82 research outputs found
Spacetime structure of 5D hypercylindrical vacuum solutions with tension
We investigate geometrical properties of 5D cylindrical vacuum solutions with
a transverse spherical symmetry. The metric is uniform along the fifth
direction and characterized by tension and mass densities. The solutions are
classified by the tension-to-mass ratio. One particular example is the
well-known Schwarzschild black string which has a curvature singularity
enclosed by a horizon. We focus mainly on geometry of other solutions which
possess a naked singularity. The light signal emitted by an object approaching
the singularity reaches a distant observer with finite time, but is infinitely
red-shifted.Comment: revtex4, 5 pages, 2 figures. To appear in the proceedings of the 10th
Asia Pacific Physics Conference (APPC10), Pohang, Korea, 21-24 Aug. 2007.
Submitted to J. Korean Phys. Soc. Penrose diagram has been adde
Plasmon-enhanced Infrared Spectroscopy Based on Metasurface Absorber with Vertical Nanogap
In this study, we introduce a sensing platform based on a plasmonic metasurface absorber (MA) with a vertical nanogap for the ultra- sensitive detection of monolayer molecules. The vertical nanogap of the MA, where the extremely high near-field is uniformly dis- tributed and exposed to the external environment, is formed by an under-cut structure between a metallic cross nanoantenna and themirror layer. The accessible sensing area and the enhanced near-field of the MA further enhance the sensitivity of surface-enhancedinfrared absorption for the target molecule of 1-octadecanethiol. To provide strong coupling between the molecular vibrations and plas- monic resonance, the design parameters of the MA with a vertical nanogap are numerically designed
DiffRef3D: A Diffusion-based Proposal Refinement Framework for 3D Object Detection
Denoising diffusion models show remarkable performances in generative tasks,
and their potential applications in perception tasks are gaining interest. In
this paper, we introduce a novel framework named DiffRef3D which adopts the
diffusion process on 3D object detection with point clouds for the first time.
Specifically, we formulate the proposal refinement stage of two-stage 3D object
detectors as a conditional diffusion process. During training, DiffRef3D
gradually adds noise to the residuals between proposals and target objects,
then applies the noisy residuals to proposals to generate hypotheses. The
refinement module utilizes these hypotheses to denoise the noisy residuals and
generate accurate box predictions. In the inference phase, DiffRef3D generates
initial hypotheses by sampling noise from a Gaussian distribution as residuals
and refines the hypotheses through iterative steps. DiffRef3D is a versatile
proposal refinement framework that consistently improves the performance of
existing 3D object detection models. We demonstrate the significance of
DiffRef3D through extensive experiments on the KITTI benchmark. Code will be
available
PG-RCNN: Semantic Surface Point Generation for 3D Object Detection
One of the main challenges in LiDAR-based 3D object detection is that the
sensors often fail to capture the complete spatial information about the
objects due to long distance and occlusion. Two-stage detectors with point
cloud completion approaches tackle this problem by adding more points to the
regions of interest (RoIs) with a pre-trained network. However, these methods
generate dense point clouds of objects for all region proposals, assuming that
objects always exist in the RoIs. This leads to the indiscriminate point
generation for incorrect proposals as well. Motivated by this, we propose Point
Generation R-CNN (PG-RCNN), a novel end-to-end detector that generates semantic
surface points of foreground objects for accurate detection. Our method uses a
jointly trained RoI point generation module to process the contextual
information of RoIs and estimate the complete shape and displacement of
foreground objects. For every generated point, PG-RCNN assigns a semantic
feature that indicates the estimated foreground probability. Extensive
experiments show that the point clouds generated by our method provide
geometrically and semantically rich information for refining false positive and
misaligned proposals. PG-RCNN achieves competitive performance on the KITTI
benchmark, with significantly fewer parameters than state-of-the-art models.
The code is available at https://github.com/quotation2520/PG-RCNN.Comment: Accepted by ICCV 202
Evolution of Tachyon Kink with Electric Field
We investigate the decay of an inhomogeneous D1-brane wrapped on a with
an electric field. The model that we consider consists of an array of tachyon
kink and anti-kink with a constant electric flux. Beginning with an initially
static configuration, we numerically evolve the tachyon field with some
perturbations under a fixed boundary condition at diametrically opposite points
on the circle . When the electric flux is smaller than the critical value,
the tachyon kink becomes unstable; the tachyon field rolls down the potential,
and the lower dimensional D0- and -brane become thin, which
resembles the caustic formation known for this type of the system in the
literature. For the supercritical values of the electric flux, the tachyon kink
remains stable.Comment: 27 pages, 8 figures, some changes, one reference added, version to
appear in JHE
Stability of self-gravitating magnetic monopoles
The stability of a spherically symmetric self-gravitating magnetic monopole
is examined in the thin wall approximation: modeling the interior false vacuum
as a region of de Sitter space; the exterior as an asymptotically flat region
of the Reissner-Nordstr\"om geometry; and the boundary separating the two as a
charged domain wall. There remains only to determine how the wall gets embedded
in these two geometries. In this approximation, the ratio of the false
vacuum to surface energy densities is a measure of the symmetry breaking scale
. Solutions are characterized by this ratio, the charge on the wall ,
and the value of the conserved total energy . We find that for each fixed
and up to some critical value, there exists a unique globally static
solution, with ; any stable radial excitation has bounded
above by , the value assumed in an extremal Reissner-Nordstr\"om geometry
and these are the only solutions with . As is raised above a black
hole forms in the exterior: (i) for low or , the wall is crushed; (ii)
for higher values, it oscillates inside the black hole. If the mass is not too
high these `collapsing' solutions co-exist with an inflating bounce; (iii) for
, or outside the above regimes, there is a unique inflating
solution. In case (i) the course of the bounce lies within a single
asymptotically flat region (AFR) and it resembles closely the bounce exhibited
by a false vacuum bubble (with Q=0). In cases (ii) and (iii) the course of the
bounce spans two consecutive AFRs.Comment: 19 pages, RevTex two cols., 11 eps figs. Submitted to Phys. Rev.
Photobiocidal-triboelectric nanolayer coating of photosensitizer/silica-alumina for reusable and visible-light-driven antibacterial/antiviral air filters
Outbreaks of airborne pathogens pose a major threat to public health. Here we present a single-step nanocoating process to endow commercial face mask filters with photobiocidal activity, triboelectric filtration capability, and washability. These functions were successfully achieved with a composite nanolayer of silica-alumina (Si-Al) sol-gel, crystal violet (CV) photosensitizer, and hydrophobic electronegative molecules of 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane (PFOTES). The transparent Si-Al matrix strongly immobilized the photosensitizer molecules while dispersing them spatially, thus suppressing self-quenching. During nanolayer formation, PFOTES was anisotropically rearranged on the Si-Al matrix, promoting moisture resistance and triboelectric charging of the Si-Al/PFOTES-CV (SAPC)-coated filter. The SAPC nanolayer stabilized the photoexcited state of the photosensitizer and promoted redox reaction. Compared to pure-photosensitizer-coated filters, the SAPC filter showed substantially higher photobiocidal efficiency (∼99.99 % for bacteria and a virus) and photodurability (∼83 % reduction in bactericidal efficiency for the pure-photosensitizer filter but ∼0.34 % for the SAPC filter after 72 h of light irradiation). Moreover, after five washes with detergent, the SAPC filter maintained its photobiocidal and filtration performance, proving its reusability potential. Therefore, this SAPC nanolayer coating provides a practical strategy for manufacturing an antimicrobial and reusable mask filter for use during the ongoing COVID-19 pandemic
A new burst scheduling algorithm for edge/core combined optical burst switched networks
Abstract. The burst contention problem in Optical Burst Switching network is an intrinsically serious problem. Many researches have tried to solve this problem, however it have been known that avoiding the burst loss is very difficult issues in the current OBS network. To improve burst blocking rate, we consider the edge/core combined OBS network where the core node performs the edge node function as well. Through this architecture, available amount of data burst that the node generates can be expected with respect to offset-time of transit data bursts. Any researches for this area has not been performed, thus we propose a new data scheduling algorithm for the edge/core combined OBS network where data bursts that the node generates do not interrupt transit data bursts from previous nodes. We analyzed the data burst loss rate and the throughput in relation with the offset-time of transit data bursts. Results show that the loss rate of the data bursts is drastically reduced and the throughput improves when the offset-time of transit data bursts increases
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