1,720,989 research outputs found
Direct and indirect assessment of the elastocaloric properties of cast NiMnTi alloys
Full text linkThe study of the elastocaloric effect of NiMnTi alloys is a key topic for developing materials for sustainable and efficient solid-state cooling and heating applications. In the current work, the mechanical behavior of two arc melted and heat treated NiMnTi alloys with 15 and 18 at% of Ti has been investigated. The effects of heat treatments and operating conditions on the mechanical and caloric properties of the alloys have been assessed through calorimetric analysis, isothermal stress-strain compressive measurements, and adiabatic tests. To evaluate the caloric performance of the NiMnTi alloys, both experimental and theoretical adiabatic temperature changes have been identified, and the isothermal entropy change involved in the stress-induced martensitic transformation has been computed from the discrete integration of the stress-strain curves. The NiMnTi alloys treated at 900 °C exhibited better caloric performance than those treated at 1000°C. Specifically, the sample that achieved the highest experimental positive and negative ΔT values (10.2 °C and −12.6 °C, respectively) was the NiMnTi alloy with 15 at% of Ti and heat treated at 900 °C. This study provides a detailed analysis of the physical properties, functionality, and caloric properties of polycrystalline NiMnTi fabricated through a melting process, considering its potential use in solid-state cooling and heat pumping technologies
NiMnGa polycrystalline magnetically activated shape memory alloy: a calorimetric investigation
No full textImplementation of a constitutive model for different annealed superelastic SMA wires with rhombohedral phase
No full textTwo aspects of NiTi are the focus of the present work. First, the austenite-rhombohedral transformation, which is often neglected by reason of its little mechanical relevance, but can be used in some applications. Second, the superelastic behavior related to a NiTi material that undergoes a low temperature annealing. Driven by the need to have a design tool for an application that uses materials with these characteristics, a model to simulate the pseudoelastic cycle has been developed. It includes the transformation kinetics rule originally presented in Zhu and Zhang (2007), which describes the evolution of the phase fraction as a function of stress and temperature with a sigmoidal law. That rule is modified in the present model by introducing in the sigmoidal law a phenomenological parameter to adapt it to different mechanical trends. Moreover, the model accounts for the presence of all three phases computing the volumetric fraction and its evolution. The calibration and validation of the model has been based on uniaxial tensile tests in thermal chamber on two types of NiTi wires, both exhibiting R-phase transformation, but prepared according to different annealing temperatures. In addition, the model was validated also for the parallel coupling of the two types of annealed wires to reproduce a real application
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
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
Fatigue life characterization and modeling of a Ni-Ti snake-like element for mini actuation
No full textThe interest in the design of shape memory alloy (SMA) actuators is recently broadened thanks to their high power density and versatility. In particular, snake-like Ni-Ti actuators demonstrated high potential at the mini- and micro-scales as SMA non-conventional active elements, due to their capacity to provide significant displacements in a very limited space and over a high number of thermo-mechanical cycles. In this study, the fatigue behavior of a snake-like Ni-Ti element has been investigated to identify the Wöhler F-N curve. Moreover, a validated digital twin of the device was prepared and used to evaluate the stress distribution throughout the fatigue tests, to convert the experimental data into a Wöhler stress-life curve. The numerical description of shape memory behavior was performed through the Petrini-Bertini constitutive model, which also allowed a better insight for future shape and functional optimization of the device
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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