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Binh Duong Province, Vietnam

Le K.C.,Ruhr University Bochum | Nguyen B.D.,Vietnamese German University
International Journal of Engineering Science

Within continuum dislocation theory (CDT) the energy functional of a bent beam, made of a single crystal having only one active slip system, is asymptotically analyzed. By relaxing the smooth minimizer of this energy functional, we construct a sequence of piecewise smooth displacements and piecewise constant plastic distortions reducing the energy and exhibiting polygonization. The number of polygons can be estimated from above by equating the surface energy of small angle tilt boundaries to the contribution of the gradient terms from the smooth minimizer in the bulk energy. The comparison with Gilman's experimental results shows a good agreement. © 2012 Elsevier Ltd. All rights reserved. Source

Nguyen-Xuan H.,Vietnamese German University | Hoang T.,Iuss Istituto Universitario Of Studi Superiori | Nguyen V.P.,University of Cardiff
Computers and Mathematics with Applications

A novel and efficient approach which is based on the framework of isogeometric analysis for elliptic homogenization problems is proposed. These problems possess highly oscillating coefficients leading to extremely high computational expenses while using traditional finite element methods. The isogeometric analysis heterogeneous multiscale method (IGA-HMM) investigated in this paper is regarded as an alternative approach to the standard finite element heterogeneous multiscale method (FE-HMM) which is currently an effective framework to solve these problems. The method utilizes non-uniform rationalB-splines (NURBS) in both macro and micro levels instead of standard Lagrange basis. Besides the ability to describe exactly the geometry, it tremendously facilitates high-order macroscopic/microscopic discretizations thanks to the flexibility of refinement and degree elevation with an arbitrary continuity level provided by NURBS basis functions. Furthermore, the nearly optimal quadrature rule for IGA (Auricchio et al., 2012) introduced recently is utilized to reduce significantly the number of micro problems, which is the main factor contributing into the computational cost in heterogeneous multiscale method. A priori error estimates of the discretization error coming from macro and micro meshes and optimal micro refinement strategies for macro/micro NURBS basis functions of arbitrary orders are derived. An efficient coupling between degrees of macro and micro basis functions is introduced. Numerical results show the excellent performance of the proposed method. © 2014 Elsevier Ltd. All rights reserved. Source

Kray T.,University of Siegen | Franke J.,Vietnamese German University | Frank W.,University of Siegen
Journal of Wind Engineering and Industrial Aerodynamics

The Magnus effect on a prototype model soccer ball rotating perpendicular to the flow direction at Reynolds numbers in the range of 0.96 × 105 < Re D < 4.62 × 105 was investigated by means of aerodynamic force measurements and of a flow field survey. Experiments were performed using a rear sting support where the soccer ball was split into two halves that were driven by a motor inside of them. In the non-rotating state the variation of force coefficients with Reynolds number and boundary layer separation points are within the range that is found for real soccer balls. In the rotating-state, considerable changes of the mean force coefficients with Reynolds number Re D and spin parameter S P occurred, which can be attributed to the altered boundary layer separation. These changes also lead to significant changes of size and deflection of the wake zones in the lateral direction. A negative Magnus effect occurs in the critical Reynolds number range. Positive Magnus force is induced when the boundary layer is either laminar or turbulent on both sides of the rotating model soccer ball. © 2013 Elsevier Ltd. Source

Truong L.T.,Monash University | Kieu L.-M.,Queensland University of Technology | Vu T.A.,Vietnamese German University
Accident Analysis and Prevention

This paper investigates factors associated with traffic crash fatalities in 63 provinces of Vietnam during the period from 2012 to 2014. Random effect negative binomial (RENB) and random parameter negative binomial (RPNB) panel data models are adopted to consider spatial heterogeneity across provinces. In addition, a spatiotemporal model with conditional autoregressive priors (ST-CAR) is utilised to account for spatiotemporal autocorrelation in the data. The statistical comparison indicates the ST-CAR model outperforms the RENB and RPNB models. Estimation results provide several significant findings. For example, traffic crash fatalities tend to be higher in provinces with greater numbers of level crossings. Passenger distance travelled and road lengths are also positively associated with fatalities. However, hospital densities are negatively associated with fatalities. The safety impact of the national highway 1A, the main transport corridor of the country, is also highlighted. © 2016 Elsevier Ltd. All rights reserved. Source

Nguyen T.N.,Vietnamese German University | Thai C.H.,Ton Duc Thang University | Nguyen-Xuan H.,China Medical University at Taichung
International Journal of Mechanical Sciences

This paper brings to the readers a unified framework on higher order shear deformation theories (HSDTs), modelling and analysis of laminated composite plates. The major objective of this work is to (1) unify all higher order shear deformation theories in a unique formulation by a polynomial form; (2) propose the new higher shear deformation models systematically based on a unified formulation. In addition, the effect of thickness stretching is taken into account by considering a quasi-3D theory. The principle of virtual displacements is exploited to derive a weak form based on the generalized displacement fields of the higher order shear deformation theories. Numerical results are computed by using isogeometric analysis and verified to show the accuracy and reliability of the present approach. It is found that the unique formulation of a polynomial form can theoretically cover all existing HSDTs models and is thus sufficient to describe the nonlinear and parabolic variation of transverse shear stress. Moreover, the proposed higher order shear deformation theories predict the proper responses for laminated composite plates in comparison with the available ones in the literature. © 2016 Elsevier Ltd. All rights reserved. Source

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