Immunization of Real Complex Communication Networks

Most communication networks are complex. In this paper, we address one of the fundamental problems we are facing nowadays, namely, how we can efficiently protect these networks. To this end, we study an immunization strategy and found that it works as good as targeted immunization, but using only local information about the network topology. Our findings are supported with numerical simulations of the Susceptible-Infected-Removed (SIR) model on top of real communication networks, where immune nodes are previously identified by a covering algorithm. The results provide useful hints in the way to design and deploying a digital immune system.Comment: 6 pages. To appear in the European Physical Journal B (2006

Kelvin-Helmholtz versus Hall Magneto-shear instability in astrophysical flows

We study the stability of shear flows in a fully ionized plasma. Kelvin-Helmholtz is a well known, macroscopic and ideal shear-driven instability. In sufficiently low density plasmas, also the microscopic Hall magneto-shear instability can take place. We performed three-dimensional simulations of the Hall-MHD equations where these two instabilities are present, and carried out a comparative study. We find that when the shear flow is so intense that its vorticity surpasses the ion-cyclotron frequency of the plasma, the Hall magneto-shear instability is not only non-negligible, but it actually displays growth rates larger than those of the Kelvin-Helmholtz instability

Speaker Recognition Using Multiple Parametric Self-Organizing Maps

Speaker Recognition is the process of automatically recognizing a person who is speaking on the basis of individual parameters included in his/her voice. This technology allows systems to automatically verify identify in applications such as banking by telephone or forensic science. A Speaker Recognition system has the following main modules: Feature Extraction and Classification. For feature extraction the most commonly used techniques are MEL-Frequency Cepstrum Coefficients (MFCC) and Linear Predictive Coding (LPC). For classification and verification, technologies such as Vector Quantization (VQ), Hidden Markov Models (HMM) and Neural Networks have been used. The contribution of this thesis is a new methodology to achieve high accuracy identification and impostor rejection. The new proposed method, Multiple Parametric Self-Organizing Maps (M-PSOM) is a classification and verification technique. The new method was successfully implemented and tested using the CSLU Speaker Recognition Corpora of the Oregon School of Engineering with excellent results

Simulations of the Kelvin-Helmholtz instability driven by coronal mass ejections in the turbulent corona

Recent high resolution AIA/SDO images show evidence of the development of the Kelvin-Helmholtz instability, as coronal mass ejections (CMEs) expand in the ambient corona. A large-scale magnetic field mostly tangential to the interface is inferred, both on the CME and on the background sides. However, the magnetic field component along the shear flow is not strong enough to quench the instability. There is also observational evidence that the ambient corona is in a turbulent regime, and therefore the criteria for the development of the instability are a-priori expected to differ from the laminar case. To study the evolution of the Kelvin-Helmholtz instability with a turbulent background, we perform three-dimensional simulations of the incompressible magnetohydrodynamic equations. The instability is driven by a velocity profile tangential to the CME-corona interface, which we simulate through a hyperbolic tangent profile. The turbulent background is generated by the application of a stationary stirring force. We compute the instability growth-rate for different values of the turbulence intensity, and find that the role of turbulence is to attenuate the growth. The fact that the Kelvin-Helmholtz instability is observed, sets an upper limit to the correlation length of the coronal background turbulence

Historical forest biomass dynamics modelled with Landsat spectral trajectories

Acknowledgements National Forest Inventory data are available online, provided by Ministerio de Agricultura, Alimentación y Medio Ambiente (España). Landsat images are available online, provided by the USGS.Peer reviewedPostprin

The Invisible Carnival: An Ecosystem of Custom Laser Controlled Devices - Final Paper

The project aims to create a visual ecosystem of analogue devices that will be used by Fortuno (the artistic name of the author) in live performances and during production. Through the development of two MIDI laser controlled devices, the artist will be able to use lasers to control various parameters of the sound. The project also aims to demonstrate Fortuno’s capabilities as a sound designer, an artist, a sound engineer, and a live engineer. Hence, he will use these devices for his electronic production and then utilize the sounds in his set. An Arduino microchip will be used to program the laser response for each device. The laser MIDI controller will be created mainly through the use of programing using C++/Arduino. Each device will be molded separately with different types of casings used. Each device will be tested and then implemented in the sound and image of Fortuno. Ultimately, making him stand out as a unique Dj and musician.https://remix.berklee.edu/graduate-studies-production-technology/1289/thumbnail.jp

FLOW OF STRESS POWER LAW FLUIDS IN CYLINDERS OF NON CIRCULAR CROSS SECTIONS

Inspired in the work of Poiseuille, and taking advantage of the much more realistic model for describing the mechanical properties of blood in large vessels derived by K. R. Rajagopal, this dissertation explains the behavior of blood on non circular cross sections, given an Implicit Constitutive Relation. First, by assuming that the axial direction is dominant in this phenomenom, an axial flow problem is solved. Given the non linear and implicit nature of the problem, a non linear system of coupled partial differential equations will be solved. Using the Minty-Browder Theorem and the theory for linear elliptic operators, some elementary results about existence and uniqueness of solutions can be stated. Next, assuming a lower order velocity field in the other two directions, a secondary flow problem in the cross sectional area is stated. Taking into account just the terms of the same order and the solution of the previous step, the problem becomes a linear coupled system of partial differential equations. Using the theorem of existence of a streamfunction in a two dimensional problem, we can actually prove that there are no secondary flows for this model. Finally, a numerical approximation directly based on the Lions-Mercier Splitting Algorithm is given. Some generalizations of the problem are proposed as future work