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The role of saturated thermal conduction in shaping electric current dynamics in jet-launching disks

Journal of High Energy Astrophysics 2025年 47卷

作者： Rezgui, Ghassen Preiner, Reinhold Department of Physics Faculty of Sciences of Tunis University of Tunis El Manar Campus Universitaire Tunis El Manar 2092 Tunisia Institute of Computer Graphics and Knowledge Visualization Graz University of Technology Inffeldgasse 16c Graz A-8010 Austria

This study investigates the dynamics of jet formation from a viscous, resistive accretion disk around a young stellar object using MHD simulations with the PLUTO code. We conducted an in-depth analysis of electric currents from various perspectives to elucidate how their dynamics, influenced by saturated thermal conduction, impact jet acceleration and collimation processes. Our simulations confirm the butterfly topology of electric current lines, as predicted by earlier analytic models. Crucially, increasing the saturation parameter ϕ_s alters the current line topology: higher saturation enhances collimation in the inner disk regions while inducing decollimation in the outer regions. By the end of our simulations (t=700, ∼112 rotational periods), higher ϕ_s results in a faster and more collimated jet compared to its lower ϕ_s counterpart, whereas at earlier times (t=200, ∼32 rotational periods), the jet exhibits lower acceleration despite enhanced collimation. In our reference case, we find that the electric current lines connect the launching region to the Alfvén and fast magnetosonic surfaces from early times, confirming the effectiveness of the acceleration mechanism at the onset of jet formation. Our study reveals that the upper jet regions are transitioning toward Kelvin–Helmholtz instability (KHI), while the jet base continues to exhibit wave activity. At t=700, doubling the saturation parameter reduces these oscillations and suppresses KHI, indicating faster plasma propagation. Analysis of the vertical profile of the current density, J_z, shows a clear correlation between increased saturation and both enhanced jet acceleration and current density. Furthermore, the ratio of electric currents at the Alfvén point, I_A, and sub-magnetosonic point, I_sm, indicates that higher saturation significantly improves the efficiency of matter propulsion and energy transfer within the jet. © 2025 Elsevier B.V.

关键词： Electric current Jet dynamics Magnetohydrodynamics simulations Saturated thermal conduction Young stellar objects

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End-to-end Color 3D reproduction of cultural heritage artifacts: Roseninsel replicas

End-to-end Color 3D reproduction of cultural heritage artifa...

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2019 Eurographics Workshop on graphics and Cultural Heritage, GCH 2019

作者： Domajnko, M. Tanksale, T. Tausch, R. Ritz, M. Knuth, M. Santos, P. Fellner, D.W. TU Darmstadt and Fraunhofer Institute for Computer Graphics Research Germany Graz University of Technology Institute of Computer Graphics and Knowledge Visualization Austria

ISBN: (纸本)9783038680826

Planning exhibitions of cultural artifacts is always challenging. Artifacts can be very sensitive to the environment and therefore their display can be risky. One way to circumvent this is to build replicas of these artifacts. Here, 3D digitization and reproduction, either physical via 3D printing or virtual, using computer graphics, can be the method of choice. For this use case we present a workflow, from photogrammetric acquisition in challenging environments to representation of the acquired 3D models in different ways, such as online visualization and color 3D printed replicas. This work can also be seen as a first step towards establishing a workflow for full color end-to-end reproduction of artifacts. Our workflow was applied on cultural artifacts found around the "Roseninsel" (Rose Island), an island in Lake Starnberg (Bavaria), in collaboration with the Bavarian State Archaeological Collection in Munich. We demonstrate the results of the end-to-end reproduction workflow leading to virtual replicas (online 3D visualization, virtual and augmented reality) and physical replicas (3D printed objects). In addition, we discuss potential optimizations and briefly present an improved state-of-the-art 3D digitization system for fully autonomous acquisition of geometry and colors of cultural heritage objects. © 2019 Eurographics Association.

关键词： Color

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Automated 3D mass digitization for the GLAM sector

Automated 3D mass digitization for the GLAM sector

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Archiving 2020 Online: Digitization, Preservation, and Access

作者： Santos, Pedro Tausch, Reimar Domajnko, Matevz Ritz, Martin Knuth, Martin Fellner, Dieter Fraunhofer Institute for Computer Graphics Research TU-Darmstadt Germany Graz University of Technology Institute of Computer Graphics and Knowledge Visualization Austria

The European Cultural Heritage Strategy for the 21st century has led to an increased demand for fast, efficient and faithful 3D digitization technologies for cultural heritage artefacts. Yet, unlike the digital acquisition of cultural goods in 2D which is widely used and automated today, 3D digitization often still requires significant manual intervention, time and money. To overcome this, the authors have developed CultLab3D, the world's first fully automatic 3D mass digitization technology for collections of three-dimensional objects. 3D scanning robots such as the CultArm3D-P are specifically designed to automate the entire 3D digitization process thus allowing to capture and archive objects on a large-scale and produce highly accurate photo-realistic representations. © 2020 Society for Imaging Science and Technology

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Next-generation 3D visualization for visual surveillance

Next-generation 3D visualization for visual surveillance

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2011 8th IEEE International Conference on Advanced Video and Signal Based Surveillance, AVSS 2011

作者： Roth, Peter M. Settgast, Volker Widhalm, Peter Lancelle, Marcel Birchbauer, Josef Brändle, Norbert Havemann, Sven Bischof, Horst Graz University of Technology Institute for Computer Graphics and Vision Austria Graz University of Technology Institute of Computer Graphics and Knowledge Visualization Austria Austrian Institute of Technology Dynamic Transportation Systems Austria Austria

ISBN: (纸本)9781457708459

Existing visual surveillance systems typically require that human operators observe video streams from different cameras, which becomes infeasible if the number of observed cameras is ever increasing. In this paper, we present a new surveillance system that combines automatic video analysis (i.e., single person tracking and crowd analysis) and interactive visualization. Our novel visualization takes advantage of a high resolution display and given 3D information to focus the operator's attention to interesting/ critical areas of the observed area. This is realized by embedding the results of automatic scene analysis techniques into the visualization. By providing different visualization modes, the user can easily switch between the different modes and can select the mode which provides most information. The system is demonstrated for a real setup on a university campus. © 2011 IEEE.

关键词： visualization

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Bridging the Distance in Education: Design and Implementation of a Synchronous, Browser-Based VR Remote Teaching Tool

Bridging the Distance in Education: Design and Implementatio...

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45th Annual Conference on European Association for computer graphics, EUROgraphics 2024

作者： Pehlić, Abdulmelik Augsdörfer, Ursula Graz University of Technology Institute of Computer Graphics and Knowledge Visualization Austria

ISBN: (纸本)9783038682387

The rapid shift to remote education has presented numerous challenges for educators and students alike. Virtual Reality (VR) has emerged as a promising solution, offering immersive and interactive learning experiences. We design and implement a synchronous, browser-based VR teaching tool. The tool is compatible with budget VR equipment and enables meaningful engagement between teachers and students in a virtual setting, as well as active participation and interaction across a range of platforms, thus solving a range of disadvantages of current approaches. © 2024 The Authors.

关键词： Virtual environments

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A repository for 3D model production and interpretation in culture and beyond 11

A repository for 3D model production and interpretation in c...

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11th International Symposium on Virtual Reality, Archaeology and Intelligent Cultural Heritage, VAST 2010

作者： Doerr, M. Tzompanaki, K. Theodoridou, M. Georgis, Ch. Axaridou, A. Havemann, S. Institute of Computer Science FORTH Crete Greece Institute of Computer Graphics and Knowledge Visualization Graz University of Technology Austria

ISBN: (纸本)9783905674293

In order to support the work of researchers in the production, processing and interpretation of complex digital objects and the dissemination of valuable and diverse information to a broad spectrum of audience there is need for an integrated high performance environment that will combine knowledge base features with content management and information retrieval (IR) technologies. In this paper we describe the design and implementation of an integrated repository to ingest, store, manipulate, and export 3D Models, their related digital objects and metadata and to enable efficient access, use, reuse and preservation of the information, ensuring referential and semantic integrity. The repository design is based on an integrated coherent conceptual schema that models complex metadata regarding provenance information, structured models, formats, compatibility of 3D models, historical events and real world objects. This repository is not implemented just to be a storage location for digital objects;it is meant to be a working integrated platform for distant users who participate in a process chain consisting of several steps. A first prototype, in the field of Cultural Heritage, has already been implemented in the context of 3D-COFORM project, an integrated research project funded by the European Community's Seventh Framework Programme (FP7/2007-2013, no 231809) and the results are satisfactory, proving the feasibility of the design decisions which are absolutely new, ambitious, and extraordinarily generic for e-science. © The Eurographics Association 2010.

关键词： Metadata

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PROBADO3D - Indexing and searching 3D CAD databases supporting planning through content-based indexing and 3D shape retrieval 10

PROBADO3D - Indexing and searching 3D CAD databases supporti...

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10th International Conference on Design and Decision Support Systems, DDSS 2010

作者： Blümel, Ina Berndt, René Ochmann, Sebastian Vock, Richard Wessel, Raoul German National Library of Science and Technology Hannover Germany Institute of Computer Graphics and Knowledge Visualization Graz University of Technology Austria Institute of Computer Science II Computer Graphics University of Bonn Germany

ISBN: (纸本)9789068141818

When modeling in 3D CAD, architects often search for already existing 3D content to complete their own design, e.g. environmental models, furniture models or detailed window profiles. 3D models are normally indexed and accessed based on textual metadata. As this metadata is expensive to obtain, PROBADO3D aims to develop workflows and tools for semi-automatic indexing of 3D models. Another goal is the development of intuitive visual search and presentation interfaces that face the needs of architects looking for 3D content. PROBADO3D is a part of the PROBADO framework designed to support multimedia objects of different domains.

关键词： Digital libraries

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3D object retrieval with parametric templates 8

3D object retrieval with parametric templates

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8th Eurographics Workshop on 3D Object Retrieval, 3DOR 2015

作者： Getto, Roman Fellner, Dieter W. Interactive Graphics Systems Group TU Darmstadt Germany Fraunhofer IGD Darmstadt Germany Institute of Computer Graphics and Knowledge Visualization TU Graz Austria

ISBN: (纸本)9783905674781

We propose a 3D object retrieval system which uses parametric templates as prior knowledge for the retrieval. A parametric template represents an object-domain and a semantic concept like 'chair' or 'plane' or a more specific concept like 'dining-char' or 'biplane'. The template can be specified at a general or specific level and can even equal actual retrieved objects. The parametric template is composed of several input parameters and an operation chain which constructs an object. Different parameter combinations lead to different object instances. We combine and evaluate a paramteric template with different descriptors. Our results show that the usage of parametric templates can raise the retrieval performance significantly. © The Eurographics Association 2015.

关键词： Semantics

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Direct limit volumes: Constant-time limit evaluation for Catmull-clark solids 26

Direct limit volumes: Constant-time limit evaluation for Cat...

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26th Pacific Conference on computer graphics and Applications, Pacific graphics 2018

作者： Altenhofen, C. Müller, J. Weber, D. Stork, A. Fellner, D.W. Fraunhofer Institute for Computer Graphics Research IGD Darmstadt Germany Technische Universität Darmstadt Darmstadt Germany Graz University of Technology Institute of Computer Graphics and Knowledge Visualization Graz Austria

ISBN: (纸本)9783038680734

We present a novel approach for efficient limit volume evaluation on Catmull-Clark (CC) subdivision solids. Although several analogies exist between subdivision surfaces and subdivision volumes, extending Stam’s limit evaluation technique from 2 to 3 dimensions is not straightforward, as irregularities and boundaries introduce new challenges in the volumetric case. We present new direct evaluation techniques for irregular volumetric topologies and boundary cells, which allow for calculating the limit of CC subdivision solids at arbitrary parameter values in constant time. Evaluation of limit points is a central aspect when using CC solids for applications such as simulation and multi-material additive manufacturing, or as a compact volumetric representation scheme for continuous scalar fields. We demonstrate that our approach is faster than existing evaluation techniques for every topological configuration or target parameter (u, v, w) that requires more than two local subdivision steps. © 2018 The Author(s).

关键词： Topology

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Elastic flattening of painted pottery surfaces

Elastic flattening of painted pottery surfaces

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2018 Eurographics Workshop on graphics and Cultural Heritage, GCH 2018

作者： Preiner, Reinhold Karl, Stephan Baye, Paul Schreck, Tobias Graz University of Technology Institute of Computer Graphics and Knowledge Visualization Austria University of Graz Department of Archaeology Austria

ISBN: (纸本)9783038680574

Generating flat images from paintings on curved surfaces is an important task in Archaeological analysis of ancient pottery. It allows comparing styles and painting techniques, e.g, for style and workshop attribution, and serves as basis for domain publications which typically use 2d images. To obtain such flat images from scanned textured 3d models of the pottery objects, current practice is to perform so-called rollouts using approximating shape primitives like cones or spheres, onto which the mesh surfaces are projected. While this process provides in intuitive deformation metaphor for the users, it naturally introduces unwanted distortions in the mapping of the surface, especially for vessels with high-curvature profiles. In this work, we perform an elastic flattening of these projected meshes, where stretch energy is minimized by simulating a physical relaxation process on a damped elastic spring model. We propose an intuitive contraction-directed physical setup which allows for an efficient relaxation while ensuring a controlled convergence. Our work has shown to produce images of significantly improved suitability for domain experts' tasks like interpretation, documentation and attribution of ancient pottery. © 2018 GCH 2018 - Eurographics Workshop on graphics and Cultural Heritage. All rights reserved.

关键词： Textures

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