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Lateral distributions of streamwise velocity in compound channels with partially vegetated floodplains

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Science China(Technological Sciences) 2009年第11期52卷 3357-3362页

作者： KNIGHT Donald w School of Civil Engineering The University of Birmingham Birmingham B15 2TT UK

Natural rivers are commonly characterized by a main channel for primary flow conveyance and a floodplain, often partially covered with vegetation such as shrubs or trees, to carry extra flow during floods. The hydraulic resistance due to vegetation on the floodplain typically causes a further reduction of flow velocity and increases the velocity difference between the main channel and the floodplain. As a consequence a strong lateral shear layer leads to the exchange of mass and momentum between the main channel and floodplain, which in turn affects the overall channel conveyance and certain fluvial processes. The prediction of the lateral velocity distribution is important for many flood alleviation schemes, as well as for studies on sediment transport and dispersion in such channels. The present paper proposes a method for predicting the depth-averaged velocity in compound channels with partially vegetated floodplains, based on an analytical solution to the depth-integrated Reynolds-Averaged Navier-Stokes equation with a term included to account for the effects of vegetation. The vegetation is modelled via an additional term in the momentum equation to account for the additional drag force. The method includes the effects of bed friction, drag force, lateral turbulence and secondary flows, via four coefficients f, CD, λ & Γ respectively. The predicted lateral distributions of depth-averaged velocity agree well with the experimental data. The analytical solutions can also be used to predict the distribution of boundary shear stresses, which adds additional weight to the method proposed.

关键词： vegetation compound channel floodplain velocity

Generalized Hopfian Property, a Minimal Haken Manifold, and Epimorphisms Between 3-Manifold Groups

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Acta Mathematica Sinica,English Series 2002年第1期18卷 157-172页

作者： REID Alan w Department of Mathematics. University of Texas Austin. TX 78712. USA

we address the question that if π_1-surjective maps between closed aspherical 3-manifolds have the same rank on π_1 they must be of non-zero degree. The positive answer is proved for Seifert manifolds, which is used in constructing the first known example of minimal Haken manifold. Another motivation is to study epimorphisms of 3-manifold groups via maps of non-zero degree between 3- manifolds. Many examples are given.

关键词： Non-zero degree maps Epimorphisms 3-Manifolds

Epidemiology of Sexual dysfunction in Asia compared to the rest of the world

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Asian Journal of Andrology 2011年第1期13卷 152-158页

作者： Ronald w Lewis Section of Urology Medical College of Georgia Augusta GA 30912 USA

There have been a limited number of epidemiological studies published on sexual disorders in persons from Asia. This paper aims to assess the reports of sexual dysfunction epidemiological studies published in the English language that involved Asian countries. Key points are summarized in this paper from nine epidemiological papers on sexual dysfunction from Asia that were published in the English language. Seven met the criteria for evidence-based studies reaching a Prins score of at least 10 or more. Papers included in this report came from national and regional representative studies in peer review journals. These results for sexual dysfunction in the nine papers are summarized for various sexual dysfunctions in men and women in Asian countries. In three of these, worldwide data were presented in the same paper allowing comparisons with Asian data on prevalence rates. Detailed descriptions from each of these studies are presented in paragraph form. More detailed data on erectile dysfunction （ED） is presented in a tabular form. Collectively, there seems to be a need for country- and population-specific further descriptive and analytical epidemiological studies in all of the sexual disorders from Asia. This critical review paper should help guide these studies for reachinj[ evidence-based literature standards.

关键词： descriptive epidemiology male and female dysfunction male ED premature ejaculation

The QT interval in Parkinson′s disease:a systematic review

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Journal of Geriatric Cardiology 2024年第9期21卷 855-864页

作者： Simon w Rabkin Division of Cardiology University of British ColumbiaVancouverBC V5Z 1M9Canada

Background PD(PD)is associated with a twofold increase in the risk of death especially sudden death.A predisposing factor for cardiac sudden death is prolongation of the QT *** study evaluated the potential association between QT interval and *** A systematic search was conducted of Medline and EMBASE using the search terms“PD”AND“QT interval”OR“Cardiac Repolarization”to identify *** Seven studies with persons with PD(n=981)and control groups were *** was a significant difference in QT interval comparing patients with PD and persons without *** odds ratio showed a significant(Pwas a significantly longer QT in patients with PD than controls of 10.7±2.8 *** analysis did not show much publication *** only on studies that related the QT interval to the severity of PD as assessed by Hoehn–Yahr classification(n=6),there was a significant(P=0.004)overall correlation between QT interval and the severity of *** was little publication *** data directly examining patients with PD taking any drug than might prolong QT do not support an association between these mediations and QT *** Individuals with PD have a longer QT interval than individuals without *** QT interval is associated with a greater severity of PD and a greater probability of developing more severe *** QT interval should be considered in assessment of PD and possibly as a target for the treatment of PD.

关键词： QT QTc Focus

Dynamic Deformation of Frozen Soil at a High Strain Rate:Experiments and Damage-Coupled Constitutive Model

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Acta Mechanica Solida Sinica 2021年第6期34卷 895-910页

作者： Z.w.Zhu w.R.Tang G.Z.Kang Applied Mechanics and Structural Safety Key Laboratory of Sichuan Province School of Mechanics and EngineeringSouthwest Jiaotong UniversityChengdu610036China Northwest institute of Eco-Environment and Resources State Key Laboratory of Frozen Soil EngineeringChinese Academy of SciencesLanzhou730000China

The dynamic compressive deformation of frozen soil was investigated by conducting the split-Hopkinson pressure bar(SHPB)experiments at three temperatures and different high strain rates,and the dynamic stress–strain responses and failure modes of the frozen soil were *** experimental results demonstrate that the frozen soil exhibits evident dependence on the strain rate and temperature under the dynamic loading *** dynamic compressive stress–strain curve of the frozen soil was divided into three parts:the linear,nonlinear rising,and strain softening *** nonlinear rising and strain softening parts were both caused by the damage attributed to the debonding between the ice particles and soil matrix,from which a rate-dependent damage evolution equation was ***,a damage-coupled dynamic viscoelastic constitutive model of frozen soil at high strain rate was derived.A comparison between the theoretically predicted results and the experimental ones showed that the developed dynamic viscoelastic model could well describe the dynamic mechanical behavior of frozen soil at high strain rate.

关键词： Frozen soil Dynamic compression High strain rate Damage Constitutive model

Microstructure and mechanical optimization of probeless friction stir spot welded joint of an Al-Li alloy

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Journal of Materials Science & Technology 2018年第10期34卷 1739-1746页

作者： Q. Chu w.Y. Li X.w. Yang J.J. Shen A. Vairis w.Y. Feng w.B. wang State Key Laboratory of Solidification Processing Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical University Xi'an710072 China Helmholtz-Zentrum Geesthacht Institute of Materials Research Materials Mechanics Geesthacht 21502 Germany Mechanical Engineering Department TEl of Crete Heraklion Crete 71004 Greece China PSw Center Beijing 100024 China

In this work, a third generation AI-Li alloy has been successfully spot welded with probeless friction stir spot welding （P-FSSw）, which is a variant of conventional friction stir welding. The Box-Behnken exper-imental design in response surface methodology （RSM） was applied to optimize the P-FSSw parameters to attain maximum tensile/shear strength of the spot joints. Results show that an optimal failure load of 7.83 kN was obtained under a dwell time of 7.2 s, rotation speed of 950 rpm and plunge rate of 30 mm/rain. Sufficient dwell time is essential for heat conduction, material flow and expansion of the stir zone to form a sound joint. Two fracture modes were observed, which were significantly affected by hook defect. In addition to mechanical testing, electron backscattering diffraction （EBSD） and differential scanning calorimetry （DSC） were used for microstructure evolution and property analysis. The precipitation of GP zone and AI3Li as well as the ultrafine grains were responsible for the high microhardness in the stir zone.

关键词： Probeless friction stir spot welding Precipitation Mechanical property Fracture mechanism

Sediment Transport in Rivers with Overbank Flow

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四川大学学报（工程科学版） 2005年第S1期37卷 16-29页

作者： Donald w KNIGHT water Eng. The Univ.of BirminghamUK

Some concepts related to sediment transport in rivers with overbank flow are *** a description of the physical processes that are involved when a river inundates its floodplains,some simple com- putational methods are presented which permit the depth-averaged velocity and boundary shear stress to be pre- dicted within a cross section of variable,but prismatic *** methoda account for the strong transverse shear in velocity that occurs when the stage is just above bankfull,as well as ...

关键词： sediment transport overbank flow

Aqueous deficiency is a contributor to evaporation-related dry eye disease

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Eye and Vision 2020年第1期7卷 58-63页

作者： Charles w.McMonnies School of Optometry and Vision Science University of New South Wales77 Cliff AvenueNorthbridgeSydneyKensingtonNew South Wales 2052Australia

Dry eye disease aetiologies can be classified dichotomously into aqueous deficient and evaporative types although many cases involve combinations of *** diagnosis can be confounded by some features of dry eye disease being common to both *** example,short tear break-up times are prime diagnostic findings of tear instability due to lipid and/or mucin deficiencies,but thin tear layers in aqueous deficient eyes also shorten tear break-up times,even at normal range rates of evaporation in eyes without lipid and/or mucin *** tear instability and short tear film break-up times due to thin tear layers can be independent of lipid and/or mucin deficiency,aqueous deficiency can be another form of evaporation-related dry ***,tear layers which are thickened by punctal occlusion can be less susceptible to tear *** inflamed lacrimal gland producing reduced quantities of warmer tears can be a basis for thin tear layers and tear instability demonstrated by shorter tear break-up *** used clinical tests for aqueous deficiency can be unreliable and less ***,failure to detect or confirm aqueous deficiency as a contributor to short tear break-up times could result in too much weight being given to a diagnosis of meibomian gland *** successful treatment outcomes may be a consequence of failing to detect aqueous *** disease classification by considering aqueous deficiency as a contributor to,or even a form of evaporation-related dry eye,could be the basis for more comprehensive and appropriate treatment *** example,some treatment methods for evaporation-related dry eye might be appropriate for aqueous and mucin-deficient as well as lipid-deficient dry ***-inflammatory treatment for the lacrimal gland as well as the conjunctiva,may result in increased aqueous production,reduced tear temperature,tear instability and evaporation rates as well as lower osmol

关键词： Aqueous deficient Evaporative Dry eyes Tear break-up

Review of mass-flow hopper design with respect to stress fields and surcharge loads

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Particuology 2010年第6期8卷 591-594页

作者： Alan w.Roberts Centre for Bulk Solids and Partculate Technologies The University of NewcastleNSWAustralia

Current procedures for mass-flow hopper design are based on the radial stress theory developed byJenike and involve the determination of the critical outlet dimensions for flow to be initiated. These procedures ignore the surcharge loads on the hopper and involve a study of the passive or arched stress field that exists under flow conditions. An alternative approach as applied to hopper wall load analysis is to employ the horizontal slice method. The arched stress field and horizontal slice methods of analysis are compared. The influence of surcharge loads in the determination of hopper geometry is investigated.

关键词： Mass-flow Surcharge pressure Cohesive arching