11,045 research outputs found
Orbiting valence quarks and their influence on the structure functions of the nucleon
It is shown that intrinsic orbital motion of the valence quarks has large
influences on the spin-dependent as well as the spin-averaged nucleon structure
functions. Its connection with the observed ``very small contribution of quark
spin to nucleon spin'' and the observed violation of Gottfried sum rule is
discussed.Comment: 10 pages (LaTeX) including 3 figure
Spin- and isospin-polarized states of nuclear matter in the Dirac-Brueckner-Hartree-Fock model
Spin-polarized isospin asymmetric nuclear matter is studied within the
Dirac-Brueckner-Hartree-Fock approach. After a brief review of the formalism,
we present and discuss the self-consistent single-particle potentials at
various levels of spin and isospin asymmetry. We then move to predictions of
the energy per particle, also under different conditions of isospin and spin
polarization. Comparison with the energy per particle in isospin symmetric or
asymmetric unpolarized nuclear matter shows no evidence for a phase transition
to a spin ordered state, neither ferromagnetic nor antiferromagnetic.Comment: 8 pages, 6 figure
Process model based development of disassembly tools
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.Disassembly processes require flexible tools for loosening and handling operations. Today, disassembly processes demand a great deal of manual labour and a vast variety of tools. Partly destructive tools which generate and use new acting surfaces are able to increase the economic viability owing to their flexibility and their promotion of the reuse of components. This article describes selected methods of acting surface generation and their application for prototypical tools.DFG, SFB 281, Demontagefabriken zur Rückgewinnung von Ressourcen in Produkt- und Materialkreisläufe
Influences of magnetic coupling process on the spectrum of a disk covered by the corona
Recently, much attention has been paid to the magnetic coupling (MC) process,
which is supported by very high emissivity indexes observed in Seyfert 1 galaxy
MCG-6-30-15 and GBHC XTE J1650-500. But the rotational energy transferred from
a black hole is simply assumed to be radiated away from the surrounding
accretion disk in black-body spectrum, which is obviously not consistent with
the observed hard power-law X-ray spectra. We intend to introduce corona into
the MC model to make it more compatible with the observations. We describe the
model and the procedure of a simplified Monte Carlo simulation, compare the
output spectra in the cases with and without the MC effects, and discuss the
influences of three parameters involved in the MC process on the output
spectra. It is shown that the MC process augments radiation fluxes in the UV or
X-ray band. The emergent spectrum is affected by the BH spin and magnetic field
strength at the BH horizon, while it is almost unaffected by the radial profile
of the magnetic field at the disk. Introducing corona into the MC model will
improve the fitting of the output spectra from AGNs and GBHCs.Comment: 15 pages, 5 figures, accepted by A&
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Modeling singular mineralization processes due to fluid pressure fluctuations
Mineralization in the Earth's crust can be regarded as a singular process resulting in large amounts of mass accumulation and element enrichment over short time or space scales. The elemental concentrations modeled by fractals and multifractals show self-similarity and scale-invariant properties. We take the view that fluid-pressure variations in response to earthquakes or fault rupture are primarily responsible for changes in solubility and trigger transient physical and chemical variations in ore-forming fluids that enhance the mineralization process. Based on this general concept, we investigated mineral precipitation processes driven by rapid fluid pressure reductions by coupling mineralization to a cellular automaton model to reveal the nonlinear mechanism of the orogenic gold mineralization process using simulation. In the model, fluid pressure can increase to the rock failure condition, which was set as lithostatic pressure at a depth of 10 km (270 MPa), due to either porosity reduction or dehydration reactions. Rapid drops in pressure resulting from fault rupture or local hydrofracture may induce repeated gold precipitation. The geochemical patterns generated by the model evolve from depletion to enrichment patterns, and from spatially random to spatially clustered structures quantified by multifractal models and geostatistics. Results show how metal elements self-organize to form high metal concentration patterns displaying self-similarity and scale-invariance. These transitions are attributed to the growth and coalescence of sub-networks with different fluid pressures up to the percolation threshold, resulting in a wide range of fluid pressure reductions and gold precipitation in the form of clusters. The results suggest that cyclic evolution of fluid pressure and its effects on gold precipitation systems can effectively mimic the repeated mineralization superposition process, and generate complex geochemical patterns characterized by a multifractal model. The nonlinear behavior exhibits scale-invariance and self-organized critical threshold, where mineral phase separations result from fluid pressure reductions associated with fault failure
Su(3) Algebraic Structure of the Cuprate Superconductors Model based on the Analogy with Atomic Nuclei
A cuprate superconductor model based on the analogy with atomic nuclei was
shown by Iachello to have an structure. The mean-field approximation
Hamiltonian can be written as a linear function of the generators of
algebra. Using algebraic method, we derive the eigenvalues of the reduced
Hamiltonian beyond the subalgebras and of
algebra. In particular, by considering the coherence between s- and d-wave
pairs as perturbation, the effects of coherent term upon the energy spectrum
are investigated
Lambda polarization in pp -> p\Lambda K^+ \pi^+\pi^-\pi^+\pi^-
We show that there is a correlation between the invariant mass of the
produced \Lambda K^+, \Lambda K^+\pi^+\pi^- or \Lambda K^+ \pi^+\pi^-\pi^+\pi^-
system in the exclusive reaction pp\to p\Lambda K^+\pi^+\pi^-\pi^+\pi^- and the
longitudinal or transverse momentum of . Together with the
longitudinal and transverse momentum dependence of Lambda polarization observed
in inclusive reactions, such a correlation implies a dependence of Lambda
polarization on these invariant masses. The qualitative features of this
dependence are consistent with the recent observation by E766 collaboration at
BNL. A quantitative estimation has been made using an event generator for
collisions. A detailed comparison with the data is made.Comment: 10 pages with 3 figures, submitted to J. Phys.
Effects of Marangoni numbers on thermocapillary drop migration: constant for quasi-steady state?
The overall {\it steady}-state energy balance with two phases in a flow
domain requires that the change in energy of the domain is equal to the
difference between the total energy entering the domain and that leaving the
domain. From the condition, the integral thermal flux across the surface is
studied for a {\it steady} thermocapillary drop migration in a flow field with
uniform temperature gradient at small and large Marangoni (Reynolds) numbers.
The drop is assumed to have only a slight axisymmetric deformation from a
sphere. It is identified that a conservative/nonconservative integral thermal
flux across the surface in the {\it steady} thermocapillary drop migration at
small/large Marangoni (Reynolds) numbers. The conservative flux confirms the
assumption of {\it quasi-steady} state in the thermocapillary drop migration at
small Marangoni (Reynolds) numbers. The nonconservative flux may well result
from the invalid assumption of {\it quasi-steady} state, which indicates that
the thermocapillary drop migration at large Marangoni (Reynolds) numbers cannot
reach {\it steady} state and is thus a {\it unsteady} process.Comment: 21 pages. arXiv admin note: text overlap with arXiv:1112.276
Azimuthal and single spin asymmetry in deep-inelastic lepton-nucleon scattering
We derive a general framework for describing semi-inclusive deep-inelastic
lepton-nucleon scattering in terms of the unintegrated parton distributions and
other higher twist parton correlations. Such a framework provides a consistent
approach to the calculation of inclusive and semi-inclusive cross sections
including higher twist effects. As an example, we calculate the azimuthal
asymmetries to the order of 1/Q in semi-inclusive process with transversely
polarized target. A non-vanishing single-spin asymmetry in the ``triggered
inclusive process'' is predicted to be 1/Q suppressed with a part of the
coefficient related to a moment of the Sivers function.Comment: 9 pages, 1 figur
Globally Polarized Quark-gluon Plasma in Non-central A+A Collisions
Produced partons have large local relative orbital angular momentum along the
direction opposite to the reaction plane in the early stage of non-central
heavy-ion collisions. Parton scattering is shown to polarize quarks along the
same direction due to spin-orbital coupling. Such global quark polarization
will lead to many observable consequences, such as left-right asymmetry of
hadron spectra, global transverse polarization of thermal photons, dileptons
and hadrons. Hadrons from the decay of polarized resonances will have azimuthal
asymmetry similar to the elliptic flow. Global hyperon polarization is
predicted within different hadronization scenarios and can be easily tested.Comment: 4 pages in RevTex with 2 postscript figures, an erratum is added to
the final published versio
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