236 research outputs found
IC-FPS: Instance-Centroid Faster Point Sampling Module for 3D Point-base Object Detection
3D object detection is one of the most important tasks in autonomous driving
and robotics. Our research focuses on tackling low efficiency issue of
point-based methods on large-scale point clouds. Existing point-based methods
adopt farthest point sampling (FPS) strategy for downsampling, which is
computationally expensive in terms of inference time and memory consumption
when the number of point cloud increases. In order to improve efficiency, we
propose a novel Instance-Centroid Faster Point Sampling Module (IC-FPS) , which
effectively replaces the first Set Abstraction (SA) layer that is extremely
tedious. IC-FPS module is comprised of two methods, local feature diffusion
based background point filter (LFDBF) and Centroid-Instance Sampling Strategy
(CISS). LFDBF is constructed to exclude most invalid background points, while
CISS substitutes FPS strategy by fast sampling centroids and instance points.
IC-FPS module can be inserted to almost every point-based models. Extensive
experiments on multiple public benchmarks have demonstrated the superiority of
IC-FPS. On Waymo dataset, the proposed module significantly improves
performance of baseline model and accelerates inference speed by 3.8 times. For
the first time, real-time detection of point-based models in large-scale point
cloud scenario is realized
Biomechanical analysis of the Maxillary Sinus Floor Membrane During internal Sinus Floor Elevation With Implants at Different angles of the Maxillary Sinus angles
OBJECTIVE: This study analyzed and compared the biomechanical properties of maxillary sinus floor mucosa with implants at three different maxillary sinus angles during a modified internal sinus floor elevation procedure.
METHODS: 3D reconstruction of the implant, maxillary sinus bone, and membrane were performed. The maxillary sinus model was set at three different angles. Two internal maxillary sinus elevation models were established, and finite element analysis was used to simulate the modified maxillary sinus elevation process. The implant was elevated to 10 mm at three maxillary sinus angles when the maxillary sinus floor membrane was separated by 0 and 4 mm. The stress of the maxillary sinus floor membrane was analyzed and compared.
RESULTS: When the maxillary sinus floor membrane was separated by 0 mm and elevated to 10 mm, the peak stress values of the implant on the maxillary sinus floor membrane at three different angles were as follows: maxillary sinus I: 5.14-78.32 MPa; maxillary sinus II: 2.81-73.89 MPa; and maxillary sinus III: 2.82-51.87 MPa. When the maxillary sinus floor membrane was separated by 4 mm and elevated to 10 mm, the corresponding values were as follows: maxillary sinus I: 0.50-7.25 MPa; maxillary sinus II: 0.81-16.55 MPa; and maxillary sinus III: 0.49-22.74 MPa.
CONCLUSION: The risk of sinus floor membrane rupture is greatly reduced after adequate dissection of the maxillary sinus floor membrane when performing modified internal sinus elevation in a narrow maxillary sinus. In a wide maxillary sinus, the risk of rupture or perforation of the wider maxillary sinus floor is reduced, regardless of whether traditional or modified internal sinus elevation is performed at the same height
Evidence for Majorana bound state in an iron-based superconductor
The search for Majorana bound state (MBS) has recently emerged as one of the
most active research areas in condensed matter physics, fueled by the prospect
of using its non-Abelian statistics for robust quantum computation. A highly
sought-after platform for MBS is two-dimensional topological superconductors,
where MBS is predicted to exist as a zero-energy mode in the core of a vortex.
A clear observation of MBS, however, is often hindered by the presence of
additional low-lying bound states inside the vortex core. By using scanning
tunneling microscope on the newly discovered superconducting Dirac surface
state of iron-based superconductor FeTe1-xSex (x = 0.45, superconducting
transition temperature Tc = 14.5 K), we clearly observe a sharp and non-split
zero-bias peak inside a vortex core. Systematic studies of its evolution under
different magnetic fields, temperatures, and tunneling barriers strongly
suggest that this is the case of tunneling to a nearly pure MBS, separated from
non-topological bound states which is moved away from the zero energy due to
the high ratio between the superconducting gap and the Fermi energy in this
material. This observation offers a new, robust platform for realizing and
manipulating MBSs at a relatively high temperature.Comment: 27 pages, 11 figures, supplementary information include
Structure and Properties of Gallic Acid Epoxy Modified Gelatin
In this study, gallic acid (GA) was used to synthesize the gallic acid epoxy (GAE) for the chemical modification of gelatin. The chemical structure, hydration properties, thermal stability, and mechanical properties of GAE modified gelatin (GAEG) were evaluated. It was found that the epoxy group of GAE reacted with the primary amine group of gelatin to form C-N bond and covalent cross-linking. The swelling ratio of GAEG in water was increased by about 5 times. With the cross-linking degree increased from 41.13% to 72.68%, the swelling ratio decreased from 7831% to 6448%. While the gelatin dissolved completely in water within 24 h, the GAEG film remained intact for 7 days, and the disintegration rate decreased significantly with the increase of cross-linking degree. The water contact angle decreased from 88.01° to 59.87° after the modification, indicating increased hydrophilicity. The reduction of dehydration rate and the increase in total dehydration ratio suggested that the water retention capacity has been improved after the modification. The denaturation temperature increased from 55.0 ℃ to 61.7 ℃, and the thermal decomposition temperature increased from 240 ℃ to 274 ℃, with a relative decrease in thermal weight loss. The modification treatment led to a slight decrease in mechanical properties. This study demonstrated that GAE improved the hydration properties and thermal stability of gelatin, contributed to the application of gelatin as water retaining agent and stabilizer in food industry
Nearly quantized conductance plateau of vortex zero mode in an iron-based superconductor
Majorana zero-modes (MZMs) are spatially-localized zero-energy fractional
quasiparticles with non-Abelian braiding statistics that hold a great promise
for topological quantum computing. Due to its particle-antiparticle
equivalence, an MZM exhibits robust resonant Andreev reflection and 2e2/h
quantized conductance at low temperature. By utilizing variable-tunnel-coupled
scanning tunneling spectroscopy, we study tunneling conductance of vortex bound
states on FeTe0.55Se0.45 superconductors. We report observations of conductance
plateaus as a function of tunnel coupling for zero-energy vortex bound states
with values close to or even reaching the 2e2/h quantum conductance. In
contrast, no such plateau behaviors were observed on either finite energy
Caroli-de Genne-Matricon bound states or in the continuum of electronic states
outside the superconducting gap. This unique behavior of the zero-mode
conductance reaching a plateau strongly supports the existence of MZMs in this
iron-based superconductor, which serves as a promising single-material platform
for Majorana braiding at a relatively high temperature
Tunable vortex Majorana zero modes in LiFeAs superconductor
The recent realization of pristine Majorana zero modes (MZMs) in vortices of
iron-based superconductors (FeSCs) provides a promising platform for
long-sought-after fault-tolerant quantum computation. A large topological gap
between the MZMs and the lowest excitations enabled detailed characterization
of vortex MZMs in those materials. Despite those achievements, a practical
implementation of topological quantum computation based on MZM braiding remains
elusive in this new Majorana platform. Among the most pressing issues are the
lack of controllable tuning methods for vortex MZMs and inhomogeneity of the
FeSC Majorana compounds that destroys MZMs during the braiding process. Thus,
the realization of tunable vortex MZMs in a truly homogeneous compound of
stoichiometric composition and with a charge neutral cleavage surface is highly
desirable. Here we demonstrate experimentally that the stoichiometric
superconductor LiFeAs is a good candidate to overcome these two obstacles.
Using scanning tunneling microscopy, we discover that the MZMs, which are
absent on the natural surface, can appear in vortices influenced by native
impurities. Our detailed analysis and model calculations clarify the mechanism
of emergence of MZMs in this material, paving a way towards MZMs tunable by
controllable methods such as electrostatic gating. The tunability of MZMs in
this homogeneous material offers an unprecedented platform to manipulate and
braid MZMs, the essential ingredients for topological quantum computation.Comment: 21 pages, 10 figures. Suggestions and comments are welcom
Two distinct superconducting states controlled by orientation of local wrinkles in LiFeAs
We observe two types of superconducting states controlled by orientations of
local wrinkles on the surface of LiFeAs. Using scanning tunneling
microscopy/spectroscopy, we find type-I wrinkles enlarge the superconducting
gaps and enhance the transition temperature, whereas type-II wrinkles
significantly suppress the superconducting gaps. The vortices on wrinkles show
a C2 symmetry, indicating the strain effects on the wrinkles. A discontinuous
switch of superconductivity occurs at the border between two different
wrinkles. Our results demonstrate that the local strain effect could affect
superconducting order parameter of LiFeAs with a possible Lifshitz transition,
by alternating crystal structure in different directions.Comment: 21 pages, 9 figure
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