Sobre el correcto uso de intervalos de confianza para la estimación de proporciones binomiales

En este breve reporte técnico se presentan valores numéricos del desempeño del método clásico de estimación de proporciones binomiales aplicados al problema de la confiabilidad diámetro acotada, conjuntamente con resultados similares y análisis teóricos obtenidos de una búsqueda bibliográfica. Dicha búsqueda mostró que la estimación de las proporciones antes mencionadas fue retomado recientemente debido a resultados experimentales que indicaban un desempeño del método estándar inferior con respecto a lo usualmente pensado. Dado lo extendido de la aplicación del método estándar, tanto en el cálculo científico, la enseñanza o en la práctica profesional, se incluyen brevemente dos alternativas al intervalo clásico para cubrir las distintas necesidades existentes

Confiabilidad diámetro acotada para el modelo hostil. Construcción de estrategias de selección de cortes minimales para el método de la reducción recursiva de la varianza

Los Sistemas Binarios Estocásticos (SBS por sus siglas en inglés) son modelos matemáticos que permiten generalizar la noción clásica de confiabilidad de redes de comunicación. Los SBS consisten en un conjunto finito de componentes sujetos a fallas aleatorias, y una función lógica que describe la operación o falla del sistema, para cada estado posible de sus componentes. Instancias particulares de estos problemas pueden ser modelados bajo funciones monótonas, clasificándolos como Sistemas Binarios Estocásticos Monótonos (SMBS), los cuales heredan el orden natural del producto cartesiano. En el marco de Internet e inspirado en aplicaciones sensibles a la latencia, el problema de Confiabilidad Diámetro Acotado analiza la probabilidad de que dos o más nodos que desean comunicarse estén conectados por caminos acotados, ante fallas en los elementos de la red. Este problema ha sido estudiado principalmente en estructuras de redes donde fallan únicamente aristas o únicamente fallan nodos, y no tanto en fallas conjuntas (o "fallas simultáneas" de nodos y aristas). El problema de Confiabilidad Diámetro Acotada para el modelo hostil es una instancia de los sistemas binarios estocásticos monótonos, y la complejidad de su evaluación se clasifica como NP-difícil. Las contribuciones de este documento son las siguientes. En primera instancia se implementa el método de Reducción Recursiva de la Varianza (RVR) para el cálculo de Confiabilidad Diámetro Acotada del modelo hostil. Se realiza un estudio de sensibilidad del método RVR ante distintas estrategias de selección de cortes minimales. Finalmente, se brinda un estudio comparativo entre el método Monte Carlo Crudo y RVR, observando el desempeño de los métodos elegidos.Stochastic Binary Systems (SBS) are mathematical models that allow extend the classical notion of reliability in communication networks. An SBS consists of a set of finite components subject to random failures, and a logical function that describes the operation or failure of the system, for each possible configuration. Particular instances of these problems are modeled under monotone functions, known as Stochastic Monotone Binary System (SMBS), which inherit the natural order of the cartesian product. Within the framework of the Internet and inspired by latency-sensitive applications, the Diameter Constrained Reliability is the probability that two or more target nodes are connected by bounded paths, in the resulting network after potential failures on its components. The scientific literature considers structural links or node failures. Here, we consider joint failures instead, what is known as the Hostile Network model. The Diameter Constrained Reliability problem for the hostile model is an instance of Stochastic Monotone Binary System, and its reliability evaluation belongs to the N P-Hard class. The contributions of this thesis can be summarized as follows. First, the Recursive Variance Reduction (RVR) method is implemented to estimate the Diameter Constrained Reliability in this novel hostile environment with joint node/link failures. Then, a sensibility analysis of RVR method is performed, following different cut-selection strategies. Finally, a performance analysis between Monte Carlo Crudo and RVR methods is provided

GRASP/VND Optimization Algorithms for Hard Combinatorial Problems

Two hard combinatorial problems are addressed in this thesis. The first one is known as the ”Max CutClique”, a combinatorial problem introduced by P. Martins in 2012. Given a simple graph, the goal is to find a clique C such that the number of links shared between C and its complement C C is maximum. In a first contribution, a GRASP/VND methodology is proposed to tackle the problem. In a second one, the N P-Completeness of the problem is mathematically proved. Finally, a further generalization with weighted links is formally presented with a mathematical programming formulation, and the previous GRASP is adapted to the new problem. The second problem under study is a celebrated optimization problem coming from network reliability analysis. We assume a graph G with perfect nodes and imperfect links, that fail independently with identical probability ρ ∈ [0,1]. The reliability RG(ρ), is the probability that the resulting subgraph has some spanning tree. Given a number of nodes and links, p and q, the goal is to find the (p,q)-graph that has the maximum reliability RG(ρ), uniformly in the compact set ρ ∈ [0,1]. In a first contribution, we exploit properties shared by all uniformly most-reliable graphs such as maximum connectivity and maximum Kirchhoff number, in order to build a novel GRASP/VND methodology. Our proposal finds the globally optimum solution under small cases, and it returns novel candidates of uniformly most-reliable graphs, such as Kantor-Mobius and Heawood graphs. We also offer a literature review, ¨ and a mathematical proof that the bipartite graph K4,4 is uniformly most-reliable. Finally, an abstract mathematical model of Stochastic Binary Systems (SBS) is also studied. It is a further generalization of network reliability models, where failures are modelled by a general logical function. A geometrical approximation of a logical function is offered, as well as a novel method to find reliability bounds for general SBS. This bounding method combines an algebraic duality, Markov inequality and Hahn-Banach separation theorem between convex and compact sets

A surface texture modeling system for solid freeform fabrication

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997.Includes bibliographical references (leaves 83-84).Solid Freeform Fabrication, SFF, is a set of manufacturing processes that fabricates parts as a bonded stack of individual layers. The Three Dimensional Printing process, 3DPTM process, is an SFF technology developed at MIT. It builds layers by ink jet printing binder onto the surface of a bed of powder. The bed of powder is lowered and fresh powder is spread onto the bed. As subsequent cross sections of the part are printed, the part exists, submerged in the powder bed. Access to the individual layers as they are fabricated gives access to the interior structure of the part. This approach allows the part to have high geometric complexity. In this work a designer centric Computer Aided Design system is proposed to allow the interactive creation of functional surface texture on mechanical parts. This system is structured to behave like a VLSI CAD system, which offers substantial process capabilities. The requirements for a Mechanical CAD, MCAD, system to behave like VLSI CAD are determined to be: 1. That the informational model of the unit cell of texture be separable into distinct logical subsets.2. That manipulations on either subset not violate the logical consistency of the other subset. This thesis shows that geometric dimensions and tolerances carry the essential information of the model of a unit cell of functional texture. A variety of Unit Cell editors are evaluated according to their ability to meet the desired system criteria. A tool, Swiss Solid Geometry, SSG, for the design of unit cells of functional texture is developed, that fulfills requirement #1. SSG is an approach to MCAD modeling that combines geometric primitives in the manner of Constructive Solid Geometry, however the primitives of SSG, are different. They consist of simple objects such as lines, but includes the spatial envelope around them of a fixed offset. Also, they are used to represent both positive and negative regions of space. The placement of the individual replications is established by a mesh, that covers the intended 3D surface region. A meshing algorithm is developed that regularizes the mesh by directly utilizing the dimensional tolerances specified in the process of Unit Cell design. The geometric dimensions are instantiated as standalone geometric entities that push and pull on the nodes of the mesh in order to bring their length into dimensional tolerance. This method fulfills requirement #2, and it is implemented into a CAM software called Vari 4. The modularity of the CAM software, Vari 4, is described in detail.by John G. Nace.S.M

Socio-environmental impacts of settlement growth under conditions of fostered infill development : a methodological framework for a multicriteria assessment

The major objective of this study is to analyze socio-environmental conditions under which a sustainable and resource-preserving settlement development can be promoted and to assess respective impacts of greenfield and infill development. By doing so, an essential part of this study is dedicated to the development of an innovative theoretical and methodological concept of a two-stepped Multicriteria Assessment scheme (MCA) for a demography-driven and scenario-based assessment of land use change. The first step of this concept is characterized by the assessment of socio-environmental prerequisites of future housing sites of a city and their contribution to a sustainable settlement development defined by the term Quality of Place (QoP). It results from a close collaboration between planners and scientists within a research-project on sustainable settlement-development. Test-runs and discussions with planners have been conducted throughout a period of three years to discuss the necessity of the socio-ecological indicators and to identify individual weights. The second step is formed by an on-site-assessment of socio-environmental impacts on the target concepts Quality of Life (QoL) and Urban Ecosystem Services (UES) due to the housing-development of varying densities within housing scenarios. A prototype of a Decision Support System (DSS) integrates both steps of assessment and is presented within this work.Sozio-ökologische Folgen von Siedlungswachstum unter Bedingungen verstärkter Innenentwicklung : ein methodisches Rahmenwerk für eine Multikriterienbewertung Hauptziel dieser Arbeit ist es, die sozio-ökologischen Bedingungen, unter denen eine nachhaltige und ressourcenschonende Siedlungsentwicklung realisierbar ist, zu analysieren und die entsprechenden Folgewirkungen von Außen- und Innenentwicklung zu bewerten. Hauptbestandteil der Arbeit ist somit die Entwicklung eines theoretisch und methodisch innovativen Konzepts einer zweistufigen Multikriterienbewertung für eine demographieorientierte und szenariobasierte Bewertung des Landnutzungswandels im Rahmen der Siedlungsentwicklung. Der erste Schritt dieses Konzepts besteht aus der Bewertung der ökologischen und sozialen Rahmenbedingungen und Standortqualitäten („Quality of Place“) von Wohnbaulandpotenzialen und ihren Beitrag zu einer nachhaltigen Siedlungsentwicklung. Er basiert auf einer engen dreijährigen Zusammenarbeit zwischen Planern und Wissenschaftlern im Rahmen eines Forschungsprojekts zur nachhaltigen Siedlungsentwicklung, in der im Rahmen von Testläufen des Bewertungsmodells und Diskussionen planungs- und entscheidungsrelevante Indikatoren extrahiert und entsprechend ihrer Bedeutung gewichtet wurden. Der zweite Schritt des Konzepts ist die Vorortbewertung potentieller Wohnbauflächen gemäß sozio-ökologischer Folgewirkungen in verschiedenen Bebauungsdichten hinsichtlich der Konzepte Lebensqualität („QoL“) und urbane Ökosystemdienstleistungen (UES). Der Prototyp eines Entscheidungsunterstützungswerkzeugs (“Decision Support System” (DSS)) wird in dieser Arbeit vorgestellt

Research-Informed Teaching in a Global Pandemic: "Opening up" Schools to Research

The teacher-research agenda has become a significant consideration for policy and professional development in a number of countries. Encouraging research-based teacher education programmes remains an important goal, where teachers are able to effectively utilize educational research as part of their work in school settings and to reflect on and enhance their professional development. In the last decade, teacher research has grown in importance across the three i’s of the teacher learning continuum: initial, induction and in-service teacher education. This has been brought into even starker relief with the global spread of COVID-19, and the enforced and emergency, wholesale move to digital education. Now, perhaps more than ever, teachers need the perspective and support of research-led practice, particularly in how to effectively use Internet technologies to mediate and enhance learning, teaching and assessment online, and new blended modalities for education that must be physically distant. The aim of this paper is to present a number of professional development open educational systems which exist or are currently being developed to support teachers internationally, to engage with, use and do research. Exemplification of the opening up of research to schools and teachers is provided in the chapter through reference to the European Union-funded Erasmus + project, BRIST: Building Research Infrastructures for School Teachers. BRIST is developing technology to coordinate and support teacher-research at a European level

Designing personalised, authentic and collaborative learning with mobile devices: Confronting the challenges of remote teaching during a pandemic.

This article offers teachers a digital pedagogical framework, research-inspired and underpinned by socio-cultural theory, to guide the design of personalised, authentic and collaborative learning scenarios for students using mobile devices in remote learning settings during this pandemic. It provides a series of freely available online resources underpinned by our framework, including a mobile learning toolkit, a professional learning app, and robust, validated surveys for evaluating tasks. Finally, it presents a set of evidence-based principles for effective innovative teaching with mobile devices

Metropolitan Research

Metropolitan research requires multidisciplinary perspectives in order to do justice to the complexities of metropolitan regions. This volume provides a scholarly and accessible overview of key methods and approaches in metropolitan research from a uniquely broad range of disciplines including architectural history, art history, heritage conservation, literary and cultural studies, spatial planning and planning theory, geoinformatics, urban sociology, economic geography, operations research, technology studies, transport planning, aquatic ecosystems research and urban epidemiology. It is this scope of disciplinary - and increasingly also interdisciplinary - approaches that allows metropolitan research to address recent societal challenges of urban life, such as mobility, health, diversity or sustainability

Metropolitan Research: Methods and Approaches

Metropolitan research requires multidisciplinary perspectives in order to do justice to the complexities of metropolitan regions. This volume provides a scholarly and accessible overview of key methods and approaches in metropolitan research from a uniquely broad range of disciplines including architectural history, art history, heritage conservation, literary and cultural studies, spatial planning and planning theory, geoinformatics, urban sociology, economic geography, operations research, technology studies, transport planning, aquatic ecosystems research and urban epidemiology. It is this scope of disciplinary - and increasingly also interdisciplinary - approaches that allows metropolitan research to address recent societal challenges of urban life, such as mobility, health, diversity or sustainability