The discovery of cosmic acceleration motivated extensive studies dynamical dark energy and modified gravity models. Of particular interest are the scalar-tensor theories, with a scalar field non-minimally coupled to matter. Cosmological constraints on these models often employ quasi-static approximation (QSA), in which dynamics perturbations is proportional perturbation matter density. Using QS...

An ab initio quantum-mechanical theoretical framework is presented to compute the thermal properties of molecular crystals. The present strategy combines dispersion-corrected density-functional-theory (DFT-D), harmonic phonon dispersion, quasi-harmonic approximation to the lattice dynamics for thermal expansion and thermodynamic functions, and quasi-static approximation for anisotropic thermo-e...

impact is one of the most important subjects which always have been considered in mechanical science. nature of impact is such that which makes its control a hard task. therefore it is required to adopt a safe and secure mechanism for transferring the impact to other vulnerable parts of a structure, when it is necessary. one of the best methods of absorbing impact energy is using thin-walled tu...

In this article, an efficient methodology is presented to optimize the topology of structural systems under transient loads. Equivalent static loads concept is used to deal with transient loads and to solve an alternate quasi-static optimization problem. The maximum strain energy of the structure under the transient load during the loading interval is used as objective function. The objective f...

A quasi-static approximation (QSA) for modified gravity can be applied in a number of ways. We consider three different analytical formulations based on applying this to: (1) the field equations; (2) equations two metric potentials; (3) use attractor solution derived within Equation State (EoS) approach. assess veracity these implementations effective gravitational constant ($\mu$) and slip par...

In this paper, the quasi static-approximation on hydrodynamics of compact objects is proposed in $f(R, T)$ gravity, where $R$ scalar curvature and $T$ trace stress-energy tensor, by exploring axial reflection symmetric space time stuffed with anisotropic dissipative matter contents. The set invariant-velocities defined to comprehend concept static-approximation. As a consequence, evolution show...