1,891 research outputs found
Quantization of the elastic modes in an isotropic plate
We quantize the elastic modes in a plate. For this, we find a complete,
orthogonal set of eigenfunctions of the elastic equations and we normalize
them. These are the phonon modes in the plate and their specific forms and
dispersion relations are manifested in low temperature experiments in
ultra-thin membranes.Comment: 14 pages, 2 figure
THE INFLUENCE OF FLUVIAL DYNAMICS ON GEOARCHAEOSITES FROM THE DANUBE BANK (THE MĂCIN BRANCH). CASE STUDY: TROESMIS FORTRESS (ROMANIA)
The influence of fluvial dynamics on geoarchaeosites from the Danube Bank (the Măcin Branch). Case study: Troesmis Fortress (Romania). Built since the first century AD, the fortresses along the right bank of the Danube river have suffered decay along the ages as a result of anthropic and geomorphological factors (weathering of construction rocks, fluvial and eolian erosion). Therefore, in order to study the evolution of the sites, analysis of the geological, geomorphological, hydrological and climatic conditions were made. Our study aims to analyze the Troesmis Geto-Dacian site (III - IV century AD) situated on the right bank of the Măcin Branch. Nowadays, the fortress stage of degradation is quite advanced, the main natural decay favouring factor being lateral erosion from the Danube. Fluvial erosion and associated geomorphological processes have determined the retreat of the right bank of the Danube, which led to the structural destruction of the archaeological sites. In order to determine the fluvial dynamics of the Măcin Branch sector, bibliographic materials (maps from different time periods etc) were analyzed and field observations were made. The result consisted mainly in the creation of maps that presents the dynamic of the Măcin Branch (Danube) and its influence on the Troesmis geoarchaeosite
Interaction of Lamb modes with two-level systems in amorphous nanoscopic membranes
Using a generalized model of interaction between a two-level system (TLS) and
an arbitrary deformation of the material, we calculate the interaction of Lamb
modes with TLSs in amorphous nanoscopic membranes. We compare the mean free
paths of the Lamb modes with different symmetries and calculate the heat
conductivity . In the limit of an infinitely wide membrane, the heat
conductivity is divergent. Nevertheless, the finite size of the membrane
imposes a lower cut-off for the phonons frequencies, which leads to the
temperature dependence . This temperature dependence
is a hallmark of the TLS-limited heat conductance at low temperature.Comment: 9 pages, 2 figure
Heat transport in ultra-thin dielectric membranes and bridges
Phonon modes and their dispersion relations in ultrathin homogenous
dielectric membranes are calculated using elasticity theory. The approach
differs from the previous ones by a rigorous account of the effect of the film
surfaces on the modes with different polarizations. We compute the heat
capacity of membranes and the heat conductivity of narrow bridges cut out of
such membranes, in a temperature range where the dimensions have a strong
influence on the results. In the high temperature regime we recover the
three-dimensional bulk results. However, in the low temperature limit the heat
capacity, , is proportional with (temperature), while the heat
conductivity, , of narrow bridges is proportional to , leading
to a thermal cut-off frequency .Comment: 6 pages and 6 figure
Non-equilibrium Landauer Transport Model for Hawking radiation from a Black Hole
We propose that the Hawking radiation energy and entropy flow rates from a
black hole can be viewed as a one-dimensional (1D), non-equilibrium Landauer
transport process. Support for this viewpoint comes from previous calculations
invoking conformal symmetry in the near-horizon region, which give radiation
rates that are identical to those of a single 1D quantum channel connected to a
thermal reservoir at the Hawking temperature. The Landauer approach shows in a
direct way the particle statistics independence of the energy and entropy
fluxes of a black hole radiating into vacuum, as well as one near thermal
equilibrium with its environment. As an application of the Landauer approach,
we show that Hawking radiation gives a net entropy production that is 50%
larger than that obtained assuming standard three-dimensional emission into
vacuum.Comment: 14 pages, 2 figures, published versio
- …