340 research outputs found
Integrated all-optical logic discriminators based on plasmonic bandgap engineering
Optical computing uses photons as information carriers, opening up the
possibility for ultrahigh-speed and ultrawide-band information processing.
Integrated all-optical logic devices are indispensible core components of
optical computing systems. However, up to now, little experimental progress has
been made in nanoscale all-optical logic discriminators, which have the
function of discriminating and encoding incident light signals according to
wavelength. Here, we report a strategy to realize a nanoscale all-optical logic
discriminator based on plasmonic bandgap engineering in a planar plasmonic
microstructure. Light signals falling within different operating wavelength
ranges are differentiated and endowed with different logic state encodings.
Compared with values previously reported, the operating bandwidth is enlarged
by one order of magnitude. Also the SPP light source is integrated with the
logic device while retaining its ultracompact size. This opens up a way to
construct on-chip all-optical information processors and artificial
intelligence systems.Comment: 4 figures 201
Ultrawide-band Unidirectional Surface Plasmon Polariton Launchers
Plasmonic devices and circuits, bridging the gap between integrated photonic
and microelectronic technology, are promising candidates to realize on-chip
ultrawide-band and ultrahigh-speed information processing. Unfortunately, the
wideband surface plasmon source, one of the most important core components of
integrated plasmonic circuits, is still unavailable up to now. This has
seriously restricted the practical applications of plasmonic circuits. Here, we
report an ultrawide-band unidirectional surface plasmon polariton launcher with
high launching efficiency ratio and large extinction ratio, realized by
combining plasmonic bandgap engineering and linear interference effect. This
device offers excellent performances over an ultrabroad wavelength range from
690 to 900 nm, together with a high average launching efficiency ratio of 1.25,
large average extinction ratio of 30 dB, and ultracompact lateral dimension of
less than 4 um. Compared with previous reports, the operating bandwidth is
enlarged 210 folds, while the largest launching efficiency ratio, largest
extinction ratio, and small feature size are maintained simultaneously. This
provides a strategy for constructing on-chip surface plasmon source, and also
paving the way for the study of integrated plasmonic circuits.Comment: 4 figure
Scene-Aware Feature Matching
Current feature matching methods focus on point-level matching, pursuing
better representation learning of individual features, but lacking further
understanding of the scene. This results in significant performance degradation
when handling challenging scenes such as scenes with large viewpoint and
illumination changes. To tackle this problem, we propose a novel model named
SAM, which applies attentional grouping to guide Scene-Aware feature Matching.
SAM handles multi-level features, i.e., image tokens and group tokens, with
attention layers, and groups the image tokens with the proposed token grouping
module. Our model can be trained by ground-truth matches only and produce
reasonable grouping results. With the sense-aware grouping guidance, SAM is not
only more accurate and robust but also more interpretable than conventional
feature matching models. Sufficient experiments on various applications,
including homography estimation, pose estimation, and image matching,
demonstrate that our model achieves state-of-the-art performance.Comment: Accepted to ICCV 202
ParaFormer: Parallel Attention Transformer for Efficient Feature Matching
Heavy computation is a bottleneck limiting deep-learningbased feature
matching algorithms to be applied in many realtime applications. However,
existing lightweight networks optimized for Euclidean data cannot address
classical feature matching tasks, since sparse keypoint based descriptors are
expected to be matched. This paper tackles this problem and proposes two
concepts: 1) a novel parallel attention model entitled ParaFormer and 2) a
graph based U-Net architecture with attentional pooling. First, ParaFormer
fuses features and keypoint positions through the concept of amplitude and
phase, and integrates self- and cross-attention in a parallel manner which
achieves a win-win performance in terms of accuracy and efficiency. Second,
with U-Net architecture and proposed attentional pooling, the ParaFormer-U
variant significantly reduces computational complexity, and minimize
performance loss caused by downsampling. Sufficient experiments on various
applications, including homography estimation, pose estimation, and image
matching, demonstrate that ParaFormer achieves state-of-the-art performance
while maintaining high efficiency. The efficient ParaFormer-U variant achieves
comparable performance with less than 50% FLOPs of the existing attention-based
models.Comment: Have been accepted by AAAI 202
An Efficient Built-in Temporal Support in MVCC-based Graph Databases
Real-world graphs are often dynamic and evolve over time. To trace the
evolving properties of graphs, it is necessary to maintain every change of both
vertices and edges in graph databases with the support of temporal features.
Existing works either maintain all changes in a single graph or periodically
materialize snapshots to maintain the historical states of each vertex and edge
and process queries over proper snapshots. The former approach presents poor
query performance due to the ever-growing graph size as time goes by, while the
latter one suffers from prohibitively high storage overheads due to large
redundant copies of graph data across different snapshots. In this paper, we
propose a hybrid data storage engine, which is based on the MVCC mechanism, to
separately manage current and historical data, which keeps the current graph as
small as possible. In our design, changes in each vertex or edge are stored
once. To further reduce the storage overhead, we simply store the changes as
opposed to storing the complete snapshot. To boost the query performance, we
place a few anchors as snapshots to avoid deep historical version traversals.
Based on the storage engine, a temporal query engine is proposed to reconstruct
subgraphs as needed on the fly. Therefore, our alternative approach can provide
fast querying capabilities over subgraphs at a past time point or range with
small storage overheads. To provide native support of temporal features, we
integrate our approach into Memgraph, and call the extended database system
TGDB(Temporal Graph Database). Extensive experiments are conducted on four real
and synthetic datasets. The results show TGDB performs better in terms of both
storage and performance against state-of-the-art methods and has almost no
performance overheads by introducing the temporal features
Create and Find Flatness: Building Flat Training Spaces in Advance for Continual Learning
Catastrophic forgetting remains a critical challenge in the field of
continual learning, where neural networks struggle to retain prior knowledge
while assimilating new information. Most existing studies emphasize mitigating
this issue only when encountering new tasks, overlooking the significance of
the pre-task phase. Therefore, we shift the attention to the current task
learning stage, presenting a novel framework, C&F (Create and Find Flatness),
which builds a flat training space for each task in advance. Specifically,
during the learning of the current task, our framework adaptively creates a
flat region around the minimum in the loss landscape. Subsequently, it finds
the parameters' importance to the current task based on their flatness degrees.
When adapting the model to a new task, constraints are applied according to the
flatness and a flat space is simultaneously prepared for the impending task. We
theoretically demonstrate the consistency between the created and found
flatness. In this manner, our framework not only accommodates ample parameter
space for learning new tasks but also preserves the preceding knowledge of
earlier tasks. Experimental results exhibit C&F's state-of-the-art performance
as a standalone continual learning approach and its efficacy as a framework
incorporating other methods. Our work is available at
https://github.com/Eric8932/Create-and-Find-Flatness.Comment: 10pages, ECAI2023 conferenc
Application of 25 MHz B-Scan Ultrasonography to Determine the Integrity of the Posterior Capsule in Posterior Polar Cataract
Purpose. To report the application of 25 MHz B-scan ultrasonography (MHzB) to determine the integrity of the posterior capsule (PC) in posterior polar cataract (PPC). Methods. Patients with whom PPC was clinically diagnosed using slit lamp microscopy who underwent 25 MHzB before phacoemulsification were retrospectively reviewed. The status of the PC was determined by 25 MHzB before phacoemulsification and confirmed during cataract surgery. Results. In total, 21 eyes in 14 clinically diagnosed PPC patients were enrolled in this study. Out of 25 MHzB images, 19 PCs were found to be intact, while 2 showed dehiscence before cataract surgery. During phacoemulsification, 17 PCs were observed to be intact, while 4 PCs showed posterior capsule rupture (PCR). These 4 PCR cases included the above 2 eyes, in which preexisting dehiscence was detected by 25 MHzB. The other 2 PCR cases showed high reflectivity between high echoes in posterior opacities and the PC, indicating synechia between the PPC and PC. Conclusion. This is the first report to show that 25 MHzB can be used to clearly visualize the status of the PC in PPC. These results, in turn, could be used to select the appropriate treatment and to thereby avoid further complications during PPC surgery
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