17 research outputs found
Rotation-limited growth of three dimensional body-centered cubic crystals
According to classical grain growth laws, grain growth is driven by the
minimization of surface energy and will continue until a single grain prevails.
These laws do not take into account the lattice anisotropy and the details of
the microscopic rearrangement of mass between grains. Here we consider
coarsening of body-centered cubic polycrystalline materials in three dimensions
using the phase field crystal model. We observe as function of the quenching
depth, a cross over between a state where grain rotation halts and the growth
stagnates and a state where grains coarsen rapidly by coalescence through
rotation and alignment of the lattices of neighboring grains. We show that the
grain rotation per volume change of a grain follows a power law with an
exponent of . The scaling exponent is consistent with theoretical
considerations based on the conservation of dislocations
Intermittent dislocation density fluctuations in crystal plasticity from a phase-field crystal model
Plastic deformation mediated by collective dislocation dynamics is
investigated in the two-dimensional phase-field crystal model of sheared single
crystals. We find that intermittent fluctuations in the dislocation population
number accompany bursts in the plastic strain-rate fluctuations. Dislocation
number fluctuations exhibit a power-law spectral density at high
frequencies . The probability distribution of number fluctuations becomes
bimodal at low driving rates corresponding to a scenario where low density of
defects alternate at irregular times with high population of defects. We
propose a simple stochastic model of dislocation reaction kinetics that is able
to capture these statistical properties of the dislocation density fluctuations
as a function of shear rate
concrete: Targeted Estimation of Survival and Competing Risks in Continuous Time
This article introduces the R package concrete, which implements a recently
developed targeted maximum likelihood estimator (TMLE) for the cause-specific
absolute risks of time-to-event outcomes measured in continuous time.
Cross-validated Super Learner machine learning ensembles are used to estimate
propensity scores and conditional cause-specific hazards, which are then
targeted to produce robust and efficient plug-in estimates of the effects of
static or dynamic interventions on a binary treatment given at baseline
quantified as risk differences or risk ratios. Influence curve-based asymptotic
inference is provided for TMLE estimates and simultaneous confidence bands can
be computed for target estimands spanning multiple multiple times or events. In
this paper we review the one-step continuous-time TMLE methodology as it is
situated in an overarching causal inference workflow, describe its
implementation, and demonstrate the use of the package on the PBC dataset.Comment: 18 pages, 4 figures, submitted to the R Journa
Intermittent Dislocation Density Fluctuations in Crystal Plasticity from a Phase-Field Crystal Model
Short Term Blood Glucose Prediction based on Continuous Glucose Monitoring Data
Continuous Glucose Monitoring (CGM) has enabled important opportunities for
diabetes management. This study explores the use of CGM data as input for
digital decision support tools. We investigate how Recurrent Neural Networks
(RNNs) can be used for Short Term Blood Glucose (STBG) prediction and compare
the RNNs to conventional time-series forecasting using Autoregressive
Integrated Moving Average (ARIMA). A prediction horizon up to 90 min into the
future is considered. In this context, we evaluate both population-based and
patient-specific RNNs and contrast them to patient-specific ARIMA models and a
simple baseline predicting future observations as the last observed. We find
that the population-based RNN model is the best performing model across the
considered prediction horizons without the need of patient-specific data. This
demonstrates the potential of RNNs for STBG prediction in diabetes patients
towards detecting/mitigating severe events in the STBG, in particular
hypoglycemic events. However, further studies are needed in regards to the
robustness and practical use of the investigated STBG prediction models.Comment: Accepted to EMBC 202