How Do Limitations in Spectrum Fungibility Impact Spectrum Trading?

Secondary markets for spectrum trading have been considered an important solution for generating spectrum opportunities in an environment where scarcity is the rule. Nonetheless, an important factor when envisioning a successful spectrum trading environment is to consider how comparable an available frequency is to the frequency an spectrum user prefers. With this aim, we consider the fungibility scores previously determined in [1] in order to explore further parameters that can influence this quantification of the level of fungibility. Further, we merge these fungibility calculations with an existing spectrum trading model, SPECTRAD [2], seeking to determine the actual impact of the limitations of spectrum fungibility in the market viability

Energy spectrum, dissipation and spatial structures in reduced Hall magnetohydrodynamic

We analyze the effect of the Hall term in the magnetohydrodynamic turbulence under a strong externally supported magnetic field, seeing how this changes the energy cascade, the characteristic scales of the flow and the dynamics of global magnitudes, with particular interest in the dissipation. Numerical simulations of freely evolving three-dimensional reduced magnetohydrodynamics (RHMHD) are performed, for different values of the Hall parameter (the ratio of the ion skin depth to the macroscopic scale of the turbulence) controlling the impact of the Hall term. The Hall effect modifies the transfer of energy across scales, slowing down the transfer of energy from the large scales up to the Hall scale (ion skin depth) and carrying faster the energy from the Hall scale to smaller scales. The final outcome is an effective shift of the dissipation scale to larger scales but also a development of smaller scales. Current sheets (fundamental structures for energy dissipation) are affected in two ways by increasing the Hall effect, with a widening but at the same time generating an internal structure within them. In the case where the Hall term is sufficiently intense, the current sheet is fully delocalized. The effect appears to reduce impulsive effects in the flow, making it less intermittent.Comment: 17 pages, 10 figure

Warp evidences in precessing galactic bar models

Most galaxies have a warped shape when they are seen from an edge-on point of view. The reason for this curious form is not completely known so far and in this work we apply dynamical system tools to contribute to its explanation. Starting from a simple, but realistic, model formed by a bar and a disc, we study the effect produced by a small misalignment between the angular momentum of the system and its angular velocity. To this end, a precession model is developed and considered, assuming that the bar behaves like a rigid body. After checking that the periodic orbits inside the bar keep being the skeleton of the inner system, even after inflicting a precession to the potential, we compute the invariant manifolds of the unstable periodic orbits departing from the equilibrium points at the ends of the bar to get evidences of their warped shapes. As it is well known, the invariant manifolds associated with these periodic orbits drive the arms and rings of barred galaxies and constitute the skeleton of these building blocks. Looking at them from a side-on viewpoint, we find that these manifolds present warped shapes as those recognized in observations. Lastly, test particle simulations have been performed to determine how the stars are affected by the applied precession, confirming this way the theoretical results obtained.Comment: 14 pages, 21 figures, Accepted for publication in A&A (15th Jan 2016

Dejar la profesión docente: análisis del papel del apoyo social, el engagement y la inteligencia emocional en la intención de abandono del profesorado

The study aimed to test mediator and moderator factors in the relationship between workplace social support (i.e., perceived support from colleagues and supervisors) and intentions to quit in a sample of teaching professionals. Specifically, utilizing job-demands-resources theory to focus on social support, we examined whether work engagement mediated the relationship between workplace social support and intentions to quit. Moreover, the potential moderator role of emotional intelligence in the proposed model was tested. The study sample comprised 1,297 teaching professionals (64.8% females) working as preschool, primary, and secondary teachers in several centers in eastern and southern Spain. The main results demonstrated that work engagement totally mediated the relationship between social support from colleagues/supervisors and intentions to quit. The findings showed that teachers’ levels of emotional intelligence significantly moderated the indirect paths between perceived support from colleagues/supervisors and intentions to quit. Teachers with the lowest levels of work engagement reported low support from colleagues or supervisors, togetherwith low emotional intelligence. Similarly, highest intentions to quit was reported by those teachers reporting low work engagement and low emotional intelligence. Finally, we discuss the relevance of these findings for basic and applied research seeking to retain a more engaged teaching force.Este estudio pretende evaluar los factores mediadores y moderadores en la relación entre el apoyo social organizacional (apoyo percibido de compañeros y supervisores) y los niveles de intención de abandono en una muestra de profesionales de la enseñanza. Específicamente, usando la teoría de demandas y recursos laborales y centrándose en el apoyo social, se examina si el engagement laboral media la relación entre apoyo social organizacional e intención de abandono. Además, se analiza el posible papel moderador de la inteligencia emocional en el modelo propuesto. La muestra del estudio esta compuesta por 1,297 profesionales de la enseñanza (64.8% mujeres) que trabajaban como docentes de Infantil, Primaria y Secundaria en varios centros del este y sur de España. Los resultados principales demostraron que el engagement laboral mediaba totalmente la relación entre el apoyo social de compañeros y supervisores y la intención de abandono. Los hallazgos mostraron que el nivel de inteligencia emocional de los docentes moderaba significativamente las relaciones indirectas entre el apoyo percibido de compañeros y supervisores y la intención de abandono. Los docentes con un nivel más bajo de engagement laboral informaron de bajo apoyo de compañeros y supervisores, así como de un bajo nivel de inteligencia emocional. Igualmente, aquellos docentes con bajo engagement laboral y baja inteligencia emocional informaron de mayores niveles de intención de abandono. Finalmente, se discute la importancia de estos hallazgos para la investigación básica y aplicada enfocada a la retención de un capital docente comprometido

Frustrated Demand for Unionisation: the Case of the United States and Canada Revisited

In this paper we demonstrate that there is a substantial union representation gap in the United States. We arrive at this conclusion by comparing Canadian and American worker responses to questions relating to desired union representation. We find that a majority of the gap in union density between Canada and the US is a function of greater frustrated demand on the part of American workers. We then estimate potential union density rates for the United States and Canada and find that, given current levels of union membership in both countries, if effective demand for unionisation among non-union workers were realised, then this would imply equivalently higher rates of unionisation (37 and 36 percent in the US and Canada respectively). These results cast some doubt on the view that even minor reforms to labour legislation in the US, to bring them in line with those in most Canadian jurisdictions, would do nothing to improve the rate of organising success in the United States. The results also have implications for countries such as Britain who have recently moved closer to a Wagner-Act model of statutory recognition.Frustrated Demand for Unionisation: the Case of the United States and Canada Revisited

Hydrodynamics of polymers in an active bath

The conformational and dynamical properties of active polymers in solution are determined by the nature of the activity, and the behavior of polymers with self-propelled, active Brownian particle-type monomers differs qualitatively from that of polymers with monomers driven externally by colored noise forces. We present simulation and theoretical results for polymers in solution in the presence of external active noise. In simulations, a semiflexible bead-spring chain is considered, in analytical calculations, a continuous linear wormlike chain. Activity is taken into account by independent monomer/site velocities, with orientations changing in a diffusive manner. In simulations, hydrodynamic interactions (HI) are taken into account by the Rotne-Prager-Yamakawa tensor, or by an implementation of the active polymer in the multiparticle collision dynamics approach for fluids. To arrive at an analytical solution, the preaveraged Oseen tensor is employed. The active process implies a dependence of the stationary-state properties on HI via polymer relaxation times. With increasing activity, HI lead to an enhanced swelling of flexible polymers, and the conformational properties differ substantially from those of polymers with self-propelled monomers in presence of HI or free-draining polymers. The polymer mean square displacement is enhanced by HI. Over a wide range of time scales, hydrodynamics leads to a subdiffusive regime of the site mean square displacement for flexible active polymers, with an exponent of (5/7), larger than that of the Rouse (1/2) and Zimm (2/3) models of passive polymers.Comment: 16 pages, 11 figure

Determination of s(x) and \bar{s}(x) from a global QCD analysis

A new global QCD analysis of DIS data is presented. The \nu Fe and \bar{\nu}Fe differential cross-section data are included to constrain the strange component of the nucleon sea. As a result we found a hard strangeness at high-x and some evidence for an asymmetry between xs(x) and x\bar{s}(x).Comment: 5 pages, 4 figure

Análisisis filogenético en la música

En este artículo preconiza el uso de ciertas herramientas matemáticas e informáticas como parte del análisis musical. Presentamos dos ejemplos de análisis musical con árboles filogenéticos: el flamenco y sus métricas ternarias, y la pieza Clapping Music, de Steve Reich, arquetipo de obra minimalista. Somos conscientes de que entre ciertos analistas de la música y musicólogos no gozan estos métodos de gran popularidad. No abogamos por la sustitución de los métodos tradicionales de análisis, sino por la incorporación de estas nuevas herramientas

Simulation and Visualization of collective dynamics

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Any: 2015, Tutors: Ignacio Pagonabarraga i Albert Diaz-GuileraI present a computational simulation and the corresponding interactive visualization of a two-dimensional system of hard disk oscillators obeying Langevin dynamics and interacting. The visualization is carried out through a real-time 3D graphics package from Python called Visual Python, which allows visualization with a higher degree of interactivity. The Kuramoto model will be implemented as a mathematical model used to describe the synchronization of a large set of weakly coupled oscillators. The simulation results confirm that in the absence of hard core interactions the time required to synchronize increases linearly with the particle density. Excluded volume interactions lead to a more involved dependence of synchronization time with particle density