Modeling of small sea floaters in the central Mediterranean Sea: seasonality of at-sea distributions

Floating marine debris represent a threat to marine and coastal ecology. Since the Mediterranean basin is one of the highly impacted regions, both by the coastal pollution as well as from sea traffic, the potential harm of a floating pollution on the marine ecology could be overwhelming in this area. Our study area covers the central Mediterranean crossing that connects the western and eastern Mediterranean and is one of the areas impacted by a high intensity of sea traffic. To identify regions in the central Mediterranean that could be more exposed by high concentration of floating marine pollutants we use Leeway model for lower windage small-size particles. We perform numerical simulation of a large ensemble of Lagrangian particles that approximate at-sea debris. The particles are forced by high-resolution sea kinematics from the Copernicus Marine Environment Monitoring Service (CMEMS) and 10 m atmospheric wind from the European Centre for Medium-Range Weather Forecasts (ECMWF) for two reference periods in summer and winter of 2013--2016. We identify the regions with a high accumulation of particles in terms of particle surface densities per unit area. Although seasonal and annual variability of ocean current and atmospheric wind is an important factor that influences accumulation regimes across the central Mediterranean, we found that the border of the Libyan shelf harbors larger percentage of particles after 30 days of simulation

Analyzing intramolecular dynamics by Fast Lyapunov Indicators

International audienceWe report an analysis of intramolecular dynamics of the highly excited planar carbonyl sulfide (OCS) below and at the dissociation threshold by the Fast Lyapunov Indicator (FLI) method. By mapping out the variety of dynamical regimes in the phase space of this molecule, we obtain the degree of regularity of the system versus its energy. We combine this stability analysis with a periodic orbit search, which yields a family of elliptic periodic orbits in the regular part of phase space an a family of in-phase collinear hyperbolic orbits associated with the chaotic regime

Analysis of Multidimensional Phase Space Hamiltonian Dynamics: Methods and Applications

Diverse complex phenomena that are found in many fundamental problems of atomic physics and chemistry can be understood in the framework of nonlinear theory. Most of simple atomic and chemical systems are classically described by the Hamiltonian models of dimension three and higher. The multidimensional nature of these problems makes widely used diagnostics of dynamics to be impractical. We demonstrate the application of rigorous and effective computational methods to treat multidimensional systems in strongly perturbative regimes. The results of a qualitative analysis of the phase space stability structures are presented for two multidimensional non--integrable Hamiltonian systems: highly excited planar carbonyl sulfide molecule and hydrogen atom in elliptically polarized microwave fields. The molecular system of the planar carbonyl sulfide and atomic system of hydrogen in elliptically polarized microwave fields are treated for different regimes of energies including regimes of classical ionization of hydrogen and dissociation of carbonyl sulfide molecule.Ph.D.Committee Chair: Turgay Uzer; Committee Member: John Wood; Committee Member: Kurt Wiesenfeld; Committee Member: M. Raymond Flannery; Committee Member: Mustafa Ara

Phase space structures and ionization dynamics of hydrogen atom in elliptically polarized microwaves

The multiphoton ionization of hydrogen atoms in a strong elliptically polarized microwave field exhibits complex features that are not observed for ionization in circular and linear polarized fields. Experimental data reveal high sensitivity of ionization dynamics to the small changes of the field polarization. The multidimensional nature of the problem makes widely used diagnostics of dynamics, such as Poincar\'{e} surfaces of section, impractical. We analyze the phase space dynamics using finite time stability analysis rendered by the fast Lyapunov Indicators technique. The concept of zero--velocity surface is used to initialize the calculations and visualize the dynamics. Our analysis provides stability maps calculated for the initial energy at the maximum and below the saddle of the zero-velocity surface. We estimate qualitatively the dependence of ionization thresholds on the parameters of the applied field, such as polarization and scaled amplitude

Modeling of Small Sea Floaters in the Central Mediterranean Sea: Seasonality of At--Sea Distributions

Floating marine debris represent a threat to marine and coastal ecology. Since the Mediterranean basin is one of the highly impacted regions, both by the coastal pollution as well as from sea traffic, the potential harm of a floating pollution on the marine ecology could be overwhelming in this area. Our study area covers the central Mediterranean crossing that connects the western and eastern Mediterranean and is one of the areas impacted by a high intensity of sea traffic. To identify regions in the central Mediterranean that could be more exposed by high concentration of floating marine pollutants we use Leeway model for lower windage small-size particles. We perform numerical simulation of a large ensemble of Lagrangian particles that approximate at-sea debris. The particles are forced by high-resolution sea kinematics from the Copernicus Marine Environment Monitoring Service (CMEMS) and 10 m atmospheric wind from the European Centre for Medium-Range Weather Forecasts (ECMWF) for two reference periods in summer and winter of 2013-2016. We identify the regions with a high accumulation of particles in terms of particle surface densities per unit area. Although seasonal and annual variability of ocean current and atmospheric wind is an important factor that influences accumulation regimes across the central Mediterranean, we found that the border of the Libyan shelf harbors larger percentage of particles after 30 days of simulation.

Effect of periodic parametric excitation on an ensemble of force-coupled self-oscillators

We report the synchronization behavior in a one-dimensional chain of identical limit cycle oscillators coupled to a mass-spring load via a force relation. We consider the effect of periodic parametric modulation on the final synchronization states of the system. Two types of external parametric excitations are investigated numerically: periodic modulation of the stiffness of the inertial oscillator and periodic excitation of the frequency of the self-oscillatory element. We show that the synchronization scenarios are ruled not only by the choice of parameters of the excitation force but depend on the initial collective state in the ensemble. We give detailed analysis of entrainment behavior for initially homogeneous and inhomogeneous states. Among other results, we describe a regime of partial synchronization. This regime is characterized by the frequency of collective oscillation being entrained to the stimulation frequency but different from the average individual oscillators frequency.Comment: Comments and suggestions are welcom

Anticipating Recessions using Inclination Analysis

Recessions are economic downturns that can be recognized from macro-indicators such as the Dow Jones Industrial Average (DJIA) and the Federal Reserve Interest Rate (FRIR). To provide early-warning signals of recessions and similar systemic transitions, here we propose a new approach based on pattern recognition, called inclination analysis [1, 2]. For this purpose, we develop a stochastic model based on time-series analysis to assess the probability of a recession to occur at a given moment in the past, present, or future. Calibrating our model to data proceeds in three steps, involving the coarse-graining of the available input time series, the identification of short series motifs that foreshadow recessions, and the optimization of key model parameters according to the model’s desired forecasting horizon