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The integration of organic solvent nanofiltration in processes of fine chemistry involving homogeneous metal catalysts has a great potentiel because this eco-friendly process, efficient at molecular scale, does not desactivate the catalyst contrary to conventionnal distillation. The aim of this study is to integrate organic solvent nanofiltration in the process of 10-undecenitrile hydroformylation in toluene. A one-step nanofiltration does not permit to fulfill the goals of the separation, which are to extract the product and to recycle the catalytic system (Rh, biphephos). Simulations of membrane cascades based on experimental data of flux and retention according to the concentration (acquired in the first part of the thesis) highlighted that a four stages cascades with recycling is realistic and competitive for an industrial plant. / L'intégration de la nanofiltration organique dans les procédés de chimie fine impliquant des catalyseurs organométalliques solubles a un fort potentiel car ce procédé éco-efficace de séparation à l'échelle moléculaire ne désactive pas les catalyseurs contrairement à la distillation classiquement utilisée. L'objectif de cette thèse est d'intégrer la nanofiltration organique dans le procédé d'hydroformylation du 10-undecenitrile dans le toluène. Un procédé en une étape de nanofiltration ne permet pas de remplir les objectifs de séparation qui sont l'extraction du produit et le recyclage du système catalytique (Rh, biphephos). Des simulations de cascades de membranes basées sur les données expérimentales de flux et de rétentions variables en fonction de la concentration, acquises en première partie de thèse, ont permis d'identifier un design de cascade à 4 étages avec recyclages réaliste et compétitif pour une conception industrielle.

Doctor of Philosophy / Agricultural Economics / Allen M. Featherstone / Christine Wilson / Farmland values have reached all-time highs and have significantly risen over the last few years. This has caused much debate about whether farmland prices are currently on a bubble and ready to burst, much like the earlier 1980s. Much research has been done on farmland values; however, work done outside of agricultural economics, looking at general asset values, can be incorporated into models of farmland value. Information cascades, or herding, are phenomenon where information in the market is sent between investors and this information is bid into the asset price, thus resulting in boom and bust periods. By using a Vector Autoregression (VAR) model, farmland price dynamics are modeled and analyzed for spatial dependencies from one region to the next. VAR allows for no a priori specification of network typology. This allows for the examination of the existence of information cascades and what form the network takes among spatially located farmland markets. This method is then compared to two other spatial estimation techniques. The first is a Spatial Autoregressive (SAR) model where network typology is imposed prior to estimation. The second is a VAR model where no network is modeled, and only the region’s own asset prices can influence future periods. It is found that information cascades exist and network typology is somewhat random. These results caution the current direction of the literature of imposing network or spatial structure. However, due to data requirements, SAR models are easier to estimate since they require less data and if network structure, which the SAR model inherently imposes by the weight matrix, could be determined by an autoregressive process instead of an adjacency rule it could prove to be the most accurate forecasting method.

O proposito deste trabalho é apresentar uma metodologia para projeto de uma turbina axial para micro aproveitamentos hidráulicos com ênfase no projeto das geometrias do rotor e distribuidor, incluindo os resultados analíticos e numéricos através do método dos painéis. Comparações do projeto analítico com testes de campo são também apresentadas. A metodologia analítica utilizada foi a teoria do escoamento não-viscoso de Wenig que avalia os fatores de interferência para modelar o quanto as características de sustentação e arrasto de uma cascata de perfis são relacionadas com as de um perfil isolado. Foi verificado que a teoria de Wenig fornece uma boa previsão do fator de interferência se o ângulo de ataque for relativamente baixo e a espessura das pás for relativamente pequena quando comparada com a distância entre as pás. A metodologia numérica usando o método de vorticidade superficial proposto por Martensen para uma cascata de perfis e para um perfil isolado foi utilizada para se ter uma comparação com os coeficientes analíticos de sustentação e arrasto. Testes de campo foram realizados em um protótipo de 20 kW de acordo com a norma IEC-60041 e sua comparação com o método analítico e por consequência o método numérico validou o método empregado para confecção das pás do rotor e distribuidor. / The purpose of this work is to present a methodology to design a small axial hydraulic turbine with emphasis on the project of the profiles of the runner and wicket gate, including both analytical and numerical results from a cascade panel method. Comparisons with field test measurements of a prototype are also presented. The analytical methodology used is the Wenigs inviscid flow theory which requires the evaluation of interference factors to model how lift and drag characteristics of the turbine cascade of blades are related to those of a single isolated airfoil. It is found that the Wenigs theory provides a reasonable prediction of the lift interference factor if both the angle of attack is relatively low and the thickness of the blades is relatively small when compared to the distance between the blades. The numerical methodology that relies the Hess and Smiths 2-D panel method for a cascade of blades and for an isolated airfoil was used in order to have a comparison with the analytical lift and drag. Prototype field test measurements of the turbine power output, in agreement with IEC-60041 standards, were carried out to evaluate the results using the analytical and numerical methods.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO / Includes bibliographical references. / by Saeed Farokhi. / Ph.D.

In the first part of the thesis, we carried out direct two-dimensional (2D) multipoint measurements of the velocity fields in a turbulent Rayleigh-Benard convection cell to study the properties of small-scale convective turbulence. The local homogeneity and isotropy of the velocity field are tested using a number of criteria and are found to hold to an excellent degree. The properties of velocity circulation Gammar are also studied. The results show that the circulation appears to be more effective to capture the effect of local anisotropy than the velocity field itself. The distribution of Gammar is found to depend on the scale r, reflecting strong intermittency. It is further found that velocity circulation has the same anomalous scaling exponents as the longitudinal and transverse structure functions for low-order moments (p ≲ 5). Whereas, for high-order moments (p ≳ 5), the anomalous scaling exponents for circulation are found to be systematically smaller than the scaling exponents of the longitudinal and transverse structure functions. / In the second part of the thesis, the simultaneous visualization of the temperature and velocity fields was used to study the properties of thermal plumes. Our visualization reveals the process of the morphological evolution between sheetlike and mushroomlike plumes, which were also quantified by the height dependence of plume numbers and of vorticity fluctuations. A direct connection between the heat transport and coherent structures, i.e. thermal plumes, was established, which shows that it is plume number that primarily determines the Nu-Ra scaling relation. Individual plumes were extracted and their statistical and geometric properties were studied. It is found that the log-normal distribution is universal for thermal plumes and the log-normal statistics may be used to model them. In addition, both our quantitative characteristic and direct 3D spatial visualizations indicate that the previously-believed sheetlike plumes should be reconsidered to be only one-dimensional structures. / In the third part of the thesis, the planar laser-induced fluorescence technique was induced to study the 2D passive scalar mixing in high-Schmidt-number buoyancy-driven turbulence. The passive scalar mixing evolution was studied and various geometric properties, such as shape complexity, fractal dimension and local curvature, were used to characterize the isoconcentration contours of the 2D passive scalar fields. It is found that when the flow gets more turbulent the shape of passive scalar packets becomes closer to a circular shape and the passive scalar mixing becomes more isotropic, indicating the increased mixing and stirring of the turbulent flow. / The objective of this thesis is to address the following three key issues in turbulent thermal convection, i.e. turbulent fluctuations in small scales, coherent structures and passive scalar mixing in buoyancy-driven turbulence. / Zhou, Quan = 對流熱湍流中能量級串, 相干結構和標量場混合的实验研究 / 周全. / Adviser: Ke-Qing Xia. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3576. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 103-117). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307. / Zhou, Quan = Dui liu re tuan liu zhong neng liang ji chuan, xiang gan jie gou he biao liang chang hun he de shi yan yan jiu / Zhou Quan.

Mafic eruptions have been the dominant form of volcanic activity in central Oregon throughout the Holocene. These eruptions have produced cinder cones, extensive lava flows, and tephra blankets. In most cases, the extent and volume of the tephra blankets has not been determined, despite the fact that future tephra production would pose considerable hazards to transportation, infrastructure, and public health. The economy of the region, which is largely based in tourism, would also be negatively impacted. For this reason, developing a better understanding of the extent and dynamics of tephra production at recent mafic vents is critical, both in terms of mitigating the hazards associated with future eruptions and in improving our scientific understanding of explosive mafic activity. Here I present detailed field and laboratory studies of tephra from recent mafic vents at Newberry Volcano and in the central Oregon High Cascades. Studies of Newberry vents show that eruption style is strongly correlated with eruptive volume, that extensive magma storage and assimilation occurred prior to the eruption of these vents, and that minimum pre-magmatic water content as recorded by plagioclase was 2.5 wt.%. Detailed mapping and physical studies of tephra deposits from High Cascades vents show that several recent eruptions produced extensive tephra deposits. These deposits are physically similar to well-documented historic eruptions that have been characterized as violent strombolian. At least one Cascade cinder cone (Sand Mountain) produced a tephra deposit that is unusually large in volume and characterized by uniformly fine-grained clasts, which is interpreted as evidence for syn-eruptive interaction with external water. Microtextural characteristics of tephra, along with an evaluation of possible water sources, support this interpretation. These investigations demonstrate that magma storage and eruption style at mafic vents is both variable and complex. Additionally, these studies show that cinder cones in central Oregon have the potential to erupt much more explosively than previously assumed. The results of this study will be an important tool for developing comprehensive regional hazard assessments. This dissertation includes previously published and unpublished co-authored material.

<p>Landscape effects on species performance currently receives much attention. Habitat loss and fragmentation are considered major threats to species diversity. Deciduous forests in southern Sweden are previous wooded pastures that have become species-rich communities appearing as islands in agricultural landscapes, varying in species composition. <i>Actaea spicata</i> is a long-lived plant occurring in these forests. In 150 populations in a 10-km² area, I studied pre-dispersal seed predation, seed dispersal and pollination. I investigated spatio-temporal dynamics of a tritrophic system including<i> Actaea</i>, a specialist seed predator, <i>Eupithecia immundata</i>, and its parasitoids. In addition, effects of biotic context on rodent fruit dispersal and effects of flowering time and flower number on seed set, seed predation and parasitization were studied. Insect incidences of both trophic levels were related to resource population size and small <i>Eupithecia</i> populations were maintained by the rescue effect. There was a unimodal relationship between seed predation and plant population size. Seed predator populations frequently went extinct in small plant populations, resulting in low average seed predation. Parasitoids were present in large plant populations but did not affect seed predator density. Seed predators aggregated at edges, relaxing seed predation in patch interiors. Flowering phenology was unrelated to seed set and insect incidence. A higher flower number did not influence seed predation but was associated with higher seed set and a tendency for a higher parasitization rate. In the study on fruit dispersal more fruits were removed inside than outside populations. Within plant populations more fruits were removed from large aggregations. Overall, this thesis underlines the importance of plant-animal interactions during different phases of the life cycle. The spatial configuration of host plants plays an important role for the outcome of plant-animal interactions and trophic cascades.</p>

Landscape effects on species performance currently receives much attention. Habitat loss and fragmentation are considered major threats to species diversity. Deciduous forests in southern Sweden are previous wooded pastures that have become species-rich communities appearing as islands in agricultural landscapes, varying in species composition. Actaea spicata is a long-lived plant occurring in these forests. In 150 populations in a 10-km2 area, I studied pre-dispersal seed predation, seed dispersal and pollination. I investigated spatio-temporal dynamics of a tritrophic system including Actaea, a specialist seed predator, Eupithecia immundata, and its parasitoids. In addition, effects of biotic context on rodent fruit dispersal and effects of flowering time and flower number on seed set, seed predation and parasitization were studied. Insect incidences of both trophic levels were related to resource population size and small Eupithecia populations were maintained by the rescue effect. There was a unimodal relationship between seed predation and plant population size. Seed predator populations frequently went extinct in small plant populations, resulting in low average seed predation. Parasitoids were present in large plant populations but did not affect seed predator density. Seed predators aggregated at edges, relaxing seed predation in patch interiors. Flowering phenology was unrelated to seed set and insect incidence. A higher flower number did not influence seed predation but was associated with higher seed set and a tendency for a higher parasitization rate. In the study on fruit dispersal more fruits were removed inside than outside populations. Within plant populations more fruits were removed from large aggregations. Overall, this thesis underlines the importance of plant-animal interactions during different phases of the life cycle. The spatial configuration of host plants plays an important role for the outcome of plant-animal interactions and trophic cascades.