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See detailEARLY FLOWERING4 Recruitment of EARLY FLOWERING3 in the Nucleus Sustains the Arabidopsis Circadian Clock
Herrero, Eva; Kolmos, Elsebeth; Bujdoso, Nora et al

in Plant Cell (2012), 24(2), 428-443

The plant circadian clock is proposed to be a network of several interconnected feedback loops, and loss of any component leads to changes in oscillator speed. We previously reported that Arabidopsis ... [more ▼]

The plant circadian clock is proposed to be a network of several interconnected feedback loops, and loss of any component leads to changes in oscillator speed. We previously reported that Arabidopsis thaliana EARLY FLOWERING4 (ELF4) is required to sustain this oscillator and that the elf4 mutant is arrhythmic. This phenotype is shared with both elf3 and lux. Here, we show that overexpression of either ELF3 or LUX ARRHYTHMO (LUX) complements the elf4 mutant phenotype. Furthermore, ELF4 causes ELF3 to form foci in the nucleus. We used expression data to direct a mathematical position of ELF3 in the clock network. This revealed direct effects on the morning clock gene PRR9, and we determined association of ELF3 to a conserved region of the PRR9 promoter. A cis-element in this region was suggestive of ELF3 recruitment by the transcription factor LUX, consistent with both ELF3 and LUX acting genetically downstream of ELF4. Taken together, using integrated approaches, we identified ELF4/ELF3 together with LUX to be pivotal for sustenance of plant circadian rhythms. [less ▲]

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See detailEcological Advanced Driver Assistance System for Optimal Energy Management in Electric Vehicles
Sajadi Alamdari, Seyed Amin UL; Voos, Holger UL; Darouach, Mohamed

in IEEE Intelligent Transportation Systems Magazine (2018)

Battery Electric Vehicles have a high potential in modern transportation, however, they are facing limited cruising range. The driving style, the road geometries including slopes, curves, the static and ... [more ▼]

Battery Electric Vehicles have a high potential in modern transportation, however, they are facing limited cruising range. The driving style, the road geometries including slopes, curves, the static and dynamic traffic conditions such as speed limits and preceding vehicles have their share of energy consumption in the host electric vehicle. Optimal energy management based on a semi-autonomous ecological advanced driver assistance system can improve the longitudinal velocity regulation in a safe and energy-efficient driving strategy. The main contribution of this paper is the design of a real-time risk-sensitive nonlinear model predictive controller to plan the online cost-effective cruising velocity in a stochastic traffic environment. The basic idea is to measure the relevant states of the electric vehicle at runtime, and account for the road slopes, the upcoming curves, and the speed limit zones, as well as uncertainty in the preceding vehicle behavior to determine the energy-efficient velocity profile. Closed-loop Entropic Value-at-Risk as a coherent risk measure is introduced to quantify the risk involved in the system constraints violation. The obtained simulation and field experimental results demonstrate the effectiveness of the proposed method for a semi-autonomous electric vehicle in terms of safe and energy-efficient states regulation and constraints satisfaction. [less ▲]

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See detailEconomies of scale in recoverable robust maintenance location routing for rolling stock
Arts, Joachim UL; Tönissen, Denise

in Transportation Research. Part B, Methodological (2018), 117

We consider the problem of locating maintenance facilities in a railway setting. Different facility sizes can be chosen for each candidate location and for each size there is an associated annual facility ... [more ▼]

We consider the problem of locating maintenance facilities in a railway setting. Different facility sizes can be chosen for each candidate location and for each size there is an associated annual facility costs that can capture economies of scale in facility size. Because of the strategic nature of facility location, the opened facilities should be able to handle the current maintenance demand, but also the demand for any of the scenarios that can occur in the future. These scenarios capture changes such as changes to the line plan and the introduction of new rolling stock types. We allow recovery in the form of opening additional facilities, closing facilities, and increasing the facility size for each scenario. We provide a two-stage robust programming formulation. In the first-stage, we decide where to open what size of facility. In the second-stage, we solve a NP-hard maintenance location routing problem. We reformulate the problem as a mixed integer program that can be used to make an efficient column-and-constraint generation algorithm. To show that our algorithm works on practical sized instances, and to gain managerial insights, we perform a case study with instances from the Netherlands Railways. A counter intuitive insight is that economies of scale only play a limited role and that it is more important to reduce the transportation cost by building many small facilities, rather than a few large ones to profit from economies of scale. [less ▲]

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See detailThe effect of workplace relocation on individuals’ activity travel behavior
Sprumont, Francois; Viti, Francesco UL

in Journal of Transport and Land Use (2018), 11(1),

On working days, homes and workplaces can be seen as anchor locations at the heart of daily mobility patterns, as well as being central to an employee’s activity pattern. In this study, we investigate how ... [more ▼]

On working days, homes and workplaces can be seen as anchor locations at the heart of daily mobility patterns, as well as being central to an employee’s activity pattern. In this study, we investigate how workplace relocation affects the entire daily activity-travel chain. While past research has shown that workplace decentralization is often associated with higher car use for the commuting trip, little is known about the effect on the whole activity travel pattern. Two waves of a two-week travel diary were completed by 43 employees of the University of Luxembourg: one before and one after the relocation of their office. Using descriptive statistics as well as standard deviational ellipses (SDE) theory combined with the results of a clustering analysis showed that workers’ activity spaces (represented by the standard deviational ellipses) were significantly modified due to the relocation of a single anchor activity location, i.e., their workplace. [less ▲]

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See detailThe effect of workplace relocation on individuals’ activity travel behaviour
Sprumont, François UL; Viti, Francesco UL

Scientific Conference (2017, July 04)

During working days, home and workplace are anchor locations shaping the daily mobility as well as the employee’s activity pattern. While past research has shown that workplace decentralization is often ... [more ▼]

During working days, home and workplace are anchor locations shaping the daily mobility as well as the employee’s activity pattern. While past research has shown that workplace decentralization is often associated with higher car use for the commuting trip, little is known concerning the effect on activity-travel patterns as whole. The objective of this paper is to assess how workplace decentralization is affecting individuals’ daily activity space. A two-weeks travel diary has been filled by 43 employees of the University of Luxembourg, both before and after the relocation of their workplace. Using descriptive statistics, as well as Standard Deviational Ellipses (SDE) combined with a cluster analysis, results of this paper show that workers’ activity spaces, represented by the Standard Deviational Ellipses, have been importantly modified due to a relocation of a single anchor activity location, i.e. their workplace [less ▲]

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See detailEffectiveness of the Two-Step Dynamic Demand Estimation model on large networks
Cantelmo, Guido UL; Viti, Francesco UL; Derrmann, Thierry UL

in Proceedings of 2017 5th IEEE International Conference on Models and Technologies for Intelligent Transportation Systems (MT-ITS) (2017, June 28)

In this paper, the authors present a Two-Step approach that sequentially adjusts generation and distribution values of the (dynamic) OD matrix. While the proposed methodology already provided excellent ... [more ▼]

In this paper, the authors present a Two-Step approach that sequentially adjusts generation and distribution values of the (dynamic) OD matrix. While the proposed methodology already provided excellent results for updating demand flows on a motorway, the aim of this paper is to validate this conclusion on a real network: Luxembourg City. This network represents the typical middle-sized European city in terms of network dimension. Moreover, Luxembourg City has the typical structure of a metropolitan area, composed of a city centre, ring, and suburb areas. An innovative element of this paper is to use mobile network data to create a time-dependent profile of the generated demand inside and outside the ring. To support the claim that the model is ready for practical implementation, it is interfaced with PTV Visum, one of the most widely adopted software tools for traffic analysis. Results of these experiments provide a solid empirical ground in order to further develop this model and to understand if its assumptions hold for urban scenarios. [less ▲]

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See detailEffects of periurban structure on air pollution: coupling CA models to understand the link between urban structure and air pollution
Schindler, Mirjam UL; Caruso, Geoffrey UL

in Pinto N, Dourado J (Ed.) Proceedings of the Symposium on Cellular Automata Models of Urban and Spatial Systems (2012)

Air quality is a major concern in urban areas worldwide not only because of its severe health impacts but also due to its influence on living quality and residential behaviour. The subsequent increasing ... [more ▼]

Air quality is a major concern in urban areas worldwide not only because of its severe health impacts but also due to its influence on living quality and residential behaviour. The subsequent increasing demand for residential areas in the greener fringes of urban agglomerations fuels the discussion about sustainability in future cities. As traffic emissions are acknowledged to be the major source of pollutants in an urban environment this residential trend has triggered research to further understand the influence of urban structure on air quality. In order to meet sustainable growth, many researchers argue that in a global perspective a compact city is the desirable urban form due to less traffic distance, just in contrast to the trend towards urban sprawl. However, quantifying the link between urban structure and air pollution has only been the aim of few research studies so far. Thus, our objective is to deepen the understanding of this link by coupling a micro-economic CA urban growth model with a traffic emission model and a CA air pollution model while focussing on the impact on residential population. [less ▲]

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See detailAn efficient goal-oriented sampling strategy using reduced basis method for parametrized elastodynamic problems
Hoang, Khac Chi; Kerfriden, Pierre; Bordas, Stéphane UL et al

in Numerical Methods for Partial Differential Equations (2014)

In this paper, we study the class of linear elastodynamic problems with a ne parameter dependence using a goal-oriented approach by finite element (FE) and reduced basis (RB) methods. The main ... [more ▼]

In this paper, we study the class of linear elastodynamic problems with a ne parameter dependence using a goal-oriented approach by finite element (FE) and reduced basis (RB) methods. The main contribution of this paper is the "goal-oriented" proper orthogonal decomposition (POD)-Greedy sampling strategy within the RB approximation context. The proposed sampling strategy looks for the parameter points such that the output error approximation will be minimized by Greedy iterations. In estimating such output error approximation, the standard POD-Greedy algorithm is invoked to provide enriched RB approximations for the FE outputs. We propose a so-called "cross-validation" process to choose adaptively the dimension of the enriched RB space corresponding with the dimension of the RB space under consideration. Numerical results show that the new goal-oriented POD-Greedy sampling procedure with the cross-validation process improves signi ficantly the space-time output computations in comparison with the ones computed by the standard POD-Greedy algorithm. The method is thus ideally suited for repeated, rapid and reliable evaluations of input-output relationships in the space-time setting. [less ▲]

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See detailEfficient modeling of random heterogeneous materials with an uniform probability density function
Paladim, Daniel; Kerfriden, Pierre; Bordas, Stéphane UL

Scientific Conference (2014, July)

Homogenised constitutive laws are largely used to predict the behaviour of composite structures. Assessing the validity of such homogenised models can be done by making use of the concept of ``modelling ... [more ▼]

Homogenised constitutive laws are largely used to predict the behaviour of composite structures. Assessing the validity of such homogenised models can be done by making use of the concept of ``modelling error''. First, a microscopic ``faithful'' -and potentially intractable- model of the structure is defined. Then, one tries to quantify the effect of the homogenisation procedure on a result that would be obtained by directly using the ``faithful'' model. Such an approach requires (a) the ``faithful'' model to be more representative of the physical phenomena of interest than the homogenised model and (b) a reliable approximation of the result obtained using the "faithful" and intractable model to be available at cheap costs. We focus here on point (b), and more precisely on the extension of the techniques developed in [3][2] to estimate the error due to the homogenisation of linear, spatially random composite materials. Particularly, we will approximate the unknown probability density function by bounding its first moment. In this paper, we will present this idea in more detail, displaying the numerical efficiencies and computational costs related to the error estimation. The fact that the probability density function is uniform is exploited to greatly reduce the computational cost. We will also show some first attempts to correct the homogenised model using non-conforming, weakly intrusive microscopic patches. [less ▲]

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See detailEfficient modeling of random heterogeneous materials with an uniform probability density function (slides)
Paladim, Daniel; Kerfriden, Pierre; Moitinho de Almeida, José et al

Scientific Conference (2014)

Homogenised constitutive laws are largely used to predict the behaviour of composite structures. Assessing the validity of such homogenised models can be done by making use of the concept of “modelling ... [more ▼]

Homogenised constitutive laws are largely used to predict the behaviour of composite structures. Assessing the validity of such homogenised models can be done by making use of the concept of “modelling error”. First, a microscopic “faithful” -and potentially intractable- model of the structure is defined. Then, one tries to quantify the effect of the homogenisation procedure on a result that would be obtained by directly using the “faithful” model. Such an approach requires (a) the “faithful” model to be more representative of the physical phenomena of interest than the homogenised model and (b) a reliable approximation of the result obtained using the ”faithful” and intractable model to be available at cheap costs. We focus here on point (b), and more precisely on the extension of the techniques devel- oped in [3] [2] to estimate the error due to the homogenisation of linear, spatially random composite materials. Particularly, we will approximate the unknown probability density function by bounding its first moment. In this paper, we will present this idea in more detail, displaying the numerical efficiencies and computational costs related to the error estimation. The fact that the probability density function is uniform is exploited to greatly reduce the computational cost. We will also show some first attempts to correct the homogenised model using non-conforming, weakly intrusive microscopic patches. [less ▲]

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See detailEfficient recovery-based error estimation for the smoothed finite element method for smooth and singular linear elasticity
González-Estrada, O. A.; Natarajan, S.; Ródenas, J. J. et al

in Computational Mechanics (2013), 52(1), 37-52

An error control technique aimed to assess the quality of smoothed finite element approximations is presented in this paper. Finite element techniques based on strain smoothing appeared in 2007 were shown ... [more ▼]

An error control technique aimed to assess the quality of smoothed finite element approximations is presented in this paper. Finite element techniques based on strain smoothing appeared in 2007 were shown to provide significant advantages compared to conventional finite element approximations. In particular, a widely cited strength of such methods is improved accuracy for the same computational cost. Yet, few attempts have been made to directly assess the quality of the results obtained during the simulation by evaluating an estimate of the discretization error. Here we propose a recovery type error estimator based on an enhanced recovery technique. The salient features of the recovery are: enforcement of local equilibrium and, for singular problems a "smooth + singular" decomposition of the recovered stress. We evaluate the proposed estimator on a number of test cases from linear elastic structural mechanics and obtain efficient error estimations whose effectivities, both at local and global levels, are improved compared to recovery procedures not implementing these features. © 2012 Springer-Verlag. [less ▲]

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See detailÉischte Weltkrich: Remembering The Great War in Luxembourg - Digital Exhibition
Camarda, Sandra UL

in Bienert, Andreas; Jazbec, Rebeka (Eds.) EVA Berlin 2017 Elekronische Medien & Kunst, Kultur und Historie (2017)

Detailed reference viewed: 48 (12 UL)
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See detailThe elastic properties of composites reinforced by a transversely isotropic random fibre-network
Lin, Xiude; Zhu, Hanxing; Yuan, Xiaoli et al

in Composite Structures (2018), 208

This research stems from the idea of introducing a fibre-network structure into composites aiming to enhance the stiffness and strength of the composites. A novel new type of composites reinforced by a ... [more ▼]

This research stems from the idea of introducing a fibre-network structure into composites aiming to enhance the stiffness and strength of the composites. A novel new type of composites reinforced by a tranversely isotropic fibre-network in which the fibres are devided into continuous segments and randomly distributed has been proposed and found to have improved elastic properties compared to other conventional fibre or particle composites mainly due to the introduction of cross linkers among the fibres. Combining with the effects of Poisson’s ratio of the constituent materials, the fibre network composite can exhibit extraordinary stiffness. A simplified analytical model has also been proposed for comparison with the numerical results, showing close prediction of the stiffness of the fibre-network composites. Moreover, as a plate structure, the thickness of the fibre network composite is adjustable and can be tailored according to the dimensions and mechanical properties as demanded in industry. [less ▲]

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See detailAn element nodal force-based large increment method for elastoplasticity
Long, Danbin; Guo, Zaoyang; Liu, Xila et al

in AIP Conference Proceedings (2010), 1233(PART 1), 1401-1405

This paper presents a new method for establishing the basic equations in the novel force-based large increment method (LIM) for continuum elastoplastic problems. In LIM, unlike traditional displacement ... [more ▼]

This paper presents a new method for establishing the basic equations in the novel force-based large increment method (LIM) for continuum elastoplastic problems. In LIM, unlike traditional displacement methods, the (generalised) elemental force variables are adopted as system unknowns. The equilibrium equations can then be obtained directly at every nodal degree of freedom without physical equations (i.e., constitutive equations) involved. The generalised inverse of the non-square system of equations is employed to obtain the set of solutions of the non-square matrix equations directly. A conjugate gradient procedure is then used to find the correct solution from this set of solutions by optimising the compatibility of the solution based on the fact that the correct solution should also satisfy the constitutive equations and the compatibility equations. In this paper, the generalised elemental force variables are defined based on the element nodal forces. The LIM framework is therefore successfully applied to elements based on this definition. The efficiency and accuracy of the LIM are illustrated with a few benchmark problems and the results are compared with the analytical solution and the conventional displacement-based finite element method. [less ▲]

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See detailEmbracing diversity in the digital transformation of primary healthcare
Lygidakis, Charilaos UL

Scientific Conference (2017, June 30)

The use of information and communication technologies for health constitutes a strategic ally to the sustainable development goals and attaining universal health coverage through enabling equitable access ... [more ▼]

The use of information and communication technologies for health constitutes a strategic ally to the sustainable development goals and attaining universal health coverage through enabling equitable access to high quality and affordable health care services. The omnipresence of mobile devices and sensors, the increasing availability of data and computational power, and the breakthroughs in imaging and genomics, are creating a perfect storm that is bound to transform health care profoundly. At the population level, the coordination of disease control and prevention programmes is facilitated, cost-effective interventions are implemented, and ultimately the quality of life of our communities is enhanced. EHealth also plays a significant role in the delivery of people-centred and integrated health services, empowers individuals to make informed decisions and self-manage their health needs. For the first time in history, the individual is placed at the centre, has timely and affordable access to data, knowledge and tools, and health care is tailored for his/her diverse background, context and needs. A second perspective to the digital revolution is how our own discipline is transformed. As technology is a catalyst for sustainable, large scale social change, health care has the opportunity to invest in inter-professional collaboration, and leverage a diverse range of expertise, stakeholders and resources to expand its horizons and tackle old and future challenges. [less ▲]

Detailed reference viewed: 73 (0 UL)
See detailThe emergence of leapfrogging in an urban growth model combining an economic approach and cellular automata
Frankhauser, Pierre; Caruso, Geoffrey UL; Peeters, Dominique et al

Scientific Conference (2009)

Detailed reference viewed: 28 (1 UL)