72 research outputs found

    Extracting Geography From Datasets in Social Sciences

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    DualSMC: Tunneling Differentiable Filtering and Planning under Continuous POMDPs

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    A major difficulty of solving continuous POMDPs is to infer the multi-modal distribution of the unobserved true states and to make the planning algorithm dependent on the perceived uncertainty. We cast POMDP filtering and planning problems as two closely related Sequential Monte Carlo (SMC) processes, one over the real states and the other over the future optimal trajectories, and combine the merits of these two parts in a new model named the DualSMC network. In particular, we first introduce an adversarial particle filter that leverages the adversarial relationship between its internal components. Based on the filtering results, we then propose a planning algorithm that extends the previous SMC planning approach [Piche et al., 2018] to continuous POMDPs with an uncertainty-dependent policy. Crucially, not only can DualSMC handle complex observations such as image input but also it remains highly interpretable. It is shown to be effective in three continuous POMDP domains: the floor positioning domain, the 3D light-dark navigation domain, and a modified Reacher domain.Comment: IJCAI 202

    Dynamic Control of Particle Separation in Deterministic Lateral Displacement Separator with Viscoelastic Fluids

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    We proposed an innovative method to achieve dynamic control of particle separation by employing viscoelastic fluids in deterministic lateral displacement (DLD) arrays. The effects of shear-thinning and elasticity of working fluids on the critical separation size in DLD arrays are investigated. It is observed that each effect can lead to the variation of the critical separation size by approximately 40%. Since the elasticity strength of the fluid is related to the shear rate, the dynamic control can for the first time be easily realized through tuning the flow rate in microchannels

    Unconventional polarization switching mechanism in (Hf, Zr)O2 ferroelectrics

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    HfO2_{2}-based ferroelectric thin films are promising for their application in ferroelectric devices. Predicting the ultimate magnitude of polarization and understanding its switching mechanism are critical to realize the optimal performance of these devices. Here, a generalized solid-state variable cell nudged elastic band (VCNEB) method is employed to predict the switching pathway associated with domain-wall motion in (Hf, Zr)O2_{2} ferroelectrics. It is found that the polarization reversal pathway, where three-fold coordinated O atoms pass across the nominal unit-cell boundaries defined by the Hf/Zr atomic planes, is energetically more favorable than the conventional pathway where the O atoms do not pass through these planes. This finding implies that the polarization orientation in the orthorhombic Pca21_{1} phase of HfO2_{2} nd its derivatives is opposite to that normally assumed, predicts the spontaneous polarization magnitude of about 70 Ī¼{\mu}C/cm2^{2} that is nearly 50% larger than the commonly accepted value, signifies a positive intrinsic longitudinal piezoelectric coefficient, and suggests growth of ferroelectric domains, in response to an applied electric field, structurally reversed to those usually anticipated. These results provide important insights into the understanding of ferroelectricity in HfO2_{2}-based ferroelectrics.Comment: 34 pages, 28 figure

    HYL1 controls the miR156-mediated juvenile phase of vegetative growth

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    HYL1 is an important regulator of microRNA (miRNA) biogenesis. A loss-of-function mutation of HYL1 causes the reduced accumulation of some miRNAs but fails to display the miRNA-deficient phenotypes of these miRNAs. In Arabidopsis, miR156 mediates phase transition through repression of SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE (SPL) genes. However, it remains unknown whether, and if so how, HYL1 enables phase transition through miR156. This study showed that a loss-of-function mutation of the HYL1 gene caused defects in the timing of the juvenile phase. In the primary leaves of hyl1-2 mutants, abaxial trichomes were generated prematurely, the leaf blades elongated, and the blade base angles enlarged, as is observed for adult leaves. In hyl1-2 p35S::miR156a and hyl1-2 spl9-4 spl15-1 plants, increased accumulation of miR156a and repressed expression of the SPL genes were concomitant with a complete or partial rescue of the hyl1-2 phenotype in phase defects. In contrast, overexpression of the SPL9 gene in hyl1-2 mutants led to total disappearance of the juvenile phase. Moreover, HYL1 prevented the premature accumulation of adult-related transcripts in the primary leaves. Taken together, these results suggest that HYL1 controls the expression levels of miR156-targeted SPL genes and enables plants to undergo the juvenile phase, an important and critical step during plant development to ensure maximum growth and productivity

    Charge redistribution and local lattice structure of (F, Zn)-codoped LaFeAsO superconductor

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    To understand the abnormal behavior of the superconducting transition temperature (T-c) because of the presence of a non-magnetic Zn impurity in the (F, Zn)-codoped LaFeAsO system (Li et al 2010 New J. Phys. 12 083008), we investigated its unique electronic and local structures via x-ray absorption spectroscopy and first-principles calculations. The data obtained showed that the presence of a Zn impurity induces an electron transfer from As to Fe atoms in both the F-underdoped and -overdoped regions. Moreover, due to the lattice mismatch, the local lattice structure is finely modulated by both F and Zn impurities. Actually, in the F-underdoped region doping by Zn is associated with regular FeAs4 tetrahedra, while distorted FeAs4 tetrahedra occur in the F-overdoped region where superconductivity is significantly suppressed

    Classification and quantification of leaf curvature

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    Various mutants of Arabidopsis thaliana deficient in polarity, cell division, and auxin response are characterized by certain types of leaf curvature. However, comparison of curvature for clarification of gene function can be difficult without a quantitative measurement of curvature. Here, a novel method for classification and quantification of leaf curvature is reported. Twenty-two mutant alleles from Arabidopsis mutants and transgenic lines deficient in leaf flatness were selected. The mutants were classified according to the direction, axis, position, and extent of leaf curvature. Based on a global measure of whole leaves and a local measure of four regions in the leaves, the curvature index (CI) was proposed to quantify the leaf curvature. The CI values accounted for the direction, axis, position, and extent of leaf curvature in all of the Arabidopsis mutants grown in growth chambers. Comparison of CI values between mutants reveals the spatial and temporal variations of leaf curvature, indicating the strength of the mutant alleles and the activities of the corresponding genes. Using the curvature indices, the extent of curvature in a complicated genetic background becomes quantitative and comparable, thus providing a useful tool for defining the genetic components of leaf development and to breed new varieties with leaf curvature desirable for the efficient capture of sunlight for photosynthesis and high yields
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