Search results for "Isolated system"
showing 5 items of 5 documents
Relation Between the State of a System as Isolated and as Open
2020
We discuss the differences in considering the description of a system as isolated or as a subsystem of a wider isolated system. In the latter case, a description in terms of a density operator directly arises without involving probability concepts, but as an orbit invariant. The non-probabilistic physical interpretation of the density operator is mathematically discussed.
Models and mecanisms in economics : attempt to clarify their relationships
2000
The article is an attempt to clarify the relationship between economic models and mechanisms. The latter refer to causal processes and interactions. What role do they play in models? One must distinguish between models as non-linguistic constructs and models in the more usual sense of formal systems of definitions and mathematical relations. Models in the second sense are interpreted as purporting to characterise or describe in part models in the first sense. Thus the fact that there is no explicit reference to process-based mechanisms in many formal models does not mean that these mechanisms do not play an essential role in the non-linguistic models that these formal models describe in an …
Multiple expansions for energy and momenta carried by gravitational waves
2007
We present expressions for the energy, linear momentum and angular momentum carried away from an isolated system by gravitational radiation based on spin-weighted spherical harmonics decomposition of the Weyl scalar $\Psi_4$. We also show that the expressions derived are equivalent to the common expressions obtained when using a framework based on perturbations of a Schwazschild background. The main idea is to collect together all the different expressions in a uniform and consistent way. The formulae presented here are directly applicable to the calculation of the radiated energy, linear momentum and angular momentum starting from the gravitational waveforms which are typically extracted f…
Simplified analytical solution for the optimal design of Tuned Mass Damper Inerter for base isolated structures
2019
Abstract In this paper the use of the Tuned Mass Damper Inerter (TMDI) to control the response of base isolated structures under stochastic horizontal base acceleration is examined. Notably, the TMDI, recently introduced as a generalization of the classical Tuned Mass Damper, allows to achieve enhanced performance compared to the other passive vibration control devices. Thus, it represents an ideal alternative for reducing displacements of base isolated structures. To this aim, firstly a straightforward numerical approach is developed for the optimal design of this device considering a white noise base excitation. Further, a simplified analytical solution for the optimal design of TMDI para…
A Simulation Analysis of VSM Control for RES plants in a Small Mediterranean Island
2020
The paper presents an application of Virtual Synchronous Machine control for managing inverter-interfaced renewable energy sources in a small Mediterranean island not supplied by the main grid. In the proposed analysis, the island's renewables-based generators area assumed interfaced to the grid by voltage source converters with a swing controller and a vector-current controller with two different options for the reference current for regulating the voltage at the Point of Common Coupling and the active power output. The system, modeled in PScad environment, allows to verify the response of the renewables-based generators with VSM control in the presence of a fault in the grid.