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Abstract Phase diagrams offer substantial predictive power for materials synthesis by identifying the stability regions of target phases. However, thermodynamic phase diagrams do not offer explicit information regarding the kinetic competitiveness of undesired by-product phases. Here we propose a quantitative and computable thermodynamic metric to identify synthesis conditions under which the propensity to form kinetically competing by-products is minimized. We hypothesize that thermodynamic competition is minimized when the difference in free energy between a target phase and the minimal energy of all other competing phases is maximized. We validate this hypothesis for aqueous materials synthesis through two empirical approaches: first, by analysing 331 aqueous synthesis recipes text-mined from the literature; and second, by systematic experimental synthesis of LiIn(IO 3 ) 4 and LiFePO 4 across a wide range of aqueous electrochemical conditions. Our results show that even for synthesis conditions that are within the stability region of a thermodynamic Pourbaix diagram, phase-pure synthesis occurs only when thermodynamic competition with undesired phases is minimized.
Detection and pose estimation of people in images are challenging tasks due to variations in articulation, viewpoint and appearance. Part detectors are a natural way to attack this problem, but identifying good parts remains an open question. Anatomical parts, such as arms and legs, are difficult to detect reliably because parallel lines are common in natural images. In contrast, a visual conjunction such as “half of a frontal face and a left shoulder” may be a perfectly good discriminative visual pattern. Bourdev and Malik [ICCV 2009] introduced new parts, called poselets, which correspond to such discriminative visual patterns. There is a wide variety of poselets – a frontal face, a profile face, a head-and-shoulder configuration, etc. We discover them by choosing a random seed patch from the image of a random person in the training set and finding the “corresponding” patches in images of other people. A corresponding patch is defined as one that has the same spatial configuration of semantic keypoints (such as joints, eyes, nose) as the seed patch. We discriminatively train detectors for these patches. To find people in a test image, we evaluate the poselet detectors at multiple locations and scales and cluster the activations into person hypotheses. The activations within each cluster form a distributed representation of the pose of a person and provide the basis for numerous high-level vision tasks. Our system is the current best performer on the task of people detection and segmentation. We are able to infer attributes (the gender, style of hair, clothes, presence of glasses, hat, etc.) and actions (phoning, running, walking, reading a book, etc.) of people under arbitrary viewpoints and articulations. These ideas extend naturally to other visual categories. Interestingly, receptive fields of neurons in inferotemporal cortex have a variety consistent with that predicted by our model.
The electrochemical reduction of CO 2 (CO 2 R) to value-added products is an attractive technology for tackling the rising atmospheric CO 2 levels and storing intermittent renewable energy into chemical bonds. Fundamental understanding of CO 2 R has progressed significantly in recent years and is critical in the development of industrial scale CO 2 R electrolyzers. 1 However, most of our understanding has been drawn from experiments optimized for aqueous-phase CO 2 R systems. These systems can be limited by mass transfer at fairly low current densities (~10 mA cm -2 ) due to unfavorable CO 2 /OH - interactions and large diffusion lengths. 2 To achieve commercially-relevant CO 2 R rates (> 100 mA cm -2 ), gas-diffusion electrodes (GDEs) play an important role as they can decrease the diffusion length of CO 2 to as small as 10 nm. 3 The thin diffusion boundary layers in GDEs allow higher CO 2 R current densities and CO 2 R to occur under environments with higher OH - concentrations. 4 However, with such drastic changes in operating condition and local environment, it is necessary to explore and better understand the transport and reaction overpotential intricacies in GDEs. For instance, conventional cell designs optimized for planar electrodes will suffer from large ohmic drops across the cell due to the higher current density; product distribution will also vary arising from higher CO 2 and OH - concentrations near the catalyst. 5 In this talk, we present a multiphysics modelling framework to design and optimize GDE systems performing CO 2 R. We then explore the performance and limitations of various cell designs guided by simulation results and examine potential methods for improving water management and tuning catalyst selectivity. Finally, we discuss the disparities in local environments between aqueous and GDE devices and propose strategies to reduce the gap in knowledge between the two systems. Acknowledgements This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993. We thank David Larson for providing experimental data for CO 2 reduction on membrane-electrode assembly devices. D. Raciti and C. Wang, ACS Energy Lett. , 2018, 3 , 1545-1556. T. Burdyny and W. A. Smith, Energy Environ. Sci. , 2019, DOI: 10.1039/c8ee03134g. L. C. Weng, A. T. Bell and A. Z. Weber, Phys. Chem. Chem. Phys. , 2018, 20 , 16973-16984. S. Verma, X. Lu, S. Ma, R. I. Masel and P. J. Kenis, Phys. Chem. Chem. Phys. , 2016, 18 , 7075-7084. C. T. Dinh, T. Burdyny, M. G. Kibria, A. Seifitokaldani, C. M. Gabardo, F. P. G. de Arquer, A. Kiani, J. P. Edwards, P. De Luna, O. S. Bushuyev, C. Q. Zou, R. Quintero-Bermudez, Y. J. Pang, D. Sinton and E. H. Sargent, Science , 2018, 360 , 783-787.
In this work, we show how to learn a visual walking policy that only uses a monocular RGB camera and proprioception. Since simulating RGB is hard, we necessarily have to learn vision in the real world. We start with a blind walking policy trained in simulation. This policy can traverse some terrains in the real world but often struggles since it lacks knowledge of the upcoming geometry. This can be resolved with the use of vision. We train a visual module in the real world to predict the upcoming terrain with our proposed algorithm Cross-Modal Supervision (CMS). CMS uses time-shifted proprioception to supervise vision and allows the policy to continually improve with more real-world experience. We evaluate our vision-based walking policy over a diverse set of terrains including stairs (up to 19cm high), slippery slopes (inclination of 35 degrees), curbs and tall steps (up to 20cm), and complex discrete terrains. We achieve this performance with less than 30 minutes of real-world data. Finally, we show that our policy can adapt to shifts in the visual field with a limited amount of real-world experience. Video results and code at https://antonilo.github.io/vision_locomotion/.
Réflexion sur le développement des émeutes urbaines dans le monde. Quel est le sens de ces violentes protestations, annoncent-elles la constitution de véritables ghettos urbains, comment ces révoltes s'inscrivent-elles dans l'évolution des sociétés avancées ? Autant de questions auxquelles l'auteur se propose de répondre.
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Summary The aim of the current study was to assess the development and stability of sleep problems from childhood to late adolescence. This was a longitudinal cohort study of 2026 children, who completed three comprehensive health surveys, at age 7–9, 11–13 and 16–19 years. Data on difficulties with initiating and/or maintaining sleep ( DIMS : assessed using a single item) and time in bed ( TIB ) were collected at all three waves, while insomnia assessed in line with the DSM ‐5 criteria and sleep duration were also assessed in the last wave. Negative binomial regression analyses were used to examine prospective associations. Sleep problems in 7–9‐year‐old children were found to persist into late adolescence for approximately one‐third of the participants, both with regard to DIMS and short TIB . Children having chronic DIMS at the first two waves had nearly twice the risk of fulfilling the DSM ‐5 criteria later for insomnia in late adolescence [adjusted relative risk RR : 1.91]. Short TIB at age 11–13 was also associated with increased risk of subsequent short sleep duration (adjusted RR : 1.32) and TIB (adjusted RR : 1.40). These findings have important implications for practitioners and families. Although the majority of children will outgrow their problems once they reach late adolescence, the results also demonstrate that sleep problems are likely to become chronic for one in every third child with a sleep problem early in life. Given the many negative consequences of insomnia in adulthood, these findings call for increased awareness of childhood sleep problems as a public health concern.
