Search results for "Correlation"

A Non-Stationary Mobile-to-Mobile Channel Model Allowing for Velocity and Trajectory Variations of the Mobile Stations

2017

In mobile-to-mobile (M2M) communication systems, both the transmitter and the receiver are moving with a certain velocity, which is usually assumed to be constant over time. However, in realistic propagation scenarios, the velocity of the mobile stations (MSs) is subject to changes resulting in a non-stationary fading process. In this paper, we develop a non-stationary narrow-band M2M multipath fading channel model, where the transmitter and the receiver experience changes in their velocities and trajectories. For this model, we derive expressions for the local autocorrelation function (ACF), the Wigner-Ville spectrum, the local average Doppler shift, and the local Doppler spread under isot…

New Development of Monte Carlo Techniques for Studying Bottle-brush Polymers

2011

Due to the complex characteristics of bottle-brush polymers, it became a challenge to develop an efficient algorithm for studying such macromolecules under various solvent conditions or some constraints in the space by using computer simulations. In the limit of a bottle-brush polymer with a rather stiff backbone (straight rigid backbone), we generalize the variant of the biased chain growth algorithm, the pruned-enriched Rosenbluth method, for simulating polymers with complex architecture, from star polymers to bottle-brush polymers, on the simple cubic lattice. With the high statistics of our Monte Carlo results, we check the theoretical predictions of side chain behavior and radial monom…

Scaling of non-Markovian Monte Carlo wave-function methods

2004

We demonstrate a scaling method for non-Markovian Monte Carlo wave-function simulations used to study open quantum systems weakly coupled to their environments. We derive a scaling equation, from which the result for the expectation values of arbitrary operators of interest can be calculated, all the quantities in the equation being easily obtainable from the scaled Monte Carlo simulations. In the optimal case, the scaling method can be used, within the weak coupling approximation, to reduce the size of the generated Monte Carlo ensemble by several orders of magnitude. Thus, the developed method allows faster simulations and makes it possible to solve the dynamics of the certain class of no…

RELIABILITY OF THE DETECTION OF THE BARYON ACOUSTIC PEAK

2008

The correlation function of the distribution of matter in the universe shows, at large scales, baryon acoustic oscillations, which were imprinted prior to recombination. This feature was first detected in the correlation function of the luminous red galaxies (LRG) of the Sloan Digital Sky Survey (SDSS). The final release (DR7) of the SDSS has been recently made available, and the useful volume is about two times bigger than in the old sample. We present here, for the first time, the redshift space correlation function of this sample at large scales together with that for one shallower, but denser volume-limited subsample drawn from the 2dF redshift survey. We test the reliability of the det…

Detection of ventricular fibrillation using the autocorrelation function analysis of the ECG

2003

A method is developed for the detection of ventricular fibrillation (VF) and life-threatening arrhythmias. The method is based on direct and simple peak analysis of the autocorrelation function (ACF). It can differentiate between VF (coarse and fine) and non-VH rhythms. ECG records during ventricular tachycardia (VT) and VF were obtained, and 4-s-long segments were digitized at 200 Hz and then split in three groups (VT, VF regular, and VF irregular). ACFs were computed, and positive peak P(j) (j=1, 2, . . .), RPL(j)=P(j)/2SE(1), TR(1)=P(1) width/lag P(1), and D(j)=P(j)-P(j+1) were measured and calculated for each sample. Results show that: (a) RPL(j)(j=1, 2, 3) together with D(j) present hi…

Master equation for cascade quantum channels: a collisional approach

2012

It has been recently shown that collisional models can be used to derive a general form for the master equations which describe the reduced time evolution of a composite multipartite quantum system, whose components "propagate" in an environmental medium which induces correlations among them via a cascade mechanism. Here we analyze the fundamental assumptions of this approach showing how some of them can be lifted when passing into a proper interaction picture representation.

Dynamic Phase Diagram of the REM

2019

International audience; By studying the two-time overlap correlation function, we give a comprehensive analysis of the phase diagram of the Random Hopping Dynamics of the Random Energy Model (REM) on time-scales that are exponential in the volume. These results are derived from the convergence properties of the clock process associated to the dynamics and fine properties of the simple random walk in the $n$-dimensional discrete cube.

Corrigendum: Spectral Entropy Based Neuronal Network Synchronization Analysis Based on Microelectrode Array Measurements

2020

Accurate Nonlinear Optical Properties for Small Molecules

2006

During the last decade it became possible to calculate by quantum chemical ab initio methods not only static but also frequency-dependent properties with high accuracy. Today, the most important tools for such calculations are coupled cluster response methods in combination with systematic hierarchies of correlation consistent basis sets. Coupled cluster response methods combine a computationally efficient treatment of electron correlation with a qualitatively correct pole structure and frequency dispersion of the response functions. Both are improved systematically within a hierarchy of coupled cluster models. The present contribution reviews recent advances in the highly accurate calculat…

Collective Excitations in Simple Liquids

2014

The dynamics of simple liquid is discussed by starting from the linearized Navier-Stokes equations. Using these equations expicit formulas for the density- and current-correlation functions are given. Mode-coupling theory is introduced, which gives a constitutive equation between the current-relaxation memory function and the density correlation function. This theory is shown to accurately describe the collective-excitation behavior of simple liquids like liquid metals.