22 research outputs found
Motion Style Transfer: Modular Low-Rank Adaptation for Deep Motion Forecasting
Deep motion forecasting models have achieved great success when trained on a
massive amount of data. Yet, they often perform poorly when training data is
limited. To address this challenge, we propose a transfer learning approach for
efficiently adapting pre-trained forecasting models to new domains, such as
unseen agent types and scene contexts. Unlike the conventional fine-tuning
approach that updates the whole encoder, our main idea is to reduce the amount
of tunable parameters that can precisely account for the target domain-specific
motion style. To this end, we introduce two components that exploit our prior
knowledge of motion style shifts: (i) a low-rank motion style adapter that
projects and adjusts the style features at a low-dimensional bottleneck; and
(ii) a modular adapter strategy that disentangles the features of scene context
and motion history to facilitate a fine-grained choice of adaptation layers.
Through extensive experimentation, we show that our proposed adapter design,
coined MoSA, outperforms prior methods on several forecasting benchmarks.Comment: CoRL 202
Opinion Dynamics in Two-Step Process: Message Sources, Opinion Leaders and Normal Agents
According to mass media theory, the dissemination of messages and the
evolution of opinions in social networks follow a two-step process. First,
opinion leaders receive the message from the message sources, and then they
transmit their opinions to normal agents. However, most opinion models only
consider the evolution of opinions within a single network, which fails to
capture the two-step process accurately. To address this limitation, we propose
a unified framework called the Two-Step Model, which analyzes the communication
process among message sources, opinion leaders, and normal agents. In this
study, we examine the steady-state opinions and stability of the Two-Step
Model. Our findings reveal that several factors, such as message distribution,
initial opinion, level of stubbornness, and preference coefficient, influence
the sample mean and variance of steady-state opinions. Notably, normal agents'
opinions tend to be influenced by opinion leaders in the two-step process. We
also conduct numerical and social experiments to validate the accuracy of the
Two-Step Model, which outperforms other models on average. Our results provide
valuable insights into the factors that shape social opinions and can guide the
development of effective strategies for opinion guidance in social networks
A Quantitative Analysis of Open Source Software Code Quality: Insights from Metric Distributions
Code quality is a crucial construct in open-source software (OSS) with three
dimensions: maintainability, reliability, and functionality. To accurately
measure them, we divide 20 distinct metrics into two types: 1) threshold-type
metrics that influence code quality in a monotonic manner; 2)
non-threshold-type metrics that lack a monotonic relationship to evaluate. We
propose a distribution-based method to provide scores for metrics, which
demonstrates great explainability on OSS adoption. Our empirical analysis
includes more than 36,460 OSS projects and their raw metrics from SonarQube and
CK. Our work contributes to the understanding of the multi-dimensional
construct of code quality and its metric measurements
Experimental investigation of kinetic instabilities driven by runaway electrons in the EXL-50 spherical torus
In this study, the first observation of high-frequency instabilities driven
by runaway electrons has been reported in the EXL-50 spherical torus using a
high-frequency magnetic pickup coil. The central frequency of these
instabilities is found to be exponentially dependent on the plasma density,
similar to the dispersion relation of the whistler wave. The instability
frequency displays chirping characteristics consistent with the Berk-Breizman
model of beam instability. Theoretically, the excitation threshold of the
instability driven by runaway electrons is related to the ratio of the runaway
electron density to the background plasma density, and such a relationship is
first demonstrated experimentally in this study. The instability can be
stabilized by increasing the plasma density, consistent with the wave-particle
resonance mechanism. This investigation demonstrates the controlled excitation
of chirping instabilities in a tokamak plasma and reveals new features of these
instabilities, thereby advancing the understanding of the mechanisms for
controlling and mitigating runaway electrons
Observation of whistler wave instability driven by temperature anisotropy of energetic electrons on EXL-50 spherical torus
Electromagnetic modes in the frequency range of 30-120MHz were observed in
electron cyclotron wave (ECW) steady state plasmas on the ENN XuanLong-50
(EXL-50) spherical torus. These modes were found to have multiple bands of
frequencies proportional to the Alfv\'en velocity. This indicates that the
observed mode frequencies satisfy the dispersion relation of whistler waves. In
addition, suppression of the whistler waves by the synergistic effect of Lower
Hybrid Wave (LHW) and ECW was also observed. This suggests that the whistler
waves were driven by temperature anisotropy of energetic electrons. These are
the first such observations (not runaway discharge) made in magnetically
confined toroidal plasmas and may have important implications for studying
wave-particle interactions, RF wave current driver, and runaway electron
control in future fusion devices
Solenoid-free current drive via ECRH in EXL-50 spherical torus plasmas
As a new spherical tokamak (ST) designed to simplify engineering requirements
of a possible future fusion power source, the EXL-50 experiment features a low
aspect ratio (A) vacuum vessel (VV), encircling a central post assembly
containing the toroidal field coil conductors without a central solenoid.
Multiple electron cyclotron resonance heating (ECRH) resonances are located
within the VV to improve current drive effectiveness. Copious energetic
electrons are produced and measured with hard X-ray detectors, carry the bulk
of the plasma current ranging from 50kA to 150kA, which is maintained for more
than 1s duration. It is observed that over one Ampere current can be maintained
per Watt of ECRH power issued from the 28-GHz gyrotrons. The plasma current
reaches Ip>80kA for high density (>5e18me-2) discharge with 150kW ECHR heating.
An analysis was carried out combining reconstructed multi-fluid equilibrium,
guiding-center orbits of energetic electrons, and resonant heating mechanisms.
It is verified that in EXL-50 a broadly distributed current of energetic
electrons creates smaller closed magnetic-flux surfaces of low aspect ratio
that in turn confine the thermal plasma electrons and ions and participate in
maintaining the equilibrium force-balance