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Effects of layer interactions on instantaneous stability of finite Stokes flows

Applied Mathematics and Mechanics(English Edition) 2024年第1期45卷 69-84页

作者： chen ZHAO Zhenli cHEN c.t.MUtASA Dong LI School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China

the stability analysis of a finite Stokes layer is of practical importance in flow control. In the present work, the instantaneous stability of a finite Stokes layer with layer interactions is studied via a linear stability analysis of the frozen phases of the base flow. the oscillations of two plates can have different velocity amplitudes, initial phases, and frequencies. the effects of the Stokes-layer interactions on the stability when two plates oscillate synchronously are analyzed. the growth rates of two most unstable modes when δ t equal, and δ = δ*/h*, where δ*and h*are the Stokes-layer thickness and the half height of the channel, respectively. However, their vorticities are different. the vorticity of the most unstable mode is symmetric, while the other is asymmetric. the Stokes-layer interactions have a destabilizing effect on the most unstable mode when δ tabilizing effect when δ > 0.68. However, the interactions always have a stabilizing effect on the other unstable mode. It is explained that one of the two unstable modes has much higher dissipation than the other one when the Stokes-layer interactions are strong. We also find that the stability of the Stokes layer is closely related to the inflectional points of the base-flow velocity profile. the effects of inconsistent velocity-amplitude, initial phase, and frequency of the oscillations on the stability are analyzed. the energy of the most unstable eigenvector is mainly distributed near the plate of higher velocity amplitude or higher oscillation frequency. the effects of the initial phase difference are complicated because the base-flow velocity is extremely sensitive to the initial phase.

关键词： finite Stokes layer instantaneous stability Stokes-layer interaction asynchronous oscillation

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Soils and Surface Waters as Affected by Long-term Swine Slurry Application in Oxisols of Southern Brazil

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Pedosphere 2014年第5期24卷 585-594页

作者： t.BROEttO c.G.tORNQUISt c.BAYER B.c.cAMPOS c.G.MERtEN B.WOttRIcH Departamento de Solos Universidade Federal do Rio Grande do Sul (UFRGS) 91540-000 Porto Alegre RS (Brazil) Instituto Federal do Rio Grande do Sul/campus Ibirubá

the accelerated expansion of swine production in Brazil has increased the generation of liquid wastes, which are usually applied to agricultural soils after a simplified treatment and pose potential environmental impacts. the objective of this study was to assess the agronomic and environmental impacts of long-term application of swine slurry(SS) on soil and stream water properties in watersheds dominated by Oxisols in Quinze de Novembro of Southern Brazil. Soil samples(0–30 cm) were collected from farms with continuous application of SS since 1990 at low(40–80 m3 SS ha-1year-1) and high(120–300 m3 SS ha-1year-1) rates of SS. Surface water samples were collected from streams adjacent to the farm fields. Long-term SS application did not change total organic c and particulate organic c compared to cropland and woodland soils without SS application. the high rates of SS increased total N, P, cu,and Zn and available P and cu in the topsoil(0–10 cm) compared to woodland and cropland soils without SS application. Surface water analyses showed that fecal coliform bacteria and biological oxygen demand exceeded the legal limits for high quality water(class 1). Other water parameters(such as NO-3, phosphate and total suspended solids) were within the acceptable limits. Long-term disposal of SS in cropland under no-tillage had impaired water quality in Quinze de Novembro, especially biological parameters. Some best management practices should be adopted, including more rigorous control of SS application to cropland as well as requiring edge-of-field and riparian vegetative buffers.

关键词： no-tillage nutrient balance swine farm water quality watershed

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Predicting recrystallized grain size in friction stir processed 304L stainless steel

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Journal of Materials Science & technology 2019年第4期35卷 491-498页

作者： M.P.Miles t.W.Nelson c.Gunter F.c.Liu L.Fourment t.Mathis Manufacturing Engineering Department Brigham Young University centre de Mise en Forme des Materiaux Mines ParisTech

A major dilemma faced in the nuclear industry is repair of stainless steel reactor components that have been exposed to neutron irradiation. When conventional fusion welding is used for repair, intergranular cracks develop in the heat-affected zone(HAZ). Friction stir processing(FSP), which operates at much lower peak temperatures than fusion welding, was studied as a crack repair method for irradiated 304 L stainless steel. A numerical simulation of the FSP process in 304 L was developed to predict temperatures and recrystallized grain size in the stir zone. the model employed an Eulerian finite element approach,where flow stresses for a large range of strain rates and temperatures inherent in FSP were used as input. temperature predictions in three locations near the stir zone were accurate to within 4%, while prediction of welding power was accurate to within 5% of experimental measurements. the predicted recrystallized grain sizes ranged from 7.6 to 10.6 μm, while the experimentally measured grains sizes in the same locations ranged from 6.0 to 7.6 μm. the maximum error in predicted recrystallized grain size was about 39%, but the associated stir zone hardness from the predicted grain sizes was only different from the experiment by about 10%.

关键词： Stainless steel Numerical simulation Friction stir welding Recrystallized grain size

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Derivation of a Non-Local Model for Diffusion Asymptotics--Application to Radiative transfer Problems

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communications in computational Physics 2010年第10期8卷 1139-1182页

作者： c.Besse t.Goudon Project team SIMPAF INRIA Lille Nord Europe Research Centre Park Plazza40 avenue HalleyF-59650 Villeneuve d’AscqFrance Laboratoire Paul Painleve UMR 8524CNRS-Universite des Sciences et Technologies de LilleCite ScientifiqueF-59655 Villeneuve d’Ascq CedexFrance

In this paper,we introduce a moment closure which is intended to provide a macroscopic approximation of the evolution of a particle distribution function,solution of a kinetic *** closure is of non local type in the sense that it involves convolution or pseudo-differential *** show it is consistent with the diffusion limit and we propose numerical approximations to treat the non local *** illustrate how this approach can be incorporated in complex models involving a coupling with hydrodynamic equations,by treating examples arising in radiative *** pay a specific attention to the conservation of the total energy by the numerical scheme.

关键词： Diffusion approximation nonlocal transport asymptotic preserving methods radiative hydrodynamics

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Oxidation of propane over substituted Keggin phosphomolybdate salts

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Journal of Natural Gas chemistry 2009年第3期18卷 319-324页

作者： t.Mazari c.Roch.Marchal S.Hocine N.Salhi c.Rabia Laboratoire de chimie du Gaz Naturel Faculté de ChimieUniversité des Sciences et de la Technologie Houari Boumediéne ILV-UMR 8180 cNRS-Université de Versailles-St Quentin-en-Yvelines Batiment Lavoisier45 avenue des Etats-Unis78035 Versailles CedexFrance

Ammonium salts, （NH4）6HPMo11MO40 （M = Ni, co, Fe）, have been investigated for the oxidation of propane, with molecular oxygen, at temperature ranging between 380 ℃ and 420 ℃ after in-situ pre-treatment performed at two heating rate of 5 or 9 ℃/min. they were characterized by BEt method, XRD, 31p NMR, UV-Vis and IR techniques. the catalysts were found active in the propane oxidation and selective to propene or acrolein, in particular for samples pre-treated with the heating rate of 9 ℃/min.

关键词： propane oxidation propene acrolein polyoxometalates phosphomolybdate

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Study of central Intensity Ratio of Seyfert Galaxies in Nearby Universe

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Research in Astronomy and Astrophysics 2023年第4期23卷 85-93页

作者： K.t.Vinod c.Baheeja S.Aswathy c.D.Ravikumar Department of Physics University of CalicutMalappuram-673635India Department of Physics Providence Women's CollegeCalicut-673009India

We use the recently discovered simple photometric parameter central Intensity Ratio(cIR)determined for a sample of 57 nearby(z<0.02)Seyfert galaxies to explore the central features of galaxies and their possible conne... 详细信息

We use the recently discovered simple photometric parameter central Intensity Ratio(cIR)determined for a sample of 57 nearby(zt galaxies to explore the central features of galaxies and their possible connection with galaxy *** sample of galaxies shows strong anti-correlation between cIR and mass of their central supermassive black holes(SMBHs).the SMBH masses of ellipticals are systematically higher for a given cIR value than those for lenticulars and spirals in the ***,the correlation between cIR and central velocity dispersion is *** appears less influenced by the excess flux produced by the central engine in these galaxies,when compared to spectroscopic parameters like velocity dispersion and OⅣflux,and proves to be a fast and reliable tool for estimating central SMBH mass.

关键词： Galaxy evolution-galaxies active-galaxies photometry-(galaxies:)quasars supermassive black holes-galaxies Seyfert

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controlling Excitation Inversion of a cooper Pair Box Interacting with a Nanomechanical Resonator

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chinese Physics Letters 2012年第8期29卷 20-24页

作者： c.Valverde H.c.B.de Oliveira A.t.Avelar B.Baseia Instituto de Química Universidade de Brasília70919-970BrasíliaDFBrazil Universidade Estadual de Goiás Rod.BR 15375132-903 AnápolisGOBrazil Universidade Paulista Rod.BR 153km 774845-090 GoianiaGOBrazil Instituto de Física Universidade Federal de Goiás74001-970 GoianiaGOBrazil

We investigate the action of time-dependent detunings upon the excitation inversion of a cooper pair box interacting with a nanomechanical *** method employs the Jaynes–cummings model with damping,assuming different decay rates of the cooper pair box and various fixed and time-dependent *** is shown that,when the presence of damping plus constant detunings destroys the collapse/revival effects,convenient choices of time-dependent detunings allow one to reconstruct such events in a perfect *** is also shown that the mean excitation of the nanomechanical resonator is more robust against damping of the cooper pair box for convenient values of time-dependent detunings.

关键词： cooper tuning excitation

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Use of Recycled Glass in Architectural Mortars

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武汉理工大学学报 2010年第17期32卷 231-234,245页

作者： POON c S LING t c B Department of civil and Structural Engineering The Hong Kong Polytechnic UniversityHong KongChina

In recent years,recycled glass has been widely used as aggregate replacements in concrete. Owing to the aesthetic potential of the coloured recycled glass,this research aims to fully utilize this advantage for their higher end uses,such as architectural mortar. In this study,architectural white cement mortar was produced with a self consolidating method using recycled glass as the aggregate. An adequate amount of Metakaolin was incorporated into the mortar to mitigate the adverse effect of alkali-silica reaction. the results show that the self-compacting method is suitable to produce architectural mortar containing up to 100% recycled glass. Overall,the performance of all the architectural mortar mixtures in terms of both fresh and hardened properties was good.

关键词： recycled glass self-compacting architectural mortar ASR flexural strength

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Bulk nanocrystalline W-ti alloys with exceptional mechanical properties and thermal stability

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Journal of Materials Science & technology 2022年第19期114卷 16-28页

作者： H.X.Xue X.c.cai B.R.Sun X.Shen c.c.Du X.J.Wang t.t.Yang S.W.Xin t.D.Shen clean Nano Energy center State Key Laboratory of Metastable Materials Science and TechnologyYanshan UniversityQinhuangdao 066004China cSSc 723rd Research Institute China State Shipbuilding Corporation LimitedYangzhou 225000China

Nanocrystalline(Nc)W metals and alloys often exhibit higher radiation tolerance and strength than their coarse-grained ***,their thermal stability is low,making it difficult to achieve bulk Nc W metals and alloys by consolidation using conventional techniques such as pressure-less sintering,hot-explosive-compaction sintering,and spark plasma *** we report the synthesis and mechanical properties of bulk Nc W_(100-x)ti_(x)(x=10 at.%-30 at.%)alloys prepared by consolidating mechanically alloyed Nc powders under a high-temperature/high-pressure *** 20 at.%-30 at.%ti largely improves the sinterability of Nc W-ti alloy *** room-temperature microhardness and compressive yield strength of consolidated bulk Nc W_(80)ti_(20) alloy are∼16.9 and 6.0 GPa,respectively,which are mainly caused by grain boundary strengthening and significantly higher than those of previously reported W and W *** ultimate compressive strength of bulk Nc W_(80)ti_(20) measured between 900 and 1100°c deceases with increasing *** behavior can be explained by the activation of Rachinger grain boundary *** grain growth is observed in bulk Nc W_(80)ti_(20) after compression at 1000°*** calculation suggests that it is the segregation of ti at grain boundaries that decreases the specific grain boundary free energy and makes the Nc W_(80)ti_(20) alloy thermodynamically stable.

关键词： Nanocrystalline W-ti alloys Segregation Grain boundary energy Strength Hardness

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Numerical simulation of a sheet metal extrusion process by using thermal-mechanical coupling EAS FEM

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Journal of University of Science and technology Beijing 2002年第5期9卷 378-382页

作者： Zhanghuachen t.c.Lee 等 AppliedScienceSchool UniversityofScienceandTechnologyBeijingBeijing100083China DepartmentofIndustrialsystemEngineering TheHongKongPolytechnicunivetsityChina

the thermal-mechanical coupling finite element method(FEM)was usedto simulate a non-isothermal sheet metal extrusion process. On thebasis of the finite plasticity consistent with multiplicativedecomposition of the deformation gradient, the enhanced as- sumedstrain(EAS)FEM was applied to carry out the numerical simulation. Inorder to make the computation reliable ad avoid hour- glass mode inthe EAS element under large compressive strains, an alterative formof the original enhanced deformation gradient was employed. Inaddition, reduced factors were used in the computation of the elementlocal internal parameters and the enhanced part of elementalstiffness.

关键词： enhanced assumed strain element thermal-mechanical coupling process houyrglass mode

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