• The Journal of Korean Academy of Prosthodontics
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• v.48 no.2
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• pp.122-127
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• 2010

Purpose: The objective of this study was to investigate the effects of calcium phosphate coated titanium implant surface on bone response and implant stability at early stage of healing period of 3 weeks and later healing period of 6 weeks. Material and methods: A total of 24 machined, screw-shaped implants (Dentium Co., Ltd., Seoul, Korea) which dimensions were 3.3 mm in diameter and 5.0 mm in length, were used in this research. All implants (n = 24), made of commercially pure (grade IV) titanium, were divided into 2 groups. Twelve implants (n = 12) were machined without any surface modification (control). The test implants (n = 12) were anodized and coated with thin film (150nm) of calcium phosphate by electron-beam deposition. The implants were placed on the proximal surface of the rabbit tibiae. The bone to implant contact (BIC) ratios was evaluated after 3 and 6 weeks of implant insertion. Results: The BIC percentage of calcium phosphate coated implants ($70.8{\pm}18.9%$) was significantly higher than that of machined implants ($44.1{\pm}16.5%$) 3 weeks after implant insertion (P = 0.0264). However, there was no significant difference between the groups after 6 weeks of healing (P > .05). Conclusion: The histomorphometric evaluation of implant surface revealed that; 1. After 3 weeks early healing period, bone to implant contact (BIC) percentage of calcium phosphate coated implants (70.8%) was much greater than that of surface untreated machined implants (44.1%) with P = 0.0264. 2. After 6 weeks healing period, however, BIC percentage of calcium phosphate coated implants group (79.0%) was similar to the machined only implant group (78.6%). There was no statistical difference between two groups (P = 0.8074). 3. We found the significant deference between the control group and experimental group during the early healing period of 3 weeks. But no statistical difference was found between two groups during the later of 6 weeks.

• Korean Journal of Remote Sensing
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• v.21 no.6
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• pp.445-456
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• 2005

The land surface parameters should be determined with sufficient accuracy, because these play an important role in climate change near the ground. As the surface reflectance presents strong anisotropy, off-nadir viewing results a strong dependency of observations on the Sun - target - sensor geometry. They contribute to the random noise which is produced by surface angular effects. The principal objective of the study is to provide a database of accurate surface reflectance eliminated the angular effects from MODIS 250m reflective channel data over Korea. The MODIS (Moderate Resolution Imaging Spectroradiometer) sensor has provided visible and near infrared channel reflectance at 250m resolution on a daily basis. The successive analytic processing steps were firstly performed on a per-pixel basis to remove cloudy pixels. And for the geometric distortion, the correction process were performed by the nearest neighbor resampling using 2nd-order polynomial obtained from the geolocation information of MODIS Data set. In order to correct the surface anisotropy effects, this paper attempted the semiempirical kernel-driven Bi- directional Reflectance Distribution Function(BRDF) model. The algorithm yields an inversion of the kernel-driven model to the angular components, such as viewing zenith angle, solar zenith angle, viewing azimuth angle, solar azimuth angle from reflectance observed by satellite. First we consider sets of the model observations comprised with a 31-day period to perform the BRDF model. In the next step, Nadir view reflectance normalization is carried out through the modification of the angular components, separated by BRDF model for each spectral band and each pixel. Modeled reflectance values show a good agreement with measured reflectance values and their RMSE(Root Mean Square Error) was totally about 0.01(maximum=0.03). Finally, we provide a normalized surface reflectance database consisted of 36 images for 2001 over Korea.

• Elastomers and Composites
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• v.35 no.1
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• pp.63-70
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• 2000

Zinc plated steel tire cords were subjected to RF plasma etching of argon, followed by plasma polymerization coating of acetylene or butadiene in order to enhance adhesion to rubber compounds. Plasma polymerization was carried out under optimized conditions of 10 W, 30 sec, 30 mTorr for acetylene and butadiene gas, while plasma etching was performed at 90W, 10min and 30mTorr. The adhesion of tire cords was evaluated via Tire Cords Adhesion Test (TCAT) and the failure surfaces of the tested samples were analyzed by SEM. Polymer coating by plasma polymerization was also characterized by FT-IR, Alpha-Step and dynamic contact angle analyzer in order to elucidate the adhesion mechanism.

• Elastomers and Composites
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• v.35 no.1
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• pp.53-62
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• 2000

Zinc plated steel tire cords were treated with RF plasma polymerization coating of acetylene or butadiene in order to enhance adhesion to rubber compounds. Plasma polymerization was carried out as a function of plasma power, treatment tune and gas pressure. In order to maximize adhesion, argon plasma etching was performed, with carrier gas such as argon, nitrogen and oxygen, while the adhesion of tire cords was evaluated via TCAT. Best results were obtained from a combination treatment of argon etching (90 W. 10 min, 30 mTorr) and acetylene plasma polymerization coating (10 W, 30 sec, 30 mTorr) with argon carrier gas (25/5:acetylene/argon). These samples exhibited a pull out force of 285N which is comparable to that obtained from the brass plated tire cords (290N).

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.733-737
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• 2012

This study reports the microfluidic preparation of monodisperse multiple emulsions using hydrodynamic control. To generate multiple emulsions, we fabricate a microfluidic capillary device based on co-flowing stream without any surface modification of microchannels. Based on the system, we can successfully generate multiple emulsions (W/O/W) using water containing 0.5 wt% Tween 20, n-hexadecane with 5 wt% Span 80, and 10 wt% poly (vinyl alcohol) (PVA) aqueous solution, respectively. Furthermore, we control the number of inner droplets by modulation of flow rate of inner fluid at fixed flow rate of middle and outer fluid. The multiple emulsions having precisely controlled inner droplets' size and number can be applicable for multiple chemical reactions as an isolated microreactor.

• Polymer(Korea)
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• v.39 no.1
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• pp.136-143
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• 2015

Poly(vinyl alcohol) (PVA) was grafted onto the multiwalled carbon nanotube (MWCNT) using ultrasound in water and modified MWCNT/PVA nanocomposite was prepared. Modified MWCNT had a good affinity with PVA matrix and showed improved dispersion state along with uniform properties. Therefore, the electrical percolation threshold was observed at 0.1 wt% MWCNT. 3.0 wt% modified MWCNT/PVA composite had 50% higher tensile strength, 430% higher elongation at break, and 100% greater modulus. Since the modified MWCNT acted as a nucleation agent, the crystallization temperature increased to $8.5^{\circ}C$ and the crystallinity increased to 11.5% at 5.0 wt% loading concentration.

• Korean Chemical Engineering Research
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• v.48 no.5
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• pp.574-582
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• 2010

In this study, the possibility of a quartz crystal micro-balance(QCM) modification of crystallization of L-Penicillamine and D-Penicillamine with a Vapor Diffused Molecular Assembly Technique and its application to the R-(-)-Mandelic acid and S-(+)- Mandelic acid measurement was investigated. The 3-dimensional structures of L-Penicillamine and D-Penicillamine on the surface of QCM were verified to be different from each other through QCM and AFM analyses. The D-Penicillamine modified QCM had specific recognition to the R-(-)-Mandelic acid, but L-Penicillamine modified QCM had no specificity to the R-(-)-Mandelic acid and S-(+)- Mandelic acid. From these results, it was known that the QCM could be modified with various selective meterials via VDMA, and the chiral isomer such as a Mandelic acid isomer could be detected by using a modified QCM.

• Journal of Adhesion and Interface
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• v.10 no.3
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• pp.148-153
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• 2009

An atmospheric plasma pre-treatment method was applied to PU foam, Leather (Action), Rubber to improve its adhesion using solvent and water soluble type pressure sensitive adhesion in atmospheric plate type reactor. In order to investigate the optimum reaction condition of plasma treatment, type of reaction gas (nitrogen), rate of gas flow (30~100 mL/min), and reaction time (0~30 s) were examined in a plate plasma reactor. The result of the surface modification with respect to the treatment procedure was characterized by using SEM. Due to a de-crease of the contact angle of various materials, the greatest adhesion strength was achieved at optimum condition such as flow rate of 100 mL/min, reaction time of 10 second for an atmospheric plasma treatment of the PU foam, EVA foam, Leather (Action) and Rubber also resulted in the improvement of the adhesion.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.65-72
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• 2014

Turbine rotor-pyrostarter coupled test was performed for the verification of thermo-structural suitability of a turbopump turbine. Newly developed solid propellant and design concept were used in pyrostarter development. In case of turbine rotor, rotor configuration modification and post EDM machining process are adopted in rotor manufacturing respectively for the thermal stress relief and the surface integrity improvement on the blade surfaces. In the test, combustion gas of pyrostarter was directly ejected from the nozzles and impinged on the stationary turbine rotor specimen through the identically shaped flow passage of turbopump. Three kind of thermal load - design to extreme condition - test were performed and no damages were found on the turbine rotor specimens.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.4
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• pp.172-178
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• 2007

Mica (muscovite) powders were synthesized by hydrothermal method (horizontal turning method). The hydrothermal conditions for the synthesis of mica were prepared by the ratio of $K_2O : Al(OH)_3 : SiO_2$ = 1 : 3 : 3 mol% as the starting materials with KOH (8 mol%) solution as the hydrothermal solvent and reaction temperature at $260^{\circ}C$ for 72hrs. The synthetic powder used for preparation of nano silver coated mica by vertical hydrothermal treatment. The hydrothermal conditions for the treated as nano silver coating were prepared by the synthetic powder as raw materials, triple distilled water ($0.5{\ell}$) solution as the hydrothermal solvent with nano silver sol (1,000 ppm) as the material of nano silver coating and reaction temperature at $160{\sim}260^{\circ}C$ for 72 hrs. After hydrothermal treatment, structural, judgment of nano silver coating and character of nano silver coated mica were examined by XRD, SEM, TEM-EDX and shake plask method.