Excitable-like chaotic pulses in the bounded-phase regime of an opto-radiofrequency oscillator

We report theoretical and experimental evidence of chaotic pulses with excitable-like properties in an opto-radiofrequency oscillator based on a self-injected dual-frequency laser. The chaotic attractor involved in the dynamics produces pulses that, albeit chaotic, are quite regular: They all have similar amplitudes, and are almost periodic in time. Thanks to these features, the system displays properties that are similar to those of excitable systems. In particular, the pulses exhibit a threshold-like response, of well-defined amplitude, to perturbations, and it appears possible to define a refractory time. At variance with excitability in injected lasers, here the excitable-like pulses are not accompanied by phase slips.Comment: 2nd versio

Accrochage de fréquence sans accrochage de phase de deux modes laser couplés

We study, experimentally and numerically, the synchronization properties of two laser modes. In order to stabilize the frequency difference, we introduce a coherent coupling by optical feedback. For a given coupling strength, we observe three synchronization regimes, depending on the detuning between the uncoupled modes. For a sufficiently weak detuning, the beat-note phase is fixed. Conversely, for strong detuning, the two modes oscillate almost independently. Besides these familiar behaviors, we identify an intermediate situation, where the relative phase fluctuates but remains bounded, and frequency locking is preserved, in spite of the absence of phase locking

Do Cross-border Patents Promote Trade?

While we would expect that cross-border patents are used to protect a technology that is made available in another country, that technology could either be produced locally or imported. International patent filings could therefore be either complements or substitutes to international trade. This study combines data on patenting and trade for 149 countries and 249 industries between 1974 and 2006 with a “three-way” panel data model that addresses several biases emphasized in the trade literature in order to provide a systematic analysis of how bilateral trade responds to cross-border patent filings. We find that cross-border patents have a positive (complementary) overall effect on the patent-filing country’s exports to the patent-granting country and no effect overall on imports flowing in the opposite direction. These effects vary substantially across industry groups, with patents promoting significantly more export growth in industries with a high demand elasticity and in industries that are relatively more downstream in supply chains. We also find that patents, once obtained, are associated with increased trade even in jurisdictions with weak intellectual property regimes

Do Cross-border Patents Promote Trade?

While we would expect that cross-border patents are used to protect a technology that is made available in another country, that technology could either be produced locally or imported. International patent filings could therefore be either complements or substitutes to international trade. This study combines data on patenting and trade for 149 countries and 249 industries between 1974 and 2006 with a "three-way" PPML panel data model that addresses several biases emphasized in the trade literature in order to provide a systematic analysis of how bilateral trade responds to cross-border patent filings. We find that cross-border patents have a positive (complementary) overall effect on the patent-filing country's exports to the patent-granting country and no effect overall on imports flowing in the opposite direction. These effects vary substantially across industries and destination markets. Patents promote significantly more bilateral export growth--and significantly less bilateral import growth--in less-differentiated industries and are found to have stronger effects on exports to more distant destinations. These findings support the interpretation that cross-border patents are mainly used to protect cost and/or quality innovations from being adopted by producers of competing products in the patent-granting country

Reconstruction-free sensitive wavefront sensor based on continuous position sensitive detectors

International audienceWe propose a new device that is able to perform highly sensitive wavefront measurements based on the use of continuous position sensitive detectors and without resorting to any reconstruction process. We demonstrate experimentally its ability to measure small wavefront distortions through the characterization of pump-induced refractive index changes in laser material. In addition, it is shown using computer-generated holograms that this device can detect phase discontinuities as well as improve the quality of sharp phase variations measurements. Results are compared to reference Shack-Hartmann measurements, and dramatic enhancements are obtained

Robust PCA for Anomaly Detection and Data Imputation in Seasonal Time Series

We propose a robust principal component analysis (RPCA) framework to recover low-rank and sparse matrices from temporal observations. We develop an online version of the batch temporal algorithm in order to process larger datasets or streaming data. We empirically compare the proposed approaches with different RPCA frameworks and show their effectiveness in practical situations

Proposition of an action layer for electrum

Electrum is an extension of Alloy that adds (1) mutable signatures and fields to the modeling layer; and (2) connectives from linear temporal logic (with past) and primed variables à la TLA+ to the constraint language. The analysis of models can then be translated into a SAT-based bounded model-checking problem, or to an LTL-based unbounded model-checking problem. Electrum has proved to be useful to model and verify dynamic systems with rich configurations. However, when specifying events, the tedious and sometimes error-prone handling of traces and frame conditions (similarly as in Alloy) remained necessary. In this paper, we introduce an extension of Electrum with a so-called “action” layer that addresses these questions.This work is financed by the ERDF - European Regional Development Fund - through the Operational Programme for Competitiveness and Internationalisation - COMPETE 2020 - and by National Funds through the Portuguese funding agency, FCT - Fundação para a Ciência e a Tecnologia, within project POCI-01-0145-FEDER016826, and the French Research Agency project FORMEDICIS ANR-16-CE25-000

Variations in North Sea sole distribution : variation in North Sea sole distribution with respect to the 56°N parallel perceived through scientific survey and commercial fisheries

The Dutch commercial fisheries report that sole (Solea solea) catches in the north of the North Sea have been increasing over the past years. While the large majority of North Sea sole catches are taken by beam trawl with 80mm mesh size, fishing with this gear is currently not allowed north of 56°N. In order to be able to get permission for a dedicated sole fishery (80 mm) in that area, scientific proof is needed for the increase in sole in the area north of 56°N. This study analyses data collected during the Beam Trawl Survey and STECF landing and effort data to investigate whether the spatial distribution of North Sea sole has changed over the last two decades. The study focusses in particular on the part of the North Sea to the north of the 56°N parallel where the main sole targeting fishery (beam trawl with 80mm mesh size) is currently not allowed to fish. Results based on the survey data show that the abundance and the extent of the distribution of sole in the area north of 56°N has increased (nearly doubled) since 2010. The proportion of the stock distributed north of 56°N also increased, but remains overall low (less than 7.5%). Over the same period, the centre of gravity of the stock has remained at a similar location. The only fleet operating at a scale large enough to provide information on sole at the scale of the North Sea was the Danish gillnet fishery. The proportion of landings of this fleet taken north of 56oN (in front of northern Denmark) has increased markedly since 2012, even when potential changes in the spatial distribution of the effort are taken into account. These results suggest an expansion of the stock at the margin of the distribution, while the core of the distribution of the stock has remained in the southern and central part of the North Sea (south of 54°N)

Best practices II : spatial distribution of the discards of the Dutch beam trawler fleet

This study aims at describing the spatial distribution – and its temporal variations - of discarding intensity (i.e. expected weight of discards for a standard trawl haul) for the 6 main species discarded by the Dutch beam trawl fisheries. For each species, the spatial distribution (quarterly maps for the period 2013 to 2017) is estimated using statistical models that take spatial and temporal correlation into account, which also allowed to test for the effect of a number of factors related to geography, environment, fishing practices and operational aspects on discarding. The data used to fit those models came from the observer trips and self-sampling program conducted at Wageningen Marine Research and from discards sampling trips conducted by the fishing industry. As by-product, the models provide descriptors of the temporal and spatial scales at which the discards of a given species are structured. The distribution of the expected discards per haul for dab was highly variable from quarter to quarter, with generally high discarding intensity in front of the southern coast of the Netherlands in quarter 1, a discarding intensity which is high on the German bight and low in front of the Dutch coast in quarter 3, and variable distributions for quarter 2 and 4. For plaice, the distribution was more stable, with high values consistently observed in the south of the area (between the south of the Netherlands and England), with occasional hot spots on the German bight. For sole, discards were not observed on the north-western part of the area, and a hotspot of sole discarding was found consistently in front of the southern coast of the Netherlands, occasionally expanding towards England or to the northern coast of the Netherlands. Discarding of turbot first occurred with a low intensity along the coast from Belgium to Germany. After the fourth quarter of 2015, high discarding started to occur, first limited to the small area in the southern North Sea, but progressively expanding to a larger area in the southern and central part of the North Sea, while discarding intensity remained low in the northern part of the area and in front of England. The distribution discarding intensity for whiting was highly variably, characterised by hotspots suddenly appearing for most years in the fourth quarter, and disappear in the following first quarter. Discarding of rays occurred mainly in the western part of the area, especially in front of southern England, with an increasing level since the fourth quarter of 2016. The distributions observed and their variability were further discussed in the light the available information on the distribution and migration of the species and on the management measures potentially influencing discarding