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Symbolic Meta-Modeling of RIS-Assisted FSO Communication Channels

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TechRxiv

TechRxiv 2023年

作者： Ndjiongue, Alain Richard Ngatched, Telex M.N. Dobre, Octavia A. Haas, Harald Shin, Hyundong The Faculty of Engineering and Applied Science Memorial University of Newfoundland Canada The Department of Electrical and Computer Engineering McMaster University Canada The LiFi Research and Development Center Dpt. Electronic and Electrical Engineering The University of Strathclyde Glasgow United Kingdom The School of Electronics and Information Kyung Hee University 1 Seocheon Kihung Kyungki Yongin446-701 Korea Republic of

Due to their advantages and role in the beyond fifth-generation mobile network, free-space optical (FSO) communication systems continue to gain attention. The line-of-sight (LoS) link in FSO communications is fundamental as it delivers all the power detected by the user. Therefore, its obstruction is detrimental to the transmission system. In the event of an obstruction, the LoS requirements can be met by introducing the reconfigurable intelligent surface (RIS) technology. However, with the implementation of an RIS infrastructure, FSO channels are divided into two sub-channels, creating an inherent diversity end-to-end (e2e) channel model. In this paper, leveraging on the Meijer G-functions, which are symbolic representations of mathematical functions, we derive symbolic models for e2e RIS-assisted FSO systems that are built on the probability density functions (PDFs) of the fading model characterizing the sub-channels. We study some of the most popular models, derive closed-form expressions of PDFs, cumulative distributions, and moment-generating functions that are further exploited to analyze systems’ performance. By comparing scenarios in which the sub-channels are similar and different, we provide a clear understanding of how the overall RIS-assisted FSO channel behaves, along with comparative results based on commonly used models. © 2023, CC BY.

关键词： Probability density function

A Proxy for Privacy: the Discreet Box

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A Proxy for Privacy: the Discreet Box

EUROCON 2007 - The International Conference on " computer as a Tool" (EUROCON 2007), vol.4

作者： Georgios V. Lioudakis Eleftherios A. Koutsoloukas Nikolaos Dellas Sofia Kapellaki George N. Prezerakos Dimitra I. Kaklamani Iakovos S. Venieris School of Electrical and Computer Engineering National and Technical University of Athens Athens Greece Dpt. of Electronic Computing Systems Technological Education Institute of Piraeus Piraeus Greece

The issue of user privacy is constantly brought to the spotlight since an ever increasing number of online services collects and processes personal information from users, in the context of personalized service provision. Although technology makes the collection of data easy, their protection against abuse is left to data protection legislation. However, the privacy requirements, other than being general and abstract terms to be regarded as legislature issues, should be brought down in the technological reality and carefully accounted for in devising technical solutions. In order to limit the disclosure and avoid the misuse of personal data, this paper discusses an architectural proposal for a middleware system that will enforce protection of user privacy through technical means. This goal is facilitated by a combination of a policy framework, a sensible interpretation of regulations into policies and the introduction of a privacy broker, named the Discreet Box.

关键词： Privacy Privacy Middleware Ontologies Privacy Legislation

Improving skip-gram based graph embeddings via centrality-weighted sampling

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arXiv 2019年

作者： Blanco, Pedro Almagro Caparrini, Fernando Sancho Departament de Física de la Matèria Condensada Universitat de Barcelona Martí Franquès 1 BarcelonaE-08028 Spain Complex Systems Modelling Group Universidad Central de Ecuador Quito170129 Ecuador Dpt. Computer Science and Artificial Intelligence University of Sevilla Sevilla41012 Spain

Network embedding techniques inspired by word2vec represent an effective unsupervised relational learning model. Commonly, by means of a Skip-Gram procedure, these techniques learn low dimensional vector representations of the nodes in a graph by sampling node-context examples. Although many ways of sampling the context of a node have been proposed, the effects of the way a node is chosen have not been analyzed in depth. To fill this gap, we have re-implemented the main four word2vec inspired graph embedding techniques under the same framework and analyzed how different sampling distributions affects embeddings performance when tested in node classification problems. We present a set of experiments on different well known real data sets that show how the use of popular centrality distributions in sampling leads to improvements, obtaining speeds of up to 2 times in learning times and increasing accuracy in all cases. Copyright © 2019, The Authors. All rights reserved.

关键词： Graph embeddings

Active flow control for external aerodynamics: from micro air vehicles to a full aircraft in stall

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Journal of Physics: Conference Series 2020年第1期1522卷

作者： Oriol Lehmkuhl Adrián Lozano-Durán Ivette Rodriguez Dpt. of Computer Applications in Science and Engineering Barcelona Supercomputing Center Spain Center for Turbulence Research Stanford University USA Dpt. of Heat Engines Universitat Politecnica de Catalunya Spain

We investigate the aerodynamic performance of active flow control of airfoils and wings using synthetic jets with zero net-mass flow. The study is conducted via wall-resolved and wall-modeled large-eddy simulation using two independent CFD solvers: Alya, a finite-element-based solver; and charLES, a finite-volume-based solver. Our approach is first validated in a NACA4412, for which numerical and experimental results are already available in the literature. The performance of synthetic jets is evaluated for two flow configurations: a SD7003 airfoil at moderate Reynolds number with laminar separation bubble, which is representative of Micro Air Vehicles, and the high-lift configuration of the JAXA Standard Model at realistic Reynolds numbers for landing. In both cases, our predictions indicate that, at high angles of attack, the control successfully eliminates the laminar/turbulent recirculations located downstream the actuator, which increases the aerodynamic performance. Our efforts illustrate the technology-readiness of large-eddy simulation in the design of control strategies for real-world external aerodynamic applications.

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Effects of the finite particle size in turbulent wall-bounded flows of dense suspensions

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arXiv 2017年

作者： Costa, Pedro Picano, Francesco Brandt, Luca Breugem, Wim-Paul Process and Energy Dpt. Multiphase Systems Delft University of Technology Leeghwaterstraat 21 Delft2628CA Netherlands Department of Industrial Engineering University of Padova Via Venezia 1 Padua35131 Italy Swedish e-Science Research Centre Linné FLOW Centre KTH Mechanics StockholmSE-100 44 Sweden

We use interface-resolved numerical simulations to study finite-size effects in turbulent channel flow of neutrally-buoyant spheres. Two cases with particle sizes differing by a factor of 2, at the same solid volume fraction of 20% and bulk Reynolds number are considered. These are complemented with two reference single-phase flows: the unladen case, and the flow of a Newtonian fluid with the effective suspension viscosity of the same mixture in the laminar regime. As recently highlighted in Costa et al. (2016), a particle-wall layer is responsible for deviations of the mesoscale-averaged statistics from what is observed in the continuum limit where the suspension is modeled as a Newtonian fluid with (higher) effective viscosity. Here we investigate in detail the fluid and particle dynamics inside this layer and in the bulk. In the particle-wall layer, the near wall inhomogeneity has an influence on the suspension micro-structure over a distance proportional to the particle size. In this layer, particles have a significant (apparent) slip velocity that is reflected in the distribution of wall shear stresses. This is characterized by extreme events (both much higher and much lower than the mean). Based on these observations we provide a scaling for the particle-to-fluid apparent slip velocity as a function of the flow parameters. We also extend the scaling laws in Costa et al. (2016) to second-order Eulerian statistics in the homogeneous suspension region away from the wall. The results show that finite-size effects in the bulk of the channel become important for larger particles, while negligible for lower-order statistics and smaller particles. Finally, we study the particle dynamics along the wall-normal direction. Our results suggest that single-point dispersion is dominated by particle-turbulence (and not particle-particle) interactions, while differences in two-point dispersion and collisional dynamics are consistent with a picture of shear-driven interactions.

关键词： Suspensions (fluids)

Modified Kirchhoff diffraction of pulsed EM waves radiated from a slot-excited Fabry-Perot resonator antenna

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Modified Kirchhoff diffraction of pulsed EM waves radiated f...

12th European Conference on Antennas and Propagation (EuCAP 2018)

作者： Martin Štumpf Guy A. E. Vandenbosch Ioan E. Lager SIX Research Centre Brno University of Technology Technická 3082/12 616 00 Brno the Czech Republic Electrical Engineering Dpt. TELEMIC Katholieke Universiteit Leuven Kasteelpark Arenberg 10 bus 2444 B-3001 Leuven Belgium Faculty of Electrical Engineering Mathematics and Computer Science Delft University of Technology Mekelweg 4 2628 CD Delft the Netherlands

ISBN: (纸本)9781785618154;9781785618161

Diffraction of pulsed electromagnetic (EM) waves in a slot excited Fabry Perot type resonator antenna is studied analytically in the modified Kirchhoff approximation. Closed-form space-time expressions for the radiated EM fields are found using the Cagniard-DeHoop technique. Illustrative numerical examples are given.

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Towards a Blockchain and Opportunistic Edge Driven Metaverse of Everything

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arXiv 2024年

作者： Fraga-Lamas, Paula Lopes, Sérgio Ivan Fernández-Caramés, Tiago M. Dpt. of Computer Engineering Centro de investigación CITIC Faculty of Computer Science Universidade da Coruña A Coruña15071 Spain ADiT-Lab Instituto Politécnico de Viana do Castelo Viana do Castelo4900-348 Portugal CiTin Centro de Interface Tecnológico Industrial Arcos de Valdevez4970-786 Portugal IT—Instituto de Telecomunicações Campus Universitário de Santiago Aveiro3810-193 Portugal

Decentralized Metaverses, built on Web 3.0 and Web 4.0 technologies, have attracted significant attention across various fields. This innovation leverages blockchain, Decentralized Autonomous Organizations (DAOs), Extended Reality (XR) and advanced technologies to create immersive and interconnected digital environments that mirror the real world. This article delves into the Metaverse of Everything (MoE), a platform that fuses the Metaverse concept with the Internet of Everything (IoE), an advanced version of the Internet of Things (IoT) that connects not only physical devices but also people, data and processes within a networked environment. Thus, the MoE integrates generated data and virtual entities, creating an extensive network of interconnected components. This article seeks to advance current MoE, examining decentralization and the application of Opportunistic Edge Computing (OEC) for interactions with surrounding IoT devices and IoE entities. Moreover, it outlines the main challenges to guide researchers and businesses towards building a future cyber-resilient opportunistic MoE. © 2024, CC BY.

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Forbidden time travel: Characterization of time-consistent tree reconciliation maps

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arXiv 2017年

作者： Nøjgaard, Nikolai Geiß, Manuela Stadler, Peter F. Merkle, Daniel Wieseke, Nicolas Hellmuth, Marc Dpt. of Mathematics and Computer Science University of Greifswald Walther- Rathenau-Strasse 47 GreifswaldD-17487 Saarland University Center for Bioinformatics Building e 2.1 P.O. Box 151150 SaarbrückenD-66041 Bioinformatics Group Department of Computer Science Interdisciplinary Center of Bioinformatics University of Leipzig Härtelstraße 16-18 LeipzigD-04107 Germany Department of Mathematics and Computer Science University of Southern Denmark Max-Planck-Institute for Mathematics in the Sciences Inselstraße 22 LeipzigD-04103 Germany Inst. F. Theoretical Chemistry University of Vienna Währingerstraße 17 WienA-1090 Austria Santa Fe Institute 1399 Hyde Park Rd. Santa Fe United States Parallel Computing and Complex Systems Group Department of Computer Science Leipzig University Augustusplatz 10 Leipzig04109 Germany

Motivation: In the absence of horizontal gene transfer it is possible to reconstruct the history of gene families from empirically determined orthology relations, which are equivalent to eventlabeled gene trees. Knowledge of the event labels considerably simplifies the problem of reconciling a gene tree T with a species trees S, relative to the reconciliation problem without prior knowledge of the event types. It is well-known that optimal reconciliations in the unlabeled case may violate time-consistency and thus are not biologically feasible. Here we investigate the mathematical structure of the event labeled reconciliation problem with horizontal transfer. Results: We investigate the issue of time-consistency for the event-labeled version of the reconciliation problem, provide a convenient axiomatic framework, and derive a complete characterization of time-consistent reconciliations. This characterization depends on certain weak conditions on the event-labeled gene trees that reflect conditions under which evolutionary events are observable at least in principle. We give an O(|V(T)|log(|V (S)|))-time algorithm to decide whether a time-consistent reconciliation map exists. It does not require the construction of explicit timing maps, but relies entirely on the comparably easy task of checking whether a small auxiliary graph is acyclic. Significance: The combinatorial characterization of time consistency and thus biologically feasible reconciliation is an important step towards the inference of gene family histories with horizontal transfer from orthology data, i.e., without presupposed gene and species trees. The fast algorithm to decide time consistency is useful in a broader context because it constitutes an attractive component for all tools that address tree reconciliation problems. Copyright © 2017, The Authors. All rights reserved.

关键词： Genes

Reconstructing gene trees from Fitch's xenology relation

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arXiv 2017年

作者： Geiß, Manuela Anders, John Stadler, Peter F. Wieseke, Nicolas Hellmuth, Marc Bioinformatics Group Department of Computer Science Interdisciplinary Center of Bioinformatics University of Leipzig Härtelstraße 16-18 LeipzigD-04107 Germany Dpt. of Mathematics and Computer Science University of Greifswald Walther- Rathenau-Strasse 47 GreifswaldD-17487 Germany Saarland University Center for Bioinformatics Building E 2.1 P.O. Box 151150 SaarbrückenD-66041 Germany Max-Planck-Institute for Mathematics in the Sciences Inselstraße 22 LeipzigD-04103 Germany Inst. f. Theoretical Chemistry University of Vienna Währingerstraße 17 WienA-1090 Austria Santa Fe Institute 1399 Hyde Park Rd. Santa Fe United States Parallel Computing and Complex Systems Group Department of Computer Science Leipzig University Augustusplatz 10 Leipzig04109 Germany

Two genes are xenologs in the sense of Fitch if they are separated by at least one horizontal gene transfer event. Horizonal gene transfer is asymmetric in the sense that the transferred copy is distinguished from the one that remains within the ancestral lineage. Hence xenology is more precisely thought of as a non-symmetric relation: y is xenologous to x if y has been horizontally transferred at least once since it diverged from the least common ancestor of x and y. We show that xenology relations are characterized by a small set of forbidden induced subgraphs on three vertices. Furthermore, each xenology relation can be derived from a unique least-resolved edge-labeled phylogenetic tree. We provide a linear-time algorithm for the recognition of xenology relations and for the construction of its least-resolved edge-labeled phylogenetic tree. The fact that being a xenology relation is a heritable graph property, finally has far-reaching consequences on approximation problems associated with xenology relations. Copyright © 2017, The Authors. All rights reserved.

关键词： Clustering algorithms