66 research outputs found
Spatial-Temporal-Aware Safe Multi-Agent Reinforcement Learning of Connected Autonomous Vehicles in Challenging Scenarios
Communication technologies enable coordination among connected and autonomous
vehicles (CAVs). However, it remains unclear how to utilize shared information
to improve the safety and efficiency of the CAV system. In this work, we
propose a framework of constrained multi-agent reinforcement learning (MARL)
with a parallel safety shield for CAVs in challenging driving scenarios. The
coordination mechanisms of the proposed MARL include information sharing and
cooperative policy learning, with Graph Convolutional Network (GCN)-Transformer
as a spatial-temporal encoder that enhances the agent's environment awareness.
The safety shield module with Control Barrier Functions (CBF)-based safety
checking protects the agents from taking unsafe actions. We design a
constrained multi-agent advantage actor-critic (CMAA2C) algorithm to train safe
and cooperative policies for CAVs. With the experiment deployed in the CARLA
simulator, we verify the effectiveness of the safety checking, spatial-temporal
encoder, and coordination mechanisms designed in our method by comparative
experiments in several challenging scenarios with the defined hazard vehicles
(HAZV). Results show that our proposed methodology significantly increases
system safety and efficiency in challenging scenarios.Comment: This paper has been accepted by the 2023 IEEE International
Conference on Robotics and Automation (ICRA 2023). 6 pages, 5 figure
Shared Information-Based Safe And Efficient Behavior Planning For Connected Autonomous Vehicles
The recent advancements in wireless technology enable connected autonomous
vehicles (CAVs) to gather data via vehicle-to-vehicle (V2V) communication, such
as processed LIDAR and camera data from other vehicles. In this work, we design
an integrated information sharing and safe multi-agent reinforcement learning
(MARL) framework for CAVs, to take advantage of the extra information when
making decisions to improve traffic efficiency and safety. We first use weight
pruned convolutional neural networks (CNN) to process the raw image and point
cloud LIDAR data locally at each autonomous vehicle, and share CNN-output data
with neighboring CAVs. We then design a safe actor-critic algorithm that
utilizes both a vehicle's local observation and the information received via
V2V communication to explore an efficient behavior planning policy with safety
guarantees. Using the CARLA simulator for experiments, we show that our
approach improves the CAV system's efficiency in terms of average velocity and
comfort under different CAV ratios and different traffic densities. We also
show that our approach avoids the execution of unsafe actions and always
maintains a safe distance from other vehicles. We construct an
obstacle-at-corner scenario to show that the shared vision can help CAVs to
observe obstacles earlier and take action to avoid traffic jams.Comment: This paper gets the Best Paper Award in the DCAA workshop of AAAI
202
Multi-Agent Reinforcement Learning Guided by Signal Temporal Logic Specifications
Reward design is a key component of deep reinforcement learning, yet some
tasks and designer's objectives may be unnatural to define as a scalar cost
function. Among the various techniques, formal methods integrated with DRL have
garnered considerable attention due to their expressiveness and flexibility to
define the reward and requirements for different states and actions of the
agent. However, how to leverage Signal Temporal Logic (STL) to guide
multi-agent reinforcement learning reward design remains unexplored. Complex
interactions, heterogeneous goals and critical safety requirements in
multi-agent systems make this problem even more challenging. In this paper, we
propose a novel STL-guided multi-agent reinforcement learning framework. The
STL requirements are designed to include both task specifications according to
the objective of each agent and safety specifications, and the robustness
values of the STL specifications are leveraged to generate rewards. We validate
the advantages of our method through empirical studies. The experimental
results demonstrate significant reward performance improvements compared to
MARL without STL guidance, along with a remarkable increase in the overall
safety rate of the multi-agent systems
Compact fiber-optic diode-laser sensor system for wide-dynamicrange relative humidity measurement
SIRT1 Activation by Resveratrol Alleviates Cardiac Dysfunction via Mitochondrial Regulation in Diabetic Cardiomyopathy Mice
Background. Diabetic cardiomyopathy (DCM) is a major threat for diabetic patients. Silent information regulator 1 (SIRT1) has a regulatory effect on mitochondrial dynamics, which is associated with DCM pathological changes. Our study aims to investigate whether resveratrol, a SRIT1 activator, could exert a protective effect against DCM. Methods and Results. Cardiac-specific SIRT1 knockout (SIRT1KO) mice were generated using Cre-loxP system. SIRT1KO mice displayed symptoms of DCM, including cardiac hypertrophy and dysfunction, insulin resistance, and abnormal glucose metabolism. DCM and SIRT1KO hearts showed impaired mitochondrial biogenesis and function, while SIRT1 activation by resveratrol reversed this in DCM mice. High glucose caused increased apoptosis, impaired mitochondrial biogenesis, and function in cardiomyocytes, which was alleviated by resveratrol. SIRT1 deletion by both SIRT1KO and shRNA abolished the beneficial effects of resveratrol. Furthermore, the function of SIRT1 is mediated via the deacetylation effect on peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), thus inducing increased expression of nuclear respiratory factor 1 (NRF-1), NRF-2, estrogen-related receptor-α (ERR-α), and mitochondrial transcription factor A (TFAM). Conclusions. Cardiac deletion of SIRT1 caused phenotypes resembling DCM. Activation of SIRT1 by resveratrol ameliorated cardiac injuries in DCM through PGC-1α-mediated mitochondrial regulation. Collectively, SIRT1 may serve as a potential therapeutic target for DCM
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A TSC signaling node at the peroxisome regulates mTORC1 and autophagy in response to ROS
Subcellular localization is emerging as an important mechanism for mTORC1 regulation. We report that the tuberous sclerosis complex (TSC) signaling node, TSC1, TSC2 and Rheb, localizes to peroxisomes, where it regulates mTORC1 in response to reactive oxygen species (ROS). TSC1 and TSC2 were bound by PEX19 and PEX5, respectively, and peroxisome-localized TSC functioned as a Rheb GAP to suppress mTORC1 and induce autophagy. Naturally occurring pathogenic mutations in TSC2 decreased PEX5 binding, abrogated peroxisome localization, Rheb GAP activity, and suppression of mTORC1 by ROS. Cells lacking peroxisomes were deficient in mTORC1 repression by ROS and peroxisome-localization deficient TSC2 mutants caused polarity defects and formation of multiple axons in neurons. These data identify a role for TSC in responding to ROS at the peroxisome, and identify the peroxisome as a signaling organelle involved in regulation of mTORC1
Searching for the nano-Hertz stochastic gravitational wave background with the Chinese Pulsar Timing Array Data Release I
Observing and timing a group of millisecond pulsars (MSPs) with high
rotational stability enables the direct detection of gravitational waves (GWs).
The GW signals can be identified from the spatial correlations encoded in the
times-of-arrival of widely spaced pulsar-pairs. The Chinese Pulsar Timing Array
(CPTA) is a collaboration aiming at the direct GW detection with observations
carried out using Chinese radio telescopes. This short article serves as a
`table of contents' for a forthcoming series of papers related to the CPTA Data
Release 1 (CPTA DR1) which uses observations from the Five-hundred-meter
Aperture Spherical radio Telescope (FAST). Here, after summarizing the time
span and accuracy of CPTA DR1, we report the key results of our statistical
inference finding a correlated signal with amplitude \log A_{\rm c}= -14.4
\,^{+1.0}_{-2.8} for spectral index in the range of
assuming a GW background (GWB) induced quadrupolar correlation. The search for
the Hellings-Downs (HD) correlation curve is also presented, where some
evidence for the HD correlation has been found that a 4.6- statistical
significance is achieved using the discrete frequency method around the
frequency of 14 nHz. We expect that the future International Pulsar Timing
Array data analysis and the next CPTA data release will be more sensitive to
the nHz GWB, which could verify the current results.Comment: 18 pages, 6 figures, submitted to "Research in astronomy and
astrophysics" 22nd March 202
Hominin occupation of the Chinese Loess Plateau since about 2.1 million years ago
Considerable attention has been paid to dating the earliest appearance of hominins outside Africa. The earliest skeletal and artefactual evidence for the genus Homo in Asia currently comes from Dmanisi, Georgia, and is dated to approximately 1.77-1.85 million years ago (Ma)(1). Two incisors that may belong to Homo erectus come from Yuanmou, south China, and are dated to 1.7 Ma(2); the next-oldest evidence is an H. erectus cranium from Lantian (Gongwangling)-which has recently been dated to 1.63 Ma(3) and the earliest hominin fossils from the Sangiran dome in Java, which are dated to about 1.5-1.6 Ma(4). Artefacts from Majuangou III5 and Shangshazui(6) in the Nihewan basin, north China, have also been dated to 1.6-1.7 Ma. Here we report an Early Pleistocene and largely continuous artefact sequence from Shangchen, which is a newly discovered Palaeolithic locality of the southern Chinese Loess Plateau, near Gongwangling in Lantian county. The site contains 17 artefact layers that extend from palaeosol S15-dated to approximately 1.26 Ma-to loess L28, which we date to about 2.12 Ma. This discovery implies that hominins left Africa earlier than indicated by the evidence from Dmanisi
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