Chaos in non lineal Alfven waves using the DNLS equations

The electro-dynamical tethers emit waves in structured denominated Alfven wings. The Derivative Nonlineal Schr��dinger Equation (DNLS) possesses the capacity to describe the propagation of circularly polarized Alfven waves of finite amplitude in cold plasmas. The DNLS equation is truncated to explore the coherent, weakly nonlinear, cubic coupling of three waves near resonance, one wave being linearly unstable and the other waves damped. In this article is presented a theoretical and numerical analysis when the growth rate of the unstable wave is next to zero considering two damping models: Landau and resistive. The DNLS equation presents a chaotic dynamics when is consider only three wave truncation. The evolution to chaos possesses three routes: hard transition, period-doubling and intermittence of type I.

Passive design strategies and performance of Net Energy Plus Houses

The first step in order to comply with the European Union goals of Near to Zero Energy Buildings is to reduce the energy consumption in buildings. Most of the building consumption is related to the use of active systems to maintain the interior comfort. Passive design strategies contribute to improve the interior comfort conditions, increasing the energy efficiency in buildings and reducing their energy consumption. In this work, an analysis of the passive strategies used in Net Energy Plus Houses has been made. The participating houses of the Solar Decathlon Europe 2012 competition were used as case studies. The passive design strategies of these houses were compared with the annual simulations, and the competition monitored data, especially during the Passive Monitored Period. The analysis included the thermal properties of the building envelope, geometric parameters, ratios and others passive solutions such as Thermal Energy Storage systems, evaporative cooling, night ventilation, solar gains and night sky radiation cooling. The results reflect the impact of passive design strategies on the houses' comfort and efficiency, as well as their influence in helping to achieve the Zero Energy Buildings category.

Instability Analysis of Incompressible Open Cavity Flows

El problema del flujo sobre una cavidad abierta ha sido estudiado en profundidad en la literatura, tanto por el inter��s acad��mico del problema como por sus aplicaciones pr��cticas en gran variedad de problemas ingenieriles, como puede ser el alojamiento del tren de aterrizaje de aeronaves, o el dep��sito de agua de aviones contraincendios. Desde hace muchos a��nos se estudian los distintos tipos de inestabilidades asociadas a este problema: los modos bidimensionales en la capa de cortadura, y los modos tridimensionales en el torbellino de recirculaci��n principal dentro de la cavidad. En esta tesis se presenta un estudio param��trico completo del l��mite incompresible del problema, empleando la herramienta de estabilidad lineal conocida como BiGlobal. Esta aproximaci��n permite contemplar la estabilidad global del flujo, y obtener tanto la forma como las caracter��sticas de los modos propios del problema f��sico, sean estables o inestables. El estudio realizado permite caracterizar con gran detalle todos los modos relevantes, as�� como la envolvente de estabilidad en el espacio param��trico del problema incompresible (Mach nulo, variaci��n de Reynolds, espesor de capa l��mite incidente, relaci��n altura/profundidad de la cavidad, y longitud caracter��stica de la perturbaci��n en la direcci��n transversal). A la luz de los resultados obtenidos se proponen una serie de relaciones entre los par��metros y caracter��sticas de los modos principales, como por ejemplo entre el Reynolds cr��tico de un modo, y la longitud caracter��stica del mismo. Los resultados num��ricos se contrastan con una campa��a experimental, siendo la principal conclusi��n de dicha comparaci��n que los modos lineales est��n presentes en el flujo real saturado, pero que existen diferencias notables en frecuencia entre las predicciones te��ricas y los experimentos. Para intentar determinar la naturaleza de dichas diferencias se realiza una simulaci��n num��rica directa tridimensional, y se utiliza un algoritmo de DMD (descomposici��n din��mica de modos) para describir el proceso de saturaci��n. ABSTRACT The problem of the flow over an open cavity has been studied in depth in the literature, both for being an interesting academical problem and due to the multitude of industrial applications, like the landing gear of aircraft, or the water deposit of firefighter airplanes. The different types of instabilities appearing in this flow studied in the literature are two: the two-dimensional shear layer modes, and the three-dimensional modes that appear in the main recirculating vortex inside the cavity. In this thesis a parametric study in the incompressible limit of the problem is presented, using the linear stability analysis known as BiGlobal. This approximation allows to obtain the global stability behaviour of the flow, and to capture both the morphological features and the characteristics of the eigenmodes of the physical problem, whether they are stable or unstable. The study presented here characterizes with great detail all the relevant eigenmodes, as well as the hypersurface of instability on the parameter space of the incompressible problem (Mach equal to zero, and variation of the Reynolds number, the incoming boundary layer thickness, the length to depth aspect ratio of the cavity and the spanwise length of the perturbation). The results allow to construct parametric relations between the characteristics of the leading eigenmodes and the parameters of the problem, like for example the one existing between the critical Reynolds number and its characteristic length. The numerical results presented here are compared with those of an experimental campaign, with the main conclusion of said comparison being that the linear eigenmode are present in the real saturated flow, albeit with some significant differences in the frequencies of the experiments and those predicted by the theory. To try to determine the nature of those differences a three-dimensional direct numerical simulation, analyzed with Dynamic Mode Decomposition algorithm, was used to describe the process of saturation.

Caracterizaci��n de la polarizaci��n de haces de luz a la salida de prismas despolarizadores anis��tropos

Los pseudo-despolarizadores espaciales, entre los que se encuentran los denominados prismas despolarizadores, son dispositivos ��pticos capaces de modificar el estado de polarizaci��n en cada punto del plano transversal de los haces de luz, obteniendo un continuo de estados de polarizaci��n y por tanto un grado de polarizaci��n est��ndar pr��ximo a cero. En la literatura, en reiteradas ocasiones se utilizan estos prismas asumiendo la aproximaci��n de que en su cara oblicua no existe doble reflexi��n. En el presente trabajo se investigan en detalle las caracter��sticas de polarizaci��n locales y globales de haces monocrom��ticos planos a la salida de un prisma despolarizador teniendo en cuenta la doble reflexi��n y se comparan los resultados con el caso de despreciar esta doble reflexi��n. Como consecuencia se obtienen las condiciones bajo las cuales el efecto de la doble reflexi��n puede ser despreciable. ABSTRACT: Spatial pseudo-depolarizers are optical devices that modify the polarization state along the transverse plane of a light beam in such a way that a continuum of polarization states are obtained. Consequently, a standard degree of polarization near to zero is reached when average over the whole beam section is taken. Depolarizing prism is an example of spatial pseudo-depolarizer. Double reflection effects are usually not considered in literature for such devices. In the present work, the polarization properties at the exit of a depolarizing prism are studied taking into account the effect of double reflection and the results are compared to those obtained when double reflection is neglected. Conditions under which the double reflection effect may be negligible on depolarizing action of this class of prisms are obtained.

Pulse-Shape Analysis of PDM-QPSK Modulation Formats for 100 and 200 Gb/s DWDM transmissions

Advanced optical modulation format polarization-division multiplexed quadrature phase shift keying (PDM-QPSK) has become a key ingredient in the design of 100 and 200-Gb/s dense wavelength-division multiplexed (DWDM) networks. The performance of this format varies according to the shape of the pulses employed by the optical carrier: non-return to zero (NRZ), return to zero (RZ) or carrier-suppressed return to zero (CSRZ). In this paper we analyze the tolerance of PDM-QPSK to linear and nonlinear optical impairments: amplified spontaneous emission (ASE) noise, crosstalk, distortion by optical filtering, chromatic dispersion (CD), polarization mode dispersion (PMD) and fiber Kerr nonlinearities. RZ formats with a low duty cycle value reduce pulse-to-pulse interaction obtaining a higher tolerance to CD, PMD and intrachannel nonlinearities.

The influence of axial microgravity on the breakage of axisymmetric slender liquid bridges

The dynamics of inviscid, axisymmetric liquid bridges permits a simplified treatment if the bridge is long enough. Under such condition the evolution of the liquid zone is satisfactorily explained through a non-linear one-dimensional model. In the case of breaking, the one-dimensional model fails when the neck radius of the liquid column is close to zero; however, the model allows the calculation of the time variation of the liquid-bridge interface as well as of the fluid velocity field and, because the last part of the evolution is not needed, the overall results such as the breaking time and the volume of each of the two drops resulting after breakage can be calculated. In this paper numerical results concerning the behavior of clinical liquid bridges subjected to a small axial gravitational field are presented.

Real-time bilateral control of a nonlinear teleoperation system

In this work, we study the bilateral control of a nonlinear teleoperator system with constant delay, proposes a control strategy by state convergence, which directly connect the local and remote manipulator through feedback signals of position and speed. The control signal allows the remote manipulator follow the local manipulator through the state convergence even if it has a delay in the communication channel. The bilateral control of the teleoperator system considers the case when the human operator applies a constant force on the local manipulator and when the interaction of the remote manipulator with the environment is considered passive. The stability analysis is performed using functional of Lyapunov-Krasovskii, it showed that using a control algorithm by state convergence for the case with constant delay, the nonlinear local and remote teleoperation system is asymptotically stable, also speeds converge to zero and position tracking is achieved.

Advances in Control of Teleoperation System by State Convergence

In this work, we proposes a control strategy by state convergence applied to bilateral control of a nonlinear teleoperator system with constant delay. The bilateral control of the teleoperator system considers the case when the human operator applies a constant force on the local manipulator and when the interaction of the remote manipulator with the environment is considered passive. The stability analysis is performed using Lyapunov-Krasovskii functional, it showed that using an control algorithm by state convergence for the case with constant delay, the nonlinear local and remote teleoperation system is asymptotically stable, also speeds converge to zero and position tracking is achieved. This work also presents the implementation of an experimental platform. The mechanical structure of the arm that is located in the remote side has been built and the electric servomechanism has been mounted to control their movement.

Influence of a liquid on the natural frequencies of almost circular plates

In this work, the influence of the surrounding fluid on the dynamic characteristics of almost circular plates is investigated. First the natural frequencies and normal modes for the plates in vacuum are calculated by a perturbation procedure. The method is applied for the case of elliptical plates with a low value of eccentricity. The results are compared with other available methods for this type of plates with good agreement. Next, the effect of the fluid is considered. The normal modes of the plate in vacuum are used as a base to express the vibration mode of the coupled plate-fluid system. By applying the Hankel transformation the nondimensional added virtual mass 2 increment (NAVMI) are calculated for elliptical plates. Results of the NAVMI factors and the effect of the fluid on the natural frequencies are given and it is shown that when the eccentricity of the plate is reduced to zero (circular plate) the known results of the natural frequencies for circular plates surrounded by liquid are recovered.

Independent doubly Adaptive Rejection Metropolis Sampling

Adaptive Rejection Metropolis Sampling (ARMS) is a wellknown MCMC scheme for generating samples from onedimensional target distributions. ARMS is widely used within Gibbs sampling, where automatic and fast samplers are often needed to draw from univariate full-conditional densities. In this work, we propose an alternative adaptive algorithm (IA2RMS) that overcomes the main drawback of ARMS (an uncomplete adaptation of the proposal in some cases), speeding up the convergence of the chain to the target. Numerical results show that IA2RMS outperforms the standard ARMS, providing a correlation among samples close to zero.

Emergencia y convergencia de las corrientes urban��sticas alternativas al desarrollo disperso. Europa y los EE.UU. 1980/2010

La presente tesis doctoral identifica el reciente fen��meno de la emergenciai de corrientes urban��sticas que act��an en la periferia urbana a partir de una concepci��n del dise��o urbano que propugna modelos m��s compactos, a escala humana, de car��cter integral y sostenible, como alternativa al desarrollo disperso y difusoii que caracteriza en gran medida a la ciudad contempor��nea. Se develan las diferencias de origen y las coincidencias entre las distintas l��neas de pensamiento que definen a estas emergentes corrientes alternativas, situ��ndolas dentro de determinados enfoques planteados en la presente tesis, y demostrando con ello, las progresivas ��reas de convergencia que permiten su ordenamiento como fen��meno hist��rico com��n. Estas distintas l��neas de pensamiento, que derivan en las corrientes urban��sticas alternativas, se manifiestan primeramente como reacci��n a las operaciones modernistas de la posguerra, pero crecientemente expresan una visi��n contestataria a la expansi��n urbana descontrolada iii, de bajas densidades, zonificaci��n excluyente y dependiente del autom��vil; modelo asociado a las autopistas urbanas, los llamados nuevos artefactos urbanos y las grandes parcelas destinadas a proyectos habitacionales. Una realidad expresada en variados contextos en el ��mbito de la globalizaci��n econ��mica y cultural que, en gran medida, se singulariza como responsable de las profundas transformaciones urbanas, de la consecuente gradual p��rdida de habitabilidad en las ciudades y del impacto sobre el medio natural; cuesti��n a tratar en el ���Marco conceptual��� referido al contexto y problema de la tesis. Se estudian los planteamientos fundamentales que postulan estas corrientes alternativas en el contexto de la expansi��n urbana horizontal, con el fin de identificar las distintas vertientes o l��neas existentes, de establecer sus or��genes, enfoques, v��nculos y alcances, permitiendo con ello caracterizar el fen��meno en s�� desde una visi��n original e integradora. Estas corrientes a tratar han surgido en diversos momentos y con diversas particularidades, pero con mayor intensidad, articulaci��n y visibilidad a partir de los a��os ochenta y especialmente en los noventa del siglo reci��n pasado, fundamentalmente en Europa y en los Estados Unidos de Am��rica, representando el ���Cuerpo te��rico��� de esta tesis. Emergen en un escenario de creciente empoderamiento ciudadano, en tiempos de una mayor conciencia ambiental y social, y desde la convicci��n extendida de las limitaciones de un desarrollismo que, en t��rminos del territorio f��sico, se manifiesta en el crecimiento urbano por extensi��n, incremental y desarticulado; tienen distintos idearios de origen, algunos en aparente contradicci��n o manifiesta oposici��n entre s��; se articulan desde diversos ��nfasis y surgen a partir de distintas aproximaciones. Para poder comprender el fen��meno de manera integral, se identifican y observan las tendencias contempor��neas y las correspondientes corrientes principales del dise��o urbano; se indaga en sus discursos cr��ticos y se ordenan en funci��n de tres enfoques, los cuales re��nen los fundamentos esenciales de las distintas miradas cr��ticas al modelo disperso y difuso: el enfoque neotradicional, el enfoque de la movilidad, y el enfoque ecol��gicoiv. Reconociendo la importancia de las operaciones de renovaci��n urbana en la ���ciudad intramuros��� y siendo part��cipes de estas intervenciones, las diferentes corrientes observadas desde los tres enfoques planteados, tienen un com��n denominador disciplinar en cuanto a su preocupaci��n por generar actuaciones urbanas viables y practicables que causen un menor impacto sobre el territorio y que ofrezcan las condiciones para mejorar la habitabilidad en la ciudad, asumiendo el crecimiento hacia las periferias desde una aproximaci��n alternativa a los modelos hoy predominantes. Las distintas corrientes, desde los particulares enfoques se��alados, pretenden en s��ntesis, un desarrollo que refuerce el rol del dise��o urbano, que promueva modelos m��s compactosv, de usos mixtos compatibles con la residencia y con espacios p��blicos de calidad, a una escala apropiada para la movilidad peatonal, favoreciendo de esta manera el uso del transporte p��blico y velando consecuentemente por aquellos aspectos que mejoren las condiciones de sostenibilidad. En definitiva, el ideario de las corrientes caracterizadas en esta tesis como alternativas, se origina y se sostiene a partir de la convicci��n de situar a la disciplina del dise��o urbano en su justa medida en el desarrollo contempor��neo, en el convencimiento de la relevancia del proyecto urbano en el ordenamiento del territorio y el crecimiento de las ciudades actuales. Una convergencia impl��cita a tratarse en la ���Discusi��n de resultados���. La preocupaci��n que reflejan las distintas corrientes estudiadas por el h��bitat construido, en cuanto a su condici��n de acoger y estimular la dimensi��n humana de las ciudades, puede resumirse en una cita del arquitecto dan��s Jan Gehl, que interpreta a muchas de las l��neas de pensamiento que se abordan en esta tesis, en cuanto al deseo de crear mejores ciudades: ���Aspiramos generar ciudades animadas, saludables, atractivas, sostenibles y seguras, con el prop��sito de mejorar la calidad de vida de la gente���. ABSTRACT This Ph.D thesis identifies the recent phenomenon of the emergence of alternative urban design currents in the city edge, that focus on a more compact, human-scale oriented, comprehensive and sustainable urban design as an alternative to the overwhelming advance of sprawl that largely characterizes the contemporary city. It singles out the differences in origin, as well as the similarities drawn from the different lines of thought that define these emergent alternative currents, placing them within certain approaches proposed in this thesis, and thereby demonstrating the progressive areas of convergence that allow to arrange them as a common historical phenomenon. Indeed, the different lines of thought that drift towards these alternative urbanistic currents, first appear as a reaction to the post- World War II Modernist housing projects, and increasingly more so as a response to urban sprawl; an ever expanding phenomemnon expressed in different contexts within the economic and cultural globalization, largely singled out as being responsible for the deep urban transformations, the consequent gradual loss of livability and the impact on natural environment, setting the ���Conceptual framework��� of this thesis. Within the context of urban sprawl, the fundamental principles of these alternative currents are studied to establish their origins, approaches, linkages and scope, in order to zero in on the various aspects or existing lines and thereby allowing the identification of the phenomenon from an original and inclusive vision. The alternative currents to be dealt with, emerged at different times and with diverse characteristics, nonetheless it is in the eighties and especially during the nineties, mainly in Europe and the United States, where they appear with greater intensity, coordination and visibility, representing the ���Theoretical body��� of this thesis. The above mentioned currents arise in a scenario of increasing citizen empowerment in times of growing environmental and social awareness, along with the widespread conviction of the limitations of a quantitative development expressed as a physical manifestation in urban sprawl. These alternative currents have a different philosophy in origin, some are in apparent contradiction or in definite opposition, being organized from different approaches and emphases. To comprehend this phenomenon, it is necessary to identify and analize the contemporary trends and the main currents of urban design, inquiring and arranging their critical discourses according to three approaches that meet the essential foundations of the various critical perspectives of urban sprawl: the neo-traditional approach, the mobility approach, the ecological approach. Acknowledging the importance of urban renovation in the ���Inner City���, and being partakers of these interventions, the different currents identified from these three approaches, concur in their concern for the development of viable and workable alternatives to urban sprawl; models that cause a lower impact on the territory, whilst improving livability in the city. The different currents recognized within the above mentioned approaches, advocate in brief, for a development that strengthens the role of urban design, that encourages more compact models, mixed-uses, and quality public spaces, considering the human scale and walkability; thereby increasing public transport and promoting consequently, the conditions for sustainable development. Ultimately, the philosophy of the so called alternative currents, is based on the belief of placing urban design as a fundamental discipline in contemporary urban development. The concern for the built habitat reflected by the various currents studied, as of their condition to accept and stimulate the human dimension of the city, can be summed up in a quote from Danish architect Jan Gehl, who represents many of the lines of thought addressed, in the belief of creating better cities: ���We aspire to create cities that are lively, healthy, attractive, sustainable and safe-and thereby improve people���s quality of life���.

On sonic anemometer measurement theory

In this paper a model for the measuring process of sonic anemometers (ultrasound pulse based) is presented. The differential equations that describe the travel of ultrasound pulses are solved in the general case of non-steady, non-uniform atmospheric flow field. The concepts of instantaneous line-average and travelling pulse-referenced average are established and employed to explain and calculate the differences between the measured turbulent speed (travelling pulse-referenced average) and the line-averaged one. The limit k1l=1 established by Kaimal in 1968, as the maximum value which permits the neglect of the influence of the sonic measuring process on the measurement of turbulent components is reviewed here. Three particular measurement cases are analysed: A non-steady, uniform flow speed field, a steady, non-uniform flow speed field and finally an atmospheric flow speed field. In the first case, for a harmonic time-dependent flow field, Mach number, M (flow speed to sound speed ratio) and time delay between pulses have revealed themselves to be important parameters in the behaviour of sonic anemometers, within the range of operation. The second case demonstrates how the spatial non-uniformity of the flow speed field leads to an influence of the finite transit time of the pulses (M���0) even in the absence of non-steady behaviour of the wind speed. In the last case, a model of the influence of the sonic anemometer processes on the measurement of wind speed spectral characteristics is presented. The new solution is compared to the line-averaging models existing in the literature. Mach number and time delay significantly distort the measurement in the normal operational range. Classical line averaging solutions are recovered when Mach number and time delay between pulses go to zero in the new proposed model. The results obtained from the mathematical model have been applied to the calculation of errors in different configurations of practical interest, such as an anemometer located on a meteorological mast and the transfer function of a sensor in an atmospheric wind. The expressions obtained can be also applied to determine the quality requirements of the flow in a wind tunnel used for ultrasonic anemometer calibrations.

Mechanical and chemical unfolding of a single protein: A comparison

Is the mechanical unraveling of protein domains by atomic force microscopy (AFM) just a technological feat or a true measurement of their unfolding? By engineering a protein made of tandem repeats of identical Ig modules, we were able to get explicit AFM data on the unfolding rate of a single protein domain that can be accurately extrapolated to zero force. We compare this with chemical unfolding rates for untethered modules extrapolated to 0 M denaturant. The unfolding rates obtained by the two methods are the same. Furthermore, the transition state for unfolding appears at the same position on the folding pathway when assessed by either method. These results indicate that mechanical unfolding of a single protein by AFM does indeed reflect the same event that is observed in traditional unfolding experiments. The way is now open for the extensive use of AFM to measure folding reactions at the single-molecule level. Single-molecule AFM recordings have the added advantage that they define the reaction coordinate and expose rare unfolding events that cannot be observed in the absence of chemical denaturants.

Dynamics of fluorescence fluctuations in green fluorescent protein observed by fluorescence correlation spectroscopy

We have investigated the pH dependence of the dynamics of conformational fluctuations of green fluorescent protein mutants EGFP (F64L/S65T) and GFP-S65T in small ensembles of molecules in solution by using fluorescence correlation spectroscopy (FCS). FCS utilizes time-resolved measurements of fluctuations in the molecular fluorescence emission for determination of the intrinsic dynamics and thermodynamics of all processes that affect the fluorescence. Fluorescence excitation of a bulk solution of EGFP decreases to zero at low pH (pKa = 5.8) paralleled by a decrease of the absorption at 488 nm and an increase at 400 nm. Protonation of the hydroxyl group of Tyr-66, which is part of the chromophore, induces these changes. When FCS is used the fluctuations in the protonation state of the chromophore are time resolved. The autocorrelation function of fluorescence emission shows contributions from two chemical relaxation processes as well as diffusional concentration fluctuations. The time constant of the fast, pH-dependent chemical process decreases with pH from 300 ��s at pH 7 to 45 ��s at pH 5, while the time-average fraction of molecules in a nonfluorescent state increases to 80% in the same range. A second, pH-independent, process with a time constant of 340 ��s and an associated fraction of 13% nonfluorescent molecules is observed between pH 8 and 11, possibly representing an internal proton transfer process and associated conformational rearrangements. The FCS data provide direct measures of the dynamics and the equilibrium properties of the protonation processes. Thus FCS is a convenient, intrinsically calibrated method for pH measurements in subfemtoliter volumes with nanomolar concentrations of EGFP.

A calcium influx is triggered and propagates in the zygote as a wavefront during in vitro fertilization of flowering plants

In this paper, we report direct measurement of an influx of extracellular Ca2+ induced by gamete fusion in flowering plants. This result was obtained during maize in vitro fertilization with the use of an extracellular Ca2+-selective vibrating probe. Ca2+ influx recorded at the surface of isolated egg cells, with or without adhesion of a male sperm cell, was close to zero and stable over time. Gamete fusion, however, triggered a Ca2+ influx in the vicinity of the sperm entry site with a delay of 1.8 �� 0.6 sec. The Ca2+ influx spread subsequently through the whole egg cell plasma membrane as a wavefront, progressing at an estimated rate of 1.13 ��m���sec���1. Once established, Ca2+ influx intensities were sustained, monotonic and homogeneous over the whole egg cell, with an average peak influx of 14.92 pmol���cm���2���sec���1 and an average duration of 24.4 min. The wavefront spread of channel activation correlates well with the cytological modifications induced by fertilization, such as egg cell contraction, and with the cytosolic Ca2+ (c[Ca2+]) elevation previously reported. Calcium influx was inhibited effectively by gadolinium, possibly implicating mechanosensitive channels. Furthermore, artificial influxes created by incubation with Ca2+ ionophores mimicked some aspects of egg activation. Taken together, these results suggest that, during fertilization in higher plants, gamete membrane fusion starts the first embryonic events by channel opening and Ca2+ influx. In turn, c[Ca2+] may work as a trigger and possibly a space and time coordinator of many aspects of egg activation.