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In this paper we introduce a novel system that comprises techniques advancing the query processing in wireless sensor networks. Our system facilitates time triggered queries that are scheduled in a distributed fashion among sensor nodes. Thus, time synchronisation is of paramount importance. Since accurate time synchronisation requires more energy, our system allows a trade off between precision of time and energy according to the user requirements. To minimize the communication overhead for query processing, our system employs new query execution mechanisms. We have implemented our query processing system on Sun TM Small Programmable Object Technology (SPOT) sensor network platform. The system was entirely programmed in Java enabling an object oriented design and implementation. It provides a friendly graphical user interface for query management and visualisation of results.

Web search engine: characteristics of user behaviors and their implication Science in China Series F-Information Sciences 44, 351 (2001); A Web-based visual analytics system for real estate data SCIENCE CHINA Information Sciences 56, 052112 (2013); PREDAV-H1: a user-friendly web server for predicting antigenic variants of influenza H1N1 viruses SCIENCE CHINA Life Sciences 62, 426 (2019); Detecting micro-blog user interest communities through the integration of explicit user relationship and implicit topic relations SCIENCE CHINA Information Sciences 60, 092105 (2017);. RESEARCH PAPER .

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The SQL query language is the 'lingua franca' of transactional databases, and is essential for scalable data analytics. Learning SQL requires practical exercises with databases, including those parts of SQL with side-effects such as DDL statements, triggers, and stored procedures. Teaching this effectively to a non-technical audience is a challenge, especially in times of COVID-19 without face-to-face classes. The Grok Learning platform allows to design self-paced online tutorials with auto-graded exercises - but it was originally built for teaching programming languages. In this demo, we show how we extended the Grok platform to teach SQL for Data Scientists with comprehensive online learning. Grok supports a rich user interface with interactive examples where students can explore and experiment with each example query. This is ideal for learning declarative querying. Each query is executed in its own sandbox on a freshly initialised database instance which allows to teach all parts of SQL including DDL statements, stored procedures, triggers and UDFs. At the same time, the platform scales to thousands of concurrent users, while maintaining interactive response times.