Études des contrôles des réseaux de distribution dans l'analyse d'écoulement de puissance multiphasé

RÉSUMÉ Ce mémoire présente un modèle permettant d’intégrer et de gérer les contrôles des prises des transformateurs et des régulateurs dans l’analyse nodale modifiée augmentée (MANA). Le modèle proposé a pour objectif de rendre l’analyse d’écoulement de puissance, basée sur l’approche MANA, plus précise et plus rapide au niveau de la gestion des prises. La solution proposée est une modélisation générale applicable à tous les types de transformateurs, autotransformateurs, et régulateurs sans être limité par les différentes configurations et/ou décalages de phase. Il permet aussi de modéliser les contrôles de noeuds éloignés (paramètres RX). En ce sens, ce travail représente une contribution significative au niveau de l’algorithme de répartition de puissance utilisant l’approche MANA. La méthodologie adoptée consiste d’abord à étudier le fonctionnement des contrôles existant pour les appareils de régulation à savoir les transformateurs et les régulateurs. Ensuite, un outil d’analyse et de test est développé sous MATLAB. Cet outil permet d’obtenir rapidement la matrice MANA de tout réseau modélisé dans le logiciel commercial CYME. Plus précisément, ce programme récupère les données de tous les équipements d’un réseau à partir du fichier de CYME. Par la suite, ces données sont enregistrées selon une formulation orientée objet, puis utilisée pour générer de façon systématique la matrice MANA correspondante. Cet outil est par la suite utilisé pour modéliser les contrôles de différents équipements ainsi que pour tester leur intégration dans la matrice MANA. La dernière étape de ce projet consiste à valider le fonctionnement des modèles proposés. La validation des modèles proposés pour le contrôle des prises sera effectuée en vérifiant que les résultats obtenus respectent les consignes spécifiées. Les résultats de l’écoulement de puissance seront comparés avec ceux du logiciel CYME. Les résultats obtenus démontrent que l’intégration du contrôle des prises dans MANA apporte une solution robuste et précise sans dégrader la performance et la flexibilité propre à l’approche matricielle.----------ABSTRACT This thesis presents a model for integrating and managing voltage control tap changers in the modified augmented nodal analysis (MANA). The objective of the proposed solution is to make the management of tap changers, in power flow analysis based on MANA, faster and more accurate. The proposed solution is a general approach suitable for all types of transformers, autotransformer and regulators without being limited by device configurations or phase shift. It also allows integrating remote voltage control (RX settings and load center), and managing regulators and transformers connected in series. This represents the main contribution to the MANA formulation for solving distribution network power flow. The adopted methodology starts by studying the existing control devices, namely transformers and regulators. Next, a development and analysis tool is developed in MATLAB. This tool provides the MANA matrix of any network modeled in commercial software CYME. More specifically, the program retrieves the data from all devices in the CYME file. Thereafter, this data is organized in an object – oriented format and used to generate systematically the corresponding matrix formulation. This tool is then used for modeling the control devices and to test their integration into the Jacobian matrix. The final stage of this project is to validate the results of the proposed control models. The validation of the proposed models will be carried out by checking that the results meet the specified desired voltage. The power flow results will be compared to those of CYME software. The results of the test cases shows that the integration of tap control in the MANA formulation provides an accurate solution without degrading the performance and flexibility which come with the MANA approach

Host-feeding patterns of Aedes (Aedimorphus) vexans arabiensis, a Rift Valley Fever virus vector in the Ferlo pastoral ecosystem of Senegal

Background: Host-vector contact is a key factor in vectorial capacity assessment and thus the transmission of mosquito-borne viruses such as Rift Valley Fever (RVF), an emerging zoonotic disease of interest in West Africa. The knowledge of the host-feeding patterns of vector species constitutes a key element in the assessment of their epidemiological importance in a given environment. The aim of this work was to identify the blood meal origins of the mosquito Aedes vexans arabiensis, the main vector of RVF virus in the Ferlo pastoral ecosystem of Senegal. Methodology/principal findings: Engorged female mosquitoes were collected in Younoufe´re´ in the pastoral ecosystem in the Ferlo region during the 2014 rainy season. CO2-baited CDC light traps were set at six points for two consecutive nights every month from July to November. Domestic animals present around traps were identified and counted for each trapping session. Blood meal sources of engorged mosquitoes were identified using a vertebrate-specific multiplexed primer set based on cytochrome b. Blood meal sources were successfully identified for 319 out of 416 blood-fed females (76.68%), of which 163 (51.1%) were single meals, 146 (45.77%) mixed meals from two different hosts and 10 (3.13%) mixed meals from three different hosts. Aedes vexans arabiensis fed preferentially on mammals especially on horse compared to other hosts (FR = 46.83). Proportions of single and mixed meals showed significant temporal and spatial variations according to the availability of the hosts. Conclusion: Aedes vexans arabiensis shows an opportunistic feeding behavior depending on the host availability. This species fed preferentially on mammals especially on horses (primary hosts) and ruminants (secondary hosts)

Measurements of the Most Significant Software Security Weaknesses

In this work, we provide a metric to calculate the most significant software security weaknesses as defined by an aggregate metric of the frequency, exploitability, and impact of related vulnerabilities. The Common Weakness Enumeration (CWE) is a well-known and used list of software security weaknesses. The CWE community publishes such an aggregate metric to calculate the `Most Dangerous Software Errors'. However, we find that the published equation highly biases frequency and almost ignores exploitability and impact in generating top lists of varying sizes. This is due to the differences in the distributions of the component metric values. To mitigate this, we linearize the frequency distribution using a double log function. We then propose a variety of other improvements, provide top lists of the most significant CWEs for 2019, provide an analysis of the identified software security weaknesses, and compare them against previously published top lists.Comment: 12 page

Flow Control in Time-Varying, Random Supply Chains

Today’s supply chains are more and more complex. They depend on a network of independent, yet interconnected moving parts. They rely on critical infrastructures and experience a lot of time variability and randomness. Designing strategies that deal with such constantly changing supply chains is necessary in this increasingly globalized economy where supply chain disruptions have impacts that propagate not only locally but also globally. In this paper we propose a randomized flow control algorithm for a time varying, random supply chain network. We formulate a constrained stochastic optimization problem that maximizes the profit function in terms of the long-run, time-average rates of the flows in the supply chain. We show that our algorithm, which is based on queueing theory and stochastic analysis concepts, can get arbitrarily close to the solution of the aforementioned optimization problem. In addition, we describe how the flow control algorithm can be extended to a multiple firms supply chain setup and present numerical simulations of our algorithm for different supply chain topologies

The Role of User-Agent Interactions on Mobile Money Practices in Kenya and Tanzania

Digital financial services have catalyzed financial inclusion in Africa. Commonly implemented as a mobile wallet service referred to as mobile money (MoMo), the technology provides enormous benefits to its users, some of whom have long been unbanked. While the benefits of mobile money services have largely been documented, the challenges that arise -- especially in the interactions between human stakeholders -- remain relatively unexplored. In this study, we investigate the practices of mobile money users in their interactions with mobile money agents. We conduct 72 structured interviews in Kenya and Tanzania (n=36 per country). The results show that users and agents design workarounds in response to limitations and challenges that users face within the ecosystem. These include advances or loans from agents, relying on the user-agent relationships in place of legal identification requirements, and altering the intended transaction execution to improve convenience. Overall, the workarounds modify one or more of what we see as the core components of mobile money: the user, the agent, and the transaction itself. The workarounds pose new risks and challenges for users and the overall ecosystem. The results suggest a need for rethinking privacy and security of various components of the ecosystem, as well as policy and regulatory controls to safeguard interactions while ensuring the usability of mobile money.Comment: To be published in IEEE Symposium on Security and Privacy 202