41 research outputs found
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Advances in Kriging-Based Autonomous X-Ray Scattering Experiments.
Autonomous experimentation is an emerging paradigm for scientific discovery, wherein measurement instruments are augmented with decision-making algorithms, allowing them to autonomously explore parameter spaces of interest. We have recently demonstrated a generalized approach to autonomous experimental control, based on generating a surrogate model to interpolate experimental data, and a corresponding uncertainty model, which are computed using a Gaussian process regression known as ordinary Kriging (OK). We demonstrated the successful application of this method to exploring materials science problems using x-ray scattering measurements at a synchrotron beamline. Here, we report several improvements to this methodology that overcome limitations of traditional Kriging methods. The variogram underlying OK is global and thus insensitive to local data variation. We augment the Kriging variance with model-based measures, for instance providing local sensitivity by including the gradient of the surrogate model. As with most statistical regression methods, OK minimizes the number of measurements required to achieve a particular model quality. However, in practice this may not be the most stringent experimental constraint; e.g. the goal may instead be to minimize experiment duration or material usage. We define an adaptive cost function, allowing the autonomous method to balance information gain against measured experimental cost. We provide synthetic and experimental demonstrations, validating that this improved algorithm yields more efficient autonomous data collection
Autonomous Materials Discovery Driven by Gaussian Process Regression with Inhomogeneous Measurement Noise and Anisotropic Kernels
A majority of experimental disciplines face the challenge of exploring large
and high-dimensional parameter spaces in search of new scientific discoveries.
Materials science is no exception; the wide variety of synthesis, processing,
and environmental conditions that influence material properties gives rise to
particularly vast parameter spaces. Recent advances have led to an increase in
efficiency of materials discovery by increasingly automating the exploration
processes. Methods for autonomous experimentation have become more
sophisticated recently, allowing for multi-dimensional parameter spaces to be
explored efficiently and with minimal human intervention, thereby liberating
the scientists to focus on interpretations and big-picture decisions. Gaussian
process regression (GPR) techniques have emerged as the method of choice for
steering many classes of experiments. We have recently demonstrated the
positive impact of GPR-driven decision-making algorithms on autonomously
steering experiments at a synchrotron beamline. However, due to the complexity
of the experiments, GPR often cannot be used in its most basic form, but rather
has to be tuned to account for the special requirements of the experiments. Two
requirements seem to be of particular importance, namely inhomogeneous
measurement noise (input dependent or non-i.i.d.) and anisotropic kernel
functions, which are the two concepts that we tackle in this paper. Our
synthetic and experimental tests demonstrate the importance of both concepts
for experiments in materials science and the benefits that result from
including them in the autonomous decision-making process
Autonomous Investigations over WS and Au{111} with Scanning Probe Microscopy
Individual atomic defects in 2D materials impact their macroscopic
functionality. Correlating the interplay is challenging, however, intelligent
hyperspectral scanning tunneling spectroscopy (STS) mapping provides a feasible
solution to this technically difficult and time consuming problem. Here, dense
spectroscopic volume is collected autonomously via Gaussian process regression,
where convolutional neural networks are used in tandem for spectral
identification. Acquired data enable defect segmentation, and a workflow is
provided for machine-driven decision making during experimentation with
capability for user customization. We provide a means towards autonomous
experimentation for the benefit of both enhanced reproducibility and
user-accessibility. Hyperspectral investigations on WS sulfur vacancy sites
are explored, which is combined with local density of states confirmation on
the Au{111} herringbone reconstruction. Chalcogen vacancies, pristine WS,
Au face-centered cubic, and Au hexagonal close packed regions are examined and
detected by machine learning methods to demonstrate the potential of artificial
intelligence for hyperspectral STS mapping.Comment: Updates from final journal publicatio
Risk factors for the onset and persistence of neck pain in undergraduate students: 1-year prospective cohort study
<p>Abstract</p> <p>Background</p> <p>Although neck pain is common in young adulthood, studies on predictive factors for its onset and persistence are scarce. It is therefore important to identify possible risk factors among young adults so as to prevent the development of neck pain later in life.</p> <p>Methods</p> <p>A prospective study was carried out in healthy undergraduate students. At baseline, a self-administered questionnaire and standardized physical examination were used to collect data on biopsychosocial factors. At 3, 6, 9, and 12 months thereafter, follow-up data were collected on the incidence of neck pain. Those who reported neck pain on ≥ 2 consecutive follow-ups were categorized as having persistent neck pain. Two regression models were built to analyze risk factors for the onset and persistence of neck pain.</p> <p>Results</p> <p>Among the recruited sample of 684 students, 46% reported the onset of neck pain between baseline and 1-year follow-up, of whom 33% reported persistent neck pain. The onset of neck pain was associated with computer screen position not being level with the eyes and mouse position being self-rated as suitable. Factors that predicted persistence of neck pain were position of the keyboard being too high, use of computer for entertainment < 70% of total computer usage time, and students being in the second year of their studies.</p> <p>Conclusion</p> <p>Neck pain is quite common among undergraduate students. This study found very few proposed risk factors that predicted onset and persistence of neck pain. The future health of undergraduate students deserves consideration. However, there is still much uncertainty about factors leading to neck pain and more research is needed on this topic.</p