53 research outputs found
Reach-SDP: Reachability Analysis of Closed-Loop Systems with Neural Network Controllers via Semidefinite Programming
There has been an increasing interest in using neural networks in closed-loop
control systems to improve performance and reduce computational costs for
on-line implementation. However, providing safety and stability guarantees for
these systems is challenging due to the nonlinear and compositional structure
of neural networks. In this paper, we propose a novel forward reachability
analysis method for the safety verification of linear time-varying systems with
neural networks in feedback interconnection. Our technical approach relies on
abstracting the nonlinear activation functions by quadratic constraints, which
leads to an outer-approximation of forward reachable sets of the closed-loop
system. We show that we can compute these approximate reachable sets using
semidefinite programming. We illustrate our method in a quadrotor example, in
which we first approximate a nonlinear model predictive controller via a deep
neural network and then apply our analysis tool to certify finite-time
reachability and constraint satisfaction of the closed-loop system
Learning-Aware Safety for Interactive Autonomy
One of the outstanding challenges for the widespread deployment of robotic
systems like autonomous vehicles is ensuring safe interaction with humans
without sacrificing efficiency. Existing safety analysis methods often neglect
the robot's ability to learn and adapt at runtime, leading to overly
conservative behavior. This paper proposes a new closed-loop paradigm for
synthesizing safe control policies that explicitly account for the system's
evolving uncertainty under possible future scenarios. The formulation reasons
jointly about the physical dynamics and the robot's learning algorithm, which
updates its internal belief over time. We leverage adversarial deep
reinforcement learning (RL) for scaling to high dimensions, enabling tractable
safety analysis even for implicit learning dynamics induced by state-of-the-art
prediction models. We demonstrate our framework's ability to work with both
Bayesian belief propagation and the implicit learning induced by a large
pre-trained neural trajectory predictor.Comment: Conference on Robot Learning 202
FaSTrack: a Modular Framework for Real-Time Motion Planning and Guaranteed Safe Tracking
Real-time, guaranteed safe trajectory planning is vital for navigation in
unknown environments. However, real-time navigation algorithms typically
sacrifice robustness for computation speed. Alternatively, provably safe
trajectory planning tends to be too computationally intensive for real-time
replanning. We propose FaSTrack, Fast and Safe Tracking, a framework that
achieves both real-time replanning and guaranteed safety. In this framework,
real-time computation is achieved by allowing any trajectory planner to use a
simplified \textit{planning model} of the system. The plan is tracked by the
system, represented by a more realistic, higher-dimensional \textit{tracking
model}. We precompute the tracking error bound (TEB) due to mismatch between
the two models and due to external disturbances. We also obtain the
corresponding tracking controller used to stay within the TEB. The
precomputation does not require prior knowledge of the environment. We
demonstrate FaSTrack using Hamilton-Jacobi reachability for precomputation and
three different real-time trajectory planners with three different
tracking-planning model pairs.Comment: Published in the IEEE Transactions on Automatic Contro
A Deep Learning Approach to Generating Photospheric Vector Magnetograms of Solar Active Regions for SOHO/MDI Using SDO/HMI and BBSO Data
Solar activity is usually caused by the evolution of solar magnetic fields.
Magnetic field parameters derived from photospheric vector magnetograms of
solar active regions have been used to analyze and forecast eruptive events
such as solar flares and coronal mass ejections. Unfortunately, the most recent
solar cycle 24 was relatively weak with few large flares, though it is the only
solar cycle in which consistent time-sequence vector magnetograms have been
available through the Helioseismic and Magnetic Imager (HMI) on board the Solar
Dynamics Observatory (SDO) since its launch in 2010. In this paper, we look
into another major instrument, namely the Michelson Doppler Imager (MDI) on
board the Solar and Heliospheric Observatory (SOHO) from 1996 to 2010. The data
archive of SOHO/MDI covers more active solar cycle 23 with many large flares.
However, SOHO/MDI data only has line-of-sight (LOS) magnetograms. We propose a
new deep learning method, named MagNet, to learn from combined LOS
magnetograms, Bx and By taken by SDO/HMI along with H-alpha observations
collected by the Big Bear Solar Observatory (BBSO), and to generate vector
components Bx' and By', which would form vector magnetograms with observed LOS
data. In this way, we can expand the availability of vector magnetograms to the
period from 1996 to present. Experimental results demonstrate the good
performance of the proposed method. To our knowledge, this is the first time
that deep learning has been used to generate photospheric vector magnetograms
of solar active regions for SOHO/MDI using SDO/HMI and H-alpha data.Comment: 15 pages, 6 figure
Unraveling the transcriptome-based network of tfh cells in primary sjogren syndrome: insights from a systems biology approach
BackgroundPrimary Sjogren Syndrome (pSS) is an autoimmune disease characterized by immune cell infiltration. While the presence of follicular T helper (Tfh) cells in the glandular microenvironment has been observed, their biological functions and clinical significance remain poorly understood.MethodsWe enrolled a total of 106 patients with pSS and 46 patients without pSS for this study. Clinical data and labial salivary gland (LSG) biopsies were collected from all participants. Histological staining was performed to assess the distribution of Tfh cells and B cells. Transcriptome analysis using RNA-sequencing (RNA-seq) was conducted on 56 patients with pSS and 26 patients without pSS to uncover the underlying molecular mechanisms of Tfh cells. To categorize patients, we employed the single-sample gene set enrichment analysis (ssGSEA) algorithm, dividing them into low- and high-Tfh groups. We then utilized gene set enrichment analysis (GSEA), weighted gene co-expression network analysis (WGCNA), and deconvolution tools to explore functional and immune infiltration differences between the low- and high-Tfh groups.ResultsPatients with pSS had a higher positive rate of the antinuclear antibody (ANA), anti-Ro52, anti-SSA, anti-SSB and hypergammaglobulinaemia and higher levels of serum IgG compared to the non-pSS. Histopathologic analyses revealed the presence of Tfh cells (CD4+CXCR5+ICOS+) in germinal centers (GC) within the labial glands of pSS patients. GSEA, WGCNA, and correlation analysis indicated that the high-Tfh group was associated with an immune response related to virus-mediated IFN response and metabolic processes, primarily characterized by hypoxia, elevated glycolysis, and oxidative phosphorylation levels. In pSS, most immune cell types exhibited significantly higher infiltration levels in the high-Tfh group compared to the low-Tfh group. Additionally, patients in the Tfh-high group demonstrated a higher positive rate of the ANA, rheumatoid factor (RF), and hypergammaglobulinaemia, as well as higher serum IgG levels.ConclusionOur study suggests that Tfh cells may play a crucial role in the pathogenesis of pSS and could serve as potential therapeutic targets in pSS patients
Large expert-curated database for benchmarking document similarity detection in biomedical literature search
Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe
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