• Proceedings of the Korean Environmental Sciences Society Conference
• /
• 2001.05a
• /
• pp.236-237
• /
• 2001

In this study, experiments were carried out to measure the variations in the corrosion potential and current density of polarization curves with amorphous $Fe_{70}Cr_5Si_{10}B_{15}$ and $Co_{70}Cr_5Si_{10}B_{15}$ alloy ribbon. The results were particularly examined to identify the influences of corrosion potential including various conditions such as hydrochloric acid, temperature, salt, pH, and oxygen. The optimum conditions were established with variations including temperature, salt, pH, oxygen, corrosion rate, and resistance of corrosion potential. The mass tranfer coefficient(${\alpha}$) value was determined with the Tafel's slope for the anodic dissolution based on the polarization effect with optimum conditions. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity($I_{r}/I_{f}$).

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
• /
• 2005.09a
• /
• pp.97-101
• /
• 2005

The ZnO:Al thin films were prepared on glass by Facing Target Sputtering (FTS) system. We investigated electrical, optical, and structural properties of AZO thin film with sputter ins current 0.1[A]-0.6[A]. We obtained the lowest resistivity $2.3{\times}\;10^{-4}[{\Omega}-cm]$ at sputtering current 0.6[A] from the 4-point probe and the strong (002) peak at sputtering current 0.3[A] from the X-ray Diffractometer (XRD). The optical transmittance of AZO thin films show a very high transmittance of $80\~95\%$ in the visible range and exhibit the absorpt ion edge of about 350 nm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.32 no.3
• /
• pp.241-245
• /
• 2019

This work presents the response characteristics of a ZnO varistor to conductive EMP. An E1 pulse, standardized to MIL-STD-188-125-1, was applied to the varistors wherein the residual current and response times were measured with the applied E1 pulse current. Additionally, the response time was measured according to the length of the connection path. Consequently, the amplitude of the residual voltage through the ZnO varistors was increased with increasing amplitude of the applied E1 pulse current. As the length of the connection path increased, the operating response time and residual peak voltage also increased. These results indicate that the response characteristics of ZnO varistors can be applied to basic data to support the use of varistors as a protective measure against conductive EMP.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.24 no.3
• /
• pp.207-214
• /
• 2019

In this study, discrete-time domain analysis is proposed to investigate the input current of a buck AC/DC light-emitting diode (LED) driver. The buck power factor correction converter can operate in both discontinuous conduction mode (DCM) and continuous conduction mode (CCM). Two discontinuous and two continuous conduction operating modes are possible depending on which event terminates the conduction of the main switch in a switching cycle. All four operating modes are considered in the discrete-time domain analysis. The peak current-mode control with slope compensation is used to design a low-cost AC/DC LED driver. A slope compensation design of the buck AC/DC LED driver is described on the basis of a discrete-time domain analysis. Experimental results are presented to confirm the usefulness of the proposed analysis.

• Restorative Dentistry and Endodontics
• /
• v.19 no.2
• /
• pp.534-548
• /
• 1994

The purpose of this study is to observe the corrosion characteristics of seven dental amalgams (CAULK FINE CUT, CAULK SPHERICAL, OPTALLOY II, DISPERSALLOY, HI VERALOY, TYTIN, VALIANT) through the anodic polarization curve obtained by using a potentiostat. After each amalgam alloy and Hg being triturated, the triturated mass was inserted into the cylindrical metal mold, and condensed by hydrolic pressure(160 kg/$cm^2$). Each specimen was removed from the metal mold. 24 hours after condensation, specimens were polished with the emery paper and stored at room temperature for 1 week. The anodic polarization curves were employed to compare the corrosion behaviours of the amalgam in 0.9% saline solution, Fusayama's artificial saliva, and stimulated parotid saliva at $37^{\circ}C$ with 3-electrode potentiostat. After the immersion of specimen in electrolyte for 1 hour, the potential scan was begun. The potential scan range was. -1700m V ~ + 400m V(vs. S. C. E) in the working electrode and the scan rate was 50m V /sec. The results were as follows, 1. The corrosion potential, the potential of anodic current peak, and transpassive potential in the stimulated parotid saliva shifted to more anodic direction than those in saline solution, and the current density in the stimulated parotid saliva was lower than that in saline solution. Those in Fusayama's artificial saliva was similar to those in stimulated parotid saliva. 2. The anodic polarization profiles in Fusayama's artificial saliva and stimulated parotid saliva indicated a region of slow slope current density, which is extending from the corrosion potential to the potential of anodic current peak, but that in 0.9% saline solution indicated no region of slow slope. 3. The corrosion potentials for CAULK FINE CUT, CAULK SPHERICAL, and OPT ALLOY II had the similarity in 0.9% saline solution, Fusayama's artificial saliva and stimulated parotid saliva, but those for high coper amalgam and VALIANT had no similarity. 4. The current density for TYTIN amalgam in stimulated parotid saliva was the lowest among the others. 5. As for current density, there was no significant difference between palladium enriched VALINAT and other high copper amalgams.

• Proceedings of the KIPE Conference
• /
• 2001.10a
• /
• pp.193-197
• /
• 2001

This paper presents a novel circuit topology of the double two-switch forward type high frequency transformer linked soft-switching PWM DC-DC power converter with tapped inductor filters that can operate under a condition of the low peak voltage stress across the power semiconductor devices and lowered peak current stress through the transformer for some high power applications. This circuit topology of an interleaved two-switch forward soft-switching power converter is proposed in the order to minimize an idle circulating current due to the tapped inductor filter without of any additional active auxiliary resonant-assisted snubber circuits, such as active resonant DC link snubbers and AC link snubbers, active resonant commutation leg link snubbers. The unique advantages of this power converter are less power circuit components and power semiconductor devices, constant frequency PWM scheme, cost effective configuration and wider soft-switching PWM operation range under PWM power regulations load variations. The practical effectiveness of the proposed soft-switching converter circuit topology is tested by simulations and is proved by experimental results received from the 500W-100kHz breadboard setup.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.27 no.5
• /
• pp.398-408
• /
• 2007

For better evaluation of material thickness by using the reflection type pulsed eddy current method, various probe models are designed and their response signals, characteristics, and sensitivities to thickness variation are investigated by a numerical analysis method. Since the sensor needs to detect magnetic fields from eddy currents induced in a test material, not from the exciter coil, two types of models that are shielded by the combination of copper and ferrite and only by ferrite are considered. By studying response signals from these shielded probe models, the peak value and the zero crossing time are selected as useful signal features for the evaluation of material thickness. Investigation of sensitivities of these two features shows that the sensitivity of peak value is more useful than that of zero crossing time and that the probe shielded only by ferrite gives much better sensitivity to thickness variation.

• Progress in Superconductivity
• /
• v.10 no.2
• /
• pp.92-98
• /
• 2009

The magnetic field profiles near the surface of a $Sm_1Ba_2Cu_3O_{7-\delta}$ coated conductor(CC-tape) under magnetic field and current that were applied simultaneously with phase differences ${\phi}s$ were measured using scanning Hall probe method. Measurements were carried out along the elliptic load lines with $\phi=90^{\circ}\;and\;45^{\circ}$ for some $B_{peak},\;I_{peak}$ values. From the measured field profiles, sheet current density J(x, $B_a,\;I_a$) and magnetic flux density $B_0(x,\;B_a,\;I_a)$ profiles in the CC-tape were calculated. Using these J(x, $B_a,\;I_a$) and $B_0(x,\;B_a,\;I_a)$ profiles, we estimated the hysteresis energy loss Q in the CC-tape. The estimated Qs, together with our previous results for $\phi=0^{\circ}$ from [9], were compared with theoretical values based on Brandt's calculation.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.45 no.6
• /
• pp.28-36
• /
• 2008

This paper describes a low-power CMOS analog front-end block for UHF band RFID tag chips. It satisfies ISO/IEC 18000-6C and includes a memory block for test. For reducing power consumption, it operates with an internally generated power supply of 1V. An ASK demodulator using a current-mode schmitt trigger is proposed and designed. The proposed demodulator can more exactly demodulate than conventional demodulator with low current consumption. It is designed using a $0.18{\mu}m$ CMOS technology. Measurement results show that it can operate properly with an input as low as $0.25V_{peak}$ and consumes $2.63{\mu}A$. The chip size is $0.12mm^2$.

• Journal of IKEEE
• /
• v.19 no.1
• /
• pp.94-100
• /
• 2015

In this paper, 50V power U-MOSFET which replace the body(PN) diode with Schottky is proposed. As already known, Schottky diode has the advantage of reduced reverse recovery loss than PN diode. Thus, the power MOSFET with integrated Schottky integrated can minimize the reverse recovery loss. The proposed Schottky body diode U-MOSFET(SU-MOS) shows reduction of reverse recovery loss with the same transfer, output characteristic and breakdown voltage. As a result, 21.09% reduction in peak reverse current, 7.68% reduction in reverse recovery time and 35% improvement in figure of merit(FOM) are observed when the Schottky width is $0.2{\mu}m$ and the Schottky barrier height is 0.8eV compared to conventional U-MOSFET(CU-MOS). The device characteristics are analyzed through the Synopsys Sentaurus TCAD tool.