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Surface stress effect on the vibration and instability of nanoscale pipes conveying fluid based on a size-dependent Timoshenko beam model

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Acta Mechanica Sinica 2015年第5期31卷 708-719页

作者： r.Ansari r.Gholami A.Norouzzadeh M.A.Darabi Department of Mechanical Engineering University of Guilan Department of Mechanical Engineering Lahijan BranchIslamic Azad University

Presented in this paper is a precise investigation of the effect of surface stress on the vibration characteristics and instability of fluid-conveying nanoscale *** this end,the nanoscale pipe is modeled as a Timoshenko *** equations of motion of the nanoscale pipe are obtained based on Hamilton＇s principle and the Gurtin-Murdoch continuum elasticity incorporating the surface stress ***,the generalized differential quadrature method is employed to discretize the governing equations and associated boundary *** what extent important parameters such as the thickness,material and surface stress modulus,residual surface stress,surface density,and boundary conditions influence the natural frequency of nanoscale pipes and the critical velocity of fluid is discussed.

关键词： Fluid-conveying pipes Vibration and instability Surface stress Gurtin-Murdoch elasticity continuum Generalized differential quadrature method

Heat Transfer Augmentation in Developing Flow Through a ribbed Square Duct

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Journal of Thermal Science 2006年第3期15卷 251-256页

作者： Khan r K Ali M.A.T Akhanda M.A.r Principal Polytechnic InstitutePotuakhaliBangladesh Department of Mechanical Engineering Bangladesh University of Engineering and Technology(BUET)DhakaBangladesh Department of Mechanical and Chemical Engineering Islamic University of Technology(IUT) OIC Gazipur-1704DhakaBangladesh

An experimental study is conducted to investigate the heat transfer augmentation in developing turbulent flow through a ribbed square duct. The duct is made of 16ram thick bakelite sheet. The bottom surface of the ribbed wall having rib pitch to height ratio of 10 is heated by passing a c current to the heater placed under it. The uniform heating is controlled using a digital temperature controller and a variac. The results of ribbed duct are compared with the results of a smooth duct under the same experimental conditions. It is observed that the heat transfer augmentation in ribbed duct is better than that of the smooth duct. At re=5.0× 10^4 , the mean temperature of air flowing through the ribbed duct increases by 2.45 percent over the smooth duct, whereas in the fibbed duct Nusselt number increases by 15.14 percent than that of the smooth duct with a 6 percent increase in pressure drop.

关键词： heat transfer square duct developing flow turbulent promoters

Effect of wall rougheners on cross-sectional flow characteristics for non-spherical particles in a horizontal rotating cylinder

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Particuology 2014年第1期12卷 44-53页

作者： Guang Lu James r.Third Christoph r.Müller ETH Zürich Department of Mechanical and Process Engineering Institute of Energy Technology Laboratory of Energy Science and Engineering8092 Zürich Switzerland

Discrete-element-method （DEM） simulations have been performed to investigate the cross-sectional flow of non-spherical particles in horizontal rotating cylinders with and without wall rougheners. The non-spherical particles were modeled using the three-dimensional super-quadric equation. The influence of wall rougheners on flow behavior of grains was studied for increasing particle blockiness. Moreover, for approximately cubic particles （squareness parameters [555]）, the rotational speed, gravitational acceleration and particle size were altered to investigate the effect of wall rougheners under a range of operating conditions. For spherical and near-spherical particles （approximately up to the squareness parameters [344]）, wall rougheners are necessary to prevent slippage of the bed against the cylinder wall. For highly cubic particle geometries （squareness parameters larger than [3441）, wall rougheners resulted in a counter-intuitive decrease in the angle of repose of the bed. In addition, wall rougheners employed in this study were demonstrated to have a higher impact on bed dynamics at higher rotational speeds and lower gravitational accelerations. Nevertheless, using wall rougheners had a comparatively small influence on particle-flow characteristics for a bed composed of finer grains.

关键词： Granular flowNon-spherical particlesrotating cylinderDiscrete element method (DEM)Kiln

Charm hadronic decays and quantum correlations at CLEO-c

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Chinese Physics C 2010年第6期34卷 765-773页

作者： r.A.Briere Department of Physics Carnegie Mellon University

Several recent CLEO-c results on hadronic decays of charm mesons are reviewed. Topics include measurements of precision branching fractions for exclusive modes, investigations of inclusive rates, and analyses of Dalitz plots. In addition, the quantum correlations of the DD pairs produced at the ψ（3770） are exploited to measure phase information that is of current interest for both D and B physics.

关键词： charm mesons hadronic decays quantum correlations CKM matrix

Inhomogeneous 2D Lennard-Jones Fluid: Theory and Computer Simulation

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Communications in Theoretical Physics 2012年第11期58卷 759-764页

作者： r. Khordad Department of Physics College of SciencesYasouj University

In this work, thermodynamical properties of a two-dimensional （21）） Lennard-Jones （L J） fluid are studied. Here, to increase the accuracy of our theoretical calculations, the correlation functions in three-particle level （triplet） are applied. To obtain the triplet correlation functions, the Attard＇s source particle method is extended to 21） systems. In the Attard＇s procedure, the inhomogeneous Ornstein Zernike （OZ） equation is solved using the Treizenberg Zwanzwig （TZ） expression and a closure relation like the hy2ernetted-chain （HNC） approximation. In the present work, we also have performed the Monte Carlo （MC） simulation. The theoretical results are in fairly agreement with the MC simulation. Also, our results show that the approach proposed here is suitable to study the 2D LJ fluid.

关键词： Lennard-Jones fluid correlation functions computer simulation three-particle level

Complex variable approach in studying modified polarization saturation model in two-dimensional semipermeable piezoelectric media

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Applied Mathematics and Mechanics(English Edition) 2017年第11期38卷 1517-1532页

作者： S. SINGH K. SHArMA r. r. BHArGAVA Department of Sciences and Humanities National Institute of Technology UttarakhandSrinagar(Garhwal)246174India Department of Mathematics Indian Institute of Technology RoorkeeRoorkee 247667India

A modified polarization saturation model is proposed and addressed math- ematically using a complex variable approach in two-dimensional （2D） semipermeable piezoelectric media. In this model, an existing polarization saturation （PS） model in 2D piezoelectric media is modified by considering a linearly varying saturated normal electric displacement load in place of a constant normal electric displacement load, applied on a saturated electric zone. A centre cracked infinite 2D piezoelectric domain subject to an arbitrary poling direction and in-plane electromechanical loadings is considered for the analytical and numerical studies. Here, the problem is mathematically modeled as a non-homogeneous riemann-Hilbert problem in terms of unknown complex potential functions representing electric displacement and stress components. Having solved the Hilbert problem, the solutions to the saturated zone length, the crack opening displace- ment （COD）, the crack opening potential （COP）, and the local stress intensity factors （SIFs） are obtained in explicit forms. A numerical study is also presented for the proposed modified model, showing the effects of the saturation condition on the applied electrical loading, the saturation zone length, and the COP. The results of fracture parameters obtained from the proposed model are compared with the existing PS model subject to electrical loading, crack face conditions, and polarization angles.

关键词： complex variable fracture parameter local stress intensity factor (SIF),piezoelectric polarization saturation (PS) model

Soil Wettability as Affected by Soil Characteristics and Land Use

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Pedosphere 2010年第1期20卷 43-54页

作者： r. HOrN Institute of Plant Nutrition and Soil Science Christian-Albrechts-University zu Kiel

Depth distribution of soil wettability and its correlations with vegetation type, soil texture, and pH were investigated under various land use (cropland, grassland, and forestland) and soil management systems. Wettability was evaluated by contact angle with the Wilhelmy plate method. Water repellency was likely to be present under permanently vegetated land, but less common on tilled agricultural land. It was mostly prevalent in the topsoil, especially in coarse-textured soils, and decreased in the subsoil. However, the depth dependency of wettability could not be derived from the investigated wide range of soils. The correlation and multiple regression analysis revealed that the wettability in repellent soils was affected more by soil organic carbon (SOC) than by soil texture and pH, whereas in wettable soils, soil texture and pH were more effective than SOC. Furthermore, the quality of SOC seemed to be more important in determining wettability than its quantity, as proofed by stronger hydrophobicity under coniferous than under deciduous forestland. Soil management had a minor effect on wettability if conventional and conservation tillage or different grazing intensities were considered.

关键词： soil management soil organic carbon soil pH soil texture

Alpha-particle decays from excited states in ^(24)Mg

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Science China(Physics,Mechanics & Astronomy) 2011年第S1期54卷 130-135页

作者： LIOTTA r J royal Institute of Technology (KTH) AlbaNova University Center Stockholm S-10691 Sweden

Using a cluster model based on the Woods-Saxon potential, alpha-particle decays from excited states in 24Mg have been system atically investigated. Calculations can in general reproduce experimental data, noticing the fact that the preformation factor P of alpha particle in alpha-decaying nuclei is of order from 100 to 10?2. This can be the evidence for the α+20Ne structure in 24Mg. Meanwhile, the results also show the existence of other configurations, such as 16O+2α. Since the calculated decay widths are very sensitive to the angular momentum carried by the outgoing cluster (α particle), our results could serve as a guide to experimental spin assignments.

关键词： alpha decay cluster structure cluster model 24Mg

Testosterone and metabolic syndrome

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Asian Journal of Andrology 2015年第2期17卷 192-196,I0006页

作者： Glenn r Cunningham Departments of Medicine and Molecular and Cellular Biology Baylor College of Medicine Baylor St. Luke's Medical Center 6624 Fannin Suite 1180 Houston TX 77030 USA.

Controversies surround the usefulness of identifying patients with the metabolic syndrome （MetS）. Many of the components are accepted risk factors for cardiovascular disease （CVD）. Although the MetS as defined includes many men with insulin resistance, insulin resistance is not universal. The low total testosterone （TT） and sex hormone binding globulin （SHBG） levels in these men are best explained by the hyperinsulinism and increased inflammatory cytokines that accompany obesity and increased waist circumference. It is informative that low SHBG levels predict future development of the MetS. Evidence is strong relating low TT levels to CVD in men with and without the MetS; however, the relationship may not be causal. The recommendations of the International Diabetes Federation for managing the MetS include cardiovascular risk assessment, lifestyle changes in diet, exercise, weight reduction and treatment of individual components of the MetS. Unfortunately, it is uncommon to see patients with the MetS lose and maintain a 10% weight loss. recent reports showing testosterone treatment induced dramatic changes in weight, waist circumference, insulin sensitivity, hemoglobin Alc levels and improvements in each of the components of the MetS are intriguing. While some observational studies have reported that testosterone replacement therapy increases cardiovascular events, the Food and Drug Administration in the United States has reviewed these reports and found them to be seriously flawed. Large, randomized, placebo-controlled trials are needed to provide more definitive data regarding the efficacy and safety of this treatment in middle and older men with the MetS and low TT levels.

关键词： cardiovascular risk metabolic syndrome sex hormone binding globulin testosterone testosterone replacement therapy