• Journal of Adhesion and Interface
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• v.20 no.1
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• pp.23-28
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• 2019

In this study, the micro- and nano-particles were used and their shapes were transferred into the polydimethylsiloxane (PDMS) film to fabricate the dry adhesives and their properties were investigated. The Cu nanoparticles of the sizes of 20 nm, 40 nm and 70 nm and the polymethylmethacrylate (PMMA) beads of the size of $5{\mu}m$ were used to transfer their images and the resultant properties of the dry adhesives were compared. The effects of particle size and materials on the mechanical property, tensile adhesion strength, light transmittance, surface morphology, water contact angle were studied. The dry adhesives obtained from the transfer process of Cu nanoparticles with the size of 20 nm resulted in the enhancement of tensile adhesion strength more than 300% compared to that of the bare PDMS. The formation of nanostructure of large surface area on the surface of the PDMS film by the Cu nanoparticles may responsible for the improvement. This study suggests that the use of nanoparticles during the fabrication of PDMS dry adhesives is easy and effective and could be applied to the fabrication of the medical patch.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.6
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• pp.270-285
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• 2018

The behavior of wave-induced pore water pressure inside the rubble mound and seabed, and the resultant structure failure are investigated, which are used in design of the composite breakwater representing the coastal and harbor structures. Numerical simulation techniques have been widely used to assess these behaviors through linear and nonlinear methods in many researches. While the combination of strongly nonlinear analytical method and turbulence model have not been applied yet, which can simulate these characteristics more accurately. In this study, olaFlow model considering the wave-breaking and turbulent phenomena is applied through VOF and LES methods, which gives more exact solution by using the multiphase flow analytical method. The verification of olaFlow model is demonstrated by comparing the experimental and numerical results for the interactions of regular waves-seabed and regular waves-composite breakwater-seabed. The characteristics of the spatial distributions of horizontal wave pressure, excess-pore-water pressure, mean flow velocity and mean vorticity on the upright caisson, and inside the rubble mound and seabed are discussed, as well as the relation between the mean distribution of vorticity size and mean turbulent kinetic energy. And the stability of composite breakwater are also discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.215-225
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• 2021

The purpose of this study was to empirically verify the correlation between the characteristics of safety officers and managers handling disaster and safety management, competence, and performance among disaster and safety work-level officers in medium-sized companies in South Korea. For this study, the researcher surveyed 509 disaster and safety management officers of various companies and analyzed the resultant data. The results of the analysis showed that, first, the characteristics of the safety officers handling the disaster and safety management systems had a significantly positive impact on performance. Second, the characteristics of the safety officers handling the disaster management systems had a significantly positive impact on competence. Third, the disaster and safety management competence of the safety officers had a significantly positive impact on performance. Fourth, in the relationship between the characteristics of the safety officers handling the disaster and safety management systems of businesses and their performance, the competence of the safety officers had a mediating effect.

• 한국노년학
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• v.36 no.4
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• pp.1141-1155
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• 2016

The purpose of this study was to compare the preventive effects of green tea and coffee drinking on postprandial hypotension in the elderly. A total of 30 women ($81.2{\pm}6.8years$) who had experience of postprandial hypotension participated 3 interventions by random order allocation. During the experimental interventions, each participant had a cup of instant coffee (60mg caffeine), or green tea (15.8mg caffeine) after lunch, and control group had only their lunch. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were measured with 15 minute interval from 30 minutes before the meal to 120 minutes after the meal. The preprandial SBP and DBP were not significantly different between three groups. Postprandial SBP reduction measured at the 1 hour after meal was significantly smaller in coffee group compared to the control group, whereas green tea group was not ($-15.1{\pm}17.9mmHg$ vs $-13.4{\pm}22.4mmHg$ vs. $-4.1{\pm}18.6mmHg$ for control, green tea, and coffee group, respectively, p=.032). Likewise, DBP decrement at the 1 hour after meal was significantly smaller in coffee than control group ($-12.8{\pm}13.0mmHg$ vs $-6.9{\pm}16.6mmHg$ vs $-0.8{\pm}13.4mmHg$ respectively, p=.033). The HR response of the three groups were not significantly different throughout the intervention. Coffee drinking was potentially beneficial for preventing postprandial hypotension and resultant falling event.

• Applied Chemistry for Engineering
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• v.32 no.1
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• pp.28-34
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• 2021

SiO2/Ag core-shell nanoparticles were synthesized by combining modified Stöber process and reverse micelle method using acetoxime as a reducing agent in water/dodecylbenzenesulfonic acid (DDBA)/cyclohexane reverse micells. The SiO2/Ag core-shells were studied for structure, morphology and size using UV-visible spectroscopy, XRD, SEM and TEM. The size of a SiO2/Ag core-shell could be controlled by changing the [water]/[DDBA] molar ratio (WR) values. The size and the polydispersity of SiO2/Ag core-shells increased with increase of the WR value. The resultant Ag nanoparticles exhibit a strong surface plasmon resonance (SPR) peak at 430 nm over the amorphous SiO2 nanoparticles. The SPR peak shifted to the red side with increase in nanoparticle size. Conductive pastes with 70 wt% SiO2/Ag core-shell were prepared, and the pastes were coated on the PET films using a screen-printing method. The printed paste film of the SiO2/Ag core-shell showed higher surface resistance than the commercial Ag paste in the range of 460~750 µΩ/sq.

• Economic and Environmental Geology
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• v.54 no.4
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• pp.475-482
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• 2021

This study proposed a strategy with literature review on effective monitoring of dispersion of the particulate matters (PM) emitted from domestic open pit lime mines. The mines generally produced a large amount of PM through the mine processes such as crushing and transportation of raw or crushed ores. The PM emission from mine facilities or transportation can be assessed using empirical equations which was prepared through the experimental tests to produce PM from ores. For effective monitoring of mine PM dispersion, this study showed a preliminary application of the monitoring network with multiple low-cost sensors around a main PM emission source for each mine site. Therefore, two domestic limestone mine sites were selected for this study, and install the monitoring network with low-cost PM sensors and LTE (Long-term evolution) data communication. Then, preliminary resultant PM data plotted according to monitoring duration showed typical PM dispersion patterns. The quantification of the PM dispersion patterns should be roughly prepared by a PM size-dependent dispersion modeling.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.6
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• pp.541-548
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• 2021

Recently, multispectral cameras are being actively utilized in various application fields such as agriculture, forest management, coastal environment monitoring, and so on, particularly onboard UAV's. Resultant multispectral images are typically georeferenced primarily based on the onboard GPS (Global Positioning System) and IMU (Inertial Measurement Unit)or accurate positional information of the pixels, or could be integrated with ground control points that are directly measured on the ground. However, due to the high cost of establishing GCP's prior to the georeferencing or for inaccessible areas, it is often required to derive the positions without such reference information. This study aims to provide a means to improve the georeferencing performance of a multispectral camera images without involving such ground reference points, but instead with the simultaneously onboard high resolution RGB camera. The exterior orientation parameters of the drone camera are first estimated through the bundle adjustment, and compared with the reference values derived with the GCP's. The results showed that the incorporation of the images from a high resolution RGB camera greatly improved both the exterior orientation estimation and the georeferencing of the multispectral camera. Additionally, an evaluation performed on the direction estimation from a ground point to the sensor showed that inclusion of RGB images can reduce the angle errors more by one order.

• Journal of the Korea Society for Simulation
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• v.31 no.1
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• pp.11-18
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• 2022

Recently, research to classify human activity using imagery has been actively conducted for the purpose of crime prevention and facility safety in public places and facilities. In order to improve the performance of human activity classification, most studies have applied deep learning based-transfer learning. However, despite the increase in the number of backbone network models that are the basis of deep learning as well as the diversification of architectures, research on finding a backbone network model suitable for the purpose of operation is insufficient due to the atmosphere of using a certain model. Thus, this study applies the transfer learning into recently developed deep learning backborn network models to build an intelligent system that classifies human activity using imagery. For this, 12 types of active and high-contact human activities based on sports, not basic human behaviors, were determined and 7,200 images were collected. After 20 epochs of transfer learning were equally applied to five backbone network models, we quantitatively analyzed them to find the best backbone network model for human activity classification in terms of learning process and resultant performance. As a result, XceptionNet model demonstrated 0.99 and 0.91 in training and validation accuracy, 0.96 and 0.91 in Top 2 accuracy and average precision, 1,566 sec in train process time and 260.4MB in model memory size. It was confirmed that the performance of XceptionNet was higher than that of other models.

• Journal of the Korea Institute of Building Construction
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• v.21 no.3
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• pp.181-188
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• 2021

In this study, the various performance of dry cement mortar for Korean floor heating system depending on water-to-dry mortar ratios (W/DM) applied in project site was evaluated. According to the experiment conducted, the importance of mixing water for dry cement mortar was revealed by resultant performance or quality of the dry cement mortar for floor finishing by changing W/DM controlled in project site by workers. As the general trend, the flow was increased, and the unit volume weight was decreased with increasing W/DM. Additionally, compressive strength and drying shrinkage were significantly influenced by W/DM. Hence, it can be stated that the adding water for dry cement mortar should be managed precisely since excessively increased W/DM for workability improvement can cause performance degradation of floor mortar with the failures such as excessive bleeding, and severe segregation during the fresh state. As a summary of the study, to achieve a desirable performance of dry cement mortar, approximately 20 % of W/DM can be suggested to be managed in project site.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.905-917
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• 2021

Atmospheric pollutant emissions, mainly exhaust gas emissions from vessels, and the resultant social costs of pollution in the Korean harbor cities of Incheon, Mokpo, Gwangyang, Busan and Ulsan, are examined in this study, and the need for an emissions reduction plan is highlighted. Busan had several vessels entering its port, while Mokpo had few vessels, yet the vessels emission contribution was high in both the cities. Ulsan had world-class heavy-chemical industries, Gwangyang had steel mills and Incheon had a manufacturing industry and more vessels entering its port than Mokpo, yet the emission contribution was low in these cities. By calculating exhaust gas emissions from the vessels, it was found that CO₂ was the highest, followed by NOx and SOx. By vessel type, Busan, Ulsan, and Incheon had more oil tank vessels, Gwangyang had more cargo vessels, and Mokpo had more ferries. As a result of social cost, Busan paid the highest, while the highest emission was PM. The use of low-sulfur oil can directly reduce PM and, SOx emissions and indirectly reduce NOx emissions. However, in order to reduce high CO₂ emissions, only low-sulfur oil will not help. Therefore, the study suggested the need for reduction plan that use of fossil fuels, by using alternative maritime power (AMP).