29,719 research outputs found
From arteries to boreholes: Steady-state response of a poroelastic cylinder to fluid injection
The radially outward flow of fluid into a porous medium occurs in many
practical problems, from transport across vascular walls to the pressurisation
of boreholes. As the driving pressure becomes non-negligible relative to the
stiffness of the solid structure, the poromechanical coupling between the fluid
and the solid has an increasingly strong impact on the flow. For very large
pressures or very soft materials, as is the case for hydraulic fracturing and
arterial flows, this coupling can lead to large deformations and, hence, to
strong deviations from a classical, linear-poroelastic response. Here, we study
this problem by analysing the steady-state response of a poroelastic cylinder
to fluid injection. We consider the qualitative and quantitative impacts of
kinematic and constitutive nonlinearity, highlighting the strong impact of
deformation-dependent permeability. We show that the wall thickness (thick vs.
thin) and the outer boundary condition (free vs. constrained) play a central
role in controlling the mechanics
Proton recoil polarization in exclusive (e,e'pp) reactions
The general formalism of nucleon recoil polarization in the () reaction is given. Numerical predictions are presented for the
components of the outgoing proton polarization and of the polarization transfer
coefficient in the specific case of the exclusive O()C knockout reaction leading to discrete states in the residual
nucleus. Reaction calculations are performed in a direct knockout framework
where final-state interactions and one-body and two-body currents are included.
The two-nucleon overlap integrals are obtained from a calculation of the
two-proton spectral function of O where long-range and short-range
correlations are consistently included. The comparison of results obtained in
different kinematics confirms that resolution of different final states in the
O()C reaction may act as a filter to
disentangle and separately investigate the reaction processes due to
short-range correlations and two-body currents and indicates that measurements
of the components of the outgoing proton polarization may offer good
opportunities to study short-range correlations.Comment: 12 pages, 6 figure
Simplified Models for a First Characterization of New Physics at the LHC
Low-energy SUSY and several other theories that address the hierarchy problem
predict pair-production at the LHC of particles with Standard Model quantum
numbers that decay to jets, missing energy, and possibly leptons. If an excess
of such events is seen in LHC data, a theoretical framework in which to
describe it will be essential to constraining the structure of the new physics.
We propose a basis of four deliberately simplified models, each specified by
only 2-3 masses and 4-5 branching ratios, for use in a first characterization
of data. Fits of these simplified models to the data furnish a quantitative
presentation of the jet structure, electroweak decays, and heavy-flavor content
of the data, independent of detector effects. These fits, together with plots
comparing their predictions to distributions in data, can be used as targets
for describing the data within any full theoretical model.Comment: 76 pages, 24 figures, 9 table
Exclusive Electro-Disintegration of 3He at high Q2: II. Decay Function Formalism
Based on the theoretical framework of generalized eikonal approximation we
study the two-nucleon emission reactions in high electro-disintegration
of . Main aim is to investigate those features of the reaction which can
be unambiguously identified with the short range properties of the ground state
nuclear wave function. To evaluate the differential cross section we work in
the formalism of the decay function which characterizes the property of the
ground state wave function as well as the decay properties of final two nucleon
spectator system. Our main motivation here is to explore the accessibility of
two-- and three--nucleon short range correlations in He as well as to
isolate unambiguously single and double rescattering processes in the reaction
dynamics. Our analysis allowed us also to identify new approaches for
investigating the role of the practically unknown three-nucleon forces in the
ground state wave function of .Comment: 37 pages, 28 figure
On the NN-final-state-interaction in the reaction
The influence of the mutual interaction between the two outgoing nucleons
(NN-FSI) in the reaction has been investigated.
Results for various kinematics are discussed. In general, the effect of
NN-FSI depends on kinematics and the chosen final state in the excitation
spectrum of .Comment: 12 pages Revtex including 4 postscript figure
Representational task formats and problem solving strategies in kinematics and work
Previous studies have reported that students employed different problem solving approaches when presented with the same task structured with different representations. In this study, we explored and compared studentsâ strategies as they attempted tasks from two topical areas, kinematics and work. Our participants were 19 engineering students taking a calculus-based physics course. The tasks were presented in linguistic, graphical, and symbolic forms and requested either a qualitative solution or a value. The analysis was both qualitative and quantitative in nature focusing principally on the characteristics
of the strategies employed as well as the underlying reasoning for their applications. A comparison was also made for the same studentâs approach with the same kind of representation across the two topics.
Additionally, the participantsâ overall strategies across the different tasks, in each topic, were considered. On the whole, we found that the students prefer manipulating equations irrespective of the representational format of the task. They rarely recognized the applicability of a ââqualitativeââ approach to solve the
problem although they were aware of the concepts involved. Even when the students included visual representations in their solutions, they seldom used these representations in conjunction with the
mathematical part of the problem. Additionally, the students were not consistent in their approach for interpreting and solving problems with the same kind of representation across the two topical areas. The representational format, level of prior knowledge, and familiarity with a topic appeared to influence their
strategies, their written responses, and their ability to recognize qualitative ways to attempt a problem. The nature of the solution does not seem to impact the strategies employed to handle the problem
Representational task formats and problem solving strategies in kinematics and work
Previous studies have reported that students employed different problem solving approaches when presented with the same task structured with different representations. In this study, we explored and compared studentsâ strategies as they attempted tasks from two topical areas, kinematics and work. Our participants were 19 engineering students taking a calculus-based physics course. The tasks were presented in linguistic, graphical, and symbolic forms and requested either a qualitative solution or a value. The analysis was both qualitative and quantitative in nature focusing principally on the characteristics
of the strategies employed as well as the underlying reasoning for their applications. A comparison was also made for the same studentâs approach with the same kind of representation across the two topics.
Additionally, the participantsâ overall strategies across the different tasks, in each topic, were considered. On the whole, we found that the students prefer manipulating equations irrespective of the representational format of the task. They rarely recognized the applicability of a ââqualitativeââ approach to solve the
problem although they were aware of the concepts involved. Even when the students included visual representations in their solutions, they seldom used these representations in conjunction with the
mathematical part of the problem. Additionally, the students were not consistent in their approach for interpreting and solving problems with the same kind of representation across the two topical areas. The representational format, level of prior knowledge, and familiarity with a topic appeared to influence their
strategies, their written responses, and their ability to recognize qualitative ways to attempt a problem. The nature of the solution does not seem to impact the strategies employed to handle the problem
Spin-dependent correlations and the semi-exclusive ^{16}O(e,e'p) reaction
The effect of central, tensor and spin-isospin nucleon-nucleon correlations
upon semi-exclusive ^{16}O(e,e'p) reactions is studied for Q^2 and Bjorken x
values in the range and 0.15
x 2. The fully unfactorized calculations are performed in
a framework that accounts not only for the dynamical coupling of virtual
photons to correlated nucleon pairs but also for meson-exchange and
-isobar currents. Tensor correlations are observed to produce
substantially larger amounts of semi-exclusive ^{16}O(e,e'p) strength than
central correlations do and are predominantly manifest in the proton-neutron
knockout channel. With the exception of the case, in all
kinematical situations studied the meson-exchange and isobar currents are a
strong source of A(e,e'p) strength at deep missing energies. This feature gives
the A(e,e'p) strength at deep missing energies a pronounced transverse
character.Comment: 14 pages, 6 figure
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