108 research outputs found
Energy exchange and transition to localization in the asymmetric Fermi-Pasta-Ulam oscilliatory chain
A finite (periodic) FPU chain is chosen as a convenient point for
investigating the energy exchange phenomenon in nonlinear oscillatory systems.
As we have recently shown, this phenomenon may occur as a consequence of the
resonant interaction between high-frequency nonlinear normal modes. This
interaction determines both the complete energy exchange between different
parts of the chain and the transition to energy localization in an excited
group of particles. In the paper, we demonstrate that this mechanism can exist
in realistic (asymmetric) models of atomic or molecular oscillatory chains.
Also, we study the resonant interaction of conjugated nonlinear normal modes
and prove a possibility of linearization of the equations of motion.
The theoretical constructions developed in this paper are based on the
concepts of "effective particles" and Limiting Phase Trajectories. In
particular, an analytical description of energy exchange between the "effective
particles" in the terms of non-smooth functions is presented. The analytical
results are confirmed with numerical simulations.Comment: 15 pages, 8 figure
Low-frequency linear vibrations of single-walled carbon nanotubes: Analytical and numerical models
Low-frequency vibrations of single-walled carbon nanotubes with various boundary conditions are considered in the framework of the SandersâKoiter thin shell theory. Two methods of analysis are proposed. The first approach is based on the RayleighâRitz method, a double series expansion in terms of Chebyshev polynomials and harmonic functions is considered for the displacement fields; free and clamped edges are analysed. This approach is partially numerical. The second approach is based on the same thin shell theory, but the goal is to obtain an analytical solution useful for future developments in nonlinear fields; the SandersâKoiter equations are strongly simplified neglecting in-plane circumferential normal strains and tangential shear strains. The model is fully validated by means of comparisons with experiments, molecular dynamics data and finite element analyses obtained from the literature. Several types of nanotubes are considered in detail by varying aspect ratio, chirality and boundary conditions. The analyses are carried out for a wide range of frequency spectrum. The strength and weakness of the proposed approaches are shown; in particular, the model shows great accuracy even though it requires minimal computational effort
Optimization and deployment of CNNs at the Edge: The ALOHA experience
Deep learning (DL) algorithms have already proved their effectiveness on a wide variety of application domains, including speech recognition, natural language processing, and image classification. To foster their pervasive adoption in applications where low latency, privacy issues and data bandwidth are paramount, the current trend is to perform inference tasks at the edge. This requires deployment of DL algorithms on low-energy and resource-constrained computing nodes, often heterogenous and parallel, that are usually more complex to program and to manage without adequate support and experience. In this paper, we present ALOHA, an integrated tool flow that tries to facilitate the design of DL applications and their porting on embedded heterogenous architectures. The proposed tool flow aims at automating different design steps and reducing development costs. ALOHA considers hardware-related variables and security, power efficiency, and adaptivity aspects during the whole development process, from pre-training hyperparameter optimization and algorithm configuration to deployment
Digital receivers for low-frequency radio telescopes UTR-2, URAN, GURT
This paper describes digital radio astronomical receivers used for decameter
and meter wavelength observations. This paper describes digital radio
astronomical receivers used for decameter and meter wavelength observations.
Since 1998, digital receivers performing on-the-fly dynamic spectrum
calculations or waveform data recording without data loss have been used at the
UTR-2 radio telescope, the URAN VLBI system, and the GURT new generation radio
telescope. Here we detail these receivers developed for operation in the strong
interference environment that prevails in the decameter wavelength range. Data
collected with these receivers allowed us to discover numerous radio
astronomical objects and phenomena at low frequencies, a summary of which is
also presented.Comment: 24 pages, 15 figure
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