Spontaneous self-ordered states of vortex-antivortex pairs in a Polariton Condensate

Polariton condensates have proved to be model systems to investigate topological defects, as they allow for direct and non-destructive imaging of the condensate complex order parameter. The fundamental topological excitations of such systems are quantized vortices. In specific configurations, further ordering can bring the formation of vortex lattices. In this work we demonstrate the spontaneous formation of ordered vortical states, consisting in geometrically self-arranged vortex-antivortex pairs. A mean-field generalized Gross-Pitaevskii model reproduces and supports the physics of the observed phenomenology

Accumulation et fonte de la neige en milieux boisé et déboisé

Les auteurs présentent une étude des caractéristiques physiques du couvert de neige en relation avec l'altitude, l'exposition et le couvert forestier. L'expérience s'est déroulée à la forêt Montmorency, sise à 80 km au nord de Québec. Au cours des hivers 1981 et 1982, l'équivalent en eau maximal de la neige, pour l'ensemble du bassin du lac Laflamme, a été de 28 et 29 cm, respectivement. Durant cette période, les mesures effectuées n'ont pas permis de détecter l'effet des faibles différences d'altitude (50 m) sur l'accumulation de la neige. L'équivalent en eau de la neige était maximal dans les milieux découverts et apparaissait plus important sous les jeunes peuplements que sous les vieux. Les jeunes sapinières, entourées d'arbres plus hauts, agissent comme des pièges à neige. L'influence de l'exposition ne ressort que durant la période de fonte, accélérée d'une semaine sur les flancs sud. La fonte en sous-bois dure un mois et demi en moyenne et est écourtée d'une à deux semaines dans les sites découverts. Un modèle de fonte, basé sur les degrés-jours, est finalement adapté. Le coefficient de fonte est rajusté en fonction de deux périodes distinctes par la densité du manteau nival ou les degrés-jours cumulés.A study of physical characteristics of the snow cover in relation to altitude, aspect and forest cover, is presented in this paper. The experimental site is located at Montmorency forest, 80 km north of Québec City. During the winters of 1981 and 1982, the snow water equivalent for the lake Laflamme watershed reached a maximum of 28 and 29 cm, respectively. The effect on snow accumulation by the small elevation range (50 m) was not detectable by our measurements. The snow water equivalent was greatest in open areas and appeared greater under the young than the older stands. The young fir associations, surrounded by higher trees, act as snow traps. The aspect plays a role during the melting period only, which is shortened by one week on south exposures. Snowmeit lasts one and a half month in average under the cover and is shortened by one to two weeks in the open. A snowmeit model, based on degree-days, is finally calibrated. The melt coefficient is readjusted for two periods separated by snow density or cumulative degree-days.Die Autoren legen eine Studie vor, die die Beziehung der physischen Merkmale der Schneedecke zu Hôhe, Himmelsrichtung und Bewaldung untersucht. Der Versuch wurde im WaId Montmorency, der 80 km nôrdlich von Québec liegt, durchgefùhrt. Wàhrend der Winter 1981 und 1982 war das maximale Wasserâquivalent der Schneemenge 28 cm bzw. 29 cm fur das gesamte Becken des Laflamme-Sees. Wahrend dieser Période konnten die durchgefuhrten Messungen keinerlei Einflup der schwachen Hôhenunterschiede (50 m) auf die Menge des angesammelten Schnees feststellen. Das der Schneemenge entsprechende Wasserâquivalent war maximal in den freien Gebieten und schien grosser unter den jungen Baumbestanden als unter den alten. Die jungen Tannenwâlder, die von hôheren Baurnen umgeben sind, wirken wie Schneefallen. Der EinfluB der Himmelsrichtung wird erst wâhrend der Zeit der Schneeschmelze spurbar, die auf den Sudflanken urn eine Woche kùrzer ist. Die Schneeschmelze im WaId dauert im Durchschnitt eineinhalb Monate und ist ein bis zwei Wochen kurzer in den offenen Gelànden. Ein Schneeschmelze-Modell auf der Basis Grade-Tage wird schlieplich geeicht. Der Schmelzkoeffizient wird zwei Perioden angepaBt, die sich durch die Dichte der Schneedecke oder die kumulierten Grade-Tage unterscheiden

Periodic squeezing in a polariton Josephson junction

The use of a Kerr nonlinearity to generate squeezed light is a well-known way to surpass the quantum noise limit along a given field quadrature. Nevertheless, in the most common regime of weak nonlinearity, a single Kerr resonator is unable to provide the proper interrelation between the field amplitude and squeezing required to induce a sizable deviation from Poissonian statistics. We demonstrate experimentally that weakly coupled bosonic modes allow exploration of the interplay between squeezing and displacement, which can give rise to strong deviations from the Poissonian statistics. In particular, we report on the periodic bunching in a Josephson junction formed by two coupled exciton-polariton modes. Quantum modeling traces the bunching back to the presence of quadrature squeezing. Our results, linking the light statistics to squeezing, are a precursor to the study of nonclassical features in semiconductor microcavities and other weakly nonlinear bosonic systems.Comment: 6 pages, 4 figure

Multimodal output combination for transcribing historical handwritten documents

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-23192-1_21Transcription of digitalised historical documents is an interesting task in the document analysis area. This transcription can be achieved by using Handwritten Text Recognition (HTR) on digitalised pages or by using Automatic Speech Recognition (ASR) on the dictation of contents. Moreover, another option is using both systems in a multimodal combination to obtain a draft transcription, given that combining the outputs of different recognition systems will generally improve the recognition accuracy. In this work, we present a new combination method based on Confusion Network. We check its effectiveness for transcribing a Spanish historical book. Results on both unimodal combination with different optical (for HTR) and acoustic (for ASR) models, and multimodal combination, show a relative reduction of Word and Character Error Rate of 14.3% and 16.6%, respectively, over the HTR baseline.Work partially supported by European Union -7th FP, under grant 600707 (tranScriptorium), and by the Spanish MEC under projects STraDA (TIN2012-37475-C02-01), Active2Trans (TIN2012-31723), and SmartWays (RTC-2014-1466-4).Granell Romero, E.; Martínez-Hinarejos, C. (2015). Multimodal output combination for transcribing historical handwritten documents. En Computer Analysis of Images and Patterns. Springer. 246-260. https://doi.org/10.1007/978-3-319-23192-1_21S246260Alabau, V., Martínez-Hinarejos, C.D., Romero, V., Lagarda, A.L.: An iterative multimodal framework for the transcription of handwritten historical documents. 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In: V Jornadas en Tecnologías del Habla (VJTH2008), pp. 75–78 (2008)Moreno, A., Poch, D., Bonafonte, A., Lleida, E., Llisterri, J., Mariño, J.B., Nadeu, C.: Albayzin speech database: design of the phonetic corpus. In: Proc. of EuroSpeech 1993, pp. 175–178 (1993)Netpbm home page. http://netpbm.sourceforge.net/Plamondon, R., Srihari, S.N.: On-Line and Off-Line Handwriting Recognition: A Comprehensive Survey. IEEE Transactions on Pattern Analysis and Machine Intelligence 22(1), 63–84 (2000)Romero, V., Leiva, L.A., Toselli, A.H., Vidal, E.: Interactive multimodal transcription of text images using a web-based demo system. In: Proc. of Conf. on Intelligent User Interfaces, pp. 477–478 (2009)Serrano, N., Castro, F., Juan, A.: The RODRIGO Database. In: Proc. of Language Resources and Evaluation Conference, pp. 2709–2712 (2010)Stolcke, A.: SRILM - an extensible language modeling toolkit. In: Proc. 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Effect of graphene additive on flexural and interlaminar shear strength properties of carbon fiber-reinforced polymer composite

Composite materials are widely used in various manufacturing fields from aeronautic and aerospace industries to the automotive industry. This is due to their outstanding mechanical properties with respect to their light weight. However, some studies showed that the major flaws of these materials are located at the fiber/matrix interface. Therefore, enhancing matrix adhesion properties could significantly improve the overall material characteristics. This study aims to analyze the effect of graphene particles on the adhesion properties of carbon fiber-reinforced polymer (CFRP) through interlaminar shear strength (ILSS) and flexural testing. Seven modified epoxy resins were prepared with different graphene contents. The CFRP laminates were next manufactured using a method that guarantees a repeatable and consistent fiber volume fraction with a low porosity level. Short beam shear and flexural tests were performed to compare the effect of graphene on the mechanical properties of the different laminates. It was found that 0.25 wt.% of graphene filler enhanced the flexural strength by 5%, whilst the higher concentrations (2 and 3 wt.%) decreased the flexural strength by about 7%. Regarding the ILSS, samples with low concentrations (0.25 and 0.5 wt.%) demonstrated a decent increase. Meanwhile, 3 wt.% slightly decreases the ILSS

Sigma-lognormal modeling of speech

Human movement studies and analyses have been fundamental in many scientific domains, ranging from neuroscience to education, pattern recognition to robotics, health care to sports, and beyond. Previous speech motor models were proposed to understand how speech movement is produced and how the resulting speech varies when some parameters are changed. However, the inverse approach, in which the muscular response parameters and the subject’s age are derived from real continuous speech, is not possible with such models. Instead, in the handwriting field, the kinematic theory of rapid human movements and its associated Sigma-lognormal model have been applied successfully to obtain the muscular response parameters. This work presents a speech kinematics-based model that can be used to study, analyze, and reconstruct complex speech kinematics in a simplified manner. A method based on the kinematic theory of rapid human movements and its associated Sigma-lognormal model are applied to describe and to parameterize the asymptotic impulse response of the neuromuscular networks involved in speech as a response to a neuromotor command. The method used to carry out transformations from formants to a movement observation is also presented. Experiments carried out with the (English) VTR-TIMIT database and the (German) Saarbrucken Voice Database, including people of different ages, with and without laryngeal pathologies, corroborate the link between the extracted parameters and aging, on the one hand, and the proportion between the first and second formants required in applying the kinematic theory of rapid human movements, on the other. The results should drive innovative developments in the modeling and understanding of speech kinematics

Spatial multistability induced by cross interactions of confined polariton modes

We demonstrate the occurrence of spatial multistability using laterally confined microcavity exciton-polaritons. By coherently exciting with a blue detuned laser a series of confined polariton modes, we investigate the effects of multistability on the transmitted laser beam as a function of the excitation power. At each threshold of the hysteresis loop, a switching of the mode profile of the laser beam is associated with a significant energy jump of each of the confined polariton modes in the mesa. A simulation of this behavior is achieved with a multimode generalization of the Gross-Pitaevskii equations in the exciton photon basis. The mechanism behind the spatial multistability is identified as a repulsive cross interaction between polaritons in different modes

Reservoir-induced decoherence of resonantly excited confined polaritons

We report on the effect of decoherence on polariton bistability. The polariton hysteresis loop is shown to collapse in a similar way when increasing the temperature or under nonresonant excitation power. The hysteresis upward threshold is pulled to lower excitation power, whereas the downward threshold remains almost constant. This effect is explained by the population of an incoherent reservoir that induces dephasing and repulsive interaction that saturates at large densities. All experimental findings are accurately simulated with the excitonic Bloch equations and indicate that reservoir-induced dephasing can be dominant over the reservoir-induced energy blueshift