• Polymer(Korea)
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• v.37 no.6
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• pp.744-752
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• 2013

The miscibility between poly(L-lactide) (PLLA) and poly(methyl methacrylate) (PMMA) was investigated using thermal analyses for the purpose of developing birefringence-free material at oriented state. The effect of methyl acrylate (MA) units as comonomer of PMMA on the miscibility was also studied. All the blends prepared in this study show composition-dependent single $T_g$'s between those of blend components and high transparency over the visible region, indicating the miscibility at molecular level and no discernible effect of MA units on it. No phase separation was observed at elevated temperature of $280^{\circ}C$, higher than the degradation of PLLA and PMMA. The interaction energy density in PLLA/PMMA blends with 17 mol% of MA was measured to be $-0.74J/cm^3$ from the equilibrium melting temperature depression based on the Hoffman-Weeks method. The blends show zero-${\Delta}$n behavior at a specific mixing ratio and the drawing ratio of 3 due to compensation of intrinsic orientation birefringence. Birefringence dispersion of PLLA/PMMA5 blends was also measured to examine the possibility for quarter-wave plates or polarizer protective films.

• Geophysics and Geophysical Exploration
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• v.8 no.1
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• pp.26-33
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• 2005

Inversion of multi-mode surface-wave phase velocity for shallow engineering site investigation has received much attention in recent years. A sensitivity analysis and inversion of both synthetic and field data demonstrates the greater effectiveness of this method over employing the fundamental mode alone. Perturbation of thickness and shear-wave velocity parameters in multi-modal Rayleigh wave phase velocities revealed that the sensitivities of higher modes: (a) concentrate in different frequency bands, and (b) are greater than the fundamental mode for deeper parameters. These observations suggest that multi-mode phase velocity inversion can provide better parameter discrimination and imaging of deep structure, especially with a velocity reversal, than can inversion of fundamental mode data alone. An inversion of the theoretical phase velocities in a model with a low velocity layer at 20 m depth can only image the soft layer when the first higher mode is incorporated. This is especially important when the lowest measurable frequency is only 6 Hz. Field tests were conducted at sites surveyed by borehole and PS logging. At the first site, an array microtremor survey, often used for deep geological surveying in Japan, was used to survey the soil down to 35 m depth. At the second site, linear multichannel spreads with a sledgehammer source were recorded, for an investigation down to 12 m depth. The f-k power spectrum method was applied for dispersion analysis, and velocities up to the second higher mode were observed in each test. The multi-mode inversion results agree well with PS logs, but models estimated from the fundamental mode alone show f large underestimation of the depth to shallow soft layers below artificial fill.

• The Journal of the Acoustical Society of Korea
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• v.40 no.5
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• pp.408-416
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• 2021

In the ultrasonic dispersion, in order to avoid direct contact of the radiation surface of ultrasonic transducers with a liquid sample, the liquid sample is separated by a glass container and it receives ultrasonic energy through an acoustic medium. The transmission efficiency of the ultrasonic energy in the multi-layered ultrasonic system is an important factor. In this study, we suggested a method that can improve the ultrasonic energy transfer efficiency by using a propylene glycol solution as a liquid matching layer in the multi-layered acoustic system. In this method, a propylene glycol solution was filled between the Langevin-type ultrasonic transducer and the luminol solution and the sonoluminescence phenomena in the luminol solution, which is caused by nonlinear effect of high power ultrasound radiated from the transducer, was examined by using a Photo Multiplier Tube (PMT). The transmission efficiency depending on the concentration of propylene glycol solution was observed, and we can see that as the concentration of the propylene glycol solution increased, the matching effect increased while the acoustic attenuation increased. It was confirmed that there is an optimal concentration compromised these two conflicting conditions, and the optimum concentration of the propylene glycol solution was determined experimentally.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.2
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• pp.371-378
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• 2021

In this study, in order to analyze the spatial distribution of cold water occurred in the Southeast Sea of Korea, the K-means clustering method was used to analyze the ocean observatory buoy of Gori and Yangpo and GHTSST Level 4 from 2016 to 2018. The buoy data was used to identify the change in sea water temperature and the cold water occurrence at Gori and Yangpo in the Southeast Sea. As a result, the sea water temperature of Gori and Yangpo decreased equally at the cold water occurrence. Therefore, the reciprocal of the sea water temperature and the variance of SST were compared to see the changes of SST when the cold water occurs. When the reciprocal of the sea water temperature increases, the dispersion of SST also increases. Through this, it can be seen that there is a change in the water temperature distribution of SST in the sea when the cold water occurs. After that, K-means clustering was used to classify the cold water. After analyzing the optimal K value for clustering by using the Elbow method, it was possible to classify a region with cold water. Through this, it is estimated that the spatial distribution and diffusion range of the cold water, and it can be estimated and used in future studies to identify damage caused by the cold water and predict spatial spread.

• Applied Chemistry for Engineering
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• v.22 no.2
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• pp.167-172
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• 2011

In this work, the effect of surface treatment on mesoporous carbons (MCs) supports was investigated by analyzing surface functional groups. MCs were prepared by a conventional templating method using mesoporous silica (SBA-15) for using catalyst supports in direct methanol fuel cells (DMFCs). The MCs were treated with different phosphoric acid ($H_3PO_4$) concentrations i.e., 0, 1, 3, 4, and 5 M at 343 K for 6 h. And then Pt-Ru was deposited onto surface treated MCs (H-MCs) by chemical reduction method. The characteristics of Pt-Ru catalysts deposited onto H-MCs were determined by specific surface area and pore size analyzer, X-ray diffraction, X-ray photoelectron, transmission electron microscopy, and inductive coupled plasma-mass spectrometer. The electrochemical properties of Pt-Ru/H-MCs catalysts were also analyzed by cyclic voltammetry experiments. From the results of surface analysis, an oxygen functional group was introduced to the surface of carbon supports. From the results, the H4M-MCs carbon supports surface treated with 4 M $H_3PO_4$ led to uniform dispersion of Pt-Ru onto H4M-MCs, resulting in enhancing the electro-catalytic activity of Pt-Ru catalysts.

• Clean Technology
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• v.26 no.4
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• pp.304-310
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• 2020

In order to apply a photocatalyst (TiO2) to various building materials, TiO2-mayenite was prepared in this study. The TiO2 was synthesized using the sol-gel method by fixing titanium isopropoxide (TTIP) and urea at a ratio of 1 : 1. Later, they were calcined in a temperature range of 400-700 ℃ to analyze the properties according to temperature. BET, TGA, and XRD were used to analyze the physical and chemical properties of TiO2. The nitrogen oxide removal test was confirmed by measuring the change in the concentration of NO for 1 h according to KS L ISO 22197-1. The prepared TiO2 samples exhibited an anatase crystal structure below 600 ℃, and TiO2 (urea)-400 showed the highest nitrogen oxide removal rate at 2.35 µmol h-1. TiO2-mayenite was prepared using two methods: spraying TiO2 dispersion solution (s/s) and sol-gel solution (g/s). Through BET and XRD analysis, it was found that 5-TiO2 (g/s) prepared by spraying a sol-gel solution has maintained its crystallinity even after heat treatment. Also, 5-TiO2 (g/s)-500 showed the highest removal rate of 0.55 µmol h-1 in the nitrogen oxide removal test. To prepare TiO2-mayenite, it was confirmed that mayenite should be blended with TiO2 in a sol-gel state to maintain the crystal structure and exhibit a high nitrogen oxide removal rate.

• Journal of Ginseng Research
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• v.45 no.2
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• pp.228-235
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• 2021

Backgroud: Ginsenoside compound K (GK) is a major metabolite of protopanaxadiol-type ginsenosides and has remarkable anticancer activities in vitro and in vivo. This work used an ionic cross-linking method to entrap GK within O-carboxymethyl chitosan (OCMC) nanoparticles (Nps) to form GK-loaded OCMC Nps (GK-OCMC Nps), which enhance the aqueous solubility and stability of GK. Methods: The GK-OCMC Nps were characterized using several physicochemical techniques, including x-ray diffraction, transmission electron microscopy, zeta potential analysis, and particle size analysis via dynamic light scattering. GK was released from GK-OCMC Nps and was conducted using the dialysis bag diffusion method. The effects of GK and GK-OCMC Nps on PC3 cell viability were measured by using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay. Fluorescent technology based on Cy5.5-labeled probes was used to explore the cellular uptake of GK-OCMC Nps. Results: The GK-OCMC NPs had a suitable particle size and zeta potential; they were spherical with good dispersion. In vitro drug release from GK-OCMC NPs was pH dependent. Moreover, the in vitro cytotoxicity study and cellular uptake assays indicated that the GK-OCMC Nps significantly enhanced the cytotoxicity and cellular uptake of GK toward the PC3 cells. GK-OCMC Nps also significantly promoted the activities of both caspase-3 and caspase-9. Conclusion: GK-OCMC Nps are potential nanocarriers for delivering hydrophobic drugs, thereby enhancing water solubility and permeability and improving the antiproliferative effects of GK.

• Journal of Environmental Impact Assessment
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• v.32 no.4
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• pp.203-213
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• 2023

The AERMOD model was the most used, accounting for 89.0%, based on the analysis of the environmental impact assessment reports published in the Environmental Impact Assessment Information Support System (EIASS) between 2021 and 2022. The mismatch of versions between AERMET and AERMOD was found to be 25.3%. There was the operational time discrepancy of 50.6% from industrial complexes, urban development projects between used in the model and applied in estimating pollutant emissions. The results of applying various versions of the AERMET and AERMOD models to both area sources and point sources in both simple and complex terrain in the Gunsan area showed similar values after AERMOD version 12 (15181). Emissions are assessed as 24-hour operation, and the predicted concentration in both simple and complex terrain when using the variable emission coefficient option that applies an 8-hour daytime operation in the model is lowered by 37.42% ~ 74.27% for area sources and by 32.06% ~ 54.45% for point sources. Therefore, to prevent the error in using the variable emission coefficient, it is required to clearly present the emission calculation process and provide a detailed explanation of the composition of modeling input data in the environmental impact assessment reports. Also, thorough reviews by special institutions are essential.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.1
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• pp.8-15
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• 2024

The CaF₂ single crystal has notable characteristics such as a large band gap (12 eV), excellent transparency over a wide wavelength range, low refractive index and dispersion. Due to these outstanding properties, CaF₂ single crystal has considered as a promising material for short-wavelength light sources in recent lithography processes. However, there is an inherent birefringence of the material at 157 nm and the resulting aberration can be compensated for through the combination of the (100) plane and the (111) plane. Therefore, it is necessary to investigate the characteristics according to the plane. In this study, we analyzed crystallinity, optical properties of commercial CaF₂ single crystal wafers grown by the Czochralski method. In particular, through chemical etching under various conditions, it was confirmed that the shape of etch pits appears differently depending on the plane and the shape and array of specific etch pits affected by dislocations and defects were examined.

• Korean Journal of Environment and Ecology
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• v.31 no.6
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• pp.485-491
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• 2017

This study examined the germination characteristics by collecting fruits and pretreatment of the diaspore from April 2014 to June 2015 to investigate the diaspore characteristics, seed dispersion, and seed germination characteristics of two myrmecochorous spring ephemerals (MCSE): -Jeffersonia dubia (Jb) and Corydalis remota (Cr)-. The diaspore of Jb was about 5mm-long yellow-dark brown, oblong seeds with the attached amorphous white elaiosome. The mean weights of diaspore, seed, and elaiosome were 15.86mg, 13.46mg, and 2.40mg, respectively, and the elaiosome ratio was 15.13%. The diaspore of Cr was about 1.2mm diameter and glossy black ovoid seeds with the attached white spatula-shaped elaiosome. The mean weights of diaspore, seed, and elaisome were 2.58mg, 2.05mg, and 0.53mg, respectively, and the elaiosome ratio was 20.54%. Camponotus niponensis and Formica japonica transported the diaspore of Jb while Formica japonica and Lasius japonicus transported the diaspore of Cr. The germination percentage of Jb seeds was statistically significant and had the significance level of 1% with the pretreatment and date of sowing. However, it was independent of attachment of elaiosome. The mean germination percentages of Jb seeds was 65.0% during sowing on June 20, 17.5% during sowing on August 19, and 0% during sowing on October 20. The germination percentage of Cr was statistically significant and had the significance level of 5% and 1% with the attachment of elaisome and date of sowing, respectively. The mean germination rates were 54.17% and 35.0% in the non-treatment section and the treatment section with elaisome detached, respectively. The mean germination percentages of Cr seeds was 75.0% during sowing on June 20, 53.75% during sowing on August 19, and 5.0% during sowing on October 20. Considering the fact that the ants transported the diaspores to the ant house when the fruits of MCSE were ripened and dropped the seeds, the direct seeding right after collecting may be most suitable to the characteristics of the evolution of these plant species and may be the best method to obtain the highest germination percentages. Since the ants distribute their seeds, the MCSE produces and attaches the elaiosome to the seed to maintain the symbiotic relationship with ants. The ants then transport the seed to the ant house where the environment is controlled for suitable temperature and humidity, and then the MCSE succeeds in germination after the embryo grows sufficiently in the next spring.