scholarly journals Propagating bands of plastic deformation in a metal alloy as critical avalanches

2020 ◽  
Vol 6 (41) ◽  
pp. eabc7350
Author(s):  
Tero Mäkinen ◽  
Pasi Karppinen ◽  
Markus Ovaska ◽  
Lasse Laurson ◽  
Mikko J. Alava
Keyword(s):  
Plastic Deformation ◽  
Tensile Deformation ◽  
Mean Field ◽  
Plastic Instability ◽  
Barkhausen Effect ◽  
Mean Field Model ◽  
Velocity Signal ◽  
Large Fluctuations ◽  
Resolution Imaging ◽  
Chatelier Effect

The plastic deformation of metal alloys localizes in the Portevin–Le Chatelier effect in bands of different types, including propagating, or type “A” bands, usually characterized by their width and a typical propagation velocity. This plastic instability arises from collective dynamics of dislocations interacting with mobile solute atoms, but the resulting sensitivity to the strain rate lacks fundamental understanding. Here, we show, by using high-resolution imaging in tensile deformation experiments of an aluminum alloy, that the band velocities exhibit large fluctuations. Each band produces a velocity signal reminiscent of crackling noise bursts observed in numerous driven avalanching systems from propagating cracks in fracture to the Barkhausen effect in ferromagnets. The statistical features of these velocity bursts including their average shapes and size distributions obey predictions of a simple mean-field model of critical avalanche dynamics. Our results thus reveal a previously unknown paradigm of criticality in the localization of deformation.

scholarly journals Effect of Deformation Temperature on the Portevin-Le Chatelier Effect in Medium-Mn Steel

Metals ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 2 ◽  
Author(s):  
Barbara Grzegorczyk ◽  
Aleksandra Kozłowska ◽  
Mateusz Morawiec ◽  
Rafał Muszyński ◽  
Adam Grajcar
Keyword(s):  
Deformation Temperature ◽  
Tensile Deformation ◽  
Plastic Instability ◽  
Manganese Steel ◽  
Experimental Investigations ◽  
Medium Manganese Steel ◽  
Medium Mn Steel ◽  
Lower Strain ◽  
Chatelier Effect ◽  
Hot Rolled

Experimental investigations of the plastic instability phenomenon in a hot-rolled medium manganese steel were performed. The effects of tensile deformation in a temperature range of 20–140°C on the microstructure, mechanical properties, and flow stress serrations were analyzed. The Portevin–Le Chatelier (PLC) phenomenon was observed for the specimens deformed at 60 °C, 100 °C, and 140 °C. It was found that the deformation temperature substantially affects the type and intensity of serrations. The type of serration was changed at different deformation temperatures. The phenomenon was not observed at room temperature. The plastic instability occurring for the steel deformed at 60 °C was detected for lower strain levels than for the specimens deformed at 100 °C and 140 °C. The increase of the deformation temperature to 100 °C and 140 °C results in shifting the PLC effect to a post uniform deformation range. The complex issues related to the interaction of work hardening, the transformation induced plasticity (TRIP) effect, and the PLC effect stimulated by the deformation temperature were addressed.

Path Integral Method in the Mean-field Model for the Magnetic Vector Potential

2020 ◽  
Vol 60 (7) ◽  
pp. 989-992
Author(s):  
E. V. Yushkov ◽  
C. R. Kamaletdinov ◽  
D. D. Sokoloff
Keyword(s):  
Path Integral ◽  
Vector Potential ◽  
Integral Method ◽  
Field Model ◽  
Mean Field ◽  
Magnetic Vector Potential ◽  
Magnetic Vector ◽  
Mean Field Model ◽  
The Mean ◽  
Path Integral Method

scholarly journals On the Throughput Optimization in Large-Scale Batch-Processing Systems

2021 ◽  
Vol 48 (3) ◽  
pp. 128-129
Author(s):  
Sounak Kar ◽  
Robin Rehrmann ◽  
Arpan Mukhopadhyay ◽  
Bastian Alt ◽  
Florin Ciucu ◽  
...  
Keyword(s):  
Large Scale ◽  
Mean Field ◽  
Queueing Network ◽  
Processing System ◽  
Batch Size ◽  
System Throughput ◽  
Throughput Optimization ◽  
Mean Field Model ◽  
Optimal Batch Size ◽  
Globally Attractive

We analyze a data-processing system with n clients producing jobs which are processed in batches by m parallel servers; the system throughput critically depends on the batch size and a corresponding sub-additive speedup function that arises due to overhead amortization. In practice, throughput optimization relies on numerical searches for the optimal batch size which is computationally cumbersome. In this paper, we model this system in terms of a closed queueing network assuming certain forms of service speedup; a standard Markovian analysis yields the optimal throughput in w n4 time. Our main contribution is a mean-field model that has a unique, globally attractive stationary point, derivable in closed form. This point characterizes the asymptotic throughput as a function of the batch size that can be calculated in O(1) time. Numerical settings from a large commercial system reveal that this asymptotic optimum is accurate in practical finite regimes.

scholarly journals Mean-Field Models for EEG/MEG: From Oscillations to Waves

2021 ◽  
Author(s):  
Áine Byrne ◽  
James Ross ◽  
Rachel Nicks ◽  
Stephen Coombes
Keyword(s):  
Gap Junction ◽  
Large Scale ◽  
Mean Field ◽  
Coarse Grained ◽  
Neural Mass Model ◽  
Neuron Network ◽  
Mass Model ◽  
Mean Field Model ◽  
Neural Mass ◽  
The Rich

AbstractNeural mass models have been used since the 1970s to model the coarse-grained activity of large populations of neurons. They have proven especially fruitful for understanding brain rhythms. However, although motivated by neurobiological considerations they are phenomenological in nature, and cannot hope to recreate some of the rich repertoire of responses seen in real neuronal tissue. Here we consider a simple spiking neuron network model that has recently been shown to admit an exact mean-field description for both synaptic and gap-junction interactions. The mean-field model takes a similar form to a standard neural mass model, with an additional dynamical equation to describe the evolution of within-population synchrony. As well as reviewing the origins of this next generation mass model we discuss its extension to describe an idealised spatially extended planar cortex. To emphasise the usefulness of this model for EEG/MEG modelling we show how it can be used to uncover the role of local gap-junction coupling in shaping large scale synaptic waves.

scholarly journals Quark mean-field model for single and double   and   hypernuclei

2014 ◽  
Vol 2014 (1) ◽  
pp. 13D02-0 ◽  
Author(s):  
J. N. Hu ◽  
A. Li ◽  
H. Shen ◽  
H. Toki
Keyword(s):  
Field Model ◽  
Mean Field ◽  
Mean Field Model

EVOLUTION OF SHELL STRUCTURE IN NUCLEI

2011 ◽  
Vol 20 (08) ◽  
pp. 1663-1675 ◽  
Author(s):  
A. BHAGWAT ◽  
Y. K. GAMBHIR
Keyword(s):  
Shell Structure ◽  
Crucial Role ◽  
Field Model ◽  
Mean Field ◽  
Mass Region ◽  
The Other ◽  
Mean Field Model ◽  
Relativistic Mean Field ◽  
Shell Closures ◽  
Low Mass

Systematic investigations of the pairing and two-neutron separation energies which play a crucial role in the evolution of shell structure in nuclei, are carried out within the framework of relativistic mean-field model. The shell closures are found to be robust, as expected, up to the lead region. New shell closures appear in low mass region. In the superheavy region, on the other hand, it is found that the shell closures are not as robust, and they depend on the particular combinations of neutron and proton numbers. Effect of deformation on the shell structure is found to be marginal.

Analysis of single-particle energies of the neutron states in the 64,66,68,70Zn isotopes within a mean field model with dispersive optical potential

2010 ◽  
Vol 74 (6) ◽  
pp. 850-853 ◽  
Author(s):  
O. V. Bespalova ◽  
I. N. Boboshin ◽  
V. V. Varlamov ◽  
T. A. Ermakova ◽  
B. S. Ishkhanov ◽  
...  
Keyword(s):  
Single Particle ◽  
Optical Potential ◽  
Field Model ◽  
Mean Field ◽  
Mean Field Model ◽  
Dispersive Optical Potential

Dynamic Mean-Field Model for the Mesoscale Morphologies of Liquid Crystalline Polymers

2001 ◽  
Vol 34 (23) ◽  
pp. 8378-8379 ◽  
Author(s):  
M. Hamm ◽  
G. Goldbeck-Wood ◽  
A. V. Zvelindovsky ◽  
G. J. A. Sevink ◽  
J. G. E. M. Fraaije
Keyword(s):  
Liquid Crystalline ◽  
Field Model ◽  
Mean Field ◽  
Liquid Crystalline Polymers ◽  
Mean Field Model ◽  
Crystalline Polymers

Bifurcation Analysis of a Mean-Field Model for Biaxial Nematics

2010 ◽  
Vol 525 (1) ◽  
pp. 29-40 ◽  
Author(s):  
Fulvio Bisi
Keyword(s):  
Bifurcation Analysis ◽  
Field Model ◽  
Mean Field ◽  
Mean Field Model ◽  
Biaxial Nematics
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