• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.54 no.1
• /
• pp.23-29
• /
• 2005

This paper presents the characteristics of leakage currents flowing through ZinC Oxide(ZnO) surge arrester blocks under mixed direct and 60 Hz alternating voltages. A mixed voltage, in which an alternating voltage is superimposed upon a direct voltage, appears on the HVDC system network. The mixed direct and alternating voltage generator with a peak open-circuit of 10 kV was designed and fabricated. The leakage currents and V-I curves for the fine and used ZnO surge arrester blocks were measured as a function of the voltage ratio k, where the voltage ratio k is defined as the ratio of the peak of alternating voltage to the peak of the mixed voltages. The resistive component in the leakage current in the low conduction region is significantly increased with increasing the voltage ratio k. The V-I characteristic curves for the mixed voltages lies between the direct and alternating characteristics, and the cross-over phenomenon in the high conduction region was appeared.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.71-72
• /
• 2008

This paper describes a circuit based simulation model for a Photovoltaic(PV) cell in order to estimate the electrical behavior of the solar cell module with changes of environmental parameters such as shunt resistance, series resistance, temperature and irradiance. An accurate I-V model of PV module is presented based on the Shockley diode model. The general model was implemented on Matlab scrip file, and used irradiance and temperature as variables and outputs of the I-V characteristic. A typical PV module was used for the evaluation, and results was compared with reference taken directly from the manufacturer's published curves leading to excellent agrement with the theoretical prediction.

• Journal of Astronomy and Space Sciences
• /
• v.14 no.2
• /
• pp.225-232
• /
• 1997

A total of 1088 observations (272 in B, 272 in V, 272 in R, and 272 in I) were made from January to February in 1995 at Chungbuk National University observatory(CbNUO). We constructed BVRI light curves with our data. The photometric solution of these light curves was obtained by means of the Wilson-Devinney method. Our result was compared with those by previous investigators.

• Journal of the Korean Vacuum Society
• /
• v.9 no.2
• /
• pp.136-143
• /
• 2000

$SrBi_2Ta_2O_9;(SBT)$ films were deposited on p-type Si(100) at room temperature by rf magnetron sputtering method to confirm the possibility of application of $Pt/SBT/Pt/Ti/SiO_2/Si$ structure (MFM) for destructive read out ferroelectric RAM (random access memory). Their structural characteristics with the various annealing times and Ar/$O_2$ gas flow ratios in sputtering were observed by XRD (X-ray diffractometer) and the surface morphologies were observed by FE-SEM (field emission scanning electron microscopy), and their electrical properties were observed by P-V (polarization-voltage measurement) and I-V (current-voltage measurement). The Ar/$O_2$ gas flow ratios of sputtering gas were changed from 1 : 4 to 4 : 1 and SBT thin films were deposited at room temperature. The films show (105), (110) peaks of SBT by XRD measurement. SBT thin films deposited at room temperature were crystallized by furnace annealing at 80$0^{\circ}C$ in oxygen atmosphere during either one hour or two hours. Among their electrical properties, P-V curves showed shaped hysteresis curves, but the SBT thin films showed the asymmetric ferroelectric properties in P-V curves. When Ar/$O_2$ gas flow ratios are 1 : 1, 2: 1, the leakage current density values of SBT thin films are good, those values of 3 V, 5 V, and 7 V are respectively $3.11\times10^{-8} \textrm{A/cm}^2$, $5\times10^{-8}\textrm{A/cm}^2$, $7\times10^{-8}\textrm{A/cm}^2$.After two hours of annealing time, their electrical properties and crystallization are improved.

• Journal of Korean Ophthalmic Optics Society
• /
• v.6 no.1
• /
• pp.149-153
• /
• 2001

Three-dimensional thermoluminescence(TL) spectra of LiF: Mg, Cu, Na, Si TL material based on temperature, wavelength and intensity were measured and analyzed. The glow curves were obtained by integration of luminescence intensity for wavelength at each temperature, and various trapping parameters related to the trap formation were determined by analyzing these curves. Computerized glow curve deconvolution(CGCD) method which based on general order kinetics(GOK) model were used for the glow curve analysis. The glow curves of LiF:Mg, Cu, Na, Si TL material were deconvoluted to six isolated glow curves which have peak temperature at 333 K, 374 K, 426 K, 466 K, 483 K and 516 K, respectively. The 466 K main glow peak had an activation energy of 2.06 eV and a kinetic order of 1.05. This TL material was also found to have three recombination centers, 1.80 eV, 2.88 eV and 3.27 eV by TL spectra analysis based on Franck-Condon model. It showed that 2.88 eV is the dominant center, followed by 3.27 eV level, and 1.80 eV center is ascertained as emission center of this material even though its very weak emission intensity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.8
• /
• pp.699-705
• /
• 2008

Capacitance versus voltage (C-V) characteristics of Ge-nanocrystal (NC)-embedded metal-oxide-semiconductor (MOS) capacitors with $HfO_2$ gate material were investigated in this work. The current versus voltage (I-V) curves obtained from Ge-NC-embedded MOS capacitors fabricated with the $NH_3$ annealed $HfO_2$ gate material reveal the reduction of leakage current, compared with those of MOS capacitors fabricated with the $O_2$ annealed $HfO_2$ gate material. The C-V curves of the Ge-NC-embedded MOS capacitor with $HfO_2$ gate material annealed in $NH_3$ ambient exhibit counterclockwise hysteresis loop of about 3.45 V memory window when bias voltage was varied from -10 to + 10 V. The observed hysteresis loop indicates the presence of charge storages in the Ge NCs caused by the Fowler-Nordheim (F-N) tunneling. In addition, capacitance versus time characteristics of Ge-NC-embedded MOS capacitors with $HfO_2$ gate material were analyzed to investigate their retention property.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.49 no.8
• /
• pp.477-486
• /
• 2000

This paper presents Pspice modeling methods for spark gaps and ZnO varistors and describes the application for the two-stage surge suppression circuit which was composed of the nonlinear components. The simulation modelings of nonlinear components were conducted on the basis of the voltage and current curves measured by the impulse current with the time-to-crest of $1~50 \mus$ and the impulse voltage with the rate of the time-to-crest of 10, 100 and 1000 V/\mus$. The firing voltages of the spark gap increased with increasing the rate of the time-to-crest of impulse voltage and the measured data were in good agreement with the simulated data. The I-V curves of the ZnO varistor were measured by applying the impulse currents of which time-to-crests range from 1 to $50 \mus$ and peak amplitudes from 10 A to 2 kA. The simulation modeling was based on the I-V curves replotted by taking away the inductive effects of the test circuit and leads. The meximum difference between the measured and calculated data was of the order of 3%. Also the two-stage surge suppression circuit made of the spark gap and the ZnO varistor was investigated with the impulse voltage of $10/1000\mus$$mutextrm{s}$ wave shape. The overall agreement between the theoretical and experimental results seems to be acceptable. As a consequence, it was known that the proposed simulation techniques could effectively be used to design the surge suppression circuits combined with nonlinear components.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.6
• /
• pp.575-579
• /
• 2008

Al-doped p-type ZnO films were fabricated on n-Si (100) and homo-buffer layers in pure oxygen at $450^{\circ}C$ of by RF magnetron sputtering. Target was ZnO ceramic mixed with 2 wt% $Al_2O_3$. XRD spectra show that the Al-doped ZnO thin films have ZnO crystal structure and homo-buffer layers are beneficial to Al-doped ZnO films to grow along c-axis. Hall Effect experiments with Van der Pauw configuration show that p-type carrier concentrations are ranged from $1.66{\times}10^{16}$ to $4.04{\times}10^{18}\;cm^{-3}$, mobilities from 0.194 to $2.3\;cm^2V^{-1}s^{-1}$ and resistivities from 7.97 to $18.4\;{\Omega}cm$. p-type sample has density of $5.40\;cm^{-3}$ which is smaller than theoretically calculated value of $5.67\;cm^{-3}$. XPS spectra show that Ols has O-O and Zn-O structures and Al2p has only Al-O structure. P-ZnO:Al/n-ZnO:Al junctions were fabricated by magnetron sputtering. V-I curves show that the p-n junctions have rectifying characteristics.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2010.05a
• /
• pp.147-148
• /
• 2010

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07b
• /
• pp.792-796
• /
• 2002

In this work, porous silicon(PS) layer is used as a sensing material to detect organic gases. To do this, PS sensors with membrane structure are fabricated. The sensors were made by applying the technologies of membrane formation by anisotropic etching of silicon, and PS layer formation by anodization in HF solution. From fabricated sensors, current-voltage (I-V) curves were measured against ethanol (called alcohol), methanol and acetone gases evaporated from 0.1 to 0.5% solution concentrations at $36^{\circ}C$. As the result, all curves showed rectifying behavior due to a diode structure between Si and PS, and the conductance of sensor devices increased largely with the organic solution concentration at high voltage of 5V.