in this paper, a new robust controller based on geometric homogeneity and adaptive integral sliding mode is proposed for a class of second order systems. the upper bound of the system disturbances is not required. fully unknown parameters have been considered in the described model and its finite–time convergence to zero equilibrium point is proved. moreover, the controller is developed in the ...

The deployment of new 5G services and future demands for 6G make it necessary to increase the performance access networks. This challenge has prompted development standardization proposals Passive Optical Networks (PONs) that offer greater bandwidth, reach a higher rate aggregation users per fiber, being Time- Wavelength-Division Multiplexing (TWDM) promising technological solution increasing c...

A simple description of the vacuum energy (cosmological constant) problem for non-experts is presented. Basic features of cosmology with non-zero vacuum energy are discussed. The astronomical data which indicate that the universe is filled with an anti-gravitating state of matter are described. The mechanisms which may lead to cancellation of almost infinite vacuum energy down to the astronomic...

In 1987, the United Nations defined sustainable development as meeting needs of present generations without compromising future generations. Today, top priority for sustainability is transition to Net Zero—that is, net zero greenhouse gas (GHG) emissions. Carbon dioxide, a GHG, major contributor global warming. pages that follow, I provide three different perspectives on how companies are most ...

Implicit time stepping procedures for the time dependent Stokes problem lead to stationary singular perturbation problems at each time step. These singular perturbation problems are systems of saddle point type, which formally approach a mixed formulation of the Poisson equation as the time step tends to zero. Preconditioners for discrete analogous of these systems are discussed. The preconditi...