• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.176-177
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• 2005

In this paper, in order to develop low temperature sintering $PbTiO_3$-system piezoelectric ceramics for thickness-vibration-mode piezoelectric transformer, $Pb_{0.76}Ca_{0.24}[(Mn_{1/3}Sb_{2/3})_{0.04}Ti_{0.96}]O_3$ ceramics using $0.25wt%CaCO_3$ and 0.2wt%$Li_2CO_3$ as sintering aids were manufactured according to the variation of poling field. Specimens could be sintered at the sintering temperature of $930^{\circ}C$. The piezoelectric properties increased according to the increase of poling field and showed the maximum values (kt=0.49, Qmt=1816, and $d_{33}$=81.4pC/N) under 6.5kV/mm.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1218-1224
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• 2023

We investigated the radiation shielding competence for TeO₂-V₂O₅-MoO₃ glasses. The Phy-X software was used to report the radiation shielding parameters for the present glasses. With an increase in TeO₂ and MoO₃ content, the samples' linear attenuation coefficient improves. However, at low energies, this change is more apparent. At low energy, the present samples have an effective atomic number (Z_eff) that is relatively high (in order of 16.17-24.48 at 0.347 MeV). In addition, the findings demonstrated that the density of the samples is a very critical factor in determining the half value layer (HVL). The minimal HVL for each sample can be found at 0.347 MeV and corresponds to 1.776, 1.519, 1.391, 1.210 and 1.167 cm for Te1 to Te5 respectively. However, the highest HVL of these glasses is recorded at 1.33 MeV, which corresponds to 3.773, 3.365, 3.218, 2.925 and 2.908 cm respectively. The tenth value layer results indicate that the thickness of the specimens needs to be increased in order to shield the photons that have a greater energy. Also, the TVL results demonstrated that the sample with the greatest TeO₂ and MoO₃ concentration has a higher capacity to attenuate photons.

• KSBB Journal
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• v.26 no.1
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• pp.13-18
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• 2011

In this study, precipitation process was developed for the recovery of the lactic acid from calcium lactate fermentation broth. Calcium lactate yield was improved by decreasing the solubility of calcium lactate through the addition of ethanol (25%, v/v) as a co-precipitant. The optimal lime type, lime concentration, stirrer speed, precipitation time, temperature, and solvent amount for $Ca(LA)_2$ precipitation were CaO, 0.0175 g/mL, 220 rpm, 24 h, $5^{\circ}C$, ethanol 25% (v/v), respectively. Lactic acid was easily and efficiently recovered from precipitated $Ca(LA)_2$ by adding sulfuric acid ($Ca(LA)_2/H_2SO_4$ molar ratio=1:1). In the model solution of organic acids and fermentation broth, the overall yields of recovered lactic acid were 62% and 55%, respectively, under the aforementioned optimal conditions.

• Journal of the Korean institute of surface engineering
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• v.13 no.1
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• pp.8-15
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• 1980

The critical voltage of hard coat range of Al alloys (K 186, 43S) at various electrolytes and the effects of voltage, temperature of electrolytes and concentration of sulfric acid were investigated, m the hope that to find the adequate voltage. Two kind of A1 alloys were anodized in three typical electrolytes and micro vickers hardness of the films were measured. With respect to the relationship between the hardness of the film and the voltage The result of this experiment are as fallows. 1. The critical voltage of hard coat rangs for the electrolytes $H_2SO_4\;10%,\;H_2SO_4\;10%\;+\;H_2C_2O_4\;2H_2O\;10g/l,\;H_2SO_4\;10%\;+\;NaHSO_4\;5%$ was 20V 22V 24V respectively. 2. $H_2SO_4\;10%\;+\;NaHSO_4$ 5% electrolyte was most adventageous among the three electrolyte in the respect of hardness. 3. The effect of concentration of sulphuric acid was not appeared.

• Journal of Life Science
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• v.18 no.7
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• pp.980-985
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• 2008

This study was carried out to develope an alcoholic drink by fermentation of onion extract using Saccharomyces cerevisiae. The optimal conditions for ethanol production were obtained by standing culture at $25^{\circ}C$ for 5 days with 5% inoculum volume. At the results by flask culture, the growth curve of used S. cerevisiae reached to the stantionary phase at 48 hr and the death phase at 90 hr, whereas ethanol production reached maximum at 114 hr. Under the above conditions, a large scale production was carried out. A standing culture in 5 l fermenter showed the similar results to its flask culture, but progressed 24 hr rapidly more than that of the flask culture. A fed-batch culture was performed by addition of the onionic medium supplemented with 10% (v/v) sucrose after 72 hr from the fermenting start. The fed-batch culture could prevent S. cerevisiae from entering into the death phase and maintain constant level of alcohol production. A continuous culture was able to carry out by adding per every 24 hr the onionic medium supplemented with 10% (v/v) sucrose after 72 hr from the fermenting start. Although S. cerevisiae used showed a little decreased growth, alcohol production maintained roughly the constant level at the maximum yield. To enhance the quality of this alcoholic drink, $2-O-{\alpha}-D-glucopyranosyl$ L-ascorbic acid (AA-2G) was supplemented into the onion extract of the substrate for fermentation. As resulted at this study, this alcoholic drink containing AA-2G should be used as a functional fermented alcohol drink strengthened with vitamin C.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.5
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• pp.362-369
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• 2001

The electrical properties of varistors consisting of Zn-Pr-Co-Cr-Er oxides were investigated in the Er$_2$O$_3$content range of 0.0 to 2.0 mol%. the varistors without Er$_2$O$_3$ exhibited a relatively low nonlinearity, which was 14.24 in the nonlinear exponent and 21.47 $\mu$A in the leakage current. However, the varistors with Er$_2$O$_3$ sintered at 1335$^{\circ}C$ for 1h exhibited very high nonlinear exponent of 70, in particular, reaching a maximum value of 78.05 in 2.0 mol% Er$_2$O$_3$, and those sintered at 1335$^{\circ}C$ for 2h exhibited the nonlinear exponent close to 50, in particular, reaching a maximum value of52.76 in 0.5 mol% Er$_2$O$_3$. The others except for 0.5 mol% Er$_2$O$_3$-added varistors exhibited very high instability resulting in a thermal runaway within a short time, even a weak DC stress. Increasing soaking time decreased the nonlinearity, but increased the stability. The varistors containing 0.5mol% Er$_2$O$_3$ sintered for 2h exhibited excellent stability, in which the variation rate of the varistor voltage and nonlinear exponent was -1.70% and -7.15%, respectively, under more severe DC stress such as (0.80 V$_{1mA}$/9$0^{\circ}C$/12h)+(0.85 V$_{1mA}$/115$^{\circ}C$/12h)+(0.90 V$_{1mA}$/12$0^{\circ}C$/12h)+(0.95 V$_{1mA}$/1$25^{\circ}C$/12h)+(0.95 V$_{1mA}$/15$0^{\circ}C$/12h).TEX>/12h).

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.15-15
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• 2002

Homogeneous and crack-free potassium lithium niobate (K₃Li/sub 2-x/Nb/sub 5+x/O/sub 15/, 0＜x＜0.5, KLN) single crystals were successfully grown by the Czochralski technique. The KLN single crystals of several different compositions were employed for the investigation of the lattice vibration spectra using infrared Raman spectroscopy. The characteristic Raman spectra of the [NbO/sub 6/]/sup 7-/ octahedral ions were strikingly influenced by the Li ion content. The symmetric stretch vibrational modes V₁, V₂ are broadened, and the symmetric bend vibration mode V/sub 5/ is broadened and even split into three peaks with increasing the Li content, supporting that the bend vibration modes of the [NbO/sub 6/]/sup 7-/ octahedrons are obviously perturbed by Li ions in the C site. Enhanced Raman peak intensities after the post annealing at 900℃ and for 24 h evidenced that a residual stress in as-grown crystals was negligible and only a defect concentration might be reduced.

• Korean Journal of Crystallography
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• v.18 no.1_2
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• pp.1-6
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• 2007

An Organometallic compound, $C_{16}H_{35}B_{10}IrS_2Si$, was synthesized from o-carborane, $Cp^*Ir(S_2C_2B{10}H_{10})$, and $Me_3SiCHN_2$. The molecular structure of this complex has been determined by X-ray diffraction. Crystallographic data : monoclinic, space group $P2_1/n$, $a=10.1986(12)\;{\AA}$, $b=14.834(5)\;{\AA}$, $c=17.139\;{\AA}$, ${\beta}=92.24(2)^{\circ}$, Z=4, $V=2591.0(14)\;{\AA}^3$. The structure was solved by direct methods and refined by full-matrix leat-squares methods to give a model with a reliability factor R=0.053 for 5080 reflections.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.5
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• pp.370-373
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• 2011

We investigated the effects of low temperature ($500^{\circ}C$) $O_2$ annealing on the characteristics of hafnium silicate ($HfSi_xO_y$) films deposited on a Si substrate by atomic layer deposition (ALD). We found that the post deposition annealing under oxidizing ambient causes the oxidation of residual Hf metal components, resulting in the improvement of electrical characteristics such as flat band voltage shift (${\Delta}V_{fb}$) by hysteresis without oxide capacitance reduction. We suggest that post deposition annealing under oxidizing ambient is necessary to improve the electrical characteristics of $HfSi_xO_y$ films deposited by ALD.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.4
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• pp.325-327
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• 2011

In this paper, nonvolatile nano-floating gate memory devices are fabricated with ZnO nanowires and Al nanoparticles on a $SiO_2/Si$ substrate. Al nanoparticles used as floating gate nodes are formed by the sputtering method. The fabricated device exhibits a threshold voltage shift of -1.5 V. In addition, we investigate the endurance and retention characteristics of the nano-floating gate memory device.