• Korean Journal of Materials Research
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• v.28 no.11
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• pp.611-614
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• 2018

Laminate composites composed of $0.95Pb(Zr_{0.52}Ti_{0.48})O_3-0.05Pb(Mn_{1/3}Sb_{2/3})O_3$ piezoelectric ceramic and Fe-Si-B based magnetostrictive amorphous alloy are fabricated, and the effect of control of the areal dimensions and the thickness of the piezoelectric layer on the magnetoelectric(ME) properties of the laminate composites is studied. As the aspect ratio of the piezoelectric layer and the magnetostrictive layer increases, the maximum value of the ME voltage coefficient(${\alpha}_{ME}$) increases and the intensity of the DC magnetic field at which the maximum ${\alpha}_{ME}$ value appears decreases. Moreover, as the thickness of the piezoelectric layer decreases, ${\alpha}_{ME}$ tends to increase. The ME composites exhibit ${\alpha}_{ME}$ values higher than $1Vcm^{-1}Oe^{-1}$ even at the non-resonance frequency of 1 kHz. This study shows that, apart from the inherent characteristics of the piezoelectric composition, small thicknesses and high aspect ratios of the piezoelectric layer are important dimensional determinants for achieving high ME performance of the piezoelectric-magnetostrictive laminate composite.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.5
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• pp.382-386
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• 2019

The alignment characteristics of liquid crystal (LC) molecules on a solution-derived lanthanum zinc oxide (LZO) film under ion-beam irradiation were demonstrated. Using the solution process, an LZO film was fabricated on the glass substrate and cured at $100^{\circ}C$. Afterwards, ion-beam irradiation was performed following the LC alignment method. Using this film, an LC cell was fabricated and the characteristics of the LC alignment were verified. Cross polarizing microscopy and the crystal rotation method were used to investigate the alignment state of the LC molecules on the LZO films. Furthermore, field emission scanning electron microscopy and X-ray photoelectron spectroscopy were used to explore the effect of the ion-beam irradiation on the LZO film. Through these, it was confirmed that the ion-beam irradiation induced surface modification, which demonstrated anisotropic physical and chemical surface characteristics. Due to this, uniform LC alignment was achieved. Finally, the residual DC and anchoring energy of the LC cell based on the LZO films were measured using a capacitance-voltage curve.

• Journal of Ceramic Processing Research
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• v.20 no.6
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• pp.603-608
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• 2019

In this study, the multilayered thin films of (Ba,Sr)TiO3/K(Ta,Nb)O3 were fabricated by the sol-gel and spin coating methods, and their structural and electrical properties were investigated. The specimen showed polycrystalline X-ray diffraction (XRD) characteristics with a tetragonal structure. The average grain size and film thickness for one coating were about 30~40nm and 60nm, respectively. The phase transition temperature of specimen was lower than 10 ℃. The dielectric constant and loss at 20 ℃ of the specimen coated six times were 1,231 and 0.69, respectively. The rate of change in dielectric constant at an applied direct current (DC) voltage of the six times coated thin films was 17.3%/V. The electrocaloric effect was the highest around the temperature at which the remanent polarization rapidly changed. When an electric field of 660kV/cm was applied to the triply coated thin films, the highest electrocaloric property of 4.41 ℃ was observed.

• Journal of Ceramic Processing Research
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• v.20 no.4
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• pp.395-400
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• 2019

This study was conducted on the structural and electrical properties of (Ba0.7Sr0.3)TiO3 thin films prepared by the sol-gel and spin-coating methods in order to investigate their applicability to electrocaloric devices. All specimens showed a tetragonal crystal structure and lattice constants of a = 3.972 Å, c = 3.970 Å. The mean grain size of specimens sintered at 800 ℃ was about 30 nm, and the average thickness of 5 times coated specimens was 304~311 nm. In the specimen sintered at 750 ℃, The relative dielectric constant and loss of specimens measured at 20 ℃ were 230 and 0.130, respectively, while dependence of the dielectric constant on unit DC voltage was -8.163 %/V. The remanent polarization and coercive fields were 95.5 μC/㎠ and 161.3 kV/cm at 21 ℃, respectively. And, the highest electrocaloric property of 2.69 ℃ was observed when the electric field of 330 kV/cm was applied.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.37-42
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• 2007

We are developing a 22.9 kV/25 MVA superconducting fault current limiting(SFCL) system for a power distribution network. A Bi-2212 bulk SFCL element, which has the merits of large current capacity and high allowable electric field during fault of the power network, was selected as a candidate for our SFCL system. In this work, we experimentally investigated important characteristics of the 190 kVA Bi-2212 SFCL element in its application to the power grid e.g. DC voltage-current characteristic, AC loss, current limiting characteristic during fault, and so on. Some experimental data related to thermal and electromagnetic behaviors were also compared with the calculated ones based on numerical method. The results show that the total AC loss at rated current of the 22.9 kV/25 MVA SFCL system, consisting of one hundred thirty five 190 kVA SFCL elements, becomes likely 763 W, which is excessively large for commercialization. Numerically calculated temperature of the SFCL element in some sections is in good agreement with the measured one during fault. Local temperature distribution in the190 kVA SFCL element is greatly influenced by non-uniform critical current along the Bi-2212 bulk SFCL element, even if its non-uniformity becomes a few percentages.

• Journal of the Semiconductor & Display Technology
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• v.22 no.4
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• pp.87-92
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• 2023

As the elderly population increases, the number of patients with various joint diseases, including degenerative arthritis, is steadily increasing. CPM medical devices are needed to effectively treat degenerative arthritis that is common in the elderly population. Domestic CPM medical devices have limited functions and are highly dependent on imports for expensive imported medical devices. To solve this problem, we designed a ROM measurement function using a current sensor that is not present in existing composite joint CPM medical devices. The algorithm was designed using the fact that the force caused by joint stiffness greatly increases the current flowing through the DC motor. In addition, the need for digital healthcare in the medical field is gradually expanding as the proportion of chronically ill patients increases due to the spread of the non-face-to-face economy due to COVID-19 and the aging population. Therefore, this paper aims to improve the performance of CPM medical devices by allowing real-time confirmation of rehabilitation exercise information and operation range measurement results in accordance with digital healthcare trends through a Bluetooth application developed as an Android studio.

• Journal of the Korean Magnetics Society
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• v.7 no.5
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• pp.265-273
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• 1997

The MR ratios and the exchange biasing field and interlayer coupling field were investigated in $Ni_{91}Fe_{19}/Co_{90}Fe_{10}/Cu/Co_{90}Fe_{10}/NiO$ spin-valve sandwiches grown on antiferromagnetic NiO films as a function of the NiO thickness, the thickness of Cu and pinning layer $Co_{90}Fe_{10}$. The spin-valve sandwiches were deposited on the Corning glass 7059 by means of the 3-gun dc and 1-gun rf magnetron sputtering at a 5 mtorrpartial Ar pressure and room temperature. The deposition field was 50 Oe. The MR curve was measured by the four-terminal method with applied magnetic soft bilayer [NiFe/CoFe] (90$\AA$) decreased dramatically to less than 10 Oe when the NiFe/CoFe bilayer used an NiFe bilayer thicker that 20$\AA$. So NiFe layer improved the softmagnetic properties in the NiFe/CoFe bilayer. The GMR ratio and the magnetic field sensitivity of the spin-valve film $Ni_{91}Fe_{19}(40{\AA})/Co_{90}Fe_{10}(50{\AA}) /Cu(30{\AA})/Co_{90}Fe_{10}(35{\AA})/NiO(800{\AA})$ was 6.3% and about 0.5 (%/Oe), respectively. The MR ratio had 5.3% below an annealing temperature of 20$0^{\circ}C$ which slowly decreased to 3% above 30$0^{\circ}C$. The large blocking temperature of the spin-valve film was taken (as being) due to the good stability of the NiO films. Thus, the spin-valve films with a free NiFe/CoFe layer clearly had a high large GMR output and showed a effective magnetic field sensitivity for a suitable spin-valve head material.

• Asian-Australasian Journal of Animal Sciences
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• v.20 no.10
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• pp.1510-1516
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• 2007

These experiments were carried out to optimize the parameters of electrical activation, methods of parthenogenetic activation and embryo culture in vitro and meanwhile to isolate embryonic stem cells-like (ESCs) derived from porcine parthenogenetic blastocysts (pPBs). These results showed that, as the electric field strength increased from 1.0 to 2.7 kV/cm, the cleavage rate of parthenogenetic embryos increased gradually but the rate of oocyte lysis was significantly increased when using 2.7 kV/cm field strength. The rate of cleavage in 2.2 and 2.7 kV/cm groups was significantly increased in comparison with that of the 1.0 kV/cm group. A voltage field strength of 2.2 kV/cm DC was used to investigate blastocyst development following activation with a single pulse of 30 or $60-{\mu}sec$ pulse duration. The optimum pulse duration was 30-${\mu}sec$, with a blastocyst rate of 20.7%. Multiple pulses were inferior to a single pulse for blastocyst yield (8.0% vs. 29.9) (p<0.05). For porcine oocyte parthenogenetic activation methods, the rates of cleavage (79.0% vs. 59.8%) and blastocysts (19.4% vs. 3.4%) were significantly increased in electrical activation in contrast to chemical activation with ionomycin/6-DMAP (p<0.05). Rates of cleavage and blastocyst formation in NCSU-23 and PZM-3 embryo media were higher than those of G1.3/G2.3 serial culture media, but there was no significant difference among the three groups. The total cell number of blastocysts in PZM-3 embryo culture media containing $5{\mu}g/ml$ insulin was significantly higher than that of the control (no insulin) ($44.3{\pm}9.1$ vs. $33.9{\pm}11.7$). For isolation of PESCs-like, the rates of porcine blastocysts attached to feeder layers and ICM colony formation in Method B (nude embryo culture) were better than those in Method A (intact embryo culture).

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.152-159
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• 2016

This paper describes an offset and 1/f noise cancellation technique based hall sensor signal processor. The hall sensor outputs a hall voltage from the input magnetic field, which direction is orthogonal to hall plate. The two major elements to complete the hall sensor operation are: the one is a hall sensor to generate hall voltage from input magentic field, and the other one is a hall signal process system to cancel the offset and 1/f noise of hall signal. The proposed hall sensor splits the hall signal and unwanted signals(i.e. offset and 1/f noise) using a spinning current biasing technique and chopper stabilizer. The hall signal converted to 100 kHz and unwanted signals stay around DC frequency pass through chopper stabilizer. The unwanted signals are bloked by highpass filter which, 60 kHz cut off freqyency. Therefore only pure hall signal is enter the ADC(analog to dogital converter) for digitalize. The hall signal and unwanted signal at the output of an amplifer and highpass filter, which increase the power level of hall signal and cancel the unwanted signals are -53.9 dBm @ 100 kHz and -101.3 dBm @ 10 kHz. The ADC output of hall sensor signal process system has -5.0 dBm hall signal at 100 kHz frequency and -55.0 dBm unwanted signals at 10 kHz frequency.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.151-151
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• 2012

A new plasma process, i.e., the combination of PIII&D and HIPIMS, was developed to implant non-gaseous ions into materials surface. HIPIMS is a special mode of operation of pulsed-DC magnetron sputtering, in which high pulsed DC power exceeding ~1 kW/$cm^2$ of its peak power density is applied to the magnetron sputtering target while the average power density remains manageable to the cooling capacity of the equipment by using a very small duty ratio of operation. Due to the high peak power density applied to the sputtering target, a large fraction of sputtered atoms is ionized. If the negative high voltage pulse applied to the sample stage in PIII&D system is synchronized with the pulsed plasma of sputtered target material by HIPIMS operation, the implantation of non-gaseous ions can be successfully accomplished. The new process has great advantage that thin film deposition and non-gaseous ion implantation along with in-situ film modification can be achieved in a single plasma chamber. Even broader application areas of PIII&D technology are believed to be envisaged by this newly developed process. In one application of non-gaseous plasma immersion ion implantation, Ge ions were implanted into SiO2 thin film at 60 keV to form Ge quantum dots embedded in SiO2 dielectric material. The crystalline Ge quantum dots were shown to be 5~10 nm in size and well dispersed in SiO2 matrix. In another application, Ag ions were implanted into SS-304 substrate to endow the anti-microbial property of the surface. Yet another bio-application was Mg ion implantation into Ti to improve its osteointegration property for bone implants. Catalyst is another promising application field of nongaseous plasma immersion ion implantation because ion implantation results in atomically dispersed catalytic agents with high surface to volume ratio. Pt ions were implanted into the surface of Al2O3 catalytic supporter and its H2 generation property was measured for DME reforming catalyst. In this talk, a newly developed, non-gaseous plasma immersion ion implantation technique and its applications would be shown and discussed.