786 research outputs found
Boundary-induced nonequilibrium phase transition into an absorbing state
We demonstrate that absorbing phase transitions in one dimension may be
induced by the dynamics of a single site. As an example we consider a
one-dimensional model of diffusing particles, where a single site at the
boundary evolves according to the dynamics of a contact process. As the rate
for offspring production at this site is varied, the model exhibits a phase
transition from a fluctuating active phase into an absorbing state. The
universal properties of the transition are analyzed by numerical simulations
and approximation techniques.Comment: 4 pages, 4 figures; minor change
Effect of Vinyl and Silicon Monomers on Mechanical and Degradation Properties of Bio-Degradable Jute-Biopol® Composite
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Composites of jute fabrics (Hessian cloth) and Biopol® were prepared by compression molding process. Three types of Biopol® (3-hydroxbutyrate-co-3-hydroxyvalarate) such as D300G, D400G and D600G, depending on the concentration of 3-hydroxyvalarate (3HV) in 3-hydroxbutyrate (3HB) were taken for this purpose. Mechanical properties such as tensile strength (TS), bending strength (BS), elongation at break (Eb) and impact strength (IS) of the jute-Biopol® composites were studied. It was found that the composite with D400G produced higher mechanical properties in comparison to the other two types of Biopol®. To increase mechanical properties as well as interfacial adhesion between fiber and matrix, 2-ethyl hydroxy acrylate (EHA), vinyl tri-methoxy silane (VMS) and 3-methacryloxypropyl tri-methoxy silane (MPS) were taken as coupling agents. Enhanced mechanical properties of the composites were obtained by using these coupling agents. Biopol® D400G composites showed the highest mechanical properties. Among the coupling agents EHA depicts the highest increase of mechanical properties such as tensile strength (80%), bending strength (81%), elongation at break (33%) and impact strength (130%) compared pure Biopol. SEM investigations demonstrate that the coupling agents improve the interfacial adhesion between fiber and matrix. The surface of the silanized jute was characterized by FTIR and found the deposition of silane on jute fiber was observed. Soil degradation test proved that the composite prepared with EHA treated jute exhibits better degradation properties in comparison to pure Biopol®
Influence of Hydrolytic and Chemical Treatment on the Mechanical Properties of Aramid and Copolyaramid Fibers
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Commercial PPTA fibers ( Kevlar 49® and Twaron 1055®) and copolyaramid fibers (Trevar®) are subjected to various hydrolytic and chemical treatments. Tensile mod ulus, tensile strength, and elongation at break are measured, and mechanical property deterioration is compared. Copolyaramid fibers show improved hydrolytic stability and chemical resistance compared to PPTA fibers. The time dependence of degradation pro cesses can be described by two decreasing exponential functions. WAXS measurements detect only slight differences in the crystalline structure and superstructure of the treated fibers. Thus, the main origin of mechanical degradation is the destruction of intercrys talline links such as tie molecules or tie crystallites
Stochastic Model and Equivalent Ferromagnetic Spin Chain with Alternation
We investigate a non-equilibrium reaction-diffusion model and equivalent
ferromagnetic spin 1/2 XY spin chain with alternating coupling constant. The
exact energy spectrum and the n-point hole correlations are considered with the
help of the Jordan-Wigner fermionization and the inter-particle distribution
function method. Although the Hamiltonian has no explicit translational
symmetry, the translational invariance is recovered after long time due to the
diffusion. We see the scaling relations for the concentration and the two-point
function in finite size analysis.Comment: 7 pages, LaTeX file, to appear in J. Phys. A: Math. and Ge
The asymmetric exclusion model with sequential update
We present a solution for the stationary state of an asymmetric exclusion
model with sequential update and open boundary conditions. We solve the model
exactly for random hopping in both directions by applying a matrix-product
formalism which was recently used to solve the model with sublattice-parallel
update[1]. It is shown that the matrix-algebra describing the sequential update
and sublattice-parallel update are identical and can be mapped onto the random
sequential case treated by Derrida et al[2].Comment: 7 pages, Late
Matrix Product Eigenstates for One-Dimensional Stochastic Models and Quantum Spin Chains
We show that all zero energy eigenstates of an arbitrary --state quantum
spin chain Hamiltonian with nearest neighbor interaction in the bulk and single
site boundary terms, which can also describe the dynamics of stochastic models,
can be written as matrix product states. This means that the weights in these
states can be expressed as expectation values in a Fock representation of an
algebra generated by operators fulfilling quadratic relations which
are defined by the Hamiltonian.Comment: 11 pages, Late
A precise approximation for directed percolation in d=1+1
We introduce an approximation specific to a continuous model for directed
percolation, which is strictly equivalent to 1+1 dimensional directed bond
percolation. We find that the critical exponent associated to the order
parameter (percolation probability) is beta=(1-1/\sqrt{5})/2=0.276393202..., in
remarkable agreement with the best current numerical estimate beta=0.276486(8).Comment: 4 pages, 3 EPS figures; Submitted to Physical Review Letters v2:
minor typos + 1 major typo in Eq. (30) correcte
From multiplicative noise to directed percolation in wetting transitions
A simple one-dimensional microscopic model of the depinning transition of an
interface from an attractive hard wall is introduced and investigated. Upon
varying a control parameter, the critical behaviour observed along the
transition line changes from a directed-percolation to a multiplicative-noise
type. Numerical simulations allow for a quantitative study of the multicritical
point separating the two regions, Mean-field arguments and the mapping on a yet
simpler model provide some further insight on the overall scenario.Comment: 4 pages, 3 figure
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