• Transactions on Electrical and Electronic Materials
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• v.14 no.4
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• pp.193-198
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• 2013

The effects of additives (Cr, Nb, Dy, and Bi) on microstructure, electrical properties, dielectric characteristics, and aging behavior of $ZnO-V_2O_5-MnO_2-Co_3O_4-La_2O_3$ (ZVMCL) ceramics were systematically investigated. The phase formed in common for all ZVMCL ceramics modified with various additives consisted of ZnO grain as a main phase, and $Zn_3(VO_4)_2$ and $ZnV_2O_4$ as the secondary phases. The sintered density and average grain size were in the range of $5.4-5.54g/cm^3$ and $3.7-5.1{\mu}m$, respectively. The ZVMCL ceramics modified with Cr exhibited the highest breakdown field (6,386 V/cm) and the ZVMCL ceramics modified with Nb exhibited the lowest breakdown field (3,517 V/cm). All additives enhanced the nonlinear coefficient (${\alpha}$), by a small or large margin, in particular, additives such as Bi and Nb noticeably increased the nonlinear coefficient, with ${\alpha}=25.5$ and ${\alpha}=23$, respectively. However, on the whole, all additives did not improve the stability against a DC stress, compared with ZVMCL ceramics.

• Journal of the Korean Magnetics Society
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• v.11 no.2
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• pp.45-49
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• 2001

Effects of multilayer structure and annealing condition on the soft magnetic properties of sputtered Fe/CoNbZr multilayers were investigated. We observed a minimum coercivity (1.1 Oe) at 5 nm thick Fe layer and the maximum permeability (2300) at 15 nm Fe layer and high saturation magnetization in the as-deposited state. As a result of increase of Fe grain size, coercivity increases with increasing Fe layer thickness. Degradation of ${\mu}$ at the thin Fe layer region may be due to the intermixed phase of high magnetostriction, such as CoFe. Optimum annealing condition was obtained through annealing at 300 $^{\circ}C$ for 40 min (${\mu}$=2500, H$\sub$c/=0.35 Oe). Enhancement of permeability was observed in the temperature range of 250∼300$^{\circ}C$. These results may closely be related with lowering the anisotropy energy by lattice deformation (0.4%) and enhanced uniaxial anisotropy.

• Korean Journal of Materials Research
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• v.13 no.10
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• pp.683-690
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• 2003

The high strength low alloy(HSLA) steels microalloyed with Nb, Ti and V have been widely used as the automobile parts to decrease weight of vehicles. The effects of process conditions are investigated in the aspects of the precipitation behavior and the mechanical properties of HSLA steel microalloyed with Nb and Ti using TEM, SANS and mechanical testing. When Ti was added to a 0.07C-1.7Mn steel which was coiled at $500^{\circ}C$, the specimen revealed the property of higher tensile strength of 853.1 MPa and the stretch-flangeability of 60%. The stretch-flangeability was increased up to 97.8% for coiling temperature above $700^{\circ}C$. The precipitation hardening cannot be achieved in the 0.045C-1.65Mn steel which was the lower density of fine precipitates. However, the 0.07C-1.7Mn steels containing Nb and/or Ti which was coiled at X$/^{\circ}C$ have a high precipitates density of $2${\times}$10^{ 5}$/$\mu$㎥. The high strength of these steels was attributed to the precipitation hardening caused by a large volume froction of (Ti, Nb)C precipitates with a size below 5 nm in ferrite matrix.

• Journal of the Korean Society of Food Culture
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• v.36 no.5
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• pp.512-521
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• 2021

This study investigated the quality characteristics of sweet pumpkin after blanching. Sweet pumpkins were blanched in distilled water, 2% citric acid and 2% NaCl water at 100℃ for 3 min. The cooking loss of sweet pumpkin in the blanching groups was lower than that in the control group, and greenness and yellowness in the blanching groups were higher than those in the control group (p<0.001). Total polyphenol content (TPC) of sweet pumpkin increased after blanching (p<0.05), and TPC true retention (TR) was measured with the highest NB. CON and NB were significantly higher in ?-carotene content (p<0.001). Lutein content in the blanching treatment groups was lower than that in the control group, but NB was the highest between the blanching groups (p<0.001). DPPH and ABTS⁺ radical scavenging activity assays revealed higher antioxidant activity in the NB groups among the blanching groups (p<0.001). The CON was 2.44 log colony-forming unit (CFU)/ g in the total bacterial count, but there were no microorganisms in the blanching groups. In conclusion, blanching with the addition of 2% NaCl can inhibit the growth of microorganisms and improve TR and antioxidant activities in sweet pumpkin.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.2
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• pp.191-196
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• 2023

In this paper, for the application of ultrasonic cleaners for cleaning dentures and transparent braces, Pb(Mn_1/3Nb_2/3)O₃-Pb(Ni_1/3 Nb_2/3)O₃-Pb(Zr,Ti)O₃ [PMN-PNN-PZT] system ceramics were manufactured and their dielectric and piezoelectric properties were investigated. Overall the best properties suitable for the device applications such as ultrasonic cleaner were obtained from the ceramics sintered at 920℃: bulk density of 7.8 g/cm³, the dielectric constant (ε_r) of 1,689, piezoelectric charge constant (d₃₃) of 433 pC/N, planar electromechanical coupling factor (k_p) of 0.64, mechanical quality factor (Qm) of 835, S₁₁^E of 13.37 (10^-12 N/m²), and Curie temperature of 315℃ By using the physical properties of this composition, the ultrasonic cleaner was designed and simulated using the commercial ATILA software. For the three-layered ceramics with the dimension of 25 mm × 25 mm × 2.5mm, an excellent displacement of 8.998 10^-3 m) and the sound pressure of 147.68 dB were recorded.

• Journal of Internet Computing and Services
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• v.22 no.6
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• pp.129-140
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• 2021

The next generation mBcN should be built to cooperate with the wireless network to support hyper-speed and hyper-connectivity. In this paper, we propose a network architecture for the cooperation mBcN and 5G commercial network and architecture of the cooperative security gateway required for the cooperation. The proposed cooperative security gateway is between gNB and UPF to support LBO, SFC, and security. Our analysis shows that the proposed architecture has several advantages. First of all, user equipment connected with the mBcN can be easily connected through the 5G commercial radio network to the mBcN. Second, the military application traffic can be transmitted to mBcN without going through the 5G core network, reducing the end-to-end transmission delay without causing the traffic load on the 5G core network. In addition, the security level of the military application can effectively be maintained because the user equipment can be connected to the cooperative security gateway, and the traffic generated by the user equipment is transmitted to the mBcN without going through the 5G core network. Finally, we demonstrate that LBO, SFC, and security modules are essential functions of the proposed gateway in the 5G test-bed environment.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1028-1030
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• 1995

In the fields of the optics, precise machine, semiconducting processing, the micro-positioning actuators are required for the control of position in the submicron range. In this study, $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb({Zn}_{1/3}Nb_{2/3})O_3-Pb({Zr}_{1/2}Ti_{1/2})O_3$ ceramics were fabricated by solid state reaction. The structural, dielectric and electric properties were investigated for sintering condition. The specimen sintered at $1,150(^\circ}C)$ for 1hr, had the highest density and dielectric contant. The resistivity, dielectric and density were increased with increasing PZN contents.

• Applied Science and Convergence Technology
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• v.24 no.3
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• pp.47-52
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• 2015

The correlation between admittance and dielectric spectroscopy of dielectric relaxation in lead scandium noibate, have been investigated. Lead scandium niobate, with composition $PbSc_{0.5}Nb_{0.5}O_3$, was prepared by conventional solid state synthesis. Conductance Y'(G), susceptance Y"(B) and capacitance C of lead scandium niobate as a function of frequency and temperature were measured. From the temperature-dependence of RLC circuit, insight into physical significance of the dielectric properties of lead scandium niobate is obtained. The relative strong frequency dependent of dielectric properties in lead scandium niobate is observed, and the phase transition occurred at a broad temperature region. Also, the value of critical exponent ${\gamma}$=1.6 showed on heating process. The long relaxation times part enlarged diffuse by conductivity effects with increasing temperature, and the ordering between $Sc^{3+}$ and $Nb^{5+}$ in PSN influences complex admittance and dielectric properties. Confirmed the typical characteristic of lead-type relaxor in the Raman spectra of lead scandium niobate and major ranges are between 400 and $900cm^{-1}$.

• Journal of Magnetics
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• v.17 no.4
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• pp.255-260
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• 2012

In this study, we determine that the electron paramagnetic resonance line-width (EPRLW) is axially symmetric about the c-axis and analyze the spin Hamiltonian with an isotopic g-factor of 1.9920 at a frequency of 9.5 GHz. It should be noted that the electron paramagnetic resonance signals are Lorentzian. Our findings show that the EPRLW decreases exponentially with an increase in the temperature; i.e., its temperature dependence in the range 300-400 K obeys Arrhenius behavior, this kind of temperature dependence indicates an off-center a motional narrowing of the spectrum when $Mn^{2+}$ impurity ions substitute for $Nb^{5+}$ ions. The specific heats follow a linear dependence suggesting a simple Debye $T^3$ behavior.

• Journal of the Korean earth science society
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• v.36 no.5
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• pp.447-459
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• 2015

Dok island comprises Pliocene volcanic products such as a series of volcanoclastic rocks and lavas ranging in composition from alkali basalts, and trachyandesites to trachytes. Compositional variation of the basaltic rocks can be attributed to fractional crystallization of olivine, clinopyroxene, plagioclase, and magnetite. Chemical variations among the trachyandesites are caused by fractionation of clinopyroxene, plagioclase, and magnetite with minor amphibole, while trachytes are controlled mainly by feldspar fractionation. Incompatible element abundance ratios and chondrite normalized LREE/HREE ratios (e.g., (La/Yb)c: 24.8 to 32.8 for basalts, 15.6 to 31.2 for trachyandesites) suggest that the origins of the basalts and trachyandesites involve both different degrees of partial melting and subsequent fractional crystallization processes. Trace element ratios of the basalts from Dok island are characterized by high Ba/Nb, La/Nb, Ba/Th and Th/U and isotopic ratios (Tasumoto and Nakamura, 1991) that are similar to the EM 1 type of oceanic island basalts such as Gough and Tristan da Cunha basalts.