1,721,111 research outputs found
Exact discrete-time realization of a Dolby B encoding/decoding architecture
Full text linkAn algebraic technique which computes nonlinear, delay-free digital filter networks is applied to model the Dolby B in the discretetime. The model preserves the topology of the analog system, and imports the characteristics of the nonlinear processing blocks which are responsible of the peculiar functioning of Dolby B. The resulting numerical system exhibits qualitatively similar dynamic behavior and performance - full compliance with the Dolby B specifications would be achieved by deriving, from comprehensive data sheets of the system, accurate discrete-time models of the analog processing blocks. Results demonstrate that the computation converges if proper iterative methods are employed
Hybrid parametric-physiological glottal modelling with application to voice quality assessment
No full textA glottal model based on physical constraints is proposed. The model describes the vocal fold as a simple oscillator, i.e. a damped mass-spring system. The oscillator is coupled with a nonlinear block, accounting for fold interaction with the airflow. The nonlinear block is modelled as a regressor-based functional with weights to be identified, and a pitch-synchronous identification procedure is outlined. The model is used to analyse voiced sounds from normal and from pathological voices, and the application of the proposed analysis procedure to voice quality assessment is discussed
Thermodynamics of non-elementary chemical reaction networks
Full text linkWe develop a thermodynamic framework for closed and open chemical networks applicable to non-elementary reactions that do not need to obey mass action kinetics. It only requires the knowledge of the kinetics and of the standard chemical potentials, and makes use of the topological properties of the network (conservation laws and cycles). Our approach is proven to be exact if the network results from a bigger network of elementary reactions where the fast-evolving species have been coarse grained. Our work should be particularly relevant for energetic considerations in biosystems where the characterization of the elementary dynamics is seldomly achieved
Efficient computation of nonlinear filter networks with delay-free loops and applications to physically-based sound models
No full textThermodynamics of chemical waves
No full textChemical waves constitute a known class of dissipative structures emerging in reaction-diffusion systems. They play a crucial role in biology, spreading information rapidly to synchronize and coordinate biological events. We develop a rigorous thermodynamic theory of reaction diffusion systems to characterize chemical waves. Our main result consists of defining the proper thermodynamic potential of the local dynamics as a nonequilibrium free energy density and establishing its balance equation. This enables us to identify the dynamics of the free energy, of the dissipation, and of the work spent to sustain the wave propagation. Two prototypical classes of chemical waves are examined. From a thermodynamic perspective, the first is sustained by relaxation toward equilibrium and the second by nonconservative forces generated by chemostats. We analytically study step-like waves, called wavefronts, using the Fisher-Kolmogorov equation as a representative of the first class and oscillating waves in the Brusselator model as a representative of the second. Given the fundamental role of chemical waves as message carriers in biosystems, our thermodynamic theory constitutes an important step toward an understanding of information transfers and processing in biology
Numerical methods for a nonlinear impact model: A comparative study with closed-form corrections
Full text linkA physically based impact modelalready known and exploited in the field of sound synthesis-is studied using both analytical tools and numerical simulations. It is shown that the Hamiltonian of a physical system composed of a mass impacting on a wall can be expressed analytically as a function of the mass velocity during contact. Moreover, an efficient and accurate approximation for the mass outbound velocity is presented, which allows to estimate the Hamiltonian at the end of the contact. Analytical results are then compared to numerical simulations obtained by discretizing the system with several numerical methods. It is shown that, for some regions of the parameter space, the trajectories of the discretized systems may significantly drift from the analytically derived curves. Two approaches, based on enforcing numerical energy consistency, are then proposed to improve the accuracy of numerical simulation
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