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Unified stability condition for particulate and aggregative fluidization—Exploring energy dissipation with direct numerical simulation

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Particuology 2013年第2期11卷 232-241页

作者： Min Wei Limin Wang Jinghai Li The EMMS Group State Key Laboratory of Multiphase Complex SystemsInstitute of Process EngineeringChinese Academy of Sciences University of Chinese Academy of Sciences

Fully resolved simulations of particulate and aggregative fluidization systems are performed suc-cessfully with the so-called combined lattice Boltzmann method and time-driven hard-sphere model （LBM-TDHS）. In this method, the discrete particle phase is described by time-driven hard-sphere model, and the governing equations of the continuous fluid phase are solved with lattice Boltz-mann method. Particle-fluid coupling is implemented by immersed moving boundary method. Time averaged flow structure of the simulated results show the formation of core-annulus structure and sigmoid distribution of voidage in the axial direction, which are typical phenomena in fluidization systems. Combining the results of the simulation, the energy consumption Nst for suspending and transporting solids is calculated from the direct numerical simulation （DNS） of fluidization, and the stability criterion Nst/NT = rain proposed in EMMS/bubbling model is verified numerically. Further-more the numerical results show that the value of Nst/NT in particulate fiuidization is much higher than that in aggregative fluidization, but Nst/NT = rain is effective for both particulate and aggregative fluidization.

关键词： Direct numerical simulation Fluidization stability condition Lattice-Boltzmann method Time-driven hard-sphere model

EIGENVALUE INTEGRAL RELATION AND stability condition FOR A MODE

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Acta Mechanica Sinica 1989年第3期5卷 278-284页

作者： Zhu Ruzeng Wu Hanming(Institute of Mechanics,Chinese Academy of Sciences) 1. Institute of Mechanics Chinese Academy of Sciences China

In this paper,we point out that for a static system the eigenvalue integral relation(iσ)~2I +iσΦ+Σ=0 derived from an eigenequation (?)Ψ=[(iσ)~2(?)_2+(iσ)(?)_1+(?)_0]Ψ(r)=0 only gives the suffi- ciency of condition Σ>0 for the stability of a certain mode,but it can not provide the necessity to the condition in *** theorems presented in this paper show that under some conditions, Σ>0 makes the mode stable,while Σ<0 makes the mode unstable.

关键词： eigenvalue integral relation stability condition

P-T stability conditions of methane hydrate in sediment from South China Sea

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Journal of Natural Gas Chemistry 2011年第5期20卷 531-536页

作者： Shicai Sun Yuguang Ye Changling Liu Fengkui Xiang Yan Ma Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention and Mitigation College of Civil Engineering and Architecture Shandong University of Science and Technology Qingdao 266510 Shandong China Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology Ministry of Land and Resources Qingdao 266071 Shandong China Qingdao Institute of Marine Geology Qingdao 266071 Shandong China

For reasonable assessment and safe exploitation of marine gas hydrate resource, it is important to determine the stability conditions of gas hydrates in marine sediment. In this paper, the seafloor water sample and sediment sample （saturated with pore water） from Shenhu Area of South China Sea were used to synthesize methane hydrates, and the stability conditions of methane hydrates were investigated by multi-step heating dissociation method. Preliminary experimental results show that the dissociation temperature of methane hydrate both in seafloor water and marine sediment, under any given pressure, is depressed by approximately -1.4 K relative to the pure water system. This phenomenon indicates that hydrate stability in marine sediment is mainly affected by pore water ions.

关键词： sediment from South China Sea seafloor water methane hydrate stability condition

stability analysis of traffic flow with extended CACC control models

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Chinese Physics B 2016年第6期25卷 123-129页

作者：郑亚周程荣军卢兆明葛红霞 Faculty of Science Ningbo University Faculty of Maritime and Transportation Ningbo University Jiangsu Key laboratory of Urban ITS Southeast University Department of Civil and Architectural Engineering City University of Hong Kong

To further investigate car-following behaviors in the cooperative adaptive cruise control（CACC） strategy,a comprehensive control system which can handle three traffic conditions to guarantee driving efficiency and safety is designed by using three CACC *** this control system,some vital comprehensive information,such as multiple preceding cars’ speed differences and headway,variable safety distance（VSD） and time-delay effect on the traffic current and the jamming transition have been investigated via analytical or numerical *** and string stability criterion for the velocity control（VC） model and gap control（GC） model are derived via linear stability *** simulations are conducted to study the performance of the simulated traffic *** simulation results show that the VC model and GC model can improve driving efficiency and suppress traffic congestion.

关键词： cooperative adaptive cruise control stability condition traffic flow variable safety distance

An improved car-following model with consideration of the lateral effect and its feedback control research

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Chinese Physics B 2014年第2期23卷 173-177页

作者：郑亚周郑彭军葛红霞 Faculty of Science Ningbo University Faculty of Maritime and Transportation Ningbo University

A car-following model is presented, in which the effects of non-motor vehicles on adjacent lanes are taken into ac- count. A control signal including the velocity differences between the following vehicle and the target vehicle is introduced according to the feedback control theory. The stability condition for the new model is derived. Numerical simulation is used to demonstrate the advantage of the new model including the control signal; the results are consistent with the analytical ones

关键词： car-following model feedback control method stability condition

Anisotropic quintessence compact star in f(T)gravity with Tolman–Kuchowicz metric potentials

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Communications in Theoretical Physics 2024年第1期76卷 61-75页

作者： Piyali Bhar Farook Rahaman Shyam Das Somi Aktar Abdelghani Errehymy Department of Mathematics Government General Degree College SingurHooghlyWest Bengal 712409India Department of Mathematics Jadavpur UniversityKolkata 700032West BengalIndia Department of Physics Malda College MaldaWest Bengal 732101India Astrophysics Research Centre School of MathematicsStatistics and Computer ScienceUniversity of KwaZulu-NatalPrivate Bag X54001Durban 4000South Africa

To obtain analytically relativistic quintessence anisotropic spherical solutions in the f(T)paradigm is the primary objective of this *** do this,the pressure anisotropy condition is imposed,and we employ a metric potential of the Tolman–Kuchowicz(TK)*** also suppose that our current model incorporates a quintessence field characterized by a parameterωq,in addition to the anisotropic matter *** the presence of the parameterα,the field equations are modified by the choice of the f(T)*** f(T)gravity parameterαadds new components to the basic physical characteristics,such as density,pressure,subliminal sound velocity,surface redshift,etc,of the present *** selecting the compact star Her X-1 and varyingαfrom 0.5 to 2.5,we examined all the physical characteristics of the model parameter of the *** graphical process demonstrates that a more compact item is produced with greater values ofα.The hydrostatic equilibrium condition of the model is discussed,as well as the mass-radius relationship for our current model is obtained.

关键词： quintessence star f(T)gravity stability condition

Extensions of nonlinear error propagation analysis for explicit pseudodynamic testing

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Earthquake Engineering and Engineering Vibration 2009年第1期8卷 77-86页

作者： Shuenn-Yih Chang Department of Civil Engineering Taipei University of Technology NTUT Box 2653 Chinese Taipei 106-08

Two important extensions of a technique to perform a nonlinear error propagation analysis for an explicit pseudodynamic algorithm （Chang, 2003） are presented. One extends the stability study from a given time step to a complete step-by-step integration procedure. It is analytically proven that ensuring stability conditions in each time step leads to a stable computation of the entire step-by-step integration procedure. The other extension shows that the nonlinear error propagation results, which are derived for a nonlinear single degree of freedom （SDOF） system, can be applied to a nonlinear multiple degree of freedom （MDOF） system. This application is dependent upon the determination of the natural frequencies of the system in each time step, since all the numerical properties and error propagation properties in the time step are closely related to these frequencies. The results are derived from the step degree of nonlinearity. An instantaneous degree of nonlinearity is introduced to replace the step degree of nonlinearity and is shown to be easier to use in practice. The extensions can be also applied to the results derived from a SDOF system based on the instantaneous degree of nonlinearity, and hence a time step might be appropriately chosen to perform a pseudodynamic test prior to testing.

关键词： nonlinear error propagation explicit pseudodynamic algorithm stability condition step-by-step integration procedure step degree of nonlinearity

Accuracy of the staggered-grid finite-difference method of the acoustic wave equation for marine seismic reflection modeling

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Chinese Journal of Oceanology and Limnology 2013年第1期31卷 169-177页

作者：钱进吴时国崔若飞 Key Laboratory of Marine Geology and Environment Institute of OceanologyChinese Academy of Sciences School of Resource and Geoscience China University of Mining and Technology

Seismic wave modeling is a cornerstone of geophysical data acquisition, processing, and interpretation, for which finite-difference methods are often applied. In this paper, we extend the velocity- pressure formulation of the acoustic wave equation to marine seismic modeling using the staggered-grid finite-difference method. The scheme is developed using a fourth-order spatial and a second-order temporal operator. Then, we define a stability coefficient (SC) and calculate its maximum value under the stability condition. Based on the dispersion relationship, we conduct a detailed dispersion analysis for submarine sediments in terms of the phase and group velocity over a range of angles, stability coefficients, and orders. We also compare the numerical solution with the exact solution for a P-wave line source in a homogeneous submarine model. Additionally, the numerical results determined by a Marmousi2 model with a rugged seafloor indicate that this method is sufficient for modeling complex submarine structures.

关键词： marine seismic reflection modeling stability condition dispersion relation staggered grid finite-difference

Nonabelian Gauged Linear Sigma Model

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Chinese Annals of Mathematics,Series B 2017年第4期38卷 963-984页

作者： Yongbin RUAN Department of Mathematics University of Michigan Ann Arbor MI 48105 USA.

The gauged linear sigma model （GLSM for short） is a 2d quantum field theory introduced by Witten twenty years ago. Since then, it has been investigated extensively in physics by Hori and others. Recently, an algebro-geometric theory （for both abelian and nonabelian GLSMs） was developed by the author and his collaborators so that he can start to rigorously compute its invariants and check against physical predications. The abelian GLSM was relatively better understood and is the focus of current mathematical investigation. In this article, the author would like to look over the horizon and consider the nonabelian GLSM. The nonabelian case possesses some new features unavailable to the ahelian GLSM. To aid the future mathematical development, the author surveys some of the key problems inspired by physics in the nonabelian GLSM.

关键词： GIT quotient stability condition GLSM