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Hanoi University of Science and Technology "), founded 1956, is the first and largest technical university in Vietnam. Wikipedia.

Le M.-Q.,Hanoi University of Science and Technology | Batra R.C.,Virginia Polytechnic Institute and State University
Computational Materials Science | Year: 2013

We use molecular dynamics simulations to study crack initiation and propagation in pre-cracked single layer arm chair graphene sheets deformed in simple tension by prescribing axial velocities to atoms at one edge and keeping atoms at the other edge fixed. It is found that the value of the J-integral depends upon the crack length, and for each initial crack length it increases with an increase in the crack length. Shorter initial cracks are found to propagate faster than longer initial cracks but shorter initial cracks begin propagating at higher values of the axial strain than longer initial cracks. Results computed for axial strain rates of 2.6 × 106, 2.6 × 107 and 2.6 × 108 s-1 reveal that values of the J-integral are essentially the same for the first two strain rates but different for the third strain rate even though the response of the pristine sheet is essentially the same for the three strain rates. © 2012 Elsevier B.V. All rights reserved. Source

Tuoc V.N.,Hanoi University of Science and Technology
Computational Materials Science | Year: 2010

We present a first-principle study on the atomic and electronic structure of II-VI wurtzite ZnO unsaturated nanowire and examine the dependence of surface stress on nanowire lateral size and shapes (hexagonal, triangular and tube-like) with diameter up to 31 Å. We investigate the unsaturated dangling bond state in the region of bandgap with varying the wire's diameter. We also calculated the surface formation energy and find that it decrease with increasing the wire diameter and a greater stability (lower surface formation energy) comes with hexagonal wires. Young's modulus calculation and various tensile tests have been applied to show the mechanical properties. The electronics properties of these wires (e.g. band structure, Density of State, charge transfer via Mulliken population analysis) also exhibit wire's diameter dependence behaviors. © 2010 Elsevier Ltd. All rights reserved. Source

Tam P.D.,Hanoi University of Science and Technology
Current Applied Physics | Year: 2015

This paper reports single-walled carbon nanotube-based biosensors for genetically modi fied organism (GMO) detection. Electrochemical electrode and single-walled carbon nanotube field effect transistor (SWCNT-FET)-based biosensors are used to determine the CaMV 35S promoter of Roundup Ready soybean. Given optimal conditions, both biosensors can effectively detect full complementarity with concentration as low as 1 nM. The sensitivity of the electrode-based biosensor is approximately 0.6 kΩ/nM while that of the SWCNT-FET-based biosensor is 0.32 nA/nM. Both biosensors were also used to determine a polymerase chain reaction-amplified sample. The obtained results showed that both sensors determined transgenic organisms well, thereby providing a useful tool for screening analysis of food samples. © 2015 Elsevier B.V. All rights reserved. Source

Le M.-Q.,Hanoi University of Science and Technology
Journal of Computational and Theoretical Nanoscience | Year: 2014

Molecular dynamics simulations were carried out to investigate the tensile mechanical behavior of hexagonal aluminum nitride (AlN), boron nitride (BN), gallium nitride (GaN), indium nitride (InN), and silicon carbide (SiC) monolayer sheets. The Tersoff and Tersoff-like potentials are used to model the interatomic interaction. Every sheet contains 4032 atoms. Stress-strain curves are established in the armchair and zigzag directions for uniaxial tensile response. Compared to graphene, hexagonal BN, SiC, AlN, InN, and GaN monolayer sheets exhibit approximately 77%, 53%, 41%, 27%, and 25% in Young's modulus; and 86%, 49%, 36%, 22% and 26% in fracture stress in the zigzag direction, respectively. Fracture strains appear about 19.5-22.8% and 15.5-17.7% in the zigzag and armchair directions, respectively. It is found that fracture stress-Young's modulus ratios of these 5 sheets and graphene are fairly different. Copyright © 2014 American Scientific Publishers. Source

Van Khang N.,Hanoi University of Science and Technology
Mechanics Research Communications | Year: 2011

The automatic derivation of motion equations is an important problem of multibody system dynamics. Firstly, an overview of the matrix calculus related to Kronecker product of two matrices is presented. A new matrix form of Lagrangian equations with multipliers for constrained multibody systems is then developed to demonstrate the usefulness of Kronecker product of two matrices in the study of dynamics of multibody systems. Finally, the equations of motion of mechanisms are derived using the proposed matrix form of Lagrangian equations as application examples. © 2011 Elsevier Ltd. Source

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