• Korean Journal of Materials Research
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• v.19 no.4
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• pp.198-202
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• 2009

For use in ultrasonic actuators, we investigated the structural and piezoelectric properties of $(1\;-\;x)Pb(Zr_{0.515}Ti_{0.485})O_3$ - $xPb(Sb_{1/2}Nb_{1/2})O_3$ + 0.5 wt% $MnO_2$ [(1 - x)PZT - xPSN + $MnO_2$] ceramics with a variation of x (x = 0.02, 0.04, 0.06, 0.08). All the ceramics, which were sintered at $1250^{\circ}C$ for 2 h, showed a typical perovskite structure, implying that they were well synthesized. A homogeneous micro structure was also developed for the specimens, and their average grain size was slightly decreased to $1.3{\mu}m$ by increasing x to 0.8. Moreover, a second phase with a pyrochlore structure appeared when x was above 0.06, which resulted in the deterioration of their piezoelectric properties. However, the 0.96PZT-0.04PSN+$MnO_2$ ceramics, which corresponds with a morphotropic phase boundary (MPB) composition in the (1 - x)PZT - xPSN + $MnO_2$ system, exhibited good piezoelectric properties: a piezoelectric constant ($d_{33}$) of 325 pC/N, an electromechanical coupling factor ($k_p$) of 70.8%, and a mechanical quality factor ($Q_m$) of 1779. The specimens with a relatively high curie temperature ($T_c$) of $305^{\circ}C$ also showed a significantly high dielectric constant (${\varepsilon}_r$) value of 1109. Therefore, the 0.96PZT - 0.04PSN + $MnO_2$ ceramics are suitable for use in ultrasonic vibrators.

• Korean Journal of Microbiology
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• v.41 no.4
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• pp.300-305
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• 2005

A transcriptionally active fragment $(P_{19})$ isolated by utilizing the promoter-probe shuttle vector pSK1Cat was analyzed. By subcloning analysis, the 180 bp region $(P_{180})$ responsible for the activity was determined. Transcriptional fusion of the C. glutamicum metX gene to $P_{180}\;(P_{180}-metX)$ resulted in a 24-fold increase in MetX activity in a complex medium, while a 13-fold increase was observed with the $P_{tac}$ promoter. Additionally, the expression conferred by $P_{180}$ was not affected by methionine added to the growth medium, suggesting that the $P_{180}$ clone is useful for the deregulated expression of biosynthetic genes in C. glutamicum during amino acid fermentation. Introduction of $P_{180}-metX$ into a lysine-producing C. glutamicum resulted in the production of methionine to 0.8 g/l.

• Korean Journal of Materials Research
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• v.33 no.8
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• pp.330-336
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• 2023

The effects of Ni²⁺ substitution for Mg²⁺-sites on the microwave dielectric properties of (Mg_1-xNi_x)(Ti_0.95(Mg_1/3Ta_2/3)_0.05)O₃ (0.01 ≤ x ≤ 0.05) (MNTMT) ceramics were investigated. MNTMT ceramics were prepared by conventional solid-state reaction. When the MgO / TiO₂ ratio was changed from 1.00 to 1.02, MgTi₂O₅ was detected as a secondary phase along with the MgTiO₃ main phase in the MNTMT specimens sintered at 1,400 ℃ for 4h. For the MNTMT specimens with MgO / TiO₂ = 1.07 sintered at 1,400 ℃ for 4h, a single phase of MgTiO₃ with an ilmenite structure was obtained from the entire range of compositions. The relative density of all the specimens sintered at 1,400 ℃ for 4h was higher than 95 %. The quality factor (Qf) of the sintered specimens depended strongly on the degree of covalency of the specimens, and the sintered specimens with x = 0.01 showed the maximum Qf value of 489,400 GHz. The dielectric constant (K) decreased with increasing Ni²⁺ content because Ni²⁺ had a lower dielectric polarizability (1.23ų) than Mg²⁺ (1.32ų). As Ni²⁺ content increased, the temperature coefficient of resonant frequency (TCF) improved, from -55.56 to -21.85 ppm/℃, due to the increase in tolerance factor (t) and the lower dielectric constant (K).

• Journal of the Korean Chemical Society
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• v.51 no.3
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• pp.240-243
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• 2007

The eight coordinated yttrium(III) complex Y(tpb)3(H2O)2 (Htpb=4,4,4-Trifluoro-1-phenyl-1,3-butanedione) has been synthesized and structurally characterized by X-ray diffraction method. The coordination polyhedron of Y(tpb)3(H2O)2 has a dodecahedron. The angle between two trapezia, Y-O2-O1-O5-O6 and Y-O4-O3-O8-O7, is 89.59°. The O1-O5 and O3-O8 distances are 2.965 and 2.995 A whereas the O2-O6 and O4-O7 distances are 4.256 and 4.403 A.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.7
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• pp.292-297
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• 2002

In this paper, a flat-type $L_{-}$-$B_{8}$ mode Ultrasonic Motor[USM] having the size of 80 x 20 x ${1.5}mm^3$($l{\times}\omega{\times}t$) was designed and fabricated to examine the characteristics of an ultrasonic vibration. We used ANSYS simulation program based on FEM to get the optimum design of this USM. As results of experiment, the fastest speed of revolution(v), the maximum torque(T) and the efficiency(n) were 37.5cm/s, 5.0 mN.m and 1.17% when 27.9KHz, 150N, 50V were applied respectively. And this flat-type $L_{-}$-$B_{8}$ mode USM could be controlled the speed of rotor revolution by applied voltage, frequency and pre-load of rotor as well as showed the characteristics of typical drooping torque-speed, large torque and high speed. So, we think that this flat-type $L_{-}$-$B_{8}$ mode USM has characteristics of enough torque and velocity to be usable for applications in forwarding device of an electric card or a paper, etc.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.25-27
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• 2007

$Eu^{2+}$-doped $Ca_2Si_5N_8$ was grown on Si(100) substrate using metal-organic deposition (MOD) method and post-annealed at $900^{\circ}C$ in various atmosphere. Luminescence properties of these thin films were investigated with variations of $Eu^{2+}$-doped concentrations and annealing atmosphere. Thin film was formed with clean surface and uniform thickness of about 72 nm. From the measurements of luminescence properties of thin films, film must be post-annealed in nitrogen or mixture of nitrogen and hydrogen atmosphere to emit a sufficient light. For $Ca_{1.5}Eu_{0.5}Si_5N_8$ thin film annealed at $900^{\circ}C$ in nitrogen atmosphere, excitation band from 380 to 420 nm was detected with the maximum intensity at 404 nm and two broad emission bands from 530 to 630 nm were observed. These broad excitation and emission bands must be attributed to the nitrogen incorporations into the films. From the results, $Ca_{2-x}Eu_xSi_5N_8$ thin film has probability for next generation thin film lighting applications such as light emitting diode (LED) or electro-luminescence (EL).

• KOREAN JOURNAL OF CROP SCIENCE
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• v.33 no.3
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• pp.215-221
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• 1988

The hop yield prediction model developed based on meteorological elements in Hoeongseong was Y=6,042.846-17.665 $X_1$-0.919 $X_2$-96.538 $X_3$-138.105 $X_4$＋86.910 $X_{5}$ ＋ $X_{6}$ with MS $E_{p}$ of 25.258, $R_{p}$$^{2}$ of 0.9991, R $a_{p}$$^{2}$ of 0.9962 and $C_{p}$ of 7.00. The minimum air temperature at early growing stage ( $X_1$), the total precipitation at cone ripening stage ( $X_2$), the maximum air temperature at flower bud differentiation stage ( $X_3$) and the maximum air temperature at flowering stage ( $X_4$) influenced on hop yield as decrement weather elements. The average air temperature at early growing stage ( $X_{5}$ ) and the total sunshine hours at cone development stage ( $X_{6}$ ) influenced on hop yield as increment weather elements.lements.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.23 no.2
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• pp.25-33
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• 1978

7 parent varieties and 21 $_{x}\textrm{F}_1 and $_{x}\textrm{F}_2 hybrids from 7 X 7 partial diallel crosses were used as the materials, and degree of heterosis was studied in 9 agronomic characters of rice. Degree of heterosis was more remarkable in $_{x}\textrm{F}_1 hybrids than $_{x}\textrm{F}_2 hybrids. and significant differences were showed in many hybrid generations. and also over dominance could be shoo wed in eight characters except 1000 kernel weight of rice.

• Journal of the Korean Magnetics Society
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• v.8 no.2
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• pp.67-73
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• 1998

Crystallographic and magnetic properties of perovskite $Gd_{1-x}Sr_xFeO_{3-y}$ (x=0.0, 0.5) substituted $Sr^{2+}$ having larger inoic radius than $Gd^{3+}$ at GdFeO$_3$have been studied by x-ary diffraction, M$\ "{o}$ssbauer spectroscopy, and VSM. The cystal structures are found to be orthorhombic with the lattice parameters : $a_o=5.53\;{\AA},\;b_o=5.608\;{AA},\;C_o=7.724\;{\AA}$ for $Gd_{0.5}Sr_{0.5}FeO_{3-y}$ (x=0.0, 0.5) have been investigated over temperature range from 4.2 to 690 K using the M$\ "{o}$ssbauer technique. The Neel temperatuer of $Gd_{1-x}Sr_xFeO_{3-y}$ system is 690 K with x value of 0.0 and 515 K with x value of 0.5. Analysis of M$\ "{o}$ssbauer spectra Mohr's salt analysis for $Gd_{1-x}Sr_xFeO_{3-y}$ demonstrated the existence of the mixed valence states of iron and the coordination state of $Fe^{3+}$ and $Fe^{4+}$ ions. The Corresponding hyperfine parameters for GdFeO$_3$ are compatible with S=5/2 $Fe^{3+}$ in octahedral cooedination.l cooedination.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.1
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• pp.24-31
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• 2000

This study was conducted to determine the effect of soil physical characteristics on rhizome rot incidence of platycodon. Sampling sites were Keochang 4, Kimhae 7, Haman 6, Chinju 6 and Koseong 3 fields in Kyongnam province and Hongcheon 6 fields in Kangwon province. The root disease incidence rate was correlated with soil depth Y=-0.747X+88.19($R^2=0.394^{***}$), soil hardness Y=4.36X+8.93($R^2=0.201^*$), bulk density Y=104.7X-80.99($R^2=0.295^{**}$), clay content Y=1.24X+14.14($R^2=0.196^*$), porosity Y=-3.11X+215.9($R^2=0.220^*$) and silt content Y=-0.75X+67.85($R^2=0.178^*$). The yield was correlated with soil depth Y=0.263X+0.971($R^2=0.105^*$), clay content Y=-0.688X+32.74($R^2=0.158^*$), porosity Y=1.974X-93.19($R^2=0.231^{**}$) and silt content Y=53.05X-108.65($R^2=0.232^*$), The optimum cultivated land of perennial platycodon was soil depth over 1m, soil hardness under $5kg\;cm^{-2}$, bulk density $1.0Mg\;m^{-3}$, moisture content 13~17%. clay content 5~10%, porosity 58~63%, silt content 38~64% and soil texture of silt loam.