ICTEAM Institute

Louvain-la-Neuve, Belgium

ICTEAM Institute

Louvain-la-Neuve, Belgium
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Rensonnet G.,ICTEAM Institute | Scherrer B.,Computational Radiology LaboratoryBoston Childrens Hospital | Warfield S.K.,Computational Radiology LaboratoryBoston Childrens Hospital | Macq B.,ICTEAM Institute | Taquet M.,Harvard University
Magnetic Resonance in Medicine | Year: 2017

Purpose: To assess the validity of the superposition approximation for crossing fascicles, i.e., the assumption that the total diffusion-weighted MRI signal is the sum of the signals arising from each fascicle independently, even when the fascicles intermingle in a voxel. Methods: Monte Carlo simulations were used to study the impact of the approximation on the diffusion-weighted MRI signal and to assess whether this approximate model allows microstructural features of interwoven fascicles to be accurately estimated, despite signal differences. Results: Small normalized signal differences were observed, typically 10-3-10-2. The use of the approximation had little impact on the estimation of the crossing angle, the axonal density index, and the radius index in clinically realistic scenarios wherein the acquisition noise was the predominant source of errors. In the absence of noise, large systematic errors due to the superposition approximation only persisted for the radius index, mainly driven by a low sensitivity of diffusion-weighted MRI signals to small radii in general. Conclusion: The use of the superposition approximation rather than a model of interwoven fascicles does not adversely impact the estimation of microstructural features of interwoven fascicles in most current clinical settings. © 2017 International Society for Magnetic Resonance in Medicine.

Wang T.,Shanghai University | Fang Y.,Shanghai University | Vandendorpe L.,ICTEAM Institute
IEEE Communications Letters | Year: 2013

This paper develops a sum-power minimized resource allocation (RA) algorithm subject to a sum-rate constraint for cooperative orthogonal frequency division modulation (OFDM) transmission with subcarrier-pair based opportunistic decode-and-forward (DF) relaying. The improved DF protocol first proposed in is used with optimized subcarrier pairing. Instrumental to the RA algorithm design is appropriate definition of variables to represent source/relay power allocation, subcarrier pairing and transmission-mode selection elegantly, so that after continuous relaxation, the dual method and the Hungarian algorithm can be used to find an (at least approximately) optimum RA with polynomial complexity. Moreover, the bisection method is used to speed up the search of the optimum Lagrange multiplier for the dual method. Numerical results are shown to illustrate the power-reduction benefit of the improved DF protocol with optimized subcarrier pairing. © 1997-2012 IEEE.

De Souza M.,State University of Maringa | Flandre D.,ICTEAM Institute | Pavanello M.A.,State University of Maringa
Chip in Curitiba 2013 - SBMicro 2013: 28th Symposium on Microelectronics Technology and Devices | Year: 2013

This paper presents an experimental analysis of channel length influence on the analog characteristics of asymmetric self-cascode association of SOI transistors. It is shown that the increase of the drain current and transconductance is more pronounced with the reduction of the length of the transistor close to the source (L1), and, differently from the symmetric self-cascode, suffers little influence of the length close to the drain (L2). On the contrary, the output conductance of symmetric and asymmetric threshold voltage structures is benefited by the increase of L 2 and L1, although the asymmetric structure may offer a reduction of up to one order of magnitude in comparison to the symmetric one. It results in larger intrinsic voltage drain for asymmetric devices. This increase has shown to reach more than 20 dB for similar dimensions, or allow for dimension reduction without intrinsic gain degradation. © 2013 IEEE.

Assalti R.,State University of Maringa | Pavanello M.A.,State University of Maringa | Flandre D.,ICTEAM Institute | De Souza M.,State University of Maringa
SBMicro 2015 - 30th Symposium on Microelectronics Technology and Devices | Year: 2015

This paper compares the performance of Asymmetric Self-Cascode and Graded-Channel SOI nMOSFETs, both proposed to improve the analog performance of fully depleted SOI nMOSFETs. The differences at device level are evaluated and the impact of their application in basic analog circuits, i.e. common-source amplifier, source-follower and common-source current mirror are explored through experimental results. © 2015 IEEE.

De Souza M.,State University of Maringa | Paz B.C.,State University of Maringa | Flandre D.,ICTEAM Institute | Pavanello M.A.,State University of Maringa
Microelectronics Reliability | Year: 2013

In this work a comparison between the performance of current mirrors implemented with uniformly doped and graded-channel (GC) transistors operating down to low temperature (150 K) is presented. This analysis has been carried out through experimental measurements of Common-source, Cascode and Wilson current mirrors architectures. The advantages of the use of graded-channel transistors for implementation of current mirrors in comparison to standard ones is discussed, focusing on the increase of output swing and output resistance. In all architectures some performance degradation has been observed with the temperature reduction, although current mirrors with GC transistors still present better performance than those implemented with standard SOI transistors. Two-dimensional numerical simulations were performed in order to further investigate the behavior of graded-channel current mirrors, looking at the bias condition of each transistor in the current mirror architectures. The obtained results indicate that good performance, compared to that of GC current mirrors, may be obtained by combining both standard and graded-channel transistors, rather than using the same channel engineering for all devices in the circuit. © 2013 Elsevier Ltd. All rights reserved.

Saltik M.B.,TU Eindhoven | Athanasopoulos N.,ICTEAM Institute | Ozkan L.,TU Eindhoven | Weiland S.,TU Eindhoven
Proceedings of the IEEE Conference on Decision and Control | Year: 2016

We consider a class of scheduling problems, common in manufacturing industries that consist of several interconnected subprocesses. We model the scheduling constraints of each subprocess and of the overall system using labeled directed graphs, forming the admissible set of schedules. Furthermore, we consider polytopic constraints on the state space. We approach the scheduling problem as a safety analysis problem utilizing reachability mappings, system and constraint structure. Consequently, we construct the safe schedules that guarantee constraint satisfaction at all times. The proposed framework is illustrated in a case study that concerns a simplified separation process. © 2015 IEEE.

PubMed | Catholic University of Louvain, Free University of Colombia, Cliniques Universitaires Saint Luc and ICTEAM institute
Type: Journal Article | Journal: PloS one | Year: 2015

Allergy afflicts one third of children, negatively impacting their quality of life and generating a significant socio-economic burden. To this day, this disorder remains difficult to diagnose early in young patients, with no predictive test available.This study was designed to correlate cytokine profiles with clinical phenotypes of allergy development.Three hundred patients were recruited and followed from birth to 18 months of age. They were given a clinical exam at birth and at 2, 6, 12, and 18 months of age, with skin prick tests at 6, and 18 months, in order to have a record of their medical history and determine their allergic status. In addition, mononuclear cells from 131 patients were isolated from cord blood and from peripheral blood samples at 2, 6 and 18 months of age, to analyse their cytokine and chemokine production.Cord blood mononuclear cells (CBMCs) from future Immunoglobulin (Ig) E-mediated allergic children produced significantly less Interleukin (IL)-12p70 and IL-15 than cells from the rest of the cohort. Multivariate analyses revealed that the best predictive model of allergy was built on cytokine data, whereas the best predictive model of IgE-mediated allergy was built on clinical parameters.Although univariate analyses can yield interesting information regarding the immune responses of allergic children, finding predictive markers of the disorder will likely rely on monitoring multiple parameters. Nonetheless these analyses suggest a potential key role for IL-15 in the development of atopic disease. In addition, the study highlights the importance of clinical parameters in predicting the development of IgE-mediated allergy.

Protasov V.Y.,Moscow State University | Jungers R.M.,ICTEAM Institute
2013 European Control Conference, ECC 2013 | Year: 2013

We introduce a new approach to evaluate the largest Lyapunov exponent of a family of matrices, which describes the stability with probability one of a randomly switching linear system. For positive systems, of particular importance in systems and control, the rate of convergence of our approximation is estimated and the efficiency of the algorithm is demonstrated on particular switching systems of different dimensions. This is done by introducing new upper and lower bounds for the largest Lyapunov exponent of nonnegative matrices. We generalize this approach to arbitrary systems (not necessarily positive), derive a new universal upper bound for the Lyapunov exponent, and show that a similar lower bound, in general, does not exist. © 2013 EUCA.

Gonze F.,ICTEAM Institute | Jungers R.M.,ICTEAM Institute | Trahtman A.N.,Bar - Ilan University
Discrete Mathematics and Theoretical Computer Science | Year: 2015

We provide a counterexample to a lemma used in a recent tentative improvement of the Pin-Frankl bound for synchronizing automata. This example naturally leads us to formulate an open question, whose answer could fix the line of the proof, and improve the bound. © 2015 Discrete Mathematics and Theoretical Computer Science (DMTCS).

Carta R.,Catholic University of Leuven | Thone J.,Catholic University of Leuven | Gosset G.,ICTEAM Institute | Cogels G.,Catholic University of Leuven | And 3 more authors.
Procedia Engineering | Year: 2011

This paper describes the design and implementation of a self-tuning inductive powering system conceived for biomedical applications. The circuit operates at 1 MHz and delivers 380 mW to the implant with an efficiency of 50%, at a distance of 1 cm. Absorption modulation is used to monitor the circuit parameters allowing the system to deal with distance increases up to 5 cm as well as small coil misalignments. The automatic-tuning system adjusts the configuration of the coil driver depending on the self-monitored coupling, acting on a bank of switchable capacitors with a pattern defined by the received data. It is demonstrated that the implemented tuning strategy boosts the transmitted power by a factor two. In addition, the combination of tuning and smart power regulation was proven to sensibly increase the system efficiency by maintaining a constant energy level at the secondary. © 2011 Published by Elsevier Ltd.

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