• Journal of the Korean Society for Precision Engineering
• /
• v.7 no.2
• /
• pp.14-27
• /
• 1990

Electromagnetic Pulse Forming is the one of the high velocity forming method. When the electric energy which is charged in the capacitor bank is suddenly discharged into the electromagnetic coil, the high magnetic field occurs at the airgap between the electromagnetic coil and workpiece. Thus we can obtain the high electromagnetic pressure, which is proportional to the square of magnetic flux density. This is the basic principle of the electromagnetic pulse forming. In this paper, the equivalent L-R-C circuit is derived by computing the magnetic field and its loss of the total system. Thus, the values of the magnetic flux density and pressure can be obtained from the equation of this circuit. As a result, the computed and measured values of the maximum magnetic flux density and pressure are compared and the characteristics of the tapered field shaper are further discussed as follows; 1) The strength of magnetic flux density and pressure can be controlled by the charged energy and the size of the airgap between the inner field shaper and the workpiece. 2) During the design of the tapered field shaper, the penetration of the magnetic flux through the sharp edge should be considered.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.3
• /
• pp.217-225
• /
• 2003

In this paper, in order to investigate the near field distribution characteristic of the Loop Antenna we simulated and measured the near field of a Loop Antenna using optical electric-field sensor in a large Chamber(8.5 m x 7 m x 7 m). The simulation methods were used MoM for frequency domain and FDTD for time domain. From the analysis results, it can be seen that the simulation and measurement results are very aggregated, and the optical electric-field sensor is a certificate of validity. In frequency domain, in case of the optical sensor with vertical polarization is located above the near vertical line of the Loop Antenna the signal strength level is more 15 ㏈ than with horizontal polarization. But in case of the optical sensor located above horizontal line of the Loop Antenna, signal strength level is not different. And, in the time domain, although input signal is positive, in the case of the optical sensor with vertical polarization is located above horizontal line of the Loop Antenna, it can be seen that the received pulse shape is negative.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.15 no.8
• /
• pp.1647-1652
• /
• 2011

This paper presents the shielding effectiveness for the IEC 61000-2-9 standard when HEMP source penetrates through an aperture in a planar conducting plane of infinite extent. An integral equation is derived and solved by applying Galerkin's method of moments for calculating the electric shielding effectiveness. The electric shielding effectiveness is examined based on changing the aperture length and width. It is shown that the electric shielding effectiveness is suddenly decreases as the aperture width of 0.4 ~ 0.45${\lambda}$. It is also found that the penetrated electric field for the IEC 61000-2-9 incident field is different from the Bell Laboratory incident field, but the frequency characteristic of the electric shielding effectiveness becomes the same shape.

• Journal of Institute of Control, Robotics and Systems
• /
• v.20 no.2
• /
• pp.143-148
• /
• 2014

Conventional wireless power transfer methods based on coupled magnetic fields need a complex winding structure on the surface of the energy transfer and shows poor efficiency near metal objects due to the eddy current effect. In this study, to mitigate these problems, we investigate an electric field-coupled power transmission system, which is less prone to metal object problems and EMI. Because of the fundamental physical limit in the size of link capacitances, a half-bridge converter with an impedance matching transformer is proposed and the design procedure is derived to provide a soft-switching scheme. Hardware implementation shows that the proposed scheme with a pair of 10cm by 10cm copper plate can power a 1.4W USB FAN in a separation of 0.2mm by using insulating paper when driven by 227 kHz gate pulse.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.59 no.12
• /
• pp.2250-2255
• /
• 2010

An fine silver particle has a variety of uses, such as in killing micrograms and as catalysts. Many techniques have been used for the production of the fine particles. Faraday cell, consisting of two silver electrodes in an electrolyte, is unique, but it is hard to get a very fine particle by this method. A finer silver nano-particle producing cell, utilizing a dielectric bed as a lower electric current and higher field controlling means, has been proposed and investigated. The I-V characteristics of the cell and effect of the dielectric bed on the producing finer silver nano-particles have been investigated. The I-V characteristics of the cell with the dielectric bed were different from that of the same system without the bed, due to the increased cell resistance and elevated electric field intensity. It is found that the proposed cell with the dielectric bed can produce finer silver nano-particles effectively, which, however, can be used as one of effective fine silver nano-particle producing means.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.13 no.4
• /
• pp.699-707
• /
• 2010

Electric-field-induced electron emission from the three kinds of $Pb(Zr_{0.56}Ti_{0.44})O_3$ ferroelectric cathodes with different electrode structure has been investigated. Regardless of the electrode structures, a threshold field of the each cathode was 2.5-2.6kV/mm, which is 3 times higher than the coercive field of $Pb(Zr_{0.56}Ti_{0.44})O_3$ material. Although the waveform of the electron currents was affected by the structure of the electrode, no significant difference for the emission properties such as the peak current and the pulse width was observed from the three kinds of the cathodes. However, the current density of the cathode was dependent on the electrode structure. From the simulation of electric field distribution, the surface flashover, and the injury region of the cathode surface, it was proved that the prime electrons were initiated at the electrode-ceramic-vacuum triple point by field emission and the emission currents were strongly enhanced by the surface plasma.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.32A no.4
• /
• pp.47-56
• /
• 1995

In this paper the model of the MQE-IMD-based neural trigger circuit is improved, where MQW-IMD is a new semiconductor device proposed and experimentally demonstrated by the author for the hardware implementation of the neural networks. The electron energy of AlXGa1-XAsbarrier is calculated by Ensemble Monte Carlo simulation according to the variation of Al mole fraction x and the applied electric field, whtich had been roughly estimated in the previous paper because of the difficulty to get the data. And in the consideration of the tunneling of the confined electrons within the quantum well the accuracy of the impact ionization rate is enhaned. Finally, the dependance of the frequency of pulse-train on the number of quantum wells can be calculated by modelling the effect of the distance of the induced positive charge from the cathode on the electric field at the cathode.

• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.1871-1873
• /
• 2000

There are many electrical accidents between bare wire and line post insulator which is degraded by long time using, causing leakage current on the surface of insulator. In this paper it is presented that the 22.9 Kv-y distribution lines are protected by binding cover which is needed from fog or rainy moisture, surges occurring by switching or lightening pulse. It is analyzed to investigate the unbalanced transfer characteristics and reflection coefficient by using binding cover and non-cover. It was tested the radio interference voltage in the test room and electric field strength by calculation between binding cover and non-cover. In the factory the leakage current causing on the surface of insulator was tested in the state of light load and heavy load.

• Proceedings of the KIEE Conference
• /
• 2006.07c
• /
• pp.1480-1481
• /
• 2006

It is very difficult and dangerous to measure partial discharge from high voltage equipment in outdoor situation. But that is very important thing for preventing serious accidents from defects which originated in insulating degradation. This paper provides useful method to detect PD signals easily without any dangerous situation. Electric field sensor by the principle of capacitor detect PD signals without direct electrical connection between sensor and high power equipment and has very wide frequency range suitable for noise rejection. Electric field sensor and related circuit for processing PD signal showed good performance as a PD sensor when it is applied to simulated high power equipment generating PD pulse.

• Journal of the Semiconductor & Display Technology
• /
• v.19 no.4
• /
• pp.84-87
• /
• 2020

The properties of ultra-thin two-dimensional (2D) organic ferroelectric Langmuir-Blodgett (LB) films of the poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] were investigated to find possible applicability in flexible and wearable electronics applications. In the C-V characteristics of the MFM capacitor of 2-monolayer of 5 nm films, a butterfly hysteresis curve due to the ferroelectricity of P(VDF-TrFE) was confirmed. Typical residual polarization value was measured at 2μC/㎠. When the MFM capacitor with ultra-thin ferroelectric film was measured by applying a 10 Hz bipolar pulse, it was shown that 65% of the initial polarization value in 105 cycles deteriorated the polarization. The leakage current density of the 2-monolayer film was maintained at about 5 × 10-8 A/㎠ for the case at a 5MV/cm electric field. The resistivity of the 2-monolayer film in the case at an electric field at 5 MV/cm was more than 2.35 × 1013 Ω·cm.