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Multifractal Characteristics of Intermittent Turbulence in the Urban Canopy Layer

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Atmospheric and Oceanic Science Letters 2015年第2期8卷 72-77页

作者： XU Jing-Jing HU Fei International Center for Climate and Environment Science (ICCES) Institute of Atmospheric Physics Chinese Academy of Science State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC) Institute of Atmospheric Physics Chinese Academy of Sciences

The multifractality of energy and thermal dissipation of fully developed intermittent turbulence is investigated in the urban canopy layer under unstable conditions by the singularity spectrum for the fractal dimensions of sets of singularities characterizing multifractals. In order to obtain high-order moment properties of smallscale turbulent dissipation in the inertial range, an ultrasonic anemometer with a high sampling frequency of 100 Hz was used. The authors found that the turbulent signal could be singular everywhere. Moreover, the singular exponents of energy and thermal dissipation rates are most frequently encountered at around 0.2, which is significantly smaller than the singular exponents for a wind tunnel at a moderate Reynolds number. The evidence indicates a higher intermittency of turbulence in the urban canopy layer at a high Reynolds number, which is demonstrated by the data with high temporal resolution. Furthermore, the temperature field is more intermittent than the velocity field. In addition, a large amount of samples could be used for verification of the results.

关键词： urban canopy layer intermittent turbulence turbulent dissipation multifractality singularity spectrum

Complexity and characteristic frequency studies in ECG signals of mice based on multiple scale factors

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Science China(Life Sciences) 2011年第6期54卷 544-552页

作者： YANG XiaoDong HE AiJun LIU Peng SUN TongFeng NING XinBao School of Computer Science and Technology China University of Mining and TechnologyXuzhou 221116China School of Electronic Science and Engineering Institute for Biomedical Electronic EngineeringNanjing UniversityNanjing 210093China

Existing methods of physiological signal analysis based on nonlinear dynamic theories only examine the complexity difference of the signals under a single sampling *** developed a technique to measure the multifractal characteristic parameter intimately associated with physiological activities through a frequency scale *** parameter is highly sensitive to physiological and pathological *** received various drugs to imitate different physiological and pathological conditions,and the distributions of mass exponent spectrum curvature with scale factors from the electrocardiogram (ECG) signals of healthy and drug injected mice were ***,we determined the characteristic frequency scope in which the signal was of the highest complexity and most sensitive to impaired cardiac function,and examined the relationships between heart rate,heartbeat dynamic complexity,and sensitive frequency scope of the ECG *** found that all animals exhibited a scale factor range in which the absolute magnitudes of ECG mass exponent spectrum curvature achieve the maximum,and this range (or frequency scope) is not changed with calculated data points or maximal coarse-grained scale ***,the heart rate of mice was not necessarily associated with the nonlinear complexity of cardiac dynamics,but closely related to the most sensitive ECG frequency scope determined by characterization of this complex dynamic features for certain heartbeat ***,we found that the health status of the hearts of mice was directly related to the heartbeat dynamic complexity,both of which were positively correlated within the scale factor around the extremum region of the multifractal *** increasing heart rate,the sensitive frequency scope increased to a relatively high *** conclusion,these data provide important theoretical and practical data for the early diagnosis of cardiac disorders.

关键词： ECG multifractality complexity frequency scale factor characteristic frequency

Multi-Fractal Analysis of Daily Air Temperature Time Series in Coastal Areas of China

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Journal of Tropical Meteorology 2020年第3期26卷 348-362页

作者： LI Zhong-liang HE Guang-xin SHEN Wei-shou ZHEN Xiao-ju HAN Jing College of Geographic Sciences Nanjing University of Information Science and TechnologyNanjing 210044 China Nanjing Institute of Environmental Science Ministry of Environmental ProtectionNanjing 210044 China Key Laboratory of Meteorological Disaster Ministry of Education(KLME)/International Joint Research Laboratory on Climate and Environment Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological DisastersNanjing University of Information Science and TechnologyNanjing 210044 China Key Laboratory of Meteorology and Ecological Environment of Hebei Province Shijiazhuang 050021 China Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province Haikou 570203 China

In this article,the Multi-Fractal Detrended Fluctuation Analysis(MF-DFA)method is adopted to study the temperature,i.e.,the maximum temperature(Tmax),mean temperature(Tavg)and minimum(Tmin)air temperature,multifractal characteristics and their formation mechanism,in the typical temperature zones in the coastal regions in Guangdong,Jiangsu and Liaoning *** are some terms and concepts used in the present *** is defined as a term that characterizes the complexity and self-similarity of objects,and fractal characteristics depict the distribution of probability over the whole set caused by different local conditions or different levels in the process of *** strength denotes the fluctuation range of the data set,and long-range correlation(LRC)measures the stability of the climate system and the trend of climate change in the *** this research,it is found that the internal stability and feedback mechanism of climate systems in different regions show regional ***,the research also proves that the Tavg,Tmaxand Tminof the above three provinces are highly *** temperature series multifractality of each province decreases in the order of temperature series multifractality of Liaoning>temperature series multifractality of Guangdong>temperature series multifractality of Jiangsu,and the corresponding long-range correlations follow the same *** reveals that the most stable temperature series is that of Liaoning,followed by the temperature series of Guangdong,and the most unstable one is that of *** has the most stable climate system,and it will thus be less responsive to the future climate *** stability of the climate system in Jiangsu is the weakest,and its temperature fluctuation will continue to increase in the future,which will probably result in the meteorological disasters of high temperature and heat wave *** possesses the strongest degree of multifr

关键词： daily temperature multifractality multifractal strength long-range correlation

A Study of Multifractal Analysis in <sup>16</sup>O-AgBr Collisions at 60A and 200A GeV

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Journal of Modern Physics 2018年第5期9卷 1039-1036页

作者： Nazeer Ahmad Tufail Ahmad Omveer Singh Shakeel Ahmad Department of Physics Aligarh Muslim University Aligarh India

A multifractal analysis to study the multiparticle dynamics in 60A and 200A GeV, 16O-AgBr collisions has been performed in the pseudorapidity phase space. Multifractal moments, Gq, as the function of pseudorapidity bin size for different order of the moments, q, have been calculated. The power-law behaviour has been observed in the considered data sets. The variations of multifractal dimension, Dq, and the multifractal spectral function, f(aq), with order of the moments, q, have been studied thoroughly. Dq is found to decrease with increasing order of moments, q, indicating thereby a self-similar behaviour in the multiparticle production for the considered collisions. We have also found a concave downward curve of multifractal spectral function with maximum at q = 0.

关键词： multifractality Pseudorapidity Fluctuation Generalized Dimension Scaling

A Study of Multifractal Spectra and Renyi Dimensions in 14.5A GeV/c <sup>28</sup>Si-Nucleus Collisions

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Journal of Modern Physics 2014年第14期5卷 1288-1293页

作者： N. Ahmad A. Kamal M. M. Khan Hushnud A. Tufail Applied Science Section University Polytechnic Aligarh Muslim University Aligarh India Department of Applied Physics Aligarh Muslim University Aligarh India Department of Basic Science Deanship of Prepratory Year Umme Al-Qura University Makkah KSA Department of Physics Aligarh Muslim University Aligarh India

A systematic analysis of the data on 14.5A GeV/c 28Si-nucleus collisions is carried out to investigate the behaviours of Renyi dimensions, Dq and Multifractal Spectral Function, f(αq). The Renyi dimensions, Dq are observed to decrease with increasing order of the moments, q. However, the Multifractal Spectra are concave downwards with their maxima occurring around αq =1.21±0.01. A continuous curve representing Multifractal Spectral Function, f(αq), characterizes manifestation of fluctuations in the rapidity space.

关键词： Nucleus-Nucleus Cillisions multifractality and Non-Statistical Fluctuatuons