4,430 research outputs found
Electromagnetic counterparts of high-frequency gravitational waves having additional polarization states: distinguishing and probing tensor-mode, vector-mode and scalar-mode gravitons
GWs from extra dimensions, very early universe, and some high-energy
astrophysical process, might have at most six polarizations: plus- and
cross-type (tensor-mode gravitons), x-, y-type (vector-mode), and b-, l-type
(scalar-mode). Peak or partial peak regions of some of such GWs are just
distributed in GHz or higher frequency band, which would be optimal band for
electromagnetic(EM) response. In this paper we investigate EM response to such
high-frequency GWs(HFGWs) having additional polarizations. For the first time
we address:(1)concrete forms of analytic solutions for perturbed EM fields
caused by HFGWs having all six possible polarizations in background stable EM
fields; (2)perturbed EM signals of HFGWs with additional polarizations in
three-dimensional-synchro-resonance-system(3DSR system) and in
galactic-extragalactic background EM fields. These perturbative EM fields are
actually EM counterparts of HFGWs, and such results provide a novel way to
simultaneously distinguish and display all possible six polarizations. It is
also shown: (i)In EM response, pure cross-, x-type and pure y-type
polarizations can independently generate perturbative photon fluxes(PPFs,
signals), while plus-, b- and l-type polarizations produce PPFs in different
combination states. (ii) All such six polarizations have separability and
detectability. (iii)In EM response to HFGWs from extra-dimensions,
distinguishing and displaying different polarizations would be quite possible
due to their very high frequencies, large energy densities and special
properties of spectrum. (iv)Detection band(10^8 to 10^12 Hz or higher) of PPFs
by 3DSR and observation range(7*10^7 to 3*10^9 Hz) of PPFs by FAST
(Five-hundred-meter-Aperture-Spherical Telescope, China), have a certain
overlapping property, so their coincidence experiments will have high
complementarity.Comment: 27 pages, 16 figure
(Z)-3-(2-Methoxyanilino)-1-phenylbut-2-en-1-one
In the title compound, C17H17NO2, the dihedral angle between the two benzene rings is 55.2 (2)°. The methoxy group is slightly twisted away from the aniline ring [dihedral angle = 10.3 (2)°]. An intramolecular N—H⋯O interaction is present. In the crystal, the molecules are linked into a three-dimensional supramolecular network through two sets of C—H⋯π interactions
Stereoscopic image stitching with rectangular boundaries
This paper proposes a novel algorithm for stereoscopic image stitching, which aims to produce stereoscopic panoramas with rectangular boundaries. As a result, it provides wider field of view and better viewing experience for users. To achieve this, we formulate stereoscopic image stitching and boundary rectangling in a global optimization framework that simultaneously handles feature alignment, disparity consistency and boundary regularity. Given two (or more) stereoscopic images with overlapping content, each containing two views (for left and right eyes), we represent each view using a mesh and our algorithm contains three main steps: We first perform a global optimization to stitch all the left views and right views simultaneously, which ensures feature alignment and disparity consistency. Then, with the optimized vertices in each view, we extract the irregular boundary in the stereoscopic panorama, by performing polygon Boolean operations in left and right views, and construct the rectangular boundary constraints. Finally, through a global energy optimization, we warp left and right views according to feature alignment, disparity consistency and rectangular boundary constraints. To show the effectiveness of our method, we further extend our method to disparity adjustment and stereoscopic stitching with large horizon. Experimental results show that our method can produce visually pleasing stereoscopic panoramas without noticeable distortion or visual fatigue, thus resulting in satisfactory 3D viewing experience
Content-preserving image stitching with piecewise rectangular boundary constraints
This paper proposes an approach to content-preserving image stitching with regular boundary constraints, which aims to stitch multiple images to generate a panoramic image with a piecewise rectangular boundary. Existing methods treat image stitching and rectangling as two separate steps, which may result in suboptimal results as the stitching process is not aware of the further warping needs for rectangling. We address these limitations by formulating image stitching with regular boundaries in a unified optimization. Starting from the initial stitching results produced by the traditional warping-based optimization, we obtain the irregular boundary from the warped meshes by polygon Boolean operations which robustly handle arbitrary mesh compositions. By analyzing the irregular boundary, we construct a piecewise rectangular boundary. Based on this, we further incorporate line and regular boundary preservation constraints into the image stitching framework, and conduct iterative optimization to obtain an optimal piecewise rectangular boundary. Thus we can make the boundary of the stitching results as close as possible to a rectangle, while reducing unwanted distortions. We further extend our method to video stitching, by integrating the temporal coherence into the optimization. Experiments show that our method efficiently produces visually pleasing panoramas with regular boundaries and unnoticeable distortions
Exploring Communities in Large Profiled Graphs
Given a graph and a vertex , the community search (CS) problem
aims to efficiently find a subgraph of whose vertices are closely related
to . Communities are prevalent in social and biological networks, and can be
used in product advertisement and social event recommendation. In this paper,
we study profiled community search (PCS), where CS is performed on a profiled
graph. This is a graph in which each vertex has labels arranged in a
hierarchical manner. Extensive experiments show that PCS can identify
communities with themes that are common to their vertices, and is more
effective than existing CS approaches. As a naive solution for PCS is highly
expensive, we have also developed a tree index, which facilitate efficient and
online solutions for PCS
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