• Journal of Powder Materials
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• v.25 no.2
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• pp.99-103
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• 2018

Spherical monosized pure aluminum (Al) particles are successfully fabricated by the pulsated orifice ejection method (POEM). The surface reaction between Al and the graphite crucible is investigated by analysing the microstructure and chemical composition of the materials. No significant chemical reaction occurs between Al and the graphite owing to the crystalline Al oxide (${\gamma}-Al_2O_3$) layer generated in the initial state. The ${\gamma}-Al_2O_3$ layer is clearly observed in all regions between the Al particles and graphite via transmission electron microscopy and confirmed by the selected area diffraction pattern. The morphology of the ${\gamma}-Al_2O_3$ layer perfectly follows the surface morphology of the graphite crucible, which showed nanoscale roughness. This implies that molten Al could not directly contact graphite even though the surface of the crucible became rough to some extent. However, this passivation phenomenon allowed the successful fabrication of monosized pure Al particles. Therefore, POEM is a useful process at least to manufacture monosized pure Al particles.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.219-219
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• 2012

The formation and thermal desorption behaviors of octanethiol (OT) SAMs on single crystalline Au (111) and polycrystalline Au, Ag, and Cu substrates were examined by X-ray photoelectron microscopy (XPS), thermal desorption spectroscopy (TDS), and contact angle (CA) measurements. XPS and CA measurements revealed that the adsorption of octanethiol (OT) molecules on these metals led to the formation of chemisorbed self-assembled monolayers (SAMs). Three main desorption fragments for dioctyl disulfide (C8SSC8+, dimer), octanethiolate (C8S+), and octanethiol (C8SH+) were monitored using TDS to understand the effects of surface morphology and the nature of metal substrates on the thermal desorption behavior of alkanethiols. TDS measurements showed that a sharp dimer peak with a very strong intensity on single crystalline Au (111) surface was dominantly observed at 370 K, whereas a broad peak on the polycrystalline Au surface was observed at 405 K. On the other hand, desorption behaviors of octanethiolates and octanethiols were quite similar. We concluded that substrate morphology strongly affects the dimerization process of alkanethiolates on Au surfaces. We also found that desorption intensity of the dimer is in the order of Au＞＞Ag＞Cu, suggesting that the dimerization process occurs efficiently when the sulfur-metal bond has a more covalent character (Au) rather than an ionic character (Ag and Cu).

• Journal of Korean Dental Science
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• v.9 no.2
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• pp.49-54
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• 2016

Purpose: The purpose of this study was to assess the relationship between gingival biotype and underlying crestal bone morphology in the maxillary anterior region. Materials and Methods: The maxillary anterior teeth from 40 subjects (20 thin biotype, 20 thick biotype) with ages from 20 to 50 years were included in this study. All subjects had healthy gingiva in the maxillary anterior region and had no history of orthodontic treatment, periodontal treatment, or hyperplastic medication. Using the probe transparency method, the scalloped distance (SCD) between the contact point-bone crest and the midface-bone crest was measured for each maxillary anterior teeth of two groups. Result: The mean SCD was $3.00{\pm}0.21mm$ in thin biotype and $2.81{\pm}0.20mm$ in thick biotype. The SCD value in the thin biotype was statistically significantly greater than in the thick biotype (t=2.982, P<0.01). Comparing the degree of crestal bone scallop in each maxillary anterior teeth in the two groups, all six teeth in the thin biotype showed higher bone scallop than in the thick biotype. Conclusion: A simple procedure using a probe could to determine gingival biotype and to predict the underlying crestal bone morphology was introduced. This may be useful for effective treatment planning.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.120.2-120.2
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• 2015

We propose a novel direct writing technique with a femtosecond laser enabling selective modification of not only the morphology of conducting polymer thin films but also the orientation and alignment of the polymer crystal. Surface relief gratings resulting from photoexpansion on P3HT:PCBM and PEDOT:PSS thin films were fabricated by femtosecond laser direct writing. The photoexpansion was induced at laser fluence below the ablation threshold of the thin film. The morphology (size and shape) of photoexpansion could be quantitatively controlled by laser writing parameters such as focused beam size, writing speed, and laser fluence. GIWAX results showed that face-on P3HT crystals were largely increased in the photoexpansion in comparison with pristine region of the thin film. In addition, the face-on P3HTs in the photoexpansion were aligned with their orientation along the polarization of the laser. The micro-RAMAN spectra confirmed that neither chemical composition change nor the polymer chain breaking was observable after femtosecond laser irradiation. We believe that this laser direct writing technique opens a new door to the fabrication of more efficient OPVs via non-contact, toxic-free approach.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.65-69
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• 2003

The effects of grapefruit seed extract and $H_2O_2$ disinfectants on Pseudomonas aeruginosa were investigated by antimicrobial assay and scanning electron microscopy. Pseudomonas aeruginosa is a Gram negative bacteria and a common causative microorganism of bacterial keratitis. After incubation of soft contact lens in Pseudomonas aeruginosa suspension for 120 minutes containing the disinfectants, the grapefruit seed extract showed antimicrobial activity as good as the chemical disinfectant. The living rates of Pseudomonas aeruginosa in grapefruit seed extract and $H_2O_2$ disinfectants were $1{\times10^3CFU/m{\ell}$ and $0.5{\times}10^3CFU/m{\ell}$, respectively showing no major difference in the killing activity. However, the mechanisms of the antimicrobial activity were quite different as indicated by scanning electron microscopy of the bacterial surface morphology. Considering chemically or other toxins induced keratitis, the natural disinfectant isolated from grapefruit seed extract shows promising results as a soft contact lens disinfectant.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.3
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• pp.207-212
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• 2010

Purpose: Rigid gas permeable (RGP) contact lenses, based on fluorosilicone acrylate, were treated with plasma in air. Methods: The chemical compositions were analyzed by using X-ray photoelectron spectroscopy (XPS), the surface morphology and roughness of RGP contact lenses were observed by using atomic force microscopy (AFM), and the wettability changes were estimated by wetting angle measurement. Results: As the contact lenses were treated by the plasma, the F contents decreased significantly, and the O and Si contents increased on the surface. The number of oxygen-containing hydrophilic radicals (C-O and Si-O) increased greatly, the hydrophobic surface decreased, and the wetting angle increased. But the C-O bonds created with exchange of the fluorine did not increase a wettability. The surface compositions were not remarkably changed for the 6 months after plasma treatment, but the wetting angle increased again. Conclusions: It was considered that the improved wettability of the RGP contact lenses of high fluorine content after plasma treatment was affected by the activation of surface, the increase of Si-O, and the decrease of hydrophobic surface.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.18 no.1
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• pp.199-220
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• 2005

Objective : This study was performed to investigate the effects of Sophorae Radix and Coptidis Rhizoma-iontophoresis in allergic contact dermatitis. Methods : Contact hypersensitivity assay, video microscope, melanin-erythema levels, pH levels, hydration levels, WBC count, RBC count, neutrophil ratio, lymphocyte ratio and total IgE levels were measured. Results : At contact hypersensitivity assay, the right ear swellings in Sophorae Radix and Coptidis Rhizoma-iontophoresis group were decreased compared with control group, but have no statistical significance. At observation of skin morphologic change, many papules were seen in control group and keratins were seen in Sophorae Radix-iontophoresis group. At melanin levels, Sophorae Radix and Coptidis Rhizoma-iontophoresis groups showed no significant difference compared with control group. At pH levels, Sophorae Radix-iontophoresis group showed significant decreased with control group. At hydration levels, Sophorae Radix and Coptidis Rhizoma-iontophoreses groups showed to significant difference compared with control group. WBC count, RBC count and neutrophil ratio were significantly increased in Sophorae Radix and Coptidis Rhizoma-iontophoresis group compared with control group. Lymphocyte ratio and total IgE levels were significantly decreased in Sophorae Radix and Coptidis Rhizoma-iontophoresis groups compared with control group. At morphology of skin, inflammation was decreased and the thickness of epidermis was well preserved in Sophorae Radix and Coptidis Rhizoma-iontophoresis group. Conclusion : Sophorae Radix and Coptidis Rhizoma-iontophoresis had some anti-allergy, anti-inflammatory effects on allergic contact dermatitis, but had no effects on melanin-erythema levels, pH levels and hydration levels of skin.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.1 s.256
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• pp.139-144
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• 2007

This paper presents development of carbon nanotube (CNT) tip modified by focused ion beam (FIB) and experimental results in non-contact mode of atomic force microscopy (AFM) using fabricated tip. We used an electric field which causes dielectrophoresis, to align and deposit CNTs on a conventional silicon tip. The morphology of the fabricated CNT tip was then modified into a desired shape using focused ion beam. We measured anodic aluminum oxide sample and trench structure to estimate the performance of FIB-modified tip and compared with those of conventional Si tip. We demonstrate that FIB modified tip in non contact mode had superior characteristics than conventional tip in the respects of wear, image resolution and sidewall measurement.

• Clean Technology
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• v.11 no.3
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• pp.153-164
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• 2005

This study found a reliable evaluation for four kinds of pb-Free plating solutions and it's layers, through pure Sn, SnAg, SnBi and SnCu. These four kind of solutions are widely used to pb-Free plating. Hull-cell, Harring-blum, coverage, throwing power, current efficiency, stability, life-time, composition, hardness, roughness, abrasion, scratch, solderability, corrosion, contact angle, morphology, SIR(Surface insulation resistance) and Whisker test were experimented. Also, Using ICP, XRF, FE-SEM, EDS, temperature/humidity chamber, solderability tester, hardness tester, roughness tester, abrasion tester, salt spray tester, contact angle tester, SIR tester, and microscope. In this paper could be shown the systematic and various analysis for reliability about four kinds of pb-Free plating solutions, processes and it's deposit surface.

• Journal of The Korean Astronomical Society
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• v.49 no.3
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• pp.65-71
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• 2016

We obtain the first complete CCD light curves (LCs) of the contact binary AP UMi in the VRI bands and analyzed them by means of the PHOEBE code. A spotted model is applied to treat the asymmetry in the LCs. The LC morphology clearly shows the O'Connell effect and the solution shows an influence of star spots on both components. Such effect of star spots is common between the RS CVn and W UMa chromospherically active stars. Based on the obtained solution of the LCs we investigate the evolutionary state of the components and conclude that the system is a pre-intermediate contact binary (f = 0.29) with mass ratio q = 0.38, and it is an A-type W UMa system where the less massive secondary component is cooler than the more massive primary one.