824 research outputs found
A DISCRETE ELEMENT FORMALISM FOR MODELLING WEAR PARTICLE FORMATION IN CONTACT BETWEEN SLIDING METALS
The paper describes an advanced discrete-element based mechanical model, which allows modelling contact interaction of ductile materials with taking into account fracture and surface adhesion by the cold welding mechanism. The model describes these competitive processes from a unified standpoint and uses plastic work of deformation as a criterion of both local fracture and chemical bonding of surfaces in contact spots. Using this model, we carried out a preliminary study of the formation of wear particles and wedges during the friction of rough metal surfaces and the influence of the type of forming third body (interfacial) elements on the dynamics of the friction coefficient. The qualitative difference of friction dynamics in the areas of the contact zone characterized by different degrees of mechanical confinement is shown
Resonant Amplification of Electroweak Baryogenesis at Preheating
We explore viable scenarios for parametric resonant amplification of
electroweak (EW) gauge fields and Chern-Simons number during preheating,
leading to baryogenesis at the electroweak (EW) scale. In this class of
scenarios time-dependent classical EW gauge fields, essentially
spatially-homogeneous on the horizon scales, carry Chern-Simons number which
can be amplified by parametric resonance up to magnitudes at which unsuppressed
topological transitions in the Higgs sector become possible. Baryon number
non-conservation associated with the gauge sector and the highly
non-equilibrium nature of preheating allow for efficient baryogenesis. The
requisite large CP violation can arise either from the time dependence of a
slowly varying Higgs field (spontaneous baryogenesis), or from a resonant
amplification of CP violation induced in the gauge sector through loops. We
identify several CP violating operators in the Standard Model and its minimal
extensions that can facilitate efficient baryogenesis at preheating, and show
how to overcome would-be exponential suppression of baryogenesis associated
with tunneling barriers.Comment: 51 pages, 8 figues; minor corrections; references adde
GEOCHRONOLOGY AND SR-ND ISOTOPE GEOCHEMISTRY OF LATE PALEOZOIC COLLISIONAL GRANITOIDS OF UNDINSKY COMPLEX (EASTERN TRANSBAIKAL REGION)
There are several geodynamic models of the Central Asian Orogenic Belt (CAOB) development [Şengör et al., 1993, Zorin, 1999; Parfenov et al., 1999, 2003; Willem et al., 2012; and others]. The Mongol-Okhotsk Orogenic Belt (MOB) represents important part of CAOB. All geodymanic models of Late Riphean to Paleozoic structures of CAOB emphasize significance of subduction processes along Northern Asian craton margin at that time. Collage of CAOB terrains formed as a result of accretion of island arc, accretionary wedge, turbidite, and continental margin terrains to the Siberian paleocontinent.There are several geodynamic models of the Central Asian Orogenic Belt (CAOB) development [Şengör et al., 1993, Zorin, 1999; Parfenov et al., 1999, 2003; Willem et al., 2012; and others]. The Mongol-Okhotsk Orogenic Belt (MOB) represents important part of CAOB. All geodymanic models of Late Riphean to Paleozoic structures of CAOB emphasize significance of subduction processes along Northern Asian craton margin at that time. Collage of CAOB terrains formed as a result of accretion of island arc, accretionary wedge, turbidite, and continental margin terrains to the Siberian paleocontinent
Oscillation of linear ordinary differential equations: on a theorem by A. Grigoriev
We give a simplified proof and an improvement of a recent theorem by A.
Grigoriev, placing an upper bound for the number of roots of linear
combinations of solutions to systems of linear equations with polynomial or
rational coefficients.Comment: 16 page
Long-term operation of a multi-channel cosmic muon system based on scintillation counters with MRS APD light readout
A Cosmic Ray Test Facility (CRTF) is the first large-scale implementation of
a scintillation triggering system based on a new scintillation technique known
as START. In START, the scintillation light is collected and transported by WLS
optical fibers, while light detection is performed by pairs of avalanche
photodiodes with the Metal-Resistor-Semiconductor structure operated in the
Geiger mode (MRS APD). START delivers 100% efficiency of cosmic muon detection,
while its intrinsic noise level is less than 10^{-2} Hz. CRTF, consisting of
160 START channels, has been continuously operated by the ALICE TOF
collaboration for more than 25 000 hours, and has demonstrated a high level of
stability. Fewer than 10% of MRS APDs had to be replaced during this period.Comment: Proceedings of NDIP-2008. 8 pages, 8 figures, 6 reference
Soliton phase near antiferromagnetic quantum critical point in Q1D conductors
In the frameworks of a nesting model for Q1D organic conductor at the
antiferromagnetic (SDW) quantum critical point the first-order transition
separates metallic state from the soliton phase having the periodic domain
structure. The low temperature phase diagram also displays the 2nd-order
transition line between the soliton and the uniformly gapped SDW phases. The
results agree with the phase diagram of (TMTSF)PF near critical
pressure [T. Vuletic et al., Eur. Phys. J. B 25, 319 (2002)]. Detection of the
2nd-order transition line is discussed. We comment on superconductivity at
lowest temperature.Comment: 4 pages, 1 figur
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