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Maintaining nano-lamellar microstructure in friction stir welding (FsW) of accumulative roll bonded (ARB) Cu-Nb nano-lamellar composites (NLC)

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Journal of Materials science & Technology 2018年第1期34卷 92-101页

作者： Judy schneider Josef Cobb John s.Carpenter Nathan A.Mara Department of Mechanical & Aerospace Engineering University of Alabama in Huntsville Department of Mechanical Engineering Mississippi State University Materials science and Technologies Division Los Alamos National Laboratory Center for Integrated Nanotechnologies and the Institute for Materials ScienceLos Alamos National Laboratory

Accumulative roll bonded （ARB） Copper Niobium （Cu-Nb） nano-lamellar composite （NLC） panels were friction stir welded （FsWed） to evaluate the ability to join panels while retaining the nano-lamellar structure. During a single pass of the friction stir welding （FsW） process, the nano-lamellar structure of the parent material （PM） was retained but was observed to fragment into equiaxed grains during the second pass. FsW has been modeled as a severe deformation process in which the material is subjected to an instantaneous high shear strain rate followed by extreme shear strains. The loss of the nano-lamellar layers was attributed to the increased strain and longer time at temperature resulting from the second pass of the FsW process. Kinematic modeling was used to predict the global average shear strain and shear strain rates experienced by the ARB material during the FsW process. The results of this study indicate that through careful selection of FsW parameters, the nano-lamellar structure and its associated higher strength can be maintained using FsW to join ARB NLC panels.

关键词： Nano-lamellar materials Accumulative roll bonded Cu-Nb FsW solid state joining

Mechanical behavior of Cu-Zr bulk metallic glasses (BMGs): A molecular dynamics approach

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Chinese Physics B 2013年第9期22卷 490-495页

作者： Muhammad Imran Fayyaz Hussain Muhammad Rashid Yongqing Cai s.A.Ahmad Department of Physics simulation Lab The Islamia University of Bahawalpur Department of Physics National University of Singapore2 Science Drive 3117542Singapore

In the present work, three-dimensional molecular dynamics simulation is carried out to elucidate the nanoinden- tation behaviors of CuZr Bulk metallic glasses （BMGs）. The substrate indenter system is modeled using hybrid interatomic potentials including both many-body Finnis sinclair （Fs） and two-body Morse potentials. A spherical rigid indenter （diameter= 60 A（1 A = 10 ^-10 m）） is employed to simulate the indentation process. Three samples of BMGs including Cu25Zr75, CusoZr50, and Cu75Zr25 are designed and the metallic glasses are formed by rapid cooling from the melt state at about 2000 K. The radial distribution functions are analyzed to reveal the dynamical evolution of the structure of the atoms with different compositions and different cooling rates. The mechanical behavior can be well understood in terms of load-depth curves and Hardness-depth curves during the nanoindentation process. Our results indicate a positive linear relationship between the hardness and the Cu concentration of the BMG sample. To reveal the importance of cooling rate provided during the processing of BMGs, we investigate the indentation behaviors of CusoZr50 at three different quenching rates. Nanoindentation results and radial distribution function （RDF） curves at room temperature indicate that a sample can be made harder and more stable by slowing down the quenching rate.

关键词： Bulk metallic glasses (BMGs) nanoindentation deformation quenching rate

Lane changing analysis for two-lane traffic flow

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Acta Mechanica sinica 2007年第1期23卷 49-54页

作者： Tieqiao Tang Haijun Huang s. C. Wong Rui Jiang Department of Automobile Engineering Beihang University Beijing 100083 China school of Management Beihang University Beijing 100083 China Department of Civil Engineering The University of Hong Kong Pokfulam Road Hong Kong China school of Engineering science University of Science and Technology of China Hefei 230026 China

In this paper, the two-lane traffic are studied by using the lane-changing rules in the car-following models. The simulation show that the frequent lane changing occurs when the lateral distance in car following activities is considered and it gives rise to oscillating waves. In contrast, if the lateral distance is not considered （or considered occasionally）, the lane changing appears infrequently and soliton waves occurs. This implies that the stabilization mechanism no longer functions when the lane changing is permitted. since the oscillating and soliton waves correspond to the unstable and metastable flow regimes, respectively, our study verifies that a phase transition may occur as a result of the lane changing.

关键词： Traffic flow Lane-changing rules Car-following models Flow stability

CuPc based organic-inorganic hetero-junction with Au electrodes

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Journal of semiconductors 2010年第7期31卷 22-25页

作者： Zubair Ahmad Muhammad H.sayyad Kh.s.Karimov Ghulam Ishaq Khan Institute of Engineering sciences and Technology TopiNWFP23460Pakistan Department of Mechanical Engineering 20 Symond Street AucklandUniversity of AucklandNew Zealand

A hetero-junction of n-silicon（n-si） and copper phthalocyanine（CuPc） has been *** current -voltage characteristics were investigated to explain the rectification and conduction *** effect of temperature and humidity on the electrical properties of n-si/CuPc hetero-junction has also been *** characteristics of the junction have been observed to be temperature and humidity dependent,so it is suggested that this junction can be used as a temperature and humidity sensor.

关键词： inorganic-organic hetero-junction n-si CuPc

Affine transformation of virtual 3D object using 2D localization of fingertips

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Virtual Reality & Intelligent Hardware 2020年第6期2卷 534-555页

作者： Mohammad Mahmudul ALAM s.M.Mahbubur RAHMAN Department of Electrical and Electronic Engineering Bangladesh University of Engineering and TechnologyDhaka 1000Bangladesh

Background Interactions with virtual 3D objects in the virtual reality(VR)environment using the gesture of fingers captured in a wearable 2D camera have emerging applications in *** This paper presents an approach of a two-stage convolutional neural network,one for the detection of hand and another for the *** purpose of VR environments is to transform a virtual 3D object with affine parameters by using the gesture of thumb and index *** To evaluate the performance of the proposed system,one existing,and another developed egocentric fingertip databases are employed so that learning involves large variations that are common in *** results show that the proposed fingertip detection system outperforms the existing systems in terms of the precision of *** The interaction performance of the proposed system in the VR environment is higher than that of the existing systems in terms of estimation error and correlation between the ground truth and estimated affine parameters.

关键词： Affine transformation Detection of fingertips Detection of hand Human-computer interaction Virtual reality

Mathematical model of micropolar fluid in two-phase immiscible fluid flow through porous channel

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Applied Mathematics and Mechanics(English Edition) 2018年第7期39卷 993-1006页

作者： P.K.YADAV s.JAIsWAL B.D.sHARMA Department of Mathematics Motilal Nehru National Institute of Technology Allahabad

This paper is concerned with the flow of two immiscible fluids through a porous horizontal channel. The fluid in the upper region is the micropolar fluid/the Eringen fluid, and the fluid in the lower region is the Newtonian viscous fluid. The flow is driven by a constant pressure gradient. The presence of micropolar fluids introduces additional rotational parameters. Also, the porous material considered in both regions has two different permeabilities. A direct method is used to obtain the analytical solu- tion of the concerned problem. In the present problem, the effects of the couple stress, the micropolarity parameter, the viscosity ratio, and the permeability on the velocity profile and the microrotational velocity are discussed. It is found that all the physical parameters play an important role in controlling the translational velocity profile and the microrotational velocity. In addition, numerical values of the different flow parameters are computed. The effects of the different flow parameters on the flow rate and the wall shear stress are also discussed graphically.

关键词： micropolar fluid immiscible fluid porous medium couple stress microp=olarity parameter

Exact solution for the unsteady flow of a semi-infinite micropolar fluid

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Acta Mechanica sinica 2011年第3期27卷 354-359页

作者： H.H. sherief M.s. Faltas E.A. Ashmawy Department of Mathematics Faculty of ScienceAlexandria University

The unsteady motion of an incompressible micropolar fluid filling a half-space bounded by a horizontal infinite plate that started to move suddenly is considered. Laplace transform techniques are used. The solution in the Laplace transform domain is obtained by using a direct approach. The inverse Laplace transforms are obtained in an exact manner using the complex inversion formula of the transform together with contour integration techniques. The solution in the case of classical viscous fluids is recovered as a special case of this work when the micropolarity coecient is assumed to be zero. Numerical computations are carried out and represented graphically.

关键词： Unsteady motion . Laplace transform . Microp-olar fluid

Jeffrey fluid flow due to curved stretching surface with Cattaneo-Christov heat flux

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Applied Mathematics and Mechanics(English Edition) 2018年第8期39卷 1173-1186页

作者： T.HAYAT s.QAYYUM M.IMTIAZ A.ALsAEDI Department of Mathematics Quaid-i-Azam University 45320 Nonlinear Analysis and Applied Mathematics (NAAM) Research Group Department of Mathematics Faculty of Science King Abdulaziz University Department of Mathematics University of Wah

The two-dimensional(2D) motion of the Jeffrey fluid by the curved stretching sheet coiled in a circle is investigated. The non-Fourier heat flux model is used for the heat transfer analysis. Feasible similarity variables are used to transform the highly nonlinear ordinary equations to partial differential equations(PDEs). The homotopy technique is used for the convergence of the velocity and temperature equations. The effects of the involved parameters on the physical properties of the fluid are described *** results show that the curvature parameter is an increasing function of velocity and temperature, and the temperature is a decreasing function of the thermal relaxation ***, the Deborah number has a reverse effect on the pressure and surface drag force.

关键词： curved stretching surface Jeffrey fluid non-Fourier heat flux model

Effects of rotation and gravity on an electro-magneto-thermoelastic medium with diffusion and voids by using the Lord-shulman and dual-phase-lag models

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Applied Mathematics and Mechanics(English Edition) 2019年第8期40卷 1135-1154页

作者： s.M.ABO-DAHAB A.M.ABD-ALLA A.A.KILANY Department of Mathematics Faculty of SciencesTaif UniversityTaif 888Saudi Arabia Department of Mathematics Faculty of ScienceSouth Valley UniversityQena 83523Egypt Department of Mathematics Faculty of ScienceSohag UniversitySohag 82524Egypt

The effects of rotation and gravity on an electro-magneto-thermoelastic medium with diffusion and voids in a generalized thermoplastic half-space are studied by using the Lord-shulman (L-s) model and the dual-phase-lag (DPL) model. The analytical solutions for the displacements, stresses, temperature, diffusion concentration, and volume fraction field with different values of the magnetic field, the rotation, the gravity, and the initial stress are obtained and portrayed graphically. The results indicate that the effects of gravity, rotation, voids, diffusion, initial stress, and electromagnetic field are very pronounced on the physical properties of the material.

关键词： electromagnetic field gravity field rotation initial stress voids diffusion normal mode analysis Lord-shulman (L-s) model dual-phase-lag (DPL) model