Dinámicas de difusión del canto en un estadio de fútbol

El simpatizante de fútbol que concurre a un espectáculo deportivo es más que un mero espectador, es el protagonista central de un espectáculo más amplio que aquí denomino el aliento. Esta práctica colectiva tiene como características centrales el uso del canto colectivo para la celebración del "nosotros", el hostigamiento de los simpatizantes rivales y la demanda de la victoria a través de la arenga. Pero además de ser un tipo de performance cultural, esta práctica es expresión de una auto-organización social que ejemplifica un proceso complejo de difusión y sincronización. En esta ponencia explicaré la dinámica de este proceso a través de un sencillo modelo de simulación (Bundio, 2011b), similar a otros desarrollados para estudiar fenómenos colectivos que implican auto-organización, como la dinámica del aplauso (Néda, Ravasz, Brechet, Vicsek, & Barabasi, 2000) y la "ola mexicana" (Farkas, Helbing, & Vicsek, 2002). Puesto que el canto colectivo es un emergente de las actuaciones individuales es posible diseñar mecanismos de interferencia como el delayed auditory feedback (Van Wijngaarden & Van Balken, 2007). Estos mecanismos pueden complementar las posibles medidas destinadas a evitar la emergencia y/o impedir la difusión de cantos ofensivos y discriminatorios durante el transcurso de un espectáculo deportivo

Identidades deportivas y prácticas discriminatorias

El simpatizante de fútbol que concurre a un espectáculo deportivo es más que un mero espectador, es el protagonista central de un espectáculo más amplio que aquí denomino el aliento. Esta práctica colectiva tiene como características centrales el uso del canto colectivo para la celebración del 'nosotros', el hostigamiento de los simpatizantes rivales y la demanda de la victoria a través de la arenga. Pero además de ser un tipo de performance cultural, esta práctica es expresión de una auto-organización social que ejemplifica un proceso complejo de difusión y sincronización. En esta ponencia explicaré la dinámica de este proceso a través de un sencillo modelo de simulación (Bundio, 2011b), similar a otros desarrollados para estudiar fenómenos colectivos que implican auto-organización, como la dinámica del aplauso (Néda, Ravasz, Brechet, Vicsek, Barabasi, 2000) y la 'ola mexicana' (Farkas, Helbing, Vicsek, 2002). Puesto que el canto colectivo es un emergente de las actuaciones individuales es posible diseñar mecanismos de interferencia como el delayed auditory feedback (Van Wijngaarden; Van Balken, 2007). Estos mecanismos pueden complementar las posibles medidas destinadas a evitar la emergencia y/o impedir la difusión de cantos ofensivos y discriminatorios durante el transcurso de un espectáculo deportivo

Identidades deportivas y prácticas discriminatorias

El simpatizante de fútbol que concurre a un espectáculo deportivo es más que un mero espectador, es el protagonista central de un espectáculo más amplio que aquí denomino el aliento. Esta práctica colectiva tiene como características centrales el uso del canto colectivo para la celebración del 'nosotros', el hostigamiento de los simpatizantes rivales y la demanda de la victoria a través de la arenga. Pero además de ser un tipo de performance cultural, esta práctica es expresión de una auto-organización social que ejemplifica un proceso complejo de difusión y sincronización. En esta ponencia explicaré la dinámica de este proceso a través de un sencillo modelo de simulación (Bundio, 2011b), similar a otros desarrollados para estudiar fenómenos colectivos que implican auto-organización, como la dinámica del aplauso (Néda, Ravasz, Brechet, Vicsek, Barabasi, 2000) y la 'ola mexicana' (Farkas, Helbing, Vicsek, 2002). Puesto que el canto colectivo es un emergente de las actuaciones individuales es posible diseñar mecanismos de interferencia como el delayed auditory feedback (Van Wijngaarden; Van Balken, 2007). Estos mecanismos pueden complementar las posibles medidas destinadas a evitar la emergencia y/o impedir la difusión de cantos ofensivos y discriminatorios durante el transcurso de un espectáculo deportivo

Dinámicas de difusión del canto en un estadio de fútbol

El simpatizante de fútbol que concurre a un espectáculo deportivo es más que un mero espectador, es el protagonista central de un espectáculo más amplio que aquí denomino el aliento. Esta práctica colectiva tiene como características centrales el uso del canto colectivo para la celebración del "nosotros", el hostigamiento de los simpatizantes rivales y la demanda de la victoria a través de la arenga. Pero además de ser un tipo de performance cultural, esta práctica es expresión de una auto-organización social que ejemplifica un proceso complejo de difusión y sincronización. En esta ponencia explicaré la dinámica de este proceso a través de un sencillo modelo de simulación (Bundio, 2011b), similar a otros desarrollados para estudiar fenómenos colectivos que implican auto-organización, como la dinámica del aplauso (Néda, Ravasz, Brechet, Vicsek, & Barabasi, 2000) y la "ola mexicana" (Farkas, Helbing, & Vicsek, 2002). Puesto que el canto colectivo es un emergente de las actuaciones individuales es posible diseñar mecanismos de interferencia como el delayed auditory feedback (Van Wijngaarden & Van Balken, 2007). Estos mecanismos pueden complementar las posibles medidas destinadas a evitar la emergencia y/o impedir la difusión de cantos ofensivos y discriminatorios durante el transcurso de un espectáculo deportivo

Model-based pilot and data power adaptation in psam with periodic delayed feedback

We consider the optimum design of pilot-symbol-assisted modulation (PSAM) schemes with feedback. The received signal is periodically fed back to the transmitter through a noiseless delayed link and the time-varying channel is modeled as a Gauss-Markov process. We optimize a lower bound on the channel capacity which incorporates the PSAM parameters and Kalman-based channel estimation and prediction. The parameters available for the capacity optimization are the data power adaptation strategy, pilot spacing and pilot power ratio, subject to an average power constraint. Compared to the optimized open-loop PSAM (i.e., the case where no feedback is provided from the receiver), our results show that even in the presence of feedback delay, the optimized power adaptation provides higher information rates at low signal-to-noise ratios (SNR) in medium-rate fading channels. However, in fast fading channels, even the presence of modest feedback delay dissipates the advantages of power adaptation.

Correlation times in stochastic equations with delayed feedback and multiplicative noise

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Noise-induced attractor annihilation in the delayed feedback logistic map

We study dynamics of the bistable logistic map with delayed feedback, under the influence of white Gaussian noise and periodic modulation applied to the variable. This system may serve as a model to describe population dynamics under finite resources in noisy environment with seasonal fluctuations. While a very small amount of noise has no effect on the global structure of the coexisting attractors in phase space, an intermediate noise totally eliminates one of the attractors. Slow periodic modulation enhances the attractor annihilation.

Noise-induced standing waves in oscillatory systems with time-delayed feedback

In oscillatory reaction-diffusion systems, time-delay feedback can lead to the instability of uniform oscillations with respect to formation of standing waves. Here, we investigate how the presence of additive, Gaussian white noise can induce the appearance of standing waves. Combining analytical solutions of the model with spatio-temporal simulations, we find that noise can promote standing waves in regimes where the deterministic uniform oscillatory modes are stabilized. As the deterministic phase boundary is approached, the spatio-temporal correlations become stronger, such that even small noise can induce standing waves in this parameter regime. With larger noise strengths, standing waves could be induced at finite distances from the (deterministic) phase boundary. The overall dynamics is defined through the interplay of noisy forcing with the inherent reaction-diffusion dynamics.

The optoelectronic swept-frequency laser and its applications in ranging, three-dimensional imaging, and coherent beam combining of chirped-seed amplifiers

This thesis explores the design, construction, and applications of the optoelectronic swept-frequency laser (SFL). The optoelectronic SFL is a feedback loop designed around a swept-frequency (chirped) semiconductor laser (SCL) to control its instantaneous optical frequency, such that the chirp characteristics are determined solely by a reference electronic oscillator. The resultant system generates precisely controlled optical frequency sweeps. In particular, we focus on linear chirps because of their numerous applications. We demonstrate optoelectronic SFLs based on vertical-cavity surface-emitting lasers (VCSELs) and distributed-feedback lasers (DFBs) at wavelengths of 1550 nm and 1060 nm. We develop an iterative bias current predistortion procedure that enables SFL operation at very high chirp rates, up to 10^16 Hz/sec. We describe commercialization efforts and implementation of the predistortion algorithm in a stand-alone embedded environment, undertaken as part of our collaboration with Telaris, Inc. We demonstrate frequency-modulated continuous-wave (FMCW) ranging and three-dimensional (3-D) imaging using a 1550 nm optoelectronic SFL.

We develop the technique of multiple source FMCW (MS-FMCW) reflectometry, in which the frequency sweeps of multiple SFLs are "stitched" together in order to increase the optical bandwidth, and hence improve the axial resolution, of an FMCW ranging measurement. We demonstrate computer-aided stitching of DFB and VCSEL sweeps at 1550 nm. We also develop and demonstrate hardware stitching, which enables MS-FMCW ranging without additional signal processing. The culmination of this work is the hardware stitching of four VCSELs at 1550 nm for a total optical bandwidth of 2 THz, and a free-space axial resolution of 75 microns.

We describe our work on the tomographic imaging camera (TomICam), a 3-D imaging system based on FMCW ranging that features non-mechanical acquisition of transverse pixels. Our approach uses a combination of electronically tuned optical sources and low-cost full-field detector arrays, completely eliminating the need for moving parts traditionally employed in 3-D imaging. We describe the basic TomICam principle, and demonstrate single-pixel TomICam ranging in a proof-of-concept experiment. We also discuss the application of compressive sensing (CS) to the TomICam platform, and perform a series of numerical simulations. These simulations show that tenfold compression is feasible in CS TomICam, which effectively improves the volume acquisition speed by a factor ten.

We develop chirped-wave phase-locking techniques, and apply them to coherent beam combining (CBC) of chirped-seed amplifiers (CSAs) in a master oscillator power amplifier configuration. The precise chirp linearity of the optoelectronic SFL enables non-mechanical compensation of optical delays using acousto-optic frequency shifters, and its high chirp rate simultaneously increases the stimulated Brillouin scattering (SBS) threshold of the active fiber. We characterize a 1550 nm chirped-seed amplifier coherent-combining system. We use a chirp rate of 5*10^14 Hz/sec to increase the amplifier SBS threshold threefold, when compared to a single-frequency seed. We demonstrate efficient phase-locking and electronic beam steering of two 3 W erbium-doped fiber amplifier channels, achieving temporal phase noise levels corresponding to interferometric fringe visibilities exceeding 98%.

Studies in nuclear reactor dynamics : I. The accuracy of point kinetics. II. The effect of delayed neutrons on the spectrum of the group-diffusion operator

This thesis is a theoretical work on the space-time dynamic behavior of a nuclear reactor without feedback. Diffusion theory with G-energy groups is used.

In the first part the accuracy of the point kinetics (lumped-parameter description) model is examined. The fundamental approximation of this model is the splitting of the neutron density into a product of a known function of space and an unknown function of time; then the properties of the system can be averaged in space through the use of appropriate weighting functions; as a result a set of ordinary differential equations is obtained for the description of time behavior. It is clear that changes of the shape of the neutron-density distribution due to space-dependent perturbations are neglected. This results to an error in the eigenvalues and it is to this error that bounds are derived. This is done by using the method of weighted residuals to reduce the original eigenvalue problem to that of a real asymmetric matrix. Then Gershgorin-type theorems .are used to find discs in the complex plane in which the eigenvalues are contained. The radii of the discs depend on the perturbation in a simple manner.

In the second part the effect of delayed neutrons on the eigenvalues of the group-diffusion operator is examined. The delayed neutrons cause a shifting of the prompt-neutron eigenvalue s and the appearance of the delayed eigenvalues. Using a simple perturbation method this shifting is calculated and the delayed eigenvalues are predicted with good accuracy.

Optoelectronic implementation of mathematical morphology

An optoelectronic implementation based on optical neighborhood operations and electronic nonlinear feedback is proposed to perform morphological image processing such as erosion, dilation, opening, closing and edge detection. Results of a numerical simulation are given and experimentally verified.

Sensitivity analysis of a time-delayed thermo-acoustic system via an adjoint-based approach

We apply adjoint-based sensitivity analysis to a time-delayed thermo-acoustic system: a Rijke tube containing a hot wire. We calculate how the growth rate and frequency of small oscillations about a base state are affected either by a generic passive control element in the system (the structural sensitivity analysis) or by a generic change to its base state (the base-state sensitivity analysis). We illustrate the structural sensitivity by calculating the effect of a second hot wire with a small heat-release parameter. In a single calculation, this shows how the second hot wire changes the growth rate and frequency of the small oscillations, as a function of its position in the tube. We then examine the components of the structural sensitivity in order to determine the passive control mechanism that has the strongest influence on the growth rate. We find that a force applied to the acoustic momentum equation in the opposite direction to the instantaneous velocity is the most stabilizing feedback mechanism. We also find that its effect is maximized when it is placed at the downstream end of the tube. This feedback mechanism could be supplied, for example, by an adiabatic mesh. We illustrate the base-state sensitivity by calculating the effects of small variations in the damping factor, the heat-release time-delay coefficient, the heat-release parameter, and the hot-wire location. The successful application of sensitivity analysis to thermo-acoustics opens up new possibilities for the passive control of thermo-acoustic oscillations by providing gradient information that can be combined with constrained optimization algorithms in order to reduce linear growth rates. © Cambridge University Press 2013.

Delayed control of a Moore-Greitzer axial compressor model

Several feedback control laws have appeared in the literature concerning the stabilization of the nonlinear Moore-Greitzer axial compression model. Motivated by magnitude and rate limitations imposed by the physical implementation of the control law, Larsen et al. studied a dynamic implementation of the S-controller suggested by Sepulchre and Kokotović. They showed the potential benefit of implementing the S-controller through a first-order lag: while the location of the closed-loop equilibrium achieved with the static control law was sensitive to poorly known parameters, the dynamic implementation resulted in a small limit cycle at a very desirable location, insensitive to parameter variations. In this paper, we investigate the more general case when the control is applied with a time delay. This can be seen as an extension of the model with a first-order lag. The delay can either be a result of system constraints or be deliberately implemented to achieve better system behavior. The resulting closed-loop system is a set of parameter-dependent delay differential equations. Numerical bifurcation analysis is used to study this model and investigate whether the positive results obtained for the first-order model persist, even for larger values of the delay.

Output feedback H2 model matching for decentralized systems with delays

This paper gives a new solution to the output feedback H2 model matching problem for a large class of delayed information sharing patterns. Existing methods for similar problems typically reduce the decentralized problem to a centralized problem of higher state dimension. In contrast, this paper demonstrates that the decentralized model matching solution can be constructed from the original centralized solution via quadratic programming. © 2013 AACC American Automatic Control Council.

InP-based optoelectronic devices for optical fiber communications

In this contribution we report the research and development of 1.55 mu m InGaAsP/InP gain-coupled DFB laser with an improved injection-carrier induced grating and of high performance 1.3 mu m and 1.55 mu m InGaAsP/InP FP and DFB lasers for communications. Long wavelength strained MQW laser diodes with a very low threshold current (7-10 mA) have been fabricated. Low pressure MOVPE technology has been employed for the preparation of the layered structure. A novel gain-coupled DFB laser structure with an improved injection-carrier modulated grating has been proposed and fabricated. The laser structures have been prepared by hybrid growth of MOVPE and LPE techniques and reasonably good characteristics have been achieved for resultant lasers. High performance 1.3 mu m and 1.55 mu m InGaAsP/InP DFB lasers have successfully been developed for CATV and trunk line optical fiber communication.