The Big Bang initial singularity problem can be solved by means of bouncing solutions. In the context extended theories gravity, we will look for covariant effective actions whose field equations contain up to fourth-order derivatives metric tensor. finding such solutions, make use an order reduction technique based on a perturbative approach. Reducing second-order, are able find solutions whic...

Fourth-order many-body corrections to matrix elements for atoms with one valence electron are derived. The obtained diagrams are classified using coupled-cluster-inspired separation into contributions from n-particle excitations from the lowest-order wave function. The complete set of fourth-order diagrams involves only connected single, double, and triple excitations and disconnected quadruple...

in this paper, the nonlinear conjugate map based on the conjugate hasofer-lind and rackwitz- fiessler (chl-rf) method is applied to evaluate the reliability index using first order reliability method of the embedded noanocompsite beam, which is made from polymer reinforced with carbon nanotubs (cnts). the structure is simulated with timoshenko beam model. the mori-tanaka model is applied for ca...

Abstract In this work, the Poincaré map numerical method was successfully developed to solve fourth-order differential equation that describes flexural vibrations of a beam, within Timoshenko beam theory. The Euler-Bernoulli continuity conditions were considered, which are valid for frequencies smaller than critical frequency. As an example, used design complex elastic structure, characterized ...

Stability of functionally graded beams with piezoelectric layers subjected to axial compressive load that is simply supported at both ends is studied in this paper. The displacement field of beam is assumed based on first order shear deformation beam theory. Applying the Hamilton's principle, the governing equation is established. The influences of applied voltage, dimensionless geometrical par...

Neutralization of external stimuli in dynamic systems has the major role in health, life, and function of the system. Today, dynamic systems are exposed to unpredicted factors. If the factors are not considered, it will lead to irreparable damages in energy consumption and manufacturing systems. Continuous systems such as beams, plates, shells, and panels that have many applications in differen...