8,697 research outputs found
Global-Scale Resource Survey and Performance Monitoring of Public OGC Web Map Services
One of the most widely-implemented service standards provided by the Open
Geospatial Consortium (OGC) to the user community is the Web Map Service (WMS).
WMS is widely employed globally, but there is limited knowledge of the global
distribution, adoption status or the service quality of these online WMS
resources. To fill this void, we investigated global WMSs resources and
performed distributed performance monitoring of these services. This paper
explicates a distributed monitoring framework that was used to monitor 46,296
WMSs continuously for over one year and a crawling method to discover these
WMSs. We analyzed server locations, provider types, themes, the spatiotemporal
coverage of map layers and the service versions for 41,703 valid WMSs.
Furthermore, we appraised the stability and performance of basic operations for
1210 selected WMSs (i.e., GetCapabilities and GetMap). We discuss the major
reasons for request errors and performance issues, as well as the relationship
between service response times and the spatiotemporal distribution of client
monitoring sites. This paper will help service providers, end users and
developers of standards to grasp the status of global WMS resources, as well as
to understand the adoption status of OGC standards. The conclusions drawn in
this paper can benefit geospatial resource discovery, service performance
evaluation and guide service performance improvements.Comment: 24 pages; 15 figure
Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction
We investigate the optical control possibilities of spin-valley qubit carried
by single electrons localized in nanostructures of monolayer TMDs, including
small quantum dots formed by lateral heterojunction and charged impurities. The
quantum controls are discussed when the confinement induces valley
hybridization and when the valley hybridization is absent. We show that the
bulk valley and spin optical selection rules can be inherited in different
forms in the two scenarios, both of which allow the definition of spin-valley
qubit with desired optical controllability. We also investigate nuclear spin
induced decoherence and quantum control of electron-nuclear spin entanglement
via intervalley terms of the hyperfine interaction. Optically controlled
two-qubit operations in a single quantum dot are discussed.Comment: 17pages, 10 figure
Less is Better: Recovering Intended-Feature Subspace to Robustify NLU Models
Datasets with significant proportions of bias present threats for training a
trustworthy model on NLU tasks. Despite yielding great progress, current
debiasing methods impose excessive reliance on the knowledge of bias
attributes. Definition of the attributes, however, is elusive and varies across
different datasets. Furthermore, leveraging these attributes at input level to
bias mitigation may leave a gap between intrinsic properties and the underlying
decision rule. To narrow down this gap and liberate the supervision on bias, we
suggest extending bias mitigation into feature space. Therefore, a novel model,
Recovering Intended-Feature Subspace with Knowledge-Free (RISK) is developed.
Assuming that shortcut features caused by various biases are unintended for
prediction, RISK views them as redundant features. When delving into a lower
manifold to remove redundancies, RISK reveals that an extremely low-dimensional
subspace with intended features can robustly represent the highly biased
dataset. Empirical results demonstrate our model can consistently improve model
generalization to out-of-distribution set, and achieves a new state-of-the-art
performance.Comment: Acceptted by COLING 202
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