1,721,124 research outputs found
Le 7 misure del mondo
No full textDal caffè alle galassie, dalle autostrade ai buchi neri, tutto l’universo si può descrivere con solo sette unità di misura. Non ci credete? A dimostrarlo basteranno le storie avvincenti raccontate in questo libro.
Da sempre misuriamo il mondo. Per conoscerlo ed esplorarlo, per viverci, per interagire con i nostri simili. L’umanità misura per conoscere il passato, comprendere il presente, progettare il futuro. Ci sono voluti però millenni perché due rivoluzioni, quella scientifica iniziata con Galileo e quella francese, avviassero il percorso per rendere il sistema di misura condiviso e non più basato su deperibili artefatti umani, ma su elementi invariabili e universali della natura. Un cammino poco noto che è però una delle principali conquiste scientifiche e sociali dell’era moderna. Oggi con solo sette unità di misura fondamentali – metro, secondo, chilogrammo, kelvin, ampere, mole e candela – misuriamo e cerchiamo di comprendere la complessità e le meraviglie della natura, dal microcosmo delle particelle elementari ai confini dell’universo. Queste unità fondamentali sono protagoniste di sette affascinanti racconti che, insieme ai grandi della scienza e a tanti inaspettati personaggi, conducono il lettore in un viaggio alla scoperta della fisica – da Galileo a Einstein, dalla meccanica di Newton alla quantistica – e di come la scienza aiuti a costruire un futuro sostenibile e rispettoso dell’ambiente. Con un finale a sorpresa
LESSONS FROM THE RFP ON MAGNETIC FEEDBACK CONTROL OF PLASMA STABILITY
No full textThis lecture was given at the 4th ITER International Summer School in May 2010 to describe the broad research program on feedback control of magnetohydrodynamic (MHD) stability performed by the reversed field pinch (RFP) community and its implication for magnetic confinement fusion. The lecture provides a bird's-eye view on RFP feedback control results obtained with active coils, and on their implications for ITER and tokamaks in general. A number of selected key examples are presented with the aim of highlighting the more innovative and broadly applicable results. RFPs provide a significant contribution to the effort of the broader fusion community on active control of MHD stability, and to fusion science in general
L'era dell'atomo
No full textIt’s so tiny that even a million of them placed in line would be no thicker than a sheet of paper. It can destroy or heal and be used in medical diagnoses or as an access key to the realm of the infinitely small. Humanity’s curse or salvation? The atom is the basic building block of matter, its nucleus fuels the Sun and could be an eternal source of safe, clean energy. This text is targeted at non-specialists and addresses prejudices that have always plagued the atom; it provides a comprehensive account of our understanding of atoms, ranging from the dawn of nuclear physics to modern atomic models, up to recent energy studies, and touches upon fields such as nanomaterials, medicine, and communication
The Roadmap to Fusion: Science and International Cooperation for Sustainable Energy
Full text linkThe transition to non-fossil energy sources is gaining a rapidly increasing attention in the international agenda. The global disruptions caused by the pandemic and more recently by the Ukrainian crisis add to the growing concern about the consequences of climate changes. All situations that have highlighted how crucial energy is for sustainable development and for international relations, and the extreme vulnerability of a world still largely depending on fossil sources. In this framework research on nuclear fusion energy is attracting a growing interest. It is an extremely attractive potential source of electricity for a future CO2-free energy basket. It uses widely available fuel, does not produce high-level radioactive waste and its plants are inherently safe. For its practical applicability, high-level research is still required. As the science progresses and the realization of fusion comes closer, it also necessitates a debate about non-technical issues, including diverse social ..
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
A mechanism for plasma heating in driven relaxing magnetic field configurations
No full textMagnetic configurations used for laboratory plasma confinement and those naturally occurring in the solar corona are both driven systems: in the former, the energy input is generally supplied by externally applied voltages; in the latter, by boundary fluid motions in the photosphere. Moreover, solar corona dynamics has been described in a very similar way to Reversed Field Pinch dynamics. Using these analogies as a starting point, a description is presented, supported by experimental results, of plasma heating in driven partially relaxed RFP configurations resulting from energy dissipation during reconnection processes. The power deposited in the plasma through this mechanism adds to the Joule heating of the mean field dissipation and may also provide a direct channel for ion heating through viscous dissipation
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