• Journal of dental hygiene science
• /
• v.13 no.4
• /
• pp.487-492
• /
• 2013

This study aimed to illuminate the correlatives between the surface processing of Zirconia core and the shear bond strength. The specimens were made by precipitating for two minutes in color liquid and drying to produce a colored Zirconia core following the manufacturer's instructions. The specimens were divided into 4 subgroups according to the surface treatment-sandblasted+liner treatment, SLT group; sandblasted treatment, ST group; liner treatment, LT group; non treatment (control), NT group. The specimens were put on the device with regard to ISO/TS 11405, then tested the shear bond strength with 1 mm shearing speed per minute using the Instron multi-purpose tester. The collected data was analysed by one way ANOVA and t-test. After applying the liner and sandblast to the Zirconia core, shear bond strength value were SLT (23.19 MPa), ST (21.17 MPa), LT (20.53 MPa) and NT (16.46 MPa) in the order. There was a significant difference in the surface roughness between NT and ST group (p<0.001), and in the compressive shear bond strength between NT and SLT group (p<0.05). Therefore, sandblasted plus liner treatment on pre-sintered substructure increased the bond strength of veneering ceramic, compared with other surface treatments.

• The korean journal of orthodontics
• /
• v.36 no.6
• /
• pp.451-464
• /
• 2006

The purpose of this study was to search for an appropriate method of coating $TiO_2$ on orthodontic appliances. $TiO_2$ thin films were deposited on orthodontic wires and brackets using sol-gel, CVD (Chemical Vapor Deposition) and PE-CVD (Plasma Enhanced-CVD) methods. The roughness of $TiO_2$-coated surfaces was investigated via scanning electron microscope (SEM) and adhesive strength of $TiO_2$ thin films was measured by adhesive tape pull test. Methylene blue degradation test was carried out to evaluate the photocatalytic activity of $TiO_2$ and the corrosion resistance of $TiO_2$ thin films against fluoride solution was also analyzed by observing the surfaces of $TiO_2$-coated wires and brackets via SEM after immersion in sodium fluoride solution. Through the comparison of properties and photocatalytic activity of $TiO_2$ thin films according to the coating methods, the following results were obtained. Smoother surfaces of $TiO_2$ thin films were generated by CVD or PE-CVD methods than through the sol-gel method or the control. Adhesive strength of the $TiO_2$ thin films was highest in PE-CVD and gradually became lower in the order of CVD, then the sol-gel method. Photocatalytic activity of $TiO_2$ thin films on methylene blue was the highest in PE-CVD and gradually became lower in the order of CVD, then the sol-gel method. Corrosion resistance of $TiO_2$ thin films against fluoride solution was stronger in CVD and PE-CVD methods than in the sol-gel method. The results of this study suggest that the CVD or PE-CVD methods is more appropriate than the sol-gel method for $TiO_2$ coating on orthodontic wires and brackets.

• Journal of the Korean Magnetics Society
• /
• v.16 no.6
• /
• pp.283-286
• /
• 2006

We have studied the role of ${\alpha}-Al_{2}O_{3}$ buffer layer as a diffusion barrier in the Ba-ferrite/$SiO_{2}$ magnetic thin films for high-density recording media. In the interface of amorphous Ba-ferrite $(1900-{\AA}-thick)/SiO_{2}$ thin film during annealing, the interfacial diffusion started to occur at ${\sim}700^{\circ}C$. As the annealing temperature increased up to $800^{\circ}C$, the interfacial diffusion abruptly proceeded resulting in the high interface roughness and the deterioration of the magnetic properties. In order to control the interfacial diffusion at the high temperature, we introduced ${\alpha}-Al_{2}O_{3}$ buffer layer ($110-{\AA}-thick$) in the interface of Ba-ferrite/$SiO_{2}$ thin film. During the annealing of Ba-ferrite/${\alpha}-Al_{2}O_{3}/SiO_{2}$ thin film even at ${\sim}800^{\circ}C$, the interface was very smooth. The magnetic properties, such as saturation magnetization and intrinsic coercivity, were also enhanced, due to the inhibition of interfacial diffusion by the ${\alpha}-Al_{2}O_{3}$ buffer layer. Our study suggests that the ${\alpha}-Al_{2}O_{3}$ buffer layer act as a useful interfacial diffusion barrier in the Ba-ferrite/$SiO_{2}$ magnetic thin films.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.44 no.2
• /
• pp.191-200
• /
• 2018

In this study, we conducted research to find anti-wrinkle skin care ingredients from natural sources via the measurement of procollagen type 1 levels in the medium of normal human dermal fibroblast (NHDF) and found that a Nelumbo nucifera leave extract (NLE) was as the best effective ingredient. By the high performance liquid chromatography analysis, we confirmed isoquercitrin was one of the main compounds of NLE. Moreover, it also increased the procollagen type 1 production without cytotoxicity of NHDF. NLE and isoquercitrin exerted free radical scavenging activity. Especially, isoquercitrin exhibited strong intracellular antioxidant capacity in human skin-derived cells, HaCaT and NHDF. Finally, we performed clinical test for the inhibitory effect of NLE on skin wrinkle formation. A randomized study was conducted in 22 healthy female volunteers, aged between 30 and 65 yrs, with moderate to moderately severe facial wrinkles. Volunteer applied a 1.7% NLE cream (isoquercitrin 51 ppm) and a control cream at each facial side (left/right) twice daily for 8 weeks. The 1.7% NLE cream improved skin roughness through reducing the wrinkle of the craw's feet significantly without any skin side effect. Our results demonstrate that NLE and isoquercitrin can increase the collagen production and exert antioxidant activity. Therefore, we expect that the new non-toxic herbal extract, isoquercitrin-containing NLE will be interesting natural ingredient of cosmetics with anti-wrinkle efficacy.

• Resources Recycling
• /
• v.29 no.1
• /
• pp.25-34
• /
• 2020

Electrochemical Quartz Crystal microbalance is a tool that is capable of measuring nanogram-scale mass change on electrode surface. When applying alternating voltage to the quartz crystal with metal electrode formed on both sides, a resonant frequency by inverse piezoelectric effect depends on its thickness. The resonant frequency changes sensitively by mass change on its electrode surface; frequency increase with metal dissolution and decrease with metal deposition on the electrode surface. The relationship between resonant frequency and mass change is shown by Sauerbrey equation so that the mass change during metal dissolution can be measured in real time. Especially, it is effective in the case of reaction mechanism and rate studies accompanied by precipitation, volatilization, compound formation, etc. resulting in difficulties on ex-situ AA or ICP analysis. However, it should be carefully considered during EQCM experiments that temperature, viscosity, and hydraulic pressure of solution, and stress and surface roughness can affect on the resonant frequency. Application of EQCM was shown as a case study on leaching of platinum using aqueous chlorine for obtaining activation energy. A platinum electrode of quartz crystal oscillator with 1000 Å thickness exposed to solution was used as leaching sample. Electrogenerated chlorine as oxidant was purged and its concentration was controlled in hydrochloric acid solution. From the experimental results, platinum dissolution by chlorine is chemical reaction control with activation energy of 83.5 kJ/mol.

• Korean Journal of Materials Research
• /
• v.31 no.2
• /
• pp.75-83
• /
• 2021

To cope with automobile exhaust gas regulations, ISG (Idling Stop & Go) and charging control systems are applied to HEVs (Hybrid Electric Vehicle) for the purpose of improving fuel economy. These systems require quick charge/discharge performance at high current. To satisfy this characteristic, improvement of the positive electrode plate is studied to improve the charge/discharge process and performance of AGM(Absorbent Glass Mat) lead-acid batteries applied to ISG automotive systems. The bonding between grid and A.M (Active Material) can be improved by applying the Sand-Blasting method to provide roughness to the surface of the positive grid. When the Sand-Blasting method is applied with conditions of ball speed 1,000 rpm and conveyor speed 5 M/min, ideal bonding is achieved between grid and A.M. The positive plate of each condition is applied to the AGM LAB (Absorbent Glass Mat Lead Acid Battery); then, the performance and ISG life characteristics are tested by the vehicle battery test method. In CCA, which evaluates the starting performance at -18 ℃ and 30 ℃ with high current, the advanced AGM LAB improves about 25 %. At 0 ℃ CA (Charge Acceptance), the initial charging current of the advanced AGM LAB increases about 25 %. Improving the bonding between the grid and A.M. by roughening the grid surface improves the flow of current and lowers the resistance, which is considered to have a significant effect on the high current charging/discharging area. In a Standard of Battery Association of Japan (SBA) S0101 test, after 300 A discharge, the voltage of the advanced AGM LAB with the Sand-Blasting method grid was 0.059 V higher than that of untreated grid. As the cycle progresses, the gap widens to 0.13 V at the point of 10,800 cycles. As the bonding between grid and A.M. increases through the Sand Blasting method, the slope of the discharge voltage declines gradually as the cycle progresses, showing excellent battery life characteristics. It is believed that system will exhibit excellent characteristics in the vehicle environment of the ISG system, in which charge/discharge occurs over a short time.

• Atmosphere
• /
• v.32 no.2
• /
• pp.103-118
• /
• 2022

This study evaluates the simulated meteorological fields with a particular focus on the low-level wind, which plays an important role in air pollutants dispersion, under the varying synoptic environment. Additionally, the effects of subgrid-scale orography parameterization and improved topography/land-use data on the simulated low-level wind is investigated. The WRF model version 4.1.3 is utilized to simulate two cases that were affected by different synoptic environments. One case from 2 to 6 April 2012 presents the substantial low-level wind speed over the Korean peninsula where the synoptic environment is characterized by the baroclinic instability. The other case from 14 to 18 April 2012 presents the relatively weak low-level wind speed and distinct diurnal cycle of low-level meteorological fields. The control simulations of both cases represent the systematic overestimation of the low-level wind speed. The positive bias for the case under the baroclinic instability is considerably alleviated by applying the subgrid-scale orography parameterization. However, the improvement of wind speed for the other case showing relatively weak low-level wind speed is not significant. Applying the high-resolution topography and land-use data also improves the simulated wind speed by reducing the positive bias. Our analysis shows that the increased roughness length in the high-resolution topography and land-use data is the key contributor that reduces the simulated wind speed. The simulated wind direction is also improved with the high-resolution data for both cases. Overall, our study indicates that wind forecasts can be improved through the application of the subgrid-scale orography parameterization and high-resolution topography/land-use data.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
• /
• v.35 no.4
• /
• pp.63-74
• /
• 2022

Objectives : Skin aging is generally characterized by wrinkles, sagging, loss of elasticity roughness, pigmentation and dryness. This changes is caused by reducing the elements constituting the extracellular matrix contributing to the physiological properties of the skin, such as collagen fiber, elastic fiber, and hyaluronic acid. Adequate skin hydration is important to maintain normal skin function and reduce skin aging. The present study is objective to observe skin moisturizing effects of Unripe apple(UA, Immature fruit of Malus pumila Mill) in vivo and its underlying molecular mechanisms. Methods : ICR mice were orally administerd UA(100, 200 and 400mg/kg/day) for 8 weeks, and skin water contents and the expression of transforming growth factor (TGF)-𝛽1, ceramide, hyaluronan and collagen type I(COL1) were measured in dorsal back skin of the mice. Gene expression of hyaluronan synthase(HAS1, HAS2, HAS3), collagen synthase(COL1A1, COL1A2) and TGF-𝛽1 were also determined by realtime RT-PCR. Results : Skin water contents and the expression of TGF-𝛽1, ceramide, COL1 and hyaluronan were significantly increased in UA group(100, 200 and 400mg/kg/day) compared to vehicle control. The mRNA expression of HAS isoform(HAS1, HAS2, HAS3), COL1A1, COL1A2, and TGF-𝛽1 were also significantly increased by UA. Conclusions : UA has skin moisturizing effects and enhancement activities in skin function related components(COL1, hyaluronan, ceramide and TGF-𝛽1). These results suggested that UA can be a developing candidate for developing alternative skin protective agent or functional food ingredient.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.6B
• /
• pp.697-707
• /
• 2008

The grid-based KIneMatic wave STOrm Runoff Model (KIMSTORM) by Kim (1998) predicts the temporal variation and spatial distribution of overland flow, subsurface flow and stream flow in a watershed. The model programmed with C++ language on Unix operating system adopts single flowpath algorithm for water balance simulation of flow at each grid element. In this study, we attempted to improve the model by converting the code into FORTRAN 90 on MS Windows operating system and named as ModKIMSTORM. The improved functions are the addition of GAML (Green-Ampt & Mein-Larson) infiltration model, control of paddy runoff rate by flow depth and Manning's roughness coefficient, addition of baseflow layer, treatment of both spatial and point rainfall data, development of the pre- and post-processor, and development of automatic model evaluation function using five evaluation criteria (Pearson's coefficient of determination, Nash and Sutcliffe model efficiency, the deviation of runoff volume, relative error of the peak runoff rate, and absolute error of the time to peak runoff). The modified model adopts Shell Sort algorithm to enhance the computational performance. Input data formats are accepted as raster and MS Excel, and model outputs viz. soil moisture, discharge, flow depth and velocity are generated as BSQ, ASCII grid, binary grid and raster formats.

• Advances in nano research
• /
• v.13 no.5
• /
• pp.417-426
• /
• 2022

Bisphenol A (BPA) is one of the chemicals used in monomer epoxy resins and polycarbonate plastics. The surface-enhanced Raman spectroscopy (SERS) method is precise for identifying biological materials and chemicals at considerably low concentrations. In the present article, the substrates coated with gold nanoparticles have been studied to identify BPA and control the diseases caused by this chemical. Gold nanoparticles were made by a simple chemical method and by applying gold salt and trisodium citrate dihydrate reductant and were coated on glass substrates by a spin-coat approach. Finally, using these SERS substrates as plasmonic sensors and Raman spectroscopy, the Raman signal enhancement of molecular vibrations of BPA was investigated. Then, the molecular vibrations of BPA in some consumer goods were identified by applying SERS substrates as plasmonic sensors and Raman spectroscopy. The fabricated gold nanoparticles are spherical and quasi-spherical nanoparticles that confirm the formation of gold nanoparticles by observing the plasmon resonance peak at 517 nm. Active SERS substrates have been coated with nanoparticles, which improve the Raman signal. The enhancement of the Raman signal is due to the resonance of the surface plasmons of the nanoparticles. Active SERS substrates, gold nanoparticles deposited on a glass substrate, were fabricated for the detection of BPA; a detection limit of 10-9 M and a relative standard deviation (RSD) equal to 4.17% were obtained for ten repeated measurements in the concentration of 10-9 M. Hence, the Raman results indicate that the active SERS substrates, gold nanoparticles for the detection of BPA along with the developed methods, show promising results for SERS-based studies and can lead to the development of microsensors. In Raman spectroscopy, SERS active substrate coated with gold nanoparticles are of interest, which is larger than gold particles due to the resonance of the surface plasmons of gold nanoparticles and the scattering of light from gold particles since the Raman signal amplifies the molecular vibrations of BPA. By decreasing the concentration of BPA deposited on the active SERS substrates, the Raman signal is also weakened due to the reduction of molecular vibrations. By increasing the surface roughness of the active SERS substrates, the Raman signal can be enhanced due to increased light scattering from rough centers, which are the same as the larger particles created throughout the deposition by the spin-coat method, and as a result, they enhance the signal by increasing the scattering of light. Then, the molecular vibrations of BPA were identified in some consumer goods by SERS substrates as plasmonic sensors and Raman spectroscopy.