Mental task classification is one of the most important problems in Brain-computer interface.This paper studies the classification of five-class mental tasks.The nonlinear parameter of mean period obtained from freque...Mental task classification is one of the most important problems in Brain-computer interface.This paper studies the classification of five-class mental tasks.The nonlinear parameter of mean period obtained from frequency domain information was used as features for classification implemented by using the method of SVM(support vector machines).The averaged classification accuracy of 85.6% over 7 subjects was achieved for 2-second EEG segments.And the results for EEG segments of 0.5s and 5.0s compared favorably to those of Garrett's.The results indicate that the parameter of mean period represents mental tasks well for classification.Furthermore,the method of mean period is less computationally demanding,which indicates its potential use for online BCI systems.展开更多
The mean wavelength of ocean waves is an important environmental parameter in ocean engineering. Owing to the difficulty in its measurement, it is usually estimated from the mean wave period according to the theoretic...The mean wavelength of ocean waves is an important environmental parameter in ocean engineering. Owing to the difficulty in its measurement, it is usually estimated from the mean wave period according to the theoretical relationship between the two wave parameters. However, the relationships that have been proposed are not very satisfactory. In this paper, some suggestions are made for improvement of the data analysis method by which the mean wavelength is estimated from surface elevation records. Laboratory experiments are conducted in a wind-wave flume, and a new relationship between the mean wavelength and mean wave period is obtained by the application of the improved data analysis method. The new relationship deviates from that of Xu et al. (1999) while it is very close to the one proposed by Kinsman (1965), although the last one is theoretically deficient.展开更多
In this paper, we present a basic theory of mean-square almost periodicity, apply the theory in random differential equation, and obtain mean-square almost periodic solution of some types stochastic differential equat...In this paper, we present a basic theory of mean-square almost periodicity, apply the theory in random differential equation, and obtain mean-square almost periodic solution of some types stochastic differential equation.展开更多
This paper summarizes the general methods,existing problems and their causes of the period analysis for the monthly mean sea level and points out that it is the key to the analysing period signals and forecasting the ...This paper summarizes the general methods,existing problems and their causes of the period analysis for the monthly mean sea level and points out that it is the key to the analysing period signals and forecasting the change trend of the monthly mean sea level that the periods of the signals are selected reasonably. As there are often many period signals in these series, nonlinear effects exist between pairs of period signals. In order to avoid the false periods that may be introduced due to the effects of side lobes and the periods with statistical phase significance coherence that may be introduced due to the effects of nonlinear effects and their restraint to other period signals, the maximum entropy spectral analysis and the corresponding significance period test may be performed repeatedly on the basis of the bispectrum analysis and meanwhile the most significant period component is filtered out by the least square filtering method, i. e., the method of the significance period analysis with mixed spectra modeled by a nonlinear system is adopted and the signal periods approaching the reality are selected one by one. The examples of the bispectrum analysis, the signal period analysis by mixed spectra and the fitting parameters for combined period components with linear trend in the time series of monthly mean sea level are given in this paper.展开更多
To study the period components in the monthly mean sea level variations in the Pacific Ocean, this paper analyses the monthly mean series of 236 tide gauge stations in the Pacific on the basis of the improved analytic...To study the period components in the monthly mean sea level variations in the Pacific Ocean, this paper analyses the monthly mean series of 236 tide gauge stations in the Pacific on the basis of the improved analytical method of the monthly mean sea level period signals. The results show that the oscillation periods of the sea level series are not fixed, but vary with stations. This paper also discusses the existences of the quasi-2 years atmospheric oscillation period, the 3~7 a period related to the El Nino events, sunspots, double sunspots and the 25~30 a overlength oscillation periods. The corresponding amplitudes and initial phase angles as well as the linear trend coefficient are obtained by using significant period components plus the linear trend to fit the monthly mean sea level series. A conspicuous features of the results are found,i. e.,taking 25°~30°S as the axial line in the Pacific, the annual lags gradually increase to the north and the south respectively, depicting a variation trend of partial symmetry. But in China seas, the north and south distributional trend of the annual period lags is almost opposite to those in most parts of the Pacific Ocean. In the low-latitude zone where El Nino events occur or impose more significant effects, the ratio of the sum of amplitudes of various periods within 2~7 a to the annual amplitude is equal to or more than 1. 0, while that of the sum of amplitudes of periods larger than 8 a to the annual amplitude is equal to or more than 0. 5. This suggests that the dominant role of annual amplitude in the monthly mean sea level series of this region has declined and that, correspondingly, there exist significant period components of El Nino events as well as the long-period oscillations of quasi-10 a and over 10 a. In the high-latitude zone, off China, in North America north of 40°N and the coast of Japan, the annual period oscillation occupies a dominant position in the various period components.展开更多
The thesis conducts its analysis fromthe perspective of cultural characteristics of Chu state of Pre-Qin period in ancient China.The culture of Chu,usually focusing on ceremony sacrifice and several other activities,p...The thesis conducts its analysis fromthe perspective of cultural characteristics of Chu state of Pre-Qin period in ancient China.The culture of Chu,usually focusing on ceremony sacrifice and several other activities,presents unique characteristics of the development of Chinese society and culture.Actually,the jade artifact at that time shows cultural features both at artistic and spiritual level and bears prominent cultural connotations like national spirit of solemnness and generosity.Chinese jade of Chu state of Pre-Qin period due to its abundant cultural connotations and meanings,poses to be an essential element of traditional Chinese culture,which shows artistic and national features of traditional jade culture and can directly influence development of modern society and culture.展开更多
An fKdV equation of two-layer how and an averaged fKdV equation (AfKdV equation) with respect to phase are derived to determine the theoretical amplitude and period of the precursor solitons in the present paper. In t...An fKdV equation of two-layer how and an averaged fKdV equation (AfKdV equation) with respect to phase are derived to determine the theoretical amplitude and period of the precursor solitons in the present paper. In terms of the AfKdV equation derived by the authors, a new theory on the precursor soliton generation based on Lee et al.'s concept is presented. Concepts of asymptotic mean hydraulic fall and level are introduced in our analysis, and the theoretical amplitude and period both depend on the asymptotic mi-an levels and stratified parameters. From the present theoretical results, it is obtained that when the moving velocity of the topography is at the resonant points, there exist two general relations: (1) amplitude relation (A) over circle = 2F, (2) period relation <(tau)over circle> = -8m(1)m(3)(-1)root 6m(4)m(3)(-1)F, in which (A) over circle and <(tau)over circle> are the amplitude and period of the precursor solitons at the resonant points respectively, m(1), m(3) and m(4) are coefficients of the fKdV equation, and F is asymptotic mean half-hydraulic fall at subcritical cutoff points. The theoretical results of this paper are compared with experiments and numerical calculations of two-layer flow over a semicircular topography and all these results are in good agreement. Due to the canonical character of the coefficients of fKdV equations, this theory also holds for any two-dimensional system, which can be reduced to fKdV equations.展开更多
The attempt to obtain long-term observed data around some sea areas we concern is usually very hard or even impossible in practical offshore and ocean engineering situations. In this paper, by means of linear mean-squ...The attempt to obtain long-term observed data around some sea areas we concern is usually very hard or even impossible in practical offshore and ocean engineering situations. In this paper, by means of linear mean-square estimation method, a new way to extend short-term data to long-term ones is developed. The long-term data about concerning sea areas can be constructed via a series of long-term data obtained from neighbor oceanographic stations, through relevance analysis of different data series. It is effective to cover the insufficiency of time series prediction method's overdependence upon the length of data series, as well as the limitation of variable numbers adopted in multiple linear regression model. The storm surge data collected from three oceanographic stations located in Shandong Peninsula are taken as examples to analyze the number-selection effect of reference oceanographic stations(adjacent to the concerning sea area) and the correlation coefficients between sea sites which are selected for reference and for engineering projects construction respectively. By comparing the N-year return-period values which are calculated from observed raw data and processed data which are extended from finite data series by means of the linear mean-square estimation method, one can draw a conclusion that this method can give considerably good estimation in practical ocean engineering, in spite of different extreme value distributions about raw and processed data.展开更多
基金This work was supportedin part by the National Natural Science Foundation of China(No.60271025,No.30370395)in part by the Science and Technology Depart ment of Shaanxi Province(No.2003K10-G24).
文摘Mental task classification is one of the most important problems in Brain-computer interface.This paper studies the classification of five-class mental tasks.The nonlinear parameter of mean period obtained from frequency domain information was used as features for classification implemented by using the method of SVM(support vector machines).The averaged classification accuracy of 85.6% over 7 subjects was achieved for 2-second EEG segments.And the results for EEG segments of 0.5s and 5.0s compared favorably to those of Garrett's.The results indicate that the parameter of mean period represents mental tasks well for classification.Furthermore,the method of mean period is less computationally demanding,which indicates its potential use for online BCI systems.
文摘The mean wavelength of ocean waves is an important environmental parameter in ocean engineering. Owing to the difficulty in its measurement, it is usually estimated from the mean wave period according to the theoretical relationship between the two wave parameters. However, the relationships that have been proposed are not very satisfactory. In this paper, some suggestions are made for improvement of the data analysis method by which the mean wavelength is estimated from surface elevation records. Laboratory experiments are conducted in a wind-wave flume, and a new relationship between the mean wavelength and mean wave period is obtained by the application of the improved data analysis method. The new relationship deviates from that of Xu et al. (1999) while it is very close to the one proposed by Kinsman (1965), although the last one is theoretically deficient.
文摘In this paper, we present a basic theory of mean-square almost periodicity, apply the theory in random differential equation, and obtain mean-square almost periodic solution of some types stochastic differential equation.
文摘This paper summarizes the general methods,existing problems and their causes of the period analysis for the monthly mean sea level and points out that it is the key to the analysing period signals and forecasting the change trend of the monthly mean sea level that the periods of the signals are selected reasonably. As there are often many period signals in these series, nonlinear effects exist between pairs of period signals. In order to avoid the false periods that may be introduced due to the effects of side lobes and the periods with statistical phase significance coherence that may be introduced due to the effects of nonlinear effects and their restraint to other period signals, the maximum entropy spectral analysis and the corresponding significance period test may be performed repeatedly on the basis of the bispectrum analysis and meanwhile the most significant period component is filtered out by the least square filtering method, i. e., the method of the significance period analysis with mixed spectra modeled by a nonlinear system is adopted and the signal periods approaching the reality are selected one by one. The examples of the bispectrum analysis, the signal period analysis by mixed spectra and the fitting parameters for combined period components with linear trend in the time series of monthly mean sea level are given in this paper.
文摘To study the period components in the monthly mean sea level variations in the Pacific Ocean, this paper analyses the monthly mean series of 236 tide gauge stations in the Pacific on the basis of the improved analytical method of the monthly mean sea level period signals. The results show that the oscillation periods of the sea level series are not fixed, but vary with stations. This paper also discusses the existences of the quasi-2 years atmospheric oscillation period, the 3~7 a period related to the El Nino events, sunspots, double sunspots and the 25~30 a overlength oscillation periods. The corresponding amplitudes and initial phase angles as well as the linear trend coefficient are obtained by using significant period components plus the linear trend to fit the monthly mean sea level series. A conspicuous features of the results are found,i. e.,taking 25°~30°S as the axial line in the Pacific, the annual lags gradually increase to the north and the south respectively, depicting a variation trend of partial symmetry. But in China seas, the north and south distributional trend of the annual period lags is almost opposite to those in most parts of the Pacific Ocean. In the low-latitude zone where El Nino events occur or impose more significant effects, the ratio of the sum of amplitudes of various periods within 2~7 a to the annual amplitude is equal to or more than 1. 0, while that of the sum of amplitudes of periods larger than 8 a to the annual amplitude is equal to or more than 0. 5. This suggests that the dominant role of annual amplitude in the monthly mean sea level series of this region has declined and that, correspondingly, there exist significant period components of El Nino events as well as the long-period oscillations of quasi-10 a and over 10 a. In the high-latitude zone, off China, in North America north of 40°N and the coast of Japan, the annual period oscillation occupies a dominant position in the various period components.
基金Humanities and Social Sciences Program of 2011 Funded by Ministry of Education:Studies on Chinese Jade for Clothes in Chu State of Pre-Qin Period(No.10YJAZHD95)
文摘The thesis conducts its analysis fromthe perspective of cultural characteristics of Chu state of Pre-Qin period in ancient China.The culture of Chu,usually focusing on ceremony sacrifice and several other activities,presents unique characteristics of the development of Chinese society and culture.Actually,the jade artifact at that time shows cultural features both at artistic and spiritual level and bears prominent cultural connotations like national spirit of solemnness and generosity.Chinese jade of Chu state of Pre-Qin period due to its abundant cultural connotations and meanings,poses to be an essential element of traditional Chinese culture,which shows artistic and national features of traditional jade culture and can directly influence development of modern society and culture.
基金The project supported by the foundation of The State Education Commission"The dynamics of upper ocean"the open grants of Physical Oceanography Laboratory
文摘An fKdV equation of two-layer how and an averaged fKdV equation (AfKdV equation) with respect to phase are derived to determine the theoretical amplitude and period of the precursor solitons in the present paper. In terms of the AfKdV equation derived by the authors, a new theory on the precursor soliton generation based on Lee et al.'s concept is presented. Concepts of asymptotic mean hydraulic fall and level are introduced in our analysis, and the theoretical amplitude and period both depend on the asymptotic mi-an levels and stratified parameters. From the present theoretical results, it is obtained that when the moving velocity of the topography is at the resonant points, there exist two general relations: (1) amplitude relation (A) over circle = 2F, (2) period relation <(tau)over circle> = -8m(1)m(3)(-1)root 6m(4)m(3)(-1)F, in which (A) over circle and <(tau)over circle> are the amplitude and period of the precursor solitons at the resonant points respectively, m(1), m(3) and m(4) are coefficients of the fKdV equation, and F is asymptotic mean half-hydraulic fall at subcritical cutoff points. The theoretical results of this paper are compared with experiments and numerical calculations of two-layer flow over a semicircular topography and all these results are in good agreement. Due to the canonical character of the coefficients of fKdV equations, this theory also holds for any two-dimensional system, which can be reduced to fKdV equations.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51379195 and 41476078)the Natural Science Foundation of Shandong Province(Grant No.ZR2013EEM034)+2 种基金the Scientific Research Foundation of Science Technology Department of Zhejiang Province(Grant No.2015C34013)the Science Research Program of Zhoushan(Grant No.2014C41003)the Innovation Fund for Graduate Student of Shandong Province(Grant No.SDYY12152)
文摘The attempt to obtain long-term observed data around some sea areas we concern is usually very hard or even impossible in practical offshore and ocean engineering situations. In this paper, by means of linear mean-square estimation method, a new way to extend short-term data to long-term ones is developed. The long-term data about concerning sea areas can be constructed via a series of long-term data obtained from neighbor oceanographic stations, through relevance analysis of different data series. It is effective to cover the insufficiency of time series prediction method's overdependence upon the length of data series, as well as the limitation of variable numbers adopted in multiple linear regression model. The storm surge data collected from three oceanographic stations located in Shandong Peninsula are taken as examples to analyze the number-selection effect of reference oceanographic stations(adjacent to the concerning sea area) and the correlation coefficients between sea sites which are selected for reference and for engineering projects construction respectively. By comparing the N-year return-period values which are calculated from observed raw data and processed data which are extended from finite data series by means of the linear mean-square estimation method, one can draw a conclusion that this method can give considerably good estimation in practical ocean engineering, in spite of different extreme value distributions about raw and processed data.
基金Acknowledgement This article is funded by the National Natural Science Foundation of China (11161052), Guangxi Natural Science Foundation of China (201 ljjA10044) and Guangxi Education Hall Project (201012MS183)