• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.7
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• pp.981-988
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• 2001

Characteristics of evaporation heat transfer in 6.2 and 5.1mm OD micro-fin tubes were investigated in the present study. The data were taken at evaporation temperatures of -5$^{\circ}C$ and 5$^{\circ}C$ and heat fluxes 5kW/$m^2$ to 10kW/$m^2$. Mass flux was consequently maintained at 210, 300 and 410kg/$m^2$s for the 6.2mm OD tube and 465, 500 and 600kg/$m^2$s for the 5.1mm OD tube. The effects of heat flux, mass flux, and outer diameter on the heat transfer coefficient are explored in the present study. The data showed that the evaporation heat transfer coefficient for the 6.2mm OD tube was averagly higher by 16% than that for a 7.0mm OD tube, while the 5.1mm OD tube had approximately 30% higher value than the 6.2mm OD tube.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.175-182
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• 2012

Light characteristics of the monochromatic red(R), blue(B), green(G) and white(W) and the mixed LED (B-R LED) were investigated by light control a Spectrometer-MMS1 and an illuminometer. The power consumption of each LED was 1W and R LED has five wavelength bands(600nm, 640nm, 660nm, 680nm, 750nm). The light intensity of each LED was changed in a range 10~100%. As a results, the wavelength and the spectrum distribution of R LED increase with increasing light intensity but the wavelength of B, G, W LED decreases. It was found that illumination of each mononochromatic and B-R LED increases linearly with increasing light intensity. It was confirmed that the illumination intensity of R-B light has greater values than those obtained by monochromatic light at the same conditions.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.154-159
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• 2008

Two-phase flow boiling heat transfer of R-410A in horizontal small tubes was reported in the present experimental study. The local heat transfer coefficients were obtained over a heat flux range of 5 to 40 kW/$m^2$, a mass flux range of 170 to 600 kg/$m^2s$, a saturation temperature range of 3 to $10^{\circ}C$, and quality up to 1.0. The test section was made of stainless steel tubes with inner diameters of 0.5 and 3.0 mm, and lengths of 330 and 3000 mm, respectively. The section was heated uniformly by applying a direct electric current to the tubes. The effects on heat transfer of mass flux, heat flux, inner tube diameter, and saturation temperature were presented. The experimental heat transfer coefficient is compared with six existing heat transfer coefficient correlations. A new boiling heat transfer coefficient correlation based on the superposition model for R-410A in small tubes was developed with mean deviation of 10.13%.

• Korean Journal of Materials Research
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• v.14 no.11
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• pp.821-827
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• 2004

Titanium oxide thin films were prepared on Si(100) substrates by R.F. magnetron reactive sputtering at $30\sim200watt$ R.F power range, and annealed at $600^{\circ}C\sim800^{\circ}C$ for 1 hour. The properties of $TiO_2$ thin films were analyzed using x-ray, ${\alpha}-step$, ellipsometer, scanning electron microscopy, and FT-IR spectrometer. Upon in-situ depositions, the initial phase of $TiO_2$ thin film showed non-crystalline phase at R.F. power $30\sim100$ watt. The crosssection of $TiO_2$ thin films were sbserved to be the columnar structure. With the increasing R.F power and annealing temperature, the grain size, crystallinity, refractive index, and void size of titanium oxides showed a tended to increase. The FT-IR transmittance spectra of titanium oxide thin films have the obsorption band of Ti-O bond, Si-O bond, Si-O-Ti bond and O-H bond. With the increase of R.F. power and annealing temperature, these films have the stronger bond structures. It is considered that such a phenomena is due to phase transition and good crystallinity

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.2
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• pp.109-117
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• 2009

In this study, thermodynamic performance of R430A is examined both numerically and experimentally in an effort to replace HFC134a used in the refrigeration system of domestic water purifiers. Even though HFC134a is used predominantly in such a system these days, it needs to be phased out in the near future in Europe and most of the developed countries due to its high global warming potential. To solve this problem, cycle simulation and experimental measurements are carried out with a new refrigerant mixture of 76%R152a124% R600a using actual domestic water purifiers. This mixture is numbered and listed as R430A by ASHRAE recently. Test results show that the system performance with R430A is greatly influenced by the amount of charge due to the small internal volume of the refrigeration system of the domestic water purifiers. With the optimum amount of charge of 21 to 22 grams, about 50% of HFC134a, the energy consumption of R430A is 13.4% lower than that of HFC 134a. The compressor dome and discharge temperatures and condenser center temperature of R430A are very similar to those of HFC134a at the optimum charge. Overall, R430A, a new long term environmentally safe refrigerant, is a good alternative for HFC134a requiring little change in the refrigeration system of the domestic water purifiers.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.657-662
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• 2006

The present paper dealt with an experimental study of condensation heat transfer coefficients with refrigerant R-22, R-407C and R-410A, and was focused on pressure gradient and heat transfer coefficient in horizontal tube-in-tube heat exchangers using inner diameter of 4 mm, 3 mm and 2 mm in a 16.91 mm tube and length of 3,000 mm. Experiments were performed at inlet saturation temperature of 35 to $45^{\circ}C$ and mass flux ranges from 200 to $600 kg/m^2s$. The pressure gradient with inner tube diameter of 4.0 mm is higher 2.5 times than that of 8.0 mm. In tube-in-tube HEX, the pressure gradient of R-410A were lower than those of R-22 and R-407C. The condensation heat transfer coefficients increased with mass flux increase, but they decreased with saturation temperature increased. Condensation heat transfer coefficients of R-410A were a little higher than those of R-22 and R-407C. The condensation heat transfer coefficients of tube-in-tube HEX were about 40% higher than those of double tube HEX.

• Oncology Letters
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• v.17 no.5
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• pp.4726-4734
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• 2019

Colorectal cancer (CRC) is one of the most common types of cancers, as evidenced by the >1.2 million patient diagnoses and 600,000 mortalities globally each year. Recently, the microRNA (miR/miRNA)-34 miRNA precursor family was revealed to participate in the tumor protein (TP)-53 pathway, which is frequently involved in CRC. Furthermore, the expression of miR-34 is reportedly regulated by DNA methylation. Accordingly, the present study investigated the correlation between the methylation status of miR-34 miRNAs and miR-34 expression in paired CRC tumor and normal tissues. The methylation status of miR-34a and miR-34b/c was determined using the MethyLight assay, and the expression of miR-34a and miR-34b/c in the same paired tissues was analyzed by reverse transcription-quantitative polymerase chain reaction. The results revealed significantly elevated miR-34a (P=0.012) and miR-34b/c (P<0.0001) methylation levels in tumor tissues when compared with normal tissues, whereas only the expression of miR-34b/c differed (P=0.005) between the paired tissues. In addition, an association between TP53 haplotypes and miR-34 family expression levels was observed. The miR-34a methylation levels in the TP53 PIN A1A1 (48.56±36.49) and TP53 MSP GG (49.00±36.44) genotypes were increased in the tumor tissues when compared with normal tissues. In conclusion, it was determined that miR-34 promoter methylation and TP53 polymorphisms may be associated with CRC pathogenesis.

• Journal of Sensor Science and Technology
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• v.21 no.6
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• pp.451-455
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• 2012

Dense Cr-precursor nano-hexaprisms were prepared by heating the Cr-nitrate aqueous solution containing Hexamethylenetetramine and polyvinylpyrrolidone, which were converted into porous $Cr_2O_3$ nano-hexaprisms containing nanoparticles by heat treatment of Cr-precursors at $600^{\circ}C$ for 2 h in air atmosphere. At the sensor temperature of $300^{\circ}C$, porous $Cr_2O_3$ nano-hexaprism showed the high response ($R_g/R_a$, $R_g$: resistance in gas, $R_a$: resistance in air) to 100 ppm $C_2H_5OH$ ($R_g/R_a=69.8$) with negligible cross-responses to 100 ppm CO and 5 ppm $C_6H_6$. The sensitive and selective detection of $C_2H_5OH$ in porous $Cr_2O_3$ nano-hexaprism were discussed in relation to the morphology of nanostructures.

• Nuclear Engineering and Technology
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• v.47 no.4
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• pp.398-406
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• 2015

In this study, R-123 flow boiling experiments were carried out to investigate the effects of nanoparticle deposition on heater surfaces on flow critical heat flux (CHF) and boiling heat transfer. It is known that CHF enhancement by nanoparticles results from porous structures that are very similar to layers of Chalk River unidentified deposit formed on nuclear fuel rod surfaces during the reactor operation period. Although previous studies have investigated the surface effects through surface modifications, most studies are limited to pool boiling conditions, and therefore, the effects of porous surfaces on flow boiling heat transfer are still unclear. In addition, there have been only few reports on suppression of wetting for decoupled approaches of reasoning. In this study, bare and $Al_2O_3$ nanoparticle-coated surfaces were prepared for the study experiments. The CHF of each surface was measured with different mass fluxes of $1,600kg/m^2s$, $1,800kg/m^2s$, $2,100kg/m^2s$, $2,400kg/m^2s$, and $2,600kg/m^2s$. The nanoparticle-coated tube showed CHF enhancement up to 17% at a mass flux of $2,400kg/m^2s$ compared with the bare tube. The factors for CHF enhancement are related to the enhanced rewetting process derived from capillary action through porous structures built-up by nanoparticles while suppressing relative wettability effects between two sample surfaces as a highly wettable R-123 refrigerant was used as a working fluid.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.3
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• pp.192-197
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• 2014

Water analyses were conducted on 1,525 underground water laid in the western district of Korea's South Gyeongsang Province, from January 2007 until July 2010, according to sections, factors, fountainheads and inter-factor correlativities. The following are the results. 1. As a result of local incongruity rate, 18.2% in inland areas, coastal areas and 24.5% showed a high value comparatively. Costal areas showed high incongruity rate. 2. As a result of local incongruity rate, they were found that the total colony count and general bactria 39.9%, 42.6% showed a high in costal areas. 3. As a result of local factorial inspection, it was found that the turbidity content counted up to 0 to 0.2 NTU in 59.4% in inland areas, 60.2% in costal areas of sections, and in other 12.6%, 14.0%, it exceeded 0.5 NTU. As a result of local factorial inspection, it was found that the nitrate-nitrogen content counted up to 0 to 10 mg/L in 98.2% in inland areas, 97.6% in costal areas of sections, and in other 1.8%, 2.4%, it exceeded 10 mg/L. As regards chloride in coastal areas, water quality standards for chloride 250 mg/L exceeds the 1.4% higher then in inland areas. 4. Hardness in inland areas was closely correlated with total solids (r = 0.910), sulfate ion (r = 0.819). Also, total solids and boron (r = 0.600) showed high correlativities. On the other hand hardness in coastal areas was closely correlated with total solids (r = 0.919), chloride (r = 0.829). Also sulfate ion was closely correlated with hardness (r = 0.599), turbidity and aluminum (r = 0.635) showed high correlativities in this research.