This paper addresses an analytical model that may be applied to different Wireless Sensor Networks (WSNs) Medium Access Control (MAC) protocols using different efficient transceivers. Our model accounts for the impact of several simultaneous factors, including periodic receive/transmit and sleep cycles, the length of the transmitted packet and data rate. The Sensor Block Acknowledgement MAC, a new innovative WSNs MAC protocol that uses a Block Acknowledgement scheme to achieve energy efficiency, is proposed as well. Our implementation takes into account the average delay, which can be clearly reduced when a Block Acknowledgement Scheme is used. In terms of energy consumption and average delay the efficient radio transceivers that operate in the 2.4GHz band have better results that the ones that use the 900MHz band. Adaptive listening (AL) enables radio transceivers to stay alert after the communication between two neighbour nodes before going to sleep, allowing for energy saving when synchronisation is involved.

As Nações aliadas, com o intuito de promover a transformação no seio da Organização do Tratado do Atlântico Norte (OTAN), acordaram em tirar partido de Centros de Excelência nacionais e multinacionais, com capacidade para serem oferecidos à OTAN. O presente estudo tem em vista fornecer contributos para o levantamento de um Centro de Excelência (CoE) em Portugal que forneça conhecimento e experiência reconhecida no treino de Postos de Comando dos escalões Batalhão, Brigada e Divisão, para benefício da Aliança, em especial no referido apoio à transformação. Determinar quais as condições a criar, foi o desafio a que nos propusemos. Do ponto de vista metodológico, tendo em vista encontrar resposta a esta questão central, limitámos o âmbito do estudo à Modelação e Simulação (M&S) construtiva e elegemos três áreas principais de análise: o conceito OTAN para CoE; o Estado da Arte da M&S a nível mundial e a M&S em Portugal. Um CoE, patrocinado de forma nacional, ou multinacional, a ser acreditado pelo Supreme Allied Command Transformation (SACT), será avaliado perante um conjunto de critérios desenvolvidos pelo SACT, em função da missão e âmbito expressos no conceito de apoio do CoE às estruturas da OTAN, aplicando-se o conceito ‘free of charge’ para os produtos e serviços disponibilizados à Aliança. O Estado da Arte da M&S passa pela racionalização de recursos, a procura da interoperabilidade e pela aplicação da mais avançada tecnologia de forma cooperativa, observando-se uma crescente centralização das tarefas de planeamento e de gestão das actividades de M&S, contribuindo para obter capacidades de treino em todo o espectro de operações militares. Neste sentido, os sistemas de simulação do ‘tempo da Guerra Fria’, onde o sistema VIGRESTE tem assumido lugar de destaque, têm vindo a ser substituídos por uma nova geração de M&S, com capacidade de interoperabilidade com outros sistemas de simulação (através de padrões como o High Level Architecture - HLA) e apresentando uma convergência crescente com Sistemas de Informação e Comunicações (SIC), onde o Sistema de Informação de Comando e Controlo do Exército (SICCE) se afirma actualmente, preparando-se para cumprir o Operational Level Test no âmbito do Multilateral Interoperability Program. No que concerne à M&S em Portugal, o Centro de Simulação de Operações Militares (CSOM), sendo uma infra-estrutura recente e desenhada para o treino de Postos de Comando, permite encarar com confiança os novos desafios da M&S, possibilitando que o Exército e as Forças Armadas em geral, retirem ainda mais dividendos da sua utilização, nomeadamente com uma maior frequência de exercícios assistidos por computador para as unidades operacionais. A Força Aérea Portuguesa (FAP) está em conversações com a Força Aérea da Argentina para obter um sistema de simulação construtiva, o ‘Juego de Guerra Aérea’. Esta situação, num momento em que o Exército planeia a evolução do sistema VIGRESTE, contemplando uma convergência com o SICCE, nomeadamente na utilização de um modelo de base de dados comum e recurso à sua interface com o utilizador, permitirá incluir requisitos e apoiar a FAP, para a obtenção de interoperabilidade com o sistema argentino. Neste sentido, é possível pensar no estabelecimento de um plano conjunto de I&D com a FAP, permitindo desta forma obter a capacidade conjunta para o CSOM. Relativamente à evolução do sistema VIGRESTE, será forçoso o levantamento de requisitos operacionais, sob pena de não se conseguir definir convenientemente um plano de Verificação, Validação e Acreditação, como garantia da qualidade do produto final. Este assunto assume particular importância na eventualidade de as Forças Armadas virem a optar por um parceiro da indústria para o seu desenvolvimento. Cremos, não só pela capacidade da chefia do Exército em reconhecer a importância da simulação, mas também pelas recentes indicações no sentido de definir e concretizar uma política de simulação, que a criação de um Gabinete Coordenador da Modelação e Simulação no Exército contribuirá para criar uma nova dinâmica na M&S nacional, assumindo um papel importante nas tarefas a realizar no sentido de acreditar o CSOM como um CoE OTAN. Com plena consciência das limitações de um estudo desta natureza, consideramos que este estudo permitiu aumentar o conhecimento na área da acreditação de CoE, bem como confirmar a importância que representa para as Forças Armadas possuir capacidades na área da M&S de operações militares, encontrando-se o Exército em situação privilegiada neste domínio. Abstract: To promote transformation within North Atlantic Treaty Organization (NATO), Nations have agreed to take advantage of national and multinational Centres of Excellence witch could be offered to the Alliance. This work intent is to provide inputs regarding the creation of one Centre of Excellence (CoE) in Portugal, which offers recognised expertise and experience regarding Command Post Training, for Battalion, Brigade and Division levels, to the benefit of the Alliance, especially in support of transformation. Determining which conditions need to be created was the challenge we proposed ourselves overcome. Regarding our methodology, having present the previous question, central to our study, we have established constructive Modelling and Simulation (M&S) as the scope of this work, electing three main analysis areas: CoE concept for NATO; The international M&S State of the Art and M&S in Portugal. One CoE, nationally or multinationally funded, in order to achieve accreditation, must be assessed against a set of criteria, developed by Supreme Allied Command Transformation (SACT), tailored to the mission and scope of that CoE, expressed in the support concept. The concept ‘free of charge’ to NATO will apply to products and services offered to the Alliance. M&S State of the Art encompasses the optimum use of resources, increased interoperability and cooperative used of advanced technology. Centralization of planning and management activities, regarding M&S, seems to be the way ahead in order to better support training and preparation for the range of military operations. ‘Cold War’ simulation systems, where VIGRESTE has a notorious performance, are being replaced by new generation M&S, with interoperability capabilities to link distinct M&S systems (using standards like the High Level Architecture – HLA) with growing convergence to Communication and Information Systems (CIS), where Portuguese Army Command and Control Information System (SICCE) presently affirms its value, preparing itself to fulfil the Operational Level Test, at the Multilateral Interoperability Program. The Portuguese Army Military Operations Simulation Centre (CSOM), designed specifically for Command Post training and recently built, provides the necessary confidence to overcome future M&S challenges, allowing the Portuguese Army (POArmy), the Armed Forces as a whole, to increase its use, by field units, for computer assisted exercises, raising even further its dividends. Portuguese Air Force (FAP) is negotiating with Argentinean Air Force to acquire the simulation system ‘Juego de Guerra Aérea’. This, and the fact that the POArmy is currently planning the evolution of VIGRESTE, including its convergence with SICCE, namely by using the same database model and user interface, will allow the inclusion of requirements and support to FAP in order to obtain interoperability with the Argentinean system. The establishment of a Joint Research and Development (R&D) program with FAP will provide CSOM with the required joint capability. Regarding the evolution of VIGRESTE, it is mandatory to develop the operational requirements, in order to create a convenient plan for Verification, Validation and Accreditation. Failing to do so will have impact on quality assurance for the system. At the prospect of M&S R&D partnership establishment, between Portuguese Armed Forces and industry, this issue assumes greater relevance. We strongly believe, not only by the capacity of the POArmy leadership to recognise the importance of M&S, but also by recent directions to define and implement one simulation policy, that the creation of the Army Modelling and Simulation Coordination Office will provide an increased momentum to national M&S, assuming an important role in tasks concerning the accreditation process of CSOM as NATO CoE. With perfect awareness of the limitations of our work, it is our believe that this study provides an increased knowledge in the area of CoE Accreditation, as well as it confirms the importance of maintaining military operations M&S capabilities for the Portuguese Armed Forces, identifying the privileged position of the POArmy in this domain.

O objetivo desta investigação é analisar a possível implementação do Centro de Treino Conjunto e de Simulação das Forças Armadas portuguesas, garantindo a eficiência e eficácia na preparação de forças conjuntas ou para operações conjuntas, tendo em atenção outras realidades e experiências nacionais e internacionais. Partindo das potencialidades da simulação aplicáveis à preparação de forças militares, analisaram-se as estruturas da OTAN e das nações aliadas, incluindo as portuguesas, que usam estas ferramentas na formação, treino e apoio às operações militares. Sistematizaram-se os requisitos operacionais essenciais à edificação deste centro e analisaram-se as respetivas implicações. Para este trabalho, no âmbito das Ciências Militares, adotou-se uma estratégia de investigação qualitativa, com reforço quantitativo, baseada num desenho de pesquisa comparativo e num raciocínio dedutivo. Como resultado desta investigação, justifica-se edificar este centro para garantir o treino adequado das nossas forças, face aos constrangimentos financeiros, humanos e materiais. Sugere-se uma possível organização, englobando um órgão de coordenação da simulação, e a sua localização no Instituto Universitário Militar, onde existem instalações apropriadas. Adicionalmente, a implementação de uma federação de centros de simulação, interligada a idênticas infraestruturas da Aliança Atlântica, permitirá o treino conjunto e combinado de forças, a troca de informação e experiências. Abstract: This research's objective is to analyse the possible implementation of the Portuguese Armed Forces joint training centre and simulation to ensure the efficiency and effectiveness in the preparation of joint forces or joint operations, considering, national and international realities and experiences. Based on the simulation potential applicable to the preparation of military forces, the NATO structures and allied nations, including the Portuguese, which use these tools in the education, training and to support military operations, are analysed. The essential operational requirements to build this centre were systematized and the respective implications were analysed. For this work, in the scope of the Military Sciences, a qualitative research strategy was adopted, with quantitative reinforcement, based on a comparative research design and deductive reasoning. As a result of this investigation, the building of this centre to ensure the adequate training of our forces is justified, owing to our financial, personnel and resources constraints. A possible organization is suggested, including a coordinating body of the simulation, and its location in the Military University Institute, where appropriate facilities are available. Additionally, the implementation of a federation of simulation centres, interconnected to identical infrastructures in the Atlantic Alliance will allow the joint and combined training of forces, the exchange of information and experiences.

The aim of this work is to simulate and design a distillation unit to produce a middle distillate, EcoGreen Power Plus, while maintaining the production of fuel oil. The purpose of Eco-Oil is to provide a sustainable fuel for marine transportation that meets the specifications of the ISO-F-DMA category for marine distillate fuels, thereby contributing to the energy transition.For this study, the SP2, feed of the existing flash tank, and SP7, fuel oil currently obtained, process streams were characterized to simulate the separation of their components. Then distillation column and flash tank models were formulated, and their numerical implementation was carried out using the GNU Octave programming language. The operating conditions and parameters that allowed a higher middle distillate production were studied. The configurations were evaluated considering a minimum pressure of 0,100 bar and a maximum temperature of 200 ºC.In configuration 1, consisting of a distillation column with side draw fed by the SP7 stream, the yield of middle distillate was 15,2 %, with the product being out of specification. In configuration 2, consisting of two flash tanks in series fed by the SP2 stream, resulted in an in-specification middle distillate with a yield of 26,2 %. In configuration 3, consisting of a flash tank fed by the SP2 stream followed by a distillation column, an in-specification middle distillate with a yield of 32,6 % was obtained. Although configuration 3 resulted in a higher yield of middle distillate, the investment and operational costs are higher, therefore future optimization of the configurations should be carried out.In this work, two scenarios were studied for configuration 2. In scenario 1, considering a fuel oil flash point of 120 ºC, a middle distillate yield of 16,9 % was obtained. In scenario 2, considering a fuel oil flash point of 140 ºC, a middle distillate yield of 29,6 % was obtained.Both flash tanks were sized considering the two scenarios of operating conditions of interest. For the first flash tank, a height of 3,24 m and a diameter of 1,05 m were obtained, resulting in a volume of 2,81 m³. For the second flash tank, a height of 3,23 m and a diameter of 0,75 m were obtained, resulting in a volume of 1,43 m³. Finally, these dimensions were adjusted considering some functional characteristics of the equipment to ensure an efficient operation.

O presente trabalho pretende desenvolver o digital twin da Unidade de Afinação de Fuel (UAF) do processo industrial de produção de fuelóleo a partir de resíduos oleosos, da Eco-Oil. Este trabalho é de extrema importância para a Eco-Oil, uma vez que a alimentação do seu processo é muito variada e, por isso, obriga o ajuste das condições de operação consoante as suas características. Para isso, desenvolveu-se um modelo matemático que compreende a formulação das principais operações unitárias que compõe a unidade e que permite prever o flash point da corrente de fuelóleo no final do seu processamento, de forma a averiguar se a especificação mínima de flash point de 65 ºC é cumprida.O modelo da UAF desenvolvido compreende duas fases. Numa primeira fase, desenvolveu-se o modelo da UAF original, compreendendo a formulação do tanque flash, permutadores de calor (HE 3.1.1, HE 3.2.1, HE 3.3.2 e HE 3.4.2), filtros vibratórios e depuradoras. Numa segunda fase, adicionou-se ao modelo desenvolvido os permutadores de integração energética (HE 3.6.2 e HE 3.7.2), adições resultantes do projeto de revamping energético da unidade. Uma vez desenvolvido o modelo da unidade, procedeu-se à sua implementação computacional, recorrendo ao software GNU Octave, e conduziu-se o exercício de simulação em estado estacionário. Por fim, comparou-se os resultados da simulação com os valores reportados por (Coelho, 2020), (Figueira, 2022) e com dados processuais. Comparou-se os resultados na simulação do tanque flash da UAF com os valores obtidos por (Coelho, 2020), cujo modelo desenvolvido no software Aspen contempla a simulação de uma coluna de destilação de três andares teóricos em estado estacionário. Os resultados obtidos são similares à previsão do modelo de (Coelho, 2020), destacando-se um maior desvio no cálculo do caudal de vapor. Comparou-se ainda os resultados obtidos na simulação dos permutadores de calor em estado estacionário, conduzida por (Figueira, 2022), cuja diferença não se mostrou significativa. Por fim, comparou-se os resultados da simulação com dados experimentais. Obteve-se um desvio de 3,08% e de 83,2% no cálculo do flash point relativamente à determinação em copo aberto e copo fechado, respetivamente. O cálculo da temperatura no tanque flash apresenta um desvio de 4,80% face à temperatura no topo da coluna e um desvio de 7,88% face à temperatura na base da coluna. Quanto à simulação dos permutadores de calor, obteve-se um desvio de 14,60% e 7,73% no cálculo da temperatura da utilidade à saída dos permutadores HE 3.2.1 e HE 3.3.2, respetivamente. Na simulação dos permutadores de integração energética, o modelo prevê a temperatura da corrente de fuelóleo à saída do HE 3.6.2 com um desvio de 19,90% e a temperatura da corrente de alimentação à saída do HE 3.2.1 com um desvio de 8,78%, face aos dados experimentais.O modelo desenvolvido apresenta algumas limitações, resultado da utilização de modelos simplistas na concretização dos balanços de massa ao tanque flash, nomeadamente a Lei de Raoult. Esta simplificação sobrevalorizou a estimativa da temperatura no tanque e comprometeu a capacidade de previsão da transferência de calor nos permutadores de aquecimento e de integração. Isto demonstra que, para o tipo de sistemas em estudo, será recomendável a utilização de modelos termodinâmicos mais rigorosos. Para além disto, o modelo calcula um valor de flash point correspondente à determinação em copo aberto, quando a correlação utilizada, a Correlação de Hshieh, é reportada como uma estimativa para copo fechado. Ainda assim, os cenários de simulação desenvolvidos demonstraram que o comportamento das variáveis e a relação entre as mesmas estão de acordo com o expectável.

Low-code frameworks strive to simplify and speed-up application development. Native support for the reuse and composition of parameterised coarse-grain components (templates) is essential to achieve these goals. OSTRICH-a rich template language for the OutSystems platform-was designed to simplify the use and creation of such templates. However, without a built-in composition mechanism, OSTRICH templates are hard to create and maintain. This paper presents a template composition mechanism and its typing and instantiation algorithms for model-driven low-code development environments. We evolve OSTRICH to support nested templates and allow the instantiation (hatching) of templates in the definition of other templates. Thus, we observe a significant increase code reuse potential, leading to a safer evolution of applications. The present definition seamlessly extends the existing Out-Systems metamodel with template constructs expressed by model annotations that maintain backward compatibility with the existing language toolchain. We present the metamodel, its annotations, and the corresponding validation and instantiation algorithms. In particular, we introduce a type-based validation procedure that ensures that using a template inside a template produces valid models. The work is validated using the OSTRICH benchmark. Our prototype is an extension of the OutSystems IDE allowing the annotation of models and their use to produce new models. We also analyse which existing OutSystems sample screens templates can be improved by using and sharing nested templates.

Vaccination has been the most effective strategy to contain and control infectious disease epidemics. Over the past decades, its success and the consequent herd immunity changed public perceptions on the disease and vaccination’s expected costs which, in some cases, resulted in vaccine hesitancy. This work extends the classical SIR model by incorporating both temporary and partial immunity, along with individual vaccination decisions driven by an imitation dynamics approach based on perceived expected costs. Our methodology relied on the stability analysis of the equilibria and the investigation of bifurcation phenomena within the model. To this end, we employed classical local asymptotic techniques, complemented by numerical continuation methods and the computation of Lyapunov exponents. The analysis of the model revealed an interplay between incomplete immune protection and imitation parameters, with rich dynamics involving oscillatory and chaotic behavior for low waning immunity rates and/or high protection against reinfection, and for high social-learning rate. Furthermore, exploring temporary immunity led to the conclusion that for diseases with shorter immunity periods and for vaccines with high relative expected cost, people will rapidly decline any vaccination efforts. These findings emphasize the importance of human behavior for a population in an epidemic landscape, and may provide insight on how to adapt and improve public health interventions.

Important requirements for the modern electric drives are the high overload capacity and a wide range of speed control. A two-phase adjustable low-power drive has these properties, but its implementation in small-scale mechanics is hindered by the need a frequency converter that provides a three-phase power grid into a two-phase network, which is important when the power of the mechanisms increases. Previous studies have already shown the possibility of using a typical frequency converter based on a three-phase full-bridge voltage inverter applying space-vector PWM method. The switching frequency of the inverter remains, unfortunately, relatively high. It is not possible to reduce this frequency without degrading the harmonic composition. The goal of this work is to develop an algorithm for controlling the two-phase electric drive system, while reducing the numberof commutations of the switching devices of the three-phase inverter, and at the same time keeping the deviations of the instantaneous values of the phase currents close enough to the reference.

Smart contracts are high-stakes software: their immutable, publicly accessible, code may govern assets worth millions, meaning that even minor defects can have severe consequences. The most used techniques to ensure smart contract correctness are testing and formal verification. Testing is almost always employed but is often restricted to unit tests (which often miss edge cases) and has limited coverage, while formal verification can provide strong guarantees but is often costly and complex to apply, demanding substantial time and expertise. Property-based testing bridges this gap by exploring large input spaces and shrinking failures to minimal counterexamples, helping uncover defects early in development. Formal verification can be left to critical features once testing has filtered out common issues. To add to the challenges smart contract developers face, most languages used were not designed with safety and security guarantees built-in. Daml is a smart contract language designed with correctness in mind, featuring a strong static type system, functional programming paradigms, and built-in abstractions for common smart contract patterns. However, Daml currently lacks support for property-based testing, limiting developers' ability to systematically explore input spaces and verify contract properties. This paper introduces Hypothesis2Daml, an open-source library that brings property-based testing to the Daml ecosystem by connecting the Hypothesis testing framework with the Daml JSON API. Hypothesis2Daml enables developers to specify invariants, preconditions, and stateful workflows over realistic ledger interactions, while providing automatic input generation, shrinking, and isolation of ledger state between test cases. The approach is evaluated using a benchmark consisting of eight contracts, three Daml templates, and twenty-eight property-based tests covering happy paths, negative cases, and alternative interaction orders. The results show that property-based testing is feasible for Daml smart contracts, can systematically expose violated properties with minimal counterexamples, and supports effective debugging of realistic, stateful workflows.

In this article we propose a binary classification model to distinguish a specific class that corresponds to a characteristic that we intend to identify (fraud, spam, disease). The classification model is based on a cloud of spheres that circumscribes the points of the class to be identified. It is intended to build a model based on a cloud and not on a disjoint set of clouds, establishing this condition on the connectivity of a graph induced by the spheres. To solve the problem, designed by a Cloud of Connected Spheres, a quadratic model with continuous and binary variables (MINLP) is proposed with the minimization of the number of spheres. The issue of connectivity implies in many models the imposition of an exponential number of constraints. However, because of the specific conditions of the problem under study, connectivity is enforced with linear constraints that scale quadratically with K, which serves as an upper bound on the number of spheres. This classification model is effective when the structure of the class to be identified is highly non-linear and non-convex, also adapting to the case of linear separation. Unlike neural networks, the classification model is transparent, with the structure perfectly identified. No kernel functions are used and it is not necessary to use meta-parameters unless it is intended also to maximize the separation margin as it is done in SVM. Finding the global optima for large instances is quite challenging, and to address this, a heuristic is proposed. The heuristic demonstrates nice results on a set of frequently tested real problems when compared to state-of-the-art algorithms.