Search results for "computational method"

Active controlled structural systems under delta-correlated random excitation: linear and nonlinear case

2006

Abstract Reduction of structural vibration in active controlled dynamical system is usually performed by means of convenient control forces dependent of the dynamic response. In this paper the existent studies will be extended to dynamical systems subjected to non-Gaussian random process accounting for the time delay involved in the application of active control actions. Control forces acting with time-delay effects will be expanded in Taylor series evaluating response statistics by means of the extended Ito differential rule to consider the effects of the non-normality of the input processes. Numerical application provided shows the feasibility of the proposed method to analyze stochastic …

H−ZSM-5 Modified Zeolite:  Quantum Chemical Models of Acidic Sites

2007

A ZSM-5 fragment, containing 52 tetrahedral moieties, each of them formed by one silicon or one aluminum atom surrounded by four oxygen atoms, was employed to model (52T systems) by quantum chemical calculations (i) the influence of the positions of the acidic sites on the energetics of 22 aluminum monosubstituted and bisubstituted 52T acidic zeolite (H-ZSM-5) systems and (ii) the local adsorption properties and acidic strength of the corresponding -OH sites. The energetics and the structural properties of simpler acid H-ZSM-5 systems containing only five Tetrahedral moieties (5T systems) were also modeled for comparison. B3LYP/6-31G(d,p) partial geometry optimization routines were performe…

Tailored pump-probe transient spectroscopy with time-dependent density-functional theory: controlling absorption spectra

2016

Recent advances in laser technology allow us to follow electronic motion at its natural time-scale with ultra-fast time resolution, leading the way towards attosecond physics experiments of extreme precision. In this work, we assess the use of tailored pumps in order to enhance (or reduce) some given features of the probe absorption (for example, absorption in the visible range of otherwise transparent samples). This type of manipulation of the system response could be helpful for its full characterization, since it would allow us to visualize transitions that are dark when using unshaped pulses. In order to investigate these possibilities, we perform first a theoretical analysis of the non…

Modeling electron dynamics coupled to continuum states in finite volumes with absorbing boundaries

2015

arXiv:1409.1689v1

A Unified Approach to Portfolio Optimization with Linear Transaction Costs

2004

In this paper we study the continuous time optimal portfolio selection problem for an investor with a finite horizon who maximizes expected utility of terminal wealth and faces transaction costs in the capital market. It is well known that, depending on a particular structure of transaction costs, such a problem is formulated and solved within either stochastic singular control or stochastic impulse control framework. In this paper we propose a unified framework, which generalizes the contemporary approaches and is capable to deal with any problem where transaction costs are a linear/piecewise-linear function of the volume of trade. We also discuss some methods for solving numerically the p…

Lifetime of the superconductive state in short and long Josephson junctions

2008

We study the transient statistical properties of short and long Josephson junctions under the influence of thermal and correlated fluctuations. In particular, we investigate the lifetime of the superconductive metastable state finding the presence of noise induced phenomena. For short Josephson junctions we investigate the lifetime as a function both of the frequency of the current driving signal and the noise intensity and we find how these noise-induced effects are modified by the presence of a correlated noise source. For long Josephson junctions we integrate numerically the sine-Gordon equation calculating the lifetime as a function of the length of the junction both for inhomogeneous a…

First-principles modelling for time-resolved ARPES under different pump-probe conditions

2021

First-principles methods for time-resolved angular resolved photoelectron spectroscopy play a pivotal role in providing interpretation and microscopic understanding of the complex experimental data and in exploring novel observables or observation conditions that may be achieved in future experiments. Here we describe an efficient, reliable and scalable first-principles method for tr-ARPES based on time-dependent density functional theory including propagation and surface effects usually discarded in the widely used many-body techniques based on computing the non-equilibrium spectral function and discuss its application to a variety of pump–probe conditions. We identify four conditions, dep…

Geostatistical computing of acoustic maps in the presence of barriers

2009

Acoustic maps are the main diagnostic tools used by authorities for addressing the growing problem of urban acoustic contamination. Geostatistics models phenomena with spatial variation, but restricted to homogeneous prediction regions. The presence of barriers such as buildings introduces discontinuities in prediction areas. In this paper we investigate how to incorporate information of a geographical nature into the process of geostatistical prediction. In addition, we study the use of a Cost-Based distance to quantify the correlation between locations.

Theoretical Determination Of The pKas Of Betalamic Acid Related To The Free-Radical Scavenger Capacity: Comparison Between Semi-Empirical And Ab Init…

2013

A Curvature Based Method for Blind Mesh Visual Quality Assessment Using a General Regression Neural Network

2016

International audience; No-reference quality assessment is a challenging issue due to the non-existence of any information related to the reference and the unknown distortion type. The main goal is to design a computational method to objectively predict the human perceived quality of a distorted mesh and deal with the practical situation when the reference is not available. In this work, we design a no reference method that relies on the general regression neural network (GRNN). Our network is trained using the mean curvature which is an important perceptual feature representing the visual aspect of a 3D mesh. Relatively to the human subjective scores, the trained network successfully asses…