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1
Goller, Bernhard F. "Reactive nano silicon : mediated processes." Thesis, University of Bath, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516960.
Повний текст джерелаАнотація:
In this thesis basic methods for the fabrication and characterisation of several nano-silicon containing systems are presented. Due to their morphology, these systems are highly reactive. Silicon wafers were used to prepare layers of porous silicon via electrochemically etching and micro– and nano– sized silicon powders were chemically etched in order to yield silicon nanoparticles. Dependent on the fabrication, particle size of the nanocrystals and porosity of the assemblies can be tailored over a wide range: mean particle sizes can be between 3 to 20 nm and porosities can be varied from 10 to 90 %. A huge surface area of up to 500m2/g which is in addition, due to the fabrication process, hydrogen terminated, entail the outstanding chemical and photo-chemical properties of nanocrystalline silicon. Both, chemical and photo-chemical properties of silicon nanocrystal structures are investigated. The emphasis lies on optical spectroscopy. The indirect band gap structure of silicon in combination with quantum confinement effects are the origin of the interesting luminescence properties of nano-silicon. The energy transfer process from photo-excited excitons confined in silicon nanocrystals to molecules present in the surrounding ambient, like oxygen or a variety of organic substances, has been studied. Measurements demonstrated that long-living excitons very efficiently transfer their energy to surrounding molecules. The low probability of creating excitons which can persist for a long time, from μs to ms, by a photon and structural properties of porous silicon, or rather its reactive surface, however, seem to be the reason for a low total quantum yield of sensitised excited singlet state oxygen.
2
Bullara, Domenico. "Nonlinear reactive processes in constrained media." Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209073.
Повний текст джерелаАнотація:
In this thesis we show how reactive processes can be affected by the presence of different types of spatial constraints, so much so that their nonlinear dynamics can be qualitatively altered or that new and unexpected behaviors can be produced. To understand how this interplay can occur in general terms, we theoretically investigate four very different examples of this situation. <p><p>The first system we study is a reversible trimolecular chemical reaction which is taking place in closed one-dimensional lattices. We show that the low dimensionality may or may not prevent the reaction from reaching its equilibrium state, depending on the microscopic properties of the molecular reactive mechanism. <p><p>The second reactive process we consider is a network of biological interactions between pigment cells on the skin of zebrafish. We show that the combination of short-range and long-range contact-mediated feedbacks can promote a Turing instability which gives rise to stationary patterns in space with intrinsic wavelength, without the need of any kind of motion.<p><p>Then we investigate the behavior of a typical chemical oscillator (the Brusselator) when it is constrained in a finite space. We show that molecular crowding can in such cases promote new nonlinear dynamical behaviors, affect the usual ones or even destroy them. <p><p>Finally we look at the situation where the constraint is given by the presence of a solid porous matrix that can react with a perfect gas in an exothermic way. We show on one hand that the interplay between reaction, heat flux and mass transport can give rise to the propagation of adsorption waves, and on the other hand that the coupling between the chemical reaction and the changes in the structural properties of the matrix can produce sustained chemomechanical oscillations. <p><p>These results show that spatial constraints can affect the kinetics of reactions, and are able to produce otherwise absent nonlinear dynamical behaviors. As a consequence of this, the usual understanding of the nonlinear dynamics of reactive systems can be put into question or even disproved. In order to have a better understanding of these systems we must acknowledge that mechanical and structural feedbacks can be important components of many reactive systems, and that they can be the very source of complex and fascinating phenomena.<p><br>Doctorat en Sciences<br>info:eu-repo/semantics/nonPublished
3
Daniel, Guido. "Conceptual design of reactive distillation processes." Thesis, University of Manchester, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503083.
Повний текст джерелаАнотація:
Integrated processes such as reactive distillation offer the potential for reduced capital and operating costs compared to conventional flowsheets. In this work new tools for the identification of the optimal reactive distillation process with the optimal degree of integration are developed. A conceptual design method based on the boundary value method is used for a set of reactive distillation processes. The combination of a reactive distillation column with a pre-reactor is a valuable alternative to standalone reactive distillation columns. This thesis presents an approach to identify promising designs for such flowsheets and the optimum distribution of the reaction extent between the pre-reactor and the reactive distillation column. The methodology uses a boundary value method for the design of the column; chemical equilibrium is assumed. The column usually consists of a reactive `core', two rectifying sections and one stripping section. This work presents an approach to identify promising designs for standalone reactive distillation columns as well as for reactor - reactive distillation column flowsheets, when reaction kinetics are available. Reaction kinetics are considered and several near-optimal flowsheet designs are generated. A new approach for the conceptual design of double-feed reactive distillation columns is presented. One of the feed streams is situated at the boundary of the reactive section and the other one can be fed into the non-reactive section of the column. Thus the column consists of an additional separating section, which offers the opportunity to add an additional function to the column. The production of methyl acetate is an example for such a column structure. The additional section in that case acts as an extractive distillation zone. Here also chemical equilibrium is assumed. The integration of further separation steps with a reactive distillation column leads to a highly integrated process: a reactive dividing wall column. Within one apparatus, more than two products can be obtained and the capital cost can be reduced drastically. Furthermore, the well-known reduction in energy demand for dividing wall columns compared to a sequence of conventional distillation columns can lead to reduced operating costs. However, the simulation, design and operation of such complex columns is complicated. A novel approach for the conceptual design of reactive dividing wall columns is presented in this work. Chemical equilibrium is assumed on every reactive stage of the column. The use of the concept of product regions and composition manifolds during all proposed design procedures leads to an increased robustness when compared to conventional approaches based on BVMs. Furthermore, the approaches can be used for n-component systems. Several column designs with different design and operating' parameters are identified for each reactive distillation process, allowing the process engineer to compare and choose from a selection of designs. These tools can assist in identifying the optimal degree of integration for reactive distillation processes ranging from reactor - reactive distillation combinations via complex double feed reactive distillation columns with additional separating sections to the most integrated reactive distillation process: the reactive dividing wall column. The new methodology offers an easy to use tool for process engineers, which assists in identifying an economical integrated reaction-distillation process and could lead to increased industrial applications of technologies coupling unit operations.
4
Harkin-Jones, Eileen M. A. "Rotational moulding of reactive plastics." Thesis, Queen's University Belfast, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317442.
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5
Ströhlein, Guido. "Modeling of reactive- and bio-chromatographic processes /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16950.
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6
Shao, Haibing. "Modelling reactive transport processes in porous media." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-61738.
Повний текст джерелаАнотація:
Reactive transport modelling has wide applications in geosciences. In the field of hydrogeology, it has been utilised to simulate the biogeochemical processes that disperse and degrade contaminants in the aquifer. For geotechnical applications, such as geological CO2 sequestration, the reaction of CO2 with the ambient saline aquifer determines the final success of storage. In a radioactive waste repository, scientists rely on reactive transport models to predict the mobilisation of hazardous radionuclides within space and time.
In this work, the multi-component mass transport code OpenGeoSys, was coupled with two geochemical solvers, the Gibbs Energy Minimization Selektor (GEM) and the Biogeochemical Reaction Network Simulator (BRNS). Both coupled codes were verified against analytical solutions and simulation results from other numerical models. Moreover, the coupling interface was developed for parallel simulation. Test runs showed that the speed-up of reaction part had a very good linearity with number of nodes in the mesh. However, for three dimensional problems with complex geochemical reactions, the model performance was dominated by solving transport equations of mobile chemical components.
OpenGeoSys-BRNS was applied to a two dimensional groundwater remediation problem. Its calculated concentration profiles fitted very well with analytical solutions and numerical results from TBC. The model revealed that natural attenuation of groundwater contaminants is mainly controlled by the mixing of carbon source and electron donor. OpenGeoSys-GEM was employed to investigate the retardation mechanism of radionuclides in the near field of a nuclear waste repository. Radium profiles in an idealised bentonite column was modelled with varying clay/water ratios. When clay content is limited, Ba-Sr-Ra sulfate solid solutions have a very strong retardation effect on the aqueous radium. Nevertheless, when clay mineral is abundant, cation exchange sites also attract Sr and Ba, thus dominates the transport of Ra.
7
Murat, Muhamad Nazri. "Novel catalytic structures for reactive distillation processes." Thesis, University of Manchester, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527418.
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8
Stein, Erik [Verfasser]. "Synthesis of Reactive Distillation Processes / Erik Stein." Aachen : Shaker, 2003. http://d-nb.info/1181602440/34.
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9
Biller, Nicholas Charles Trinder. "Modelling and control of reactive distillation processes." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405850.
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10
Thomson, Douglas W. "Generation of reactive intermediates by reductive processes." Thesis, University of Strathclyde, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424308.
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11
Greskowiak, Janek Johannes. "Reactive transport processes in artificially recharged aquifers." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2006. http://dx.doi.org/10.18452/15582.
Повний текст джерелаАнотація:
In der vorliegenden Dissertation sollten die hydrogeochemischen Prozesse herausgearbeitet werden, die für die Wasserqualitätsänderung während eines ASR Experiments in Bolivar, Südaustralien und während der Versickerung in einem künstlichen Grundwasseranreicherungsbecken in Berlin von Bedeutung waren. Reaktive Stofftransportmodellierung des ASR Experiments in Bolivar, Südaustralien zeigte, dass die hydrochemischen Veränderungen in der direkten Umgebung des Injektionsbrunnens während der Speicherphase nur durch rapide Änderungen der Sauerstoff- und Nitrat reduzierenden Bakterienmasse erklärt werden können. Die hydrochemischen Veränderungen in größerer Distanz zum Injektionsbrunnen wurden überwiegend durch Ionenaustauschprozesse und Kalzitlösung verursacht. Geochemische und hydraulische Messungen unter einem Sickerbecken in Berlin zeigten, dass die beobachteten geochemischen Änderungen im Sickerwasser mit den periodisch auftretenden wassergesättigten/wasserungesättigen Bedingungen unter dem Becken einhergehen. Während der ungesättigten Periode wird Luft unter das Becken gezogen und führt zur plötzlichen Reoxidierung von bereits in der gesättigten Periode gebildeten Eisensulfiden und zur beschleunigten Mineralisation von sedimentärem organischem Kohlenstoff. Reaktive Stofftransportmodellierung auf größerer Skale zeigte, dass allein die saisonalen Temperaturunterschiede im Infiltrationswasser für die beobachtete zeitliche und räumliche Dynamik der Redoxzonen im weiteren Abstrom des Sickerbeckens verantwortlich sind. Das Abbauverhalten der Arzneimittelsubstanz Phenazon hängt ausschließlich von der Verfügbarkeit von gelöstem Sauerstoff und damit indirekt von der Wassertemperatur im Aquifer ab. In der vorliegenden Arbeit wird deutlich, dass ein adäquates Verständnis der wasserqualitätsändernden Prozesse in künstlichen Anreicherungsystemen nur dann erreicht werden kann wenn Strömung, Transport und reaktive Prozesse, im Feld als auch in der Modellierung, simultan betrachtet werden.<br>In this thesis, three major studies were carried out in order to understand the key factors controlling the water quality changes that occurred during a reclaimed water Aquifer Storage and Recovery (ASR) experiment at Bolivar, South Australia and during ponded infiltration in Berlin, Germany. Multi-component reactive transport modelling of the ASR experiment suggested that during the storage phase, dynamic changes in bacterial mass have a significant influence on the local geochemistry in the vicinity of the injection well. Water quality changes further away from the injection well were mainly driven by ion exchange and calcite dissolution. Geochemical and hydraulic measurements below an artificial recharge pond in Berlin, Germany, showed that the observed dynamic changes of the hydrochemistry within the seepage water are strongly linked to the periodic saturated/unsaturated hydraulic conditions below the pond. During unsaturated conditions, atmospheric oxygen penetrates from the pond margins to the centre below the pond, leading to (i) a sudden re-oxidation of sulphide minerals that have formed previously during saturated conditions and (ii) an enhanced mineralisation of sedimentary particulate organic carbon. Reactive transport modelling showed that at larger scale, seasonal temperature changes of the infiltration water are the key control for the observed temporal and spatial redox dynamics further downstream the recharge pond. Moreover, the degradation behaviour of the pharmaceutically residue phenazone solely depends on the availability of dissolved oxygen, and thus indirectly on the water temperature within the aquifer. Overall this thesis shows that a sound understanding and analysis of the key processes affecting the water quality changes during artificial recharge of groundwater could only be achieved when flow, transport and reactive processes are considered simultaneously, both in the field and during modelling.
12
Amikiya, Emmanuel Adoliwine. "Flow and reactive transport processes in porous media." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/85838.
Повний текст джерелаАнотація:
Thesis (MSc)--Stellenbosch University, 2013.<br>ENGLISH ABSTRACT: Flow and reactive transport of chemical species is a very common phenomenon that occurs
in natural and artificial systems. However in this study, the topic is related to acid
mine drainage in the South African mining environment. Due to the hazards associated
with acid mine drainage, prevention or treatment of mine effluent water before discharging
to receiving waters and other environments is a necessity. A new time-dependent
mathematical model is developed for a passive treatment method, based on multi-scale
modelling of the coupled physico-chemical processes such as diffusion, convection, reactions
and filtration, that are involved in the treatment process. The time-dependent
model is simulated on a two-dimensional domain using finite volume discretization to
obtain chemical species distributions.<br>AFRIKAANSE OPSOMMING: Vloei en reagerende transport van chemiese spesies is ’n baie algemene verskynsel wat
in natuurlike en kunsmatige stelsels plaasvind. In hierdie studie is die onderwerp egter
verwant aan suurmyndreinering in die Suid-Afrikaanse mynbou-omgewing. As gevolg van
die gevare wat verband hou met suurmyndreinering, is die voorkoming of die behandeling
van die afval-mynwater voor dit in opvangswaters en ander omgewings beland ’n noodsaaklikheid.
’n Nuwe tydafhanklike wiskundige model vir ’n passiewe behandelingsmetode
is ontwikkel. Dit is gebaseer op die multi-skaal modulering van gekoppelde fisies-chemiese
prosesse soos diffusie, konveksie, reaksies en filtrasie, wat by die behandelingsproses betrokke
is. Die tydafhanklike model word gesimuleer op ’n twee-dimensionele domein met
behulp van eindige volume diskretisasie om die verspreiding van chemiese spesies te bepaal.
13
Giessler, Sabine. "Synthesis and Dynamic Optimization of Reactive Distillation Processes." Kyoto University, 2000. http://hdl.handle.net/2433/180939.
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14
Ait, Aissa Belaid. "Contribution to the synthesis of reactive distillation processes." Clausthal-Zellerfeld Papierflieger, 2008. http://d-nb.info/992300991/04.
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15
Siougkrou, Eirini. "Systematic methods for solvent design : towards better reactive processes." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/18827.
Повний текст джерелаАнотація:
The focus of this thesis is the development of novel methodologies for systematic identification of optimal solvents for chemical reactions. Two aspects are considered: the integrated solvent and process design using a mixed solvent, and the design of an optimal solvent using ab initio methods that do not rely on experimental data. A methodology is developed for the integrated design of a CO2-expanded solvent in a reaction process. Posing as objective function the cost of the process, for a defined production rate, an optimisation problem is formulated, with decision variables that include the organic co-solvent, the composition and the mass of the mixed solvent. Emphasis is placed on the prediction of the reaction rate, for which the solvatochromic equation combined with a preferential solvation model are used, and on solid-vapour-liquid phase equilibrium, for which the group-contribution volume translated Peng-Robinson equation of state is used. The proposed methodology is applied to the Diels-Alder reaction of anthracene and 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD), and three CO2-expanded solvents are considered (acetone, acetonitrile and methanol). Acetonitrile and acetone are found to offer good performance over a range of CO2 concentrations. The importance of taking into account multiple process performance indicators, when designing gas-expanded liquids, is highlighted. As a further step toward systematic solvent design approaches that are not limited by the availability of experimental data and consider a large number of candidate solvents, an ab initio methodology is developed for the design of optimal solvents for reactions. The developed method combines quantum mechanical calculations with a computer-aided molecular design formulation. In order to limit the number of QM calculations but also retain accuracy and ensure convergence, the Kriging approach is used. Kriging is a response surface approach, which has recently attracted a lot of attention because it is an exact extrapolator with a statistical interpretation which makes it stand out from other methods. The proposed approach is used successfully to identify promising solvents for the Menschutkin reaction of phenacyl bromide and pyridine and the Cope elimination of methylamine oxide. The use of Kriging as the surrogate model is found to lead to improved solvents when compared to the simpler solvatochromic equation used in previous work.
16
Africano, Fatima. "Reactive processes during the discharge of high temperature volcanic gases." Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211070.
Повний текст джерелаАнотація:
This study shows how the composition of gases released from a single magmatic source may be modified during their ascending path. The main processes that influence the composition of the gases in these high temperature fumarolic environments, are: 1) interactions with wallrocks during gas ascent, which change the fugacities of the metal volatile species and affect the equilibrium between major species (fH2S/fSO2; fH2/fH2O); 2) mixing with meteoric water with consequent Cl adsorption, which may account for the Cl depletion of the gases; 3) remobilisation of previously formed sublimates and/or incrustation deposits. Comparison between the thermochemical models and the mineralogical composition of the silica tubes at Kudryavy and Satsuma-Iwojima volcanoes suggests that high fO2 due to the mixing of the gases with air during their injection into the atmosphere significantly reduces the volatility of several trace elements (As, Sb, Sn, Na, K, Tl, Te, Se and Cd). Comparisons between the enriched metals in aerosols and in the gases suggest that Mo, Pb, Bi, Na, K, Cu, Zn or Fe, which are enriched in the gases, are preferentially deposited in the gas conduits and vents whereas the highly volatile metals (Te, Tl, Sb, As and Se) and Cd condense in the plume.<p>This study determines the reactions that may occur during the alteration of rocks in high temperature fumarolic environments. Three different processes of alteration prevail: <p>(1) Acidic alteration which is characterized by the complete absence of clays, because the constant supply of gases to these systems allows for the pH values of the acidic fluids to be maintained low enough to prevent the precipitation of clay minerals. Complete leaching of all cations, except Si, from the primary silicates leads to important "silicification" of the wall rock. The primary mineral cations are leached in the following order: K, Na > Ca > Fe, Mg > Al > Si, Ti. The fluids enriched in these cations circulate in microcracks at different temperatures and different redox conditions and lead to the precipitation of secondary incrustations. At Kudryavy the incrustations are mainly sulfates. At Usu the lower sulfur/fluoride ratio of the gases allows the occurrence of aluminum fluoride incrustations. The order of primary minerals dissolution (olivine > plagioclase > pyroxene > matrix glass > Fe-Ti oxides) is established for both sites studied. <p>(2) Alteration by an oxidized volcanic gas, resulting from mixing with the atmosphere (500 to 300°C). At Kudryavy, thermochemical modeling suggests that anhydrite and anhydrous sulfates, which occur at intermediate temperatures, are formed by interactions of the rock with oxidized gas. <p>(3) The most important outcome of this work is the identification of the features of alteration by the volcanic gas that directly reacts with the rock at high temperatures (T > 500°C). The Kudryavy rocks show evidences for mineral transformations, which occur in the presence of the volcanic gas phase. Volcanic gas directly reacts with rocks at high temperatures (T > 500°C). The gas destabilizes the primary minerals, remobilizes the rock-bearing cations, and leads to the formation of second mineral assemblages. These transformations occur in situ, without significant mobility (gain or loss) of the cations. The high temperature secondary associations are characterized by the presence of andradite, hedenbergite, hercynite, tridymite/cristobalite. Anhydrite and anhydrous Al sulfate may occur within these mineral assemblages if the gas is oxidized.<p><br>Doctorat en sciences, Spécialisation géologie<br>info:eu-repo/semantics/nonPublished
17
Al-Rashed, Mohsen Hassan Jaber. "A study of reactive precipitation processes using computational fluid dynamics." Thesis, University College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286284.
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18
Wagner, M. G. "Process modelling using neural networks : an application to a reactive plasticating extruder." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309823.
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19
Nureldin, Hazem M. "An artificial neural network architecture system for real time reactive scheduling and control." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246499.
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20
Lau, C. C. "Development and assessment of a reactive simulation-based manufacturing planning and control system." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269057.
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21
Mayer, Jens-Christopher. "Transport processes of reactive trace gases in the atmospheric boundary layer." kostenfrei, 2008. http://opus.ub.uni-bayreuth.de/volltexte/2009/573/.
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22
Garge, Swapnil. "Development of an inference based control scheme for reactive extrusion processes." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 236 p, 2007. http://proquest.umi.com/pqdweb?did=1362532031&sid=11&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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23
Bunting, Andrew Stuart. "Characterisation of reactive ion etch processes for ternary III-V semiconductors." Thesis, University of Glasgow, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361772.
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24
Reiter, Elke Christine. "Reactive oxygen species/antioxydants as redox-signalling modulators in inflammatory processes /." Bern : [s.n.], 2008. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000277019.
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25
Niesbach, Alexander [Verfasser]. "Design of Reactive Distillation Processes Using Bio-based Raw Materials / Alexander Niesbach." München : Verlag Dr. Hut, 2014. http://d-nb.info/1063221722/34.
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26
Chastaing, Delphine. "Reactive and inelastic processes in the gas-phase at ultra-low temperatures." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367745.
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27
Porkert, Sebastian. "Physico-Chemical Processes during Reactive Paper Sizing with Alkenyl Succinic Anhydride (ASA)." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-219620.
Повний текст джерелаАнотація:
Sizing (hydrophobization) is one of the most important process steps within the added-value chain of about 1/3rd of the worldwide produced paper & board products. Even though sizing with so-called reactive sizing agents, such as alkenyl succinic anhydride (ASA) was implemented in the paper industry decades ago, there is no total clarity yet about the detailed chemical and physical mechanisms that lead to their performance. Previous research was carried out on the role of different factors influencing the sizing performance, such as bonding between ASA and cellulose, ASA hydrolysis, size revision as well as the most important interactions with stock components, process parameters and additives during the paper making process. However, it was not yet possible to develop a holistic model for the explanation of the sizing performance given in real life application. This thesis describes a novel physico-chemical approach to this problem by including results from previous research and combining these with a wide field of own basic research and a newly developed method that allows tracing back the actual localization of ASA within the sheet structure.
The carried out measurements and trial sets for the basic field of research served to evaluate the stock and process parameters that most dominantly influence the sizing performance of ASA. Interactions with additives other than retention aids were not taken into account. The results show that parameters, such as the content of secondary fibers, the degree of refining, the water hardness as well as the suspension conductivity, are of highest significance. The sample sets of the trials with the major impacting parameters were additionally analyzed by a newly developed localization method in order to better understand the main influencing factors.
This method is based on optical localization of ASA within the sheet structure by confocal white light microscopy. In order to fulfill the requirements at magnification rates of factor 100 optical zoom, it was necessary to improve the contrast between ASA and cellulose. Therefore, ASA was pretreated with an inert red diazo dye, which does not have any impact on neither the sizing nor the handling properties of ASA. Laboratory hand sheets that were sized with dyed ASA, were analyzed by means of their sizing performance in correlation to measurable ASA agglomerations in the sheet structure. The sizing performance was measured by ultrasonic penetration analysis. The agglomeration behavior of ASA was analyzed automatically by multiple random imaging of a sample area of approx. 8650 µm² with a minimum resolution for particles of 500 nm in size. The gained results were interpreted by full factorial design of experiments (DOE). The trials were carried out with ASA dosages between 0% and 0.8% on laboratory hand sheets, made of 80% bleached eucalyptus short fiber kraft pulp and 20% northern bleached softwood kraft pulp, beaten to SR° 30, produced with a RDA sheet former at a base weight of 100 g/m² oven dry.
The results show that there is a defined correlation between the ASA dosage, the sizing performance and the number and area of ASA agglomerates to be found in the sheet structure. It was also possible to show that the agglomeration behavior is highly influenced by external factors like furnish composition and process parameters. This enables a new approach to the explanation of sizing performance, by making it possible to not only examine the performance of the sizing agent, but to closely look at the predominant position where it is located in the sheet structure. These results lead to the explanation that the phenomenon of sizing is by far not a pure chemical process but rather a more physical one. Based on the gained findings it was possible so far to optimize the ASA sizing process in industrial-scale by means of ~ 50% less ASA consumption at a steady degree of sizing and improved physical sheet properties.
28
Schröder, Benjamin. "Theoretical high-resolution spectroscopy for reactive molecules in astrochemistry and combustion processes." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://hdl.handle.net/21.11130/00-1735-0000-0005-12DA-1.
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Li, Wei Ph D. Massachusetts Institute of Technology Department of Civil and Environmental Engineering. "Experimental and theoretical studies of reactive transport processes in soluble porous rocks." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123229.
Повний текст джерелаАнотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2019<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 207-219).<br>Underground reactive transport processes involve fluid flow and reactions (dissolution, precipitation, and pressure solution) driving the evolution of the rock-fluid systems, which may result in favorable processes such as increased oil production by reservoir acid stimulation, or undesired processes such as caves and subsidence. Flow and reaction in the rock matrix often induce wormholes, which are long, finger-like channels that form due to the dissolution heterogeneity in the matrix. These wormholes become major flow pathways, which greatly increase the permeability of the rock. To study the reactive transport processes and the formation of wormholes, experimental and theoretical studies were conducted. More specifically, a new experimental setup and data analysis methods were introduced to the tube flow tests and core flood tests to experimentally study the evolution of the rock-fluid system. Theoretical studies with analytical and numerical models were used to simulate the experimental results and provide theoretical explanation for the experimental observations. Through the experimental and theoretical studies, this research improved the fundamental understanding of reactive transport processes in rock-fluid systems. This in turn provided accurate prediction of the evolution of the rock-fluid systems driven by the reactive transport processes.<br>by Wei Li.<br>Ph. D.<br>Ph.D. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering
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Vegh, Rusell. "Mechanisms and applications of photoinduced processes in fluorescent proteins." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50126.
Повний текст джерелаАнотація:
In the current work, the photophysics and photochemistry of the phototoxic red fluorescent protein (RFP) KillerRed was investigated. KillerRed's phototoxicity makes it useful for studying oxidative stress on cell physiology and for cell killing in photodynamic therapy. Spectroscopic probes were used to show that the phototoxicity of KillerRed stems primarily from a type I photosensitization mechanism producing radicals. The production of radicals was supported by electron paramagnetic resonance (EPR) studies, where a long-lived radical was observed in KillerRed and two other RFPs (mRFP and DsRed) following excitation. Transient absorption spectroscopy, various other spectroscopic techniques, and the published crystal structure of KillerRed indicate that the long-filled water channel is likely responsible for the increased phototoxicity of KillerRed. In the blue fluorescent protein (BFP) mKalama1, some of the same techniques were applied to understand the photophysics and photochemistry on the timescale ranging from femtoseconds to seconds. Transient absorption spectroscopy and previously published results demonstrate that two-photon excitation of mKalama1 likely results in the formation of a radical cation and solvated electrons. This may explain the blinking behavior which has been observed on the single molecule level for many fluorescent proteins, the identity of which has remained elusive. It was also shown that the chromophore, while neutral in the ground state, does not exhibit excited-state proton transfer (ESPT) during its nanosecond excited-state lifetime; however, the chromophore undergoes a deprotonation in the ground state after electronic relaxation. This work plays a key role in our understanding of fluorescent proteins and will help pave the way to developing new ones. The research on the BFPs was extended to improve them for cellular imaging. This was accomplished by identification of dark states in the BFPs which are longer in wavelength than the collected fluorescence. Using dual lasers, it was shown that these dark states could be optically depleted, thereby increasing the overall fluorescence without enhancing the background fluorescence. Rational site-directed mutagenesis was carried out on the BFPs and the mutants were screened for fluorescence enhancement. These proteins were then analyzed using transient absorption spectroscopy to elucidate the identity of the dark state(s) used for fluorescence enhancement.
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Gebhardt, Christoph R. "Reactive cluster impact dynamics and ion processes investigated by cluster impact mass spectrometry." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=962138657.
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García, Montaño Julia. "Combination of Advanced Oxidation Processes and Biological Treatments for Commercial Reactive Azo Dyes Removal." Doctoral thesis, Universitat Autònoma de Barcelona, 2007. http://hdl.handle.net/10803/3252.
Повний текст джерелаАнотація:
La industria textil produce grandes cantidades de agua residual con un alto contenido de materia orgánica y color. Debido a la amenaza ambiental que supone su naturaleza refractaria, surge la necesidad del tratamiento antes de la descarga. Los procesos biológicos, físicos y químicos convencionales resultan ineficaces en la decoloración y mineralización completa de estos efluentes. Como alternativa emergen los Procesos Avanzados de Oxidación (PAOs), basados principalmente en la generación de radicales hidroxilo (HO·) altamente reactivos. Éstos pueden aplicarse de forma exclusiva o combinados con tratamientos biológicos con el fin de reducir su elevado consumo de reactivos y energía. Entre los diferentes PAOs disponibles, los procesos de Fenton y, particularmente, los procesos de foto-Fenton (basados en la generación de HO· mediante la adición de peróxido de hidrógeno y una sal ferrosa en disolución acuosa) suponen la mejor opción debido a su elevada eficacia y bajo coste económico. Adicionalmente, los procesos de foto-Fenton pueden llevarse a cabo bajo radiación solar, ofreciendo nuevas ventajas económicas y medioambientales. <br/>Esta tesis doctoral se centra básicamente en la aplicación del proceso de foto-Fenton como etapa previa en la degradación de soluciones de azo colorantes reactivos biorrecalcitrantes, con el propósito de generar un nuevo efluente compatible con un tratamiento biológico aerobio posterior de menor coste e impacto ambiental que el primero. La evolución de parámetros clave como el color, el carbono orgánico total, la aromaticidad, la toxicidad, la biodegradabilidad, la naturaleza de los intermedios de degradación, así como el efecto de la fuente de irradiación (luz artificial, luz solar), la temperatura, el tiempo de reacción y la concentración de reactivos, proporcionan información acerca de las condiciones idóneas para el acoplamiento PAO/tratamiento biológico. <br/>Los resultados obtenidos confirman la idoneidad del PAO propuesto con este fin, tanto a escala de laboratorio como en planta piloto. Mediante el proceso de foto-Fenton aplicado bajo condiciones de oxidación suaves, las soluciones bajo estudio resultan incoloras, de naturaleza biodegradable y no tóxica. De este modo, el tratamiento combinado foto-Fenton/tratamiento biológico aerobio permite su degradación completa. La luz solar como fuente de radiación en el proceso de foto-Fenton proporciona los mejores resultados. Por otro lado, la secuencia oxidativa parece comenzar por la decoloración por rotura del grupo azo seguida de la degradación de aromáticos para formar ácidos carboxílicos alifáticos -dando lugar a la formación de CO2 y H2O- o el anillo triazina de naturaleza recalcitrante. Una parte importante de los heteroátomos presentes en la molécula original aparecen como productos finales de naturaleza inorgánica inocua.<br/>El trabajo está ampliado con un estudio económico y medioambiental del proceso secuencial foto-Fenton (luz artificial)/tratamiento biológico. La evaluación medioambiental se ha realizado mediante la herramienta de Análisis de Ciclo de Vida. En comparación con los procesos simples foto-Fenton bajo luz artificial y foto-Fenton bajo luz solar, el tratamiento combinado resulta la mejor opción en ambos contextos. Los mayores impactos se asocian, en este orden, al consumo de peróxido de hidrógeno y de energía para alimentar la luz artificial. En consecuencia, y atendiendo a los resultados obtenidos previamente, es posible concluir que el proceso de foto-Fenton asistido con luz solar como pre-tratamiento de un proceso biológico sería la mejor opción en términos de efectividad, impacto medioambiental y coste operacional. <br/>Finalmente, como alternativa a la estrategia de oxidación química/tratamiento biológico aerobio, el PAO se aplica como post-tratamiento a un proceso biológico anaerobio. Los PAOs considerados son la ozonización y el proceso de foto-Fenton. Los resultados obtenidos manifiestan la idoneidad de la secuencia propuesta, obteniéndose unos mejores niveles de degradación mediante el proceso con ozono. Estos resultados son de especial interés en futuras aplicaciones para el tratamiento de aguas residuales textiles reales.<br>The textile industry produces large quantities of wastewater that is highly coloured and contains large concentrations of organic matter. Due to the environmental threat that supposes its recalcitrant nature, the application of specific treatment is required prior discharge. Conventional biological, physical and chemical processes are quite inefficient to completely mineralise and decolourise these effluents. Alternatively appear the Advanced Oxidation Processes (AOPs), principally based on the generation of highly reactive hydroxyl radicals (HO·). They may be applied as exclusive processes or combined with biological treatments in an attempt to reduce their large chemicals and energy consumption. Among available AOPs, the Fenton and, particularly, the photo-Fenton processes (based on HO· generation by means of hydrogen peroxide and a ferrous salt addition in aqueous solution) are of special interest since they achieve high reaction yields with a lower operational cost. Additionally, the photoassisted reaction presents the possibility of be driven under solar irradiation, offering further economic and environmental advantages. <br/>This doctoral dissertation is basically centred in the performance of the photo-Fenton process as a previous step to treat biorecalcitrant solutions polluted with commercial reactive azo dyes, aiming to generate a new effluent amenable to aerobic biotreatment (with a lower economic and environmental impact than the AOP). The evolution of key parameters such as the colour, the total organic carbon, the aromatic compounds content, the toxicity, the biodegradability, the generated by-products nature, as well as the type of irradiation effect (artificial light, solar light), the temperature, the reaction time and the reagents concentrations, provide information about the most suitable conditions to carry out the AOP/biological coupled treatment. <br/>Obtained results evidence the aptness of the AOP proposed with this aim, either at laboratory and pilot plant scale. With a partial oxidation run under proper mild conditions, the studied dye solutions become decolourised, biodegradable as well as non toxic. In this way, the combined photo-Fenton/biological treatment allows the complete mineralisation. The solar light as a source of irradiation provides the best results. On the other hand, the oxidative sequence appears to begin with the hydroxyl radical attack to azo groups, giving place to the solutions decolourisation. The following aromatics degradation generates either short chain carboxylic acids -finally yielding CO2 and water- or the recalcitrant triazine moiety. An important part of the heteroatoms initially present in the molecule gradually appear as innocuous final products of inorganic nature.<br/>The work is extended with an economic and environmental study of the sequential photo-Fenton (artificial light)/biological treatment process. The environmental evaluation has been realised by means of the Life Cycle Assessment tool. In comparison with single artificial light photo-Fenton process and solar driven photo-Fenton process, the combined treatment supposes the best option in both contexts. The major burdens are mainly attributed to the hydrogen peroxide requirements and the electrical energy consumption to run the artificial light, in this order. Consequently, and attaining to previously obtained results, the solar driven photo-Fenton process as a pre-treatment of a biological treatment would be the best option in terms of effectiveness, environmental impact and operational cost. <br/>Finally, as an alternative to the chemical/aerobic biological treatment, the AOP is performed as a post-treatment of an ensuing anaerobic biotreatment. Ozonation and photo-Fenton processes have been chosen for this role. Obtained results manifest the suitability of the proposed sequence, attaining the best degradation levels by means of ozonation process. These results are of special interest for real wastewater applications.
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Wolf, Leah Michelle. "A field study of non-reactive transport behavior and evaluation of diffusion mediated processes." Thesis, The University of Arizona, 2003. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_etd_hy0264_sip1_w.pdf&type=application/pdf.
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Haßkerl, Daniel [Verfasser]. "Economic Performance Optimization by Direct Optimizing Control Applied to Reactive Distillation Processes / Daniel Haßkerl." Düren : Shaker, 2019. http://d-nb.info/1190525496/34.
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Kunze, Anna-Katharina [Verfasser]. "Intensified reactive absorption processes for CO2 separation using enzyme accelerated solvents / Anna-Katharina Kunze." München : Verlag Dr. Hut, 2016. http://d-nb.info/1084385406/34.
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Hall, Nicola Rachel. "The effects of C-reactive protein (CRP) isoforms on inflammation and wound healing processes." Thesis, Manchester Metropolitan University, 2017. http://e-space.mmu.ac.uk/618364/.
Повний текст джерелаАнотація:
C-reactive protein (CRP) is a homopentameric acute-phase inflammatory protein that exhibits elevated expression during inflammation. CRP can be found in its pentameric form (nCRP) or monomeric form (mCRP). To date there has been little research investigating the effects of these CRP isoforms in wound healing processes and age-related impaired healing, which is known to have an altered inflammatory response. The study investigated CRP isoform localisation in murine wounds (detected by immunohistochemistry) and circulating blood (measured by immunoblotting) using models of acute healing in young adults and age-related impaired healing (n=3). Using in vitro inflammatory cell assays developed with the monocytic U937 cell line this study investigated the effects of CRP isoforms in nitric oxide release (detected by an immunoassay), phagocytosis (measured by a bacterial recovery assay), apoptosis (detected via DNA fragmentation) and cytokine secretion (measured by a multiplex immunoassay) in both monocyte and macrophage-like cells (n=6). Pharmacological inhibitors were used to determine the potential CRP-induced pathways or mechanisms. Both isoforms were localised to sites of inflammation, implying that they may play an active inflammatory role during wound repair. Moreover, the ratio of CRP isoforms (mCRP:nCRP) reflected the degree of inflammation, with higher values indicating elevated mCRP localisation and pronounced inflammation in the model of age-related impaired healing. In in vitro inflammatory cell assays, nCRP exhibited a more anti-inflammatory effect leading to significantly (P=0.01) increased phagocytosis, increased apoptosis, decreased nitric oxide (NO) production, and reduced overall pro-inflammatory cytokine production in monocytes and macrophages. The mCRP isoform significantly (P < 0.001) increased NO production and overall levels of pro-inflammatory cytokines, thus confirming its pro-inflammatory nature indicated in the literature. This research highlighted that estrogen mediated CRP-induced responses in a cell type- and status-specific manner, being pro-inflammatory in circulating cells (monocytes) but anti-inflammatory in wound tissue cells (mature activated macrophages). The profile of CRP isoforms shifted in age-related (estrogen-deprived) impaired healing to relatively higher levels of mCRP compared to nCRP, suggesting impaired healing in the elderly may result from the dissociation of nCRP to mCRP following the decline in estrogen with increasing age. In conclusion, this study has provided novel data showing that both isoforms of CRP may differentially mediate inflammatory responses during wound healing and may play key roles in age-related impaired healing and may ultimately provide potential therapeutic strategies for the treatment of chronic wounds in the elderly.
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Schröder, Benjamin [Verfasser]. "Theoretical high-resolution spectroscopy for reactive molecules in astrochemistry and combustion processes / Benjamin Schröder." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://d-nb.info/1216330557/34.
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Ndjaka, Ange. "THERMOPHYSICAL PROCESSES AND REACTIVE TRANSPORT MECHANISMS INDUCED BY CO2 INJECTION IN DEEP SALINE AQUIFERS." Electronic Thesis or Diss., Pau, 2022. http://www.theses.fr/2022PAUU3003.
Повний текст джерелаАнотація:
Le stockage du CO2 dans les aquifères salins profonds a été reconnu comme l'une des voies les plus prometteuses pour atténuer les émissions atmosphériques de CO2 et répondre ainsi aux enjeux du changement climatique. Cependant, l’injection du CO2 dans le milieu poreux perturbe considérablement son équilibre thermodynamique. La zone proche du puits d’injection est particulièrement impactée avec une forte réactivité géochimique associée à d’intenses échanges thermiques. Cela a un impact majeur sur l’injectivité du réservoir et l’intégrité du stockage. A ces effets s’ajoute une complexité supplémentaire liée à la présence de deux phases non miscibles : la saumure et le CO2. Ces effets conduisent à des processus Thermo-Hydro-Mécaniques-Chimiques (THMC) fortement couplés, dont les interprétations ne sont pas encore abouties ni formellement implémentées dans les modèles numériques.Ce travail de thèse, associant des mesures expérimentales et des modélisations numériques, porte sur l’étude du couplage entre les gradients thermiques et les processus diffusifs de transport réactif se déroulant dans les aquifères salins, notamment dans la zone proche du puits d’injection. Nous avons étudié les échanges entre une phase froide CO2 anhydre qui s’écoule dans des zones de forte perméabilité, et une phase aqueuse salée chaude piégée dans la porosité de la roche. La stratégie de l'étude commence par une approche simple en milieu libre sans flux de CO2 afin d'étudier la réactivité des solutions salines de différentes compositions chimiques et d’évaluer l'impact d'un gradient thermique sur ce réseau réactionnel.Nous avons développé une cellule expérimentale permettant de superposer 2 à 3 couches de solution de concentration et composition chimique différentes. L’analyse de la lumière diffusée par les fluctuations de non-équilibre de la concentration et de la température permet de remonter aux coefficients de diffusion des sels dans l’eau. Nos résultats sont en bon accord avec les valeurs de la littérature. Pour ce qui est de l’étude du transport réactif diffusif, l’analyse du contraste des images a permis de mettre en évidence le fait que la précipitation de minéral, par mise en contact de deux couches aqueuses de sels réactifs, s’accompagne d’une instabilité convective qui s’estompe dans le temps. La modélisation numérique des résultats expérimentaux avec PHREEQC par une approche de diffusion multi-espèce hétérogène permet de rendre compte des instabilités convectives. Différents gradients de température ont été appliqués au système réactif, tout en conservant une température moyenne de 25 °C. Les observations expérimentales et les interprétations numériques montrent que le gradient de température n'a pas d’influence significative sur le comportement du système.Ensuite, nous avons étudié numériquement le processus de dessiccation (évaporation de l’eau) à l’interface entre une saumure piégée dans la porosité de la roche et du CO2 circulant dans une structure porale drainante, simulant les conditions de l’aquifère du Dogger du bassin parisien. Un modèle couplant l’évaporation de l’eau dans le flux de CO2 et la diffusion multi-espèces hétérogène des sels prévoit l’apparition d’un assemblage minéral au niveau du front d’évaporation, principalement composé d’halite et d’anhydrite. La modélisation de ce phénomène à l’échelle du réservoir nécessite la prise en compte de la vitesse d’évaporation en fonction du taux d’injection du CO2 et de l’évolution de la porosité au niveau de l’interface.Ce travail de thèse a permis de mettre en évidence plusieurs phénomènes physico-chimiques, thermo-physiques et de transport diffusif aux interfaces de phase. Ce qui ouvre de nouvelles perspectives d’amélioration des approches numériques et de modélisation à grande échelle notamment du proche puits d’injection du CO2 et des réservoirs de stockage géologique et soutenir les futurs développements industriels et technologiques pour la transition écologique<br>CO2 storage in deep saline aquifers has been recognised as one of the most promising ways to mitigate atmospheric CO2 emissions and thus respond to the challenges of climate change. However, the injection of CO2 into the porous medium considerabely disturbs its thermodynamic equilibrium. The near-well injection zone is particularly impacted with a strong geochemical reactivity associated with intense heat exchanges. This has a major impact on injectivity of the reservoir and the integrity of the storage. In addition to these effects, there is the added complexity of the presence of two immiscible phases: brine (wetting fluid) and CO2 (non-wetting fluid). These effects lead to highly coupled Thermo-Hydro-Mechanical-Chemical (THMC) processes, whose interpretations have not yet been completed nor formally implemented into the numerical models.This thesis work, combining experimental measurements and numerical modelling, focuses on the study of the coupling between the thermal gradients and the diffusive reactive transport processes taking place in the deep saline aquifers, particularly in the near-well injection zone. We studied the exchanges between a cold anhydrous CO2 phase flowing in high permeability zones, and a hot salty aqueous phase trapped in the porosity of the rock. The strategy of the study starts with a simple approach in a free medium without CO2 flow, in order to study the reactivity of saline solutions of different chemical compositions, and to evaluate the impact of a thermal gradient on this reaction network.We have developed an experimental cell that allow to superimpose 2 to 3 layers of solution of different concentration and chemical composition. The analysis of the light scattered by the non-equilibrium fluctuations of concentration and temperature allows to obtain the diffusion coefficients of salts in water. Our results are in good agreement with literature values. Regarding the study of diffusive reactive transport, the analysis of the contrast of the images allowed us to highlight the fact that the precipitation of minerals, obtained by superimposing two aqueous layers of reactive, is accompanied by a convective instability that fades with time. Numerical modelling of the experimental results with PHREEQC using a heterogeneous multicomponent diffusion approach has allowed us to account for these convective instabilities. Different temperature gradients were applied to the reactive system, while keeping a mean temperature of 25 °C. The experimental observations and numerical interpretations swhow that the temperature gradient has no significant influence on the behaviour of the system. Subsequently, we numerically studied the desiccation process (evaporation of water) at the interface between a brine trapped in the rock porosity and the CO2 flowing in a draining pore structure, simulating the conditions of the Dogger aquifer of the Paris basin. A model coupling the evaporation of water in the CO2 stream and the heterogeneous multicomponent diffusion of salts predicts the appearance of a mineral assemblage at the evaporation front, mainly composed by halite and anhydrite. Modelling this phenomenon at the reservoir scale would requires taking into account the evaporation rate as a function of the CO2 injection rate and the change in porosity at the interface.This thesis work has made it possible to highlight several physicochemical, thermophysical and diffusive transport phenomena at phase interfaces. This opens up new perspectives for improving numerical approaches and large-scale modelling, in particular of near-well injection of CO2 and geological storage reservoirs, and supports future industrial developments and technologies for the ecological transition
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Rahim, Ismail Soraya. "A generalised modular framework for the the synthesis of nonideal separation and reactive separation processes." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/8765.
Повний текст джерелаАнотація:
This thesis presents a systematic approach for the synthesis of azeotropic separation and combined reactive/separation systems, utilising a mass and heat transfer phenomena based representation. The developed framework does not explicitly prepostulate process alternatives but instead investigates them as mass and heat exchange possibilities. The building block of process alternatives is based on a mass/heat transfer module between two properly defined streams consisting of two parts: a mass/heat exchange block, whereby mass and heat transfer takes place between streams, and a pure heat exchanger, where only heat is exchanged and matching streams do not come into contact. In this work, the module is developed focusing on nonideal separation and separation reactive mass transfer phenomena. Gibbs free energy based constraints are derived and introduced in each block, to determine the direction of mass transfer for each component and ensure feasibility of both phase change and reactive mass transfer. Phase and reaction equilibria are not necessarily reached in the mass/heat transfer module but are instead utilised to define the limiting case. Process operations are viewed as sets of mass and heat exchange, such that a set of properly connected blocks can be realised as process alternatives. The synthesis model is formulated as a mixed integer nonlinear optimisation problem, for which a decomposition strategy is developed for its solution. The main feature of this representation is that with no prepostulation of process units, different structures and mass transfer patterns, rather than detailed designs, are captured. In the first part of this work, the proposed framework is developed for the synthesis of homogeneous azeotropic separation systems. For this class of systems, it is shown that sequencing and entrainer selection can be addressed in a single optimisation problem. Modelling aspects towards the synthesis of heterogeneous systems are outlined. The approach is further developed to encompass combined reaction and separation processes, where it is illustrated that process alternatives including hybrid process units, such as reactive separation units, as well as conventional separation and reaction units, can be generated within the framework. An application of the framework to an industrial methanol case study is also presented.
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Maibaum, Elaine Catherine. "Spectro-electro-array spectroscopy and the in-vitro modelling of metabolic processes and reactive intermediates." Thesis, Imperial College London, 2004. http://hdl.handle.net/10044/1/8599.
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Raza, Mohsin. "Synthesis of hydrogenated amorphous carbon (a-C:H) thin films by HiPIMS-based processes." Thesis, Linköpings universitet, Plasma och beläggningsfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-84320.
Повний текст джерелаАнотація:
This thesis explores the feasibility of high power impulse magnetron sputtering (HiPIMS) to synthesize hydrogenated amorphous carbon (a-C:H) thin films in Ar-hydrocarbon ambient and the relationship between process parameters, gas phase composition and film properties. To this purpose a stable process based on HiPIMS and direct current magnetron sputtering (DCMS) has been developed. Four series of amorphous carbon thin films were deposited by hybrid HiPIMS-DCMS and pure DCMS processes at 15 mTorr pressure using different Ar-acetylene compositions and a substrate bias from 0 to -350 V. The effect of Ar-acetylene compositions and depositions processes on the film properties was investigated by characterizing the films using scanning electron microscopy (SEM), x-ray reflectometry (XRR), nanoindentation and elastic recoil detection analysis (ERDA). Moreover the process characterization was done by recording the optical emission spectrum and current and voltage waveforms of the hybrid HiPIMS-DCMS discharge. The characterization of the films revealed that the hybrid HiPIMS-DCMS process is a powerful tool for controlling the amorphous carbon film properties such as density, deposition rate, hardness and hydrogen content.
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Ivanova, Chalakova Mariyana. "Conceptual design and analysis of reactive distillation processes for the production of isooctane via indirect alkylation." Magdeburg docupoint, 2009. http://d-nb.info/1001012348/04.
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Falcone, Manuel [Verfasser], Dieter [Akademischer Betreuer] Bothe, and Michael [Akademischer Betreuer] Schäfer. "Direct Numerical Simulations of Reactive Transport Processes at Single Bubbles / Manuel Falcone ; Dieter Bothe, Michael Schäfer." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://d-nb.info/1183911602/34.
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Harris, Sean Anthony. "Studies of ion molecule reactive processes, electron impact ionisation, and inelastic collisions in state selected molecular beams." Thesis, University of Canterbury. Chemistry, 1997. http://hdl.handle.net/10092/7863.
Повний текст джерелаАнотація:
Alkali metal ion sources have been designed for the production of Li+, Na+ and K+ ion beams. The thermionic emission of alkali metal ions from heated synthetic zeolites is utilised to produce the alkali ions. As a precursor to crossed beam studies of the reactions of the alkali metal ions with spatially oriented symmetric top alkyl halides, the ion molecule chemistry of K⁺ with CH₃X and tertiary C₄H₉X where X= Cl or Br has been examined for collision energies up to 5 e V using a Drift Tube Mass Spectrometer.
The electron impact ionisation cross sections for the inert gases, H₂, N₂, SF₆, CC1₃H and the molecules CH₃X where X= H, F, Cl, Br, I, have been measured. The ionisation efficiency curves for Ar, CH₄, CH₃F, CH₃Cl and CH₃Br from threshold up to 200 e V have been determined.
The cross sections for the loss of hexapole focused upper Stark state molecules from ∣JKM〉 rotational state selected molecular beams of CH₃F, CH₃Cl and CF₃H have been measured. The upper Stark state molecules are defocused from the beam in rotationally inelastic collisions with a. scattering gas introduced to the hexapole. The long range attractive van der Waals interaction between the colliding species has been used to account for the magnitude of the cross sections from consideration of rotational transitions of the ∣JKM〉 state selected beam molecules where ∆M = ±1 or ∆J = ±1. The seeded beam technique has been used to determine the velocity dependence of the defocusing cross sections.
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Greskowiak, Janek Johannes [Verfasser], Asaf [Gutachter] Pekdeger, Gunnar [Gutachter] Nützmann, and Wilfried [Gutachter] Endlicher. "Reactive transport processes in artificially recharged aquifers / Janek Johannes Greskowiak ; Gutachter: Asaf Pekdeger, Gunnar Nützmann, Wilfried Endlicher." Berlin : Humboldt-Universität zu Berlin, 2006. http://d-nb.info/1208079069/34.
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Aqar, Dhia Y. "Modelling and Optimization of Conventional and Unconventional Batch Reactive Distillation Processes. Investigation of Different Types Batch Reactive Distillation Columns for the Production of a Number of Esters such as Methyl Lactate, Methyl Decanoate, Ethyl Benzoate, and Benzyl Acetate using gPROMS." Thesis, University of Bradford, 2018. http://hdl.handle.net/10454/17139.
Повний текст джерелаАнотація:
The synthesis of a number of alkyl esters such as methyl lactate, methyl decanoate, and ethyl benzoate via esterification in a reactive distillation is quite challenging. It is due to the complexity in the thermodynamic behaviour of the chemical species in the reaction mixture in addition to the difficulty of keeping the reactants together in the reaction section. One of the reactants (in these esterification reactions) having the lowest boiling point can separate from the other reactant as the distillation continues. This can result in a significant drop in the reaction conversion in a conventional reactive distillation whether it is a batch or a continuous column.
To overcome this challenge, new different types of batch reactive distillation column configurations: (1) integrated conventional (2) semi-batch (3) integrated semi-batch (4) integrated dividing-wall batch distillation columns have been proposed here.
Four esterification reaction schemes such as (a) esterification of lactic acid (b) esterification of decanoic acid (c) esterification of benzoic acid (d) esterification of acetic acid are investigated here. A detailed dynamic model based on mass, energy balances, chemical reaction, and rigorous thermodynamic (chemical and physical) properties is considered and incorporated in the optimisation framework within gPROMS (general PROcess Modelling System) software.
It is found that for the methyl lactate system, the i-SBD operation outperforms the classical batch operations (CBD or SBD columns) to satisfy the product constraints. While, for the methyl decanoate system, the i-DWCBD operation outperforms all CBD, DWBD and sr-DWBD configurations by achieving the higher reaction conversion and the maximum product purity. For the ethyl benzoate system, the performance of i-CBD column is superior to the CBD process in terms of product quality, and conversion rate of acid. The CBD process is found to be a more attractive in terms of operating time saving, and annual profit improvement compared to the IBD, and MVD processes for the benzyl acetate system.<br>The Higher Committee for Education Development in Iraq (HCED)
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Willmann, Matthias. "Scaling of subsurface processes in heterogeneous aquifers: from hydraulic testing to the use of memory functions." Doctoral thesis, Universitat Politècnica de Catalunya, 2008. http://hdl.handle.net/10803/32780.
Повний текст джерелаАнотація:
La heterogeneidad de la conductividad hidráulica es bien conocida, pudiendo cambiar varios órdenes de magnitud en poca distancia. Esto afecta nuestras observaciones de los procesos naturales. Para poder explicar la realidad normalmente nos basamos en modelos simplificados. Pero para incorporar correctamente en ellos las propiedades de los acuíferos, se debe pasar de escala local a escala de soporte y a escala de la malla del modelo numérico. Este proceso se llama Upscaling y puede comportar cambiar los parámetros de la ecuación conocida a escala local, o bien la derivación de una nueva ecuación de Upscaling. El Upscaling dependede la complejidad de los procesos que se consideran. El objetivo de esta tesis es investigar estos cambios de escala a partir de diferentes procesos subterráneos, incrementando la complejidad: flujo radial, transporte conservativo y transporte reactivo.
Se investiga el Upscaling de flujo por medio de la interpretación de un ensayo hidráulico en un medio heterogéneo. Los ensayos de recuperación se basan en la estimación de la transmisividad, T, a partir de la recuperación de los niveles una vez parado el bombeo. Este tipo de ensayo se puede realizar en pozos donde no es posible llevar a cabo un ensayo convencional a caudal constante. La interpretación del ensayo de recuperación se basa en el modelo simplificado de Jacob. Pero, a menudo los datos de campo no se pueden interpretar usando la teoría basada en la homogeneidad. Se muestra que la heterogeneidad de T puede explicar estas observaciones de campo. También se muestra que el valor local de T alrededor del pozo puede ser deducido de los primeros tiempos de la recuperación del bombeo, asumiendo condiciones ideales, mientras que los datos de los últimos tiempos de la recuperación corresponden a valores representativos a escala regional.
Se considera el Upscaling en transporte conservativo a partir de la interpretación de las colas de curvas de llegada (BTC) de un ensayo de trazadores. La cola se atribuye a la heterogeneidad del acuífero, y no puede ser modelada por medio de la ecuación de advección-dispersión (ADE) en medio homogéneo. Para reproducir las colas observadas se han aplicado ampliamente los modelos de transferencia de masa utilizando memoria (e.g, CTRW, MRMT o fADE). La relación entre los parámetros de memoria obtenidos del ajuste de las BTC y los parámetros que caracterizan la heterogeneidad de las propiedades hidráulicas aun esta por aclarar. En esta tesis se investiga bajo qué condiciones la heterogeneidad produce el tipo de colas observadas en campo, y como las funciones de memoria están influenciadas por parámetros de la heterogeneidad que se pueden medir (e.g, varianza de los campos de transmisividad). Se ha observado que la pendiente de una BTC en un log-log plot está mayoritariamente influenciada por la conectividad del campo de permeabilidades, pero es insensible a su varianza. La pendiente del BTC llega asindóticamente a un valor de 2 cuando aumenta la conectividad.
El modelo expuesto anteriormente se extiende al transporte reactivo multi-componente controlado por la mezcla. A escala de campo, las ecuaciones de transporte reactivo basadas en la ADE sobrestiman las reacciones. El objetivo es ensayar si un modelo MRMT derivado de las observaciones de transporte reactivo, puede ser utilizado para describir el transporte reactivo en medio heterogéneo. La solución numérica del MRMT de transporte conservativo se extiende al caso reactivo. Las tasas de reacción se comparan, entre un modelo heterogéneo y su correspondiente modelo MRMT. Se ha encontrado un excelente acuerdo entre los dos modelos en términos de masa precipitada acumulada y el acuerdo es también muy bueno en relación a la distribución espacial del mineral precipitado. Estos resultados indican que los modelos de transferencia de masa son una herramienta excelente para el Upscaling del transporte reactivo controlado por la mezcla.<br>Heterogeneity of hydraulic conductivity is known to vary orders of magnitudes within small distances. This affects our observations of natural processes. To explain reality we usually rely on simplified models. But to apply them properly information of aquifer properties has to be transferred from local scale where the process can be described directly to the support scale of the measurement and to the grid scale of a numerical model. This procedure is termed upscaling and might involve changing the parameters of the known local scale equation or derivation of a new upscaled equation. Upscaling depends strongly on the complexity of the process under consideration. The objective of this thesis is to investigate these changes of scales for different subsurface processes with increasing complexity: radial flow, conservative transport and reactive transport.First, flow upscaling is investigated for the example of the interpretation of a hydraulic test in a heterogeneous aquifer. Recovery tests are based on estimating transmissivity, T, from the heads that rebound after pumping has stopped. Recovery tests can be performed in wells where conventional constant-rate pumping tests would not be possible. Test interpretation is based on the simple Jacob’s method, related to late time drawdown in an infinite homogeneous aquifer. Yet, field data often cannot be explained by the homogeneous theory. Numerical simulations are performed to show that heterogeneity in T can explain these field observations. It is also shown that the local T value around the well can be inferred from early time recovery data, assuming ideal conditions, whereas late time data yield a large scale (regional) representative value. Even when recovery is observed for a short time, indirect information about the regional value can also be obtained.Second, conservative transport upscaling is considered by interpreting the tailing of breakthrough curves of tracer tests. Tailing is attributed to heterogeneity of aquifer properties and cannot be properly modelled by means of the homogeneous advection-dispersion equation (ADE). Mass-transfer models (e.g., CTRW, MRMT or fADE) using memory have been widely applied for reproducing observed tails. The relationship between memory parameters obtained from BTC fitting and the parameters characterizing the heterogeneity of hydraulic properties is still unclear. Here, the conditions are investigated under which heterogeneity produces the type of tailing observed in the field and how memory functions are influenced by measurable heterogeneity parameters (e.g., variance of the underlying transmissivity field). The slope of a BTC in a log-log plot is found to be mainly influenced by the connectivity of the underlying permeability field, but insensitive to its variance. The slope BTC reaches asymptotically 2 as connectivity increases.And finally, the above model is extended to mixing controlled multi-component reactive transport. At the field scale, reactive transport equations based on the ADE are known tooverestimate reactions. The objective is to test whether a model based on effective dynamics, such as e.g. the Multi-Rate Mass Transfer Method (MRMT), derived from conservative transport observations, can be used to describe effective reactive transport in heterogeneous media. The numerical solution of conservative transport MRMT is extended to the reactive case. The reaction rates are then compared for a binary system computed with the heterogeneous transport model to those corresponding to the reactive MRMT. An excellent agreement is found between the two models in terms of cumulative precipitated mass, and depending on the local heterogeneous structure the match is also very good regarding the spatial distribution of precipitated mineral. These results indicate that mass transfer models are an excellent tool for upscaling of mixing controlled reactive transport.
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Tekelu, Geberetsadike Tegenne. "Modelling reactive transport of acid mine drainage in groundwater : Effect of geochemical processes spatially variable flow source location and distribution." Thesis, KTH, Industriell ekologi, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32579.
Повний текст джерелаАнотація:
Impacts from mining waste deposits on groundwater resources have been recognized invarious parts of the world; though varied in scale depending on the composition of mineralsbeing mined, the level of technology employed and environmental commitment of thedevelopers. Mining activities usually involve milling, concentrating, and processing of oreswhich will result in a huge amount of waste, called tailings, usually deposited inimpoundments as a slurry, composed of fine grained geological material (uneconomicalminerals), chemicals utilized in the processs, and water. Oxidation of these deposits, usuallycontaining sulphide minerals, may result in generation of an acidic, metal laden leachate,callled Acid Mine Drainage (AMD), which may have a devastating impact on thesurrounding groundwater resources. In this study, the stochastic LaSAR-PHREEQC reactive transport modeling approach is usedin order to evaluate the coupled effect of geochemical reactions and physical heterogeneity ofthe subsurface in the breakthrough of acidity and metal downstream of the source while theAMD transported in the water saturated zone of an impoundment. The tailings depositcalled Impoundment 1 at the Kristineberg mining site at the Skellefteå field, in northernSweden, is used as a case study to simulate pH buffering processes and attenuation of Zn.The objectives of the study are 1) to evaluate the relevance of different possible geochemicalprocesses in pH buffering and Zn attenuation; 2) to evaluate the effect of spatial variability ofthe physical processes of the groundwater system on the breakthrough of contaminants; and3) to evaluate the effect of the location and distribution of the source zone in terms of thedistance from the impoundment boundary. Simulation results of the presented model revealed that pH buffering from calcite andchlorite are important processes capable of counteracting the acidification from AMD.Dissolution of secondary Al(OH)3(s) is another important process capable of buffering pH.Precipitation of smithsonite, ZnCO3, is an important process for attenuation of Zn2+.Moreover, sorption of Zn2+ on ferric iron surfaces is found to be an important process forattenuation of the metal, depending on the available sorption surface sites. Flow variabilityhighly affects the breakthrough of the contaminants such that with increasing subsurfaceheterogeneity, earlier breakthrough of contaminants occurs. Moreover, increased variabilityresults in decreased peak loads, but longer duration of the load.<br>www.ima.kth.se
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Gallager, Kevin A. "Mass transfer and biosorption processes with Rhizopus oryzae as an absorbent of reactive dye and metal ions from aqueous effluent." Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364591.
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Kremin, Christoph [Verfasser], Martin [Akademischer Betreuer] Hoffmann, Peter [Akademischer Betreuer] Schaaf, and Uwe [Akademischer Betreuer] Schnakenberg. "Fabrication and application of self-masked silicon nanostructures in deep reactive ion etching processes / Christoph Kremin. Martin Hoffmann. Peter Schaaf. Uwe Schnakenberg." Ilmenau : Universitätsbibliothek Ilmenau, 2010. http://d-nb.info/1008088250/34.
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