77 research outputs found
Game-theoretic Objective Space Planning
Autonomous Racing awards agents that react to opponents' behaviors with agile
maneuvers towards progressing along the track while penalizing both
over-aggressive and over-conservative agents. Understanding the intent of other
agents is crucial to deploying autonomous systems in adversarial multi-agent
environments. Current approaches either oversimplify the discretization of the
action space of agents or fail to recognize the long-term effect of actions and
become myopic. Our work focuses on addressing these two challenges. First, we
propose a novel dimension reduction method that encapsulates diverse agent
behaviors while conserving the continuity of agent actions. Second, we
formulate the two-agent racing game as a regret minimization problem and
provide a solution for tractable counterfactual regret minimization with a
regret prediction model. Finally, we validate our findings experimentally on
scaled autonomous vehicles. We demonstrate that using the proposed
game-theoretic planner using agent characterization with the objective space
significantly improves the win rate against different opponents, and the
improvement is transferable to unseen opponents in an unseen environment.Comment: Submitted to 2023 IEEE International Conference on Robotics and
Automation (ICRA 2023
Winning the 3rd Japan Automotive AI Challenge -- Autonomous Racing with the Autoware.Auto Open Source Software Stack
The 3rd Japan Automotive AI Challenge was an international online autonomous
racing challenge where 164 teams competed in December 2021. This paper outlines
the winning strategy to this competition, and the advantages and challenges of
using the Autoware.Auto open source autonomous driving platform for multi-agent
racing. Our winning approach includes a lane-switching opponent overtaking
strategy, a global raceline optimization, and the integration of various tools
from Autoware.Auto including a Model-Predictive Controller. We describe the use
of perception, planning and control modules for high-speed racing applications
and provide experience-based insights on working with Autoware.Auto. While our
approach is a rule-based strategy that is suitable for non-interactive
opponents, it provides a good reference and benchmark for learning-enabled
approaches.Comment: Accepted at Autoware Workshop at IV 202
HOFA: Twitter Bot Detection with Homophily-Oriented Augmentation and Frequency Adaptive Attention
Twitter bot detection has become an increasingly important and challenging
task to combat online misinformation, facilitate social content moderation, and
safeguard the integrity of social platforms. Though existing graph-based
Twitter bot detection methods achieved state-of-the-art performance, they are
all based on the homophily assumption, which assumes users with the same label
are more likely to be connected, making it easy for Twitter bots to disguise
themselves by following a large number of genuine users. To address this issue,
we proposed HOFA, a novel graph-based Twitter bot detection framework that
combats the heterophilous disguise challenge with a homophily-oriented graph
augmentation module (Homo-Aug) and a frequency adaptive attention module
(FaAt). Specifically, the Homo-Aug extracts user representations and computes a
k-NN graph using an MLP and improves Twitter's homophily by injecting the k-NN
graph. For the FaAt, we propose an attention mechanism that adaptively serves
as a low-pass filter along a homophilic edge and a high-pass filter along a
heterophilic edge, preventing user features from being over-smoothed by their
neighborhood. We also introduce a weight guidance loss to guide the frequency
adaptive attention module. Our experiments demonstrate that HOFA achieves
state-of-the-art performance on three widely-acknowledged Twitter bot detection
benchmarks, which significantly outperforms vanilla graph-based bot detection
techniques and strong heterophilic baselines. Furthermore, extensive studies
confirm the effectiveness of our Homo-Aug and FaAt module, and HOFA's ability
to demystify the heterophilous disguise challenge.Comment: 11 pages, 7 figure
Accelerating Online Reinforcement Learning via Supervisory Safety Systems
Deep reinforcement learning (DRL) is a promising method to learn control
policies for robots only from demonstration and experience. To cover the whole
dynamic behaviour of the robot, the DRL training is an active exploration
process typically derived in simulation environments. Although this simulation
training is cheap and fast, applying DRL algorithms to real-world settings is
difficult. If agents are trained until they perform safely in simulation,
transferring them to physical systems is difficult due to the sim-to-real gap
caused by the difference between the simulation dynamics and the physical
robot.
In this paper, we present a method of online training a DRL agent to drive
autonomously on a physical vehicle by using a model-based safety supervisor.
Our solution uses a supervisory system to check if the action selected by the
agent is safe or unsafe and ensure that a safe action is always implemented on
the vehicle. With this, we can bypass the sim-to-real problem while training
the DRL algorithm safely, quickly, and efficiently. We provide a variety of
real-world experiments where we train online a small-scale, physical vehicle to
drive autonomously with no prior simulation training. The evaluation results
show that our method trains agents with improved sample efficiency while never
crashing, and the trained agents demonstrate better driving performance than
those trained in simulation.Comment: 7 Pages, 10 Figures, 1 Table. Submitted to 2023 IEEE International
Conference on Robotics and Automation (ICRA 2023
Teaching Autonomous Systems Hands-On: Leveraging Modular Small-Scale Hardware in the Robotics Classroom
Although robotics courses are well established in higher education, the
courses often focus on theory and sometimes lack the systematic coverage of the
techniques involved in developing, deploying, and applying software to real
hardware. Additionally, most hardware platforms for robotics teaching are
low-level toys aimed at younger students at middle-school levels. To address
this gap, an autonomous vehicle hardware platform, called F1TENTH, is developed
for teaching autonomous systems hands-on. This article describes the teaching
modules and software stack for teaching at various educational levels with the
theme of "racing" and competitions that replace exams. The F1TENTH vehicles
offer a modular hardware platform and its related software for teaching the
fundamentals of autonomous driving algorithms. From basic reactive methods to
advanced planning algorithms, the teaching modules enhance students'
computational thinking through autonomous driving with the F1TENTH vehicle. The
F1TENTH car fills the gap between research platforms and low-end toy cars and
offers hands-on experience in learning the topics in autonomous systems. Four
universities have adopted the teaching modules for their semester-long
undergraduate and graduate courses for multiple years. Student feedback is used
to analyze the effectiveness of the F1TENTH platform. More than 80% of the
students strongly agree that the hardware platform and modules greatly motivate
their learning, and more than 70% of the students strongly agree that the
hardware-enhanced their understanding of the subjects. The survey results show
that more than 80% of the students strongly agree that the competitions
motivate them for the course.Comment: 15 pages, 12 figures, 3 table
A simple and efficient method for extraction of Taq DNA polymerase
Background: Thermostable DNA polymerase (Taq Pol \u399) from Thermus
aquaticus has beenwidely used in PCR, which was usually extracted
with Pluthero's method. Themethod used ammonium sulfate to precipitate
the enzyme, and it saved effort and money but not time. Moreover, we
found that 30\u201340% activity of Taq Pol I was lost at the ammonium
sulfate precipitation step, and the product contained a small amount of
DNA. Results: We provided a novel, simplified and low-costmethod to
purify the Taq Pol \u399 after overproduction of the enzyme in
Escherichia coli , which used ethanol instead of ammonium sulfate to
precipitate the enzyme. The precipitate can be directly dissolved in
the storage buffer without dialysis. In addition, DNA and RNA
contamination was removed with DNase I and RNase A before
precipitation, and the extraction procedure was optimized. Our
improvements increase recovery rate and specific activity of the
enzyme, and save labor, time, and cost. Conclusions: Our method uses
ethanol, DNase I, and RNase A to purify the Taq Pol \u399, and
simplifies the operation, and increases the enzyme recovery rate and
quality
Distributional effects of vehicle tax in the framework of transportation externalities
Figure S2.The relationship between perivascular CD4 infiltration and 12 months follow-up DLCO (p = 0.134, r = −0.205). (PPT 43 kb
Viral infection of an estuarine Synechococcus influences its co-occurring heterotrophic bacterial community in the culture
Viruses are infectious and abundant in the marine environment. Viral lysis of host cells releases organic matter and nutrients that affect the surrounding microbial community. Synechococcus are important primary producers in the ocean and they are subject to frequent viral infection. In the laboratory, Synechococcus cultures are often associated with bacteria and such a co-existence relationship appears to be important to the growth and stability of Synechococcus. However, we know little about how viral lysis of Synechococcus affects the co-existing bacteria in the culture. This study investigated the influence of viral infection of Synechococcus on co-occurring bacterial community in the culture. We analyzed the community composition, diversity, predicted functions of the bacterial community, and its correlations with fluorescent dissolved organic matter (FDOM) components and nutrients after introducing a cyanophage to the Synechococcus culture. Cyanophage infection altered the bacterial community structure and increased the bacterial diversity and richness. Increased bacterial groups such as Bacteroidetes and Alphaproteobacteria and decreased bacterial groups such as Gammaproteobacteria were observed. Moreover, cyanophage infection reduced bacterial interactions but enhanced correlations between the dominant bacterial taxa and nutrients. Unique FDOM components were observed in the cyanophage-added culture. Fluorescence intensities of FDOM components varied across the cyanophage-infection process. Decreased nitrate and increased ammonium and phosphate in the cyanophage-added culture coupled with the viral progeny production and increased substance transport and metabolism potentials of the bacterial community. Furthermore, increased potentials in methane metabolism and aromatic compound degradation of the bacterial community were observed in the cyanophage-added culture, suggesting that cyanophage infections contribute to the production of methane-related compounds and refractory organic matter in a microcosm like environment. This study has the potential to deepen our understanding of the impact of viral lysis of cyanobacteria on microbial community in the surrounding water
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