Discovering Implicational Knowledge in Wikidata

Knowledge graphs have recently become the state-of-the-art tool for representing the diverse and complex knowledge of the world. Examples include the proprietary knowledge graphs of companies such as Google, Facebook, IBM, or Microsoft, but also freely available ones such as YAGO, DBpedia, and Wikidata. A distinguishing feature of Wikidata is that the knowledge is collaboratively edited and curated. While this greatly enhances the scope of Wikidata, it also makes it impossible for a single individual to grasp complex connections between properties or understand the global impact of edits in the graph. We apply Formal Concept Analysis to efficiently identify comprehensible implications that are implicitly present in the data. Although the complex structure of data modelling in Wikidata is not amenable to a direct approach, we overcome this limitation by extracting contextual representations of parts of Wikidata in a systematic fashion. We demonstrate the practical feasibility of our approach through several experiments and show that the results may lead to the discovery of interesting implicational knowledge. Besides providing a method for obtaining large real-world data sets for FCA, we sketch potential applications in offering semantic assistance for editing and curating Wikidata

Histoire des tribunaux de l'Inquisition en France

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Guided acoustic wave resonators using an acoustic Bragg mirror

Lamb wave devices have recently gained an interest for providing narrow bandpass filters in wireless transmission systems. Their cointegration with film bulk acoustic wave resonators is a major advantage, enabling the possibility to provide simultaneously several radio frequency and intermediate-frequency filters in a single fabrication. Similarly, in this work, we report the fabrication of resonators using waves guided in a piezoelectric layer deposited atop a Bragg mirror. Such waves exhibit a behavior close to Lamb waves, thanks to the acoustic isolation provided by the mirror, while being cointegrated along with solidly mounted resonator structures