5 research outputs found
Feature-based Transferable Disruption Prediction for future tokamaks using domain adaptation
The high acquisition cost and the significant demand for disruptive
discharges for data-driven disruption prediction models in future tokamaks pose
an inherent contradiction in disruption prediction research. In this paper, we
demonstrated a novel approach to predict disruption in a future tokamak only
using a few discharges based on a domain adaptation algorithm called CORAL. It
is the first attempt at applying domain adaptation in the disruption prediction
task. In this paper, this disruption prediction approach aligns a few data from
the future tokamak (target domain) and a large amount of data from the existing
tokamak (source domain) to train a machine learning model in the existing
tokamak. To simulate the existing and future tokamak case, we selected J-TEXT
as the existing tokamak and EAST as the future tokamak. To simulate the lack of
disruptive data in future tokamak, we only selected 100 non-disruptive
discharges and 10 disruptive discharges from EAST as the target domain training
data. We have improved CORAL to make it more suitable for the disruption
prediction task, called supervised CORAL. Compared to the model trained by
mixing data from the two tokamaks, the supervised CORAL model can enhance the
disruption prediction performance for future tokamaks (AUC value from 0.764 to
0.890). Through interpretable analysis, we discovered that using the supervised
CORAL enables the transformation of data distribution to be more similar to
future tokamak. An assessment method for evaluating whether a model has learned
a trend of similar features is designed based on SHAP analysis. It demonstrates
that the supervised CORAL model exhibits more similarities to the model trained
on large data sizes of EAST. FTDP provides a light, interpretable, and
few-data-required way by aligning features to predict disruption using small
data sizes from the future tokamak.Comment: 15 pages, 9 figure
Disruption Precursor Onset Time Study Based on Semi-supervised Anomaly Detection
The full understanding of plasma disruption in tokamaks is currently lacking,
and data-driven methods are extensively used for disruption prediction.
However, most existing data-driven disruption predictors employ supervised
learning techniques, which require labeled training data. The manual labeling
of disruption precursors is a tedious and challenging task, as some precursors
are difficult to accurately identify, limiting the potential of machine
learning models. To address this issue, commonly used labeling methods assume
that the precursor onset occurs at a fixed time before the disruption, which
may not be consistent for different types of disruptions or even the same type
of disruption, due to the different speeds at which plasma instabilities
escalate. This leads to mislabeled samples and suboptimal performance of the
supervised learning predictor. In this paper, we present a disruption
prediction method based on anomaly detection that overcomes the drawbacks of
unbalanced positive and negative data samples and inaccurately labeled
disruption precursor samples. We demonstrate the effectiveness and reliability
of anomaly detection predictors based on different algorithms on J-TEXT and
EAST to evaluate the reliability of the precursor onset time inferred by the
anomaly detection predictor. The precursor onset times inferred by these
predictors reveal that the labeling methods have room for improvement as the
onset times of different shots are not necessarily the same. Finally, we
optimize precursor labeling using the onset times inferred by the anomaly
detection predictor and test the optimized labels on supervised learning
disruption predictors. The results on J-TEXT and EAST show that the models
trained on the optimized labels outperform those trained on fixed onset time
labels.Comment: 21 pages, 11 figure
Broadly neutralizing antibodies derived from the earliest COVID-19 convalescents protect mice from SARS-CoV-2 variants challenge
Abstract Coronavirus disease 2019 (COVID-19) was first reported three years ago, when a group of individuals were infected with the original SARS-CoV-2 strain, based on which vaccines were developed. Here, we develop six human monoclonal antibodies (mAbs) from two elite convalescents in Wuhan and show that these mAbs recognize diverse epitopes on the receptor binding domain (RBD) and can inhibit the infection of SARS-CoV-2 original strain and variants of concern (VOCs) to varying degrees, including Omicron strains XBB and XBB.1.5. Of these mAbs, the two most broadly and potently neutralizing mAbs (7B3 and 14B1) exhibit prophylactic activity against SARS-CoV-2 WT infection and therapeutic effects against SARS-CoV-2 Delta variant challenge in K18-hACE2 KI mice. Furthermore, post-exposure treatment with 7B3 protects mice from lethal Omicron variants infection. Cryo-EM analysis of the spike trimer complexed with 14B1 or 7B3 reveals that these two mAbs bind partially overlapped epitopes onto the RBD of the spike, and sterically disrupt the binding of human angiotensin-converting enzyme 2 (hACE2) to RBD. Our results suggest that mAbs with broadly neutralizing activity against different SARS-CoV-2 variants are present in COVID-19 convalescents infected by the ancestral SARS-CoV-2 strain, indicating that people can benefit from former infections or vaccines despite the extensive immune escape of SARS-CoV-2