• Journal of Mechanical Science and Technology
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• v.19 no.10
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• pp.1957-1963
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• 2005

In this study, external condensation heat transfer coefficients (HTCs) of six flammable refrigerants of propylene (RI270), propane (R290), isobutane (R600a), butane (R600), dimethylether (RE170), and HFC32 were measured at the vapor temperature of $39^{\circ}C$ on a 1023 fpm low fin and Turbo-C tubes. All data were taken under the heat flux of $32\~116\;and\;42\~142kW/m^2$ for the low fin and Turbo-C tubes respectively. Flammable refrigerants' data obtained on enhanced tubes showed a typical trend that external condensation HTCs decrease with increasing wall subcooling. HFC32 and DME showed up to $30\%$ higher HTCs than those of HCFC22 due to their excellent thermophysical properties. Propylene, propane, isobutane, and butane showed similar or lower HTCs than those of HCFC22. Beatty and Katz' correlation predicted the HTCs of the flammable refrigerants obtained on a low fin tube within a mean deviation of $7.3\%$. Turbo-C tube showed the best performance due to its 3 dimensional surface geometry for fast removal of condensate.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1147-1152
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• 2004

This paper presents the design of a multi-standard NTSC/PAL video encoder. The encoder converts International Telecommunication Union-Recommendation (ITU-R) BT.601 4:2:2, ITU-R BT.656 or RGB inputs from various video sources into National Television Standards Committee (NTSC) or phase-alternate line (PAL) TV signals in both S-video and composite video baseband signals (CVBS). The encoder adopts multiplier-free structures to reduce hardware complexity. The hardware bit width of programmable digital filters for luminance and chrominance signals, along with other operating blocks, are carefully determined to produce high-quality digital video signals of 1 least significant bit (LSB) error or less. The proposed encode. is experimentally demonstrated by using the Altera APEX20K600EBC652-3 device.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.7
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• pp.639-644
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• 2004

This paper deals with the heat transfer characteristics of R-1270 (Propylene), R-600a (Iso-butane) and R-290 (Propane) as an environment friendly refrigerant and R-22 for condensing. The experimental apparatus has been set-up as a conventional vapor compression type heat pump system. The test section is a horizontal double pipe heat exchanger. A tube diameter of 12.70 mm with 1.32 mm wall thickness is used for this investigation. The test results showed that the local condensing heat transfer coefficients of hydrocarbon refrigerants were higher than that of R-22. The average condensing heat transfer coefficient was obtained with the maximum value in R-1270 and the minimum one in R-22. Comparing the heat transfer coefficient of experimental results with that of other correlations, the presented results had a good agreement with the Cavallini-Zecchin's correlation. It reveals that the natural refrigerants can be used as substitute for R-22.

• The Journal of the Korea Contents Association
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• v.21 no.10
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• pp.668-678
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• 2021

This study aimed to identify the factors influencing the clinical competence of nurses, using a descriptive correlational study design. Data were collected through questionnaires administered to 170 nurses working in a general hospital in Gwangju city and Jeollanam-do province from March 24 to May 27, 2021. There were significant differences in clinical competence according to age, marital status, and educational level. Clinical competence was significantly correlated with nursing professionalism (r=.600, p<.001), critical-thinking disposition (r=.568, p<.001), communication skills (r=.658, p<.001), and nursing practice environment (r=.353, p<.001). Factors influencing clinical competence were communication skills, nursing professionalism, critical-thinking disposition, and age, which explained 54.0% of the total variance. It is necessary to develop educational programs to improve the communication skills, nursing professionalism, and critical-thinking disposition of nurses. Additionally, Institutional and national measures are needed so that nurses can continue to work in hospitals.

• Applied Chemistry for Engineering
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• v.7 no.1
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• pp.59-66
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• 1996

Novel chitosan beads containing a series of bisamino-terminated polyethylene glycol (Bisamino-PEG, $Jeffamine^{(R)}ED$ series) have been prepared via capillary extrusion method using an alkaline solution. The results of swelling kinetics of chitosan beads showed that as the chain length of PEG in chitosan beads increased, the swelling process of the beads proceeded slowly. In order to study the releasing kinetics quantitatively, fluorescamine was coupled to the pendant amino groups and the releasing processes were followed by UV spectra. The results revealed that the releasing process was retarded in the order of $Jeffamine^{(R)}ED$-600 < $Jeffamine^{(R)}ED$-900 < $Jeffamine^{(R)}ED$-2001 as the chain length of PEG was increased. The slow release of PEG from the beads is considered to be governed by the chain length of PEG and interpolymeric hydrogen bonding between PEG and the chitosan molecule.

• Microbiology and Biotechnology Letters
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• v.23 no.3
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• pp.275-281
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• 1995

From the plasmid pYA300 carring a CMCase of Rhizobium fredii USDA193 plasmid was subcloned into pBluescript II KS(+)/pBluescript II SK(+) vectors and designated pYA500 and pYA600, respectively. Escherchia coli cells transformed with pYA500 porduced the CMCase more than with pYA600. The orientation of the cloned fragment in pBluescript vector had the effect on gene expression in E. coli background. When the 1.7 kb CMCase gene fragment of R. fredii USDA193 was hybridized to EcoRI-digested total DNA from R. meliloti and R. fredii USDA 191 the unique bands hybridized respectively, indicating that some genetic diversity exists in the EcoRI restriction enzyme site for CMCase gene in Rhizobium strains. The optimum pH of enzyme activity was 7 and the optimum temperature of that was nearly 37$\circ$C. The cellulase-minus derivatives of pYA500 were constructed by Tn5 insertional mutation. Among 6000 transconjugants, two mutant plasmids (designated pYA500::Tn5a and pYA500::Tn5b) were detected from the cellulase- negative transconjugants. The product of CMCase gene was analyzed by one dimensional SDS- PAGE of the cell extracts. About 45 kDa protein was considered to be a product of CMCase gene.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2195-2201
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• 2009

This paper considers the influence of suction-line heat exchangers on the efficiency of a refrigeration cycle using hydrocarbon refrigerants such as R290, R600a and R1270. These suction-line heat exchangers can, in some cases, yield improved system performance while in other cases they degrade system performance. A steady state mathematical model is used to analyze the performance characteristics of refrigeration cycle with suction-line heat exchanger. The influence of operating conditions, such as the mass flowrate of hydrocarbon refrigerants, inner diameter tube and length of suction-line heat exchanger, to the performance of the cycle is also analyzed in the paper. Results showed that the mass flowrate of hydrocarbon refrigerants, inner diameter tube and length of suction-line heat exchanger, and effectiveness have an effect on the cooling capacity, compressor work and RCI(Relative Capacity Index) of this system. With a thorough grasp of these effect, it is necessary to design the compression refrigeration cycle of hydrocarbon refrigerants using suction-line heat exchanger.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1A
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• pp.48-57
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• 2006

TWTA is to perform the function that amplifies the input RF signal and outputs it to the antenna. This paper proposes a method that is to improve the cathode ripple or the SHF TWTA for satellite communications. Through the embodiment and experiment of 600W SHF TWTA, this method satisfies the design specifications. Also, RF performance is improved by reducing the noise of auxiliary power sources supplied to the RF part and eliminating the unexpected noise. Therefore, this method is very effective and can be used to develop the similar equipments.

• Journal of the Korean institute of surface engineering
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• v.47 no.4
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• pp.181-185
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• 2014

We investigated the structural, electrical and optical characteristics of IGZO thin films deposited by a room-temperature RF reactive magnetron sputtering. The thin films deposited were annealed for 2 hours at various temperatures of 300, 400, 500 and $600^{\circ}C$ and analyzed by using X-ray diffractometer, transmission electron microscopy, atomic force microscope and Hall effects measurement system. The films annealed at $600^{\circ}C$ were found to be crystallized and their surface roughness was decreased from 0.73 nm to 0.67 nm. According to XPS measurements, concentration of oxygen vacancies were decreased at $600^{\circ}C$. Optical band gap were increased to 3.31eV. The carrier concentration and Hall mobility were sharply increased at 600oC. Our results indicate that the IGZO films deposited at a room temperature can show better thin film properties through a heat treatment.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.8
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• pp.870-876
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• 2005

This study of the performance characteristics of natural refrigerants such as R-290 (propane), R-6OOa (iso-butane) and R-1270 (propylene) has investigated to compare with conventional HCFC's refrigerant R-22 for water-cooled heat pump system. The experimental apparatus has basic parts of cycle that uses the water as a heat source. The Performance of the water-cooled system using hydrocarbon refrigerants had been getting better than R-22 from start-up to the similar evaporating temperature after stabilizing system. Through the above it is possible that hydrocarbon refrigerants could be drop-in alternatives for R-22.