51 research outputs found
An Evaluation of Non-Contrastive Self-Supervised Learning for Federated Medical Image Analysis
Privacy and annotation bottlenecks are two major issues that profoundly
affect the practicality of machine learning-based medical image analysis.
Although significant progress has been made in these areas, these issues are
not yet fully resolved. In this paper, we seek to tackle these concerns head-on
and systematically explore the applicability of non-contrastive self-supervised
learning (SSL) algorithms under federated learning (FL) simulations for medical
image analysis. We conduct thorough experimentation of recently proposed
state-of-the-art non-contrastive frameworks under standard FL setups. With the
SoTA Contrastive Learning algorithm, SimCLR as our comparative baseline, we
benchmark the performances of our 4 chosen non-contrastive algorithms under
non-i.i.d. data conditions and with a varying number of clients. We present a
holistic evaluation of these techniques on 6 standardized medical imaging
datasets. We further analyse different trends inferred from the findings of our
research, with the aim to find directions for further research based on ours.
To the best of our knowledge, ours is the first to perform such a thorough
analysis of federated self-supervised learning for medical imaging. All of our
source code will be made public upon acceptance of the paper
Segmenting Scientific Abstracts into Discourse Categories: A Deep Learning-Based Approach for Sparse Labeled Data
The abstract of a scientific paper distills the contents of the paper into a
short paragraph. In the biomedical literature, it is customary to structure an
abstract into discourse categories like BACKGROUND, OBJECTIVE, METHOD, RESULT,
and CONCLUSION, but this segmentation is uncommon in other fields like computer
science. Explicit categories could be helpful for more granular, that is,
discourse-level search and recommendation. The sparsity of labeled data makes
it challenging to construct supervised machine learning solutions for automatic
discourse-level segmentation of abstracts in non-bio domains. In this paper, we
address this problem using transfer learning. In particular, we define three
discourse categories BACKGROUND, TECHNIQUE, OBSERVATION-for an abstract because
these three categories are the most common. We train a deep neural network on
structured abstracts from PubMed, then fine-tune it on a small hand-labeled
corpus of computer science papers. We observe an accuracy of 75% on the test
corpus. We perform an ablation study to highlight the roles of the different
parts of the model. Our method appears to be a promising solution to the
automatic segmentation of abstracts, where the labeled data is sparse.Comment: to appear in the proceedings of JCDL'202
A lightweight QRS detector for single lead ECG signals using a max-min difference algorithm
Background and objectives - Detection of the R-peak pertaining to the QRS complex of an ECG signal plays an important role for the diagnosis of a patient's heart condition. To accurately identify the QRS locations from the acquired raw ECG signals, we need to handle a number of challenges, which include noise, baseline wander, varying peak amplitudes, and signal abnormality. This research aims to address these challenges by developing an efficient lightweight algorithm for QRS (i.e., R-peak) detection from raw ECG signals.
Methods - A lightweight real-time sliding window-based Max-Min Difference (MMD) algorithm for QRS detection from Lead II ECG signals is proposed. Targeting to achieve the best trade-off between computational efficiency and detection accuracy, the proposed algorithm consists of five key steps for QRS detection, namely, baseline correction, MMD curve generation, dynamic threshold computation, R-peak detection, and error correction. Five annotated databases from Physionet are used for evaluating the proposed algorithm in R-peak detection. Integrated with a feature extraction technique and a neural network classifier, the proposed ORS detection algorithm has also been extended to undertake normal and abnormal heartbeat detection from ECG signals.
Results - The proposed algorithm exhibits a high degree of robustness in QRS detection and achieves an average sensitivity of 99.62% and an average positive predictivity of 99.67%. Its performance compares favorably with those from the existing state-of-the-art models reported in the literature. In regards to normal and abnormal heartbeat detection, the proposed QRS detection algorithm in combination with the feature extraction technique and neural network classifier achieves an overall accuracy rate of 93.44% based on an empirical evaluation using the MIT-BIH Arrhythmia data set with 10-fold cross validation.
Conclusions - In comparison with other related studies, the proposed algorithm offers a lightweight adaptive alternative for R-peak detection with good computational efficiency. The empirical results indicate that it not only yields a high accuracy rate in QRS detection, but also exhibits efficient computational complexity at the order of O(n), where n is the length of an ECG signal
Generation of Highlights from Research Papers Using Pointer-Generator Networks and SciBERT Embeddings
Nowadays many research articles are prefaced with research highlights to
summarize the main findings of the paper. Highlights not only help researchers
precisely and quickly identify the contributions of a paper, they also enhance
the discoverability of the article via search engines. We aim to automatically
construct research highlights given certain segments of the research paper. We
use a pointer-generator network with coverage mechanism and a contextual
embedding layer at the input that encodes the input tokens into SciBERT
embeddings. We test our model on a benchmark dataset, CSPubSum and also present
MixSub, a new multi-disciplinary corpus of papers for automatic research
highlight generation. For both CSPubSum and MixSub, we have observed that the
proposed model achieves the best performance compared to related variants and
other models proposed in the literature. On the CSPubSum data set, our model
achieves the best performance when the input is only the abstract of a paper as
opposed to other segments of the paper. It produces ROUGE-1, ROUGE-2 and
ROUGE-L F1-scores of 38.26, 14.26 and 35.51, respectively, METEOR F1-score of
32.62, and BERTScore F1 of 86.65 which outperform all other baselines. On the
new MixSub data set, where only the abstract is the input, our proposed model
(when trained on the whole training corpus without distinguishing between the
subject categories) achieves ROUGE-1, ROUGE-2 and ROUGE-L F1-scores of 31.78,
9.76 and 29.3, respectively, METEOR F1-score of 24.00, and BERTScore F1 of
85.25, outperforming other models.Comment: 18 pages, 7 figures, 7 table
A scattering and repulsive swarm intelligence algorithm for solving global optimization problems
The firefly algorithm (FA), as a metaheuristic search method, is useful for solving diverse optimization problems. However, it is challenging to use FA in tackling high dimensional optimization problems, and the random movement of FA has a high likelihood to be trapped in local optima. In this research, we propose three improved algorithms, i.e., Repulsive Firefly Algorithm (RFA), Scattering Repulsive Firefly Algorithm (SRFA), and Enhanced SRFA (ESRFA), to mitigate the premature convergence problem of the original FA model. RFA adopts a repulsive force strategy to accelerate fireflies (i.e. solutions) to move away from unpromising search regions, in order to reach global optimality in fewer iterations. SRFA employs a scattering mechanism along with the repulsive force strategy to divert weak neighbouring solutions to new search regions, in order to increase global exploration. Motivated by the survival tactics of hawk-moths, ESRFA incorporates a hovering-driven attractiveness operation, an exploration-driven evading mechanism, and a learning scheme based on the historical best experience in the neighbourhood to further enhance SRFA. Standard and CEC2014 benchmark optimization functions are used for evaluation of the proposed FA-based models. The empirical results indicate that ESRFA, SRFA and RFA significantly outperform the original FA model, a number of state-of-the-art FA variants, and other swarm-based algorithms, which include Simulated Annealing, Cuckoo Search, Particle Swarm, Bat Swarm, Dragonfly, and Ant-Lion Optimization, in diverse challenging benchmark functions
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