检索结果-南通市图书馆

Is Brenner＇s Modification to the Classical Navier-Stokes Equations Able to Describe Sound Propagation in Gases？

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2008年第4期25卷 1355-1358页

作者： w. Marques jr. Departamento de Fisica Universidade Federal do Parana Calxa Postal 19044 81531-990 Curitiba Brazil

we analyse the problem concerning the propagation of sound waves in gases by using the modified hydrodynamic theory proposed recently by Brenner for single-component fluids. The modifications introduced by Brenner are based on his proposal that the translational momentum in fluid motion is not given by the mass flux. Comparison of the sound propagation results derived from Brenner＇s theory with available experimental data for monatomic gases shows that this modified continuum theory is unable to describe the acoustic measurements not even in the low-frequency limit, a result that from our point of view makes Brenner＇s proposal questionable.

关键词： NAVIER-Stokes equations PARTIAL differential equations FLUID dynamics CONTINUUM mechanics

Development of a 3D model for particle-wall collision and induced rotation and its influence on particle trajectories

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Particuology 2024年第11期94卷 211-228页

作者： Cairen Miranda John Palmore jr. Department of Mechanical Engineering Virginia TechBlacksburg24060VAUSA Department of Mechanical Engineering University of WashingtonSeattle98195WAUSA

The present research focuses on improving the prediction of rotating particle *** particle-surface collision models do not accurately predict the particle rebound when taking rotation into *** data,such as the studies by Gorham and Kharaz(2000),Buck,Tang,Heinrich,Deen and Kuipers(2017),and Dong and Moys(2006)show that the Tsuji,Oshima and Morikawa(1985)model is inaccurate due to the incorrect tangential coefficient of restitution ***,Kuipers,Mohd Salleh,Stein,and Seville(2001)introduced a similar model to the work by Tsuji et al.(1985)which includes a tangential coefficient of restitution but is only in two dimensions and does not consider out of plane *** work re-derives the particle collision model from the impulse equations for binary collisions in 3D while considering rotating *** derived equations in this work compares well to experimental particle-surface impact *** implications of this model are seen by investigating erosion due to particle collision in a simple pipe *** is shown that Tsuji et al.(1985)over predicts the *** small differences in particle trajectories between the present model and the Tsuji et al.(1985)model will grow in complex flows with multiple close range particle impacts leading to inaccurate erosion predictions which will negatively impact the design of turbomachinery and pneumatic pipes.

关键词： Particle collisions CFD Rotation Three dimensional

The Strengths and weaknesses of Conceptual Metaphor Theory： A View from Cognitive Science

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

外国语 2008年第2期31卷 2-12页

作者： Raymond w. Gibbs, jr. Department of Psychology University of California Santa Cruz CA 95064 USA

A major revolution in the study of metaphor occurred over 25 year ago with the introduction of "conceptual metaphor theory." Unlike previous theories of metaphor and metaphorical meaning,conceptual metaphor theory,or CMT,proposed that metaphor is not just an aspect of language,but also a fundamental part of human ***,most metaphorical language arises from pre-existing patterns of metaphorical thought or conceptual *** paper provides a brief overview of the linguistic and psychological evidence supporting CMT and describes some of the criticisms of CMT offered by various scholars within cognitive *** of CMT must address these weaknesses in the theory,while critics must acknowledge the strengths of CMT as metaphor scholars from all academic fields work toward a comprehensive theory of metaphoric language and thought.

关键词：隐喻思想认知概念性

Fabrication and characterization of Cu–Zn–Sn shape memory alloys via an electrodeposition–annealing route

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2019年第11期26卷 1436-1449页

作者： Richard Espiritu Alberto Amorsolo jr. Department of Mining Metallurgical and Materials Engineering University of the Philippines Diliman

Cu–Zn–Sn shape memory alloys(SMAs)with an average composition of 56.0 at%,36.1 at%,and 7.9 at%for Cu,Zn,and Sn,respectively,were successfully fabricated via an electrodeposition–annealing *** produced SMAs were assessed for shape memory response in terms of percent displacement(martensite phase recovery)by subjecting the ternary alloys to flame tests and subsequently characterizing them via differential scanning calorimetry(DSC),optical microscopy,scanning electron microscopy in conjunction with energy-dispersive spectroscopy(SEM-EDS),and X-ray diffraction(XRD)*** flame tests showed that the highest displacement was ca.93%,with average austenite and martensitic start transformation temperature of 225°C and 222°C,*** analysis revealed that the intermetallic phases responsible for the observed shape memory properties have substitutional Zn in the lattice occupied by Cu and Sn,leading to the formation of Cu(Zn,Sn)and Cu6(Zn,Sn)5 *** formation of these variants was attributed to the faster interdiffusion of Cu into Sn,driven by an activation energy of 34.82 kJ·mol^-*** cycles of repeated torching–annealing revealed an essentially constant shape memory response,suggesting that the fabricated SMAs were consistent and sufficiently reliable for their intended service application.

关键词： electrodeposition annealing intermetallics martensitic transformation shape memory alloy

Dietary free fatty acids complex with amylose creating another form of resistant starch: Gastrointestinal formation with fowl and swine

在线全文

学校读者我要写书评

暂无评论

Animal Nutrition 2021年第4期7卷 1124-1132页

作者： Edwin T.Moran jr. Poultry Science Department Auburn UniversityAL36849-5416USA

Fat added to poultry and swine feeds often contains abundant free fatty acids(FFA)that can impair digestible energy(DE).Placement of the fatty acid(FA)hydrocarbon chain in the helix core reformed from amylose creates a complex of both *** modifications create a new structure termed the V-helix that becomes resistant toα-*** in grain naturally contain minimal amounts of these complexes with more being generated during food manufacturing when moisture and heat release amylose in the presence of FFA.A paucity of FFA usually exists in complete feeds without sources of poorquality *** fats and by-product meals from rendering are prominent in their saturated FFA content which favorably complex within the helix.V-helix-FA complexes may arise during their concurrent encounter of FFA together with amylose during feed manufacture,particularly *** in the gastrointestinal tract(GIT)are speculated to further form complexes when present together with *** amylose may be dissolved in the gastric and small intestinal milieu,FFA separately coalesce into hydrophobic fat droplets along with other dietary *** of complexes is likely restricted until FFA are released into the aqueous phase during fat ***α-amylase may be prominent,V-helix-FA complexes being resistant to enzymic attack pass into the large *** microbial catabolism of V-helices may generate volatile fatty acids that are absorbed by the mucosa;however,an inability to use FFA once released leads to their excretion and basis for decreased *** microbial populations with young animals usually lack the capacity to fully catabolize the V-helix,further extending the loss in DE.

关键词： Amylose Digestible energy Free fatty acid Feed manufacture

Cenozoic reactivation along the Late Triassic Ganzi-Litang suture,eastern Tibetan Plateau

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2020年第3期11卷 1069-1080页

作者： w.T.Jackson jr. D.M.Robinson A.L.weislogel X.Jian Department of Earth Sciences University of South AlabamaMobileAL36688USA Department of Geological Sciences and Center for Sedimentary Basin Studies The University of AlabamaTuscaloosaAL35487USA Department of Geography and Geology West Virginia UniversityMorgantownWV26506USA State Key Laboratory of Marine Environmental Science College of Ocean and Earth SciencesXiamen UniversityXiamen 361102China

The spatial-temporal development of Cenozoic reactivation along Mesozoic suture zones in the Tibetan Plateau are first-order parameters needed for assessing models of plateau *** Ganzi-Litang suture,in the eastern Tibetan Plateau,developed in the Late Triassic because of subduction and closure along the eastern branch of the Paleo-Tethys *** the city of Litang,the Ganzi-Litang suture is defined by a melange sequence with faultbound,synorogenic nonmarine strata along the western and eastern flanks,suggesting post-Triassic structural *** present detrital zircon U-Pb geochronology and field data to determine the timing and style of reactivation along the Ganzi-Litang suture,as well as sedimentary provenance of nonmarine strata.A reverse fault placing melange rock on top of nonmarine strata along the eastern flank of the Ganzi-Litang suture indicates a contractional deformational regime during *** clast counts indicate a local sediment source of recycled Ganzi-Litang suture and Yidun terrane *** zircons indicate a localized provenance consisting of recycled material from Triassic Yidun Arc plutons and Triassic Yidun Group turbidite rock.A weighted mean average of Cenozoic zircon grains(n=10) establishes a maximum depositional age of41.5 ± 1.2 Ma for nonmarine strata in the Ganzi-Litang *** interpret the maximum depositional age of the nonmarine strata to represent the upper-limit for structural reactivation along the Ganzi-Litang suture while undeformed Neogene strata in the suture zone represent the lower-limit;thereby bracketing structural reactivation from ca.42-25 *** results provide enhanced spatial-temporal resolution for Cenozoic deformation in the eastern Tibetan Plateau.

关键词： Nonmarine strata Yidun terrane Tibetan plateau Zircon Suture zone Reactivation

ERROR ESTIMATES FOR THE TIME DISCRETIZATION FOR NONLINEAR MAXwELL'S EQUATIONS

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2008年第5期26卷 677-688页

作者： Mavián Slodika Ján Bua jr. Department of Mathematical Analysis Ghent University

This paper is devoted to the study of a nonlinear evolution eddy current model of the type δtB（H）＋ △↓× （ △↓ × H） =0 subject to homogeneous Dirichlet boundary conditions H × v = 0 and a given initial datum. Here, the magnetic properties of a soft ferromagnet are linked by a nonlinear material law described by B（H）. we apply the backward Euler method for the time discretization and we derive the error estimates in suitable function spaces. The results depend on the nonlinearity of B（H）.

关键词： Electromagnetic field Nonlinear eddy current problem Time discretization,Error estimate.

在线全文

学校读者我要写书评

暂无评论

Magnetic Cooling

Journal of Rare Earths 2005年第4期23卷 I0001-I0002页

作者： Karl A. Gschneidner jr. Materials and Engineering Physics Ames Laboratory Department of Materials Science and Engineering Iowa State University Ames IA 50011-3020 USAMaterials and Engineering Physics Ames Laboratory Department of Materials Science and Engineering Iowa State University Ames IA 50011-3020 USA

The world has become highly dependent on reliable refrigeration technology. without it, our food supply would be still seasonal and limited to locally produced nonperishable items; comfortable living conditions via climate control would be impossible; and certain medical advancements, e.g. MRI diagnostics, organ transplantation, organ and tissue cryo-storage, and cryo-surgery would be impossible. This technology remains essentially unchanged since it was invented 100 years ago.

关键词： Magnetic Cooling

Model-based framework for multi-axial real-time hybrid simulation testing

在线全文

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2017年第4期16卷 671-691页

作者： Gaston A.Fermandois Billie F.Spencer,jr. Department of Civil and Environmental Engineering University of Illinois at Urbana-ChampaignUrbanaIL 61801USA

Real-time hybrid simulation is an efficient and cost-effective dynamic testing technique for performance evaluation of structural systems subjected to earthquake loading with rate-dependent behavior. A loading assembly with multiple actuators is required to impose realistic boundary conditions on physical specimens. However, such a testing system is expected to exhibit significant dynamic coupling of the actuators and suffer from time lags that are associated with the dynamics of the servo-hydraulic system, as well as control-structure interaction （CSI）. One approach to reducing experimental errors considers a multi-input, multi-output （MIMO） controller design, yielding accurate reference tracking and noise rejection. In this paper, a framework for multi-axial real-time hybrid simulation （maRTHS） testing is presented. The methodology employs a real-time feedback-feedforward controller for multiple actuators commanded in Cartesian coordinates. Kinematic transformations between actuator space and Cartesian space are derived for all six-degrees-of- freedom of the moving platform. Then, a frequency domain identification technique is used to develop an accurate MIMO transfer function of the system. Further, a Cartesian-domain model-based feedforward-feedback controller is implemented for time lag compensation and to increase the robustness of the reference tracking for given model uncertainty. The framework is implemented using the 1/5th-scale Load and Boundary Condition Box （LBCB） located at the University of Illinois at Urbana- Champaign. To demonstrate the efficacy of the proposed methodology, a single-story frame subjected to earthquake loading is tested. One of the columns in the fraane is represented physically in the laboratory as a cantilevered steel column. For real- time execution, the numerical substructure, kinematic transformations, and controllers are implemented on a digital signal processor. Results show excellent performance of the maRTHS framework when

关键词： real-time hybrid simulation multiple actuators dynamic coupling kinematic transformations model-basedcompensation