35,259 research outputs found
Data-driven Design of Engineering Processes with COREPROModeler
Enterprises increasingly demand IT support for the coordination of their engineering processes, which often consist of hundreds up to thousands of sub-processes. From a technical viewpoint, these sub-processes have to be concurrently executed and synchronized considering numerous interdependencies.
So far, this coordination has mainly been accomplished manually, which has resulted in errors and inconsistencies. In order to deal with this problem, we have to better understand the interdependencies between the subprocesses to be coordinated. In particular, we can benefit from the fact that sub-processes are often correlated to the assembly of a product (represented by a product data structure). This information can be utilized for the modeling and execution of so-called data-driven process structures. In this paper, we present the COREPRO demonstrator that supports the data-driven modeling of these process structures. The approach explicitly establishes a close linkage between product data structures and engineering processes
Generalized Parton Distributions of ^3He
A realistic microscopic calculation of the unpolarized quark Generalized
Parton Distribution (GPD) of the nucleus is presented. In
Impulse Approximation, is obtained as a convolution between the GPD of
the internal nucleon and the non-diagonal spectral function, describing
properly Fermi motion and binding effects. The proposed scheme is valid at low
values of , the momentum transfer to the target, the most relevant
kinematical region for the coherent channel of hard exclusive processes. The
obtained formula has the correct forward limit, corresponding to the standard
deep inelastic nuclear parton distributions, and first moment, giving the
charge form factor of . Nuclear effects, evaluated by a modern realistic
potential, are found to be larger than in the forward case. In particular, they
increase with increasing the momentum transfer when the asymmetry of the
process is kept fixed, and they increase with the asymmetry at fixed momentum
transfer. Another relevant feature of the obtained results is that the nuclear
GPD cannot be factorized into a -dependent and a
-independent term, as suggested in prescriptions proposed for finite
nuclei. The size of nuclear effects reaches 8 % even in the most important part
of the kinematical range under scrutiny. The relevance of the obtained results
to study the feasibility of experiments is addressed.Comment: 23 pages, 8 figures; Discussion in section II enlarged; discussion in
section IV shortened. Final version accepted by Phys. Rev.
Future dynamics in f(R) theories
The gravity theories provide an alternative way to explain the current
cosmic acceleration without invoking dark energy matter component. However, the
freedom in the choice of the functional forms of gives rise to the
problem of how to constrain and break the degeneracy among these gravity
theories on theoretical and/or observational grounds. In this paper to proceed
further with the investigation on the potentialities, difficulties and
limitations of gravity, we examine the question as to whether the future
dynamics can be used to break the degeneracy between gravity theories by
investigating the future dynamics of spatially homogeneous and isotropic dust
flat models in two gravity theories, namely the well known gravity and another by A. Aviles et al., whose motivation comes
from the cosmographic approach to gravity. To this end we perform a
detailed numerical study of the future dynamic of these flat model in these
theories taking into account the recent constraints on the cosmological
parameters made by the Planck team. We show that besides being powerful for
discriminating between gravity theories, the future dynamics technique
can also be used to determine the fate of the Universe in the framework of
these gravity theories. Moreover, there emerges from our numerical
analysis that if we do not invoke a dark energy component with
equation-of-state parameter one still has dust flat FLRW solution
with a big rip, if gravity deviates from general relativity via . We also show that FLRW dust solutions with do not
necessarily lead to singularity.Comment: 12 pages, 8 figures. V2: Generality and implications of the results
are emphasized, connection with the recent literature improved, typos
corrected, references adde
Systematic Mapping of the Hubbard Model to the Generalized t-J Model
The generalized t-J model conserving the number of double occupancies is
constructed from the Hubbard model at and in the vicinity of half-filling at
strong coupling. The construction is realized by a self-similar continuous
unitary transformation. The flow equation is closed by a truncation scheme
based on the spatial range of processes. We analyze the conditions under which
the t-J model can be set up and we find that it can only be defined for
sufficiently large interaction. There, the parameters of the effective model
are determined.Comment: 16 pages, 13 figures included. v2: Order of sections changed.
Calculation and discussion of apparent gap in Section IV.A correcte
Prewetting transition on a weakly disordered substrate : evidence for a creeping film dynamics
We present the first microscopic images of the prewetting transition of a
liquid film on a solid surface. Pictures of the local coverage map of a helium
film on a cesium metal surface are taken while the temperature is raised
through the transition. The film edge is found to advance at constant
temperature by successive avalanches in a creep motion with a macroscopic
correlation length. The creep velocity varies strongly in a narrow temperature
range. The retreat motion is obtained only at much lower temperature,
conforming to the strong hysteresis observed for prewetting transition on a
disordered surface. Prewetting transition on such disordered surfaces appears
to give rise to dynamical phenomena similar to what is observed for domain wall
motions in 2D magnets.Comment: 7 pages, 3 figures, to be published in Euro.Phys.Let
Survival of branching random walks in random environment
We study survival of nearest-neighbour branching random walks in random
environment (BRWRE) on . A priori there are three different
regimes of survival: global survival, local survival, and strong local
survival. We show that local and strong local survival regimes coincide for
BRWRE and that they can be characterized with the spectral radius of the first
moment matrix of the process. These results are generalizations of the
classification of BRWRE in recurrent and transient regimes. Our main result is
a characterization of global survival that is given in terms of Lyapunov
exponents of an infinite product of i.i.d. random matrices.Comment: 17 pages; to appear in Journal of Theoretical Probabilit
Intrinsic profiles and capillary waves at homopolymer interfaces: a Monte Carlo study
A popular concept which describes the structure of polymer interfaces by
``intrinsic profiles'' centered around a two dimensional surface, the ``local
interface position'', is tested by extensive Monte Carlo simulations of
interfaces between demixed homopolymer phases in symmetric binary (AB)
homopolymer blends, using the bond fluctuation model. The simulations are done
in an LxLxD geometry. The interface is forced to run parallel to the LxL planes
by imposing periodic boundary conditions in these directions and fixed boundary
conditions in the D direction, with one side favoring A and the other side
favoring B. Intrinsic profiles are calculated as a function of the ``coarse
graining length'' B by splitting the system into columns of size BxBxD and
averaging in each column over profiles relative to the local interface
position. The results are compared to predictions of the self-consistent field
theory. It is shown that the coarse graining length can be chosen such that the
interfacial width matches that of the self-consistent field profiles, and that
for this choice of B the ``intrinsic'' profiles compare well with the
theoretical predictions.Comment: to appear in Phys. Rev.
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