• Journal of Adhesion and Interface
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• v.21 no.4
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• pp.129-134
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• 2020

Understanding charge trapping at the interface between conjugated semiconductor and polymer dielectric basically gives insight into the development of long-term stable organic field-effect transistors (OFET). Here, the charge transport properties of OFETs using polymer dielectric with various molecular weights (MWs) have been investigated. The conjugated semiconductor, pentacene exhibited morphology and crystallinity, insensitive to MWs of polymethyl methacrylate (PMMA) dielectric. Consequently, transfer curves and field-effect mobilities of as-prepared devices are independent of MWs. Under bias stress in humid environment, however, the drain current decay as well as transfer curve shift are found to increase as the MW of PMMA decreases (MW effect). The charge trapping induced by MW effect is irreversible, that is, the localized charges are difficult to be delocalized. The MW effect is caused by the variation in the density of polymer chain ends in the PMMA: the free volumes at the PMMA chain ends act as charge trap sites, corresponding to drain current decay depending on MWs of PMMA.

• Journal of Aerospace System Engineering
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• v.15 no.1
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• pp.102-110
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• 2021

Recently, multi-copters equipped with various collision avoidance sensors have been introduced to improve flight stability. LiDAR is used to recognize a three-dimensional position. Multiple cameras and real-time SLAM technology are also used to calculate the relative position to obstacles. A three-dimensional depth sensor with a small process and camera is also used. In this study, a small collision-avoidance multi-copter system capable of in-door flight was developed as a platform for the development of collision avoidance software technology. The multi-copter system was equipped with LiDAR, 3D depth sensor, and small image processing board. Object recognition and collision avoidance functions based on the YOLO algorithm were verified through flight tests. This paper deals with recent trends in drone collision avoidance technology, system design/manufacturing process, and flight test results.

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.139-144
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• 2022

This study reports a microfluidic approach to produce monodisperse hydrogel microparticles in a simple and highly efficient manner. Specifically, we produce double emulsion drops with a thin oil shell surrounding an aqueous prepolymer solution, which is solidified via UV-induced free radical polymerization. When they are dispersed in an aqueous solution, the oil shell is dewetted due to the absence of surfactants, resulting in production of highly uniform hydrogel microparticles (C.V.=1%). Results show that production of monodisperse hydrogel microparticles with controllable size and composition can be achieved with minimal use of oil unlike water-in-oil (w/o) single emulsion-based approach. Furthermore, in-depth study of flow patterns in microfluidic device using a phase diagram exhibits a crucial relationship among relative flow rates while providing windows of readily controllable parameters for reliable manufacturing of hydrogel microparticles.

• Journal of Korea Port Economic Association
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• v.38 no.4
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• pp.187-198
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• 2022

This study attempted to examine whether the spread of infectious diseases and quarantine measures such as border blockade and restrictions on movement due to the global spread of the COVID-19 pandemic is the cause of a decrease in product trade. To this end, a gravity model analysis was conducted using commodity trade statistics from Korea and major trading partners. As a result of the analysis, it was empirically confirmed that in 2020, the time of the spread of COVID-19, the influence of the COVID-19 pandemic was an obstacle to reducing Korea's trade. However, in the case of 2021, it was not possible to confirm whether the impact of the pandemic had a significant effect on commodity trade. As the impact of the COVID-19 pandemic in 2020 and 2021 is different, the commodity trade situation in 2022 when the COVID-19 epidemic is stably managed is also likely to change. Since factors such as response to COVID-19 and the spread of vaccines vary from country to country, it is thought that such various factors should be fully considered in the process of establishing policies to end the COVID-19 era

• Journal of the Korean Geotechnical Society
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• v.22 no.12
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• pp.77-88
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• 2006

A series of model tests were performed to investigate the ground deformation during trench excavation for diaphragm walls. An apparatus was manufactured to observe the failure pattern of a slurry-supported trench in sandy ground. Ground deformations including settlement and lateral displacement of the surrounding ground adjacent to the trench were carefully monitored during excavation. Experimental observations indicated that the settlement of the adjacent ground increased with closing to the trench. Especially, the considerable settlement occurred at the distance which was equal to 40% of the excavation depth. And, the higher settlement was obtained when the relative density of ground was looser and the ground water table was higher. Also, the lateral wall face of excavated trench was bulged with lowering the slurry level In stages and then the upper part of trench failed finally. The envelope of ground surface settlement could be represented as a hyperbolic line and the measured settlement was smaller than those predicted by Clough and O'Rourke (1990).

• Journal of the Korean Geotechnical Society
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• v.38 no.2
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• pp.5-13
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• 2022

The unsaturated behavior of sandy silt (SM soil) was investigated experimentally. Special attention was given to the stress-strain behavior of unsaturated weathered soil (SM) prior to failure and behavior at failure under monotonic loading. A sandy silt (SM) weathered soil containing a certain amount of fine contents distributed in Korea, was chosen to form samples with different densities of Dr=25%, 60%, and 75%. and matric suctions. The isotopically Consolidated Drain test (CD-test) was performed to maintain a constant matric suction during the shearing process. Based on the experimental results, it was qualitatively identified that the higher the relative density, the greater the virtual friction angle (ϕ^b) value and AEV (Air Entry Value) were induced. Also it is found that the internal friction angle (ϕ') is more or less constant. even if the matric suction is increased.

• Analytical Science and Technology
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• v.21 no.1
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• pp.14-19
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• 2008

Among the many odor materials, aldehyde has bad influences not only on human nose, but also on human health. Aldehyde has a strong odor at infinitesimal level, such as down to ppt concentration. Also aldehydes are highly reactive and have poor stability. Therefore, manufacture of standard gases, analysis of aldehydes are very difficult compare to other air pollution analysis. Aldehyde CRM containing 4 different aldehydes at $10{\mu}mol/mol$ (ppm) is developed by using gravimetry method according to ISO 6142 guide. The standard gases were reproduced again, and examined its reproducibility of preparation by GC-FID. The developed aldehyde CRM's certified value showed a relative expanded uncertainties of 2.11 % (95 % of confidence level, k=2).

• Economic and Environmental Geology
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• v.46 no.4
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• pp.339-344
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• 2013

Water vapor isotopes can be excellent tools for understanding complex mechanisms in the water cycle and atmospheric hydrological cycle and they can be applied to various fields of paleoclimatology, atmospheric science, hydrogeology, oceanography, and ecohydrology. Thus, studies of global or local transport of water vapor may be able to provide a very useful clue to better understand the movements of water and energy in the atmosphere, hydrosphere and biosphere. In this study, the isotopic compositions of water vapor have been observed for moisture transport during the passage of Typhoon Bolaven at Korea Polar Research Institute (KOPRI), Incheon, in the western part of Korea, from August 27 to August 29, 2012. In the clear sky, the isotopic compositions of water vapor at KOPRI exhibited relatively higher isotopic ratios, which were near isotopic equilibrium with sea surface water (${\delta}^{18}O$=-14‰). On the other hand, a largely depleted isotopic ratios in surface water vapor were observed in association with the passage of Typhoon Bolaven (approximately 10‰ depleted compared to the clear sky). The fact that the isotopic minima in water vapor are encountered during the onset period of the Typhoon Bolaven with increases of relative humidity, which is consistent with, so called, "the amount effect".

• Journal of the Korean Chemical Society
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• v.40 no.8
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• pp.542-548
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• 1996

Electrodes modified with threonine, methionine and serine as ligands, which are incorporated by ion exchange into a polycationic film of electropolymerized $[Ru(v-bpy)_3]^{2+}$, have been employed in the determination of mercury in solution. The redox response of the surface-immobilized mercury/ligand complex was used as the analytical signal. When the polymeric film was electropolymerized, the supporting electrolytes were TBAP and $KPF_6$ to compare the morphology and anodic stripping of resulted polymer electrodes. At the case of the latter, the film had high porosity to give an easy incorporation of dopant anions into polymeric film matrix and a high sensitivity in determination of mercury ion. Especially, this polymer modified electrode exhibited possibility of multiple use in mercury determination over ten times. In all cases, calibration curves which were plotted by log of the surface coverage-normalized redox response vs. log[Hg] exhibited an excellent correlation (r=0.99) for mercury concentrations ranging from 1.0{\times}10^{-8}{\sim}1.0{\times}10^{-2}M$. At these curves relative standard deviation was 5∼8% and saturation response was not observed at high concentration region. Serine of the employed ligands had the best sensitivity in analytical application, which had greater stability constant in forming a complex with mercury than others as $pK_{Hg}=8.54$. The formation constants of threonine and methionine were respectively 7.04 and 7.80.

• Journal of Life Science
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• v.28 no.2
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• pp.170-175
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• 2018

Parkinson's disease (PD) is the most common movement disorder and the second most common neurodegenerative disease after Alzheimer's disease. Approximately 5~10% of PD patients are familial PD cases. Leucine-rich repeat kinase 2 (LRRK2) has been known to be a causal gene of PD when it is mutated. LRRK2 contains the functional kinase and GTPase domains as well as leucine-rich repeat (LRR) and WD40 domains that are known to play critical roles for protein-protein interaction, suggesting that LRRK2-interacting proteins are important regulators for PD pathogenesis. In an effort to identify proteins interacting with LRRK2, we carried out co-immunoprecipitation of LRRK2 antibody using extracts of NIH3T3 cells that express LRRK2 at a relatively high level. The mass spectrometry analysis of a precipitated band revealed that the co-precipitated band was methionyl-tRNA synthetase (MRS), an ancient enzyme that transfers methionin to its cognate tRNA. The interaction of MRS with LRRK2 was confirmed again by co-immunoprecipitation of endogenous proteins and GST pull-down assays. However, LRRK2 did not phosphorylate recombinant MRS protein in in vitro kinase assays, and over-expression of LRRK2 or MRS did not affect the stability of its partner protein. Our data indicate that LRRK2 interacts with but does not phosphorylate MRS, and the stability of each partner is not affected by the other.