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Steeves, Laura. "SIMPLIFYING TECHNIQUES APPLIED TO COMPUTATIONAL FLUID DYNAMICS MODELING OF METHANE EXPLOSIONS." UKnowledge, 2019. https://uknowledge.uky.edu/mng_etds/47.
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Traditional methods of studying underground coal mine explosions are limited to observations and data collected during experimental explosions. These experiments are expensive, time-consuming, and require major facilities, such as the Lake Lynn Experimental Mine. The development of computational fluid dynamics (CFD) modeling of explosions can help minimize the need for large-scale testing. This thesis utilized the commercial CFD software, SC/Tetra, to examine three case studies. The first case study modeled the combustion of methane in a scaled shock tube, measuring approximately 1 foot by 1 foot, by 20.5 feet long, with a methane cloud of 2.5 feet in length, at a concentration of 9% methane. The numerical results from the CFD model were in good agreement with experimental data gathered, with all pressure peaks within 0.25 psi of the recorded pressure data. However, the model had an extensive run-time of 16 hours to reach the peak pressures. The second case study modeled the same explosion, but utilized a total pressure boundary condition at the location of the membrane, instead of the combustion of methane. A pressure-time curve was assigned to this boundary, recreating the release of pressure by the explosion. This was made possible with the knowledge of the experimental data. The numerical results from the CFD model were in excellent agreement with experimental data gathered, with all pressure peaks within 0.07 psi of the recorded pressure data. Alternatively, this model had a run-time of 40 minutes. The third case study modeled a methane explosion in a large shock tube, measuring 8 feet by 8 feet, by 40 feet long, with a methane cloud of 4 feet in length, at a concentration of 9% methane. The bursting balloon technique was employed, which did not model the combustion of methane, but instead the equivalent energy release. The numerical results from the CFD model were in good agreement with the experimental data gathered, with all pressure peaks within 0.025 psi of the recorded pressure data. Additionally, the numerical results modeled the negative pressure phenomenon observed in the experimental results, caused by suction or negative pressure created by the blast wave, immediately following the positive wave. This model had a run-time of 20 minutes. The results of this researched provided validation that there are alternative ways to successfully model methane explosion, without having to model the chemical reactions involved in the combustion of methane, providing quicker run-times and in this case, more accurate results.
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Lee, Julian. "Detonation mechanisms in a condensed-phase porous explosive." Thèse, Université de Sherbrooke, 1997. http://savoirs.usherbrooke.ca/handle/11143/1677.
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In the present study, we experimentally investigate detonation mechanisms in heterogeneous media using a model explosive in which the physical and chemical properties can be easily varied. The model explosive is composed of a packed bed of solid inert beads with a liquid explosive completely filling the voids between the beads. The liquid explosive consists of NM chemically sensitized with diethylenetriamine (DETA), and glass beads ranging in size from 66 µm to 2.4 mm. By changing the bead size in a mixture of NM with 15% DETA in glass beads, we have found two very different types of critical diameter behavior for small and large beads. For beads smaller than 1 mm in diameter (regime II), the critical diameter of the mixture increases with increasing bead size. For beads larger than 1 mm (regime I), the trend is reversed . Velocity measurements in the three regimes of propagation show a weak diameter-effect for regimes I and II and unstable velocities in regime III. Hence we have found three distinct regimes of detonation propagation that depend on the local physical and chemical length-scales of the heterogeneous explosive. Reducing the amount of DETA was found to cause a sharp increase in the critical diameter in regime I and a slight decrease in the critical diameter in regime II, further emphasizing the difference in the propagation mechanisms. To interpret the observed regimes of detonation behavior, we propose two competing propagation mechanisms within the explosive. In regime I, the global detonation front is controlled by local detonation wavelets that propagate in the pores between the beads. Here, the local diffraction and reinitiation of the wavelets is assumed to play an important role in the macroscopic detonation properties. In regime II, the global detonation is controlled by a sympathetic mechanism of shock initiation of isolated explosive pockets in the porous bead bed. A simple qualitative model was developed based on hot spot generation from both particles and natural detonation-front instabilities. The competition between these two types of hot spots is found to play a crucial role in the transition from one detonation propagation regime to the other. Natural hot spots dominate the detonation propagation in the regime I while particle-generated hot spots dominate the regime II. The model agrees qualitatively with the experimental results, and hence provides a promising approach to modeling the two propagation regimes in the present packed-bead explosive. The present study thus lends insight into two types of micro-mechanisms in heterogeneous condensed phase explosives and provides a qualitative model capable describing the detonation properties caused by multiple-regime behavior."--Résumé abrégé par UMI
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Mendonça, Filho Letivan Gonçalves de. "Propostas de distancias de segurança para edificações com base em estudos de efeitos de explosões referenciados ao equivalente TNT." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266212.
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Orientador: Reginaldo Guirardello, Demetrio Bastos NettoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
Made available in DSpace on 2018-08-07T08:23:33Z (GMT). No. of bitstreams: 1 MendoncaFilho_LetivanGoncalvesde_D.pdf: 5427915 bytes, checksum: 7869e5fa656a6b2cc31cdebb6074d24c (MD5) Previous issue date: 2006
Resumo: Este trabalho utiliza o conhecimento científico relativo a explosões e efeitos associados para sugerir distâncias de segurança para proteção de edificações nas proximidades de explosivos e atmosferas inflamáveis, para aplicação nas áreas civil e militar. Através da análise de um inquérito de um acidente ocorrido em 1964 foi possível relacionar as duas metodologias utilizadas para estabelecer as distâncias atuais de segurança para habitações. Verificou-se algumas falhas em um dos trabalhos originais e com a correção proposta foram apresentadas novas equações relacionando massa de explosivo, distância e o custo de reparos para residências. Avaliou-se as distâncias de segurança adotadas no Brasil por meio de diversas correlações estatísticas. Foi realizado um estudo experimental consistindo na montagem e posicionamento de uma carga de explosivo em frente a uma edificação, a uma distancia variável de uma vidraça fixa. Com base neste estudo foram identificados diversos aspectos referentes à fragmentação de vidraças como: Relação entre espessura, impulso e velocidade de fragmentos. Novas distâncias de segurança foram propostas considerando uma diferenciação em relação ao tipo de estabelecimento, uso de taludes e o equivalente TNT da massa de explosivo. Uma alternativa de armazenagem é mostrada baseada no conceito de separação em compartimentos dos materiais explosivos para adequar os valores de distância de segurança praticados com os valores idealizados. No caso de explosões gasosas, tratou-se um caso real envolvendo uma explosão em um navio de transporte de material inflamável. Com base neste estudo foram propostas novas distâncias de segurança para atmosferas explosivas, usando o método multi-energético e o conhecimento da relação entre danos e sobrepressão desenvolvidos
Abstract: This work uses the original military scientific know how on explosions and its effects to suggest safety distances to cases dealing with explosives and inflammable atmospheres. Considering the information contained in an investigation of an accident which took place in 1964 in a production line of gunpowder at the "Fabrica Presidente Vargas",in the city of Piquete, São Paulo, it was possible to relate and review the two main techniques used as the basis of the actual safety distances in inhabited building in USA and Europe. Based on this study it was suggested some corrections at the american technique. With the correction it was possible to suggest two probit equations relating distance, weight of explosives and the repair costs to brick and wood houses. As the American analysis to determinate the safety distances was based on a patrimonial criterion and we were interested in establishing a criterion centered in the human being, severa I statistical correlations were employed to evaluate the effect of explosions on the human being, considering the safety distances of the Brazilian legislation. Due to the relevance of the risks associated with the glass hazards generated in window breakage by . overpressure an experimental study was performed. The experiment consisted in blasting explosive charge close to window so that the initial velocity was measured using a laser system with an electronic chronometer. The overpressure generated by the blast broke the window and threw the fragments against a special kind of foam glued on a wood wall. Some of the fragments were caught by the foam, in such away that it was possible to identify aspects concerning window breakaging relations between fragments thickness and ~nitial velocity .Also the effect of drag on the terminal velocity of fragments. Based on these studies new safety distances were suggested take in account the diversity of the establishments. '.The attenuation effect by the use of barriers and the TNT equivalents of explosives- and propellants were considered also in the new safety distances. The new values were compared with the Brazilian legislation leading to a proposal for storage of explosive materiais dividing them into severa I compartments to be adequate the actual values of the legislation with the suggested one. Considering the case of gas/vapor explosion, we dealt with a real case of explosion. Aspects related to evaporation, dispersion and development of inflammable and explosives atmospheres were considered along with the analysis of sensitivity of stimulus to ignition. A mechanism of the storage vessel rupture was suggested. based on the thermodynamic and kinetics analysis of the combustion system. Having the motivation of the necessity to define safety distances in similar cases it was suggested safety distances using the multi energy method developed by the TNO and the knowledge of the relation between damage and overpressure
Doutorado
Desenvolvimento de Processos Químicos
Doutor em Engenharia Química
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Leuret, Frédéric. "Etude de la transition déflagration-détonation dans une composition explosive à faible porosité." Poitiers, 1996. http://www.theses.fr/1996POIT2285.
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L'objet de ce travail est de contribuer a une meilleure comprehension des mecanismes conduisant a la transition deflagration-detonation (tdd) dans les explosifs condenses. Il s'agit d'un probleme qui a des applications pratiques importantes dans le domaine de la securite des explosifs et des propergols. Pour cela, la transition deflagration-detonation a ete etudiee dans le cas d'une composition explosive a base d'octogene et a faible porosite. L'amorcage de l'explosif etait obtenu par un dispositif thermique de facon a simuler une sollicitation de type incendie. Les experiences ont ete effectuees principalement avec des charges cylindriques de diametre 16 mm et de 400 mm ou 1000 mm de longueur, contenues dans des confinements en acier de resistance a la rupture comprise entre 5,4 et 14,3 kbar. Les resultats obtenus indiquent que pour l'explosif considere, la formation de la detonation normale est pratiquement toujours precedee de deux regimes intermediaires: la combustion convective et la detonation lente. La detonation lente a fait l'objet d'une attention particuliere. Il apparait que ce regime peut se propager de maniere quasi-stationnaire jusqu'a des distances correspondant a 50 fois le diametre de la charge. Sa celerite est legerement supersonique (1,11 m 1,40) et croit avec la resistance du confinement. Sa structure est celle d'une onde de compression (qui n'est pas un choc) couplee a une zone de reaction ou la combustion de l'explosif est incomplete. Dans la configuration etudiee, la transition vers la detonation n'a ete observee que dans un nombre limite de cas. La transition deflagration-detonation est d'autant plus probable que le confinement est resistant et que la distance de propagation est grande
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Sutherland, B. J. "Smoke Explosions." University of Canterbury. Civil Engineering, 1999. http://hdl.handle.net/10092/8328.
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Eleven experiments were conducted at the University of Canterbury using a 1.0 metre by 1.0 metre by 1.5 metre compartment and wooden crib fires. The main objective of these experiments was to produce smoke explosions, and to develop a mechanism that explains their occurrence.
Spontaneous smoke explosions were produced in four experiments. The largest of these explosions produced pressures in excess of 2.5 kPa. All the smoke explosions produced were the result of smouldering fires, all of which started out as under-ventilated fires. Of the six smoke explosions produced, investigation of the results indicates that a single process was responsible for the occurrence of each explosion.
A mechanism was developed for the smoke explosions. Oxygen concentration is suspected as the trigger that determines when the explosion occurs.
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Marceau, Claude. "Explosions : roman." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1989. http://theses.uqac.ca.
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Thèse (M.A.)--Université du Québec à Trois-Rivières, 1989.Ce mémoire a été réalisé à l'Université du Québec à Chicoutimi dans le cadre du programme de maîtrise en études littéraires de l'Université du Québec à Trois-Rivières extensionné à l'Université du Québec à Chicoutimi. CaQCU Document électronique également accessible en format PDF. CaQCU
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Saji, Santander Carlos Andrés. "Skyrmion explosions." Tesis, Universidad de Chile, 2018. http://repositorio.uchile.cl/handle/2250/168342.
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Magíster en Ciencias, Mención Física.
Ingeniero Civil MatemáticoLos skyrmions son texturas magnéticas las cuales poseen propiedades que las hacen el objeto de estudio de diversas areas de la física teórica, matemática, nanotecnología, etc. Una de ellas es su protección topológica y estabilidad. En éste contexto es de mucha importancia el estudiar las pequeñas fluctuaciones en torno al skyrmion, las cuales se conocen como ondas de spin o campo de magnones [10]. En esta tésis, estudiaremos la dinámica conjunta del sistema skyrmion-magnones en, en contraste con la literatura, donde típicamente son consideradas como independientes. Específicamente veremos como la dinámica propia del skyrmion genera ondas de spin, y como estas a su vez afectan al skyrmion en forma de reacción de radiación. Estudiaremos además el origen de la masa de los skyrmion. Por otra parte, actualmente los skyrmions son de mucho interés en el posible nuevo desarrollo de circuitos lógicos, en los cuales los skirmions representan bits binarios [31]. De ésta manera el estudio de la aniquilación de un skyrmions es de suma importancia. Estudiaremos el problema de la explosión de un skymion (blow up) y derivaremos la dynamica de la explosión con la consecuente emisión de ondas de spin en forma de radiación.
Este trabajo ha sido parcialmente financiado por Proyecto Fondecyt N° 1150072 and Center for the Development of Nanoscience and Nanotechnology CEDENNA FB0807
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Fakandu, Bala Mohammed. "Vented gas explosions." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/7340/.
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This investigation generated new experimental data on premixed gas/air vented explosions. A small (0.01 m3) and medium scale (0.2 m3) cylindrical vessels were used with L/D of 2.8 and 2 respectively, with range of vent area coefficients Kv of 2.7-21.7. The initial set of experiments considered free venting, so that the flame propagation during the venting process was laminar and also the short distance of the vessels would reduce the effects of flame self-accelleration. Covered vents were later used with vent static burst pressure Pstat from 35 to 450mb in the 10L vessel. Different gas mixtures were used throughout this work including methane-air (10%), propane-air (4 and 4.5%), ethylene-air (6.5 and 7.5%), and hydrogen-air (30 and 40%) gas mixtures. The ignition position at the far end opposite the vent and central location mid-way the length of the vessels were compared. Current venting guidance is based on experimental vented explosions with central ignition, but this work shows that end ignition opposite the vent is the worst case. The current design procedures for the protection of explosions using venting is shown to be inadequate for hydrogen-air explosions. New data has been presented which indicates that for hydrogen explosions, the vent flow behaves differently as compared to other gas mixtures investigated. Hence, the need for more research in hydrogen-air mixtures in order to have better understanding of hydrogen venting process. Experimental data from the current work also shows that multiple vents and vent shapes have significant effects on explosion overpressure and flame speeds. This is contrary to the assumption of the current venting standards. The effect of static burst pressure on explosion venting was shown to be quite different to that in the design standards, which is supported by other work in larger vessels. Other aspects of vent design that the standards say are not important were shown to be significant: the number of vents, the position of the vent, the shape of the vent, the ignition position. Laminar flame venting theory was shown to be a good predictor of the results and those from the literature where larger vessels were used.
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Kasmani, Rafiziana Md. "Vented gas explosions." Thesis, University of Leeds, 2008. http://etheses.whiterose.ac.uk/1604/.
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Explosion venting technology is widely accepted as the effective constructional protection measures against gas and dust explosions.The key problem in venting is the appropriate design of the vent area necessary for an effective release of the material i.e. the pressure developed during explosion did not cause any damage to the plant protected.Current gas explosion vent design standards in the USA (NFPA68, 2002) and European (2007) rely on the vent correlation first published by Bartknecht in 1993 (Siwek, 1996).N FPA 68 also recommends the correlation of Swift (Swift,1983)at low overpressures. For a vent to give no increase in overpressure other than that due to the pressure difference created by the mass flow of unburnt gases through the vent, the vent mass flow rate is assumed to be equal to the maximum mass burning rate of the flame and this consideration should be used as the design mass flow through the vent. Two different methods ( Method I and Method 2) have been proposed based on the Sμ and Sμ (E-1) to describe the maximum mass burning rate given as, mb = ASμpμ=CdeA(2pPμred)o.5 mb =ASgPm =AgSμ(E-I)P μ=Cde4,(2pu Pred)0,5 (2) The equation given in (2) is slightly different from (1) as is about 6.5 times the mass flow of the first method as it takes the effect of (E-1) where E is the expansion ratio. A critical review were carried out for the applicability, validity and limitation on the venting correlations adopted in NFPA 68 and European Standard with 470 literature experimental data, covering a wide range of values for vessel volume and geometries, bursting vent pressure, Pv L/D ratio, maximum reduced pressure, Pred and ignition location. The fuels involved are methane, propane, hydrogen, town gas, ethylene, acetone/air mixtures with the most hazardous near-stoichiornetric fuel-air concentration. Besides, Molkov's equation (Molkov, 2001) which is regarded as alternative venting design offered in NFPA 68 and Bradley and Mitcheson's equation for safe venting design were also analysed on the experimental data for their validity and limitation as well as the proposed methods. From the results, it is clear that Bartknecht's equation gave a satisfactory result with experimental data for K <-5 and Swift's equation (Swift, 1983) can be extended to wider range for Pred> 200 mbar, providing the parameter PV is added into the equation. Method 2 gave a good agreement to most of the experimental data as it followed assumptions applied for correlations given by Bradley and Mitcheson for safe venting design (Bradley and Mitcheson, 1978a,B radley and Mitcheson, 1978b). It is also proven that the vent coefficient, K is confident to be used in quantifying the vessel's geometry for cubic vessel and the use of As/Av term is more favourable for non-cubic vessels. To justify the validity and applicability of the proposed methods, series of simply vented experiments were carried out, involving two different cylindrical volumes i.e. 0.2 and 0.0065 M3. It is found that self acceleration plays important role in bigger vessel in determining the final Pmax inside the vessel. Method 2 gave closer prediction on Pmax in respect with other studied correlations. The investigation of vented gas explosion is explored further with the relief pipe been connected to the vessel at different fuel/air equivalence ratios, ignition position and Pv. The results demonstrate that the magnitude of Pmax was increased corresponding to the increase of Pv- From the experiments,it is found that peak pressure with strong acoustic behaviour is observed related to increase in Pv and in some cases,significant detonation spike was also observed particularly in high burning velocity mixtures. It is found that substantial amount of unburnt gases left inside the vessel after the vent burst is the leading factor in increase of Pmax for high burning velocity mixtures at centrally ignited. The associate gas velocities ahead of the flame create high unburnt gas flows conditions at entry to the vent and this give rise to high back pressures which lead to the severity in final Pmax inside the vessel. It was observed that end ignition leads to a higher explosion severity than central ignition in most cases, implying that central ignition is not a worst-case scenario in gas vented explosions as reported previously.
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Craft, Neil Hirsh. "An experimental study of hybrid explosive dust-gas-air mixtures /." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66071.
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Pfannes, Jan M. M. "Explosions of rotating white dwarfs." Doctoral thesis, [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=983425930.
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Roach, Matthew Douglas. "Physically based simulation of explosions." Thesis, Texas A&M University, 2005. http://hdl.handle.net/1969.1/2409.
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This thesis describes a method for using physically based techniques to model an explosion and the resulting side effects. Explosions are some of the most visually exciting phenomena known to humankind and have become nearly ubiquitous in action films. A realistic computer simulation of this powerful event would be cheaper, quicker, and much less complicated than safely creating the real thing. The immense energy released by a detonation creates a discontinuous localized increase in pressure and temperature. Physicists and engineers have shown that the dissipation of this concentration of energy, which creates all the visible effects, adheres closely to the compressible Navier-Stokes equation. This program models the most noticeable of these results. In order to simulate the pressure and temperature changes in the environment, a three dimensional grid is placed throughout the area around the detonation and a discretized version of the Navier-Stokes equation is applied to the resulting voxels. Objects in the scene are represented as rigid bodies that are animated by the forces created by varying pressure on their hulls. Fireballs, perhaps the most awe-inspiring side effects of an explosion, are simulated using massless particles that flow out from the center of the blast and follow the currents created by the dissipating pressure. The results can then be brought into Maya for evaluation and tweaking.
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Kristoffersen, Kjetil. "Gas explosions in process pipes." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-235.
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In this thesis, gas explosions inside pipes are considered. Laboratory experiments and numerical simulations are the basis of the thesis. The target of the work was to develop numerical models that could predict accidental gas explosions inside pipes.
Experiments were performed in circular steel pipes, with an inner diameter of 22.3 mm, and a plexiglass pipe, with an inner diameter of 40 mm. Propane, acetylene and hydrogen at various equivalence ratios in air were used. Pressure was recorded by Kistler pressure transducers and flame propagation was captured by photodiodes, a SLR camera and a high-speed camera. The experiments showed that acoustic oscillations would occur in the pipes, and that the frequencies of these oscillations are determined by the pipe length. Several inversions of the flame front can occur during the flame propagation in a pipe. These inversions are appearing due to quenching of the flame front at the pipe wall and due to interactions of the flame front with the longitudinal pressure waves in the pipe. Transition to detonation was achieved in acetylene-air mixtures in a 5 m steel pipe with 4 small obstructions.
Simulations of the flame propagation in smooth pipes were performed with an 1D MATLAB version of the Random Choice Method (RCMLAB). Methods for estimation of quasi 1D burning velocities and of pipe outlet conditions from experimental pressure data were implemented into this code. The simulated pressure waves and flame propagation were compared to the experimental results and there are good agreements between the results.
Simulations were also performed with the commercial CFD code FLACS. They indicated that to properly handle the longitudinal pressure oscillations in pipes, at least 7 grid cells in each direction of the pipe cross-section and a Courant number of maximum 1 should be used. It was shown that the current combustion model in FLACS gave too high flame speeds initially for gas explosions in a pipe with an inner width of 40 mm.
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Holmgren, Cecilia. "Split Trees, Cuttings and Explosions." Doctoral thesis, Uppsala universitet, Matematiska institutionen, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-112239.
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This thesis is based on four papers investigating properties of split trees and also introducing new methods for studying such trees. Split trees comprise a large class of random trees of logarithmic height and include e.g., binary search trees, m-ary search trees, quadtrees, median of (2k+1)-trees, simplex trees, tries and digital search trees. Split trees are constructed recursively, using “split vectors”, to distribute n “balls” to the vertices/nodes. The vertices of a split tree may contain different numbers of balls; in computer science applications these balls often represent “key numbers”. In the first paper, it was tested whether a recently described method for determining the asymptotic distribution of the number of records (or cuts) in a deterministic complete binary tree could be extended to binary search trees. This method used a classical triangular array theorem to study the convergence of sums of triangular arrays to infinitely divisible distributions. It was shown that with modifications, the same approach could be used to determine the asymptotic distribution of the number of records (or cuts) in binary search trees, i.e., in a well-characterized type of random split trees. In the second paper, renewal theory was introduced as a novel approach for studying split trees. It was shown that this theory is highly useful for investigating these types of trees. It was shown that the expected number of vertices (a random number) divided by the number of balls, n, converges to a constant as n tends to infinity. Furthermore, it was demonstrated that the number of vertices is concentrated around its mean value. New results were also presented regarding depths of balls and vertices in split trees. In the third paper, it was tested whether the methods of proof to determine the asymptotic distribution of the number of records (or cuts) used in the binary search tree, could be extended to split trees in general. Using renewal theory it was demonstrated for the overall class of random split trees that the normalized number of records (or cuts) has asymptotically a weakly 1-stable distribution. In the fourth paper, branching Markov chains were introduced to investigate split trees with immigration, i.e., CTM protocols and their generalizations. It was shown that there is a natural relationship between the Markov chain and a multi-type (Galton-Watson) process that is well adapted to study stability in the corresponding tree. A stability condition was presented to describe a phase transition deciding when the process is stable or unstable (i.e., the tree explodes). Further, the use of renewal theory also proved to be useful for studying split trees with immigration. Using this method it was demonstrated that when the tree is stable (i.e., finite), there is the same type of expression for the number of vertices as for normal split trees.
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Ren, Wei Min. "Mechanistic modeling of steam explosions." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/15855.
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Barsanti, Patricia Sylvia. "Simulations of confined turbulent explosions." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261538.
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Ogilvy, Iver. "Fluid dynamics of underwater explosions." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/8840/.
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The detonation of an explosive in water leads to a complex set of chemical and physical phenomena. When the detonation wave reaches the surface of the explosive it reacts violently with the water, producing a shock wave propagating outwards and also a nearly spherical gaseous bubble of detonation products. The fact that the characteristic time scales of these two phenomena differ by approximately two orders of magnitude has often been exploited by utilising independent models to describe the shock and the bubble. In this thesis both the shock and the bubble are examined using a range of methods from a differential equation solver approach through to full hydrocode simulation. With the increasing use of the hydrocode approach for the underwater explosion (UNDEX) problem and the subsequent loading of a structure, then a verification and validation process is required to ensure its accuracy. In this study the capability of the hydrocode to model the shock and the bubble and also their interaction with a rigid structure and with a flexible structure, has been assessed. This has been done computationally, by using faster running purpose built codes, and also by comparison with experimental data. A familiarisation work-up of the boundary integral code for the incompressible bubble flow, which included incorporating modifications into the code in order to investigate the pathlines swept out by the particles in the fluid during the expansion and collapse of the bubble. The boundary integral code was also used to provide a comparison with the Kelvin impulse method with respect to the computation of the zones of explosion bubble collapse direction in a shallow water environment. The validation and verification work carried out and the comparisons of the various computational approaches, make this multifaceted study a useful reference for research workers in the field of UNDEX phenomena.
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Sattar, Hamed. "Combustion and explosions of biomass." Thesis, University of Leeds, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.659126.
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The use of biomass in power generation is increasing due to legislative pressures and incentives to move away from coal and towards more carbon neutral fuels. In this context, the number of power plants using biomass and biomass-coal blends is rapidly increasing. Biomass has already established its role as a co-fired fuel and there is considerable interest in the use of 100% pulverised biomass as fuel for the generation of electricity. The risks involved with the handling of pulverised biomass are quantatively unknown and there have been several biomass dust explosions incidents in recent past years within the pulverisers and the dust transport pipe-work. This research was aimed at providing some of the required explosion safety data and of developing test methods for woody fibrous biomass that is common in power station usage. Explosion protection data as well as basic burning velocity data for pulverised biomass (non-fibrous and fibrous) with pulverised coal (for comparison) were generated using the ISO 1m3 dust explosion equipment. A large part of the work involved the modification of the ISO method to enable it to be used with fibrous biomass and to calibrate these modifications so that Kst data could be compared with the standard method. A new fibrous biomass injection system was developed and calibrated. In addition to the determination of Kst and maximum pressure, P max, constant pressure flame speeds were measured, from which the burning velocity and global heat release rates per unit area was calculated. This study provides data for ATEX compliance, design of biomass dust explosion protection systems and will also help in the design and modelling of burners for the power generation plants using biomass.
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McGrath, Thomas Peter. "Numerical modeling of multiphase explosions." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8825.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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MARONGIU, MARCO. "Broadband modelling of relativistic explosions." Doctoral thesis, Università degli studi di Ferrara, 2020. http://hdl.handle.net/11392/2488013.
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In the new transient sky era, the progenitors of relativistic explosions, such as gamma-ray bursts (GRBs) and relativistic supernovae (SNe), are the focus of forefront research.
Broadband observations of nearby short GRB170817A -whose gravitational waves were detected by LIGO/VIRGO- and the recent detection at TeV energies of two bright GRB afterglows (190114C and 180720B) with the MAGIC and HESS Cherenkov telescopes heralded the birth of so-called multi-messenger astronomy.
GRB afterglows, originating from the interaction between the ejecta and the circumburst medium, help constrain the radiation mechanism, the relativistic shock microphysics, the circumburst environment, the structure and geometry of the relativistic jet. Observations of radio afterglows are key to understand the reverse shock, which links directly to the nature of the outflow and, consequently, to the progenitor itself. On the other hand, they can hardly be observed with current radiotelescopes because of their faintness (mJy or sub-mJy). Recently, several radio followup campaigns improved the observational coverage of the lower part of the emission spectrum, but an exhaustive picture of GRB afterglows is still missing.
I developed an approach focused on broadband modelling (with particular attention to the radio frequencies) through the Python code called sAGa (Software for AfterGlow Analysis). After successfully testing it on various GRB afterglows (120521C, 090423, and 050904), I applied it to long GRB160131A, whose data show evidence for energy injection and jetted emission. Radio light curves are characterised by several peaks, that could be due to either interstellar scintillation (ISS) effects or multi-component structure. My results show that the data can hardly be explained self-consistently with the standard model of GRB afterglows.
To help collect more radio data on GRB afterglows, I coordinated radio campaigns with Sardinia Radio Telescope (SRT) to observe two GRB radio afterglows (181201A and 190114C).
Although they have come up with no detection, they fostered the definition and the comparative analysis of three detection methods for faint radio sources through single-dish imaging, in terms of sensitivity and robustness: quick-look (a smart but rough approach), source extraction (typical of high-energy astronomy), and fitting procedure with a 2-Dimensional Gaussian (a more sophisticated approach). The new methodology for the SRT data analysis (1) pushes down the sensitivity limits of this radiotelescope -with respect to more traditional techniques- at ~1.8 mJy, and (2) highlights the need for accurate knowledge of the background.
L-GRBs are associated with type Ic broad-line supernovae (Ic-BL SNe). This connection can be observed only at redshift z < 1 because of the intrinsic faintness of SNe. In this context, I analysed Ic-BL SN2014ad, detected only in optical. The proximity of the source (~26 Mpc) and the radio/X-ray observations turned into very deep constraints on (1) the progenitor mass-loss rate, (2) the total energy of the ejecta, and (3) the explosion geometry. I considered two synchrotron emission regimes (uncollimated non-relativistic ejecta, typical of ordinary SNe); off-axis relativistic jet, such as those seen in GRBs), showing that off-axis low-energy jets expanding in a low-density medium cannot be ruled out even in the most nearby BL-Ic SNe.Nella nuova era dell'esplorazione del cielo transiente, i progenitori di esplosioni relativistiche -come i lampi gamma (GRB) e le supernovae relativistiche (SN)- sono tra i protagonisti più importanti della ricerca. Le osservazioni multi-frequenza del vicino GRB170817A -le cui onde gravitazionali sono state rilevate dagli interferometri LIGO/VIRGO- e la recente scoperta alle altissime energie degli afterglow associati a due GRB brillanti (190114C e 180720B) con i telescopi Cherenkov MAGIC e HESS hanno suggellato la nascita dell'astronomia multi-messaggera. Lo studio dell'afterglow dei GRB, originato dall'interazione tra la materia espulsa e il mezzo circostante, è fondamentale per comprendere i meccanismi di emissione, la microfisica dello shock relativistico, le proprietà del mezzo circostante e del getto. Gli afterglow radio dei GRB -per quanto difficili da osservare per la loro intrinseca debolezza (dell'ordine del sub-mJy)- sono cruciali per comprendere appieno questi aspetti, e in particolare lo shock inverso, che a sua volta dipende dalle proprietà della materia espulsa e quindi dal progenitore stesso del GRB. Anche se diverse campagne osservative hanno migliorato la copertura della parte radio dello spettro di emissione, ad oggi manca un quadro esaustivo degli afterglow. In questo contesto mi sono occupato di modellizzare l'emissione multi-frequenza degli afterglow, con particolare attenzione al radio, con la realizzazione del codice Python sAGa (Software for AfterGlow Analysis). Dopo aver testato con successo {\sc sAGa} su vari afterglow di GRB (120521C, 090423 e 050904), l'ho utilizzato nel caso di GRB160131A, i cui dati suggeriscono l'iniezione di energia da parte del progenitore, e la presenza di un getto. Inoltre, l'insolita presenza di picchi nelle curve di luce radio potrebbe essere dovuta a effetti di scintillazione interstellare. I miei risultati mostrano che i dati multi-frequenza sono difficilmente spiegabili nell'ambito del modello standard degli afterglow. Al fine di incrementare i dati radio, ho coordinato una serie di campagne osservative con il Sardinia Radio Telescope (SRT) per gli afterglow di GRB181201A e GRB190114C. Nonostante queste non abbiano portato alla rivelazione degli stessi, mi hanno offerto la possibilità di confrontare tre metodi per rivelare sorgenti deboli: quick-look (il meno accurato), source extraction (tipico dell'analisi ad alte energie) e il fit con una Gaussiana bi-dimensionale. La messa a punto di una nuova metodologia per l'analisi dei dati di SRT (1) ottimizza la rivelazione di una sorgente debole ad un flusso minimo rivelabile di ~1.8 mJy, e (2) evidenzia l'importanza di un'accurata conoscenza del fondo. I GRB lunghi sono associati alle Ic broad-line (Ic-BL) SNe. Ad oggi il legame GRB/SN è testabile solo per i GRB a redshift z < 1 per la debolezza intrinseca delle SNe. In questo contesto ho analizzato Ic-BL SN2014ad, rivelata solo in ottico. La vicinanza di questa sorgente (~26 Mpc) e le osservazioni in radio e raggi-X hanno permesso di vincolare profondamente (1) il tasso di perdita di massa del progenitore, (2) l'energia totale della materia espulsa a grande velocità e (3) la geometria dell'esplosione. Ho considerato due regimi di emissione di sincrotrone (isotropa con espansione sub-relativistica, tipica delle normali SN; relativistica con getto osservato fuori asse, come nei GRB), dimostrando che i getti poco energetici osservati fuori asse in un mezzo a bassa densità non possono essere esclusi nemmeno per una BL-Ic SN così vicina.
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Martins, Claude. "Visually believable explosions in real time." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0015/MQ59185.pdf.
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Griffith, Eric F. "Vapor explosions in thermite-generated melts." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/16800.
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Wu, Yajue. "The gas dynamics of venting explosions." Thesis, University of Sheffield, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297677.
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Chen, Anqi. "Structural response to vapour cloud explosions." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/23922.
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Over the last few decades, a number of major industrial blast accidents involving oil and gas installations occurred worldwide. These include the blast explosion that occurred in an industrial facility at Buncefield in the United Kingdom in 2005. Extensive damage occurred due to the blast, both to the industrial plant and surrounding buildings, as a consequence of much higher overpressures than would normally be expected from a vapour cloud explosion of this nature. In response to this event, a great deal of work was carried out on collecting and analysing available evidence from the incident in order to understand the explosion mechanism and estimate the overpressure levels within the gas cloud that formed. Subsequent investigations included the examination of steel switch boxes on the site located within the area covered by the vapour cloud. These boxes suffered varying degrees of damage and could therefore be used as overpressure indicators. A series of tests were commissioned after the event in order to compare the damage of the field boxes with detonation tests on similar boxes. The thesis firstly reports on numerical studies carried out on assessing the damage to steel boxes subjected to both detonation and deflagration scenarios in order to aid the investigation of the explosion. Several modelling approaches are adopted in the numerical studies, including: Pure Lagrangian, Uncoupled Lagrangian-Eulerian and Coupled Lagrangian-Eulerian techniques. The numerical models are validated against data collected from gas detonation experiments on similar steel boxes. It is found that the coupled approach is able to predict the results accurately, although such an approach cannot be used in detailed parametric investigations due to its prohibitive computational demand. The pure Lagrangian approach is therefore used instead, but the overpressure range in the parametric assessments is limited to 4 bar (side-on) as an adequate level of accuracy from this modelling technique cannot be ensured beyond this range. The results are summarised in the form of pressure-impulse diagrams, and typical residual shapes are selected with the aim of aiding forensic investigations of future explosion incidents. The investigation is extended thereafter to the response of a steel-clad portal frame structures located outside the gas cloud and which suffered varying degrees of damage. A typical warehouse building is studied through a pure Lagrangian approach. A non-linear finite element model of a representative sub-structure of the warehouse wall is validated against a full scale test carried out at Imperial College London. A series of pressure-impulse diagrams of the sub-structure is then constructed based on the results of parametric non-linear dynamic assessments using the developed numerical model under various combinations of overpressures and impulses. A new failure criterion based on the total failure of the self-tapping screws is proposed in conjunction with pressure-impulse diagrams. This failure condition provides a more direct assessment of the damage to the side walls of the warehouse. The pressure-impulse diagrams can be used to assess the response of a typical warehouse structure to blast loading, and to provide some guidance on the safe siting in a hazardous environment around oil and storage sites. Simplified approaches based on single degree of freedom representations are also employed, and their results are compared with those from the detailed non-linear finite element models. The findings show that the simplified approaches offer a reasonably reliable and practical tool for predicting the response of the side rails. However, it is illustrated that such idealisations are not suited for assessing the ultimate response of cladding panels, as the side rail-cladding interactions cannot be captured by simplified approaches and necessitate the deployment of detailed numerical procedures.
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Soderberg, Alicia Margarita Phinney E. Sterl Kulkarni S. R. "The many facets of cosmic explosions /." Diss., Pasadena, Calif. : California Institute of Technology, 2007. http://resolver.caltech.edu/CaltechETD:etd-05252007-140338.
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Willacy, Sarah. "Homogeneous and stratified vented gas explosions." Thesis, University of Leeds, 2008. http://etheses.whiterose.ac.uk/1584/.
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Explosion tests were carried out in four medium-scale test-vessels incorporating closed, vented, duct vented and interconnected vessels. A systematic investigation into the influence of homogeneous and stratified mixtures was undertaken by varying mixture reactivity, ignition position, injection position and mixture composition. A feature of this work has been the similarities in explosion phenomena between stratified and homogeneous explosions and between partially filled and fully filled geometries to the conclusion that the explosion severity recorded in stratified mixtures towards the lean flammability limit was in many cases much higher than the fuel concentration would normally suggest. Stratified mixtures with global equivalence ratio around stoichiometric produced significantly lower pressures than their homogeneous equivalents. However, stratified (globally) near-limit mixtures produced overpressures that were several hundred mbar higher than those of the equivalent homogeneous mixtures. Even beyond the flammable range (globally) the stratified mixtures produced significant overpressures. The phenomena discussed in this thesis illustrate the difficulty in designing adequate protection for such vented, duct vented and interconnected geometries, since even relatively small pocket of weak fuel-air mixtures produced relatively severe explosions. This can have implications for the safety design of inter-connected installations which are not intended to be subject to flammable mixtures. While it is an important conclusion from the work presented in this chapter that close to the flammability limits the stratified explosion severity was greater than its global concentration would normally indicate, it should be stressed that homogeneous stoichiometric tests still constitute the worst case tests. Therefore, it is not the suggestion of this work that the design of vented vessels should be modified to represent the maxima obtained in stratified work. However, the value of this research in the field of post-explosion investigation is clear.
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Mitropetros, Konstantinos. "Shock induced bubble explosions in liquid cyclohexane." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=974965936.
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Ip, Bill Man-Biu. "Effects of polymeric additive on vapor explosions." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/16079.
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Hadjipanayis, Michalis. "Novel propagation mechanisms of vapour cloud explosions." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/23987.
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This thesis considers the possibility of a novel propagation mechanism of vapour cloud explosions. The hypothesis is based on the potential of forward thermal radiation from hot combustion products to initiate combustion ahead of the main flame front by igniting particles suspended in the unburnt gas mixture. The formation of such local ignition events may cause an augmented explosion. An experimental investigation is described in which a laser source is used to heat various types of particles in flammable butane-air mixtures. It is found that fine powders can ignite an adjacent charge upon irradiation. Ignition times are established for a range of particles with widely different characteristics (size, type, morphology, etc.). In particular, ignition times scales ~100 ms could be obtained at an irradiance of 600 kW/m^2 using glass substrates coated with a carbon black. The relationship between absorption-emission properties of different powders is investigated further by determining particle temperatures under relevant radiation levels using time-resolved emission spectroscopy. Two different ignition regimes were observed, ignition temperatures appeared to be constant for non-reactive silicon carbide, while for reactive powders, temperature appeared to be not the sole ignition criterion. In response to the lack of radiation measurements for large scale premixed systems, a tool is developed for estimating the radiation flux emitted from such systems along with the corresponding level of irradiance posed on particles raised in the unburnt gas mixture. This information permits an assessment of the potential role of forward thermal radiation on the flame propagation. The comparison of such theoretical estimates with the experimentally measured ignition time data is vital for evaluation purposes. The analysis shows that the estimated and required fluxes are comparatively close and, hence, the proposed flame propagation mechanism is credible.
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Berger, Edo. "Cosmic Explosions: The Beasts and Their Lair." Thesis, Boca Raton, Fla. : Dissertation.Com, 2004. https://thesis.library.caltech.edu/1892/2/intro.pdf.
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The diversity of stellar death is revealed in the energy, velocity and geometry of the explosion debris ("ejecta"). Using multi-wavelength observations of gamma-ray burst (GRB) afterglows I show that GRBs, arising from the death of massive stars, are marked by relativistic, collimated ejecta ("jets") with a wide range of opening angles. I further show that the jet opening angles are strongly correlated with the isotropic-equivalent kinetic energies, such that the true relativistic energy of GRBs is nearly standard, with a value of few times 10^51 erg. A geometry-independent analysis which relies on the simple non-relativistic dynamics of GRBs at late time confirms these inferences. Still, the energy in the highest velocity ejecta, which give rise to the prompt gamma-ray emission, is highly variable. These results suggest that various cosmic explosions are powered by a common energy source, an "engine" (possibly an accreting stellar-mass black hole), with their diverse appearances determined solely by the variable high velocity output. On the other hand, using radio observations I show that local type Ibc core-collapse supernovae generally lack relativistic ejecta and are therefore not powered by engines. Instead, the highest velocity debris in these sources, typically with a velocity lower than 100,000 km/sec, are produced in the (effectively) spherical ejection of the stellar envelope. The relative rates of engine- and collapse-powered explosions suggest that the former account for only a small fraction of the stellar death rate. Motivated by the connection of GRBs to massive stars, and by their ability to overcome the biases inhenert in current galaxy surveys, I investigate the relation between GRB hosts and the underlying population of star-forming galaxies. Using the first radio and submillimeter observations of GRB hosts, I show that some are extreme starburst galaxies with the bursts directly associated with the regions of most intense star formation. I suggest, by comparison to other well-studied samples, that GRBs preferentially occur in sub-luminous, low mass galaxies, undergoing the early stages of a starburst process. If confirmed with future observations, this trend will place GRBs in the forefront of star formation and galaxy evolution studies.
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Akser, Marielle. "Detections of nuclear explosions by triple coincidence." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-448930.
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When a nuclear explosion occurs certain radionuclides are emitted, notably xenon. Due to the fact that xenon is a noble gas, it is hard to contain and can therefore be detected far from the explosion site. There are four isotopes of xenon that are of interest in the detection of a nuclear explosion: 131mXe, 133mXe, 133Xe and 135Xe. By constantly measuring the amount of these isotopes in the air, changes in the concentration in an indication that a nuclear explosion has occurred. In this thesis a detector was modelled in GEANT4 and focuses on one kind of noble gas detector: SAUNA - the Swedish Automatic Unit for Noble gas Acquisition. SAUNA uses the coincidence technique in order to determine the concentration of xenon there is in the air. By using the coincidence technique, it is possible to reduce the impact of the background radiation and therefore increase the efficiency of the detector. 133Xe has a coincidence when it first undergoes beta decay, with an endpoint energy of 346 keV, and then emits a 80 keV gamma particle. 135Xe has also a dual coincidence, a beta decay with an endpoint energy of 910 keV together with a 250 keV gamma-ray. However both these isotopes have a triple coincidence decay that also can be exploited: for 133Xe, a beta particle with endpoint energy of 346 keV, a 30 keV X-ray and a 45 keV conversion electron, while for 135Xe there is instead of the gamma particle a 30 keV X-ray and a 214keV conversion electron that can be emitted together with the beta particle. The 30 keV X-ray together with the beta particle for 133Xe can also be used as a dual coincidence, in that case the conversion electron is ignored. For 133Xe, when a beta particle, a 45 keV conversion electron, and a 30 keV X-ray are emitted, the model was able to detect all three particles in 69.2% ± 0.1 of the cases. However, when only the particles with a detected energy within a 5 keV interval of their generated energies are considered to be in coincidence, then for 133Xe triple coincidence occurs in 22.9% ± 0.2 of the cases. For 135Xe the model was able to detect the triple coincidence (between a beta, 214 keV CE and 30 keV X-ray) in 63.5% ± 0.1 of the cases. This work shows that adding another particle in a coincidence reduces the chance to detect the coincidence. The positive effect of adding another particle in a coincidence is that the minimum detectable concentration of xenon should be smaller. The goal for future detectors should be to make it possible for the detector to take advantage of the triple coincidences but at the same time be also able to use the dual coincidences.
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Berger, Edo Harrison Fiona A. "Cosmic explosions : the beasts and their lair /." Diss., Pasadena, Calif. : California Institute of Technology, 2004. http://resolver.caltech.edu/CaltechETD:etd-05202004-165422.
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Thesis (Ph. D.)--PQ# 3203853.Paper copy has xvii, 311 leaves because the type-face is larger; chapter numbers are different, also, but the contents are the same; no color in paper copy. Includes bibliographical references.
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Fong, Heung Wah. "Editing explosion simulations /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?COMP%202004%20FONG.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 69-71). Also available in electronic version. Access restricted to campus users.
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Morales, Garoffolo Antonia. "Observation and interpretation of type IIB supernova explosions." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/393870.
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Core-collapse supernovae (CC-SNe) explosions represent the final demise of massive stars. Among the various types, there is a group of relatively infrequent CC-SNe termed type IIb, which appear to be hybrids between normal type II SNe (those characterised by H emission) and type Ib (those that lack H features in their spectra but exhibit prominent HeI lines). The nature of the stellar progenitors leading to type IIb SNe is currently unknown, although two channels are contemplated: single massive stars that have lost part of their outer envelope as a consequence of stellar winds, and massive stars that shed mass by Roche-Lobe overflow to a companion. The latter is in fact the favoured scenario for most of the objects observed up to now. In the majority of cases, when there are no direct progenitor detections, some hints about type IIb SN progenitors (e.g., initial mass) can be derived indirectly from the objects' light curves (LCs) and spectra. Motivated by the relatively few well-sampled observational datasets that exist up to date for type IIb SNe and the unknowns on their progenitors, we carried out extensive observations (mainly in the optical domain) for the young type IIb SNe 2011fu and 2013df. Both these SNe are particularly interesting because they show a first LC peak caused by shock breakout, followed by a secondary 56Ni-decay-powered maximum. The analysis of the data for SNe 2011fu and 2013df points to precursors that seem to have been stars with large radii (of the order of 100~RSun), with low mass hydrogen envelopes (tenths of MSun), and relatively low initial masses (12-18 MSun), which could have formed part of interacting binary systems.
The nature of a third SN IIb candidate, OGLE-2013-SN-100, proved to be enigmatic.
OGLE-2013-SN-100, shows a first peak in the LC, and other characteristics somewhat similar to those of type IIb SNe. However, after a deeper analysis, we conclude OGLE-2013-SN-100 is likely not a SN of type IIb. We provide an alternative possible explanation for this object, which implies a combination of a SN explosion and interaction of its ejecta with circumstellar-material.
SNe~2011fu and 2013df were included in a larger sample of type IIb SNe to carry out a comparative study of their observables and environment. Regarding the host galaxies, 90% of the objects are located in giant (r<-18 mag) hosts. In addition, the SNe are about equally split in low star formation and high star formation rate spiral galaxies. Concerning the SN ultra-violet (UV), optical, and near-infrared (NIR) LCs, we find a dispersion in both shape and brightness. Particularly, a few objects show a sharp declining early phase in the UV and double-peaked optical-NIR LCs.
However, the absence of a first LC peak, in some of the cases, may be due to lack of early observations. In addition, we found dispersion in the evolution of the colour indices of the SNe, making the colour comparison method not suitable to estimate extinction toward a type IIb SN. In the optical domain, the study of the (secondary) peak brightness in the R band shows that low luminosity events could be uncommon and the average brightness of the sample is ~-17.5 mag. As for the spectral properties, the SNe that show an early spike in their LCs exhibit blue, shallow-lined early-time spectra and arise from extended progenitors (R~100 RSun). Additionally, while there is an overall resemblance of the measured ejecta velocities, there is also dispersion of equivalent widths, nebular line luminosities and ratios among all the objects that could indicate differences in the ionisation state of the ejecta and mixing. All in all, we find heterogeineity in the studied observables of the sample of type IIb SNe, which reflects the variety of their explosion parameters and progenitor properties.Las supernovas de colapso gravitatorio (CC-SNe) representan el fin de la evolución de estrellas masivas. Entre otros tipos, hay un grupo de CC-SNe relativamente infrecuentes denominado SNe IIb, que aparentan ser híbridos entre SNe de tipo II (con emisión de H) y tipo Ib (que carecen de H pero sí presentan HeI). La naturaleza de los progenitores de las SNe IIb es desconocida, aunque se contemplan dos escenarios: estrellas muy masivas, que pierden parte de su envoltura por vientos estelares, y estrellas masivas, que forman parte de un sistema binario y han cedido masa a una compañera antes de explotar. Este segundo escenario es de hecho el más favorable para la mayor parte de las SNe IIb observadas hasta ahora. En la mayoría de los casos, cuando no hay detecciones directas de los progenitores de las SNe IIb, pueden obtenerse pistas sobre su naturaleza (e.g. masa inicial) a partir de las curvas de luz (LC) y espectros de las SNe. Motivados por el bajo número de SNe IIb observadas en detalle y las incógnitas sobre sus progenitores, hemos hecho observaciones intensivas (principalmente en el rango óptico) de dos SNe IIb jóvenes: SNe 2011fu y 2013df. Ambas SNe son particularmente interesantes porque presentan un primer máximo en su LC, debido al shock breakout y que ha sido escasamente observado para otras SNe, seguido de un segundo máximo provocado por el decaimiento radiactivo del 56Ni. El análisis de los datos de SNe 2011fu y 2013df apunta a que sus precursores parecen haber sido estrellas con radios del orden de 100 Rsol, con envolturas de H de baja masa (décimas de Msol) y con masas iniciales relativamente bajas (12-18 Msol), lo que apunta a que podrían haber formado parte de sistemas estelares binarios. La naturaleza de un tercer objeto candidato a SN IIb, OGLE-2013-SN-100, resultó ser enigmática. OGLE-2013-SN-100, presenta un primer máximo en su LC y otras características parecidas a las SNe IIb. Sin embargo, tras un análisis profundo de sus datos, concluimos que probablemente no sea una SN IIb y damos una posible explicación alternativa para este objeto, que implica la combinación de una SN y la interacción del material eyectado con material circunestelar. SNe 2011fu y 2013df fueron incluidas en una muestra de SNe IIb para hacer un estudio comparativo de sus observables y entorno. Con respecto a las galaxias en las que tienen lugar, 90% de los objetos están localizados en galaxias gigantes (r<-18 mag). Además las SNe están divididas prácticamente por igual en galaxias con alta y con baja formación estelar. En relación a las LCs en el ultravioleta (UV), óptico e infrarrojo cercano (NIR), encontramos dispersión tanto en la forma como en el brillo. Particularmente, algunos objetos presentan LC con una caída pronunciada en fases tempranas en el UV y curvas de luz con dos máximos en el óptico-NIR. Hemos encontrado además dispersión en la evolución de los índices de color de las SNe, lo que hace que el método de comparación de colores no sea adecuado para estimar la extinción hacia una SN IIb. En el rango óptico, el estudio del máximo (secundario) en las curvas de luz en banda R muestra que los objetos de baja luminosidad podrían ser poco comunes y que la magnitud media del máximo está en torno a -17.5 mag. Con respecto a las propiedades espectrales, las SNe que muestran un primer máximo en la LC tienen espectros tempranos azules con líneas poco pronunciadas y provienen de progenitores extensos (R~100Rsol). Además, mientras que las velocidades del material eyectado en la explosiones de las distintas SNe son parecidas, hay dispersión en las anchuras equivalentes de las líneas y en las luminosidades y ratios de las líneas nebulares de los distintos objetos lo que podría indicar diferencias en el estado de ionización y grado de mezcla. En definitiva, encontramos heterogeneidad en los observables de la muestra de SNe IIb, lo que refleja la variedad en los parámetros de explosión y en las características de sus progenitores.
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Socha, Jessica. "Graph-Based Fracture Models for Rigid Body Explosions." Thesis, University of Waterloo, 2005. http://hdl.handle.net/10012/1105.
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Explosions are one of the most powerful and devastating natural phenomena. The pressure front from the blast wave of an explosion can cause fracture of objects in its vicinity and create flying debris. In this thesis, I outline a previously proposed explosion model. An explosion is treated as a fluid with its behaviour governed by the Navier-Stokes equations and the gaseous products modeled using particles. Explosions are simulated as a means for initiating fracture of rigid bodies in the vicinity of an explosion. In contrast to fracture models that are based on physics, I propose a new approach to simulating fracture which treats fracturing the rigid body as a pre-processing step. A rigid body can be pre-fractured by treating it as graph and using one of the two proposed graph partitioning algorithms to divide the object into the desired number of pieces. By treating fracture as a pre-processing step, much less computation need be done during the simulation than models based on physics.
It is shown that the recursive breadth-first search graph partitioning algorithm produces physically realistic results for shattering windows that are consistent with observations of real broken windows. The curvature-driven spectral partitioning algorithm fractures objects into two pieces where the object is weakest, where weakest is defined by the area with largest curvature. Numerical simulations of explosions and fracture were conducted to produce data that was used by a ray tracer and volume renderer to create images which were assembled into animations.
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Ramasamy, Arul. "Lower limb blast injuries from under vehicle explosions." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/39482.
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The signature weapon of the conflicts in Iraq and Afghanistan has been the roadside bomb (anti-vehicle mine, AV) or improvised explosive device (IED). Detonation of the explosive under a vehicle leads to rapid deflection of the vehicle floor, transmitting a very short duration, high amplitude load into the foot and ankle complex in contact with it. To date, there has been no clinical data on the pattern of lower limb injury or clinical outcome following an under-vehicle explosion. Using contemporary battlefield casualty data of UK service personnel injured in Iraq and Afghanistan, 63 casualties (89 injured limbs) were identified with lower leg injuries from explosion. Fifty percent of casualties sustained multi-segmental injuries to the foot and ankle complex and 29% required amputation, with 74% having on-going clinical problems at mean 33 months follow-up. Sub-group analysis showed that casualties standing at the time of explosion had significantly greater injury severity and poorer clinical outcome. In order to investigate the effect of limb orientation on injury severity, both finite element analysis and experimental approach was used. A traumatic injury simulator (Anti-vehicle mine underbelly blast injury simulator, AnUBIS) was developed to recreate the impulse witnessed in explosions within a laboratory setting. Initial experiments with instrumented cadaveric limbs impacted at 8.2-8.6 m/s demonstrated that for the same impulse the standing cadaveric limb sustained significantly severe injuries compared to the seated position. The data presented in this thesis has shown that lower limb injuries from AV mine explosions are associated with a poor clinical outcome. Primary prevention remains key in reducing the injury burden to the combat soldier. The development of realistic traumatic injury simulations allows for better understanding of the underlying injury mechanics, thereby focusing future research in injury mitigation and the development of improved lower limb test surrogates.
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Christie, Elizabeth, and elizabeth christie@unisa edu au. "Explosions in the Narrative: Action films with Lacan." Flinders University. Screen Studies, 2006. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20071121.092301.
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Since the late seventies, the violence, speed and spectacle associated with the genres of war films, Westerns and the spectacular melodramas of early cinema have developed into a distinct genre of its own the action film. With the development of the stylistic language at the core of this generic universe came derogatory generalisations and a tendency to categorise simplistically. To overcome these simplifications, this thesis explores the shifts in generic language to distinguish its subtleties and complexities of logic. Overwhelmingly the genre is considered masculine, but the purpose of this thesis is to explore the logic of this masculinity and analyse the effect of the feminine upon it.
Beginning with overviews of the theoretical attempts to grasp the concept of genre that focus primarily on the limitations of the view of their having distinct boundaries, the theory that genre theory has failed is investigated. Leaving this view of boundaries through an exploration of symbolic universes that have translucent boundaries, the filmic movement of genre passes back and forth through the theoretical frameworks. The intention is not to analyse the overall concept of genre, but to focus on the symbolic universe and the language intrinsic to action films. The rules of action cannot be simply transposed onto other generic categories but stand-alone. Genre theory does not fail if approached from a perspective of discourse analysis focusing on the development of symbolic universes. Using Jacques Lacans theory of the four discourses, and focusing primarily on the oppositions of the Masters and the Analysts discourse, the question moves from the listing of conventions as the markers of the boundaries of genre, to exploring why the combination of certain conventions and signifiers coming together created the genre.
Through Lacanian discourse analysis it becomes apparent that the generally acknowledged logic of masculine and feminine are limited. The masculine is the norm that appears to need no explanation, but the feminine has transgressed the norm and shown the construction of fantasy inherent in the genre. This has led to post-action films that are ambiguous both in their generic structure and symbolic language.
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Mendham, Kirstie Joanna. "Energetic cluster explosions in intense femtosecond laser fields." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396421.
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Morgan, Tony. "The arresting of explosions to minimise environmental damage." Thesis, Brunel University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324654.
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Gibson, Sarah L. "Understanding the most powerful explosions in the Universe." Thesis, University of Leicester, 2018. http://hdl.handle.net/2381/43098.
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Gamma-ray bursts (GRBs) are the most luminous transient events in the Universe. The population of observed GRBs is organised into two categories: long and short, separated by a two second divide in gamma-ray emission duration. The short type (lasting less than two seconds) have been shown to originate from the merger of two neutron stars, whereas as long bursts (lasting longer than two seconds) originate from the collapse of massive stars. There are subtypes within both classes that challenge the standard model for GRBs. For shorts, some bursts exhibit a re-brightening in their high-energy emission becoming dominant shortly after the initial emission spike known as extended emission bursts. For long bursts, some exhibit flares in their X-ray afterglows that contain a comparable amount of energy to the prompt emission. These are so-called giant X-ray flares. This thesis examines the central engine that drives these extreme types of bursts since they have the potential to discern between various proposed GRB models. A potential explanation for these events may be a highly magnetised, rapidly rotating neutron star (magnetar) fed by fallback accretion. The motivation for using this model is the late-time plateaux seen in some short GRBs that can be interpreted as a long-lived magnetar losing angular momentum along magnetic field lines. The fallback accretion component extends the global energy budget of the system and allows the rotational energy reservoir of the magnetar to be refreshed.
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Erfort, Gareth. "Investigation into the electromagnetic field generated by explosions." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/11887.
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Includes abstract.Includes bibliographical references.
This project was undertaken to identify any discernible field or wave in the low frequency EM spectrum, focusing particularly on the magnetic field. The work published by Soloviev in 2002 and Adushkin in 2004 served as guidelines on test procedure and setup. Testing of this nature was not found in the literature to have been previously conducted in South Africa and is multi-disciplinary, involving the fields of detonics and signal processing.
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Beetge, Frans Jacobus. "Impulse loading of near-field shallow-buried explosions." Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/5555.
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Includes bibliographical references (leaves 202-208).Prediction of the total impulse for a mine-protected vehicle must be empirically determined for South African Paardefontein soil pit soil at the start-up phase of a new vehicle project, particularly when experimental data are not yet available for the calibration of computational efforts. The total impulse on a mine-protected vehicle is influenced by a number of factors, such as size of the exposed target area, explosive mass, explosive diameter to height ratio, standoff distance, depth of burial, and soil properties. This investigation entails the development of an empirical equation for predicting total impulse by applying regression analysis. A series of comparative test results were obtained with the Scientific Instrumented Impulse Measurement Apparatus (SIIMA) for TNT equivalent surrogate mines of 2.13 kg - 8 kg mass and diameter to height ratio of 5: 1, and are reported. The lethal aspects of buried mines (target loading mechanisms), such as the detonation shock load, impact load and distributed load, are identified and discussed. Important parameters influencing anti-vehicular blasts, such as standoff distance, soil effects, mine composition and geometry and target shape, are investigated and reported. In conclusion, a SIIMA empirical equation is established which, although limited in standoff distance, can be used as an affordable and quick tool to calculate the vertical impulse on a flat bottom mine-protected vehicle. The SIIMA results show reasonable agreement with the published data of Westine et al (1985) (Braid [1], Williams et al [2] and Williams and Poon [3]), and with the computational predictions provided by the CSIR DPSS-LS. The results provide a better understanding of the complex behaviour of shallow-buried mines in dry sand as an anti-vehicular mine threat, when considering parameters such as standoff distance and depth of burial for constant conditions of explosive aspect ratio (diameter to height values).
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Na'inna, Abdulmajid Muhammed. "Effects of obstacle separation distance on gas explosions." Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/5856/.
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The separation distance (pitch) between obstacles is an area that has not received adequate attention by gas explosion researchers despite general recognition of the important role it plays in determining the explosion severity. Either too large or too small a separation distance between the obstacles would lead to lower explosion severity. Therefore obstacles would need to have “optimal” separation distance to produce the worst case explosions overpressures and flame speeds. Most studies to date with multi-obstacles had the obstacles too closely packed resulting in data that most likely do not represent the worst case scenarios. The major objective of this project was to investigate the influence of spacing between obstacles in gas explosions by systematically varying the distance in order to determine the worst case separation that will produce the maximum explosion severity. A long vented cylindrical vessel 162 mm internal diameter with an overall length to diameter ratio (L/D) of 27 was used in the experimental study. The vessel was closed at the ignition end and its open end connected to a large cylindrical dump-vessel with a volume of 50 m3. The spacing between the obstacles in the test vessel was systematically varied from 0.25 m to 2.75 m. The influence of obstacle spacing was studied with obstacles of different blockage ratios, shapes, number and scale. Tests were carried out with methane, propane, ethylene and hydrogen mixtures with air. A correlation was developed and applied in this research to predict the position to maximum intensity of turbulence downstream of an obstacle, xmax dimensionalised with obstacle scale, b as a function of obstacle blockage ratio, BR, using steady state experiments from the limited available data in the literature as, ( ) for t/d < 0.6 (thin/sharp obstacles) A clearly defined separation distance which gave the most severe explosions in terms of both maximum flame speed and overpressure was found in this research. The profile of effects with separation distance agreed with the cold flow turbulence profile determined in cold flows by other researchers. However, the present results showed that the maximum effect in explosions is experienced further downstream than the position of maximum turbulence determined in the cold flow studies. It is suggested that this may be due to the convection of the turbulence profile by the propagating flame, after the flame has moved passed the obstacle. The predicted model on position to maximum intensity of turbulence from cold flow data agreed with the worst case obstacle separation distance in the current research if multiplied by a factor of three. Turbulence parameters were estimated from pressure differential measurements and geometrical obstacle dimensions. This enabled the calculation of the explosions induced gas velocities, r.m.s turbulent velocity, turbulent Reynolds number and Karlovitz number. By expressing these parameters in terms of turbulent combustion regimes, the bulk of the tests in this study was shown to be within the thickened-wrinkled flames regime. Turbulent burning velocity, ST models with dependence on obstacle scale, higher than the ones in the existing gas explosion scaling techniques were obtained as, for single hole-obstacles for single flat-bar obstacles From the newly obtained ST correlation for single flat-bar obstacles, an overpressure correlation, P for scaling relationship was derived and validated against both small and large scale experimental data and the results were encouraging. [( √ ) ][ ] In planning the layout of new installations, it is appropriate to identify the relevant worst case obstacle separation in order to avoid it. In assessing the risk to existing installations and taking appropriate mitigation measures it is important to evaluate such risk on the basis of a clear understanding of the effects of separation distance and congestion. The present research would suggest that in many previous studies of repeated obstacles the separation distance investigated might not have included the worst case set up, and therefore existing explosion protection guidelines may not correspond to worst case scenarios.
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Krueger, Seth R. "Simulation of cylinder implosion initiated by an underwater explosion." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Jun%5FKrueger.pdf.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2006.Thesis Advisor(s): Young S. Shin. "June 2006." Includes bibliographical references (p. 99-100). Also available in print.
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Southwick, Leslie. "Knightly armour in England in the age of the black prince." Thesis, Birkbeck (University of London), 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325983.
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Ismail, Mohamed Mohamed. "Blast wave parameter studies of fuel-air explosives." Thesis, Cranfield University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316143.
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Morye, Shantaram Suryakant. "High performance polymer composites for ballistic protection." Thesis, University of Leeds, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270045.
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Stephenson, M. S. "A study of ballistic performance of lightweight armours against small arms ammunition." Thesis, City University London, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304857.
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Fellows, N. A. "Behaviour of ceramic armours subjected to high velocity impact." Thesis, Cranfield University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339810.
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Luebcke, Peter Elliott. "The deflagration-to-detonation transition in granular secondary explosives." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387730.
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