Ho Chi Minh City, Vietnam

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Loc B.M.,Tel Aviv University | Loc B.M.,Ho Chi Minh City University of Pedagogy | Auerbach N.,Tel Aviv University | Khoa D.T.,Institute for Nuclear Science and Technology
Physical Review C | Year: 2017

In this paper, we study the charge-exchange reaction to the isobaric analog state using two types of transition densities. One transition density is equal to the difference of the total neutron density minus the total proton density and the other one is the density of the excess neutrons only. We show that for projectiles that do not probe the interior of the nucleus but mostly the surface of this nucleus, distinct differences in the cross section arise when two types of transition densities are employed. We demonstrate this by considering the (He3,t) reaction. © 2017 American Physical Society.


Hoang T.-T.-P.,Ho Chi Minh City University of Pedagogy | Vo D.C.H.,University of Science | Ong T.H.,University of Science
Computers and Mathematics with Applications | Year: 2017

The paper is concerned with a low-order finite element method, namely the staggered cell-centered finite element method, which has been proposed and analyzed in Ong et al. (2015) for two-dimensional compressible and nearly incompressible linear elasticity problems. In this work, we extend the results to the three-dimensional case and focus on the creating of the meshes. In particular, from a general primal mesh M, we construct a polygonal dual mesh M* and its submesh M** in a way such that each dual control volume of M* corresponds to a primal vertex and is a union (macro-element) of some fixed number of adjacent tetrahedral elements of M**. The displacement is approximated by piecewise trilinear functions on the subdual mesh M** and the pressure by piecewise constant functions on the dual mesh M*. As for two-dimensional case, such construction of the meshes and approximation spaces satisfies the macroelement condition, which implies stability and convergence of the scheme. Numerical experiments are carried out to investigate the performance of the proposed method on various mesh types. © 2017 Elsevier Ltd.


Tuan-Anh T.,University of Science | Ly L.T.,Ho Chi Minh City International University | Viet N.Q.,Ho Chi Minh City University of Pedagogy | Bao P.T.,University of Science
BMC Bioinformatics | Year: 2017

Background: Since the recombinant protein was discovered, it has become more popular in many aspects of life science. The value of global pharmaceutical market was $87 billion in 2008 and the sales for industrial enzyme exceeded $4 billion in 2012. This is strong evidence showing the great potential of recombinant protein. However, native genes introduced into a host can cause incompatibility of codon usage bias, GC content, repeat region, Shine-Dalgarno sequence with host's expression system, so the yields can fall down significantly. Hence, we propose novel methods for gene optimization based on neural network, Bayesian theory, and Euclidian distance. Result: The correlation coefficients of our neural network are 0.86, 0.73, and 0.90 in training, validation, and testing process. In addition, genes optimized by our methods seem to associate with highly expressed genes and give reasonable codon adaptation index values. Furthermore, genes optimized by the proposed methods are highly matched with the previous experimental data. Conclusion: The proposed methods have high potential for gene optimization and further researches in gene expression. We built a demonstrative program using Matlab R2014a under Mac OS X. The program was published in both standalone executable program and Matlab function files. The developed program can be accessed from http://www.math.hcmus.edu.vn/~ptbao/paper_soft/GeneOptProg/. © 2017 The Author(s).


Dinh T.H.,Ho Chi Minh City University of Pedagogy | Dzuba V.A.,University of New South Wales
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2016

We apply a recently developed method [V. A. Dzuba, Phys. Rev. A 90, 012517 (2014)PLRAAN1050-294710.1103/PhysRevA.90.012517; J. S. M. Ginges and V. A. Dzuba, Phys. Rev. A 91, 042505 (2015)PLRAAN1050-294710.1103/PhysRevA.91.042505] to calculate energy levels of superheavy elements Uut (Z=113), Fl (Z=114), and Fl+. The method combines the linearized single-double coupled-cluster technique, the all-order correlation potential method, and configuration-interaction method. Breit and quantum electrodynamic corrections are included. The role of relativistic and correlation effects is discussed. Similar calculations for Tl, Pb, and Pb+ are used to gauge the accuracy of the calculations. © 2016 American Physical Society.


Khanh P.D.,Ho Chi Minh City University of Pedagogy | Khanh P.D.,University of Chile
Numerical Functional Analysis and Optimization | Year: 2016

This article proposes a new extragradient solution method for strongly pseudomonotone variational inequalities. A detailed analysis of the iterative sequences’ convergence and of the range of applicability of the method is provided. Moreover, an interesting class of strongly pseudomonotone infinite dimensional variational inequality problems is considered. © 2016, Copyright © Taylor & Francis Group, LLC.


Dinh N.,Vietnam National University, Ho Chi Minh City | Mordukhovich B.,Wayne State University | Nghia T.T.A.,Wayne State University | Nghia T.T.A.,Ho Chi Minh City University of Pedagogy
Mathematical Programming | Year: 2010

The paper concerns the study of new classes of parametric optimization problems of the so-called infinite programming that are generally defined on infinite-dimensional spaces of decision variables and contain, among other constraints, infinitely many inequality constraints. These problems reduce to semi-infinite programs in the case of finite-dimensional spaces of decision variables. We focus on DC infinite programs with objectives given as the difference of convex functions subject to convex inequality constraints. The main results establish efficient upper estimates of certain subdifferentials of (intrinsically nonsmooth) value functions in DC infinite programs based on advanced tools of variational analysis and generalized differentiation. The value/marginal functions and their subdifferential estimates play a crucial role in many aspects of parametric optimization including well-posedness and sensitivity. In this paper we apply the obtained subdifferential estimates to establishing verifiable conditions for the local Lipschitz continuity of the value functions and deriving necessary optimality conditions in parametric DC infinite programs and their remarkable specifications. Finally, we employ the value function approach and the established subdifferential estimates to the study of bilevel finite and infinite programs with convex data on both lower and upper level of hierarchical optimization. The results obtained in the paper are new not only for the classes of infinite programs under consideration but also for their semi-infinite counterparts. © 2009 Springer and Mathematical Programming Society.


Loc B.M.,Ho Chi Minh City University of Pedagogy | Khoa D.T.,Institute for Nuclear Science and Technology | Zegers R.G.T.,Michigan State University
Physical Review C - Nuclear Physics | Year: 2014

The charge-exchange (He3,t) scattering to the isobaric analog state (IAS) of the target can be considered as "elastic" scattering of He3 by the isovector term of the optical potential (OP) that flips the projectile isospin. Therefore, the accurately measured charge-exchange scattering cross section for the IAS can be a good probe of the isospin dependence of the OP, which is determined exclusively within the folding model by the difference between the neutron and proton densities and isospin dependence of the nucleon-nucleon interaction. Given the neutron skin of the target related directly to the same density difference, it can be well probed in the analysis of the charge-exchange (He3,t) reactions at medium energies when the two-step processes can be neglected and the t-matrix interaction can be used in the folding calculation. For this purpose, the data of the (He3,t) scattering to the IAS of Zr90 and Pb208 targets at Elab=420 MeV have been analyzed in the distorted wave Born approximation using the double-folded charge-exchange form factor. The neutron skin deduced for these two nuclei turned out to be in a good agreement with the existing database. © 2014 American Physical Society.


Loan D.T.,Institute for Nuclear Science and Technology | Loc B.M.,Ho Chi Minh City University of Pedagogy | Khoa D.T.,Institute for Nuclear Science and Technology
Physical Review C - Nuclear Physics | Year: 2015

The nucleon mean-field potential has been thoroughly investigated in an extended Hartree-Fock (HF) calculation of nuclear matter (NM) using the CDM3Y3 and CDM3Y6 density dependent versions of the M3Y interaction. The single-particle (SP) energies of nucleons in NM are determined according to the Hugenholtz-Van Hove theorem, which gives rise naturally to a rearrangement term (RT) of the SP potential at the Fermi momentum. Using the RT obtained exactly at the different NM densities and neutron-proton asymmetries, a consistent method is suggested to take into account effectively the momentum dependence of the RT of the SP potential within the standard HF scheme. To obtain a realistic momentum dependence of the nucleon optical potential (OP), the high-momentum part of the SP potential was accurately readjusted to reproduce the observed energy dependence of the nucleon OP over a wide range of energies. The impact of the RT and momentum dependence of the SP potential on the density dependence of the nuclear symmetry energy and nucleon effective mass has been studied in detail. The high-momentum tail of the SP potential was found to have a sizable effect on the slope of the symmetry energy and the neutron-proton effective mass splitting at supranuclear densities of the NM. Based on a local density approximation, the folding model of the nucleon OP of finite nuclei has been extended to take into account consistently the RT and momentum dependence of the nucleon OP in the same mean-field manner, and successfully applied to study the elastic neutron scattering on the lead target at the energies around the Fermi energy. © 2015 American Physical Society.


Nguyen N.-T.,Ho Chi Minh City University of Pedagogy | Hoang V.-H.,Ho Chi Minh City University of Pedagogy | Le V.-H.,Ho Chi Minh City University of Pedagogy
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

We point out the possibility of probing the nuclear vibration by using the high-order harmonic generation (HHG) with ultrashort laser pulses. By analyzing the HHG spectra obtained from the numerical solution of the time-dependent Schrödinger equation, we find that the intensity of the emitted harmonics is strongly determined not only by the molecular configuration but also by the initial velocity of nuclei. The calculations show that the intensity of HHG is enhanced nearly the time when the internuclear separation takes the equilibrium value and the nuclei are moving closer together. In contrast, with the same initial internuclear separation but with the opposite direction of nuclear velocity, the intensity of emitted light is reduced noticeably. We use that evidence as a tool to probe the nuclear vibration. © 2013 American Physical Society.


Khanh P.D.,Ho Chi Minh City University of Pedagogy | Vuong P.T.,University of Technical Education
Journal of Global Optimization | Year: 2014

A modified projection method for strongly pseudomonotone variational inequalities is considered. Strong convergence and error estimates for the sequences generated by this method are studied in two versions of the method: the stepsizes are chosen arbitrarily from a given fixed closed interval and the stepsizes form a non-summable decreasing sequence of positive real numbers. We also propose some interesting examples to analyze the obtained results. © 2013 Springer Science+Business Media New York.

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