• Journal of the Korean Geotechnical Society
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• v.36 no.6
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• pp.35-46
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• 2020

The input parameters for numerical simulation of the liquefaction phenomenon need to be properly evaluated from laboratory and field tests, which are difficult to be performed in practical situations. In this study, the numerical simulation of the cyclic direct simple shear test was performed to analyze the applicability of Finn and PM4Sand models among the constitutive models for liquefaction simulation. The analysis results showed that the Finn model properly predicted the time when the excess pore water pressure reached the maximum, but failed to simulate the pore pressure response and the stress-strain behavior of post-liquefaction. On the other hand, the PM4Sand model properly simulated those behaviors of the post liquefaction. Finally, the evaluation procedure and the equations of the input parameters in the PM4Sand model were developed to mach the liquefaction cyclic resistance ratio corresponding to design conditions.

• Journal of Radiation Protection and Research
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• v.3 no.1
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• pp.23-28
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• 1978

In order to investigate corelation between contents of dioctylphthalate in polyvinylchloride blent dibutyl tin dilaulate with dibutyl tin maleate as stabilizer and the behaviors of radiation resistance as well as electrical conductivity on irradiated specimens, several observations were carried out. A characteristic peak observed in the range of $1,540-1,640cm^{-1}$ on infrared spectra shows such a sensitive response to radiation as the intensity decreases with increasing doses and that this tendency strongly depressed in the presence of plasticizer. It is seemingly attributed for origin of the peak to the existence of RCOO- ion resulting from dissociation of stabilizere, further the depressive effect of decreasing peak intensity influenced by radiation seems to be caused by resonance absorption in benzen ring being a consistituent of plasticizer. It is also suggestive to be use the peak behavior influenced by radiation as a criterion for the evaluation of radiation resistance of PVC. Further the results obtained from electrical conductivity measurement also exhibit reasonable characteristics explainable with views used for the interpretation of the peak behavior mentioned previousely.

• 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.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.2
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• pp.85-91
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• 2016

The most important factor in the structural design of ships and offshore structures operating in arctic region is ice load, which results from ice-structure interaction during the ice collision process. The mechanical properties of ice related to strength and failure, however, show very complicated aspect varying with temperature, volume fraction of brine, grain size, strain rate and etc. So it is nearly impossible to establish a perfect material model of ice satisfying all the mechanical characteristics completely. Therefore, in general, ice collision analysis was carried out by relatively simple material models considering only specific aspects of mechanical characteristics of ice and it would be the most significant cause of inevitable errors in the analysis. Especially, it is well-known that the most distinctive mechanical property of ice is high dependency on strain rate. Ice shows brittle attribute in higher strain rate while it becomes ductile in lower strain rate range. In this study, the simulation method of ice collision to ship hull using the nonlinear dynamic FE analysis was dealt with. To consider the strain rate effects of ice during ice-structural interaction, strain rate dependent constitutive model in which yield stress and hardening behaviors vary with strain rate was adopted. To reduce the huge amount of computing time, the modeling range of ice and ship structure were restricted to the confined region of interest. Under the various scenario of ice-ship hull collision, the structural behavior of hull panels and failure modes of ice were examined by nonlinear FE analysis technique.

• The Journal of Korean Society for School & Community Health Education
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• v.18 no.3
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• pp.55-68
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• 2017

Objectives: Republic of Korea has entered an aged society, recently. As chronic diseases increase, elderly inpatients has been increasing and they have used caregivers for convenience. Accordingly, this study aims to investigate the oral health knowledge and attitude of caregivers on oral health management of elderly inpatients, which would affect the general health and quality of life. Methods: A survey questionnaire was distributed to the caregiver(n=165), at a neurosurgery or orthopedic hospital inpatient ward in Seoul, Gyeonggi-do from April 1 to 14, 2017. We analyzed the data with descriptive statistics analysis, chi-squared analysis and logistic regression analysis by using SPSS 23.0. Results: The response rate to the questionnaire was 92%. Oral health management provided by caregivers to inpatients in the elderly was prevention of oral diseases(92.8%), tooth brushing (89.5%), use of oral care products(68.4%), denture cleaning(90.8%) and oral cleaning(90.8%). Frequency analysis of oral health management in accordance with the educational needs of caregivers was all confirmed statistically significant(p<0.05). In the logistics regression model, oral health knowledge was significantly associated with low oral cleaning(OR=1.58) and oral health attitude was significantly associated with high denture cleaning(OR=1.29) and oral cleaning(OR=1.28) after adjustment for other covariates including gender, age, certification, education level, ward, working years. Conclusions: It is necessary to expand the scope and improve the quality of education that can change the attitudes and behaviors of the caregivers on the oral health management of the elderly on the basis of the current oral health education.

• The Journal of the Korea Contents Association
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• v.19 no.7
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• pp.574-586
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• 2019

This study was conducted to obtain meaningful information about job management of child care center teachers, who take charge of child care policy at the front line, social meaning of which is being greatly highlighted these days. Especially, the research was designed with causal relationships in mind, in which certain job-related thoughts or consciousness forms attitudes, thus leading to behavior. In this light, the present study selected the following variables for analysis: job attitudes including job calling, job engagement, and job burnout; and job behavior such as creative behavior, active behavior, and ethical behavior. Data collected from 209 child care center teachers' response to structured questionnaires was analyzed, using t-test, one-way analysis of variance (one-way ANOVA), and hierarchical regression analysis. The results indicate that job burnout increased at a statistically significant level as extra workhours increased, and that only job engagement, among job attitude variables, and creative behavior and active behaviors, among job behavior variables, had significant effects. Moreover, job engagement was the only variable that was found to work as a mediator in relationships between job calling and active behavior.

• Smart Structures and Systems
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• v.23 no.6
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• pp.653-667
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• 2019

Using cross-ties to connect cables together when forming a cable network is regarded as an efficient method of mitigating cable vibrations. Cross-ties have been extended and fixed on bridge decks or towers in some engineering applications. However, the dynamics of this kind of system need to be further studied, and the effects of extending cross-links to bridge decks/towers on the modal response of the system should be assessed in detail. In this paper, a system of two cables connected by an inter-supported cross-link with another lower cross-link extended to the ground is proposed and analyzed. The characteristic equation of the system is derived, and some limiting solutions in closed form of the system are derived. Roots of cable system with special configurations are also discussed, attention being given to the case when the two cables are identical. A predictable mode behavior was found when the stiffness of inter-connection cross-link and the cross-link extended to the ground were the same. The vector of mode energy distribution and the degree of mode localization index are proposed so as to distinguish global and local modes. The change of mode behaviors is further discussed in the case when the two cables are not identical. Effects of cross-link stiffness, cross-link location, mass-tension ratio, cable length ratio and frequency ratio on $1^{st}$ mode frequency and mode shape are addressed.

• The Journal of the Korea Contents Association
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• v.19 no.1
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• pp.108-116
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• 2019

In this paper, we propose a method to apply artificial intelligence technology efficiently to integrated security control technology. In other words, by applying machine learning learning to artificial intelligence based on big data collected in integrated security control system, cyber attacks are detected and appropriately responded. As technology develops, many large capacity Is limited to analyzing individual logs. The analysis method should also be applied to the integrated security control more quickly because it needs to correlate the logs of various heterogeneous security devices rather than one log. We have newly proposed an integrated security service model based on artificial intelligence, which analyzes and responds to these behaviors gradually evolves and matures through effective learning methods. We sought a solution to the key problems expected in the proposed model. And we developed a learning method based on normal behavior based learning model to strengthen the response ability against unidentified abnormal behavior threat. In addition, future research directions for security management that can efficiently support analysis and correspondence of security personnel through proposed security service model are suggested.

• Food Engineering Progress
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• v.21 no.3
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• pp.233-241
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• 2017

Scaffolds of cell substrates are biophysical platforms for cell attachment, proliferation, and differentiation. They ultimately play a leading-edge role in the regeneration of tissues. Recent studies have shown the potential of bioactive scaffolds (i.e., osteo-inductive) through 3D printing. In this study, rice bran-derived biocomposite was fabricated for fused deposition modeling (FDM)-based 3D printing as a potential bone-graft analogue. Rice bran by-product was blended with poly caprolactone (PCL), a synthetic commercial biodegradable polymer. An extruder with extrusion process molding was adopted to manufacture the newly blended "green material." Processing conditions affected the performance of these blends. Bio-filament composite was characterized using field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDX). Mechanical characterization of bio-filament composite was carried out to determine stress-strain and compressive strength. Biological behaviors of bio-filament composites were also investigated by assessing cell cytotoxicity and water contact angle. EDX results of bio-filament composites indicated the presence of organic compounds. These bio-filament composites were found to have higher tensile strength than conventional PCL filament. They exhibited positive response in cytotoxicity. Biological analysis revealed better compatibility of r-PCL with rice bran. Such rice bran blended bio-filament composite was found to have higher elongation and strength compared to control PCL.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.2
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• pp.309-315
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• 2021

Risks and uncertainty are unavoidable problems in management of projects. Therefore, project managers should not only prevent risks, but also have to respond and manage them. Risk management has become a critical interest subject in the construction industry for both practitioners and researchers. This paper presents critical risk factors of office building projects in the construction phase in Ho Chi Minh City, Vietnam. Data was collected through a questionnaire survey based on the likelihood and consequence level of risk factors. These factors fell into five groups: (i) financial risk factors; (ii) management risk factors; (iii) schedule risk factors; (iv) construction risk factors; and (v) environment risk factors. The research results showed that critical factors affecting office building projects are natural (i.e., prolonged rain, storms, climate effects) and human-made issues (i.e., soil instability, safety behaviors, owner's design change) and the schedule-related risk factors contributed to the most significant risks for office buildings projects in the construction phase in Ho Chi Minh City. They give construction management and project management practitioners a new perspective on risks and risk management of office buildings projects in Ho Chi Minh City and are proactive in the awareness, response, and management of risk factors comprehensively.