1,156 research outputs found
Period Integrals of CY and General Type Complete Intersections
We develop a global Poincar\'e residue formula to study period integrals of
families of complex manifolds. For any compact complex manifold equipped
with a linear system of generically smooth CY hypersurfaces, the formula
expresses period integrals in terms of a canonical global meromorphic top form
on . Two important ingredients of our construction are the notion of a CY
principal bundle, and a classification of such rank one bundles. We also
generalize our construction to CY and general type complete intersections. When
is an algebraic manifold having a sufficiently large automorphism group
and is a linear representation of , we construct a holonomic D-module
that governs the period integrals. The construction is based in part on the
theory of tautological systems we have developed in the paper \cite{LSY1},
joint with R. Song. The approach allows us to explicitly describe a
Picard-Fuchs type system for complete intersection varieties of general types,
as well as CY, in any Fano variety, and in a homogeneous space in particular.
In addition, the approach provides a new perspective of old examples such as CY
complete intersections in a toric variety or partial flag variety.Comment: An erratum is included to correct Theorem 3.12 (Uniqueness of CY
structure
Randomizable phenology-dependent corn canopy for simulated remote sensing of agricultural scenes
Crop health assessment and yield prediction from multi-spectral remote sensing imagery are ongoing areas of interest in precision agriculture. It is in these contexts that simulation-based techniques are useful to investigate system parameters, perform preliminary experiments, etc., because remote sensing systems can be prohibitively expensive to design, deploy, and operate. However, such techniques require realistic and reliable models of the real world. We thus present a randomizable time-dependent model of corn (Zea mays L.) canopy, which is suitable for procedural generation of high-fidelity virtual corn fields at any time in the vegetative growth phase, with application to simulated remote sensing of agricultural scenes. This model unifies a physiological description of corn growth subject to environmental factors with a parametric description of corn canopy geometry, and prioritizes computational efficiency in the context of ray tracing for light transport simulation. We provide a reference implementation in C++, which includes a software plug-in for the 5th edition of the Digital Imaging and Remote Sensing Image Generation tool (DIRSIG5), in order to make simulation of agricultural scenes more readily accessible. For validation, we use our DIRSIG5 plug-in to simulate multi-spectral images of virtual corn plots that correspond to those of a United States Department of Agriculture (USDA) site at the Beltsville Agricultural Research Center (BARC), where reference data were collected in the summer of 2018. We show in particular that 1) the canopy geometry as a function of time is in agreement with field measurements, and 2) the radiance predicted by a DIRSIG5 simulation of the virtual corn plots is in agreement with radiance-calibrated imagery collected by a drone-mounted MicaSense RedEdge imaging system. We lastly remark that DIRSIG5 is able to simulate imagery directly as digital counts provided detailed knowledge of the detector array, e.g., quantum efficiency, read noise, and well capacity. That being the case, it is feasible to investigate the parameter space of a remote sensing system via âend-to-endâ simulation
The Decomposition Theorem and the topology of algebraic maps
We give a motivated introduction to the theory of perverse sheaves,
culminating in the Decomposition Theorem of Beilinson, Bernstein, Deligne and
Gabber. A goal of this survey is to show how the theory develops naturally from
classical constructions used in the study of topological properties of
algebraic varieties. While most proofs are omitted, we discuss several
approaches to the Decomposition Theorem, indicate some important applications
and examples.Comment: 117 pages. New title. Major structure changes. Final version of a
survey to appear in the Bulletin of the AM
SSR-2D: Semantic 3D Scene Reconstruction from 2D Images
Most deep learning approaches to comprehensive semantic modeling of 3D indoor
spaces require costly dense annotations in the 3D domain. In this work, we
explore a central 3D scene modeling task, namely, semantic scene reconstruction
without using any 3D annotations. The key idea of our approach is to design a
trainable model that employs both incomplete 3D reconstructions and their
corresponding source RGB-D images, fusing cross-domain features into volumetric
embeddings to predict complete 3D geometry, color, and semantics with only 2D
labeling which can be either manual or machine-generated. Our key technical
innovation is to leverage differentiable rendering of color and semantics to
bridge 2D observations and unknown 3D space, using the observed RGB images and
2D semantics as supervision, respectively. We additionally develop a learning
pipeline and corresponding method to enable learning from imperfect predicted
2D labels, which could be additionally acquired by synthesizing in an augmented
set of virtual training views complementing the original real captures,
enabling more efficient self-supervision loop for semantics. In this work, we
propose an end-to-end trainable solution jointly addressing geometry
completion, colorization, and semantic mapping from limited RGB-D images,
without relying on any 3D ground-truth information. Our method achieves
state-of-the-art performance of semantic scene reconstruction on two
large-scale benchmark datasets MatterPort3D and ScanNet, surpasses baselines
even with costly 3D annotations. To our knowledge, our method is also the first
2D-driven method addressing completion and semantic segmentation of real-world
3D scans
Learning Sequential Acquisition Policies for Robot-Assisted Feeding
A robot providing mealtime assistance must perform specialized maneuvers with
various utensils in order to pick up and feed a range of food items. Beyond
these dexterous low-level skills, an assistive robot must also plan these
strategies in sequence over a long horizon to clear a plate and complete a
meal. Previous methods in robot-assisted feeding introduce highly specialized
primitives for food handling without a means to compose them together.
Meanwhile, existing approaches to long-horizon manipulation lack the
flexibility to embed highly specialized primitives into their frameworks. We
propose Visual Action Planning OveR Sequences (VAPORS), a framework for
long-horizon food acquisition. VAPORS learns a policy for high-level action
selection by leveraging learned latent plate dynamics in simulation. To carry
out sequential plans in the real world, VAPORS delegates action execution to
visually parameterized primitives. We validate our approach on complex
real-world acquisition trials involving noodle acquisition and bimanual
scooping of jelly beans. Across 38 plates, VAPORS acquires much more
efficiently than baselines, generalizes across realistic plate variations such
as toppings and sauces, and qualitatively appeals to user feeding preferences
in a survey conducted across 49 individuals. Code, datasets, videos, and
supplementary materials can be found on our website:
https://sites.google.com/view/vaporsbot
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