403 research outputs found
Very fast relaxation in polycarbonate glass
Low-frequency Raman and inelastic neutron scattering of amorphous bis-phenol
A polycarbonate is measured at low temperature, and compared. The vibrational
density of states and light-vibration coupling coefficient are determined. The
frequency dependences of these parameters are explained by propagating
vibration modes up to an energy of about 1 meV, and fracton-like modes in more
cohesive domains at higher energies. The vibrational dynamics is in agreement
with a disorder in the glass, which is principally of bonding or of elasticity
instead of density.Comment: 15 pages, 6 figures, to be pub. in EPJ
Attitude toward Advertising in General and Attitude toward a Specific Type of Advertising – A First Empirical Approach
The paper examines based on international research the differences between results of studies focused on consumers’ attitude toward advertising. The aim of this paper is to show that it is possible to find situations where the influence of attitudes towards specific ads in general (ASG) on attitudes toward advertising (Aad) can be observed and also it is possible to find no influence of attitudes toward ads in general (AG) on Aad. The paper shows that the problem comes from the definition of AG. The experiments described in this paper detect attitudinal differences toward advertising in general among studied nations depending on the type of advertising. The research encompasses respondents from three countries with different economic and cultural backgrounds (Germany, Ukraine and USA). The data were collected based on a quantitative survey and experiment among university students. The results show that the concept of AG is in some cases too broad. Differences between AG were confirmed between Ukraine and other countries. The respondents from Germany are according to AG more pessimistic and the respondents from the USA are more optimistic. This disparity was explained by a significant difference in Orthodox and Atheist religion compared to the other religions
Spin glass freezing and superconductivity in YBa2(Cu(1-x)Fe(x))3O7 alloys
The dynamics were studied of the iron spins in superconducting YBa2(Cu(0.94)Fe(0.06))3O7 by neutron time of flight measurements. Two samples were studied with slightly different characteristics, as shown by resistivity and neutron diffraction measurements. The same dynamical anomalies are observed by neutrons in both samples. Differences appear qualitative but not quantitative. In the whole temperature range, the q-dependence of the magnetic intensity mainly reflects the magnetic form factor of iron which shows that the iron spins are almost uncorrelated. The elastic and quasielastic intensities strongly vary with temperature. A spin glass like freezing is revealed at low temperature by a sharp decrease of the quasielastic intensity, an increase of the 'elastic' or resolution limited intensity and a minimum in the quasielastic width. The freezing temperature (T sub f - 18 K) corresponds to that already determined by a magnetic splitting in Mossbauer experiments. Above T sub f, the relaxation of the iron spins in the paramagnetic state is modified by the occurrence of superconductivity. An increase was observed of the quasielastic intensity and of the quasielastic width at the superconducting transition
Low-energy vibrational density of states of plasticized poly(methyl methacrylate)
The low-energy vibrational density of states (VDOS)of hydrogenated or
deuterated poly(methyl methacrylate)(PMMA)plasticized by dibutyl phtalate (DBP)
is determined by inelastic neutron scattering.From experiment, it is equal to
the sum of the ones of the PMMA and DBP components.However, a partition of the
total low-energy VDOS among PMMA and DBP was observed.Contrary to Raman
scattering, neutron scattering does not show enhancement of the boson peak due
to plasticization.Comment: 9 pages, 2 figures (Workshop on Disordered Systems, Andalo
Incoherent Quasielastic Neutron Scattering Study of Molecular dynamics of 4-n-cyano-4'-octylbiphenyl
We report incoherent quasielastic neutron scattering experiments on the
thermotropic liquid crystal 4-n-cyano-4'-octylbiphenyl. The combination of
time-of-flight and backscattering data allows analyzing the intermediate
scattering function over about three decades of relaxation times. Translational
diffusion and uniaxial molecular rotations are clearly identified as the major
relaxation processes in respectively the nanosecond and picosecond time scales.
The comparison with literature data obtained by other techniques is discussed.Comment: Accepted in Phys. Chem. Chem. Phy
EXPERIMENTAL VALIDATION OF A URBAN TRAFFIC NOISE ANNOYANCE MODEL
International audienceThis study deals with noise annoyance in urban environments. It is based on a previous work that resulted in two main outputs. First, a measurement tool that identifies and extracts sonic properties of the main urban noises sources, i.e. the different types of vehicles. Second, a modeling tool that estimates the perceived annoyance level by adapting from the literature, and implementing, a current multi-class psychoacoustic model. The present work follows these outcomes and aims at validating the annoyance estimations given by the model with an experimental approach. A listening test is designed in order to be able to collect perceived annoyance in a virtual environment (in lab test). Sound scenes made of urban soundscapes (background) and vehicles passing-by (foreground) are built and encoded in a 2D-audio immersive format (2D to multichannel algorithm), in order to create a listening experience as ecological as possible. Within this frame, an important experimental protocol is designed in order to measure the perceived annoyance caused by each synthesized sound scene and to control the cognitive load (attention on a list of words to play back afterwards) of the participants. The first rounds of data analysis show consistent results, especially in terms of influence of sound level or source typicality on the measured annoyance. A deeper round of analysis is currently being processed in order to examine the fine correlation between measured and predicted annoyance values, with regards to psychoacoustic features of source signals. All the results will be presented and discussed in the course of the conference
Vibrations of amorphous, nanometric structures: When does continuum theory apply?
Structures involving solid particles of nanometric dimensions play an
increasingly important role in material sciences. These structures are often
characterized through the vibrational properties of their constituent
particles, which can be probed by spectroscopic methods. Interpretation of such
experimental data requires an extension of continuum elasticity theory down to
increasingly small scales. Using numerical simulation and exact diagonalization
for simple models, we show that continuum elasticity, applied to disordered
system, actually breaks down below a length scale of typically 30 to 50
molecular sizes. This length scale is likely related to the one which is
generally invoked to explain the peculiar vibrational properties of glassy
systems.Comment: 4 pages, 5 figures, LATEX, Europhysics Letters accepte
Specific heat of the quantum Bragg Glass
We study the thermodynamics of the vibrational modes of a lattice pinned by
impurity disorder in the absence of topological defects (Bragg glass phase).
Using a replica variational method we compute the specific heat in the
quantum regime and find at low temperatures in dimension
three and two. The prefactor is controlled by the pinning length. The non
trivial cancellation of the linear term in arises from the so-called
marginality condition and has important consequences for other mean field
models.Comment: 5 pages, RevTex, strongly revised versio
Phonons and Colossal Thermal Expansion Behavior of Ag3Co(CN)6 and Ag3Fe(CN)6
Recently colossal positive volume thermal expansion has been found in the
framework compounds Ag3Co(CN)6 and Ag3Fe(CN)6. Phonon spectra have been
measured using the inelastic neutron scattering technique as a function of
temperature and pressure. The data has been analyzed using ab-initio
calculations. We find that the bonding is very similar in both compounds. At
ambient pressure modes in the intermediate frequency part of the vibrational
spectra in the Co compound are shifted to slightly higher energies as compared
to the Fe compound. The temperature dependence of the phonon spectra gives
evidence for large explicit anharmonic contribution to the total anharmonicity
for low-energy modes below 5 meV. We found that modes are mainly affected by
the change in the size of unit cell, which in turn changes the bond lengths and
vibrational frequencies. Thermal expansion has been calculated via the volume
dependence of phonon spectra. Our analysis indicates that Ag phonon modes in
the energy range from 2 to 5 meV are strongly anharmonic and major contributors
to thermal expansion in both compounds. The application of pressure hardens the
low-energy part of the phonon spectra involving Ag vibrations and confirms the
highly anharmonic nature of these modes.Comment: 19 pages, 14 figures and one tabl
Inelastic light, neutron, and X-ray scatterings related to the heterogeneous elasticity of glasses
The effects of plasticization of poly(methyl methacrylate) glass on the boson
peaks observed by Raman and neutron scattering are compared. In plasticized
glass the cohesion heterogeneities are responsible for the neutron boson peak
and partially for the Raman one, which is enhanced by the composition
heterogeneities. Because the composition heterogeneities have a size similar to
that of the cohesion ones and form quasiperiodic clusters, as observed by small
angle X-ray scattering, it is inferred that the cohesion heterogeneities in a
normal glass form nearly periodic arrangements too. Such structure at the
nanometric scale explains the linear dispersion of the vibrational frequency
versus the transfer momentum observed by inelastic X-ray scattering.Comment: 9 pages, 2 figures, to be published in J. Non-Cryst. Solids
(Proceedings of the 4th IDMRCS
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