Alireza Bahraminasab

Localization of Elastic Waves in Heterogeneous Media with Off-Diagonal Disorder and Long-Range Correlations

Using the Martin-Siggia-Rose method, we study propagation of acoustic waves in strongly heterogeneous media which are characterized by a broad distribution of the elastic constants. Gaussian-white distributed elastic constants, as well as those with long-range correlations with nondecaying power-law correlation functions, are considered. The study is motivated in part by a recent discovery that the elastic moduli of rock at large length scales may be characterized by long-range power-law correlation functions. Depending on the disorder, the renormalization group (RG) flows exhibit a transition to localized regime in any dimension. We have numerically checked the RG results using the transfer-matrix method and direct numerical simulations for one- and two-dimensional systems, respectively.

Dynamic renormalization group analysis of propagation of elastic waves in two-dimensional heterogeneous media

We study localization of elastic waves in two-dimensional heterogeneous solids with randomly distributed Lame coefficients, as well as those with long-range correlations with a power-law correlation function. The Matin-Siggia-Rose method is used, and the one-loop renormalization group RG equations for the coupling constants are derived in the limit of long wavelengths. The various phases of the coupling constants space, which depend on the value , the exponent that characterizes the power-law correlation function, are determined and described. Qualitatively different behaviors emerge for 1 and 1. The Gaussian fixed point FP is stable unstable for 1 1. For 1, there is a region of the coupling constants space in which the RG flows are toward the Gaussian FP, implying that the disorder is irrelevant and the waves are delocalized. In the rest of the disorder space, the elastic waves are localized. We compare the results with those obtained previously for acoustic wave propagation in the same type of heterogeneous media and describe the similarities and differences between the two phenomena.

Pedestrian Direction of Movement Determination Using Smartphone

These days smart phones have changed the concept of mobile platform. Due to rapid growth in affordability, increased sensory and computational power has opened the ways for some interesting applications like activity recognition, gaming, navigation/tracking, augmented reality etc. In all these applications orientation of mobile phone is very important, once we know the correct orientation of the device, it becomes easy to develop such applications. Orientation can be determined by sensor fusion of accelerometer and magnetometer but it provides good accuracy as long as device is stationary or not moving linearly and also it suffers from surrounding magnetic interference. Orientation estimation systems often use gyroscope to increase reliability and accuracy. Although gyroscopes provide a quick response to change in angles and do not have problems like interference, they suffer from bias and integration errors which introduce drift in signal. In this paper an efficient and less complicated approach is utilized which minimizes the drift and noise in output orientation. In most of smart phone navigation applications these days, it is assumed that mobile is at fixed position like holding in hand facing forward, in trouser/jacket pocket or attached to waist. But if we assume that mobile position is changing arbitrary then situation becomes complicated. The goal of this work is to find accurately the direction of movement of a pedestrian while holding mobile in any position. In this work an accelerometer based approach is presented for pedestrian direction of movement estimation.

Indoor pedestrian displacement estimation using Smart phone inertial sensors

The embedded inertial sensors in todays Smart phones have added the facility to use them for localisation and tracking applications. The benefit of using them for localisation purpose is that no extra infrastructure is to be installed in contrast to other existing positioning technologies. Inertial navigation only provides the information relative to initial point, so it is suitable for short distance positioning. However, integration of inertial navigation with other positioning technologies can be used for precise localisation. In this paper we introduce a mechanism for indoor pedestrian positioning using a combination of accelerometer and compass. Three different Smart phone placement modes (idle, hand held and listening) are investigated and a comparison of different pedestrian dead reckoning (PDR) techniques is presented.

Competition between noise and coupling in the induction of synchronisation

We apply a Fokker-Planck analysis to investigate the relative influences of coupling strength and noise on the synchronisation of two phase oscillators. We go beyond earlier studies of noise-induced synchronisation (without couplings) and coupling-induced synchronisation (without common noise) to consider both effects together, and we obtain a result that is very different from a straightforward superposition of the effects of each agent acting alone: two regimes are possible depending on which agent is inducing the synchronisation. In each regime, one agent induces and the other hinders the synchronisation. In particular we show that, counterintuitively, coupling can sometimes inhibit synchronisation.

Physics of brain dynamics: Fokker–Planck analysis reveals changes in EEG δ–θ interactions in anæsthesia

We use drift and diffusion coefficients to reveal interactions between different oscillatory processes underlying a complex signal and apply the method to EEG and frequencies in the brain. By analysis of data recorded from rats during anaesthesia, we consider the stability and basins of attraction of fixed points in the phase portrait of the deterministic part of the retrieved stochastic process. We show that different classes of dynamics are associated with deep and light anaesthesia, and we demonstrate that the predominant directionality of the interaction is such that drives .

Sensor Placement Modes for Smartphone based Pedestrian Dead Reckoning

These days, most of the smartphones come with integrated MEMS (Microelectromechanicalsystems) sensors like accelerometer, magnetometer, gyros etc. It has opened the ways to use them for location based applications. The big advantage of these sensor based navigation system is that they are environment independent in contrast to other existing positioning technologies. A lot of work is already done on fixed position sensor based systems where sensors are either attached to foot or belt. This work is focussed on developing a smartphone based pedestrian dead reckoning (PDR) system. The big issue with smartphone’s sensor based PDR system is that the position of mobile is not deterministic in contrast to fixed position inertial measuring unit. In this work, three different modes of smartphone placement (Idle, Handheld and Listening) are investigated and accelerometer and magnetic sensors are used for step detection and heading determination respectively. Various step detection and stride length estimation methods are implemented and a comparison is given at the end.

CHARACTERISTIC ANGULAR SCALES IN COSMIC MICROWAVE BACKGROUND RADIATION

We investigate the stochasticity in temperature fluctuations in the cosmic microwave background (CMB) radiation data from the Wilkinson Microwave Anisotropy Probe. We show that the angular fluctuation of the temperature is a Markov process with a Markov angular scale, ΘMarkov = 1.01−0.07+0.09. We characterize the complexity of the CMB fluctuations by means of a Fokker–Planck or Langevin equation and measure the associated Kramers–Moyal coefficients for the fluctuating temperature field and its increment, . Through this method we show that temperature fluctuations in the CMB have fat tails compared to a Gaussian distribution.

Stochastic φ4-theory in the strong coupling limit

The stochastic

The cardiorespiratory interaction: a nonlinear stochastic model and its synchronization properties

\phi^4