3,685 research outputs found
The 2D/3D dynamics of wall-bounded low-Rm magnetohydrodynamic (MHD) turbulence
No full textWith this experimental study, we give evidence that the dynamics of low-Rm MHD turbulence depends on the diffusion length l_z, which corresponds to the distance over which the Lorentz force is able to diffuse momentum before it is balanced by inertia
DLR-RM/stable-baselines3: Stable-Baselines3 v2.3.2: Hotfix for PyTorch 1.13
No full text<h2>Bug fixes</h2>
<ul>
<li>Reverted <code>torch.load()</code> to be called <code>weights_only=False</code> as it caused loading issue with old version of PyTorch. https://github.com/DLR-RM/stable-baselines3/pull/1913</li>
<li>Cast learning_rate to float lambda for pickle safety when doing model.load by @markscsmith in https://github.com/DLR-RM/stable-baselines3/pull/1901</li>
</ul>
<h2>Documentation</h2>
<ul>
<li>Fix typo in changelog by @araffin in https://github.com/DLR-RM/stable-baselines3/pull/1882</li>
<li>Fixed broken link in ppo.rst by @chaitanyabisht in https://github.com/DLR-RM/stable-baselines3/pull/1884</li>
<li>Adding ER-MRL to community project by @corentinlger in https://github.com/DLR-RM/stable-baselines3/pull/1904</li>
<li>Fix tensorboad video slow numpy->torch conversion by @NickLucche in https://github.com/DLR-RM/stable-baselines3/pull/1910</li>
</ul>
<h2>New Contributors</h2>
<ul>
<li>@chaitanyabisht made their first contribution in https://github.com/DLR-RM/stable-baselines3/pull/1884</li>
<li>@markscsmith made their first contribution in https://github.com/DLR-RM/stable-baselines3/pull/1901</li>
<li>@NickLucche made their first contribution in https://github.com/DLR-RM/stable-baselines3/pull/1910</li>
</ul>
<p><strong>Full Changelog</strong>: https://github.com/DLR-RM/stable-baselines3/compare/v2.3.0...v2.3.2</p>
Muhammad Taqi al-Majlisi and Safavid Shi‘Ism: Akhbarism and Anti-sunni Polemic During the Reigns of Shah ‘Abbas the Great and Shah Safi
No full textThis is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this record.The rise of the Akhbari school in the Safavid period has been portrayed as a challenge to both the clerical power of the ʿulamaʾ and sometimes even as in opposition to the Safavid state. As a counter example to these characterisations of Akhbarism, one might consider the example Muhammad Taqi al-Majlisi (d.1070/1659), known as “The First Majlisi”, and father of the famous Safavid scholar Muhammad Baqir al-Majlisi (“The Second Majlisi”, d.1110/1699 or 1111/1700). He had close relations with the Safavid court, dedicating a work to Shah Abbas II, and generally accepting royal patronage when it was offered. His system of legal interpretation and the analysis of hadith in particular, is thoroughly Akhbari. In this article I analyse Taqi al-Majlisi’s ideas as found in the introductory sections to his Lawamiʿ-i Sahibqirani, a Persian language commentary on an early collection of Twelver Shiʿi reports from the Imams. As an appendix, I translate one section which demonstrates not only his thoroughly Akhbari methodology, but also his originality within the Akhbari school. He should, I argue, be particularly remembered for promoting the authority of the ʿulamaʾ from an Akhbari perspective, and here he links the rejection of ijtihad (a hallmark of the Akhbari school) to the Shiʿi rejection of the selection of Abu Bakr as caliph. In doing this, he establishes and exploits a link between the support of ijtihad (that is, the Usuli position), the heresy of Sunnism and the betrayal of fundamental Shi‘i beliefs
Triangular Constellations in Flows
No full textParticles advected on the surface of a fluid can exhibit fractal clustering. The local structure of a fractal set is described by its dimension , which is the exponent of a power-law relating the mass in a ball to its radius : . It is desirable to characterise the {\em shapes} of constellations of points sampling a fractal measure, as well as their masses. The simplest example is the distribution of shapes of triangles formed by triplets of points, which we investigate for fractals generated by chaotic dynamical systems. The most significant parameter describing the triangle shape is the ratio of its area to the radius of gyration squared. We show that the probability density of has a phase transition: is independent of and approximately uniform below a critical flow compressibility , which we estimate. For the distribution appears to be described by two power laws: when , and when
Exact two-dimensionalization of low-magnetic-Reynolds-number flows subject to a strong magnetic field
No full textWe investigate the behavior of flows, including turbulent flows, driven by a horizontal body-force and subject to a vertical magnetic field, with the following question in mind: for very strong applied magnetic field, is the flow mostly two-dimensional, with remaining weak three-dimensional fluctuations, or does it become exactly 2D, with no dependence along the vertical? We restrict attention to low-magnetic-Reynolds number (Rm) flow. Because liquid metals have low magnetic Prandtl number, such low- flows can have a kinetic Reynolds number as large as one million and therefore be strongly turbulent. We first focus on the quasi-static approximation, i.e. the asymptotic limit of vanishing magnetic Reynolds number Rm << 1: we prove that the flow becomes exactly 2D asymptotically in time, regardless of the initial condition and provided the interaction parameter N is larger than a threshold value. We call this property absolute two-dimensionalization: the attractor of the system is necessarily a (possibly turbulent) 2D flow. We then consider the full-magnetohydrodynamic equations and we prove that, for low enough Rm and large enough N, the flow becomes exactly two-dimensional in the long-time limit provided the initial vertically-dependent perturbations are infinitesimal. We call this phenomenon linear two-dimensionalization: the (possibly turbulent) 2D flow is an attractor of the dynamics, but it is not necessarily the only attractor of the system. Some 3D attractors may also exist and be attained for strong enough initial 3D perturbations. These results shed some light on the existence of a dissipative anomaly for magnetohydrodynamic flows subject to a strong external magnetic field
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