166,542 research outputs found
Exchange of Geometric Information Between Applications
The Web Geometry Laboratory (WGL) is a collaborative and adaptive e-learning
Web platform integrating a well known dynamic geometry system. Thousands of
Geometric problems for Geometric Theorem Provers (TGTP) is a Web-based
repository of geometric problems to support the testing and evaluation of
geometric automated theorem proving systems.
The users of these systems should be able to profit from each other. The TGTP
corpus must be made available to the WGL user, allowing, in this way, the
exploration of TGTP problems and their proofs. On the other direction TGTP
could gain by the possibility of a wider users base submitting new problems.
Such information exchange between clients (e.g. WGL) and servers (e.g. TGTP)
raises many issues: geometric search - someone, working in a geometric problem,
must be able to ask for more information regarding that construction; levels of
geometric knowledge and interest - the problems in the servers must be
classified in such a way that, in response to a client query, only the problems
in the user's level and/or interest are returned; different aims of each tool -
e.g. WGL is about secondary school geometry, TGTP is about formal proofs in
semi-analytic and algebraic proof methods, not a perfect match indeed;
localisation issues, e.g. a Portuguese user obliged to make the query and
process the answer in English; technical issues-many technical issues need to
be addressed to make this exchange of geometric information possible and
useful.
Instead of a giant (difficult to maintain) tool, trying to cover all, the
interconnection of specialised tools seems much more promising. The challenges
to make that connection work are many and difficult, but, it is the authors
impression, not insurmountable.Comment: In Proceedings ThEdu'17, arXiv:1803.0072
Ab initio amorphous spin Hamiltonian for the description of topological spin textures in FeGe
Topological spin textures in magnetic materials such as skyrmions and
hopfions are interesting manifestations of geometric structures in real
materials, concurrently having potential applications as information carriers.
In the crystalline systems, the formation of these topological spin textures is
well understood as a result of the competition between interactions due to
symmetry breaking and frustration. However, in systems without translation
symmetry such as amorphous materials, a fundamental understanding of the
driving mechanisms of non-trivial spin structures is lacking owing to the
structural and interaction complexity in these systems. In this work, we use a
suite of first-principles-based calculations to propose an ab initio spin
Hamiltonian that accurately represents the diversity of structural and magnetic
properties in the exemplar amorphous FeGe. Monte Carlo simulations of our
amorphous Hamiltonian find emergent skyrmions that are driven by frustrated
geometric and magnetic exchange, consistent with those observed in experiment.
Moreover, we find that the diversity of local structural motifs results in a
large range of exchange interactions, far beyond those found in crystalline
materials. Finally, we observe the formation of large-scale emergent structures
in amorphous materials, far beyond the relevant interaction length-scale in the
systems, suggesting a new route to emergent correlated phases beyond the
crystalline limit
SBVLC:Secure Barcode-based Visible Light Communication for Smartphones
2D barcodes have enjoyed a significant penetration rate in mobile applications. This is largely due to the extremely low barrier to adoption – almost every camera-enabled smartphone can scan 2D barcodes. As an alternative to NFC technology, 2D barcodes have been increasingly used for security-sensitive mobile applications including mobile payments and personal identification. However, the security of barcode-based communication in mobile applications has not been systematically studied. Due to the visual nature, 2D barcodes are subject to eavesdropping when they are displayed on the smartphone screens. On the other hand, the fundamental design principles of 2D barcodes make it difficult to add security features. In this paper, we propose SBVLC - a secure system for barcode-based visible light communication (VLC) between smartphones. We formally analyze the security of SBVLC based on geometric models and propose physical security enhancement mechanisms for barcode communication by manipulating screen view angles and leveraging user-induced motions. We then develop three secure data exchange schemes that encode information in barcode streams. These schemes are useful in many security-sensitive mobile applications including private information sharing, secure device pairing, and contactless payment. SBVLC is evaluated through extensive experiments on both Android and iOS smartphones
Including widespread geometry formats in semantic graphs using RDF literals
The exchange of building data involves both geometric and non-geometric data. A promising Linked Data approach is to embed data from existing geometry formats inside Resource Description Framework (RDF) literals. Based on a study of relevant specifications and related work, this toolset-independent approach was found suitable for the exchange of geometric construction data. To implement the approach in practice, the File Ontology for Geometry formats (FOG) and accompanying modelling method is developed. In a proof-of-concept web application that uses FOG, is demonstrated how geometry descriptions of different existing formats are automatically recognised and parsed
Methodology for automatic recovering of 3D partitions from unstitched faces of non-manifold CAD models
Data exchanges between different software are currently used in industry to speed up the preparation of digital prototypes for Finite Element Analysis (FEA). Unfortunately, due to data loss, the yield of the transfer of manifold models rarely reaches 1. In the case of non-manifold models, the transfer results are even less satisfactory. This is particularly true for partitioned 3D models: during the data transfer based on the well-known exchange formats, all 3D partitions are generally lost. Partitions are mainly used for preparing mesh models required for advanced FEA: mapped meshing, material separation, definition of specific boundary conditions, etc. This paper sets up a methodology to automatically recover 3D partitions from exported non-manifold CAD models in order to increase the yield of the data exchange. Our fully automatic approach is based on three steps. First, starting from a set of potentially disconnected faces, the CAD model is stitched. Then, the shells used to create the 3D partitions are recovered using an iterative propagation strategy which starts from the so-called manifold vertices. Finally, using the identified closed shells, the 3D partitions can be reconstructed. The proposed methodology has been validated on academic as well as industrial examples.This work has been carried out under a research contract between the Research and Development Direction of the EDF Group and the Arts et Métiers ParisTech Aix-en-Provence
The Building Information Model and the IFC standard: analysis of the characteristics necessary for the acoustic and energy simulation of buildings
The new European Directive 2014/24 / EU requires for all member States the use of BIM procedures in the construction of public buildings. The countries belonging to the European Union shall be obliged to transpose the Directive and adapt their procedures to that effect. The paper analyzes the IFC format, the only recognized by the European Directive Standards for BIM procedures, in order to assess its use for simulations of buildings. IFC, described by the ISO 16739 (2013), is today a standard that describes the topology of the constructive elements of the building and what belongs to it overall. The format includes geometrical information on the room and on all building components, including details of the type for performance (transmittance, fire resistance, sound insulation), in other words it is an independent object file for the software producers to which, according to the European Directive, it will be compulsory to refer in the near future, during the different stages of the life of a building from the design phase, to management and possible demolition at the end of life. The IFC initiative began in 1994, when an industry consortium invested in the development of a set of C ++ classes that can support the development of integrated applications. Twelve US companies joined the consortium: these companies that were included initially are called the consortium "Industry Alliance for Interoperability". In September 1995 the Alliance opened up membership to all interested parties, and in 1997 changed its name to "International Alliance for Interoperability". The new alliance was reconstituted as a non-profit organization, with the aim of developing and promoting the '' Industry Foundation Class "(IFC) as a neutral data model for the building product that were useful to gather information throughout the life cycle of a building facility. Since 2005 the Alliance has been carrying out its activities through its national chapters called SMART building. The present study aims at evaluating the IFC, comparing the information and data contained in it, with other formats already used for energy simulations of buildings such as the gbXML (Green Building XML), highlighting the missing required information and proposing the inclusion of new ones to issue the energy and acoustic simulation. More generally the attention is focused to building physics simulation software devoted to exploit the BIM model potential enabling interoperability
Forman-Ricci flow for change detection in large dynamic data sets
We present a viable solution to the challenging question of change detection
in complex networks inferred from large dynamic data sets. Building on Forman's
discretization of the classical notion of Ricci curvature, we introduce a novel
geometric method to characterize different types of real-world networks with an
emphasis on peer-to-peer networks. Furthermore we adapt the classical Ricci
flow that already proved to be a powerful tool in image processing and
graphics, to the case of undirected and weighted networks. The application of
the proposed method on peer-to-peer networks yields insights into topological
properties and the structure of their underlying data.Comment: Conference paper, accepted at ICICS 2016. (Updated version
Relating geometry descriptions to its derivatives on the web
Sharing building information over the Web is becoming more popular, leading to advances in describing building models in a Semantic Web context. However, those descriptions lack unified approaches for linking geometry descriptions to building elements, derived properties and derived other geometry descriptions. To bridge this gap, we analyse the basic characteristics of geometric dependencies and propose the Ontology for Managing Geometry (OMG) based on this analysis. In this paper, we present our results and show how the OMG provides means to link geometric and non-geometric data in meaningful ways. Thus, exchanging building data, including geometry, on the Web becomes more efficient
Greedy Gossip with Eavesdropping
This paper presents greedy gossip with eavesdropping (GGE), a novel
randomized gossip algorithm for distributed computation of the average
consensus problem. In gossip algorithms, nodes in the network randomly
communicate with their neighbors and exchange information iteratively. The
algorithms are simple and decentralized, making them attractive for wireless
network applications. In general, gossip algorithms are robust to unreliable
wireless conditions and time varying network topologies. In this paper we
introduce GGE and demonstrate that greedy updates lead to rapid convergence. We
do not require nodes to have any location information. Instead, greedy updates
are made possible by exploiting the broadcast nature of wireless
communications. During the operation of GGE, when a node decides to gossip,
instead of choosing one of its neighbors at random, it makes a greedy
selection, choosing the node which has the value most different from its own.
In order to make this selection, nodes need to know their neighbors' values.
Therefore, we assume that all transmissions are wireless broadcasts and nodes
keep track of their neighbors' values by eavesdropping on their communications.
We show that the convergence of GGE is guaranteed for connected network
topologies. We also study the rates of convergence and illustrate, through
theoretical bounds and numerical simulations, that GGE consistently outperforms
randomized gossip and performs comparably to geographic gossip on
moderate-sized random geometric graph topologies.Comment: 25 pages, 7 figure
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