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probability distribution function of a Forced Passive Tracer in the Lower Stratosphere

Advances in Atmospheric Sciences 2007年第2期24卷 163-180页

作者：胡永云 Department of Atmospheric Sciences School of Physics Peking University

The probability distribution function （PDF） of a passive tracer, forced by a ＂mean gradient＂, is studied. First, we take two theoretical approaches, the Lagrangian and the conditional closure formalisms, to study the PDFs of such an externally forced passive tracer. Then, we carry out numerical simulations for an idealized random flow on a sphere and for European Center for Medium-Range Weather Forecasts （ECMWF） stratospheric winds to test whether the mean-gradient model can be applied to studying stratospheric tracer mixing in midlatitude surf zones, in which a weak and poleward zonal-mean gradient is maintained by tracer leakage through polar and tropical mixing barriers, and whether the PDFs of tracer fluctuations in midlatitudes are consistent with the theoretical predictions. The numerical simulations show that when diffusive dissipation is balanced by the mean-gradient forcing, the PDF in the random flow and the Southern-Hemisphere PDFs in ECMWF winds show time-invariant exponential tails, consistent with theoretical predictions. In the Northern Hemisphere, the PDFs exhibit non-Gaussian tails. However, the PDF tails are not consistent with theoretical expectations. The long-term behavior of the PDF tails of the forced tracer is compared to that of a decaying tracer. It is found that the PDF tails of the decaying tracer are time-dependent, and evolve toward flatter than exponential.

关键词： chaotic mixing probability distribution function stratosphere turbulence passive tracer

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probability distribution function inspired structural optimization for frequency response problems

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2017年 318卷 783-802页

作者： Seong, Hong Kyoung Yoo, Jeonghoon Yonsei Univ Grad Sch Mech Engn 50 Yonsei Ro Seoul 03722 South Korea Yonsei Univ Sch Mech Engn 50 Yonsei Ro Seoul 03722 South Korea

This study introduces an innovative topological optimization scheme for frequency response problems using the phase field design method. In the proposed approach, the frequency response function is mapped onto a probability distribution function where the mean value of the probability distribution function becomes the resonance frequency and the variance corresponds to its bandwidth. Using the mapping concept, the frequency characteristics such as the resonance frequency and bandwidth can be directly included in the formulation of the design objective function. Therefore, the mapping process enables to handle frequency characteristics in topological design for frequency response problems. As numerical examples, the resonance frequency maximization problem of a cantilever beam, bandwidth maximization of a clamped end beam and the bandwidth minimization problem of a plasmonic grating coupler are presented to demonstrate the validity of the proposed method. (C) 2017 Elsevier B.V. All rights reserved.

关键词： Topology optimization probability distribution function Frequency response problem Phase field design method

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probability distribution function FOR THE EUCLIDEAN DISTANCE BETWEEN TWO TELEGRAPH PROCESSES

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ADVANCES IN APPLIED probability 2014年第4期46卷 1172-1193页

作者： Kolesnik, Alexander D. Moldavian Acad Sci Inst Math & Comp Sci Kishinev 2028 Moldova

Consider two independent Goldstein-Kac telegraph processes X-1(t) and X-2(t) on the real line R. The processes X-k(t), k = 1, 2, describe stochastic motions at finite constant velocities c(1) > 0 and c(2) > 0 that start at the initial time instant t = 0 from the origin of R and are controlled by two independent homogeneous Poisson processes of rates lambda(1) > 0 and lambda(2) > 0, respectively. We obtain a closed-form expression for the probability distribution function of the Euclidean distance rho(t) = vertical bar X-1(t) - X-2(t)vertical bar, t > 0, between these processes at an arbitrary time instant t > 0. Some numerical results are also presented.

关键词： Telegraph process telegraph equation persistent random walk probability distribution function Euclidean distance

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probability distribution function of the order parameter: Mixing fields and universality

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COMPUTER PHYSICS COMMUNICATIONS 2013年第2期184卷 259-269页

作者： Plascak, J. A. Martins, P. H. L. Univ Fed Minas Gerais Dept Fis Inst Ciencias Exatas BR-30123970 Belo Horizonte MG Brazil Univ Georgia Ctr Simulat Phys Athens GA 30602 USA Univ Fed Mato Grosso Inst Fis Cuiaba MT Brazil

We briefly review the use of the order parameter probability distribution function as a useful tool to obtain the critical properties of statistical mechanical models using computer Monte Carlo simulations. Some simple discrete spin magnetic systems on a lattice, such as Ising, general spin-S Blume-Capel and Baxter-Wu, Q-state Potts, among other models, will be considered as examples. The importance and the necessity of the role of mixing fields in asymmetric magnetic models will be discussed in more detail, as well as the corresponding distributions of the extensive conjugate variables. (C) 2012 Elsevier B.V. All rights reserved.

关键词： Multicritical points probability distribution function Monte Carlo simulations Mixing fields

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probability distribution function OF NEAR-WALL TURBULENT VELOCITY FLUCTUATIONS

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Applied Mathematics and Mechanics(English Edition) 2005年第10期26卷 1245-1254页

作者：周济福张强李家春 Institute of Mechanics Chinese Academy of Sciences Beijing 100080 P.R.China

By large eddy simulation （LES）, turbulent databases of channel flows at different Reynolds numbers were established. Then, the probability distribution functions of the streamwise and wall-normal velocity fluctuations were obtained and compared with the corresponding normal distributions. By hypothesis test, the deviation from the normal distribution was analyzed quantitatively. The skewness and flatness factors were also calculated. And the variations of these two factors in the viscous sublayer, buffer layer and log-law layer were discussed. Still illustrated were the relations between the probability distribution functions and the burst events-sweep of high-speed fluids and ejection of low-speed fluidsIin the viscous sub-layer, buffer layer and loglaw layer. Finally the variations of the probability distribution functions with Reynolds number were examined.

关键词： near-wall turbulence large eddy simulation velocity fluctuation probability distribution function skewness flatness

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probability distribution function-based classification of structural MRI for the detection of Alzheimer's disease

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COMPUTERS IN BIOLOGY AND MEDICINE 2015年 64卷 208-216页

作者： Beheshti, I. Demirel, H. Eastern Mediterranean Univ Dept Elect & Elect Engn Biomed Image Proc Lab TR-10 Gazimagusa Mersin Turkey

High-dimensional classification methods have been a major target of machine learning for the automatic classification of patients who suffer from Alzheimer's disease (AD). One major issue of automatic classification is the feature-selection method from high-dimensional data. In this paper, a novel approach for statistical feature reduction and selection in high-dimensional magnetic resonance imaging (MM) data based on the probability distribution function (PDF) is introduced. To develop an automatic computer-aided diagnosis (CAD) technique, this research explores the statistical patterns extracted from structural MRI (sMRI) data on four systematic levels. First, global and local differences of gray matter in patients with AD compared to healthy controls (HCs) using the voxel-based morphometric (VBM) technique with 3-Tesla 3D T1-weighted MRI are investigated. Second, feature extraction based on the voxel clusters detected by VBM on sMRI and voxel values as volume of interest (VOI) is used. Third, a novel statistical feature-selection process is employed, utilizing the PDF of the VOI to represent statistical patterns of the respective high-dimensional sMRI sample. Finally, the proposed feature-selection method for early detection of AD with support vector machine (SVM) classifiers compared to other standard feature selection methods, such as partial least squares (PLS) techniques, is assessed. The performance of the proposed technique is evaluated using 130 AD and 130 HC MRI data from the ADNI dataset with 10-fold cross validationl. The results show that the PDF-based feature selection approach is a reliable technique that is highly competitive with respect to the state-of-the-art techniques in classifying AD from high-dimensional sMRI samples. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Alzheimer's disease Voxel-based morphometry probability distribution function Structural MRI Statistical feature extraction Computer-aided diagnosis Classification Fisher criterion

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probability distribution function based Iris Recognition Boosted by The Mean Rule

Probability Distribution Function based Iris Recognition Boo...

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International Conference on Intelligent Computing and Internet of Things

作者： Pjatkin, Kert Daneshmand, Morteza Rasti, Pejman Anbarjafari, Gholamreza Univ Tartu Inst Technol IMS Lab iCV Grp Nooruse 1 EE-50411 Tartu Estonia

ISBN: (纸本)9781479975341

In this work, a new iris recognition algorithm based on tonal distribution of iris images is introduced. During the process of identification probability distribution functions of colored irises are generated in HSI and YCbCr color spaces. The discrimination between classes is obtained by using Kullback-Leibler divergence. In order to obtain the final decision on recognition, the multi decision on various color channels has been combined by employing mean rule. The decisions of H, S, Y, Cb and Cr color channels have been combined. The proposed technique overcome the conventional principle component analysis technique and achieved a recognition rate of 100% using the UPOL database. The major advantage is the fact that it is computationally less complex than the Daugman's algorithm and it is suitable for using visible light camera as opposed to the one proposed by Daugman where NIR cameras are used for obtaining the irises.

关键词： probability distribution function Kullback-Leibler divergence Iris recognition Classification Mean rule

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Rupture of single receptor-ligand bonds: A new insight into probability distribution function

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COLLOIDS AND SURFACES B-BIOINTERFACES 2013年 101卷 501-509页

作者： Gupta, V. K. Univ Maryland Baltimore Cty Baltimore MD 21250 USA

Single molecule force spectroscopy is widely used to determine kinetic parameters of dissociation by analyzing bond rupture data obtained via applying mechanical force to cells, capsules, and beads that are attached to an intermolecular bond. The current analysis assumes that the intermolecular bond force is equal to the externally applied mechanical force. We confirm that viscous drag alone or in combination with cellular deformation resulting in viscoelasticity modulates bond force so that the instantaneous intermolecular bond force is not equivalent to the applied force. The bond force modulation leads to bond rupture time and force histograms that differ from those predicted by probability distribution function (PDF) using the current approach. A new methodology that accounts for bond force modulation in obtaining PDF is presented. The predicted histograms from the new methodology are in excellent agreement with the respective histograms obtained from Monte Carlo simulation. (C) 2012 Elsevier B.V. All rights reserved.

关键词： Cellular adhesion Cellular deformation Bond force modulation probability distribution function Kinetic off-rate

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Variations in the probability distribution function of air temperature anomalies in winter and summer from 1961 to 2016 over China

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INTERNATIONAL JOURNAL OF CLIMATOLOGY 2022年第9期42卷 4740-4752页

作者： Wu, Guocan Tian, Yuan Gong, Fang Du, Jizeng Shi, Chunming Beijing Normal Univ Coll Global Change & Earth Syst Sci State Key Lab Earth Surface Proc & Resource Ecol Beijing Peoples R China CPC Qingdao West Coast New Area Working Comm Mil Qingdao Peoples R China Beijing Normal Univ Sch Environm Beijing Peoples R China

The rising of near-surface air temperature is the most obvious manifestation of global warming. The analysis of the probability distribution function (PDF) of temperature can deep our understanding of the current characteristics of climate and extreme temperature changes. In this study, the daily maximum, minimum and mean temperature observations from meteorological stations are analysed to construct the temperature anomaly PDF during 1961-2016 over China. The skewness and kurtosis of the PDF are compared between the 1961-1990 and 1991-2016 periods. The non-Gaussian tails of the PDF are also identified to qualify the deviation of the temperature probability density curve. The results show that near-surface air temperature in China increased during the recent decades. The daily minimum temperature increased more than the daily maximum temperature did, while the temperature increase in winter was larger than that in summer. The largest increase detected was 1.29 degrees C for the daily minimum temperature in winter, contrasting with the smallest increase of 0.51 degrees C recorded for the daily minimum temperature in summer between the two study periods. The temperature anomaly PDF generally presented a positive skewness in winter and a slightly negative skewness in summer. Obvious non-Gaussian tails in the temperature anomaly PDF were present in the majority of the study sites. Most areas showed a short cold tail in winter (except for southwestern China), and long cold tails were mainly observed in summer. These results can improve our understanding of the variation of extreme temperatures, and of the responses to global warming.

关键词： kurtosis near-surface air temperature normal distribution probability distribution function skewness

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Dynamical probability distribution function of the SK model at high temperatures

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JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 1996年第1期65卷 3-6页

作者： Nishimori, H Yamana, M Department of Physics Tokyo Institute of Technology Oh-okayama Meguro-ku Tokyo 152

The microscopic probability distribution function of the Sherrington-Kirkpatrick (SK) model of spin glasses is calculated explicitly as a function of time by a high-temperature expansion. The resulting formula to the third order of the inverse temperature shows that an assumption made by Coolen, Laughton and Sherrington in their recent theory of dynamics is violated. Deviations of their theory from exact results are estimated quantitatively. Our formula also yields explicit expressions of the time dependence of various macroscopic physical quantities when the temperature is suddenly changed within the high-temperature region.

关键词： SK model dynamics high-temperature expansion probability distribution function equipartitioning

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