Evidence and modeling of mechanoluminescence in a transparent glass particulate composite

International audienceMechanoluminescence (ML) of a transparent alkali-phosphate glass composite with SrAl2O4:Eu, Dy particles is reported. Uniaxial compression experiments show the linear dependence of the mechanoluminescence intensity with the mechanical power. A theoretical model, based on the physics of delayed processes (in analogy of viscoelasticity), is proposed. This model accurately predicts the ML intensity changes induced by a complex mechanical loading and provides a convincing description of the mechanoluminescence response

Indentation-induced stress distribution and pressure effect on the resistivity of YSZ

International audienceIonic conductivities measured under GPa-order high pressure provide various information about ion hopping mechanisms such as the activation volume (ΔV). Traditionally, anvil cells have been used for high-pressure measurements. We previously reported a new method for high-pressure impedance measurements, up to a few GPa, employing an indentation-induced local stress field. In this method, both mechanical and electrical (Young's modulus and high pressure impedance) properties can be obtained simultaneously. However, in this method, high pressures are induced only around the tip of the indenter, and such stress distribution should be considered for the estimation of ΔV accurately. In the present study, employing a finite element method (FEM) calculation, the stress distribution around the tip of the indenter, and effects of such GPa-order high pressures on the O2− ion conduction of Y2O3-doped zirconia (YSZ) are shown

Physical properties of the GexSe1 − x glasses in the 0 < x < 0.42 range in correlation with their structure

International audiencePhysical properties, including mechanical, thermal and optical properties, have been investigated for chalcogenide glasses in the GexSe1 − x system, for x ranging between 0 and 0.42. In the 0 = 2.4). Conversely, the chemical threshold ( = 2.67) clearly induces a change in the compositional trend of these properties. In the x > 1/3 range, Tg decreases and the elastic moduli markedly increase, which is not expected from the continuously reticulated model. The change of the physical properties in this range is an indicator of the existence of separated Ge-rich domains

Towards an FPGA-Based Compilation Flow for Ultra-Low Latency Audio Signal Processing

International audienceField Programmable Gate Arrays (FPGAs) have been increasingly used in recent years for real-time audio Digital Signal Processing (DSP) applications. They provide unparalleled audio latency and processing power performances. They can target extremely high audio sampling rates and their large number of General Purpose Inputs and Outputs (GPIOs) make them particularly adapted to the development of large scale systems with an extended number of analog audio inputs and outputs. On the other hand, programming them is extremely complex and out of reach to non-specialized engineers as well as to most people in the audio community. In this paper, we introduce a comprehensive FPGA-based environment for real-time audio DSP programmable at a high level with the FAUST programming language. Our system reaches unequaled latency performances (11 µs round-trip) and can be easily controlled using both a software graphical user interface and a dedicated hardware controller taking the form of a sister board for our FPGA board. The implementation of the system is described in details and its performances are evaluated. Directions for future work and potential applications are presented as well

Towards an FPGA-Based Compilation Flow for Ultra-Low Latency Audio Signal Processing

International audienceField Programmable Gate Arrays (FPGAs) have been increasingly used in recent years for real-time audio Digital Signal Processing (DSP) applications. They provide unparalleled audio latency and processing power performances. They can target extremely high audio sampling rates and their large number of General Purpose Inputs and Outputs (GPIOs) make them particularly adapted to the development of large scale systems with an extended number of analog audio inputs and outputs. On the other hand, programming them is extremely complex and out of reach to non-specialized engineers as well as to most people in the audio community. In this paper, we introduce a comprehensive FPGA-based environment for real-time audio DSP programmable at a high level with the FAUST programming language. Our system reaches unequaled latency performances (11 µs round-trip) and can be easily controlled using both a software graphical user interface and a dedicated hardware controller taking the form of a sister board for our FPGA board. The implementation of the system is described in details and its performances are evaluated. Directions for future work and potential applications are presented as well

A relationship between non-exponential stress relaxation and delayed elasticity in the viscoelastic process in amorphous solids: Illustration on a chalcogenide glass

International audienceInorganic glasses are viscoelastic materials since they exhibit, below as well as above their glass transition temperature, a viscoelas-tic deformation under stress, which can be decomposed into a sum of an elastic part, an inelastic (or viscous) part and a delayed elastic part. The delayed elastic part is responsible for the non-linear primary creep stage observed during creep tests. During a stress relaxation test, the strain, imposed, is initially fully elastic, but is transformed, as the stress relaxes, into an inelastic and a delayed elastic strains. For linear viscoelastic materials, if the stress relaxation function can be fitted by a stretched exponential function, the evolution of each part of the strain can be predicted using the Boltzmann superposition principle. We develop here the equations of these evolutions, and we illustrate their accuracy by comparing them with experimental evolutions measured on GeSe 9 glass fibers. We illustrate also, by simple equations, the relationship between any kind of relaxation function based on additive contribution of different relaxation processes and the delayed elastic contribution to stress relaxation: the delayed elasticity is directly correlated to the dispersion of relaxations times of the processes involved during relaxation

Photoinduced fluidity in chalcogenide glasses at low and high intensities: A model accounting for photon efficiency

International audienceDetailed measurements of photoinduced fluidity in Ge-Se glasses were performed using a novel shear relaxation test in torsion mode. It is shown that photofluidity is significant even at a very low intensity and that there is no apparent threshold for activating the photostructural processes. Instead, the mechanism of photofluidity is described as a cumulative process involving photoinduced motions of every atom within the irradiated volume. Based on this assumption, a model is proposed, which is shown to accurately predict the power and wavelength dependence of photofluidity using a single fitting parameter n. The factor n represents the photon efficiency for inducing an atomic motion. Photofluidity experiments performed on glass fibers of various mean coordination number indicate that the process is rapidly reduced in overconstrained glasses. The values of n obtained for these glasses correlate remarkably well with the mean coordination dependence of other photostructural changes (photodarkening, photoexpansion). This indicates that the model is physically sound. Moreover, the model is shown to quantitatively describe photofluidity data from other glass systems from literature, therefore suggesting that it could be universally applied to all chalcogenide glasses

Faust2FPGA for Ultra-Low Audio Latency: Preliminary work in the Syfala project

International audienceFPGAs are increasingly present in every field of computer science. The generalization of High Level Synthesis (HLS) improves the productivity of the FPGA programmer. However, even with HLS, FPGA configuration requires advanced engineering. This paper investigates the use of FPGA in the context of very low latency (less than 500µs) audio digital signal processing. We propose a methodology to compile FAUST programs on FPGA platforms towards ultra-low latency. We expose the challenges it raises and report about the first steps of a future faust2FPGA compiler

Pathological lesions in colonic biopsies during Parkinson's disease.

International audiencePas de résum