• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.261-267
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• 2023

Crystal structure, microstructure, and dielectric properties of the (Ca, Sr)(Zr, Ti)O₃ (CSZT) system has been studied as a function of sintering temperature and MgO addition for microwave applications. A single-phase CSZT powder with the orthorhombic crystal structure was obtained by the solid-state reaction method. The powder compacts were sintered at 1200℃, 1300℃, and 1400℃ respectively. All the sintered samples had a single-phase orthorhombic crystal structure and grain size increased with sintering temperature. In the case of 1 mol% MgO addition, the orthorhombic crystal structure was the main phase; however, a secondary phase appeared during sintering at 1400℃, as determined by EDS analysis. At 1400℃, the undoped and MgO-doped CSZT had almost similar grain size distribution and densification but the grain size distribution became slightly narrow. The MgO-doped CSZT showed excellent low-loss dielectric properties: ε_r = 34.14, tanδ = 0.00047, τ_ε = -3.58 ppm/℃ at 1 MHz.

• Journal of The Korean Society of Grassland and Forage Science
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• v.33 no.1
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• pp.1-5
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• 2013

Andaok, a new single cross variety, is a yellow dent maize hybrid (Zea mays L.) developed by the maize breeding team at the National Institute of Crop Science (NICS), RDA in 2011. This hybrid, which has a high yield of grain, was produced by crossing two inbred lines, KS161 and KS162. KS161 is the seed parent and KS162 is the pollen parent of Andaok. Silking date of Andaok is 3 days later than that of the check hybrid, Jangdaok. Plant height of Andaok is longer than that of Jangdaok. Ear numbers per 100 plants of Andaok is more than that of Jangdaok. Ear length of Andaok is shorter than that of Jangdaok. The weight of 100 seeds of Andaok is heavier than that of Jangdaok. It has moderate resistance to southern corn leaf blight (Bipolaris maydis), black streaked dwarf virus (BSDV) and corn borer. It has strong resistance to northern corn leaf blight (Exserohilum turcicum). It has resistance to lodging. Andaok was evaluated for its yield of grain at three locations from 2009 to 2011. The grain yield of Andaok was 7.80 ton/ha. Seed production of Andaok has gone well due to a good match during crossing between the seed parent, KS161, and the pollen parent, KS162, in Yeongwol.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.12
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• pp.962-968
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• 2011

In this study, we investigated the effects of Mn dopant (0.1~3.0 at% $Mn_3O_4$ sintered at 1000$^{\circ}C$ for 1 h in air) on the bulk trap (i.e. defect) and grain boundary properties of ZnO, ZM(0.1~3.0) using admittance spectroscopy (AS), and impedance-modulus spectroscopy (IS & MS). As a result, three kinds of defect were found below the conduction band edge of ZnO as 0.09~0.14 eV (attractive coulombic center), 0.22~25 eV ($Zn^{{\cdot}{\cdot}}_i$), and 0.32~0.33 eV ($V^{\cdot}_o$). The oxygen vacancy increased with Mn doping. In ZM, an electrically single grain boundary as double Schottky barrier was formed with 0.82~1.0 eV of activation energies by IS & MS. We also find out that the barriers of grain boundary of Mn-doped ZnO (${\alpha}$-factor=0.13) were more stabilized and homogenized with temperature compared to pure ZnO.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.12
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• pp.961-968
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• 2012

In this study, we have investigated the effects of Mn and Co co-doping on defects, J-E curves and grain boundary characteristics of ZnO-$Bi_2O_3$ (ZB) varistor. Admittance spectra and dielectric functions show two bulk defects of $Zn_i^{{\cdot}{\cdot}}$ (0.17~0.18 eV) and $V_o^{\cdot}$ (0.30~0.33 eV). From J-E characteristics the nonlinear coefficient (${\alpha}$) and resistivity (${\rho}_{gb}$) of pre-breakdown region decreased as 30 to 24 and 5.1 to 0.08 $G{\Omega}cm$ with sintering temperature, respectively. The double Schottky barrier of grain boundaries in ZB(MCo) ($ZnO-Bi_2O_3-Mn_3O_4-Co_3O_4$) could be electrochemically single type. However, its thermal stability was slightly disturbed by ambient oxygen because the apparent activation energy of grain boundaries was changed from 0.64 eV at lower temperature to 1.06 eV at higher temperature. It was revealed that a co-doping of Mn and Co in ZB reduced the heterogeneity of the barrier in grain boundaries and stabilized the barrier against an ambient temperature (${\alpha}$-factor= 0.136).

• Korean Journal of Plant Resources
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• v.22 no.4
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• pp.359-363
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• 2009

In order to establish labor-saving culture technology in Tartary buckwheat, three cultural practices: hand planting, drill sowing machine and soil cover direct seeding machine, were compared.The highest grain yield was found in soil cover direct seeding plot with a value of 3.4 g per plant. As a result, grain yield may be estimated to be 113kg in soil cover direct seeding and 80kg in hand scattering. In addition, for the weed control, three herbicide treatments: single use of Alachlor, mixture and combination of Alachlor and Paraquat dichloride were conducted. the mixture showed over 90% weed control value, and the highest grain yield was found in the combination treatment. Combine machine was effective to reduce the ratio of grain loss and working hour by enhancing the working efficiency to 15${\sim}$20min/10a.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.12
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• pp.936-941
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• 2010

In this study, we have investigated the effects of Mn dopant on the bulk trap levels and grain boundary characteristics of $Bi_2O_3$-based ZnO (ZB) varistor using admittance spectroscopy and dielectric functions (such as $Z^*,\;Y^*,\;M^*,\;\varepsilon^*$, and $tan\delta$). Admittance spectra and dielectric functions show two bulk traps of $Zn_i^{..}$ (0.20 eV) and $V^{\bullet}_o$ (0.29~0.33 eV) in ZnO-$Bi_2O_3-Mn_3O_4$ (ZBM). The barrier of grain boundaries in ZBM could be electrochemically single type. However, its thermal stability was slightly disturbed by ambient oxygen because the apparent activation energy of grain boundaries was changed from 0.79 eV at lower temperature to 1.08 eV at higher temperature. The grain boundary capacitance $C_{gb}$ was decreased slightly with temperature as 1.3~1.8 nF but resistance $R_{gb}$ decreased exponentially. The relaxation time distribution can result from the heterogeneity of the barriers constituting the varistor. It is revealed that Mn dopant in ZB reduced the heterogeneity of the barrier in grain boundaries and stabilized the barrier against the ambient temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.11
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• pp.882-889
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• 2011

In this study, we have investigated the effects of Co doping on I-V curves, bulk trap levels and grain boundary characteristics of ZnO-$Bi_2O_3$ (ZB) varistor. From I-V characteristics the nonlinear coefficient (a) and the grain boundary resistivity (${\rho}_{gb}$) decreased as 32${\rightarrow}$22 and 18.4${\rightarrow}0.6{\times}10^9{\Omega}cm$ with sintering temperature (900~1,300$^{\circ}C$), respectively. Admittance spectra and dielectric functions show two bulk traps of zinc interstitial, $Zn_i^{{\cdot}{\cdot}}$(0.16~0.18 eV) and oxygen vacancy, $V_o^{{\cdot}}$ (0.28~0.33 eV). The barrier of grain boundaries in ZBCo (ZnO-$Bi_2O_3-Co_3O_4$) could be electrochemically single type. However, its thermal stability was slightly disturbed by ambient oxygen because the apparent activation energy of grain boundaries was changed from 0.93 eV at the 460~580 K to 1.13 eV at the 620~700 K. It is revealed that Co dopant in ZB reduced the heterogeneity of the barrier in grain boundaries and stabilized the barrier against the ambient temperature.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.398-401
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• 2007

The performance characteristics of Polyethylene-Nitrous oxide (PE-N2O) hybrid rocket motor with the variation of the grain geometry was investigated. To compare the performance parameters under the different port number, single and four port grains were used in this study. In order to improve the performance by enhancing mixing between fuel and oxidizer, the fuel grain having the mixing chamber was additionally studied. From the motor firing tests, it is found that the motor having 4-port fuel grain with the mixing chamber showed the highest performance among all cases. Therefore we have confirmed that with only the geometrical change of the fuel grain, it was possible to give quite influential improvement on the motor performance

• KOREAN JOURNAL OF CROP SCIENCE
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• v.53 no.spc
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• pp.78-83
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• 2008

Soybean [Glycine max (L.)] is a major source of protein for human and animal feed. Inter- and intra-genotype variation of soybean protein has been investigated by soybean researchers. However, limited sample amount of soybean single seed there is no report that investigated intra-plant variation of soybean protein within soybean plant. Recently a non-destructive NIR (near-infrared reflectance) spectroscopy using single seed grain to analyze seed protein was developed. The objectives of this study were to understand variation of seed protein content within plant and to determine the amount of minimum sample size which can represent protein content for a soybean plant. Frequency distribution of protein content within plant showed normal distribution. There was an intra-cultivar variation for protein content in soybean cultivar Seonnogkong. Difference of protein content among single plants of Seonnokong was recognized at 5% level. Seeds in lower position on plant stem tended to accumulate more protein than in higher position. There was significant difference for protein content between sample size 5 seeds and sample size of more than 5 seeds (10, 20, 30, 40, and 50 seeds) at a soybean plant with 57 seeds however no difference was recognized among sample size (5, 10, 20, and 30 seeds) at a soybean plant with 33 seeds. Around 20% seeds of soybean from single plant needed to determine the protein content to represent protein content of single soybean plant. This study is the first one to report evidence of intra-plant variation for proteincontent which detected by non-destructive NIR spectroscopy using single seed grain in soybean.

• Journal of Magnetics
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• v.13 no.3
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• pp.102-105
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• 2008

This study examined the feasibility of the combining HDDR-process (hydrogenation, disproportionation, desorption and recombination) with mechanical milling to prepare single domain $Nd_2Fe_{14}B$ particles from a Nd-Fe-B alloy ingot. The $Nd_{15}Fe_{77}B_8$ alloy was HDDR-treated and then subjected to a roller-milling. In the HDDR-treated $Nd_{15}Fe_{77}B_8$ alloy, very small $Nd_2Fe_{14}B$ grains comparable to their critical single domain size(0.3 ${\mu}m$) were observed. These fine individual grains were separated successfully along the grain boundaries by a roller-milling. The separated $Nd_2Fe_{14}B$ grains were found to be single domain particles. These results suggest that single domain particles of the $Nd_2Fe_{14}B$ phase can be prepared from a Nd-Fe-B ingot alloy by combining a HDDR-process with mechanical milling.