• Journal of the Korean earth science society
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• v.32 no.7
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• pp.860-870
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• 2011

This study is to explore the Pedagogical Content Knowledge of beginning earth science teachers about the porphyritic texture of igneous rocks, and to suggest the teaching device that can prevent a trial and error of students in earth science instruction. We developed an interview guideline concerned with basic perception on the porphyritic texture, formation condition and formation process of porphyritic rocks, teaching and learning on porphyritic rocks for it. And data was collected from 5 beginning earth science teachers (3 high schools, 2 middle schools) through a group discussion method. In result, despite the porphyritic texture can be found at hypabyssal rocks as well as volcano rocks and plutonic rocks, most beginning earth science teachers cognized that it could be found at hypabyssal rocks only by focusing the formation depth of hypabyssal rocks. Also, the formation of porphyritic texture should be considered the factors such as cooling rate, nucleation density, growth rate, growth time, etc. However they mainly reflected the formation temperature and growth rate as it's parameter. Participants have wrongly perceived that a phenocryst necessarily differs from a groundmass on chemical composition. And they are inclined to discriminate phenocryst from groundmass through their chemical differences, instead of grain size.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.1
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• pp.25-29
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• 2020

This study demonstrates direct-patternable amorphous TiO_x resistive switching (RS) device and the fabrication method using photochemical metal-organic deposition (PMOD). For making photosensitive stock solutions, Ti(IV) 2-ethylhexanoate was used as starting precursor. Photochemical reaction by UV exposure was observed and analyzed by Fourier transform infrared spectroscopy and the reaction was completed within 10 minutes. Uniformly formed 20 nm thick amorphous TiO_x film was confirmed by atomic force microscopy. Amorphous TiO_x RS device, formed as 6 × 6 ㎛ square on 4 ㎛ width electrode, showed forming-less RS behavior in ±4 V and on/off ratio ≈ 20 at 0.1 V. This result shows PMOD process could be applied for low temperature processed ReRAM device and/or low cost, flexible memory device.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.3
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• pp.141-146
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• 2010

$LiFePO_4$ doped with Cr showed improved electrochemical properties as a cathode material of lithium-ion batteries compared to the undoped. The improvement was thought that the doping would raise the electronic conductivity of the compounds. The electrical conductivity of $LiFe_{0.965}Cr_{0.03}B_{0.005}PO_4$ and $LiFe_{0.965}Cr_{0.03}Al_{0.005}PO_4$ powder was measured in the temperature range from 30 to $80^{\circ}C$. The doped powders were synthesized via mechanochemical milling and subsequent heat treatment at 675~$750^{\circ}C$ for 5~10h. The doping enhanced grain growth and electrical conductivity. The electrical conductivity of the $LiFe_{0.965}Cr_{0.03}Al_{0.005}PO_4$ powder at $30^{\circ}C$ was $1{\times}10^{-8}S/cm$, which was higher two orders of magnitude than that of the undoped.

• The Korean Journal of Malacology
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• v.32 no.3
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• pp.149-155
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• 2016

To assess the effects of environmental factors on the sustainability of cultured ark shell Scapharca broughtonii production, we investigated the habitat characteristics of shellfish-farming bays (Gangjin Bay, Yeoja Bay, Keoje Bay and Deukryang Bay). We measured the physiochemical parameters (temperature, salinity, dissolved oxygen, nutrients, chemical oxygen demand and Chlorophyll a) and the geochemical characteristics (chemical oxygen demand, ignition loss, C/N ratio and C/S ratio). Surface sediments were collected from several shellfish-farming bays to examine the geochemical characteristics of both the benthic environment and heavy metal pollution. The grain sizes for Gangjin Bay, Yeoja Bay and Keoje Bay were similar, at the ratio of silt and clay in comparison with Deukryang bay of it. The C/N ratio was more than 5.9, reflecting the range arising from the mix of marine organisms and organic matter. The C/S ratio (more than 4.2) showed that the survey area had anoxic or sub-anoxic bottom conditions. The index of accumulation rate (Igeo) of the metals showed that those research areas can be classified as heavily polluted, heavily to moderately polluted, or more or less unpolluted, respectively. We suggested that the growth of ark shell Scapharca broughtonii in the shellfish-farming bay was effected by the various environmental conditions.

• Journal of Microbiology and Biotechnology
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• v.27 no.12
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• pp.2119-2128
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• 2017

Citrinin (CIT) is a toxic secondary metabolite produced by fungi belonging to the Penicillium, Aspergillus, and Monascus spp. This toxin has been detected in many agricultural products. In this study, a strain Y3 with the ability to eliminate CIT was screened and identified as Cryptococcus podzolicus, based on the sequence analysis of the internal transcribed spacer region. Neither uptake of CIT by cells nor adsorption by cell wall was involved in CIT elimination by Cryptococcus podzolicus Y3. The extracellular metabolites of Cryptococcus podzolicus Y3 stimulated by CIT or not showed no degradation for CIT. It indicated that CIT elimination was attributed to the degradation of intracellular enzyme(s). The degradation of CIT by C. podzolicus Y3 was dependent on the type of media, yeast concentration, temperature, pH, and initial concentration of CIT. Most of the CIT was degraded by C. podzolicus Y3 in NYDB medium at 42 h but not in PDB medium. The degradation rate of CIT was the highest (94%) when the concentration of C. podzolicus Y3 was $1{\times}10^8cells/ml$. The quantity of CIT degradation was highest at $28^{\circ}C$, and there was no degradation observed at 3$5^{\circ}C$. The study also showed that acidic condition (pH 4.0) was the most favorable for CIT degradation by C. podzolicus Y3. The degradation rate of CIT increased to 98% as the concentration of CIT was increased to $20{\mu}g/ml$. The toxicity of CIT degradation product(s) toward HEK293 was much lower than that of CIT.

• Journal of the Mineralogical Society of Korea
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• v.6 no.2
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• pp.94-104
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• 1993

The compositional variation of electrums from gold-silver and antimony deposits in the Dunjeon Baegjeon mining area, range from 22.6 to 69.5 atom% of Ag. Ag contents in electrums vary with paragenetic sequences and associated minerals. Ag contents increase from core to margin in a single grain. Compositional range of electrums from the North ore deposits of the Dunjeon gold mine are from 22.6 to 29.5 atom% of Ag. Electrums contain Cu(0.40 to 0.55 atom%) and Bi(0.35 to 0.67 atom%). Composition of electrums from the South ore deposits of the Dunjeon gold mine vasies from 33.6 to 69.5 atom% of Ag. Cu and As contents in electrums range from 0.20 to 1.92 and from 0.70 to 1.90 atom%, respectively. As the content of Ag in electrums increase, the contents of Bi and As in electrums increase but that of Cu decrease. Electrums of the Baegjeon gold deposits contain 35.6 to 63.5 atom% of Ag, suggesting that Au contents in electrums associated with base metal sulfied be higher than those associate with Ag-minerals. Ag/Au rations in electrums increase with decreasing temperature, salinity and $fs_2$ of the mineralizing solution.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.323-327
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• 2003

Microwave dielectric properties of (P $b_{0.4}$C $a_{0.6}$)[($Fe_{\frac{1}{2}}$N $b_{\frac{1}{2}}$)$_{1-x}$ (M $g_{1}$ 3/N $b_{2}$ 3/)x] $O_3$ (PCFMN) ceramics were investigated as a function of (M $g_{1}$ 3/N $b_{2}$ 3/)$^{4+}$ content (0.1$\leq$x$\leq$0.8). A single perovskite phase with the cubic structure was obtained through the given composition range. The unit cell volume was increased with (M $g_{1}$ 3/N $b_{2}$ 3/)$^{4+}$, due to the larger average ionic size of (M $g_{1}$ 3/N $b_{2}$ 3/)$^{4+}$ than that of ($Fe_{\frac{1}{2}}$N $b_{\frac{1}{2}}$)$^{4+}$ for B-site ion. Dielectric constant (K) and Temperature Coefficient of Resonant Frequency(TCF) of PCFMN ceramics were dependent on (M $g_{1}$ 3/N $b_{2}$ 3/)$^{4+}$ content due to the decrease of ionic polarizability and B-site bond valence, respectively. Qf value was decreased with (M $g_{1}$ 3/N $b_{2}$ 3/)$^{4+}$ content due to the decrease of grain size. Typically, K of 73.56, Qf of 5,074 GHz and TCF of -6.45 ppm/$^{\circ}C$ were obtained for the specimens with x=0.4 sintered at 125$0^{\circ}C$ for 3 h.125$0^{\circ}C$ for 3 h.

• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.928-934
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• 2002

Gallium doped Zinc Oxide(GZO) films were deposited by dc magnetron sputtering using a GZO ceramic target at various conditions such as substrate temperature (RT, 400), residual water pressure ($P_{H_2O}$; 1.61${\times}10^{-4}∼2.2{\times}10^{-3}$ Pa), introduction of $H_2$ gas (8.5%) and different magnetic field strengths(250, 1000G). GZO films deposited without substrate heating showed clear degradation in film crystallinity and electrical properties with increasing $P_{H_2O}$. The resistivity increased from 3.0${\times}10^{-3}$ to 3.1${\times}10^{-2}{\Omega}㎝$ and the grain size of the films decreased from 24 to 3 nm when PH2O was increased from 1.61${\times}10^{-4}$ to 2.2${\times}10^{-3}$ Pa. However, degradation in electrical properties with increasing $P_{H_2O}$ was not observed for the films deposited with introduction of 8.5% $H_2$. When magnetic field strength of the cathode increased from 250G to 1000G, crystallinity and electrical properties of GZO films improved remarkably about all the $P_{H_2O}$. This result could be attributed to the decrease in film damage caused by the decrease in plasma impedance.

• Journal of the Korean Ceramic Society
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• v.24 no.3
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• pp.243-250
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• 1987

The effects aging on some properties and thermal-shock behavior of zirconia partially stabilized with 9 mol% MgO (9MZ) were studied. 9MZ specimens were aged over $1200^{\circ}$-$1400^{\circ}C$ for 12hours subsequently, after sintering at $1650^{\circ}C$ for 4 hours. Fracture strength(both before and after thermal-shock test), linear thermal expansion, monoclinic fraction and phase transition by XRD, density, galvanic potential and microstructure were measured. Quantitative chemical analysis around the grain-boundary of the specimen aged at $1350^{\circ}C$ was also conducted by EDX. The aging of 9MZ specimen causes a thermal decomposition of cubic-$ZrO^{2}$ into the formation metastable tetragonal-$ZrO^{2}$ and MgO. The former increases the residual strength after thermal-shock test and the latter improves the thermal-shock resistance due to thermal conduction through the continuous magnesia phase and the formation of monoclinic phase content in matrix were increased with decreasing the aging temperature from $1400^{\circ}C$ to $1200^{\circ}C$. Galvanic potential of the aged specimen exhibited a proper emf characteristic.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.7
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• pp.639-647
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• 2009

In this work, wrapping conductors with thin magnetic materials is proposed as a magnetic shielding method. The 0.1 mm thick metal sheets of mu-metal, grain-oriented electrical steel, and non-oriented electrical steel were produced from commercial alloy sheets through cold rolling and followed high temperature annealing. In case of 3-phase electric currents, mu-metal was the best in shielding performance at a B-field magnitude of about 100 ${\mu}T$, whereas silicon steels were better than mu-metal at a B-magnitude over 500 ${\mu}T$. In addition, wrapping with silicon steel(inner) together with mu-metal(outer) resulted in a shielding factor less than 0.1 even at 500 ${\mu}T$. These results are due to changes in hierarchy of magnetic permeabilities of the materials with increasing magnetic field strength. In case of single-phase electric current, B-magnitude outside the magnetic shell was rather increased compared to the unshielded case. This result is explained by vector composition of B-fields near magnetic shielding materials.