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.
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.
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.
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.
Lai N.A.,Hanoi University of Science and Technology |
Fischer J.,University of Vienna
Energy | Year: 2012
Power flash cycles (PFC) are a generalization of trilateral cycles (TLC) in which the compressed liquid is heated up to its boiling point and then performs a flash expansion during which it delivers power. The end point of the expansion may be in the wet vapour region (TLC) or in the dry vapour region. Here model results are presented for PFC-systems including the heat transfer to and from the cycles with aromates, siloxanes, and alkanes as working fluids. Optimization criterion is the exergy efficiency for power production at different pairs of heat carrier and cooling agent inlet temperatures ranging from (350 °C, 62 °C) to (150 °C, 15 °C). Comparisons with TLC for water, organic Rankine cycles (ORC) and water Clausius-Rankine cycles are made. General findings are that PFC has higher power production efficiencies than ORC but larger volume flows at the expander outlet. Moreover, TLC with water have in all cases the highest or nearly highest power production efficiencies. The disadvantage of water are the large outlet volume flows at low temperatures. For these cases alkanes like cyclopentane are to be preferred in PFC which can have significantly smaller outlet volume flows and rather high power production efficiencies. © 2012 Elsevier Ltd.