1,720,980 research outputs found
An Open Transmission Line Method for the Dielectric Investigation of Bound Soil Water
No full textA dielectric measuring technique, denoted open transmission line (OTL) method, has been developed. The
OTL method is suitable for performing accurate permittivity measurements as a function of the sample
moisture content, by allowing a free exchange of water with the environment. The characteristics of the
OTL cell are presented, together with an electromagnetic model and a measurement approach to obtain
the dielectric properties of porous materials as a function of the water content. A sensitivity analysis is
conducted, comparing the performances of the OTL technique to those of other well known methods. The
measurement results on a few dielectric materials are presented and discussed
Coordinating multiple robots with assigned paths
No full textThis paper describes a method for coordinating the motions of a group of robotsfollowing predefined paths in a common workspace. Coordination Diagrams (CD) are used forrepresenting the possible collisions among the robots. We propose an algorithm that computesa complete coordination plan for the overall missions that each vehicle have to execute. Thealgorithm generates a set of possible coordination plans and then gives the optimal one. Previousworks apply traditional path planning techniques (such as D* or A*) to compute a coordinatedmotion. However these techniques do not take into account the fact that the CD has a cylindricalstructure. This important features enables our algorithm to explore the CD in a more efficientlyway
An Efficient Control Strategy for the Traffic Coordination of AGVs
No full textIn this paper we propose an algorithm for coordinating a fleet of Automated Guided Vehicles (AGVs) that go through predefined paths in a dynamic industrial environment. Coordination diagrams are used to define a mapping between the configuration space of the fleet and a set of motion constraints that the vehicles must satisfy in order to avoid mutual collisions. The motion actions that maximize the advancement of the fleet while respecting the constraints are determined by a polynomial time heuristic algorithm
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Non invasive techniques for identification and characterization of polymers in contemporary artworks.
No full textContemporary art collections include a huge variety of polymeric materials - briefly identified as “plastics” - that react differently to the same environmental conditions and can undergo dramatically diverse degradation processes. Hence, a fundamental starting point in any plan of preservation of plastics artworks is the identification of types of polymers constituting the objects and, when possible, the assessment of the degradation stage for each polymer identified. At present, tests available for plastics identification are borrowed from industrial field: in most cases they require sampling and are destructive or, at least, micro-destructive. This fact limits their applicability in the museums context, where the integrity of the artwork is a fundamental value to be taken into account. Nowadays, methodologies based on evaluation of visual appearance and odors remain the most practiced alternative for a simple, non destructive classification of materials in plastic artworks. Thus, non invasive methods for rapid identification of materials and diagnosis of degradation are highly required for preservation of contemporary art collections. The aim of this work is to study applicability and potentialities of two non-invasive spectroscopic techniques, namely FORS (Fiber Optic Reflectance Spectroscopy) and Dielectric Spectroscopy, as measurement principles of portable systems for the quick identification of plastics and characterization of most frequent degradation phenomena. FORS is an optical technique based on acquisition of the reflectance spectrum in the UV-Vis-NIR spectral region (300-2100nm). By means of a portable spectrophotometer equipped with optical fibers probe-head, the spectrum is recorded in-situ in a totally non-invasive way, and, thanks to the versatility of optical fiber accessories, any point of the object can be measured without constraints due to size or shape of the object. The spectral data on the extended UV-Vis-NIR are exploitable for different purposes: the NIR spectrum can provide indications about the occurrence of chemical species characteristics of a given polymeric class. Instead, the spectral reflectance in the visible region is used for colorimetric analysis and is a powerful tool for monitoring changes in appearance that are symptoms of several degradation phenomena. Dielectric Spectroscopy consists in the measurement of the dielectric permittivity of materials using sensors operating in a very broad frequency region of the electromagnetic spectrum (from a few Hz up to tens of GHz). Dielectric permittivity is a physical parameter that can be related to the capability of polarization of the material in presence of an applied electrical field, and hence its measurement provides information about the tendency of molecular dipoles to follow the orientation of the applied field. This is in turn related to chemical and physical properties of materials. In this context dielectric spectroscopy can be useful for distinguishing between given classes of polymers (e.g. nitrate and acetate of cellulose), as well as for assessing structural molecular alterations (chain length changes) and monitoring ageing phenomena. Both these techniques are already used in conservation field for non-invasive diagnostic on artworks. Nevertheless, so far they have been employed and optimized for characterization of antique artifacts and ‘traditional’ artistic materials: the idea is now to apply these approaches to contemporary artworks, and in particular to polymeric materials. To this purpose, the first unavoidable step is to build specific spectral references databases of polymers of interests in the museum context. Therefore, a set of certified standards (Resinkit®) of the most common polymers has been characterized using both FORS and dielectric spectroscopy, and preliminary results are discussed here. This work is carried out in the framework of the on-going EC Research Project “Popart” (Preservation Of Plastic ARTefacts in museum collections). The research leading to these results has received funding from the European Community’s Seventh Framework Programme FP7/2007-2013 under grant agreement n° 212218
Coordinating the motion of multiple AGVs in automatic warehouses
No full textIn this paper an algorithm for planning a coordinated motion of a fleet of Autonomous Guided Vehicles (AGVs)
delivering goods in an automatic warehouse is proposed. The AGVs travel along a common segmented layout and a path
is assigned to each robot by a mission planner. Coordination diagrams are used for representing possible collisions among the robots and a novel algorithm for efficiently determining a coordinated motion of the fleet is proposed. The coordination approach proposed in the paper is validated through experiments on real plants layouts. We present an example in which the coordinated motion of 10 vehicles is computed in only 12.4 sec. on a common PC
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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