Abstract: The governing equations of motion for a drill string considering coupling between axial, lateral and torsional vibrations are obtained using a Lagrangian approach. The result leads to a set of non-linear equations with time varying coefficients. A fully coupled model for axial, lateral, and torsional vibrations of drill strings is presented. The bit/formation interactions are assumed ...

Statins are most effective pharmacologically agents to decrease total plasma cholesterol level by competitive inhibition of HMG-Co A reductase. Apart from the well-known LDL and cholesterol lowering effect, statins have been postulated to exert other beneficial effects also called pleotropic or non-lipid effects. Better understanding of various pleotropic effects of statins has prompted a new s...

In this paper, surface and piezoelectric effects on the vibration behavior of nanowires (NWs) are investigated by using a Timoshenko beam model. The electric field equations and the governing equations of motion for the piezoelectric NWs are derived with the consideration of surface effects. By the exact solution of the governing equations, an expression for the natural frequencies of NWs with ...