Anticoloraciones en gráficas

114 páginas. Doctorado en Optimización.Uno de los problemas más conocidos y estudiados de la teoría de gráficas es el problema de coloración. Un caso especial del problema de coloración supuso una de las preguntas matemáticas más controvertidas de la humanidad, conocido ahora como el teorema de los cuatro colores. Controvertida por dos razones, la dificultad para encontrar su respuesta y porque en su demostración se emplearon por primera vez computadoras. En el mismo sentido de los problemas de coloración, Berge propuso en los 70’s un problema que 30 años después provocaría la creación de una teoría bajo el nombre del problema de anticoloración. El problema de Berge versa sobre lo siguiente. Dado un tablero de ajedrez de n_n, b reinas negras y w reinas blancas. ¿Es posible colocar las reinas negras y blancas en el tablero sin que se ataquen mutuamente? En las anticoloraciones se le pide a la coloración la condición opuesta a la coloración clásica, es decir si dos vértices son adyacentes estos deben tener el mismo color. Para que esto tenga sentido se deben agregar algunas condiciones al problema, como la existencia de vértices incoloros y que las cardinalidades de las clases de color sean fijas. En esta tesis se presenta la demostración de una conjetura que deriva del problema de Berge con caballos en lugar de reinas. Además de que se proponen modelos de programación lineal entera, no lineal entera y multiobjetivo para poder resolver problemas de anticoloración con dos colores por medio de algoritmos exactos. Además de lo anterior se presenta una mejora de las heurísticas parados colores y se propone una nueva heurística basada en algoritmos genéticos. Por último, se dan las extensiones necesarias para trabajar el problema de anticoloración con más de dos colores, tanto con algoritmos exactos como con métodos heurísticos

UAS in the Airspace: A Review on Integration, Simulation, Optimization, and Open Challenges

Air transportation is essential for society, and it is increasing gradually due to its importance. To improve the airspace operation, new technologies are under development, such as Unmanned Aircraft Systems (UAS). In fact, in the past few years, there has been a growth in UAS numbers in segregated airspace. However, there is an interest in integrating these aircraft into the National Airspace System (NAS). The UAS is vital to different industries due to its advantages brought to the airspace (e.g., efficiency). Conversely, the relationship between UAS and Air Traffic Control (ATC) needs to be well-defined due to the impacts on ATC capacity these aircraft may present. Throughout the years, this impact may be lower than it is nowadays because the current lack of familiarity in this relationship contributes to higher workload levels. Thereupon, the primary goal of this research is to present a comprehensive review of the advancements in the integration of UAS in the National Airspace System (NAS) from different perspectives. We consider the challenges regarding simulation, final approach, and optimization of problems related to the interoperability of such systems in the airspace. Finally, we identify several open challenges in the field based on the existing state-of-the-art proposals

Relative posture-based kinematic calibration of a 6-RSS parallel robot by optical coordinate measurement machine

In this article, a relative posture-based algorithm is proposed to solve the kinematic calibration problem of a 6-RSS parallel robot using the optical coordinate measurement machine system. In the research, the relative posture of robot is estimated using the detected pose with respect to the sensor frame through several reflectors which are fixed on the robot end-effector. Based on the relative posture, a calibration algorithm is proposed to determine the optimal error parameters of the robot kinematic model and external parameters introduced by the optical sensor. This method considers both the position and orientation variations and does not need the accurate location information of the detection sensor. The simulation results validate the superiority of the algorithm by comparing with the classic implicit calibration method. And the experimental results demonstrate that the proposal relative posture-based algorithm using optical coordinate measurement machine is an implementable and effective method for the parallel robot calibration

Otimização da Alocação de PMUs em Redes Elétricas com Infraestrutura de Comunicações

Este trabalho apresenta um novo algoritmo de otimização de custos totais dos Sistemas de Monitoramento em Grandes Areas (SMGA) de redes de transmissão de energia com base em Unidades de Medição Fasorial (UMFs) ou Phasor Measure units (PMU). Busca-se combinar a alocação ótima de UMFs com o dimensionamento de infraestrutura de comunicações, restringido ao menor custo total do sistema de medição. A Estimação de Estados (EE) é um estágio imperativo do monitoramento de sistemas de potência, da segurança do sistema e dos fluxos adequados de potência. Até recentemente, Unidades Terminais Remotas (UTRs) ou Remote Terminal Units (RTUs) em inglês, eram os principais responsáveis por recolher medidas de fluxos de potência ativa e reativa, injeção de potância ativa e reativa e o módulo da tensão nos barramentos para o sistema SCADA (Supervisory Control And Data Acquisition), que por sua vez fornecia dados para a EE. A introdução de PMUs em 1990 trouxe uma vantagem comparativa pois as medições são sincronizadas pela utilização do GPS (Global Positioning Sistem), o que permite constituir SMGA eficientes no controle e operação. Outra vantagem é a alta amostragem das PMUs conjugada com a estimação de estados, o que assegura controle rápido da tensão, comparado com o sistema de medição convencional (UTR e medidas). Porém, a utilização da tecnologia de PMUs acarreta um custo considerável e, por isso, desde cedo colocou-se o problema de otimizar a alocação destas unidades numa rede de transmissão, sem comprometer a EE. Muitos algoritmos de otimização de alocação de PMUs têm sido propostos, considerando critérios como observabilidade, contingências como perdas de PMU, perdas de linha, medidas críticas e conjuntos críticos. Mas a maioria dos trabalhos foca na simples minimização de PMUs e sua localização. Alguns poucos e recentes trabalhos vêm chamando a atenção para outros custos, como a Infraestrutura de Comunicação (IC), que apresentam um peso maior nos custos de uma SMGA que o de PMUs. Assim, o problema seria formulado de uma forma mais abrangente, buscando otimizar os custos totais, o que significaria otimizar a alocação de PMUs e IC. Este trabalho propõe ser uma contribuição nesta direção, formulando a alocação de PMUs como um problema de Conjunto Dominante Conexo Mínimo, que é um problema bem conhecido na teoria de grafos. Assim, implementa-se uma metodologia através da metaheurística Busca em Vizinhança Variável, combinado com mais dois algoritmos, Dijkstra (menores caminhos) e Kruskal (árvore geradora mínima). Também explora-se várias métricas da teoria dos grafos e propõe-se novas para melhorar o desempenho do algoritmo e incorpora-se ao modelo os aspetos e restrições mais próximos da realidade prática dos SMGA. Adiciona-se também ao algoritmo uma característica escalável, aplicável desde pequenos sistemas até os grandes e complexos

Intelligent control of PV co-located storage for feeder capacity optimization

Battery energy storage is identified as a strong enabler and a core element of the next generation grid. However, at present the widespread deployment of storage is constrained by the concerns that surround the techno-economic viability. This thesis addresses this issue through optimal integration of storage to improve the efficiency of the electricity grid. A holistic approach to optimal integration includes the development of methodologies for optimal siting, sizing and dispatch coordination of storage

Education and Security: Design and Evaluation Tools for Deliberate Disease Risks Mitigation

This thesis addresses the role of education to mitigate the risks of deliberate disease, including biological weapons. Specifically, it aims to analyse how education was constructed as a potential instrument to mitigate specific security risks; if and how education could impact on risks; and how effectiveness of education as a risk mitigation measure could be improved. The research framework combines concepts of security, risk and education within a general constructionist approach. Securitization is used to analyse attempts to construct education as a tool to mitigate specific security risks; risk assessment is used to identify and characterize risk scenarios and potential for risks mitigation; and instructional design and evaluation models are used for the design and evaluation of education. The thesis contends that education has been constructed as a mitigation tool for what were presented as urgent security risks of deliberate disease. Nine attempted securitization moves are identified and assessed. Improved competences identified in four thematic areas, and built with education, can mitigate risks in specific scenarios via impacting factors that primarily influence risk likelihood. The thesis presents several examples of achieved learning objectives, and tools that can be useful to evaluate behavioural and risk impacts, though empirical results on these levels here are still scarce. Design and evaluation tools, illustrated through a large amount of original and pre-existing data from a range of countries and contexts, are presented that can improve effectiveness of education as a deliberate disease risks mitigation measure

Literature search of publications concerning the prediction of dynamic inlet flow distortion and related topics

Publications prior to March 1981 were surveyed to determine inlet flow dynamic distortion prediction methods and to catalog experimental and analytical information concerning inlet flow dynamic distortion prediction methods and to catalog experimental and analytical information concerning inlet flow dynamics at the engine-inlet interface of conventional aircraft (excluding V/STOL). The sixty-five publications found are briefly summarized and tabulated according to topic and are cross-referenced according to content and nature of the investigation (e.g., predictive, experimental, analytical and types of tests). Three appendices include lists of references, authors, organizations and agencies conducting the studies. Also, selected materials summaries, introductions and conclusions - from the reports are included. Few reports were found covering methods for predicting the probable maximum distortion. The three predictive methods found are those of Melick, Jacox and Motycka. The latter two require extensive high response pressure measurements at the compressor face, while the Melick Technique can function with as few as one or two measurements

Resource allocation and performance analysis problems in optical networks

Optical networks pose a rich variety of new design and performance analysis problems. Typically, the static design problems belong to the field of combinatorial optimisation, whereas decision-making and performance analysis problems are best treated using appropriate stochastic models. This dissertation focuses on certain issues in resource allocation and performance evaluation of backbone wavelength-routed (WR) networks and metropolitan area optical burst switching (OBS) networks. The first two parts of the thesis consider heuristic algorithms for the static routing and wavelength assignment (RWA) and logical topology design (LTD) problems that arise in the context of WR networks. In a static RWA problem, one is asked to establish a given set of lightpaths (or light trees) in an optical WR network with given constraints, where the objective often is to minimise the number of wavelength channels required. In LTD problem, the number of wavelength channels is given and one is asked to decide on the set of lightpaths so that, for instance, the mean sojourn time of packets travelling at the logical layer is minimised. In the thesis, several heuristic algorithms for both the RWA and LTD problems are described and numerical results are presented. The third part of the thesis studies the dynamic control problem where connection requests, i.e. lightpath requests, arrive according to a certain traffic pattern and the task is to establish one lightpath at a time in the WR optical network so that the expected revenue is maximised or the expected cost is minimised. Typically, the goal of optimisation is to minimise some infinite time horizon cost function, such as the blocking probability. In this thesis, the dynamic RWA problem is studied in the framework of Markov decision processes (MDP). An algorithmic approach is proposed by which any given heuristic algorithm can be improved by applying the so-called first policy iteration (FPI) step of the MDP theory. Relative costs of states needed in FPI are estimated by on-the-fly simulations. The computational burden of the approach is alleviated by introducing the importance sampling (IS) technique with FPI, for which an adaptive algorithm is proposed for adjusting the optimal IS parameters at the same time as data are collected for the decision-making analysis. The last part of the thesis considers OBS networks, which represent an intermediate step towards full optical packet switching networks. In OBS networks, the data are transferred using optical bursts consisting of several IP packets going to the same destination. On the route of the burst, temporary reservations are made only for the time during which the burst is transmitted. This thesis focuses on fairness issues in OBS networks. It is demonstrated that fairness can be improved by using fibre delay lines together with Just-Enough-Time protocol (JET). Furthermore, by choosing the routes in an appropriate way one can also reach a satisfactory level of fairness and, at the same time, lower the overall blocking probability. Possible scheduling policies for metropolitan area OBS ring networks are also studied.reviewe

The Daily Egyptian, October 28, 1983

A man and woman standing beside a carriage