185 research outputs found
Compact Supercell Method Based on Opposite Parity for Bragg Fibers
The supercell- based orthonormal basis method is proposed to investigate the modal properties of the Bragg fibers. A square lattice is constructed by the whole Bragg fiber which is considered a supercell, and the periodical dielectric structure of the square lattice is decomposed using periodic functions (cosine). The modal electric field is expanded as the sum of the orthonormal set of Hermite-Gaussian basis functions based on the opposite parity of the transverse electric field. The propagation characteristics of Bragg fibers can be obtained after recasting the wave equation into an eigenvalue system. This method is implemented with very high efficiency and accuracy
Deep Active Alignment of Knowledge Graph Entities and Schemata
Knowledge graphs (KGs) store rich facts about the real world. In this paper,
we study KG alignment, which aims to find alignment between not only entities
but also relations and classes in different KGs. Alignment at the entity level
can cross-fertilize alignment at the schema level. We propose a new KG
alignment approach, called DAAKG, based on deep learning and active learning.
With deep learning, it learns the embeddings of entities, relations and
classes, and jointly aligns them in a semi-supervised manner. With active
learning, it estimates how likely an entity, relation or class pair can be
inferred, and selects the best batch for human labeling. We design two
approximation algorithms for efficient solution to batch selection. Our
experiments on benchmark datasets show the superior accuracy and generalization
of DAAKG and validate the effectiveness of all its modules.Comment: Accepted in the ACM SIGMOD/PODS International Conference on
Management of Data (SIGMOD 2023
Near Isometric Biomass Partitioning in Forest Ecosystems of China
Based on the isometric hypothesis, belowground plant biomass (MB) should scale isometrically with aboveground biomass (MA) and the scaling exponent should not vary with environmental factors. We tested this hypothesis using a large forest biomass database collected in China. Allometric scaling functions relating MB and MA were developed for the entire database and for different groups based on tree age, diameter at breast height, height, latitude, longitude or elevation. To investigate whether the scaling exponent is independent of these biotic and abiotic factors, we analyzed the relationship between the scaling exponent and these factors. Overall MB was significantly related to MA with a scaling exponent of 0.964. The scaling exponent of the allometric function did not vary with tree age, density, latitude, or longitude, but varied with diameter at breast height, height, and elevation. The mean of the scaling exponent over all groups was 0.986. Among 57 scaling relationships developed, 26 of the scaling exponents were not significantly different from 1. Our results generally support the isometric hypothesis. MB scaled near isometrically with MA and the scaling exponent did not vary with tree age, density, latitude, or longitude, but increased with tree size and elevation. While fitting a single allometric scaling relationship may be adequate, the estimation of MB from MA could be improved with size-specific scaling relationships
Self-Organized Polynomial-Time Coordination Graphs
Coordination graph is a promising approach to model agent collaboration in
multi-agent reinforcement learning. It conducts a graph-based value
factorization and induces explicit coordination among agents to complete
complicated tasks. However, one critical challenge in this paradigm is the
complexity of greedy action selection with respect to the factorized values. It
refers to the decentralized constraint optimization problem (DCOP), which and
whose constant-ratio approximation are NP-hard problems. To bypass this
systematic hardness, this paper proposes a novel method, named Self-Organized
Polynomial-time Coordination Graphs (SOP-CG), which uses structured graph
classes to guarantee the accuracy and the computational efficiency of
collaborated action selection. SOP-CG employs dynamic graph topology to ensure
sufficient value function expressiveness. The graph selection is unified into
an end-to-end learning paradigm. In experiments, we show that our approach
learns succinct and well-adapted graph topologies, induces effective
coordination, and improves performance across a variety of cooperative
multi-agent tasks
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