373 research outputs found
Collectively Simplifying Trajectories in a Database: A Query Accuracy Driven Approach
Increasing and massive volumes of trajectory data are being accumulated that
may serve a variety of applications, such as mining popular routes or
identifying ridesharing candidates. As storing and querying massive trajectory
data is costly, trajectory simplification techniques have been introduced that
intuitively aim to reduce the sizes of trajectories, thus reducing storage and
speeding up querying, while preserving as much information as possible.
Existing techniques rely mainly on hand-crafted error measures when deciding
which point to drop when simplifying a trajectory. While the hope may be that
such simplification affects the subsequent usability of the data only
minimally, the usability of the simplified data remains largely unexplored.
Instead of using error measures that indirectly may to some extent yield
simplified trajectories with high usability, we adopt a direct approach to
simplification and present the first study of query accuracy driven trajectory
simplification, where the direct objective is to achieve a simplified
trajectory database that preserves the query accuracy of the original database
as much as possible. Specifically, we propose a multi-agent reinforcement
learning based solution with two agents working cooperatively to collectively
simplify trajectories in a database while optimizing query usability. Extensive
experiments on four real-world trajectory datasets show that the solution is
capable of consistently outperforming baseline solutions over various query
types and dynamics.Comment: This paper has been accepted by ICDE 202
And\^o dilations for a pair of commuting contractions: two explicit constructions and functional models
One of the most important results in operator theory is And\^o's \cite{ando}
generalization of dilation theory for a single contraction to a pair of
commuting contractions acting on a Hilbert space. While there are two explicit
constructions (Sch\"affer \cite{sfr} and Douglas \cite{Doug-Dilation}) of the
minimal isometric dilation of a single contraction, there was no such explicit
construction of an And\^o dilation for a commuting pair of
contractions, except in some special cases \cite{A-M-Dist-Var, D-S, D-S-S}. In
this paper, we give two new proofs of And\^o's dilation theorem by giving both
Sch\"affer-type and Douglas-type explicit constructions of an And\^o dilation
with function-theoretic interpretation, for the general case. The results, in
particular, give a complete description of all possible factorizations of a
given contraction into the product of two commuting contractions. Unlike
the one-variable case, two minimal And\^o dilations need not be unitarily
equivalent. However, we show that the compressions of the two And\^o dilations
constructed in this paper to the minimal dilation spaces of the contraction
, are unitarily equivalent.
In the special case when the product is pure, i.e., if strongly, an And\^o dilation was constructed recently in \cite{D-S-S},
which, as this paper will show, is a corollary to the Douglas-type
construction.
We define a notion of characteristic triple for a pair of commuting
contractions and a notion of coincidence for such triples. We prove that two
pairs of commuting contractions with their products being pure contractions are
unitarily equivalent if and only if their characteristic triples coincide. We
also characterize triples which qualify as the characteristic triple for some
pair of commuting contractions such that is a pure
contraction.Comment: 24 page
CPSAA: Accelerating Sparse Attention using Crossbar-based Processing-In-Memory Architecture
The attention mechanism requires huge computational efforts to process
unnecessary calculations, significantly limiting the system's performance.
Researchers propose sparse attention to convert some DDMM operations to SDDMM
and SpMM operations. However, current sparse attention solutions introduce
massive off-chip random memory access. We propose CPSAA, a novel crossbar-based
PIM-featured sparse attention accelerator. First, we present a novel attention
calculation mode. Second, we design a novel PIM-based sparsity pruning
architecture. Finally, we present novel crossbar-based methods. Experimental
results show that CPSAA has an average of 89.6X, 32.2X, 17.8X, 3.39X, and 3.84X
performance improvement and 755.6X, 55.3X, 21.3X, 5.7X, and 4.9X energy-saving
when compare with GPU, FPGA, SANGER, ReBERT, and ReTransformer.Comment: 14 pages, 19 figure
Inhibition of A/Human/Hubei/3/2005 (H3N2) influenza virus infection by silver nanoparticles in vitro and in vivo
Phytochemical and Pharmacological Studies on the Genus Psoralea
The genus Psoralea, which belongs to the family Fabaceae, comprises ca. 130 species distributed all over the world, and some of the plants are used as folk medicine to treat various diseases. Psoralea corylifolia is a typical example, whose seeds have been widely used in many traditional Chinese medicine formulas for the treatment of various diseases such as leucoderma and other skin diseases, cardiovascular diseases, nephritis, osteoporosis, and cancer. So, the chemical and pharmacological studies on this genus were performed in the past decades. Here, we give a mini review on this genus about its phytochemical and pharmacological studies from 1910 to 2015
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