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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Efficient and High-Yielding Routes to Diaryliodonium Salts

Bielawski, Marcin January 2008 (has links)
This thesis summarizes three novel and general reaction protocols for the synthesis of diaryliodonium salts. All protocols utilize mCPBA as oxidant and the acids used are either TfOH, to obtain triflate salts, or BF3•Et2O that gives the corresponding tetrafluoroborate salts in situ. Chapter two describes the reaction of various arenes and aryl iodides, delivering electron-rich and electron-deficient triflates in moderate to excellent yields. In chapter three, it is shown that the need of aryl iodides can be circumvented, as molecular iodine can be used together with arenes in a direct one-pot, three-step synthesis of symmetric diaryliodonium triflates. The final and fourth chapter describes the development of a sequential one-pot reaction from aryl iodides and boronic acids, delivering symmetric and unsymmetric, electron-rich and electron-deficient iodonium tetrafluoroborates in moderate to excellent yields. This protocol was developed to overcome mechanistic limitations existing in the protocols described in chapter two and three. The methodology described in this thesis is the most general, efficient and high-yielding existing up to date, making diaryliodonium salts easily available for various applications in synthesis.
122

Process Study, Simulation, and Optimization of the Direct Conversion of Biomass to Ethyl Levulinate

Woloszyn, Joanne 31 August 2023 (has links)
Lignocellulosic biomass is a promising alternative to non-renewable fossil fuel resources for the sustainable production of fuels and chemicals. Levulinic acid (LA) is considered to be a versatile platform chemical which can be derived from biomass and further upgraded to high-value products like levulinate esters. In this work, the direct chemical conversion of lignocellulosic biomass to ethyl levulinate (EL) through LA was studied in collaboration with Gascon Biomass Research Inc. in an effort to valorize their surplus of lignocellulosic feedstock obtained from biomass recycling activities. A novel one-pot, biphasic, acid-catalyzed hydrolysis-esterification process developed by Prof. Tom Baker's lab (uOttawa Chemistry) was used. Kinetic analyses of the overall reaction pathway and major reaction steps were performed to investigate the effect of reaction conditions such as time, temperature, alcohol concentration, and catalyst concentration and evaluate the kinetic and thermodynamic parameters. Reactions were well modeled by power law rate equations with applicability of the Arrhenius expression and exhibited nearly first-order dependence with respect to each of the corresponding reactants and catalyst, as expected. Kinetic studies of LA esterification to various levulinate esters showed that the reaction is endothermic, endergonic, non-spontaneous, and non-rate-limiting. Increased alcohol alkyl chain length and branching reduced the thermodynamic favourability of LA esterification, likely due to steric effects. Process considerations such as reactor pressure, LA and EL partitioning, solvent:feedstock ratio, solvent recycling, and alternative feedstocks were investigated through various lab-scale studies and simulation case studies with UniSim® Design. The results of experimental studies informed the development of a preliminary potential process flow diagram consisting of eleven batch slurry reactors under agitation in parallel. The product streams feed into a continuous separation process composed of flash vessels and distillation columns to separate and purify the various products, intermediates, unconsumed reactants, and recoverable catalyst and solvent. This work ultimately informs decisions regarding future pilot-scale experiments, process design, and optimization for the envisioned large-scale biorefinery to produce EL.
123

Terracotta Vessels : Food storage addressing global challenges / Terracotta Vessels : Matförvaring för hantering av globala utmaningar

Björklund, Malin January 2021 (has links)
Terracotta vessels are about understanding how we can store food by using a new product solution and how we could use less energy and waste less food in doing so. This project is an attempt to minimise the energy usage in our homes but also to gain greater understanding about the food we choose to bring into our homes and what we can do to avoid throwing it away.
124

Unusual dimer formation of cyclometalated ruthenium NHC p-cymene complexes

Schleicher, David, Tronnier, Alexander, Leopold, Hendrik, Borrmann, Horst, Strassner, Thomas 27 February 2017 (has links) (PDF)
We present the synthesis and structural characterization of novel ruthenium complexes containing C^C* cyclometalated N-heterocyclic carbene ligands, η6-arene (p-cymene) ligands and one bridging chlorine ion. Complexes of the general formula [Ru(p-cymene)(C^C*)Cl] were prepared via a one-pot synthesis using in situ transmetalation from the correspondent silver NHC complexes. These complexes react with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBArF4) to form dinuclear complexes of the general structure [Ru(p-cymene)(C^C*)-μ-Cl-(p-cymene)(C^C*)Ru]+[BArF4]−. Solid-state structures confirm that the pseudo-tetrahedral coordination around the metal center with the η6-ligand aligned perpendicularly to the C^C* ligand and the i-Pr group “atop” is retained in the bimetallic complexes.
125

Reflexe Pol Potova režimu v komunistickém Československu / Reflexion of Pol Pot's Regime in Communist Czechoslovakia

Židlický, Jan January 2014 (has links)
This diploma thesis at first analyzes the brutal regime in Cambodia beetween the years 1975-1979. The goal for the readers is briefly to describe this Khmer Rouge regime. It was inhuman and genocide regime which, after taking control of this land began to implement a huge social experiment. This experiment resulted into two milions deads. One half of the diseases, overwork and starvation, one half of the executions. The purpose of this big disaster was a attempt to put this southeast Asia land into self-sufficiency agriculture state. This situation was a work of a small group of people. The main of them was o Pol Pot. In the second part diploma describes a reflection of this regime in communist Czechoslovakia. This part is based on the research in newspapers of this era and research in archive of Ministry of external affairs. The regime in Czechoslovakia was a communist and very conform to foreign policy of the Soviet Union. So the articles in the communist press was not the official statepoint of Czechoslovak govement. At first the governement was a very happy of winning the new regime, because the previous Lon Nol's was very fixed to the United States. After the year 1976 the locals confrontations beetween Cambodia and Vietnam began. In this time carried on the clash beetween China and Soviet...
126

Reflexe Pol Potova režimu v komunistickém Československu / Reflexion of Pol Pot's Regime in Communist Czechoslovakia

Židlický, Jan January 2014 (has links)
This diploma thesis at first analyzes the brutal regime in Cambodia beetween the years 1975-1979. The goal for the readers is briefly to describe this Khmer Rouge regime. It was inhuman and genocide regime which, after taking control of this land began to implement a huge social experiment. This experiment resulted into two milions deads. One half of the diseases, overwork and starvation, one half of the executions. The purpose of this big disaster was a attempt to put this southeast Asia land into self-sufficiency agriculture state. This situation was a work of a small group of people. The main of them was o Pol Pot. In the second part diploma describes a reflection of this regime in communist Czechoslovakia. This part is based on the research in newspapers of this era and research in archive of Ministry of external affairs. The regime in Czechoslovakia was a communist and very conform to foreign policy of the Soviet Union. So the articles in the communist press was not the official statepoint of Czechoslovak govement. At first the governement was a very happy of winning the new regime, because the previous Lon Nol's was very fixed to the United States. After the year 1976 the locals confrontations beetween Cambodia and Vietnam began. In this time carried on the clash beetween China and Soviet...
127

Stigmata a stigmatizovaní ve středověku / Stigmata and stigmatized persons in the Middle Age

Janatová, Nikola January 2014 (has links)
(in English): The diploma thesis examines phenomenon of stigmas and stigmatised persons in the Middle Ages. This diploma thesis contains of three parts. The goal of first part is description of Crucifixion symbolism from beginning of Christianity up to first stigmas about Francis of Assisi from 1224. Main part presents its own phenomenon of stigmas: their definition, base and reception in religious and expert field. Final part focuses on significant middle-aged holders of stigmas and analysis of their hagiography. Klíčová slova (anglicky): Stigmas, Jesus Christ, cross, crucifixion, bloody sweat, bloody tears, thorn crown, mysticism, self-identification.
128

VoIP Networks Monitoring and Intrusion Detection / Monitorage et Détection d'Intrusion dans les Réseaux Voix sur IP

Nassar, Mohamed 31 March 2009 (has links)
La Voix sur IP (VoIP) est devenue un paradigme majeur pour fournir des services de télécommunications flexibles tout en réduisant les coûts opérationnels. Le déploiement à large échelle de la VoIP est soutenu par l'accès haut débit à l'Internet et par la standardisation des protocoles dédiés. Cependant, la VoIP doit également faire face à plusieurs risques comprenant des vulnérabilités héritées de la couche IP auxquelles s'ajoutent des vulnérabilités spécifiques. Notre objectif est de concevoir, implanter et valider de nouveaux modèles et architectures pour assurer une défense préventive, permettre le monitorage et la détection d'intrusion dans les réseaux VoIP. Notre travail combine deux domaines: celui de la sécurité des réseaux et celui de l'intelligence artificielle. Nous renforçons les mécanismes de sécurité existants en apportant des contributions sur trois axes : Une approche basée sur des mécanismes d'apprentissage pour le monitorage de trafic de signalisation VoIP, un pot de miel spécifique, et un modèle de corrélation des événements pour la détection d'intrusion. Pour l'évaluation de nos solutions, nous avons développés des agents VoIP distribués et gérés par une entité centrale. Nous avons développé un outil d'analyse des traces réseaux de la signalisation que nous avons utilisé pour expérimenter avec des traces de monde réel. Enfin, nous avons implanté un prototype de détection d'intrusion basé sur des règles de corrélation des événements. / Voice over IP (VoIP) has become a major paradigm for providing flexible telecommunication services and reducing operational costs. The large-scale deployment of VoIP has been leveraged by the high-speed broadband access to the Internet and the standardization of dedicated protocols. However, VoIP faces multiple security issues including vulnerabilities inherited from the IP layer as well as specific ones. Our objective is to design, implement and validate new models and architectures for performing proactive defense, monitoring and intrusion detection in VoIP networks. Our work combines two domains: network security and artificial intelligence. We reinforce existent security mechanisms by working on three axes: a machine learning approach for VoIP signaling traffic monitoring, a VoIP specific honeypot and a security event correlation model for intrusion detection. In order to experiment our solutions, we have developed VoIP agents which are distributed and managed by a central entity. We have developed an analyzer of signaling network traces and we used it to analyze real-world traces. Finally, we have implemented a prototype of a rule-based event-driven intrusion detection system.
129

Vliv textilní membrány na dynamiku změn fyziologických ukazatelů zátěže / Impact textile membranes on the dynamics of changes physiological indicators of workload

Funfálek, Tomáš January 2015 (has links)
Title: Impact textile membranes on the dynamics of changes physiological indicators of workload Goals: Compare measurements of clothing technical parameters and laboratory measurement workload in this outfit. Describe and explain the relationship between the results of the technical and functional measurements and physiological issues associated with the use of different textile membranes during a workout. Method: Laboratory quantitative measurement of selected physiological parameters, clothings technical parameters, skin temperature and subjective perception of thermophysiological comfort. Subsequent comparative analysis of measurement results. Key words: clothes, textile membranes, workload, oxygen consuption (VO2), thermophysiological comfort, sweat, clothing physiology
130

Aplicação de reatores anaeróbios para remoção de sulfato de águas de drenagem ácida de minas

Rodriguez, Renata Piacentini 30 April 2010 (has links)
O presente trabalho teve, por objetivo principal, analisar a remoção de sulfato em águas de drenagem ácida de minas em dois tipos de reatores anaeróbios, um com crescimento granular (UASB) e outro com biomassa aderida (RAHLF). Estudos anteriores publicados na literatura apresentam resultados positivos quanto ao tratamento anaeróbio de drenagem ácida de minas, entretanto, na maioria deles, é aplicado um tratamento preliminar à água residuária antes do tratamento principal. Esse trabalho avaliou a operação de reatores anaeróbios sem prévio tratamento da drenagem ácida sob diferentes variáveis. Para o reator anaeróbio horizontal de leito fixo (RAHLF), foram analisadas as variáveis relação DQO/\'SO IND.4\'POT.2-\', correção do pH afluente, carga de sulfato aplicada e a recirculação da fase líquida. Os resultados mostraram que a redução da carga de sulfato aplicada foi o fator determinante para os bons resultados de remoção, encontrados ao longo da operação dos reatores (70% de remoção de sulfato e 75% de remoção de DQO). A relação DQO/\'SO IND.4\'POT.2-\' também foi importante e quando utilizada a relação estequiométrica de 0,67, a eficiência de remoção de sulfato atingiu níveis superiores a 70% com pequeno acúmulo de ácido acético no efluente. Para a operação do reator anaeróbio de manta de lodo (UASB), as variáveis analisadas foram o volume da manta de lodo, a relação DQO/\'SO IND.4\'POT.2-\', a carga de sulfato aplicada e a recirculação da fase líquida. Como para o RAHLF, a redução da carga de sulfato aplicada foi essencial para o melhor funcionamento do UASB. A relação DQO/\'SO IND.4\'POT.2-\' de 1,0 promoveu melhora na eficiência do reator, quando comparada à relação estequiométrica e a recirculação no reator só foi positiva quando realizada com água de abastecimento, tendo o reator entrado em colapso quando a recirculação foi realizada com o efluente tratado. / The main objective of this work was to evaluate the sulfate removal from acid mine drainage in two types of anaerobic reactors, one with a granular sludge (UASB) and another with immobilized biomass (HAIB reactor). Previous published studies have showed positive results for the anaerobic treatment of acid mine drainage, however, in most of them, it was applied a pre-treatment operation. This study evaluated the operation of anaerobic reactors without pre-treatment of the acid mine drainage under different parameters. The parameters COD/\'SO IND.4\'POT.2-\' ratio, correction of affluent pH, sulfate loading and recirculation of the liquid phase were tested for horizontal-flow anaerobic immobilized biomass (HAIB) reactor. The results showed that the decrease in the sulfate loading was a determining factor for the successful sulfate removal found throughout the operation of the reactors. The COD/\'SO IND.4\'POT.2-\' ratio was also important and the removal efficiency of sulfate reached levels above 70% with a small accumulation of acetic acid in the effluent when using stoichiometric ratio of 0.67. For the operation of the upflow anaerobic sludge blanket (UASB) reactor, the parameters were the volume of the sludge blanket, the COD/\'SO IND.4\'POT.2-\' ratio, the sulfate loading and the recirculation of the liquid phase. Similarly ti the HAIB reactor, reducing the sulfate load was essential for obtaining better results. The COD/\'SO IND.4\'POT.2-\' ratio of 1.0 showed a improved sulfate removal efficiency for the UASB reactor when compared to stoichiometric ratio at 0.67 ant the recirculation in this reactor was only positive when carried out with tap water. The UASB reactor collapsed when recirculation was carried out whit the treated effluent.

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