12 research outputs found
Point-DAE: Denoising Autoencoders for Self-supervised Point Cloud Learning
Masked autoencoder has demonstrated its effectiveness in self-supervised
point cloud learning. Considering that masking is a kind of corruption, in this
work we explore a more general denoising autoencoder for point cloud learning
(Point-DAE) by investigating more types of corruptions beyond masking.
Specifically, we degrade the point cloud with certain corruptions as input, and
learn an encoder-decoder model to reconstruct the original point cloud from its
corrupted version. Three corruption families (\ie, density/masking, noise, and
affine transformation) and a total of fourteen corruption types are
investigated with traditional non-Transformer encoders. Besides the popular
masking corruption, we identify another effective corruption family, \ie,
affine transformation. The affine transformation disturbs all points globally,
which is complementary to the masking corruption where some local regions are
dropped. We also validate the effectiveness of affine transformation corruption
with the Transformer backbones, where we decompose the reconstruction of the
complete point cloud into the reconstructions of detailed local patches and
rough global shape, alleviating the position leakage problem in the
reconstruction. Extensive experiments on tasks of object classification,
few-shot learning, robustness testing, part segmentation, and 3D object
detection validate the effectiveness of the proposed method. The codes are
available at \url{https://github.com/YBZh/Point-DAE}.Comment: The codes are available at \url{https://github.com/YBZh/Point-DAE
Dicylopentadienyl[4-(4-vinylbenzyloxy)pyridine-2,6-dicarboxylato]titanium(IV) monohydrate
The title compound, [Ti(C5H5)2(C16H11NO5)]·H2O, exhibits a titanocene unit coordinated to a styrene-substituted pyridine-2,6-dicarboxylate ligand synthesized for use as a monomer for polymerization or copolymerization yielding metallocene-containing polymers. The compound crystallized as a monohydrate and the solvent water molecule forms strong O—H⋯O hydrogen bonds with the carboxylate O atoms of the Ti complex, which play an important role in the connection of adjacent molecules. In addition, weak intermolecular C—H⋯O hydrogen bonds also contribute to the crystal packing arrangement
Masked Surfel Prediction for Self-Supervised Point Cloud Learning
Masked auto-encoding is a popular and effective self-supervised learning
approach to point cloud learning. However, most of the existing methods
reconstruct only the masked points and overlook the local geometry information,
which is also important to understand the point cloud data. In this work, we
make the first attempt, to the best of our knowledge, to consider the local
geometry information explicitly into the masked auto-encoding, and propose a
novel Masked Surfel Prediction (MaskSurf) method. Specifically, given the input
point cloud masked at a high ratio, we learn a transformer-based
encoder-decoder network to estimate the underlying masked surfels by
simultaneously predicting the surfel positions (i.e., points) and per-surfel
orientations (i.e., normals). The predictions of points and normals are
supervised by the Chamfer Distance and a newly introduced Position-Indexed
Normal Distance in a set-to-set manner. Our MaskSurf is validated on six
downstream tasks under three fine-tuning strategies. In particular, MaskSurf
outperforms its closest competitor, Point-MAE, by 1.2\% on the real-world
dataset of ScanObjectNN under the OBJ-BG setting, justifying the advantages of
masked surfel prediction over masked point cloud reconstruction. Codes will be
available at https://github.com/YBZh/MaskSurf.Comment: Codes will be available at https://github.com/YBZh/MaskSur
MoS2/TiO2 van der Waals heterostructures for promising photocatalytic performance: a first-principles study
Heterostructures have attracted extensive attention due to their van der Waals interactions between layers. The photocatalysts of Two-dimensional (2D) heterostructure based on MoS _2 have tempted more and more attention because of their eminent photocatalytic performance, but they are still limited by the weak absorption of visible light and lesser conversion efficiency of solar-to-hydrogen. In this work, we exhaustively investigate the electronic, optical and the structural properties of 2D MoS _2 /TiO _2 heterostructures by using first-principles calculations. The result shows that both MoS _2 /TiO _2 (100) and MoS _2 /TiO _2 (001) heterostructures are stable interfaces and direct Z-scheme photocatalysts, which is favourable for the separation and migration of electron and hole pairs under the excitation of light. And what’s more, both the MoS _2 /TiO _2 (100) and MoS _2 /TiO _2 (001) heterostructures exhibit direct band gap at the Γ point, this is conductive to better electronic transition and absorption of light because of lower energy depletion than indirect band gap semiconductors. The relatively small band gap (1.08 eV of MoS _2 /TiO _2 (001) and 0.52 eV of MoS _2 /TiO _2 (100)) cause the entire visible light region can be covered by the light absorption spectrum. The result is that building heterostructures of TiO _2 with MoS _2 advances the absorption of light and hastens the separation and migration of electron and hole pairs, the activity of photocatalysis could be advanced by all of these. The results provide a basis of heterostructure photocatalysts based on monolayer MoS _2 and deep comprehension of their physical mechanism
Preparation and Perfomance of an Aging-Resistant Nanocomposite Film of Binary Natural Polymer–Graphene Oxide
As
one of the materials having a bionic structure, nacrelike layered
composites, inspired by their natural hybrid structures, have been
studied via a variety of approaches. Graphene oxide (GO), which differed
from inert graphene, was used as a new building block because it could
be readily chemically functionalized. Rather than natural polymers,
synthetic polymers were most commonly used to fabricate nacrelike
GO–polymer materials. However, naturally occurring polymers
complied more easily with the requirements of biocompatibility, biodegradability,
and nontoxicity. Here, a simple solution-casting method was used to
mimic natural nacre and fabricate a self-assembled and aging-resistant
binary natural polymer, (κ-carrageenan (κ-CAR)–Konjac
glucomannan (KGM))–GO nanocomposites, with varying GO concentrations.
The investigation results revealed that κ-CAR–KGM and
GO mostly self-assemble via the formation of intermolecular hydrogen
bonds to form a well-defined layered structure. The mechanical properties
of the natural polymer–GO films were improved significantly
compared to those of pure natural polymer films. With the addition
of 7.5 wt % GO, the tensile strength (TS) and Young’s modulus
were found to increase by 129.5 and 491.5%, respectively. In addition,
the composite films demonstrated high reliability and aging resistance
as well as a definite TS after cold and hot shock and ozone aging
tests, especially showing a superior ozone resistance. The composite
films can potentially be used as biomaterials or packing materials
External Quality Assessment for the Detection of Measles Virus by Reverse Transcription-PCR Using Armored RNA.
In recent years, nucleic acid tests for detection of measles virus RNA have been widely applied in laboratories belonging to the measles surveillance system of China. An external quality assessment program was established by the National Center for Clinical Laboratories to evaluate the performance of nucleic acid tests for measles virus. The external quality assessment panel, which consisted of 10 specimens, was prepared using armored RNAs, complex of noninfectious MS2 bacteriophage coat proteins encapsulated RNA of measles virus, as measles virus surrogate controls. Conserved sequences amplified from a circulating measles virus strain or from a vaccine strain were encapsulated into these armored RNAs. Forty-one participating laboratories from 15 provinces, municipalities, or autonomous regions that currently conduct molecular detection of measles virus enrolled in the external quality assessment program, including 40 measles surveillance system laboratories and one diagnostic reagent manufacturer. Forty laboratories used commercial reverse transcription-quantitative PCR kits, with only one laboratory applying a conventional PCR method developed in-house. The results indicated that most of the participants (38/41, 92.7%) were able to accurately detect the panel with 100% sensitivity and 100% specificity. Although a wide range of commercially available kits for nucleic acid extraction and reverse transcription polymerase chain reaction were used by the participants, only two false-negative results and one false-positive result were generated; these were generated by three separate laboratories. Both false-negative results were obtained with tests performed on specimens with the lowest concentration (1.2 × 104 genomic equivalents/mL). In addition, all 18 participants from Beijing achieved 100% sensitivity and 100% specificity. Overall, we conclude that the majority of the laboratories evaluated have reliable diagnostic capacities for the detection of measles virus
Composition of the EQA panel and qRT-PCR results.
<p>Composition of the EQA panel and qRT-PCR results.</p