Determinant of Smartphone Purchase Intention of the Office Staffs in the North of Vietnam

Nowadays, smartphone is one of the most popular mobile devices to make calls and send texts. Moreover, you can use smartphone to take pictures with high quality, listen music or play video. This study investigates the relationship between product quality, price, design, features, band name and purchase intention of a smart phone. To do so, a survey was conducted by distributing 250 questionnaires in some of different offices in North of Vietnam. The Pearson Correlation was applied for the data analysis. The results show that there is a positive and significant relationship among product quality, price, design, features, band name and purchase intention. Based on these results, it seems that the smart phone company needs to develop marketing strategy to increase purchase intention of office staffs. Keywords: smartphone, purchase intention, office staff, in the North of Vietnam DOI: 10.7176/RJFA/11-24-02 Publication date: December 31st 202

Preparation and characterization of magnesium hydroxyapatite coatings on 316L stainless steel

Magnesium hydroxyapatite coatings (MgHAp) were deposited on the surface of 316L stainless steel (316L SS) substrates by electrodeposition technique. Different concentrations of Mg2+ ion were incorporated into the apatite structure by adding Mg(NO3)2 into electrolyte solution containing 3×10-2 M Ca(NO3)2, 1.8×10-2 M NH4H2PO4 and   6×10-2 M NaNO3. With Mg2+ concentration 1×10-3 M, the obtained coatings have 0.2 wt% Mg2+. The influences of scanning potential ranges, scanning times to deposit MgHAp coatings were researched. The analytical results FTIR, SEM, X-ray, EDX, thickness and adhension strength showed that MgHAp coatings were single phase of HAp, fibrous shapes, thickness 8.1 µm and adhesion strength 7.20 MPa at the scanning potential ranges of 0÷-1.7 V/SCE and scanning times of 5 scans. Keywords. 316L SS, Electrodeposition, MgHAp

Electrodeposition of HAp coatings on Ti6Al4V alloy and its electrochemical behavior in simulated body fluid solution

Hydroxyapatite (HAp) coatings were prepared on Ti6Al4V substrate by electrodeposition method from electrolyte solution containing Ca(NO3)2, NH4H2PO4 and NaNO3. The results show that the HAp coatings were single phase crystals of HAp. Scanning electron microscope (SEM) images present that HAp/Ti6Al4V have flake shapes which arrange to form like-coral agglomerates. In vitro test of the Ti6Al4V and HAp/Ti6Al4V in simulated body fluid (SBF) solution was investigated with different immersion times. pH of SBF solution decreased and the mass of materials increased. SEM images prove the formation of apatite on the surface of Ti6Al4V and HAp/Ti6Al4V. The corrosion current density during immersion time of substrate is always higher than the one of HAp/Ti6Al4V because the deposited HAp can protect well for the substrate

POTENTIAL INTOXICATION BY TOXIC CYANOBACTERIA AND THEIR TOXINS IN SOME VIETNAMESE FRESH WATERBODIES

Joint Research on Environmental Science and Technology for the Eart

FREE VIBRATION OF TWO-DIRECTIONAL FGM BEAMS USING A HIGHER-ORDER TIMOSHENKO BEAM ELEMENT

Free vibration of two-directional functionally graded material (2-D FGM) beams is studied by the finite element method (FEM). The material properties are assumed to be graded in both the thickness and longitudinal directions by a power-law distribution. Equations of motion based on Timoshenko beam theory are derived from Hamilton's principle. A higher-order beam element using hierarchical functions to interpolate the displacements and rotation is formulated and employed in the analysis. In order to improve the efficiency of the element, the shear strain is constrained to constant. Validation of the derived element is confirmed by comparing the natural frequencies obtained in the present paper with the data available in the literature. Numerical investigations show that the proposed beam element is efficient, and it is capable to give accurate frequencies by a small number of elements. The effects of the material composition and aspect ratio on the vibration characteristics of the beams are examined in detail and highlighted

Free vibration analysis of 2-D FGM beams in thermal environment based on a new third-order shear deformation theory

Free vibration analysis of two-directional functionally graded material (2-D FGM) beams in thermal environment based on a new third-order shear deformation theory is presented. The material properties are assumed to be graded in both the thickness and longitudinal directions by a power law distribution, and they are considered to be temperature-dependent. Equations of motion, in which the shear rotation rather than the cross-sectional rotation is considered to be an independent variable, are constructed from Hamilton's principle. A finite element formulation is derived and employed to compute the vibration characteristics of the beams. The numerical results reveal that the developed formulation is accurate, and it is capable to give accurate natural frequencies by using a small number of elements. A parametric study is carried out to highlight the effects of material composition, temperature rise on the vibration characteristics of the beams

ELECTRODEPOSITION OF HYDROXYAPATITE/FUNCTIONALIZED CARBON NANOTUBES (HAp/fCNTs) COATINGS ON THE SURFACE OF 316L STAINLESS STEEL

The coatings of hydroxyapatite/functionalized carbon nanotubes (HAp/fCNTs) were successfully synthesized on the surface of 316L stainless steel (316L SS) by electrodeposition. To improve the dispersion of CNTs into the electrolyte, CNTs were functionalized in the mixture of 67 % HNO3 and 98 % H2SO4 before electrodeposition coatings to form fCNTs. Different amounts of fCNTs were  incorporated into the apatite coatings by adding fCNTs into the  electrolyte solution. In this study, Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Thermal Gravimetric Analysis (TGA) and mechanical techniques were used to analyze characteristic of fCNTs and the HAp/fCNTs coatings. The FTIR spectra of CNTs before and after acid treated process show that CNTs are functionalized by chemically method with carboxylic acid groups (–COOH) on their surface. The SEM images confirm that the functionalized process by the acid mixture does not change the morphology of CNTs. The nanocomposite coatings contain single phase of HAp and CNTs with the coating thickness of 6.9 µm and the amount of fCNTs in the coatings is 7.25 %. With 0.5 g/L of fCNTs in the electrolyte solution, the solubility of the coating decreases in comparision with pure HAp coatings

Elasto-plastic analysis of functionally graded metal-ceramic beams under mechanical loading

The elasto-plastic analysis of functionally graded (FG) metal-ceramic beams under mechanical loading by using the finite element method is presented. A bilinear stress-strain relation with isotropic hardening is assumed for elasto-plastic behaviour of metal, and the effective elasto-plastic properties of the functionally graded material are evaluated by using Tamura-Tomota-Ozawa (TTO) model.  A nonlinear beam element based on the classical beam theory is formulated and employed in the analysis. The element employed nonlinear von K\'am\'an strain-displacement relationship is derived by using the neutral surface as reference plane. The layer beam approach, in which the plastic rate equation is solved at Gauss points,  is adopted in updating the stress and evaluating the element nodal force vector and tangent stiffness matrix. Numerical examples are given to show the accuracy of the derived formulation and to illustrate the effect of the material distribution and plastic deformation on the behavior of the beams. The formation and propagation of plastic zone during the loading process is also examined and highlighted