A cylindrically symmetric perfect fluid spacetime with no curvature singularity is shown. The equation of state for the perfect fluid is that of a stiff fluid. The metric is diagonal and non-separable in comoving coordinates for the fluid. It is proven that the spacetime is geodesically complete and globally hyperbolic. PACS 04.20.Jb, 98.80.Hw

This letter 1 presents the application of the model-free control approach to the microgrid control. We show in simulation that the method allows to control , with a simple controller , voltage , current and power of inverter-based microgrids .

A novel robot learning algorithm called Predictive Sequence Learning (PSL) is presented and evaluated. PSL is a model-free prediction algorithm inspired by the dynamic temporal difference algorithm S-Learning. While S-Learning has previously been applied as a reinforcement learning algorithm for robots, PSL is here applied to a Learning from Demonstration problem. The proposed algorithm is eval...

Some robotic tasks require an accurate control to follow the desired trajectory in the presence of unforeseen external disturbances and system parameters variations. In this case conventional control techniques such as PID must be constantly readjusted and a compromise solution must be adopted. This problem can be avoided using a learning process that automatically learns the appropriate contro...

This article describes a 3D CFD (computational fluid dynamics) simulation implementation of the stepped planning hull in calm water. The turbulent free surface flow around the stepped planing hull is computed with a RANSE method, using the solver ANSYS-CFX. The turbulence model used is standard k–ε. In order to simulate the disturbed free surface, VOF model is implemented. The CFD model has bee...

Conventional model-free reinforcement learning algorithms are limited to performing only one task, such as navigating to a single goal location in a maze, or reaching one goal state in the Tower of Hanoi block manipulation problem. It has been thought that only model-based algorithms could perform goal-directed actions, optimally adapting to new reward structures in the environment. In this wor...

Free electron model, constructed by Drude and Lorentz near 1900 (well before quantum mechanics was developed), can qualitatively explain the DC electrical conductivity, AC electrical conductivity, Hall effect, and magnetoresistance. Later inclusion of Fermi-Dirac distribution (as opposed to Boltzmann distribution) helps to explain the thermal conductivity and specific heat of electrons. However...