• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.406-414
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• 1996

We studied the phase formation and the effect of electrical properties of PZT thin films with changing the oxygen partial pressure in cooling after deposition of PZT thin film by reactive sputtering method. The roughness of thin film increased with decreasing the oxygen partial pressure in cooling due to the evaporation on the surface ofthin films and the grain size was not changed very much. The hysteresis property of PZT thin film was improved toward having a good squareness with increasing the cooling oxygen partial pressure. We observed the decrease of remanent polarization, retained polarization and coercive field with decreasing the oxygen partial pressure. Dielectric constant decreased gradually and internal bias field increased in the measurement of dielectric constant-voltage property with decreasing cooling oxygen partial pressure. We observed the increase of nonswitched polarization in the measurement of field accelerated retention and the decrease of nonswitched polarization with increasing the bias time.

• Journal of the Optical Society of Korea
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• v.13 no.4
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• pp.472-477
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• 2009

A Stokes polarimetry imaging (SPI) system was developed and utilized to detect tendon tears by constructing the degree of linear polarization (DOLP) image maps after linearly polarized light illumination. The micro and partial-thickness tears of turkey tendons were made and imaged by the SPI system at different incident polarization angles (IPA) with different mechanical loads on the tendon. The micro and partial-thickness tendon tears were detected by the DOLP images due to weak birefringence around the tears. The tendon tears were detected by a highest DOLP contrast at longest visible wavelength (Red, 650 ${\pm}$ 50 nm). All polarized images showed modulated DOLP as the incident polarization angle (IPA) was varied. The varying DOLP allowed the optimal detection of the micro and partial-thickness tendon tears at a certain IPA. The SPI system with variable IPA and spectral information can improve the detection of the tendon tears by higher visibility of fiber orientations, and thereby improve diagnosis and treatment of the tendon related injuries.

• Electrical & Electronic Materials
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• v.11 no.10
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• pp.46-52
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• 1998

In this study, polarization switching characteristics of Pb(ZrxTil-x)O3 (PZT) thin films were investigated. Switching times(ts) were found to be decreased as the Zr mol% was increased. But, the switching peak currents(Imax) showed the largest value at 50 mol% Zr. As a result of this experiment, ts was found to be depended on the remanent polarization and coercive field and also Imax strongly depended on the dielectric constant of PZT thin films. In order to investigate the partial switching kinetics of PZT thin films, short and relatively small voltage pulses were applied to the MFM(metalferroelectric metal) PZT capacitors and polarization switching curves were measured with a variation of the total width of the applied pulses. Also, the switching curves were measured at different applied voltages(4, 8, 10, 12 and 14 volts). As the applied voltages increased, ts and Imax were found to be decreased and increased, respectively. In case of fatigued specimen which we applied $\pm$10 volts square pulse for 1010 cycles, ts and Imax were found to be shorter and smaller than those of virgin specimens. This is due to the decrease of the remanent polarization and the increase of the coercive field.

• The Korean Journal of Ceramics
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• v.4 no.2
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• pp.114-121
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• 1998

Using Hebb-Wagner's asymmetric cell, partial conductivities of holes and electrons in yttria stabilized zirconia doped with 10 mol% TiO2 have been estimated by a dc polarization measurement. The current interrruption method and ac impedance measurements have been also made to evaluate the ionic conductivity and to examine the consistency of the partial conductivities. Partial conductivities of electrons(σn) and holes (σp) were found to be pro-peortional to -1/4 and 1/4 power of partial pressure of oxygen gas, respectively, except for σn at reducing conditions. In comparison with 5 mol% doped YSZ, σn was found to increase with the increase of TiO2 concentration, but σp stayed at almost a constant value.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.122-126
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• 2002

A diagnostic test of 15.4kV cross-linked polyethylene(XLPE) ultra high voltage power cables from generator in the Soyanggang hydro electric power plant was conducted over 3 months, beginning April 2001. According to the results, in the case of the power cables from generator 1, there was little possibility of proceeding rapid1y to failure or defect because the data from diagnosis doesn't indicate any failure, deterioration or partial discharge. However, in the case of the power cables from generator 2, the. polarization index show a slight abnormal condition of the insulator that is not severe, and the deterioration was also identified as not severe. However, the partial discharge had an abnormal condition which was severe.

• Transactions on Electrical and Electronic Materials
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• v.7 no.6
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• pp.319-323
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• 2006

The problem of the partial discharge (PD) extinction is investigated. The transient process takes place in a small spherical inclusion which is located in the dielectric. Both the losses caused by polarization and ohmic losses as the dielectric parameters are taken into account. From the inclusion standpoint the dielectric is considered as an active two-pole element (equivalent generator) and inclusion represents by own current-voltage curve. PD extinction voltage was shown to depend on the polarization loss tangent.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.299-303
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• 2015

The electrolyte is an important component in determining the performance of Fuel Cells. Especially, investigation of the conduction properties of electrolytes plays a key role in determining the performance of the electrolyte. The electrochemical properties of Yttrium stabilized zirconia (YSZ) were measured to allow the use of this material as an electrolyte for solid oxide fuel cells (SOFC) in the temperature range of $700-1000^{\circ}C$ and in $0.21{\leq}pO_2/atm{\leq}10^{-23}$. A Hebb-Wagner polarization experimental cell was optimally manufactured; here we discuss typical problems associated with making cells. The partial conductivities due to electrons and holes for 8YSZ, which is known as a superior oxygen conductor, were obtained using I-V characteristics based on the Hebb-Wagner polarization method. Activation energies for holes and electrons are $3.99{\pm}0.17eV$ and $1.70{\pm}0.06eV$ respectively. Further, we calculated the oxygen ion conductivity with electron, hole, and total conductivity, which was obtained by DC four probe conductivity measurements. The oxygen ion conductivity was dependent on the temperature; the activation energy was $0.80{\pm}0.10eV$. The electrolyte domain was determined from the top limit, bottom limit, and boundary (p=n) of the oxygen partial pressure. As a result, the electrolyte domain was widely presented in an extensive range of oxygen partial pressures and temperatures.

• Atmosphere
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• v.27 no.4
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• pp.467-481
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• 2017

A correction method of reflectivity in partial beam blockage (PBB) area is suggested, which is based on the combination of digital terrain information and self-consistency principle between polarimetric observation. First, the reflectivity was corrected by adding the radar energy loss estimated from beam blockage simulation using digital elevation model (DEM) and beam propagation geometry in standard atmosphere. The additional energy loss by unexpected obstacles and non-standard beam propagation was estimated by using the coefficient between accumulated reflectivity ($Z_H$) and differences of differential phase shift (${\Phi}_{DP}$) along radial direction. The proposed method was applied to operational S-band dual-polarization radar at Jindo and its performance was compared with those of simulation method and self-consistency method for six rainfall cases. When the accumulated reflectivity and increment of ${\Phi}_{DP}$ along radial direction are too small, the self-consistency method has failed to correct the reflectivity while the combined method has corrected the reflectivity bias reasonably. The correction based on beam simulation showed the underestimation. For evaluation of rainfall estimation, the FBs (FRMSEs) of simulation method and self-consistency principle were -0.32 (0.59) and -0.30 (0.57), respectively. The proposed method showed the lowest FB (-0.24) and FRMSE (0.50). The FB and FMSE were improved by about 18% and by 19% in comparison to those before correction (-0.42 and 0.70). We can conclude that the proposed method can improve the accuracy of rainfall estimation in PBB area.

• Journal of Integrative Natural Science
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• v.3 no.4
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• pp.226-230
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• 2010

Calculation of partial charge is important in chemistry. However, because there are many methods developed, it is of considerable interest to know how to calculate and apply properly to address various chemical problems. For basis set, usually double zeta quality is acceptable, and double zeta polarization function would be enough for most cases. To describe electronic state more accurately, Many electron configurations would be necessary to describe highly strained or anionic species. The NPA population introduced new concept about amide bonds, i.e., the planar geometry of nitrogen atom may not come from resonance, but from the lowering of p-orbital energy by electronegative carbonyl carbon atom. The issues for hypervalent atomic charges was also addressed by various charge derivation scheme. When the charge schemes were applied to organolithium compounds, the ionic nature of boding was revealed. This comes from the fact that previous Mulliken partial atomic charges overemphasized the covalent character, wihout much justification. The other partial charge derivation schemes such as NPA(natural population analysis), IPP (Integrated Projected Population) showed that much more ionic picture. ESP potential derived charges are generally believed to be suitable to describe intermolecular interactions, therefore they are used for molecular dynamics simulations and CoMFA (comparative molecular field analysis). The charge derivation schemes using multipole polarization was mainly applied to reproduce experimental infrared spectroscopy. In some reports these schemes are also suitable for intermecular electrostatic interactions. Charges derived from electron density gradient have shown the some bonds are not straight, but actually bent. The proper choice of charge-calculation method along with suitable level of theory and basis set are briefly discussed.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.233-234
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• 1996

For obtaining estimates of a total magnetic flux, we propose to use measurements of ${\partial}I/{\partial}{\lambda}$. obtained by a modulation method which is formally identical to Stokes V-parameter measurements. In this case the polarization is not analyzed. It is advisable to use in measurements two parts of the spectral line wing.