Search results for "Discrete variable"

Discrete variable design of frames subjected to seismic actions accounting for element slenderness

2015

An optimal design problem formulation of elastic plastic frames under different combinations of fixed and seismic loads is presented. The optimal structure must behave elastically for the fixed loads, shakedown for serviceability conditions and prevent instantaneous collapse for fixed and high seismic loads. P-Delta effects and element buckling are considered. An appropriate modal technique is utilized. The design variables can have components in a continuous field or, alternatively, in chosen discrete sets or, yet, both kind of variables can be present. The design problem is formulated on the ground of a statical approach. The applications are related to steel frames.

Dynamics of a Quantum Particle in Asymmetric Bistable Potential with Environmental Noise

2011

In this work we analyze the dynamics of a quantum particle subject to an asymmetric bistable potential and interacting with a thermal reservoir. We obtain the time evolution of the population distributions in both energy and position eigenstates of the particle, for different values of the coupling strength with the thermal bath. The calculation is carried out using the Feynman-Vernon functional under the discrete variable representation.

Minimum volume design of structures with constraints on ductility and stability

2014

Abstract A minimum volume design problem of elastic perfectly plastic frame structures subjected to different combinations of fixed and seismic loads is presented, in which the design variables are considered as appertaining alternatively to a continuous assigned range as well as to appropriate discrete sets. The structure is designed so as to behave elastically for the applied fixed loads, to shakedown in presence of serviceability seismic conditions and to prevent the instantaneous collapse for suitably chosen combinations of fixed and high seismic loadings. In order to avoid further undesired collapse modes, the P-Delta effects are considered and the structure is also constrained to prev…

Enhancing Metastability by Dissipation and Driving in an Asymmetric Bistable Quantum System.

2018

The stabilizing effect of quantum fluctuations on the escape process and the relaxation dynamics from a quantum metastable state are investigated. Specifically, the quantum dynamics of a multilevel bistable system coupled to a bosonic Ohmic thermal bath in strong dissipation regime is analyzed. The study is performed by a non-perturbative method based on the real-time path integral approach of the Feynman-Vernon influence functional. We consider a strongly asymmetric double well potential with and without a monochromatic external driving, and with an out-of-equilibrium initial condition. In the absence of driving we observe a nonmonotonic behavior of the escape time from the metastable regi…

Discrete variables structural design of frames safe against buckling

2014

Analysis and design of elastic plastic structures subjected to dynamic loads

In the last decades, the concept of “optimization” has reached considerable value in many different fields of scientific research and, in particular, it has assumed great importance in the field of structural mechanics. The present study describes and shows the scientific path followed in the three years of doctoral studies. The state of the art concerning the optimization of elastic plastic structures subjected to quasi-static loads was already well established at the beginning of the Ph.D. course. Actually, it was already faced the study of structures subjected to quasi-static cyclic loads able to ensure different structural behaviors in relation to different intensity levels of the appli…

Quantum Relaxation Time in Asymmetric Bistable Potential

2010

Quantum tunneling effect occurs often in condensed matter physics, examples are JJs, heteronanostructures, etc.. The tunneling effect plays an important role in the nonlinear relaxation time from a metastable state in an open quantum system, interacting with a thermal bath. Symmetrical and asymmetric bistable systems are good quantum model systems for analysis of the "superconducting quantum bits" and decoherence phenomena. To obtain very long coherence times in the presence of interaction between the qubit and the noisy environment is one of the greatest challenges of physics. The inf1uence of the environment in quantum tunneling has been in the focus of intense research over the last year…

Nonlinear relaxation in quantum and mesoscopic systems

2013

The nonlinear relaxation of three mesoscopic and quantum systems are investigated. Specifically we study the nonlinear relaxation in: (i) a long Josephson junction (LJJ) driven by a non-Gaussian Lévy noise current; (ii) a metastable quantum open system driven by an external periodical driving; and (iii) the electron spin relaxation process in n-type GaAs crystals driven by a fluctuating electric field. In the first system the LJJ phase evolution is described by the perturbed sine-Gordon equation. Two well known noise induced effects are found: the noise enhanced stability and resonant activation phenomena. We investigate the mean escape time as a function of the bias current frequency, nois…