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Interval design point method for calculating the reliability of structural systems

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Science China(Physics,Mechanics & Astronomy) 2013年第11期56卷 2151-2161页

作者： ni Zao QIU ZhiPing Shanghai Aircraft Design and Research institute COMAC Institute of Solid Mechanics Beijing University of Aeronautics and Astronautics

The evaluation of reliability for structural system is important in engineering *** this paper,by combining the design point method,JC method,interval analysis theory,and increment load method,we propose a new interval design point method for the reliability of structural systems in which the distribution parameters of random variables are described as interval *** proposed method may provide exact probabilistic interval reliability of structures whose random variables can have either a normal or abnormal distribution *** last,we show the feasibility of the proposed approach through a typical example.

关键词： probability design point method interval analysis probabilistic interval reliability parameters uncertainty

Ensemble Classifier Design Based on Perturbation Binary Salp Swarm Algorithm for Classification

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Computer Modeling in Engineering & Sciences 2023年第4期135卷 653-671页

作者： Xuhui Zhu Pingfan Xia Qizhi He Zhiwei ni Liping ni School of Management Hefei University of TechnologyHefei230009China School of Statistics Zhejiang Gongshang UniversityHangzhou310018China Key Laboratory of Process Optimization and Intelligent Decision-Making Ministry of EducationHefei230009China Collaborative Innovation Center for Statistical Data Engineering Technology and Application ZhejiangGongshang UniversityHangzhou310018China

Multiple classifier system exhibits strong classification capacity compared with single classifiers,but they require significant computational *** ensemble system aims to attain equivalent or better classification accuracy with fewer ***,current methods fail to identify precise solutions for constructing an ensemble *** this study,we propose an ensemble classifier design technique based on the perturbation binary salp swarm algorithm(ECDPB).Considering that extreme learning machines(ELMs)have rapid learning rates and good generalization ability,they can serve as the basic classifier for creating multiple candidates while using fewer computational ***,we introduce a combined diversity measure by taking the complementarity and accuracy of ELMs into account;it is used to identify the ELMs that have good diversity and low *** addition,we propose an ECDPB with powerful optimizing ability;it is employed to find the optimal subset of *** selected ELMs can then be used to forman ensemble *** on 10 benchmark datasets have been conducted,and the results demonstrate that the proposed ECDPB delivers superior classification capacity when compared with alternative methods.

关键词： Ensemble classifier salp swarmalgorithm diversity measure multiple classifiers system extreme learning machine

The Cotorsion Pair Cogenerated by the Subcategory of Stable Functors in ((R-mod)^op, Ab)

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Algebra Colloquium 2019年第2期26卷 259-270页

作者： Xianhui Fu Meiyuan ni School of Mathematics and Statistics Northeast Normal University Changchun 130024 China

Let R be an associative ring with identity. Denote by ((R-mod)^op, Ab) the category consisting of contravariant functors from the category of finitely presented left R-modules R-mod to the category of abelian groups Ab. An object in ((R-mod)^op, Ab) is said to be a stable functor if it vanishes on the regular module R. Let T be the subcategory of stable functors. There are two torsion pairs t1=(Gen(-,R),T)and t2=(T,F1), where 1 is the subcategory of ((R-mod)^op, Ab) consisting of functors with flat dimension at most 1. In this article, let R be a ring of weakly global dimension at most 1, and assume R satisfies that for any exact sequence 0 → M → N → K → 0, if M and N are pure injective, then K is also pure injective. We calculate the cotorsion pair (⊥T,(⊥T)⊥)cogenerated by T clearly. It is shown that G∈⊥T if and only if G/t1(G) is a projective object in T, i.e., G/t1(G)=(-,M) for some R-module M;and G∈(⊥T)⊥ if and only if G/t2(G) is of the form (-, E), where E is an injective R-module.

关键词： stable functors cotorsion pairs torsion pairs

Reconstruction of solid oxide fuel cell electrode microstructure and analysis of its effective conductivity

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Science Bulletin 2016年第1期61卷 78-85页

作者： Keqing Zheng Meng ni Building Energy Research Group Department of Building and Real Estate The Hong Kong Polytechnic University Environmental Energy Research Group Research Institute for Sustainable Urban Development (RISUD) The Hong Kong Polytechnic University

The effective conductivity （aeff） of solid oxide fuel cell （SOFC） electrode is an important parameter for predicting the ohmic loss in SOFC. This paper investigates the effective conductivity of SOFC electrodes recon- structed numerically by packing spherical particles in a computational domain, followed by a dilation process to simulate the sintering procedure. The effects of various parameters on the effective conductivity of the electrodes are investigated, including material composition, porosity, particle size and contact angle. Results show that the effective conductivity ratio （aeff/ao） of the computed con- ducting phase is mainly affected by its total volume frac- tion （VF） in electrode （including the porosity）. The effective conductivity can be improved by increasing the VF, electrode particle size or the contact angle between electrode particles. Based on the numerical results, the conventional percolation model for the calculation of O＇eft is improved by adjusting the Bruggeman factor from 1.5 to 2.7. The results are useful for understanding the microstructure properties of SOFC composite electrode and for subsequent electrode optimization.

关键词： Fuel cell Electrode Conductivity Modeling Random particle packing

Influences of different forces on the bubble entrainment into a stationary Gaussian vortex

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Science China(Physics,Mechanics & Astronomy) 2013年第11期56卷 2162-2169页

作者： ZHANG AMan ni BaoYu College of Shipbuilding Engineering Harbin Engineering University

Simulations of bubble entrainment into a stationary Gaussian vortex are performed by using the combined particle tracking method(PTM)and boundary element method(BEM).Before the bubble is captured by the vortex core,oscillation and migration of the quasi-spherical nucleus are solved by using improved RP equation and the momentum theorem in the Lagrangian reference frame simultaneously,and the trajectory of the nucleus presents a kind of reduced helix *** captured by the vortex core,the bubble grows immediately and moves and deforms along the vortex core *** non-spherical evolution and deformation of the bubble is simulated by adopting a mixed Eulerian-Lagrangian *** output of quasi-spherical stage is taken as the input of non-spherical stage,and all the behaviors of the entrained bubble can be simulated such as inception,motion,deformation and *** results agree well with published experimental *** this basis,the influences of various factors such as viscosity,surface tension,buoyancy are studied *** the results from this paper would provide some insight into the control on vortex bubble entrainment.

关键词： bubble entrainment gaussian vortex trajectory split

NUMERICAL　SIMULATION　OF　THE　TURBULENT　FLUID　FLOW　AND　PREDICTION　OF　INCIPIENT　CAVITATION　NUMBER　ON　ISOLATED　SURFACE　TRIANGULAR　PROTRUSION

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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

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

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

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