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Nguyen T.T.,Ton Duc Thang University | Vo D.N.,Ho Chi Minh City University of Technology | Truong A.V.,Ho Chi Minh City University of Technology and Education
Applied Energy | Year: 2014

This paper proposes a cuckoo search algorithm (CSA) for solving short-term fixed-head hydrothermal scheduling (HTS) problem considering power losses in transmission systems and valve point loading effects in fuel cost function of thermal units. The CSA method is a new meta-heuristic algorithm inspired from the obligate brood parasitism of some cuckoo species by laying their eggs in the nests of other host birds of other species for solving optimization problems. The advantages of the CSA method are few control parameters and effective for optimization problems with complicated constraints. The effectiveness of the proposed CSA has been tested on different hydrothermal systems and the obtained test results have been compared to those from other methods in the literature. The result comparison has shown that the CSA can obtain higher quality solutions than many other methods. Therefore, the proposed CSA can be an efficient method for solving short-term fixed head hydrothermal scheduling problems. © 2014 Elsevier Ltd.

Thai H.-T.,University of New South Wales | Nguyen T.-K.,Ho Chi Minh City University of Technology and Education | Vo T.P.,Northumbria University | Lee J.,Sejong University
European Journal of Mechanics, A/Solids | Year: 2014

In this paper, a new first-order shear deformation theory is presented for functionally graded sandwich plates composed of functionally graded face sheets and an isotropic homogeneous core. By making a further assumption to the existing first-order shear deformation theory, the number of unknowns and governing equations of the present theory is reduced, thereby making it simple to use. In addition, the use of shear correction factor is no longer necessary in the present theory since the transverse shear stresses are directly computed from the transverse shear forces by using equilibrium equations. Equations of motion are derived from Hamilton's principle. Analytical solutions for bending, buckling and free vibration analysis of rectangular plates under various boundary conditions are presented. Verification studies show that the present first-order shear deformation theory is not only more accurate than the conventional one, but also comparable with higher-order shear deformation theories which have a greater number of unknowns. © 2013 Elsevier Masson SAS. All rights reserved.

Thai H.-T.,University of New South Wales | Vo T.P.,Northumbria University | Nguyen T.-K.,Ho Chi Minh City University of Technology and Education | Lee J.,Sejong University
Composite Structures | Year: 2015

Static bending, buckling and free vibration behaviors of size-dependent functionally graded (FG) sandwich microbeams are examined in this paper based on the modified couple stress theory and Timoshenko beam theory. To avoid the use of a shear correction factor, equilibrium equations were used to compute the transverse shear force and shear stress. Two types of sandwich beams were considered: (1) homogeneous core and FG skins and (2) FG core and homogeneous skins. Numerical results were presented to illustrate the small scale effects on the behaviors of FG sandwich beams. The results reveals that the inclusion of the size effects results in an increase in the beam stiffness, and consequently, leads to a reduction of deflections and stresses and an increase in natural frequencies and critical buckling loads. Such effects are more pronounced when the beam depth was small, but they become negligible with the increase of the beam depth. © 2014 Elsevier Ltd.

Nguyen T.-K.,Ho Chi Minh City University of Technology and Education | Vo T.P.,GlyndAr University | Thai H.-T.,Hanyang University
Composites Part B: Engineering | Year: 2013

The first-order shear deformation beam theory for static and free vibration of axially loaded rectangular functionally graded beams is developed. In this theory, the improved transverse shear stiffness is derived from the in-plane stress and equilibrium equation and thus, associated shear correction factor is then obtained analytically. Equations of motion are derived from the Hamilton's principle. Analytical solutions are presented for simply-supported functionally graded beams. The obtained results are compared with the existing solutions to verify the validity of the developed theory. Effects of the power-law index, material contrast and Poisson's ratio on the displacements, natural frequencies, buckling loads and load-frequency curves as well as corresponding mode shapes are investigated. © 2013 Elsevier Ltd. All rights reserved.

Vu T.N.L.,Ho Chi Minh City University of Technology and Education | Lee M.,Yeungnam University
ISA Transactions | Year: 2013

A new design method of fractional-order proportional-integral controllers is proposed based on fractional calculus and Bode's ideal transfer function for a first-order-plus-dead-time process model. It can be extended to be applied to various dynamic models. Tuning rules were analytically derived to cope with both set-point tracking and disturbance rejection problems. Simulations of a broad range of processes are reported, with each simulated controller being tuned to have a similar degree of robustness in terms of resonant peak to other reported controllers. The proposed controller consistently showed improved performance over other similar controllers and established integer PI controllers. © 2013 ISA.

Van Phan C.,Ho Chi Minh City University of Technology and Education
2014 IEEE 5th International Conference on Communications and Electronics, IEEE ICCE 2014 | Year: 2014

We propose a game-theoretic framework for opportunistic transmission strategy for wireless networks that operate in a strict energy-constrained environment. To reduce unsuccessful transmissions due to channel error and packet collision causing a waste of energy, the opportunistic transmission strategy attempts to transmit at good channel conditions while meeting the delay constraint under time-varying wireless channel. We formulate Constrained cost-coupled stochastic game to obtain the optimum threshold for successful transmission in the opportunistic transmission manner. © 2014 IEEE.

Nguyen T.-K.,Ho Chi Minh City University of Technology and Education
International Journal of Mechanics and Materials in Design | Year: 2015

This paper presents a new higher-order hyperbolic shear deformation theory for analysis of functionally graded plates. In this theory, the transverse shear stresses account for a hyperbolic distribution and satisfy the free-traction boundary conditions on the top and bottom surfaces of the plate. By making a further assumption, the present theory contains only four unknowns and its governing equations is therefore reduced. Equations of motion are derived from Hamilton’s principle and Navier-type analytical solutions for simply-supported plates are compared with the existing solutions to verify the validity of the developed theory. The material properties are continuously varied through the plate thickness by the power-law and exponential form. Numerical results are obtained to investigate the effects of the power-law index and side-to-thickness ratio on the deflections, stresses, critical buckling load and natural frequencies. © 2014, Springer Science+Business Media Dordrecht.

Kien L.C.,Ho Chi Minh City University of Technology and Education
Journal of Electrical Engineering and Technology | Year: 2013

This paper examines the effects of magnetic induction attenuation on current distribution in the exit regions of the Faraday-type, non-equilibrium plasma Magnetohydrodynamic (MHD) generator by numerical calculation using cesium-seeded helium. Calculations show that reasonable magnetic induction attenuation creates a very uniform current distribution near the exit region of generator channel. Furthermore, it was determined that the current distribution in the middle part of generator is negligible, and the output electrodes can be used without large ballast resistors. In addition, the inside resistance of the exit region and the current concentration at the exit electrode edges, both decrease with the attenuation of magnetic flux density. The author illustrates that the exit electrodes of the diagonal Faraday-type, non-equilibrium plasma MHD generator should be arranged in the attenuation region of the magnetic induction, in order to improve the electrical parameters of the generator.

Suc N.V.,Ho Chi Minh City University of Technology and Education | Ly H.T.Y.,Ho Chi Minh City University of Technology and Education
Journal of Chemical Technology and Biotechnology | Year: 2013

BACKGROUND: Chitosan flake is a bio-adsorbent that has been studied for adsorption of lead. However, its adsorption capacity for lead was low. To enhance its adsorption capacity, chitosan flakes were modified with citric acid by crosslinking with glutaraldehyde to supplement the functional groups with high affinity for Pb(II) ions. RESULTS: Modified chitosan flakes with citric were prepared with maximum capacity for Pb(II) of 101.7mg g-1 at 303K, pH 5, and 300min contact time. The experimental data were used to fit kinetic and isotherm models. The results show that the adsorption of Pb(II) on modified chitosan flake followed a pseudo-second-order model, and the rate of adsorption was controlled by the mass transport mechanism and intraparticle diffusion. In an equilibrium study, it was found that the Langmuir and Freundlich isotherm models were appropriate to describe the adsorption process, indicating a chemisorption process of Pb(II) on the modified chitosan flake. The negative value of the free energy (ΔG) and the positive values of the enthalpy (ΔH) and entropy (ΔS) indicated an endothermic and spontaneous adsorption process of lead (II) on citric acid grafted chitosan flakes (C-Gch). CONCLUSION: Chitosan flake modified with citric acid by crosslinking with glutaraldehyde remarkably enhanced the adsorption capacity for Pb(II) ions. This material could be used as an effective adsorbent for the removal of Pb(II) from wastewater and contaminated water sources. © 2012 Society of Chemical Industry.

Vo M.-H.,Ho Chi Minh City University of Technology and Education
IEEE Joint Conference - International Conference on IC Design and Technology, ICICDT 2016 and Solid State Systems Symposium, 4S 2016 | Year: 2016

The proposed achieves dynamic power reduction of 56 % at 200 MHz, zero-static current compared to the static multiplier which is used commonly in construction of digital logic circuits. The proposed multiplier is just 17% to 34% static current, 45% critical path delay compared to CMOS array multiplier. The power-delay-product achieves 52%, 36% the static and the CMOS array, correspondingly. © 2016 IEEE.

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