223 research outputs found
On symbology and differential equations of Feynman integrals from Schubert analysis
We take the first step in generalizing the so-called "Schubert analysis",
originally proposed in twistor space for four-dimensional kinematics, to the
study of symbol letters and more detailed information on canonical differential
equations for Feynman integral families in general dimensions with general
masses. The basic idea is to work in embedding space and compute possible
cross-ratios built from (Lorentz products of) maximal cut solutions for all
integrals in the family. We demonstrate the power of the method using the most
general one-loop integrals, as well as various two-loop planar integral
families (such as sunrise, double-triangle and double-box) in general
dimensions. Not only can we obtain all symbol letters as cross-ratios from
maximal-cut solutions, but we also reproduce entries in the canonical
differential equations satisfied by a basis of dlog integrals.Comment: 51 pages, many figure
KERM: Knowledge Enhanced Reasoning for Vision-and-Language Navigation
Vision-and-language navigation (VLN) is the task to enable an embodied agent
to navigate to a remote location following the natural language instruction in
real scenes. Most of the previous approaches utilize the entire features or
object-centric features to represent navigable candidates. However, these
representations are not efficient enough for an agent to perform actions to
arrive the target location. As knowledge provides crucial information which is
complementary to visible content, in this paper, we propose a Knowledge
Enhanced Reasoning Model (KERM) to leverage knowledge to improve agent
navigation ability. Specifically, we first retrieve facts (i.e., knowledge
described by language descriptions) for the navigation views based on local
regions from the constructed knowledge base. The retrieved facts range from
properties of a single object (e.g., color, shape) to relationships between
objects (e.g., action, spatial position), providing crucial information for
VLN. We further present the KERM which contains the purification, fact-aware
interaction, and instruction-guided aggregation modules to integrate visual,
history, instruction, and fact features. The proposed KERM can automatically
select and gather crucial and relevant cues, obtaining more accurate action
prediction. Experimental results on the REVERIE, R2R, and SOON datasets
demonstrate the effectiveness of the proposed method.Comment: Accepted by CVPR 2023. The code is available at
https://github.com/XiangyangLi20/KER
GridMM: Grid Memory Map for Vision-and-Language Navigation
Vision-and-language navigation (VLN) enables the agent to navigate to a
remote location following the natural language instruction in 3D environments.
To represent the previously visited environment, most approaches for VLN
implement memory using recurrent states, topological maps, or top-down semantic
maps. In contrast to these approaches, we build the top-down egocentric and
dynamically growing Grid Memory Map (i.e., GridMM) to structure the visited
environment. From a global perspective, historical observations are projected
into a unified grid map in a top-down view, which can better represent the
spatial relations of the environment. From a local perspective, we further
propose an instruction relevance aggregation method to capture fine-grained
visual clues in each grid region. Extensive experiments are conducted on both
the REVERIE, R2R, SOON datasets in the discrete environments, and the R2R-CE
dataset in the continuous environments, showing the superiority of our proposed
method
Dynamic analysis and control of strip mill vibration under the coupling effect of roll and rolled piece
According to the “Hill rolling force formula”, taking particular account of the influence from horizontal vibration of rolled piece in roll gap, a dynamic rolling force model is analyzed. Considering the interaction between vibration of strip and roll, the dynamic vibration model of rolling mill is established. On this basis, the time delayed feedback is introduced to control the vibration of the roll system. The amplitude frequency response of the coupled vibration control equation is obtained by using the multiple scales method. Different time delay parameters are selected to test the control effect. Research results show that the unstable vibration of the roll system can be suppressed with appropriate time delay feedback parameters. Because it is simpler and has good control effect in solving nonlinear mechanical vibration, so these results will make a difference for the research of strip mill vibration, and provide theoretical basis for strip steel production
Anomalous Nernst effect in compensated ferrimagnetic CoxGd1-x films
The anomalous Nernst effect (ANE) is one of the most intriguing
thermoelectric phenomena which has attracted growing interest both for its
underlying physics and potential applications. Typically, a large ANE response
is observed in magnets with pronounced magnetizations or nontrivial Berry
curvature. Here, we report a significant ANE signal in compensated
ferrimagnetic CoxGd1-x alloy films, which exhibit vanishingly small
magnetization. In particular, we found that the polarity of ANE signal is
dominated by the magnetization orientation of the transition metal Co
sublattices, rather than the net magnetization of CoxGd1-x films. This
observation is not expected from the conventional understanding of ANE but is
analogous to the anomalous Hall effect in compensated ferrimagnets. We
attribute the origin of ANE and its Co-dominant property to the Co-dominant
Berry curvature. Our work could trigger a more comprehensive understanding of
ANE and may be useful for building energy-harvesting devices by employing ANE
in compensated ferrimagnets
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