973 research outputs found
An extended finite element method with smooth nodal stress
The enrichment formulation of double-interpolation finite element method
(DFEM) is developed in this paper. DFEM is first proposed by Zheng \emph{et al}
(2011) and it requires two stages of interpolation to construct the trial
function. The first stage of interpolation is the same as the standard finite
element interpolation. Then the interpolation is reproduced by an additional
procedure using the nodal values and nodal gradients which are derived from the
first stage as interpolants. The re-constructed trial functions are now able to
produce continuous nodal gradients, smooth nodal stress without post-processing
and higher order basis without increasing the total degrees of freedom. Several
benchmark numerical examples are performed to investigate accuracy and
efficiency of DFEM and enriched DFEM. When compared with standard FEM,
super-convergence rate and better accuracy are obtained by DFEM. For the
numerical simulation of crack propagation, better accuracy is obtained in the
evaluation of displacement norm, energy norm and the stress intensity factor
Egg production response of sex-linked albino (sa1) and colored (S) hens to high and low light intensities during brooding-rearing
International audienc
Leptonic secondary emission in a hadronic microquasar model
Context: It has been proposed that the origin of the very high-energy photons
emitted from high-mass X-ray binaries with jet-like features, so-called
microquasars (MQs), is related to hadronic interactions between relativistic
protons in the jet and cold protons of the stellar wind. Leptonic secondary
emission should be calculated in a complete hadronic model that include the
effects of pairs from charged pion decays inside the jets and the emission from
pairs generated by gamma-ray absorption in the photosphere of the system. Aims:
We aim at predicting the broadband spectrum from a general hadronic microquasar
model, taking into account the emission from secondaries created by charged
pion decay inside the jet. Methods: The particle energy distribution for
secondary leptons injected along the jets is consistently derived taking the
energy losses into account. We also compute the spectral energy distribution
resulting from these leptons is calculated after assuming different values of
the magnetic field inside the jets. The spectrum of the gamma-rays produced by
neutral pion-decay and processed by electromagnetic cascades under the stellar
photon field. Results: We show that the secondary emission can dominate the
spectral energy distribution at low energies (~1 MeV). At high energies, the
production spectrum can be significantly distorted by the effect of
electromagnetic cascades. These effects are phase-dependent, and some
variability modulated by the orbital period is predicted.Comment: 8 pages, 5 figures. Accepted for publication in Astronomy &
Astrophysic
Constructing IGA-suitable planar parameterization from complex CAD boundary by domain partition and global/local optimization
In this paper, we propose a general framework for constructing IGA-suitable
planar B-spline parameterizations from given complex CAD boundaries consisting
of a set of B-spline curves. Instead of forming the computational domain by a
simple boundary, planar domains with high genus and more complex boundary
curves are considered. Firstly, some pre-processing operations including
B\'ezier extraction and subdivision are performed on each boundary curve in
order to generate a high-quality planar parameterization; then a robust planar
domain partition framework is proposed to construct high-quality patch-meshing
results with few singularities from the discrete boundary formed by connecting
the end points of the resulting boundary segments. After the topology
information generation of quadrilateral decomposition, the optimal placement of
interior B\'ezier curves corresponding to the interior edges of the
quadrangulation is constructed by a global optimization method to achieve a
patch-partition with high quality. Finally, after the imposition of
C1=G1-continuity constraints on the interface of neighboring B\'ezier patches
with respect to each quad in the quadrangulation, the high-quality B\'ezier
patch parameterization is obtained by a C1-constrained local optimization
method to achieve uniform and orthogonal iso-parametric structures while
keeping the continuity conditions between patches. The efficiency and
robustness of the proposed method are demonstrated by several examples which
are compared to results obtained by the skeleton-based parameterization
approach
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