• Korean Journal of Optics and Photonics
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• v.8 no.5
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• pp.377-381
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• 1997

Poling condition in 2 mol% MgO-doped $LiNbO_3$ crystals is investigated by varying the amplitude of poling electric field from 3V/cm to 7V/cm. It is found that 5V/cm is the best value for the formation of single domain by analysing the characteristics of the second harmonic generation(SHG) as the function of temperature. The temperature dependence of the phase-matching profile of SHG for the crystal applied by a spatially modulated electric field is observed to be very different from the simple sinc function. The distorted profile can be consistently fitted with the numerical simulations. This shows that the crystal homogeneity can be tested by the SHG temperature phase-matching profile. In addition, the thermo birefringence coefficient and electro birefringence coefficient of SHG were measured from the temperature dependence of phase-matching profile and shifts of phase-matching temperature by appling electric field along c-axis.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.5
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• pp.9-15
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• 2000

The 3 ${\mu}{\textrm}{m}$-thick PVDF (polyvinylidene fluoride) thin film have been prepared using physical vapor deposition with electric field, and its FT-IR spectrum, dielectric property and electric conduction phenomenon have been investigated. Since the characteristic peaks are detected at 509.45 ［$cm^{-1}$ /］ and 1273.6 ［$cm^{-1}$ /］in the FT-IR spectrum, we are confirmed that the $\beta$ -phase is dominant in the PVDF thin film. In the results of dielectric properties, the PVDF thin film shows anomalous dispersion, i.e. gradual decrease of dielectric constant with increase of frequency, and also that the dielectric absorption point changes from 200 Hz to 7000 Hz with increasing temperature of thin film, which is consistent with the Debye's theory. The activation energy ( $\Delta$H) obtained from temperature dependence of dielectric loss is 21.64 ㎉/mole. We confirm that the electric conduction mechanism of PVDF thin film is dominated by ionic conduction by investigating the dependence of the leakage current of the thin film on the temperature and the electric field.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.4
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• pp.273-279
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• 2016

In this paper, a high-performance control of the induction motor for electric car was implemented to escape dependence of the rare earth magnet. Proposed high-efficiency control algorithm is a Direct Rotor Field-Oriented Control method that is insensitive to the fluctuation of motor parameters. In the DRFOC method, we need to compensate fluctuation of stator transient inductance and magnetizing inductance caused by the magnetic saturation of induction motor in high-speed area. This paper proposes Back-EMF Observer based on stator current estimator of Luenberger style. Motor control system applied the Voltage Feedback Flux Weakening Control method for high-speed operation. The proposed algorithm was verified through tests by the power train of Extended Range Electric Vehicle consists of induction motor and differential gear.

• Korean Journal of Materials Research
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• v.9 no.1
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• pp.81-85
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• 1999

Polarization and strain induced by unipolar electric field (P\ulcorner, S\ulcorner), those induced by bipolar electric field (P, S) and remanent polarization (P\ulcorner) were investigated in 0.9Pb(Mg\ulcornerNb\ulcorner)O$_3$-$0.1PbTiO_3$relaxor ferroelectric ceramics in the temperature range of $-50^{\circ}C$~$90^{\circ}C$. From the temperature dependence of polarization and strain, the transition from predominantly paraelectric (electrostrictive) to partially ferroelectric (piezoelectric) is visualized. Under the given temperature, the P\ulcorner/P\ulcorner is always larger than the S\ulcorner/S\ulcorner and the difference between them becomes larger ass the temperature decrease. The S\ulcorner/P\ulcorner increases as the temperature decreased below phase transition temperature. It was suggested that these experimental results might be explained with a simple rigid ion model concentrating on BO\ulcorner octahedron.

• Korean Journal of Optics and Photonics
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• v.4 no.1
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• pp.84-89
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• 1993

Spatial homogenity of Mg (4 mole %):LiNb$O_3$ is investigated by studying the characteristic of Second Harmonic Generation in Mg:LiNb$O_3$ as a function of temperature and DC Electric Field. It is found that the temperaturs at which the intensity of the second harmonic is reduced to the first zero from its maximum for the phase matching condition is shifted linearly to the strength of DC Electric field applied to optic axis of Mg:LiNb$O_3$. From these results, the electro-optic coefficient of Mg:LiNb$O_3$ is estimated to be higher than that of Congruent LiNb$O_3$ by a factor of 1.5.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.323-329
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• 2004

The electrical and rheological properties pertaining to the electrorheological (ER) behavior of chitosan derivatives, chitosan, chitosan ammonium salt and chitosan phosphate suspensions in silicone oil were investigated. Chitosan derivative suspensions showed a typical ER response (Bingham flow behavior) upon application of an electric field. However, chitosan phosphate suspension exhibited an excellent shear yield stress compared with chitosan and chitosan ammonium salt suspensions. The difference in behavior results from the difference in the conductivity of the disperse phases due to the difference of their polarizability. The shear stress for the chitosan, chitosan ammonium salt and chitosan phosphate suspensions exhibited a linear dependence on the volume fraction of particles and 1.18 ,1.41 and 1.67 powers of the electric field. On the basis of the experimental results, the newly synthesized chitosan derivative suspensions found to be an ER fluid.

• KSTLE International Journal
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• v.5 no.2
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• pp.49-51
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• 2004

The electrical and rheological properties pertaining to the electrorheological (ER) behavior of chitosan derivatives, chitosan, chitosan ammonium salt and chitosan phosphated suspensions in silicone oil were investigated. Chitosan derivative suspensions showed a typical ER response (Bingham flow behavior) upon application of an electric field. However, chitosan phosphate suspension exhibited an excellent shear yield stress compared with chitosan and chitosan ammonium salt suspensions. The difference in behavior results from the difference in the conductivity of the disperse phases due to the difference of their polarizability. The shear stress for the chitosan, chitosan ammonium salt and chitosan phosphate suspensions exhibited a linear dependence on the volume fraction of particles and 1.18, 1.41 and 1.67 powers of the electric field. On athe basis of the experimental results, the newly synthesized chitosan dervative suspensions found to be an ER fluid.

• Korea-Australia Rheology Journal
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• v.13 no.4
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• pp.197-203
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• 2001

We reported on the eletrorheological (ER) properties of several semiconducting polymers including poly (p-phenylene) (PPP), poly (acene quinone) radicals (PAQRs), microencapsulated polyaniline (MPANI) and polyaniline (PANI) those we synthesized. The yield stress dependence on electric field strength for the ER fluids using these semiconducting polymers was mainly examined. The yield stress, which is an important design parameter for ER fluids, was observed to satisfy a universal scaling function, allowing that yield stress data for all the ER fluids examined in this study collapse onto a single curve for a broad range of electric field strengths. The proposed scaling function incorporates both the polarization and conductivity models.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.6
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• pp.281-287
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• 2001

In order to obtain guidelines for design and operation of a new plasma source by a magnetic neutral loop discharge(NLD), the electron behavior was studied experimentally and numerically. Experimentally, the magnetic field gradient was changed over a wide range, and it was found that there existed an optimum value for efficient plasma production. Analyses of the electron behavior were performed using a model that included effects of a three dimensional electromagnetic field configuration considering the spatial decay of the electric field, and the limitation to the motion of electron caused by the existence of walls and thus electron loss at wall surfaces. These three dimensional factors were found to explain the existence of the optimum magnetic field gradient. It was shown that the L dependence of the plasma production efficiency was firstly decided by the finite decay length of the electric field strength, which was further modified by electron elastic collisions with neutral atoms which drove the electron to walls. The latter effect tends to reduce the optimum value of L.

• Journal of Environmental Science International
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• v.7 no.1
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• pp.36-40
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• 1998

This study was carried out to investigate the collection Efficiency of mass in collector step at the different of physical gas characterization. This work has focused on the dependence of the collection efficiency of mass in the collector zone of a two-stage set up field with gas temperature T and the dew point tmeperature. To identify the dependence of the mass collection efficiency on the Bounded plate of the collector zone MP.k by the spectre electric resistance of dust $p_e$. and the relative humidify ${\varphi}$, 20 at- tempts have been made with three different gas temperature ($50{\circ}C, 80{\circ}C, 110{\circ}C$) at different dew point. At the specific electric resistance of dust $p_e$=$10^6{\Omega}m$ which relative humidity corresponds to $\phi$ > 15%, a easy rise of the sounded plate secluded dust mass share was measured atwain. As the result of the higher cohesion imprisonment power due to the adsorbtion of particle, the rinse of the relative humidity developed on the particle surface. Therefore, the collection efficiency of mass was not predominant the high temperature T in the collector zone, neither was the pecific ellectric resistance of dust dependent.