2,107 research outputs found
SeqTrack: Sequence to Sequence Learning for Visual Object Tracking
In this paper, we present a new sequence-to-sequence learning framework for
visual tracking, dubbed SeqTrack. It casts visual tracking as a sequence
generation problem, which predicts object bounding boxes in an autoregressive
fashion. This is different from prior Siamese trackers and transformer
trackers, which rely on designing complicated head networks, such as
classification and regression heads. SeqTrack only adopts a simple
encoder-decoder transformer architecture. The encoder extracts visual features
with a bidirectional transformer, while the decoder generates a sequence of
bounding box values autoregressively with a causal transformer. The loss
function is a plain cross-entropy. Such a sequence learning paradigm not only
simplifies tracking framework, but also achieves competitive performance on
benchmarks. For instance, SeqTrack gets 72.5% AUC on LaSOT, establishing a new
state-of-the-art performance. Code and models are available at here.Comment: CVPR2023 pape
Determining layer number of two dimensional flakes of transition-metal dichalcogenides by the Raman intensity from substrate
Transition-metal dichalcogenide (TMD) semiconductors have been widely studied
due to their distinctive electronic and optical properties. The property of TMD
flakes is a function of its thickness, or layer number (N). How to determine N
of ultrathin TMDs materials is of primary importance for fundamental study and
practical applications. Raman mode intensity from substrates has been used to
identify N of intrinsic and defective multilayer graphenes up to N=100.
However, such analysis is not applicable for ultrathin TMD flakes due to the
lack of a unified complex refractive index () from monolayer to bulk
TMDs. Here, we discuss the N identification of TMD flakes on the SiO/Si
substrate by the intensity ratio between the Si peak from 100-nm (or 89-nm)
SiO/Si substrates underneath TMD flakes and that from bare SiO/Si
substrates. We assume the real part of of TMD flakes as that of
monolayer TMD and treat the imaginary part of as a fitting
parameter to fit the experimental intensity ratio. An empirical ,
namely, , of ultrathin MoS, WS and WSe
flakes from monolayer to multilayer is obtained for typical laser excitations
(2.54 eV, 2.34 eV, or 2.09 eV). The fitted of MoS has
been used to identify N of MoS flakes deposited on 302-nm SiO/Si
substrate, which agrees well with that determined from their shear and
layer-breathing modes. This technique by measuring Raman intensity from the
substrate can be extended to identify N of ultrathin 2D flakes with N-dependent
. For the application purpose, the intensity ratio excited by
specific laser excitations has been provided for MoS, WS and
WSe flakes and multilayer graphene flakes deposited on Si substrates
covered by 80-110 nm or 280-310 nm SiO layer.Comment: 10 pages, 4 figures. Accepted by Nanotechnolog
The ultra-low-frequency shear modes of 2-4 layer graphenes observed in their scroll structures at edges
The in-plane shear modes between neighbor-layers of 2-4 layer graphenes (LGs)
and the corresponding graphene scrolls rolled up by 2-4LGs were investigated by
Raman scattering. In contrast to that just one shear mode was observed in
3-4LGs, all the shear modes of 3-4LGs were observed in 3-4 layer scrolls (LSs),
whose frequencies agree well with the theoretical predication by both a
force-constant model and a linear chain model. In comparison to the broad width
(about 12cm) for the G band in graphite, all the shear modes exhibit an
intrinsic line width of about 1.0 cm. The local electronic structures
dependent on the local staking configurations enhance the intensity of the
shear modes in corresponding 2-4LSs zones, which makes it possible to observe
all the shear modes. It provides a direct evidence that how the band structures
of FLGs can be sensitive to local staking configurations. This result can be
extended to n layer graphene (n > 4) for the understanding of the basic phonon
properties of multi-layer graphenes. This observation of all-scale shear modes
can be foreseen in other 2D materials with similar scroll structures.Comment: 14 pages, 5 figure
Retro-FPN: Retrospective Feature Pyramid Network for Point Cloud Semantic Segmentation
Learning per-point semantic features from the hierarchical feature pyramid is
essential for point cloud semantic segmentation. However, most previous methods
suffered from ambiguous region features or failed to refine per-point features
effectively, which leads to information loss and ambiguous semantic
identification. To resolve this, we propose Retro-FPN to model the per-point
feature prediction as an explicit and retrospective refining process, which
goes through all the pyramid layers to extract semantic features explicitly for
each point. Its key novelty is a retro-transformer for summarizing semantic
contexts from the previous layer and accordingly refining the features in the
current stage. In this way, the categorization of each point is conditioned on
its local semantic pattern. Specifically, the retro-transformer consists of a
local cross-attention block and a semantic gate unit. The cross-attention
serves to summarize the semantic pattern retrospectively from the previous
layer. And the gate unit carefully incorporates the summarized contexts and
refines the current semantic features. Retro-FPN is a pluggable neural network
that applies to hierarchical decoders. By integrating Retro-FPN with three
representative backbones, including both point-based and voxel-based methods,
we show that Retro-FPN can significantly improve performance over
state-of-the-art backbones. Comprehensive experiments on widely used benchmarks
can justify the effectiveness of our design. The source is available at
https://github.com/AllenXiangX/Retro-FPNComment: Accepted by ICCV 202
2,5-Bis[2-(2-methoxyethoxy)phenyl]-1,3,4-oxadiazole
In the title compound, C20H22N2O5, the central 1,3,4-oxadiazole ring is essentially planar [r.m.s. deviation from the best plane of 0.0011 Å] and makes dihedral angles of 4.10 (3) and 13.32 (4)° with the two benzene rings. In the crystal structure, the packing is stabilized by weak non-classical intermolecular C—H⋯N hydrogen bonds, which link the molecules into an extended network
Snowflake Point Deconvolution for Point Cloud Completion and Generation with Skip-Transformer
Most existing point cloud completion methods suffer from the discrete nature
of point clouds and the unstructured prediction of points in local regions,
which makes it difficult to reveal fine local geometric details. To resolve
this issue, we propose SnowflakeNet with snowflake point deconvolution (SPD) to
generate complete point clouds. SPD models the generation of point clouds as
the snowflake-like growth of points, where child points are generated
progressively by splitting their parent points after each SPD. Our insight into
the detailed geometry is to introduce a skip-transformer in the SPD to learn
the point splitting patterns that can best fit the local regions. The
skip-transformer leverages attention mechanism to summarize the splitting
patterns used in the previous SPD layer to produce the splitting in the current
layer. The locally compact and structured point clouds generated by SPD
precisely reveal the structural characteristics of the 3D shape in local
patches, which enables us to predict highly detailed geometries. Moreover,
since SPD is a general operation that is not limited to completion, we explore
its applications in other generative tasks, including point cloud
auto-encoding, generation, single image reconstruction, and upsampling. Our
experimental results outperform state-of-the-art methods under widely used
benchmarks.Comment: IEEE Transactions on Pattern Analysis and Machine Intelligence
(TPAMI), 2022. This work is a journal extension of our ICCV 2021 paper
arXiv:2108.04444 . The first two authors contributed equall
Colorectal cancer screening with fecal occult blood test: A 22-year cohort study.
The aim of the present study was to investigate the efficacy of colorectal cancer (CRC) screening with a three-tier fecal occult blood test (FOBT) in the Chinese population. The study was performed between 1987 and 2008 at the Beijing Military General Hospital, in a cohort of army service males and females aged >50 years. Between 1987 and 2005, a three-tier screening program, comprising guaiac-based FOBTs (gFOBTs), followed by immunochemical FOBTs for positive guaiac test samples and then colonoscopy for positive immunochemical test subjects, was performed annually. The cohort was followed up until 2008. The cohort included 5,104 subjects, of which, 3,863 subjects participated in screening (screening group) and 1,241 did not (non-screening group). The two groups did not differ in age, gender or other major risk factors for colon cancer. Overall, 36 CRCs occurred in the screening group and 21 in the non-screening group. Compared with the non-screening group, the relative risk for the incidence and mortality of CRC was 0.51 [95% confidence interval (CI), 0.30-0.87] and 0.36 (95% CI, 0.18-0.71), respectively, in the screening group. The general sensitivity of this three-tier FOBT was 80.6% (95% CI, 65.3-91.1). Thus, annual screening using the three-tier FOBT program may reduce the CRC incidence and mortality rate
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