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See detailEffect of Voltage Constraints on the Exchange of Flexibility Services in Distribution Networks
Mathieu, Sébastien ULiege; Olivier, Frédéric ULiege; Ernst, Damien ULiege et al

in Proceedings of the 9th Conference on Innovative Smart Grid Technology North America (ISGT 2018) (in press)

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See detailOperation of distribution systems within secure limits using real-time Model Predictive Control
Soleimani Bidgoli, Hamid ULiege; Valverde, Gustavo; Aristidou, Petros et al

in Rueda Torres, Jose (Ed.) Dynamic Vulnerability Assessment and Intelligent Control for Sustainable Power Systems (in press)

Detailed reference viewed: 94 (18 ULiège)
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See detailSteady-State, Nonlinear Analysis of Large Arrays of Electrically Actuated Micromembranes Vibrating in a Fluid
Halbach, Alexandre ULiege; Geuzaine, Christophe ULiege

in Engineering with Computers (in press)

This paper describes a robust and efficient method to obtain the steady-state, nonlinear behaviour of large arrays of electrically actuated micromembranes vibrating in a fluid. The nonlinear ... [more ▼]

This paper describes a robust and efficient method to obtain the steady-state, nonlinear behaviour of large arrays of electrically actuated micromembranes vibrating in a fluid. The nonlinear electromechanical behavior and the multiple vibration harmonics it creates are fully taken into account thanks to a multiharmonic finite element formulation, generated automatically using symbolic calculation. A domain decomposition method allows to consider large arrays of micromembranes by efficiently distributing the computational cost on parallel computers. Two- and three- dimensional examples highlight the main properties of the proposed method. [less ▲]

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See detailAutomated multimodal volume registration based on supervised 3D anatomical landmark detection
Vandaele, Rémy ULiege; LALLEMAND, François ULiege; MARTINIVE, Philippe ULiege et al

in SCITEPRESS Digital Library (in press)

We propose a new method for automatic 3D multimodal registration based on anatomical landmark detection. Landmark detectors are learned independantly in the two imaging modalities using Extremely ... [more ▼]

We propose a new method for automatic 3D multimodal registration based on anatomical landmark detection. Landmark detectors are learned independantly in the two imaging modalities using Extremely Randomized Trees and multi-resolution voxel windows. A least-squares fitting algorithm is then used for rigid registration based on the landmark positions as predicted by these detectors in the two imaging modalities. Experiments are carried out with this method on a dataset of pelvis CT and CBCT scans related to 45 patients. On this dataset, our fully automatic approach yields results very competitive with respect to a manually assisted state-of-the-art rigid registration algorithm. [less ▲]

Detailed reference viewed: 167 (33 ULiège)
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See detailEnhancement of Transmission System Voltage Stability through Local Control of Distribution Networks
Valverde, Gustavo; Aristidou, Petros; Van Cutsem, Thierry ULiege

in Rueda Torres, Jose (Ed.) Dynamic Vulnerability Assessment and Intelligent Control for Sustainable Power Systems (in press)

Detailed reference viewed: 63 (4 ULiège)
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See detailProbabilistic Reliability Management Approach and Criteria for Power System Short-term Operational Planning
Karangelos, Efthymios ULiege; Wehenkel, Louis ULiege

in Probabilistic Reliability Management Approach and Criteria for Power System Short-term Operational Planning (in press)

This paper develops a probabilistic decision making framework for reliability management in the short-term operational planning context. We build upon our recent work, which proposed a probabilistic ... [more ▼]

This paper develops a probabilistic decision making framework for reliability management in the short-term operational planning context. We build upon our recent work, which proposed a probabilistic reliability management approach and criterion (RMAC) for the latest decision making opportunity of real-time system operation. Here, we transpose the RMAC to the preceding problem instance of short-term operational planning, wherein i) risk is aggravated by the uncertainty on power injections and weather conditions, and, ii) the problem scope concerns choosing `strategic' actions (e.g., starting additional generating units, granting outage requests for maintenance, etc.) to facilitate decision making during the forthcoming real-time system operation. To anticipate on the latter, we formalize the notion of a real-time `proxy' as a simplified model of the real-time decision making context, adequately accurate for the purpose of operational planning decision making. Stating a first proposal for such a proxy, we mathematically formulate the RMAC for short-term operational planning as a multi-stage stochastic decision making problem and demonstrate its main features by case studies on a modified version of the single area IEEE RTS-96 system. [less ▲]

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See detailSearching for Plausible N-k Contingencies Endangering Voltage Stability
Weckesser, Johannes ULiege; Van Cutsem, Thierry ULiege

in IEEE International Conference on Innovative Smart Grid Technologies IEEE ISGT Europe 2017, Turin 26-29 September 2017 (in press)

This paper presents a novel search algorithm using time-domain simulations to identify plausible N-k contingencies endangering voltage stability. Starting from an initial list of disturbances ... [more ▼]

This paper presents a novel search algorithm using time-domain simulations to identify plausible N-k contingencies endangering voltage stability. Starting from an initial list of disturbances, progressively more severe contingencies are investigated. After simulation of a N-k contingency, the simulation results are assessed. If the system response is unstable, a plausible harmful contingency sequence has been found. Otherwise, components affected by the contingencies are considered as candidate next event leading to N-(k+1) contingencies. This implicitly takes into account hidden failures of component protections. The performance of the proposed search algorithm is compared to a brute-force algorithm and demonstrated on the IEEE Nordic test system. [less ▲]

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See detailCombined Local and Centralized Voltage Control in Active Distribution Networks
Soleimani Bidgoli, Hamid ULiege; Van Cutsem, Thierry ULiege

in IEEE Transactions on Power Systems (in press)

A two-level real-time voltage control scheme is proposed to keep voltages within specified limits in distribution grids using Distributed Generation Units (DGUs). It combines a local and a centralized ... [more ▼]

A two-level real-time voltage control scheme is proposed to keep voltages within specified limits in distribution grids using Distributed Generation Units (DGUs). It combines a local and a centralized control of their reactive powers. The local control provides fast response after a disturbance, reducing its impact and enhancing voltage quality. The centralized control uses measurements collected throughout the network to bring the voltages inside tighter limits and balance the various DGU contributions. To this purpose, it adjusts in a coordinated way their reactive power set-points, taking into account the local controls. This discrete control solves at each time step a multi-time-step constrained optimization inspired of Model Predictive Control. The method effectiveness is demonstrated on a 75-bus test system hosting 22 DGUs. [less ▲]

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See detailElectric Power Network State Tracking from Multirate Measurements
Alcaide-Moreno, Boris; Fuerte-Esquivel, Claudio; Glavic, Mevludin ULiege et al

in IEEE Transactions on Instrumentation and Measurement (in press)

This paper proposes a novel tracking state estimator to process both fast-rate synchronized phasor and slow rate SCADA measurements. The former are assumed to be in limited number. The latter are ... [more ▼]

This paper proposes a novel tracking state estimator to process both fast-rate synchronized phasor and slow rate SCADA measurements. The former are assumed to be in limited number. The latter are exploited as and when they arrive to the control center. In order to restore observability, after each execution of the tracking state estimator, forecasted SCADA measurements are used as pseudo-measurements in the next estimation. An event detection analysis allows assessing if the system is in quasi steady-state. If so, an innovation analysis is performed to identify and eliminate erroneous SCADA measurements. The system state is computed by Hachtel’s augmented matrix method. The option of exploiting time-tagged SCADA measurements is also considered. The method is illustrated through detailed dynamic simulations of a test system evolving towards voltage collapse, with and without emergency control. [less ▲]

Detailed reference viewed: 72 (11 ULiège)
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See detailCharacterization of superconductor magnetic properties in crossed magnetic fields
Vanderbemden, Philippe ULiege

in Larbalestier, David; Cardwell, David (Eds.) Handbook of Superconducting Materials (2nd edition) (in press)

This chapter deals with the characterization of the magnetic properties of superconductors which are subjected to magnetic fields that have been applied along two orthogonal directions, which is commonly ... [more ▼]

This chapter deals with the characterization of the magnetic properties of superconductors which are subjected to magnetic fields that have been applied along two orthogonal directions, which is commonly referred to as a “crossed” magnetic field configuration. The purpose of this chapter is to describe the techniques that are useful to perform crossed field experiments, with an emphasis placed on practical aspects that are useful for designing the system and for understanding the measured data. This chapter is organized as follows. In Section 2, the key terms involved in the literature dealing with crossed field effects are defined. Section 3 deals with experimental methods and some key parameters will be outlined. In Section 4, practical conclusions will be drawn and next challenges in this area will be discussed. [less ▲]

Detailed reference viewed: 34 (7 ULiège)
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See detailIPCAPS: an R package for iterative pruning to capture population structure
Chaichoompu, Kridsadakorn ULiege; Abegaz Yazew, Fentaw; Tongsima, Sissades et al

in Bioinformatics : Application Notes (in press)

Resolving population genetic structure is challenging, especially when dealing with closely related populations. Although Principal Component Analysis (PCA)-based methods and genomic var- iation with ... [more ▼]

Resolving population genetic structure is challenging, especially when dealing with closely related populations. Although Principal Component Analysis (PCA)-based methods and genomic var- iation with single nucleotide polymorphisms (SNPs) are widely used to describe shared genetic an- cestry, improvements can be made targeting fine-level population structure. This work presents an R package called IPCAPS, which uses SNP information for resolving possibly fine-level population structure. The IPCAPS routines are built on the iterative pruning Principal Component Analysis (ipP- CA) framework to systematically assign individuals to genetically similar subgroups. Our tool is able to detect and eliminate outliers in each iteration to avoid misclassification. It can be extended to de- tect subtle subgrouping in patients as well. In addition, IPCAPS supports different measurement scales for variables used to identify substructure. Hence, panels of gene expression and methylation data can be accommodated. [less ▲]

Detailed reference viewed: 60 (12 ULiège)
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See detailA biased random key genetic algorithm applied to the electric distribution network reconfiguration problem
de Faria Jr., Haroldo; Resende, Mauricio; Ernst, Damien ULiege

in Journal of Heuristics (in press)

This work presents a biased random-key genetic algorithm (BRKGA) to solve the electric distribution network reconfiguration problem (DNR). The DNR is one of the most studied combinatorial optimization ... [more ▼]

This work presents a biased random-key genetic algorithm (BRKGA) to solve the electric distribution network reconfiguration problem (DNR). The DNR is one of the most studied combinatorial optimization problems in power system analysis. Given a set of switches of an electric network that can be opened or closed, the objective is to select the best configuration of the switches to optimize a given network objective while at the same time satisfying a set of operational constraints. The good performance of BRKGAs on many combinatorial optimization problems and the fact that it has never been applied to solve DNR problems are the main motivation for this research. A BRKGA is a variant of random-key genetic algorithms, where one of the parents used for mating is biased to be of higher fitness than the other parent. Solutions are encoded by using random keys, which are represented as vectors of real numbers in the interval (0,1), thus enabling an indirect search of the solution inside a proprietary search space. The genetic operators do not need to be modified to generate only feasible solutions, which is an exclusive task of the decoder of the problem. Tests were performed on standard distribution systems used in DNR studies found in the technical literature and the performance and robustness of the BRKGA were compared with other GA implementations. [less ▲]

Detailed reference viewed: 123 (3 ULiège)
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See detailDynamic Equivalent of a Distribution Grid Hosting Dispersed Photovoltaic Units
Chaspierre, Gilles ULiege; Panciatici, Patrick; Van Cutsem, Thierry ULiege

in IREP’2017 Symposium: X Bulk Power Systems Dynamics and Control Symposium (in press)

This paper deals with the derivation of a simplified model of a distribution network hosting dispersed photovoltaic units. The model is aimed at short-term dynamic simulations of a transmission grid in ... [more ▼]

This paper deals with the derivation of a simplified model of a distribution network hosting dispersed photovoltaic units. The model is aimed at short-term dynamic simulations of a transmission grid in response to large disturbances. In a first step, a generic dynamic model of a photovoltaic unit is proposed, focusing on its interactions with the grid, in particular the controls triggered by voltage disturbances. The model takes into account various present and near-future grid codes. In a second step, a dynamic equivalent is derived accounting for the distribution network, the dispersed photovoltaic units, as well as static and dynamic (motor) loads. This equivalent is of the “grey-box” type and its parameters are tuned in the least-square sense to match the dynamic response of the original, unreduced system. Simulation results are reported on a detailed 913-bus distribution system subject to faults at transmission level. [less ▲]

Detailed reference viewed: 103 (25 ULiège)
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See detailPulse-Based Control Using Koopman Operator Under Parametric Uncertainty
Sootla, Aivar; Ernst, Damien ULiege

in IEEE Transactions on Automatic Control (in press)

In applications, such as biomedicine and systems/synthetic biology, technical limitations in actuation complicate implementation of time-varying control signals. In order to alleviate some of these ... [more ▼]

In applications, such as biomedicine and systems/synthetic biology, technical limitations in actuation complicate implementation of time-varying control signals. In order to alleviate some of these limitations, it may be desirable to derive simple control policies, such as step functions with fixed magnitude and length (or temporal pulses). In this technical note, we further develop a recently proposed pulse-based solution to the convergence problem, i.e., minimizing the convergence time to the target exponentially stable equilibrium, for monotone systems. In particular, we extend this solution to monotone systems with parametric uncertainty. Our solutions also provide worst-case estimates on convergence times. Furthermore, we indicate how our tools can be used for a class of non-monotone systems, and more importantly how these tools can be extended to other control problems. We illustrate our approach on switching under parametric uncertainty and regulation around a saddle point problems in a genetic toggle switch system. [less ▲]

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See detailAn Optimal Control Formulation of Pulse-Based Control Using Koopman Operator
Sootla, Aivar; Mauroy, Alexandre; Ernst, Damien ULiege

in Automatica (in press)

In many applications, and in systems/synthetic biology in particular, it is desirable to compute control policies that force the trajectory of a bistable system from one equilibrium (the initial point) to ... [more ▼]

In many applications, and in systems/synthetic biology in particular, it is desirable to compute control policies that force the trajectory of a bistable system from one equilibrium (the initial point) to another equilibrium (the target point), or in other words to solve the switching problem. It was recently shown that, for monotone bistable systems, this problem admits easyto-implement open-loop solutions in terms of temporal pulses (i.e., step functions of fixed length and fixed magnitude). In this paper, we develop this idea further and formulate a problem of convergence to an equilibrium from an arbitrary initial point. We show that this problem can be solved using a static optimization problem in the case of monotone systems. Changing the initial point to an arbitrary state allows to build closed-loop, event-based or open-loop policies for the switching/convergence problems. In our derivations we exploit the Koopman operator, which offers a linear infinite-dimensional representation of an autonomous nonlinear system. One of the main advantages of using the Koopman operator is the powerful computational tools developed for this framework. Besides the presence of numerical solutions, the switching/convergence problem can also serve as a building block for solving more complicated control problems and can potentially be applied to non-monotone systems. We illustrate this argument on the problem of synchronizing cardiac cells by defibrillation. Potentially, our approach can be extended to problems with different parametrizations of control signals since the only fundamental limitation is the finite time application of the control signal. [less ▲]

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See detail355nm UV laser patterning and post-processing of FR4 PCB for fine pitch components integration
Dupont, François ULiege; Stoukatch, Serguei ULiege; Laurent, Philippe ULiege et al

in Optics & Lasers in Engineering (2018), 100

Detailed reference viewed: 29 (6 ULiège)
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See detailAn Observation-Based Middlebox Policy Taxonomy
Edeline, Korian ULiege; Donnet, Benoît ULiege

in 13th International Conference on emerging Networking EXperiments and Technologies Student Workshop (2017, December 12)

Recent years have seen the rise of middleboxes, such as NATs, firewalls, or TCP accelerators. Those middleboxes play an important role in today's Internet, including enterprise networks and cellular ... [more ▼]

Recent years have seen the rise of middleboxes, such as NATs, firewalls, or TCP accelerators. Those middleboxes play an important role in today's Internet, including enterprise networks and cellular networks. However, despite their undisputable success in modern network architecture, their actual impact on packets, traffic, and network performance is not that much understood. In this paper, we propose a path impairment oriented middlebox classification that aims at categorizing the initial purpose of a middlebox policy as well as its potential complications. [less ▲]

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See detailDiscovering Routers in Load-balanced Paths
Grailet, Jean-François ULiege; Donnet, Benoît ULiege

in 13th International Conference on emerging Networking EXperiments and Technologies Student Workshop (2017, December 12)

Usually, a set of Traceroute measurements collected for a large amount of target IPs contain one or several route hops at which the IP interfaces vary from one measurement to another. These variations ... [more ▼]

Usually, a set of Traceroute measurements collected for a large amount of target IPs contain one or several route hops at which the IP interfaces vary from one measurement to another. These variations occur even if several measurements share the same length and the same last hops. This is likely a consequence of load balancing, a traffic engineering policy which aims at sharing the load to ensure quality of service. In this paper, we consider the problem of conducting alias resolution on IP interfaces discovered via Traceroute and which are involved in load balancing. By conducting alias resolution in such a context, we want to verify if the IP interfaces involved in load balancing belong to unique routers, and more broadly, how relevant is alias resolution in this context. To do so, we use a slightly edited version of TreeNET, a topology discovery tool which relies on a tree-like structure based on Traceroute measurements to map a target domain. The upgraded TreeNET along the measurements described in this paper are both freely available online. [less ▲]

Detailed reference viewed: 38 (12 ULiège)
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See detailSepsis prediction in critically ill patients by platelet activation markers on ICU admission: a prospective pilot study
LAYIOS, Nathalie ULiege; Delierneux, Céline ULiege; Hego, Alexandre ULiege et al

in Intensive Care Medicine Experimental (2017), 5(1), 32

Background: Platelets have been involved in both surveillance and host defense against severe infection. To date, whether platelet phenotype or other hemostasis components could be associated with ... [more ▼]

Background: Platelets have been involved in both surveillance and host defense against severe infection. To date, whether platelet phenotype or other hemostasis components could be associated with predisposition to sepsis in critical illness remains unknown. The aim of this work was to identify platelet markers that could predict sepsis occurrence in critically ill injured patients. Results: This single-center, prospective, observational, 7-month study was based on a cohort of 99 non-infected adult patients admitted to ICUs for elective cardiac surgery, trauma, acute brain injury and post-operative prolonged ventilation and followed up during ICU stay. Clinical characteristics and severity score (SOFA) were recorded on admission. Platelet activation markers, including fibrinogen binding to platelets, platelet membrane P-selectin expression, plasma soluble CD40L, and platelet-leukocytes aggregates were assayed by flow cytometry at admission and 48h later, and also at the time of sepsis diagnosis (Sepsis-3 criteria) and 7 days later for sepsis patients. Hospitalization data and outcomes were also recorded. Of the 99 patients, 19 developed sepsis after a median time of 5 days. SOFA at admission was higher; their levels of fibrinogen binding to platelets (platelet-Fg) and of D-dimers were significantly increased compared to the other patients. Levels 48h after ICU admission were no longer significant. Platelet-Fg % was an independent predictor of sepsis (P = 0.030). By ROC curve analysis cutoff points for SOFA (AUC=0.85) and Platelet-Fg (AUC=0.75) were 8 and 50%, respectively. The prior risk of sepsis (19%) increased to 50% when SOFA was above 8, to 46% when Platelet-Fg was above 50%, and to 87% when both SOFA and Platelet-Fg were above their cutoff values. By contrast, when the two parameters were below their cutoffs, the risk of sepsis was negligible (3.8%). Patients with sepsis had longer ICU and hospital stays and higher death rate. Conclusion: In addition to SOFA, platelet-bound fibrinogen levels assayed by flow cytometry within 24h of ICU admission help identifying critically ill patients at risk of developing sepsis. [less ▲]

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See detailTime to make a choice between a fully liberal or fully regulated model for the electrical industry
Ernst, Damien ULiege

Conference given outside the academic context (2017)

Detailed reference viewed: 40 (2 ULiège)