658 research outputs found
The One-Armed Spiral Instability in Neutron Star Mergers and its Detectability in Gravitational Waves
No full text<p>We distribute complete gravitational-wave signals in the Advanced LIGO band (10 Hz - 8192 Hz) of the inspiral and merger of two neutron stars. These waveforms been constructed by hybridizing numerical-relativity data obtained with the WhiskyTHC code [1] with tidal effective-one-body waveforms [2,3]. More details on the procedure used to generate these waveforms are given in [4]. </p>
<p>The waveforms are distributed as HDF5 files containing the amplitude and phase of the -2 spin-weighted spherical harmonics multipoles of the strain:</p>
<p><span class="math-tex"></span></p>
<p>where <span class="math-tex"></span> is the distance in cm from the source.</p>
<p>The data files include a machine readable "/metadata" group with:</p>
<ul>
<li>/metadata/EOS: name of the equation of state</li>
<li>/metadata/M_{A|B}: mass in isolation of star A (or B) in grams</li>
<li>/metadata/R_{A|B}: radius of star A (or B) in cm</li>
<li>/metadata/k2T: tidal coupling constant of the binary (see [3])</li>
<li>/metadata/kl_{A|B}: l=2,3,4 dimensionless Love numbers of star A (or B)</li>
</ul>
<p>We store amplitude and phase for multipoles modes up to l=4 as time series sampled at 16384 Hz.</p>
<p>We make these waveforms freely available in the hope that they will be useful. We kindly ask you to cite [3] and [4] in any publication resulting from the use of these waveforms.</p>
<p>---<br />
[1] http://www.tapir.caltech.edu/~david_e/whiskythc.html<br />
[2] https://eob.ihes.fr/<br />
[3] S. Bernuzzi, A. Nagar, T. Dietrich, T. Damour; Modeling the Dynamics of Tidally Interacting Binary Neutron Stars up to the Merger; Phys.Rev.Lett. 114 (2015) 16, 161103.<br />
[4] D. Radice, S. Bernuzzi, C. D. Ott; The One-Armed Spiral Instability in Neutron Star Mergers and its Detectability in Gravitational Waves; arXiv:1603.05726.</p>
Turbulence modelling in neutron star merger simulations
No full textObservations of neutron star mergers have the potential to unveil detailed physics of matter and gravity in regimes inaccessible by other experiments. Quantitative comparisons to theory and parameter estimation require nonlinear numerical simulations. However, the detailed physics of energy and momentum transfer between different scales, and the formation and interaction of small scale structures, which can be probed by detectors, are not captured by current simulations. This is where turbulence enters neutron star modelling. This review will outline the theory and current status of turbulence modelling for relativistic neutron star merger simulations
Aristotele, Politica (voll. V-VIII)
No full textTraduzione della Politica di Aristotele in conformità dei commentari di David Keyt e Richard Kraut
Letture gramsciane di Giuseppe Lombardo Radice (II parte)
No full textIn Gramsci’s intellectual development is not a place on the periphery is occupied by the figure of Lombrado Root. Prominent character of pedagogy idealism and importer in Italy, activist of instances (even American), socialist “romantic, sentimental, unscientific.” Lombardo Radice was a careful student of the drama of the South and Gramsci was always very interested in the work of the Sicilian and there are many similarities (apparent) between the two intellectuals: 1) the focus on popular culture, 2) the combination between educational and political problems, and 3) the reference to the figure of Leonardo and other similarities yet. The author has done a thorough research work and significant
The Letter Collection of Abelard and Heloise, edited by David Luscombe, translated by Betty Radice and revised by David Luscombe
No full textDavid Luscombe’s new book becomes the first critical edition of the correspondence of Abelard and Heloise to draw on all twelve of the extant manuscripts. It is also – at long last – the first Latin edition with facing page English translation. The translation used is the familiar 1974 Penguin translation by Betty Radice, revised in 2003 by Michael Clanchy, and now again by Luscombe. This career-capping accomplishment has been many years in the works, possibly since the early 1970s when the a..
The Letter Collection of Abelard and Heloise, edited by David Luscombe, translated by Betty Radice and revised by David Luscombe
No full textDavid Luscombe’s new book becomes the first critical edition of the correspondence of Abelard and Heloise to draw on all twelve of the extant manuscripts. It is also – at long last – the first Latin edition with facing page English translation. The translation used is the familiar 1974 Penguin translation by Betty Radice, revised in 2003 by Michael Clanchy, and now again by Luscombe. This career-capping accomplishment has been many years in the works, possibly since the early 1970s when the a..
Radice: Data-driven Risk Analysis of Sustainable Cloud Infrastructure using Simulation
No full textCloud datacenters underpin our increasingly digital society, serving stakeholders across industry, government, and academia. These stakeholders have come to expect reliable operation and high quality of service, yet demand low cost, high scalability, and corporate (environmental) responsibility. Datacenter operators are confronted frequently with highly complex decisions that involve numerous aspects of risk. The consequence of bad decisions can be financial penalties or even loss of customers on the one hand, or a competitive disadvantage or unsustainable environmental impact on the other hand. Despite risk analysis being an integral part of the design and operation of cloud infrastructure, relatively few comprehensive approaches and tools exist, leaving many datacenter operators ill-equipped to make informed decisions with confidence.We propose Radice, an instrument for data-driven analysis of IT-related operational risks in sustainable cloud datacenters. Unlike most state-of-the-art approaches used by the industry, Radice automates the process of risk analysis in datacenters and utilizes the large and diverse volume of data reported by the monitoring systems in datacenters, including environmental data. Underpinning this system is the trace-based, discrete-event simulator OpenDC, which enables the exploration of many risk scenarios through its support for diverse workloads, datacenter topologies, and operational phenomena. Radice’s interactive and explorative user interface assists datacenter operators in addressing complex decisions involving risks, providing them with actionable insights, automated visualizations, and suggestions to reduce risk.We implement Radice and conduct a comprehensive evaluation of the system to demonstrate how it can aid datacenter operators when confronted with fundamental risk trade-offs. Although Radice is designed to work across many kinds of datacenters, in this work, we focus on private-cloud, business-critical workloads, and on public-cloud operations, representing the majority of workloads in Dutch datacenters. Our experiments show many interesting findings, supporting our claim for a need for data-driven risk analysis in datacenters. We highlight the increasing risk faced by datacenter operators due to price surges in the electricity and CO2 bond markets, and demonstrate how Radice can be used to control such risks. We further show that Radice can automatically optimize topology and operational settings in datacenters for risk, revealing configurations that reduce the overall risk by 10%–30%. Following extensive performance engineering, Radice is able to evaluate risk scenarios by a factor 70x–330x faster than others, opening possibilities for interactive risk exploration. We release Radice as free and open-source software for the community to inspect and re-use.Computer Scienc
Designing for Audience Participation within Museums: Operative Insights from the Exhibit Everyday History
No full textThis paper aims at exploring the shifting from the role of museums as provider of contents and designer of experience, to the role of facilitator of experiences around contents, as the emergence of new patterns for culture transmission opened to new possibilities for participatory approaches in the design of heritage experiences. Starting from the description of the participatory exhibit “Everyday History,” designed by the author at the Santa Cruz Museum of Art and History, CA, United States, as part of her doctoral research, this paper outlines methods and tools for the design of effective participatory experiences, capable of catalyzing visitor voices in supporting and contributing to cultural experiences. This approach has the goal to change the traditional top down way of communicating to the visitors, in favor of a multidirectional flow of information between the cultural institutions and the audience. Insights from this case study and literature highlight that designing for participation, in which community engagement is the final outcome of the design process, does not necessarily implies—but does not exclude—participatory design processes. The author proposes a design methodology led by institutional staff, in which visitors are involved in recursive evaluation phases, conceiving the exhibition itself as an ongoing and never-finished product
Experimental censorship of bed load particle motions, and bias correction of the associated frequency distributions
No full textKnowledge of the statistical distributions of particle hop properties (distances, travel, and
rest times) enables a deeper understanding of bed load sediment transport. However, the measurement of
particle hops is prone to censorship: Since many hops cross the boundaries of a spatial-temporal
observation window, one knows that they exist but does not know how long they are. An option is to build
particle hop samples considering only the hops that are completely observed and excluding (censoring)
those observed only partially. Such a choice, however, biases the frequency distributions of the hop
properties. Moreover, censorship acts in both space and time, and a hop censored in time will also not
contribute to a sample of hop lengths, and vice versa. Time censorship similarly applies to particle rest
times. This paper presents a theoretical formulation of censorship that leads to nonparametric bias
corrections recovering estimates of values of the underlying distributions of hop distance, travel time,
and rest time up to sampling window dimensions. We illustrate the occurrence and consequences of
experimental censorship, and the benefit of applying the bias corrections, for both synthetic and laboratory
samples of particle hops. The corrections reasonably recover the relative proportions of frequency
distributions represented by the data up to the sampling dimensions and improve the estimates of the
first two moments of particle hop properties. Recommendations are given regarding how the size of an
observation window may be chosen to reduce the bias to below some prescribed value, if the forms of the
underlying distributions are known
Optimization of Finite-Differencing Kernels for Numerical Relativity Applications
No full textA simple optimization strategy for the computation of 3D finite-differencing kernels on many-cores architectures is proposed. The 3D finite-differencing computation is split direction-by-direction and exploits two level of parallelism: in-core vectorization and multi-threads shared-memory parallelization. The main application of this method is to accelerate the high-order stencil computations in numerical relativity codes. Our proposed method provides substantial speedup in computations involving tensor contractions and 3D stencil calculations on different processor microarchitectures, including Intel Knight Landing
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