• Journal of Korea Water Resources Association
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• v.30 no.6
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• pp.641-648
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• 1997

Mutual information is useful for analyzing nonlinear dependence in time series in much the same way as correlation is used to characterize linear dependence. We use multivariate kernel density estimators for the estimation of mutual information at different time lags for single and multiple time series. This approach is tested on a variety of hydrologic data sets, and suggested an appropriate delay time $ au$ at which the mutual information is almost zerothen multi-dimensional phase portraits could be constructed from measurements of a single scalar time series.

• Journal of the Korean earth science society
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• v.26 no.5
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• pp.429-435
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• 2005

3D RMR (Rock Mass Rating) analysis has been performed by applying the Geostatistical integration technique for geophysical and borehole data. Of the various geostatistical techniques for the integrated data analysis, in this study, we applied the SKlvm (Simple Kriging with local varying means) method that substitutes the values of the interpreted geophysical result with the mean values of the RMR at the location to be inferred. The substitution is performed by the indicator transform between the result of geophysical interpretation and the observed RMR values at borehole sites. The used geophysical data are the electrical resistivity and MT result, and 10 borehole sites are investigated to obtain the RMR values. This integrated analysis makes the interpretation to be more practical for identifying the realistic RMR distribution that supports the regional geological situation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.4
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• pp.730-736
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• 2012

PN(Pseudo Noise) sequences play an important role in wireless communications, such as in a CDMA(code division multiple access) communication system. If there is a crash when multiple users simultaneously connected to a system, then PN sequences with low correlation help to minimize multiple access interference in such communication system. In this paper we propose a family of non-linear extended binary sequences with low cross-correlations and the family include $m$-sequence, GMW sequence, Kasami sequence and No sequence with optimal cross-correlation in terms of Welch bound. And we analyze cross-correlation of these sequences.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.2
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• pp.128-135
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• 2007

In response to anthropogenic global warming due to a buildup greenhouse gas, the effect of the air temperature on water temperature has been noticed. Therefore, effects have been made to build an air/water temperature relationship at three study regions using the data collected by the Ministry of the Maritime Affairs and Fisheries (MOMAF). The air/water relationship varies with time-scale and weekly time-scale was chosen for the study. The data were fitted to the S-shaped non-linear relationship, and the parameters for the S-curve were derived using a single-criteria multi-parameter optimization scheme. Separate regression curves were fitted to consider seasonal hysteresis at the Masan site. The study results support the S-shaped non-linear relationship is the best fit for the air/water relationship at the Korean coastal zone. This study will contribute to determine the future policy regarding water quality and ecosystem for the decision-driving organization.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06e
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• pp.115-118
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• 1998

본 연구에서는 매우 작은 틈새를 갖는 미세 크랙을 초음파가 투과할 때, 크랙 면의 부분 접촉의 의한 새로운 음향 비선형성의 발생 구조를 제안하고 그 정당성을 검증하는데 목적을 두고 있다. 이를 위하여, 초음파가 미세 크랙을 투과할 때 부분 접촉 효과에 의해 나타나게 되는 파형을 반파 모델로 모델링하고 이를 통해 고주파 조화 성분(Harmonics)이 발생하는 원인을 제시하였으며 틈새의 크기와 음향 비선형성의 크기와의 상관 관계를 시뮬레이션과 실험을 통하여 확인하였다. 이를 통해 미세 틈새와 음향 비선형성과의 상관 관계를 밝히고 틈새의 크기가 증가해 감에 따라 음향 비선형성이 증가함을 확인할 수 있었다.

• Water for future
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• v.26 no.4
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• pp.85-95
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• 1993

Three purposes of this study are as follows: The first was the development of the extention method for the limited data observed in an urban drainage basin. The second was the analysis of the correlation between storm water runoff and NPS(non-point source) pollutant discharge, The last was the calculation of the monthly and annual specific NPS loads using the established correlation. the selected model was the SWMM monthly and annual specific NPs loads using the established correlation. The selected model was the SWMM (Storm Water Management model) developed by the US EPA(environmental Protection Agency). As a result of this study, the best correlation between storm wate runoff and NPS pollutants discharge was produced by the non-linear correlation between runoff rate(mm/hr)and specific loads rate(g/ha/sec)for all pollutants studied ; SS, COD, BOD, and TN. The best correlation through the analysis based on evently total mass was made by the linear correlation between the specific accumulated runoff(mm) and the specific accumulated loads(kg/ha) for CASE 1., and by the non-linear correlation for CASE 2. The NPS annual specific loads for the urban basin studied were 4933 kg/ha/year for SS, 775kg/ha/year for BOD, 3094kg/ha /year for COD,257kg/ha/year for TN, respectively. And the proportion of the NPS annual specific loads to the total annual specific loads were 42 % for SS, 13 % for BOD, 29% for COD, and 21 % for TN.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.8
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• pp.1686-1692
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• 2012

Spreading sequence play an important role in wireless communications, such as in a CDMA(code division multiple access) communication system and multi-carrier spectrum communication system. Spreading sequences with low cross-correlation, in a direct-sequence spread spectrum communication system, help to minimize multiple access interference and to increase security degree of system. Analysis of cross-correlations between the sequences is a necessary process to design sequences. However it require lots of computing time for analysis of cross-correlations between sequences. In this paper we propose a method which is possible to compute effectively cross-correlation using subfield in the process of practical computation of cross-correlation between nonlinear binary sequences.

• Journal of Korea Water Resources Association
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• v.32 no.6
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• pp.731-740
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• 1999

Autocorrelation function is widely used as a tool measuring linear dependence of hydrologic time series. However, it may not be appropriate for choosing decorrelation time or delay time ${\tau}_d$ which is essential in nonlinear dynamics domain and the mutual information have recommended for measuring nonlinear dependence of time series. Furthermore, some researchers have suggested that one should not choose a fixed delay time ${\tau}_d$ but, rather, one should choose an appropriate value for the delay time window ${\tau}_d={\tau}(m-1)$, which is the total time spanned by the components of each embedded point for the analysis of chaotic dynamics. Unfortunately, the delay time window cannot be estimated using the autocorrelation function or the mutual information. Basically, the delay time window is the optimal time for independence of time series and the delay time is the first locally optimal time. In this study, we estimate general dependence of hydrologic time series using the C-C method which can estimate both the delay time and the delay time window and the results may give us whether hydrologic time series depends on its linear or nonlinear characteristics which are very important for modeling and forecasting of underlying system.

• Journal of Environmental Policy
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• v.13 no.2
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• pp.21-38
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• 2014

In response to global warming, the effect of the air temperature on water temperature has been noticed. The change in water temperature in river environment results in the change in water quality and ecosystem, especially Dissolved Oxygen (DO) level, and shifts in aquatic biota. Efforts need to be made to predict future water temperature in order to understand the timing of the projected river temperature. To do this, the data collected by the Ministry of Environment and the Korea Meteororlogical Administration has been used to build a nonlinear relationship between air and water temperature. The logistic function that includes four different parameters was selected as a working model and the parameters were optimized using SCE algorithm. Weekly average values were used to remove time scaling effect because the time scale affects maximum and minimum temperature and then river environment. Generally speaking nonlinear logistic model shows better performance in NSC and RMSE and nonlinear logistic function is recommendable to build a relationship between air and water temperature in Korea. The results will contribute to determine the future policy regarding water quality and ecosystem for the decision-driving organization.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.12
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• pp.2875-2882
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• 2013

The design of PN(Pseudo Noise) sequences with good cross-correlation properties is important for many research areas in communication systems. Also analyses of cross-correlation frequency between designed sequences have been researched. In this paper we analyze of cross-correlation distribution and properties of non-linear binary sequences family $S^r=\{Tr^m_1\{[Tr^n_m(a{\alpha}^t+{\alpha}^{dt}]^r\}{\mid}a{\in}GF(2^m),0{\leq}t < 2^n-1\}$, where $gcd(r,2^m-1)=1$ with 5-valued cross-correlation.