8,102 research outputs found
Removing the cell resonance error in the multiscale finite element method via a Petrov-Galerkin formulation
We continue the study of the nonconforming multiscale finite element method (Ms- FEM) introduced in 17, 14 for second order elliptic equations with highly oscillatory coefficients. The main difficulty in MsFEM, as well as other numerical upscaling methods, is the scale resonance effect. It has been show that the leading order resonance error can be effectively removed by using an over-sampling technique. Nonetheless, there is still a secondary cell resonance error of O(Š^2/h^2). Here, we introduce a Petrov-Galerkin MsFEM formulation with nonconforming multiscale trial functions and linear test functions. We show that the cell resonance error is eliminated in this formulation and hence the convergence rate is greatly improved. Moreover, we show that a similar formulation can be used to enhance the convergence of an immersed-interface finite element method for elliptic interface problems
RELATIVE EFFECTIVENESS OF USDA'S NONPRICE EXPORT PROMOTION INSTRUMENTS
The USDA'Ćās Foreign Agricultural Service funds three types of activities to promote agricultural exports: consumer promotion, technical assistance, and trade servicing. These "instruments" are analyzed using an adaptation of Muth's model. Results indicate that consumer promotion always increases the derived demand for the U.S. agricultural commodity, but that under certain conditions technical assistance and trade servicing can have a perverse effect. Applying the model to cotton promotion in Japan, the results suggest that, owing to cotton's modest share of retail value, the current emphasis on consumer promotion may be misplaced. Specifically, it appears that producer returns can be enhanced by emphasizing technical assistance projects that save on the marketing input.Agricultural and Food Policy, International Relations/Trade,
Role of quark-interchange processes in evolution of mesonic matter
We divide the cross section for a meson-meson reaction into three parts. The
first part is for the quark-interchange process, the second for quark-antiquark
annihilation processes and the third for resonant processes. Master rate
equations are established to yield time dependence of fugacities of pions,
rhos, kaons and vetor kaons. The equations include cross sections for inelastic
scattering of pions, rhos, kaons and vector kaons. Cross sections for
quark-interchange-induced reactions, that were obtained in a potential model,
are parametrized for convenient use. The number densities of pion and rho (kaon
and vector kaon) are altered by quark-interchange processes in equal magnitudes
but opposite signs. The master rate equations combined with the hydrodynamic
equations for longitudinal and transverse expansion are solved with many sets
of initial meson fugacities. Quark-interchange processes are shown to be
important in the contribution of the inelastic meson-meson scattering to
evolution of mesonic matter.Comment: 28 pages, 1 figure, 8 table
Neutron Density Distributions of Neutron-Rich Nuclei Studied with the Isobaric Yield Ratio Difference
The isobaric yield ratio difference (IBD) between two reactions of similar
experimental setups is found to be sensitive to nuclear density differences
between projectiles. In this article, the IBD probe is used to study the
density variation in neutron-rich Ca. By adjusting diffuseness in the
neutron density distribution, three different neutron density distributions of
Ca are obtained. The yields of fragments in the 80 MeV Ca
+ C reactions are calculated by using a modified statistical
abrasion-ablation model. It is found that the IBD results obtained from the
prefragments are sensitive to the density distribution of the projectile, while
the IBD results from the final fragments are less sensitive to the density
distribution of the projectile.Comment: 3 figure
Light-Cone Sum Rules Analysis of Weak Decays
In this work, we investigate the semi-leptonic weak decays of spin-1/2
doubly-heavy baryons into spin-3/2 singly-heavy baryons
within light-cone sum rules. Using the parallel
components of the light-cone distribution amplitudes of
, the transition form factors for these decays are
calculated both analytically and numerically. The numerical results for these
semi-leptonic weak decays widths and branching ratios are also predicted, which
are compared with the same predictions by other theoretical approaches in the
literatures. These phenomenology predictions can be tested by the experiments
in the future.Comment: 19 pages, 2 figures, 4 table
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