1,721,353 research outputs found
Computer simulation studies of complex magnetic materials
No full textWith the development of both computing power and software engineering, computer simulation of the micromagnetic model or atomistic spin model, has become an important tool for studying a wide range of different complex phenomena in magnetic materials. Meanwhile, the rapid improvement of advanced measurement techniques has allowed the probing of ultrafast magnetization dynamics, as well as the magnetic phenomena involving charge current, heat and light. The simulation of magnetism is now moving towards a multiphysics method. Therefore, fast, user-friendly, and extensible codes with accurate algorithms are helpful in understanding the physics and designing novel magnetic devices on the nanoscale.In the preparation of this thesis we have developed Fidimag, which is a Python/C simulation tool supporting both micromagnetic and atomistic spin models. The software has also been extended to support the Landau-Lifshitz-Baryakhtar (LLBar) equation. Using Fidimag, we have performed simulations to study the domain-wall motion and spin-wave decay with the LLBar equation. We also explain the exchange damping in the LLBar equation as the phenomenological nonlocal damping by linking it to spin pumping, therefore, LLBar equation can be considered as a phenomenological equation of the nonlocal damping.We studied magnon-induced domain-wall motion in the presence of Dzyaloshinskii-Moriya interaction (DMI) numerically and theoretically. We find that the presence of DMI and easy-plane anisotropy can drive the domain wall very effectively and that the domain-wall velocity depends on the sign of DMI constant. While the negative velocity is considered as a result of angular momentum conservation, we attribute this fast domain-wall motion to linear momentum transfer between magnons and the domain wall. By numerically solving the Landau-Lifshitz-Gilbert equation with a classical spin model on a two-dimensional system, we show that both magnetic skyrmions and skyrmion lattices can be moved with microwave magnetic fields. The mechanism is enabled by breaking the axial symmetry of the skyrmion with a static in-plane external field
Tort Liability of Suppliers of Raw Materials and Components Integrated into a Product: A Comparative Analysis of Chinese, E.U. and U.S. Law
Full text linkSupplementary data: Dynamics of skyrmionic states in confined helimagnetic nanostructures
No full textData for the paper: Beg, Marijan, Albert, Maximilian, Bisotti, Marc-Antonio, Cortes-Ortuno, David, Wang, Weiwei, Carey, Rebecca, Vousden, Mark, Hovorka, Ondrej, Ciccarelli, Chiara, Spencer, Charles S., Marrows, Christopher H. and Fangohr, Hans (2016) Dynamics of skyrmionic states in confined helimagnetic nanostructures. Physical Review B, 1-17.
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Funded by EPSRC (Spin-Torque and Spin Polarisation in Epitaxial Magnetic Silicides, EP/J007110/1, 2011 to 2014).</span
Armonia sotto controllo: la regolazione del credito sociale nelle ‘città modello’ cinesi
Full text linkNel 2014 il governo cinese ha annunciato l’istituzione di un programma nazionale di credito sociale. L’iniziativa è sovente descritta in Occidente come uno strumento tecnologicamente avanzato di controllo autocratico attraverso l’attribuzione di un punteggio sociale. Scopo del presente contributo è dimostrare come una simile descrizione trovi fondamento in, e dia adito a, incomprensioni e pregiudizi rispetto al sistema giuridico cinese, esprimendo e perpetuando una visione ‘orientalistica’ di quest’ultimo. A questo fine, l’articolo si centra sulla regolazione dei programmi pilota di credito sociale attivi nelle ventotto città designate nel 2017 e nel 2019 come ‘modello’ dallo stesso governo cinese. L’analisi comparata di tali programmi dimostrerà come le città modello, almeno per il momento, evitino di ricorrere a sistemi di punteggio sociale facciano uso di tecnologie low-tech e di natura descrittiva, prevedano sanzioni limitate e, soprattutto, abbiano adottato un quadro giuridico relativamente trasparente e attento ai diritti dei soggetti valutati, specie per quanto concerne il trattamento, la circolazione e la pubblicazione dei dati. Il quadro che ne risulta invita alla cautela nel giudicare il programma cinese di credito sociale, specie alla luce delle numerose forme di quantificazione delle performances e di misurazione delle persone il cui impiego è diffuso in Occidente.In 2014 the Chinese State Council announced the establishment of a nationwide comprehensive social credit system. Western narratives often describe the initiative as a technologically enhanced tool of autocratic control for scoring people. Yet, as the paper aims to show, similar accounts are tainted by several misunderstandings which perpetuate Western orientalist postures towards Chinese law. For the purpose of comparatively assessing the Chinese social credit system, the paper analyses the pilot programs set up to monitor people and enterprises’ behaviour by twenty-eight Chinese cities. The analysis will demonstrate that these pilot programs rely on low-tech methodologies, have limited strings attached, and are based on a relatively transparent legal framework. From a comparative perspective, our findings suggest that Chinese cities’ experiments raise equal, if not fewer, problems than those posed by measurement practices widely employed in the West
Magnonic analog of relativistic Zitterbewegung in an antiferromagnetic spin chain
No full textWe theoretically investigate the spin-wave (magnon) excitations in a classical antiferromagnetic spin chain with easy-axis anisotropy. We obtain a Dirac-like equation by linearizing the Landau-Lifshitz-Gilbert equation in this antiferromagnetic system, in contrast to the ferromagnetic system in which a Schrödinger-type equation is derived. The Hamiltonian operator in the Dirac-like equation is a pseudo-Hermitian. We compute and demonstrate relativistic Zitterbewegung (trembling motion) in the antiferromagnetic spin chain by measuring the expectation values of the wave-packet position
Driving magnetic skyrmions with microwave fields
Full text linkWe show theoretically by numerically solving the Landau-Lifshitz-Gilbert equation with a classical spin model on a two-dimensional system that both magnetic skyrmions and skyrmion lattices can be moved with microwave magnetic fields. The mechanism is enabled by breaking the axial symmetry of the skyrmion, for example, through application of a static in-plane external field. The net velocity of the skyrmion depends on the frequency and amplitude of the microwave fields as well as the strength of the in-plane field. The maximum velocity is found where the frequency of the microwave coincides with the resonance frequency of the breathing mode of the skyrmion
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
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