In this paper, an efficient and simple refined shear deformation theory is presented for the vibration and buckling of exponentially graded material sandwich plate resting on elastic foundations under various boundary conditions. The displacement field of the present theory is chosen based on nonlinear variations in the in-plane displacements through the thickness of the plate. By dividing the transverse displacement into the bending and shear parts and making further assumptions, the number of unknowns and equations of motion of the present theory is reduced and hence makes them simple to use. Equations of motion are derived from Hamilton’s principle. Numerical results for the natural frequencies and critical buckling loads of several types of symmetric exponentially graded material sandwich plates are presented. The accuracy of the present theory is verified by comparing the obtained results with solutions available in the literature. Numerical results show that the present theory can archive accuracy comparable to the existing higher order shear deformation theories that contain more number of unknowns.
Purpose This study was designed to compare videolaryngoscopy with direct laryngoscopy with respect to ease of intubation when inserting a double lumen tube (DLT). Methods In this prospective randomized study 68 patients American Society of Anesthesiologists (ASA) physical status I and II were included. Patients with criteria indicating possible difficult intubation were excluded. The patients were randomized into two groups, depending on the tool used to facilitate intubation: videolaryngoscope (VL group) or direct laryngoscopy (DL group). The time required for intubation was the primary endpoint. Cormack and Lehane glottic visualization (CL) scores, the need for external laryngeal maneuvers and the number of attempts were measured. Results Glottic visualization was better in the VL group than in the DL group. The CL scores were I, II and III in 24, eight and two patients, respectively, in the VL group compared with 13, 11 and eight in the DL group (P = 0.025). Patients in the VL group required fewer attempts than the DL group (P = 0.019). Intubation time was 39.9 ± 4.4 sec in the VL group and 47.9 ± 5.4 sec in the DL group (P \ 0.001). No intubation failure was noted in group VL compared with two in the DL group (not significant). Conclusion The use of a videolaryngoscope reduces the time required for intubation with a DLT compared with the direct laryngoscopy in elective thoracic surgery.
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