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Journal of Hydrodynamics 1996年第1期8卷 67-75页

作者： Ren, Bing ni, Hangen Dalian Univ of Technology Dalian China

For any type of 2-dimensional flowing field, this paper has developed a very effective numerical technique in generating orthogonal computation grids, which shows a wide promise especially for microscale arbitrary shapes concerned. In simulating high speed flowing, it has been verified that Dynamic SGS model is a reliable tool available to engineers, especially in predicting inhomogeneous turbulence nowing. On the basis of physical and numerical methods, this paper has presented, respectively, experimental expression and numerical results for incipient cavitation number. For velocity no more than 15m/s, it was verified that the value of incipient cavitation number from the two different sources approximately coincided with each other.

关键词： numerical simulations turbulence model incipient cavitation

Super-biderivations on twisted N=1 Schrodinger-Neveu-Schwarz algebra

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Frontiers of Mathematics in China 2019年第5期14卷 907-922页

作者： Zhenyuan ni Jiancai SUN Department of Mathematics Shanghai UniversityShanghai 200444China

Let tsns^~ denote the twisted N=1 Schrodinger-Neveu-Schwarz algebra over the complex field *** this paper,we determine the superskewsymmetric super-biderivations of tsns^~.Furthermore,we prove that every super-skewsym... 详细信息

关键词： Lie super-algebra super-biderivation super-skewsymmetric

Molecular dynamics simulation for aggregation phenomena of nanocolloids

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Science China(Technological Sciences) 2009年第2期52卷 484-490页

作者： ni ZhongHua ZHANG XinJie School of Mechanical Engineering Southeast UniversityNanjing 210096China

Nonequilibrium molecular dynamics (MD) method was used to study the dielectrophoresis (DEP) motion of nanocolloids in non-uniform electric field. By changing the electric field strength and system temperature, aggregation phenomena of nanocolloids was analyzed. Simulation results showed that at normal temperature, though the Brownian force can affect the motion of colloids, the attractive force will increase quickly with the distance between colloids down to 12σ , which makes colloids aggregate. When the Brownian force is weak to colloid's motion, for the enhancement of electric field strength, the DEP force of colloid will increase and so did the attractive force, which finally quickens the aggregate speed. Simulation results also showed that the temperature' enhancement will increase the Brownian force of colloids, hence disturbing the colloids aggregation. Moreover, the DLVO theory was used to study the motion of a pair of interactional colloids, both the potential energy and the attractive force versus distance of colloids were presented, then the latter graph was used to compare with another graph elicited by MD method. Results showed that the two graphs were nearly the same, indicating the MD model accorded with the theory.

关键词： MD DEP nanocolloid aggregation DLVO theory

Continuous-time Distributed Heavy-ball Algorithm for Distributed Convex Optimization over Undirected and Directed Graphs

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Machine Intelligence Research 2022年第1期19卷 75-88页

作者： Hao-Ran Yang Wei ni School of Science Nanchang UniversityNanchang 330031China

This paper proposes second-order distributed algorithms over multi-agent networks to solve the convex optimization problem by utilizing the gradient tracking strategy, with convergence acceleration being achieved. Both the undirected and unbalanced directed graphs are considered, extending existing algorithms that primarily focus on undirected or balanced directed graphs. Our algorithms also have the advantage of abandoning the diminishing step-size strategy so that slow convergence can be avoided. Furthermore, the exact convergence to the optimal solution can be realized even under the constant step size adopted in this paper. Finally, two numerical examples are presented to show the convergence performance of our algorithms.

关键词： Distributed convex optimization second-order distributed algorithm multi-agent systems gradient tracking directed graph

Aubry-Mather theory for contact Hamiltonian systems Ⅲ

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Science China Mathematics 2024年第11期67卷 2541-2570页

作者： Panrui ni Lin Wang Shanghai Center for Mathematical Sciences Fudan UniversityShanghai 200433China School of Mathematics and Statistics Beijing Institute of TechnologyBeijing 100081China

By exploiting the contact Hamiltonian dynamics(T*M×R,Φ_(t))around the Aubry set of contact Hamiltonian systems,we provide a relation among the Mather set,theΦ_(t)-recurrent set,the strongly static set,the Aubry set,the Ma?éset,and theΦ_(t)-non-wandering ***,we consider the strongly static set,as a new flow-invariant set between the Mather set and the Aubry set in the strictly increasing *** show that this set plays an essential role in the representation of certain minimal forward weak Kolmogorov-Arnold-Moser(KAM)solutions and the existence of transitive orbits around the Aubry set.

关键词： Aubry-Mather theory weak KAM theory contact Hamiltonian systems Hamilton-Jacobi equations

A DIRECT SEARCH FRAME-BASED ADAPTIVE BARZILAI-BORWEIN METHOD

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Journal of Computational Mathematics 2015年第2期33卷 179-190页

作者： Xiaowei Fang Qin ni College of Sciences Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Department of Mathematics Huzhou University Huzhou 313000 China

This paper proposes a direct search frame-based adaptive Barzilai-Borwein method for unconstrained minimization. The method is based on the framework of frame-based algorithms proposed by Coope and Price, but we use the strategy of ABB method and the rotational minimal positive basis to reduce the computation work at each iteration. Under some mild assumptions, the convergence of this approach will be established. Through five hundreds and twenty numerical tests using the CUTEr test problem library, we show that the proposed method is promising.

关键词： Direct search Rotational minimal positive basis Adaptive Barzilai-Borweinmethod.

A new cellular automaton model accounting for stochasticity in traffic flow induced by heterogeneity in driving behavior

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Chinese Physics B 2019年第9期28卷 399-409页

作者： Xiaoyong ni Hong Huang Institute of Public Safety Research Department of Engineering PhysicsTsinghua UniversityBeijing 100084China Beijing Key Laboratory of City Integrated Emergency Response Science Tsinghua UniversityBeijing 100084China

A new reliable cellular automaon(CA) model designed to account for stochasticity in traffic flow induced by heterogeneity in driving behavior is *** proposed model differs from most existing CA models in that this new model focuses on describing traffic phenomena by coding into its rules the key idea that a vehicle's moving state is directly determined by a driver stepping on the accelerator or on the brake(the vehicle's acceleration).Acceleration obeys a deformed continuous distribution function when considering the heterogeneity in driving behavior and the safe distance, rather than equaling a fixed acceleration value with a probability, as is the rule in many existing CA *** results show that the new proposed model is capable of reproducing empirical findings in real traffic ***, this new model makes it possible to implement in-depth analysis of correlations between a vehicle's state parameters.

关键词： cellular automaton numerical simulations traffic models

Sediment-copper distributions in hyper-concentrated turbulent solid-liquid system

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Journal of Environmental Sciences 2007年第1期19卷 123-127页

作者： YANG Jun ni Jin-ren Department of Environmental Engineering Beihang University Beijing 100083 China College of Environmental Sciences Peking University Key Laboratory for Water and Sediment Sciences Ministry of Education Beijing 100871 China

This study presents a special problem on vertical distribution for sediment and copper in hyper-concentrated turbulent solid-liquid system that is essentially different from the ordinary low-concentrated turbulent system. A resonance type turbulent simulation equipment is used for the experimental study in which a vertically uniform turbulent field of the mixture of loess and water is produced in a testing cylinder with a grille stirrer that moves up and down harmoniously with varying vibration frequencies, in order to compare the variations of the vertical profiles of sediment and copper in low- and hyper-concentratod solid-liquid system, different scenarios for input sediment content ranging from 5 to 800 kg/m^3 was considered in the experimental studies. It was found that solids copper content increases with input sediment content, So, and reaches its peak as So goes to 10 kg/m^3 and then decreases rapidly with increasing input sediment content. Such a behavior is possibly resulted from the joint effect of the specific adsorption of copper on loess, precipitation of carbonate and hydroxide of copper due to high carbonate content in the loess and the so-called ＂particulate concentration effect＂ due to the present of the sediment variation in water. The vertical sediment concentration distribution resulted from the uniform turbulence is generally uniform, but slight non-uniformity does occur as sediment concentration exceeds certain value. However, the vertical concentration distributions of soluble copper seem not to be affected much by the variation of sediment concentrations.

关键词： hyper-concentrated system loess copper vertical sediment distribution

Stronger Versions of Sensitivity for Minimal Group Actions

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Acta Mathematica Sinica,English Series 2021年第12期37卷 1933-1946页

作者： Jian LI Yi ni YANG Department of Mathematics Shantou UniversityShantou 515063P.R.China

We study several stronger versions of sensitivity for minimal group actions,including nsensitivity,thick n-sensitivity and blockily thick n-sensitivity,and characterize them by the regionally proximal relation.

关键词： Sensitivity minimal group actions maximal equicontinuous factors regionally proximal relation

Formaldehyde intermediate participating in the conversion of methanol to aromatics over zinc modified H-ZSM-5

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Journal of Energy Chemistry 2021年第3期30卷 174-178页

作者： Youming ni Wenliang Zhu Zhongmin Liu National Engineering Laboratory for Methanol to Olefins Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023LiaoningChina Dalian National Laboratory for Clean Energy Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023LiaoningChina

Metal-modified H-ZSM-5 has a high selectivity of aromatics in methanol to aromatics(MTA)reaction,which is often attributed to the metal promoting the aromatization of intermediate ***,the effect of methanol dehydrogenation on aromatics formation over these catalysts is rarely ***,we report that HCHO,which is formed by methanol dehydrogenation over Zn/H-ZSM-5 prepared by Zn impregnation,can participate in the synthesis of *** conversion can produce more aromatics than olefins(propylene or ethylene)conversion over Zn/H-ZSM-5,indicating the conventional MTA pathway including methanol-to-olefins and olefins-to-aromatics is not ***,an MTA mechanism including the conventional pathway and the methanol and HCHO coupling pathway is systematically proposed.

关键词： Methanol Formaldehyde Aromatics Zn H-ZSM-5