1,318 research outputs found
Yang-Lee Singularity in BCS Superconductivity
We investigate the Yang-Lee singularity in BCS superconductivity, and find
that the zeros of the partition function accumulate on the boundary of a
quantum phase transition, which is accompanied by nonunitary quantum critical
phenomena. By applying the renormalization-group analysis, we show that
Yang-Lee zeros distribute on a semicircle in the complex plane of interaction
strength for general marginally interacting systems.Comment: 5pages, 1 figure+14 pages, 5 figure
Construction of all-in-focus images assisted by depth sensing
Multi-focus image fusion is a technique for obtaining an all-in-focus image
in which all objects are in focus to extend the limited depth of field (DoF) of
an imaging system. Different from traditional RGB-based methods, this paper
presents a new multi-focus image fusion method assisted by depth sensing. In
this work, a depth sensor is used together with a color camera to capture
images of a scene. A graph-based segmentation algorithm is used to segment the
depth map from the depth sensor, and the segmented regions are used to guide a
focus algorithm to locate in-focus image blocks from among multi-focus source
images to construct the reference all-in-focus image. Five test scenes and six
evaluation metrics were used to compare the proposed method and representative
state-of-the-art algorithms. Experimental results quantitatively demonstrate
that this method outperforms existing methods in both speed and quality (in
terms of comprehensive fusion metrics). The generated images can potentially be
used as reference all-in-focus images.Comment: 18 pages. This paper has been submitted to Computer Vision and Image
Understandin
MSAT: Matrix stability analysis tool for shock-capturing schemes
The simulation of supersonic or hypersonic flows often suffers from numerical
shock instabilities if the flow field contains strong shocks, limiting the
further application of shock-capturing schemes. In this paper, we develop the
unified matrix stability analysis method for schemes with three-point stencils
and present MSAT, an open-source tool to quantitatively analyze the shock
instability problem. Based on the finite-volume approach on the structured
grid, MSAT can be employed to investigate the mechanism of the shock
instability problem, evaluate the robustness of numerical schemes, and then
help to develop robust schemes. Also, MSAT has the ability to analyze the
practical simulation of supersonic or hypersonic flows, evaluate whether it
will suffer from shock instabilities, and then assist in selecting appropriate
numerical schemes accordingly. As a result, MSAT is a helpful tool that can
investigate the shock instability problem and help to cure it.Comment: 18 pages, 6 figure
A Novel Method for Extrinsic Calibration of Multiple RGB-D Cameras Using Descriptor-Based Patterns
This letter presents a novel method to estimate the relative poses between
RGB-D cameras with minimal overlapping fields of view in a panoramic RGB-D
camera system. This calibration problem is relevant to applications such as
indoor 3D mapping and robot navigation that can benefit from a 360
field of view using RGB-D cameras. The proposed approach relies on
descriptor-based patterns to provide well-matched 2D keypoints in the case of a
minimal overlapping field of view between cameras. Integrating the matched 2D
keypoints with corresponding depth values, a set of 3D matched keypoints are
constructed to calibrate multiple RGB-D cameras. Experiments validated the
accuracy and efficiency of the proposed calibration approach, both superior to
those of existing methods (800 ms vs. 5 seconds; rotation error of 0.56 degrees
vs. 1.6 degrees; and translation error of 1.80 cm vs. 2.5 cm.Comment: 6 pages, 7 figures, under review by IEEE Robotics and Automation
Letters & ICR
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