Ho Chi Minh City, Vietnam
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Hieu N.N.,Duy Tan University | Nhan L.C.,Saigon University
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2014

Electronic energy band structure of deformed armchair graphene nanoribbons with bond alternation is studied by the tight-binding approximation. In the presence of bond alternation, all armchair graphene nanoribbons become semiconducting with small band gap opened at center of the Brillouin zone. Under tensional strain, armchair graphene nanoribbons can become metallic at the critical values of deformation and we can control the band gap of nanoribbon by its strain. © 2014 Elsevier B.V.


Hoa N.,Saigon University | Hieu T.D.,Vietnam Academy of Science and Technology
2013 IEEE 3rd International Conference on Information Science and Technology, ICIST 2013 | Year: 2013

This paper introduces a probabilistic relational data base model (PRDB). In this model, the tuple attribute value of relations is uncertain and represented by a probabilistic triple. Every probabilistic triple consists of a set of relational attribute values and two upper and lower bound probability distributions over the set of the attribute values. Semantics of such representation indicating that the attribute has a value in the set with a probability belongs to an interval from the upper and lower bound of the set. On the base and using probabilistic combination strategies in Eiter et al (2001), we define the notions of uncertain values, schemas, probabilistic relations, and selection operation as respective extensions of the notions of values, schemas, relations, and selection operation in the conventional relational database model. © 2013 IEEE.


Le T.M.N.,La Trobe University | Le T.M.N.,SaiGon University | Cao J.,La Trobe University | He Z.,La Trobe University
Information Sciences | Year: 2016

Although skyline queries are very useful in such areas such as decision support, market analysis and personalized services, they have not been extensively studied in the context of uncertain data. The existing work on answering probabilistic skyline queries either requires a user to define a threshold (Pei et al., 2007), or return all probabilistic skyline objects (Atallah and Qi, 2009). However, it is difficult to set the threshold because if set too high, important results may be lost, but if set too low or if there is no threshold, a lot of low quality results may be returned (Hua et al., 2011; Le and Cao, 2012; Le et al., 2013) [17]. In this paper, we identify two main challenges in answering probabilistic skyline queries. The first is defining what are the interesting probabilistic skyline tuples to return to the users. The second is efficiently finding these tuples without enumerating all possible worlds. We overcome the first challenge by introducing the bestpro-skyline query, which extends the dominance principle to also include the skyline probability of the probabilistic skyline tuples. This approach results in pruning the result set to just a very small number of the most interesting probabilistic skyline tuples without the need to set any user-defined threshold. We overcome the second challenge by using formulas based on the probabilistic theory to directly calculate the skyline probabilities without considering any possible worlds and develop algorithms to prune the search space. Experiments show that our solution is able to find the 17 interesting probabilistic skyline tuples from 13,095 tuples within 19 s in a real data set. Our solution outperforms a Naïve solution by up to three orders of magnitude for computational time. © 2016 Elsevier Inc. All rights reserved.


Chuong T.D.,Saigon University | Kim D.S.,Pukyong National University
Mathematics of Operations Research | Year: 2016

We introduce concepts of metric regularity and metric subregularity of a positive-order for an implicit multifunction and provide new sufficient conditions for the implicit multifunctions to achieve the addressed properties. The conditions provided are presented in terms of the Fréchet/Mordukhovich coderivative of the corresponding parametric multifunction formulated the implicit multifunction. We show that such sufficient conditions are also necessary for the metric regularity/subregularity of a positive-order of the implicit multifunction when the corresponding parametric multifunction is (locally) convex and closed. In this way, we establish criteria ensuring that an implicit multifunction is Hölder-like and calm of a positive-order at a given point. As applications, we derive sufficient conditions in terms of coderivatives for a multifunction (resp., its inverse multifunction) to have the open covering property and the metric regularity/subregularity of a positive-order (resp., the Hölder-like/calm property). © 2016 INFORMS.


Thai P.-T.C.,Saigon University | Cong H.T.,Post and Telecommunications Institute of Technology
Studies in Computational Intelligence | Year: 2013

Due to the fast growths of computer networks, traffic engineering (TE) which tries to satisfy both quality of services and resource utilization requirements is an important research area. Among TE mechanisms, routing algorithm - a strategy to select paths for traffic - plays a crucial role and there have been many TE routing proposals. This paper gives a thorough study of these algorithms by presenting their key ideas and mathematical descriptions, and then by various experiments so to analyse their performances with different metrics. The paper also discusses the trend of routing algorithms and future research directions. © Springer-Verlag Berlin Heidelberg 2013.


Chuong T.D.,Saigon University
Numerical Functional Analysis and Optimization | Year: 2011

This article is devoted to developing the generalized proximal algorithm of finding efficient solutions to the vector optimization problem for a mapping from a uniformly convex and uniformly smooth Banach space to a real Banach space with respect to the partial order induced by a pointed closed convex cone. In contrast to most published literature on this subject, our algorithm does not depend on the nonemptiness of ordering cone of the space under consideration and deals with finding efficient solutions of the vector optimization problem in question. We prove that under some suitable conditions the sequence generated by our method weakly converges to an efficient solution of this problem. Copyright © Taylor & Francis Group, LLC.


Nguyen T.H.,Polish Academy of Sciences | Nguyen T.H.,Silesian University of Technology | Nguyen T.H.,Saigon University | Lamacz A.,Polish Academy of Sciences | And 6 more authors.
Applied Catalysis B: Environmental | Year: 2014

The transformation of perovskite to an oxide-supported metal during reaction of partial oxidation of methane (POM) has been very often cited in literature as the "reduction" of the perovskite, without any detailed mechanism. In this work, the in situ transformation of initial LaNiO3 perovskite to Ni0/La2O3 was studied under flowing CH4/Ar and CH4+O2/Ar (POM mixture) in temperature-programmed conditions. The catalyst was characterized before, during and after these experiments using X-ray diffraction (XRD), thermogravimetric analysis (TGA) and high resolution transmission electron microscopy (HRTEM/EDS) with Fast Fourier Transform (FFT) and Reverse FFT. Total oxidation of methane over LaNiO3 and lanthanum oxide (La2O3), as well as formation of syngas over the resulting Ni0/La2O3 catalysts, were studied for interpreting the three-step evolution of LaNiO3 to Ni0/La2O3, and evidencing NiO demixing from perovskite. A new global kinetic model of POM process over the final bifunctional Ni0/La2O3 catalyst was described. © 2014 Elsevier B.V.


Van Huan N.,Saigon University | Van Quang N.,Vinh University
Kybernetika | Year: 2012

We establish the Doob inequality for martingale difference arrays and provide a sufficient condition so that the strong law of large numbers would hold for an arbitrary array of random elements without imposing any geometric condition on the Banach space. Some corollaries are derived from the main results, they are more general than some well-known ones.


Le T.M.,State University of New York at Buffalo | Le T.M.,Saigon University
Annales Henri Poincare | Year: 2016

We study a classical lattice dipole gas with low activity in dimension (Formula presented.). We investigate long distance properties by a renormalization group analysis. We prove that various correlation functions have an infinite volume limit. We also get estimates on the decay of correlation functions. © 2016 Springer International Publishing


Tuan N.H.,Saigon University | Trong D.D.,Vietnam National University, Ho Chi Minh City
Nonlinear Analysis: Real World Applications | Year: 2011

We introduce two new methods for solving a backward heat conduction problem. For these two methods, we give a stability analysis with new error estimates. Meanwhile, we investigate the roles of the regularization parameters in these two methods. Numerical results show that our algorithm is effective. © 2010 Elsevier Ltd. All rights reserved.

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