Bioethanol is an appealing alternative to petroleum-based liquid fuel due to drivers such as environmental regulations and government mandates. Second generation lignocellulosic feedstocks are abundant, but their resistance to hydrolysis continues to be problematic. Different pretreatments have been proposed to increase cellulose reactivity. Softwood pine autohydrolyzed at different severities was subjected to further treatment to increase fibre reactivity. Liquid hot water is most effective at removing barriers, with the highest increase in sugar yield after enzymatic hydrolysis. Alkaline (NaOH) is found to be the worst option compared to dilute acid and organosolv. In addition, higher chemical concentrations and longer treatment times do not guarantee higher enzymatic hydrolysis yield. Process modifications such as fiber washing and multistage enzymatic hydrolysis are observed to be effective at increasing yield. However, more research is required to bring the enzymatic hydrolysis yield to a level where commercialization is feasible.

Bioethanol is an appealing alternative to petroleum-based liquid fuel due to drivers such as environmental regulations and government mandates. Second generation lignocellulosic feedstocks are abundant, but their resistance to hydrolysis continues to be problematic. Different pretreatments have been proposed to increase cellulose reactivity. Softwood pine autohydrolyzed at different severities was subjected to further treatment to increase fibre reactivity. Liquid hot water is most effective at removing barriers, with the highest increase in sugar yield after enzymatic hydrolysis. Alkaline (NaOH) is found to be the worst option compared to dilute acid and organosolv. In addition, higher chemical concentrations and longer treatment times do not guarantee higher enzymatic hydrolysis yield. Process modifications such as fiber washing and multistage enzymatic hydrolysis are observed to be effective at increasing yield. However, more research is required to bring the enzymatic hydrolysis yield to a level where commercialization is feasible.

An algorithm for extracting event information from a Coulomb Explosion Imaging (CEI) position sensitive detector (PSD) is developed and compared with previously employed schemes. The PSD is calibrated using a newly designed grid overlay and validates the quality of the described algorithm. Precision calculations are performed to determine how best the CEI apparatus at The University of Waterloo can be improved. An algorithm for optimizing coincidence measurements of polyatomic molecules in CEI experiments is developed. Predictions of improved efficiency based on this algorithm are performed and compared with experiments using a triatomic molecule. Analysis of an OCS targeted CEI experiment using highly charged Argon ions to initiate ionization is performed. The resulting measurements are presented using a variety of visualization tools to reveal asynchronous and sequential fragmentation channels of OCS3+.

Zugl.: Marburg, Universiẗat, Diss., 2007.

Techn. Universiẗat, Diss., 2003--Berlin.

Les explosions de mélanges de gaz inflammables/solides combustibles ne sont pas bien comprises en raison de la complexité des transferts thermiques, des mécanismes de cinétiques et des interactions entre la turbulence /combustion. L'objectif principal de ce travail est d'étudier la sévérité des explosions des nanoparticules de carbone noir/méthane afin de comprendre l'influence de l'insertion des nanoparticules sur les explosions de gaz. Des tests ont été effectués sur ces mélanges dans un tube de propagation de la flamme et dans une sphère d'explosion standard de 20 L. L'influence de la turbulence initiale et de la taille de particule élémentaire du noir de carbone a également été étudiée. Il semble que l'insertion de nanoparticules de noir de carbone augmente d'environ 10% la sévérité de l’explosion pour les mélanges pauvres en méthane. Par conséquent, il semble que les nanoparticules ont un impact sur la sévérité de l'explosion même pour les systèmes à basse turbulence, contrairement aux systèmes impliquant des poudres de taille micrométrique qui nécessitent une dispersion à des niveaux élevés de turbulence. L'augmentation de la vitesse maximale de montée en pression est plus élevée pour des poudres avec un petit diamètre de particule, notamment en raison des phénomènes de fragmentation. En outre, un modèle numérique de propagation de front de flamme associé à un mélange gaz/noir de carbone a été développé pour examiner l'influence du noir de carbone sur la propagation de la flamme. Les résultats du modèle numérique suggèrent que la contribution de la chaleur radiative favorise l'accélération de la flamme. Ces résultats sont en accord avec les résultats expérimentaux de sévérité de l'explosion pour certains mélanges hybrides / Flammable gas/solid hybrid mixture explosions are not well understood because of the interaction of the thermal transfer process, the combustion kinetics mechanisms and the interactions between turbulence and combustion. The main objective on this work is to study the explosion severity and flame burning velocities of carbon black nanoparticles/methane to better understand the influence of added nanopowders in gas explosions. Tests have been performed in a flame propagation tube and in the standard 20 L explosion sphere. The influence of carbon black particles on the explosions severity and in the front flame propagation has been appreciated by comparing the results obtained for pure gas mixtures. It appeared that the carbon black nanoparticles insertion increases around 10% the explosion severity for lean methane mixtures. Therefore, it seems that nanoparticles has an impact on the severity of the explosion even for quiescent systems, contrary to systems involving micro-sized powders that requires a dispersion at high turbulence levels. The increment on the maximum rate of pressure rise is higher for powders with lower elementary particle diameter, which is notably due to the fragmentation phenomena. A flame propagation numerical model associated to a gas/carbon black mixture has been developed to examine the influence of carbon blacks on the flame propagation. The results of the numerical model suggest that the radiative heat contribution promotes the flame acceleration. This result is consistent with the experimental increase on the explosion severity for some hybrid mixtures

This thesis deals with the problem of hydrogen explosions in nuclear power plants, and evaluates if the reactor hall is to be seen as a safety barrier for such events. Today, the reactor hall is not seen as a safety barrier that is able to withstand an internal explosion. In the analysis Abaqus was used for the FEM calculations, where a main scenario of a wall subjected to a hydrogen explosion was used. In conclusion, the results showed that a reactor hall with the assumed dimensions cannot be seen as a safety barrier, since the deformation after a hydrogen explosion near the LEL was too great. However, it is also concluded that with increased wall and rebar dimensions it is possible to construct a wall of this kind that fulfills the requirements of a safety barrier.

Pellets from haylage, respectively hay were extruded in an extruder working with a high temperature according to the utility model CZ 21314 with different parameters. The researched parameters of extrusion with a constant time delay were a pressure extrusion and volatile solids. The highest production of methane (CH4) at a fermentation with the temperature 40 °C was monitored from the haylage with a content of the volatile solids 10,6 - 11 % by extrusion with the pressure 1,37 MPa. The highest production of CH4 at a fermentation with the temperature 50 °C was monitored from the haylage with a content of the volatile solids 13,5 - 16,7 % by extrusion with the pressure 1,37 - 1,66 MPa. A kontent of the volatile solids 11,5 % of haylage and extrusion with the pressure 1,35 ? 1,4 were estimated like optimum parameters for a fermentation with the temperature 40 - 50 °C with the highest production of CH4. For evaluation of the effectiveness of investment was used the metod of net present value (NPV). This method is the most commonly used and in most cases the most appropriate.

The name and the topic of this diploma thesis, Crash simulation vehicle carrying explosives, impacts and solutions, illustrates its main goal. That is, using the TerEx software program, to simulate a crash of vehicle transporting explosives, the impacts resulting from such an incident and, as a secondary goal, to propose solutions of such an incident for the Emergency Service units, with the connection to public safety. After resolving these tasks, it will be possible to answer the research question: What are the dangers of a crash of vehicle transporting explosives? In the beginning, the theoretical part of the thesis focuses on explosives as such. The history of their inventions, usage and development is outlined. In the next chapter, explosives are defined as substances capable of explosive transformation that can release a large amount of energy in a very short time upon a sudden external impulse. For the classification of explosives, it was necessary to characterize types of explosive transformations and general principles that lead to releasing energy. Very important are then the theoretical chapters of this thesis, where are described in detail the effects and phenomena of an explosion, which are necessary for the identification of imminent harmful effects and impacts on the environment in the case of their unwanted initiation. These phenomena include shock wave, thermal and fragmentational effect, recoil, routing, blocking and multiplication of the shock wave. Follows the part, where explosives are classified according to various aspects, from which the most important is the aspect of speed of explosive transformation, which cardinally affects the explosives' properties. This part is followed by a chapter that describes those characteristics. The second half of the theoretical part is concerned with transportation of hazardous materials, especially explosives. Packing and marking requirements, duties of transportation participants and training of the participants are specified there. One must not forget traffic requirements and other necessities connected with transportation, including the need for accompanying documents, transport staff, traffic unit, its construction and equipment and the course of transportation. The last section of the theoretical part of this thesis is dedicated to specific rules of explosives' transportation, which in the Czech Republic are set by the law. It includes mainly a duty to notify the Police Prezidium of the Czech Republic at least 24 hours prior to transportation of explosives and the duty for the vehicle used for transportation to be equipped with a tracking device. In this sense the explosives are the only group of hazardous materials, for which these stricter rules apply. In order to find an answer to the research question, it was necessary in the empirical part of the thesis to gather input data for the TerEx program, where the event was then simulated. These data were collected by an analysis of usage and occurrence of explosives in the area of the South Bohemian region. On the basis of this analysis, a highly brisant explosive NKG-500, which is commonly used for quarrying, special destructive works, underwater tasks and for priming of industrial explosives. It is a place, where the density and complexity of traffic has not yet been tackled accordingly. On the basis of output from thus performed simulation it was possible to assess that in such a densely populated area with the large number of residential and administrative buildings an accident of vehicle transporting explosives poses a considerable threat. In connection with the threats and impacts discovered in relation with such an incident, a unified course of action of the Emergency Service for their solution was designed, whereupon specific actions of its respective units were considered.

Armoured vehicles in current military service are requiring ever more protection to enable them to carry out their mission in a safe, effective manner. This requirement is driving vehicle weight up to such an extent that the logistics of vehicle transport is becoming increasingly difficult. Composite materials are an important material group whose high specific properties can enable structures to be manufactured for a far lower weight than might otherwise be possible. Composite materials in an armoured vehicle will require structural performance as well as ballistic performance. The mechanical and ballistic performance of tl-kk armour and structural composites has been investigated against dcformable and armour-piercing ammunitions, over a range of impact velocities. Testing has indicated that heavy/coarse reinforcement weaves perform well against deformable ammunition and light/fine weaves well against armour piercing ammunition. The effect of individual mechanical properties on ballistic performance has been investigated as has the damage morphology of impacted materials. High tensile strength combined with low fracture toughness has been identified as an important requirement. Failure mechanisms have been identified from sections of ballistic impacts and through the use of mechanical test data the energy absorbed by each mechanism has been calculated. An energy audit has been carried out of all materials tested and a modelling procedure developed based on mechanical characteristics, damage morphology and failure mechanisms. This model has been tested against literature results and found to give very satisfactory performance.