1,720,960 research outputs found
Radiographic method for measuring the continuum hard X-ray output spectrum of a Plasma Focus device
Get PDFA radiographic method is proposed and then applied to infer the continuum part of the hard X-ray spectrum of a 4.7 kJ Plasma Focus from differential absorption measurements on metals. Copper, nickel, titanium and silver samples with thicknesses spanning between 0.1 and 10 mm were employed as filters. The X-ray radiation was detected using a standard radiographic screen-film system. The results show the presence of a dominant peak around 75 keV with significant spectral components in the range of 40 to 200 keV. The method is easy to follow, inexpensive, and allows for calibrated, single shot, spectral measurements. © 2009 Elsevier B.V. All rights reserved.Fil: Raspa, Veronica Diana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: Moreno, Cesar Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentin
Conceptual Engineering of Plasma-Focus Thermonuclear Pulsors
Get PDFA new method of significant efficiency enhancement, which is based on simultaneous interaction of electrons with an opposite wave at the second cyclotron harmonic, and a forward wave of the same frequency, at the fundamental cyclotron resonance, is proposed for the backward wave oscillator (gyro-BWO). Excitation of the forward wave results in significant efficiency enhancement, whereas the opposite wave provides a broadband feedback. This allows realizing a high-efficiency, frequency-tunable oscillator. Index Terms-Broadband gyro-oscillator, cyclotron resonance maser, gyro-BWO, gyro-TWT. )Fil: Moreno, Cesar Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; ArgentinaFil: Bruzzone, Horacio. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; ArgentinaFil: Martínez, Javier. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; ArgentinaFil: Clausse, Alejandro. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
Temporal Variation of the Current Sheet Inductance from PACO Plasma Focus Device
Get PDFThe temporal variation of the current sheet (CS) inductance in a plasma focus device can be calculated using the current derivative and the voltage signal acquired on the anode electrode, which are very common measurements in this type of device. The value of that inductance contains important information about the discharge performed including the CS lift-off from the insulator, voltage between the pinch extremes, maximum energy of the X-ray, energy delivered to the pinch and information about the actuating fusion mechanisms if the filling pressure is deuterium. This work discusses the values of the CS inductance extracted from several discharges of the Plasma Auto Confinado (PACO) plasma focus, installed in the National University of the Center of Buenos Aires—Argentina (2 kJ total energy, capacitor bank of 4 μF charged to 31 kV and a maximum current of 250 kA).Fil: Barbaglia, Mario Oscar. Universidad Nacional del Centro de la Provincia de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Milanese, Maria Magdalena. Universidad Nacional del Centro de la Provincia de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Soto, L.. Comisión Chilena de Energía Nuclear; Chile. Universidad Andrés Bello; ChileFil: Clausse, Alejandro. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Moreno, J.. Comisión Chilena de Energía Nuclear; Chile. Universidad Andrés Bello; ChileFil: Pavez, C.. Comisión Chilena de Energía Nuclear; Chile. Universidad Andrés Bello; ChileFil: Moreno, Cesar Hugo. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Experimental study and two-dimensional modelling of the plasma dynamics of magnetically driven shock waves in a coaxial tube
Get PDFPlasma shocks can be magnetically driven during high current discharges in low-pressure gases, induced by an external electric circuit. Radial currents between two coaxial electrodes can be accelerated to velocities of the order of 10 cmìs−1, thus being an effective method to transform potential energy in kinetic energy. A series of experiments were conducted using a low energy plasma focus device to measure the dynamics of plasma shocks in coaxial tubes. The radial position of the current sheath near the closed end of the electrodes was determined by means of a magnetic probe. The pinching time at the open end of the electrodes was measured using a Rogowski coil. Both, the movement and shaping of the plasma sheath were modelled by means of finite elements. The sheath was represented by coupled conical segments carrying current, mass, internal energy and momentum. The Lorentz force accelerates each element in its normal direction, which leads to the continuous reshaping of the sheath. The numerical results are compared against the experimental data showing good agreement.ìs−1, thus being an effective method to transform potential energy in kinetic energy. A series of experiments were conducted using a low energy plasma focus device to measure the dynamics of plasma shocks in coaxial tubes. The radial position of the current sheath near the closed end of the electrodes was determined by means of a magnetic probe. The pinching time at the open end of the electrodes was measured using a Rogowski coil. Both, the movement and shaping of the plasma sheath were modelled by means of finite elements. The sheath was represented by coupled conical segments carrying current, mass, internal energy and momentum. The Lorentz force accelerates each element in its normal direction, which leads to the continuous reshaping of the sheath. The numerical results are compared against the experimental data showing good agreement.Fil: Moreno, Cesar Hugo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; ArgentinaFil: Casanova, F.. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; ArgentinaFil: Correa, G.. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; ArgentinaFil: Clausse, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentin
Intelligent Weed Management Based on Object Detection Neural Networks in Tomato Crops
No full textAs the tomato (Solanum lycopersicum L.) is one of the most important crops worldwide, and the conventional approach for weed control compromises its potential productivity. Thus, the automatic detection of the most aggressive weed species is necessary to carry out selective control of them. Precision agriculture associated with computer vision is a powerful tool to deal with this issue. In recent years, advances in digital cameras and neural networks have led to novel approaches and technologies in PA. Convolutional neural networks (CNNs) have significantly improved the precision and accuracy of the process of weed detection. In order to apply on-the-spot herbicide spraying, robotic weeding, or precise mechanical weed control, it is necessary to identify crop plants and weeds. This work evaluates a novel method to automatically detect and classify, in one step, the most problematic weed species of tomato crops. The procedure is based on object detection neural networks called RetinaNet. Moreover, two current mainstream object detection models, namelyYOLOv7 and Faster-RCNN, as a one and two-step NN, respectively, were also assessed in comparison to RetinaNet. CNNs model were trained on RGB images monocotyledonous (Cyperus rotundus L., Echinochloa crus galli L., Setaria verticillata L.) and dicotyledonous (Portulaca oleracea L., Solanum nigrum L.) weeds. The prediction model was validated with images not used during the training under the mean average precision (mAP) metric. RetinaNet performed best with an AP ranging from 0.900 to 0.977, depending on the weed species. Faster-RCNN and YOLOv7 also achieved satisfactory results, in terms of mAP, particularly through data augmentation. In contrast to Faster CNN, YOLOv7 was less precise when discriminating monocot weed species. The results provide a better insight on how weed identification methods based on CNN can be made more broadly applicable for real-time applications.Fil: López Correa, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Consejo Superior de Investigaciones Científicas; EspañaFil: Moreno, Cesar Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Consejo Superior de Investigaciones Científicas; EspañaFil: Ribeiro, Angela. Consejo Superior de Investigaciones Científicas; EspañaFil: Andújar, Dionisio. Consejo Superior de Investigaciones Científicas; Españ
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
- …
