Stuttgart, Universiẗat, Diss., 2001.

Zugl.: Hamburg, Techn. Univ., Diss.

Universiẗat, Diss., 2003--Marburg.

A hybrid rocket is a propulsion system that uses propellants in two different phases, typically a solid fuel inside the combustion chamber and a separate gaseous or liquid oxidizer stored in a tank. Hybrid rockets are an area of research interest because of their low explosive risk, inexpensive components, and high degree of reliability. In the Propulsion Research Laboratory at Utah State University, pure oxygen is among the top choice for hybrid rocket oxidizers due to its low cost and ease of storage. When paired with a solid fuel known as ABS (acrylonitrile butadiene styrene) plastic, specific impulse values exceed 200 seconds at one atmosphere. This metric outperforms hydrazine, which is a propellant standard for in-space propulsion that exhibits high vapor toxicity and explosive hazards. However, due to the low density of oxygen, propulsion applications require storage pressures up to 3000 psig. At this high pressure, the use of oxygen can present a fire hazard. As a result, this thesis investigates the feasibility of replacing oxygen with a moderately enriched compressed air containing oxygen levels up to 40%, while maintaining performance metrics equal to or above hydrazine. To demonstrate the performance of moderately enriched air as a hybrid rocket oxidizer, comparisons to tests using pure oxygen are presented.

Made available in DSpace on 2014-06-11T19:22:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-21Bitstream added on 2014-06-13T19:07:30Z : No. of bitstreams: 1 pivetta_lg_me_botfca.pdf: 604700 bytes, checksum: 401bec4e674660b23636e2a136d38729 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / A mamona é uma cultura de grande importância econômica para o Brasil, porém a produtividade nacional é baixa, devido principalmente a reduzida tecnologia utilizada no cultivo. O objetivo do estudo foi avaliar a resposta de híbridos do Programa de Melhoramento de Mamona da UNESP-FCA e de cultivares de mamona a níveis de adubação. O experimento foi conduzido durante o ano agrícola 2009/ 2010 utilizando dois híbridos (A e B), e duas cultivares (FCA-PB e IAC 2028). Os genótipos foram cultivados em três níveis de adubação: 0, 50 e 100% da dose recomendada com base na análise de solo. O delineamento utilizado foi de blocos ao acaso, em esquema fatorial 4x3, com quatro repetições. De acordo com a análise dos resultados as cultivares apresentaram médias maiores para as variáveis vegetativas altura total, altura de inserção do racemo primário, número de nós até o racemo primário, diâmetro do colmo e comprimento do internódio. Em relação aos níveis de adubação, com exceção do número de nós em que não houve diferença, todas as variáveis vegetativas apresentaram médias maiores no nível 100% em relação aos níveis 0 e 50%. As cultivares apresentaram maior contribuição do racemo primário na produção total do que os híbridos. Já estes obtiveram mais racemos por plantas que as cultivares, e consequentemente, tiveram maior contribuição dos racemos de ordem superior na produção total. Isso ocorreu porque os híbridos emitiram o racemo primário em época de grande incidência de chuvas, ocorrendo ataque de mofo-cinzento (Amphobotrys ricini). Com relação à produtividade, dentre os genótipos, o híbrido B foi superior às cultivares e, dentro dos níveis de adubação, o nível 100% foi superior aos níveis 0 e 50%. Na avaliação da resposta de cada genótipo aos níveis de adubação o híbrido B não apresentou resposta à adubação... / Castor bean is a crop of great economic importance for Brazil, but national productivity is low, mainly due to low technology applied. The aim of this study was to evaluate the response of hybrids Castor Bean Breeding Program of UNESP and castor bean cultivars to fertilizer levels. The experiment was conducted in 2010 season using two hybrids (A and B) and two cultivars (FCA-PB and IAC 2028). The genotypes were applied three fertilization levels 0, 50 and 100% rates recommended by soil analysis. The design was randomized blocks in factorial scheme 4x3, with four replications. The results show higher values for vegetative variables height, insertion height of raceme primary, stem diameter and internode length for 100% level of fertilization, but no response these factors to number of nodes until insertion of primary raceme. The cultivars showed higher contribution of the primary raceme in total production than hybrids. Hybrids had more racemes per plant than cultivars, and consequently had greater contribution of racemes of order higher in total production. This occurred because hybrids issued primary raceme in time of great rainfall, occurring gray mold (Amphobotrys ricini). The productivity of hybrid B was higher than others cultivars and genotypes in 100% of rate, only. In estimate of agronomic efficiency (AE), the hybrid B was higher efficient at level 0% than cultivars and not showed response to fertilization. Other genotypes had answers positively to fertilization, but the hybrid A had major yield in level of 100%. Concluded that hybrids have great characteristics for mechanized harvesting and great yields, that allows its use in crops technicality

Orientador: Maurício Dutra Zanotto / Banca: Rogério Peres Soratto / Banca: Tammy Aparecida Manabe Kiihl / Resumo: A mamona é uma cultura de grande importância econômica para o Brasil, porém a produtividade nacional é baixa, devido principalmente a reduzida tecnologia utilizada no cultivo. O objetivo do estudo foi avaliar a resposta de híbridos do Programa de Melhoramento de Mamona da UNESP-FCA e de cultivares de mamona a níveis de adubação. O experimento foi conduzido durante o ano agrícola 2009/ 2010 utilizando dois híbridos (A e B), e duas cultivares (FCA-PB e IAC 2028). Os genótipos foram cultivados em três níveis de adubação: 0, 50 e 100% da dose recomendada com base na análise de solo. O delineamento utilizado foi de blocos ao acaso, em esquema fatorial 4x3, com quatro repetições. De acordo com a análise dos resultados as cultivares apresentaram médias maiores para as variáveis vegetativas altura total, altura de inserção do racemo primário, número de nós até o racemo primário, diâmetro do colmo e comprimento do internódio. Em relação aos níveis de adubação, com exceção do número de nós em que não houve diferença, todas as variáveis vegetativas apresentaram médias maiores no nível 100% em relação aos níveis 0 e 50%. As cultivares apresentaram maior contribuição do racemo primário na produção total do que os híbridos. Já estes obtiveram mais racemos por plantas que as cultivares, e consequentemente, tiveram maior contribuição dos racemos de ordem superior na produção total. Isso ocorreu porque os híbridos emitiram o racemo primário em época de grande incidência de chuvas, ocorrendo ataque de mofo-cinzento (Amphobotrys ricini). Com relação à produtividade, dentre os genótipos, o híbrido B foi superior às cultivares e, dentro dos níveis de adubação, o nível 100% foi superior aos níveis 0 e 50%. Na avaliação da resposta de cada genótipo aos níveis de adubação o híbrido B não apresentou resposta à adubação... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Castor bean is a crop of great economic importance for Brazil, but national productivity is low, mainly due to low technology applied. The aim of this study was to evaluate the response of hybrids Castor Bean Breeding Program of UNESP and castor bean cultivars to fertilizer levels. The experiment was conducted in 2010 season using two hybrids (A and B) and two cultivars (FCA-PB and IAC 2028). The genotypes were applied three fertilization levels 0, 50 and 100% rates recommended by soil analysis. The design was randomized blocks in factorial scheme 4x3, with four replications. The results show higher values for vegetative variables height, insertion height of raceme primary, stem diameter and internode length for 100% level of fertilization, but no response these factors to number of nodes until insertion of primary raceme. The cultivars showed higher contribution of the primary raceme in total production than hybrids. Hybrids had more racemes per plant than cultivars, and consequently had greater contribution of racemes of order higher in total production. This occurred because hybrids issued primary raceme in time of great rainfall, occurring gray mold (Amphobotrys ricini). The productivity of hybrid B was higher than others cultivars and genotypes in 100% of rate, only. In estimate of agronomic efficiency (AE), the hybrid B was higher efficient at level 0% than cultivars and not showed response to fertilization. Other genotypes had answers positively to fertilization, but the hybrid A had major yield in level of 100%. Concluded that hybrids have great characteristics for mechanized harvesting and great yields, that allows its use in crops technicality / Mestre

Groundwater is one of the main sources for drinking water and agricultural activities. Various activities of both humans and nature may lead to groundwater pollution. Very often, pollution, or contamination, of groundwater goes undetected for long periods of time until it begins to affect human health and/or the environment. Cleanup technologies used to remediate pollution can be costly and remediation processes are often protracted. A more practical and feasible way to manage groundwater contamination is to monitor and predict contamination and act as soon as there is risk to the population and the environment. Predicting groundwater contamination requires advanced numerical models of groundwater flow and solute transport. Such numerical modeling is increasingly becoming a reference criterion for water resources assessment and environmental protection. Subsurface numerical models are, however, subject to many sources of uncertainties from unknown parameters and approximate dynamics. This dissertation considers the sequential data assimilation approach and tackles the groundwater contamination problem at the port of Rotterdam in the Netherlands. Industrial concentration data are used to monitor and predict the fate of organic contaminants using a three dimensional coupled flow and reactive transport model. We propose a number of 5 novel assimilation techniques that address different challenges, including prohibitive computational burden, the nonlinearity and coupling of the subsurface dynamics, and the structural and parametric uncertainties. We also investigate the problem of optimal observational designs to optimize the location and the number of wells. The proposed new methods are based on the ensemble Kalman Filter (EnKF), which provides an efficient numerical solution to the Bayesian filtering problem. The dissertation first investigates in depth the popular joint and dual filtering formulations of the state-parameters estimation problem. New methodologies, algorithmically similar, but more efficient numerically, are then proposed based on a more consistent derivation with the Bayesian filtering approach. To reduce computational cost, I further extend the formulation of the hybrid EnKF-variational approach to the state parameter estimation problem and propose an adaptive scheme for the specification of the weights of the flow-dependent and static background covariance matrices. The new adaptive hybrid scheme is shown to provide much better results than the EnKF while using a fraction of the ensemble size. The new methods are implemented and successfully tested with a realistic coupled subsurface and transport-reaction model of the port of Rotterdam by assimilating industrial data on biodegradable chlorinated hydrocarbons. The observational design problem for placing hydrologic wells is subsequently considered and a new efficient solution is proposed that combines concepts from both information theory and data assimilation

No description available.

In this work, 22-pole ion trap machines have been applied to investigate protonated water clusters H+(H2O)n (n=4..10) and ionic hydrocarbons CHn+ (n=2..5) at low temperatures. Protonated water clusters H+(H2O)n play an important role in atmospheric chemistry and in interstellar space. The Taipei 22-pole ion trap machine has been applied to kinetic and spectroscopic investigations of these clusters produced from a supersonic expansion in a corona discharge source. Using low-pressure He buffer gas for collisional thermalization, refrigeration of the ion trap by liquid nitrogen allows a good control of the cluster temperature over the range 80K-350K. This method provides an accurate means of determining the dissociation energies of the cluster ions by measuring their dissociation rates as a function of temperature and calculating their internal energies from vibrational frequencies provided by density functional theory. Results of the thermochemical measurements at well-defined cluster temperatures have been given for H+(H2O)n, n=4..10. The feasibility of using the ion trap to acquire temperature-dependent infrared spectra is presented. The deuteration and abstraction reactions of small ionic hydrocarbons CHn+ (n=2..5) with H2, HD and D2 and the subsequent association processes have been explored at temperatures down to 15K in the Chemnitz 22-pole apparatus. The reactions of the investigated ionic species and their isotopic variants are important for understanding ion-molecule processes in the interstellar medium. One of the starting points of the research program was the question whether protonated methane, CH5+, is subject to H-D-exchange in collisions with HD at low temperatures. It turns out that the rate coefficient for this deuteration process is very small, whereas CH3+ deuterates with HD by three subsequent fast exchange reactions to CD3+ at a temperature of 15K. The latter process is very efficient and happens close to the collision limit. The methane cation, CH4+, on the other hand, shows also some interesting features in collisions with H2, HD and D2. It exhibits an inverse temperature dependence with the rate coefficient increasing at least one order of magnitude going from 300K to 15K. Furthermore, reacting with HD at the temperature of 15K, the reaction channel leading to CH5+ is preferred over the D-atom abstraction channel (isotope effect). / Im Rahmen dieser Arbeit wurden zwei Apparaturen mit 22-Pol-Ionenfallen benutzt, um protonierte Wassercluster H+(H2O)n (n=4..10) und kleine ionische Kohlenwasserstoffe CHn+ (n=2..5) bei tiefen Temperaturen zu untersuchen. Die in einer Koronaentladungsquelle erzeugten Cluster H+(H2O)n wurden kinetisch und spektroskopisch untersucht. Dazu wurden sie in einem 22-Pol-Speicher mithilfe eines He-Puffergases auf einer Temperatur zwischen 80K und 350K thermalisiert. Die Bestimmung der Bindungsenergien fuer Cluster der Groesse n=4..10 wird ermoeglicht durch die Messung der temperaturabhaengigen Dissoziationsraten und durch die Ermittlung der inneren Energien mittels berechneter Schwingungsfrequenzen. Temperaturabhaengige IR-Spektren im Bereich der freien OH-Streckschwingung wurden aufgenommen. Die Austausch- und Abstreifreaktionen von ionischen Kohlenwasserstoffen CHn+ (n=2..5) mit H2, HD und D2 und die darauffolgenden Assoziationsprozesse wurden im Temperaturbereich 15K bis 300K untersucht. Es stellt sich z.B. heraus, dass der H-D-Austauschprozess zwischen CH5+ und HD bei 15K sehr langsam ist, wogegen CH3+ mit jeder Kollision einen Austausch ausfuehrt. In der Abstreifreaktion von CH4+ mit Wasserstoffmolekuelen beobachtet man eine inverse Temperaturabhaengigkeit. Dies wird vorlaeufig mit einer laengeren Komplexlebensdauer bei tiefen Temperaturen erklaert.

Wireless communication is facing an increasingly severe spectrum scarcity problem. Hybrid free space optical (FSO)/ millimetre wavelength (MMW) radio frequency (RF) systems and cognitive radios are two candidate solutions. Hybrid FSO/RF can achieve high data rate transmission for wireless back haul. Cognitive radio transceivers can opportunistically access the underutilized spectrum resource of existing systems for new wireless services. In this work we carry out accurate performance analysis on these two transmission techniques. In particular, we present and analyze a switching based transmission scheme for a hybrid FSO/RF system. Specifically, either the FSO or RF link will be active at a certain time instance, with the FSO link enjoying a higher priority. We consider both a single threshold case and a dual threshold case for FSO link operation. Analytical expressions are obtained for the outage probability, average bit error rate and ergodic capacity for the resulting system. We also investigate the delay performance of secondary cognitive transmission with interweave implementation. We first derive the exact statistics of the extended delivery time, that includes both transmission time and waiting time, for a fixed-size secondary packet. Both work-preserving strategy (i.e. interrupted packets will resume transmission from where interrupted) and non-work-preserving strategy (i.e. interrupted packets will be retransmitted) are considered with various sensing schemes. Finally, we consider a M/G/1 queue set-up at the secondary user and derive the closed-form expressions for the expected delay with Poisson traffic. The analytical results will greatly facilitate the design of the secondary system for particular target application. / Graduate