Effet d'échelle sur la simulation du ruissellement en milieu urbain

Ce travail consiste en l’élaboration d’une méthodologie systématique qui permet de substituer une modélisation hydraulique simplifiée à une modélisation détaillée d’un réseau d’assainissement. L’approche préconisée est basée sur une analyse multi-paramètre du processus du drainage en milieu urbain. Les paramètres adimensionnels retenus dans cette analyse font intervenir les caractéristiques du bassin versant, les caractéristiques du réseau et celles de la pluie. Pour donner à cette approche un cadre plus général, les auteurs ont mené cette analyse sur des réseaux et des pluies synthétiques couvrant un spectre très large de cas concrets. La méthodologie élaborée a fait l’objet d’une étude de validation sur le bassin No1 de l’arrondissement de Verdun (Montréal). La concordance entre les débits mesurés à l’exutoire du bassin et les débits simulés par cette approche est avantageusement satisfaisante. Les modèles de transformation découlant de cette analyse, permettant le passage d’une modélisation globale à une modélisation détaillée constituent une avancée très significative pour une gestion en temps réel et optimisée des réseaux d’assainissement.It is possible to simulate the hydraulic functioning of a given network either with a detailed “microscopic” model at the street section scale or with a global “macroscopic” model which generates total flow rates at the outlet of a basin. The microscopic model is useful when one is concerned with the hydraulic performance of individual conduit sections and the precise locations of problematic areas within a network. Macroscopic modeling is mainly useful when one is interested exclusively by the exit flow rates of a basin. This may be the case in interceptor management where the flow rate is a parameter of the global optimization procedure, within the framework of real time management of regulators. In this case, detailed modeling of a network is unnecessary. On the other hand, detailed modeling requires that a voluminous data base be built and maintained, implying expenditures exceeding the resources of small municipalities.The present work consists in elaborating a systematic method which allows one to substitute simplified hydraulic modeling for detailed modeling of a drainage network. The approach is based on the analysis of the drainage parameters in an urban environment. The non-dimensional groupings retained in this analysis comprise the characteristics a of the basin, of the network and of rainfall. In order to provide a greater generality to this approach, the authors applied the analysis to synthetic networks and rainfalls covering a wide range of specific cases.From a practical viewpoint, the objective was to link the peak flow rates and the time to peak of the global model to those of the detailed model of a basin. Two transfer functions have thus been proposed in order to obtain the peak flow rate and the time to peak of the detailed model as functions of the same parameters provided by the global model. The parameters retained for the transfer function are the density of the drainage network and the rate of filling of the network.In order to implement the proposed method and perform the required hydraulic and hydrological simulations, the authors have used the SWMM program (Storm Water Management Model). 180 simulations have thus been completed, 15 for each type of network and for each type of rainfall. For every combination, one computes the peak flow rate and the time to peak as obtained by the global and detailed models of the basin.The proposed multi-criterion analysis revealed that the total discrepancy between simplified and detailed modeling of a drainage network is very important. Within the range of the assumed densities, the difference can be as great as 50%. This discrepancy between global and detailed modeling is explained by the storage capacity of the different types of networks. Indeed, for a same given drained area, a network provides additional storage with increasing length of the network and therefore with increasing drainage density.On the basis of the above finding, a global model cannot replace a detailed model without the use of required corrections for the computation of peak flow rates for a given specific case. In order to resolve this difficulty, it is recommended to use the empirical models proposed herein to reduce the discrepancy and thereby obtain the appropriate corrections.The proposed method has been subjected to a validation program on basin No.1 of the Verdun borough. Agreement between the flow rates measured at the entrance of the Rhéaume pumping station and those simulated by the proposed method is very satisfactory. The transformation models derived from the analysis allow for the transition from a global model to a detailed one and provide a significant improvement in optimized real time management of drainage networks

Measuring Thickness and Pretilt in Reflective Vertically Aligned Nematic Liquid Crystal Displays

Pretilt angle is a parameter of the utmost importance in the ultimate performance of vertically-aligned negative nematic LC displays. When these devices work in reflective mode, as is the LCOS microdisplays, accurate measurement of pretilt angles becomes a difficult problem, since usual experimental setups based on retardation of the polarization components of the impinging light are proportional to the product effective birefringence (neff - no) times thickness, and any attempt to separate these variables is cancelled out by symmetry. This work shows a relatively simple method capable of separating both variables. An experimental setup specifically aimed at vertically aligned reflective cells has been prepared. At the same time, a simulation model has been developed taking into account the properties of actual reflective displays. Comparison between experimental and theoretical results shows some discrepancies that can be explained assuming that the LC profile contains a residual twist. Including that twist in the model, an excellent agreement between theory and experiment has been achieved. Matching of simulations and measurements yields to the separate determination of pretilt angle and thickness and gives good estimates for the residual twist angle

V-Shape Liquid Crystal-Based Retromodulator Air to Ground Optical Communications

This paper describes the use of a 2D liquid crystal retro-modulator as a free space, wireless, optical link. The retro-modulator is made up of a retro-reflecting cornercube onto which 2 cascaded V-shape smectics liquid crystal modulators are mounted. The communication link differs with respect to more conventional optical links in not using amplitude (nor frequency) modulation, but instead state-of-polarisation (SOP) modulation known as Polarisation Shift Keying (PolSK). PolSK has the advantage over amplitude modulation, that it is less sensitive to changes in the visibility of the atmosphere, and increases inherently the bandwidth of the link. The implementation of PolSK both in liquid crystal based and in retro-modulated communication are novelties

On modeling and real-time simulation of a robust adaptive controller applied to a multicellular power converter

Introduction. This paper describes the simulation and the robustness assessment of a DC-DC power converter designed to interface a dual-battery conversion system. The adopted converter is a Buck unidirectional and non-isolated converter, composed of three cells interconnected in parallel and operating in continuous conduction mode. Purpose. In order to address the growing challenges of high switching frequencies, a more stable, efficient, and fixed-frequency-operating power system is desired. Originality. Conventional sliding mode controller suffers from high-frequency oscillation caused by practical limitations of system components and switching frequency variation. So, we have explored a soft-switching technology to deal with interface problems and switching losses, and we developed a procedure to choose the high-pass filter parameters in a sliding mode-controlled multicell converter. Methods. We suggest that the sliding mode is controlled by hysteresis bands as the excesses of the band. This delay in state exchanges gives a signal to control the switching frequency of the converter, which, in turn, produces a controlled trajectory. We are seeking an adaptive current control solution to address this issue and adapt a variable-bandwidth of the hysteresis modulation to mitigate nonlinearity in conventional sliding mode control, which struggles to set the switching frequency. Chatter problems are therefore avoided. A boundary layer-based control scheme allows multicell converters to operate with a fixed-switching-frequency. Practical value. Simulation studies in the MATLAB / Simulink environment are performed to analyze system performance and assess its robustness and stability. Thus, our converter is more efficient and able to cope with parametric variation.Вступ. У статті описується моделювання та оцінка надійності силового перетворювача постійного струму, призначеного для взаємодії із системою перетворення з двома батареями. Прийнятий перетворювач є односпрямованим і неізольованим перетворювачем Бака, що складається з трьох паралельно з’єднаних між собою осередків, що працюють в режимі безперервної провідності. Мета. Для вирішення проблем, пов’язаних з високими частотами перемикання, потрібна більш стабільна, ефективна система живлення з фіксованою частотою. Оригінальність. Звичайний регулятор ковзного режиму страждає від високочастотних коливань, викликаних практичними обмеженнями компонентів системи та зміною частоти перемикання. Отже, ми дослідили технологію м’якого перемикання для вирішення проблем інтерфейсу та комутаційних втрат, а також розробили процедуру вибору параметрів фільтра верхніх частот у багатоосередковому перетворювачі зі ковзним режимом. Методи. Ми припускаємо, що ковзний режим управляється смугами гістерезису як надлишками смуги. Ця затримка обміну станами дає сигнал управління частотою перемикання перетворювача, який, своєю чергою, створює керовану траєкторію. Ми шукаємо рішення для адаптивного керування струмом, щоб вирішити цю проблему і адаптувати гістерезисну модуляцію зі змінною смугою пропускання для пом’якшення нелінійності у звичайному ковзному режимі керування, яке щосили намагається встановити частоту перемикання. Таким чином вдається уникнути проблем із деренчанням. Схема керування на основі прикордонного шару дозволяє перетворювачам з кількома осередками працювати з фіксованою частотою перемикання. Практична цінність. Імітаційне моделювання у середовищі MATLAB/Simulink виконується для аналізу продуктивності системи та оцінки її надійності та стабільності. Таким чином, наш перетворювач ефективніший і здатний справлятися зі зміною параметрів

Marine Propulsion by the Injection of Compressed Air

International audienc

Federated Learning and Meta Learning: Approaches, Applications, and Directions

Over the past few years, significant advancements have been made in the field of machine learning (ML) to address resource management, interference management, autonomy, and decision-making in wireless networks. Traditional ML approaches rely on centralized methods, where data is collected at a central server for training. However, this approach poses a challenge in terms of preserving the data privacy of devices. To address this issue, federated learning (FL) has emerged as an effective solution that allows edge devices to collaboratively train ML models without compromising data privacy. In FL, local datasets are not shared, and the focus is on learning a global model for a specific task involving all devices. However, FL has limitations when it comes to adapting the model to devices with different data distributions. In such cases, meta learning is considered, as it enables the adaptation of learning models to different data distributions using only a few data samples. In this tutorial, we present a comprehensive review of FL, meta learning, and federated meta learning (FedMeta). Unlike other tutorial papers, our objective is to explore how FL, meta learning, and FedMeta methodologies can be designed, optimized, and evolved, and their applications over wireless networks. We also analyze the relationships among these learning algorithms and examine their advantages and disadvantages in real-world applications