Tuy Hoa, Vietnam

Hong Duc University

www.hdu.edu.vn
Tuy Hoa, Vietnam

The Hong Duc University is a regional university located in Vietnam, belonging to the government in the province of Thanh Hoa. It offers bachelor's and master's degrees, mainly in teacher training, economics, technology and agriculture. Wikipedia.

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Ha G.,Hong Duc University | Hale J.M.,Newcastle University
Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering | Year: 2013

This article describes the research on the characteristics of various grades of PZT ceramic powder for use in the manufacture of piezoelectric paint. Batches of water-based acrylic paint were made using these lead zirconate titanate powders and evaluated according to their effectiveness as a paint and the quality of the piezoelectric sensors made from them. Four types of nominally similar PZT (Navy type II) were tested, and a clear conclusion drawn that Piezo Kinetics PKI-502 was the best in this application. © 2012 IMechE.


Bau L.V.,Hong Duc University | An N.M.,Hong Duc University
Journal of Magnetism and Magnetic Materials | Year: 2016

The ceramic samples of La0.7Sr0.3Mn1−xTixO3(x=0; 0.05; 0.1; 0.2 and 0.3) were synthesized by the conventional solid state reaction method. Their electric, magnetic and magnetocaloric properties have been investigated. The transition temperature declines and a significant influence on the width of the ferro-paramagnetic phase transition is observed as increasing Ti concentration. Moreover, the sign of spin-glass is expected to exist in the high concentration samples. For fully replacing Ti4+ for Mn4+, the canted spin state is formed. The substitution Ti for Mn increases resistivity quickly and the insulating–metallic transition temperature shifts toward lower temperature. For x>0.1 samples, the insulating state is observed even in ferromagnetic phase. The substitution Ti shifts the CME to room temperature while almost persists the value of entropy change. Although the maximum value of CME reduces slightly, the temperature range happening MCE is expended and then improves the relative cooling power. These properties could be explained in term of DE interaction and phase separation phenomenon. © 2016 Elsevier B.V.


Ou Y.-C.,National Taiwan University of Science and Technology | Ngo S.-H.,Hong Duc University
Advances in Structural Engineering | Year: 2016

Based on the actual, discrete locations of interception points between the critical shear crack and transverse reinforcement, this study developed the discrete computational shear strength models for 5-, 6-, and 11-circular-hoop and spiral reinforcement. Moreover, conventional simplified calculation method was revised for use for 5-, 6-, and 11-circular-hoop and spiral reinforcement. Examination of the difference between the discrete computational shear strength models and simplified calculation shows that the error of the simplified calculation increases with increasing ratios of spacing to diameter of circular hoops or spirals. Limiting values of spacing to diameter ratios were proposed to control the error of the simplification calculation to be equal to or less than 10%. Plots of modification factors were proposed to be used with the simplification calculation when the spacing to diameter ratio is large. © The Author(s) 2016 Reprints and permissions.


Karapnar E.,Atilim University | Luong N.V.,Hong Duc University
Computers and Mathematics with Applications | Year: 2012

The notion of coupled fixed point is introduced by Gnana-Bhaskar and Lakshmikantham. Very recently, the concept of tripled fixed point was introduced by Berinde and Borcut. In this manuscript, a quadruple fixed point is considered and some new related fixed point theorems are obtained. We also give some examples to illustrate our results. © 2012 Elsevier Ltd. All rights reserved.


Pham T.A.,Hong Duc University
Computer Communications | Year: 2011

In this paper, I propose an improvement of knapsack cipher. This improvement makes the cipher more high security and efficient. With the enhancement, the new knapsack cipher can be applied widely in the systems which need high security. © 2010 Elsevier B.V. All rights reserved.


Farzad B.,Brock University | Lau L.C.,Chinese University of Hong Kong | Le V.B.,University of Rostock | Tuy N.N.,Hong Duc University
Algorithmica (New York) | Year: 2012

Graph G is the square of graph H if two vertices x,y have an edge in G if and only if x,y are of distance at most two in H. Given H it is easy to compute its square H 2, however Motwani and Sudan proved that it is NP-complete to determine if a given graph G is the square of some graph H (of girth 3). In this paper we consider the characterization and recognition problems of graphs that are squares of graphs of small girth, i.e. to determine if G=H 2 for some graph H of small girth. The main results are the following. There is a graph theoretical characterization for graphs that are squares of some graph of girth at least 7. A corollary is that if a graph G has a square root H of girth at least 7 then H is unique up to isomorphism. There is a polynomial time algorithm to recognize if G=H 2 for some graph H of girth at least 6. It is NP-complete to recognize if G=H 2 for some graph H of girth 4. These results almost provide a dichotomy theorem for the complexity of the recognition problem in terms of girth of the square roots. The algorithmic and graph theoretical results generalize previous results on tree square roots, and provide polynomial time algorithms to compute a graph square root of small girth if it exists. Some open questions and conjectures will also be discussed. © 2010 Springer Science+Business Media, LLC.


Luong N.V.,Hong Duc University | Thuan N.X.,Hong Duc University
Mathematical and Computer Modelling | Year: 2012

In this paper, we prove some coupled fixed point theorems for nonlinear contractive mappings having the mixed monotone property in partially ordered G-metric spaces. The results on fixed point theorems are generalizations of the recent results of Choudhury and Maity [B.S. Choudhury, P. Maity, Coupled fixed point results in generalized metric spaces, Math. Comput. Modelling 54 (2011) 73-79]. © 2011 Elsevier Ltd.


Le V.B.,University of Rostock | Nguyen N.T.,Hong Duc University
Information Processing Letters | Year: 2011

The square H2 of a graph H is obtained from H by adding new edges between every two vertices having distance two in H. Lau and Corneil [Recognizing powers of proper interval, split and chordal graphs, SIAM J. Discrete Math. 18 (2004) 83-102] proved that recognizing squares of split graphs is an NP-complete problem. In contrast, we show that squares of strongly chordal split graphs can be recognized in quadratic-time by giving a structural characterization of these graph class. © 2010 Elsevier B.V. All rights reserved.


Luong N.V.,Hong Duc University | Thuan N.X.,Hong Duc University
Computers and Mathematics with Applications | Year: 2011

In this paper, we extend the coupled fixed point theorems for a mixed monotone mapping F:X×X→X in partially ordered metric spaces established by Bhaskar and Lakshmikantham [T. Gnana Bhaskar, V. Lakshmikantham, Fixed point theorems in partially ordered metric spaces and applications, Nonlinear Anal. TMA 65 (2006) 13791393]. An application to nonlinear integral equations is also given to illustrate our results. © 2011 Elsevier Ltd. All rights reserved.


Ou Y.-C.,National Taiwan University of Science and Technology | Ngo S.-H.,Hong Duc University
ACI Structural Journal | Year: 2016

This study developed discrete computational shear strength (DCSS) models for two-circular-hoop, two-spiral, seven-circular-hoop, and seven-spiral transverse reinforcement for reinforced concrete columns. The DCSS models show that as a shear crack moves along the column, the reinforcement shear strength varies periodically. The critical shear crack, which yields the smallest shear strength, can be from any of the shear cracks that intercept at least one edge of a hoop series or spiral. The conditions are presented for when a shear crack intercepts the two edges of every hoop series or spiral, which leads to a drastic reduction in shear strength. At the critical shear crack condition, the DCSS models yield shear strength lower than the integral averaging method. To control the error of the integral averaging method, the ratio of the reinforcement spacing to hoop or spiral diameter should be limited. Charts to correct the error are presented for use in practice. © 2016, American Concrete Institute. All rights reserved.

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