Search results for "Names"
showing 10 items of 6843 documents
A Network Formation Game Approach to Study BitTorrent Tit-for-Tat
2007
The Tit-for-Tat strategy implemented in BitTorrent (BT) clients is generally considered robust to selfish behaviours. The authors of [1] support this belief studying how Tit-for-Tat can affect selfish peers who are able to set their upload bandwidth. They show that there is a "good" Nash Equilibrium at which each peer uploads at the maximum rate. In this paper we consider a different game where BT clients can change the number of connections to open in order to improve their performance. We study this game using the analytical framework of network formation games [2]. In particular we characterize the set of pairwise stable networks the peers can form and how the peers can dynamically reach…
The GAPS programme at TNG
2020
Understanding stellar activity in M dwarfs is fundamental to improving our knowledge of the physics of stellar atmospheres and for planet search programmes. High levels of stellar activity (also with flare events) can cause additional variations in the stellar emission that contaminate the signal induced by a planet and that need to be corrected. The study of activity indicators in active stars can improve our capability of modelling this signal. Our aim is to understand the behaviour of stellar chromospheres of M stars, studying the more sensitive chromospheric activity indicators, characterising their variability and on finding the correlations among these indicators to obtain information…
Photometric and spectroscopic variability of the B5IIIe star HD 171219
2017
We analyzed the star HD 171219, one of the relatively bright Be stars observed in the seismo field of the CoRoT satellite, in order to determine its physical and pulsation characteristics. Classical Be stars are main-sequence objects of mainly B-type, whose spectra show, or have shown at some epoch, Balmer lines in emission and an infrared excess. Both characteristics are attributed to an equatorially concentrated circumstellar disk fed by non-periodic mass-loss episodes (outbursts). Be stars often show nonradial pulsation gravity modes and, as more recently discovered, stochastically excited oscillations. Applying the CLEANEST algorithm to the high-cadence and highly photometrically precis…
Analysis of multi degree of freedom systems with fractional derivative elements of rational order
2014
In this paper a novel method based on complex eigenanalysis in the state variables domain is proposed to uncouple the set of rational order fractional differential equations governing the dynamics of multi-degree-of-freedom system. The traditional complex eigenanalysis is appropriately modified to be applicable to the coupled fractional differential equations. This is done by expanding the dimension of the problem and solving the system in the state variable domain. Examples of applications are given pertaining to multi-degree-of-freedom systems under both deterministic and stochastic loads.
Time delay induced effects on control of linear systems under random excitation
2001
Recursive formulas in terms of statistics of the response of linear systems with time delay under normal white noise input are developed. Two alternative methods are presented, in order to capture the time delay effects. The first is given in an approximate solution obtained by expanding the control force in a Taylor series. The second, available for the stationary solution (if it exists) gets the variance of the controlled system, with time delay in an analytical form. The efficacy loss in terms of statistics of the response is discussed in detail.
Statistical correlation of fractional oscillator response by complex spectral moments and state variable expansion
2016
Abstract The statistical characterization of the oscillator response with non-integer order damping under Gaussian noise represents an important challenge in the modern stochastic mechanics. In fact, this kind of problem appears in several issues of different type (wave propagation in viscoelastic media, Brownian motion, fluid dynamics, RLC circuit, etc.). The aim of this paper is to provide a stochastic characterization of the stationary response of linear fractional oscillator forced by normal white noise. In particular, this paper shows a new method to obtain the correlation function by exact complex spectral moments. These complex quantities contain all the information to describe the r…
A Bayesian analysis of the thermal challenge problem
2008
Abstract A major question for the application of computer models is Does the computer model adequately represent reality? Viewing the computer models as a potentially biased representation of reality, Bayarri et al. [M. Bayarri, J. Berger, R. Paulo, J. Sacks, J. Cafeo, J. Cavendish, C. Lin, J. Tu, A framework for validation of computer models, Technometrics 49 (2) (2007) 138–154] develop the simulator assessment and validation engine ( SAVE ) method as a general framework for answering this question. In this paper, we apply the SAVE method to the challenge problem which involves a thermal computer model designed for certain devices. We develop a statement of confidence that the devices mode…
Modelling and Simulation of Ego-Noise of Unmanned Aerial Vehicles
2020
In this paper, we develop a simulation model for the ego-noise of unmanned aerial vehicles (UAVs). The ego-noise is composed of spike noise and background noise. The spike noise is modelled by a finite sum of sinusoids, while the background noise is modelled by a coloured Gaussian stationary process. The main property of our model is that it only depends on physical characteristics of the UAV and it does not need real-time audio inputs to be developed. This model is very useful for training novel noise cancelling algorithms and for evaluating their performance. To validate the proposed model, we compare the statistical properties of the ego-noise simulated using our model with actual ego-no…
Non-Gaussian probability density function of SDOF linear structures under wind actions
1998
Abstract Wind velocity is usually analytically described adding a static mean term to a zero mean fluctuation stationary process. The corresponding aerodynamic alongwind force acting on a single degree of freedom (SDOF) structure can be considered as a sum of three terms proportional to the mean wind velocity, to the product between mean and fluctuating part of the wind velocity and to the square power of the fluctuating wind velocity, respectively. The latter term, often neglected in the literature, is responsible for the non-Gaussian behaviour of the response. In this paper a method for the evaluation of the stationary probability density function of SDOF structures subjected to non-Gauss…
Ornstein-Zernike equation and Percus-Yevick theory for molecular crystals
2004
We derive the Ornstein-Zernike equation for molecular crystals of axially symmetric particles and apply the Percus-Yevick approximation to this system. The one-particle orientational distribution function has a nontrivial dependence on the orientation and is needed as an input. Despite some differences, the Ornstein-Zernike equation for molecular crystals has a similar structure as for liquids. We solve both equations for hard ellipsoids on a sc lattice. Compared to molecular liquids, the tensorial orientational correlators exhibit less structure. However, depending on the lengths a and b of the rotation axis and the perpendicular axes of the ellipsoids, different behavior is found. For obl…