• 한국분말재료학회지
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• 제25권6호
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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.

• 자원리싸이클링
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• 제24권2호
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• pp.13-22
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• 2015

건설 분야 중 건설 재료와 건자재 산업에서 발생하는 $CO_2$는 약 6,700만톤으로 건설 분야에서 발생하는 $CO_2$의 약 30%를 점유하고 있다. 건설 분야에서 $CO_2$ 저감은 건자재 산업에서 $CO_2$를 발생시키는 2차, 3차 양생을 줄여 소비되는 화석연료 사용과 배출 가스 저감의 조절이 필수적이다. 따라서 본 연구는 저에너지양생용 혼합재(Low energy curing Admixture 이하 LA)를 압출성형패널에 적용한 후 그 혼입량, 섬유종류, 섬유 혼입율에 따른 물리적 특성을 관찰하였다. 섬유종류가 강도에 영향을 나타내는 주요한 인자는 아닌 것으로 나타났으며, LA 혼입율과 섬유 혼입량은 강도에 영향을 주는 주요한 인자인 것으로 나타났다. 특히 LA 혼입율 dl 40% 일 때 가장 높은 강도발현을 나타냈으며, 50% 인 시험체의 경우 강도가 하락하는 결과를 나타냈다, 또한 섬유 혼입율은 휨강도에 크게 영향을 주었으며 혼입율이 증가할수록 휨강도는 증가하는 것으로 나타났다.

• Journal of the korean society of oceanography
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• 제36권3호
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• pp.59-71
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• 2001

In order to investigate the temporal variability of dissolved and particulate trace metals in the Han River, water samples were collected intermittently at two sites for 3 years (August 91 to December 94). Surface seawaters covering the range of salinity were also collected at the estuarine region to evaluate the role of estuary for the riverine fluxes of trace metals within the estuary during October 95 and 96. During the study period, dissolved metal concentrations in riverwaters varied by a factor of 5-10 for Fe, Ni, Co and Cu and 50-100 for Mn, Cd and Pb depending upon the water level; high concentration during the low water and low concentration in high water period except for Fe. The concentration of dissolved Fe increased with increasing water discharge. These concentration-discharge relationships of the studied trace metals are explained by the successive dilution of waters from two different origins, which can be presumably identified as anthropogenic discharges and watershed flushing. Although estuarine waters at early mixing region were not collected due to the difficulty of sampling, mixing behaviors of metals were inferred from the concentration-salinity relationships through the laboratory mixing experiment and field sampling, and distribution coefficients between dissolved and labile particulate phases. It is suggested that the Han River estuary plays a role of accumulating Fe, Mn, Co and Pb from riverine sources due to high turbidity caused by strong tidal current, whereas this system serves as a source of dissolved Cd due to release caused by extended residence time of riverine particles.

• 한국세라믹학회지
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• 제47권2호
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• pp.163-168
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• 2010

Effects of compositions on the microwave dielectric properties of the MgO-$TiO_2$ system were investigated as a function of the molar ratio of MgO to $TiO_2$ ($0.9{\leq}MgO/TiO_2\;(x){\leq}1.2$). With the compositional changes, secondary phases of $MgTi_2O_5$ and $Mg_2TiO_4$ were also detected along with $MgTiO_3$. Microwave dielectric properties of the specimens were dependent on the types of phases developed in the sintered specimens. A single phase of $MgTiO_3$ showed a dielectric constant (K) of 18.2, a quality factor (Qf) of 198,000 GHz, and a temperature coefficient of resonant frequency (TCF) of $-51\;ppm/^{\circ}C$. However, the dielectric properties of the specimens with a secondary phase of $MgTi_2O_5$ (K=19.9, Qf=48,000 GHz) and/or $Mg_2TiO_4$ (K=15.6, Qf=56,000 GHz) were worsened. Dependence of the microwave dielectric properties on the secondary phase of the MgO-$TiO_2$ system was also discussed in terms of dielectric mixing rules.

• Macromolecular Research
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• 제17권6호
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• pp.411-416
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• 2009

The color stabilization of antimicrobial blends was studied by using poly(hexamethylene guanidine) phosphate (PHMG) as a highly efficient biocidal and nontoxic agent. The Taguchi method was used to determine the optimum conditions for the blending of PHMG in polypropylene (PP) matrix. To improve the yellowing phenomena, two kinds of stabilizer were used together: tetrakis[methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)](IN1010) from phenol and tris(2,4-di-t-butylphenylphosphite) (IF168) from phosphorus. According to blend composition and mixing condition, six factors were chosen, with five levels being set for each factor. The orthogonal array was selected as the most suitable for fabricating the experimental design, L25, with 6 columns and 25 variations. The-smaller-the-better was used as an optimization criterion. The optimum conditions for these parameters were 10 phr for PHMG, 2 phr for IN1010, 1 phr for IF168, 10 min for mixing time, $210^{\circ}C$ for mixing temperature, and 30 rpm for rotation speed. Under these conditions, the yellowness index of the blend was 1.52. The processibility of the blends was investigated by Advanced Rheometric Expansion System (ARES). The blend with 0.5 w% PHMG content, diluted with PP, exhibited an antimicrobial characteristic in the shake flask method.

• 한국분말재료학회지
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• 제11권2호
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• pp.137-142
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• 2004

In this study, chemical solution mixing and hydrogen reduction method was used to fabricate nanostructured $Fe_xCo_{1-x}$ alloy powders. Fe-Co chloride mixture, FeCl$_2$ and COCI$_2$ with 99.9％ purity, were reduced in hydrogen atmosphere. Nanostructured Fe-Co alloy powders with a grain size of 50 nm were successfully fabricated. Magnetic properties of fabricated $Fe_xCo_{1-x}$(x=0, 10, 30, 50, 70, 100) alloy powders with the same grain size were measured because size factor can affect magnetic properties. Coercivity of Fe-Co alloy powders were increased with increasing Co contents. Maximum value of coercivity in various Co contented Fe-Co alloy powders with similar grain size was 125 Oe at Fe$_{100}$. Saturation magnetization value at Fe$_{70}$Co$_{30}$ composition showed maximum value of 219 emu/g and saturation magnetization value decreased with increasing Co contents and minimum value of 155 emu/g was observed at Co$_{100}$.

• 농업과학연구
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• 제47권4호
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• pp.921-931
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• 2020

This study was carried out to determine the factor of a separating system according to the pepper varieties and the absence of a card cleaner system. The pepper varieties of Jeokyoung and AR-Legend were transplanted on November 20, 2019 and tested on March 18, 2020 with a harvesting speed of 0.2 m·s-1 for 10 pepper plants. The performance evaluation was determined by analyzing the separation efficiency of the peppers and the foreign matter mixing rate. The pepper harvester with a card cleaner showed a higher separation efficiency of the peppers compared to the pepper harvester without a card cleaner. The average separation efficiency of peppers on the pepper harvester with a card cleaner was higher at 13.5% for Jeokyoung and 1.9% for AR-Legend than that without a card cleaner. The mixing ratio of foreign materials on the pepper harvester with a card cleaner was lower at 8.7% and 2.5% for Jeokyoung and AR-Legend than that without a card cleaner, respectively. For the two-way ANOVA results according to the variety and the card cleaner, there was no effect on the separation efficiency of the peppers, but there was an effect on the foreign matter mixing rate.

• 한국환경과학회지
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• 제11권6호
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• pp.543-551
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• 2002

A Numerical simulation on the thermal flow performance was carried out to propose the incinerator type for the domestic refuses and to investigate the design factor and operating conditions. The SSTI(Standard Stoker Type Incinerator) proposed in this study was modified from the type with central f)ow. It has the characteristics of good mixing between refuse and hot combustion gas in primary combustion chamber and between unburned gas inflowing and secondary air jet in secondary chamber. By predictive results, the SSTI was no recirculation zone in secondary chamber so that mixing time was increased with high residence time. It has good characteristics of combustion and low emission. Parametric screening studies have been understood with phenomenon of combustion in incinerator.

• 한국가시화정보학회지
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• 제3권2호
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• pp.45-50
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• 2005

Electro-osmotic flow (EOF) instability in a microchannel has been experimentally investigated using a micro-PIV system. The micro-PIV system consisting of a two-head Nd:Yag laser and cooled CCD camera was used to measure instantaneous velocity fields and vorticity contours of the EOF instability in a T-shape glass microchannel. The electrokinetic flow instability occurs in the presence of electric conductivity gradients. Charge accumulation at the interface of conductivity gradients leads to electric body forces, driving the coupled flow and electric field into an unstable dynamics. The threshold electric field above which the flow becomes unstable and rapid mixing occurs is about 1000V/cm. As the electric field increases, the flow pattern becomes unstable and vortical motion is enhanced. This kind of instability is a key factor limiting the robust performance of complex electrokinetic bio-analytical devices, but can also be used for rapid mixing and effective flow control fer micro-scale bio-chips.

• 유통과학연구
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• 제3권1호
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• pp.43-67
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• 2005

Recently retail market has been rapidly expanded in the large cities of in Korea and the competition among individual companies in retail market is also being increased. Tenant MD of mixing is one of the most important factor for the company to continuously operate or to fail. The aim of this study is to examine the processes of systematically evaluating the merchandising of the established companies in retail market a part of chain operation in discount store. The basic problem of decision making in general and tenant MD of mixing in particular is to choose a best one in a set of competing alternatives that are evaluated under conflicting criteria. The purpose of research of a paper carries out a duty searching examination with making a tenant MD include by retail research, simultaneously defined when I will show an example for the tenant mix of the profitability side of the domestic discount store market which is tenant MD importance proposing the existing problem arrangement by chain operation management, and is intensifying - tenant MD of standardization in discount store of T-company.