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Very Low Bitrate Spatial Audio Coding with Dimensionality Reduction
No full textInternational audienceIn this paper, we show that tensor compression techniques based on randomization and partial observations are very useful for spatial audio object coding. In this application, we aim at transmitting several audio signals called objects from a coder to a decoder. A common strategy is to transmit only the downmix of the objects along some small information permitting reconstruction at the decoder. In practice , this is done by transmitting compressed versions of the objects spectrograms and separating the mix with Wiener filters. Previous research used nonnegative tensor factorizations in this context, with bitrates as low as 1 kbps per object. Building on recent advances on tensor compression, we show that the computation time for encoding can be extremely reduced. Then, we demonstrate how the mixture can be exploited at the de-coder to avoid the transmission of many parameters, permitting bi-trates as low as 0.1 kbps per object for comparable performance
A multi-resolution approach to common fate-based audio separation
No full textInternational audienceWe propose the Multi-resolution Common Fate Transform (MCFT), a signal representation that increases the separabil-ity of audio sources with significant energy overlap in the time-frequency domain. The MCFT combines the desirable features of two existing representations: the invertibility of the recently proposed Common Fate Transform (CFT) and the multi-resolution property of the cortical stage output of an auditory model. We compare the utility of the MCFT to the CFT by measuring the quality of source separation performed via ideal binary masking using each representation. Experiments on harmonic sounds with overlapping fundamental frequencies and different spectro-temporal modulation patterns show that ideal masks based on the MCFT yield better separation than those based on the CFT
Limit order book modelling with high dimensional Hawkes processes
No full textThe quality of various Hawkes-process-based order book models are assessed using some objectivecriteria. We start with a precise empirical analysis of the dependenciesbetween order arrivals of various types, then, models built from multivariate, possibly nonlinear,Hawkes processes with multiple exponential kernels are introduced. Models areevaluated based on the distribution of forward recurrence times and the signature plot.This approach allows us to discriminate between various Hawkes-process-based models, and provide a financial interpretation of the more successful ones in terms of theirbehaviour at various time scales, and the presence of inhibition as well as excitation effects
Formal Verification of a Floating-Point Expansion Renormalization Algorithm
No full textInternational audienceMany numerical problems require a higher computing precision than the one offered by standard floating-point formats. A common way of extending the precision is to use floating-point expansions. As the problems may be critical and as the algorithms used have very complex proofs (many sub-cases), a formal guarantee of correctness is a wish that can now be fulfilled, using interactive theorem proving. In this article we give a formal proof in Coq for one of the algorithms used as a basic brick when computing with floating-point expansions, the renormaliza-tion, which is usually applied after each operation. It is a critical step needed to ensure that the resulted expansion has the same property as the input one, and is more " compressed ". The formal proof uncovered several gaps in the pen-and-paper proof and gives the algorithm a very high level of guarantee
Étude et conception d'une antenne compacte ultra large-bande à diversité de polarisation. Application à la radiogoniométrie.
No full textRadio direction finding (DF) allows for the measurement of the direction of arrival of incoming electromagnetic signals. Its main applications include spectrum monitoring and electronic warfare. DF antennas and arrays are subject to new problematics (bandwidth, compactness and polarization diversity) while DF algorithms have kept on improving. Previous works have initiated the design of such antennas and arrays.This work aims at designing an antenna with reduced dimensions for the VHF and UHF frequency bands and with a polarization diversity. This antenna shall then be integrated in a functional DF array. For this purpose, a planar antenna has been designed and measured in the 500-3000 MHz frequency band. Its final dimensions are 150mm x 150mm (λ/4 x λ/4). This antenna has then been integrated in the final DF array whose accuracy onthe same frequency band is of the order of 2° for a final size of 260mm (diameter) x 150mm (height), that is λ/2,3 x λ/4. This study has also allowed for the design of a low-profile absorber (with a height of 25mm, that is λ/24 at its lowest frequency of operation). An increase of 10dB in the front to back ratio of the proposed antenna has been enabled by this absorber on its whole frequency band.La radiogoniométrie consiste à mesurer l’angle d’incidence de signaux électromagnétiques. Elle a pour applications principales le contrôle du spectre et la guerre électronique. Dans le domaine des réseaux d’antennes pour la radiogoniométrie, de nouvelles problématiques sont apparues alors que les algorithmes de traitement d’antenne se perfectionnent. Ces dernières concernent la largeur de bande, la compacité et la diversité de polarisation. De précédents travaux ont initié la démarche de conception de telles antennes et réseaux pour la radiogoniométrie.L’objectif de ce travail de recherche a consisté en premier lieu à proposer une antenne de dimensions réduites opérant dans les bandes V/UHF et présentant une diversité de polarisation. Par la suite, il s’est agi de concevoir un réseau fonctionnel de radiogoniométrie intégrant l’antenne développée. Une antenne planaire de dimensions 150mm x 150mm (λ/4 x λ/4) a alors été conçue et réalisée entre 500 MHz et 3000 MHz. Sa mise en réseau permet des performances angulaires de l’ordre de 2° et moins sur la même bande pour des dimensions de 260mm (diamètre) x 150mm (hauteur) soit λ/2,3 x λ/4. Par la même occasion, un absorbant de faible épaisseur (25mm soit λ/24) a été développé et mesuré. Il permet une augmentation du rapport avant/arrière d’au moins 10dB de l’antenne développée sur sa bande de fonctionnement
Drop size distribution monitoring of oil-in-water emulsions in SMX+ static mixers: Effect of operating and geometrical conditions
No full textInternational audienceStatic mixers provide enhanced mixing via a motionless element inside a rigid pipe, and are widely used for continuous mixing and blending in industry. This study focuses on the emulsification of a silicon oil-in-water system stabilized by a surfactant through SMX+ ® static mixers involving no mass transfer between the two phases. The experiments covered a large domain of dispersed fraction from dilute conditions (5 %vol.) up to concentrated ones (60 %vol.) close to phase inversion and three different viscosities from 20 to 350 mPa s with transitional or turbulent flow regimes. The number of static mixers was studied until a constant drop size distribution monitored at line with a video probe was obtained. With the considered flow rates, only the five first SMX+ elements were necessary to achieve a complete drop breakup and coalescence equilibrium, the following ones only causing a supplementary pressure drop. The influence of the number of SMX+ and energy dissipation rate was found to be of first order 2 compared to the volume fraction or viscosity of the dispersed phase. According to the large amount of data, it was possible to establish a new form of a Middleman correlation dedicated to this type of mixer of new generation. The formula takes into account the number of static mixers besides other hydrodynamic and physicochemical parameters
Median based calculus for lattice polynomials and monotone Boolean functions
No full textInternational audienceIn this document, we consider a median-based calculus for efficiently representing polynomial functions over distributive lattices. We extend an equational specification of median forms from the domain of Boolean functions to the domain of lattice polynomials. We show that it is sound and complete, and we illustrate its usefulness when simplifying median formulas algebraically. Furthermore, we propose a definition of median normal forms (MNF), that are thought of as minimal median formulas with respect to a structural ordering of expressions. We also investigate related complexity issues and show that the problem of deciding whether a formula is in MNF is in Σ^P_2. Moreover, we explore polynomial approximations of solutions to this problem through a sound term rewriting system extracted from the proposed equational specification
Multicore Runtime for Dynamic Dataflow Video Decoders
No full textThe emergence of massively parallel architectures, along with the increasing complexity of signal processing applications, has revived the interest in the dataflow programming paradigm. Indeed, dataflow programming is well-suited to describe complex and modular applications while expressing parallelism explicitly. Paradoxically, most of the studies stay focused on static dataflow programming, even if a pragmatic development process requires the expressiveness and the practicality offered by dynamic dataflow programming. However, dynamic dataflow programs come up with the need of runtime scheduling decisions because of their unpredictable behavior. This paper introduces a run-time mapping/scheduling system dedicated to the execution of dynamic dataflow programs on multi-core platforms.The program behavior is profiled and analyzed on-the-fly, thus allowing the system to adapt to changing environments (e.g. different video streams) on real time thanks to dynamic reconfiguration. Our system has been implemented into an open-source tool and demonstrated on well-known video decoders including one based on the new High Efficiency Video Coding (HEVC) standard. The acceleration factor reaches 7,75 on a 8-core x86 processor over single-core execution showing the scalability of our approach
Mixtures of hyaluronic acid and liposomes for drug delivery: Phase behavior, microstructure and mobility of liposomes
No full textInternational audienceHyaluronic acid liposomal gels have previously demonstrated in vivo their great potential for drugdelivery. Elucidating their phase behavior and structure would provide a better understanding of theiruse properties. This work evaluates the microstructure and the phase behavior of mixtures of hyaluronicacid (HA) and liposomes and their impact on the vesicle mobility. HA concentration and surfaceproperties of liposomes (positively or negatively charged, neutral, with a polyethylene glycol corona) arevaried while the liposome concentration remains constant. Below the entanglement concentration of HA(0.4%), the mixtures exhibit a depletion phase separation except for positively charged liposomes thatinteract with anionic HA through attractive electrostatic interactions. At high HA concentration, nomacroscopic phase separation is observed, except a slight syneresis with cationic liposomes. Themicrostructure shows aggregates of liposomes homogeneously distributed into a HA network except forPEGylated liposomes, which seem to form bicontinuous interpenetrating networks. The diffusion ofliposomes is controlled by HA concentration and their surface properties. Finally, PEGylated liposomesdisplay the highest mobility at high HA concentration (2.28%) both macro- and microscopically. Themicrostructure of HA-liposomes mixtures and the diffusion of liposomes are key parameters that must betaken into account for drug delivery
Correlation between polarization modes in VCSEL with optical feedback
No full textInternational audienceVertical Cavity Surface Emitting Lasers (VCSELs) with isotropic optical feedback are studied especially in the so-called low frequency fluctuations regime. Correlation properties between linear polarizations are analyzed both analytically and numerically. The RF spectrum shows a double peak structure close to the external cavity frequency which can be predicted by our adapted Spin-Flip Model (SFM). We provide here numerical evidence of the interplay between modes and anti- modes which are solutions of the stability analysis of the VCSEL with feedback and demonstrate that this interplay is responsible for the double peak structure. © (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only