scholarly journals The Long Term Behaviour of Classical Old Novae

1990 ◽  
Vol 122 ◽  
pp. 13-23
Author(s):  
A. Bianchini
Keyword(s):  
Mass Transfer ◽  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Time Scales ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Solar Type ◽  
Definition Of

AbstractQuiescent novae are more stable against mass transfer rate than dwarf novae. They may however show cyclical variations of their quiescent magnitudes on time scales of years, probably caused by solar–type cycles of activity of the secondary. The probability density function of the periods of the cycles observed in CVs is similar to that for single stars. Sometimes, periodic or quasi periodic light variations on time scales of tens to hundreds of days are also observed. Although the magnitudes of prenovae and postnovae are essentially the same, the definition of the magnitude of a quiescent nova is still uncertain. At present, the hibernation theory for old novae seems to be supported only by the observations of two very old novae.

AN EMPIRICAL STUDY OF THE PROBABILITY DENSITY FUNCTION OF HF NOISE (PART II)

2008 ◽  
Vol 08 (03n04) ◽  
pp. L305-L314 ◽  
Author(s):  
J. GIESBRECHT
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
South Australia ◽  
Noise Model ◽  
Modulation Recognition ◽  
Noise Sources ◽  
Noise Density ◽  
Automatic Modulation Recognition ◽  
Definition Of

The impetus for investigating the probability density function of high-frequency (HF) noise arises from the requirement for a better noise model for automatic modulation recognition techniques. Many current modulation recognition methods still assume Gaussian noise models for the transmission medium. For HF communications this can be an incorrect assumption. Whereas a previous investigation [1] focuses on the noise density function in an urban area of Adelaide Australia, this work studies the noise density function in a remote country location east of Adelaide near Swan Reach, South Australia. Here, the definition of HF noise is primarily of natural origins – it is therefore impulsive – and excludes man-made noise sources. A new method for measuring HF noise is introduced that is used over a 153 kHz bandwidth at various frequencies across the HF band. The method excises man-made signals and calculates the noise PDF from the residue. Indeed, the suitability of the Bi-Kappa distribution at modeling HF noise is found to be even more compelling than suggested by the results of the earlier investigation.

scholarly journals Maximum-likelihood estimation of the parameters of a four-parameter class of probability distributions

1988 ◽  
Vol 31 (2) ◽  
pp. 271-283 ◽  
Author(s):  
Siegfried H. Lehnigk
Keyword(s):  
Maximum Likelihood ◽  
Probability Density Function ◽  
Maximum Likelihood Estimation ◽  
Probability Density ◽  
Density Function ◽  
Probability Distributions ◽  
Likelihood Estimation ◽  
Initial Shape ◽  
Definition Of ◽  
Image Position

We shall concern ourselves with the class of continuous, four-parameter, one-sided probability distributions which can be characterized by the probability density function (pdf) classIt depends on the four parameters: shift c ∈ R, scale b > 0, initial shape p < 1, and terminal shape β > 0. For p ≦ 0, the definition of f(x) can be completed by setting f(c) = β/bΓ(β−1)>0 if p = 0, and f(c) = 0 if p < 0. For 0 < p < 1, f(x) remains undefined at x = c; f(x)↑ + ∞ as x↓c.

Methods of Computing the Probability of Failure Under Extreme Values of Bending Moment

1972 ◽  
Vol 16 (02) ◽  
pp. 113-123
Author(s):  
Alaa Mansour
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Extreme Values ◽  
Bending Moment ◽  
Random Variable ◽  
Probability Of Failure ◽  
Short Term ◽  
Term Analysis

Methods for predicting the probability of failure under extreme values of bending moment (primary loading only) are developed. In order to obtain an accurate estimate of the extreme values of the bending moment, order statistics are used. The wave bending moment amplitude treated as a random variable is considered to follow, in general, Weibull distribution so that the results could be used for short-term as well as long-term analysis. The probability density function of the extreme values of the wave bending moment is obtained and an estimate is made of the most probable value (that is, the mode) and other relevant statistics. The probability of exceeding a given value of wave bending moment in "n" records and during the operational lifetime of the ship is derived. Using this information, the probability of failure is obtained on the basis of an assumed normal probability density function of the resistive strength and deterministic still-water bending moment. Charts showing the relation of the parameters in a nondimensional form are presented. Examples of the use of the charts for long-term and short-term analysis for predicting extreme values of wave bending moment and the corresponding probability of failure are given.

OPTIMAL CONTROL OF CHAOTIC SYSTEMS

2001 ◽  
Vol 11 (07) ◽  
pp. 2007-2018 ◽  
Author(s):  
PAWEŁ GÓRA ◽  
ABRAHAM BOYARSKY
Keyword(s):  
Optimal Control ◽  
Probability Density Function ◽  
Probability Measure ◽  
Probability Density ◽  
Density Function ◽  
Chaotic Systems ◽  
Invariant Probability Measure ◽  
Optimization Methods ◽  
Point Transformation

The problem of controlling a chaotic system is treated from a long term statistical basis. Unlike the OGY targeting method that exploits individual unstable orbits, this approach is concerned with targeting the density function of an invariant probability measure. Given a point transformation T, possessing a density function f, we choose [Formula: see text], a different probability density function, to be the target. Using optimization methods, we construct a point transformation [Formula: see text], close to T, whose invariant probability density function is [Formula: see text], or close to [Formula: see text].

scholarly journals Exploring Finite-Sized Scale Invariance in Stochastic Variability with Toy Models: The Ornstein–Uhlenbeck Model

Symmetry ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 1927
Author(s):  
Nachiketa Chakraborty
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Scale Invariance ◽  
Finite Size ◽  
Fundamental Property ◽  
Cosmic Ray ◽  
Self Similarity ◽  
Definition Of ◽  
Stochastic Properties

Stochastic variability is ubiquitous among astrophysical sources. Quantifying stochastic properties of observed time-series or lightcurves, can provide insights into the underlying physical mechanisms driving variability, especially those of the particles that radiate the observed emission. Toy models mimicking cosmic ray transport are particularly useful in providing a means of linking the statistical analyses of observed lightcurves to the physical properties and parameters. Here, we explore a very commonly observed feature; finite sized self-similarity or scale invariance which is a fundamental property of complex, dynamical systems. This is important to the general theme of physics and symmetry. We investigate it through the probability density function of time-varying fluxes arising from a Ornstein–Uhlenbeck Model, as this model provides an excellent description of several time-domain observations of sources like active galactic nuclei. The probability density function approach stems directly from the mathematical definition of self-similarity and is nonparametric. We show that the OU model provides an intuitive description of scale-limited self-similarity and stationary Gaussian distribution while potentially showing a way to link to the underlying cosmic ray transport. This finite size of the scale invariance depends upon the decay time in the OU model.

scholarly journals The New View on the Long-Therm Flickering in T CrB

2004 ◽  
Vol 194 ◽  
pp. 235-235
Author(s):  
A. Dobrotka ◽  
L. Hric ◽  
K. Petrík
Keyword(s):  
Mass Transfer ◽  
Light Curve ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Variable Mass ◽  
Lagrangian Point ◽  
Turbulent Eddies ◽  
Theoretical Assumptions ◽  
Powerful Flare

The big scatter of data on the light curve of T CRB is identified with the flickering activity of the system. The data performed during April 1996 have a falling trend and they can be a part of a downward branch of a long-term and energetically powerful flare. Estimated energy 2 1035 J and the duration of this event were compared with the theoretical assumptions based on three typical physical scenarios, which can be the source of flickering. The dissipation of magnetic loops and the existence of the turbulent eddies are energetically deficient, but these scenarios are real in the case of less powerfull flares. The real explanation could be the instability of the secondary and variable mass transfer rate through the Lagrangian point, therefore through whole disc.

The cost of a carrier-borne epidemic

1974 ◽  
Vol 11 (4) ◽  
pp. 642-651 ◽  
Author(s):  
D. Jerwood
Keyword(s):  
Probability Density Function ◽  
Probability Distribution ◽  
Probability Density ◽  
Density Function ◽  
Expected Number ◽  
Stochastic Epidemic ◽  
Definition Of ◽  
The Cost ◽  
General Stochastic

In this paper, the cost of the carrier-borne epidemic is considered. The definition of duration, as used by Weiss (1965) and subsequent authors, is generalised and the probability distribution for the number of located carriers is obtained. One component of cost, namely the area generated by the trajectory of carriers, is examined and its probability density function derived. The expected area generated is then shown to be proportional to the expected number of carriers located during the epidemic, a result which has an analogue in the general stochastic epidemic.

scholarly journals Nova Outbursts and the Secular Evolution of Cataclysmic Variables

1996 ◽  
Vol 158 ◽  
pp. 447-448
Author(s):  
K. Schenker ◽  
U. Kolb ◽  
H. Ritter
Keyword(s):  
Mass Transfer ◽  
Angular Momentum ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Secular Evolution ◽  
Term Evolution ◽  
Angular Momentum Loss ◽  
The Mean ◽  
Nova Outbursts

AbstractWe present calculations of the long-term evolution of CVs which include the influence of nova outbursts. In particular we investigate the consequences of the discontinuous mass loss due to recurring outburst events and the effects of frictional angular momentum loss (FAML), i.e. the interaction of the expanding nova envelope with the secondary. We show that a description assuming continuous mass loss – averaged over a complete nova cycle – is applicable for determining the mean mass transfer rate and the secular evolution both with and without FAML. Between two subsequent outbursts, deviations from the mean evolution depend on the strength of FAML and on the mass ejected during the outburst. Formally FAML is a consequential angular momentum loss [1] and therefore increases the mean mass transfer rate by pushing the systems closer to mass transfer instability. Depending on the actual strenghth of FAML the long-term evolution of CVs could be significantly different from the standard model predictions.

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