A new MILP based approach for unit commitment in power production planning

This paper presents a complete, quadratic programming formulation of the standard thermal unit commitment problem in power generation planning, together with a novel iterative optimisation algorithm for its solution. The algorithm, based on a mixed-integer formulation of the problem, considers piecewise linear approximations of the quadratic fuel cost function that are dynamically updated in an iterative way, converging to the optimum; this avoids the requirement of resorting to quadratic programming, making the solution process much quicker. From extensive computational tests on a broad set of benchmark instances of this problem, the algorithm was found to be flexible and capable of easily incorporating different problem constraints. Indeed, it is able to tackle ramp constraints, which although very important in practice were rarely considered in previous publications. Most importantly, optimal solutions were obtained for several well-known benchmark instances, including instances of practical relevance, that are not yet known to have been solved to optimality. Computational experiments and their results showed that the method proposed is both simple and extremely effective.

Sistema pericial para suporte à decisão na alocação de recursos de emergência

O panorama atual da emergência e socorro de primeira linha em Portugal, carateriza-se por uma grande aposta ao longo dos últimos anos num incremento contínuo da qualidade e da eficiência que estes serviços prestam às populações locais. Com vista à prossecução do objetivo de melhoria contínua dos serviços, foram realizados ao longo dos últimos anos investimentos avultados ao nível dos recursos técnicos e ao nível da contratação e formação de recursos humanos altamente qualificados. Atualmente as instituições que prestam socorro e emergência de primeira linha estão bem dotadas ao nível físico e ao nível humano dos recursos necessários para fazerem face aos mais diversos tipos de ocorrências. Contudo, ao nível dos sistemas de informação de apoio à emergência e socorro de primeira linha, verifica-se uma inadequação (e por vezes inexistência) de sistemas informáticos capazes de suportar convenientemente o atual contexto de exigência e complexidade da emergência e socorro. Foi feita ao longo dos últimos anos, uma forte aposta na melhoria dos recursos físicos e dos recursos humanos encarregues da resposta àsemergência de primeira linha, mas descurou-se a área da gestão e análise da informação sobre as ocorrências, assim como, o delinear de possíveis estratégias de prevenção que uma análise sistematizada da informação sobre as ocorrências possibilita. Nas instituições de emergência e socorro de primeira linha em Portugal (bombeiros, proteção civil municipal, PSP, GNR, polícia municipal), prevalecem ainda hoje os sistemas informáticos apenas para o registo das ocorrências à posteriori e a total inexistência de sistemas de registo de informação e de apoio à decisão na alocação de recursos que operem em tempo real. A generalidade dos sistemas informáticos atualmente existentes nas instituições são unicamente de sistemas de backoffice, que não aproveitam a todas as potencialidades da informação operacional neles armazenada. Verificou-se também, que a geo-localização por via informática dos recursos físicos e de pontos de interesse relevantes em situações críticas é inexistente a este nível. Neste contexto, consideramos ser possível e importante alinhar o nível dos sistemas informáticos das instituições encarregues da emergência e socorro de primeira linha, com o nível dos recursos físicos e humanos que já dispõem atualmente. Dado que a emergência e socorro de primeira linha é um domínio claramente elegível para a aplicação de tecnologias provenientes dos domínios da inteligência artificial (nomeadamente sistemas periciais para apoio à decisão) e da geo-localização, decidimos no âmbito desta tese desenvolver um sistema informático capaz de colmatar muitas das lacunas por nós identificadas ao nível dos sistemas informáticos destas instituições. Pretendemos colocar as suas plataformas informáticas num nível similar ao dos seus recursos físicos e humanos. Assim, foram por nós identificadas duas áreas chave onde a implementação de sistemas informáticos adequados às reais necessidades das instituições podem ter um impacto muito proporcionar uma melhor gestão e otimização dos recursos físicos e humanos. As duas áreas chave por nós identificadas são o suporte à decisão na alocação dos recursos físicos e a geolocalização dos recursos físicos, das ocorrências e dos pontos de interesse. Procurando fornecer uma resposta válida e adequada a estas duas necessidades prementes, foi desenvolvido no âmbito desta tese o sistema CRITICAL DECISIONS. O sistema CRITICAL DECISIONS incorpora um conjunto de funcionalidades típicas de um sistema pericial, para o apoio na decisão de alocação de recursos físicos às ocorrências. A inferência automática dos recursos físicos, assenta num conjunto de regra de inferência armazenadas numa base de conhecimento, em constante crescimento e atualização, com base nas respostas bem sucedidas a ocorrências passadas. Para suprimir as carências aos nível da geo-localização dos recursos físicos, das ocorrências e dos pontos de interesse, o sistema CRITICAL DECISIONS incorpora também um conjunto de funcionalidades de geo-localização. Estas permitem a geo-localização de todos os recursos físicos da instituição, a geo-localização dos locais e as áreas das várias ocorrências, assim como, dos vários tipos de pontos de interesse. O sistema CRITICAL DECISIONS visa ainda suprimir um conjunto de outras carências por nós identificadas, ao nível da gestão documental (planos de emergência, plantas dos edifícios) , da comunicação, da partilha de informação entre as instituições de socorro e emergência locais, da contabilização dos tempos de serviço, entre outros. O sistema CRITICAL DECISIONS é o culminar de um esforço colaborativo e contínuo com várias instituições, responsáveis pela emergência e socorro de primeira linha a nível local. Esperamos com o sistema CRITICAL DECISIONS, dotar estas instituições de uma plataforma informática atual, inovadora, evolutiva, com baixos custos de implementação e de operação, capaz de proporcionar melhorias contínuas e significativas ao nível da qualidade da resposta às ocorrências, das capacidades de prevenção e de uma melhor otimização de todos os tipos de recursos que têm ao dispor.

BabeLO : an extensible converter of programming exercises formats

In the last two decades, there was a proliferation of programming exercise formats that hinders interoperability in automatic assessment. In the lack of a widely accepted standard, a pragmatic solution is to convert content among the existing formats. BabeLO is a programming exercise converter providing services to a network of heterogeneous e-learning systems such as contest management systems, programming exercise authoring tools, evaluation engines and repositories of learning objects. Its main feature is the use of a pivotal format to achieve greater extensibility. This approach simplifies the extension to other formats, just requiring the conversion to and from the pivotal format. This paper starts with an analysis of programming exercise formats representative of the existing diversity. This analysis sets the context for the proposed approach to exercise conversion and to the description of the pivotal data format. The abstract service definition is the basis for the design of BabeLO, its components and web service interface. This paper includes a report on the use of BabeLO in two concrete scenarios: to relocate exercises to a different repository, and to use an evaluation engine in a network of heterogeneous systems.

A distributed system for learning programming on-line

Several Web-based on-line judges or on-line programming trainers have been developed in order to allow students to train their programming skills. However, their pedagogical functionalities in the learning of programming have not been clearly defined. EduJudge is a project which aims to integrate the “UVA On-line Judge”, an existing on-line programming trainer with an important number of problems and users, into an effective educational environment consisting of the e-learning platform Moodle and the competitive learning tool QUESTOURnament. The result is the EduJudge system which allows teachers to apply different pedagogical approaches using a proven e-learning platform, makes problems easy to search through an effective search engine, and provides an automated evaluation of the solutions submitted to these problems. The final objective is to provide new learning strategies to motivate students and present programming as an easy and attractive challenge. EduJudge has been tried and tested in three algorithms and programming courses in three different Engineering degrees. The students’ motivation and satisfaction levels were analysed alongside the effects of the EduJudge system on students’ academic outcomes. Results indicate that both students and teachers found that among other multiple benefits the EduJudge system facilitates the learning process. Furthermore, the experi- ment also showed an improvement in students’ academic outcomes. It must be noted that the students’ level of satisfaction did not depend on their computer skills or their gender.

CrimsonHex: a learning objects repository for programming exercises

A repository of learning objects is a system that stores electronic resources in a technology-mediated learning process. The need for this kind of repository is growing as more educators become eager to use digital educa- tional contents and more of it becomes available. The sharing and use of these resources relies on the use of content and communication standards as a means to describe and exchange educational resources, commonly known as learning objects. This paper presents the design and implementation of a service-oriented reposi- tory of learning objects called crimsonHex. This repository supports new definitions of learning objects for specialized domains and we illustrate this feature with the definition of programming exercises as learning objects and its validation by the repository. The repository is also fully compliant with existing commu- nication standards and we propose extensions by adding new functions, formalizing message interchange and providing a REST interface. To validate the interoperability features of the repository, we developed a repository plug-in for Moodle that is expected to be included in the next release of this popular learning management system.

Orchestration of e-learning services for automatic evaluation of programming exercises

Managing programming exercises require several heterogeneous systems such as evaluation engines, learning objects repositories and exercise resolution environments. The coordination of networks of such disparate systems is rather complex. These tools would be too specific to incorporate in an e-Learning platform. Even if they could be provided as pluggable components, the burden of maintaining them would be prohibitive to institutions with few courses in those domains. This work presents a standard based approach for the coordination of a network of e-Learning systems participating on the automatic evaluation of programming exercises. The proposed approach uses a pivot component to orchestrate the interaction among all the systems using communication standards. This approach was validated through its effective use on classroom and we present some preliminary results.

Mixed integer non linear programming and artificial neural network based approach to ancillary services dispatch in competitive electricity markets

Ancillary services represent a good business opportunity that must be considered by market players. This paper presents a new methodology for ancillary services market dispatch. The method considers the bids submitted to the market and includes a market clearing mechanism based on deterministic optimization. An Artificial Neural Network is used for day-ahead prediction of Regulation Down, regulation-up, Spin Reserve and Non-Spin Reserve requirements. Two test cases based on California Independent System Operator data concerning dispatch of Regulation Down, Regulation Up, Spin Reserve and Non-Spin Reserve services are included in this paper to illustrate the application of the proposed method: (1) dispatch considering simple bids; (2) dispatch considering complex bids.

“Something there that wasn’t there before”: representação do amor romântico em Beauty and the Beast (1991)

Dissertação apresentada à Escola Superior de Comunicação Social como parte dos requisitos para obtenção de grau de mestre em Audiovisual e Multimédia.

Programming atomic multicasts in CAN

In Distributed Computer-Controlled Systems (DCCS), a special emphasis must be given to the communication infrastructure, which must provide timely and reliable communication services. CAN networks are usually suitable to support small-scale DCCS. However, they are known to present some reliability problems, which can lead to an unreliable behaviour of the supported applications. In this paper, an atomic multicast protocol for CAN networks is proposed. This protocol explores the CAN synchronous properties, providing a timely and reliable service to the supported applications. The implementation of such protocol in Ada, on top of the Ada version of Real-Time Linux is presented, which is used to demonstrate the advantages and disadvantages of the platform to support reliable communications in DCCS.

A framework for the development of parallel and distributed real-time embedded systems

Embedded real-time applications increasingly present high computation requirements, which need to be completed within specific deadlines, but that present highly variable patterns, depending on the set of data available in a determined instant. The current trend to provide parallel processing in the embedded domain allows providing higher processing power; however, it does not address the variability in the processing pattern. Dimensioning each device for its worst-case scenario implies lower average utilization, and increased available, but unusable, processing in the overall system. A solution for this problem is to extend the parallel execution of the applications, allowing networked nodes to distribute the workload, on peak situations, to neighbour nodes. In this context, this report proposes a framework to develop parallel and distributed real-time embedded applications, transparently using OpenMP and Message Passing Interface (MPI), within a programming model based on OpenMP. The technical report also devises an integrated timing model, which enables the structured reasoning on the timing behaviour of these hybrid architectures.

EMMON - EMbedded MONitoring

Despite the steady increase in experimental deployments, most of research work on WSNs has focused only on communication protocols and algorithms, with a clear lack of effective, feasible and usable system architectures, integrated in a modular platform able to address both functional and non–functional requirements. In this paper, we outline EMMON [1], a full WSN-based system architecture for large–scale, dense and real–time embedded monitoring [3] applications. EMMON provides a hierarchical communication architecture together with integrated middleware and command and control software. Then, EM-Set, the EMMON engineering toolset will be presented. EM-Set includes a network deployment planning, worst–case analysis and dimensioning, protocol simulation and automatic remote programming and hardware testing tools. This toolset was crucial for the development of EMMON which was designed to use standard commercially available technologies, while maintaining as much flexibility as possible to meet specific applications requirements. Finally, the EMMON architecture has been validated through extensive simulation and experimental evaluation, including a 300+ nodes testbed.

Nano-CF: a Coordination Framework for macro-programming in wireless sensor networks

Wireless Sensor Networks (WSN) are being used for a number of applications involving infrastructure monitoring, building energy monitoring and industrial sensing. The difficulty of programming individual sensor nodes and the associated overhead have encouraged researchers to design macro-programming systems which can help program the network as a whole or as a combination of subnets. Most of the current macro-programming schemes do not support multiple users seamlessly deploying diverse applications on the same shared sensor network. As WSNs are becoming more common, it is important to provide such support, since it enables higher-level optimizations such as code reuse, energy savings, and traffic reduction. In this paper, we propose a macro-programming framework called Nano-CF, which, in addition to supporting in-network programming, allows multiple applications written by different programmers to be executed simultaneously on a sensor networking infrastructure. This framework enables the use of a common sensing infrastructure for a number of applications without the users having to worrying about the applications already deployed on the network. The framework also supports timing constraints and resource reservations using the Nano-RK operating system. Nano- CF is efficient at improving WSN performance by (a) combining multiple user programs, (b) aggregating packets for data delivery, and (c) satisfying timing and energy specifications using Rate- Harmonized Scheduling. Using representative applications, we demonstrate that Nano-CF achieves 90% reduction in Source Lines-of-Code (SLoC) and 50% energy savings from aggregated data delivery.

A parallel programming model for ada

Over the last three decades, computer architects have been able to achieve an increase in performance for single processors by, e.g., increasing clock speed, introducing cache memories and using instruction level parallelism. However, because of power consumption and heat dissipation constraints, this trend is going to cease. In recent times, hardware engineers have instead moved to new chip architectures with multiple processor cores on a single chip. With multi-core processors, applications can complete more total work than with one core alone. To take advantage of multi-core processors, parallel programming models are proposed as promising solutions for more effectively using multi-core processors. This paper discusses some of the existent models and frameworks for parallel programming, leading to outline a draft parallel programming model for Ada.

A framework for programming sensor networks with scheduling and resource-sharing optimizations

Several projects in the recent past have aimed at promoting Wireless Sensor Networks as an infrastructure technology, where several independent users can submit applications that execute concurrently across the network. Concurrent multiple applications cause significant energy-usage overhead on sensor nodes, that cannot be eliminated by traditional schemes optimized for single-application scenarios. In this paper, we outline two main optimization techniques for reducing power consumption across applications. First, we describe a compiler based approach that identifies redundant sensing requests across applications and eliminates those. Second, we cluster the radio transmissions together by concatenating packets from independent applications based on Rate-Harmonized Scheduling.

sMapReduce: a programming pattern for wireless sensor networks

Wireless Sensor Networks (WSNs) are increasingly used in various application domains like home-automation, agriculture, industries and infrastructure monitoring. As applications tend to leverage larger geographical deployments of sensor networks, the availability of an intuitive and user friendly programming abstraction becomes a crucial factor in enabling faster and more efficient development, and reprogramming of applications. We propose a programming pattern named sMapReduce, inspired by the Google MapReduce framework, for mapping application behaviors on to a sensor network and enabling complex data aggregation. The proposed pattern requires a user to create a network-level application in two functions: sMap and Reduce, in order to abstract away from the low-level details without sacrificing the control to develop complex logic. Such a two-fold division of programming logic is a natural-fit to typical sensor networking operation which makes sensing and topological modalities accessible to the user.