759 research outputs found
Time series compression: a survey
No full textThe presence of smart objects is increasingly widespread and their ecosystem,
also known as Internet of Things, is relevant in many different application
scenarios. The huge amount of temporally annotated data produced by these smart
devices demand for efficient techniques for transfer and storage of time series
data. Compression techniques play an important role toward this goal and,
despite the fact that standard compression methods could be used with some
benefit, there exist several ones that specifically address the case of time
series by exploiting their peculiarities to achieve a more effective
compression and a more accurate decompression in the case of lossy compression
techniques. This paper provides a state-of-the-art survey of the principal time
series compression techniques, proposing a taxonomy to classify them
considering their overall approach and their characteristics. Furthermore, we
analyze the performances of the selected algorithms by discussing and comparing
the experimental results that where provided in the original articles. The goal
of this paper is to provide a comprehensive and homogeneous reconstruction of
the state-of-the-art which is currently fragmented across many papers that use
different notations and where the proposed methods are not organized according
to a classification.Comment: 33 pages, author versio
Multi-Line Customized Bus Planner for On-Demand Origin-Destination Travel Requests
No full textReplacing private transport in large cities with public and shared alternatives is increasingly relevant to reduce congestion during rush hours and air pollution. The activation of customized bus services is one of the possible strategies toward that goal, and automatic bus route design is needed when the amount of pickup addresses to manage is large. The approaches described in the literature are not suitable for real-world applications because they tend to generate many more lines than necessary, or they don't work if addresses do not form clusters. In this paper, we propose a novel bus line generation approach suitable for any address database
gpuDCI: Exploiting GPUs in Frequent Itemset Mining
No full textFrequent itemset mining (FIM) algorithms extract subsets of items that occurs frequently in a collection of sets. FIM is a key analysis in several data mining applications, and the FIM tools are among the most computationally intensive data mining ones. In this work we present a many-core parallel version of a state-of-the-art FIM algorithm, DCI, whose sequential version resulted, for most of the tested datasets, better than FP-Growth, one of the most efficient algorithms for FIM. We propose a couple of parallelization strategies for Graphics Processing Units (GPU) suitable for different resource availability, and we present the results of several experiments conducted on real-world and synthetic datasets. © 2012 IEEE
Il ritorno di Ulisse
No full textCome Ulisse, il padre del modello paidocentrico
- ha acquisito un’esperienza del suo percorso di maturazione che lo ha reso ancora più consapevole, saggio, capace di affrontare ostacoli, disposto alla rinuncia, pur di conservare la possibilità di scegliere, pronto a perdere per vincere, a guardarsi, sentirsi;
- è interessato a vivere la paternità sia come valore che come istituto;
- preferisce l’intraprendenza, la sincerità, la trasparenza, il mutuo sostegno, la sfida, mantiene (insieme al desiderio di sollecitare la stessa autonoma passione nei figli) una curiosità ingovernabile verso tutto ciò che esiste al di là delle soglie geografiche e simboliche, verso la profondità e l’intimità dei rapporti familiari, verso le caratteristiche di nuovi limiti spostati sempre più in avanti, quindi non considera il superamento delle colonne d’Ercole come una violazione d’ordine morale;
- valorizza la rigenerazione continua e coerente, il dialogo ed il silenzio significativi, la meraviglia, lo stupore;
- valorizza la famiglia come risorsa, si propone l’obiettivo dell’autorevolezza, è aperto e proiettato verso il futuro.
Nuove forme di genitorialità devono rafforzare soluzioni di dinamicità ed interesse, scelte volontarie, atteggiamenti e comportamenti innovativi nel linguaggio, nel tipo di comunicazione, nei modelli di rappresentazione della vita, nei modelli di condivisione e selezione dei problemi, nel tipo di attenzione e regolazione dell’apparente e del vero, non sulle regole o sulla conoscenza delle modalità di relazione, ma su competenze caratteristiche, personali, autonome, basate su significato e scelte di senso
Approximate Mining of Frequent Patterns on Streams
No full textMany critical applications, like intrusion detection or stock market analysis, require a nearly immediate result based on a continuous and infinite stream of data. In most cases finding an exact solution is not compatible with limited availability of resources and real time constraints, but an approximation of the exact result is enough for most purposes. This paper introduces a new algorithm for approximate mining of frequent itemsets from streams of transactions using a limited amount of memory. The proposed algorithm is based on the computation of frequent itemsets in recent data and an effective method for inferring the global support of previously infrequent itemsets. Both upper and lower bounds on the support of each pattern found are returned along with the interpolated support. An extensive experimental evaluation shows that APstream, the proposed algorithm, yields a good approximation of the exact global result considering both the set of patterns found and their supports
- …
