159 research outputs found
Uniquely circular colourable and uniquely fractional colourable graphs of large girth
Given any rational numbers and an integer , we
prove that there is a graph of girth at least , which is
uniquely -colourable and uniquely -fractional colourable
Subsampling and Jackknifing: A Practically Convenient Solution for Large Data Analysis with Limited Computational Resources
Modern statistical analysis often encounters datasets with large sizes. For
these datasets, conventional estimation methods can hardly be used immediately
because practitioners often suffer from limited computational resources. In
most cases, they do not have powerful computational resources (e.g., Hadoop or
Spark). How to practically analyze large datasets with limited computational
resources then becomes a problem of great importance. To solve this problem, we
propose here a novel subsampling-based method with jackknifing. The key idea is
to treat the whole sample data as if they were the population. Then, multiple
subsamples with greatly reduced sizes are obtained by the method of simple
random sampling with replacement. It is remarkable that we do not recommend
sampling methods without replacement because this would incur a significant
cost for data processing on the hard drive. Such cost does not exist if the
data are processed in memory. Because subsampled data have relatively small
sizes, they can be comfortably read into computer memory as a whole and then
processed easily. Based on subsampled datasets, jackknife-debiased estimators
can be obtained for the target parameter. The resulting estimators are
statistically consistent, with an extremely small bias. Finally, the
jackknife-debiased estimators from different subsamples are averaged together
to form the final estimator. We theoretically show that the final estimator is
consistent and asymptotically normal. Its asymptotic statistical efficiency can
be as good as that of the whole sample estimator under very mild conditions.
The proposed method is simple enough to be easily implemented on most practical
computer systems and thus should have very wide applicability
Deterministic Spin-Orbit Torque Switching of Mn3Sn with the Interplay between Spin Polarization and Kagome Plane
Previous studies have demonstrated spin-orbit torque (SOT) switching of Mn3Sn
where the spin polarization lies in the kagome plane (configuration I).
However, the critical current density () is unrealistically large (= A/) and independent on the external field (). The stabilized magnetic state also depends on the initial state.
These features conflict with the ferromagnet (FM) switching scheme as claimed
in those studies, and thus call for other explanations. Alternatively, the
system with the spin polarization perpendicular to the kagome plane
(configuration II) is more like the FM based system since the spin polarization
is orthogonal to all magnetic moments. In this work, we show SOT switching of
Mn3Sn in configuration II. Similar to the FM, Jcrit and Hext are in the order
of A/ and hundreds of Oersted, respectively. The switching
result is also independent of the initial state. Interestingly, the unique spin
structure of Mn3Sn also leads to distinct features from FM systems. We
demonstrate that Jcrit increases linearly with Hext, and extrapolation gives
ultralow for the field-free switching system. In addition, the
switching polarity is opposite to the FM. We also provide the switching phase
diagram as a guideline for experimental demonstration. Our work provides
comprehensive understanding for the switching mechanism in both configurations.
The switching protocol proposed in this work is more advantageous in realistic
spintronic applications. We also clearly reveal the fundamental difference
between FM and noncollinear antiferromagnetic switching
Select2Col: Leveraging Spatial-Temporal Importance of Semantic Information for Efficient Collaborative Perception
Collaboration by leveraging the shared semantic information plays a crucial
role in overcoming the perception capability limitations of isolated agents.
However, existing collaborative perception methods tend to focus solely on the
spatial features of semantic information, while neglecting the importance of
the temporal dimension. Consequently, the potential benefits of collaboration
remain underutilized. In this article, we propose Select2Col, a novel
collaborative perception framework that takes into account the
{s}patial-t{e}mpora{l} importanc{e} of semanti{c} informa{t}ion. Within the
Select2Col, we develop a collaborator selection method that utilizes a
lightweight graph neural network (GNN) to estimate the importance of semantic
information (IoSI) in enhancing perception performance, thereby identifying
contributive collaborators while excluding those that bring negative impact.
Moreover, we present a semantic information fusion algorithm called HPHA
(historical prior hybrid attention), which integrates multi-scale attention and
short-term attention modules to capture the IoSI in feature representation from
the spatial and temporal dimensions respectively, and assigns IoSI-consistent
weights for efficient fusion of information from selected collaborators.
Extensive experiments on two open datasets demonstrate that our proposed
Select2Col significantly improves the perception performance compared to
state-of-the-art approaches. The code associated with this research is publicly
available at https://github.com/huangqzj/Select2Col/
- …