1,028 research outputs found
Uncertainty Quantification of geochemical and mechanical compaction in layered sedimentary basins
In this work we propose an Uncertainty Quantification methodology for
sedimentary basins evolution under mechanical and geochemical compaction
processes, which we model as a coupled, time-dependent, non-linear,
monodimensional (depth-only) system of PDEs with uncertain parameters. While in
previous works (Formaggia et al. 2013, Porta et al., 2014) we assumed a
simplified depositional history with only one material, in this work we
consider multi-layered basins, in which each layer is characterized by a
different material, and hence by different properties. This setting requires
several improvements with respect to our earlier works, both concerning the
deterministic solver and the stochastic discretization. On the deterministic
side, we replace the previous fixed-point iterative solver with a more
efficient Newton solver at each step of the time-discretization. On the
stochastic side, the multi-layered structure gives rise to discontinuities in
the dependence of the state variables on the uncertain parameters, that need an
appropriate treatment for surrogate modeling techniques, such as sparse grids,
to be effective. We propose an innovative methodology to this end which relies
on a change of coordinate system to align the discontinuities of the target
function within the random parameter space. The reference coordinate system is
built upon exploiting physical features of the problem at hand. We employ the
locations of material interfaces, which display a smooth dependence on the
random parameters and are therefore amenable to sparse grid polynomial
approximations. We showcase the capabilities of our numerical methodologies
through two synthetic test cases. In particular, we show that our methodology
reproduces with high accuracy multi-modal probability density functions
displayed by target state variables (e.g., porosity).Comment: 25 pages, 30 figure
GridFormer: Towards Accurate Table Structure Recognition via Grid Prediction
All tables can be represented as grids. Based on this observation, we propose
GridFormer, a novel approach for interpreting unconstrained table structures by
predicting the vertex and edge of a grid. First, we propose a flexible table
representation in the form of an MXN grid. In this representation, the vertexes
and edges of the grid store the localization and adjacency information of the
table. Then, we introduce a DETR-style table structure recognizer to
efficiently predict this multi-objective information of the grid in a single
shot. Specifically, given a set of learned row and column queries, the
recognizer directly outputs the vertexes and edges information of the
corresponding rows and columns. Extensive experiments on five challenging
benchmarks which include wired, wireless, multi-merge-cell, oriented, and
distorted tables demonstrate the competitive performance of our model over
other methods.Comment: ACMMM202
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
We present observations of 10 type Ia supernovae (SNe Ia) between 0.16 < z <
0.62. With previous data from our High-Z Supernova Search Team, this expanded
set of 16 high-redshift supernovae and 34 nearby supernovae are used to place
constraints on the Hubble constant (H_0), the mass density (Omega_M), the
cosmological constant (Omega_Lambda), the deceleration parameter (q_0), and the
dynamical age of the Universe (t_0). The distances of the high-redshift SNe Ia
are, on average, 10% to 15% farther than expected in a low mass density
(Omega_M=0.2) Universe without a cosmological constant. Different light curve
fitting methods, SN Ia subsamples, and prior constraints unanimously favor
eternally expanding models with positive cosmological constant (i.e.,
Omega_Lambda > 0) and a current acceleration of the expansion (i.e., q_0 < 0).
With no prior constraint on mass density other than Omega_M > 0, the
spectroscopically confirmed SNe Ia are consistent with q_0 <0 at the 2.8 sigma
and 3.9 sigma confidence levels, and with Omega_Lambda >0 at the 3.0 sigma and
4.0 sigma confidence levels, for two fitting methods respectively. Fixing a
``minimal'' mass density, Omega_M=0.2, results in the weakest detection,
Omega_Lambda>0 at the 3.0 sigma confidence level. For a flat-Universe prior
(Omega_M+Omega_Lambda=1), the spectroscopically confirmed SNe Ia require
Omega_Lambda >0 at 7 sigma and 9 sigma level for the two fitting methods. A
Universe closed by ordinary matter (i.e., Omega_M=1) is ruled out at the 7
sigma to 8 sigma level. We estimate the size of systematic errors, including
evolution, extinction, sample selection bias, local flows, gravitational
lensing, and sample contamination. Presently, none of these effects reconciles
the data with Omega_Lambda=0 and q_0 > 0.Comment: 36 pages, 13 figures, 3 table files Accepted to the Astronomical
Journa
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