Liu Z.,Guangxi University for Nationalities |
Van Loi N.,PetroVietnam University |
Obukhovskii V.,Voronezh State Pedagogical University
International Journal of Bifurcation and Chaos | Year: 2013
In this paper, by using the topological degree theory for multivalued maps and the method of guiding functions, the existence and global bifurcation for periodic solutions of a class of differential variational inequalities are studied. © World Scientific Publishing Company.
Nam N.D.,PetroVietnam University
Journal of the Electrochemical Society | Year: 2016
Mg-5Ca-xZn alloys were prepared using various zinc contents from 1 to 5 wt% for use as degradable biomaterials in medical implant applications. The influence of zinc on the corrosion properties of Mg-5Ca alloys prepared in Hanks' solution was examined using electrochemical and surface analysis techniques. The electrochemical tests reveal that the addition of zinc improves the corrosion resistance of Mg-5Ca alloys compared with untreated alloys. The improved corrosion resistance is attributed to the increased refinement of the precipitates, the grain refinement, and the continuous precipitation of Mg-Ca and MgCaZn compounds as a corrosion barrier. © 2015 The Electrochemical Society.
Van Sy L.,PetroVietnam University
Particulate Science and Technology | Year: 2016
Gas-liquid cylindrical cyclone (GLCC) separator is widely used in the petroleum industry with potential field applications. Its performance is strongly influenced by the inlet configuration. The 27° optimal inclined inlet angle has been experimentally observed for GLCC with the same diameter of body and inlet. For other GLCCs, the effect of inlet angle on flow pattern and their performances have not been investigated. The main target of the current study is to deeply understand the changes of flow pattern with respect to different inclined angles and flow conditions. Twelve GLCCs with different inclined angles were numerically investigated by using the Reynold stress turbulence model to predict the flow pattern with GLCC. The distribution of radial, axial, and tangential velocity profiles and their maximum magnitudes with respect to the change of inlet angle were carefully considered in this study. 2016 Copyright © Taylor & Francis Group, LLC
Sy L.V.,PetroVietnam University |
Nam N.T.,National Key Laboratory of Digital Control and System Engineering
Journal of Manufacturing Technology Research | Year: 2015
In this paper, the formability of magnesium alloy sheet (AZ31) is analyzed through effect of strain rate (in terms of depth step and feedrate) and temperature in a warmincremental forming process. This novel manufacturing process is utilized to produce easily the complex products from sheet materials with low cost and short setting time by using a CNC movement of non-cutting hemispherical tool. For this research, the results of the tensile tests and microstructure of AZ31 sheet at various temperatures between 25◦C and 300◦C are analyzed and discussed relative to strain rate sensitivity, ductility, strength and anisotropy. The series of incremental forming experiments with respect to the temperatures and strain rates were also carried out to identify these effects on the formability of AZ31 sheet. Their effects on the formability of incremental forming process are demonstrated and discussed. The results showed that the higher the testing temperature is set, the higher the strain at fracture is, while the influence of the strain rate is opposite. Reduction of the forming time by increasing both depth step and feedrate with respect to certain temperature can be identified. The optimum temperature of 300◦C for high value of strain rate and 250◦C for intermediate value of strain rate should be applied for warm incremental forming process. © Nova Science Publishers, Inc.
Nam N.D.,Petrovietnam University |
Bui Q.V.,Sungkyunkwan University |
Nhan H.T.,Petrovietnam University |
Phuong D.V.,Nanjing Southeast University |
Bian M.Z.,Monash University
Journal of Electronic Materials | Year: 2014
The corrosion resistance of a multilayered (NiP-Pd-Au) coating with various thicknesses of palladium (Pd) interlayer deposited on copper by an electroless method was investigated using electrochemical techniques including potentiodynamic polarization and electrochemical impedance spectroscopy. In addition, the surface finish was examined by x-ray diffraction analysis and scanning electron microscopy, and the contact angle of the liquid-solid interface was recorded. The corrosion resistance of the copper substrate was considerably improved by Pd interlayer addition. Increase of the thickness of the Pd interlayer enhanced the performance of the Cu-NiP-Pd-Au coating due to low porosity, high protective efficiency, high charge-transfer resistance, and contact angle. These are attributed to the diffusion of layers in the Cu-NiP-Pd-Au coating acting as a physical barrier layer, leading to the protection provided by the coating. © 2014 TMS.
Nam N.D.,Petrovietnam University |
Vaka M.,Deakin University |
Tran Hung N.,Institute of Chemistry and Materials Science
Journal of Power Sources | Year: 2014
To gain high hardness, good thermal stability and corrosion resistance, multicomponent TiAlSiN coating has been developed using different deposition methods. In this study, the influence of Al and Si on the electrochemical properties of TiN-coated 316L stainless steel as bipolar plate (BP) materials has been investigated in simulated proton exchange membrane fuel cell environment. The deposited TiN, TiAlN and TiAlSiN possess high hardness of 23.9, 31.7, 35.0 GPa, respectively. The coating performance of the TiN coating is enhanced by Al and Si addition due to lower corrosion current density and higher Rcoating and Rct values. This result could be attributed to the formation of crystalline-refined TiN(200), which improves the surface roughness, surface resistance, corrosion performance, and decreased passive current density. © 2014 Elsevier B.V. All rights reserved.
Nam N.D.,Petrovietnam University
Journal of Magnesium and Alloys | Year: 2014
The corrosion properties of four Mg-5Al alloys with M-alloying elements (tin, manganese and zinc) in a 3.5 wt.% NaCl solution were examined using electrochemical tests and surface analyses. The electrochemical results indicated that the addition of 1 wt.% M metal decreased the corrosion rate and hydrogen evolution rate of the Mg-5Al specimens. Moreover, the addition of 1Zn resulted in having the best corrosion resistance due to the interaction of Zn oxide with Mg and Al oxides which acted as a corrosion barrier. © 2014 National Engineering Research Center for Magnesium Alloys of China, Chongqing University.
Nguyen T.P.N.,French National Center for Scientific Research |
Nguyen T.P.N.,CNRS Institute of Electronics, Microelectronics and Nanotechnology |
Nguyen T.P.N.,PetroVietnam University |
Boukherroub R.,French National Center for Scientific Research |
And 2 more authors.
Journal of Colloid and Interface Science | Year: 2014
We report on the fabrication of silicon nanostructured superhydrophobic and superoleophobic surfaces also called "superomniphobic" surfaces. For this purpose, silicon interfaces with different surface morphologies, single or double scale structuration, were investigated. These structured surfaces were chemically treated with perfluorodecyltrichlorosilane (PFTS), a low surface energy molecule. The morphology of the resulting surfaces was characterized using scanning electron microscopy (SEM). Their wetting properties: static contact angle (CA) and contact angle hysteresis (CAH) were investigated using liquids of various surface tensions. Despite that we found that all the different morphologies display a superhydrophobic character (CA > 150° for water) and superoleophobic behavior (CA. ≈. 140° for hexadecane), values of hysteresis are strongly dependent on the liquid surface tension and surface morphology. The best surface described in this study was composed of a dual scale texturation i.e. silicon micropillars covered by silicon nanowires. Indeed, this surface displayed high static contact angles and low hysteresis for all tested liquids. © 2013 Elsevier Inc.
Sy L.V.,PetroVietnam University
Lecture Notes in Electrical Engineering | Year: 2016
Incremental sheet forming (ISF) is an innovative die-less technique for forming the product from sheet materials. This process has been attracted a considerable interest of the scientific community due to its high formability, flexibility, short lead-time and inexpensive equipment. However, applicability of this process in practices is limited by anticipating mechanical failures during the forming process. This paper presents implementing a developing fracture model into finite element simulation to predict the occurrence of fracture in forming a cone shape. The works were begun by analyzing material properties, choosing fracture criteria, and implementing into ABAQUS environment. Finally, the simulated results were validated by one of practical experiments in aspects of, for instance, geometric accuracy and formability. They showed an excellent agreement between the simulated work and the experiment conducted in this study. © Springer International Publishing Switzerland 2016.
Hung V.M.,PetroVietnam University |
Trung T.Q.,PetroVietnam University
2013 International Conference on Control, Automation and Information Sciences, ICCAIS 2013 | Year: 2013
A new dynamic model and impedance control algorithm of a haptic feedback device for robotic teleoperation is analyzed in this paper. User forces applied to the haptic device through human hand movements are modeled as disturbances to the control system. Detailed analysis for modeling haptic device and human hand is provided and then a self-tuning Fuzzy PID control scheme is proposed to improve system transparency by achieving good force tracking performances. This control is developed to tune PID parameters based on the environment-slave contact force and the human-haptic device contact force in real-time. Experiment results show good force tracking comparison for the 6-DOF haptic teleoperation system. © 2013 IEEE.