A new inverse trigonometric shear deformation theory for isotropic and functionally graded sandwich plates

A new inverse trigonometric shear deformation theory is proposed for the static, buckling and free vibration analyses of isotropic and functionally graded (FG) sandwich plates. It accounts for a inverse trigonometric distribution of transverse shear stress and satisfies the traction free boundary conditions. Equations of motion obtained here are solved for three types of FG plates: FG plates, sandwich plates with FG core and sandwich plates with FG faces. Closed-form solutions are obtained to predict the deflections, stresses, critical buckling loads and natural frequencies of simply supported plates. A good agreement between the obtained predictions and the available solutions of existing shear deformation theories is found to demonstrate the accuracy of the proposed theory

A nonlocal sinusoidal plate model for micro/nanoscale plates

A nonlocal sinusoidal plate model for micro/nanoscale plates is developed based on Eringen’s nonlocal elasticity theory and sinusoidal shear deformation plate theory. The small scale effect is considered in the former theory while the transverse shear deformation effect is included in the latter theory. The proposed model accounts for sinusoidal variations of transverse shear strains through the thickness of the plate, and satisfies the stress-free boundary conditions on the plate surfaces, thus a shear correction factor is not required. Equations of motion and boundary conditions are derived from Hamilton’s principle. Analytical solutions for bending, buckling, and vibration of simply supported plates are presented, and the obtained results are compared with the existing solutions. The effects of small scale and shear deformation on the responses of the micro/nanoscale plates are investigated

Size-dependent behaviour of functionally graded sandwich microbeams based on the modified couple stress theory

Abstract Static bending, buckling and free vibration behaviours of size-dependent functionally graded (FG) sandwich microbeams are examined in this paper based on the modified couple stress theory and Timoshenko beam theory. To avoid the use of a shear correction factor, equilibrium equations were used to compute the transverse shear force and shear stress. Two types of sandwich beams were considered: (1) homogeneous core and FG skins and (2) FG core and homogeneous skins. Numerical results were presented to illustrate the small scale effects on the behaviours of FG sandwich beams. The results reveals that the inclusion of the size effects results in an increase in the beam stiffness, and consequently, leads to a reduction of deflections and stresses and an increase in natural frequencies and critical buckling loads. Such effects are more pronounced when the beam depth was small, but they become negligible with the increase of the beam depth

A quasi-3D hyperbolic shear deformation theory for functionally graded plates

A quasi-3D hyperbolic shear deformation theory for functionally graded plates is developed. The theory accounts for both shear deformation and thickness-stretching effects by a hyperbolic variation of all displacements across the thickness, and satisfies the stress-free boundary conditions on the top and bottom surfaces of the plate without requiring any shear correction factor. The benefit of the present theory is that it contains a smaller number of unknowns and governing equations than the existing quasi-3D theories, but its solutions compare well with 3D and quasi-3D solutions. Equations of motion are derived from the Hamilton principle. Analytical solutions for bending and free vibration problems are obtained for simply supported plates. Numerical examples are presented to verify the accuracy of the present theory

The Influence of Investor's Characteristics on the Perception About the Selling Price of Luxury Apartments in Hanoi

This research was conducted to investigate the impact of investor's characteristics on the perception about the selling price of luxury apartments in Hanoi, Vietnam. Data were collected through a survey with 458 real estate employees from Hanoi. With this data, we have used descriptive statistics, Cronbach's Alpha to determine the level of impact of the independent variable on the dependent variable, i.e. the perception about the selling price of luxury apartments. The results showed that the determinant is the investor's characteristics which have positive relationships with the perception about the selling price of luxury apartments in Hanoi. Based on this finding, this paper gives several recommendations for improvement the perception about the selling price of luxury apartments in Hanoi. Keywords: the perception about the selling price of luxury apartme, investor's characteristics, real estate JEL codes: G12, G13, G14, L80, L85 DOI: 10.7176/EJBM/12-9-06 Publication date:March 31st 202

Investigating Effects of Teacher’s Using Authentic Texts on Cognitive Reading Engagement of Vietnamese EFL Students

The study examines the effects of teacher’s using authentic texts on EFL students’ cognitive reading engagement related to four variables including (i) reading comprehension, (ii) oral response to reading, (iii) reaction paragraph, and (iv) students’ perceptions of learning to read. Participants included 52 Vietnamese undergraduate students of EFL pre-intermediate level. The data of the study were collected through reading tests for the first three variables and a 32- item questionnaire for the fourth variable. Results revealed that students in the experimental condition achieved significantly better understanding of reading comprehension after the intervention course. In terms of reflection after reading and creating a reaction paragraph, the holistic quality of oral response and the reaction paragraph was significantly improved for both groups from a peer rating. However, students in the experimental group showed a more dramatic increase. Moreover, the findings of the questionnaire showed that students in the intervention course achieved a more positive perception of their learning to read

Trigonometric-series solution for analysis of laminated composite beams

A new analytical solution based on a higher-order beam theory for static, buckling and vibration of laminated composite beams is proposed in this paper. The governing equations of motion are derived from Lagrange’s equations. An analytical solution based on trigonometric series, which satisfies various boundary conditions, is developed to solve the problem. Numerical results are obtained to compare with previous studies and to investigate the effects of length-to-depth ratio, fibre angles and material anisotropy on the deflections, stresses, natural frequencies and critical buckling loads of composite beams with various configurations

SOLUTIONS OF TEACHING AND LEARNING PHYSICAL EDUCATION AT HO CHI MINH CITY COLLEGE OF ECONOMICS, VIETNAM

Physical education is one of the compulsory courses at Ho Chi Minh City College of Economics. However, students have been observed to be less engaged in physical activities. Therefore, this study aims to investigate the solutions of teaching and learning physical education at this institution. In particular, fifteen solutions are proposed to enhance the quality of teaching and learning physical education.  Article visualizations

An analytical method for the vibration and buckling of functionally graded beams under mechanical and thermal loads

An analytical method for vibration and buckling behaviours of Functionally Graded (FG) beams with various boundary conditions under mechanical and thermal loads is presented. Based on linear strain-displacement relations, equations of motion and essential boundary conditions are derived from Hamilton’s principle. In order to account for thermal effects, three cases of the temperature rise through the thickness, which are uniform, linear and nonlinear, are considered. The exact solutions are derived using the state space approach. Numerical results are presented to investigate the effects of boundary conditions, temperature distributions, material parameters and slenderness ratios on the critical temperatures, critical buckling loads, and natural frequencies as well as load-frequencies curves, temperature-frequencies curves of FG beams under thermal/mechanical loads. The accuracy and effectiveness of proposed model are verified by comparison with previous research

Size-dependent vibration of bi-directional functionally graded microbeams with arbitrary boundary conditions

In this paper, the free vibration behaviour of bi-dimensional functionally graded (BDFG) microbeams under arbitrary boundary conditions (BCs) is studied. Based on the frame work of the modified couple stress theory and Hamilton's principle, governing equations of motion are developed for the BDFG microbeams using a quasi-3D theory. The formula then can be reduced to a higher-order beam theory (HOBT) of conventional functionally graded (FG) microbeams with the material properties varying along the thickness direction only. Two types of BDFG microbeams with different patterns of material volume distribution are considered. The material properties used in this study are assumed to vary exponentially along both longitudinal and thickness directions of microbeams. Based on the state-space concept, the governing equations are solved for natural frequencies and vibration mode shapes of microbeams under various BCs. The effects of material distribution, geometric parameters and BCs are also investigated to examine the size-dependent behaviour of BDFG microbeams