• Journal of the Korean Ceramic Society
• /
• v.38 no.6
• /
• pp.499-505
• /
• 2001

The behaviour of ionic compound crystals under combined chemical and externally applied electrical potential gradients is discussed. Firstly, a systematic overview is given. Then a formal analysis follows. The transport equations of the ions and the electric defects predict that even with reversible electrodes demixing, and in particular decomposition of the compound will occur if the applied d.c. current density is sufficiently high. These predictions are illustrated by appropriate experiments. With the help of the solid solution (Me, Fe)O, where Fe-ions are the dilute species, we investigate experimentally the behaviour of a ternary ionic crystal under a d.c. electric current load. All the compounds were placed in a galvanic cell, and the internal reactions which then could be observed were driven by the electric field in this cell. In addition, we discuss the influence of the electric field on the classical solid state reaction AX+BX=ABX$_2$, if again the reaction couple is placed in a galvanic cell.

• Journal of the Korean Vacuum Society
• /
• v.8 no.3B
• /
• pp.368-375
• /
• 1999

The Maxwell equation and the transformer equivalent-circuit model are applied to a radio frequency planar inductively coupled plasma. The spatial distribution of the vector potential, the magnetic field, and the electric field are obtained analytically. As a result, the plasma current, the mutual inductance between the coil and the plasma, and the self inductance of plasma are found to increase with increasing skin depth. The spatial distribution of absorbed power has maximum where the antenna coil exists, and has a similar profile to that of the induced electric field. The power transfer efficiency is found to increase with increasing gas pressure before a saturation around p+ 20mTorr, while it shows an increase with the plasma density before a slight decrease around a density of $5\times10^{11}/\textrm{cm}^3$.

• Journal of Information Display
• /
• v.10 no.4
• /
• pp.143-148
• /
• 2009

The theoretical current density equations for organic semiconductors was derived according to the internal carrier emission equation based on the diffusion model at the Schottky barrier contact and the mobility equation based on the field dependence model, the so-called "Poole-Frenkel mobility model." The electric field becomes constant because of the absence of a space charge effect in the case of a higher injection barrier height and a lower sample thickness, but there is distribution in the electric field because of the space charge effect in the case of a lower injection barrier height and a higher sample thickness. The transition between the injection- and bulk-limited currents was presented according to the Schottky barrier height and the sample thickness change.

• Proceedings of the KIEE Conference
• /
• 2003.07a
• /
• pp.439-441
• /
• 2003

In this study the formula of electro magnetic fields under 3-phase power lines with vertical or horizontal line-configurations were deduced and the effect of the earth was considered in the formula. Using the formula the electric field and the magnetic flux density under distribution and transmission lines constucted currently in our country were calculated and the components of each field were investigated with horizontal distance from tower and height above the earth.

• Journal of Korea Society of Industrial Information Systems
• /
• v.25 no.5
• /
• pp.49-57
• /
• 2020

Conventional electric motors are not suitable for aircraft because of their large size and weight. High-temperature superconducting (HTS) motors have high current density, high magnetic field density, and low loss, so they can significantly reduce the size and weight compared to general electric motors. This paper presents the conceptual design and analysis results of HTS motors for electric propulsion in future aircraft. A 2.5 MW HTS motor with a rotational speed of 7,200 RPM was designed and the specific power (kW/kg) was analyzed. The operating temperature of the field coil of the HTS motor is 20K in consideration of LH2 cooling. The stator winding were connected in a multi-phase configuration and Litz wires were used to minimize eddy current losses. As a result, it was confirmed that the specific power of the motor is about 18.67 kW/kg, which is much higher than that of the conventional electric motor.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.10
• /
• pp.2706-2711
• /
• 1994

In this work, an experimental type of torque converter has been constructed and its characteristics have been evaluated by adapting an electrorheological fluid(ERF) as an operating medium. The device was designed by using the equations which were proposed by Carlson et al. The correlation between the rheological behaviour of an ERF and mechanical parameters of the clutch has been investigated. The torque generated by an ERF in this device is sum of one due to the yield strength by polarizing dispersed particles in dielectric oil and one due to the viscous drag. The experimental results are presented in terms of torque and current density as a function of rotational speed at various electric field strength applied. Experimental results showed that the measured torque was rapidly increased with the increase of the electric field, generally being proportional to the rotational speed of the motor. The measured current was shown to be increased with the increased electric field. Also, the current was decreased with the increase of increased with the increased electric field. Also, the current was decreased with the increase of the rotational speed of the motor and reached plateau region after f = 5 Hz.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.05a
• /
• pp.3.2-3.2
• /
• 2011

In recent years, inkjet printing technology has received significant attention as a micro/nanofabrication technique for flexible printing of electronic circuits and solar cells, as well for biomaterial patterning. It eliminates the need for physical masks, causes fewer environment problems, lowers fabrication costs, and offers good layer-to-layer registration. To fulfill the requirements for use in the above applications, however, the inkjet system must meet certain criteria such as high frequency jetting, uniform droplet size, high density nozzle array, etc. Existing inkjet devices are either based on thermal bubbles or piezoelectric pumping; they have several drawbacks for flexible printing. For instance, thermal bubble jetting has limitations in terms of size and density of the nozzle array as well as the ejection frequency. Piezoelectric based devices suffer from poor pumping energy in addition to inadequate ejection frequency. Recently, an electrohydrodynamic (EHD) printing technique has been suggested and proposed as an alternative to thermal bubble or piezoelectric devices. In EHD jetting, a liquid (ink) is pumped through a nozzle and a strong electric field is applied between the nozzle and an extractor plate, which induce charges at the surfaces of the liquid meniscus. This electric field creates an electric stress that stretches the meniscus in the direction of the electric field. Once the electric field force is larger than the surface tension force, a liquid droplet is formed. An EHD inkjet head can produce droplets smaller than the size of the nozzle that produce them. Furthermore, the EHD nano-inkjet can eject high viscosity liquid through the nozzle forming tiny structures. These unique features distinguish EHD printing from conventional methods for sub-micron resolution printing. In this presentation, I will introduce the recent research results regarding the EHD nano-inkjet and the printing system, which has been applied to solar cell or thin film transistor applications.

• Tribology and Lubricants
• /
• v.14 no.2
• /
• pp.1-9
• /
• 1998

The electrorheological (ER) behavior of suspensions in silicone oil of phosphated cellulose particles (average particle size 17.77 ${\mu}{\textrm}{m}$) was investigated at room temperature with electric fields up to 2.5 KV/mm. In this paper, for development of anhydrous ER suspensions using at wide temperature range, we would like to know fundamental understandings on the ER activity. As a first step, the anhydrous ER suspensions dispersed the phosphated cellulose particles were measured, and not only the electrical characteristics such as dielectric constant, current density and electrical conductivity but also the rheological properties on strength of electric field and quantity of dispersed phase were studied. From the experimental results, the anhydrous ER suspensions dispersed phosphated cellulose particles showed a stable current density and very high performance of ER effect $(\tau/\tau_0=1030)$ on the 2.5 KV/mm and the dynamic yield stress $(\tau_y)$ was in exponential proportion to the strength of electric fields.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.49 no.1
• /
• pp.24-29
• /
• 2000

We propose a simple method to control the crystallization depth of amorphous silicon (a-Si) deposited by PECVD or LPCVD during the excimer laser annealing (ELA). Employing the new method, we have formed poly-Si/a-Si double film and fabricated a new poly-Si TFT with vertical a-Si offsets between the poly-Si channel and the source/drain of TFT without any additional photo-lithography process. The maximum leakage current of the new poly-Si TFT decreased about 80% due to the highly resistive vertical a-Si offsets which reduce the peak electric field in drain depletion region and suppress electron-hole pair generation. In ON state, current flows spreading down through broad a-Si cross-section in the vertical a-Si offsets and the current density in the drain depletion region where large electric field is applied is reduced. The stability of poly-Si TFT has been improved noticeably by suppressing trap state generation in drain region which is caused by high current density and large electric field. For example, ON current of the new TFT decreased only 7% at a stress condition where ON current of conventional TFT decreased 89%.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.2
• /
• pp.102.1-102.1
• /
• 2011

In this study we use three-dimensional magnetohydrodynamic simulations to investigate how the dynamic state of emerging magnetic field is related to the twist of field lines. Emerging magnetic field forms a magnetic structure on the Sun where various kinds of activity such as solar flares, jets, and coronal mass ejections are observed. To understand the physical mechanism for producing such activity, we have to know the dynamic nature of this structure. Since flares are the manifestation of rapidly dissipating electric current in the corona, we also investigate the distribution of current density inside the structure and examine how it depends on the field-line twist. To demonstrate the dynamic structure of emerging magnetic field, we focus on the factors characterizing the geometric property and stratification of emerging magnetic field, such as the curvature of field line and the scale height of field strength. These two factors show that emerging field forms a two-part structure in which the central part is close to a force-free state while the outer marginal part is in a fairly dynamic state where magnetic pressure force is dominant. We discuss how the field-line twist affects the two-part structure and also explain a possible relation between electric current structure and sigmoid observed in a preflare phase.