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See detailA Hybrid Machine Learning and Schedulability Method for the Verification of TSN Networks
Mai, Tieu Long UL; Navet, Nicolas UL; Migge, Jörn

in 15th IEEE International Workshop on Factory Communication Systems (WFCS2019) (2019, March)

Machine learning (ML), and supervised learning in particular, can be used to learn what makes it hard for a network to be feasible and try to predict whether a network configuration will be feasible ... [more ▼]

Machine learning (ML), and supervised learning in particular, can be used to learn what makes it hard for a network to be feasible and try to predict whether a network configuration will be feasible without executing a conventional schedulability analysis. A disadvantage of ML-based timing verification with respect to schedulability analysis is the possibility of "false positives": configurations deemed feasible while they are not. In this work, in order to minimize the rate of false positives, we propose the use of a measure of the uncertainty of the prediction to drop it when the uncertainty is too high, and rely instead on schedulability analysis. In this hybrid verification strategy, the clear-cut decisions are taken by ML, while the more difficult ones are taken by a conventional schedulability analysis. Importantly, the trade-off achieved between prediction accuracy and computing time can be controlled. We apply this hybrid verification method to Ethernet TSN networks and obtain, for instance in the case of priority scheduling with 8 traffic classes, a 99% prediction accuracy with a speedup factor of 5.7 with respect to conventional schedulability analysis and a reduction of 46% of the false positives compared to ML alone. [less ▲]

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See detailHybrid mesh/particle meshless method for geological flows with discontinuous transport properties
Bourantas, Georgios UL; Lavier, Luc; Claus, Susanne et al

Scientific Conference (2015, April 12)

Geodynamic modeling is an important branch of Earth Sciences. Direct observation of geodynamic processes is limited in both time and space, while on the other hand numerical methods are capable of ... [more ▼]

Geodynamic modeling is an important branch of Earth Sciences. Direct observation of geodynamic processes is limited in both time and space, while on the other hand numerical methods are capable of simulating millions of years in a matter of days on a desktop computer. The model equations can be reduced to a set of Partial Differential Equations with possibly discontinuous coefficients, governing mass, momentum and heat transfer over the domain. Some of the major challenges associated with such simulations are (1) geological time scales, which require long (in physical time) simulations using small time steps; (2) the presence of localization zones over which large gradients are present and which are much smaller than the overall physical dimensions of the computational domain and require much more refined discretization than for the rest of the domain, much like in fracture or shear band mechanics. An added difficulty is that such structures in the solution may appear after long periods of stagnant behaviour; (3) the definition of boundary conditions, material parameters and that of a suitable computational domain in terms of size; (4) a posteriori error estimation, sensitivity analysis and discretization adaptivity for the resulting coupled problem, including error propagation between different unknown fields. Consequently, it is arguable that any suitable numerical methods aimed at the solution of such problems on a large scale must be able to (i) provide ease of discretization refinement, including possible partition of unity enrichment; (ii) offer a large stability domain, so that “large” time steps can be chosen; (iii) ease of parallelization and good scalability. Our approach is to rely on “meshless” methods based on a point collocation strategy for the discretization of the set of PDEs. The method is hybrid Eulerian/Lagrangian, which enables to switch easily between stagnant periods and periods of localization. Mass and momentum equations are solved using a meshless point collocation Eulerian method, while energy equation are solved using a set of particles, distributed over the spatial domain, with the solution interpolated back to the Eulerian grid at every time step. This hybrid approach allows for the accurate calculation of fine thermal structures, through the ease of adaptivity offered by the flexibility of the particle method. The approximation space is constructed using the Discretization Correction Particle Strength Exchange (DC PSE) method. The proposed scheme gives the capability of solving flow equations (Stokes flow) in fully irregular geometries while particles, “sprinkled” in the spatial domain, are used to solve convection-diffusion problems avoiding the oscillation produced in the Eulerian approach. The resulting algebraic linear systems were solved using direct solvers. Our hybrid approach can capture sharp variations of stresses and thermal gradients in problems with a strongly variable viscosity and thermal conductivity as demonstrated through various benchmarking test cases such as the development of Rayleigh-Taylor instabilities, viscous heating and flows with non-Newtonian rheology. [less ▲]

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See detailHybrid mesh/particle meshless method for modeling geological flows with discontinuous transport properties
Bourantas, Georgios UL; Lavier, Luc; van Dam, Tonie UL et al

E-print/Working paper (2016)

In the present paper, we introduce the Finite Difference Method-Meshless Method (FDM-MM) in the context of geodynamical simulations. The proposed numerical scheme relies on the well-established FD method ... [more ▼]

In the present paper, we introduce the Finite Difference Method-Meshless Method (FDM-MM) in the context of geodynamical simulations. The proposed numerical scheme relies on the well-established FD method along with the newly developed “meshless” method and, is considered as a hybrid Eulerian/Lagrangian scheme. Mass, momentum, and energy equations are solved using an FDM method, while material properties are distributed over a set of markers (particles), which represent the spatial domain, with the solution interpolated back to the Eulerian grid. The proposed scheme is capable of solving flow equations (Stokes flow) in uniform geometries with particles, “sprinkled” in the spatial domain and is used to solve convection- diffusion problems avoiding the oscillation produced in the Eulerian approach. The resulting algebraic linear systems were solved using direct solvers. Our hybrid approach can capture sharp variations of stresses and thermal gradients in problems with a strongly variable viscosity and thermal conductivity as demonstrated through various benchmarking test cases. The present hybrid approach allows for the accurate calculation of fine thermal structures, offering local type adaptivity through the flexibility of the particle method. [less ▲]

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See detailA hybrid metal–dielectric zero mode waveguide for enhanced single molecule detection
Zambrana-Puyalto, Xavier; Ponzellini, Paolo; Maccaferri, Nicolò UL et al

in Chemical Communications (2019)

We fabricated hybrid metal–dielectric nanoslots and measured their optical response at three different wavelengths. The nanostructure is fabricated on a bilayer film formed by the sequential deposition of ... [more ▼]

We fabricated hybrid metal–dielectric nanoslots and measured their optical response at three different wavelengths. The nanostructure is fabricated on a bilayer film formed by the sequential deposition of silicon and gold on a transparent substrate. The optical characterization is done via fluorescence spectroscopy measurements. We characterized the fluorescence enhancement, as well as the lifetime and the detection volume reduction for each wavelength. We observe that the hybrid metal–dielectric nanoslots behave as enhanced zero mode waveguides in the near-infrared spectral region. Their detection volume is such that they can perform enhanced single-molecule detection at tens of μM. We compared their behavior with that of a golden ZMW, and we demonstrated that the dielectric silicon layer improves both the optical performance and the stability of the device. [less ▲]

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See detailHybrid mobility model with pheromones for UAV detection task
Kieffer, Emmanuel UL; Danoy, Grégoire UL; Bouvry, Pascal UL et al

in Hybrid mobility model with pheromones for UAV detection task (2016)

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See detailHybrid MPI+OpenMP Implementation of eXtended Discrete Element Method
Mainassara Chekaraou, Abdoul Wahid UL; Rousset, Alban UL; Besseron, Xavier UL et al

in Proc. of the 9th Workshop on Applications for Multi-Core Architectures (WAMCA'18), part of 30th Intl. Symp. on Computer Architecture and High Performance Computing (SBAC-PAD 2018) (2018, September)

The Extended Discrete Element Method (XDEM) is a novel and innovative numerical simulation technique that ex- tends classical Discrete Element Method (DEM) (which simulates the motion of granular material ... [more ▼]

The Extended Discrete Element Method (XDEM) is a novel and innovative numerical simulation technique that ex- tends classical Discrete Element Method (DEM) (which simulates the motion of granular material), by additional properties such as the chemical composition, thermodynamic state, stress/strain for each particle. It has been applied successfully to numerous industries involving the processing of granular materials such as sand, rock, wood or coke [16], [17]. In this context, computational simulation with (X)DEM has become a more and more essential tool for researchers and scientific engineers to set up and explore their experimental processes. However, increasing the size or the accuracy of a model requires the use of High Performance Computing (HPC) platforms over a parallelized implementation to accommodate the growing needs in terms of memory and computation time. In practice, such a parallelization is traditionally obtained using either MPI (distributed memory computing), OpenMP (shared memory computing) or hybrid approaches combining both of them. In this paper, we present the results of our effort to implement an OpenMP version of XDEM allowing hybrid MPI+OpenMP simulations (XDEM being already parallelized with MPI). Far from the basic OpenMP paradigm and recommendations (which simply summarizes by decorating the main computation loops with a set of OpenMP pragma), the OpenMP parallelization of XDEM required a fundamental code re-factoring and careful tuning in order to reach good performance. There are two main reasons for those difficulties. Firstly, XDEM is a legacy code devel- oped for more than 10 years, initially focused on accuracy rather than performance. Secondly, the particles in a DEM simulation are highly dynamic: they can be added, deleted and interaction relations can change at any timestep of the simulation. Thus this article details the multiple layers of optimization applied, such as a deep data structure profiling and reorganization, the usage of fast multithreaded memory allocators and of advanced process/thread-to-core pinning techniques. Experimental results evaluate the benefit of each optimization individually and validate the implementation using a real-world application executed on the HPC platform of the University of Luxembourg. Finally, we present our Hybrid MPI+OpenMP results with a 15%-20% performance gain and how it overcomes scalability limits (by increasing the number of compute cores without dropping of performances) of XDEM-based pure MPI simulations. [less ▲]

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See detailHybrid Ni/SiO2/Au dimer arrays for high-resolution refractive index sensing
Pourjamal, Sara; Kataja, Mikko; Maccaferri, Nicolò UL et al

in Nanophotonics (2018), 7(5), 905-912

We introduce a novel magnetoplasmonic sensor concept for sensitive detection of refractive index changes. The sensor consists of a periodic array of Ni/SiO2/Au direr nanodisks. Combined effects of near ... [more ▼]

We introduce a novel magnetoplasmonic sensor concept for sensitive detection of refractive index changes. The sensor consists of a periodic array of Ni/SiO2/Au direr nanodisks. Combined effects of near-field interactions between the Ni and Au disks within the individual dimers and far-field diffractive coupling between the dimers of the array produce narrow linewidth features in the magneto-optical Faraday spectrum. We associate these features with the excitation of surface lattice resonances and show that they exhibit a spectral shift when the refractive index of the surrounding environment is varied. Because the resonances are sharp, refractive index changes are accurately detected by tracking the wavelength where the Faraday signal crosses 0. Compared to random distributions of pure Ni nanodisks or Ni/SiO2/Au dimers or periodic arrays of Ni nanodisks, the sensing figure of merit of the hybrid magnetoplasmonic array is more than one order of magnitude larger. [less ▲]

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See detailA hybrid particle-mesh method for incompressible active polar viscous gels
Ramaswamy, Rajesh; Bourantas, Georgios UL; Jülicher, Frank et al

in Journal of Computational Physics (2015), 291

We present a hybrid particle-mesh method for numerically solving the hydrodynamic equations of incompressible active polar viscous gels. These equations model the dynamics of polar active agents, embedded ... [more ▼]

We present a hybrid particle-mesh method for numerically solving the hydrodynamic equations of incompressible active polar viscous gels. These equations model the dynamics of polar active agents, embedded in a viscous medium, in which stresses are induced through constant consumption of energy. The numerical method is based on Lagrangian particles and staggered Cartesian finite-difference meshes. We show that the method is second-order and first-order accurate with respect to grid and time-step sizes, respectively. Using the present method, we simulate the hydrodynamics in rectangular geometries, of a passive liquid crystal, of an active polar film and of active gels with topological defects in polarization. We show the emergence of spontaneous flow due to Fréedericksz transition, and transformation in the nature of topological defects by tuning the activity of the system. [less ▲]

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See detailHybrid plasmonic lattices with tunable magneto-optical activity
Kataja, Mikko; Pourjamal, Sara; Maccaferri, Nicolò UL et al

in Optics Express (2016), 24(4), 3652-3662

We report on the optical and magneto-optical response of hybrid plasmonic lattices that consist of pure nickel and gold nanoparticles in a checkerboard arrangement. Diffractive far-field coupling between ... [more ▼]

We report on the optical and magneto-optical response of hybrid plasmonic lattices that consist of pure nickel and gold nanoparticles in a checkerboard arrangement. Diffractive far-field coupling between the individual emitters of the lattices results in the excitation of two orthogonal surface lattice resonance modes. Local analyses of the radiation fields indicate that both the nickel and gold nanoparticles contribute to these collective resonances and, thereby, to the magneto-optical activity of the hybrid arrays. The strong effect of noble metal nanoparticles on the magneto-optical response of hybrid lattices opens up new avenues for the realization of sensitive and tunable magneto-plasmonic nanostructures. [less ▲]

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See detailHybrid plasmonic nanostructures based on controlled integration of MoS2 flakes on metallic nanoholes
Garoli, Denis; Mosconi, Dario; Miele, Ermanno et al

in Nanoscale (2018), 10(36), 17105-17111

Here, we propose an easy and robust strategy for the versatile preparation of hybrid plasmonic nanopores by means of controlled deposition of single flakes of MoS2 directly on top of metallic holes. The ... [more ▼]

Here, we propose an easy and robust strategy for the versatile preparation of hybrid plasmonic nanopores by means of controlled deposition of single flakes of MoS2 directly on top of metallic holes. The device is realized on silicon nitride membranes and can be further refined by TEM or FIB milling to achieve the passing of molecules or nanometric particles through a pore. Importantly, we show that the plasmonic enhancement provided by the nanohole is strongly accumulated in the 2D nanopore, thus representing an ideal system for single-molecule sensing and sequencing in a flow-through configuration. Here, we also demonstrate that the prepared 2D material can be decorated with metallic nanoparticles that can couple their resonance with the nanopore resonance to further enhance the electromagnetic field confinement at the nanoscale level. This method can be applied to any gold nanopore with a high level of reproducibility and parallelization; hence, it can pave the way to the next generation of solid-state nanopores with plasmonic functionalities. Moreover, the controlled/ordered integration of 2D materials on plasmonic nanostructures opens a pathway towards new investigation of the following: enhanced light emission; strong coupling from plasmonic hybrid structures; hot electron generation; and sensors in general based on 2D materials. [less ▲]

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See detailA hybrid smoothed extended finite element/level set method for modeling equilibrium shapes of nano-inhomogeneities
Zhao, X.; Bordas, Stéphane UL; Qu, J.

in Computational Mechanics (2013)

Interfacial energy plays an important role in equilibrium morphologies of nanosized microstructures of solid materials due to the high interface-to-volume ratio, and can no longer be neglected as it does ... [more ▼]

Interfacial energy plays an important role in equilibrium morphologies of nanosized microstructures of solid materials due to the high interface-to-volume ratio, and can no longer be neglected as it does in conventional mechanics analysis. When designing nanodevices and to understand the behavior of materials at the nano-scale, this interfacial energy must therefore be taken into account. The present work develops an effective numerical approach by means of a hybrid smoothed extended finite element/level set method to model nanoscale inhomogeneities with interfacial energy effect, in which the finite element mesh can be completely independent of the interface geometry. The Gurtin-Murdoch surface elasticity model is used to account for the interface stress effect and the Wachspress interpolants are used for the first time to construct the shape functions in the smoothed extended finite element method. Selected numerical results are presented to study the accuracy and efficiency of the proposed method as well as the equilibrium shapes of misfit particles in elastic solids. The presented results compare very well with those obtained from theoretical solutions and experimental observations, and the computational efficiency of the method is shown to be superior to that of its most advanced competitor. © 2013 Springer-Verlag Berlin Heidelberg. [less ▲]

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See detailHybrid Societies: Challenges and Perspectives in the Design of Collective Behavior in Self-Organizing Systems
Hamann, Heiko; Khaluf, Yara; Botev, Jean UL et al

in Frontiers in Robotics and AI (2016), 3(14),

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See detailHybrid software and system development in practice: Waterfall, scrum, and beyond
Kuhrmann, Marco; Diebold, Philipp; Münch, Jürgen et al

in Proceedings of International Conference on Software and Systems Process (ICSSP) (2017, July)

Software and system development faces numerous challenges of rapidly changing markets. To address such challenges, companies and projects design and adopt specific development approaches by combining well ... [more ▼]

Software and system development faces numerous challenges of rapidly changing markets. To address such challenges, companies and projects design and adopt specific development approaches by combining well-structured comprehensive methods and flexible agile practices. Yet, the number of methods and practices is large, and available studies argue that the actual process composition is carried out in a fairly ad-hoc manner. The present paper reports on a survey on hybrid software development approaches. We study which approaches are used in practice, how different approaches are combined, and what contextual factors influence the use and combination of hybrid software development approaches. Our results from 69 study participants show a variety of development approaches used and combined in practice. We show that most combinations follow a pattern in which a traditional process model serves as framework in which several fine-grained (agile) practices are plugged in. We further show that hybrid software development approaches are independent from the company size and external triggers. We conclude that such approaches are the results of a natural process evolution, which is mainly driven by experience, learning, and pragmatism. [less ▲]

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See detailA hybrid T-Trefftz polygonal finite element for linear elasticity
Bhattacharjee, Kalyan; Natarajan, Sundararajan; Bordas, Stéphane UL

E-print/Working paper (2014)

In this paper, we construct hybrid T-Trefftz polygonal finite elements. The displacement field within the polygon is repre- sented by the homogeneous solution to the governing differential equation, also ... [more ▼]

In this paper, we construct hybrid T-Trefftz polygonal finite elements. The displacement field within the polygon is repre- sented by the homogeneous solution to the governing differential equation, also called as the T-complete set. On the boundary of the polygon, a conforming displacement field is independently defined to enforce continuity of the displacements across the element boundary. An optimal number of T-complete functions are chosen based on the number of nodes of the polygon and degrees of freedom per node. The stiffness matrix is computed by the hybrid formulation with auxiliary displacement frame. Results from the numerical studies presented for a few benchmark problems in the context of linear elasticity shows that the proposed method yield highly accurate results. [less ▲]

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See detailHybrid Transceivers Design for Large-Scale Antenna Arrays Using Majorization-Minimization Algorithms
Arora, Aakash UL; Tsinos, Christos UL; Shankar, Bhavani UL et al

in IEEE Transactions on Signal Processing (in press)

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See detailHybrid User Pairing for Spectral and Energy Efficiencies in Multiuser MISO-NOMA Networks with SWIPT
Nguyen, Toan-Van; Nguyen, van Dinh UL; Costa, Daniel Benevides Da et al

in IEEE Transactions on Communications (2020), 68(8), 4874-4890

In this paper, we propose a novel hybrid user pairing (HUP) scheme in multiuser multiple-input single-output nonorthogonal multiple access networks with simultaneous wireless information and power ... [more ▼]

In this paper, we propose a novel hybrid user pairing (HUP) scheme in multiuser multiple-input single-output nonorthogonal multiple access networks with simultaneous wireless information and power transfer. In this system, two information users with distinct channel conditions are optimally paired while energy users perform energy harvesting (EH) under non-linearity of the EH circuits. We consider the problem of jointly optimizing user pairing and power allocation to maximize the overall spectral efficiency (SE) and energy efficiency (EE) subject to userspecific quality-of-service and harvested power requirements. A new paradigm for the EE-EH trade-off is then proposed to achieve a good balance of network power consumption. Such design problems are formulated as the maximization of nonconcave functions subject to the class of mixed-integer non-convex constraints, which are very challenging to solve optimally. To address these challenges, we first relax binary pairing variables to be continuous and transform the design problems into equivalent non-convex ones, but with more tractable forms. We then develop low-complexity iterative algorithms to improve the objectives and converge to a local optimum by means of the inner approximation framework. Simulation results show the convergence of proposed algorithms and the SE and EE improvements of the proposed HUP scheme over state-of-the-art designs. In addition, the effects of key parameters such as the number of antennas and dynamic power at the BS, target data rates, and energy threshold, on the system performance are evaluated to show the effectiveness of the proposed schemes in balancing resource utilization. [less ▲]

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See detailHybride Praktiken. Methodologische Überlegungen zu einer erziehungswissenschaftlichen Ethnographie kindermedizinischer Vorsorgeuntersuchungen.
Bollig, Sabine UL; Kelle, Helga

in Hünersdorf, Bettina; Maeder, Christoph; Müller, Burkhard (Eds.) Ethnographie und Erziehungswissenschaft. Methodologische Reflexionen und empirische Annäherungen (2008)

Dieser Beitrag ist methodologischen Fragen nach dem Verhältnis von Ethnographie und Pädagogik gewidmet. Anhand eines empirischen Beispiels aus dem Forschungsprojekt „Kinderkörper in der Praxis“ wird für ... [more ▼]

Dieser Beitrag ist methodologischen Fragen nach dem Verhältnis von Ethnographie und Pädagogik gewidmet. Anhand eines empirischen Beispiels aus dem Forschungsprojekt „Kinderkörper in der Praxis“ wird für einen wissenssoziologisch informierten und praxisanalytisch orientierten Ansatz erziehungswissenschaftlicher Ethnographie plädiert, der sich nicht vorrangig über – ihrem Selbstverständnis nach – pädagogische Handlungsfelder definiert. Vielmehr versteht dieser Ansatz den Begriff des „Feldes“ im Sin-ne einer reflexiven Anthropologie auch und zunächst als einen rekursiven „Modus der Objektkonstruktion“ (Bourdieu/Wacquant 1996, S. 262). Solch ein heuristischer Feldbegriff in Verbindung mit einem formbezogenen Begriff von Pädagogik als Wissensordnung ermöglicht es, einerseits Konstruktionsbedingungen, Funktionen und Verfahrensweisen pädagogischer Praxisformen in vielfältigen Kontexten empirisch zu explorieren und gleichzeitig die je gewählten Forschungsfelder nicht vorgängig durch eine Fokussierung der Fragen auf „das Pädagogische“ weiter künstlich einzugrenzen. [less ▲]

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See detailHybridisation Schemes for Communication Satellite Payload Configuration Optimisation
Stathakis, Apostolos; Danoy, Grégoire UL; Talbi, El-Ghazali et al

in 17th European Conference on Applications of Evolutionary Computation (EvoApplications 2014) (2014, April)

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See detailHybridisierung von Berufs- und Hochschulbildung in Deutschland, Österreich und der Schweiz
Graf, Lukas UL

in Banscherus, Ulf; Engel, Ole; Mindt, Anne (Eds.) et al Differenzierung im Hochschulsystem: Nationale und internationale Entwicklungen und Herausforderungen (2015)

Detailed reference viewed: 132 (5 UL)