A simple analytical description of the non-stationary dynamics in Ising spin systems

The analytical description of the dynamics in models with discrete variables (e.g. Isingspins) is a notoriously difficult problem, that can be tackled only undersome approximation.Recently a novel variational approach to solve the stationary dynamical regime has beenintroduced by Pelizzola [Eur. Phys. J. B, 86 (2013) 120], where simpleclosed equations arederived under mean-field approximations based on the cluster variational method. Here wepropose to use the same approximation based on the cluster variational method also for thenon-stationary regime, which has not been considered up to now within this framework. Wecheck the validity of this approximation in describing the non-stationary dynamical regime ofseveral Ising models defined on Erdos-R ́enyi random graphs: westudy ferromagnetic modelswith symmetric and partially asymmetric couplings, models with randomfields and also spinglass models. A comparison with the actual Glauber dynamics, solvednumerically, showsthat one of the two studied approximations (the so-called ‘diamond’approximation) providesvery accurate results in all the systems studied. Only for the spin glass models we find somesmall discrepancies in the very low temperature phase, probably due to the existence of alarge number of metastable states. Given the simplicity of the equations to be solved, webelieve the diamond approximation should be considered as the ‘minimalstandard’ in thedescription of the non-stationary regime of Ising-like models: any new method pretending toprovide a better approximate description to the dynamics of Ising-like models should performat least as good as the diamond approximation

Nonequilibrium critical dynamics of the three-dimensional gauge glass

We study the non-equilibrium aging behavior of the gauge glass model in three dimensions at the critical temperature. We perform Monte Carlo simulations with a Metropolis update, and correlation and response functions are calculated for different waiting times. We obtain a multiplicative aging scaling of the correlation and response functions, calculating the aging exponent $b$ and the nonequilibrium autocorrelation decay exponent $\lambda_c/z_c$. We also analyze the fluctuation-dissipation relationship at the critical temperature, obtaining the critical fluctuation-dissipation ratio $X_\infty$. By comparing our results with the aging scaling reported previously for a model of interacting flux lines in the vortex glass regime, we found that the exponents for both models are very different.Comment: 7 pages, 4 figures. Manuscript accpeted for publication in PR

Gauge-free cluster variational method by maximal messages and moment matching

We present an implementation of the cluster variational method (CVM) as a message passing algorithm. The kind of message passing algorithm used for CVM, usually named generalized belief propagation (GBP), is a generalization of the belief propagation algorithm in the same way that CVM is a generalization of the Bethe approximation for estimating the partition function. However, the connection between fixed points of GBP and the extremal points of the CVM free energy is usually not a one-to-one correspondence because of the existence of a gauge transformation involving the GBP messages. Our contribution is twofold. First, we propose a way of defining messages (fields) in a generic CVM approximation, such that messages arrive on a given region from all its ancestors, and not only from its direct parents, as in the standard parent-to-child GBP. We call this approach maximal messages. Second, we focus on the case of binary variables, reinterpreting the messages as fields enforcing the consistency between the moments of the local (marginal) probability distributions. We provide a precise rule to enforce all consistencies, avoiding any redundancy, that would otherwise lead to a gauge transformation on the messages. This moment matching method is gauge free, i.e., it guarantees that the resulting GBP is not gauge invariant. We apply our maximal messages and moment matching GBP to obtain an analytical expression for the critical temperature of the Ising model in general dimensions at the level of plaquette CVM. The values obtained outperform Bethe estimates, and are comparable with loop corrected belief propagation equations. The method allows for a straightforward generalization to disordered systems

Exploiting partial reconfiguration through PCIe for a microphone array network emulator

The current Microelectromechanical Systems (MEMS) technology enables the deployment of relatively low-cost wireless sensor networks composed of MEMS microphone arrays for accurate sound source localization. However, the evaluation and the selection of the most accurate and power-efficient network’s topology are not trivial when considering dynamic MEMS microphone arrays. Although software simulators are usually considered, they consist of high-computational intensive tasks, which require hours to days to be completed. In this paper, we present an FPGA-based platform to emulate a network of microphone arrays. Our platform provides a controlled simulated acoustic environment, able to evaluate the impact of different network configurations such as the number of microphones per array, the network’s topology, or the used detection method. Data fusion techniques, combining the data collected by each node, are used in this platform. The platform is designed to exploit the FPGA’s partial reconfiguration feature to increase the flexibility of the network emulator as well as to increase performance thanks to the use of the PCI-express high-bandwidth interface. On the one hand, the network emulator presents a higher flexibility by partially reconfiguring the nodes’ architecture in runtime. On the other hand, a set of strategies and heuristics to properly use partial reconfiguration allows the acceleration of the emulation by exploiting the execution parallelism. Several experiments are presented to demonstrate some of the capabilities of our platform and the benefits of using partial reconfiguration

Games for peace: Design of historical cooperative games in the classroom

Planteamos el empleo de una metodología novedosa para el aprendizaje del pasado en ámbito universitario con dos objetivos: la educación en la justicia social y la formación de ciudadanos activos en una cultura de paz. El caso de estudio afecta tanto a la narración del pasado (y por consiguiente a procesos identitarios presentes conectados a ese pasado mediante la memoria) como a la conciencia de ciudadanía global y procesos de transición ecológica, especialmente en el antropoceno. Para ello hemos recurrido a categorías y herramientas postcoloniales y feministas, así como a procesos de trabajo de grupo y cooperativos. El caso de estudio consiste en la creación de juegos de mesa cooperativos en el aula en materias del grado de Estudios Internacionales y del grado de Historia en la Universidad Autónoma de Madrid durante tres cursos académicos consecutivos, apoyado en parte por un proyecto de innovación docente. En la introducción planteamos el estado de la cuestión de los métodos pedagógicos lúdicos en ámbito universitario, particularmente su problemática en relación con el tratamiento del pasado y sus consecuencias para la formación en la paz y la justicia social de una ciudadanía activa global. Posteriormente explicamos su relevancia para la historia. Pasamos a exponer la metodología seguida en el estudio de campo, describiendo los materiales y dinámicas empleados. A partir de esos datos discutimos los resultados de la investigación, en relación con los objetivos planteados y las posibles mejoras a realizar. Finalmente concluimos, explicando las ventajas e inconvenientes de aplicar dicho método y sus posibilidades de futuroThe current paper offers an original methodology in university-based learning on history, focusing on social justice education and the formation of active citizens on peace culture. These deals not only with narratives about the past (identity processes connecting the past with the present through the mechanisms of memory) but also with citizen conscience and process of transition to ecology. Thus, we employ categories and a toolkit drawn from postcolonialism and feminism, while encouraging collaborative work to promote a culture based in peace. The case study is the design of cooperative tabletop games applied in the undergraduate curricula of International Studies and History Grades at Autonomous University of Madrid. In the introduction, we consider the pedagogic methodologies in a context of college education, discussing issues regarding the role of the past in the formation of a globally active citizenship and the training in peace. Secondly, we analyze its relevance for the teaching of history. Thirdly, we explain the methodology followed in our fieldwork and describe both the tools and dynamics employed. The analysis of the resulting data allows us to discuss the results of our research in relation with the initial goals, and how the project can be further improved. Finally, we explain the advantages and disadvantages of applying such a methodology and its future possibilitie

SoundCompass: a distributed MEMS microphone array-based sensor for sound source localization

Sound source localization is a well-researched subject with applications ranging from localizing sniper fire in urban battlefields to cataloging wildlife in rural areas. One critical application is the localization of noise pollution sources in urban environments, due to an increasing body of evidence linking noise pollution to adverse effects on human health. Current noise mapping techniques often fail to accurately identify noise pollution sources, because they rely on the interpolation of a limited number of scattered sound sensors. Aiming to produce accurate noise pollution maps, we developed the SoundCompass, a low-cost sound sensor capable of measuring local noise levels and sound field directionality. Our first prototype is composed of a sensor array of 52 Microelectromechanical systems (MEMS) microphones, an inertial measuring unit and a low-power field-programmable gate array (FPGA). This article presents the SoundCompass's hardware and firmware design together with a data fusion technique that exploits the sensing capabilities of the SoundCompass in a wireless sensor network to localize noise pollution sources. Live tests produced a sound source localization accuracy of a few centimeters in a 25-m2 anechoic chamber, while simulation results accurately located up to five broadband sound sources in a 10,000-m2 open field

Sociedades plurales, multiculturalismo y derechos indígenas en América Latina

El propósito del presente artículo es explorar la legislación constitucional en América Latina en lo concerniente a los derechos indígenas. Se parte de una reflexión histórica del concepto de autodeterminación de los pueblos y del reconocimiento de la pluralidad étnica y cultural de los Estados, y de la noción de pluralismo jurídico y democracia de ciudadanía. Se concluye que la refundación de los Estados latinoamericanos necesariamente deberá alcanzar los sistemas jurídicos, haciéndolos más sensibles a las especificidades étnicas y al derecho consuetudinario. _______________________________________________________________________________________ ABSTRACTThe paper explores the constitutional legislation and the indigenous rights in Latin America. At the beginning, the paper make a historical reflection of the concept of self-determination and the recognition of the ethnic and cultural plurality of the States, as well like as the notion of legal pluralism and democracy of citizenship. It concludes that the reformulation of the Latin American States necessarily will have to reach the legal systems, making them more sensible to the ethnic specificities and the indigenous rights

Degradabilidad Ruminal in situ de granos de genotipos contrastantes de maíz en bovinos

El grano de cereal más utilizado en la alimentación de ganado, en engorde a corral o suplementación a pastoreo, es el de maíz (Zea mays), Durante muchos años se ha estudiado la forma de mejorar la utilización digestiva de este grano por los rumiantes, con especial énfasis en los diferentes métodos de procesamiento físico. No obstante, la conveniencia de aplicar dicho tipo de tratamiento a los granos es materia de controversia. El objetivo de este trabajo fue la evaluación de la digestión ruminal de grano entero y sus fracciones obtenidas por molienda, de tres híbridos de maíz con características de grano contrastantes. El estudio se realizó en la Facultad de Agronomía, UNLPam, con granos de híbridos de maíz, seleccionados en un ensayo comparativo realizado en la EEA Anguil, INTA. Se eligieron tres materiales contrastantes: Flint (PROZEA 33), semideruado (AW 190 MG) Y dentado (EXP 849 CL). Los granos cosechados de dichos híbridos se procesaron en un molino de martillos, y se tamizaron para obtener tres fracciones de distinta granulometría: (a) <1 mm; (b) >1 mm 2mm. Dichas fracciones, junto con el grano entero, conformaron los cuatro tipos de sustrato de cada híbrido a evaluar. Cada uno de estos materiales se incubó en el rumen, en bolsitas de tela de nylon con tamaño de poro de 50 Jm. Las incubaciones se llevaron a cabo en 3 novillos Hereford provistos de fistula ruminal permanente, y alimentados con heno de alfalfa ad libitum. Los tiempos de incubación fueron: 3,6,9, 12,24 y 48 h para las tres fracciones producto de la molienda, y 48 h solamente para el grano entero. La desaparición de sustrato a tiempo cero se determinó por incubación en baño lennostatizado a 39°C durante 15 min., con agitación. Los datos de desaparición ruminal de los sustratos se ajustaron a un modelo exponencial con tiempo dc retardo. Los parámetros de la dinámica de degradación estimados por el ajuste a dicho modelo fueron: fracción soluble (A); fracción insoluble, lentamente degradable (8); fracción potencialmente degradable (A+B); tasa de degradación de la fracción 8 (e); y degradabilidad efectiva (DE) a una tasa de pasaje k de 0,05 h-1. Para el grano entero sólo se estimó la desaparición a las 48 h de incubación, y se incluyó en el análisis junto con la DE de las fracciones evaluadas. Los resultados para cada una de estas variables se sometieron a análisis de varianza, y prueba de Tukey (a = 0,05). Las comparaciones entre los distintos híbridos muestran que no se presentaron diferencias significativas (p>0,05) en los parámetros estimados, con excepción de la DE. La DE más alta fue para el híbrido dentado, seguido por el semidentado y finalmente el flint, aunque estos dos últimos no mostraron diferencias significativas. El tamaño de molienda tuvo una marcada influencia sobre los parámetros estimados disminuyendo A y aumentando 8 al incrementarse el tamaño de partícula. La DE fue claramente mayor para la fracción más fina, y similar para las otras dos. La degradabilidad ruminal de los granos de maíz enteros fue muy baja (<13 %) para todos los híbridos, demostrando que, si se ofrecen enteros, sólo pueden ser digeridos en rumen con ruptura previa por la masticación. Se concluye que el tamaño de las partículas obtenidas por molienda y el tipo de híbrido utilizado afectan su digestión y que los granos enteros son digeridos pobremente.