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Analysis of realistic rough surface for its globally dominant parameters using continuous wavelets

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Applied Mathematics and Mechanics(English Edition) 2014年第6期35卷 741-748页

作者：吴彦华任慧颖 School of Mechanical and Aerospace Engineering Nanyang Technological University Hydrology Technical Group Pacific Northwest National LaboratoryP. O. Box 999

Continuous morlet and Mexican hat wavelets are used to analyze a highly irregular rough surface replicated from real turbine blades which are roughened by deposi-tion of foreign materials. The globally dominant aspect ratio, length scale, and orientation of the roughness elements are determined. These parameters extracted from this highly irregular rough surface are important for the future studies of their effects on turbulent flows over this kind of rough surfaces encountered in Washington aerospace and power generating industries.

关键词： continuous wavelet morlet wavelet Mexican wavelet roughness

Arrival time measurements of first arrival phases P and PKIKP using the method of fixed scale wavelet transformation ratio

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Acta Seismologica Sinica(English Edition) 2005年第4期18卷 410-418,499页

作者：何小波周蕙兰 Computational Geodynamics Laboratory Graduate School of Chinese Academy of Sciences Beijing 100049 China

The arrival times of first teleseismic phases are difficult to be measured precisely because of slowly and gradually changed onsets and weak amplitudes. The arrival times measured manually are usually behind the real ones. In this paper, using the ratio method of fixed scale wavelet transformations improved by us, the arrival times for the first arrival phases (such as P and PKIKP) at the teleseismic and far-teleseismic distances were measured. The results are reasonable and reliable based on the analysis and discussion of the reliabilities and errors.

关键词： morlet wavelet wavelet transformation ratio first arrival phase first arrival time signal to noise ratio

The interannual periodicity of precipitation and its links to the large-scale circulations over the Third Pole

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Journal of Geographical Sciences 2024年第8期34卷 1457-1471页

作者： LIANG Liqiao LIU Qiang LI Jiuyi State Key Laboratory of Tibetan Plateau Earth System Environment and Resources(TPESER)Institute of Tibetan Plateau ResearchCASBeijing 100101China State Key Laboratory of Water Environment Simulation School of EnvironmentBeijing Normal UniversityBeijing 100875China Key Laboratory for Water and Sediment Sciences Ministry of EducationSchool of EnvironmentBeijing Normal UniversityBeijing 100875China Key Laboratory of Water Cycle and Related Land Surface Processes Institute of Geographic Sciences and Natural Resources ResearchCASBeijing 100101China

To understand the spatio-temporal variability of precipitation(P)in the Third Pole region(centered on the Tibetan Plateau-TP),it is necessary to quantify the interannual periodicity of P and its relationship with large-scale *** this study,morlet wavelet transform was used to detect significant(pwavelet transform results were as follows.(1)Significant quasiperiodicity varied from 2 to 11 *** high-frequency variability mode(2 to 6 years quasi-periods)was universal,and the low-frequency variability mode(7 to 11 years quasi-periods)was rare,occurring mainly in the westerlies and Indian monsoon domains.(2)The majority of periods were base periods(53%),followed by two-base *** all stations in the Third Pole(95%)showed one or two periods.(3)Periodicity was widely detected in the majority of years(84%).(4)The power spectra of P in the four domains were dominated by statistically significant high-frequency oscillations(ie.,with short periodicity).(5)Large-scale circulations directly and indirectly influenced the periodic P variability in the different *** mode of P variability in the different domains was influenced by interactions between large-scale circulation features and not only by the dominant circulation and its control of water vapour *** results of this study will contribute to better understanding of the causal mechanisms associated with P variability,which is important for hydrological science and waterresourcemanagement.

关键词： precipitation interannual periodicity morlet wavelet large-scale circulations Third Pole

Revealing the Fluttering Motions of Mid-Water Trawl Codend Through Sea Trials:Case Study of Antarctic Krill Trawl Codend

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Journal of Ocean University of China 2023年第2期22卷 555-564页

作者： LIU Wei TANG Hao NYATCHOUBA NSANGUE Bruno Thierry ZHANG Feng YIN Liqiang XU Liuxiong HU Fuxiang LIU Pengfei College of Marine Sciences Shanghai Ocean UniversityShanghai 201306China National Engineering Research Center for Oceanic Fisheries Shanghai 201306China Key Laboratory of Oceanic Fisheries Exploration Ministry of Agriculture and Rural AffairsShanghai 201306China The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources Shanghai Ocean UniversityMinistry of EducationShanghai 201306China Scientific Observing and Experimental Station of Oceanic Fishery Resources Ministry of Agriculture and Rural AffairsShanghai 201306China Faculty of Marine Science Tokyo University of Marine Science and TechnologyMinatoTokyo 108-8477Japan Tendering Office Shanghai Ocean UniversityShanghai 201306China

The dynamic coupling between the fluttering motions and hydrodynamic characteristics of codend is essential in understanding the trawl selectivity through fish response and the drag force acting on the whole *** study investigated the effect of towing speed,warp length,warp tension,and catch size on the fluttering motions of Antarctic krill trawl codend during net shooting,towing,and hauling by using sea trial *** time-periodicity of codend oscillation was analyzed by the morlet wavelet transform *** indicated that the period of codend oscillation was between 50 s and 90 s and showed an increasing trend with the warp tension but a decreased value at the towing *** coefficient amplitude of codend oscillation was between 0 and 4 at the net shooting and hauling stages,and between 0.2 and 0.6 at the towing *** amplitude of codend oscillation increased with the warp tension,towing speed,and catch size,but decreased with the increase of the warp *** addition,the period of codend oscillation increased with the towing speed at the net shooting and hauling stages,but decreased at the towing *** results from codend fluttering motions can improve the understanding of fish behavior and gear shape that modify the hydrodynamic force on the codend instantaneously.

关键词： codend fluttering motions sea trials morlet wavelet periodicity

Periodical characteristics of baseflow in the source region of the Yangtze River

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Journal of Arid Land 2012年第2期4卷 113-122页

作者： KaiZhu QIAN Li WAN XuSheng WANG JingJing LV SiHai LIANG School of Water Resources and Environment China University of Geosciences(Beijing)Beijing 100083China

Baseflow, which represents the drainage of groundwater aquifers, is an essential component of runoff in hydrological basins. In the source region of the Yangtze River, the change of baseflow typically reflects the in- teractions between groundwater system and climatic factors in cold and arid areas. With modified Kalinen separa- tion method, annual baseflow between 1957 and 2009 in this region was estimated and calculated. In comparison with the inner-annual variations of total streamflow, baseflow showed a weaker fluctuation. Before the 1980s, it was in a steady state; and after then, it demonstrated dramatic variations and large amplitudes. Based on the calculation results of baseflow, the real morlet wavelet method was applied to reveal the periodical characteristics of baseflow as well as the precipitation and air temperature in the study area. It was found that annual baseflow has a 43-year trend as well as a 21-year period and a 7-year period. The 21-year period is most significant, with its wavelet coef- ficient having the largest fluctuation and amplitude. Summation of wavelet coefficients on these periods exhibits a similar change pattern with respect to that of annual baseflow. The summation curve takes a ＂W＂ shape, which means that the baseflow follows a four-stage sequence of descending-ascending-descending-ascending. As analyzed, the relationship among baseflow, precipitation and temperature is implied in the correlation between their normalized wavelet coefficients at different temporal scales. By the significant positive linear correlations both be- tween precipitation and baseflow （correlation coefficient is 0.98） and between temperature and baseflow （correla- tion coefficient is 0.90） for the 43-year wavelet coefficients, it is suggested that the long-term increasing trends of precipitation and air temperature will lead to an increasing trend of baseflow. For wavelet coefficients of 21-year and 7-year periods, the positive linear correlation between

关键词： baseflow climate Kalinen separation method morlet wavelet Yangtze River

Anovel multi-dimensional features fusion algorithm for the EEG signal recognition of brain’s sensorimotor region activated tasks

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International Journal of Intelligent Computing and Cybernetics 2020年第2期13卷 239-260页

作者： Minghua Wei Feng Lin Department of Information and Technology Fuzhou PolytechnicFuzhouChina

Purpose-Aiming at the shortcomings of EEG signals generated by brain’s sensorimotor region activated tasks,such as poor performance,low efficiency and weak robustness,this paper proposes an EEG signals classification method based on multi-dimensional fusion ***/methodology/approach-First,the improved morlet wavelet is used to extract the spectrum feature maps from EEG ***,the spatial-frequency features are extracted from the PSD maps by using the three-dimensional convolutional neural networks(3DCNNs)***,the spatial-frequency features are incorporated to the bidirectional gated recurrent units(Bi-GRUs)models to extract the spatial-frequencysequential multi-dimensional fusion features for recognition of brain’s sensorimotor region activated ***-In the comparative experiments,the data sets of motor imagery(MI)/action observation(AO)/action execution(AE)tasks are selected to test the classification performance and robustness of the proposed *** addition,the impact of extracted features on the sensorimotor region and the impact on the classification processing are also analyzed by visualization during ***/value-The experimental results show that the proposed algorithm extracts the corresponding brain activation features for different action related tasks,so as to achieve more stable classification performance in dealing with AO/MI/AE tasks,and has the best robustness on EEGsignals of different subjects.

关键词： Brain’s sensorimotor region activated tasks Brain-computer interface morlet wavelet 3DCNNs model Bi-GRUs model

Characteristics of the Nujiang River runoff for a long term and its response to climate change

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Science Bulletin 2007年第S2期 156-163页

作者： ZHANG WanCheng~(1+) XIAO ZiNiu~1 ZHENG JianMeng~2 REN JuZhang~2 1 Yunnan Institute of Meteorology,Kunming 650034,China 2 Yunnan Climate Center,Kunming 650034,China

The Nujiang River runoff increases obviously from May each year,and the runoff dominated 81.9% of the gross annual columns during the period from May to October,which is the rainy season over the *** the mean runoff accounts for 13.65% of the annual columns in each month during the rainy season but only 3% during the dry *** another word,the menstrual runoff in rainy season is as much as 4.5 times that in other *** shows that runoff varies greatly with season and the runoff in the rainy season takes the dominant role in annual *** analysis of the relationship between the river runoff and precipitation results in that the synchronous correlation coefficient is significant from January to April but the correlation with 1 month lag in the other months except in *** on the analyses of precipitation effecUng on the river runoff,it is noticed that the precipitation in May af- fects annual runoff greatly and has a close relationship to the dry *** annual,rainy season and dry season runoff and precipitation are analyzed by wavelet *** results show that the change of precipitation and runoff exhibits the dominant periods with low frequency fluctuation（about 2-4 years）,decadal（about 8 years）and interdecadal（about 16 years）*** change of the annual,rainy season and dry season runoff are consistent with an increased trend,which is evident with 0.05 confidence level except in June and *** data indicate that the average runoff is in- creased by 57.6,28.1 and 85.7 m3/s in every 10 years respectively for annual columns,dry season and rainy *** most obvious change is in October,which increased 111.3 m3/s every 10 *** variation of runoff,temperature and precipitation in Nujiang River drainage basin is primarily consis- *** is revealed that the climate change has resulted in the runoff change in *** is increased maximally in October,secondly in May and the increase amount of yearly runoff can a

关键词： precipitation of drainage area climatic variability monthly runoff morlet wavelet tendency runoff

The Quantitative Identification of Regional Mine and Natural Earthquakes and Its Application

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Earthquake Research in China 2005年第3期19卷 269-281页

作者： Liu Xiqiang Du Yihe Xu Bo Li Hong Shen Ping Zhang Ping Earthquake Administration of Shandong Province Jinan 250014 China Earthquake Administration of Jinan City Jinan 250001. China Institute of Geophysics China Earthquake Administration Beijing 100081 China Earthquake Administration of Liaoning Province Shenyang 100031 China

Based on the morlet wavelet transform and digital data from the Fushun and Beizhen seismic stations, Liaoning Province, we put forward a new method in the paper, called time-frequency energy attenuation factor （α-value）. The characteristics of the α-value and its variation with magnitude of natural and mine earthquakes are studied, and the statistic relations between the α-value and specific earthquake magnitude are obtained. From the results, some conclusions can be drawn as follows：（1） in general, the α-values of mine and natural earthquakes of the same intensity have obvious difference and the ranges of their variation do not overlap each other; （2） the α-value decreases with the increase of earthquake magnitude, and the α-value of mine earthquake decreases faster than that of natural earthquake; （3） based on the earthquake magnitude and on the relations between the α-value and earthquake magnitude, we can distinguish the mine earthquakes from the natural ones; （4） the difference in focal mechanism of mine and natural earthquakes would be the main cause for obvious difference of the α-value; （5） the α-value variation is relatively steady for mine and natural earthquakes that occur in the same region, but it has obvious regional difference. The above results are of inspirational meaning for the study of abnormal change of the α-value before strong earthquakes.

关键词： morlet wavelet Time-frequency energy attenuation factor The identification of mine and natural earthquakes Regional characteristics

Prediction of Tight Sand Reservoir with Multi-wavelet Decomposition and Reconstructing Method

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International Journal of Geosciences 2016年第4期7卷 529-538页

作者： Lifang Cheng Yanchun Wang Zhiguo Li Fuxiu Gong School of Geophysics and Information Technology China University of Geosciences Beijing China

Special reservoir or fluid has an abnormal response to some certain frequencies, so that seismic decomposition and reconstruction are used to highlight the seismic reflection at certain frequencies useful to identify special geological bodies. Because seismic wavelets are time-varying and spatial-variable in the propagation, synthetic traces based on single wavelet make some weak but useful information lost, and make artifacts form. However, morlet wavelet aggregation with mathematical analytical expression is able to fully and correctly reflect the variations of wavelet in the propagation of underground medium. The matching pursuit algorithm on the basis of morlet wavelet improves the calculating efficiency in decomposition and reconstruction greatly. This method is applied to the actual study area to do conjoint analysis of single well and well-tie multi-wavelet decomposition. It is found that frequencies sensitive to interest reservoirs range from 8 to 34 Hz. Reconstructing the wavelets at those special frequencies and analyzing the reconstructed seismic data, it is pointed out that interest reservoirs have abnormal characteristics with respectively strong RMS amplitude in the reconstructed data. Crossplot of gamma value at wells and reconstructed RMS amplitude suggests that anomalies caused by interest reservoirs are well separated from the background anomalies when the reconstructed RMS amplitude is greater than 3650. Quantitative prediction results of interest reservoirs distribution in the study area reveal that interest reservoirs of western and northern study area are distributed annularly and bandedly, while most contiguous sandstone in eastern regions appears sporadically.

关键词： morlet wavelet Matching Pursuit Decomposition and Reconstruction Tight Sandstone Reservoir Prediction