• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.8
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• pp.376-381
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• 2001

The(1-x) MgTiO$_3$-xSrTiO$_3$(x=0.03~0.04) ceramics were fabricated by the conventional mixed oxide method. The structural and microwave dielectric properties were investigated by XRD, SEM, EDS and network analyzer. The sintering temperature and time were 1275$^{\circ}C$~135$0^{\circ}C$ and 2hours, respectively. In the XRD results of 0.96MgTiO$_3$-0.04SrTiO$_3$ceramics, the perovskite structure of SrTiO$_3$and ilmenite structure of MgTiO$_3$phase were coexisted. The dielectric constant($\varepsilon$(sub)${\gamma}$) and temperature coefficient of resonant frequency($\tau$(sub)f) were increased with addition of SrTiO$_3$. In thie case of 0.96MgTiO$_3$-0.04SrTiO$_3$ ceramics sintered at 13$25^{\circ}C$, the dielectric constant, quality factor(Q) and temperature coefficient of resonant frequency($\tau$(sub)f) were 20.13, 7956(at 7.27GHz), and +1.76ppm/$^{\circ}C$, respectively.

• Culinary science and hospitality research
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• v.9 no.2
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• pp.22-32
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• 2003

The cheese cakes of three family restaurants (A, B, and q were compared for water activity, Brix, free sugar contents, color difference, viscosity, and sensory evaluation. The carbohydrate contents of cheese cake made in B is higher than the others. However, the products in C have the highest values for the crude protein contents. In viscosity, the products in C have the lowest values in cutting strength and compression strength. In order to measure the quality of cheese cake for different family restaurants, 83 undergraduate students were selected. It is found that they like the products in A better than those in Band C for aroma, sweetness, and taste. The results suggest that the taste is the most important factor for quality, and the aroma is the secondary effective factor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.127-130
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• 2002

In this study, development of a new LTCC material using a non-glassy system was attempted with respect to reducing the fabrication process steps and cost down. Lowering the sintering temperature can be achieved by liquid phase sintering. For LTCC application, the starting material must have quality factor as high as possible in microwave frequency range. And also, the material should have a low dielectric constant for enhancing the signal propagation speed. Regarding these factors, dielectric constants of various materials were estimated by the Clausius-Mosotti equation. Among them, CaWO$_4$ was tamed out the suitable LTCC material. CaWO$_4$ can be sintered up to 98% of full density at 1200$^{\circ}C$ for 3 hours. It's measured dielectric constant, quality factor, and temperature coefficient of resonant frequency were 10.15, 62880GHz, and -27.8ppm/$^{\circ}C$, respectively. In order to modify the dielectric properties and densification temperature, 0.5∼1.5 wt% LiF were added to CaWO$_4$. LiF addition reduced the sintering temperature/time down to 800$^{\circ}C$/10∼30min due to the reactive liquid phase sintering. Dielectric constant lowered from 10.15 to 9.38 and Q x fo increased up to 92000GHz with increasing LiF content.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.5
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• pp.501-505
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• 2008

In this paper, we present a multi-turn circular loop antenna for portable terrestrial DMB. In order to satisfy the two contradictory requirements of small antenna size and high receiving capability, the proposed antenna's diameter and turns are fixed to be 4 mm and 80 turns, respectively and its quality factor $\mathcal{Q}$ is set 1 in order to have high transfer function. The fabricated antenna length is 30 mm as small and its measured gain is -15 dBd. The antenna receiving power is verified by measurement very comparable with the receiving power of a commercial terrestrial DMB monopole antenna of length 190 mm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.9
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• pp.794-797
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• 2002

Piezoelectric properties of PZT-PSN ceramics were investigated as a function of WO$_3$ addition from 0 wt% to 6.0 wt%. The dielectric and piezoelectric characteristics of PZT-PSN ceramics have been investigated at different calcination (80$0^{\circ}C$~90$0^{\circ}C$) and sintering (110$0^{\circ}C$~130$0^{\circ}C$) temperatures. The grain size was increased with the addition of WO$_3$and the sintering temperatures. Anisotropic properties of electromechanical coupling coefficient and piezoelectric coefficient are proven to be dependent on processing temperatures and amount of addition. At the specimen with 0.6 wt% WO$_3$ addition, using calcination temperature of 80$0^{\circ}C$ and sintering temperature of 110$0^{\circ}C$ , mechanical quality factor(Q$_{m}$) and electromechanical coupling coefficient(k$_{p}$) showed the excellent results of 1560 and 0.48, respectively Experimental results indicated that the PZT-PSN system ceramics with WO$_3$impurity could be effectively used for the microtransformer and actuator applications, etc.etc.

• Journal of Magnetics
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• v.16 no.3
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• pp.271-275
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• 2011

This paper proposes a magnetoelectric (ME) composite transducer structure consisting of a magnetostrictive H-type Fe-Ni fork substrate and piezoelectric PZT plates. The fork composite structure has a higher ME voltage coefficient compared to other ME composite structures due to the higher quality (Q) factor. The ME sensitivity of the fork structure reaches 12 V/Oe (i.e., 150 V/cm Oe). The fork composite with two PZT plates electrically connected in series exhibits over 5 times higher ME voltage coefficient than the output of the rectangle structure in the same size. The experiment shows the composite of a Fe-Ni fork substrate and PZT plates has a significantly enhanced ME voltage coefficient and a higher ME sensitivity relative to the prior sandwiched composite laminates. By the use of a lock-in amplifier with 10 nV resolution, this transducer can detect a weak magnetic field of less than $10^{-12}$ T. This transducer can also be designed for a magnetoelectric energy harvester due to its passive high-efficiency ME energy conversion.

• Journal of Environmental Health Sciences
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• v.27 no.2
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• pp.30-36
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• 2001

This review begins with a brief expression of aerosol capture mechanism of fibrous filter(s) and performance of particulate removing respirators. The more complicated and detailed discussion is not included in this articles. Filtration efficiency and pressure drop are introduced as quality factor ( $q_{F}$) and the way in which filtration efficiency varies with particle size is discussed. Quality factors fro filters recently certified in USA were found to be very higher than those of filters made in Korea, China and USA filters certified with old certified standards. Electrically charged filters are widely used because they have high filtration efficiency and low pressure drop, but their efficiency decreases sharply at the condition occurring wet and oil mist. A discussion is given of respirator leakage through face seal and filter media with fit testing and total inward leakage testing. Since fit factor (FF) refers to the reciprocal of the fraction of the total air entering a respirator through face seal leakage , the degree of fitting performance for respirators is expected with FF. Because respirators made in Korea had generally lower FFs than respirators made in USA, it is necessary to develope respirators that fit properly for Koreans or establish regulations for fit testing.g.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1719-1723
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• 2014

In this study, the microwave dielectric properties of nano spheroidization glass powders added $Ba(Zn_{1/3}Ta_{2/3})O_3$ ceramics prepared by solid state reaction have been investigated. Adding $(Ba_{0.4}Ca_{0.6})SiO_3$ nano spheroidization glass powders could effectively promote the densification even in the case of decreasing the sintering temperature. When the glass frit is 0.3 wt% and sintering is carried out at a temperature of $1500^{\circ}C$ for 6 hr, a temperature stable microwave dielectric ceramic could be obtained, which has a dielectric constant (${\varepsilon}_r$) of 30.2, a quality factor ($Q{\times}f_0$) of 124,000 GHz and a temperature coefficient of resonance frequency (${\tau}_f$) of $2ppm/^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.5
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• pp.379-382
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• 2010

In this study, in order to develop the lead-free piezoelectric ceramics with high piezoelectric and dielectric properties, $(K_{0.5}Na_{0.5})(Nb_{0.97}Sb_{0.03})O_3$ ceramics were fabricated using a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated according to the $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition. $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition enhanced density, electromechanical coupling factor($k_p$) piezoelectric constant $d_{33}$ and mechanical quality factor($Q_m$). At the 0.9 mol% $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition, density, electromechanical coupling factor($k_p$), dielectric constant(${\varepsilon}_r$) and piezoelectric constant($d_{33}$) of specimen showed the optimum values of 0.46, 471, and 148 pC/N, respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.684-688
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• 2016

The magnetic resonance method requires high quality factor(Q-factor) of resonators. Superconductor coils were used in this study to increase the Q-factor of wireless power transfer(WPT) systems in the magnetic resonance method. The results showed better transfer efficiency compared to copper coils. However, as superconducting coils should be cooled below critical temperatures, they require cooling containers. In this viewpoint, shielding materials for the cooling containers were applied for the analysis of the WPT characteristics. The shielding materials were applied at both ends of the transmitter and receiver coils. Iron, aluminum, and plastic were used for shielding. The electric field distribution and S-parameters (S11, S21) of superconducting coils were compared and analyzed according to the shield materials. As a result, plastic shielding showed better transfer efficiency, while iron and aluminum had less efficiency. Also, the maximum magnetic field distribution of the coils according to the shielding materials was analyzed. It was found that plastic shielding had 5 times bigger power transfer rate than iron or aluminum. It is suggested that the reliability of superconducting WPT systems can be secured if plastic is used for the cooling containers of superconducting resonance coils.