• Journal of Magnetics
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• v.19 no.2
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• pp.197-204
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• 2014

A transcranial magnetic stimulation device is a complicated appliance that employs a switching power device designed for discharging and charging a capacitor to more than 1 kV. For a simple transcranial magnetic stimulation device, this study used commercial power and controlled the firing angle using a Triac power device. AC 220V 60 Hz, the power device was used directly on the tanscranial magnetic stimulation device. The power supply device does not require a current limiting resistance in the rectifying device, energy storage capacitor or discharge circuit. To control the output power of the tanscranial magnetic stimulation device, the pulse repetition rate was regulated at 60 Hz. The change trigger of the Triac gate could be varied from $45^{\circ}$ to $135^{\circ}$. The AVR 182 (Zero Cross Detector) Chip and AVR one chip microprocessor could control the gate signal of the Triac precisely. The stimulation frequency of 50 Hz could be implemented when the initial charging voltage Vi was 1,000 V. The amplitude, pulse duration, frequency stimulation, train duration and power consumption was 0.1-2.2T, $250{\sim}300{\mu}s$, 0.1-60 Hz, 1-100 Sec and < 1 kW, respectively. Based on the results of this study, TMS can be an effective method of treating dysfunction and improving function of brain cells in brain damage caused by ischemia.

• Macromolecular Research
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• v.12 no.4
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• pp.325-335
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• 2004

Molecular weight distributions of poly(vinyl neo-decanoate) produced by the bulk polymerization of the monomer to low conversions were investigated to obtain values of the rate constants for the chain transfer to monomer ( $C_{M}$). The value of $C_{M}$ of 7.5($\pm$0.6)${\times}$10$^{-4}$ was obtained from a logarithmic plot of the number distribution at 5,25, and 5$0^{\circ}C$, which suggests that the activation energy for chain transfer is on the order of 20-25 kJ ㏖$^{-1}$ . These plots were linear between the number and weight-average degrees of polymerization, but not over the whole molecular weight range for which a significant signal was observed in the gel permeation chromatography (GPC) trace. Modeling suggests that the deviations observed at high molecular weights can be explained by branching of the chains through chain transfer to the polymer, with a branching density as low as 10$^{-5}$ , without affecting the slope at low values of the number of monomer unit, N. This deviation from the expected distribution of linear chains was used to estimate the branching densities at low conversion.ion.

• Geophysics and Geophysical Exploration
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• v.7 no.1
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• pp.70-79
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• 2004

We have examined the applicability of the triaxial drill-bit VSP method (TAD-VSP) to the geological survey of possible sites for a high-level radioactive waste disposal repository. The seismic energy generated by a drill bit is measured by a downhole multi-component detector, and the resulting signals are processed to image the geological structure deep underground. In order to apply the TAD-VSP method to civil-engineering-scale drilling, we have developed a small but highly sensitive and precise three-component downhole seismic measurement system, and recorded drill-bit signals at a granite quarry. We have successfully imaged discontinuities in the granite, possibly related to fractures, as highly reflective zones. The discontinuities imaged by the TAD-VSP method correlate well with the results of other borehole observations. In conclusion, the TAD-VSP method is usable in geological investigations for civil engineering because the equipment is compact and it is simple to acquire the drill-bit signal.

• Journal of Digital Contents Society
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• v.5 no.3
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• pp.219-224
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• 2004

In This paper, we have analyzed the power spectrum of DS-TH Ulhawideband (Direct Sequence-Time Hopping UWB) system which used pseudo-noise (PN) code. The DS-TH UWB system proposed in this paper multiplies the information signal with PN code to construct pulse train with random pattern and then the chips in pulse train are bundled into several groups to map to the particular value. The (+)/(-) pulse is tented in the time slot of frame by comparing a particular value with timing information that was stored in the lookup table. Thus, the energy spark (Comb Line) which is generated certainly in convantional system can be suppressed efficiently by PN code. And we knew that the proposed DS-TH UWB System even could have very smoothing power spectrum ctaracteristic without applying high speed Time-Hopping code.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2109-2118
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• 2016

Based on the space vector pulse width modulation (SVPWM) theory, this paper realizes an easier SVPWM strategy, which is equivalently implemented by CBSPWM with zero-sequence voltage injection. The traditional SVPWM strategy has no effect on controlling the neutral-point voltage balance. In order to solve the neutral-point voltage unbalance problem for neutral-point-clamped (NPC) three-level inverters, this paper proposes a neutral-point voltage balance controller. The proposed controller realizes controlling the neutral-point voltage balance by dynamically calculating the offset superimposed to the three-phase modulation waves of an equivalent SVPWM strategy. Compared with the traditional SVPWM strategy, the proposed neutral-point voltage balance controller has a strong ability to balance the neutral-point voltage, has good steady-state performance, improves the output waveforms quality and is easy for digital implementation. An experiment has been carried out on a NPC three-level inverter prototype based on a digital signal processor-complex programmable logic device (DSP-CPLD). The obtained experimental results verify the effectiveness of the proposed neutral-point voltage balance controller.

• Journal of Astronomy and Space Sciences
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• v.9 no.1
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• pp.69-88
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• 1992

The effects of the ionosphere on the radio wave propagation are scattering of radio waves, attenuation, angle error, ranging error, and time delay. If ionospheric conditions are suitable, the charged particles can remove energy from radio waves and thus attenuate the signal. Also, a radio wave traveling a path along which the electron density is not constant undergoes changes in direction, positon and time of propagation. The present study is based on Korean ionospheric data obtained at the AnYang Radio Research Institute from Jan. 1985 through Oct. 1989. The data are used to simulate the Korean ionosphere following the Chapman law. The effects of the model ionosphere on the radio wave propagation, such as the angle, position error, time delay, and the attenuation, are studied for the various cases of the wave frequency and the altitude.

• Proceedings of the IEEK Conference
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• summer
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• pp.92-96
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• 2004

The researches of the emotions are currently great interest in speech processing as well as in human-machine interaction domain. In the recent years, more and more of researches relating to emotion synthesis or emotion recognition are developed for the different purposes. Each approach uses its methods and its various parameters measured on the speech signal. In this paper, we proposed using a short-time parameter: MFCC coefficients (Mel­Frequency Cepstrum Coefficients) and a simple but efficient classifying method: Vector Quantification (VQ) for speaker-dependent emotion recognition. Many other features: energy, pitch, zero crossing, phonetic rate, LPC... and their derivatives are also tested and combined with MFCC coefficients in order to find the best combination. The other models: GMM and HMM (Discrete and Continuous Hidden Markov Model) are studied as well in the hope that the usage of continuous distribution and the temporal behaviour of this set of features will improve the quality of emotion recognition. The maximum accuracy recognizing five different emotions exceeds $88\%$ by using only MFCC coefficients with VQ model. This is a simple but efficient approach, the result is even much better than those obtained with the same database in human evaluation by listening and judging without returning permission nor comparison between sentences [8]; And this result is positively comparable with the other approaches.

• Journal of the Korean Chemical Society
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• v.21 no.2
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• pp.94-101
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• 1977

The NMR spectra of 2,4-disubstituted or 2,4,6-trisubstituted anisole derivative were examined to study the chemical shift of the ring proton signal. It was found that the chemical shift of the ring proton nearest to the 2-substituted group was influenced by the deshielding effect of the neighboring substituted groups in order of the Van der Waals radii of those groups. These observations were interpreted as a steric influence of 2-substituted group on the reactivity of the neighboring ring proton itself. The spectroscopical data were presented and the results were discussed with views of the above conceptions.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.1
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• pp.23-28
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• 2015

Measuring the distances between signals in the signal space is usually determined by obtaining the ideal metric which is not easy to obtain. In this research we have investigated the scheme that measures the distances between the signals constructed with the measured voltage signals connected to electric apparatus using Kalman filter and exponential mapping. The metric is defined on the feature signals obtained via the estimation process of a Kalman filter and the mapping process using the exponential transformation. Diagnosis is on the voltage fluctuations is applied to determining whether the system is in the stable state or not due to the unexpected accidents, such as power overcharge, discharge, outages flow may be the cause of the accident. The decision making scheme evaluated with respect to the effectiveness and the degree of complication with different variances. Two methods, the Hard Limit Threshold Scheme(HLTS) and the Interval Energy Scheme(IES) are proposed and compared. In experiments the IES shows better tolerance to impulse noise than the HLTS.

• The KIPS Transactions:PartB
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• v.15B no.6
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• pp.595-602
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• 2008

The focused word of each sentence is a help in recognizing and understanding spoken Korean. To find the method of focused word spotting at spoken speech signal, we made an analysis of the average and variance of Fundamental Frequency and the average energy extracted from a focused word and the other words in a sentence by experiments with the speech data from 100 spoken sentences. The result showed that focused words have either higher relative average F0 or higher relative variances of F0 than other words. Our findings are to make a contribution to getting prosodic characteristics of spoken Korean and keyword extraction based on natural language processing.