• Journal of Communications and Networks
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• v.7 no.1
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• pp.45-53
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• 2005

In this paper, we present a cross-layer analysis of wireless TCP systems over correlated channels. The effects of error correlation on the behavior of link retransmission strategy and the end-to-end throughput of TCP layer are investigated. Based on the cross-layer analysis, an efficient refinement of link layer protocol is proposed by consciously utilizing the information of channel correlations, which leads to the performance improvement of wireless TCP systems.

• Structural Engineering and Mechanics
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• v.63 no.6
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• pp.751-760
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• 2017

In recent years, multifractal-based analysis methods have been widely applied in engineering. Among these methods, multifractal detrended cross-correlation analysis (MFDXA), a branch of fractal analysis, has been successfully applied in the fields of finance and biomedicine. For its great potential in reflecting the subtle characteristic among signals, a structural health monitoring (SHM) system based on MFDXA is proposed. In this system, damage assessment is conducted by exploiting the concept of multifractal theory to quantify the complexity of the vibration signal measured from a structure. According to the proposed algorithm, the damage condition is first distinguished by multifractal detrended fluctuation analysis. Subsequently, the relationship between the q-order, q-order detrended covariance, and length of segment is further explored. The dissimilarity between damaged and undamaged cases is visualized on contour diagrams, and the damage location can thus be detected using signals measured from different floors. Moreover, a damage index is proposed to efficiently enhance the SHM process. A seven-story benchmark structure, located at the National Center for Research on Earthquake Engineering (NCREE), was employed for an experimental verification to demonstrate the performance of the proposed SHM algorithm. According to the results, the damage condition and orientation could be correctly identified using the MFDXA algorithm and the proposed damage index. Since only the ambient vibration signal is required along with a set of initial reference measurements, the proposed SHM system can provide a lower cost, efficient, and reliable monitoring process.

• The Journal of the Korea Contents Association
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• v.17 no.1
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• pp.201-212
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• 2017

This study presented the new evaluation index which can evaluate the discrimination of DEA models. To evaluate the discrimination of DEA models, data were analyzed using importance index as suggested in previous study and the coefficient of variation as suggested in this study for the discrimination evaluation. This study selected the CCR-DEA, BCC-DEA, entropy, bootstrap, super efficiency, and cross efficiency DEA model for the discrimination evaluation and accomplished empirical analysis. In order to grasp the rank correlation of the models, this study implemented the rank correlation analysis between the efficiency of CCR model and BCC model and entropy, bootstrap, super efficiency, and efficiency of the cross efficiency model. The obtained results of this study are as follows. First, the discrimination rank of models using the importance index and the coefficient of variation was shown to be identical. Therefore, the coefficient of variation can be used the discrimination evaluation index of DEA model. Second, the discrimination of the super efficiency model was found to be the highest rank among 4 models according to the analysis of this present study. Third, the highest rank correlation with CCR model was the super efficiency model. In addition, the super efficiency model was found to be the highest rank correlation with BCC model.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.155-158
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• 2004

To investigate the in-situ REV, cross-correlations between the ablsolute value of iu/outflux in tested boreholes and fracture frequency with various window widths were calculated. The changes of vertical flow rates can be considered as iu/outflux into/out of borehole. The results of cross-correlation analysis shows that 7m can be the most appropriate width of the appliable window.

• Child Health Nursing Research
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• v.15 no.3
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• pp.261-270
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• 2009

Purpose: The purpose of this study was to compare the result of one-way ANOVA with that of cross-correlation time series analysis in order to evaluate physiologic responses of premature infants to human voices. Methods: Four premature infants born prior to 32 weeks gestational age were included in the study. The Gould 4000TA Recording System recorded the preterm infant's heart and respiratory rate while they were listening to a pre-recorded voice recording. Each infant listened to both male and female voices (1 min each) at each testing session. Results: The results of both one-wayANOVA and cross-correlation time series analysis using heart and respiratory rate data were not consistent in some of premature infants. A cross-correlation time series analysis revealed that the responses of premature infant to vocal stimulation occurred at a varying number of seconds after the stimulus was presented and lasted for over 20-30 sec. Conclusion: The results indicate that a time series analysis can provide more detailed information on the rapidly changing physiologic status of premature infant to the auditory stimulus. In addition, the results provide an insight into an auditory responsitivity of premature infants to a naturally occurring sound, the human voice, in the neonatal intensive care unit.

• The Journal of Churna Manual Medicine for Spine and Nerves
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• v.8 no.2
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• pp.39-46
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• 2013

Objectives : To identify the association between cross-sectional area of lumbar regional muscle and stability(ST), center of pressure(COP) assessed by tetrax. Methods : Patients(n=55) who had taken L-SPINE MRI and Tetrax(Sunlight, Israel) were analyzed retrospectively. To evaluate the cross-sectional area of lumbar regional muscle, L-SPINE MRI was used. Data of ST, COP were accumulated by using dynamic equilibrium analysis by Tetrax. Of the lumbar regional muscles, the Psoas muscles and the Paraspinalis muscles were examined. Using Pearson correlation, we analyzed COP, ST and the difference between the cross-sectional area of lumbar regional muscles. Results : The variance of cross-sectional area of both sides of Psoas muscle and COP had moderate positive correlation(r=0.621). Between variance of cross-sectional area of both sides of Paraspinalis and lumbar regional muscle and COP there was low positive correlation(r=0.287, r=0.329) ST also had low correlation with variance of cross-sectional area of both sides of Psoas muscle. Conclusion : The variance of cross-sectional area between both sides of Psoas muscle had moderate correlation with COP.

• Journal of Mechanical Science and Technology
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• v.18 no.8
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• pp.1428-1434
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• 2004

This paper presents the mean streamline analysis using the empirical loss correlations for performance prediction of cross-flow fans. Comparison of overall performance predictions with test data of a cross-flow fan system with a simplified vortex wall scroll casing and with the published experimental characteristics for a cross-flow fan has been carried out to demonstrate the accuracy of the proposed method. Predicted performance curves by the present mean streamline analysis agree well with experimental data for two different cross-flow fans over the normal operating conditions. The prediction method presented herein can be used efficiently as a tool for the preliminary design and performance analysis of general-purpose cross-flow fans.

• Earthquakes and Structures
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• v.11 no.6
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• pp.1143-1164
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• 2016

Time Delay of Arrival (TDOA) estimation methods based on correlation function analysis play an important role in the micro-seismic event monitoring. It makes full use of the similarity in the recorded signals that are from the same source. However, those methods are subjected to the noise effect, particularly when the global similarity of the signals is low. This paper proposes a new approach for micro-seismic monitoring based on cross wavelet transform. The cross wavelet transform is utilized to analyse the measured signals under micro-seismic events, and the cross wavelet power spectrum is used to measure the similarity of two signals in a multi-scale dimension and subsequently identify TDOA. The offset time instant associated with the maximum cross wavelet transform spectrum power is identified as TDOA, and then the location of micro-seismic event can be identified. Individual and statistical identification tests are performed with measurement data from an in-field mine. Experimental studies demonstrate that the proposed approach significantly improves the robustness and accuracy of micro-seismic source locating in mines compared to several existing methods, such as the cross-correlation, multi-correlation, STA/LTA and Kurtosis methods.

• Journal of Environmental Science International
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• v.17 no.2
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• pp.257-267
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• 2008

Groundwater recharge characteristics in a fractured granite area, Mt. Geumjeong, Korea. was interpreted using bedrock groundwater and wet-land water data. Time series analysis using autocorreclation, cross-correlation and spectral density was conducted for characterizing water level variation and recharge rate in low water and high water seasons. Autocorrelation analysis using water levels resulted in short delay time with weak linearity and memory. Cross-correlation function from cross-correlation analysis was lower in the low water season than the high water season for the bedrock groundwater. The result of water level decline analysis identified groundwater recharge rate of about 11% in the study area.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.4
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• pp.821-826
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• 2012

p-ary sequences of period $N=2^k-1$ are widely used in many areas of engineering and sciences. Some well-known applications include coding theory, code-division multiple-access (CDMA) communications, and stream cipher systems. The analysis of cross-correlations of these sequences is a very important problem in p-ary sequences research. In this paper, we analyze cross-correlations of p-ary sequences which is associated with the equation $(x+1)^d=x^d+1$ over finite fields.