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moment inequalities and weak convergence for negatively associated sequences

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Science China Mathematics 1997年第2期40卷 172-182页

作者：苏淳赵林城王岳宝 Department of Statistics and Finance University of Science and Technology of China Hefei 230026 China Department of Mathematics Zhanjiang Normal Institute Zhanjiang 524048 China

A probability inequality for Sn and some pth moment (p≥2) inequalities for | Sn| and max 1≤k≤n |Sk|are established. Here Sn is the partial sum of a negatively associated sequence Based on these inequalities, a weak in variance principle for strictly stationary negatively associated sequences is proved under some general conditions

关键词： NA (negatively associated) sequences partial sums maximum partial sums moment inequalities weak invariance principle.

Estimating moment capacity of ferrocement members using self-evolving network

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Frontiers of Structural and Civil Engineering 2019年第4期13卷 926-936页

作者： Abdussamad ISMAIL Department of Civil Engineering Bayero University Kano Kano State PMB 3011 Nigeria

In this paper, an empirical model based on self-evolving neural network is proposed for predicting the flexural behavior of ferrocement elements. The model is meant to serve as a simple but reliable tool for estimating the moment capacity of ferrocement members. The proposed model is trained and validated using experimental data obtained from the literature. The data consists of information regarding flexural tests on ferrocement specimens which include moment capacity and cross-sectional dimensions of specimens, concrete cube compressive strength, tensile strength and volume fraction of wire mesh. Comparisons of predictions of the proposed models with experimental data indicated that the models are capable of accurately estimating the moment capacity of ferrocement members. The proposed models also make better predictions compared to methods such as the plastic analysis method and the mechanism approach. Further comparisons with other data mining techniques including the back-propagation network, the adaptive spline, and the Kriging regression models indicated that the proposed models are superior in terms prediction accuracy despite being much simpler models. The performance of the proposed models was also found to be comparable to the GEP-based surrogate model.

关键词： ferrocement moment capacity self-evolving neural network

Quadrature-based moment methods for the population balance equation: An algorithm review

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Chinese Journal of Chemical Engineering 2019年第3期27卷 483-500页

作者： Dongyue Li Zhipeng Li Zhengming Gao State Key Laboratory of Chemical Resource Engineering School of Chemical Engineering Beijing University of Chemical Technology State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing

The dispersed phase in multiphase flows can be modeled by the population balance model(PBM). A typical population balance equation(PBE) contains terms for spatial transport, loss/growth and breakage/coalescence source terms. The equation is therefore quite complex and difficult to solve analytically or numerically. The quadrature-based moment methods(QBMMs) are a class of methods that solve the PBE by converting the transport equation of the number density function(NDF) into moment transport equations. The unknown source terms are closed by numerical quadrature. Over the years, many QBMMs have been developed for different problems, such as the quadrature method of moments(QMOM), direct quadrature method of moments(DQMOM),extended quadrature method of moments(EQMOM), conditional quadrature method of moments(CQMOM),extended conditional quadrature method of moments(ECQMOM) and hyperbolic quadrature method of moments(Hy QMOM). In this paper, we present a comprehensive algorithm review of these QBMMs. The mathematical equations for spatially homogeneous systems with first-order point processes and second-order point processes are derived in detail. The algorithms are further extended to the inhomogeneous system for multiphase flows, in which the computational fluid dynamics(CFD) can be coupled with the PBE. The physical limitations and the challenging numerical problems of these QBMMs are discussed. Possible solutions are also summarized.

关键词： Population balance equation Quadrature-based moment method Multiphase flow Computational fluid dynamics

Validity of extracting photoionization time delay from the first moment of streaking spectrogram

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Chinese Physics B 2019年第1期28卷 330-339页

作者： Chang-Li Wei Xi Zhao School of Physics and Electronics Qiannan Normal College for Nationalities Department of Physics Kansas State University

Photoionization time delays have been studied in many streaking experiments in which an attosecond pulse is used to ionize the atomic or solid state target in the presence of a dressing infrared laser field. Among the methods of extracting the time delay from the streaking spectrogram, the simplest one is to calculate the first moment of the spectrogram and to measure its offset relative to the vector potential of the infrared field. The first moment method has been used in many theoretical simulations and analysis of experimental data, but the meaning of this offset needs to be investigated. We simulate the spectrograms and compare the extracted time delay from the first moment with the input Wigner delay. In this study, we show that the first moment method is valid only when the group delay dispersions corresponding to both the spectral phase of the attosecond pulse and the phase of the single-photon transition dipole matrix element of the target are small. Under such circumstance, the electron wave packet behaves like a classical particle and the extracted time delay can be related to a group delay in the photoionization process. To avoid ambiguity and confusion, we also suggest that the photoionization time delay be replaced by photoionization group delay and the Wigner time delay be replaced by Wigner group delay.

关键词： photoionization time delay strong laser field attosecond science first moment

Torque and bending moment acting on a flexible shaft agitated by disk turbines in a gas–liquid stirred vessel

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Chinese Journal of Chemical Engineering 2019年第4期27卷 781-793页

作者： Yangyang Liang Zhengming Gao Dai'en Shi Haotian Li Yuyun Bao Ziqi Cai State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical Technology Beijing 100029 China Mechanical Engineering School Yancheng Institute of Technology Yancheng 224051 China

The torque and bending moment acting on a flexible overhung shaft in a gas–liquid stirred vessel agitated by a Rushton turbine and three different curved-blade disk turbines(half circular blades disk turbine, half elliptical blades disk turbine, and parabolic blades disk turbine) were experimentally measured by a customized moment sensor. The results show that the amplitude distribution of torque can be fitted by a symmetric bimodal distribution for disk turbines, and generally the distribution is more dispersive as the blade curvature or the gas flow rate increases. The amplitude distribution of shaft bending moment can be fitted by an asymmetric Weibull distribution for disk turbines. The relative shaft bending moment manifests a "rising-falling-rising" trend over the gas flow number, which is a corporate contribution of the unstable gas–liquid flow around the impeller, the gas cavities behind the blades, and the direct impact of gas on the impeller. And the "falling" stage is greater and lasts wider over the gas flow number for Rushton turbine than for the curved-blade disk turbines.

关键词： Shaft bending moment Torque Disk turbines Gas–liquid flow Fluid structure interaction

Development and application of moment method on nanoparticles evolution due to coagulation and deposition

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Journal of Hydrodynamics 2019年第5期31卷 1011-1020页

作者： Guang-ping Xu Jia-song Wang School of Naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China

In this study,the Taylor-series expansion method of moments is developed to describe the dynamic behaviour of nanoparticles considering both the effects of coagulation and deposition in closed environments,where the two effects have always been studied separately *** with traditional methods of moments,the new method could give more accurate results for solving the general dynamics *** addition,moment equations with respect to coagulation and deposition considering the fractal dimension(Df)of particles are acquired,and the results are compared with experimental data and are more accurate than the simulation results under the assumption of spherical *** new dynamic model could be applied in more real conditions with different microstructures of *** decreasing Dt,the particle number concentration decreases more rapidly,additionally,Df has a relatively greater effect on the agglomeration of smaller particles under the same initial ***,the effect of the initial number concentration on coagulation is also *** results show that a higher initial number concentration or a smaller particle size could have a greater effect of coagulation on the evolution of particles.

关键词： moment method nanoparticle deposition coagulation fractal dimension

Analysis on Origin of Oscillation of H moment in High-Energy hh Collision

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Chinese Physics Letters 2000年第11期17卷 792-794页

作者： WU Tao ZHOU Dai-Cui Institute of Particle Physics Huazhong Normal UniversityWuhan 430079

Multiplicity distributions of negative binomial distribution(NBD)and modified NBD are obtained from a birth process model with an *** ratio of factorial cumulant moment to factorial moment,i.e.,H moment is calculated from different multiplicity distributions of NBD,modified NBD and the three fireball model,which shows an oscillatory behavior when there is a truncation of *** oscillation of H moment is related to the common character of the truncated multiplicity distributions.

关键词： multiplicity moment factorial

Formulation of moment Analysis on fJ(1710) for Incomplete Phase Space in J/ψ → γK^(+)K^(-)

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Chinese Physics Letters 2001年第3期18卷 358-360页

作者： CHEN Jie LI Xue-Qian LU Yong ZOU Bing-Song CCAST(World Laboratory) P.O.Box 8730Beijing 100080 Department of Physics Nankai UniversityTianjin 300071 Institute of High Energy Physics Chinese Academy of SciencesBeijing 100039 Institute of Theoretical Physics Chinese Academy of SciencesBeijing 100080

We discuss the moment analysis method for the 0^(++)and 2^(++)coupling mode of fJ(1710)for incomplete phase space in the radiative decay J/ψ→γK^(+)K^(-),and give a new formulation of analyzing the fJ(1710)structure for the Beijing Spectrometer detector at the Beijing Electron-Positron *** incomplete detection phase space results in a significant effect on the moment analysis.

关键词： incomplete (1) moment

Identification of ultra-high-frequency PD signals in gas-insulated switchgear based on moment features considering electromagnetic mode

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High Voltage 2020年第6期5卷 688-696页

作者： Feng Bin Feng Wang Qiuqin Sun She Chen Jingmin Fan Huisheng Ye College of Electrical and Information Engineering Hunan UniversityChangsha 410082People's Republic of China College of Electronic and Information Engineering Yili Normal UniversityYili 835000People's Republic of China School of Automation Guangdong University of TechnologyGuangzhou 510012People's Republic of China Equipment Condition Assessment Center Hunan Electric Power Research InstituteChangsha 410000People's Republic of China

The feature extraction and pattern recognition techniques are of great importance to assess the insulation condition of gas-insulated *** this work,the ultra-high-frequency partial discharge(PD)signals generated from four types of typical insulation defects are analysed using S-transform,and the greyscale image in time-frequency representation is divided into five regions according to the cutoff frequencies of TEm1 ***,the three low-order moments of every subregion are extracted and the feature selection is performed based on the J *** confirm the effectiveness of selected moment features after considering the electromagnetic modes,the support vector machine,k-nearest neighbour and particle swarm-optimised extreme learning machine(ELM)are utilised to classify the type of PD,and they achieve the recognition accuracies of 92,88.5 and 95%,*** addition,the results show that the ELM offers good generalisation performance at the fastest learning and testing speeds,thus more suitable for a real-time PD detection.

关键词： insulation moment features