• 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 Korean Elementary Science Education
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• v.37 no.4
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• pp.402-415
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• 2018

This study aims to inquire into the U. S. elementary school teachers' storylines for science teaching methods, scientific knowledge and interactions with students. As research subjects, two American elementary school teachers, named Christina and Melissa, were selected. As test tools, this study adopted Storyline Test and semi-structured interviews. Firstly, in regard to the science teaching method, Christina evaluated that she gradually improved her science teaching skills up to positive 6 points, starting from 2 points in the first year of teaching career, while Melissa sustained a stable state with 5 points in the 9th year of teaching career, starting from 1 point in the first year of teaching career. It was found that both the teachers had more confidence in their science teaching methods by participating in various training programs. Secondly, Christina evaluated her scientific knowledge in the first year of teaching career as 4 points, but evaluated her present scientific knowledge as stable as 6 points since she started studying teaching materials actively, discussing with other teachers and having more ability of application through science class integrated with other school subjects, in the 7th year of her teaching career. On the other hand, Melissa evaluated her scientific knowledge in the first year of teaching career as 1 point since she did not exactly know what to teach elementary school students, but in the 6th year of teaching career, she sustained a stable state with points through joint-activities with other teachers. It was found that chances to research with other teachers had important effect on both the teachers' confidence in scientific knowledge. Thirdly, in regard to interactions with students in science class, Christina said that she did not have any interaction with students when instructing inquiry activities in the first year of teaching career, but since the 10th year of her teaching career, she had sustained a stable state with 6 points through active interaction with students, by leading learning projects and science competitive exhibitions, etc. On the other hand, Melissa evaluated her interaction with students in the first year of teaching career as 1 point because her class was reading-oriented, but since the 9th year of teaching career, she had sustained a stable state with 6 points so far, by developing inquiry activity strategies to improve interaction with students. Overall, it was found that inquiry activities played a central role in improving both the teachers' interaction with students.

• Applied Chemistry for Engineering
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• v.18 no.3
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• pp.218-226
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• 2007

The stereoselective synthesis of chiral terminal epoxides is of immense academic and industrial interest due to their utility as versatile starting materials as well as chiral intermediates. In this study, new dinuclear chiral Co (salen) complexes bearing gallium-, indium- and tallium-chloride have been synthesized and characterized. The mass and EXAFS spectra provided the direct evidence of formation of dinuclear complex. Their catalytic activity and selectivity have been demonstrated for the asymmetric ring opening of various terminal epoxides having ether or ester groups by hydrolytic kinetic resolution technology. The easily prepared dimeric complexes exhibited very high enantioselectivity for the asymmetric ring opening of epoxides with $H_2O$ nucleophile, providing enantiomerically enriched terminal epoxides (> 99% ee). The dimeric structured chiral salen showed remarkably enhanced reactivity and may be employed substantially lower loadings than its monomeric analogues. The system described in this work is very efficient for the synthesis of chiral epoxide and 1,2-diol intermediates

• Journal of Gastric Cancer
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• v.17 no.1
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• pp.11-20
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• 2017

Purpose: Acupuncture has recently been accepted as a treatment option for managing postoperative ileus (POI) and various functional gastrointestinal disorders. Therefore, we conducted a prospective randomized study to evaluate the effect of acupuncture on POI and other surgical outcomes in patients who underwent gastric surgery. Materials and Methods: Thirty-six patients who underwent distal gastrectomy for gastric cancer from March to December 2015 were randomly assigned to acupuncture or non-acupuncture (NA) groups at 1:1 ratio. The acupuncture treatment was administered treatment once daily for 5 consecutive days starting at postoperative day 1. The primary outcome measure was the number of remnant sitz markers in the small intestine on abdominal radiograph. The secondary outcome measure was the surgical outcome, including the times to first flatus, first defecation, start of water intake, and start of soft diet, as well as length of hospital stay and laboratory findings. Results: The acupuncture group had significantly fewer remnant sitz markers in the small intestine on postoperative days 3 and 5 compared to those in the NA group. A significant difference was observed in the numbers of remnant sitz markers in the small intestine with respect to group differences by time (P<0.0001). The acupuncture group showed relatively better surgical outcomes than those in the NA group, but the differences were not statistically significant. Conclusions: In this clinical trial, acupuncture promoted the passage of sitz markers, which may reflect the possibility of reducing POI after distal gastrectomy.

• Textile Coloration and Finishing
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• v.8 no.2
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• pp.25-34
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• 1996

Diphenyl ethanolamidophosphate(DPEAD) was synthesized for the purpose of developing a new flame retardant for cotton fabric. As the intermediate material was used diphenyl chlorophosphate(DPCP) and it was synthesized by using phosphorus oxychloride and phenol as the starting materials. The final product DPEAP was obtained by the reaction of DPCP and ethanolamine. The flame retardancy of cotton fabrics treated by DPEAP through pad-dry-cure(PDC) process was examined at various conditions. The physical property change of the DPEAP treated cotton fabrics were investigated by examining the drape stiffness, the wrinkle recovery, and the tensile strength. The results are summarized as follows: (1) DPEAP has shown excellent flame retardancy on cotton fabrics in comparison to other flame retardants for cotton fabrics available commercially. (2) The optimal condition for PDC process found was that the curing temperature was 16$0^{\circ}C$, the DPEAP concentration was 10%, the catalyst $({NH_{4})_{2}HPO_{4}$ concentration was 7.0%, and the fixing agent hexamethylol melamine (HMM)/DPEAP weight ratio was 1/8. (3) The wrinkle recovery of the processed fabrics increased with increasing DPEAP concentration. (4) The drape stiffness of the cotton fabrics treated by DPEAP have shown essentially no change until increasing DPEAP concentration to 15 %, however DPEAP concentration exceeds 20% the drape stiffness increased drastically with increasing DPEAP concentration. When DPEAP concentration is kept constant the drape stiffness increased with increasing $({NH_{4})_{2}HPO_{4}$ concentration and HMM/DPEAP weight ratio. (5) The tensile strength of the processed fabrics was lower than that of untreated fabrics, but the tensile strength retention increased with increasing DPEAP concentration.

• The Journal of the Korea Contents Association
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• v.8 no.6
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• pp.121-129
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• 2008

With the help of information technology The problem of building a concrete form with a shapeless media is the starting point of presenting information by means of sound. Audio-Visual System using sound as a medium is a method that presents an auditory material visually and has a role of linking different sensory organs. In a sense, Audio-Visual System transfers a non-concrete sensation to a concrete one. Audio-Visual System presentation by late methods using active and non-active images produced by computerized irregular procedures can be limited because of the limited ways of visual output. On the other side, visualization using active images can induce more diverse expressions using sound as a medium. This study suggests a new way of expression in animations using visualization of various auditory materials and sounds built by Audio-Visual System with active images.

• Journal of the Korean Applied Science and Technology
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• v.32 no.3
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• pp.546-567
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• 2015

Silicone-based surfactants consist of a hydrophobic organosilicone group coupled to one or more hydrophilic polar groups, while the hydrophobic groups of hydrocarbon surfactants are hydrocarbons. Silicone surfactants have been widely used in many industrial fields starting from polyurethane foam to construction materials, cosmetics, paints & inks, agrochemicals, etc., because of their low surface tension, lubricity, spreading, water repellency and thermal and chemical stability. A wide range of silicone surfactant structures are required to provide the functional diversity for reflecting the necessities in the various applications. This review covers the basic properties and the synthetic schemes of polydimethylsiloxane and reactive polysiloxanes as hydrophobic siloxane backbones, the main reaction schemes, such as hydrosilylation reaction, for coupling reactive polysiloxanes to hydrophilic groups, and the synthetic schemes of the main polysiloxane surfactants including polyether-, ionic-, carbohydrate-type surfactants.

• The Journal of the Korea Contents Association
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• v.13 no.1
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• pp.64-72
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• 2013

In this study, we contemplated types, essence, characteristics of text data which is material for visual expression of text visualization part of data visualization research and also analysed the multidirectional means of expressive approach for it. Studies of text visualization are spread dramastically under the influence of computer development, open data, wide use of visualization tools, etc. For these reasons, text visualization works have been creating as art works or output of research through various inter-discipline convergent research with engineering, art, humanities, sociology, etc. Nevertheless the theoretical studies on text data itself and its visualization, and also systematic analysis of its approach are rarely made. Data is target of understanding and interpretation, and it has infinite information and possibility with process and approach for it. Considering the attainable status of data in future human society, text visualization which is convergent academic field of study starting with understanding and interpretation of data needs further methodological research and theoretical accumulate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.386-389
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• 2001

In this study, development of a new LTCC material using non-glassy system was attempted with repsect to reducing the fabrication process steps and cost down. Lowering the sintering temperature can be achieved by liquid phase sintering. However, presence of liquid phases usually decrease dielectric properties, especially the quality factor. Therefore, the starting material must have quality factor as high as possible in microwave frequency range. And also, the material should have a low dielectric constant for enhancing the signal propagation speed. Regarding these factors, dielectric constants of various materials were estimated by the Clausius-Mosotti equation. Among them, $ZnWO_4$ was turned out the suitable LTCC material. $ZnWO_4$ can be sintered up to 98% of full density at $1050^{\circ}C$ for 3 hours. It's measured dielectric constant, quality factor, and temperature coefficient of resonant frequency were 15.5, 74380GHz, and $-70ppm/^{\circ}C$, respectively. In order to modify the dielectric properties and densification temperature, $B_{2}O_{3}$ and $V_{2}O_{5}$ were added to $ZnWO_4$. 40 mol% $B_{2}O_{3}$ addition reduced the dielectric constant from 15.5 to 12. And the temperature coefficient of resonant frequency was improved from -70 to $-7.6ppm/^{\circ}C$. However, sintering temperature did not change due to either lack of liquid phase or high viscosity of liquid phase. Incorporation of small amount of $V_{2}O_{5}$ in $ZnWO_{4}-B_{2}O_{3}$ system enhanced liquid phase sintering. 0.1 wt% $V_{2}O_{5}$ addition to the $0.6ZnWO_{4}-0.4B_{2}O_{3}$ system, reduced the sintering temperature down to $950^{\circ}C$. Dielectric constant, quality factor, and temperature coefficient of resonant frequency were 9.5, 16737GHz, and $-21.6ppm/^{\circ}C$, respectively.

• Journal of the Korean Vacuum Society
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• v.8 no.1
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• pp.70-74
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• 1999

MgO-CaO protective layers with various composition were prepared by electron beam evaporation to improve the characteristics of conventional pure MgO thin films as a protective layer for AC-PDP. The maximum deposition rate of pure MgO was 1025 $\AA$/min and decreased with increasing [(CaO/(MgO+CaO)] ratio of evaporation starting materials. From XRD analyses, a trend of peak shift to the lower 2$\theta$ angle side was shown as CaO content increased and it stoped when the concentration of CaO was 0.13, which corresponds to the maximum solubility of CaO in MgO. The optimum composition of the protective thin films was Mg 47.1 at%, Ca 1.3 at%, O 51.6 at%, and firing voltage, memory margin and deposition rate of the film with this composition was 176 V, 0.5 and 515 $\AA$/min, respectively.