11,002 research outputs found
Kovacs Effect in a Fragile Glass Model
The Kovacs protocol, based on the temperature shift experiment originally
conceived by A.J. Kovacs for glassy polymers, is implemented in an exactly
solvable dynamical model. This model is characterized by interacting fast and
slow modes represented respectively by spherical spins and harmonic oscillator
variables. Due to this fundamental property, the model reproduces the
characteristic non-monotonic evolution known as the ``Kovacs effect'', observed
in polymers, in granular materials and models of molecular liquids, when
similar experimental protocols are implemented.Comment: 8 pages, 6 figure
Optimized regulator for the quantized anharmonic oscillator
The energy gap between the first excited state and the ground state is
calculated for the quantized anharmonic oscillator in the framework of the
functional renormalization group method. The compactly supported smooth
regulator is used which includes various types of regulators as limiting cases.
It was found that the value of the energy gap depends on the regulator
parameters. We argue that the optimization based on the disappearance of the
false, broken symmetric phase of the model leads to the Litim's regulator. The
least sensitivity on the regulator parameters leads however to an IR regulator
being somewhat different of the Litim's one, but it can be described as a
perturbatively improved, or generalized Litim's regulator and provides analytic
evolution equations, too.Comment: 8 pages, 4 figure
Chopped basalt fibres: A new perspective in reinforcing poly(lactic acid) to produce injection moulded engineering composites from renewable and natural resources
This paper focuses on the reinforcing of Poly(lactic acid) with chopped basalt fibres by using silane treated and
untreated basalt fibres. Composite materials with 5–10–15–20–30–40 wt% basalt fibre contents were prepared from silane
sized basalt fibres using extrusion, and injection moulding, while composites with 5–10–15 wt% basalt fibre contents were
also prepared by using untreated basalt fibres as control. The properties of the injection moulded composites were extensively
examined by using quasi-static (tensile, three-point bending) and dynamic mechanical tests (notched and unnotched
Charpy impact tests), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), heat deflection temperature
(HDT) analysis, dimensional stability test, as well as melt flow index (MFI) analysis and scanning electron microscopic
(SEM) observations. It was found that silane treated chopped basalt fibres are much more effective in reinforcing
Poly(lactic acid) than natural fibres; although basalt fibres are not biodegradable but they are still considered as natural (can
be found in nature in the form of volcanic rocks) and biologically inert. It is demonstrated in this paper that by using basalt
fibre reinforcement, a renewable and natural resource based composite can be produced by injection moulding with excellent
mechanical properties suitable even for engineering applications. Finally it was shown that by using adequate drying of
the materials, composites with higher mechanical properties can be achieved compared to literature data
The rich frequency spectrum of the triple-mode variable AC And
Fourier analysis of the light curve of AC And from the HATNet database
reveals the rich frequency structure of this object. Above 30 components are
found down to the amplitude of 3 mmag. Several of these frequencies are not the
linear combinations of the three basic components. We detect period increase in
all three components that may lend support to the Pop I classification of this
variable.Comment: Poster presented at IAU Symposium 301, "Precision Asteroseismology -
Celebration of the Scientific Opus of Wojtek Dziembowski", 19-23 August 2013,
Wroclaw, Polan
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