Electro-magneto-thermo-mechanical Behaviors of a Radially Polarized FGPM Thick Hollow Sphere

ABSTRACT In this study an analytical method is developed to obtain the response of electro-magneto-thermoelastic stress and perturbation of a magnetic field vector for a thick-walled spherical functionally graded piezoelectric material (FGPM). The hollow sphere, which is placed in a uniform magnetic field, is subjected to a temperature gradient, inner and outer pressures and a constant electric potential difference between its inner and outer surfaces. The thermal, piezoelectric and mechanical properties except the Poisson's ratio are assumed to vary with the power law functions through the thickness of the hollow sphere. By solving the heat transfer equation, in the first step, a symmetric distribution of temperature is obtained. Using the infinitesimal electro-magnetothermo-elasticity theory, then, the Navier's equation is solved and exact solutions for stresses, electric displacement, electric potential and perturbation of magnetic field vector in the FGPM hollow sphere are obtained. Moreover, the effects of magnetic field vector, electric potential and material in-homogeneity on the stresses and displacements distributions are investigated. The presented results indicate that the material in-homogeneity has a significant influence on the electro-magneto-thermo-mechanical behaviors of the FGPM hollow sphere and should therefore be considered in its optimum design

Flexural Behavior of Functionally Graded-Graphene Reinforced Composite Plates

A first order shear deformation theory based finite element numerical investigation on flexure behaviour of functionally graded thin, moderately thick and thick composite plates reinforced with graphene platelets (GPLs) is presented in this paper. The maximum deflection plays a major role in the design of composite structures. Therefore, maximum deflection and percentage maximum deflection ratio of reinforced to unreinforced composite plate are investigated for a range of GPL distribution patterns along plan and thickness directions of the composite plate. Modified Halpin-Tsai equation is used to determine the effective Young’s modulus for each layer in thickness direction for different distribution patterns. The rule of mixture is used to calculate effective mass density and Poisson’s ratio for each layer. Initially, the results from this study are verified by comparing with the reported results from the literature. Thereafter, validated methodology is used to conduct case study for a simply supported plate, focusing on the effect of thickness, GPL distribution patterns along plan and thickness directions, percentage weight fraction of GPL on the maximum deflection and percentage maximum deflection ratio of reinforced to unreinforced composite plate. It is found that by adding just 1% weight fraction of GPL, the maximum deflection can be reduced by almost 65% to 90% for all thicknesses and distribution patterns considered

Designing the Model of Student Support System in the Virtual Learning Environment: A Necessity in the Face of the Corona Crisis

Introduction: Process of e-learning in universities because of coronavirus (Covid-19)  outbreak was developed. Since the success of students in this type of education requires appropriate and effective support,  the present study has been done  to develop a model of support system  in virtual  learning environment in medical universities. Methods: This  is an applied  qualitative research. To design the model, data obtained from  searching  information  sources  in the period  of 1990 to 2020  was used as well as thematic analysis to analyze the  results of  interviews with experts. The validity and reliability of the interview data were confirmed based on Lincol & Guba evaluative criteria. Based on the data, the model of the student support system of medical universities in the virtual  learning environment was developed by creative mental synthesis. Results: In  this  model, seven key supports  have been introduced as important dimensions of the student support system in the virtual education environment. in addition to student support, professors and staff  need to be supported. Also, student support before, during, and  after  graduation  is  required for students' success in this model.  Conclusion: According to the research findings, since  the necessity of student support system  in the environment of e-learning and  virtual learning is inevitable for students' academic success, therefore, it is recommended  that university officials and administrators use the results of this study to implement a student support system in the virtual learning  environment at their university