63 research outputs found
The jet-disk symbiosis without maximal jets: 1D hydrodynamical jets revisited
No full textIn this work we discuss the recent criticism by Zdziarski (2016, A&A, 586, A18) of the maximal jet model derived in Falcke & Biermann (1995, A&A, 293, 665). We agree with Zdziarski that in general a jet’s internal energy is not bounded by its rest-mass energy density. We describe the effects of the mistake on conclusions that have been made using the maximal jet model and show when a maximal jet is an appropriate assumption. The maximal jet model was used to derive a 1D hydrodynamical model of jets in agnjet, a model that does multiwavelength fitting of quiescent/hard state X-ray binaries and low-luminosity active galactic nuclei. We correct algebraic mistakes made in the derivation of the 1D Euler equation and relax the maximal jet assumption. We show that the corrections cause minor differences as long as the jet has a small opening angle and a small terminal Lorentz factor. We find that the major conclusion from the maximal jet model, the jet-disk symbiosis, can be generally applied to astrophysical jets. We also show that isothermal jets are required to match the flat radio spectra seen in low-luminosity X-ray binaries and active galactic nuclei, in agreement with other works
Voxel-space shape grammars
No full textThe field of Procedural Generation is being increasingly used in modern content generation for its ability to significantly decrease the cost and time involved. One such area of Procedural Generation is Shape Grammars, a type of formal grammar that operates on geometric shapes instead of symbols. Conventional shape grammar implementations use mesh representations of shapes, but this has two significant drawbacks. Firstly, mesh representations make Boolean geometry operations on shapes difficult to accomplish. Boolean geometry operations allow us to combine shapes using Boolean operators (and, or, not), producing complex, composite shapes. A second drawback is that sub-, or trans-shape detailing is challenging to achieve. To address these two problems with conventional mesh-based shape grammars, we present a novel extension to shape grammars, in which a voxel representation of the generated shapes is used
Planetary stewardship in an urbanizing world: beyond city limits
No full textCities are rapidly increasing in importance as a major factor shaping the Earth system, and as such must take corresponding responsibility. With currently over half of the world population, cities are supported by resources originating from primarily rural regions that are often located around the world far distant from the urban loci of use. The multiple and complex environmental and social challenges the world faces require interconnected solutions and a coordinated governance approach to planetary stewardship. There is a new opportunity to conceptualize a key component of planetary stewardship as a global system of cities that develop sustainable processes and policies in concert with its non-urban areas. The potential for cities to cooperate as a system and with rural connectivity could not only increase their capacity to effect change and foster stewardship at the planetary scale but also increase their resource security
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On the nature of emission from relativistic jets
No full texttextSeveral longstanding questions in astrophysics center on the make up of relativistic astrophysical jets seen in microquasars, blazars, gamma-ray bursts, and super-Eddington tidal disruption events. What carries the energy in these jets? Is the majority of the energy carried by Poynting flux or by the baryonic matter? How is this energy converted into the non-thermal gamma-rays and X-rays seen in these systems? While there are many different theoretical models for launching a relativistic jet and producing the non-thermal emission observed in these astrophysical systems, often times the observational data are not good enough to convincingly discriminate between models. This thesis is comprised of several different projects that address these questions for several different astrophysical systems. First I discuss some general considerations of the synchrotron radiation from electrons accelerated by magnetic reconnection in a Poynting dominated jet. I show that the super-Eddington tidal disruption events (TDE) represent an unique opportunity to test different emission mechanisms in relativistic jets. I find that a magnetic dominated jet model can most easily explain the broadband observations in the observed super-Eddington TDE Sw J1644+57. In gamma-ray bursts, that hadronic emission models cannot explain the high energy ( >100 MeV) gamma-rays observed by the Fermi Large Area Telescope. I also include a chapter that suggests using the radio monitoring of the diffuse cloud in the galactic center object G2's to distinguish between different models of G2. Early observations of G2 after periapse passage suggests this prediction was correct.Physic
Romanzo poliziesco, filosofia e critica sociale
No full textTraduction de Polars, philosophie et critique sociale par Luca MartignaniInternational audienceQual è il senso della nostra vita nel caos della vita moderna? Il genere poliziesco, in particolare il romanzo noir di tradizione americana, può aiutarci a esplorare tale questione attraverso le trame oscure e grigie di cui sono intessute le dimensioni dell’esistenza contemporanea. Lo fa attraverso lo strumento della critica sociale contrapposta alle sregolatezze e alle fragilità generate dalle nostre società inegualitarie. Philippe Corcuff coniuga in maniera originale i nostri romanzi polizieschi preferiti con brillanti intuizioni filosofiche e sociologiche. Ne derivano un’etica della conservazione della propria integrità personale e una saggezza velata di pessimismo. Troveremo sul cammino tracciato dall’autore i contributi di scrittori classici (Davin Goodis, Howard Fast, Dashiell Hammett, Ross Macdonald e Jim Thompson) e contemporanei (James Lee Burke, James Crumley, Dennis Lehane, Jean-Patrick Manchette, Georges Pelecanos e James Sallis)
Romanzo poliziesco, filosofia e critica sociale
No full textQual è il senso della nostra vita nel caos della vita moderna? Il genere poliziesco, in particolare il romanzo noir di tradizione americana, può aiutarci a esplorare tale questione attraverso le trame oscure e grigie di cui sono intessute le dimensioni dell’esistenza contemporanea. Lo fa attraverso lo strumento della critica sociale contrapposta alle sregolatezze e alle fragilità generate dalle nostre società inegualitarie. Philippe Corcuff coniuga in maniera originale i nostri romanzi polizieschi preferiti con brillanti intuizioni filosofiche e sociologiche. Ne derivano un’etica della conservazione della propria integrità personale e una saggezza velata di pessimismo. Troveremo sul cammino tracciato dall’autore i contributi di scrittori classici (Davin Goodis, Howard Fast, Dashiell Hammett, Ross Macdonald e Jim Thompson) e contemporanei (James Lee Burke, James Crumley, Dennis Lehane, Jean-Patrick Manchette, Georges Pelecanos e James Sallis)
Romanzo poliziesco, filosofia e critica sociale
No full textTraduction de Polars, philosophie et critique sociale par Luca MartignaniInternational audienceQual è il senso della nostra vita nel caos della vita moderna? Il genere poliziesco, in particolare il romanzo noir di tradizione americana, può aiutarci a esplorare tale questione attraverso le trame oscure e grigie di cui sono intessute le dimensioni dell’esistenza contemporanea. Lo fa attraverso lo strumento della critica sociale contrapposta alle sregolatezze e alle fragilità generate dalle nostre società inegualitarie. Philippe Corcuff coniuga in maniera originale i nostri romanzi polizieschi preferiti con brillanti intuizioni filosofiche e sociologiche. Ne derivano un’etica della conservazione della propria integrità personale e una saggezza velata di pessimismo. Troveremo sul cammino tracciato dall’autore i contributi di scrittori classici (Davin Goodis, Howard Fast, Dashiell Hammett, Ross Macdonald e Jim Thompson) e contemporanei (James Lee Burke, James Crumley, Dennis Lehane, Jean-Patrick Manchette, Georges Pelecanos e James Sallis)
Voxel-Space Shape Grammars
No full textWe present a novel extension to shape grammars, in which the generated shapes are voxelized. This allows easy Boolean geometry operations on the shapes, and detailing of generated models at a sub-shape level, both of which are extremely difficult to do in conventional shape grammar implementations. We outline a four step algorithm for using these extensions, discuss a number of optional enhancements and optimizations, and test our extension’s performance and range of output. The results show that our unoptimized algorithm is slower than conventional shape grammar implementations, with a running time that is O(N^3) for a N^3 voxel grid, but is able to produce a broad range of detailed outputs
Review of \u3ci\u3eTalking Up a Storm: Voices of the New West\u3c/i\u3e By Gregory L. Morris
No full textMorris\u27s subjects include a handful of very well-known writers: Amy Tan, Thomas McGuane, Ron Hansen, and Richard Ford, winner of this year\u27s Pulitzer Prize. Mixed in with these are interviews with lesser known western writers such as James Crumley, Elizabeth Cook-Lynn, Mary Clearman Blew, and Ralph Beer. For readers interested in Western literature, an especially useful feature of Talking Up a Storm is the bibliography following each interview. As with any collection like this one, a reader is likely to be left with some questions: Why is this author included but that one left out? Why is the West seemingly defined to include one state but not its neighbor? But these questions shouldn\u27t detract from the basic pleasures of Talking Up a Storm, a book that should provide both pleasure and enlightenment to anyone interested in the best contemporary literature of the American West
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