation. Four un-similar patterns of reinforcement distribution functions are investigated for the CNTRC beam. Porosity is another consideration taken into account due to its significant effect on functionally graded materials (FGMs) properties. Three types of uneven porosity distributions are studied in this study. The damping coefficient and Winkler's and Pasternak's parameters are considered in investigating the viscosity effect on the foundation. Moreover, the impact of different parameters on the vibration of the CNTRC beam supported by a viscoelastic foundation is discussed. A comparison to other works is made to validate numerical results in addition to analytical discussions. The findings indicate that incorporating a damping coefficient can improve the vibration performance, especially when the spring constant factors are raised. Additionally, it has been noted that the fundamental frequency of a beam increases as the porosity coefficient increases, indicating that porosity may have a significant impact on the vibrational characteristics of beams.