The apparent integral diffusion coefficients of ceric sulphate solutions, 4 normal in sulphuric acid, were measured for concentrations ranging from 0.05 normal to 0.415 normal at 25°C with the use of a pyrex sintered glass diaphragm diffusion cell. A graph obtained by plotting the calculated integral diffusion coefficients versus the square root of the initial concentration is similar to the graphs obtained for uni-univalent salts. The rate of diffusion, however, is less by a factor of ten. The sintered glass diaphragm cell was calibrated with 0.1 normal potassium chloride at 25°C and the value of the cell constant was determined to be 0.1111 ± 0.0002 cm⁻². / Science, Faculty of / Chemistry, Department of / Graduate

SECTION I AN EXPERIMENTAL METHOD FOR THE MEASUREMENT OF EFFECTIVE GAS DIFFUSIVITIES IN POROUS PELLETS, AND THE LONGITUDINAL DISPERSION COEFFICIENT IN PACKED BEDS Present methods of measurement of effective diffusivities are not generally adaptable to the pellets in a packed bed, for example a catalytic reactor. An unsteady state pulse method has been developed employing simple gas chromatographic rate theory. The method is generally applicable to pellet sizes down to about 2mm. With homogeneous pellets reasonable agreement was obtained on comparison of effective diffusivities measured by a steady state method. For anisotropic solids the unsteady state diffusivity can be quite different from the steady state value due to differences in diffusion path. Pulse dispersions measured in beds of non porous pellets have revealed a laminar flow regime where the dispersion coefficient is dependent on the square of the velocity. This regime was reported for flow, in straight pipes but has not previously been demonstrated in packed beds. SECTION II DEVELOPMENT OF AN UNSTEADY STATE FLOW METHOD FOR MEASURING BINARY GAS DIFFUSION COEFFICIENTS Effusion measurements of one gas from a packed bed of known geometry (porosity and tortuosity) into a second flowing gas have been evaluated as a versatile technique for the determination of binary gas diffusion coefficients. The molecular diffusivities measured (± 10%) approached the scatter encountered by other methods (±5%) and satisfactory results (± 3%) are envisaged by optimising parameters in the method. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

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Thesis (Ph. D.)--University of Wisconsin--Madison, 1950. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 94-95).

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Networks are ubiquitous, underlying systems as diverse as the Internet, food webs, societal interactions, the cell, and the brain. Of crucial importance is the coupling of network structure with system dynamics, and much recent attention has focused on how information, such as pathogens, mutations, or ideas, ow through networks. In this dissertation, we advance the understanding of how network structure a ects information ow in two important classes of models. The rst is an independent interaction model, which is used to investigate the propagation of advantageous alleles in evolutionary algorithms. The second is a threshold model, which is used to study the dissemination of ideas, fads, and innovations throughout populations. This journal-format dissertation comprises three interrelated studies, in which we investigate the in uence of network structure on the dynamical properties of information ow. In the rst study, we develop an analytical technique to approximate system dynamics in arbitrarily structured regular interaction topologies. In the second study, we investigate the ow of advantageous alleles in degree-correlated scale-free population structures, and provide a simple topological metric for assessing the selective pressures induced by these networks. In the third study, we characterize the conditions in which global information cascades occur in threshold models of binary decisions with externalities, structured on degree-correlated Poisson-distributed random networks.

Cette thèse vise à approfondir les recherches théoriques et empiriques sur la diffusion spatiale des connaissances en France métropolitaine. La thèse offre tout d’abord une revue de la littérature économique sur la relation connaissance-externalités-innovation. Elle propose ensuite une analyse empirique utilisant deux approches. La première est l’approche par les cercles concentriques. Nous l’utilisons de deux façons : sur des données en coupe transversale puis sur des données de panel. Les résultats trouvés sont divergents ce qui nous pousse utiliser une deuxième approche plus précise basée sur les techniques de l’économétrie spatiale. Après avoir décrit de manière détaillée les dynamiques spatiales de l’innovation entre 2002 et 2008, nous estimons des modèles spatiaux (SAR, SEM et SDM) sur nos données de panel. Ensuite, cette deuxième approche propose une décomposition spatiale de l’impact de la R&D en effet direct et effet indirect. Cela permet une mesure plus fine des externalités de connaissance. Les résultats principaux de cette thèse sont que la proximité géographique a des effets positifs sur la productivité de la R&D; que le contenu de la R&D interne en connaissances tacites lui donne un avantage sur la R&D externe ; que la diversité industrielle des territoires a des effets positifs sur l’innovation ; et que les pôles de compétitivité améliorent la productivité de l’innovation grâce à la richesse des canaux retransmission des connaissances dont ils disposent. / The aim of this thesis is to further theoretical and empirical research on the spatial diffusion of knowledge in France. First, this thesis provides a review of the economic literature on the relation knowledge-innovation-externalities. It then offers an empirical analysis using two main approaches. The first one is the concentric circles method. The use of this approach is conducted in two stages: with cross-sectional data and with panel data. The results are divergent which pushed us to use a second more precise approach based on the techniques of spatial econometrics. After comparing the spatial dynamics of innovation between 2002 and2008, we made estimates using spatial models (SAR, SEM and SDM). Then, we propose in this second approach a spatial decomposition of the R&D impact into a direct and indirect effect. It provides a more precise measure of knowledge spillovers. The main results of this thesis are that geographical proximity has a positive effect on the productivity of R&D; that internal R&D has higher productivity than external R&D because of its tacit knowledge content; that industrial diversity of territories has positive effects on innovation ; and that clusters enhance the productivity of innovation through the richness of their knowledge transmission channels.

<p>Husqvarna AB uppmärksammade att det kommer införas nya miljöregler i Kalifornien gällande diffusionsutsläpp. De åkgräsklippare som går under namnet Rider och tillverkas av Husqvarna idag uppfyller ej dessa krav. Dagens bränsletank är tillverkad i plastmaterialet HDPE och avdunstande bränsleångor klättrar lätt igenom tankväggen ut i atmosfären vilket ej är tillåtet enligt de nya reglerna. Vi blev tillfrågade om vi kunde lösa problematiken och ta fram ett system som kontrollerar de avdunstade bränsleångorna och se till att detta system uppfyller de krav som ställs i Kalifornien. </p><p>Som blivande ingenjörer tyckte vi att detta var ett passande examensarbete med många olika områden involverade som materialkunskap, tillverkningsprocesser, produktutveckling samt inblick i ett större företags arbete.</p><p>Vi har med detta examensarbete tagit fram ett system som minskar det miljövådliga diffusionsutsläppet med cirka 90 %. Vi har arbetat med projektet så att det är klart för implementering samt gjort en modell som visar hur ett färdigt system kan se ut. Erfarenhet visar att de regler som uppkommer i Kalifornien sedan sprids till övriga USA. Även Europa förväntas skärpa sina diffusionsregler. Detta gör att vår lösning kan få en betydande spridning och få stora positiva effekter på miljön.</p>