• Proceedings of the Acoustical Society of Korea Conference
• /
• spring
• /
• pp.275-278
• /
• 2000

In this study, the acoustic transducer of a thin circular disc-type with PZT/Metal was designed. The dielectric and piezoelectric properties of $0.5wt\%$ $MnO_2$ and NiO doped 0.1Pb($Mg_{1/3}$$Nb_{2/3}$)$O_3$-$0.45PbTiO_3$-$0.45PbZrO_3$ ceramics were investigated aiming at acoustic transducer applications. The vibration characteristics for the laminated circular plate was analyzed for the various thickness and diameter of the piezoceramic layer and metal layer. The acoustic characteristics which is radiated from the acoustic transducer within the finite space was simulated using the finite element method. It has been observed that the characteristics of the sound pressure ard impedance response calculated for the various models of the size and geometry of acoustic transducer.

• Journal of Korean Society for Atmospheric Environment
• /
• v.13 no.6
• /
• pp.475-486
• /
• 1997

The characteristics of atmospheric aerosols were investigated as a function of particle size and water solubility. The atmospheric aerosols were sampled with classifying into 12 size ranges by the use of Andersen low-pressure impactor. Collected aerosol particles were extracted by ultrapure water and filtered to be separated into water-soluble and insoluble components. The concentrations 12 elements in both components were determined by PIXE analysis. And the concentrations of 8 ions in the soluble component were analyzed by ion chromatography. In general, the mass size distribution of particulate matter was represented as a bimodal distribution. The mass size distributions of S$(SO_4^{2-}), K(K^+), Zn and NH_4^+$ skewed to the smaller size range and those of Si, Ca$(Ca^{2+}), Fe, Na^+ and Mg^{2+}$ skewed to the larger size range. They had roughly one peak in the fine and coarse particle region,respectively. On the other hand, the mass size distribution of Ti, Mn, Ni, Cu, $Cl^- and NO_3^-$ were represented as the bimodal distribution. Fe and Si in the aerosol particles extracted into pure water are existing in high insoluble state. Conversely, almost the whole of S is dissolved in water.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.1
• /
• pp.20-25
• /
• 2001

To develop the piezoelectric actuator, the structural, dielectric and piezoelectric properties and electric fieldinduced strain of the ceramics(Pb$\_$1-2/Ba$\_$x/)[Mg$\_$1/2/W$\_$1/2/)$\_$0.03/-Ni$\_$1/3/Nb$\_$2/3/)$\_$0.12/-(Zr$\_$0.5/Ti$\_$0.5/)$\_$0.85/]O$_3$(x=0, 0.01, 0.03, 0.05, 0.07, 0.1) were investigated with the substitution of Ba. The tetragonality of crystal structure and grain size decreased by the substitution of Ba. Curie temperature decreased due to the decrease of the tetragonality, and dielectric constants increased with the substitution of Ba. The coercive field, remnant polarization and electromechanical coupling factor also decreased, whereas the piezoelectric constatns d$\_$33/ and d$\_$31/ were showed the highest value of 430 and 209(x10$\^$-12/C/N), respectively, because of the increase of dielectric constant. The strain induced by 60Hz AC electric field had the maximum value of 204x10$\^$-6/Δℓ/ℓ at the substitution of Ba 3mol%. As the applied electric field approaches to the coercive field, the piezoelectric element is depolarized and the electric field induced strain revealed non-linearity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.28 no.3
• /
• pp.165-169
• /
• 2015

In this paper, in order to develop the composition ceramics with the excellent dielectric properties, $Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.09}(Zr_{0.5}Ti_{0.5})_{0.88}O_3$ ceramics were fabricated by the conventional solid-state method. The effects of ZnO addition on their microstructure and piezoelectric properties were systematically investigated. The rhombohedral-tetragonal phase coexistence has been found in the ceramics without ZnO content and then with further increasing ZnO content, specimens exhibited tetragonal phase. The optimized ZnO content formed liquid phase and aided the grain growth of specimens. When 0.4 wt% ZnO was added, the optimal physical properties ($d_{33}=422pC/N$, $d_{31}=161pC/N$, ${\varepsilon}_r=1,905$, $k_p=0.55$, $Q_m=160$) were obtained.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.28 no.3
• /
• pp.160-164
• /
• 2015

In this study, $(1-x)Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.09}(Zr_{0.5}Ti_{0.5})_{0.88}O_3+xCeMnO_3$ (x= 0~0.02) ceramics were prepared by Columbite precursor method. The phase structure, ferroelectric and piezoelectric properties were systematically investigated. It was found that PMW-PNN-PZT possessed superior electrical properties due to its composition close to the MPB (morphotropic phase boundary). Coercive electric field of 10.05 [kV/cm] and density of 7.88 [$g/cm^3$] were obtained when the substitution amount of $CeMnO_3$ is x=0.02. In contrast, specimens with x=0.01 showed the mechanical quality factor($Q_m$) of 1,091 and the electromechanical coupling factor($k_p$) of 0.613.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.212-212
• /
• 2010

Recently, lithium transition metal phosphates with an ordered olivine-type structure, $LiMPO_4$ (M=Fe, Mn, Ni, and Co), have attracted extensive attention due to a high theoretical specific capacity (170 mAh/g). The $LiMPO_4$ is the most attractive because of its high stability, low cost, high compatibility with environment. However, it is difficult to attain its full capacity because its electronic conductivity is very low, and diffusion of Li-ion in the olivine structure is slow and the supervalue cation doping was used. In this research, we are used the supervalue cation doping methode such as Cu, Ti, and Mg were partially replace the Fe. The cycling performance resulted of the used $LiM_xFe_{1_x}PO_4$ cathode materials for lithium batteries exhibit excellent high capacity than $LiFePO_4$/Li cells.

• The Bulletin of The Korean Astronomical Society
• /
• v.42 no.1
• /
• pp.42.3-42.3
• /
• 2017

We present the analysis of chemical abundances and kinematics for six hypervelocity star (HVS) candidates. These objects are G/K-type low-mass stars in the Galactic disk, while other HVSs previously found are B-type high-mass objects in the Galactic halo. The stellar orbits and kinematics of our HVS candidates suggest that they do not originate in the Galactic center or in an accretion event, indicative of yet-unknown mechanisms that produce kinematically-extreme disk stars. In order to study in detail their origin, we obtained medium-resolution (R~6000) spectra of these stars and derived abundances of several chemical elements (Mg, Ca, Si, Ti, Cr, Fe, and Ni). From the comparison of the chemical abundances with the Galactic stellar components (disk, bulge, halo, and dwarf galaxies) and the kinematic properties of our HVSs, we conclude that two of them are likely ejected from the Galactic disk, one originated from the Galactic center as for the young B-type HVSs, and the other one might be ejected from either the Galactic disk or other regions.

• Journal of Korean Society for Atmospheric Environment
• /
• v.13 no.5
• /
• pp.345-353
• /
• 1997

The purpose of the study was to stastically classify individual PM-10 measured by SEM/EDX (scanning electron microscopy/energy dispersive x-ray analyzer). The SEM/EDX provided various physical parameters like optical diameter, as well as major 18 chemical information (Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Pb) for a particle-by-particle basis. The total of 1,419 particles were analyzed for the study. Thus density and mass of each particle can be estimated based on its chemical composition. Further the study developed 4 semisource profiles including highway, oil boiler, incinerator, and soil emissions, where each sample was collected near the source in the ambient air The profiles developed were consisted of mass fractions and their uncertainties based on a particle class concept. To obtain mass fraction of each particle class, an agglomerative hierarchical cluster analysis was initially applied to create particle classes for each sample. Then uncertainties were calculated for each class based on the jacknife method. The 1,258 particles out of 1,419 (88.7%) were assorted in newly generated particle classes. The study provides opportunities to identify particle's source quantitatively and to develope various receptor models.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.11a
• /
• pp.212-213
• /
• 2005

In this study, in order to develop low temperature sintering piezoelectric actuator, $Pb_{0.985}Bi_{0.01}(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.13}(Zr_{0.50},Ti_{0.50})_{0.84}$ (PMW-PNN-PZT) ceramic systems were fabricated using $CaCO_3-Li_2CO_3$, sintering aid through a post-annealing process. The sinterability of PMW-PNN-PZT ceranics was remarkably enhanced by liquid phase sintering of $CaCO_3$ and $Li_2CO_3$. But, it was confimed form the X-ray diffraction pattern that the secondary phase along grain boundaries, deteriorated the piezoelectric properties. The secondary phase along grain boundaries was significantly removed by annealing after sintering. The 0.2wt% $Li_2CO_3$-0.25wt% $CaCO_3$-added PMW-PNN-PZT ceramics post-annealed at 900$^{\circ}C$ for 90min exhibited the excellent electromechanical coupling factor($k_p$) of 63.3% and piezoelectric constant($d_{33}$) of 452pC/N, respectively, for multilayer piezoelectricactuatorapplication.

• Journal of the korean society of oceanography
• /
• v.32 no.3
• /
• pp.112-119
• /
• 1997

Coastal sediments collected near the Youngkwang Nuclear Power Plant were analysed for major(Al$_2$O$^_3$, Fe$^_2$O$^_3$, MgO, CaO, Na$^_2$O, K$^_2$O, TiO$^_2$, MnO), trace (Ba, Sr, V, Co, Cr, Cu, Ni, Zn, Pb) metal, and P$^_2$O$^_5$ contents. The composition of bulk metals from most stations fits within the range as those in the average crustal and sedimentary rocks, suggesting that the anthropogenic perturbation of these components is insignificant. The abundance and distribution of total contents for the majority of metals in the surface sediment could be explained by the grain size and were associated with mud (<63 ${\mu}$m) contents. However, distributions of Ca, K, Sr and Ba did not have any significant association with the sediment grain size. This may be due to the geochemical coherence among these metals in certain minerals abundant in coarse grained fractions. The distribution of Pb appears to be partly affected by the contribution from aerosol fallout. Using the R'-mode factor analysis, we show that the variance of the metal contents could be explained by four factors which account for 93.7% of the total variance. It appears that texturally controlled and/or sorting factors influenced by fine fraction are the most dominant factors which determine the relative abundance and distribution of metals in the study area.