135 research outputs found
On the convergence of a regularization scheme for approximating cavitation solutions with prescribed cavity volume size
Let , , be the region occupied by a hyperelastic body in its reference configuration. Let be the stored energy functional, and let be a flaw point in (i.e., a point of possible discontinuity for admissible deformations of the body). For V>0 fixed, let be a minimizer of among the set of discontinuous deformations constrained to form a hole of prescribed volume at and satisfying the homogeneous boundary data for . In this paper we describe a regularization scheme for the computation of both and and study its convergence properties. In particular, we show that as the regularization parameter goes to zero, (a subsequence) of the regularized constrained minimizers converge weakly in to a minimizer for any \delta>0. We obtain various sensitivity results for the dependence of the energies and Lagrange multipliers of the regularized constrained minimizers on the boundary data and on the volume parameter . We show that both the regularized constrained minimizers and satisfy suitable weak versions of the corresponding Euler--Lagrange equations. In addition we describe the main features of a numerical scheme for approximating and and give numerical examples for the case of a stored energy function of an elastic fluid and in the case of the incompressible limit
Infinite energy cavitating solutions: a variational approach
We study the phenomenon of cavitation for the displacement boundary value
problem of radial, isotropic compressible elasticity for a class of stored
energy functions of the form , where grows like
, and is the space dimension. In this case it follows (from a
result of Vodopyanov, Goldshtein and Reshetnyak) that discontinuous
deformations must have infinite energy. After characterizing the rate at which
this energy blows up, we introduce a modified energy functional which differs
from the original by a null lagrangian, and for which cavitating energy
minimizers with finite energy exist. In particular, the Euler--Lagrange
equations for the modified energy functional are identical to those for the
original problem except for the boundary condition at the inner cavity. This
new boundary condition states that a certain modified radial Cauchy stress
function has to vanish at the inner cavity. This condition corresponds to the
radial Cauchy stress for the original functional diverging to at the
cavity surface. Many previously known variational results for finite energy
cavitating solutions now follow for the modified functional, such as the
existence of radial energy minimizers, satisfaction of the Euler-Lagrange
equations for such minimizers, and the existence of a critical boundary
displacement for cavitation. We also discuss a numerical scheme for computing
these singular cavitating solutions using regular solutions for punctured
balls. We show the convergence of this numerical scheme and give some numerical
examples including one for the incompressible limit case. Our approach is
motivated in part by the use of the renormalized energy for Ginzberg-Landau
vortices.Comment: 23 pages, 4 figure
On the convergence of a regularization scheme for approximating cavitation solutions with prescribed cavity volume size
Controls on terrestrial carbon feedbacks by productivity versus turnover in the CMIP5 Earth System Models
PublishedJournal Article© Author(s) 2015. To better understand sources of uncertainty in projections of terrestrial carbon cycle feedbacks, we present an approach to separate the controls on modeled carbon changes. We separate carbon changes into four categories using a linearized, equilibrium approach: those arising from changed inputs (productivity-driven changes), and outputs (turnover-driven changes), of both the live and dead carbon pools. Using Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations for five models, we find that changes to the live pools are primarily explained by productivity-driven changes, with only one model showing large compensating changes to live carbon turnover times. For dead carbon pools, the situation is more complex as all models predict a large reduction in turnover times in response to increases in productivity. This response arises from the common representation of a broad spectrum of decomposition turnover times via a multi-pool approach, in which flux-weighted turnover times are faster than mass-weighted turnover times. This leads to a shift in the distribution of carbon among dead pools in response to changes in inputs, and therefore a transient but long-lived reduction in turnover times. Since this behavior, a reduction in inferred turnover times resulting from an increase in inputs, is superficially similar to priming processes, but occurring without the mechanisms responsible for priming, we call the phenomenon "false priming", and show that it masks much of the intrinsic changes to dead carbon turnover times as a result of changing climate. These patterns hold across the fully coupled, biogeochemically coupled, and radiatively coupled 1 % yr-1 increasing CO2 experiments. We disaggregate inter-model uncertainty in the globally integrated equilibrium carbon responses to initial turnover times, initial productivity, fractional changes in turnover, and fractional changes in productivity. For both the live and dead carbon pools, inter-model spread in carbon changes arising from initial conditions is dominated by model disagreement on turnover times, whereas inter-model spread in carbon changes from fractional changes to these terms is dominated by model disagreement on changes to productivity in response to both warming and CO2 fertilization. However, the lack of changing turnover time control on carbon responses, for both live and dead carbon pools, in response to the imposed forcings may arise from a common lack of process representation behind changing turnover times (e.g., allocation and mortality for live carbon; permafrost, microbial dynamics, and mineral stabilization for dead carbon), rather than a true estimate of the importance of these processes.This research was supported by the Director,
Office of Science, Office of Biological and Environmental
Research of the U.S. Department of Energy under Contract no.
DE-AC02-05CH11231 as part of their Regional and Global
Climate Modeling Program. We acknowledge the World Climate
Research Programmeâs Working Group on Coupled Modelling,
which is responsible for CMIP, and we thank the climate modeling
groups listed in Table 1 for producing and making available their
model output. For CMIP the U.S. Department of Energyâs Program
for Climate Model Diagnosis and Intercomparison provides coordinating
support and led development of software infrastructure in
partnership with the Global Organization for Earth System Science
Portals. CDJ was supported by the Joint UK DECC/Defra Met
Office Hadley Centre Climate Programme (GA01101)
The 3rd World Conference on Kisspeptin, Ăą Kisspeptin 2017: Brain and BeyondĂą : Unresolved questions, challenges and future directions for the field
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/144298/1/jne12600-sup-0001-FigS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144298/2/jne12600-sup-0002-FigS2.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144298/3/jne12600_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144298/4/jne12600.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144298/5/jne12600-sup-0003-FigS3.pd
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