Current stoichiometric spark-ignited engine technologies require costly catalytic converters for reductions in tailpipe emissions. Load control is achieved by using a throttle, which is a leading contributor to reductions in efficiency. Spark-ignited lean burn natural gas engines have been proven to be more efficient and emit fewer pollutants than their stoichiometric counterparts. Load reduction in these engines can be achieved by regulating the air/fuel ratio of the intake charge thereby reducing the efficiency penalties inherent to throttling. Partially stratified charge (PSC) can provide further reductions in emissions and improvements in efficiency by extending the lean limit of operation. PSC is achieved by the ignition of a small quantity of natural gas in the vicinity of the spark plug. This creates an easily ignitable mixture at the spark plug electrodes, thereby providing a high energy ignition source for the ultra-lean bulk charge. Stratified charge engine operation using direct injection (DI) has been proposed as a method of bridging the throttleless load reduction gap between idle and ultra-lean conditions. A previous study was conducted to determine if PSC can provide a high-energy ignition source in a direct injected stratified charge engine. Difficulties with igniting the PSC injections in an air-only bulk charge were encountered. This study focuses on a fundamental Schlieren image-based analysis of PSC combustion. Natural gas was injected through a modified spark plug located in an optically accessible combustion bomb. The relationships between PSC injection timing, fuel supply pressure and spark timing were investigated. Spark timing is defined as the duration between commanded start of injection and the time of spark. As the fuel supply pressure was increased, the minimum spark timing that lead to successful combustion also increased. The largest spark timing window that led to successful combustion was determined to be 80 ms wide at an injection fuel supply pressure of 300 psi. The amount of unburned natural gas increased with increasing spark timing. A cold flow study of the PSC injection system was also conducted. The PSC injection solenoid was found to have a consistent average injection delay of 1.95 ms. The slope of the linear response region of observed injection duration to commanded injection duration was 8.4. Due to plenum effects, the average observed injection duration of the entire PSC system was an order of magnitude longer than the commanded injection duration and was found to vary significantly with fuel supply pressure.

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisor: John A. Pelesko, Dept. of Mathematical Sciences. Includes bibliographical references.

This thesis discusses several topics related to interpolation and how it is used in numerical analysis. It begins with an overview of the aspects of interpolation theory that are relevant to the discussion at hand before presenting three new contributions to the field. The first new result is a detailed error analysis of the barycentric formula for trigonometric interpolation in equally-spaced points. We show that, unlike the barycentric formula for polynomial interpolation in Chebyshev points (and contrary to the main view in the literature), this formula is not always stable. We demonstrate how to correct this instability via a rewriting of the formula and establish the forward stability of the resulting algorithm. Second, we consider the problem of trigonometric interpolation in grids that are perturbations of equally-spaced grids in which each point is allowed to move by at most a fixed fraction of the grid spacing. We prove that the Lebesgue constant for these grids grows at a rate that is at most algebraic in the number of points, thus answering questions put forth by Trefethen and Weideman about the robustness of numerical methods based on trigonometric interpolation in points that are uniformly distributed but not equally-spaced. We use this bound to derive theorems about the convergence rate of trigonometric interpolation in these grids and also discuss the related question of quadrature. Specifically, we prove that if a function has V ≥ 1 derivatives, the Vth of which is Hölder continuous (with a Hölder exponent that depends on the size of the maximum allowable perturbation), then the interpolants converge uniformly to the function at an algebraic rate; larger values of V lead to more rapid convergence. A similar statement holds for the corresponding quadrature rule. We also consider what analogue, if any, there is for trigonometric interpolation of the famous 1/4 theorem of Kadec from sampling theory that restricts the size of the perturbations one can make to the integers and still be guaranteed to have a set of stable sampling for the Paley-Wiener space. We present numerical evidence suggesting that in the discrete case, the 1/4 threshold takes the form of a threshold for the boundedness of a "2-norm Lebesgue constant" and does not appear to have much significance in practice. We believe that these are the first results regarding this problem to appear in the literature. While we do not believe the results we establish are the best possible quantitatively, they do (rigorously) capture the main features of trigonometric interpolation in perturbations of equally-spaced grids. We make several conjectures as to what the optimal results may be, backed by extensive numerical results. Finally, we consider a new application of interpolation to numerical linear algebra. We show that recently developed methods for computing the eigenvalues of a matrix by dis- cretizing contour integrals of its resolvent are equivalent to computing a rational interpolant to the resolvent and finding its poles. Using this observation as the foundation, we develop a method for computing the eigenvalues of real symmetric matrices that enjoys the same advantages as contour integral methods with respect to parallelism but employs only real arithmetic, thereby cutting the computational cost and storage requirements in half.

Charles University Faculty of Pharmacy in Hradec Králové Department of biophysics and physical chemistry Author: Pavla Tomanová Supervisor: Ing. Vladimír Kubíček, CSc. Thesis title: Physico-Chemical properties of drugs This thesis deals with measuring dissociation constants (the pKa value) and the lipophilicity of nitrogenous heterocycle derivatives produced at the Faculty of Pharmacy in Hradec Králové. Two methods were used to determine the pK value: potentiometric titration and spectrophotometry. Potentiometric titration almost invariably produced relatively exact results, however the results of pK value obtained by spectrophotometry were sometimes difficult to replicate. Dissociation constants were compared on the basis of the method applied, and also with the theoretically determined dissociation constant calculated by means of the ChemDraw Ultra 12.0 software. The results obtained by the two experimental methods turned out to be very similar, corresponding to the theoretical pK value. Lipophilicity is another essential property of drugs tested in the preclinical stage. It specifies the aqueous or lipophilic phase affinity of a drug, substantially affecting the drug's ADMET in organism. Lipophilicity was determined on the basis of capacity factor value identified by RP-HPLC measurement using...

An extensive research program was performed to investigate the load interaction effect of the combined action of small amplitude high R ratio cycles and large amplitude low R ratio underloads on the crack growth of large cracks. The study was driven by the needs of the damage tolerance approach in the helicopter structures, which requires robust knowledge on the crack growth behaviour of the advance high strength alloys under the characteristic helicopter spectra loading. The study was conducted on three metallic alloys, Ti-10V-2Fe-3Al, Al8090 T852 and Al7010 T76351 using compact tension specimens (w=70mm, t=17mm). The potential drop technique was used for the measurements of the crack length. The crack opening loads were determined from the applied load versus crack opening mouth displacement curve using a curve fitting technique and crack opening displacement gauge. The experimental results show that cracks can grow faster than the life predictions with no load interaction effects under spectra containing tensile underloads. The acceleration effects are different depending on the number of the small cycles, the Kmax, the R ratio of the small cycles, the underload cycle and the material. Significant closure observations on the underloads and on the small cycles of variable amplitude loading spectra were made. Based on the test finding and on the studies of other researchers, it is suggested that the acceleration effects are mainly due to the reduction of crack opening point of the tensile underloads comparing with the Constant Amplitude Loading (CAL) data. An extensive evaluation of the ability of FASTRAN model to predict the fatigue lives under the tested loading spectra was carried out. The evaluation focuses on the influence of the constraint factor a and the ∆Keff curve inputs on the predictions. The model produces very good and consistent predictions for the three alloys, when the inputs represent adequately the actual fatigue mechanism. The model predicts the measured acceleration effects by reducing the closure level of the underloads.

No description available.

Este trabalho tem o objetivo de determinar as constantes elásticas de laminados compósitos de carbono/epóxi através do método não destrutivo de ultrassom, utilizando a técnica da imersão. Foram implementados dois métodos de imersão em água para a determinação das constantes elásticas. Um que utiliza o percurso na água sem a amostra como referência (FRM), e outro que utiliza o percurso com incidência normal na amostra como referência (SRM). Laminados unidirecionais e biaxiais foram ensaiados em um goniômetro com elevada precisão de movimento angular, e a aquisição de sinais feita com alta taxa de amostragem e grande resolução de amplitude. Uma análise da influência da variação da temperatura e espessura foi feita e comprovada a superioridade do método SRM sobre o FRM. A compensação da temperatura através de um par de transdutores, bem como através de um termômetro com resolução de 0.01°C foi implementada e comparada. As curvas de velocidade foram obtidas com transdutores de diferentes frequências centrais e comparadas. Foi realizada uma análise detalhada da sensibilidade das constantes elásticas com relação as velocidades em cada plano de medição, e através desta análise foram utilizados os planos mais adequados para reconstrução das constantes elásticas. Também foi verificada a polarização das ondas de cisalhamento para cada plano de medição, uma vez que é necessária a correta associação da velocidade experimental com a velocidade calculada para o procedimento de otimização. Um algoritmo de otimização foi utilizado para reconstruir as constantes elásticas dos laminados compósitos a partir da medição experimental das velocidades, onde foi avaliada a convergência utilizando a equação de Christoffel na forma implícita e explícita, para os materiais de simetria tetragonal e hexagonal. / The objective of this work is to obtain the elastic constants of carbon/epoxy composite laminates using ultrasonic non destructive testing, with immersion technique. Two immersion methods were implemented. One method uses as reference the path without sample, called fluid reference method (FRM), the second method uses the path with the specimen in normal incidence, called self-reference method (SRM). Unidirectional and biaxial laminates were tested using a goniometer with high angular resolution, and the signals were acquired with a high sample rate and amplitude resolution. Analyses of the influence of temperature and thickness variations were performed and concluded the superiority of the SRM over the FRM method. Temperature compensation using a pair of transducers and a 0.01° resolution thermometer was implemented and compared. Velocity curves were obtained and compared using transducers with different frequencies. A detailed analysis was performed to evaluate the sensitivity of the elastic constants to each velocity in different acquisition planes, and the results were used to reconstruct the elastic constants in the planes/velocities which they were most sensible to. As the correct association of each experimental velocity with the calculated velocities from Christoffel\'s equation is necessary, an analysis of the polarization mode of each velocity in the acquisition planes was also performed. An optimization algorithm was used to reconstruct the elastic constants of composite laminates from experimental velocities. Its convergence was evaluated for the implicit and explicit form of Christoffel\'s equation, and for materials with tetragonal and hexagonal symmetry.

Realizamos medidas dielétricas a baixas freqüências (10-2-40Hz) em cristais de KCN empregando uma ponte de ultra-baixas freqüências, bem como a altas freqüências (50-104 Hz) empregando uma ponte de capacitância comercial (General Radio). As curvas de perda dielétrica mostraram um bom ajuste entre altas e baixas freqüências. Obtivemos picos de perda dielétrica num intervalo de cinco décadas e entre 53 e 78K. Os picos destas curvas foram ajustados segundo uma equação de Arrhenius, e obtivemos uma energia de ativação de 0,148 eV e um tempo de relaxação característico de 6,53 x 10-15s para os dipolos CN-. Para temperaturas entre 53 e 59K observamos o aparecimento gradual de um segundo pico de perdas de 25Hz. Sua origem ainda não é conhecida, mas isto sugere que o cristal de KCN pode apresentar propriedades de um dielétrico composto, com dois mecanismos de relaxação distintos. / Dielectric measurements were performed at low frequencies (10-2- 40Hz) with an ultra-low frequency bridge in KCN crystals , as well as at high frequencies (50-10-4 Hz) employing a commercial capacitance bridge (General Radio). The dielectric loss curves show a good adjustment between the high and low frequencies. We obtain dielectric loss peaks in a window of five decades and in the range of 53 and 78 K. The peaks of these curves were fitted with an Arrhenius expression giving for the CN- dipoles an activation energy of 0,148eV and an attempt relaxation time of 6,53x10-15. At temperatures between 53 and 59K we observed the gradual appearing of a second loss peak for frequency of 25Hz. Its origin is not yet known butt his suggestt that the KCN, crystal may present compound dielectric properties , with - two distinct relaxation mechanisms.

O sistema cobalto(II)/tiocianato foi estudado em meio aquoso com o objetivo de se obter dados reais das constantes de formação globais dos complexos. Foram utilizados os métodos potenciométrico indireto e espectrofotométrico em meio de força iônica 2,0 M (NaCl04) a 25,0 &#177; O,l&#176;C. O sistema cádmio(II)/tiocianato foi utilizado como indicador no método potenciométrico indireto com o eletrodo de gota pendente de amálgama de cádmio. As seguintes constantes de equilíbrio foram obtidas para os complexos formados entre o cádmio e o tiocianato, a 25&#176;C e força iônica 2,0 M (NaCl04): &#946;1 = 21,51 &#177; 0,09 M-1, &#946;2 = 123,3 &#177; 1,2 M-2, &#946;3 = 129,9 &#177; 3,1 M-3 e &#946;4 = 173,5 &#177; 1,2 M-4. Valores do número médio de ligantes, &#241;, foram obtidos para várias concentrações de tiocianato, até 2,0 M, pela adição de Co(Cl04)2 (0,1 M) à solução contendo cádmio(II) e tiocianato. A integração da curva de formação e o tratamento das funções de Leden, pelo método dos mínimos quadrados desenvolvido, levou às seguintes constantes de formação globais para o sistema cobalto(II)/tiocianato: &#946;1 = 11,0 M-1, &#946;2 = 22,0 M-2, &#946;3 = 11,2 M-3 e &#946;4 = 1,63 M-4. Um estudo do sistema zinco(II)/tiocianato foi realizado com o objetivo de avaliar o método potenciométrico indireto, visto que esse sistema foi anteriormente estudado por um método direto confiável. A curva de formação obtida apresenta uma boa concordância até &#241; = 1. Depois desse ponto um desvio negativo é observado, com relação a curva obtida pelo método direto, devido à causas não bem compreendidas. Várias curvas de absortividade molar média, &#949; vs. concentração analítica de ligante foram obtidas em três comprimentos de onda (515, 590 e 615 nm) em tres concentraçoes de cobalto(II) diferentes: 0,01, 0,05 e 0,1 M. A análise com base no método das soluções correspondentes permitiu obter a curva &#241; vs. concentração de tiocianato livre, com as seguintes constantes de equilíbrio: &#946;1 = 6,9 M-1, &#946;2 = 28,9 M-2, &#946;3 = 12,1 M-3</SUP e &#946;>SUB>4 = 1,30 M-4. Ambos os métodos revelaram uma tendência à formaçao de duas espécies e uma diminuição acentuada na afinidade com o ligante para formar os complexos &#8204;Co(SCN)3&#8204;- e &#8204;Co(SCN)4&#8204;2-. Uma relação linear entre o número médio de ligantes e a absortividade molar média foi observado em 515 nm, o que permitiu obter o valor de &#949;4. Entretanto, em 590 e 615 nm, observou-se somente uma linearidade entre &#949; e o grau de formação calculado, &#945;4, correspondente a espécie &#8204;Co(SCN)4&#8204;2-, com uma intersecção muito próxima da origem. Isto é uma evidência que &#8204;Co(SCN)4&#8204;2- existe virtualmente como uma espécie tetraédrica com absortividade molar relativamente alta. Foram obtidos os seguintes valores de &#949;n individuais: a) &#949;o = 4,31, &#949;1 = 22,6, &#949;2 = 26,3, &#949;3 = 42,8 e &#949;4 = 50,3 cm-1.M-1 em 515 nm; b) &#949;o = 0,29, &#949;1 = 1,3, &#949;2 = 3,2, &#949;3 = 3,9 e &#949;4 = 215 cm-1.M-1 em 590 nm; c) &#949;o = 0,20, &#949;1 = 0,90, &#949;2 1,5, &#949;3 = 2,2 e &#949;4 = 294 cm-1.M-1 em 615 nm. Especulações com os dados sugerem que somente 1% das espécies tetraédricas estão em equilíbrio com as espécies octaédricas correspondentes com 1,2 e 3 tiocianatos coordenados. Com o emprego de um computador foi realizado um estudo efetuando uma simulação dos métooos espectrofotométricos da razão molar e das variações contínuas. As Simulações, com sistemas reais e hipotéticos, foram muito úteis para mostrar as conclusões ambíguas que podem ser obtidas, a partir de dados experimentais, para se estimar o número de espécies complexas. / The cobalt (II) /thiocyanate system in aqueous medium was studied with the purpose to obtain reliables data of overall stepwise formation constants to complexes. An indirect potentiometric method and a spectrophotometric one were used at 2,0 M ionic strength (NaCl04), at 25,0 &#177; O,l&#176;oC. The cadmium(II)/thiocyanate system was used as indicator in the indirect potentiometric method with hanging drop electrode with cadmium amalgam. The following equilibrium constants of the cadmium(II)/thiocyanate complexes were obtained at 25&#176;C and 2,O M ionic strenght (NaCl04: &#946;1 = 21.51 &#177; 0.09 M-1, &#946;2 = 123.3 &#177; 1,2 M-2, &#946;3 = 129.9 &#177; 3.1 M-3 and &#946;4 = 173.5 &#177; 1.2 M-4. Average 1igands number data, &#241;, were obtained for several thiocyanate concentrations, up to 2 M, by adding Co(Cl04)2 (0.1 M) to the working solution of cadmium (II)/thiocyanate. The integration of the formation curve and treatment of Leden\'s functions by a self developed least square method, lead to the following overall formation constants of the cobalt(II)/thiocyanate system: &#946;1 = 11.0 M-1, &#946;2 = 22.0 M-2, &#946;3 = 11.2 M-3 and &#946;4 = 1.63 M-4. A study of the zinc(II)/thiocyanate system was performed with the purpose to check the indirect potentiometric method inasmuch as this system was formerly studied by a re1iable direct method. The formation curve presented a good agreement until the average ligand number 1. After this point a negative desviation is observed with regard the direct method by not well understood causes. Severa1 curves of average molar absorbtivity, &#949; vs the analytical ligand concentration were obtained at three wave lengths (515, 590 and 615 nm) and three differents cobalt(II) cation concentrations: 0.01, 0.05 and 0.1 M. The analysis on base of corresponding solutions permited to obtain &#241; vs free thiocyanate ion concentrations, with the following equilibrium constants: &#946;1 = 6.9 M-1, &#946;2 = 28.9 M-2, &#946;3 = 12.1 M-3</SUP e &#946; = 1.30 M-4. Both methods revealed a tendency to form two species and a marked decrease in affinity with the 1igand to form &#8204;Co(SCN)3&#8204;<SUP- and &#8204;Co(SCN)4&#8204;2-. A linear relationship between calculated &#241; and &#949; was observed at 515 nm and this permited to obtain &#949;4. However, at 590 and 615 nm linearity of &#949; was achieved only for calculated formation degree, &#945;4, corresponding to specie &#8204;Co(SCN)4&#8204;2-, with an intercept very close to the origin. This is an evidence that the &#8204;CoO(SCN)4&#8204;2- exists virtually as tetrahedra1 specie with relative1y high molar absorbtivity. The fol1owing individual &#949;n were obtained: a) &#949;0 = 4.31, &#949;1 = 22.6, &#949;2 = 26.3, &#949;3 = 42.8 and &#949;4 = 50.3 cm-1.M-1 at 515 nm; b) &#949;0 = 0.29, &#949;1 = 1.3, &#949;2 = 3.2, &#949;3 3.9 and &#949;4 = 215 cm-1.M-1 at 590 nm; c) &#949;0 = 0.20, &#949;1 = 0.90, &#949;2 1.5, &#949;3 = 2.2 and &#949;4 = 294 cm-1 .m-1 at 615 nm. Speculations with the data suggest that on1y 1% of tetrahedral species are in equi1ibrium with the corresponding octahedral ones with 1, 2 and 3 thiocyanate 1igands. An extension of the study was a computer assisted simulation of the molar ratio spectrophotometric titration as well as the continuous variations method. This simulation study with real and hypothetica1 systems,was very usefu1l to show how ambiguous can be the conclusions, taken from experimental data,when the number of species are to be estimated.

O aminoácido selenocisteína (Sec) representa a principal forma biológica de selênio sendo requerida uma complexa maquinaria molecular para sua síntese e incorporação co-traducional em selenoproteínas. A Seril-tRNA sintetase (SerRS) inicia essa via, aminoacilando o Ser-tRNASec (SelC) com uma serina e também aminoacila os tRNAsSer. Sendo assim, um dos focos deste trabalho foi estudar a interação da SerRS de Trypanosoma brucei (T. brucei) com os tRNAsSer e o SelC utilizando a técnica de anisotropia de fluorescência para determinar suas constantes de dissociação. Em Kinetoplastidae, além da via de síntese de selenocisteína, há três selenoproteínas: SelT, SelK e SelTryp. No entanto, pouco se sabe a respeito das mesmas, sendo o estudo destas selenoproteínas o outro foco deste trabalho. Os fragmentos de DNA que codificam estas selenoproteínas foram subclonados em vetor de expressão pET 28a e 29a para posterior uso em células de Escherichia coli (E. coli). Para as proteínas SelK e SelTryp os ensaios de expressão apresentaram resultados insuficientes para dar continuidade aos experimentos planejados, pois o rendimento foi baixo e a purificação não foi possível. Já com a proteína SelT, devido à grande dificuldade encontrada para tornà-la solúvel, descobriu-se, no decorrer do trabalho, que tratava-se de uma proteína de membrana, ocasionando mudanças de alguns objetivos previamente propostos e consequentemente busca por novas estratégias. Conseguiu-se expressá-la na de forma solúvel e purificá-la por cromatografias. Ensaios realizados no SEC-MALLS mostraram uma estabilidade do complexo proteína-detergente. Com a TbSerRS é possível concluir que a organização de especificidade de ligação da enzima com seus ligantes se dá crescentemente: SelC>tRNASer7>tRNASer3a>tRNASer3b. E com as selenoproteínas do T. brucei faz-se necessários novas contruções para SelK e SelTryp e dar continuidade aos experimentos com a SelT tentando cristalizá-la, já que prototolo para a obtenção do complexo proteína-detergente está montado e estabilizado. / Selenocysteine (Sec) amino acid is the major biological form of selenium and requires a complex molecular machinery for its synthesis and co-translational incorporation into selenoproteins. The Seryl-tRNA synthetase (SerRS) starts this biosynthesis and matches the tRNASec (SELC) with a serine and the tRNAsSer, therefore the focus of this study is on SerRS of Trypanosoma brucei (T. brucei) and tRNAsSer and SELC interactions, with fluorescence anisotropy techinic to determinat dissociation constants. Three selenoproteins, namely SelT, SelK and SelTryp, besides the route of selenocysteine synthesis there be in Kinetoplastidae. DNA fragments that coding for these selenoproteins were subcloned in 28a and 29a to use into Escherichia coli (E. coli) cells. For Selk and SelTryp proteins, the expression protocol did not show an unsatisfactory result to continue the experiments. Many difficulties were encountered in studies with Selt protein, mainly in attempts to make it soluble. Our analyses revealed SelT was a membrane protein, therefore it could cause changes in some objectives and search for new strategies. It could be expressed and purified in cromatographis. SEC-MALLS assays showed a stability of the protein detergent complex. With TbSerRS is possible to conclude that the organization of binding specificity of the enzyme with its ligands occurs increasingly: SelC>tRNASer7>tRNASer3a>tRNASer3b. And selenoproteins in T. brucei, it is necessary for new constructions to SelK and SelTryp to continue the experiments trying to crystallizes SelT, since prototolo for obtaining the protein-detergent complex is assembled and stabilized.