• Journal of Powder Materials
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• v.25 no.6
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• pp.487-493
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• 2018

The impact of different mixing methods and sintering temperatures on the microstructure and piezoelectric properties of PZNN-PZT ceramics is investigated. To improve the sinterability and piezoelectric properties of these ceramics, the composition of $0.13Pb((Zn_{0.8}Ni_{0.2})_{1/3}Nb_{2/3})O_3-0.87Pb(Zr_{0.5}Ti_{0.5})O_3$ (PZNN-PZT) containing a Pb-based relaxor component is selected. Two methods are used to create the powder for the PZNN-PZT ceramics. The first involves blending all source powders at once, followed by calcination. The second involves the preferential creation of columbite as a precursor, by reacting NiO with $Nb_2O_5$ powder. Subsequently, PZNN-PZT powder can be prepared by mixing the columbite powder, PbO, and other components, followed by an additional calcination step. All the PZNN-PZT powder samples in this study show a nearly-pure perovskite phase. High-density PZNN-PZT ceramics can be fabricated using powders prepared by a two-step calcination process, with the addition of 0.3 wt% MnO2 at even relatively low sintering temperatures from $800^{\circ}C$ to $1000^{\circ}C$. The grain size of the ceramics at sintering temperatures above $900^{\circ}C$ is increased to approximately $3{\mu}m$. The optimized PZNN-PZT piezoelectric ceramics show a piezoelectric constant ($d_{33}$) of 360 pC/N, an electromechanical coupling factor ($k_p$) of 0.61, and a quality factor ($Q_m$) of 275.

• Journal of IKEEE
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• v.24 no.4
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• pp.1122-1128
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• 2020

Bandwidth Extension refers to restoring and expanding a narrow band signal(NB) that is damaged or damaged in the encoding and decoding process due to the lack of channel capacity or the characteristics of the codec installed in the mobile communication device. It means converting to a wideband signal(WB). Bandwidth extension research mainly focuses on voice signals and converts high bands into frequency domains, such as SBR (Spectral Band Replication) and IGF (Intelligent Gap Filling), and restores disappeared or damaged high bands based on complex feature extraction processes. In this paper, we propose a model that outputs an bandwidth extended signal based on an autoencoder among deep learning models, using the residual connection of one-dimensional convolutional neural networks (CNN), the bandwidth is extended by inputting a time domain signal of a certain length without complicated pre-processing. In addition, it was confirmed that the damaged high band can be restored even by training on a dataset containing various types of sound sources including music that is not limited to the speech.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.25 no.3
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• pp.47-62
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• 2022

The Ministry of Environment has been working to reduce the impact on biodiversity, ecosystems, and social costs caused by soil runoff from highland Agricultural fields by setting up non-point pollution source management districts. To reduce soil loss, runoff path reduction technology has been applied, but it has been less cost effective. In addition, non-point pollution sources cause environmental conflicts in downstream areas, and recently highland Agricultural fields are becoming vulnerable to climate change. The Ministry of Environment is promoting the optimal management plan in earnest to convert arable land into forests and grasslands, but since non-point pollution is not a simple environmental problem, it is necessary to approach it from the aspect of NbS(Nature-Based Solution). In this study, a scenario for applying the nature-based solution was established for three subwatersheds west of Haean-myeon, Yanggu-gun, Gangwon-do. The soil loss distribution was spatialized through GeoWEPP and the amount of soil loss was compared for the non-point pollution reduction effect of mixed forests and grasslands. When cultivated land with a slope of 20% or more and ginseng fields were restored to perennial grasslands and mixed forests, non-point pollution reduction effects of about 32% and 29.000 tons compared to the current land use were shown. Also, it was confirmed that mixed forest rather than perennial grassland is an effective nature-based solution to reduce non-point pollution.

• Korean Journal of Materials Research
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• v.32 no.1
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• pp.44-50
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• 2022

Transition metal carbides (TMCs) are used to process difficult-to-cut materials due to the trend of requiring superior wear and corrosion properties compared to those of cemented carbides used in the cutting industry. In this study, TMC (TiC, TaC, Mo₂C, and NbC)-based cermets were consolidated by spark plasma sintering at 1,300 ℃ (60 ℃min) with a pressure of 60 MPa with Co addition. The sintering behavior of TMCs depended exponentially on the function of the sintering exponent. The Mo₂C-6Co cermet was fully densified, with a relative density of 100.0 %. The Co-binder penetrated the hard phase (carbides) by dissolving and re-precipitating, which completely densified the material. The mechanical properties of the TMCs were determined according to their grain size and elastic modulus: TiC-6Co showed the highest hardness of 1,872.9 MPa, while NbC-6Co showed the highest fracture toughness of 10.6 MPa^*m^1/2. The strengthened grain boundaries due to high interfacial energy could cause a high elastic modules; therefore, TiC-6Co showed a value of 452 ± 12 GPa.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.134-136
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• 2001

In this paper, we investigated the electrical and piezoelectric characteristics of $Pb(Sb,Nb)O_3-Pb(Zr,Ti)O_3$ for piezoelectric transformer and actuator etc. Effect of $WO_3$ addition($0\;wt%{\sim}0.6\;wt%$) on the PSN-PZT ceramic was investigated. Anisotropic properties of electromechanical coupling factor and piezoelectric properties were proved to be varied with amount of $WO_3$ impurity and sintering temperature($1100{\sim}1300^{\circ}C$). The electromechanical coupling factor $k_p$ of 0.41 and the mechanical quality factor am of 1243 were obtained from the specimen with 0.6 wt% $WO_3$ addition sintered at $1100^{\circ}C$ Experimental results indicated that the PZT-PSN ceramics with $WO_3$ impurity can be effectively used for piezoelectric transformer and actuator. etc.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.3
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• pp.7-12
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• 1999

In this paper, dielectric and strain properties of (1-f-y)PMN-yPT-xST ceramics investigated with the amount of $\textrm{SrTiO}^3$(ST). The $\textrm{SrTiO}^3$ content is ranged within 1~6㏖%. Another compositions with excess MgO also investigated. As the amount of ST is increased, dielectric constant has a maximum value at 5㏖% composition. The Curie temperature is decreased linearly with increasing the amount of ST. Coercive field and ramnant polarization has a maximum value at l㏖% composition. As for the effects of excess MgO, the dielectric constant has been increased by the addition of excess MgO up to 3㏖% to a 0.8PMN-0.12PT-0.04ST specimen. But the strain has been decreased by the addition of excess MgO.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.11a
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• pp.42-45
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• 1992

In this study, the structural, dielectric and electrical properties of $0.85Pb(Zn_{1/3}Nb_{2/3})O_3-0.1BaTiO_3-0.05PbTiO_3$ ceramics were investigated with respect to the variations of $La_2O_3$ addition amount. The specimen with 0.2 [wt%] $La_2O_3$ addition amount, which has the coupling constants with the value of $k_p$=44.8[%]. $k_{31}$=25.4[%] and the piezoelectric constant with $d_{31}=100{\times}10^{-12}$[C/N] respectively, exhibits the relatively good values in the applications of electrostriction actuators.

• Nuclear Engineering and Technology
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• v.46 no.5
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• pp.681-688
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• 2014

Hydride reorientation behaviors of PWR cladding tubes under typical interim dry storage conditions were investigated with the use of as-received 250 and 485ppm hydrogen-charged Zr-Nb alloy cladding tubes. In order to evaluate the effect of typical cool-down processes on the radial hydride precipitation, two terminal heat-up temperatures of 300 and $400^{\circ}C$, as well as two terminal cool-down temperatures of 200 and $300^{\circ}C$, were considered. In addition, two cooling rates of 2.5 and $8.0^{\circ}C/min$ during the cool-down processes were taken into account along with zero stress or a tensile hoop stress of 150MPa. It was found that the 250ppm hydrogen-charged specimen experiencing the higher terminal heat-up temperature and the lower terminal cool-down temperature generated the highest number of radial hydrides during the cool-down process under 150MPa hoop tensile stress, which may be explained by terminal solid hydrogen solubilities for precipitation, and dissolution and remaining circumferential hydrides at the terminal heat-up temperatures. In addition, the slower cool-down rate generates the larger number of radial hydrides due to a cooling rate-dependent, longer residence time at a relatively high temperature that can accelerate the radial hydride nucleation and growth.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.694-695
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• 2006

As a candidate for lead-free piezoelectric materials, dense $95(Na_{0.5}K_{0.5})NbO_3-5LiTaO_3$ (NKN-5LT) ceramics were developed by conventional sintering process. Sintering temperature was lowered by adding $Li_2O$ as a sintering aid. The electrical properties of NKN-5LT ceramics were investigated as a function of $Li_2O$ concentration. At the addition of 1 mol% $Li_2O$, electromechanical coupling factor $(k_P)$ and piezoelectric coefficient $(d_{33})$ of NKN-5LT ceramics were found to reach the highest values of 0.37 and 250 pC/N, respectively.

• Korean Journal of Food Science and Technology
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• v.43 no.5
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• pp.597-602
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• 2011

Small black beans (SBB) were germinated up to 72 h at 23$^{\circ}C$, and 48 h germinated SBBs having the highest isoflavone content were chosen for noodle preparation. Some of the germinated SBB were treated by 20 min boiling (B) but some were not boiled (NB). For noodles, the germinated SBB flour replaced 15% or 20% of wheat flour, so five kinds of noodles were prepared and tested: control, 15B, 15NB, 20B, and 20NB. Higher amount of bean flour resulted in significant decrease of $L^*$ and increase of $b^*$ values in noodle. After 20 min cooking, the noodles containing germinated SBB flour showed less soluble sugar content in cooked water than control, and the lowest value was observed in 15B. For textural properties, the addition of SBB flour lowered hardness and adhesiveness of noodle, but increased chewiness than control. In sensory tests, the most acceptable sample was 15B because of developed texture and better appearance which seem to be good for health.