• Journal of Powder Materials
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• v.22 no.6
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• pp.413-419
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• 2015

Lanthanum zirconate, $La_2Zr_2O_7$, is one of the most promising candidates for next-generation thermal barrier coating (TBC) applications in high efficient gas turbines due to its low thermal conductivity and chemical stability at high temperature. In this study, bulk specimens and thermal barrier coatings are fabricated via a variety of sintering processes as well as suspension plasma spray in lanthanum zirconates with reduced rare-earth contents. The phase formation, microstructure, and thermo-physical properties of these oxide ceramics and coatings are examined. In particular, lanthanum zirconates with reduced rare-earth contents in a $La_2Zr_2O_7-4YSZ$ composite system exhibit a single phase of fluorite or pyrochlore after fabricated by suspension plasma spray or spark plasma sintering. The potential of lanthanum zirconate ceramics for TBC applications is also discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.3
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• pp.275-279
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• 2023

La_0.7Sr_0.3-xMg_xMnO₃ (LSMMO) (x=0.05~0.20) specimens are fabricated by a solid phase sintering method, and the sintering temperature and time are 1,300℃ and 2 hours, respectively. The dependence of the crystalline structure according to the amount of Mg²⁺ contents is not observed, and all specimens show a polycrystalline rhombohedral crystal structure, the X-ray diffraction (110) peaks move to the high angle side with increasing the amount of Mg²⁺ contents. LSMMO specimens exhibit a granule-shaped microstructure with an average grain size of 1 ㎛ or less. Resistivity gradually decrease as the amount of Mg²⁺ contents increased. And in the La_0.7Sr_0.1Mg_0.2MnO₃ specimen, resistivity and B_25/65-value are 36.7 Ω-cm and 394 K at room temperature, respectively. LSMMO specimens show a variable-range hopping (VRH) electrical conduction mechanism, and the negative temperature of coefficient of resistance (NTCR) is approximately 0.37~0.38%/℃.

• Composites Research
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• v.33 no.2
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• pp.55-60
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• 2020

A study on the heating behavior and adhesion property of structural epoxy adhesive through induction heating have been conducted. An adhesive for induction heating was manufactured through mixing with nano and micro sized Fe₃O₄. From the results, it was observed that induction heating is less affected by adherend (GFRP) thickness than oven heating. The heating rate of Fe₃O₄ embedded epoxy adhesive using induction heating much higher than that of oven curing process and it is more appreciable when the contents of Fe₃O₄ increased. Furthermore, adhesion strength increased with increase of Fe₃O₄ particle contents.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.29-36
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• 2000

The shape of the polymers in the mixed alkoxide solutions of Si(OC2H5)4 and Zr(n-OC3H7)4 with various water contents (1, 2, 4, and 8 in molar ratio to alkoxide, r) and catalysts was examined by rheological measurements, and its relation with fiber drawing behavior of the solutions was described. It was found that fibers could be drawn in the viscosity range 1~100 P from the acid-catalyzed solutions with lower water contents of the molar ratio H2O/alkoxide, $r{\leq}2$. On the other hand, no fiber could be drawn from the acid-catalyzed solutions including a large amount of water($r{\geq}4$) and the base-catalyzed solutions. The relation between the intrinsic viscosity [${\eta}$] and number average molecular weight ${\bar{M}}n$, namely $[{\eta}]=K{\bar{M}}n{\alpha}$, has shown that the acid-catalyzed spinnable solution (r = 1 and 2) had linear polymers where the exponent a's were about 0.56 and 0.81, whereas non-spinnable solutions (r = 4 and 8) had three dimensional network polymers or spherical particles where the exponent a's were 0.41-0.51 and 0.35.

• Transactions of the Korean hydrogen and new energy society
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• v.4 no.1
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• pp.31-39
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• 1993

In order to improve the hydrogen storage capacity and the activation property of the $MmNi_{4.5}Al_{0.5}$ alloy, the multiphase alloy system are prepared by adding the excess Zr in $MmNi_{4.5}Al_{0.5}$ alloy. It is estimated from the X-ray diffraction pattern and the energy dispersive X-ray analysis that the 2nd phases in $MmNi_{4.5}Al_{0.5}Zr_x$ alloys are $ZrNi_3$, ${\beta}$-Zr. Their morphology is also examined by the scanning electron microscope, and it shows the needle-like precipitation. As the Zr contents increase, the activation time and the plateau pressure decrease, sloping of the plateau pressure increase. Amount of the 2nd phases increase with Zr contents in $MmNi_44.5Al_{0.5}Zr_x$ alloys. The $MmNi_44.5Al_{0.5}Zr_{0.05}$ alloy, which shows the maximum storage capacity and the strong resistance to intrinsic degradation, is considered as a proper alloy for hydrogen storage.

• Journal of the Semiconductor & Display Technology
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• v.16 no.4
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• pp.11-15
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• 2017

Red phosphors, $Sr_2Si_5N_8:Eu^{2+}$, were synthesized as a single-phase crystal structure by optimizing carbon and $Eu^{2+}$ contents in a carbothermal reduction nitridation method. With increasing $Eu^{2+}$ contents, the photoluminescence spectra were red-shifted from 600 nm peak for 1 mol% for to 700 nm for 7 mol%. It was suggested that this red shift is attributed to the energy transfer from one low-energy sited $Eu^{2+}$ (1) to other high-energy sited $Eu^{2+}$ (2). Finally, the best red sample (620 nm emission peak and 80 nm half width for 3 mole% of $Eu^{2+}$) was packaged on a Blue LED together with two additional green and yellow phosphors, the fabricated White LED showed a high color-rendering index of 90 and white color coordinates of x= 0.321 and y = 0.305.

• Journal of the Korean Society of Food Culture
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• v.37 no.6
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• pp.547-554
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• 2022

This study aimed to investigate the physicochemical characteristics and antioxidant activity of cereal bars containing various concentrations (0, 10, 20, or 30%) of apple pomace (AP). Highest vitamin B₁ and C contents were observed in 30% AP-containing bars, but vitamin B₂ and B₃ contents were highest in the control (0.347 and 3.566 mg/100 g, respectively). Cutting strength decreased significantly in an AP concentration-dependent manner. Total polyphenol and flavonoid contents in 10% AP bars were 2.949±0.157 mg of GAE/g and 1.001±0.009 mg of CE/g, respectively. Antioxidant activities were assessed by measuring free radical scavenging activities, and 10% AP bars had the highest activities, as determined by ABTS (2,2'azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) and DPPH (α-α-diphenyl-β-picrylhydrazyl) assays (0.412±0.008 and 0.492±0.021 mg GAE/g, respectively). These results suggested that apple pomace should be regarded a potential nutritional and antioxidant source.

• Korean Journal of Child Studies
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• v.25 no.6
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• pp.53-68
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• 2004

The purpose of this study was to develop an instrument for adolescent's image about their father. The preliminary survey was performed for 318 adolescents in Seoul. It was a free-writing style survey for adolescent's image, feeling, and thoughts about their father. The main survey which included 121 contents were performed for 400 students in Seoul and finally 75 contents were selected by the results of factor analysis and contents validation. The contents were categorized into 10 sub-variables based on previous studies. 10 sub-variables are Father of mature character, Father who do love me, Father who is devoted to his parents, Father as a friend, Father as a counsellor, Father who is very domestic, Father who is exhausted with work, Father who is hard to be familiar for me, Father with financial competence, Father responsible for supporting the family. This study showed construct validity and concurrent evidence because the correlation among the sub-variables and total score were high.

• The Korean Journal of Food And Nutrition
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• v.32 no.6
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• pp.620-629
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• 2019

To examine the possibility of ear mushroom (EM) as a source of natural vitamin D, the UVB (ultraviolet B) was treated according to sample drying status, drying methods before UVB treatment and harvest time. And then, vitamin D₂ and ergosterol contents were investigated. According to the sample drying status, the vitamin D₂ contents of fresh and freeze-dried EM (whole) increased to 4,634.4~4,780.9 ㎍/100 g D.W. (dry weight) under UVB dose 52.5~70.0 kJ/㎡ and above 18,693.1 ㎍/100 g D.W. under above 105 kJ/㎡, respectively. By drying methods before UVB treatment, vitamin D₂ contents of EM powder (below 500 ㎛) that dried in the vinyl house and freeze-dryer increased to 4,886.2~5,132.9 ㎍/100 g D.W. under above 105 kJ/㎡ and 17,103.7 ㎍/100 g D.W. under 70 kJ/㎡, respectively. Ergosterol content decreased with increasing UVB dose in all experiments. According to the harvest time, vitamin D₂ content under UVB dose 210 kJ/㎡ showed marked difference and in order of June, July, August, October and April. As for the results, the optimum harvest time, drying method before UVB treatment, sample size, UVB dose for the EM contained high vitamin D₂ content were June, freeze-drying, whole, and 105 kJ/㎡, respectively.

• Korean Journal of Food Science and Technology
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• v.54 no.1
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• pp.109-113
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• 2022

Vitamin K is a group of fat-soluble vitamins that naturally exist in phylloquinone (vitamin K₁) and menaquinone (vitamin K₂). In this study, the vitamin K content in different meats commonly consumed in Korea was analyzed using HPLC, and the analytical method was validated. Vitamin K₁ was not detected in any of the meat samples. Vitamin K₂ contents in different cuts of beef ranged from 0.00 to 5.87 ㎍/100 g, whereas the corresponding value in different parts of chicken ranged from 16.59 to 46.64 ㎍/100 g. In the case of pork, vitamin K₂ contents varied from 4.33 to 22.90 ㎍/100 g. Among the different types of meat, the highest vitamin K₂ content was found in boiled chicken meat and skin (46.64 ㎍/100 g). The analytical method was found to be reliable and had high accuracy. These results provide accurate nutritional information and contribute a food composition database for meat consumption.