• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.86-89
• /
• 2000

The detection technique both the polarization and the mobile charge density at the same time in ferroelectric films on Si using TVS method have been proposed. This method yields a polarizable and an ionic displacement current peaks whose areas are proportional to the total polarization reversal charge and the total moble ionic space charge, respectively. The calculated polarization and the mobile charge density were 0.42 [$\mu$C/$\textrm{cm}^2$] and 5.5$\times$10$^{11}$ (ions/$\textrm{cm}^2$) in the SBT film of MFIS structure measured at 25$0^{\circ}C$, and 1.4 [$\mu$C/$\textrm{cm}^2$] in the LiNbO$_3$ film of MFS structure measured at 30$0^{\circ}C$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.11a
• /
• pp.25-28
• /
• 1999

Metal ferroelectric semiconductor Field Effect- Transistors(MFSFET) with various gate electrodes, that are aluminum, platinum and poly -Si, using LiNbO$_3$/Si(100) structures were fabricated and the properties of the FETs have been discussed. The drain current of the state of FET with Pt electrode was more than 3 orders of magnitude larger than the state current at the same gate voltage of 1.5 V, 7.rich means the memory operation of the MFSFET. A write voltage as low as about $\pm$4 V, which is applicable to low power integrated circuits, was used for polarization reversal. The retention properties of the FET using Al electrode were quite good up to about 10$^3$s and using Pt electrode remained almost the same value of its initial value over 2 days at room temperature.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.36D no.11
• /
• pp.27-32
• /
• 1999

Metal-ferroelectric-semiconductor devices by susing rapid thermal annealed $LiNbO_3/Si$(100) structures were fabricated and demonstrated nonvolatile memory operations. The estimated field-effect electron mobility and transconductance on a linear region of the fabricated FET were about $600cm^2/V{\cdot}s$ and 0.16mS/mm, respectively. The ID-VG characteristics of MFSFET's showed a hysteresis loop due to the ferroelectric nature of the $LiNbO_3 films. The drain current of the on state was more than 4 orders of magnitude larger than the off state current at the same read gate voltage of 0.5V, which means the memory operation of the MFSFET. A write voltage as low as ${\pm}3V$, which is applicable to low power integrated circuits, was used for polarization reversal. The ferroelectric capacitors showed no polarization degradation up to $10^{10}$ switching cycles with the application of symmetric bipolar voltage pulse (peak-to-peak 6V, 50% duty cycle) of 500kHz.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.44 no.3 s.357
• /
• pp.20-25
• /
• 2007

The periodic domain-inversion in the selective areas of $Ti:LiNbO_3$ Mach-Zender waveguides was performed and band-pass modulators and single sideband (SSB) modulators were fabricated by using domain-reversal. The domain wall velocity was precisely controlled by real-time analysis of a poling-induced response current under an applied voltage. The domain wall velocity was significantly affected by the crystal orientation of the domain wall propagation which influenced the final domain geometry. In a certain case, the decomposition of $LiNbO_3$ crystal was observed, for example, under the condition of too fast domain wall propagation. The fabricated band-pass modulator with a periodic domain-inversion structure showed the maximum modulation efficiency at 30.3 GHz with 5.1 GHz 3dB-bandwidth, and SSB modulator was measured to show 33 dB USB suppression over LSB at 5.8 GHz RF.

• The Korean Journal of Physiology
• /
• v.26 no.1
• /
• pp.15-25
• /
• 1992

In order to elucidate the properties of the background current whole cell patch clamp studies were performed in rabbit ventricular cells. Ramp pulses of ${\pm}80\;mV$ from holding potential of 40 mV(or 20 mV) at the speed of 0.8 V/sec were given every 30 sec(or 10 sec) and current-voltage diagrams(I-V curve) were obtained. For the activation of the background current isoprenaline, adenosine 3',5'-cyclic monophosphate(dBcAMP), guanosine 3',5'-cyclic monophosphate(cGMP), and $N^6$-2'-o-dibutyryladenosine 3',5'-cyclic monophosphate(dBcAMP) were applied after all known current systems were blocked with 2mM Ba, 1 mM Cd ,5 mM Ni, 10 ${\mu}M$ diltiazem, 10 ${\mu}m$ ouabain, and 20 mM tetraethylammonium(TEA). The conductance of background current in control was $0.65{\pm}0.69$ nS at 0 mV, its I-V curves was almost linear and reversed near 50 mV. When there was no taurine in pipette solution, isoprenaline hardly activated the background current but when taurine existed in pipette solution, isoprenaline activated the larger background current. Cyclic AMP or cyclic GMP alone had little effect on the activation of the background current, while cGMP potentiated cGMP effect. When the background current was activated with cGMP and cAMP, isoprenaline could not further increased the background current. The background current activated by isoprenaline depended on extracellular $Cl^-$ concentration and its reversal potential was shifted according to chloride equilibrium potential. The change of extracellular $Na+$ concentration had little effect on reversal potential of the background current activated by isoprenaline.

• Geomechanics and Engineering
• /
• v.1 no.4
• /
• pp.275-289
• /
• 2009

Electroosmosis (EO) is the movement of water in a porous medium under the influence of a direct current (dc). In past decades, electro-osmosis has been successfully employed in many soil improvement and other geotechnical engineering projects. Metal electrodes, such as steel, copper and aluminum have been used traditionally to conduct current. The shortcoming of these electrodes is that they corrode easily during an EO treatment, which results in reduced effectiveness and environmental concerns. More recently, conductive polymers are developed to replace metal electrodes in EO treatment. Electrical vertical drainages (EVDs) are one of these products under trial. The goal of this study is to assess the performance of EVDs for soil improvement and to further understand the scientific principle of the EO process, including the voltage drop at the soil-EVD interface, electrical current density, polarity reversal, and changes in soil physico-chemical properties generated by electroosmosis. It is found from the study that after 19 days of EO treatment with a constant applied dc electric field intensity of 133 V/m, the soil's moisture content decreased by 28%, the shear strength and pre-consolidation pressure increased more than 400%. It is also found that the current density required triggering the water flow in the soil tested, the Korean Yulchon marine clay, is 0.7 $A/m^2$. The project demonstrates that EVDs can serve as both electrodes and drains for soil improvement in short term. However, the EVDs, as tested, are not suitable for polarity reversal in EO treatment and their service life is limited to only 15 days.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.31A no.1
• /
• pp.65-70
• /
• 1994

GaAs power MESFETs with 0.8$\mu$m gate lengths are fabricated using image reversal (IR) methods on the wafer with an undoped surface layer grown by MOCVD. The fabricated GaAs power MESFETs with an undoped surface layer show that an ideality factor 1.17, a built-in potential 0.83 V, a pinch-off voltage -2.7 V, a specfic contact resistance 1.21$\times$10$^{5}$ ~3.42$\times$10$^{2}$$\Omega$-cm$^{2}$ and an extrinsic g$_{m}$ = 103.5 mS/mm. The maximum RF output power densities of the 0.8$\mu$m devices are 360 mW/mm and 499 mW/mm, and power added efficiencies 29.67% and 29.05%, for the unit gate width 150$\mu$m and 200$\mu$m at 12 GHz.

• Proceedings of the KIEE Conference
• /
• 1999.07e
• /
• pp.2215-2217
• /
• 1999

The high current pulsed power systems(PPS) for rail guns, ET and ETC accelerators require many components of very high cost. If one failed to select component specifications based on optimal design, cost effective and reliable PPS could not be obtained. It is very significant to study a preliminary circuit scheme and to determine optimal specifications via circuit simulation before constructing the PPS based on modulized capacitor banks. The optimal crowbar resistor value, module inductance was determined in view of energy loss, the voltage reversal of capacitors and the transient current of crowbar diodes.

• Proceedings of the KIPE Conference
• /
• 2015.07a
• /
• pp.189-190
• /
• 2015

This paper investigates an economic and highly efficient power converter topology and its modulation scheme for 60kW rapid EV charger system. The target system consists of three-phase three-switch buck-type rectifier topology. A new Carrier Based PWM scheme along with its simple implementation using logic gates is introduced in this paper. This PWM scheme replaces the diode rectifier equivalent switching state with an active switching state producing the effectively same current flowing path. As a result, the distortion of input current during the polarity reversal of capacitor line voltage can be mitigated. The proposed modulation technique is confirmed through simulation verification. The proposed modulation technique and its implementation scheme can expand the operation range of the three-phase three-switch buck-type rectifier having ac input and capacitor ripple current of high quality.

• Proceedings of the KIEE Conference
• /
• 2005.07b
• /
• pp.969-971
• /
• 2005

본 논문에서는 전력용 차단기의 성능 평가시험용 설비인 간이합성시험설비의 안전성과 신뢰성을 향상시키기 위해 새롭게 설계 및 제작하여 성능평가시험을 통해 개발한 고역전압율을 가진 자기소호형 필름콘덴서를 소개하고, 이것을 적용한 새로운 간이합성시험설비용 전류원 콘덴서뱅크 구조를 제안하고자 한다.