• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.6
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• pp.465-474
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• 2014

To validate the accuracy of the boiling heat flux partitioning model, an experiment was performed to investigate how the wall heat flux is divided into the three heat transfer modes of evaporation, quenching, and single-phase convection during subcooled nucleate boiling on a vertical wall. For the experimental partitioning of the wall heat flux, the wall heat flux and liquid-vapor distributions were simultaneously obtained using synchronized infrared thermometry and the total reflection technique. Boiling experiments of water with subcooling of $10^{\circ}C$ were conducted under atmospheric pressure, and the results obtained at the wall superheat of $12^{\circ}C$ and average heat flux of $283kW/m^2$were analyzed. There was a large difference in the heat flux partitioning results between the experiment and correlation, and the bubble departure diameter and bubble influence factor, which account for a portion of the surrounding superheated liquid layer detached by the departure of a bubble, were found to be important fundamental boiling parameters.

• Journal of Korean Dental Science
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• v.10 no.1
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• pp.10-21
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• 2017

Purpose: The purpose of this study was to investigate the electrochemical characteristics of nanotubular Ti-25Nb-xZr ternary alloys for dental implant materials. Materials and Methods: Ti-25Nb-xZr alloys with different Zr contents (0, 3, 7, and 15 wt.%) were manufactured using commercially pure titanium (CP-Ti), niobium (Nb), and zirconium (Zr) (99.95 wt.% purity). The alloys were prepared by arc melting in argon (Ar) atmosphere. The Ti-25Nb-xZr alloys were homogenized in Ar atmosphere at $1,000^{\circ}C$ for 12 hours followed by quenching into ice water. The microstructure of the Ti-25Nb-xZr alloys was examined by a field emission scanning electron microscope. The phases in the alloys were identified by an X-ray diffractometer. The chemical composition of the nanotube-formed surfaces was determined by energy-dispersive X-ray spectroscopy. Self-organized $TiO_2$ was prepared by electrochemical oxidation of the samples in a $1.0M\;H_3PO_4+0.8wt.%$ NaF electrolyte. The anodization potential was 30 V and time was 1 hour by DC supplier. Surface wettability was evaluated for both the metallographically polished and nanotube-formed surfaces using a contact-angle goniometer. The corrosion properties of the specimens were investigated using a 0.9 wt.% aqueous solution of NaCl at $36^{\circ}C{\pm}5^{\circ}C$ using a potentiodynamic polarization test. Result: Needle-like structure of Ti-25Nb-xZr alloys was transform to equiaxed structure as Zr content increased. Nanotube formed on Ti-25Nb-xZr alloys show two sizes of nanotube structure. The diameters of the large tubes decreased and small tubes increased as Zr content increased. The lower contact angles for nanotube formed Ti-25NbxZr alloys surfaces showed compare to non-nanotube formed surface. The corrosion resistance of alloy increased as Zr content increased, and nanotube formed surface showed longer the passive regions compared to non-treatment surface. Conclusion: It is confirmed that corrosion resistance of alloy increased as Zr content increased, and nanotube formed surface has longer passive region compared to without treatment surface.

• Korean Journal of Pharmacognosy
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• v.47 no.3
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• pp.264-272
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• 2016

This study was carried out to evaluate the preventive effect of the Corni Fructus (SSU) 50 % EtOH extract (SSU-E50) against bisphenol A (BPA) toxicity in Leydig cells and improving testosterone deficiency syndrome in orchidectomized Sprague-Dawly (SD) rats. Antioxidant properties were measured by radical scavenging activity of SSU-E50 in ABTS assay and DPPH assay. Also, real-time polymerase chain reaction(real-time PCR) was performed to quantify the mRNA expression levels of antioxidant enzyme. SD rats were divided into eight group: normal, sham operation (Sham), orchidectomized (ORX), ORX treated with testosterone 1 mg/kg (Tes. 1), ORX treated with SSU water extract 100 mg/kg (SSU-A 100) and 300 mg/kg (SSU-A 300), ORX treated with SSU 50 % EtOH extract 100 mg/kg (SSU-E 100) and 300 mg/kg (SSU-E 300). On a comparative basis, the SSU showed better activity quenching ABTS with an IC50 value of 0.29 mg/ml and DPPH with an IC50 value of 0.33 mg/ml. Cell viability was evaluated by MTS assay as described not cytotoxic at the highest concentration of $500{\mu}g/ml$. Cytotoxicity of BPA showed in $200{\mu}M$, but definitely survived by treatment with SSU in Leydig cells. In addition, SSU increased the mRNA expression levels of antioxidant enzyme in BPA induced Leydig cells. Superoxide dismutase (SOD) level was slightly increased and malondialdehyde (MDA) level was decreased with SSU-A 100 in in-vivo. These results suggest that Corni Fructus extracts have the greatest property as a natural anti-oxidative and improves testosterone deficiency syndrome source.

• Korean Journal of Food Science and Technology
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• v.31 no.6
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• pp.1661-1666
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• 1999

Yungmijihwgang-Won, Yollyunggobon-Dan and Palmi-Hwan, Korea traditional prescriptions composed of oriental medical herbs, have been used successfully to improve human health and regimen. This study was designed to examine the mechanism of healthful effects of the Korea traditional prescriptions through its antioxidative potentials. Using in vitro antioxidative activity assay system such as DPPH radical quenching assay, superoxide anion radical scavenging assay and inhibition of TBARS production, three Korea traditional prescriptions were observed to have nearly the same antioxidative potentials as ascorbic acid, a well-known strong water-soluble antioxidant. Moreover, we observed reinforced antioxidative effects of these drugs in liver from mouse fed these drugs with 4 weeks. When liver homogenate was incubated with 2.2'-azobis(amidinopropane) dihydrochloride(AAPH), as a free radical initiator, we observed that oxidative damages were decreased and antioxidative potentials were increased in liver homogenate treated these drugs. However, enzymatic antioxidative system as superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase was not affected by drug administration.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.898-904
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• 2021

This experimental study aims to investigate the use of a wet electrostatic precipitator as a post-treatment device to satisfy the strict emission regulations for sulfur oxides and particulate matter (PM). The inlet/outlet of a wet electrostatic precipitator was installed in a funnel using a marine four-stroke diesel engine (STX-MAN B&W) consuming marine heavy fuel oil (HFO) with a sulfur content of about 2.1%. Measurements were then obtained at the outlet of the wet electrostatic precipitator; an optical measuring instrument (OPA-102), and the weight concentration measurement method (Method 5 Isokinetic Train) were used for the PM measurements and the Fourier transform infrared (FT-IR; DX-4000) approach was used for the sulfur oxide measurements. The experimenst were conducted by varying the engine load from 50%, to 75% and 100%; it was noted that the PM reduction efficiency was a high at about 94 to 98% under all load conditions. Additionally, during the process of lowering the exhaust gas temperature in the quenching zone of the wet electrostatic precipitator, the sulfur dioxide (SO₂) values reduced because of the cleaning water, and the reduction rate was confirmed to be 55% to 81% depending on the engine load.

• Journal of Bio-Environment Control
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• v.33 no.1
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• pp.12-21
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• 2024

The aim of this research was to investigate the effect of gibberellin on improving seedling growth characteristics and enhancing strawberry quality in cutting propagation. Cuttings of the cultivar 'Seolhyang' were treated with GA₃ for 30 and 60 minutes at concentrations of 50, 100, and 150 mg·L^-1, with distilled water used for dipping as the control. Evaluation of seedling growth showed a positive correlation between the duration of gibberellin dipping and growth characteristics such as leaf number and SPAD value. Plant height, petiole length, leaf length and width, and leaf area varied significantly based on the interaction between dipping time and concentration. Crown diameter exhibited differences depending on the dipping time, with cuttings producing superior seedlings having a diameter of 8.0 mm or more for all treatments except the 30-minute, 100 mg·L^-1 treatment. The T/R ratio was significantly lower in the 30-minute, 50 mg·L^-1 treatment, indicating the highest plant vigor. Quantum yield was lower at a concentration of 150 mg·L^-1, showing a decreasing trend with increasing gibberellin concentration. Nonphotochemical quenching was significantly smaller in the 30-minute, 150 mg·L^-1 treatment, indicating an effective reduction of stress in the cuttings. Antioxidant content was highest in the 30-minute, 50 mg·L^-1 treatment and the 60-minute, 150 mg·L^-1 treatment. Moreover, the results of post-transplanting growth assessment showed no negative effect of gibberellin on flowering induction. Therefore, it was confirmed that gibberellin treatment during the cutting propagation of 'Seolhyang' strawberries had a positive effect on the production of high-quality seedlings. Dipping the cuttings in 50 mg·L^-1 gibberellin for 30 minutes is considered to be the most suitable method for improving growth and quality compared to the control.