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Le H.M.,University of Lorraine | Thi H.A.L.,University of Lorraine | Dinh T.P.,National Institute for Applied Sciences, Strasbourg | Huynh V.N.,Quy Nhon University
Neural Computation | Year: 2013

We investigate difference of convex functions (DC) programming and the DC algorithm (DCA) to solve the block clustering problem in the continuous framework, which traditionally requires solving a hard combinatorial optimization problem. DC reformulation techniques and exact penalty in DC programming are developed to build an appropriate equivalent DC program of the block clustering problem. They lead to an elegant and explicit DCA scheme for the resulting DC program. Computational experiments show the robustness and efficiency of the proposed algorithm and its superiority over standard algorithms such as two-mode K-means, two-mode fuzzy clustering, and block classification EM. © 2013 Massachusetts Institute of Technology.


Thuan L.Q.,University of Groningen | Thuan L.Q.,Quy Nhon University | Camlibel M.K.,University of Groningen | Camlibel M.K.,Dogus University
IEEE Transactions on Automatic Control | Year: 2011

In the context of continuous piecewise affine dynamical systems, we study the Zeno behavior, i.e., infinite number of mode transitions in finite time interval, in this note. The main result reveals that piecewise affine dynamical systems do not exhibit Zeno behavior. A direct benefit of the main result is that one can apply smooth ordinary differential equations theory in a local manner for the analysis of piecewise affine systems. © 2010 IEEE.


Nguyen T.M.D.,CNRS Physiology of Reproduction and Behaviors | Nguyen T.M.D.,Quy Nhon University
Frontiers in Cell and Developmental Biology | Year: 2017

As we already know, the male reproductive system requires less energetic investment than the female one. Nevertheless, energy balance is an important feature for spermatozoa production in the testis and for spermatozoa properties after ejaculation. The 5'-AMP-activated protein kinase, AMPK, is a sensor of cell energy, that regulates many metabolic pathways and that has been recently shown to control spermatozoa quality and functions. It is indeed involved in the regulation of spermatozoa quality through its action on the proliferation of testicular somatic cells (Sertoli and Leydig), on spermatozoa motility and acrosome reaction. It also favors spermatozoa quality through the management of lipid peroxidation and antioxidant enzymes. I review here the most recent data available on the roles of AMPK in vertebrate spermatozoa functions. © 2017 Nguyen.


Phat V.N.,Institute of Mathematics | Nam P.T.,Quy Nhon University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2010

This Letter deals with the problem of exponential stability for a class of delayed Hopfield neural networks. Based on augmented parameter-dependent Lyapunov-Krasovskii functionals, new delay-dependent conditions for the global exponential stability are obtained for two cases of time-varying delays: the delays are differentiable and have an upper bound of the delay-derivatives, and the delays are bounded but not necessary to be differentiable. The conditions are presented in terms of linear matrix inequalities, which allow to compute simultaneously two bounds that characterize the exponential stability rate of the solution. Numerical examples are included to illustrate the effectiveness of our results. © 2010 Elsevier B.V. All rights reserved.


Huynh V.N.,Quy Nhon University | Nguyen H.T.,Quy Nhon University | Thera M.,CNRS XLIM Research Institute, Limoges
Mathematical Programming | Year: 2013

In this paper, we establish some new characterizations of metric regularity of implicit multifunctions in complete metric spaces by using lower semicontinuous envelopes of the distance functions to set-valued mappings. Through these new characterizations it is possible to investigate implicit multifunction theorems based on coderivatives and on contingent derivatives as well as the perturbation stability of implicit multifunctions. © 2013 Springer-Verlag Berlin Heidelberg and Mathematical Optimization Society.


Trung N.T.,Quy Nhon University | Hung N.P.,Quy Nhon University | Hue T.T.,Hanoi National University of Education | Nguyen M.T.,Catholic University of Leuven
Physical Chemistry Chemical Physics | Year: 2011

In this study, 16 gas phase complexes of the pairs of XCHZ and CO 2 (X = F, Cl, Br; Z = O, S) have been identified. Interaction energies calculated at the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ level including both BSSE and ZPE corrections range from -5.6 to -10.5 kJ mol-1 for XCHO⋯CO2 and from -5.7 to -9.1 kJ mol-1 for XCHS⋯CO2. Substitution of one H atom by one halogen in formaldehyde and thioformaldehyde reduces the interaction energy of XCHZ⋯CO2, while a CH3 substitution increases the interaction energy of both CH3CHO⋯CO2 and CH 3CHS⋯CO2. NBO and AIM analyses also point out that the strength of Lewis acid-base interactions decreases going from >C1S3⋯C6 to >C1O3⋯C6 and to >C1-X4⋯C6. This result suggests the higher capacity of solubility of thiocarbonyl compounds in scCO2, providing an enormous potential application for designing CO2-philic materials based on the >CS functional group in competition with >CO. The Lewis acid-base interaction of the types >CS⋯C, >C-Cl⋯C and >C-Br⋯C is demonstrated for the first time. The contribution of the hydrogen bonding interaction to the total interaction energy is larger for XCHS⋯CO2 than for XCHO⋯CO2. Upon complexation, a contraction of the C1-H2 bond length and a blue shift of its stretching frequency have been observed, as compared to the isolated monomer, indicating the existence of a blue-shifting hydrogen bond in all complexes examined. Calculated results also lend further support for the viewpoint that when acting as proton donor, a C-H bond having a weaker polarization will induce a stronger distance contraction and frequency blue shift upon complexation, and vice versa. © the Owner Societies 2011.


Trung N.T.,Quy Nhon University | Nguyen M.T.,Catholic University of Leuven
Chemical Physics Letters | Year: 2013

Interaction energies obtained using CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ computations including both ZPE and BSSE corrections range from -2.9 to -14.2 kJ mol-1. While formic acid forms the most stable complex with CO 2, formaldehyde yields the least stable complex. Lewis acid-base interaction such as C-Nâ";C(CO2), COâ""; C(CO2), which overcomes C-Hâ"";O blue-shifting hydrogen bond, plays a significant role in stabilizing most complexes. However, the strength of (HCOOH, CO2) is mainly determined by O-Hâ"";O red-shifting hydrogen bond. The C- Hâ"";O blue-shifting hydrogen bond is revealed upon complexation of CH3OH, HCHO, HCOOH, CH3COCH3 and HCOOCH3 with CO2. Remarkably, existence of weak hydrogen bonded C-Hâ"";O interaction is not found in the (CH 3OCH3, CO2) and (CH3NH2, CO2) pairs. © 2013 Elsevier B.V. All rights reserved.


Ngan V.T.,Catholic University of Leuven | Ngan V.T.,Quy Nhon University | Pierloot K.,Catholic University of Leuven | Nguyen M.T.,Catholic University of Leuven
Physical Chemistry Chemical Physics | Year: 2013

The electronic structure of Mn@Si14 + is determined using DFT and CASPT2/CASSCF(14,15) computations with large basis sets. The endohedrally Mn-doped Si cationic cluster has a D3h fullerene-like structure featuring a closed-shell singlet ground state with a singlet-triplet gap of ∼1 eV. A strong stabilizing interaction occurs between the 3d(Mn) and the 2D-shell(Si14) orbitals, and a large amount of charge is transferred from the Si14 cage to the Mn dopant. The 3d(Mn) orbitals are filled by encapsulation, and the magnetic moment of Mn is completely quenched. Full occupation of [2S, 2P, 2D] shell orbitals by 18 delocalized electrons confers the doped Mn@Si14 + cluster a spherically aromatic character. © 2013 the Owner Societies.


Van Ngai H.,Quy Nhon University
SIAM Journal on Optimization | Year: 2015

This paper is devoted to studying the Lipschitzian/Hölderian-type global error bound for systems of finitely many convex polynomial inequalities over a polyhedral constraint. First, for systems of this type, we show that under a suitable asymptotic qualification condition the Lipschitzian-type global error bound property is equivalent to the Abadie qualification condition; in particular, the Lipschitzian-type global error bound is satisfied under the Slater condition. Second, without regularity conditions, the Hölderian global error bound with an explicit exponent is investigated. © 2015 Society for Industrial and Applied Mathematics.


Nhan N.D.V.,Quy Nhon University | Duc D.T.,Quy Nhon University
Complex Analysis and Operator Theory | Year: 2013

We establish some norm inequalities for Mellin convolutions and their applications to obtain the boundedness of integral transforms and solutions of partial differential equations. © 2012 Springer Basel AG.

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