• Natural Product Sciences
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• v.24 no.1
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• pp.36-39
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• 2018

Phytochemical analysis of Boehmeria nivea (Bn) leaves by medium pressure liquid chromatography led to the isolation of a flavonoid glycoside identified by spectroscopic analysis as rutin. The amount of rutin in the leaves of Bn harvested from nine regions in South Korea (Bn 1-9) which were collected on the months of June, July, August, and September was determined by HPLC-UV analysis. A gradient elution program that utilizes a $Discovery^{(R)}$ C18 ($4.6{\times}250mm$, $5{\mu}m$) column and mobile phase composed of 1% acetic acid-water: acetonitrile (90:10 to 60:40 for min) was followed. The injection volume and flow rate were $10{\mu}l$ and 1 mL/ min, respectively. UV detection was set at 350 nm. Results show that Bn-8 harvested in September reported the highest content of rutin among the samples analyzed. This study provides a basis for the optimal harvest time of Bn which maximizes the yield of rutin.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.3
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• pp.95-104
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• 2007

This study was focused on the effect of concrete strength and lateral ties of concrete columns subjected to eccentric compressive loads. The twenty-four concrete columns with $200mm{\times}200mm$ square cross-section were tested. The main variables were concrete strength, spacing and configuration of lateral ties, and eccentricity ratios. From the experiment, the followings were investigated ; 1) In all cases, it was observed that the increase of concrete compressive strength led to the decrease of ductility. Also, as the eccentricity ratios increased, the effect of ductility enhancement by lateral ties decreased. 2) As the ties spacing decreased from 100mm to 30mm, the magnitude of axial load acting on the concrete column showed an enhancement of 1.1~1.2 times and the descending curve after a peak moment presented a smooth decline. 3) The high-strength concrete columns required a design of lateral ties to increase the volumetric ratios and density of tie spacing to sustain a proper strength and ductility. Accordingly, regardless of concrete strength, the current AIK design code to specify the maximum tie spacing of concrete columns was proven to lead to the poor strength and ductility for seismic design. Therefore, it is necessary to develop a new seismic design code that connects volumetric ratios and tie spacing of concrete columns with concrete strength.

• Journal of the Korea Organic Resources Recycling Association
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• v.24 no.2
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• pp.67-74
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• 2016

This study was purposed to evaluate the characteristic changes of the solidified livestock manure fuel(SLMF) through the application of compression treatment process. The compression process led to an increase of VS/TS ratio (Volatile solids/Total solids ratio) and moisture removal effect of SLMF. The amount of leachate withdrawn from dairy cattle manure and Hanwoo manure by compression were 21~26%(w/w) and 15~20%(w/w), respectively. The specific gravity of the leachate of dairy cattle manure and Hanwoo manure were 1.01 and 0.99, respectively. The dehydrated cow manure was easily processed into ball-shaped solidified fuel. The drying time of the SLMF was proportional to the diameter of the solidified fuel. The highest heating value was observed in diameter range of 10~15mm SLMF. It is concluded that the higher heating value of 10~15mm SLMF was related with the amount of fibrous matter contained in the SLMF.

• Progress in Medical Physics
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• v.18 no.2
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• pp.55-64
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• 2007

Our objective was to evaluate the clinical feasibility of spatial domain filtering as an alternative to additional image reconstruction using different kernels in CT. Kernels were grouped as H30 (head medium smooth), B30 (body medium smooth), S80 (special) and U95 (ultra sharp). Derived from thin coilimated source images, four sets of images were generated using phantom kernels. MTF (50%, 10%, 2%) measured with H30 (3.25, 5.68, 7.45 Ip/cm) B30 (3.84, 6.25, 7.72 Ip/cm), S80 (4.69, 9.49, 12.34 Ip/cm), and U95 (14.19, 20.31, 24.67 Ip/cm). Spatial resolution for the U95 kernel (0.6 mm) was 33.3% greater than that of the H30 and B30 (0.8 mm) kernels. Initially scanned kernels images were rated for subjective image qualify, using a five-point scale. Image scanned with a convolution kernel led to an increase in noise (U95), whereas the results for CT attenuation coefficient were comparable. CT images increase the diagnostic accuracy in head (H30), abdomen (B30), temporal bone and lung (U95) kernels may be controlled by adjusting CT various algorithms, which should be adjusted to take into account the kernels of the CT undergoing the examination.

• Korean Journal of Optics and Photonics
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• v.24 no.5
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• pp.224-230
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• 2013

Laser Lift-Off (LLO) is a process that removes a GaN or AIN thin layer from a sapphire wafer to manufacture vertical-type LEDs. It consists of a light source, an attenuator, a mask, a projection lens and a beam homogenizer. In this paper, we design an attenuator and a projection lens. We use the 'ZEMAX' optical design software for analysis of depth of focus and for a projection lens design which makes $7{\times}7mm^2$ beam size by projecting a beam on a wafer. Using the 'LightTools' lighting design software, we analyze the size and uniformity of the beam projected by the projection lens on the wafer. The performance analysis found that the size of the square-shaped beam is $6.97{\times}6.96mm^2$, with 91.8 % uniformity and ${\pm}30{\mu}m$ focus depth. In addition, this study performs dielectric coating using the 'Essential Macleod' to increase the transmittance of an attenuator. As a result, for 23 layers of thin films, the transmittance total has 10-96% at angle of incidence $45-60^{\circ}$ in S-polarization.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1200-1205
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• 2014

The effect of nanofluids on the heat transfer performance of a pulsating heat pipe has been experimentally investigated. Water-based diamond nanofluid and aluminium oxide ($Al_2O_3$) nanofluid were tested in the concentration range of 0.5-5%. The pulsating heat pipe was constructed using clear Pyrex tubes of 1.85 mm in inner diameter in order to visualize the pulsating action. The total number of turns was eight each for heated and cooled parts. The supply temperatures of heating water and cooling water were fixed at $80^{\circ}C$ and $25^{\circ}C$ respectively. The liquid charging ratio of the nanofluid was 50-70%. The test results showed that the case of 5% concentration of diamond nanofluid showed 18% increase in heat transfer rate compared to pure water. The case of 0.5% concentration of $Al_2O_3$ nanofluid showed 24% increase in heat transfer rate compared to pure water. But the increase of $Al_2O_3$ nanofluid concentration up to 3% did not show further enhancement in heat transfer. It is also observed that the deposited nanoparticles on the tube wall played a major role in enhanced evaporation of working fluid and this could be the reason for the enhancement of heat transfer by a nanofluid, not the enhanced thermal conductivity of the nanofluid.

• Journal of the Ergonomics Society of Korea
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• v.31 no.2
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• pp.397-406
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• 2012

Objective: The aim of this study is to determine legible Korean font sizes within in-vehicle information systems(IVISs) in diving conditions. Background: Font legibility within IVISs is one of important causes on its' safe operations during driving. Several researches proposed some guidelines on the legible English font sizes within IVISs. On the contrary, appropriate Korean font sizes have been hardly known in spite of the typological differences between English and Korean. Therefore, more systematic researches for improving the legibility on Korean font size within IVISs have been required. Method: In this study, an experiment was performed with the following experimental factors: the existence of vibration, the color contrasts(white on black, black on white), the font types(HDR, CubeR, Gothic), and the font sizes(6, 8, 10, 12, 14, 16, 18, 20, 22, 24pt). To fit the experimental conditions into real driving environments, the illuminance was controlled to 15lx by using LED lamp and the distance between IVIS and participants was kept to 70cm. Moreover, all participants took the shutter glasses for employing well-known occlusion techniques. Results: The experimental results showed that 'HDR' and 'Non-vibration + Black on white' group took the shortest response time, and decreasing slopes of the response time with increasing font sizes were slowing down at 14pt then flattened out at 22pt regardless of the existence of vibration and color contrasts. Conclusion: The minimum size for legible Korean font would be about 14pt(5.47mm) and the optimum size would be about 22pt(8.59mm). Application: The guideline on the Korean font sizes from this study will be applied to design an IVIS in the future.

• Korean Journal of Materials Research
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• v.26 no.3
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• pp.130-135
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• 2016

To alloy high melting point elements such as boron, ruthenium, and iridium with copper, heat treatment was performed using metal oxides of $B_2O_3$, $RuO_2$, and $IrO_2$ at the temperature of $1200^{\circ}C$ in vacuum for 30 minutes. The microstructure analysis of the alloyed sample was confirmed using an optical microscope and FE-SEM. Hardness and trace element analyses were performed using Vickers hardness and WD-XRF, respectively. Diffusion profile analysis was performed using D-SIMS. From the microstructure analysis results, crystal grains were found to have formed with sizes of 2.97 mm. For the copper alloys formed using metal oxides of $B_2O_3$, $RuO_2$, and $IrO_2$ the sizes of the crystal grains were 1.24, 1.77, and 2.23 mm, respectively, while these sizes were smaller than pure copper. From the Vickers hardness results, the hardness of the Ir-copper alloy was found to have increased by a maximum of 2.2 times compared to pure copper. From the trace element analysis, the copper alloy was fabricated with the expected composition. From the diffusion profile analysis results, it can be seen that 0.059 wt%, 0.030 wt%, and 0.114 wt% of B, Ru, and Ir, respectively, were alloyed in the copper, and it led to change the hardness. Therefore, we verified that alloying of high melting point elements is possible at the low temperature of $1200^{\circ}C$.

• Journal of Korean Dental Science
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• v.8 no.2
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• pp.49-56
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• 2015

Purpose: The effect of accelerated aging on color stability of various dual-cured self-adhesive resin cements were evaluated in this study. Materials and Methods: Color stability was examined using three different brands of dual-cured self-adhesive resin cements: G-CEM LinkAce (GC America), MaxCem Elite (Kerr), and PermaCem 2.0 (DMG) with the equivalent color shade. Each resin cement was filled with Teflon mold which has 6 mm diameter and 2 mm thickness. Each specimen was light cured for 20 seconds using light emitting diode (LED) light curing unit. In order to evaluate the effect of accelerated aging on color stability, color parameters (Commission Internationale de l'Eclairage, CIE $L^*$, $a^*$, $b^*$) and color differences (${\Delta}E^*$) were measured at three times: immediately, after 24 hours, and after thermocycling. The $L^*$, $a^*$, $b^*$ values were analyzed using Friedman test and ${\Delta}E^*$ values on the effect of 24 hours and accelerated aging were analyzed using t-test. These values were compared with the limit value of color difference (${\Delta}E^*=3.7$) for dental restoration. One-way ANOVA and Scheff's test (P<0.05) were performed to analyze each ${\Delta}E^*$ values between cements at each test period. Result: There was statistically significant difference in comparison of color specification ($L^*$, $a^*$, $b^*$) values after accelerated aging except $L^*$ value of G-CEM LinkAce (P<0.05). After 24 hours, color difference (${\Delta}E^*$) values were ranged from 2.47 to 3.48 and $L^*$ values decreased and $b^*$ values increased in all types of cement and MaxCem Elite had high color stability (P<0.05). After thermocycling, color change's tendency of cement was varied and color difference (${\Delta}E^*$) values were ranged from 0.82 to 2.87 and G-CEM LinkAce had high color stability (P<0.05). Conclusion: Color stability of dual-cured self-adhesive resin cements after accelerated aging was evaluated and statistically significant color changes occurred within clinically acceptable range.

• Journal of Life Science
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• v.24 no.6
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• pp.671-676
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• 2014

In recent years, the growing interest in the health care benefits of sugared-plant fermented enzymes has led to increased consumption. This study investigated the fermentation of sugared-buchu (Leek:sugar, 1:3) by lactic acid bacteria (Lactobacillus acidophilus AML 0422, Lactobacillus brevis HLJ 59, Lactobacillus helveticus AML0410, Lactobacillus plantarium KCTC 13093) and the antibacterial activity, antioxidant activity, and functionality (e.g., anti-hypertensive activity) of the fermented product. The fermented sugared-buchu showed high antibacterial activity against Staphylococcus aureus KCTC 1916, at 31.43 mm, and its total polyphenols, total flavonoid content, and DPPH scavenging activity were 160.8-178 mg/ml, 100-108 mg/ml, and 51.4-58.1%, respectively. DPPH scavenging activity was to that of vitamin C (50 ppm). ACE inhibitory activity was 50.4-67%, depending on the strain of lactic acid bacteria, and the control of sugared-buchu activity was higher than 32.6%. These results suggest that sugared-buchu fermented with lactic acid bacteria has strong antibacterial, antioxidant, and ACE inhibitory activities.