1,721,045 research outputs found
Vibrational Dynamics of Non-Crystalline Solids
No full textThe boson peak (BP) is an excess of vibrational states over the Debye law appearing at terahertz frequencies. It is found in all glasses and marks the crossover between the long-wavelength behavior, where the solid can be considered as an isotropic continuum, and the region where the wavelength of the sound wave starts to experience the microscopic details of the structure. This chapter is devoted to a review of the main experimental observations regarding the vibrational dynamics of amorphous solids, as detected by neutron and X-ray scattering techniques. A first part of the chapter is devoted to the measurements of the BP and its evolution as a function of external parameters, such as temperature, pressure, or density. The second part of the chapter reviews the wavevector evolution of the dynamic structure factor, which provides evidence of a pseudo-acoustic propagating mode up to frequencies comparable to those of the BP. This longitudinal mode has a sound attenuation which follows ..
Toolkit for wearable electrical impedance tomography (TWEIT): a software library for real-time image reconstruction on mobile devices.
No full textSound Attenuation at Terahertz Frequencies and the Boson Peak of Vitreous Silica
No full textThe propagation and damping of the acoustic excitations in vitreous silica is measured at terahertz frequencies using inelastic x-ray scattering. The apparent sound velocity shows a marked dispersion with frequency while the sound attenuation undergoes a crossover from a fourth to a second power law frequency dependence. This finding solves a recent controversy concerning the location of this crossover in vitreous silica, clarifying that it occurs at the position of the glass-characteristic excess of vibrational modes known as boson peak, and thus establishing a direct connection between boson peak and acoustic dispersion curves
Method and system for preparing code to be executed by programmable control devices
No full textThe present invention is directed to methods and systems for preparing
and transferring code to a memory of a programmable control device, particularly
a non-volatile memory image representing ROM of a device hosting a virtual
machine (VM)
Elastic anomalies at terahertz frequencies and excess density of vibrational states in silica glass
No full textWe study the temperature dependence of acousticlike excitations measured by means of inelastic x-ray scattering at terahertz frequencies in silica glass. The apparent sound velocity shows, between 300 and 1600 K, the same temperature variation measured, at lower frequencies, by Brillouin light scattering. On the contrary the vibrations at the boson peak (BP) present a much stronger temperature dependence, as indicated by neutron scattering data. The measured dispersion and damping are used to compute the contribution to the vibrational density of states (VDOS) coming from the propagating acousticlike modes. This part of the VDOS accounts only for a fraction of the BP intensity, indicating that other kinds of excitation accumulate in this frequency range. It is consequently not surprising that the BP does not follow the temperature evolution of the Debye frequency, which describes the modification of the continuum medium. Finally we present a comparison between the experimentally accessible quantities and a recently proposed model for the vibrations in glasses, based on the assumption of random spatial variations of the shear modulus [Schirmacher, Europhys. Lett. 73, 892 (2006)]
Changing the programming paradigm for the embedded in the IoT domain
No full textThe enormous growth of the IoT with the simultaneous explosion of the interest on prototyping boards pushed the research to rethink also the way to making the embedded world easy accessible to several targets: designers, artists, but also engineer without a strong background in low level programming. In this paper the technical specifications of a comprehensive design suite for IoT prototyping are described and a possible implementation of a software suite for the design of smart objects is presented. The suite represents a design environment where different software tools are integrated in an integrated and user friendly framework
A full stack for quick prototyping of IoT solutions
No full textThe paper presents a novel approach to the prototyping of interconnected products belonging to the Internet of Things field. The chosen solution tries to merge the benefits of monolithic vertical approaches (where everything is chosen from the board to the cloud) with those of horizontal solutions (where every time all the elements can be chosen and the code for integrating them written). The proposed solution allows to speed up the prototyping process and to let the developers focus on coding the product behaviours instead of solving customization issues. The advantages of the proposed solution goes beyond the prototyping, as the prototyped solution can be easily converted in an industrial grade one. The paper ends with a real case application that shows how an IoT industrial refrigerator smar-tification unit has been developed thanks to the horizontal stack here proposed
A full stack for quick prototyping of IoT solutions
Full text linkThe paper presents a novel approach for prototyping interconnected products belonging to the Internet of Things context. The proposed solution aims at merging the benefits provided by monolithic vertical approaches (where all the IoT elements are pre-selected, from the hardware to the cloud) with those of horizontal solutions (that leave the freedom to select the single components and write the integration code). The proposed solution allows to speed up the prototyping process and lets the developers focus on coding the product behaviors rather than solving customization issues. The advantages of the proposed solution goes beyond the prototyping, as the prototype can be easily converted into an industrially viable solution. The paper ends with a real case application where the proposed stack is used for the development of an IoT unit that converts industrial refrigerators into smart connected systems
Compressed correlation functions and fast aging dynamics in metallic glasses
No full textWe present x-ray photon correlation spectroscopy measurements of the atomic dynamics in a Zr67 Ni 33 metallic glass, well below its glass transition temperature. We find that the decay of the density fluctuations can be well described by compressed, thus faster than exponential, correlation functions which can be modeled by the well-known Kohlrausch-Williams-Watts function with a shape exponent β larger than one. This parameter is furthermore found to be independent of both waiting time and wave-vector, leading to the possibility to rescale all the correlation functions to a single master curve. The dynamics in the glassy state is additionally characterized by different aging regimes which persist in the deep glassy state. These features seem to be universal in metallic glasses and suggest a nondiffusive nature of the dynamics. This universality is supported by the possibility of describing the fast increase of the structural relaxation time with waiting time using a unique model function, independently of the microscopic details of the system
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