• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.3
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• pp.221-228
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• 1998

In this study, the $\beta$-Polyvinylidene fluoride(PVDF) thin films were fabricated by physical vapor deposition method. Also, the properties of dielectric relaxation were studied to understand carrier's behavior of PVDF thin films, to be regarded as the excellent piezo and pyroelectricity. In the process of vapor deposition, the $\beta$-PVDF thin films have been fabricated under the condition of the substrate temperature at 3$0^{\circ}C$, the applied electric field at 142.8kV/cm and the pressure at 2.0${\times}10^{-5}$torr. The dielectric properties of PVDF have been studied in the frequency range 10Hz to 1MHz at temperature from 30 to $100^{\circ}C$. The relative dielectric constant of $\alpha$ and $\beta$-PVDF were 6.8 and 9.8, respectively, under a frequency of 1kHz. Such a phenomenon was caused by the decrease in intermolecular forces originated by the phase-transition from the TGTG' molecular conformation to the TT planar zig-zag conformation. And the relative dielectric constant is increased as a measuring temperature increases, because of the reduction of relaxation time caused by the decrease of intermolecular force.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.10
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• pp.559-563
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• 2000

The $(Sr_{1-x}Ca_x)TiO_3(SCT)$ thin films are deposited on Pt-coated(Pt/TiN/$SiO_2$/Si) using RF sputtering method with substitutional contents of Ca. The maximum grain of thin films is obtained by substitution of Ca at 15[mol%]. Also the composition of SCT thin films were closed to stoichiometry(1.081∼1.117 in A/B/ ratio). The dielectric constant was increased with increasing the substitutional contents of Ca, while it was decreased if the substitutional contents of Ca exceeded over 15[mol%]. The dielectric constant changes almost linearly in temperature ranges of -80∼+90[^${\circ}C$]. The temperature properties of the dielectric loss have a stable value within 0.02 independent of the substitutional contents of Ca. All SCT thin films used in this study show the phenomena of dielectric relaxation with the increase of frequency, and the relaxation frequency is observed above 2000[kHz]. The current-voltage characteristics of SCT15 thin films showed the increasing leakage current as the measuring temperature increase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.160-161
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• 2005

The $(Sr_{1-x}Ca_x)TiO_3$(SCT) thin films are deposited on Pt-coated electrode (Pt/TiN/$SiO_2$/Si) using RF sputtering method with substitutional contents of Ca. The optimum conditions of RF power and $Ar/O_2$ ratio were 140[W] and 80/20, respectively. Deposition rate of SCT thin film was about 18.75$[{\AA}/min]$. The dielectric constant was increased with increasing the substitutional contents of Ca, while it was decreased if the substitutional contents of Ca exceeded over 15[mol%]. All SCT thin films used in this study show the phenomena of dielectric relaxation with the increase of frequency, and the relaxation frequency is observed above 200[kHz].

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.735-738
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• 2002

This paper a new simple PWM (Pulse Width Modulation) signal generation based on modified relaxation oscillator is introduced. Its advantages of the proposed principle are that the precise PWM signal can be easily achieved with a high frequency range up to several megahertz and a low-voltage power supply. The proposed circuit can accept either voltage or current modulating signal. It is very suitable for developing into Integrated Circuits (ICs) form in communication applications. The simulation and experimental results are also depicted, they shown good agreement with theoretical anticipation.

• Korean Journal of Veterinary Research
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• v.37 no.1
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• pp.119-128
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• 1997

The relaxation of gastric fundus smooth muscles is the primary physiological event which induces the receptive relaxation of monogastric animals. L-arginine/Nitric oxide(L-arg/NO) system is known to mediate the inhibitory non-adrenergic non-cholinergic(NANC) neurotransmission in various tissues including gastrointestinal smooth muscles. The longitudinal smooth muscles of porcine gastric fundus showed fast relaxation during electrical field stimulation(EFS) and rebound contraction after EFS in NANC condition. So, the purpose of present study was elucidation of the neurotrasmitters related to the NANC relaxation and explanation of the relation between NANC relaxation and L-arg/NO system. The longitdinal smooth muscles of porcine gastric fundus were hung in the organ bath and under the presence of guanethidine($5{\times}10^{-5}M$), precontraction was induced by carbachol($1{\times}10^{-6}M$). The muscle responses to EFS and drugs were isomerically recorded. The rusults were summarized as follows. 1. The longtudinal muscles of porcine gastric fundus showed frequency-dependent relaxation and rebound contraction to electrical field stimulaton(1ms, 8V, 1~16Hz, 20sec, EFS). These responses were blocked by tetrodotoxin($1{\times}10^{-6}M$). 2. The relaxation and rebound contraction of the longitudinal muscles of porcine gastric fundus to EFS were inhibited by L-NAME($2{\times}10^{-5}M$). The inhibitory effect of L-NAME was antagonized by L-arginine($1{\times}10^{-3}M$), but not by D-arginine($1{\times}10^{-3}M$). 3. Exogenous NO($NaNO_2$, $1{\times}10^{-5}{\sim}1{\times}10^{-4}M$, pH=2.0) caused concentration-dependent relaxation as EFS did. 4. Methylene Blue($2{\times}10^{-5}M$), a soluble guanylate cyclase inhibitor, inhibited the relaxation and rebound contraction of the longitudinal muscles of porcine gastric fundus induced by EFS, but N-ethlmaleimide, a adenylate cyclase inhibitor, did not. 5. 8-Br-cGMP($1{\times}10^{-6}{\sim}3{\times}10^{-6}M$), permeable cGMP analogue, induced dose-dependent relaxation. but 8-Br-cAMP($1{\times}10^{-6}{\sim}3{\times}10^{-6}M$), permeable cAMP analogue, did not. Both did not evoked rebound contraction. 6. ${\alpha}$-chymotrypsin did not affect the relaxation of the longitudinal muscles of porcine gastric fundus. 7. Reactive blue 2($1{\times}10^{-4}M$, 40min) siginificantly inhibited the rebound contraction induced by EFS and inhibited contraction caused by exogenous ATP($1{\times}10^{-4}{\sim}1{\times}10^{-3}M$). These results suggests that NANC relaxation of the longitudinal muscles of porcine gastric fundus mainly mediated by NO and the rebound contraction is related to NO and other neurotransmitters.

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.3
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• pp.70-74
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• 2001

Admittance or impedance spectroscopy is one of the powerful tools to study dielectric relaxation and loss processes in organic and inorganic materials. In this study, the frequency dependent properties of an indium tin oxide/tris(8-hydroxyquinoline) aluminum($Alq_3$)/aluminum structure have been studied. The conductance of the $Alq_3$ film increases with the DC applied voltage up to 4V and decreases above 4V in the low frequency region. This indicates that the resistance of the device decreases with the applied bias due to the carrier injection enhancement, thereafter the injected carriers form the space charge and the additional injection of carriers is prevented. The Cole-Cole plot of the admittance takes a one-semicircle shape, which means that the device can be modeled as a parallel resistor-capacitor network. The resistance and capacitance were estimated as 8.62k${\Omega}$ and 2.7nF, respectively, at 3V in the low frequency region. The dielectric constant ( ${\epsilon}'$ ) of the $Alq_3$ film is independent of the frequency in the low frequency region below 100kHz, while the frequency dependency was observed at above 100kHz. The dielectric loss factor ( ${\epsilon}"$ ) of the $Alq_3$ film shows the dielectric dispersion below 100kHz and dielectric absorption in higher frequency domain. The dispersion is thought to be related to the hopping process of the carriers. The ${\epsilon}"$ is proportional to the reciprocal of the frequency. The dielectric relaxation time was extracted to about 0.318${\mu}s$ from the dielectric absorption spectrum.

• Structural Engineering and Mechanics
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• v.28 no.1
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• pp.19-38
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• 2008

A general solution to the field equations of homogeneous isotropic generalized thermoelastic diffusion with two relaxation times (Green and Lindsay theory) has been obtained using the Fourier transform. Assuming the disturbances to be harmonically time.dependent, the transformed solution is obtained in the frequency domain. The application of a time harmonic concentrated and distributed loads have been considered to show the utility of the solution obtained. The transformed components of displacement, stress, temperature distribution and chemical potential distribution are inverted numerically, using a numerical inversion technique. Effect of diffusion on the resulting expressions have been depicted graphically for Green and Lindsay (G-L) and coupled (C-T) theories of thermoelasticity.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1786-1790
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• 2007

The $(SrCa)TiO_3(SCT)$ thin films are deposited on Pt-coated electrode ($Pt/TiN/SiO_2/Si$) using RF sputtering method at various deposition temperature. The dielectric constant of SCT thin films were increased with the increase of deposition temperature, and changed almost linearly in temperature ranges of $-80{\sim}+90[^{\circ}C]$. Also, SCT thin films was observed the phenomena of dielectric relaxation with the increase of frequency, and the relaxation frequency was observed above 200[kHz]. V-I characteristics of SCT thin films show the increasing leakage current with the increases of deposition temperature. The conduction mechanism of the SCT thin films observed in the temperature range of $25{\sim}100[^{\circ}C]$ can be divided into three characteristic regions with different mechanism by the increasing current. The region 1 below 0.8[MV/cm] shows the ohmic conduction. The region 2 can be explained by the Child's law, and the region 3 is dominated by the tunneling effect.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.1084-1087
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• 2001

The (Sr$\sub$0.85/Ca$\sub$0.15/)TiO$_3$(SCT) thin films are deposited on Pt-coated electrode(Pt/TiN/SiO$_2$/Si) using RF sputtering method. The crystallinity of SCT thin films is increased with increase of substrate temperature in the temperature range of 100[$^{\circ}C$]∼500[$^{\circ}C$]. Also, the crystallinity of SCT thin films are obtained at the substrate temperature above 400[$^{\circ}C$]. SCT thin films had (111) preferred orientation. The dielectric constant changes almost linearly in temperature ranges of-80∼+90[$^{\circ}C$]. The temperature properties of the dielectric loss have a stable value within 0.1. SCT thin films used in this study show the phenomena of dielectric relaxation with the increase of frequency, and the relaxation frequency is observed above 200[kHz].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.413-416
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• 1996

The ceramic dielectrics were fabricated by mixing of Mn $O_2$ and ZnO at (B $a_{0.85}$ $Ca_{0.15}$)Ti $O_3$ and studied for dielectric relaxation characteristics. The dielectric relaxation time was increased by space charge polarization of palaelectric layer at the low temperature and frequency but it was decreased by Interface polarization at the high temperature and frequency. The remnant polarization and coercive field of ceramic dielectrics was decreased by rising temperature.ure.