The Steam Boiler Controller Problem in Signal-Coq

Among the various formalisms for the design of reactive systems, the SIGNAL-CO- Q formal approach, i.e. the combined use of the synchronous dataflow language SIGNAL and the proof assistant COQ, seems to be especially suited and practical. Indeed, the deterministic concurrency implied by the synchronous model on which SIGNAL is founded strongly simplifies the specification and the verification of such systems. Moreover, COQ is not limited to some kind of properties and so, its use enables to disregard what can be checked during the specification stage. In this article, we underline the various features of this SIGNAL-COQ formal approach with a large scale case study, namely the Steam Boiler problem

A comparative study of two formal semantics of the SIGNAL language

International audienceSIGNAL is a part of the synchronous languages family, which are broadly used in the design of safety-critical real-time systems such as avionics, space systems, and nuclear power plants. There exist several semantics for SIGNAL, such as denotational semantics based on traces (called trace semantics), denotational semantics based on tags (called tagged model semantics), operational semantics presented by structural style through an inductive definition of the set of possible transitions, operational semantics defined by synchronous transition systems (STS), etc. However, there is little research about the equivalence between these semantics.In this work, we would like to prove the equivalence between the trace semantics and the tagged model semantics, to get a determined and precise semantics of the SIGNAL language. These two semantics have several different definitions respectively, we select appropriate ones and mechanize them in the Coq platform, the Coq expressions of the abstract syntax of SIGNAL and the two semantics domains, i.e., the trace model and the tagged model, are also given. The distance between these two semantics discourages a direct proof of equivalence. Instead, we transformthem to an intermediate model, which mixes the features of both the trace semantics and the tagged model semantics. Finally, we get a determined and precise semantics of SIGNAL

Evaporative Cooling Garment System /ECGS/, part 1 Final report

Evaporative Cooling Garment System /ECGS/ for body cooling during extravehicular activity in spac

Actes des 14e journées sur les Approches Formelles dans l'Assistance au Développement de Logiciels

National audienceCet ouvrage présente les actes des 14èmes journées sur les Approches Formelles dans l'Assistance au Développement de Logiciels (AFADL'2015) qui se sont tenues à Bordeaux les 9 et 10 juin 2015

Fifteen-foot diameter modular space station Kennedy Space Center launch site support definition (space station program Phase B extension definition)

This document defines the facilities, equipment, and operational plans required to support the MSS Program at KSC. Included is an analysis of KSC operations, a definition of flow plans, facility utilization and modifications, test plans and concepts, activation, and tradeoff studies. Existing GSE and facilities that have a potential utilization are identified, and new items are defined where possible. The study concludes that the existing facilities are suitable for use in the space station program without major modification from the Saturn-Apollo configuration

Integration of a model for volatile release in the CFD simulation of an industrial biomass boiler

Doctoral Thesis for PhD degree in Leaders for Technical IndustriesMotivada por sua disponibilidade, abundância generalizada e preocupações ambientais, a biomassa sólida tornou-se uma opção competitiva para diversificar a produção de eletricidade entre os recursos de energia renovável. Este trabalho tem como objetivo caraterizar o comportamento da combustão de espécies de biomassa frequentemente utilizadas em centrais termoelétricas para suportar o desenvolvimento de um modelo numérico para modelação eficiente e precisa da conversão de biomassa numa caldeira industrial a grelha. A eficiência da caldeira numa central de 35 MWth foi calculada como sendo aproximadamente 80%. Amostras selecionadas de biomassa de eucalipto, pinheiro, acácia e oliveira foram testadas com o analisador térmico Hot Disk TPS 2500S. A condutividade térmica ficou compreendida entre 0,239 e 0,404 W/mK. Além disso, a capacidade calorífica apresentou uma variação entre 0,855 e 2,442 MJ/m3K, e a difusividade térmica entre 0,187 e 0,258 mm2/s. Para a análise final e aproximada foram utilizados os equipamentos LECO TruSpec CHN Macro e LECO CS-200 e uma mufla, respetivamente. Os dados revelaram uma maior reatividade do eucalipto, cerca de 2 vezes superior aos outros combustíveis, e a propensão da acácia a produzir emissões poluentes (principalmente à base de azoto) e problemas de deposição de cinzas devido à sua composição química. Amostras de pequenas dimensões (cerca de 10 mg) foram usadas para medir a perda de massa e a sua reatividade num analisador termogravimétrico (TGA) da TA Instruments, modelo SDT 2960. Os testes foram realizados em atmosfera oxidante, a uma taxa de aquecimento entre 5 e 100 ºC/min, até 900 ºC. Observou-se que numa ampla faixa de temperaturas, a conversão do combustível segue uma sequência de secagem, desvolatilização e combustão do resíduo carbonoso. Amostras de maiores dimensões foram testadas num reator construído para esse fim, e que simula o processo de desvolatilização de forma controlável. Neste, a perda de massa foi medida continuamente ao longo do tempo enquanto os compostos da fase gasosa foram recolhidos em sacos para posterior análise num cromatógrafo gasoso da Bruker Scion 456-GC equipado com um detetor de condutividade térmica. Ao contrário dos dados do TGA, concluiu-se que na oxidação de biomassas, utilizando partículas maiores, não é possível distinguir as sucessivas etapas de conversão, devido à maior resistência interna de difusão. Avaliando a influência da esbelteza da amostra (rácio comprimento/espessura), concluiu-se que a taxa de desvolatilização depende apenas da sua espessura e não do volume. Além disso, para temperaturas mais altas do reator, a taxa de perda de massa é independente do tipo de biomassa. Os compostos gasosos libertados durante a conversão térmica do eucalipto apresentaram forte correlação com a temperatura do reator, sendo CO2 e CO sempre os principais produtos de desvolatilização. A dependência da temperatura de ambos os compostos apresentam, para o CO, um aumento de 8 a 13% entre 600 e 800°C, enquanto o de CO2 aumenta apenas ligeiramente de 11 a 12%. O modelo eXtended Discrete Element Method foi usado para descrever a desvolatilização no reator. Os resultados foram comparados com os dados experimentais e, embora tenha sido observada uma boa concordância, concluiu-se que a oxidação do resíduo carbonoso necessita de um modelo de difusão. A simulação do escoamento no interior da caldeira foi feita utilizando o software ANSYS Fluent. Neste, um modelo empírico externo para prever a conversão de biomassa ao longo da grelha é acoplado a um modelo CFD para prever o escoamento reativo dentro da caldeira. Os resultados destacaram a contribuição da contração na seção intermédia da fornalha, e a necessidade de um maior caudal de ar secundário para reduzir as emissões de CO. Os resultados mostram que modificando a razão entre o ar primário e secundário de 79/21 para 40/60, obteve-se uma redução da fração mássica de CO de 0.009 para 0.0003.Motivated by their availability, widespread abundance, and environmental concerns, solid biomass has become a competitive option to diversify electricity production amongst the renewable energy resources. This work aims to characterize the combustion behavior of solid biomass species frequently used in power plants as a route to support the development of a numerical model for efficient and accurate modeling of biomass conversion in an industrial grate-fired boiler. The boiler efficiency of a power plant rated at 35 MWth was calculated as approximately 80%. Selected samples of biomass (eucalyptus, pine, acacia, and olive) were tested with a Hot Disk Thermal Constants Analyzer TPS 2500S. The thermal conductivity, varied in the range of 0.239 to 0.404 W/mK. In addition, the heat capacity is within 0.855 to 2.442 MJ/m3K, and the thermal diffusivity is between 0.187 and 0.258 mm2/s. The ultimate and proximity analysis was carried out on the fuel samples using LECO TruSpec CHN Macro and LECO CS-200 equipment and a muffle furnace, respectively. The data revealed a higher reactivity of eucalyptus, which is around 2 times higher than that of other fuels, and the propensity of the acacia to produce pollutant emissions (mostly Nitrogen based) and ash deposition problems due to their chemical composition. Small size samples (around 10 mg each) were used to measure the mass loss and their reactivity in a thermogravimetric analyzer (TGA) from TA Instruments, model SDT 2960. The tests were carried out on an oxidizing atmosphere at a heating rate between 5 and 100 ºC/min up to 900 ºC. It was observed that over a wide range of temperatures, fuel conversion follows a sequence of drying, devolatilization, and char combustion. Larger samples of heartwood were tested in a purpose built reactor that simulates the devolatilization process under a controllable manner. In this, the mass loss was continuously measured along the time while the gas phase compounds were collected in bags for subsequent analysis in a gas chromatograph Bruker Scion 456-GC equipped with a thermal conductivity detector. As opposed to the TGA data, it was concluded that all fuels show that the combustion of large particles does not exhibit separate consecutive conversion stages, due to internal diffusion resistance. This was further highlighted by varying the sample aspect ratio. It was concluded that the devolatilization rate depends on the smallest dimension and not on the bulk size. Furthermore, at higher reactor temperatures, the mass loss profile is independent of the biomass. The gas compounds released with eucalyptus presented a strong correlation with the reactor temperature, being CO2 and CO always the main devolatilization products. The temperature dependence of both compounds shows, for CO, an increase from 8 to 13% between 600 and 800 °C, while the CO2 yield is only slightly increasing from 11 to 12%. The eXtended Discrete Element Method model was implemented to describe the devolatilization inside the reactor. The results were compared with the experimental data and, while a good agreement was observed, it was concluded that the char oxidation needs to be also represented by a diffusion model. The numerical model was developed using the ANSYS Fluent software. In this, a user defined empirical model to predict the biomass conversion along the grate was coupled with a freeboard model to predict reactive flow inside the boiler. The results highlighted the contribution of the converging sections in the middle section of the furnace and the need for a higher secondary air flow rate to reduce CO emissions. The results show that a reduction of the CO mass fraction from 0.009 to 0.0003 was possible with a modification of the primary to secondary air split ratio from 79/21 to 40/60.Fundação para a Ciência e a Tecnologia for sponsoring my research, through the grant SFRH/BD/130588/2017