5,032 research outputs found
Boundary conditions and defect lines in the Abelian sandpile model
We add a defect line of dissipation, or crack, to the Abelian sandpile model.
We find that the defect line renormalizes to separate the two-dimensional plane
into two half planes with open boundary conditions. We also show that varying
the amount of dissipation at a boundary of the Abelian sandpile model does not
affect the universality class of the boundary condition. We demonstrate that a
universal coefficient associated with height probabilities near the defect can
be used to classify boundary conditions.Comment: 8 pages, 1 figure; suggestions from referees incorporated; to be
published in Phys. Rev.
Answer quality characteristics and prediction on an academic QandA site: A case study on researchgate
Despite various studies on examining and predicting answer quality on generic social QandA sites such as Yahoo! Answers, little is known about why answers on academic QandA sites are voted on by scholars who follow the discussion threads to be high quality answers. Using 1021 answers obtained from the QandA part of an academic social network site ResearchGate (RG), we firstly explored whether various web-captured features and human-coded features can be the critical factors that influence the peer-judged answer quality. Then using the identified critical features, we constructed three classification models to predict the peer-judged rating. Our results identify four main findings. Firstly, responders' authority, shorter response time and greater answer length are the critical features that positively associate with the peer-judged answer quality. Secondly, answers containing social elements are very likely to harm the peer-judged answer quality. Thirdly, an optimized SVM algorithm has an overwhelming advantage over other models in terms of accuracy. Finally, the prediction based on web-captured features had better performance when comparing to prediction on human-coded features. We hope that these interesting insights on ResearchGate's answer quality can help the further design of academic QandA sites
Efficient search approaches for K-medoids-based algorithms
In this paper, the concept of previous medoid index is introduced. The utilization of memory for efficient medoid search is also presented. We propose a hybrid search approach for the problem of nearest neighbor search. The hybrid search approach combines the previous medoid index, the utilization of memory, the criterion of triangular inequality elimination and the partial distance search. The proposed hybrid search approach is applied to the k-medoids-based algorithms. Experimental results based on Gauss-Markov source, curve data set and elliptic clusters demonstrate that the proposed algorithm applied to the CLARANS algorithm may reduce the number of distance calculations from 88.4% to 95.2% with the same average distance per object compared with CLARANS. The proposed hybrid search approach can also be applied to nearest neighbor searching and the other clustering algorithms
Selective interlayer ferromagnetic coupling between the Cu spins in YBa Cu O grown on top of La Ca MnO
Studies to date on ferromagnet/d-wave superconductor heterostructures focus
mainly on the effects at or near the interfaces while the response of bulk
properties to heterostructuring is overlooked. Here we use resonant soft x-ray
scattering spectroscopy to reveal a novel c-axis ferromagnetic coupling between
the in-plane Cu spins in YBa Cu O (YBCO) superconductor when it
is grown on top of ferromagnetic La Ca MnO (LCMO) manganite
layer. This coupling, present in both normal and superconducting states of
YBCO, is sensitive to the interfacial termination such that it is only observed
in bilayers with MnO_2but not with La Ca interfacial
termination. Such contrasting behaviors, we propose, are due to distinct
energetic of CuO chain and CuO plane at the La Ca and
MnO terminated interfaces respectively, therefore influencing the transfer
of spin-polarized electrons from manganite to cuprate differently. Our findings
suggest that the superconducting/ferromagnetic bilayers with proper interfacial
engineering can be good candidates for searching the theorized
Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state in cuprates and studying the
competing quantum orders in highly correlated electron systems.Comment: Please note the change of the title. Text might be slightly different
from the published versio
Hadamard transform based Equal-average Equal-variance Equal-norm nearest neighbor codeword search algorithm
New York, US
Transport properties in FeSe0.5Te0.5 nanobridges
FeSeTe nanobridges of different widths have been fabricated on MgO substrates using focused ion beams. These nanobridges exhibit the Josephson effects. The current-voltage curves of junctions with 248–564 nm wide follow the resistively and capacitatively shunted junction model. Shapiro steps under microwave radiation were clearly observed in these nanobridges. The products of the critical current and normal state resistance (I c R n) are remarkably high. The temperature dependence of I c R n product followed the Ambegaokar-Baratoff (A-B) relation. The value of energy gap of FeSeTe calculated from the A-B relation is 3.5kBTc. The nanobridge junctions have a strong potential for high frequency applications
Partially incoherent optical vortices in self-focusing nonlinear media
We observe stable propagation of spatially localized single- and
double-charge optical vortices in a self-focusing nonlinear medium. The
vortices are created by self-trapping of partially incoherent light carrying a
phase dislocation, and they are stabilized when the spatial incoherence of
light exceeds a certain threshold. We confirm the vortex stabilization effect
by numerical simulations and also show that the similar mechanism of
stabilization applies to higher-order vortices.Comment: 4 pages and 6 figures (including 3 experimental figures
The mechanism of the recrystallization process in epitaxial GaN under dynamic stress field: atomistic origin of planar defect formation
The mechanism of the recrystallization in epitaxial (0001) GaN film, introduced by the indentation technique, is probed by lattice dynamic studies using Raman spectroscopy. The recrystallized region is identified by micro-Raman area mapping. 'Pop-in' bursts in loading lines indicate nucleation of dislocations and climb of dislocations. These processes set in plastic motion of lattice atoms under stress field at the center of indentation for the initiation of the recrystallization process. A planar defect migration mechanism is evolved. A pivotal role of vacancy migration is noted, for the first time, as the rate-limiting factor for the dislocation dynamics initiating the recrystallization process in GaN
CMS endcap RPC gas gap production for upgrade
The CMS experiment will install a RE4 layer of 144 new Resistive Plate Chambers (RPCs) on the existing york YE3 at both endcap regions to trigger high momentum muons from the proton-proton interaction. In this paper, we present the detailed procedures used in the production of new RPC gas gaps adopted in the CMS upgrade. Quality assurance is enforced as ways to maintain the same quality of RPC gas gaps as the existing 432 endcap RPC chambers that have been operational since the beginning of the LHC operation
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