• Journal of the Korean Electrochemical Society
• /
• v.2 no.1
• /
• pp.23-26
• /
• 1999

The Langmuir adsorption isotherm at the $(Pt)/0.1M\;H_2SO_4$ electrolyte interface has been qualitatively analyzed using the ac impedance measurement and phase-shift method. The phase shift $(\phi)$ depends on both the cathode potential (E<0) and frequency (f) and is inversely proportional to the factional surface coverage $(\theta)$. At an intermediate frequency band (ca. $1\~100$ Hz), the phase-shift profile $(\phi\;vs.\;E)$ can be related to the fractional surface coverage $(\theta\;vs.\;E)$. The phase-shift profile $(\phi\;vs.\;E)$ can be used as an experimental method to estimate and analyze the Langmuir adsorption isotherm $(\theta\;vs.\;E)$. The equilibrium constant (K) and the standard free energy $({\Delta}G_{ads})$ of the adsorbed hydrogen atom $(H_{ads})\;and\;3\times10^{-4}$ and 20.1 kJ/mol, respectively.

• Proceedings of the KIEE Conference
• /
• 2003.04a
• /
• pp.157-162
• /
• 2003

This paper presents the loss analysis of Phase-Shift Full-Bridge Converter. Full-Bridge DC/DC Converter presented in this paper used a phase shift control in the primary side to achieve ZVS (Zero-Voltage-Switching) for main switch. Phase-Shaft Full-Bridge converter have an effect on the high power system. This paper analyses the loss of each component and the various losses in the circuit assessed. The result of the analysis are verified using 2.5kW, 50kHz prototype.

• Korean Journal of Optics and Photonics
• /
• v.27 no.3
• /
• pp.101-105
• /
• 2016

In this study we propose the novel optimization method of the phase-only computer-generated hologram (CGH), to improve calculation speed compared to the conventional method. While the conventional method is calculated using numerical analysis, the novel method is calculated using the phase-shift characteristic of Fourier transformation. In addition, the selectivity of noise filtering lets it decrease the calculation time. The validity of the reconstructed image using the novel method is verified by comparing simulation results to ideal and conventional data, and the improvement of texture and sharpness of the reconstructed image is confirmed by simulation.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.10 no.8
• /
• pp.1471-1477
• /
• 2006

Electrocorticogram (ECoG) was recorded in one young adult suffering from medically refractory partial seizures a few weeks before resection. ECoG of intractable focal epilepsy was analyzed usins AR model, wavelet analysis and cross-correlation analysis. The cross-correlation of the epileptic discharges was calculated between the electrodes in every unit of time, to get the phase shift. A contour map of the phase shift and the sequential two-dimensional phase shift maps were utilized to localize the epileptic foci and to study their propagation process. More than two epileptogenic foci were localized and two kinds of propagating process were shown. These investigations suggest that epileptic phenomena can be caused by at least two kinds of mechanisms in one patient.

• Journal of electromagnetic engineering and science
• /
• v.14 no.1
• /
• pp.15-24
• /
• 2014

A compact dual-band three-way metamaterial power divider is proposed that has three in-phase outputs. Fully printed composite rightand left-handed (CRLH) unequal and equal power dividers are first implemented for 900-MHz and 2.4-GHz bands with the power-division ratios of 2:1 and 1:1, respectively. An initial 1:1:1 power divider is then achieved by incorporating the input of the two-way equal block into an output of the unequal block, and trimming the interconnection parameters. The condition of an identical phase at the three outputs of the power divider is then met by devising a hybrid CRLH phase-shift line to compensate for the different phase errors at the two frequencies. This scheme is confirmed by predicting the performance of the power divider with circuit analysis and full-wave simulation and measuring the fabricated prototype. They results show agreement; the in-phase outputs as well as the desirable power-division are accomplished and outdo the conventional techniques.

• Proceedings of the KIPE Conference
• /
• 2003.07a
• /
• pp.227-230
• /
• 2003

In this paper, a full bridge edge-resonant zero voltage mode based soft-switching PWM DC-DC power converter with a high frequency center tapped transformer link stage is presented from a practical point of view. The power MOSFETS operating as synchronous rectifier devices are implemented in the rectifier center tapped stage to reduce conduction power losses and also to extend the transformer primary side power MOSFETS ZVS commutation area from the rated to zero-load without a requirement of a magnetizing current. The steady-state operation of this phase-shift PWM controlled power converter is described in comparison with a conventional ZVS phase-shift PWM DC-DC converter using the diodes rectifier. Moreover, the experimental results of the switching power losses analysis are evaluated and discussed in this paper. The practical effectiveness of the ZVS phase-shift PWM DC-DC power converter treated here is actually proved by using 2.5kW-32kHz breadboard circuit. An actual efficiency of this converter is estimated in experiment and is achieved as 97$\%$ at maximum.

• Proceedings of the Korea Contents Association Conference
• /
• 2003.11a
• /
• pp.303-307
• /
• 2003

In this paper, the W(ultra widebend) system is used for high speed transmission applying BPSK(Binary Phase Shift Keying) and QPSK (Quadrature Phase Shift Keying), and utilizing the convolution coding with code rate, 1/2 and constraint length, K=7 in order to reduce the bit error rate. And the performance of system is analyzed in the AWGN(Additive White Gaussian Noise) channel environment by using the Viterbi decoding algorithm and adopting the time-hopping sequence as a multiple access method in order to avoid the multiuser interference.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.10 no.6
• /
• pp.598-609
• /
• 2005

Conventional phase shift full bridge (PSFB) converter has serious voltage oscillation problem across the secondary rectifier diodes, which would require the dissipate snubber circuit, thus degrades the overall efficiency. To overcome this problem a new simple voltage oscillation reduction technique (VORT) which effectively reduce the voltage oscillation of the secondary rectifier diodes for phase shift full bridge converter is proposed. Therefore, no dissipate snubber for rectifier diodes is needed. In addition, since it has wide zero voltage switching (ZVS) range, high efficiency can be achieved. Operational principle, analysis of voltage oscillation, and design consideration are presented compare with that of the conventional PSFB converter. To confirm the validity of the proposed VORT, experimental results from a 420W prototype are presented.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2012.10a
• /
• pp.629-630
• /
• 2012

• Journal of Power Electronics
• /
• v.10 no.2
• /
• pp.132-137
• /
• 2010

Interleaving techniques are widely used to reduce input/output ripples and to increase the power capacity of boost converters operating in critical conduction mode. Two types of phase-shift control schemes are studied in this paper, the turn-on time shifting method and the turn-off time shifting method. It is found that although the turn-off time shifting method exhibits better performance, it suffers from sub-harmonic oscillations at high input voltages. To solve this problem, an intensive quantitative analysis of the sub-harmonic oscillation phenomenon is made in this paper. Based upon that, a novel modified turn off time shifting control scheme for interleaved boost converters operating in critical conduction mode is proposed. An important advantage of this scheme is that both the master phase and the slave phase can operate stably in critical conduction mode without any oscillations in the full input voltage range. This method is implemented with a FPGA based digital PWM control platform, and tests were carried out on a two-phase interleaved boost PFC converter prototype. Experimental results demonstrated the feasibility and performance of the proposed phase-shift control scheme.