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Aims: COVID-19 Vaccination Hesitancy is a public health concern in the world. The present study aimed to determine the prevalence of vaccination hesitancy and its relevant factors using the health belief model among people in northeast Iran.
Instrument & Methods: The present cross-sectional study examined 626 people using convenience sampling. Data were collected through an online survey using a questionnaire based on the health belief model at intervals of 10 September 2021 and 15 October 2021. Data were analyzed by using SPSS 16.
Findings: Overall, 70.6% of the samples reported that they would use the vaccine for free after it becomes available. Health belief model constructs predicted 40% of the variance of vaccination behavioral intention. The results indicated that the perceived barriers were significantly related to using the vaccine, thereby reducing the probability of using the vaccine by 10% (Relative Risk Ratio=0.90, 95% CI: 0.82-0.99). Perceived benefits (Relative Risk Ratio =1.21, 95% CI: 1.11-1.32), perceived susceptibility (Relative Risk Ratio =1.54, 95% Cl: 1.23-1.92), and behavioral intention (Relative Risk Ratio =3.06, 95% CI: 2.23-4.20) had a significant relationship with the probability of using the vaccine.
Conclusion: About one-third of the participants had COVID-19 vaccination hesitancy. Interventions are necessary to increase compliance with vaccination, especially among people with low education levels. The health belief model constructs have a high power of predicting hesitancy and acceptance of COVID-19 vaccination and can be used in intervention programs.
 

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In this study, single-objective and multi-objective optimization of curved sandwich panel with composite face sheets and magneto-rheological core have been done to maximize the first modal loss factor and minimize the mass by using genetic algorithm. The studied sandwich panel was curved with simply support boundary condition. In order to derive the governing equations of motion, an improved high order sandwich panel theory and Hamilton's principle were used for the first time. The face sheet thickness, core thickness, fiber angles and intensity of the magnetic field have been considered as optimization variables. In single-objective optimization, the optimized values of variables were calculated. The results showed that the structures tend to have thick core and thin face sheets which seems physically true. As the magneto-rheological fluid placed in the core, it has a significant effect on the increasing of the modal loss factor. For the multi-objective optimization the Pareto front of optimal technique was presented. Then for the first time at this field, the set of optimal points are selected based on TOPSIS method and it was showed that in the case of similar size and mass, modal loss factor of double-curved panel is more than sigle-curved.

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This study dealt with the flutter and biaxial buckling of composite sandwich panels based on a higher order theory. The formulation was based on an enhanced higher order sandwich panel theory that the vertical displacement component of the face sheets were assumed as quadratic one while a cubic pattern was used for the in-plane displacement components of the face sheets and the all displacement components of the core. The transverse normal stress in the face sheets and the in-plane stresses in the core were considered. For the first time, the continuity conditions of the displacements, transverse shear and normal stress at the layer interfaces, as well as the conditions of zero transverse shear stresses on the upper and lower surfaces of the sandwich panel are simultaneously satisfied. The aerodynamic loading was obtained by the first-order piston theory. The equations of motion and boundary conditions were derived via the Hamilton principle. Moreover, effects of some important parameters like lay-up of the face sheets, length to width ratio, length to panel thickness ratio, thickness ratio of the face sheets to panel, fiber angle, elastic modulus ratio and thickness ratio of the face sheets on the stability boundaries were investigated. The results were validated by those published in the literature. The results revealed that by increasing length to width ratio, length to panel thickness ratio and elastic modulus ratio of the face sheets, the stability boundaries were decreased and the largest nondimensional buckling load was occurred at the angle ply sandwich panel.