153 research outputs found
Invertible normalizing flow neural networks by JKO scheme
Normalizing flow is a class of deep generative models for efficient sampling
and density estimation. In practice, the flow often appears as a chain of
invertible neural network blocks; to facilitate training, existing works have
regularized flow trajectories and designed special network architectures. The
current paper develops a neural ODE flow network inspired by the
Jordan-Kinderleherer-Otto (JKO) scheme, which allows efficient block-wise
training of the residual blocks without sampling SDE trajectories or inner
loops of score matching or variational learning. As the JKO scheme unfolds the
dynamic of gradient flow, the proposed model naturally stacks residual network
blocks one by one, reducing the memory load and difficulty in performing
end-to-end deep flow network training. We also develop adaptive time
reparameterization of the flow network with a progressive refinement of the
trajectory in probability space, which improves the model training efficiency
and accuracy in practice. Using numerical experiments with synthetic and real
data, we show that the proposed JKO-iFlow model achieves similar or better
performance in generating new samples compared with the existing flow and
diffusion models at a significantly reduced computational and memory cost
ANALYSIS OF VALGUS CHARACT,ERISTICS OF OSSEOUS STRUCTURE OF THE FEET WITH THREE-DIMENSIONAL RECONSTRUCTION TECHNIQUES
Using the advanced MR images scan technique combined with three-dimensional reconstruction software, the study went deep into the research of feet's osseous tissue structure. After an investigation of 37 sUbjects' 10 indexes including valgus index and rear foot angle, the study showed distinct differences between normal foot and flatfoot. The correlation modulus of the X-ray images of flatfoot with valgus index is 0.75, and the correlation modulus with rear foot angle is 0.29. The phenomenon that most people with flatfeet had anklebone moving outside illuminated ,that flatfoot resulted from monstrosity of the navicular, cuneiform and metatarsus. However, rear foot angle only embodyed the relative position between calcaneus and shankbone. It couldn't explain the structure differences between flatfoot and normal foot
AutoEval-Video: An Automatic Benchmark for Assessing Large Vision Language Models in Open-Ended Video Question Answering
We propose a novel and challenging benchmark, AutoEval-Video, to
comprehensively evaluate large vision-language models in open-ended video
question answering. The comprehensiveness of AutoEval-Video is demonstrated in
two aspects: 1) AutoEval-Video constructs open-ended video-questions across 9
skill dimensions, addressing capabilities of perception, comprehension, and
generation. 2) AutoEval-Video contains newly collected videos that cover over
40 distinct themes. To efficiently evaluate responses to the open-ended
questions, we employ an LLM-based evaluation approach, but instead of merely
providing a reference answer, we annotate unique evaluation rules for every
single instance (video-question pair). To maximize the robustness of these
rules, we develop a novel adversarial annotation mechanism. By using
instance-specific rules as prompt, GPT-4, as an automatic evaluator, can
achieve a stable evaluation accuracy of around 97.0\%, comparable to the 94.9\%
- 97.5\% accuracy of a human evaluator. Furthermore, we assess the performance
of eight large vision-language models on AutoEval-Video. Among them,
GPT-4V(ision) significantly outperforms other models, achieving an accuracy of
32.2\%. However, there is still substantial room for improvement compared to
human accuracy of 72.8\%. By conducting an extensive case study, we uncover
several drawbacks of GPT-4V, such as limited temporal and dynamic
comprehension, and overly general responses. Code is available at
\href{https://github.com/Xiuyuan-Chen/AutoEval-Video}{\color{magenta}https://github.com/Xiuyuan-Chen/AutoEval-Video}
Kinetic and mechanistic analysis of NH3 decomposition on Ru(0001), Ru(111) and Ir(111) surfaces
We investigated the NH3 catalytic decomposition on Ru and Ir metal surfaces using density functional theory. The reaction mechanisms were unraveled on both metals, considering that, at nano-scale, Ru particles may also present an fcc structure, hence, leading to three energy profiles. We implemented thermodynamic and kinetic parameters obtained from DFT into microkinetic simulations. Batch reactor simulations suggest that hydrogen generation starts at 400 K, 425 K and 600 K on Ru(111), Ru(0001) and Ir(111) surfaces respectively, in excellent agreement with experiments. During the reaction, the main surface species on Ru are NH, N and H, whereas, on Ir(111), it is mainly NH. The rate-determining step for all surfaces is the formation of molecular nitrogen. We also performed temperature-programmed reaction simulations and inspected the desorption spectra of N2 and H2 as a function of the temperature, which highlighted the importance of N coverage on the desorption rate
Food resources for Spoon-billed Sandpipers (<i>Calidris pygmaea</i>) in the mudflats of Leizhou Bay, southern China
Leizhou Bay in Guangdong Province is the most important wintering site in China for the critically endangered Spoon-billed Sandpipers (Calidris pygmaea). As food is usually a strong predictor of presence, in the winters of 2019-2022 we studied arthropod food resources and diet on the intertidal mudflats at the Tujiao and Hebei mudflats in Leizhou Bay. In December 2020, using a sampling device that encloses mobile epibenthic prey before the human sampler would disturb them in shallow pools, we visited 34 stations in their core foraging area at Tujiao. A total of 15 mobile benthic species were identified, including 13 arthropod and 2 fish species, with a total density of 106 animals/m2 (range= 0.2-48 animals/m2), with the lengths of the animals ranging from 1-19 mm. Two amphipod and one cumacean species contributed 85%. On the basis of photographs of foraging during low tide in 2019-2022, the visibly ingested prey items appeared to mainly consist of small shrimp, but also included crabs and fish. At 27 mm (compared with the 22 mm long bill of Spoon-billed Sandpipers) the average visibly ingested prey showed a strong size bias. Among the measured environmental covarying factors (sediment pH, salinity, TOC content, median particle size and distance from the seawall etc.) potentiually affecting the mobile epibenthic prey in shallow pools, only distance from the seawall was significantly and negatively correlated. Densities were higher within 1 km of the seawall (126 animals/m2) than further offshore (69 animals/m2). This may relate to the mangrove forests growing in abundance near the seawall providing released minerals, nutrients, bacterial production and diatoms for the benthic community in the adjacent mudflats. However, the potential negative impact of artificial mangrove expansion in Leizhou mudflats need to be carefully monitored and assessed to balance both mangrove and Spoon-billed Sandpipers conservation
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