352 research outputs found
ODN: Opening the Deep Network for Open-set Action Recognition
In recent years, the performance of action recognition has been significantly
improved with the help of deep neural networks. Most of the existing action
recognition works hold the \textit{closed-set} assumption that all action
categories are known beforehand while deep networks can be well trained for
these categories. However, action recognition in the real world is essentially
an \textit{open-set} problem, namely, it is impossible to know all action
categories beforehand and consequently infeasible to prepare sufficient
training samples for those emerging categories. In this case, applying
closed-set recognition methods will definitely lead to unseen-category errors.
To address this challenge, we propose the Open Deep Network (ODN) for the
open-set action recognition task. Technologically, ODN detects new categories
by applying a multi-class triplet thresholding method, and then dynamically
reconstructs the classification layer and "opens" the deep network by adding
predictors for new categories continually. In order to transfer the learned
knowledge to the new category, two novel methods, Emphasis Initialization and
Allometry Training, are adopted to initialize and incrementally train the new
predictor so that only few samples are needed to fine-tune the model. Extensive
experiments show that ODN can effectively detect and recognize new categories
with little human intervention, thus applicable to the open-set action
recognition tasks in the real world. Moreover, ODN can even achieve comparable
performance to some closed-set methods.Comment: 6 pages, 3 figures, ICME 201
Margin-Based Few-Shot Class-Incremental Learning with Class-Level Overfitting Mitigation
Few-shot class-incremental learning (FSCIL) is designed to incrementally
recognize novel classes with only few training samples after the (pre-)training
on base classes with sufficient samples, which focuses on both base-class
performance and novel-class generalization. A well known modification to the
base-class training is to apply a margin to the base-class classification.
However, a dilemma exists that we can hardly achieve both good base-class
performance and novel-class generalization simultaneously by applying the
margin during the base-class training, which is still under explored. In this
paper, we study the cause of such dilemma for FSCIL. We first interpret this
dilemma as a class-level overfitting (CO) problem from the aspect of pattern
learning, and then find its cause lies in the easily-satisfied constraint of
learning margin-based patterns. Based on the analysis, we propose a novel
margin-based FSCIL method to mitigate the CO problem by providing the pattern
learning process with extra constraint from the margin-based patterns
themselves. Extensive experiments on CIFAR100, Caltech-USCD Birds-200-2011
(CUB200), and miniImageNet demonstrate that the proposed method effectively
mitigates the CO problem and achieves state-of-the-art performance
Annotation Efficient Person Re-Identification with Diverse Cluster-Based Pair Selection
Person Re-identification (Re-ID) has attracted great attention due to its
promising real-world applications. However, in practice, it is always costly to
annotate the training data to train a Re-ID model, and it still remains
challenging to reduce the annotation cost while maintaining the performance for
the Re-ID task. To solve this problem, we propose the Annotation Efficient
Person Re-Identification method to select image pairs from an alternative pair
set according to the fallibility and diversity of pairs, and train the Re-ID
model based on the annotation. Specifically, we design an annotation and
training framework to firstly reduce the size of the alternative pair set by
clustering all images considering the locality of features, secondly select
images pairs from intra-/inter-cluster samples for human to annotate, thirdly
re-assign clusters according to the annotation, and finally train the model
with the re-assigned clusters. During the pair selection, we seek for valuable
pairs according to pairs' fallibility and diversity, which includes an
intra-cluster criterion to construct image pairs with the most chaotic samples
and the representative samples within clusters, an inter-cluster criterion to
construct image pairs between clusters based on the second-order Wasserstein
distance, and a diversity criterion for clusterbased pair selection. Combining
all criteria above, a greedy strategy is developed to solve the pair selection
problem. Finally, the above
clustering-selecting-annotating-reassigning-training procedure will be repeated
until the annotation budget is reached. Extensive experiments on three widely
adopted Re-ID datasets show that we can greatly reduce the annotation cost
while achieving better performance compared with state-of-the-art works
Regulating Blood Clot Fibrin Films to Manipulate Biomaterial-Mediated Foreign Body Responses
The clinical efficacy of implanted biomaterials is often compromised by host immune recognition and subsequent foreign body responses (FBRs). During the implantation, biomaterials inevitably come into direct contact with the blood, absorbing blood protein and forming blood clot. Many studies have been carried out to regulate protein adsorption, thus manipulating FBR. However, the role of clot surface fibrin films formed by clotting shrinkage in host reactions and FBR is often ignored. Because of the principle of fibrin film formation being relevant to fibrinogen or clotting factor absorption, it is feasible to manipulate the fibrin film formation via tuning the absorption of fibrinogen and clotting factor. As biological hydroxyapatite reserved bone architecture and microporous structure, the smaller particle size may expose more microporous structures and adsorb more fibrinogen or clotting factor. Therefore, we set up 3 sizes (small, <0.2 mm; medium, 1 to 2 mm; large, 3 to 4 mm) of biological hydroxyapatite (porcine bone-derived hydroxyapatite) with different microporous structures to investigate the absorption of blood protein, the formation of clot surface fibrin films, and the subsequent FBR. We found that small group adsorbed more clotting factors because of more microporous structures and formed the thinnest and sparsest fibrin films. These thinnest and sparsest fibrin films increased inflammation and profibrosis of macrophages through a potential signaling pathway of cell adhesion–cytoskeleton–autophagy, leading to the stronger FBR. Large group adsorbed lesser clotting factors, forming the thickest and densest fibrin films, easing inflammation and profibrosis of macrophages, and finally mitigating FBR. Thus, this study deepens the understanding of the role of fibrin films in host recognition and FBR and demonstrates the feasibility of a strategy to regulate FBR by modulating fibrin films via tuning the absorption of blood proteins
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