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Segregation behavior of a ternary mixture of titanium dioxide particles in a pseudo two-dimensional fluidized bed

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Particuology 2021年第1期19卷 78-90页

作者： Mojtaba Rasteh alireza Bahramian Goodarz Ahmadi Department of Chemical Engineering Hamedan University of TechnologyHamedanP.O.Box65155-579Iran Department of Mechanical and Aeronautical Engineering Clarkson UniversityPotsdamNY 13699-5725USA

The segregation behavior of a mixture of silica-coated titanium dioxide(TiO2)particles of three different sizes in a pseudo two-dimensional fluidized bed was studied experimentally by the freeze-sieving method and numerically by the multi-fluid model(MFM).Three-dimensional computational fluid dynamics(CFD)simulations were carried out to evaluate the effects of the solid wall boundary conditions on particle segregation in terms of specularity and particle-wall restitution *** quantitative indexes of segregation tendency and segregation degree were used to determine the axial segregation of the mixture in triangular *** simulation results revealed that the axial segregation increased with the specularity coefficient,whereas the particle-wall restitution coefficient had a minor effect on axial *** of the simulation results with experimental data showed that the appropriate value of the specularity coefficient used in the CFD model depended on superficial gas *** study of the effects of superficial gas velocity on segregation behavior demonstrated that the greatest segregation was obtained at minimum fluidization velocity and the segregation decreased as the gas velocity gradually increased.

关键词： Ternary mixture Segregation tendency Segregation degree Two-fluid model Computational fluid dynamics(CFD)

Strength evolution and deformation behaviour of cemented paste backfill at early ages： Effect of curing stress, filling strategy and drainage

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International Journal of Mining Science and Technology 2016年第5期26卷 809-817页

作者： Ghirian alireza Fall Mamadou Department of Civil Engineering University of Ottawa 161 Louis Pasteur Ottawa K1N 6N5 ON Canada

In this study, a pressure cell apparatus is developed to investigate the early age evolution of the strength and deformation behaviour of cemented paste backfill(CPB) when subjected to various loading conditions under different curing scenarios. The different curing scenarios that are simulated include:(1)drained and undrained conditions,(2) different filling rates,(3) different filling sequences, and(4) different curing stresses. The findings show that drainage, curing stress, curing time and filling rate influence the mechanical and deformation behaviours of CPB materials. The coupled effects of consolidation, drainage and suction contribute to the strength development of drained CPB subjected to curing stress. On the other hand, particle rearrangement caused by the applied pressure and suction development due to self-desiccation plays a significant role in the strength gain of undrained CPB cured under ***, curing stress induces slightly faster rate of cement hydration, which can contribute to strength acquisition.

关键词： Cemented paste backfill Tailings Pore pressure Curing under stress Plug fill Cement

Characterization of Operators on the Dual of Hypergroups which Commute with Translations and Convolutions

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Acta Mathematica Sinica,English Series 2004年第2期20卷 201-208页

作者： Ali Ghaffari alireza Medghalchi Department of Mathematics Semnan UniversityP.O.Box 35195-363SemnanIran Department of Mathematics Teacher Training UniversityTehranIran.

For a locally compact group G, L 1(G) is its group algebra and L ∞(G) is the dual of L 1(G). Lau has studied the bounded linear operators T : L ∞(G) → L ∞(G) which commute with convolutions and translations. For a subspace H of L ∞(G), we know that M(L ∞(G),H), the Banach algebra of all bounded linear operators on L ∞(G) into H which commute with convolutions, has been studied by Pym and Lau. In this paper, we generalize these problems to L(K)*, the dual of a hypergroup algebra L(K) in a very general setting, i. e. we do not assume that K admits a Haar measure. It should be noted that these algebras include not only the group algebra L 1(G) but also most of the semigroup algebras. Compact hypergroups have a Haar measure, however, in general it is not known that every hypergroup has a Haar measure. The lack of the Haar measure and involution presents many difficulties; however, we succeed in getting some interesting results.

关键词： Hypergroup algebras Group algebras Operators Translations Convolutions Invariant

Scaling granular material with polygonal particles in discrete element modeling

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Particuology 2023年第4期75卷 151-164页

作者： alireza Ahmadi Stefan Larsson Carl Wersall KTH Royal Institute of Technology Division of Soil and Rock MechanicsBrinellvagen 2310044StockholmSweden

Despite advancements in computational resources,the discrete element method(DEM)still requires considerable computational time to solve detailed problems,especially when it comes to the large-scale *** addition to the geometry scale of the problem,the particle shape has a dramatic effect on the computational cost of ***,many studies have been performed with simplified spherical particles or *** scaling is an approach to increase the particle size to reduce the number of particles in the *** several particle scaling methods have been introduced,there are still some disagreements regarding their applicability to certain aspects of *** this study,the effect of particle scalping on the shear behavior of granular material is *** granular particles were scanned and imported as polygonal particles in the direct shear *** effect of particle size distri-bution,particle angularity,and the amount of scalping were *** results show that particle scalping can simulate the correct shear behavior of the model with significant improvement in computational ***,the accuracy of the scalping method depends on the particle angularity and particle size range.

关键词： Particle scaling Direct shear test Discrete element method PFC Polygonal shape Granular material

Enhancing PIV image and fractal descriptor for velocity and shear stresses propagation around a circular pier

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Geoscience Frontiers 2017年第4期8卷 869-883页

作者： alireza Keshavarzi James Ball Water Department Shiraz University School of Civil and Environmental Engineering University of Technology Sydney

In this study,the fractal dimensions of velocity fluctuations and the Reynolds shear stresses propagation for flow around a circular bridge pier are *** the study reported herein,the fractal dimension of velocity fluctuations（u′,v′,w′） and the Reynolds shear stresses（u′v′ and u′w′） of flow around a bridge pier were computed using a Fractal Interpolation Function（FIF） *** velocity fluctuations of flow along a horizontal plane above the bed were measured using Acoustic Doppler Velocity meter（ADV）and Particle Image Velocimetry（P1V）.The PIV is a powerful technique which enables us to attain high resolution spatial and temporal information of turbulent flow using instantaneous time *** this study,PIV was used for detection of high resolution fractal scaling around a bridge *** results showed that the fractal dimension of flow fluctuated significantly in the longitudinal and transverse directions in the vicinity of the *** was also found that the fractal dimension of velocity fluctuations and shear stresses increased rapidly at vicinity of pier at downstream whereas it remained approximately unchanged far downstream of the *** higher value of fractal dimension was found at a distance equal to one times of the pier diameter in the back of the ***,the average fractal dimension for the streamwise and transverse velocity fluctuations decreased from the centreline to the side wall of the ***,the results from ADV measurement were consistent with the result from PIV,therefore,the ADV enables to detect turbulent characteristics of flow around a circular bridge pier.

关键词： Fractal dimension Fractal interpolation function Fractal scaling Bridge pier Turbulent flow

AntLP: ant-based label propagation algorithm for community detection in social networks

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CAAI Transactions on Intelligence Technology 2020年第1期5卷 34-41页

作者： Razieh Hosseini alireza Rezvanian Department of Computer Engineering Alzahra UniversityTehranIran Department of Computer Engineering University of Science and CultureTehranIran School of Computer Science Institute for Research in Fundamental Sciences(IPM)TehranIran

In social network analysis,community detection is one of the significant tasks to study the structure and characteristics of the *** recent years,several intelligent and meta-heuristic algorithms have been presented for community detection in complex social networks,among them label propagation algorithm(LPA)is one of the fastest algorithms for discovering community ***,due to the randomness of the LPA,its performance is not suitable for the general purpose of network *** this study,the authors propose an improved version of the label propagation(called AntLP)algorithm using similarity indices and ant colony optimisation(ACO).The AntLP consists of two steps:in the first step,the algorithm assigns weights for edges of the input network using several similarity indices,and in the second step,the AntLP using ACO tries to propagate labels and optimise modularity measure by grouping similar vertices in each community based on the local similarities among the vertices of the *** order to study the performance of the AntLP,several experiments are conducted on some well-known social network *** simulations demonstrated that the AntLP is better than some community detection algorithms for social networks in terms of modularity,normalised mutual information and running time.

关键词： network networks algorithm

An Approximate Approach for Systems of Singular Volterra Integral Equations Based on Taylor Expansion

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Communications in Theoretical Physics 2018年第8期69卷 145-152页

作者： Mohsen Didgar alireza Vahidi Department of Mathematics Guilan Science and Research Branch Islamic Azad University Department of Mathematics Rasht Branch Islamic Azad University Department of Mathematics College of Science Yadegar-e-Emam Khomeyni (RAH) Shahr-e-Rey Branch Islamic Azad University

In this article, an extended Taylor expansion method is proposed to estimate the solution of linear singular Volterra integral equations systems. The method is based on combining the m-th order Taylor polynomial of unknown functions at an arbitrary point and integration method, such that the given system of singular integral equations is converted into a system of linear equations with respect to unknown functions and their derivatives. The required solutions are obtained by solving the resulting linear system. The proposed method gives a very satisfactory solution,which can be performed by any symbolic mathematical packages such as Maple, Mathematica, etc. Our proposed approach provides a significant advantage that the m-th order approximate solutions are equal to exact solutions if the exact solutions are polynomial functions of degree less than or equal to m. We present an error analysis for the proposed method to emphasize its reliability. Six numerical examples are provided to show the accuracy and the efficiency of the suggested scheme for which the exact solutions are known in advance.

关键词： systems of singular Volterra integral equations (SSVIEs) systems of generalized Abel's integral equations error analysis Taylor expansion

Bending efficiency analysis of horizontal single-and multiple-slot waveguide microrings

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Optoelectronics Letters 2011年第1期7卷 5-9页

作者： alireza Kargar Department of Electrical and Computer Engineering Shiraz University

The bending efficiencies of three-dimensional(3D) horizontal single-and multiple-slot waveguide microrings are analyzed using the effective index and modified transfer matrix *** effects of waveguide parameters,low-index material,high-index material,asymmetric structure,and asymmetric slots on the bending loss are *** results show that the bending efficiency can be enhanced by applying asymmetric structures and asymmetric *** addition,it is demonstrated that the bending loss increases with the increase of the number of ***,by using proper thicknesses for different high-index layers of the horizontal multiple-slot waveguide,it is possible that the horizontal multiple-slot waveguide can provide a lower bending loss than the single-slot one.

关键词：弯曲损耗槽波导效率分析卧式微环非对称结构传输矩阵方法波导参数

Intracavity configuration for tuning and obtaining simultaneous dual-wavelength operation from CW Nd:YAG laser

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Chinese Optics Letters 2011年第7期9卷 55-58页

作者： alireza Khorsandi Saeed Ghavami Sabouri Department of Physics Isfahan University

In this letter, a thin slab of glass is used as Fabry-Perot etalon inside a cavity of a continuous wave （CW） Nd：YAG laser to change the behavior of its output longitudinal modes. The slab etalon is used as tuning element when it turns around the laser cavity axis. Two simultaneous longitudinal modes with a relatively wide tuning range from 5.83 MHz to 0,02 THz are obtained when the Nd：YAG laser is operated at moderate output power of about 120 roW. The mode structure of this configuration is modeled and simulated. Computer-generated diagrams are also presented schematically and compared with the experimental results.

关键词： YAG Intracavity configuration for tuning and obtaining simultaneous dual-wavelength operation from CW Nd Nd CW