1,720,996 research outputs found
Spurious ferromagnetic remanence detected by hybrid magnetometer
No full textNuclear magnetic resonance detection in ultra-low-field regime enables the measurement of different components of a spurious remanence in the polymeric material constituting the sample container. A differential atomic magnetometer detects simultaneously the static field generated by the container and the time-dependent signal from the precessing nuclei. The nuclear precession responds with frequency shifts and decay rate variations to the container magnetization. Two components of the latter act independently on the atomic sensor and on the nuclear sample. A model of the measured signal allows a detailed interpretation on the basis of the interaction geometry. Published under license by AIP Publishing
Real-Time non-invasive detection of hidden objects in parcels and packages with sub-THz systems
No full textTerahertz technology exploits the so-called frequency gap between the infrared and microwaves, typically referred to as the frequency band from 100 GHz to 30 Terahertz. The use of techniques based on the Terahertz radiation has long been studied in fields such as astronomy and solid state physics. Being a non harmful radiation for human beings, the Terahertz radiation is very interesting for applications since it can be used without worrying for the safety of users and operators. Recent innovations in Terahertz technologies are bringing a wide variety of applications, from non-destructive evaluation, to homeland security, from quality control of food and agricultural products to the biomedical sector. We report about an implementation of a sub-Terahertz investigation setup based on commercial solutions. The system is currently being used for non-invasive detection of metals inside parcels and boxes in security applications and in vivo studies of water leaf contents in smart agriculture
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
Development of a Terahertz scanning apparatus with automatic object detection capabilities
No full textTerahertz radiation is the part of the electromagnetic spectrum ranging from hundreds of MHz up to several THz. Recent advances in detector technology enable us to develop compact and affordable systems able to generate and detect THz radiation, thus filling the so-called “Terahertz gap”. Terahertz cameras with thousands of pixels arranged in one or two dimensions allow for real-time imaging applications. THz imaging techniques can be used to detect materials that are opaque to that radiation, such as metal or ceramic objects embedded in THz-transparent materials (e.g. paper, textiles, etc.). Due to its non-ionising nature, THz radiation does not require special shielding precautions compared to X-ray systems, and can be safely applied to living tissue. Terahertz imaging can be employed to detect forbidden objects in security checks with parcels scanners and full body scanners. This paper will describe our recent developments towards an innovative application of a sub-THz imaging system based on a commercially available detector. The setup is used to detect objects inside parcels and packages using a conveyor belt and a THz imaging system. An automatic detection system based on convolutional neural networks has been developed allowing for a real-time selection of targets against a set of images. The performance of the setup will be shown and newest results on the recognition capability will be presented
Ferromagnetic contamination of ultra-low-field-NMR sample containers. Quantification of the problem and possible solutions
Full text linkThe presence of a weak remanence in Ultra-Low-Field (ULF) NMR sample containers is investigated on the basis of proton precession. The high-sensitivity magnetometer used for the NMR detection, enables simultaneously the measurement of the static field produced in the sample proximity by ferromagnetic contaminants. The presence of the latter is studied by high resolution chemical analyses of the surface, based on X-ray fluorescence spectroscopy and secondary ions mass spectroscopy. Methodologies to reduce the contamination are explored and characterized. This study is of relevance in any ULF-NMR experiment, as in the ULF regime spurious ferromagnetism becomes easily a dominant cause of artefacts
A low noise modular current source for stable magnetic field control
No full textA low cost, stable, programmable, unipolar current source is described. The circuit is designed in view of a modular arrangement, suitable for applications where several DC sources must be controlled at once. A hybrid switching/linear design helps in improving the stability and in reducing the power dissipation and cross-talking. Multiple units can be supplied by a single DC power supply, while allowing for a variety of maximal current values and compliance voltages at the outputs. The circuit is analogically controlled by a unipolar voltage, enabling current programmability and control through commercial digital-to-analogue conversion cards
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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