15,757 research outputs found
Methods for detection and characterization of signals in noisy data with the Hilbert-Huang Transform
The Hilbert-Huang Transform is a novel, adaptive approach to time series
analysis that does not make assumptions about the data form. Its adaptive,
local character allows the decomposition of non-stationary signals with
hightime-frequency resolution but also renders it susceptible to degradation
from noise. We show that complementing the HHT with techniques such as
zero-phase filtering, kernel density estimation and Fourier analysis allows it
to be used effectively to detect and characterize signals with low signal to
noise ratio.Comment: submitted to PRD, 10 pages, 9 figures in colo
Cosmological Information Contents on the Light-Cone
We develop a theoretical framework to describe the cosmological observables
on the past light cone such as the luminosity distance, weak lensing, galaxy
clustering, and the cosmic microwave background anisotropies. We consider that
all the cosmological observables include not only the background quantity, but
also the perturbation quantity, and they are subject to cosmic variance, which
sets the fundamental limits on the cosmological information that can be derived
from such observables, even in an idealized survey with an infinite number of
observations. To quantify the maximum cosmological information content, we
apply the Fisher information matrix formalism and spherical harmonic analysis
to cosmological observations, in which the angular and the radial positions of
the observables on the light cone carry different information. We discuss the
maximum cosmological information that can be derived from five different
observables: (1) type Ia supernovae, (2) cosmic microwave background
anisotropies, (3) weak gravitational lensing, (4) local baryon density, and (5)
galaxy clustering. We compare our results with the cosmic variance obtained in
the standard approaches, which treat the light cone volume as a cubic box of
simultaneity. We discuss implications of our formalism and ways to overcome the
fundamental limit.Comment: 39 pages, no figures, submitted to JCA
A General Spatio-Temporal Clustering-Based Non-local Formulation for Multiscale Modeling of Compartmentalized Reservoirs
Representing the reservoir as a network of discrete compartments with
neighbor and non-neighbor connections is a fast, yet accurate method for
analyzing oil and gas reservoirs. Automatic and rapid detection of coarse-scale
compartments with distinct static and dynamic properties is an integral part of
such high-level reservoir analysis. In this work, we present a hybrid framework
specific to reservoir analysis for an automatic detection of clusters in space
using spatial and temporal field data, coupled with a physics-based multiscale
modeling approach. In this work a novel hybrid approach is presented in which
we couple a physics-based non-local modeling framework with data-driven
clustering techniques to provide a fast and accurate multiscale modeling of
compartmentalized reservoirs. This research also adds to the literature by
presenting a comprehensive work on spatio-temporal clustering for reservoir
studies applications that well considers the clustering complexities, the
intrinsic sparse and noisy nature of the data, and the interpretability of the
outcome.
Keywords: Artificial Intelligence; Machine Learning; Spatio-Temporal
Clustering; Physics-Based Data-Driven Formulation; Multiscale Modelin
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