CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / FAPEMIG - Fundação de Amparo a Pesquisa do Estado de Minas Gerais / Atualmente, tem-se estudado diversos tipos de pré- tratamentos para reduzir a recalcitrância da biomassa lignocelulósica com intuito de aumentar sua digestibilidade química/enzimática, para que esta possa ser utilizada na produção de etanol e/ou outros bioprodutos de valor agregado. Neste estudo avaliou-se o efeito do pré-tratamento de explosão a vapor catalisada por ácido cítrico e hidróxido de sódio, e do pré-tratamento de deslignificação alcalina nas propriedades químicas e estruturais do bagaço de cana-de-açúcar (BCA), bem como sobre o processo de hidrólise enzimática. O pré-tratamento de explosão a vapor foi realizado em reator de 1,4L sob temperatura de 180 °C com tempo de retenção de 5 min. A etapa de deslignificação com NaOH (2% m:m) foi realizada a 120 °C, sob refluxo de 4h. A caracterização química e estrutural da biomassa in natura e pré-tratada foi realizada por FTIR, MEV, DRX. A hidrólise enzimática foi realizada com volume final de 20 mL constituído de 3% de BCA (massa seca), tampão de citrato de sódio 50 mM (pH=5,0) e 10 FPU do complexo enzimático Cellic® CTec 3. Os frascos foram mantidos sob agitação de 150 rpm a 50ºC por 72 h. Retirou-se alíquotas de 1,5 mL após 0, 12, 24, 36, 48 e 72h para determinação de açúcares redutores totais (ART) pelo método do ácido 3,5-dinitrosalicílico (DNS). O bagaço de cana-de-açúcar apresentou 24,22% de lignina, 27,61% de hemiceluloses e 42,77% de celulose, no entanto após o pré-tratamento de explosão a vapor catalisado com ácido cítrico, obteve-se uma biomassa com menor quantidade de hemiceluloses (16,16%) e com formação de fissuras na parede celular da fibra. O bagaço pré-tratado por explosão a vapor com NaOH apresentou completa desestruturação da fibra, remoção de 65% da lignina e preservação da fração hemicelulósica. Depois de submeter à biomassa lignocelulósica sem tratamento e pré-tratada por explosão a vapor ao processo de deslignificação alcalina observou-se a completa desestruturação da matriz lignocelulósica e a solubilização de 85-90% da lignina em todas as amostras. O índice de cristalinidade da biomassa após os prétratamentos teve uma aumento quando comparado ao material in natura, podendo este ser associado à remoção de componentes amorfos, como a lignina e hemiceluloses, e também da fração amorfa da celulose. Frente ao percentual mássico de biomassa utilizada no processo de hidrólise enzimática valor teórico correspondente a 100% de sacarificação equivale, aproximadamente, a 33,0 g.L-1. Após a hidrólise enzimática (72h) da biomassa in natura e pré-tratada por explosão a vapor obteve-se uma maior concentração de ART e um maior percentual de sacarificação para o bagaço de cana obtido a partir da explosão a vapor com NaOH (23,05 g.L-1, 69,15% de sacarificação). Já na hidrólise da biomassa in natura após processo de deslignificação alcalina a concentração de ART aumentou em 18,33 g.L-1, enquanto que para o bagaço pré-tratado por explosão a vapor com água, ácido cítrico e NaOH seguido da deslignificação alcalina o aumento de ART, correspondeu a 19,67 g.L-1, 19,93 g.L-1 e 6,87 g.L-1. Diante da produção de ART após deslignificação notou-se que o percentual de sacarificação para a biomassa sem tratamento elevou-se de 11,88% para 69,15%, enquanto que para o bagaço após explosão a vapor e deslignificação este percentual ficou entre 82,05% - 89,79%. Por fim, cabe ressaltar que no BCA previamente pré-tratado por explosão a vapor com NaOH, a remoção de lignina após o segundo pré-tratamento teve um acréscimo de apenas 20% e a concentração de ART de 6,87 g.L-1. Dessa forma, acredita-se que ao aumentar a concentração da solução de NaOH para realizar a explosão a vapor poderia-se não necessitar da realização da etapa de deslignificação. / Nowadays, there is various types of studied pre-treatments to reduce the lignocellulosic biomass recalcitrance in order to increase its chemical / enzymatic digestibility, so that it can be used in ethanol production and / or other bioproducts value. This study evaluated the effect of steam explosion pretreatment catalyzed by citric acid and sodium hydroxide, and alkaline delignification pretreatment over chemical and structural properties of sugarcane bagasse, as well as the enzymatic hydrolysis process. Steam explosion pretreatment was conducted in a 1.4 L reactor at temperature of 180 °C and 5 min hold time. The delignification step with NaOH (2% m:m) was performed at 120 °C under reflux for 4 hours. Chemical and structural characterization of raw and pretreated biomass was performed by FTIR, SEM and XRD. Enzymatic hydrolysis was performed with final volume of 20 mL consisting 3% SCB on dryweight basis, sodium citrate buffer 50 mM (pH = 5.0) and 10 FPU of Cellic® Ctec 3 enzyme complex. Flasks were kept under agitation of 150 rpm at 50 °C during 72 h. It was analyzed 1.5 mL aliquots after 0, 12, 24, 36, 48 and 72 hours to determinate total reducing sugars (TRS) by acid 3,5-dinitrosalicílic method (DNS). Sugarcane bagasse showed 24.22% lignin, 27.61% hemicelluloses and 42.77% of cellulose, however after steam explosion pretreatment catalyzed by citric acid, it was obtained a biomass with lesser hemicelluloses amount (16.16%) and cracks formation on fiber cell wall were observed. The bagasse pretreated by steam explosion by NaOH showed complete destructuring of fiber and lignin removal was 65%, while hemicellulosic fraction was preserved. After submitting untreated and pretreated lignocellulosic biomass by steam explosion to alkaline delignification process, complete destructuring and solubilization of the lignocellulosic matrix was observed with 85-90% lignin removal in all samples. The crystallinity index of biomass after pretreatments increased when compared to raw material and this could be associated to amorphous components removal, such as lignin and hemicelluloses, and also the amorphous cellulose fraction. The theoretical value corresponding to 100% of saccharification corresponds to approximately 33.0 g·L-1, compared to the mass percentage of biomass used in the enzymatic hydrolysis process. After 72 h enzymatic hydrolysis of raw and pretreated biomass by steam explosion, the highest concentration of total reducing sugars (TRS) and the highest percentage of saccharification were obtained for sugarcane bagasse (23.05 g·L-1, 69,15% saccharification). In in nature biomass hydrolysis, after alkaline delignification process, ART concentration increased 18.33 g·L-1, while pretreated biomass by steam explosion with water, citric acid and NaOH followed by alkaline delignification increase TRS to 19.67 g·L-1, 19.93 g·L-1 and 6.87 g·L-1. After delignification, it was noted that saccharification percentage for untreated biomass increased from 11.88% to 69.15%, while for bagasse after steam explosion and delignification this percentage was between 82.05% - 89.79%. Lastly, it should be noted that in biomass previously pretreated by NaOH steam explosion, lignin solubilization after the second pretreatment had an increase of only 20% and TRS concentration of 6.87 g·L-1. Thus, it is believed that increasing NaOH solution concentration to perform steam explosion could not need to implement delignification step. / Dissertação (Mestrado)

Dans cette thèse, une nouvelle loi d'endommagement en traction des roches sous chargement exploisif est établie. Basée sur l'approche micro-mécanique et énergétique, la loi d'évolution d'endommagement dynamique est conçue à l'aide de la méthode mathématique d'homogénéisation basée sur le développement asymptotique, et en tenant compte de l'effet inertiel lors de la propagation de fissure. Les simulations numériques sont présentées en vue d'illustrer la capacité du modèle à décrire les comportements connus comme les effets de taille pour la réponse structurelle, la sensibilité au taux de déformation, la transition fragile-ductile et la dispersion de l'onde.<p><p>La loi est implémentée dans le code aux éléments finis LAGAMINE pour étudier la réponse macroscopique du modèle. Plusieurs cas d'applications en dynamique ont été examinés.\\<p><p>- En 1D, les problèmes de localisation ont été étudiés dans une barre sollicitée en traction dynamique par une rampe de chargement. Selon l'amplitude de chargement, trois réponses ont été identifiées: a) comportement purement élastique pour des faibles charges, b) localisation à l'extrémité encastrée de la barre pour des chargements modérés et c) localisation à la tête de la barre pour des chargements élevés. L'influence de la taille microstrurelle sur la localisation a été examinée. Des simulations numériques de l'essai de traction dynamique par écaillage ont été éffectuées. Des essais expérimentaux de traction dynamique par écaillage ont été réalisés sur la bauxite et ont permis de valider le modèle en comparant l'analyse post mortem de l'éprouvette aux résultats des simulations numériques d'écaillage. Ces essais ont aussi permis de déterminer les caractéristiques mécaniques du matériau, la résistance mécanique en traction dynamique, l'instant de rupture et la vitesse de déformation à rupture.\\<p><p>- En 2D, des simulations numériques sont efféctuées pour reproduire le comportement d'une mine sous charge explosive. Le modèle a été capable de reproduire l'endommagement en traction sous charge explosive. L'influence des paramètres du modèle tels que: l'orientation de fissures, la taille de microstructure et la valeur initial d'endommagement sur la distribution de l'endommagement autour du trou de charge a été étudiée. Enfin, un cas d'application sur les mines de bauxite de Guinée a été étudié, incluant un calcul de l'extension de la zone endommagée ainsi qu'une prédiction numérique du niveau de vibration engendrée suite aux tirs à l'explosif. La prédiction du modèle est globalement en accord avec les résultats de la littérature. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

An unreliable failure detector is a basic building block widely used to implement fault tolerance techniques in asynchronous distributed systems. The use of failure detectors comes from the impossibility to implement deterministic agreement protocols in these environments, since it is not possible to distinguish a crashed process from a very slow process. However, the massive use of distributed computational resources claims for solutions applicable in large scale distributed systems. In these systers, traditional failure detector algorithms can present scalability problems, such as control message explosion problem, because a large number of messages could compromise the quality of service of failure detectors and the system scalability. The goal of this dissertation is minimize the problem of control message explosion generated by failure detector algorithms in large scale processes monitoring. To do that, we propose a new approach to reduce the number of control messages from reusing messages. Our approach explores the manipulation of the interrogation period or heartbeat period, maximizing the reuse of messages, and it is organized by two strategies: ATF (Frequency Rate Adaptation), that reuses failure detector messages to suppress control messages; and AMA (Reusing of Application Message), that reuses client application messages to suppress control messages. As result, the resulting approach is generic, in the sense that it could be applied to any failure detector algorithm, and practical, in the sense that for its, the traditional failure detectors algorithms need only to change the semantic of control messages. From our experimental results, we demonstrate that our approach reduces the number of control messages, minimizing the message explosion problem, without compromising the quality of service of the failure detector / Detectores de defeitos não con�áveis são amplamente utilizados como bloco básico na implementa ção de técnicas de tolerância a falhas em sistemas distribuídos assíncronos. Sua utilização nestes ambientes é motivada pela impossibilidade de implementação de protocolos de acordo determinísticos, pois não há como distinguir processos defeituosos daqueles de acesso mais lento. Entretanto, o uso maciço de recursos computacionais exige soluções aplicáveis a sistemas distribuídos de larga escala. Neste contexto, algoritmos tradicionais de detecção de defeitos podem apresentar problemas de escalabilidade, tal como o de explosão de mensagens. O grande número de mensagens enviadas pode comprometer a qualidade de serviço do detector de defeitos e a escalabilidade do sistema. Esta dissertação visa minimizar o problema da explosão de mensagens de controle geradas pelos algoritmos de detecção de defeitos em ações de monitoramento de processos. Para tal, propõe-se uma nova abordagem para redução do número de mensagens de controle através do reaproveitamento de mensagens. A abordagem explora a manipulação da periodicidade de envio das mensagens de controle, maximizando o reaproveitamento de mensagens, e é composta por duas estratégias: ATF (Adaptação da Taxa de Freqüência), a qual reaproveita mensagens dos próprios algoritmos de detecção para suprir mensagem de controle; e AMA (Aproveitamento de Mensagens da Aplicação), a qual reaproveita mensagens das aplicações clientes para o mesmo objetivo da ATF. Como resultado, têm-se uma abordagem genérica, no sentido que pode ser aplicada a qualquer algoritmo de detecção, e prática, no sentido que algoritmos tradicionais de detectores de defeitos necessitam apenas alterar a semântica das mensagens de controle para utilizá-la. Através de experimentos demonstra-se que sua aplicação reduz o número de mensagens de controle, minimizando o problema da explosão de mensagens, sem comprometer a qualidade de serviço do detector de defeitos

Off-gassing of hazardous compounds is, together with self-heating and dust explosions, the main safety hazards within large-scale biomass storage and handling. Formation of CO, CO2, and VOCs with concurrent O2 depletion can occur to hazardous levels in enclosed stored forest products. Several incidents of CO poisoning and suffocation of oxygen depletion have resulted in fatalities and injuries during cargo vessel discharge of forest products and in conjunction with wood pellet storage rooms and silos. Technologies for torrefaction and steam explosion for thermal treatment of biomass are under development and approaching commercialization, but their off-gassing behavior is essentially unknown. The overall objective of this thesis was to provide answers to one main question: “What is the off-gassing behaviour of thermally treated lignocellulosic biomass during storage?”. This was achieved by experimental studies and detailed analysis of off-gassing compounds sampled under realistic conditions, with special emphasis on the VOCs. Presented results show that off-gassing behavior is influenced by numerous factors, in the following ways. CO, CO2 and CH4 off-gassing levels from torrefied and stream-exploded biomass and pellets, and accompanying O2 depletion, are comparable to or lower than corresponding from untreated biomass. The treatments also cause major compositional shifts in VOCs; emissions of terpenes and native aldehydes decline, but levels of volatile cell wall degradation products (notably furans and aromatics) increase. The severity of the thermal treatment is also important; increases in torrefaction severity increase CO off-gassing from torrefied pine to levels comparable to emissions from conventional pellets, and increase O2 depletion for both torrefied chips and pellets. Both treatment temperature and duration also influence degradation rates and VOC composition. The product cooling technique is influential too; water spraying in addition to heat exchange increased CO2 and VOCs off-gassing from torrefied pine chips, as well as O2 depletion. Moreover, the composition of emitted gases co-varied with pellets’ moisture content; pellets of more severely treated material retained less moisture, regardless of their pre-conditioning moisture content. However, no co-variance was found between off-gassing and pelletization settings, the resulting pellet quality, or storage time of torrefied chips before pelletization. Pelletization of steam-exploded bark increased subsequent VOC off-gassing, and induced compositional shifts relative to emissions from unpelletized steam-exploded material. In addition, CO, CO2 and CH4 off-gassing, and O2 depletion, were positively correlated with the storage temperature of torrefied softwood. Similarly, CO and CH4 emissions from steam-exploded softwood increased with increases in storage temperature, and VOC off-gassing from both torrefied and steam-exploded softwood was more affected by storage temperature than by treatment severity. Levels of CO, CO2 and CH4 increased, while levels of O2 and most VOCs decreased, during storage of both torrefied and steam-exploded softwood.CO, CO2 and O2 levels were more affected by storage time than by treatment severity. Levels of VOCs were not significantly decreased or altered by nitrogen purging of storage spaces of steam-exploded or torrefied softwood, or controlled headspace gas exchange (intermittent ventilation) during storage of steam-exploded bark. In conclusion, rates of off-gassing of CO and CO2 from thermally treated biomass, and associated O2 depletion, are comparable to or lower than corresponding rates for untreated biomass. Thermal treatment induces shifts in both concentrations and profiles of VOCs. It is believed that the knowledge and insights gained provide refined foundations for future research and safe implementation of thermally treated fuels as energy carriers in renewable energy process chains.

Les explosions gamma (GRB) sont des évènements extrêmement violents. Ils sont sommairement classifiés en deux groupes par leur durée : les courts et les longs. Cette classification a permis de déterminer l'origine des GRBs : une collision entre deux objets compacts pour les courts ou l'explosion d'une étoile très massive pour les longs. Une meilleure classification des GRBs longs pourrait mieux contraindre leurs propriétés. Dans ma thèse, je présente des évidences de l'existence d'une sous-classification des GRBs basés sur la faible luminosité de leurs derniers reflets. Ces explosions sont appelées Low-Luminosity Afterflow (LLA). Je présente la technique de réduction des données, la méthode de sélection de ces GRBs ainsi que leurs principales propriétés. Leur lien avec les supernovæ (SN) est mis en évidence car 64 % de tous les GRBs associés à des Sns sont des LLA GRBs. Finalement, je présente d'autres propriétés comme leur fréquence, qui semble indiquer une nouvelle distincte classe, les propriétés de leurs galaxies hôte qui montrent que ces explosions ont pour origines des galaxies formant beaucoup d'étoiles. De plus, je montre qu'il est difficile de réconcilier les différences entre les GRBs normaux et les LLA GRBs en ne considérant que des effets instrumentaux et environnementaux, ou bien une géométrie différente. Donc je conclue que les deux classes de GRBs ont des propriétés différentes. En basant l'argumentation sur la fonction de masse initiale, sur la fréquence des LLA GRBs et sur le type de SNs qui les accompagnent, j'indique qu'un système binaire est favorisé pour leur origine. / Gamma-ray bursts (GRB) are extreme events. They are crudely classified into two groups based on their duration, namely the short and long bursts. Such a classification has proven to be useful to determine their progenitors: the merger of two compact objects for short bursts and the explosion of a massive star for long bursts. Further classifying the long GRBs might give tighter constraints on their progenitor and on the emission mechanism(s). In my thesis, I present evidence for the existence of a sub-class of long GRBs, based on their faint afterglow emission. These bursts were named low-luminosity afterglow (LLA) GRBs. I discuss the data analysis and the selection method, and their main properties are described. Their link to supernova is strong as 64\% of all the bursts firmly associated to SNe is LLA GRBs. Finally, I present additional properties of LLA GRBs: the study of their rate density, which seems to indicate a new distinct third class of events, the properties of their host galaxies, which show that they take place in young star-forming galaxies. Additionally, I show that it is difficult to reconcile all differences between normal long GRBs and LLA GRBs only by considering instrumental or environmental effects, different ejecta content or a different geometry for the burst. Thus, I conclude that LLA GRBs and normal long GRBs should have different properties. In a very rudimentary discussion, I indicate that a binary system is favored in the case of LLA GRB. The argument is based on the initial mass function of massive stars, on the larger rate density of LLA GRBs compared to the rate of normal long GRBs and on the type of accompanying SNe.

The current shortage of crude oil from conventional sources has increased interest in developing unconventional resources such as oil sands. Heavy crudes and bitumen are found in Northern Alberta and their exploration, processing, and transport to market pose challenges in the use of these resources. Part of the solution to these challenges involves the reactive thermal processing of heavy crudes and bitumen. This thesis focused on mild thermal cracking reactions, and two studies regarding these reactions were presented. The first was an experimental study performed in a pilot-scale semi-batch reactor. The three crude oils were heated to 350, 400, 425, and 450°C at 1240 kPa. A five-lump reaction model combined with a process simulator with VLE calculations was fitted with the experimental data obtained. The goodness of fit between the model predicted values and experimental values for the Hardisty (MBL), Albian Heavy Synthetic (AHS), and Christina Lake Dilute Bitumen (CDB) were determined to be 0.99, 0.99, and 0.98, respectively. Moreover, 80, 85, and 89% of the optimized model’s predicted values had less than 10% error for MBL, AHS, and CDB, respectively. The second study described the implementation of a mild thermal cracking reaction model to the development of a train car fire-model for the assessment of safety aspects in the design of train cars used to transport crude oil. Case studies were conducted using the UniSim® depressuring utility and a previously developed mild thermal cracking reaction model to demonstrate the effect of compositional change. Three crude oils with varying properties and representative of the types of crudes transported by rail in Canada were used here: MBL, AHS, and CDB. The case studies conducted showed the performance of a train car fire-model to be dependent on the crude oil characteristics: up to -57% and -99% difference in model predicted variables for AHS and CDB, respectively, when compared to MBL. Furthermore, the model’s performance was also shown to be affected by the compositional change of a given crude oil due to mild thermal cracking reactions: up to 42% difference in model predicted variables when compared to the base case.

This master's thesis consists of three parts. The theoretical part deals with short-circuit conditions in the electricity supply system and with the method of their calculation. The practical part includes the programming process of a programme; description of programme properties and functionality. The third part contains the verification of an accurate programme calculation of the examples.

Risk Analysis of Construction Chemicals Storge Diplom Thesis, Institute of Metrollogy and Quality Assurance Testing, Brno University of Technology, Faculty of Mechanical Engineering This diploma thesis focuses on risk assessment and possible assessment measure necessary when the amount of storage load containing Ethylbenzen increases by 300 percent.

Der Umgang mit brennbaren Stoffen erfordert ein hohes Maß an Sicherheit und Aufmerksamkeit. Auf diese Anforderungen wird selbst in alltäglichen Situationen wie beispielsweise bei der Nutzung eines Gaskochers- und -grills hingewiesen. Fehler in der Handhabung können zu schwerwiegenden Folgen führen. Jedoch ist der Einsatz von brennbaren Stoffen in industriellen Prozessen und Produktionen notwendig. Unter definierten Bedingungen kann dabei der brennbare Stoff mit dem Sauerstoff aus der Luft eine explosionsfähige Atmosphäre bilden, die durch eine Zündquelle entzündet werden kann. Die Folge ist „eine plötzliche Oxidations- oder Zerfallsreaktion mit Anstieg der Temperatur, des Druckes oder beider gleichzeitig“ (ISO 8421 1987), eine Explosion. Durch Explosionen werden Menschen, Maschinen und Umwelt gefährdet. Die Zündquellen werden durch unterschiedlichste Ursachen bedingt. Am 07. Februar 2008 verursachte ein heiß gelaufenes Lager eine Explosion in einer Zuckerraffinerie, die 14 Menschen das Leben kostete (CSB 2009). Durch den Einsatz des Explosionsschutzes sollen solche Katastrophen und Unfälle verhindert werden. Dieses Gebiet der Sicherheitstechnik wird dabei in den elektrischen und nicht-elektrischen Explosionsschutz unterschieden. Im Rahmen des nicht-elektrischen Explosionsschutzes werden Geräte und Baugruppen betrachtet, die ihre Funktion mechanisch erfüllen (ISO 80079-36 2016). Essenzielle Komponenten sind dabei die klassischen Maschinenelemente wie Lager, Riemen oder Kupplungen. Diese Bauteile müssen alleinstehend und in Kombination die Anforderungen einer explosionsschutzgerechten Auslegung erfüllen. Diese Bedingung kann jedoch eine Herausforderung darstellen.

The purpose of this study was to examine the impact of social media on crisis communication. To evaluate this impact, a case study method was utilized examining the crisis communication response of the Deepwater Horizon Oil Spill on April 20, 2010. This study focused on the response of the responsible party, British Petroleum, and the general public over three social media: Facebook, Twitter, and blogs. Through extensive analysis of both the company's and public response to the Gulf spill, nine implications were identified regarding social media's influence on crisis communication. These implications highlighted the potential for organizations to build interpersonal relationships with its publics. These relationships were found to be crucial in times of crises. The implications of this study also pointed to interactivity, using a "human voice," trust, and credibility as crucial factors in building these relationships and leading an effective crisis response across social media. This study also noted the new stress for organization's to respond quickly to crises as a result of instant news brought by social media. Implications of this study also highlighted social media's influence on individuals becoming contributing members of a crisis response. While social media has influenced the practice of crisis communication in many ways, this study found that the principles and ethics of the field have remained the same. In conclusion, analysis suggests that BP neglected using social media in its crisis response, a channel which has entered the mainstream of crisis communication. As a result, this study recommends the use of social media before, during, and after a crisis to ensure the welfare of a company and its relationship with its publics.