Reverse spatial visual top-k query

With the wide application of mobile Internet techniques an location-based services (LBS), massive multimedia data with geo-tags has been generated and collected. In this paper, we investigate a novel type of spatial query problem, named reverse spatial visual top- $k$ query (RSVQ k ) that aims to retrieve a set of geo-images that have the query as one of the most relevant geo-images in both geographical proximity and visual similarity. Existing approaches for reverse top- $k$ queries are not suitable to address this problem because they cannot effectively process unstructured data, such as image. To this end, firstly we propose the definition of RSVQ k problem and introduce the similarity measurement. A novel hybrid index, named VR 2 -Tree is designed, which is a combination of visual representation of geo-image and R-Tree. Besides, an extension of VR 2 -Tree, called CVR 2 -Tree is introduced and then we discuss the calculation of lower/upper bound, and then propose the optimization technique via CVR 2 -Tree for further pruning. In addition, a search algorithm named RSVQ k algorithm is developed to support the efficient RSVQ k query. Comprehensive experiments are conducted on four geo-image datasets, and the results illustrate that our approach can address the RSVQ k problem effectively and efficiently

SVS-JOIN : efficient spatial visual similarity join for geo-multimedia

In the big data era, massive amount of multimedia data with geo-tags has been generated and collected by smart devices equipped with mobile communications module and position sensor module. This trend has put forward higher request on large-scale geo-multimedia retrieval. Spatial similarity join is one of the significant problems in the area of spatial database. Previous works focused on spatial textual document search problem, rather than geo-multimedia retrieval. In this paper, we investigate a novel geo-multimedia retrieval paradigm named spatial visual similarity join (SVS-JOIN for short), which aims to search similar geo-image pairs in both aspects of geo-location and visual content. Firstly, the definition of SVS-JOIN is proposed and then we present the geographical similarity and visual similarity measurement. Inspired by the approach for textual similarity join, we develop an algorithm named SVS-JOIN B by combining the PPJOIN algorithm and visual similarity. Besides, an extension of it named SVS-JOIN G is developed, which utilizes spatial grid strategy to improve the search efficiency. To further speed up the search, a novel approach called SVS-JOIN Q is carefully designed, in which a quadtree and a global inverted index are employed. Comprehensive experiments are conducted on two geo-image datasets and the results demonstrate that our solution can address the SVS-JOIN problem effectively and efficiently

An Efficient Failure Recovery Scheme for Service Composition in Pervasive Computing

During the execution of service composition, if one component service fails, a failure recovery mechanism is needed to ensure that the running process is not interrupted and the failed service can be replaced quickly and efficiently. In this paper, we propose an efficient failure recovery scheme for rapid reconstruction of services compositions. Sufficient conditions about substitution and keeping state-consistent between services are proposed. Further, the algorithm for keeping state-consistent between services is proposed. The innovation of this paper is that the failure service will be substituted and the failure service’ state will be transformed into the substituting service’ state to improve the performance of the failure recovery scheme. And the prototype system is implemented. Simulation experiments demonstrate the good performance of the proposed failure recovery scheme

Acoustic Frequency Multiplication and Pure Second Harmonic Generation of Phonons by Magnetic Transducers

We predict frequency multiplication of surface acoustic waves in dielectric substrates via the ferromagnetic resonance of adjacent magnetic transducers when driven by microwaves. We find pure second harmonic generation (SHG) without any linear and third harmonic components by a magnetic nanowire. The SHG and linear phonon pumping are switched by varying the saturated magnetization direction of the wire, or resolved directionally when pumped by magnetic nano-disc. We address the high efficiency of SHG with comparable magnitude to that of linear response, as well as unique non-reciprocal phonon transport that is remarkably distinct in different phonon harmonics. Such acoustic frequency comb driven by microwaves should bring unprecedented tunability for the miniaturized phononic and spintronic devices.Comment: 7 pages, 3 figure

Die Konkurrenz zwischen Gewährleistungsrecht und Informationspflicht

Schon vor der Schuldrechtsreform wurde die Konkurrenz zwischen Gewährleistungsrecht und Informationspflicht heftig diskutiert. Seit der Schuldrechtsreform sind neue Meinungen hinzugetreten. Zwar ist an der bereits vor der Reform herrschenden Meinung festzuhalten. Sie bedarf aber einer neuen Fundierung. Statt auf die Beschränkung der Schadensersatzhaftung kann sie sich auf die Gestaltung des Mangelbegriffs stützen

Chirality Enables Thermal Magnon Transistors

We report a theory of thermal spin pumping into proximity magnets under a transverse-bias-driven heat flow of magnons in magnetic films when the dipolar coupling to the magnetic gate is tuned to be "chiral". While there is no rectification of the magnon current in the film, we predict that chirality diverts a large percentage (50$\%$ for perfect chirality) of it into the gate. This transverse thermal spin pumping effect can be controlled by rotating the film magnetization and may help manage the heat flow in future magnonic circuits.Comment: 7 pages, 3 figure

Formation of new stellar populations from gas accreted by massive young star clusters

Stars in star clusters are thought to form in a single burst from a common progenitor cloud of molecular gas. However, massive, old globular clusters -- with ages greater than 10 billion years and masses of several hundred thousand solar masses -- often harbour multiple stellar populations, indicating that more than one star-forming event occurred during their lifetimes. Colliding stellar winds from late-stage, asymptotic-giant-branch stars are often invoked as second-generation star-formation trigger. The initial cluster masses should be at least 10 times more massive than they are today for this to work. However, large populations of clusters with masses greater than a few million solar masses are not found in the local Universe. Here we report on three 1-2 billion-year-old, massive star clusters in the Magellanic Clouds, which show clear evidence of burst-like star formation that occurred a few hundred million years after their initial formation era. We show that such clusters could accrete sufficient gas reservoirs to form new stars if the clusters orbited in their host galaxies' gaseous discs throughout the period between their initial formation and the more recent bursts of star formation. This may eventually give rise to the ubiquitous multiple stellar populations in globular clusters.Comment: 10 pages, 11 figures, Authors' version of a letter published in Nature (27 January 2016), including Methods and Extended Dat

Edge and corner skin effects of chirally coupled magnons characterized by a topological winding tuple

We investigate a long-ranged coupled and non-Hermitian two-dimensional array of nanomagnets, fabricated on a thin magnetic substrate and subjected to an in-plane magnetic field. We predict topology-driven edge and corner skin effects of magnetic eigenmodes with the localization position at boundaries precisely characterized by a topological winding tuple $({\cal W}_1,{\cal W}_2)$. By varying the direction of the in-plane field, all magnon states pile up either at different edges of the array with $({\cal W}_1=\pm 1,{\cal W}_2=0)$ or $({\cal W}_1=0,{\cal W}_2=\pm 1)$, or at different corners characterized by $({\cal W}_1=\pm 1,{\cal W}_2=\pm 1)$. Exploiting the non-Hermitian topology is potentially helpful for designing useful magnonic metasurface in the future.Comment: 7 pages, 2 figures, 1 table. Comments are welcom