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See detailFastMotif: Spectral Sequence Motif Discovery
Colombo, Nicolo UL; Vlassis, Nikos UL

in Bioinformatics (2015)

Motivation: Sequence discovery tools play a central role in several fields of computational biology. In the framework of Transcription Factor binding studies, most of the existing motif finding algorithms ... [more ▼]

Motivation: Sequence discovery tools play a central role in several fields of computational biology. In the framework of Transcription Factor binding studies, most of the existing motif finding algorithms are computationally demanding, and they may not be able to support the increasingly large datasets produced by modern high-throughput sequencing technologies. Results: We present FastMotif, a new motif discovery algorithm that is built on a recent machine learning technique referred to as Method of Moments. Based on spectral decompositions, our method is robust to model misspecifications and is not prone to locally optimal solutions. We obtain an algorithm that is extremely fast and designed for the analysis of big sequencing data. On HT-Selex data, FastMotif extracts motif profiles that match those computed by various state-of- the-art algorithms, but one order of magnitude faster. We provide a theoretical and numerical analysis of the algorithm’s robustness and discuss its sensitivity with respect to the free parameters. [less ▲]

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See detailFinding surface Lyapunov functions through sum-of-squares Programming
Spanos, D.; Goncalves, Jorge UL

in Proceedings of the American Control Conference 2004 (2004)

This work presents a sum-of-squares method to construct polynomial surface Lyapunov functions (SuLF) of arbitrary order for the impact maps of limit cycles in piecewise linear systems (PLS). This work ... [more ▼]

This work presents a sum-of-squares method to construct polynomial surface Lyapunov functions (SuLF) of arbitrary order for the impact maps of limit cycles in piecewise linear systems (PLS). This work extends previous results on stability analysis of such limit cycles, which utilized quadratic SuLFs. This paper also discusses an initial study of hierarchical jump linear systems where the switching is driven by feedback of low-level dynamical system states and a Markovian process. [less ▲]

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See detailFinite deformations govern the anisotropic shear-induced area reduction of soft elastic contacts
Lengiewicz, Jakub UL; de Souza, Mariana; Lahmar, Mohamed A. et al

in Journal of the Mechanics and Physics of Solids (2020), 143

Solid contacts involving soft materials are important in mechanical engineering or biomechanics. Experimentally, such contacts have been shown to shrink significantly under shear, an effect which is ... [more ▼]

Solid contacts involving soft materials are important in mechanical engineering or biomechanics. Experimentally, such contacts have been shown to shrink significantly under shear, an effect which is usually explained using adhesion models. Here we show that quantitative agreement with recent high-load experiments can be obtained, with no adjustable parameter, using a non-adhesive model, provided that finite deformations are taken into account. Analysis of the model uncovers the basic mechanisms underlying anisotropic shear-induced area reduction, local contact lifting being the dominant one. We confirm experimentally the relevance of all those mechanisms, by tracking the shear-induced evolution of tracers inserted close to the surface of a smooth elastomer sphere in contact with a smooth glass plate. Our results suggest that finite deformations are an alternative to adhesion, when interpreting a variety of sheared contact experiments involving soft materials. [less ▲]

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See detailFinite element analysis on implicitly defined domains: An accurate representation based on arbitrary parametric surfaces
Moumnassi, M.; Belouettar, S.; Béchet, T. et al

in Computer Methods in Applied Mechanics & Engineering (2011), 200(5-8), 774-796

In this paper, we present some novel results and ideas for robust and accurate implicit representation of geometric surfaces in finite element analysis. The novel contributions of this paper are threefold ... [more ▼]

In this paper, we present some novel results and ideas for robust and accurate implicit representation of geometric surfaces in finite element analysis. The novel contributions of this paper are threefold: (1) describe and validate a method to represent arbitrary parametric surfaces implicitly; (2) represent arbitrary solids implicitly, including sharp features using level sets and boolean operations; (3) impose arbitrary Dirichlet and Neumann boundary conditions on the resulting implicitly defined boundaries. The methods proposed do not require local refinement of the finite element mesh in regions of high curvature, ensure the independence of the domain's volume on the mesh, do not rely on boundary regularization, and are well suited to methods based on fixed grids such as the extended finite element method (XFEM). Numerical examples are presented to demonstrate the robustness and effectiveness of the proposed approach and show that it is possible to achieve optimal convergence rates using a fully implicit representation of object boundaries. This approach is one step in the desired direction of tying numerical simulations to computer aided design (CAD), similarly to the isogeometric analysis paradigm. © 2010 Elsevier B.V. [less ▲]

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See detailFinite-time road grade computation for a vehicle platoon
Yang, Tao; Yuan, Ye; Li, Kezhi et al

in IEEE (2014)

Given a platoon of vehicles traveling uphill, this paper considers the finite-time road grade computation problem. We propose a decentralized algorithm for an arbitrarily chosen vehicle to compute the ... [more ▼]

Given a platoon of vehicles traveling uphill, this paper considers the finite-time road grade computation problem. We propose a decentralized algorithm for an arbitrarily chosen vehicle to compute the road grade in a finite number of time-steps by using only its own successive velocity measurements. Simulations then illustrate the theoretical results. These new results can be applied to real-world vehicle platooning problems to reduce fuel consumption and carbon dioxide emissions. [less ▲]

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See detailFleet readiness: Stocking spare parts and high tech assets
Basten, Rob; Arts, Joachim UL

in IISE Transactions (2017), 49(4), 429-441

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See detailFLEXCAP – Cost competitive flexible process for highly aesthetic closures manufacturing
Kakogiannos, Ioannis UL; Hichri, Bassem UL; Plapper, Peter UL

in Kakogiannos, Ioannis; Hichri, Bassem; Plapper, Peter (Eds.) Robotix-Academy Conference for Industrial Robotics (RACIR) 2018 (2018, November)

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See detailFlood Detection On Low Cost Orbital Hardware
Mateo-Garcia, Gonzalo; Oprea, Silviu; Smith, Lewis et al

Scientific Conference (2019, October)

Satellite imaging is a critical technology for monitoring and responding to natural disasters such as flooding. Despite the capabilities of modern satellites, there is still much to be desired from the ... [more ▼]

Satellite imaging is a critical technology for monitoring and responding to natural disasters such as flooding. Despite the capabilities of modern satellites, there is still much to be desired from the perspective of first response organisations like UNICEF. Two main challenges are rapid access to data, and the ability to automatically identify flooded regions in images. We describe a prototypical flood segmentation system, identifying cloud, water and land, that could be deployed on a constellation of small satellites, performing processing on board to reduce downlink bandwidth by 2 orders of magnitude. We target PhiSat-1, part of the FSSCAT mission, which is planned to be launched by the European Space Agency (ESA) near the start of 2020 as a proof of concept for this new technology. [less ▲]

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See detailFluctuations and Limitations of a Multi-Sector Economic Model with Delays
Tonita, R.; Lestas, I.; Goncalves, Jorge UL et al

in The proceedings of the 2010 American Control Conference (ACC) (2010)

A general multi-sector model of the economy is investigated. A sector's input to production, labor, evolves according to a jump Markov process. Labor jumps between sectors to balance supply and demand ... [more ▼]

A general multi-sector model of the economy is investigated. A sector's input to production, labor, evolves according to a jump Markov process. Labor jumps between sectors to balance supply and demand, where each sector differs by its productivity. The jump model captures the intrinsic noise of the micro agents on the macro level, which is represented by the random timing of labor jumps. Quantifying this noise is a central theme of this paper. An operator theoretic approach is utilized to capture the fluctuations of a linearized jump system exactly. As an illustrative example two sector and three sector economies are studied. In each case the optimal aggressiveness, gain, of a sector is determined for minimal variance. Delays are then introduced into the model. It is shown that the presence of a delay creates a limit on the minimum variance achievable and that high gain is destabilizing. For both the two and three sector models the nonlinear jump systems are simulated. It is shown that the operator theoretic approach is an appropriate method for quantifying the second moments. [less ▲]

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See detailFM Discriminator for AIS Satellite Detection
Jurado Gallardo, Maria De Los Angeles UL; Ruy, Ghislain

in Personal Satellite Services (2010)

The Automatic Identification System (AIS) is a tracking system used on ships for several decades to improve traffic monitoring and safety at sea in a short range. The modulation technique used is Gaussian ... [more ▼]

The Automatic Identification System (AIS) is a tracking system used on ships for several decades to improve traffic monitoring and safety at sea in a short range. The modulation technique used is Gaussian Minimum Shift Keying (GMSK). Recently, the idea of receiving AIS signals from space arose. This presents mainly two challenges. The first one is that received signals present a large Doppler range due to the satellite speed. The second one is the simultaneous reception of signals from ships because of the broad satellite coverage. In this paper, a novel non-coherent GMSK demodulator is proposed to handle the large Doppler shift problem based on several FM discriminators in parallel. A frame collision detection algorithm is presented but the collision problem is not addressed. In addition, computer simulated and real signals are used to study the receiver performance on an AWGN channel. [less ▲]

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See detailA force-based large increment method for 2D continuum solids and the mesh convergence study
Long, D.; Guo, Z.; Liu, X. et al

in AIP Conference Proceedings (2012), 1504

In this paper, a triangular plane stress element is implemented based on the large increment method (LIM) to solve 2D continuum mechanics problems. In the LIM, after the governing equations are ... [more ▼]

In this paper, a triangular plane stress element is implemented based on the large increment method (LIM) to solve 2D continuum mechanics problems. In the LIM, after the governing equations are established using the generalized elemental force variables as primary unknowns, an iteration procedure is employed to obtain an optimised approximate solution of the problem. Two numerical examples are investigated to study the mesh convergence of the proposed triangular LIM element. Structured meshes as well as unstructured meshes with different element densities are generated to illustrate the convergence of the total strain energy in both examples. The numerical results obtained from the LIM (including the total strain energy, the displacement and the stress) are compared with the analytical solutions as well as the results from the commercial FEM software ABAQUS. All the results show that the performance of the LIM is as good as the FEM in linear elastic problems. A simple elastoplastic example suggests that the LIM may obtain better result than the FEM. © 2012 American Institute of Physics. [less ▲]

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See detailFostering sustainable user behaviour: exploring meaning and its creation in products and services
Waltersdorfer, Gregor UL; Gericke, Kilian UL; Blessing, Lucienne UL

in Valentine, Louise; Borja de Mozota, Brigitte; Nelson, Julien (Eds.) et al The Value of Design Research, Proceedings of the 11th International Conference of the European Academy of Design (2015)

This paper is integrated in our research project on fostering sustainable user behaviour by designing meaning. It explores different types of meaning in products and services, and their creation. For that ... [more ▼]

This paper is integrated in our research project on fostering sustainable user behaviour by designing meaning. It explores different types of meaning in products and services, and their creation. For that, the results of a literature study are integrated into an initial taxonomy of meaning and an initial framework for creating meaning. From the taxonomy we derive four roles that products and services can play in meaning making. Additionally we discuss how five possible interventions in users meaning making for behavioural change can be pursued by design on the basis of the framework. We illustrate the role of designers in creating meaning with examples, touch on its potential for behavioural change of users and outline further research needs. [less ▲]

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See detailFracture in augmented reality
Bilger, Alexandre UL; Cotin, Stephane; Dequidt, Jeremie et al

Poster (2015, August)

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See detailFracture mechanism simulation of inhomogeneous anisotropic rocks by extended finite element method
Mohtarami, Ehsan; Baghbanan, Alireza; Hashemolhosseini, Hamid et al

in Theoretical and Applied Fracture Mechanics (2019), 104

The vast majority of rock masses is anisotropic due to factors such as layering, unequal in-situ stresses, joint sets, and discontinuities. Meanwhile, given the frequently asymmetric distribution of pores ... [more ▼]

The vast majority of rock masses is anisotropic due to factors such as layering, unequal in-situ stresses, joint sets, and discontinuities. Meanwhile, given the frequently asymmetric distribution of pores, grain sizes or different mineralogical compounds in different locations, they are often classified as inhomogeneous materials. In such materials, stress intensity factors (SIFs) at the crack tip, which control the initiation of failure, strongly depend on mechanical properties of the material near that area. On the other hand, crack propagation trajectories highly depend on the orthotropic properties of the rock mass. In this study, the SIFs are calculated by means of anisotropic crack tip enrichments and an interaction integral are developed for inhomogeneous materials with the help of the extended finite element method (XFEM). We also use the T-stress within the crack tip fields to develop a new criterion to estimate the crack initiation angles and propagation in rock masses. To verify and validate the proposed approach, the results are compared with experimental test results and those reported in the literature. It is found that the ratio of elastic moduli, shear stiffnesses, and material orientation angles have a significant impact on the SIFs. However, the rate of change in material properties is found to have a moderate effect on these factors and a more pronounced effect on the failure force. The results highlight the potential of the proposed formulation in the estimation of SIFs and crack propagation paths in inhomogeneous anisotropic materials. [less ▲]

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See detailA Framework for Comparing Design Modelling Approaches Across Disciplines
Eisenbart, Boris UL; Gericke, Kilian UL; Blessing, Lucienne UL

in Proceedings of the 18th International Conference on Engineering Design (2011)

Design models are an important means for the representation of design information in product development processes. Designers use design models to visualise and communicate their ideas to other members of ... [more ▼]

Design models are an important means for the representation of design information in product development processes. Designers use design models to visualise and communicate their ideas to other members of a design team, the project manager or a costumer. Communication between experts from different disciplines using design models is often hindered by different terminology and different ways of modelling. Potential consequences are design flaws, which may lead to time-consuming iterations and – if undetected – to problems during production or use. In order to enhance the communication through design models across disciplines, and to address the mentioned problems, an understanding of similarities as well as differences between modelling approaches needs to be established. For that purpose, this paper discusses different design states which represent a distinct level of available information in the development process. They are derived through comparing different design models proposed in literature and provide the basis of a framework for a detailed comparison of modelling approaches across disciplines. Further, first insights into different ways of modelling are discussed. [less ▲]

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See detailA Framework to Reason about the Legal Compliance of Security Standards
Bartolini, Cesare UL; Giurgiu, Andra UL; Lenzini, Gabriele UL et al

in Proceedings of the Tenth International Workshop on Juris-informatics (JURISIN) (2016, November)

Achieving compliance with legal regulations is no easy task. Normally, laws state general requirements but do not provide clear parameters to determine when such requirements are met. On a different level ... [more ▼]

Achieving compliance with legal regulations is no easy task. Normally, laws state general requirements but do not provide clear parameters to determine when such requirements are met. On a different level, industrial standards and best practices define specific objectives that can be certified by means of auditing procedures from qualified bodies. Implementing a standard does not per se guarantee legal compliance, with the rare exception when the standard is also endorsed by the law itself. But standards and laws in the same domain may have overlaps and correlations, so adopting the former may provide an argument to demonstrate that adequate measures were taken to achieve legal compliance. In this paper, we introduce a framework that, using state-of-the-art Natural Language Semantics techniques, helps process legal documents and standards to build a knowledge base to store their logic representations, and the correlations between them. The knowledge base will help legal experts assess what requirements of the law are met by the standard and, consequently, recognize what requirements still need to be implemented to fill the remaining gaps. An application of the framework is exemplified by comparing a provision of the European General Data Protection Regulation against the ISO/IEC 27001:2013 standard. [less ▲]

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See detailFree boundary problems: numerical methods and data-driven simulations
Bordas, Stéphane UL

Presentation (2018, March 05)

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See detailFriendly Batch Routing (FBR)
Medard de Chardon, Cyrille UL; Caruso, Geoffrey UL

Software (2012)

The Friendly Batch Routing (FBR) application uses the Google Maps API to easily and simply gather route data for many origin-destination pairs. FBR is designed with usability in mind so that errors do not ... [more ▼]

The Friendly Batch Routing (FBR) application uses the Google Maps API to easily and simply gather route data for many origin-destination pairs. FBR is designed with usability in mind so that errors do not interrupt processing and skipped records can easily be resubmitted for processing. Additionally the FBR output can easily be imported into GIS packages. [less ▲]

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See detailFrom image to analysis: an extended finite element method to simulate the mechanical response of soft-tissue
Hale, Jack UL; Bordas, Stéphane UL; Kerfriden, Pierre

Presentation (2014, April 10)

In this seminar we consider the problem of constructing a numerical method particularly well suited to modelling domains described by segmented image data of the human body. Instead of constructing a ... [more ▼]

In this seminar we consider the problem of constructing a numerical method particularly well suited to modelling domains described by segmented image data of the human body. Instead of constructing a conforming mesh of the problem domain, we use implicitly defined domains described using the level-set method. We then include information about the implicitly defined domains by enriching the usual finite element basis functions defined on a cartesian quadtree or octree mesh with hanging nodes. This approach introduces significant complexities compared with classical finite element methods. We will discuss difficulties with the treatment of hanging nodes, numerical integration and imposing Dirichlet boundary conditions. We will discuss the possible future of extensions of this work, including cutting of soft tissue, multiscale problems with complex microstructure, and model order reduction problems. [less ▲]

Detailed reference viewed: 154 (8 UL)