• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3213-3214
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• 2011

• 한국자기공명학회:학술대회논문집
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• 한국자기공명학회 2002년도 제20회 학술발표회
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• pp.15-15
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• 2002

• E2M - 전기 전자와 첨단 소재
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• 제16권9호
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• pp.64.1-64
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• 2003

A metal-ferroelectric [SrBi$_2$Ta$_2$O$\_$9/ (SBT)-high-k-insulator(PrOx)-semiconductor(Si) structure has been fabricated and evaluated as a key part of metal-ferroelectric-insulator-semiconductor-field-effect-transistor MFIS-FET memory, aiming to improve the memory retention characteristics by increasing the dielectric constant in the insulator layer and suppressing the depolarization field in the SBT layer. A 20-nm PrOx film grown on Si(100) showed both a high of about 12 and a low leakage current density of less than 1${\times}$ 10e-8 A/$\textrm{cm}^2$ at 105 MV/cm. A 400-nm SBT film prepared on PrOx/Si shows a preferentially oriented (105) crystalline structure, grain size of about 130 nm and subface roughness of 3.2 nm. A capacitance-voltage hysteresis is confirmed on the Pt/SBT/PrOx/Si diode with a memory window of 0.3V at a sweep voltage width of 12 V. The memory retention time was about 1 104s, comparable to the conventional Pt/SBT/SiO$\_$x/N$\_$y/(SiO$\_$N/)/Si. The gradual change of the capacitance indicates that some memory degradation mechanism is different from that in the Pt/SBT/SiON/Si structure.

• Archives of Metallurgy and Materials
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• 제67권4호
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• pp.1543-1546
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• 2022

The aluminum composite with dispersed high entropy alloy were developed by stir casting involving the powder-in-tube method. First, Al_0.5CoCrCuFeNi high entropy alloy (HEA) powder was made by mechanical alloying, and the powder was extruded in a tube-type aluminum container to form HEA precursor. The extruded HEA precursor was then dispersed in the aluminum matrix via stir casting. As a result, Fe-Cr-Ni based high-entropy phases was uniformly formed in the aluminum matrix, revealing ~158, 166, 235% enhancement of tensile strength by incorporating 1, 3, and 5 wt% HEA particles, respectively.

• 한국과학교육학회지
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• 제17권1호
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• pp.65-73
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• 1997

The purpose of this study is to develop a valid and reliable instrument, applicable to high school Earth Science class experiment. In advance of developing items, I was selected 14 inquiry process skills and specified evaluative objectives for each of them to develop scales and criteria for them. I developed 28 evaluation items for 5 experiment subjects among those of high school Earth Science class. The first field trial was performed a sample of 5 high school students, and the second one using a sample of 25 high school students. The results are as follows. (1) The content validity and reliability(Cronbach $\alpha$) of the developed items were 82.7% and .86, respectively, the developed instrument in this study is considered valid and reliable. (2) The average difficulty index was .69 and the discrimination index was .30. (3) Answer sheets based on the reported results were rated 5 teachers and Inter-rater Reliabilitiy and Inter-rater Consistency were analyzed, its indices were .80 and .76, respectively. (4) The developed items show a low coefficient of .45 with TESIS, a set of paper-and-pencil test items developed by Lee, Hang-Ro(1991). That the experiment assessment is solely subject to the rater's viewpoint has been one of the major problems raised concerning the matter. This research, however, shows that a set of more specified scales and criteria for the evaluation will make it more valid, reliable and efficient.

• 한국전기전자재료학회논문지
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• 제25권4호
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• pp.298-303
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• 2012

$Y_{1-x}VO_4:Eu_x^{3+}$ red phosphors were synthesized with changing the mol ratios of $Eu^{3+}$ ions by using the solid-state reaction method. The crystalline structure of phosphors was found to be a tetragonal system with the maximum diffraction intensity at $25.02^{\circ}$. The grain particles showed the truncated hexagonal patterns with a very homogeneous size distribution at 0.05 mol of $Eu^{3+}$ ion. The excitation spectra of the phosphor ceramics were composed of a broad band centered at 303 nm and weak narrow multilines peaked in the range of 360-420 nm. The dominant emission spectrum was the strong red emission centered at 619 nm due to the $^5D_0{\rightarrow}^7F_2$ electric dipole transition. The experimental results suggest that the optimum doping mol ratio of $Eu^{3+}$ ions for preparing the red phosphors is 0.10 mol with the asymmetry ratio of 5.21.

• 과학교육연구지
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• 제34권2호
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• pp.327-341
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• 2010

이 연구는 과학고등학교 학생들이 과학자들과 함께 하는 녹색탐사활동에 참여하기 전과 참여하고 난 후에 과학자와 과학자가 일하는 곳에 대한 인식을 알아보고, 활동이 학생들의 인식에 영향을 미칠 가능성에 대해 알아보고자 수행되었다. 변형된 DAST를 이용하여 과학고등학교 1학년 64명의 학생들을 대상으로 활동에 참여하기 전과 후에 과학자의 이미지와 일하는 곳에 대해 조사하였다. 참여자들은 과학자에 대해 실험복을 입은 20-30대 남성이 시험관, 플라스크, 기계들을 있는 실험실에서 혼자 연구하는 전형적인 이미지를 가지고 있는 것으로 나타났다. 과학자의 전형적인 이미지를 나타내는 항목들과 하는 일에 대해서는 활동 전(M=1.69, SD=1.14)과 활동 후(M=1.96, SD=1.24, t=4.43, p<0.001)에 유의한 수준에서 차이를 보여 과학자와의 활동이 과학자와 그들이 하는 일에 대한 인식의 변화에 영향을 미칠 가능성이 있음을 시사한다고 볼 수 있다. 따라서 학생들이 과학자들과 함께하는 녹색탐사활동을 지속적으로 계발시키고 보급시킬 필요가 있다.

• 한국포장학회지
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• 제27권2호
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• pp.115-121
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• 2021

The evaluation of package temperature for fresh preservation of cucumber was investigated. The fresh cucumber is available in markets of Korea during whole seasons, for the help of farmer, distributor and consumer. Cucumbers were stored within cardboard boxes packaging covered with low density polyethylene (LDPE) at different temperatures (5, 10, 15 and 20℃). Changes in weight loss, hue angle, firmness, moisture content and general appearance (shape of cucumber) were investigated during storage of cucumbers. General appearance index with non-packaging decreased more than with LDPE film packaging at 5℃ and 10℃. During storage of cucumbers, general appearance index as freshness showed packaging effect at low temperature than room temperature. In the fresh weight loss, the packaged cucumbers were less reduced than that of the non-packaging ones. At color change, Hue angle of cucumber stored within low temperature with film packaging decreased gradually during storage. However remarkable change in hue angle were observed in cucumber within LDPE film packaging treatments of 15℃ and 20℃ storage. The effect of hue angle with packaging appears differently depending on the storage temperature conditions. The firmness and moisture content of cucumber flesh were not affected by packaging and storage temperature. In this experiment, cucumbers packaged with LDPE film at 5℃ and 10℃ were the most desirable for extending the quality. These results suggest that packaging of low temperature treatments in combination could be effective in prolonging the shelf life of cucumber.

• 한국분말재료학회지
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• 제29권3호
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• pp.213-218
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• 2022

This study investigates the interfacial reaction between powder-metallurgy high-entropy alloys (HEAs) and cast aluminum. HEA pellets are produced by the spark plasma sintering of Al_0.5CoCrCu_0.5FeNi HEA powder. These sintered pellets are then placed in molten Al, and the phases formed at the interface between the HEA pellets and cast Al are analyzed. First, Kirkendall voids are observed due to the difference in the diffusion rates between the liquid Al and solid HEA phases. In addition, although Co, Fe, and Ni atoms, which have low mixing enthalpies with Al, diffuse toward Al, Cu atoms, which have a high mixing enthalpy with Al, tend to form Al-Cu intermetallic compounds. These results provide guidelines for designing Al matrix composites containing high-entropy phases.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.148-154
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• 2020

The radiation induced segregation of Cr at grain boundaries (GBs) in Ferritic/Martensitic steels was modeled assuming vacancy and interstitialcy diffusion mechanisms. In particular, the dependence of segregation on temperature and grain boundary misorientation angle was analyzed. It is found that Cr enriches at grain boundaries at low temperatures primarily through the interstitialcy mechanism while depletes at high temperatures predominantly through the vacancy mechanism. There is a crossover from Cr enrichment to depletion at an intermediate temperature where the Cr:Fe vacancy and interstitialcy diffusion coefficient ratios intersect. The bell-shape Cr enrichment response is attributed to the decreasing void sinks inside the grains as temperature rises. It is also shown that low angle grain boundaries (LAGBs) and special Σ coincidence-site lattice (CSL) grain boundaries exhibit suppressed radiation induced segregation (RIS) response while high angle grain boundaries (HAGBs) have high RIS segregation. This different behavior is attributed to the variations in dislocation density at different grain boundaries.