We study diffusion-reaction-advection models describing population dynamics of aquatic organisms subject to a constant drift, with reflecting upstream and outflow downstream boundary conditions. We consider three different models: single logistically growing species, two and three competing species. In the case of a single population, we determine conditions for existence, uniqueness and stability of non-trivial steady-state solutions. We analyze the dependence of such solutions on advection speed, growth rate and length of the habitat. Such analysis offers a possible explanation of the "drift paradox" in our context. We also introduce a spatially implicit ODE (nonspatial approximation) model which captures the essential behavior of the original PDE model. In the case of two competing species, we use a diffusion-advection version of the Lotka-Volterra competition model. Combining numerical and analytical techniques, in both the spatial and nonspatial approximation settings, we describe the effect of advection on competitive outcomes. Finally, in the case of three species, we use the nonspatial approximation approach to analyze and classify the possible scenarios as we change the flow speed in the habitat.

Traditionally, void ratio, e has been used as a state variable for predicting the liquefaction behaviour of soils under the Critical State (Steady State) framework. Recent publications show that void ratio, e may not be a good parameter for characterizing sand with fines as the steady state, SS data points move downward in e-log(p) space up to certain fines content termed as threshold fines content, TFC. Thus, it was difficult to apply SS concept on sand with fines as a small variation of fines content may lead to different SS line. Many researchers proposed to used equivalent granular void ratio, e* as an alternative state variable (i.e. in lieu of void ratio, e) in attempt to obtain a narrow trend line for SS data points irrespective of fc provided fc  TFC. The e* is obtained from e. For the conversion from e to e*, one need a parameter b which presents the active fraction of fines in overall force structure of sand. However, predicting the b is problematic. Most, if not all, of the b reported were determined by case-specific back-analysis, that is, the b-value was selected so that the test results for a given sand-fines type could be correlated with the equivalent granular void ratio, e* irrespective of fines content. This thesis examines the factors that affecting the b value by examining published work on binary packing. This leads to a simple semi-empirical equation for predicting the value of b based onparticle size ratio,  and fines content, fc. Published data and experimental results on Sydney sand appears to be in support of the proposed equation. The single relation of SS data points in e*-log(p) space for sand with fines is referred as Equivalent Granular Steady State Line, EG-SSL. The EG-SSL is then used to define the equivalent granular state parameter,*. A good correlation observed between * and q-p, q- q responses in undrained shearing. The e* and * are also used to modified a state dependent constitutive model. Seven model input parameters are needed in addition four to critical state input parameters. These parameters are obtained from drained test. The model is used to predict q-pand q- q responses for flow, non-flow and limited flow behaviour for 0% to 30% fines contents. The model predictions are in good agreement with experimental results. The effect of fines types (in terms of plasticity and angularity) on the prediction equation of b are also examined with four different types of fines. A negligible effect of fines type on the prediction equation of b is observed. The link between monotonic and cyclic loading behaviour for sand with fines are also examined with emphasis on cyclic instability and strain hardening behaviour after quasi steady state, QSS for a range of fines contents (provided that fc < TFC). It is found that a single set of rules could be used to correlate monotonic and cyclic behaviour for a range of fines contents at same *.

Στην παρούσα μεταπτυχιακή αυτή εργασία μελετήσαμε την συμπεριφορά για πρώτη φορά ενώσεων που είχαν σαν βάση την βενζοδισθιαζόλη. Συγκεκριμένα οι ενώσεις αυτές μελετήθηκαν με την χρήση των τεχνικών της φασματοσκοπίας διφωτονικής απορρόφησης της φασματοσκοπίας σταθερής κατάστασης και της φασματοσκοπίας φθορισμού χρονικής ανάλυσης. Αρχικά όσον αφορά την φασματοσκοπία διφωτονικής απορρόφησης, μπορέσαμε να οδηγηθούμε στα εξής συμπεράσματα: οι καλύτερες ενώσεις που παρουσιάζουν αρκετά μεγάλη διφωτονική απορρόφηση είναι τα γραμμικά μόρια (PK-439 και PK-452) σε σχέση με τα U-shaped μόρια με μέγιστη ενεργό διατομή ΔΦΑ ~2000GM. Επιπλέον παρατηρήσαμε ότι η χρήση της βενζοδισθιαζόλης σαν κεντρικός πυρήνας προκαλεί σημαντική αύξηση της διφωτονικής απορρόφησης, σε σχέση με την βενζοθιαζόλη. Τέλος, με την τεχνική της φασματοσκοπίας φθορισμού χρονικής ανάλυσης μπορέσαμε να οδηγηθούμε σε κάποιες διαπιστώσεις: συγκεκριμένα παρατηρήσαμε ότι όσο το μήκος κύματος καταγραφής μεγαλώνει, τόσο οι καμπύλες αποδιέγερσης γίνονται πιο αργές. Ακόμα διαπιστώσαμε ότι από την σύγκριση μορίων στο μήκος κύματος του μεγίστου, σε εκείνα τα μόρια που αποδιεγείρονται γρήγορα, ευνοούνται οι μη-ακτινοβολητικές διεργασίες και ταυτόχρονα παρουσιάζουν μικρή ενεργό διατομή ΔΦΑ. / --

Orientador: Angela Maria Sitta / Banca: Maria Aparecida Soares Ruas / Banca: Claudio Aguinaldo Buzzi / Resumo: Neste trabalho classificamos problemas de bifurcação Z2-equivariantes de corank 2 até co- dimensão 3 via técnicas da Teoria de Singularidades. A abordagem para classificar tais problemas é baseada no processo de redução à forma normal de Birkhoff para estudar a interação de modos Hopf-Pontos de Equilíbrio. O comportamento geométrico das soluções dos desdobramentos das formas normais obtidas é descrito pelos diagramas de bifurcação e estudamos a estabilidade assintótica desses ramos. / Abstract: In this work we classify the Z2-equivariant corank 2 bifurcation problems up to codimension 3 via Singularity Theory techniques. The approach to classify such problems is based on the Birkhoff normal form to study Hopf-Steady- State mode interaction. The geometrical behavior of the solutions of the unfolding of the normal forms is described by the bifurcation diagrams and we study the asymptotic stability of such branches. / Mestre

The calibration of modern internal combustion engines requires ever improving measurement data quality such that they comply with increasingly stringent emissions legislation. This study establishes methodology and a software tool to improve the quality of steady-state emissions measurements from engine dynamometer tests. Literature shows state of the art instrumentation are necessary to monitor the cycle-by-cycle variations that significantly alter emissions measurements. Test methodologies that consider emissions formation mechanisms invariably focus on thermal transients and preconditioning of internal surfaces. This work sought data quality improvements using three principle approaches. An adapted steady-state identifier to more reliably indicate when the test conditions reached steady-state; engine preconditioning to reduce the influence of the prior day’s operating conditions on the measurements; and test point ordering to reduce measurement deviation. Selection of an improved steady-state indicator was identified using correlations in test data. It was shown by repeating forty steady-state test points that a more robust steady-state indicator has the potential to reduce the measurement deviation of particulate number by 6%, unburned hydrocarbons by 24%, carbon monoxide by 10% and oxides of nitrogen by 29%. The variation of emissions measurements from those normally observed at a repeat baseline test point were significantly influenced by varying the preconditioning power. Preconditioning at the baseline operating condition converged emissions measurements with the mean of those typically observed. Changing the sequence of steady-state test points caused significant differences in the measured engine performance. Examining the causes of measurement deviation allowed an optimised test point sequencing method to be developed. A 30% reduction in measurement deviation of a targeted engine response (particulate number emissions) was obtained using the developed test methodology. This was achieved by selecting an appropriate steady-state indicator and sequencing test points. The benefits of preconditioning were deemed short-lived and impractical to apply in every-day engine testing although the principles were considered when developing the sequencing methodology.

This thesis is devoted to the theoretical study of slow thermodynamic processes in non-equilibrium stochastic systems. Its main result is a physically and mathematically consistent construction of relevant thermodynamic quantities in the quasistatic limit for a large class of non-equilibrium models. As an application of general methods a natural non-equilibrium generalization of heat capacity is introduced and its properties are analyzed in detail, including an anomalous far-from-equilibrium behavior. The developed methods are further applied to the related problem of time-scale separation where they enable to describe the effective dynamics of both slow and fast degrees of freedom in a more precise way. Powered by TCPDF (www.tcpdf.org)

Individuals with high working memory capacity (WMC) appear to be particularly good at focusing their attention (McCabe, Roediger, McDaniel, Balota, &amp; Hambrick, 2010). Therefore, we studied the correlation between WMC and the ability to suppress neurological activity from a task-irrelevant stimulus. The research question tests the foundations of Lavie’s perceptual load theory; that early selection occurs, by testing if higher WMC enhances people’s ability to inhibit processing of task-irrelevant stimuli from low versus high load (i.e. the difference from low to high load should be smaller for high WMC than for low WMC). This was operationalised by measuring the correlation of WMC and auditory processing under low versus high visual load. Auditory processing was measured with auditory steady state responses (ASSR), and WMC was measured with an operation-letter span task. The results showed no significant correlation between WMC and ability to suppress task-irrelevant stimuli. Based on the data, it is not possible to conclude with certainty that effects of load on auditory processing are unaffected by WMC, because confidence intervals were large.

Made available in DSpace on 2014-06-11T19:22:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-07-18Bitstream added on 2014-06-13T18:49:50Z : No. of bitstreams: 1 oliveira_mfm_me_rcla.pdf: 189165 bytes, checksum: a4bab800dd002ebdbcf3ba192de703c9 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O principal objetivo deste estudo foi comparar a velocidade, concentração de lactato sanguíneo e os índices técnicos correspondentes à máxima fase estável de lactato sanguíneo obtida de forma contínua e intermitente na natação. Participaram deste estudo, 5 nadadores fundistas e 8 triatletas (23 + 9 anos, 1,76 + 0,1 m e 71,3 + 9,8 kg), com pelo menos 3 anos de experiência nas respectivas modalidades. Os indivíduos realizaram em diferentes dias, os seguintes testes, em uma piscina de 25 m: 1) repetição máxima na distância de 400 m; 2) teste incremental para a determinação do limiar de lactato (LL) e limiar anaeróbio (LAn); 3) 2 a 4 repetições com duração de 30 min em diferentes intensidades, para a determinação da máxima fase estável de lactato sanguíneo contínua (MLSSC), e; 4) 2 a 4 tentativas de 12 x 150 s com intervalo de 30 s (5:1) em diferentes intensidades, para a determinação da máxima fase estável de lactato sanguíneo intermitente (MLSSI). O LAn foi determinado por meio de interpolação linear entre a velocidade e a concentração de lactato, considerando uma concentração fixa de lactato de 3,5 mM. O critério de determinação da MLSSC e da MLSSI foi um aumento menor ou igual a 1 mM de lactato entre o décimo e o trigésimo min de exercício. Os índices técnicos taxa de braçada (TB), comprimento de braçada (CB) e índice de braçada (IB) foram determinados em todos os testes. A TB foi calculada por meio de filmagem utilizando o tempo necessário para se realizar cinco ciclos completos de braçadas. O CB foi calculado dividindo a velocidade pela TB. O IB foi determinado pelo produto da velocidade e o CB. De acordo com os dados do presente estudo, a máxima fase estável de lactato sanguínea é atingida em uma velocidade maior quando esta é determinada de forma intermitente (1,17 + 0,09 m.s-1) do que de forma contínua (1,13 + 0,08 m.s-1)... / The main objective of this study was to compare the speed, blood lactate concentration and technical indexes corresponding to the maximal lactate steady state obtained with continuous and intermittent protocols. Thirteen endurance swimmers and triathletes (23.8 ± 9.5 yr., 1.76 ± 0.1 m and 71.3 ± 9.8 kg) participated of this study. The athletes had at least 3 years of experience in swimming. The individuals performed in different days, the following tests: 1) Maximal performance tests of 400 m; 2) Progressive test until exhaustion to determine the anaerobic threshold (AT); 3) 2 to 4 30-min repetitions in different intensities, to determine continuous maximal lactate steady state (MLSSC), and; 4) 2 to 4 trials of 12 x 150 s with 30 s of rest (5:1) at different intensities, to determine the intermittent maximal lactate steady state (MLSSI). The AT was determined trough linear interpolation between the speed and blood lactate concentration, considering a fixed blood lactate value of 3.5 mM. The criterion for the determination of MLSSC and MLSSI was an increase lower or equal to 1 mM of lactate between tenth and thirty min of exercise. Technical indexes stroke rate (SR), stroke length (SL) and stroke index (SI) were determined in all tests. The TB was calculated trough film using the time to perform five complete stroke cycles. The CB was calculated trough the quotient between the speed and SR. The SI was determined by the product of the speed and SL... (Complete abstract click electronic access below)

Neste trabalho apresentamos e comparamos diferentes técnicas de tomografia bidimensional por RMN implementados num sistema de tomografia de campo magnético ultra-baixo (O.05T). A partir da seqüência convencional \"Spin Echo\" (SE), utilizada rotineiramente, implementamos a seqüência \"Gradient Recalled Echo\" (GRE) e duas seqüências que utilizam o principio de Steady-State Free Precession (SSFP), sendo \"Fast Low Angle Shot\" (FLASH) e \"Fast Acquisition Double Echo\" (FADE). Com as seqüências de SSFP conseguimos diminuir drasticamente a duração de um exame de tomografia convencional (seqüência SE). A seqüência FADE ainda permite adquirir duas imagens com contrastes claramente diferentes sem aumentar significativamente a duração do exame. Desenvolvemos procedimentos de calibração indispensáveis para as técnicas de SSFP que também melhoraram a relação sinal ruído de 15 por cento na técnica SE . Analisamos teórica e experimentalmente o comportamento do contraste das seqüências apresentadas. Fizemos ainda uma serie de imagens de um phantom e da cabeça de um voluntário com as diferentes seqüências e sugerimos algumas combinações dos parâmetros (protocolos) como tempo de repetição, tempo ao eco e angulo de excitação. Um destes protocolos esta sendo testado em casos clínicos para comparar a utilidade das seqüências apresentadas no diagnóstico medico. Com este trabalho ganhamos uma experiência na utilização de técnicas rápidas indispensáveis para a elaboração de uma metodologia para obter imagens tridimensionais / In this work we present and compare different techniques for bidimensional tomography in NMR which were implemented on a ultra low magnetic field (O.05T) tomographic system. Based on the conventional spin echo pulse sequence (SE), which is routinely used, we implemented the gradient recalled echo (GRE) pulse sequence and two sequences that use the principle of Steady-State Free Precession (SSFP) being \"Fast Low Angle Shot\" (FLASH) and \"Fast Acquisition Double Echo\" (FADE). With the SSFP sequences we shorten drastically the duration of the conventional SE tomography sequence. Besides this the FADE sequence gives two images with clearly different contrast without extending significantly the duration of the experiment. Needed for the SSFP techniques, we developed calibration procedures, which improved as well the SE sequence signal to noise ratio of about 15 percent. We analyzed theoretically and experimentally the behavior of the contrast of the presented sequences. Moreover we acquired various images of a phantom and the human brain of a normal volunteer using the different sequences and proposed some combinations of the parameters (protocols) repetition time, time to echo and flip angle. One of these protocols is being tested in clinical cases to compare the usefulness of the presented techniques for medical diagnostic. With this work we gained a wide experience in using SSFP techniques that will be indispensable in the elaboration of three-dimensional tomography methodologies

Os aços de alta resistência e baixa liga são amplamente utilizados em dutos transportadores de óleo e gás e, atualmente, o desenvolvimento de novos projetos de liga e o uso de técnicas altamente avançadas de fabricação e processamento dos aços se tornaram essenciais para obtenção de estruturas que resistam aos danos provocados por H, principal motivo de falha de oleodutos e gasodutos em meios ricos em H2S. No presente trabalho, avaliou-se o efeito de características microestruturais na difusividade do H em dois aços grau API X65, com diferentes teores de Mn. Uma das chapas ainda está em fase experimental de desenvolvimento, tem baixo teor de Mn e foi produzida para aplicação em ambientes sour. A outra chapa tem alto teor de Mn, já é usada comercialmente há alguns anos e foi desenvolvida para trabalho em ambientes doces. Os dois materiais passaram por caracterização microestrutural nas três seções da chapa: longitudinal e transversal à direção de laminação e do topo da chapa (paralela à direção de laminação). Após a caracterização, amostras de cada seção dos aços foram submetidas a ensaios de permeabilidade ao H; o aço baixo Mn passou por análises de EBSD (Difração de Elétrons Retroespalhados), para determinação de textura. O aço baixo Mn tem microestrutura homogênea ao longo da espessura da chapa, composta por ferrita refinada e pequenas ilhas de perlita. O aço alto Mn, por sua vez, apresenta microestrutura heterogênea ao longo da espessura, formada por bandas de ferrita e perlita, com marcada presença de segregação central de elementos de liga. Os ensaios de permeabilidade ao H mostraram que os coeficientes de difusão efetiva do H, Deff, do aço baixo Mn são ligeiramente superiores aos do aço alto Mn. Outros dois importantes parâmetros que foram calculados para os dois aços são a concentração de H na sub-superfície do material, C0, e o número de traps por unidade de volume, Nt. Contrariando expectativas, o aço baixo Mn apresentou maiores valores de C0 e Nt do que o aço alto Mn. Ensaios preliminares de dessorção térmica realizados nos dois aços mostraram os mesmos resultados: o aço baixo Mn aprisiona mais H do que o aço alto Mn. Estes resultados contraditórios de C0 e Nt foram atribuídos à presença de nanoprecipitados de microadições de liga no aço baixo Mn, não detectáveis por microscopia óptica e eletrônica de varredura. Ainda, para os dois aços, os valores de Deff variaram em função da seção analisada da seguinte maneira: Deff longitudinal ? Deff transversal > Deff topo. Para entender melhor o comportamento anisotrópico da difusão do H nos dois aços calculou-se um novo coeficiente de difusão, que foi chamado de coeficiente de difusão no estado estacionário, Dss. O Dss considera que todos os traps do aço estão saturados, permitindo, assim que se avalie somente o efeito de obstáculos físicos à difusão do H. No aço alto Mn, o Dss variou da mesma maneira que o Deff: Dss longitudinal ? Dss transversal > Dss topo; este comportamento foi atribuído ao bandeamento presente no material. No aço baixo Mn, o Dss variou de forma diferente do Deff: Dss transversal > Dss longitudinal >= Dss topo, indicando que a difusão do H pode ser auxiliada por contornos de grão enquanto os traps estão sendo saturados, e que a textura cristalográfica pode influenciar a difusão após o estado estacionário ser atingido. / High strength low alloy steels are widely applied as pipelines for crude oil and natural gas transportation and, currently, new approaches to alloy design, in addition to the use of advanced steelmaking and processing techniques, have become essential for obtaining structures that resist to hydrogen damage, which is the main cause of pipelines failure in H2S-rich environments. The main objective of the present work is to evaluate the influence of microstructural features on hydrogen diffusivity in two API X65 steels, with different Mn contents. One of the steel plates has been recently developed for usage in sour environments, is on its experimental stage and has a low Mn content. The other one is a commercial plate steel, with high Mn content, developed for sweet applications. Both steel plates were characterized in its three sections, in relation to the rolling direction: longitudinal, transverse and top surface of the plate (parallell to the rolling direction). After that, samples obtained from each section of the plates were submitted to hydrogen permeation tests; the low Mn steel was also analysed with EBSD, for texture determination. The low Mn steel presents a homogeneous microstructure through plate thickness, composed of refined ferrite and small pearlite islands. The high Mn steel has a heterogeneous microstructure through the plate thickness, composed of ferrite and pearlite bands, and presents centerline segregation. Hydrogen permeation tests showed that the Deff obtained for the low Mn steel sections are slightly higher than for the high Mn steel. Another two important parameters that were calculated for both steels are the subsurface hydrogen concentration, C0, and the number of traps per unit volume, Nt. Contrary to what was expected, the low Mn steel presented the higher C0 and Nt values. Thermal dessorption spectroscopy analysis confirmed that the low Mn steel traps more H atoms than the high Mn one. These results, along with the similar Deff values, were related to the presence of nanoprecipitates of microalloying elements, that cannot be detected via optical and scanning electron microscopy. Additionally, also for both steels, the Deff values varied in function of the analyzed section as it follows: Deff longitudinal ? Deff transverse > Deff top. In order to better understand this anisotropic behavior, a new diffusion coefficient, which was called diffusion coefficient at the steady state, Dss, was determined. Dss considers that all the trapping sites are saturated, enabling, thus, the evaluation of physical obstacles to H diffusion. For the high Mn steel, the Dss varied in the same matter as the Deff: Dss longitudinal ? Dss transverse > Dss top; this behavior was associated with the microstructural banding present in the material. For the low Mn steel, the Dss exhibited a different behavior: Dss transverse > Dss longitudinal >= Dss top, suggesting that H diffusion can be aided by grain boundaries while the trapping sites are being filled and that crystallographic texture may play its role after the steady state is reached.