1,507 research outputs found

    City indicators : now to Nanjing

    Get PDF
    This paper provides the key elements to develop an integrated approach for measuring and monitoring city performance globally. The paper reviews the role of cities and why indicators are important. Then it discusses past approaches to city indicators and the systems developed to date, including the World Bank's initiatives. After identifying the strengths and weaknesses of past experiences, it discusses the characteristics of optimal indicators. The paper concludes with a proposed plan to develop standardized indicators that emphasize the importance of indicators that are measurable, replicable, potentially predictive, and most important, consistent and comparable over time and across cities. As an innovative characteristic, the paper includes subjective measures in city indicators, such as well-being, happy citizens, and trust.Cultural Policy,City Development Strategies,Cultural Heritage&Preservation,ICT Policy and Strategies,Housing&Human Habitats

    Bio-Inspired Synchronization of Pulse-Coupled Oscillators and its Application to Wireless Sensor Networks

    Get PDF
    Precise synchronization among networked agents is responsible for phenomena as diverse as coral spawning and consistency in stock market transactions. The importance of synchronization in biological and engineering systems has triggered an avalanche of studies analyzing the emergence of a synchronized behavior within a network of, possibly heterogeneous, agents. In particular, synchronization of networks of coupled oscillators has received great attention since limit cycle oscillators are a natural abstraction for systems where periodicity is a distinctive property. Examples of such systems include circadian rhythms and alternate-current power generators. This work deals with synchronization of pulse-coupled limit cycle oscillators (PCOs). A reverse engineering approach is taken with the objective of obtaining an abstraction for PCO networks able to capture the key properties observed in the classical biological PCO model, to finally implement it in an en gineering system. To this end, we first reformulate the PCO model as a hybrid system, able to integrate in a smooth manner the continuous-time dynamics of the individual oscillators and the impulsive effect of the coupling. Using our new model, we analyze the existence and stability of synchronization in a variety of PCO network topologies, starting from the simplest all-to-all network where global synchronization is proven to exist, to end giving synchronization conditions in the general strongly connected network case. Inspired by the strong synchronization properties of PCO networks we design a PCO-inspired time synchronization protocol for wireless sensor networks that enjoys all the advantages of our optimized PCO setup. A pilot implementation is presented going from a simulation stage to a hardware implementation in Gumstix development boards and industrial acoustic sensors. To test the potential of the protocol in a real application, we implement the PCO-based time synchronization protocol in a distributed acoustic event detection system, where a sensor network combines local measurements over an infrastructure-free wireless network to find the source of an acoustic event. An evaluation by simulation is given to illustrate the advantages of using the pulse-coupled synchronization strategy.The contributions of this thesis range from the theoretical synchronization conditions for a variety of PCO networks to the design and implementation of a synchronization strategy for wireless sensor networks that seems to be the natural choice when using an infrastructure-free wireless network due to its simple formulation and natural scalability

    A tale of two cascades: Higgsing and Seiberg-duality cascades from type IIB string theory

    Full text link
    We construct explicitly new solutions of type IIB supergravity with brane sources, the duals of which are N = 1 supersymmetric field theories exhibiting two very interesting phenomena. The far UV dynamics is controlled by a cascade of Seiberg dualities analogous to the Klebanov- Strassler backgrounds. At intermediate scales a cascade of Higgsing appears, in the sense that the gauge group undergoes a sequence of spontaneous symmetry breaking steps which reduces its rank. Deep in the IR, the theory confines, and the gravity background has a non-singular end of space. We explain in detail how to generate such solutions, discuss some of the Physics associated with them and briefly comment on the possible applications.Comment: 34 pages plus appendices. Typos corrected and references added, version to appear in JHE

    Efectos de los musculos aductores sobre la actividad electromiografica de los musculos vasto medial oblicuo y vasto lateral durante un semisquat de 45 en sujetos con sindrome de dolor femoropatelar

    Get PDF
    76 p.El propósito de este estudio fue determinar la actividad eléctrica de los músculos vasto medial oblicuo y vasto lateral, y establecer la existencia de un aumento en la relación de actividad electromiográfica entre ambos músculos, al realizar una aducción isométrica de caderas en sujetos con síndrome de dolor femoropatelar durante un semisquat de 45º en cadena cinética cerrada. La muestra consistió en 14 sujetos (7 sanos y 7 con SDFP). Para evaluar la actividad electromiográfica de los músculos, se realizó un semisquat de 45° en cadena cinética cerrada, y otro semisquat con aducción isométrica de caderas de 45° en cadena cinética cerrada, mientras se realizaba un registro de la señal mioeléctrica con electrodos de superficie localizados en los músculos vasto medial oblicuo y vasto lateral del miembro inferior seleccionado. La ventana de tiempo utilizada fue de 6 segundos para determinar la activación de los músculos VMO y VL en relación con la amplitud de la señal. Para procesar las señales se utilizó el programa Igor Pro 6.0. La estadística utilizada para analizar los resultados y atribuirle significancia fue la prueba Mann-Whitney para dos poblaciones independientes. Los resultados obtenidos indican que no hubo diferencias estadísticamente significativas, con un nivel de significancia de 0.05, en la relación de la actividad electromiográfica VMO/VL entre sujetos sanos y con SDFP al asociarle a un semisquat de 45º de flexión de rodilla una aducción isométrica de caderas. Por lo tanto, según la investigación realizada, se concluye que las características anatómicas que relacionan el vasto medial oblicuo con los músculos aductores, no tienen relevancia al evaluarlo de forma dinámica

    Multimodal Bayesian Network for Artificial Perception

    Get PDF
    In order to make machines perceive their external environment coherently, multiple sources of sensory information derived from several different modalities can be used (e.g. cameras, LIDAR, stereo, RGB-D, and radars). All these different sources of information can be efficiently merged to form a robust perception of the environment. Some of the mechanisms that underlie this merging of the sensor information are highlighted in this chapter, showing that depending on the type of information, different combination and integration strategies can be used and that prior knowledge are often required for interpreting the sensory signals efficiently. The notion that perception involves Bayesian inference is an increasingly popular position taken by a considerable number of researchers. Bayesian models have provided insights into many perceptual phenomena, showing that they are a valid approach to deal with real-world uncertainties and for robust classification, including classification in time-dependent problems. This chapter addresses the use of Bayesian networks applied to sensory perception in the following areas: mobile robotics, autonomous driving systems, advanced driver assistance systems, sensor fusion for object detection, and EEG-based mental states classification

    Kutasov-like duality from D5-branes wrapping hyperbolic cycles

    Full text link
    We study the addition of N_f flavor D5-branes to supergravity solutions describing D5-branes wrapping two-cycles of genus g>1 inside a six-dimensional space equipped with an SU(3)-structure. The non-zero genus g on the gravity side is dual to the existence of massless adjoint chiral superfields. Three types of internal manifolds are considered, each involving one of the following fibered products: H_2 x SL_2, S^2 x SL_2 or H_2 x S^3, where SL_2 stands for the universal cover of SL(2,R). For the first one, we investigate the dual field theories. We show that some of the solutions with N_f non-zero are dual to four-dimensional N = 1 field theories exhibiting a Kutasov-like duality taking N_c to k N_f - N_c, and keeping N_f fixed. Computed from the supergravity picture, k is in general a rational number, which can be made integer to fit the expectation from the field theory side. We finally study some other properties of those field theories.Comment: 39 pages plus appendices; v2: minor changes, references added; v3: version published in Nuc.Phys.

    Polycrystalline Ni nanotubes under compression: a molecular dynamics study

    Get PDF
    Mechanical properties of nanomaterials, such as nanowires and nanotubes, are an important feature for the design of novel electromechanical nano-architectures. Since grain boundary structures and surface modifications can be used as a route to modify nanostructured materials, it is of interest to understand how they affect material strength and plasticity. We report large-scale atomistic simulations to determine the mechanical response of nickel nanowires and nanotubes subject to uniaxial compression. Our results suggest that the incorporation of nanocrystalline structure allows completely flexible deformation, in sharp contrast with single crystals. While crystalline structures at high compression are dominated by dislocation pinning and the multiplication of highly localized shear regions, in nanocrystalline systems the dislocation distribution is significantly more homogeneous. Therefore, for large compressions (large strains) coiling instead of bulging is the dominant deformation mode. Additionally, it is observed that nanotubes with only 70% of the nanowire mass but of the same diameter, exhibit similar mechanical behavior up to 0.3 strain. Our results are useful for the design of new flexible and light-weight metamaterials, when highly deformable struts are required.Fil: Rojas Nunez, J.. Universidad de Santiago de Chile; ChileFil: Baltazar, S. E.. Universidad de Santiago de Chile; ChileFil: Gonzalez, R. I.. Universidad Mayor; ChileFil: Bringa, Eduardo Marcial. Universidad Mayor; Chile. Universidad de Mendoza. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Allende, S.. Universidad de Santiago de Chile; ChileFil: Kiwi, M.. Universidad de Santiago de Chile; ChileFil: Valencia, F. J.. Universidad de Santiago de Chile; Chile. Universidad Mayor; Chil

    Design and development of a magnetically-driven ventricular assist device (MVAD): in vitro implementation in the fontan circulation

    Get PDF
    A rapidly testable novel Magnetically-Driven Ventricular Assist Device (MVAD) with no m ving parts that can be used to provide assistance to the cardiovascular circulation while reducing caval pressure in patients who have undergone the Fontan procedure to palliate the Hypoplastic Left Heart Syndrome (HLHS) is proposed and studied. A benchtop Mock Flow Loop (MFL) of the cardiovascular circulation with a Fontan total cavopulmonary connection (TCPC) is configured to validate this hypothesis. The MFL is based on a Lumped-Parameter Model (LPM) comprised of upper and lower systemic circulation as well as left and right pulmonary circulation compartments. Needle valves are used to accurately replicate vascular resistance (R) while compliance chambers are used to mimic vascular compliance (C). The MFL centerpiece is the truncated aortic arch with an implanted MVAD. A ferro-fluid solution is mixed in water to simulate magnetically-charged blood. The pulsating flow is induced by drawing the ferro-fluid from a main reservoir with a Harvard Apparatus Medical pump while the MVAD provides assistive momentum to the TCPC. Flow and pressure sensor data at specific points in the MFL are acquired via a National Instruments multichannel data acquisition board and processed using LabView. Different prototypes of the MVAD are tested to validate the hypothesis
    corecore