<p>The methods HPLC, microcalorimetry and FTIR together with chemometry, provide good analytical tools to follow the degradation of nitro-cellulose.</p><p>The degradation products formed from diphenylamine (DPA) during storage can be followed with HPLC. FTIR, together with chemometry, also gives the precision needed for safety control of propellants.</p><p>Nitro-cellulose (NC) containing DPA obtained a green colour already after 1 day storage at 70°C. About 10% of the stabilizer, and its derivatives, added were not extractable giving an extended time to autocatalysis. This time could be extended up to 70 days at 70°C for an extracted sample compared to about 3 days for non-stabilized NC. This was not shown before.</p><p>Aged and extracted NC samples contained a non-extractable nitro compound. The most likely compound is 2,4´-dinitroDPA, probably bonded to NC via the amine nitrogen. The bonding to NC occurs after the formation of NNODPA. This is something not described before.</p><p>Using another batch of nitro-cellulose to find out if a chemical bonding occurs gave inconclusive results as a blue NC was formed. Low molecular NC with high stability was obtained. A chemical bonding probably occurs when using NNODPA as a stabilizer, indicating NNODPA plays a key role.</p><p>The use of FTIR/chemometry is a promising method to use when studying small chemical changes. The described methodology should be used to find out more about the compound(s) being bonded to NC.</p>

Die vorliegende Arbeit beschäftigt sich mit der Synthese und den Eigenschaften von linearen und verzweigten amphiphilen Polypeptid-Blockcopolymeren. Die Frage nach dem Einfluss der Topologie und Konformation der Blockcopolymere auf die supramolekularen und kolloidalen Eigenschaften bildete einen wichtigen Aspekt bei den Untersuchungen. Die Blockcopolymere wurden nach einem mehrstufigen Reaktionsschema durch Kombination von anionischer und ringöffnender Polymerisation von Aminosäuren-N-Carboxyanhydriden (NCA) synthetisiert. Die Untersuchung der Polypeptid-Blockcopolymere hinsichtlich ihres Aggregationsverhaltens in fester Phase sowie in verdünnter wässriger Lösung erfolgte mittels Streumethoden (SAXS, WAXS, DLS) sowie abbildender Methoden (TEM). Durch Einsatz der Blockcopolymere als polymere Stabilisatoren in der Emulsionspolymerisation wurden Oberflächen funktionalisierte Latizes erhalten. Als Beispiel für eine pharmazeutische Anwendung wurden bioverträgliche Polypeptid-Blockcopolymere als Wirkstoff-Trägersysteme in der Krebstherapie eingesetzt. / This work describes the synthesis and characterization of linear and branched polypeptide block copolymers having amphiphilic character. The studies focused on the impact of the block copolymers' conformation and architecture on the supramolecular and colloidal properties. The polypeptide block copolymers were prepared in a multi-step process involving the anionic synthesis of (poly)amino-functional polymers (polystyrene and polybutadiene) which where used as macroinitiators for the ring-opening polymerization of N-carboxyanhydrides (NCA) of protected a-aminoacids. Supramolecular structures of the block copolymers in the solid state as well as in diluted aqueous solution were investigated using scattering (SAXS, WAXS, DLS) and microscopic (TEM) methods. Both linear and branched polypeptide block copolymers were used as polymeric stabilizers in the emulsion polymerization of styrene to yield polypeptide-decorated latexes. Biocompatible block copolymers were used as drug-delivery systems in lymphatic cancer therapy.

The methods HPLC, microcalorimetry and FTIR together with chemometry, provide good analytical tools to follow the degradation of nitro-cellulose. The degradation products formed from diphenylamine (DPA) during storage can be followed with HPLC. FTIR, together with chemometry, also gives the precision needed for safety control of propellants. Nitro-cellulose (NC) containing DPA obtained a green colour already after 1 day storage at 70°C. About 10% of the stabilizer, and its derivatives, added were not extractable giving an extended time to autocatalysis. This time could be extended up to 70 days at 70°C for an extracted sample compared to about 3 days for non-stabilized NC. This was not shown before. Aged and extracted NC samples contained a non-extractable nitro compound. The most likely compound is 2,4´-dinitroDPA, probably bonded to NC via the amine nitrogen. The bonding to NC occurs after the formation of NNODPA. This is something not described before. Using another batch of nitro-cellulose to find out if a chemical bonding occurs gave inconclusive results as a blue NC was formed. Low molecular NC with high stability was obtained. A chemical bonding probably occurs when using NNODPA as a stabilizer, indicating NNODPA plays a key role. The use of FTIR/chemometry is a promising method to use when studying small chemical changes. The described methodology should be used to find out more about the compound(s) being bonded to NC.

The current study discusses the preparation and long-term performance of polymer composites used for various purposes under different ageing conditions. The first part deals with the preparation and characterization of polymer nanocomposites based on poly(ethylene-co-butyl acrylate) (EBA–13 and EBA–28 with 13 and 28 wt % butyl acrylate, respectively) and 2–12 wt % (0.5–3 vol %) of aluminum oxide nanoparticles (two types with different specific surface areas and different hydroxyl-group concentrations; uncoated and coated with, respectively, octyltriethoxysilane and aminopropyltriethoxysilane). The nanocomposite with EBA–13 showed better overall nanoparticle dispersion while EBA–28 resulted in poor dispersion, probably due to insufficiently high shear forces acting during extrusion mixing which were unable to break down nanoparticle agglomerates. The activity of hindered phenolic antioxidant (0.2 wt%) in all EBA nanocomposites was assessed by determining the oxidation induction time using DSC. The composites containing uncoated aluminium oxide nanoparticles showed a much shorter initial OIT than the pristine polymer with the same initial concentration of antioxidant, indicating adsorption of antioxidant onto the nanoparticle surfaces. Composites containing coated nanoparticles showed a significantly smaller decrease in the initial OIT, suggesting the replacement of hydroxyl groups with organic silane tails, decreasing the concentration of available adsorption sites on the nanoparticle surfaces. The decrease in OIT with increasing ageing time in dry air at 90 °C of the nanocomposites was slower than that of the unfilled pristine polymer, suggesting a slow release of antioxidant from adsorption sites. The EBA nanocomposites exposed to liquid water at 90°C showed faster decrease of OIT than samples exposed to dry or humid air. The migration rate of antioxidant was controlled by the boundary conditions in the case of ageing in humid air and liquid water. The antioxidant diffusivity was lower for the composites containing uncoated ND than for the composites containing ND coated with octyltriethoxysilane or aminopropyltriethoxysilane. The migration and chemical consumption of deltamethrin DM, (synthetic pyrethroid) and synergist piperonyl butoxide from molded polyethylene sheets was also studied. Deltamethrin and piperonyl butoxide are often used for food  storage and insect control purposes. DM showed no signs of crystallization and remained in a liquid state after being cooled to room temperature. Exposure of polyethylene compound sheets to liquid water (at 80 &amp; 95 °C), caused degradation and hydrolysis of the ester bond in the DM, present in the prepared material, and generated species containing hydroxyl groups. Liquid chromatography and infrared spectroscopy showed a significant migration of the active species in liquid water, whereas in air at 80 °C (60 and 80 %RH) the loss of DM and PBO was negligible over 30 days. The long-term performance of medium-density polyethylene stabilized with six different phenolic antioxidants (0.1 wt%) in aqueous chlorinated media at 70 °C was studied. The results were compared with data for previously studied solutions of antioxidants in squalane (a liquid, low molar mass analogue of polyethylene). A linear relationship was established between the time to reach antioxidant depletion in polyethylene tape samples and the time in squalane samples. Infrared spectroscopy and scanning electron microscopy of drawn samples revealed the onset of surface oxidation and surface embrittlement in tape samples exposed beyond the time for antioxidant depletion. / <p>QC 20121109</p> / Cable insulation materials / Loss of deltamethrin and pipronyl butoxide from polyethylene / long-term performance of polyethylene in chlorine dioxide water

nÃo hà / Este trabalho apresenta a aplicaÃÃo do algoritmo de OtimizaÃÃo por Enxame de PartÃculas (PSO â Particle Swarm Optimization) para sintonia Ãtima de controladores associados à regulaÃÃo de tensÃo e ao aumento do amortecimento de geradores sÃncronos utilizados em plantas termelÃtricas de ciclo combinado. Para representaÃÃo matemÃtica do gerador sÃncrono, utiliza-se o modelo linearizado de terceira ordem do sistema mÃquina conectada a uma barra infinita, vÃlido para estudos de estabilidade a pequenos sinais. Os parÃmetros do regulador automÃtico de tensÃo (AVR â Automatic Voltage Regulator) e do estabilizador de sistema de potÃncia (PSS â Power System Stabilizer) sÃo determinados de maneira Ãtima pela ferramenta computacional proposta. Os parÃmetros obtidos para o AVR e PSS sÃo comparados com valores calculados por tÃcnicas de sintonia convencionais, baseadas em aproximaÃÃes das equaÃÃes que descrevem o sistema. Os resultados de simulaÃÃes a variaÃÃes na tensÃo de referÃncia, considerando a anÃlise da resposta temporal do sistema controlado, demonstram que o PSO à uma tÃcnica eficiente na sintonia dos parÃmetros do AVR e PSS, destacando-se sua simplicidade, baixo esforÃo computacional e boa caracterÃsticas de convergÃncia. / This work presents the application of the Particle Swarm Optimization (PSO) algorithm for optimal tuning of controllers associated with voltage regulation and damping enhancement of synchronous generators used in combined cycle power station. For mathematic representation of the synchronous generator, the third order linearized model of a single machine connected to an infinite bus, valid for small signal stability studies, is used. The Automatic Voltage Regulator (AVR) and Power System Stabilizer (PSS) parameters are optimally determined by the proposed computational tool. The parameters obtained for AVR and PSS are compared with values calculated by conventional tuning techniques based on approximations of the equations that describe the system. The simulations results to reference voltage disturbances, considering the time response analysis of the controlled system, show that PSO is an efficient technique in the tuning of AVR and PSS parameters, with emphasis on its simplicity, low computational effort and good convergence characteristics.

Dans les années 80, Shimomura a déterminé les groupes d'homotopie du spectre de Moore V(0) localisé par rapport à K(2) la deuxième K-théorie de Morava. Plus tard, avec les travaux de Devinatz et Hopkins est apparu une autre suite spectrale convergeant vers les précédents groupes d'homotopies. Lorsque le paramètre premier p de la théorie K(2) est supérieur ou égal à cinq, la précédente suite spectrale dégénère. Ainsi, déterminer ces groupes d'homotopie revient à calculer les groupes de cohomologie du groupe stabilisateur de Morava à coefficients dans l'anneau de Lubin-Tate modulo p. En 2007, Henn a démontré l'existence, lorsque p > 3, d'une résolution projective du groupe de Morava de longueur quatre. Dans cette thèse, nous précisons une telle résolution projective. On l'applique ensuite au calcul effectif des groupes de cohomologie à coefficients dans l'anneau de Lubin-Tate modulo p. Enfin, on donne une seconde application, en redémontrant un résultat de Hopkins non publié sur le groupe de Picard de la catégorie des spectres K(2)-locaux. / In the 80's, Shimomura has computed the homotopy groups of the Moore spectrum V(0) localized with respect to Morava K-theory K(2). Some years later, Devinatz and Hopkins found an other spectral sequence converging to those homotopy groups. When the prime paramater p of K(2) is greather or equal to five, the preceding spectral collapses. Thus, computing those homotopy groups consists in computing the cohomology groups of Morava Stabilizer Group with coefficients in the Lubin-Tate ring mod p. In 2007, Henn has showed that there exists, when p >3, a projective resolution of the Morava stabilizer group of length four. In this thesis, we give a more precise description of this resolution. Then, we use it for the computation of the cohomology groups of Morava Stabilizer Group with coefficients in the Lubin-Tate ring mod p. As a second application, we give an other proof of the unpublished result of Hopkins on the Picard group of the K(2)-local spectrum category.

No description available.

Small signal oscillation has been always a major concern in the operation of power systems. In a generator, the electromechanical coupling between the rotor and the rest of the system causes it to behave in a manner similar to a spring mass damper system, which exhibits an oscillatory behaviour around the equilibrium state, following any disturbance, such as sudden change in loads, fluctuations in the output of turbine and faults etc. The use of fast acting high gain AVRs and evolution of large interconnected power systems with transfer of bulk power across weak transmission links have further aggravated the problem of these low frequency oscillations. Small oscillations in the range of about 0.1Hz to 3.5Hz can persist for long periods, limiting the power transfer capability of the transmission lines. Power System Stabilizers (PSS’s) were developed as auxiliary controllers on the generators excitation system to produce additional damping by modulating the generator excitation voltage. Designing effective PSS for all operating conditions specially in large interconnected power systems still remains a difficult and challenging task. The conventionally designed Power System Stabilizer (CPSS) is the most cost-effective electromechanical damping controller till date. However, continual changes in the operating condition and network parameters in large systems result in corresponding large changes in system dynamics. This constantly changing nature of power system makes the design of CPSS a difficult task. The design and tuning of PSS for robust operation is a laborious process. The existing PSS design techniques require considerable expertise, the complete system information and extensive eigenvalue calculations which increases the computational burden as the system size increases. This thesis proposes a method for designing robust power system damping controllers that ensures a minimum robustness under model uncertainties. The minimum performance required for the PSS is set a priori and accomplished over a range of operating conditions. A generalized robust controller design methodology has been first implemented on a Single Machine Infinite Bus (SMIB) power system model. The robust controller places the closed loop rotor modes of the system to the desire location while keeping the electrical modes intact. Unlike conventional lead/lag PSS design, the proposed PSS design is based on pole assignment technique which takes into account of various model uncertainties. For the proposed stabilizer design in a multi-machine systems a new decentralized method has been used which requires system data only upto secondary bus of the unit transformer in a generating station. The proposed robust controller design based on modified Nevanlinna-Pick theory has been designed and tested extensively on SMIB and multi-machine systems to establish the efficacy of the controller in damping small signal oscillations. The thesis is organized in four chapters as follows. The first chapter discusses the basic concepts related to the rotor angle stability in power system. The conventional and other methods of countering this instability by power system stabilizers have been described. The relative merits of the various stabilization techniques have been discussed. The scope of present work, i.e design of decentralized robust power system controllers has been defined. In second chapter a modified robust power system stabilizer for SMIB system is developed. It has been shown that under specific conditions the modified Nevanlinna-Pick theory can also be applied for designing damping controllers in system with lightly damped rotor modes. Third chapter proposes a decentralized approach based on modified Nevanlinna-Pick theory for designing a power system stabilizer for interconnected power systems. The performance of the controller which is not based on external system information has been investigated on three widely used multi-machine test systems to established its efficacy in damping out low frequency oscillations. The fourth chapter gives a brief summary of the work done and also includes a section on the scope of future work relating to design of power system stabilizers.

L’objectif de ce travail de thèse était de développer des encres organiques de polymères semi-conducteurs. Il s’est ainsi agi de synthétiser des latex de poly (3,4-éthylènedioxythiophène) (PEDOT) dispersibles en milieux organiques (cyclohexane ou toluène) par polymérisation oxydative de l’EDOT en présence de stabilisant stériques et/ou électrostatiques. Le stabilisant est un polymère fonctionnalisé par une unité ou plusieurs unités fonctionnelles qui peuvent réagir avec la chaîne de PEDOT en croissance assurant ainsi des liaisons covalentes ou électrostatiques entre celui-ci et le stabilisant. La taille des particules de PEDOT est contrôlée par la masse molaire, la concentration et par la fonctionnalité du stabilisant. Le PEDOT obtenu est caractérisé par diffusion de la lumière (DLS), par microscopie électronique à balayage (MEB) microscopie électronique à transmission (TEM) et par des mesures de conductivité. / Spherical poly(3,4-ethylenedioxythiophene) nano-particles with narrow size distribution were prepared in organic dispersant media in the presence of iron(III) chloride FeCl3 or iron(III) dodecylbenzenesulfonate {Fe(DBS)3} as oxidant and a functionalized polyisoprene (ω-R-PI) as a stabilizer. Two kinds of functionalized polyisoprene were used as stabilizers. Pyrrole, fluorene, Thiophene and methylthiophene end caped polyisoprenes were used as reactive stabilizers. Lithium sulfonate end caped polyisoprene was used as steric stabilizer. The effect of the nature of the solvent, the molar mass, the concentration, and the nature of the functional end unit of the stabilizer on the size and morphology of PEDOT particles were investigated. Polyisoprenes containing sulfonate groups were also used as steric/electrostatic stabilizers. By this way, the sulfonate groups act as counter ions for oxidized PEDOT leading to electrostatic attraction between it and the stabilizer, ensuring stabilization of the latex. Four kinds of polyisoprene-based steric electrostatic stabilizers having one or many sulfonate groups were prepared: sulfonate end-capped polyisoprene (PI-SO3Li), partially sulfonated polyisoprene (PIS), polyisoprene grafted to polystyrene sulfonate (PI-g-PSS) and polyisoprene grafted to polyisoprene sulfonate (PI-g-PIS). The effects of the molar mass of the stabilizer and the sulfonate group content on the PEDOT particle morphology were studied.PEDOT samples were characterized with transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning electron microscopy (SEM), dynamic light scattering (DLS) analysis and conductivity measurements.

This thesis deals with the use of by–products from the production of cement–bonded particle boards as an alternative raw material for the stabilization of the subsoil or into a ground solid. The theoretical part briefly describes the current status of waste management. A set of alterantive raw materials used to hydraulically cemented mixtures is listed here as well as the recherche of the foreign research is elaborated from this area. The experimental part of the thesis firstly deals with the choice of raw materials and basic recipes. In the advanced stage the laboratory analyses are carried out on the modified formulas. Based on the results of these analyses the posibility of using by–products from the production of cement–bonded boards for the stabilization of the subsoil is evaluated here.