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Fiorillo F.,INRIM - Istituto Nazionale di Ricerca Metrologica
Metrologia | Year: 2010

Major methods to measure the magnetic properties of materials are systematically discussed in the light of the general phenomenology of magnetism in matter and its physical interpretation. Attention is paid to the problems of measurement traceability and reproducibility and the related standards. While the discussion is focused on the characterization of the soft and hard ferromagnetic materials relevant for electromagnetic applications, brief consideration is given to the special problems posed by measurements on feebly magnetic materials. It is stressed how geometrical and physical properties can often combine to make the determination of the true magnetic properties of materials a somewhat elusive goal. Measurement reproducibility can nevertheless be attained under the guidance provided by written standards. Recent evolution of the magnetic measuring techniques has occurred in response to the digital revolution and the development of novel high-performance materials (e.g. extra-hard rare-earth based magnets, multilayers, micro/nanostructures, etc). It is stressed, however, that the drive to progress in measurements ultimately stems from the search for new fundamental phenomena in materials and their understanding. © 2010 BIPM & IOP Publishing Ltd. Source


Giorgi G.L.,INRIM - Istituto Nazionale di Ricerca Metrologica
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

The role played by quantum discord in mixed-state computation is widely debated since, in spite of evidence of its importance in creating quantum advantages, even in the absence of entanglement, there are not direct proofs of its necessity in these computational tasks. Recently, the presence of discord was shown to be necessary and sufficient for remote state preparation for a broad class of quantum channels. Here, we show that this property is not universal. There are states whose discord cannot be considered as a quantum resource since it has been produced locally that are useful for remote state preparation, and there are bona fide discordant states that are of no help. © 2013 American Physical Society. Source


Bich W.,INRIM - Istituto Nazionale di Ricerca Metrologica
IEEE Transactions on Instrumentation and Measurement | Year: 2012

The concept of uncertainty in measurement stems from that of (probable) error and is intimately intertwined with it. Both concepts can be viewed as measures of the quality of a measurement or, better, of the corresponding estimate. There is an endless list of misunderstandings, false beliefs, and misinterpretations on this subject. People tend also to use the same word with different meanings. In this paper, while giving an overview of the evolution of the concept, from the initial unawareness of the need for a quality assessment (still present in many areas) to the present views, the author also tries to shed some light and some clarity on the most popular and debated misunderstandings, particularly about the concepts of error, true quantity value(s), and measured quantity value. The author is the convener of the Joint Committee for Guides in Metrology Working Group 1 (Guide to the expression of uncertainty in measurement). The opinion expressed in this paper does not necessarily represent the view of this working group. © 1963-2012 IEEE. Source


D'Errico G.E.,INRIM - Istituto Nazionale di Ricerca Metrologica
Measurement: Journal of the International Measurement Confederation | Year: 2014

Aggregation of comparisons data to rank experimental results and take decisions is being more and more practiced in diverse areas, spanning over a variety of disciplines including, e.g., quality function deployment in industrial engineering, scientometrics, and recovery rate testing of new medications. Problems in decision making may be accrued from the presence of hidden confounding interactions, spurious relationships, lurking variables at work. An analysis of partitioned datasets is carried-on using contingency tables and conditional probabilities. The focus is on intermediate interpretation of evidence to avoid paradoxical reversal of statistical inference when passing from sub-level data to the global level: to this aim, care in partitioning criteria is needed to balance distribution of partitioned data over successive levels, not to incur statistical dependence. An example of counter-intuitive amalgamation effects - also known as Yule-Simpson's "paradox" - is presented and discussed, showing how to prevent such effects by proper design of experiments. © 2014 Elsevier Ltd. All rights reserved. Source


Basso V.,INRIM - Istituto Nazionale di Ricerca Metrologica
Journal of Physics Condensed Matter | Year: 2011

This paper presents a study of the magnetocaloric effect at the first-order magneto-elastic phase transition. The entropy change Δs at the transition temperature is given by the sum of the magnetic and the structural contributions. By using a thermodynamic model, it is shown that the sign and amplitude of the structural contribution to Δs are determined by the dimensionless parameter ζ (zeta) which depends on β, the steepness of the change of exchange forces with volume, and on αp, the thermal expansion coefficient of the structural lattice. For ζ < 0 the change Δs can be larger than the magnetic contribution alone, because the structural entropy change and the magnetic entropy change have the same sign, giving rise to the giant magnetocaloric effect. For 0 < ζ < 1 the two contributions partially cancel each other and the total entropy change is lower than the magnetic entropy change. For ζ > 1 the structural entropy dominates and a transition occurs upon heating from a low temperature paramagnet to a high temperature ferromagnet. © 2011 IOP Publishing Ltd. Source

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