• Journal of The Korean Association For Science Education
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• v.24 no.2
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• pp.387-398
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• 2004

The purpose of this study was to investigate high school students' preference for science(PS) and its causal factors in terms of gender difference, and to suggest the way to improve students' preference for science. A questionnaire to evaluate the PS of high school students and its causal factors was specially designed by researchers. It was administered to 429 boys and 449 girls in eight high schools. The average score of the PS was 3.16 of 5.00 which was not high, but the PS scores of students who had wanted to be engaged in jobs related to science or medical field, were higher than the students who would be in other fields. There was no statistically significant difference between the boys' PS scores and girls', but the average scores of causal factors were higher in boys than in girls. Path analysis using a structural equation model was indicated that the pathways showing how causal factors made effects on each category of the boys' PS were simpler than those of girls. Particularly, while educational factors made indirect effects on three categories of the boys' PS, they did direct effects as well as indirect effect on the girls' PS. This means that the girls' PS is possible to be improved by applying the educational programs specially developed for girls.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.2
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• pp.27-35
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• 2016

A Low jitter dual output frequency synthesizer for smart audio devices is described in this paper. It has been fabricated in a 1.8 V Dongbu $0.18-{\mu}m$ CMOS process. Output frequency is controlled by 3 rd order Sigma-Delta Modulation and digital divider. The frequency synthesizer has a size of $0.6mm^2$, frequency range of 0.6-200 MHz, loop bandwidth of 350 kHz, and rms jitter of 11.4 ps-21.6 ps.

• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.7-17
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• 2006

In this paper, we proposed an optical true time-delay (TTD) for planar phased array antennas (PAAs), which is composed of a wavelength-dependent optical true time delay (WDOTTD) followed by a wavelength-independent optical true time delay (WIOTTD). The WDOTTD is a fiber Bragg gratings (FBGs) Prism and the WDOTTD is a fiber delay-lines matrix of which each component consists of a certain length of fiber connected to cross-ports of a 2${\times}$2 MEMS switch. A 10-GHz 2-bit${\times}$4-bit two-dimensional optical TTD has been fabricated by cascading a WDOTTD with a maximum time delay of 810 ps to a WIOTTD of $\pm$50 ps. Time delay and insertion loss for each radiation angle have been measured. Time delay error for the WIOTTD has been measured to be less than $\pm$1 ps. We have also designed a two-dimensional 10-GHz PAA composed of 8${\times}$8 microstrip patch antenna elements driven by the proposed TTD. The radiation patterns of this PAA have been obtained by simulation and analyzed.

• Macromolecular Research
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• v.16 no.7
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• pp.637-643
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• 2008

A combination of magnetic and temperature-responsive properties in the same polymer composites is expected to increase their potential applications in the biomedical field. Accordingly, micron-sized magnetite/polystyrene/poly(2-dimethylaminoethyl methacrylate-ethyleneglycol dimethacrylate), which are abbreviated as $Fe_3O_4$/PS/P (DM-EGDM) composite polymer particles, were prepared by the seeded copolymerization of DM and EGDM in the presence of magnetite/polystyrene ($Fe_3O_4$/PS) particles. $Fe_3O_4$/PS/P(DM-EGDM) composite particles with magnetic properties showed a temperature-sensitive phase transition at approximately $31^{\circ}C$. The adsorption behavior of the low molecular weight emulsifiers and trypsin (TR) as biomolecules were examined on $Fe_3O_4$/PS/P(DM-EGDM) composite polymer particles at different temperatures. The native conformation of TR was followed by measuring the specific activity under various adsorption conditions. The activity of the adsorbed TR on composite polymer particles was higher than those of the tree TR and TR adsorbed on $Fe_3O_4$/PS particles.

• BMB Reports
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• v.38 no.3
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• pp.350-353
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• 2005

Alanine at residue 73 (Ala-73) and aspartate at residue 9 (Asp-9) are characteristic to both Cw6 and Cw7 alleles of HLA-C gene and have been suggested as possible markers for psoriasis vulgaris (PsV). However, the results from various ethnic groups/populations are contradictory and inconclusive. In this study, an attempt has been made to examine the association between HLA-C (Ala-73 and Asp-9) and susceptibility to PsV among Saudi patients. Genomic DNA was extracted from 25 Saudi PsV patients and 75 control subjects. Polymerase chain reaction (PCR) was performed to amplify HLA-C sequences using earlier reported primers, C133P and C243PR. Sequence-specific primers were used to specifically detect nucleotide coding for Ala-73 and Asp-9 in all the subjects. The results showed significantly higher frequency of Asp-9 (84.0% versus 61.3%) in PsV patients as compared to controls (p < 0.05, 2-tailed Fisher's exact test). The frequencies of Ala-73 among PsV patients (92%) and controls (88%) did not differ significantly.

• Journal of Fisheries and Marine Sciences Education
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• v.5 no.2
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• pp.90-97
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• 1993

Pair trawling is one of the important fishing methods for Korean fisheries, and is working in the western sea of Korea - the Yellow Sea and the East China Sea. On the engine power of the trawlers, 72% of 190 pairs of trawlers were equipped with 450ps class engine, and 21% with 450~750ps and merely 7% with in 750ps class 1980. Thereafter the engine power has grown up, so that 450~750ps occupy 28% and 750ps or more 27% in 1992. Main objective fishes of pair trawling were traditionally flat fishes, so the fundamental shape of pair trawl net was a four - seam net, but by the gradual shortage of flat fishes, roundfishes has been noticed. So the six - seam net which performs high opening of net mouth has been used widely since 1985. In the six - seam net, the length of wing was not so short in the beginning but became short in the later instead of the net pendant elongated, and also the pendant was separated into three pieces according to the change of wing structure. Since the 1990's, the objective fishes has gradually been changed into pelagic fishes, the fishing technique is required to fit the behavior of fishes. So the midwater trawling or the multi -layer trawling became required.

• Neonatal Medicine
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• v.18 no.2
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• pp.409-411
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• 2011

In Korea, pulmonary surfactant (PS) replacement therapy in respiratory distress syndrome (RDS) was started in 1991 since when Surfacten$^{(R)}$ was imported from Japan. At the present time, Surfacten$^{(R)}$, Newfactan$^{(R)}$, Curosurf$^{(R)}$, and Infasurf$^{(R)}$ are available in Korea. The governmental health insurance covers the expense for multiple dose treatment since 2002 and the early prophylactic treatment (BW: <1,250 g or GP: <30 wks) since 2011. We undertook a multi-institutional collective study to evaluate the outcomes of PS over past 20 years in Korea (Period-I; 1990/91, P-II; 1996, P-III; 2002, and P-IV; 2007, P-V; 2010). There were 60 RDS neonates with PS treatment in P-I (16 hospitals), 1,179 in P-II (64), 1,595 in P-III (62), 1,921 in P-IV (57), and 3,160 in P-V (72). Decreased mortality rate, defined as the percentage of neonates who died within 28 days of birth, was seen between periods, P-V vs P-I, II, III, and IV (mortality rate: 10.1% vs. 40.0%, 30.0%, 18.7%, and 14.3%). We conclude that PS therapy contributed to improve remarkable outcome in RDS neonates over the last 20 years in Korea. However, more efforts should be made to optimize PS therapy for better outcome. Multiple PS doses for relapse and poor response, early prophylactic use, and better supportive care for pre-term infants are mandatory.

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1011-1017
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• 1998

$YBa_2Cu_3O_{6+x}(Y123)-Ag$ high-Tc superconducting wires were fabricated by plastic extrusion technique using pyrophoric synthetic and mechanical mixing powder with and without Ag addition(20 wt.%). This method involves powder preparation, plastic paste making, die extrusion, binder burn-out and the sintering process. In order to fabricate a good-quality superconducting body, it is required to use homogeneous and fine-size power as a starting materials. $Y_2O_3-BaCO_3-CuO$ precursor powders with/without Ag addition were prepared both by pyrophoric synthetic(PS) and mechanical mixing(MM) method of raw powders. The formation kinetics of the powder mixtures into Y123 phase was investigated at various temperatures and times in air atmosphere. The powder prepared by PS method was more easily converted into a Y123 phase than the MM powder. The fine size and good chemical homogeneity of the powder prepared by PS method is attributable to the fast formation into a Y123 phase. The critical current density($J_c$) of the Y123-Ag superconducting wires made by plastic extrusion method were in the range of $150A/cm^2{\sim}230A/cm^2$. depending on the charateristics of starting material powders. $J_c$ of the wire prepared by pyrophoric synthetic powder with 20 wt.% Ag addition was $230A/cm^2$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.1
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• pp.137-142
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• 2016

We investigated the anti-proliferative effects of solar salt and purified salt (PS) on HepG2 human hepatocellular cancer cells as well as their effects on mRNA and protein expression of apoptosis- and cell cycle-related genes, including Bcl-2, Bax, p53, and p21. Each salt sample suppressed cancer cell proliferation when treated at a concentration of 0.5% or 1%. Especially solar salt from T salt field (SS-T) and solar salt from Y salt field (SS-Y) significantly suppressed proliferation of cancer cells in comparison with PS. Treatment of HepG2 cells with salt samples at a concentration of 1% suppressed expression of Bcl-2 and promoted expression of Bax, p53, and p21 at the mRNA and protein levels in comparison with the control group. Inductively coupled plasma optical emission spectrometry (ICP-OES) showed that SS-T and SS-Y had higher concentrations of Ca, Mg, S, and K than PS, and SS-T contained higher concentrations of these minerals than SS-Y. It seems that Na and mineral contents in solar salt may contribute to regulation of the genes. Taken together, salt, especially mineral rich solar salt, inhibits cancer cell growth by regulating apoptosis and cell cycle-related genes.

• Food Science and Preservation
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• v.20 no.1
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• pp.7-13
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• 2013

Mushrooms have a shorter shelf-life than most vegetables because of their very high respiration rates, sensitivity to enzymatic browning and susceptibility to microbial spoilage. This study was conducted to investigate effects of various packaging materials and precooling on the quality of mushrooms (Agaricus bisporus). Mushrooms were precooled at $4^{\circ}C$ for three hours and packaged using the following packaging materials; 1) polyethylene (PE) film bags of 0.03 mm thickness, 2) polypropylene (PP) film bags of 0.03 mm thickness, and 3) polystyrene (PS) tray+polyvinyl chloride (PVC) wrapper. The physiological changes (weight loss, gas composition, color, firmness, and sensory evaluation) associated with postharvest deterioration were monitored for 17 days at $10^{\circ}C$. The results showed that the PP film bag maintained quality of mushrooms most effectively, especially PP film bags inhibited decreasing firmness. The samples also exhibited smaller decreases in weight loss rate (0.57%) and Hunter L value (84.44) than PS tray+PVC wrapper (7.73%, 82.19) and PE film bags (0.89%, 82.96). Sensory evaluation level in all samples remained relatively constant during the first 5 days of storage. However, PE film bags and PS tray+PVC wrapper showed lower score of flavor, texture and color than PP film bags after 8 days of storage. This study suggested that PP film bag packaging effectively extends shelf-life of mushrooms during storage.