This paper deals with modeling and analysis of complex mechanical systems that deteriorate age. As age, the questions on their availability reliability start to surface. The system is believed suffer from internal stochastic degradation mechanism described as a gradual continuous process performance deterioration. Therefore, it becomes difficult for maintenance engineer model such system. Semi-...

Abstract Borehole breakout initiation, progression, and stabilization are modeled using a semi-analytical method based on Melentiev’s graphical conformal mapping procedure, Kolosov–Muskhelishvili complex stress potentials. The only input data required the elastic moduli of rock, Coulomb strength parameters (cohesion angle internal friction), far-field stresses. stresses around borehole wall com...

A highly accurate and efficient finite-difference method for phase-change problems with multiple moving boundaries of irregular shape is developed by employing a coordinate transformation that immobilizes moving boundaries and preserves the conservative forms of the original governing equations. The numerical method is first presented for one-dimensional phase-change problems (involving large d...

First order Fermi acceleration at astrophysical shocks is often invoked as a mechanism for the generation of non-thermal particles. This mechanism is especially simple in the approximation that the accelerated particles behave like test particles, not affecting the shocked fluid. Many complications enter the calculations when the accelerated particles have a backreaction on the fluid, in which ...