Nha Trang, Vietnam

Nha Trang University

Nha Trang, Vietnam

Nha Trang University is a university in Nha Trang, Khánh Hòa Province, in Vietnam's South Central Coast. This a multidisciplinary university with 29 specialities from vocational training to doctor's degree. Wikipedia.

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Dang X.-P.,Nha Trang University
Materials and Manufacturing Processes | Year: 2017

This paper investigates the highly nonlinear relationship between process parameters and machining responses, including material removal rate (MRR), surface roughness (SR), and electrode wear rate (EWR) of electric discharge machining (EDM) using Kriging model. Subsequently, an emerging multi-objective optimization algorithm called particle swarm is used to determine the best machining conditions that not only maximize the machining speed but also minimize the EWR with a constraint of the SR. The experiment was carried out with P20 steel on a CNC EDM machine using copper electrode. The research result shows that the MRR increases sharply when increasing the discharge current just like other researches pointed out. However, the relationship between EWR and current is complicated. EWR appears the minimum value when the current is around 30 A. The speed of change of MRR per unit of EWR is the highest when the SR is around 14.5 µm. The combination of Kriging regression model and particle swarm optimization is considered as an intelligent process modeling and optimization of EDM machining. The proper selection of process parameters helps the EDM operator to reduce the machining time and cost. © 2017 Taylor & Francis

Duc N.D.,Vietnam National University, Hanoi | Van Thu P.,Nha Trang University
Composite Structures | Year: 2014

This paper presents an analytical investigation on the nonlinear response of the thin imperfect laminated three-phase polymer composite plate in thermal environments. The formulations are based on the classical plate theory taking into account the interaction between the matrix and the particles, geometrical nonlinearity, initial geometrical imperfection. By applying Galerkin method, explicit relations of load-deflection curves are determined. Obtained results show effects of the fibers and the particles, material, geometrical properties and temperature on the buckling and post-buckling loading capacity of the three phase composite plate, therefore we can proactively design materials and structural composite meet the technical requirements as desired when adjustment components. © 2013 Elsevier Ltd.

Can V.V.,University of Tromsø | Can V.V.,Nha Trang University
Transportation Research Part A: Policy and Practice | Year: 2013

The purpose of this study is to examine how the characteristics of domestic tourists and attributes of travel modes influence the tourists' modal choice to Nha Trang, Viet Nam by applying the multinomial probit model. The analysis is based on primary data surveyed from tourists visiting Nha Trang in March, 2011. A total of 402 valid samples were used from 554 initial samples. The study provides several important findings concerning tourists' modal choice. Travel time per kilometer, per-kilometer travel cost to income ratio, mode quality variables, and income are key elements in explaining the tourists' modal choice decision. In addition, tourists with a lower income tend to be more sensitive to change in per-kilometer cost. Furthermore, the high-income tourists are much more likely to choose plane or train rather than coach. Understanding the tourists' modal choice behavior may help tourism transport companies to develop appropriate marketing strategies. © 2013 Elsevier Ltd.

Nguyen V.H.,Yeungnam University | Nguyen V.H.,Nha Trang University | Shim J.-J.,Yeungnam University
Electrochimica Acta | Year: 2015

Hierarchical mesoporous NiCo2S4@MnO2 core-shell structured arrays on nickel foam were designed and fabricated using a facile hydrothermal method for supercapacitor applications. The electrodes exhibited rapid electron and ion transport, large electroactive surface area, and excellent structural stability owing to the highly conducting nature of the well-defined mesoporous NiCo2S4 nanowire arrays in combination with the large surface area provided by the ultrathin MnO2 nanosheets and ultralong MnO2 nanowires, as well as to the open framework of the three-dimensional nanoarchitectures. The specific capacitance of the resulting electrode was as high as 17.5 F cm-2 at a very high current density of 100 mA cm-2, highlighting its potential as an efficient electrode for electrochemical capacitors. © 2015 Elsevier Ltd. All rights reserved.

Nguyen V.H.,Yeungnam University | Nguyen V.H.,Nha Trang University | Shim J.-J.,Yeungnam University
Journal of Power Sources | Year: 2015

A facile and efficient two-step method for the decoration of graphene sheets and nickel cobalt oxide (NiCo2O4) nanoparticles on conducting nickel foam was developed. First, graphene and a bimetallic (Ni, Co) hydroxide precursor were deposited on a Ni foam support by electrodeposition followed by a thermal transformation of the bimetallic hydroxide to NiCo2O4. The graphene layer with a thickness of a few nanometers was decorated with NiCo2O4 nanoparticles, ranging in size from 3 to 5 nm. The nickel foam electrode supported graphene and NiCo2O4 exhibited rapid electron and ion transport, large electroactive surface area, and excellent structural stability. The specific capacitance of the obtained electrode was as high as 1950 F g-1 at a high current density of 7.5 A g-1, suggesting its promising applications as an efficient electrode for electrochemical capacitors. © 2014 Elsevier B.V. All rights reserved.

Hoa Nguyen V.,Yeungnam University | Hoa Nguyen V.,Nha Trang University | Shim J.-J.,Yeungnam University
Materials Letters | Year: 2015

Nickel foam was decorated with graphene and cobalt oxide (Co3O4) sheets by chemical vapor deposition and electrochemical deposition, respectively. After coated by a thin graphene layer, the nickel foam was decorated with Co3O4 nanoparticles, ranging in size from 3 to 5 nm. The resulted electrode allowed the rapid transportation of electrons and ions with a large electroactive surface area, and showed excellent structural stability. The specific capacitance of the electrode was as high as 1126 F g-1 at a high current density of 7.5 A g-1 in KOH 3 M electrolyte, highlighting its promising applications as a high performance electrode for supercapacitors. © 2014 Elsevier B.V. All rights reserved.

Lunestad B.T.,National Institute of Nutrition And Seafood Research | Truong T.T.T.,Nha Trang University | Lindstedt B.-A.,Norwegian Institute of Public Health
Epidemiology and Infection | Year: 2013

The objective of this study was to characterize Listeria monocytogenes isolated from farmed Atlantic salmon (Salmo salar) and the processing environment in three different Norwegian factories, and compare these to clinical isolates by multiple-locus variable-number tandem repeat analysis (MLVA). The 65 L. monocytogenes isolates obtained gave 15 distinct MLVA profiles. There was great heterogeneity in the distribution of MLVA profiles in factories and within each factory. Nine of the 15 MLVA profiles found in the fish-associated isolates were found to match human profiles. The MLVA profile 07-07-09-10-06 was the most common strain in Norwegian listeriosis patients. L. monocytogenes with this profile has previously been associated with at least two known listeriosis outbreaks in Norway, neither determined to be due to fish consumption. However, since this profile was also found in fish and in the processing environment, fish should be considered as a possible food vehicle during sporadic cases and outbreaks of listeriosis. © Cambridge University Press 2012.

Tra T.H.,Nha Trang University | Okazaki M.,Nagaoka University of Technology | Suzuki K.,Niigata University
International Journal of Fatigue | Year: 2012

Behavior of fatigue crack which was propagated at some representative areas in the friction stir welded (FSWed) joint of aluminum alloy 6063-T5 was studied. By extracting the T-L orientation specimens so that the loading axis on the fatigue test and the crack propagation direction were transverse and longitudinal to the welding direction, respectively, the crack propagation tests were carried out for both the as-welded and post-weld heat treated (PWHTed) FSWs at room temperature and 200°C. The experiments showed that the fatigue crack propagation (FCP) rates were sensitive to the propagating location, the test temperature, and the PWHT condition as well. It was also found that the different FCP rates were driven by the microstructural influences in and around the welded zone. While the residual stress was remarkable in the shoulder limit areas, it had a minor effect on the FCP behavior. © 2012 Elsevier Ltd. All rights reserved.

Long V.T.,Nha Trang University | Nhan N.V.,Nha Trang University
International Journal of Automotive Technology | Year: 2012

This paper presents the optimization of key component sizes and control strategy for parallel hybrid electric vehicles (parallel HEVs) using the bees algorithm (BA). The BA is an intelligent optimization tool that mimics the food foraging behavior of honey bees. Parallel HEV configuration and electric assist control strategy were used to conduct the research. The values of the key component size and the control strategy parameters were adjusted according to the BA to minimize the weighted sum of fuel consumption (FC) and emissions, while the vehicle performance satisfies the PNGV constraints. In this research, the software ADVISOR was used as the simulation tool, and the driving cycles FTP, ECE-EUDC and UDDS were employed to evaluate FC, emission and dynamic performance. The results demonstrate that the BA is a powerful tool in parallel HEV optimization to determine the optimal parameters of component sizes and control strategy, resulting in the improvement of FC and emissions without sacrificing vehicle performance. In addition, the BA is able to define a global solution with a high rate of convergence. © 2012 The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg.

Dang X.-P.,Nha Trang University
Simulation Modelling Practice and Theory | Year: 2014

Plastic injection molding is widely used for manufacturing a variety of parts. Molding conditions or process parameters play a decisive role that affects the quality and productivity of plastic products. This work reviews the state-of-the-art of the process parameter optimization for plastic injection molding. The characteristics, advantages, disadvantages, and scope of application of all of the common optimization approaches such as response surface model, Kriging model, artificial neural network, genetic algorithms, and hybrid approaches are addressed. In addition, two general frameworks for simulation-based optimization of injection molding process parameter, including direct optimization and metamodeling optimization, are proposed as recommended paradigms. Two case studies are illustrated in order to demonstrate the implementation of the suggested frameworks and to compare among these optimization methods. This work is intended as a contribution to facilitate the optimization of plastic injection molding process parameter. © 2013 Elsevier B.V. All rights reserved.

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