Dynamical Modelling of a Wastewater Treatment Process of the Metallurgical Industry

In this paper we consider the dynamical modelling and parameter identification of a biological wastewater treatment process from the galvanisation industry used to remove a mixture of organic matter and surface-active agents. In the present study we have considered mainly the measurements of dissolved oxygen and COD (Chemical Oxygen Demand) collected on laboratory and pilot-scale processes. From the identification study, we can conclude that the degradation is characterized by two reactions: one part of the easily biodegradable effluent is degraded with fast kinetics while the remaining part of the effluent is degraded via a slower reaction. This has been modelled by considering two different classes of substrates that indeed correspond to real components of the mixture

Named Entities In Conversation Fingerprinting For Knowledge Dissemination Detection

The overall context is about how to evaluate the interactions between employees in an organization and their ability to disseminate the knowledge throughout the different departments and teams. This is highly relevant for Human Resources Department in order to identify the skills in the organization, the bottleneck in communication between teams and the optimization of resources in the case of the same skill or knowledge appear in different places in the organization

A tighter continuous time formulation for the cyclic scheduling of a mixed plant

Abstract In this paper, based on the cyclic scheduling formulation of Schilling and Pantelides [22], we propose a continuous time mixed integer linear programming (MILP) formulation for the cyclic scheduling of a mixed plant, i.e. a plant composed of batch and continuous tasks. The cycle duration is a variable of the model and the objective is to maximize productivity. By using strengthening techniques and the analysis of small polytopes related to the problem formulation, we strengthen the initial formulation by tightening some initial constraints and by adding valid inequalities. We show that this strengthened formulation is able to solve moderate size problems quicker than the initial one. However, for real size cases, it remains difficult to obtain the optimal solution of the scheduling problem quickly. Therefore, we introduce MILP-based heuristic methods in order to solve these larger instances, and show that they can provide quite good feasible solutions quickly

A tighter continuous time formulation for the cyclic scheduling of a mixed plant

In this paper, based on the cyclic scheduling formulation of Schilling and Pantelides [22], we propose a continuous time mixed integer linear programming (MILP) formulation for the cyclic scheduling of a mixed plant, i.e. a plant composed of batch and continuous tasks. The cycle duration is a variable of the model and the objective is to maximize productivity. By using strengthening techniques and the analysis of small polytopes related to the problem formulation, we strengthen the initial formulation by tightening some initial constraints and by adding valid inequalities. We show that this strengthened formulation is able to solve moderate size problems quicker than the initial one. However, for real size cases, it remains difficult to obtain the optimal solution of the scheduling problem quickly. Therefore, we introduce MILP-based heuristic methods in order to solve these larger instances, and show that they can provide quite good feasible solutions quickly

From the measurement of synchrophasors to the identification of inter-area oscillations in power transmission systems

In the early 1980s, relaying engineers conceived a technology allowing a huge step forward in the monitoring of power system behavior: the synchrophasor, i.e. the estimation of a phasor representation - amplitude and phase - of a sinusoidal waveform at a given point in time thanks to highly accurate time synchronization of a digital relay. By measuring synchrophasors across the power system several times per second, and centralizing the appropriate information in a hierarchical way through a telecommunication network link, it is now possible to continuously monitor the state of very large systems at a high refresh rate. At the beginning, the phase angle information of synchrophasors was used to support or improve the performance of classic monitoring applications, such as state estimation and post-mortem analysis. Later, synchrophasors were found to be valuable for the detection and analysis of phenomena that were not monitored previously, such as system islanding and angular stability. This allows a better understanding of system behavior and the design of remedial actions in cases where system security appears to be endangered. Early detection and even prediction of instabilities, as well as validation and improvement of the dynamic models used for studies, have thus become possible.However, a power system is rarely stationary and the assumptions behind the definition of “phasor” are not completely fulfilled because the waveforms' frequency and amplitude are not constant over a signal cycle at fundamental frequency. Therefore, accuracy of synchrophasor measurements during dynamic events is an important performance criterion. Furthermore, when discontinuities (phase jumps and high magnitude variations) and harmonics disturb the measured analog signals as a consequence of switching actions or external disturbances, measurements provided to the “user” (the operator or the algorithms that will take decisions such as triggering alarms and remedial actions) require a certain robustness. The efforts underpinning this thesis have lead to the development of a method that ensures the robustness of the measurement. This scheme is described and tested in various conditions. In order to achieve a closer alignment between required and actual measurement performance, it is recommended to add an online indicator of phasor accuracy to the phasor data. Fast automated corrective actions and closed-loop control schemes relying on synchrophasors are increasingly deployed in power systems. The delay introduced in the measurement and the telecommunication can have a negative impact on the efficiency of these schemes. Therefore, measurement latency is also a major performance indicator of the synchrophasor measurement. This thesis illustrates the full measurement chain, from the measurement of analog voltages and currents in the power system to the use of these measurements for various purposes, with an emphasis on real-time applications: visualization, triggering of alarms in the control room or remedial actions, and integration in closed-loop controls. It highlights the various elements along this chain, which influence the availability, accuracy and delay of the data. The main focus is on the algorithm to estimate synchrophasors and on the tradeoff between accuracy and latency that arises in applications for which measurements are taken during dynamic events and the data must be processed within a very limited timeframe. If both fast phasors and slower, more accurate phasors are made available, the user would be able to select the set of phasors that are the most suitable for each application, by giving priority to either accuracy or a short delay.This thesis also tentatively identifies gaps between requirements and typical measurements in order to identify current barriers and challenges to the use of wide area measurement systems. A specific application, the continuous monitoring of oscillatory stability, was selected in order to illustrate the benefits of synchrophasors for the monitoring, analysis and control of power system behavior. This application requires a good phasor accuracy but can allow for some measurement delay, unless phasor data are used in an oscillation damping controller. In addition, it also relies on modal estimators, i.e. techniques for the online identification of the characteristics of oscillatory modes from measurements. This field of ongoing research is also introduced in this thesis.Doctorat en Sciences de l'ingénieurinfo:eu-repo/semantics/nonPublishe

hp-adaptivity in finite element methods for viscoelastic flow simulation

Doctorat en sciences appliquées -- UCL, 199

Scheduling of mixed batch-continuous production lines

The aim of this thesis is to solve scheduling problems for mixed production lines, i.e., involving batch and continuous processes, and some resource restrictions. Discrete time mixed integer programming (MIP) formulations were initially proposed in the literature in order to solve such problems, but their drawback is the large size of formulations for solving real industrial cases. This is why continuous time MIP formulations were then proposed. Various authors did compare different types of continuous time formulations, but did not try to improve or tighten such formulations. We first study a continuous time MIP formulation in order to model the cyclic scheduling of a mixed plant composed of batch and continuous processes. By improving the initial continuous time formulation of various special cases of the general problem, we obtain a tighter model formulation for these special cases. Then, we show for all special cases of the general problem that the improved formulations give better results (quality of solutions and/or running times) than the initial one but the exact resolution of large instances remains difficult. So, we investigated MIP based heuristic methods in order to obtain good feasible solutions quickly. We show that, for some large instances, the heuristic solutions given by the exact methods (truncated Branch-and-Bound) were not better than the feasible solutions given by the MIP based heuristic methods, and the latter use less CPU solution time. Finally, in contrast to the earlier models, we consider a scheduling problem in which we model the dynamics of the process. The processing times of the batch tasks are therefore considered to be variable in this case. They are determined as the solution of the system of differential equations describing the process dynamics, and influenced by process parameters that have to be optimized. For two test cases, we compare four solution methods and we show that a piecewise linear approximation method, based on the discretization of the space of state and command variables into simplices and on the discretization of time, gives a good feasible solution offering the best compromise between quality of the approximation of the solution of the differential equations and CPU solution time.Doctorat en sciences appliquées (FSA 3)--UCL, 200

La reconnaissance de l'indépendance du Kosovo, un enjeu pour l'avenir du droit international et une légitimation pour certains actes commis par le passé

Master [120] en droit, Université catholique de Louvain, 201

Efficient management of a connected microgrid in Belgium

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