473 research outputs found
Tunneling, dissipation, and superfluid transition in quantum Hall bilayers
We study bilayer quantum Hall systems at total Landau level filling factor
in the presence of interlayer tunneling and coupling to a dissipative
normal fluid. Describing the dynamics of the interlayer phase by an effective
quantum dissipative XY model, we show that there exists a critical dissipation
set by the conductance of the normal fluid. For ,
interlayer tunnel splitting drives the system to a quantum Hall state.
For , interlayer tunneling is irrelevant at low temperatures,
the system exhibits a superfluid transition to a collective quantum Hall state
supported by spontaneous interlayer phase coherence. The resulting phase
structure and the behavior of the in-plane and tunneling currents are studied
in connection to experiments.Comment: 4 RevTex pages, revised version, to appear in Phys. Rev. Let
Flutter Influence Mode Analysis of High Speed Wing Model
AbstractIn flutter wind tunnel test, the matching degree between scaled model and prototype would directly affect the reliability of test results. It is difficult to achieve completely dynamic similarity because of some material or technological constrains, and only lower order modes including mode shape and frequency are accurately simulated to construct a compromised model. Theoretical support would be necessary to answer the question which modes must be simulated to guarantee data validity of wind tunnel flutter test. An analytical study of a sweepback winghas been undertaken to estimate the flutter influence mode needed for accurate flutter prediction by analyzing generalized aerodynamic stiffness coefficient, unsteady aerodynamic force and flutter results. The results show that the aerodynamic stiffness coefficient with expression of mode shape could be taken as a quick criterion for mode selection in flutter model design and analysis
Calculation and Analysis of the Instream Ecological Flow for the Irtysh River
AbstractInstream ecological flow is essential determinant of river health. In this paper, the monthly minimum flow calculation method, the (new) monthly frequency calculation method were applied to calculate and evaluate the minimum instream ecological flow and the optimal instream ecological flow for the Irtysh River, and the different criteria of instream ecological flow was calculated by the improved Tennant method. It is expected to provide a scientific basis for the reasonable allocation of water resource in Irtysh River basin by calculating the instream ecological flow
ACNet: Approaching-and-Centralizing Network for Zero-Shot Sketch-Based Image Retrieval
The huge domain gap between sketches and photos and the highly abstract
sketch representations pose challenges for sketch-based image retrieval
(\underline{SBIR}). The zero-shot sketch-based image retrieval
(\underline{ZS-SBIR}) is more generic and practical but poses an even greater
challenge because of the additional knowledge gap between the seen and unseen
categories. To simultaneously mitigate both gaps, we propose an
\textbf{A}pproaching-and-\textbf{C}entralizing \textbf{Net}work (termed
"\textbf{ACNet}") to jointly optimize sketch-to-photo synthesis and the image
retrieval. The retrieval module guides the synthesis module to generate large
amounts of diverse photo-like images which gradually approach the photo domain,
and thus better serve the retrieval module than ever to learn domain-agnostic
representations and category-agnostic common knowledge for generalizing to
unseen categories. These diverse images generated with retrieval guidance can
effectively alleviate the overfitting problem troubling concrete
category-specific training samples with high gradients. We also discover the
use of proxy-based NormSoftmax loss is effective in the zero-shot setting
because its centralizing effect can stabilize our joint training and promote
the generalization ability to unseen categories. Our approach is simple yet
effective, which achieves state-of-the-art performance on two widely used
ZS-SBIR datasets and surpasses previous methods by a large margin.Comment: the paper is under consideration at IEEE Transactions on Circuits and
Systems for Video Technolog
Time2Graph: Revisiting Time Series Modeling with Dynamic Shapelets
Time series modeling has attracted extensive research efforts; however,
achieving both reliable efficiency and interpretability from a unified model
still remains a challenging problem. Among the literature, shapelets offer
interpretable and explanatory insights in the classification tasks, while most
existing works ignore the differing representative power at different time
slices, as well as (more importantly) the evolution pattern of shapelets. In
this paper, we propose to extract time-aware shapelets by designing a two-level
timing factor. Moreover, we define and construct the shapelet evolution graph,
which captures how shapelets evolve over time and can be incorporated into the
time series embeddings by graph embedding algorithms. To validate whether the
representations obtained in this way can be applied effectively in various
scenarios, we conduct experiments based on three public time series datasets,
and two real-world datasets from different domains. Experimental results
clearly show the improvements achieved by our approach compared with 17
state-of-the-art baselines.Comment: An extended version with 11 pages including appendix; Accepted by
AAAI'202
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