• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.3
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• pp.159-165
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• 2003

The fault detection and diagnosis technology may be applied in order to decrease the energy consumption and the maintenance cost of the air-conditioning system. To detect partial faults of the air-conditioning system, a neural network algorithm may be used. In this study, the neural network algorithm using normalized input data by the standard deviation was applied. And the [7$\times$10$\times$10$\times$1] neural network structure was selected. Test results showed that the neural network algorithm using normalized input data was very effective to detect the condenser fouling and the evaporator fan fault of an air-conditioning system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.7
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• pp.605-608
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• 2011

In this study, OSA (the obstructive sleep apnea) periods were detected in patients with OSA during sleep because of the treatment was different according to the frequency and symptoms of obstructive sleep apnea. ANS (autonomic nervous activity) was changed by obstructive sleep apnea periods so we intended to detect the periods to care the obstructive sleep apnea patients. RR intervals, SDNN (standard deviation of normal to normal) and RMSSD (root mean square standard deviation) were calculated in time domain analysis and LF (low frequency), HF (high frequency), NHF (normalized high frequency), NLF (normalized low frequency) were calculated in frequency domain analysis of HRV (heart rate variability) with obstructive sleep apnea patients. In this paper, SDNN (standard deviation of normal to normal) of time domain analysis were decreased in the obstructive sleep apnea periods. And NLF and LF/HF ratio were increased and NHF (normalized high frequency) was decreased in the frequency domain analysis. The parameters can be used to treat obstructive sleep apnea patients by detecting the obstructive sleep apnea periods such as CPAP (continuous positive airway pressure).

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.9
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• pp.616-623
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• 2001

Effects of the grating period fluctuation on the wavelength distribution have been studied by an effective index transfer matrix method in quarter wavelength shifted (QWS) DFB lasers. The wavelength distribution is expressed by a probability density that is an analytical function of the correlation coefficient and normalized standard deviation of the grating period fluctuation. The probability density function of wavelength distribution is shown to be nearly Gaussian, and its standard deviation increases with normalized standard deviation of the grating period fluctuation, and decreases with the negative correlation between adjacent half-periods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.2
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• pp.114-120
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• 1992

In this paper we derived the asymptotic distribution of the MUSIC null-spectrum, form which an exact expression of the asymptotic variance of the MUSIC null-spectrum can be obtained. From this result in addition an explicit expression of the normalized standard deviation has been derived and it is shown that the normalized standard deviation depends only on the number of sensors and the number of signals.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.10
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• pp.981-985
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• 2007

We present a MEMS-based portable Direct Methanol Fuel Cell (micro-DFMC), featured by a platinum sputtered microcolumn electrode and a built-in fuel chamber containing a limited amount of methanol fuel. Also presented is a micro-DMFC stack structure having a common electrolyte sandwiched by the microcolumn electrodes. The single cells with ME16 and PE16 electrodes show the maximum power densities of $31.04{\pm}0.29{\mu}W/cm^2$ and $9.75{\pm}0.29{\mu}W/cm^2$, respectively; thus indicating the microcolumn electrode (ME16) generates the power density (3.2 times) higher than the planar electrode (PE16). The single cell tests of ME16 and ME4 electrodes (Fig.8) show the maximum power of $31.04{\pm}0.29{\mu}W/cm^2$, and $25.23{\pm}2.7{\mu}W/cm^2$, respectively; thus demonstrating the increased window frame reduces the normalized standard power deviation (standard deviation over the average power). The normalized deviation of 0.11 in ME4 cell has been reduced to 0.01 in ME16 cell due to the increased window frames. The maximum power density of 4-cell stack is 15.7 times higher than that of the single cell. 4-cell stack produces the power capacity of 20.3mWh/g during 980min operation at the voltage of 450mV with the load resistance of $800{\Omega}$.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.4
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• pp.253-265
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• 2016

We propose an obstacle classification method using multi-decision factors and decision sections based on Single 2D LiDAR. The existing obstacle classification method based on single 2D LiDAR has two specific advantages: accuracy and decreased calculation time. However, it was difficult to classify obstacle type, and therefore accurate path planning was not possible. To overcome this problem, a method of classifying obstacle type based on width data was proposed. However, width data was not sufficient to enable accurate obstacle classification. The proposed algorithm of this paper involves the comparison between decision factor and decision section to classify obstacle type. Decision factor and decision section was determined using width, standard deviation of distance, average normalized intensity, and standard deviation of normalized intensity data. Experiments using a real autonomous vehicle in a real environment showed that calculation time decreased in comparison with 2D LiDAR-based method, thus demonstrating the possibility of obstacle type classification using single 2D LiDAR.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1571-1584
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• 2023

In this study, a numerical analysis was performed as part of an international joint research project to reproduce a real cable tray fire that occurred in the heater bay area of the turbine building of a nuclear power plant. A sensitivity analysis was performed on various input parameters to derive results consistent with the sprinkler activation time obtained from the fire event analysis. For all sensitive parameters, the normalized sprinkler activation time correlated well with the power function of the normalized sprinkler height. A correlation equation was developed to identify the sprinkler activation time at any location when determining the slope or fire growth rate under the conditions assuming a linear or t-squared heat release rate (HRR) time curve. Various cable fire growth assumptions were used to determine which assumption was better to provide the prediction coincident with the information given from the fire event analysis in terms of the sprinkler activation time and total energy generated from cables damaged by fire. In the comprehensive analysis of all the sensitive parameters, the standard deviation of the input parameters increased as the sprinkler height decreased. Within the range of the sensitivity parameter values given in this study, when considering all sprinkler heights, the standard deviation of the cable model change was the largest and that of the overhang position change was the smallest.

• The Journal of the Acoustical Society of Korea
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• v.26 no.3E
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• pp.87-96
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• 2007

In this paper we propose a new noise reduction algorithm for stationary and nonstationary noisy environments. Our algorithm classifies the speech and noise signal contributions in time-frequency bins, and is not based on a spectral algorithm or a minimum statistics approach. It relies on calculating the ratio of the standard deviation of the noisy power spectrum in time-frequency bins to its normalized time-frequency average. We show that good quality can be achieved for enhancement speech signal by choosing appropriate values for ${\delta}_t\;and\;{\delta}_f$. The proposed method greatly reduces the noise while providing enhanced speech with lower residual noise and somewhat higher mean opinion score (MOS), background intrusiveness (BAK) and signal distortion (SIG) scores than conventional methods.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.4
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• pp.599-607
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• 2000

In this study, experiments have been performed to examine the effects of background gray-level on the depth-of-field and on the in-focus criteria. The normalized value of contrast(VC) and the gradient indicator(GI) were used as the in-focus criteria for the small and the large size-ranges of particles, respectively. The slightly larger number of pixels were detected with the brighter background. The maximum of the normalized value of contrast(VCmax) is decreased with the brighter background and its deviation from that with the background gray-level of 160 turned out to be about $pm$15% when the background gray-level changes from 100 to 200. However, the maximum gradient indicator(GImax) changes with the background gray-level within only $pm$5%. The depth-of-field for the VC-applicable particle-size range is largely dependent on the background gray-level. On the other hand, the depth-of-field for the GI-applicable particle-size range changes only slightly with the background gray-level. To keep the normalized standard deviation of the particle size within 0.1, the background gray-level should be set 160$pm$20 for both the VC-applicable and GI-applicable ranges which cover the particle size between $10{\mu}m$ and $300{\mu}m$.

• Journal of Korea Water Resources Association
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• v.53 no.5
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• pp.337-345
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• 2020

In order to provide information for proper management of groundwater resources, an analysis of the effects of precipitation and groundwater withdrawal on groundwater levels is needed. In this study, we analyzed the correlation of precipitation-groundwater level and groundwater withdrawal-groundwater level using time series data converted by normalized standard deviation (Nor.St.Dev) and cross correlation coefficient (CCC) for nine groundwater monitoring wells in the middle mountainous area in the southeastern Jeju Island. First, the CCCs of precipitation-groundwater level were estimated using daily time series data, and the low CCCs of up to 0.3 were obtained. However, the result of using the Nor.St.Dev showed a clearer correlation by obtaining a CCC of up to 0.8. In addition, in most cases, precipitation variability and groundwater level variability had positive CCCs, whereas groundwater withdrawal variability and groundwater level variability had negative CCCs. Therefore, the groundwater level in this study area was largely influenced by precipitation with little effect of groundwater withdrawal. Lastly, as a result of analyzing the relative effects of Seongpanak and Gyorae rainfall station on the groundwater level, the rainfall at the relatively downstream Gyorae rainfall station has more influence. The analysis method used in this study can be easily used for analyzing the effects of precipitation and groundwater withdrawal on groundwater level variability in other regions in the future.