• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.338-341
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• 1993

A EEG(ElectroEncephaloGram) compression scheme based on subband coding techniques is presented in this paper. Considering the frequency characteristics of EEG, the raw signal was decomposed into different frequency bands. After decomposition, optimal bit allocation was done by adapting to the standard deviation in each frequency bands, and decomposed signals were quantized using pdf(probability density function)-optimized nonuniform quantizer. Based on the above mentioned coding scheme, coding results of various multichannel EEG signal were shown with compression ratio and SNR(signal-to-noise ratio).

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.177-178
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• 2015

This paper proposes a power smoothing scheme of a doubly-fed induction generator. The proposed scheme aims to mitigate system frequency deviation caused by the variable wind. To achieve this, a dynamic droop loop is used and its gain changes with rate of change of frequency so that it can release a large amount of kinetic energy at the initial stage of a frequency event. The performance of the proposed scheme was investigated in a model system with high wind penetration using EMTP-RV simulator. The test results indicate that the scheme can smooth the output power by absorbing or releasing the output power under a varying wind condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.8 s.227
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• pp.1065-1074
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• 2004

A robust optimal design considering fabrication influence has been performed for the decoupled vibratory microgyroscope fabricated by the bulk micromachining. For the analysis of the gyroscope, a design tool has been developed, by which user can perform the system level design considering electric signal process and the fabrication influence as well as mechanical characteristics. An initial design of the gyroscope is performed satisfying the performances of scale factor (or sensitivity) and phase delay, which depend on the frequency difference between driving and sensing resonant frequencies. The objective functions are formulated in order to reduce the variances of the frequency difference and the frequency in itself by fabrication error. To certify the results, the standard deviations are calculated through the Monte Caries Simulation (MCS) and compared initial deviation that is measured fabricated gyroscope chip.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.267-273
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• 2001

In this study, welding phenomena involved in formation of penetrators during high frequency electric resistance welding were investigated. High speed cinematography of the process revealer that a molten bridge between neighboring skelp edges forms at apex point and travels along narrow gap toward to welding point at a speed ranging from 100 to 400 m/min. The bridge while moving along the narrow gap swept away oxide containing molten metal from the gap, providing oxide-free surface for a forge-welding at upsetting stand frequency of the budge formation, travel distance and speed of the bridge were affected by the heat input rate into strip. The travel distance and its standard deviation were found to have a strong relationship with the weld defect density. Based on the observation, a new mechanism of the penetrator formation during HF ERW process is proposed.

• Structural Engineering and Mechanics
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• v.31 no.5
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• pp.481-506
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• 2009

The present study is concerned with the stochastic linear free vibration study of laminated composite plate embedded with piezoelectric layers with random material properties. The system equations are derived using higher order shear deformation theory. The lamina material properties of the laminate are modeled as basic random variables for accurate prediction of the system behavior. A $C^0$ finite element is used for spatial descretization of the laminate. First order Taylor series based mean centered perturbation technique in conjunction with finite element method is outlined for the problem. The outlined probabilistic approach is used to obtain typical numerical results, i.e., the mean and standard deviation of natural frequency. Different combinations of simply supported, clamped and free boundary conditions are considered. The effect of side to thickness ratio, aspect ratio, lamination scheme on scattering of natural frequency is studied. The results are compared with those available in literature and an independent Monte Carlo simulation.

• Journal of the Ergonomics Society of Korea
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• v.16 no.2
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• pp.15-27
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• 1997

Brain potential is described using the mesocolumnar activity defined by averaged firings of excitatory and inhibitory neuron of neocortex. Lagrangian is constructed based on SMNI(Statistical Mechanics of Neocortical Interaction) and then Euler Lagrange equation is obtained. Excitatory neuron firing is assumed to be amplitude- modulated dominantly by the sum of two modes of frequency .omega. and 2 .omega. . Time series of this neuron firing is calculated numerically by Euler Lagrangian equation. I .omega. L related to low frequency distribution of power spectrum, I .omega. H hight frequency, and Sd(standard deviation) were introduced for the effective extraction of the dynamic property in the simulated brain potential. The relative behavior of I .omega. L, I .omega. H, and Sd was found by parameters .epsilon. and .gamma. related to nonlinearity and harmonics respectively. Experimental I .omega L, I .omega. H, and Sd were obtained from EEG of human in rest state and of canine in deep sleep state and were compared with theoretical ones.

• Journal of the Korean Society of Physical Medicine
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• v.4 no.4
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• pp.241-247
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• 2009

Purpose：The purpose of this study is to investigate the effect of transcutaneous electrical stimulation on autonomic nervous system using heart rate variability analysis. Methods：31 subjects were evaluated with HRV before and after a single high-frequency TENS for 15minutes treatment. The standard deviation of all the normal RR-interval(SDNN) and lower frequency/high frequency ratio(LF/HF ratio) were recorded with TAS-9. Results：After single TENS treatment, autonomic adaptation as analyzed by SDNN was increased from $42.47\pm12.96$ to $4.43\pm16.76$(p>0.05) and autonomic balance as analyzed by LF/HF ratio was increased from $1.4\pm0.45$ to $1.45\pm0.41$(p>0.05). Conclusion：In this study, SDNN and LF/HF ratio changed in health young students as a result of single TENS treatment. But there is no significant difference between pre-treatment and post-treatment of SDNN and LF/HF ratio.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.152-156
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• 1989

Parameters of a microstrip patch antenna such as the resonant frequency, radiation conductance, and the bandwidth are calculated. The rectangular microstrip patch antenna fed by a microstrip transmission line is fabricated and its resonant frequency, radiation pattern, and input voltage standing wave ratio are measured. The measured resonant frequency for 13.0mm$\times$9.7mm copper clad woven PTFE/glass laminate plate is 9.06Ghz, where the calculative is 9.00Ghz. And the measured vswr shows that the bandwidth of the antenna is 225MHz for vswr less then 2.0 which the calculated quality factor of the patch gives the bandwidth OF 280ghZ. The measured radiation pattern for 5 element as well as 4 element patch array shows less then 4dB deviation in the first side lobes from the designed values for both E and H plane pattern. This diviation is believed to be the power division errors of the power divider.

• Journal of Korean Society for Atmospheric Environment
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• v.5 no.1
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• pp.88-95
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• 1989

The aspects of the occurence frequency of $SO_2$ concentration were studied with the observed data in Seoul and the scheme that is capable of estimating not only highest concentration for a variety of averaging times but also concentrations for arbitary occurrence frequency with long term arithmatic mean and geometric standard deviation data, was evaluated. The results of the statistical analysis show that the occurrence frequency is almost log normal except a few cases, and 3rd highest values of daily mean concentration were about 4.2 $\sim$ 5.2 times higher than annual arithmatic mean. The evaluation with the observed hourly concentration shows that the scheme fairly well estimate the short concentration of arbitary occurrence frequence and it can be used for air quality management and environmental impact assessment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.1871-1878
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• 2015

Recently, research on the Visual-MIMO by applying the concept of MIMO to communication between the LED array and camera is in progress. Although we already introduced the method for bit decision by using reference LED array pattern, it has the disadvantage of measuring the ISI each time when there is a change in the distance. To overcome this, in this paper, we propose a bit decision and error correction method used by using the luminance deviation without using the reference array pattern. First, we execute the bit decision using experimentally determined threshold. Next, we execute the error checking on the ON-LED and make a correction only if it is found to be error. Correction is determined by using the value of brightness deviation corresponding to the range of 68.2% (1) around the maximum frequency of the histogram for each ON-LED. We verify the performance of the proposed method according to the variation of ISI with distance by using both numerical and experimental analysis.