• Journal of the Semiconductor & Display Technology
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• v.9 no.2
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• pp.33-39
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• 2010

The moisture absorption properties such as diffusion coefficient and moisture content ratio of liquid type epoxy resin systems with the filler were investigated. Bisphenol A type and Bisphenol F type epoxy resin, Kayahard MCD as hardener and 2-methylimidazole as catalyst were used in these epoxy resin systems. The nano-sized spherical type fused silica as filler were used in order to study the moisture absorption properties of these liquid type epoxy encapsulant according to the change of filler size. The temperature of glass transition (Tg) of these epoxy resin systems was measured using Dynamic Scanning Calorimeter (DSC), and the moisture absorption properties of these epoxy resin systems according to the change of time were observed at $85^{\circ}C$ and 85% relative humidity condition using a thermo-hygrostat. The diffusion coefficients in these systems were calculated in terms of modified Crank equation based on Ficks' law. An increase of Tg and diffusion coefficient with filler size in these systems can be observed, which are attributed to the increase of free volume with Tg. The change of maximum moisture absorption ratio according to the filler size and filler content cannot be observed; however, the diffusion coefficients of these systems decreased with filler content. The diffusion via free volume is dominant in the epoxy resin systems with low nano-sized filler content; however, the diffusion with the interaction of absorption according the increase of the filler surface area is dominant in the liquid type epoxy encapsulant with high nano-sized filler content.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.4
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• pp.331-340
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• 2021

The blast damage behavior of reinforced concrete (RC) structures exposed to unexpected extreme loading was investigated. To enhance the accuracy of numerical simulation for blast loading on RC structures with seven blast points, the calculation of blast loads using the Euler-flux-corrected-transport method, the proposed Euler-Lagrange coupling method for fluid-structure interaction, and the concrete dynamic damage constitutive model including the strain rate-dependent strength and failure models was implemented in the ANSYS-AUTODYN solver. In the analysis results, in the case of 20 kg TNT, only the slab member at three blast points showed moderate and light damage. In the case of 100 kg TNT, the slab and girder members at three blast points showed moderate damage, while the slab member at two blast points showed severe damage.

• Structural Engineering and Mechanics
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• v.68 no.6
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• pp.747-760
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• 2018

In the present study, a methodology for developing fragilities of arch concrete dams to assess their performance against seismic hazards is introduced. Firstly, the probability risk and fragility curves are presented, followed by implementation and representation of the way this method is used. Amirkabir arch concrete dam was subjected to non-linear dynamic analyses. A modified three dimensional rotating smeared crack model was used to take the nonlinear behavior of mass concrete into account. The proposed model considers major characteristics of mass concrete. These characteristics are pre-softening behavior, softening initiation criteria, fracture energy conservation, suitable damping mechanism and strain rate effect. In the present analysis, complete fluid-structure interaction is included to account for appropriate fluid compressibility and absorptive reservoir boundary conditions. In this study, the Amirkabir arch concrete dam is subjected to a set of 8 three-component earthquakes each scaled to 10 increasing intensity levels. Using proposed nonlinear smeared crack model, nonlinear analysis is performed where the structure is subjected to a large set of scaled and un-scaled ground motions and the maximum responses are extracted for each one and plotted. Based on the results, fragility curves were plotted according to various and possible damages indexes. Discrete damage probabilities were calculated using statistical methods for each considered performance level and incremental nonlinear analysis. Then, fragility curves were constructed based on the lognormal distribution assumption. Two damage indexes were introduced and compared to one another. The results indicate that the dam has a proper stability under earthquake conditions at MCE level. Moreover, displacement damages index is more conservative and impractical in the fragility analysis than tensional damage index.

• Environmental Engineering Research
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• v.24 no.3
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• pp.463-473
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• 2019

Nanoscale zero-valent iron (nZVI) has proved to be an effective tool in applied environmental nanotechnology, where the decreased particle diameter provides a drastic change in the properties and efficiency of nanomaterials used in water purification. However, the agglomeration and colloidal instability represent a problematic and a remarkable reduction in nZVI reactivity. In view of that, this study reports a simple and cost-effective new strategy for ultra-small (< 7.5%) distributed functionalized nZVI-EG (1-9 nm), with high colloidal stability and reduction capacity. These were obtained without inert conditions, using a simple, economical synthesis methodology employing two stabilization mechanisms based on the use of non-aqueous solvent (methanol) and ethylene glycol (EG) as a stabilizer. The information from UV-Vis absorption spectroscopy and Fourier transform infrared spectroscopy suggests iron ion coordination by interaction with methanol molecules. Subsequently, after nZVI formation, particle-surface modification occurs by the addition of the EG. Size distribution analysis shows an average diameter of 4.23 nm and the predominance (> 90%) of particles with sizes < 6.10 nm. Evaluation of the stability of functionalized nZVI by sedimentation test and a dynamic light-scattering technique, demonstrated very high colloidal stability. The ultra-small particles displayed a rapid and high nitrate removal capacity from water.

• Journal of the Korea Computer Graphics Society
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• v.24 no.5
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• pp.41-48
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• 2018

The most natural way to increase immersion and provide free interaction in a virtual environment is to provide a gesture interface using the user's hand. However, most studies about hand gesture recognition require specialized sensors or equipment, or show low recognition rates. This paper proposes a three-dimensional DenseNet Convolutional Neural Network that enables recognition of hand gestures with no sensors or equipment other than an RGB camera for hand gesture input and introduces a virtual reality game based on it. Experimental results on 4 static hand gestures and 6 dynamic hand gestures showed that they could be used as real-time user interfaces for virtual reality games with an average recognition rate of 94.2% at 50ms. Results of this research can be used as a hand gesture interface not only for games but also for education, medicine, and shopping.

• Tuberculosis and Respiratory Diseases
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• v.82 no.2
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• pp.126-132
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• 2019

Background: The development of lung cancer results from the interaction between genetic mutations and dynamic epigenetic alterations, although the exact mechanisms are not completely understood. Changes in DNA methylation may be a promising biomarker for early detection and prognosis of lung cancer. We evaluated the serial changes in genome-wide DNA methylation patterns in blood samples of lung cancer patients. Methods: Blood samples were obtained for three consecutive years from three patients (2 years before, 1 year before, and after lung cancer detection) and from three control subjects (without lung cancer). We used the MethylationEPIC BeadChip method, which covers the 850,000 bp cytosine-phosphate-guanine (CpG) site, to conduct an epigenome-wide analysis. Significant differentially methylated regions (DMRs) were identified using p-values <0.05 in a correlation test identifying serial methylation changes and serial increase or decrease in ${\beta}$ value above 0.1 for three consecutive years. Results: We found three significant CpG sites with differentially methylated ${\beta}$ values and 7,105 CpG sites with significant correlation from control patients without lung cancer. However, there were no significant DMRs. In contrast, we found 11 significant CpG sites with differentially methylated ${\beta}$ values and 10,562 CpG sites with significant correlation from patients with lung cancer. There were two significant DMRs: cg21126229 (RNF212) and cg27098574 (BCAR1). Conclusion: This study revealed DNA methylation changes that might be implicated in lung cancer development. The DNA methylation changes may be the possible candidate target regions for the early detection and prevention of lung cancer.

• Communications of Mathematical Education
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• v.35 no.1
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• pp.37-74
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• 2021

In this study, the student participation-centered class, which takes students' mathematical thinking as an important issues of the class, is named as student thinking-based math class. The main characteristics of student thinking-based mathematics classes were examined in terms of tasks, students engagement, and the role of teachers. According to the results of analysis of class cases practiced by five secondary mathematics teachers, student thinking-based mathematics classes were conducted in the intersection of the rich mathematics tasks, students' cognitive and social engagement, and the role of teachers' formative facilitator. The results of this study showed that the student's thinking is more important than the activity itself. And it is meaningful in that it examines the influence of the dynamic interaction of the three components of the mathematics class on the direction and outcome of the class.

• International Journal of Internet, Broadcasting and Communication
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• v.13 no.1
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• pp.47-53
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• 2021

Gait kinematics and kinetics have a similar tendency between men and women, yet it remains unclear how walking while carrying a load affects the gait mechanism. Twenty adults walked with preferred velocity on level ground of 20 m relative to change of a load carriage (no load, 15%, 30% of the body weights) aimed to observe gait mechanism. We measured gait posture using the three-dimensional image analysis and ground reaction force system during stance phase on left foot. In main effect of gender difference, men showed increased displacement of center of gravity (COG) compared to women, and it showed more extended joint angle of hip and knee in sagittal plane. In main effect of a load difference, knee joint showed more flexed postuel relative to increase of load carriage. In main effect of load difference on the kinetic variables, medial-lateral force, anterior-posterior force (1st breaking, 2nd propulsive), vertical force, center of pressure (COP) area, leg stiffness, and whole body stiffness showed more increased values relative to increase of load carriage. Also, men showed more increased COP area compared to women. Interaction showed in the 1st anterior-posterior force, and as a result of one-way variance analysis, it was found that a load main effect had a greater influence on the increase in the magnitude of the braking force than the gender. The data in this study explains that women require little kinematic alteration compared to men, while men in more stiff posture accommodate an added load compared to women during gait. Additionally, it suggests that dynamic stability is maintained by adopting different gait strategies relative to gender and load difference.

• The Korean Journal of Franchise Management
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• v.10 no.3
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• pp.13-23
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• 2019

Purpose - The recent franchise industry is rapidly developing. Some franchisees have a low barriers to entry and competition among companies is intensifying. In this dynamic competitive environment, companies need to focus on customer preferences, quality, and technical interfaces to gain competitive advantage. As a result, companies are required to measure the performance of service values in order to provide differentiated services from competitors. In the franchise industry, customer experience marketing of service values will enable companies to create new businesses. Franchise firms should explore a variety of services to increase service value and reduce failures. Research design, data, methodology - The questionnaire of this study was based on the previous research. Surveys were conducted on panels of online surveys. Surveys were conducted on the panel who had visited the restaurant franchise within the past month. The survey was conducted for about 7 days from February 13, 2019 to February 19, 2019. Total 300 samples, 293 were used in the analysis except for seven unfair questionnaires. Results - The findings of this study are as follows: Emotional, monetary, and reputation values have positive effects on cognitive and affective attitudes. Quality value and behavioral value did not effect cognitive attitude and affective attitude significantly. In addition, affective attitude has positive effect on loyalty, but cognitive attitude did not significant effect on loyalty. Conclusions - First, food-service franchise company should develop a service that enables customers to use the store conveniently. We need to develop a comfortable environment for our customers and provide intangible services. Second, food-service franchise company should provide a reasonable price service. Food-service franchise company needs to sell a high quality menu at a reasonable price to generate profits. Third, food-service franchise companies need to strategically respond to their reputation. In other words, food-service franchise company needs to constantly monitor the reputation of its customers and respond appropriately to market conditions. Fourth, food-service franchise company needs to develop a service method capable of emotional interaction with customers. Food-service franchise firms need to develop ongoing service methods and educate their staff.

• Journal of the Korea Society for Simulation
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• v.30 no.1
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• pp.43-54
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• 2021

Since COVID-19 (Severe acute respiratory syndrome coronavirus type 2, SARS-Cov-2) was first discovered at the end of 2019, it has spread rapidly around the world. This study introduces an agent-based simulation model representing COVID-19 spread in South Korea to investigate the effect of detect level (contact tracing) on the virus spread. To develop the model, related data are aggregated and probability distributions are inferred based on the data. The entire process of infection, quarantine, recovery, and death is schematically described and the interaction of people is modeled based on the traffic data. A composite logistic functions are utilized to represent the compliance of people to the government move control such as social distancing. To demonstrate to effect of detect level on the virus spread, detect level is changed from 0% to 100%. The results indicate active contact tracing inhibits the virus spread and the inhibitory effect increases geometrically as the detect level increases.