A Relation-Based Page Rank Algorithm for Semantic Web Search Engines

With the tremendous growth of information available to end users through the Web, search engines come to play ever a more critical role. Nevertheless, because of their general-purpose approach, it is always less uncommon that obtained result sets provide a burden of useless pages. The next-generation Web architecture, represented by the Semantic Web, provides the layered architecture possibly allowing overcoming this limitation. Several search engines have been proposed, which allow increasing information retrieval accuracy by exploiting a key content of Semantic Web resources, that is, relations. However, in order to rank results, most of the existing solutions need to work on the whole annotated knowledge base. In this paper, we propose a relation-based page rank algorithm to be used in conjunction with Semantic Web search engines that simply relies on information that could be extracted from user queries and on annotated resources. Relevance is measured as the probability that a retrieved resource actually contains those relations whose existence was assumed by the user at the time of query definitio

Deriving the extinction to young stellar objects using [FeII] near-infrared emission lines. Prescriptions from GIANO high-resolution spectra

The near-infrared emission lines of Fe$^{+}$ at 1.257, 1.321, and 1.644 $\mu$m share the same upper level; their ratios can then be exploited to derive the extinction to a line emitting region once the relevant spontaneous emission coefficients are known. This is commonly done, normally from low-resolution spectra, in observations of shocked gas from jets driven by Young Stellar Objects. In this paper we review this method, provide the relevant equations, and test it by analyzing high-resolution ($R \sim 50000$) near-infrared spectra oftwo young stars, namely the Herbig Be star HD 200775 and the Be star V1478 Cyg, which exhibit intense emission lines. The spectra were obtained with the new GIANO echelle spectrograph at the Telescopio Nazionale Galileo. Notably, the high-resolution spectra allowed checking the effects of overlapping telluric absorption lines. A set of various determinations of the Einstein coefficients are compared to show how much the available computations affect extinction derivation. The most recently obtained values are probably good enough to allow reddening determination within 1 visual mag of accuracy. Furthermore, we show that [FeII] line ratios from low-resolution pure emission-line spectra in general are likely to be in error due to the impossibility to properly account for telluric absorption lines. If low-resolution spectra are used for reddening determinations, we advice that the ratio 1.644/1.257, rather than 1.644/1.321, should be used, being less affected by the effects of telluric absorption lines.Comment: 17 pages, 6 figures, to be published in PAS

Mixed marker-based/marker-less visual odometry system for mobile robots

When moving in generic indoor environments, robotic platforms generally rely solely on information provided by onboard sensors to determine their position and orientation. However, the lack of absolute references often leads to the introduction of severe drifts in estimates computed, making autonomous operations really hard to accomplish. This paper proposes a solution to alleviate the impact of the above issues by combining two vision‐based pose estimation techniques working on relative and absolute coordinate systems, respectively. In particular, the unknown ground features in the images that are captured by the vertical camera of a mobile platform are processed by a vision‐based odometry algorithm, which is capable of estimating the relative frame‐to‐frame movements. Then, errors accumulated in the above step are corrected using artificial markers displaced at known positions in the environment. The markers are framed from time to time, which allows the robot to maintain the drifts bounded by additionally providing it with the navigation commands needed for autonomous flight. Accuracy and robustness of the designed technique are demonstrated using an off‐the‐shelf quadrotor via extensive experimental test

Single view vs. multiple views scatterplots

Among all the available visualization tools, the scatterplot has been deeply analyzed through the years and many researchers investigated how to improve this tool to face new challenges. The scatterplot visualization diagram is considered one of the most functional among the variety of data visual representations, due to its relative simplicity compared to other multivariable visualization techniques. Even so, one of the most significant and unsolved challenge in data visualization consists in effectively displaying datasets with many attributes or dimensions, such as multidimensional or multivariate ones. The focus of this research is to compare the single view and the multiple views visualization paradigms for displaying multivariable dataset using scatterplots. A multivariable scatterplot has been developed as a web application to provide the single view tool, whereas for the multiple views visualization, the ScatterDice web app has been slightly modified and adopted as a traditional, yet interactive, scatterplot matrix. Finally, a taxonomy of tasks for visualization tools has been chosen to define the use case and the tests to compare the two paradigms

Computer-assisted analysis of painting brushstrokes: digital image processing for unsupervised extraction of visible features from van Gogh's works

The automatic extraction of objective features from paintings, like brushstroke distribution, orientation, and shape, could be particularly useful for different artwork analyses and management tasks. In fact, these features contribute to provide a unique signature of the artists' style and can be effectively used for artist identification and classification, artwork examination and retrieval, etc. In this paper, an automatic technique for unsupervised extraction of individual brushstrokes from digital reproductions of van Gogh's paintings is presented. Through the iterative application of segmentation, characterization, and validation steps, valid brushstrokes complying with specific area and shape constraints are identified. On the extracted brushstrokes, several representative features can then be calculated, like orientation, length, and width. The accuracy of the devised method is evaluated by comparing numerical results obtained on a dataset of digital reproductions of van Gogh's oil-on-canvas works with observations made by human subjects and with another recent approach for automatic brushstroke analysis. Experimental tests showed that the devised methodology produces results that are rather close to those obtained by human subjects and, for some of the metrics considered, can provide improved performances with respect to alternative techniques

La scultura decorativa nell’area gallego-portoghese durante il periodo svevo-visigotico (secoli V-VIII)

Attraverso questo contributo si vuole polarizzare l’attenzione sulla produzione scultorea del periodo svevo-visigotico nelle aree storiche della Gallaecia e della Lusitania, corrispondenti attualmente ai territori del Portogallo e della Galizia spagnola. In relazione alla documentazione lapidea, analizzata di volta in volta rispetto al contesto politico-culturale di pertinenza, relativo al regno svevo o al regno visigotico, si considereranno gli aspetti stilistici, tipologico-formali e quelli relativi alle tecniche di esecuzione, distinguendo gli apporti artistici locali da quelli di provenienza esterna, e specificando, per quanto possibile, i tempi cronologici e le diverse modalità di irradiazione. Parallelamente all’individuazione e allo studio dei principali centri artistici svevo-visigotici, suddivisi in tre grandi aree: lusitanica, sveva e olissiponense (pertinente alle botteghe di Lisbona), l’attenzione sarà poi spostata sulle problematiche attestazioni scultoree di Saamasas (Lugo) e di Lisbona, le quali, considerate dagli studi di volta in volta visigotiche o mozarabiche, rappresentano a tutt’oggi un difficoltoso caso interpretativo sia cronologico sia stilistico. Rispetto alle sculture di Saamasas si argomenterà un’attribuzione all’ambito culturale visigotico, mentre per le sculture di Lisbona, provenienti dal convento di Chelas, si evidenzierà il legame con un orizzonte artistico mozarabico.Through this contribution we want to focus on the sculpture production of the Swabian -Visigothic period and on the historical areas of Gallaecia and Lusitania, at the moment corresponding to the Portugal and Spanish Galicia territories. According to the stone documentation, analyzed step by step according to the political-cultural, relating to the Swabian kingdom or the Visigothic kingdom, we are going to consider the stylistic, typological and formal aspects and those related to technical implementation, distinguishing local artistic contributions from those that have outside origin and specifying, as much as possible, the chronological time and the different procedures of irradiation. In parallel to the identification and study of the major Swabian-Visigoths art centers, divided into three main areas: lusitanica, Swabian and olissiponense (relevant to workshops of Lisbon), then the focus will move on problems about the Saamasas (Lugo) and Lisbon sculptural attestations, which, taken from studies from time to time Visigothic or Mozarabic, still represent a difficult case of interpretation, both from a chronological and stylistic point of view. As regards the Saamasas sculptures, we will deal with the attribution of Visigothic culture, whereas for the sculptures of Lisbon, from the convent of Chelas, we will highlight the link with a Mozarabic artististic horizon.

L’apporto di modelli artistici toledani nella scultura begastrense d’epoca visigota

The purpose of the article is to analyze the technical-stylistic and formal specificities of the Visi- gothic sculpture coming from the site of Begastri (Cehegín-Murcia) - located in the south-eastern Iberian peninsular - within the framework of the Visigothic artistic culture of the second half of the sixth century. In the above-mentioned study, it will be argued that the begastrense workshops, unlike the other manufac- turing contexts the Iberian south-east, are characterized by strong artistic contributions of Toledan filiation assimilated, in our opinion, following the Lovigildian conquest of the Orospeda (historical region that in- cluded the same Begastri) in the Greek-Gothic conflict between Empire and Visigothic Kingdom. Further- more, it will be highlighted how the diffusion of these courtly stylistic models had, in our opinion, an eminently ideological-propagandistic function in an anti-Byzantine perspective.il contributo vuole analizzare le specificità tecnico-stilistiche e formali della scultura visigota proveniente dal sito di Begastri (Cehegín-Murcia) -ubicato nel sud-est peninsulare iberico-nel quadro della cul- tura artistica visigota della seconda metà del VI secolo. Nel suddetto studio si argomenterà come le botteghe begastrensi, contrariamente agli altri contesti produttivi del sud-est iberico, siano caratterizzate da forti ap- porti artistici di filiazione toledana assimilati, a nostro giudizio, in seguito alla conquista leovigildiana dell’Orospeda (regione storica che includeva la stessa Begastri) nell’ambito del confitto greco-gotico tra Im- pero e Regno visigoto. Si evidenzierà, inoltre, come la diffusione di questi modelli stilistici cortigiani ebbe, probabilmente, una funzione eminentemente ideologico-propagandistica in chiave anti bizantina