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The field of education has never been indifferent to the new technologies, and eventually to the Internet. Technology-Enhanced Learning, progressively, has grown to be the area for research and practice on the application of information and communication technologies to teaching and learning. In particular for the teaching activity, the numerous standard compliant Learning Object Repositories available via the Internet, and Open Educational Resources repositories, provide formidable support to teachers when they need to develop a course that can also make use of already available learning materials. The search and selection of Learning Objects, however, can be an inherently complex operation involving accessing various repositories, each potentially involving different software tools, and different organization and specification formats for the learning resources. This complexity may hinder the very success of an e-learning course. Cross-repository aggregators, i.e., systems that can roam through different repositories to satisfy the user's/teacher's query, can help to reduce such complexity, although problems of course delivery may remain. This paper proposes a hybrid recommender system, MoodleRec, implemented as a plug-in of the Moodle Learning Management System. MoodleRec can sort through a set of supported standard compliant Learning Object Repositories, and suggest a ranked list of Learning Objects following a simple keyword-based query. The various recommendation strategies operate on two levels. First, a ranked list of Learning Objects is created, ordered by their correspondence to the query, and by their quality, as indicated by the repository of origin. Social generated features are then used to show the teacher how the Learning Objects listed have been exploited in other courses. A real life experimental study is also presented, and the validity of the MoodleRec approach discussed.

This paper presents an algorithm for evaluating an arithmetic expression over "big" rational numbers. The method exploits p -adic arithmetic and parallelism to achieve efficiency. Roughly, the algorithm begins by mapping the input rational numbers to the related p -adic codes for several prime bases, then the corresponding expression is evaluated over these codes and finally the rational output is recovered from the resulting codes. All these three steps are parallelized. An efficient algorithm to compute the recovery step is proposed. Let p be the maximum of the prime bases for the codes, let r be their truncation order and let k be the number of processors. The asymptotic bit-wise complexity of the proposed recovery step is O ( r ( k log p ) log 2 3 . The previous known bound was O ( r 2 ( k log p ) log 2 3 ). Let n be the number of operations in the given expression: the asymptotic bitwise complexity of the proposed algorithm for evaluating arithmetic expressions is O ( n r 2 log p ).