102,686 research outputs found
Sopj: A scalable online provenance join for data integration
No full textData integration is a technique used to combine different sources of data together to provide an unified view among them. MOMIS[1] is an open-source data integration framework developed by the DBGroup1. The goal of our work is to make MOMIS be able to scale-out as the input data sources increase without introducing noticeable performance penalty. In particular, we present a full outer join method capable to efficiently integrate multiple sources at the same time by using data streams and provenance information. To evaluate the scalability of this innovative approach, we developed a join engine employing a distributed data processing framework. Our solution is able to process input data sources in the form of continuous stream, execute the join operation on-the-fly and produce outputs as soon as they are generated. In this way, the join can return partial results before the input streams have been completely received or processed optimizing the entire execution
Geotechnical Investigations to Characterize the Upper Quaternary Basin of Venice
No full textThe paper concerns with the evaluation of soil stiffness in both loading-unloading condition, comparing site results with laboratory and in-situ tests measurements. Effects of ageing / secondary compression / structuration on stiffness is also discussed
Predicting the load-displacement behaviour of spread footings on sand
No full textThe paper concerns with the prediction of the behaviour of real shallow footings on sand
Efficient Stream Join Processing: Novel Approaches and Challenges
No full textStream join is a fundamental data operator for processing real-time data, but it faces computational challenges during stream inequality join (theta join operators) due to frequent updates in indexing data structures. To tackle this problem, we identify three key insights: 1) identifying skewed data distributions in real-time and implementing dedicated indexing structures for skewed keys to reduce index update costs; 2) leveraging optimized data structures, including insert-efficient mutable and search-efficient immutable structures to optimize the search stream join process and 3) adopting learned indexes instead of conventional ones, which can provide up to 4x better performance.In this Ph.D. work, we propose novel solutions for distributed and multi-core stream join processing, including an indexing solution that uses a space-efficient dedicated filter and a two-stage data structure that effectively holds and processes sliding window items (bounded streaming contents). We are also exploring the adoption and benefits of learned indexes for real-time stream join processing. Despite non-trivial challenges like state management for distributed processing, processing guarantees, and efficient concurrency mechanisms, experiments on distributed stream processing systems show superior performance compared to state-of-the-art solutions
Stress-Strain Behaviour of Sands in Triaxial and Simple Shear Tests
No full textThe behaviour of a natural sand in triaxial compression and direct simple shear was compared by means of dimensionless analysis of parameters controlling the evolution of stresses and strains: A criterion based on the equivalence between major principal strain in the two tests was considered to compare the result
Modelling of failure behaviour in shallow footings under inclined loads
No full textThe failure behaviour of shallow strip footings on granular soils under inclined loads is modelled using and analytical and experimental approac
Enhancing entity resolution efficiency with loosely schema-aware techniques - Discussion paper
No full textEntity Resolution, the task of identifying records that refer to the same real-world entity, is a fundamental step in data integration. Blocking is a widely employed technique to avoid the comparison of all possible record pairs in a dataset (an inefficient approach). Renouncing to exploit schema information for blocking has been proved to limit the chance of missing matches (i.e., it guarantees high recall), at the cost of a low precision. Meta-blocking alleviates this issue by restructuring a block collection, removing redundant and superfluous comparisons. Yet, existing meta-blocking techniques exclusively rely on schema-agnostic features. In this paper, we investigate how loose schema information, induced directly from the data, can be exploited in an holistic loosely schema-aware (meta-)blocking approach that outperforms the state-of-the-art meta-blocking in terms of precision, without renouncing high level of recall. We implemented our idea in a system called Blast, and experimentally evaluated it on real-world datasets
Curvatura dell'inviluppo a rottura e capacità portante di fondazioni superficiali in terreni granulari
No full textNella ricerca viene presa in esame l'influenza della curvatura dell'inviluppo a rottura sulla capacità portante delle fondazioni superficial
Modelling the behaviour of shallow footings on geotextile reinforced sand
No full textThe research examines the effect of geosynthetics reinforcements the bearing capacity of shallow footings on reinforced sands by using 1g physical modelling
The viscoplastic behaviour of a geogrid-reinforced modell wall
No full textThe paper deals with the time-dependent behaviour of retaining walls reinforced with polypropylene geogrids and subjected to increasing loads applied to the soil surface behind the wall. The experimental program involved fully automatic small-scale 1g physical models of a geogrid-reinforced wall. Long term model tests were carried out using different plate loading rates in order to investigate the time-dependent response of the reinforced walls. The paper presents details of the physical model, testing procedure and principal test results. An analytical interpretation of the time-dependent viscoplastic behaviour using a simple three parameter time-rate equation is shown to fit the experimental data and is then proposed to predict the long term displacements of the reinforced walls
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