• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.04a
• /
• pp.63-64
• /
• 2008

Electrokinetic motion of fullerene ($C_{60}$) particles in liquid crystal (LC) medium under an in-plane electric field has been studied for the application to the electronic paper display. Fullerenes move in the direction of applied electric field due to interaction between the induced dipole moment on $C_{60}$ and external electric field at lower threshold voltages compared to other devices such as QR-LPD (Quick Response Liquid Powder Display) and TBD (Twisting Ball Display). We also confirmed the bistability of fullerene particles in LC medium and the results showed that the 87% and 81% of original reflectance or transmittance of image was retained after 24 hours and 48 hours respectively. Our studies show the possibility that fullerenes can be used for electronic paper display.

• Journal of The Korean Astronomical Society
• /
• v.38 no.2
• /
• pp.283-287
• /
• 2005

The slow evolution of global magnetic fields and other dynamical processes in atmospheres of CP magnetic stars lead to the development of induced electric currents in all conductive atmospheric layers. The Lorentz force, which results from the interaction between a magnetic field and the induced currents, may modify the atmospheric structure and provide insight into the formation and evolution of stellar magnetic fields. This modification of the pressure-temperature structure influences the formation of absorption spectral features producing characteristic rotational variability of some spectral lines, especially the Balmer lines (Valyavin et al., 2004 and references therein). In order to study these theoretical predictions we began systematic spectroscopic survey of Balmer line variability in spectra of brightest CP magnetic stars. Here we present the first results of the program. A0p star $\Theta$ Aur revealed significant variability of the Balmer profiles during the star's rotation. Character of this variablity corresponds to that classified by Kroll (1989) as a result of an impact of significant Lorentz force. From the obtained data we estimate that amplitudes of the variation at H$\alpha$, H$\beta$, H$\gamma$ and H$\delta$ profiles reach up to $2.4\%$during full rotation cycle of the star. Using computation of our model atmospheres (Valyavin et al., 2004) we interpret these data within the framework of the simplest model of the evolution of global magnetic fields in chemically peculiar stars. Assuming that the field is represented by a dipole, we estimate the characteristic e.m.f. induced by the field decay electric current (and the Lorentz force as the result) on the order of $E {\~} 10^{-11}$ cgs units, which may indicate very fast (< < $10^{10}$ years) evolution rate of the field. This result strongly contradicts the theoretical point of view that global stellar magnetic fields of CP stars are fossil and their the characteristic decay time of about $10^{10}$ yr. Alternatively, we briefly discuss concurring effects (like the ambipolar diffusion) which may also lead to significant atmospheric currents producing the observable Lorentz force.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.50 no.10
• /
• pp.509-516
• /
• 2001

Isolated phase bus(IPS) has a special structure for carrying large current generated by a generator to a main transformer. In the analysis of IPB, the understanding of the magnetic field distribution generated by large current is important. Especially, while the bus conductor current is flowing, almost same amount of current as bus conductor current is induced in the enclosures under the influence of time varying magnetic field, and therefore the large electric loss and the deterioration of insulating capability might occur due to Joule heating effect. Hence for the optimal design of IPB satisfying the condition to minimize the loss, the accurate analysis of magnetic field distribution and the eddy current characteristics of three phase isolated phase bus have been investigated. In the analysis of time varying magnetic field, instead of finite difference method(FDM) which is generally used, finite element method with phasor concept is investigated under the assumption that the bus current is purely sinusoidal. The characteristics is studied along the phase angle by comparing the effect of eddy current on the magnetic field distribution with the case that eddy current is not considered, and also the effect of material, thickness and radius of enclosure on the eddy current distribution is discussed.

• Journal of the Korean Ceramic Society
• /
• v.55 no.3
• /
• pp.290-298
• /
• 2018

In order to investigate the effect of thickness on the dielectric and piezoelectric properties of (001) PMN-29PT single crystals, three different types of PMN-29PT samples were prepared using the solid-state single crystal growth (SSCG) method: high density crystal [99%], low density crystal [95%], and high density crystal doped with Mn [98.5%]. When their thickness decreased from 0.5 mm to 0.05 mm, their dielectric constant ($K_3{^T}$), piezoelectric constants ($d_{33}$ and $g_{33}$), and electromechanical coupling factor ($k_t$) decreased continuously. However, their dielectric loss (tan ${\delta}$) increased. The addition of Mn to PMN-PT induced an internal bias electric field ($E_I$), increased the coercive electric field ($E_C$), and prevented local depoling. Therefore, Mn-doped PMN-PT crystals show high stability as well as high performance, even in the form of very thin plates (< 0.2 mm), and thus are suitable for application to high frequency composites, medical ultrasound probes, non-destructive testing devices (NDT), and flexible devices.

• Korean Journal of Veterinary Research
• /
• v.35 no.2
• /
• pp.279-285
• /
• 1995

To characterize non-adrenergic non-cholinergic(NANC) nerve mediated contractile responses in circular smooth muscle of bovine reticular groove, we investigated NANC relaxation and contraction induced by electric field stimulation to enteric nerves. In the presence of atropine($1{\mu}M$) and guanethidine($50{\mu}M$), electric field stimulation at frequency of 1 to 16Hz(square pulses, 0.5ms duration, 70V) evoked clear-cut relaxations through stimulations. Transient 'rebound contraction' was occured when the stimulus was switched off. All of the responses (relaxation and rebound contraction) were dose-dependently blocked by Nw-nitro-$_{\small{L}}$-arginine methyl ester(L-NAME), an inhibitor of nitric oxide synthesis, and methylene blue, and inhibitor of soluble guanylate cyclase. Tetraethyl ammonium(TEA), a potassium channel blocker, did not block the NANC relaxations.

• Proceedings of the KIEE Conference
• /
• 1990.07a
• /
• pp.195-198
• /
• 1990

In order to investigate the radiation effects induced to electrical properties of Biaxially-Oriented Polypropylen film, several observations were carried out to the sample irradiated to various dose by $Co^{60}-{\gamma}$ ray, on the characteristics of TSC spectra measuered as a function of electric field applied to a sample of 15[ ${\mu}m$] thick. The TSC spectra observed in the temperature range of $153{\sim}403[K]$ with the electric field of intensity $10{\sim}60$ [MV/m], have shown two of the distinguished peak such as ${\beta}$, ${\alpha}$, each of which appeared at $-5{\sim}20$ [ $^{\circ}C$] and 90 [ $^{\circ}C$] respectively. As the conclusions, obtained from the studies, the origin of ${\alpha}$ peak in TSC seems to be attributed by thermal excitation of ions trapped with $0.4{\sim}0.8[eV]$ deep, at the defects formed by $Co^{60}-{\gamma}$ irradiation in a crystaline region. The origin of ${\beta}$ peak was regarded as the depolarization process of "OH" or "CO" dipole with the activation energy of $0.4{\sim}0.6[eV]$ in an amorphous region.

• Resources Recycling
• /
• v.11 no.3
• /
• pp.37-45
• /
• 2002

Triboelectrostatic Separation procese is a technology that different particles charged after contact and rubbing different materials are separated in an electric field. At this time, charged polarity of different materials depends on their own work function. Therefore this study discovers work functions of various plastics and determines charging characteristics for the specific optimum operation condition. The experiment is conducted with two sample sets composed of various different plastics. Each sample is charged by contact and rubbing different materials. Surface charge of charged particles is measured by Faraday Cage. The specific work function of an each plastic is driven by measured charging amount and charged particles are separated in a certain electric field ($\pm$20 kV). At last, the relationship between charging amount and separation efficiency is induced by the separation experiment.

• Korea-Australia Rheology Journal
• /
• v.17 no.4
• /
• pp.207-215
• /
• 2005

We present a finite difference solution for electrokinetic flow in rectangular microchannels encompassing Navier's fluid slip phenomena. The externally applied body force originated from between the nonlinear Poisson-Boltzmann field around the channel wall and the flow-induced electric field is employed in the equation of motion. The basic principle of net current conservation is applied in the ion transport. The effects of the slip length and the long-range repulsion upon the velocity profile are examined in conjunction with the friction factor. It is evident that the fluid slip counteracts the effect by the electric double layer and induces a larger flow rate. Particle streak imaging by fluorescent microscope and the data processing method developed ourselves are applied to straight channel designed to allow for flow visualization of dilute latex colloids underlying the condition of simple fluid. The reliability of the velocity profile determined by the flow imaging is justified by comparing with the finite difference solution. We recognized the behavior of fluid slip in velocity profiles at the hydrophobic surface of polydimethylsiloxane wall, from which the slip length was evaluated for different conditions.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.39 no.5
• /
• pp.425-433
• /
• 2015

In this paper, we have numerically investigated two-dimensional dielectrophoretic (DEP) motions of a single particle suspended freely in a viscous fluid, interacting with a nearby nonconducting planar wall, under an externally applied uniform direct-current electric field. Particularly, we solve the Maxwell equation with a large sharp jump in the electric conductivity at the particle-fluid interface and then integrate the Maxwell stress tensor to compute the DEP force on the particle. Results show that, under an electric field parallel to the wall, one particle is always repelled to move far away from the wall and the motion depends strongly on the particle-wall spacing and the particle conductivity. The motion strength vanishes when the particle is as conductive as the fluid and increases as the conductivity deviates further from that of the fluid.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.6 s.183
• /
• pp.160-165
• /
• 2006

We have designed a high-transmission nano aperture in a perfect electric conductor film with the incident beam of 532 nm wavelength. The aperture basically has a C-shape and is known to produce a bright spot nearby the aperture in small size less than diffraction limit. The bright spot is strongly coupled with the local plasmon excited through the aperture hole. The characteristics of transmission and peak power of the aperture output were calculated using finite differential time domain (FDTD) technique, and the geometry of the aperture was determined to get a maximum transmission and peak power. To find the effect of the surface plasmon induced near by the aperture, we calculated the variations of the transmittance and the beam sizes by changing the size of the input beam irradiated on the aperture.