283 research outputs found
Topological structure bifurcation of temperature field of deformable drop in Marangoni migration
AbstractThe unsteady processes of the Marangoni migration of deformable liquid drops are simulated numerically in a wider range of Marangoni number (up to Ma = 500) in the present work. A steady terminal state can always be reached, and the scaled terminal velocity is a monotonic function decreasing with increasing Marangoni number, which is generally in agreement with corresponding experimental data. The topological structure of flow field in the steady terminal state does not change as the Marangoni number increases, while bifurcation of the topological structure of temperature field occurs twice at two corresponding critical Marangoni numbers. A third critical value of Marangoni number also exists, beyond which the coldest point jumps from the rear stagnation to inside the drop though the topological structure of the temperature field does not change. It is found that the inner and outer thermal boundary layers may exist along the interface both inside and outside the drop if Ma > 70. But the thickness decreases with increasing Marangoni number more slowly than the prediction of potential flow at large Marangoni and Reynolds numbers
Dancing Avatar: Pose and Text-Guided Human Motion Videos Synthesis with Image Diffusion Model
The rising demand for creating lifelike avatars in the digital realm has led
to an increased need for generating high-quality human videos guided by textual
descriptions and poses. We propose Dancing Avatar, designed to fabricate human
motion videos driven by poses and textual cues. Our approach employs a
pretrained T2I diffusion model to generate each video frame in an
autoregressive fashion. The crux of innovation lies in our adept utilization of
the T2I diffusion model for producing video frames successively while
preserving contextual relevance. We surmount the hurdles posed by maintaining
human character and clothing consistency across varying poses, along with
upholding the background's continuity amidst diverse human movements. To ensure
consistent human appearances across the entire video, we devise an intra-frame
alignment module. This module assimilates text-guided synthesized human
character knowledge into the pretrained T2I diffusion model, synergizing
insights from ChatGPT. For preserving background continuity, we put forth a
background alignment pipeline, amalgamating insights from segment anything and
image inpainting techniques. Furthermore, we propose an inter-frame alignment
module that draws inspiration from an auto-regressive pipeline to augment
temporal consistency between adjacent frames, where the preceding frame guides
the synthesis process of the current frame. Comparisons with state-of-the-art
methods demonstrate that Dancing Avatar exhibits the capacity to generate human
videos with markedly superior quality, both in terms of human and background
fidelity, as well as temporal coherence compared to existing state-of-the-art
approaches.Comment: 11 pages, 3 figure
EarnHFT: Efficient Hierarchical Reinforcement Learning for High Frequency Trading
High-frequency trading (HFT) uses computer algorithms to make trading
decisions in short time scales (e.g., second-level), which is widely used in
the Cryptocurrency (Crypto) market (e.g., Bitcoin). Reinforcement learning (RL)
in financial research has shown stellar performance on many quantitative
trading tasks. However, most methods focus on low-frequency trading, e.g.,
day-level, which cannot be directly applied to HFT because of two challenges.
First, RL for HFT involves dealing with extremely long trajectories (e.g., 2.4
million steps per month), which is hard to optimize and evaluate. Second, the
dramatic price fluctuations and market trend changes of Crypto make existing
algorithms fail to maintain satisfactory performance. To tackle these
challenges, we propose an Efficient hieArchical Reinforcement learNing method
for High Frequency Trading (EarnHFT), a novel three-stage hierarchical RL
framework for HFT. In stage I, we compute a Q-teacher, i.e., the optimal action
value based on dynamic programming, for enhancing the performance and training
efficiency of second-level RL agents. In stage II, we construct a pool of
diverse RL agents for different market trends, distinguished by return rates,
where hundreds of RL agents are trained with different preferences of return
rates and only a tiny fraction of them will be selected into the pool based on
their profitability. In stage III, we train a minute-level router which
dynamically picks a second-level agent from the pool to achieve stable
performance across different markets. Through extensive experiments in various
market trends on Crypto markets in a high-fidelity simulation trading
environment, we demonstrate that EarnHFT significantly outperforms 6
state-of-art baselines in 6 popular financial criteria, exceeding the runner-up
by 30% in profitability
Ultrasound cavitation induced nucleation in metal solidification: an analytical model and validation by real-time experiments
Microstructural refinement of metallic alloys via ultrasonic melt processing (USMP) is an environmentally friendly and promising method. However, so far there has been no report in open literature on how to predict the solidified microstructures and grain size based on the ultrasound processing parameters.In this paper, an analytical model is developed to calculate the cavitation enhanced undercooling and the USMP refined solidification microstructure and grain size for Al-Cu alloys. Ultrafast synchrotron X-ray imaging and tomography techniques were used to collect the real-time experimental data for validating the model and the calculated results. The comparison between modeling and experiments reveal that there exists an effective ultrasound input power intensity for maximizing the grain refinement effects for the Al-Cu alloys, which is in the range of 20-45 MW/m2. In addition, a monotonous increase in temperature during USMP has negative effect on producing new nuclei, deteriorating the benefit of microstructure refinement due to the application of ultrasound
Effects of fiber orientation on tool wear evolution and wear mechanism when cutting carbon fiber reinforced plastics
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