75 research outputs found
Hierarchical Few-Shot Object Detection: Problem, Benchmark and Method
Few-shot object detection (FSOD) is to detect objects with a few examples.
However, existing FSOD methods do not consider hierarchical fine-grained
category structures of objects that exist widely in real life. For example,
animals are taxonomically classified into orders, families, genera and species
etc. In this paper, we propose and solve a new problem called hierarchical
few-shot object detection (Hi-FSOD), which aims to detect objects with
hierarchical categories in the FSOD paradigm. To this end, on the one hand, we
build the first large-scale and high-quality Hi-FSOD benchmark dataset
HiFSOD-Bird, which contains 176,350 wild-bird images falling to 1,432
categories. All the categories are organized into a 4-level taxonomy,
consisting of 32 orders, 132 families, 572 genera and 1,432 species. On the
other hand, we propose the first Hi-FSOD method HiCLPL, where a hierarchical
contrastive learning approach is developed to constrain the feature space so
that the feature distribution of objects is consistent with the hierarchical
taxonomy and the model's generalization power is strengthened. Meanwhile, a
probabilistic loss is designed to enable the child nodes to correct the
classification errors of their parent nodes in the taxonomy. Extensive
experiments on the benchmark dataset HiFSOD-Bird show that our method HiCLPL
outperforms the existing FSOD methods.Comment: Accepted by ACM MM 202
Employing Higher Order Cladding Modes of Fiber Bragg Grating for Analysis of Refractive Index Change in Volume and at the Surface
In this work, a detailed study on volume and surface refractive index (RI) sensitivity of cladding modes for a fiber Bragg grating (FBG) based sensor is presented. Surface RI sensitivity of the cladding mode of FBGs has been illustrated and quantified with the concept of add-layer sensitivity for the first time to the best of our knowledge. A detailed investigation of mode transition of higher-order cladding modes has been revisited and important characteristics of the cladding modes are observed which could open a new designing path of fabrication and innovative way of the use of this family of optical fiber grating-based sensors. The effect of āmode transitionā of higher-order cladding modes, higher operating wavelength for respective cladding mode and āmode stretchingā effects are combined together to achieve higher volume and surface RI sensitivity of cladding mode of FBG. It has been shown numerically that with proper designing, sub-nanometer (ā¼0.04 nm) attachment of target analyte could be recognized by cladding mode of FBG which is quite promising for application in optical fiber grating bio-sensors. This critical designing method of FBG based surface refractometer would be very helpful in case of the fabrication of highly sensitive sensors for distinct biochemical applications
Nanoparticle manipulation using plasmonic optical tweezers based on particle sizes and refractive indices
As an effective tool for micro/nano-scale particle manipulation, plasmonic optical tweezers can be used to manipulate cells, DNA, and macromolecules. Related research is of great significance to the development of nanoscience. In this work, we investigated a sub-wavelength particle manipulation technique based on plasmonic optical tweezers. When the local plasmonic resonance is excited on the gold nanostructure arrays, the local electromagnetic field will be enhanced to generate a strong gradient force acting on nanoparticles, which could achieve particle sorting in sub-wavelength scale. On this basis, we explored the plasmonic enhancement effect of the sorting device and the corresponding optical force and optical potential well distributions. Additionally, the sorting effect of the sorting device was investigated in statistical methods, which showed that the sorting device could effectively sort particles of different diameters and refractive indices
UMIX: Improving Importance Weighting for Subpopulation Shift via Uncertainty-Aware Mixup
Subpopulation shift widely exists in many real-world machine learning
applications, referring to the training and test distributions containing the
same subpopulation groups but varying in subpopulation frequencies. Importance
reweighting is a normal way to handle the subpopulation shift issue by imposing
constant or adaptive sampling weights on each sample in the training dataset.
However, some recent studies have recognized that most of these approaches fail
to improve the performance over empirical risk minimization especially when
applied to over-parameterized neural networks. In this work, we propose a
simple yet practical framework, called uncertainty-aware mixup (UMIX), to
mitigate the overfitting issue in over-parameterized models by reweighting the
''mixed'' samples according to the sample uncertainty. The
training-trajectories-based uncertainty estimation is equipped in the proposed
UMIX for each sample to flexibly characterize the subpopulation distribution.
We also provide insightful theoretical analysis to verify that UMIX achieves
better generalization bounds over prior works. Further, we conduct extensive
empirical studies across a wide range of tasks to validate the effectiveness of
our method both qualitatively and quantitatively. Code is available at
https://github.com/TencentAILabHealthcare/UMIX.Comment: NeurIPS 202
Reweighted Mixup for Subpopulation Shift
Subpopulation shift exists widely in many real-world applications, which
refers to the training and test distributions that contain the same
subpopulation groups but with different subpopulation proportions. Ignoring
subpopulation shifts may lead to significant performance degradation and
fairness concerns. Importance reweighting is a classical and effective way to
handle the subpopulation shift. However, recent studies have recognized that
most of these approaches fail to improve the performance especially when
applied to over-parameterized neural networks which are capable of fitting any
training samples. In this work, we propose a simple yet practical framework,
called reweighted mixup (RMIX), to mitigate the overfitting issue in
over-parameterized models by conducting importance weighting on the ''mixed''
samples. Benefiting from leveraging reweighting in mixup, RMIX allows the model
to explore the vicinal space of minority samples more, thereby obtaining more
robust model against subpopulation shift. When the subpopulation memberships
are unknown, the training-trajectories-based uncertainty estimation is equipped
in the proposed RMIX to flexibly characterize the subpopulation distribution.
We also provide insightful theoretical analysis to verify that RMIX achieves
better generalization bounds over prior works. Further, we conduct extensive
empirical studies across a wide range of tasks to validate the effectiveness of
the proposed method.Comment: Journal version of arXiv:2209.0892
Solution-processed perovskite light emitting diodes with efficiency exceeding 15% through additive-controlled nanostructure tailoring.
Organometal halide perovskites (OHP) are promising materials for low-cost, high-efficiency light-emitting diodes. In films with a distribution of two-dimensional OHP nanosheets and small three-dimensional nanocrystals, an energy funnel can be realized that concentrates the excitations in highly efficient radiative recombination centers. However, this energy funnel is likely to contain inefficient pathways as the size distribution of nanocrystals, the phase separation between the OHP and the organic phase. Here, we demonstrate that the OHP crystallite distribution and phase separation can be precisely controlled by adding a molecule that suppresses crystallization of the organic phase. We use these improved material properties to achieve OHP light-emitting diodes with an external quantum efficiency of 15.5%. Our results demonstrate that through the addition of judiciously selected molecular additives, sufficient carrier confinement with first-order recombination characteristics, and efficient suppression of non-radiative recombination can be achieved while retaining efficient charge transport characteristics
Automated Battery Making Fault Classification Using Over-Sampled Image Data CNN Features
Due to the tremendous expectations placed on batteries to produce a reliable and secure product, fault detection has become a critical part of the manufacturing process. Manually, it takes much labor and effort to test each battery individually for manufacturing faults including burning, welding that is too high, missing welds, shifting, welding holes, and so forth. Additionally, manual battery fault detection takes too much time and is extremely expensive. We solved this issue by using image processing and machine learning techniques to automatically detect faults in the battery manufacturing process. Our approach will reduce the need for human intervention, save time, and be easy to implement. A CMOS camera was used to collect a large number of images belonging to eight common battery manufacturing faults. The welding area of the batteries’ positive and negative terminals was captured from different distances, between 40 and 50 cm. Before deploying the learning models, first, we used the CNN for feature extraction from the image data. To over-sample the dataset, we used the Synthetic Minority Over-sampling Technique (SMOTE) since the dataset was highly imbalanced, resulting in over-fitting of the learning model. Several machine learning and deep learning models were deployed on the CNN-extracted features and over-sampled data. Random forest achieved a significant 84% accuracy with our proposed approach. Additionally, we applied K-fold cross-validation with the proposed approach to validate the significance of the approach, and the logistic regression achieved an 81.897% mean accuracy score and a +/− 0.0255 standard deviation
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