66 research outputs found
A Theoretically Guaranteed Deep Optimization Framework for Robust Compressive Sensing MRI
Magnetic Resonance Imaging (MRI) is one of the most dynamic and safe imaging
techniques available for clinical applications. However, the rather slow speed
of MRI acquisitions limits the patient throughput and potential indi cations.
Compressive Sensing (CS) has proven to be an efficient technique for
accelerating MRI acquisition. The most widely used CS-MRI model, founded on the
premise of reconstructing an image from an incompletely filled k-space, leads
to an ill-posed inverse problem. In the past years, lots of efforts have been
made to efficiently optimize the CS-MRI model. Inspired by deep learning
techniques, some preliminary works have tried to incorporate deep architectures
into CS-MRI process. Unfortunately, the convergence issues (due to the
experience-based networks) and the robustness (i.e., lack real-world noise
modeling) of these deeply trained optimization methods are still missing. In
this work, we develop a new paradigm to integrate designed numerical solvers
and the data-driven architectures for CS-MRI. By introducing an optimal
condition checking mechanism, we can successfully prove the convergence of our
established deep CS-MRI optimization scheme. Furthermore, we explicitly
formulate the Rician noise distributions within our framework and obtain an
extended CS-MRI network to handle the real-world nosies in the MRI process.
Extensive experimental results verify that the proposed paradigm outperforms
the existing state-of-the-art techniques both in reconstruction accuracy and
efficiency as well as robustness to noises in real scene
Spin-glass ground state in a triangular-lattice compound YbZnGaO
We report on comprehensive results identifying the ground state of a
triangular-lattice structured YbZnGaO to be spin glass, including no
long-range magnetic order, prominent broad excitation continua, and absence of
magnetic thermal conductivity. More crucially, from the ultralow-temperature
a.c. susceptibility measurements, we unambiguously observe frequency-dependent
peaks around 0.1 K, indicating the spin-glass ground state. We suggest this
conclusion to hold also for its sister compound YbMgGaO, which is confirmed
by the observation of spin freezing at low temperatures. We consider disorder
and frustration to be the main driving force for the spin-glass phase.Comment: Version as accepted to PR
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