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See detailDimensions of Digital History Collaborations
Kemman, Max UL

Scientific Conference (2016)

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See detailDirect image-analysis methods for surgical simulation and mixed meshfree methods
Hale, Jack UL; Bordas, Stéphane UL; Kerfriden, Pierre et al

Presentation (2014, May 28)

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See detailDirectionality of Attacks in Natural Language Argumentation
Cramer, Marcos UL; Guillaume, Mathieu UL

in CEUR Workshop Proceedings (2018)

In formal (abstract and structured) argumentation theory, a central notion is that of an attack between a counterargument and the argument that it is challenging. Unlike the notion of an inconsistency ... [more ▼]

In formal (abstract and structured) argumentation theory, a central notion is that of an attack between a counterargument and the argument that it is challenging. Unlike the notion of an inconsistency between two statements in classical logic, this notion of an attack between arguments can be asymmetric, i.e. an argument A can attack an argument B without B attacking A. While this property of the formal systems studied by argumentation theorist has been motivated by considerations about the human practice of argumentation in natural language, there have not been any systematic studies on the connection between the directionality of attacks in argumentation-theoretic formalisms and the way humans actually interpret conflicts between arguments in a non-symmetric way. In this paper, we report on the result of two empirical cognitive studies that aim at filling this gap, one study with ordinary adults (undergraduate students) and one study with adult experts in formal argumentation theory. We interpret the results in light of the notions and distinctions defined in the ASPIC+ framework for structured argumentation, and discuss the relevance of our findings to past and future empirical studies about the link between human argumentation and formal argumentation theory. [less ▲]

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See detailDiscrete mechanical models and upscaling techniques for discrete materials
Beex, Lars UL; Bordas, Stéphane UL

Poster (2016)

Numerous natural and man-made materials are essentially discrete structures at the mesoscale or microscale (see Fig. 1). Discrete mechanical models can be formulated to capture typical mechanical ... [more ▼]

Numerous natural and man-made materials are essentially discrete structures at the mesoscale or microscale (see Fig. 1). Discrete mechanical models can be formulated to capture typical mechanical phenomena arising from this discreteness. Failure in these materials, which often starts with the fracture of an individual bond, can be predicted based on the small-scale mechanics with these models. For failure, but also for non-local mechanics, no phenomenological descriptions are required in these models. This makes them more predictive than constitutive material models for this type of materials. [less ▲]

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See detailDiscrete Multiscale Modelling and Future Research Plans concerning Metals
Beex, Lars UL; Bordas, Stéphane UL; Rappel, Hussein UL et al

Presentation (2014, October 14)

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See detailA discrete-continuous approach to describe CaCO3 decarbonation in non-steady thermal conditions
Copertaro, Edoardo UL; Chiariotti, Paolo; Estupinan Donoso, Alvaro Antonio et al

in Powder Technology (2015), 275

In cement production, direct measurements of thermal and chemical variables are often unfeasible as a consequence of aggressive environments, moving parts and physical inaccessibility, and therefore ... [more ▼]

In cement production, direct measurements of thermal and chemical variables are often unfeasible as a consequence of aggressive environments, moving parts and physical inaccessibility, and therefore prediction models are essential tools in these types of industrial applications. This article addresses the problem of the numerical prediction of the CaCO3 calcination process, which is the first and the most energy expensive process in clinker production. This study was conducted using the Extended Discrete Element Method (XDEM), a framework which allows a Eulerian approach for the gas phase to be combined with a Lagrange one for the powder phase. A detailed validation of the numerical model was performed by comparison to non-isothermal TG curves for mass loss during the CaCO3 decarbonation process. The complex three-dimensional predictions for solid and gas phases are believed to represent a first step towards a new insight into the cement production process. Thus, the high accuracy and detailed description of the problem addressed, serve as a basis to assess the uncertainty of more simplified models such as those used in soft sensors. [less ▲]

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See detailDiscretisation and Model Selection for Interface Problems in Mechanics
Bordas, Stéphane UL

in International Journal of Computational Methods (2017, August 04)

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See detailDistributed attitude synchronization control
Thunberg, Johan UL; Montijano, E.; Hu, X.

in Proceedings of the 50th IEEE Conference on Decision and Control and European Control Conference (CDC-ECC) (2011)

In this paper we consider the problem of constructing feedback control laws for a system of n agents that shall synchronize their attitudes in SO(3). We propose distributed controllers for two ... [more ▼]

In this paper we consider the problem of constructing feedback control laws for a system of n agents that shall synchronize their attitudes in SO(3). We propose distributed controllers for two synchronization problems, in which the objective is the same, to synchronize the orientations, but what the agents can perceive or communicate differs. In the first problem the agents can measure their orientation to a common reference object, and either communicate with the neighbors or estimate the relative orientation to their neighbors. In the second problem the agents can, without communication, only measure the relative orientation to the neighbors. For the first problem we present a controller which will lead to synchronization, provided the neighborhood graph is connected. For the second problem we present a controller that will lead to synchronization provided the neighborhood graph is connected and the agents initially are contained within a geodesic ball of radius π/2, which is the maximal convex set in SO(3). [less ▲]

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See detailDistributed attitude synchronization control of multi-agent systems with directed topologies
Thunberg, Johan UL; Song, W.; Hong, Y. et al

in the proceedings of the 10th World Congress on Intelligent Control and Automation (2012)

In the present paper we consider the problem of attitude synchronization for a system of rigid body agents. We provide distributed kinematic control laws for two different synchronization problems. In the ... [more ▼]

In the present paper we consider the problem of attitude synchronization for a system of rigid body agents. We provide distributed kinematic control laws for two different synchronization problems. In the two problems the objective is the same, i.e., to synchronize the orientations of the agents, but what is assumed to be measurable by the agents differs. In problem 1 the agents measure their own orientations in a global reference frame, and obtain the orientations of their neighbors by means of communication. In problem 2 the agents only measure the relative orientations to their neighbors. By using the axis-angle representation of the orientation, we show that simple linear control laws solve both synchronization problems. Moreover we show that our proposed control laws work for directed and connected topologies on almost all SO(3) for problem 1 and on convex balls in SO(3) for problem 2. [less ▲]

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See detailDistributed attitude synchronization control of multi-agent systems with switching topologies
Thunberg, Johan UL; Song, W.; Montijano, E. et al

in Automatica (2014), 50(3), 832-840

This paper addresses the attitude synchronization problem in multi-agent systems with directed and switching interconnection topologies. Two cases for the synchronization problem are discussed under ... [more ▼]

This paper addresses the attitude synchronization problem in multi-agent systems with directed and switching interconnection topologies. Two cases for the synchronization problem are discussed under different assumptions about the measurable information. In the first case the agents can measure their rotations relative to a global reference coordinate frame, whilst in the second case they can only measure the relative rotations between each other. Two intuitive distributed control laws based on the axis–angle representations of the rotations are proposed for the two cases, respectively. The invariance of convex balls in SO(3) is guaranteed. Moreover, attitude synchronization is ensured under the well-known mild switching assumptions, the joint strong connection for the first case and joint quasi-strong connection for the second case. To show the effectiveness of the proposed control schemes, illustrative examples are provided. [less ▲]

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See detailDistributed attitude synchronization control of multi-agent systems with time-varying topologies
Song, W.; Thunberg, Johan UL; Hong, Y. et al

in Proceedings of the 10th World Congress on Intelligent Control and Automation (2012)

This paper addresses the attitude synchronization problem of multiple rigid body agents in SO(3) with directed and switching interconnection topologies. Using the axis-angle representation of the ... [more ▼]

This paper addresses the attitude synchronization problem of multiple rigid body agents in SO(3) with directed and switching interconnection topologies. Using the axis-angle representation of the orientation, a distributed controller based on differences between the orientations of agents in a global frame is proposed. In the case of the balanced interconnection graph, the attitude synchronization is achieved with the well-known mild assumption (that is, uniform joint strong connection). To demonstrate the effectiveness of the proposed control scheme, an illustrative example is provided. [less ▲]

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See detailDistributed attitude synchronization using backstepping and sliding mode control
Thunberg, Johan UL; Song, W.; Hong, Y. et al

in Control Theory and Technology (2014), 12(1), 48-55

We consider the problem of attitude synchronization for systems of rigid body agents with directed topologies. Two different scenarios for the rotation matrices of the agents are considered. In the first ... [more ▼]

We consider the problem of attitude synchronization for systems of rigid body agents with directed topologies. Two different scenarios for the rotation matrices of the agents are considered. In the first scenario, the rotations are contained in a convex subset of SO(3), which is a ball of radius less than π/2, whereas in the second scenario the agents are contained in a subset of SO(3), which is a ball of radius less than π. Using a control law based on backstepping and sliding mode control, we provide distributed, semi-global, torque control laws for the agents so that the rotations asymptotically synchronize. The control laws for the agents in the first scenario only depend on the relative rotations between neighboring agents, whereas the control laws in the second scenario depend on rotations defined in a global coordinate frame. Illustrative examples are provided where the synchronization is shown for both scenarios. [less ▲]

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See detailDistributed Automatic Vehicle Location (AVL) System Based on Connected Vehicle Technology
Smietanka, Piotr; Szczypiorski, Krzysztof; Viti, Francesco UL et al

in Proceedings of IEEE-ITS Conference (2015, September)

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See detailDistributed high-gain attitude synchronization using rotation vectors
Song, W.; Thunberg, Johan UL; Hu, X. et al

in Journal of Systems Science and Complexity (2015), 28(2), 289-304

This paper addresses attitude synchronization problems for systems of multiple rigid-body agents with directed interconnection topologies. Two scenarios which differ in available information are ... [more ▼]

This paper addresses attitude synchronization problems for systems of multiple rigid-body agents with directed interconnection topologies. Two scenarios which differ in available information are considered. In the first scenario the agents can obtain their rotations and angular velocities relative to an inertial reference frame and transmit these information to their neighbors, while in the second scenario the agents can only obtain their own angular velocities and measure the relative rotations and relative angular velocities of their neighbors. By using rotation vectors and the high gain control, the authors provide torque control laws asymptotically synchronizing the rotations of the system almost globally for the first scenario and with initial rotations of the agents contained in a convex ball of SO(3) for the second scenario. An illustrative example is provided to show the synchronization results for both scenarios. [less ▲]

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See detailDistributed identification of the Cell Transmission traffic model: A case study
Rinaldi, Marco UL; Capisani, L.; Ferrara, A. et al

in Procedings of the 2012 American Control Conference, ACC 2012 (2012)

The problem of the distributed identification of a macroscopic first-order traffic model, viz. the Cell Transmission Model (CTM), is considered in the paper. The parameters to be identified characterize ... [more ▼]

The problem of the distributed identification of a macroscopic first-order traffic model, viz. the Cell Transmission Model (CTM), is considered in the paper. The parameters to be identified characterize the dynamics of the density in different sections of the freeway (cells). We explore different distributed identification schemes. The purposes of the approach are mainly to obtain good prediction models through the minimization of the one-step ahead prediction error of the densities of the cells, and to reduce the computational time and the effort required to perform the identification. The methodology is validated relying on real-life data measured on a portion of the A12 freeway in The Netherlands. An evaluation of the performance of the identified model used as a set of virtual sensors in different scenarios is presented. © 2012 AACC American Automatic Control Council). [less ▲]

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See detailDistributed Kalman Filter with minimum-time covariance computation
Thia, Jerry; Yuan, Ye; Shi, Ling et al

in The proceedings of the IEEE 52nd Annual Conference on Decision and Control (2013)

This paper considerably improves the well-known Distributed Kalman Filter (DKF) algorithm by Olfati-Saber (2007) by introducing a novel decentralised consensus value computation scheme, using only local ... [more ▼]

This paper considerably improves the well-known Distributed Kalman Filter (DKF) algorithm by Olfati-Saber (2007) by introducing a novel decentralised consensus value computation scheme, using only local observations of sensors. It has been shown that the state estimates obtained in [8] and [9] approaches those of the Central Kalman Filter (CKF) asymptotically. However, the convergence to the CKF can sometimes be too slow. This paper proposes an algorithm that enables every node in a sensor network to compute the global average consensus matrix of measurement noise covariance in minimum time without accessing global information. Compared with the algorithm in [8], our theoretical analysis and simulation results show that the new algorithm can offer improved performance in terms of time taken for the state estimates to converge to that of the CKF. [less ▲]

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See detailDistributed reconstruction of nonlinear networks: An ADMM approach
Pan, Wei UL; Sootla, Aivar; Stan, Guy-Bart

in Proceedings of the 19th World Congress of the International Federation of Automatic Control (IFAC 2014) (2014)

In this paper, we present a distributed algorithm for the reconstruction of large-scale nonlinear networks. In particular, we focus on the identification from time-series data of the nonlinear functional ... [more ▼]

In this paper, we present a distributed algorithm for the reconstruction of large-scale nonlinear networks. In particular, we focus on the identification from time-series data of the nonlinear functional forms and associated parameters of large-scale nonlinear networks. In (Pan et al. (2013)), a nonlinear network reconstruction problem was formulated as a nonconvex optimisation problem based on the combination of a marginal likelihood maximisation procedure with sparsity inducing priors. Using a convex-concave procedure (CCCP), an iterative reweighted lasso algorithm was derived to solve the initial nonconvex optimisation problem. By exploiting the structure of the objective function of this reweighted lasso algorithm, a distributed algorithm can be designed. To this end, we apply the alternating direction method of multipliers (ADMM) to decompose the original problem into several subproblems. To illustrate the effectiveness of the proposed methods, we use our approach to identify a network of interconnected Kuramoto oscillators with different network sizes (500∼100,000 nodes). [less ▲]

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See detailDistributedFBA.jl: High-level, high-performance flux balance analysis in Julia.
Heirendt, Laurent UL; Thiele, Ines UL; Fleming, Ronan MT UL

in Bioinformatics (2017)

MOTIVATION: Flux balance analysis, and its variants, are widely used methods for predicting steady-state reaction rates in biochemical reaction networks. The exploration of high dimensional networks with ... [more ▼]

MOTIVATION: Flux balance analysis, and its variants, are widely used methods for predicting steady-state reaction rates in biochemical reaction networks. The exploration of high dimensional networks with such methods is currently hampered by software performance limitations. RESULTS: DistributedFBA.jl is a high-level, high-performance, open-source implementation of flux balance analysis in Julia. It is tailored to solve multiple flux balance analyses on a subset or all the reactions of large and huge-scale networks, on any number of threads or nodes. AVAILABILITY: The code is freely available on github.com/opencobra/COBRA.jl. The documentation can be found at opencobra.github.io/COBRA.jl. [less ▲]

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See detailDrawing ER diagrams with TikZ
Fiandrino, Claudio UL

in Ars TeXnica (2013), 15

The paper will illustrate some techniques to represent Entity-Relationship (ER) diagrams with TikZ. In particular, it will focus on the standard internal library \library{er}, on the external package TikZ ... [more ▼]

The paper will illustrate some techniques to represent Entity-Relationship (ER) diagrams with TikZ. In particular, it will focus on the standard internal library \library{er}, on the external package TikZ-er2, on the external tool Graphviz and on the object-oriented approach provided by the er-oo library. [less ▲]

Detailed reference viewed: 120 (8 UL)