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EXACt SOLUtIONS OF A DIPOLAR FLUID FLOW

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Acta Mechanica Sinica 2003年第4期19卷 308-314页

作者： t.HAYAt DepartmentofMathematics Quaid-i-AzamUniversityIslamabad44000Pakistan

Exact solutions for three canonical flow problems of a dipolar fluid are obtained: (i) the flow of a dipolar fluid due to a suddenly accelerated plate, (ii) the flow generated by periodic oscillation of a plate, (iii) the flow due to plate oscillation in the presence of a transverse magnetic field. the solutions of some interesting flows caused by an arbitrary velocity of the plate and of certain special oscillations are also obtained.

关键词： unsteady flows dipolar fluid periodic oscillations MHD flow

Large deformation plasticity From basic relations to finite deformation

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Acta Mechanica Sinica 2020年第2期36卷 472-492页

作者： Otto t.Bruhns Institute of Mechanics Ruhr-University Bochum44780 BochumGermany

the theory of plasticity as a special field of continuum mechanics deals with the irreversible,***,deformation of *** the action of given loads or deformations,the state of the stresses and strains or the strain rates in these bodies is *** this way,it complements the theory of elasticity for the reversible behavior of *** practice,it has been observed that many materials behave elastically up to a certain load(yield point),beyond that load,however,increasingly plastic or *** combination of these two material properties is known as *** classical elastoplastic material behavior is assumed to be time-independent or *** contrast,we call a time-or rate-dependent behavior visco-elastoplastic and visco-plastic—if the elastic part of the deformation is *** plasticity theory,because of the given loads the states of the state variables stress,strain and temperature as well as their changes are *** this purpose,the observed phenomena are introduced and put into mathematical *** constitutive relations describing the specific material behavior are finally embedded in the fundamental relations of continuum theory and ***,the theory of plasticity was introduced in order to better estimate the strength of *** analysis based purely on elastic codes is not in a position to do this,and can occasionally even lead to incorrect *** the other hand,the entire field of forming techniques requires a theory for the description of plastic *** from the classical description of plastic behavior with small deformations,the present review is intended to provide an insight into the state of the art when taking into account finite deformations.

关键词： Finite deformation Elasto-plasticity Constitutive relations thermodynamics History of plasticity

Late Ordovician Mass Extinction: Earth, fire and ice

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National Science Review 2024年第1期11卷 51-65页

作者： David A.t.Harper Palaeoecosystems Group Department of Earth SciencesDurham University

the Late Ordovician Mass Extinction was the earliest of the ‘big’ five extinction events and the earliest to affect the trajectory of metazoan life. two phases have been identified near the start of the Hirnantian period and in the middle. It was a massive taxonomic extinction, a weak phylogenetic extinction and a relatively benign ecological extinction. A rapid cooling, triggering a major ice age that reduced the temperature of surface waters, prompted a drop in sea level of some 100 m and introduced toxic bottom waters onto the shelves. these symptoms of more fundamental planetary processes have been associated with a range of factors with an underlying driver identified as volcanicity. Volcanic eruptions, and other products, may have extended back in time to at least the Sandbian and early Katian, suggesting the extinctions were more protracted and influential than hitherto documented.

关键词： Ordovician LOME paleoecology palaeobiogeography biotas

Preparation of microparticles and nanoparticles using membrane-assisted dispersion,micromixing,and evaporation processes

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Particuology 2024年第1期84卷 30-44页

作者： Goran t.Vladisavljevic Chemical Engineering Department Loughborough UniversityLoughboroughLeicestershire LE113TUUnited Kingdom

Synthetic microporous membranes are increasingly used for energy-efficient and controlled production of micro-and nanoparticles and micro-and nanoemulsions with tuneable morphology and physico-chemical properties through various micromixing,emulsification,and evaporation *** emul-sification processes,the membrane pores are used for dispersed phase injection and size-controlled generation of droplets and droplet-templated *** micromixing processes,membrane is utilised as a micromixer for mixing two miscible liquids,usually solvent and antisolvent-rich solutions,which leads to the creation of supersaturation and subsequent nanoprecipitation or *** mem-brane evaporation processes,membrane is used to prevent phase dispersion while allowing efficient molecular diffusion of solvent and/or antisolvent vapour through gas-filled *** dispersion processes can be operated continuously by decoupling shear stress on the membrane surface from cross flow using tube insets,flow pulsations,swirling flow,membrane oscillations or membrane *** generation and solidification can be performed continuously in a single pass by connecting membrane module with a downstream *** dispersion processes can be used for pro-duction of nanoparticles such as nanovesicles(liposomes,micelles,ethosomes,and niosomes),nanogels,polymeric,lipid and metallic nanoparticles,and *** main advantages of membrane-assisted particle generation are in low energy consumption,controlled geometry and hydrodynamic conditions at the microscale level,flexible throughput due to modular and scalable design of membrane devices,and a wide choice of available microporous membranes with various wall porosities,wetta-bilities,pore sizes,and pore morphologies to suit different applications.

关键词： Nanoparticles Microparticles Nanoemulsions Microemulsions Microporous membrane Crystallisation Flash nanoprecipitation Emulsification Zero liquid discharge

Investigation of structural,magnetic and optical properties of rare earth substituted bismuth ferrite

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Journal of Rare Earths 2013年第4期31卷 370-375页

作者： t.Durga Rao t.Karthik Saket Asthana Advanced Functional Materials Laboratory Department of PhysicsIndian Institute of Technology Hyderabad Department of Materials Science and Engineering Indian Institute of Technology Hyderabad

Polycrystalline BiFeO3 and rare earth substituted ***3 （BRFO, R=Y, Ho and Er） compounds were prepared by rapid solid state sintering technique. Structural phase analysis indicated that all the compounds stabilized in rhombohedral structure （R3c space group） and a small orthorhombic phase fraction was observed in BRFO compounds. From the Raman spectra results, the changes in the phonon frequencies （A1） and line widths suggested lattice distortion in the BRFO compounds as was evidenced in the XRD analysis. Compared to the linear variation of magnetization with magnetic field （M-H） shown by BFO, an obvious M-H loop was observed in BRFO compounds which could be due to the suppression of space modulated spin structure and was explained on the basis of weak ferromagnetism and field induced spin reorientation. UV-Vis spectroscopy evidenced a change in local FeO6 envi- ronment due to shift in the 6Alg→4t2g energy transition band. BRFO compounds with improved remnant magnetization and coercive field are applicable for magnetoelectric devices.

关键词： structural distortion spin-reorientation G-type antiferromagnet rare earths

Performance and Internal Flow of Sirocco Fan Using Contra-Rotating Rotors

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Journal of thermal Science 2008年第1期17卷 35-41页

作者： J.Fukutomi t.Shigemitsu t.Yasunobu Institute of Science and technology The University of Tokushima2-1 Minamijyosanjima-choTokushima 770-8506JAPAN Institute of Science and technology The University of Tokushima2-1 Minamijyosanjima-choTokushima 770-8506JAPAN Research Associate Graduate School of Advanced technology and Science The University of Tokushima2-1 Minamijyosanjima-choTokushima 770-8506JAPAN

A sirocco fan using contra-rotating rotors in which an inner rotor is settled inside the sirocco fan rotor and each rotor rotates in an opposite direction was proposed for the purpose of getting the higher pressure and making the structure of a sirocco fan more compact. If the high discharge pressure is obtained with the adoption of the contra-rotating rotors, it could be used for various purposes. Pressure coefficient of a sirocco fan with contra-rotating rotors is 2.5 times as high as the conventional sirocco fan and the maximum efficiency point of contra-rotating rotors shifts to larger flow rate than a conventional sirocco fan. On the other hand, it was clarified from the flow measurement results that circumferential velocity component at the outlet of the outer rotor of contra-rotating ro- tors becomes larger than a conventional one. In the present paper, the performance of a conventional sirocco fan and a sirocco fan with contra-rotating rotors are shown and the internal flow field at the outlet of outer rotor of both cases is clarified. then, the effect of different kind of contra-rotating rotors on the performance and internal flow field is investigated and the rotor design with higher performance would be discussed.

关键词： Sirocco fan High pressure Contra-rotating rotors Slow angle Circular arc blade Aerofoil blade

A kinetic model for a single step biodiesel production from a high free fatty acid (FFA) biodiesel feedstock over a solid heteropolyacid catalyst

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Green Energy & Environment 2019年第3期4卷 328-341页

作者： Aashish Gaurav Stéphane Dumas Chau t.Q.Mai Flora t.t.Ng Department of Chemical Engineering University of Waterloo

Production of biodiesel from yellow grease(waste cooking oil and waste animal fats) is fast emerging as a promising alternative to address the twin challenges before the biodiesel industry today-fluctuation in prices of vegetable oil and the food versus fuel debate. Yellow grease has a high percentage of free fatty acids(FFA) and proves to be an unsuitable feedstock for biodiesel production from commercially viable alkalicatalyzed production systems due to saponification problems.'Green' methodologies based on heterogeneous solid acid catalyzed reactions have the potential to simultaneously promote esterification and transesterification reactions of yellow grease to produce biodiesel without soap formation and offer easy catalyst separation without generation of toxic streams. this paper presents kinetic studies for the conversion of model yellow grease feeds to biodiesel using a heteropolyacid supported on alumina(HSiW/Al2O3) using a batch autoclave. three model yellow grease feeds were prepared using canola oil with added FFA such as palmitic, oleic and linoleic acid. A pseudo homogeneous kinetic model for the parallel esterification and transesterification was developed. the rate constants and activation parameters for esterification and transesterification reactions for the model yellow grease feeds were determined. the rate constants for esterification are higher than the transesterification rate constants. the kinetic model was validated using the experimental biodiesel data obtained from processing a commercial yellow grease feed. the kinetic model could be used to design novel processes to convert various low-value waste oils, fats and non-food grade oils to sustainable biodiesel.

关键词： Yellow grease Canola oil Free fatty acids Heteropolyacid Kinetics for esterification and transesterification

Breather solutions of modified Benjamin-Bona-Mahony equation

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Chinese Physics B 2021年第2期30卷 220-226页

作者： G t Adamashvili technical University of Georgia Kostava Street 77Tbilisi0179Georgia

New two-component vector breather solution of the modified Benjamin-Bona-Mahony(MBBM)equation is *** the generalized perturbation reduction method,the MBBM equation is reduced to the coupled nonlinear Schr¨odinger equations for auxiliary *** analytical expressions for the profile and parameters of the vector breather oscillating with the sum and difference of the frequencies and wavenumbers are *** two-component vector breather and single-component scalar breather of the MBBM equation is compared.

关键词： modified Benjamin-Bona-Mahony equation generalized perturbation reduction method vector breather nonlinear waves

Real-time per-pixel focusing method for light field rendering

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Computational Visual Media 2021年第3期7卷 319-333页

作者： t.Chlubna t.Milet P.Zemcík Faculty of Information technology Brno University of Technology61200 BrnoCzech Republic

Light field rendering is an image-based rendering method that does not use 3 D models but only images of the scene as input to render new *** field approximation,represented as a set of images,suffers from so-called refocusing artifacts due to different depth values of the pixels in the *** information about depths in the scene,proper focusing of the light field scene is limited to a single focusing *** correct focusing method is addressed in this work and a real-time solution is proposed for focusing of light field scenes,based on statistical analysis of the pixel values contributing to the final *** existing techniques,this method does not need precomputed or acquired depth *** requirements and streaming bandwidth are reduced and real-time rendering is possible even for high resolution light field data,yielding visually satisfactory *** evaluation of the proposed method,implemented on a GPU,is presented in this paper.

关键词： image-based rendering light field plenoptic function computational photography