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1
Kawesha, David Mukuma. "A mass transfer model for structured packing." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52647.
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Thesis (MScEng) -- Stellenbosch University , 2002.ENGLISH ABSTRACT: The distillation process is the most widely used separating process in the chemical process industry. The optimal design of the distillation units can lead to reduced capital costs and improved energy utilisation. This is particularly the case for structured packed distillation column where design methods tend to over-predict the column efficiency. This work seeks to contribute to the development of a reliable mass transfer model for structured packing. A gas phase mass transfer correlation was developed based on the evaporation of pure components into an air stream. The mass transfer rates were measured in a short triangular wetted wall channel with a corrugated surface wall. The influence that the geometric configuration as well as surface structure has on the mass transfer rates was investigated. The channel geometry and surface wall structure resembled that of the structured packing (Flexipac 350Y). The influence of the channel geometry on the gas mass transfer rates was not significant except at low flow conditions. The liquid phase resistance was investigated for binary mixtures in the triangular wetted wall channel. It was found that the overall mass transfer rate decreased with increasing composition of the volatile component. The enhancement of the gas phase mass transfer rate masked the presence of the liquid resistance. ii The gas phase mass transfer correlations were used in the mass transfer model to predict the separation efficiency of a structured packed distillation column. The structured packing used to validate the mass transfer model was high-capacity Flexipac 350Y and normal Flexipac 350Y. The binary distillation experiments were done at total reflux conditions for the pressure range O.33-1atm. The accuracy of the separation efficiencies of the mass transfer model improved with increasing pressure for both materials. The mass transfer model was able to predict the variation of separation efficiencies with column loadings.
AFRIKAANSE OPSOMMING: Distillasie is die skeidingsmetode wat die meeste in die chemiese industrie gebruik word. Die optimale ontwerp van distillasie eenhede kan lei tot verlagings in kapitaalkostes en 'n verbeterde gebruik van energie. Dit is veral waar in die geval van kolomme met gestruktureerde pakking waar huidige ontwerpsmetodes, die kolomeffektiwiteit nie akkuraat beskryf nie. Hierdie studie het ten doelom 'n bydrae te lewer tot die ontwikkeling van 'n betroubare massa-oordragsmodel vir gestruktureerde pakking. 'n Gasfase massa-oordragskorrelasie is ontwikkel gebaseer op metings van die verdampingstempo van suiwer komponente in 'n lugstroom. Die massaoordragstempos is gemeet in 'n kort driehoekige benatle wand kanaal waarin die wand 'n bepaalde oppervlakprofiel het. Die invloed van beide die kanaalgeometrie en die oppervlakprofiel is ondersoek. Die geometrie en oppervlakprofiel is soorgelyk aan die van Flexipac 350Y gestruktureerde pakking. Die invloed van die kanaalgeometrie op die gasfase massaoordragstempos is slegs beduidend by lae vloeitempos. Die vloeistoffase weerstand vir binêre mengsels is ondersoek in die driehoekige kanaal. Dit is gevind dat die algehele massa-oordragstempo verlaag met 'n verhoging in die konsentrasie van die vlugtige komponent. Die verhoging in die gasfase massa-oordragstempo verberg die invloed van die vloeistoffase weerstand. Die gasfase massa-oordragskorrelasies is in 'n massa-oordragsmodel gebruik om die skeidingseffektiwiteit van gestruktureerde pakking in "n kolom te voorspel. Metings op hoë-kapasiteit Flexipac 350Y en normale Flexipac 350Y is gebruik om die modelvoorspellings te evalueer. Die binêre distillasies is by totale terugvloei gedoen in die drukbereik 0.33 - 1.0 atm. Daar is gevind dat die model meer akkuraat is by hoër drukke. Die massa-oordragsmodel is in staat om die variasie in skeidingseffektiwiteit met veranderende kolomlading te voorspel.
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Caulkin, Richard. "Applications of the DigiPac Model for Particle Packing." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491658.
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Wilkerson, Mary Elizabeth. "Circle Packing in Euclidean and Hyperbolic Geometries." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/32390.
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Given a graph that defines a triangulation of a simply connected surface, it is possible to associate a radius with each vertex so that the vertices represent centers of circles, and the edges denote patterns of tangency. Such a configuration of circles is called a circle packing. We shall give evidence for the existence and uniqueness of circle packings generated by such graphs, as well as an explanation of the algorithms used to find and output a circle packing on the complex plane and hyperbolic disc.Master of Science
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Farhadifar, Reza. "Dynamics of Cell Packing and Polar Order in Developing Epithelia." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244035271841-50183.
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During development, organs with different shape and functionality form from a single fertilized egg cell. Mechanisms that control shape, size and morphology of tissues pose challenges for developmental biology. These mechanisms are tightly controlled by an underlying signaling system by which cells communicate to each other. However, these signaling networks can affect tissue size and morphology through limited processes such as cell proliferation, cell death and cell shape changes,which are controlled by cell mechanics and cell adhesion. One example of such a signaling system is the network of interacting proteins that control planar polarization of cells. These proteins distribute asymmetrically within cells and their distribution in each cell determines of the polarity of the neighboring cells. These proteins control the pattern of hairs in the adult Drosophila wing as well as hexagonal repacking of wing cells during development. Planar polarity proteins also control developmental processes such as convergent-extension. We present a theoretical study of cell packing geometry in developing epithelia. We use a vertex model to describe the packing geometry of tissues, for which forces are balanced throughout the tissue. We introduce a cell division algorithm and show that repeated cell division results in the formation of a distinct pattern of cells, which is controlled by cell mechanics and cell-cell interactions. We compare the vertex model with experimental measurements in the wing disc of Drosophila and quantify for the first time cell adhesion and perimeter contractility of cells. We also present a simple model for the dynamics of polarity order in tissues. We identify a basic mechanism by which long-range polarity order throughout the tissue can be established. In particular we study the role of shear deformations on polarity pattern and show that the polarity of the tissue reorients during shear flow. Our simple mechanisms for ordering can account for the processes observed during development of the Drosophila wing.
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Farhadifar, Reza. "Dynamics of Cell Packing and Polar Order in Developing Epithelia." Doctoral thesis, Technische Universität Dresden, 2009. https://tud.qucosa.de/id/qucosa%3A23750.
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During development, organs with different shape and functionality form from a single fertilized egg cell. Mechanisms that control shape, size and morphology of tissues pose challenges for developmental biology. These mechanisms are tightly controlled by an underlying signaling system by which cells communicate to each other. However, these signaling networks can affect tissue size and morphology through limited processes such as cell proliferation, cell death and cell shape changes,which are controlled by cell mechanics and cell adhesion. One example of such a signaling system is the network of interacting proteins that control planar polarization of cells. These proteins distribute asymmetrically within cells and their distribution in each cell determines of the polarity of the neighboring cells. These proteins control the pattern of hairs in the adult Drosophila wing as well as hexagonal repacking of wing cells during development. Planar polarity proteins also control developmental processes such as convergent-extension. We present a theoretical study of cell packing geometry in developing epithelia. We use a vertex model to describe the packing geometry of tissues, for which forces are balanced throughout the tissue. We introduce a cell division algorithm and show that repeated cell division results in the formation of a distinct pattern of cells, which is controlled by cell mechanics and cell-cell interactions. We compare the vertex model with experimental measurements in the wing disc of Drosophila and quantify for the first time cell adhesion and perimeter contractility of cells. We also present a simple model for the dynamics of polarity order in tissues. We identify a basic mechanism by which long-range polarity order throughout the tissue can be established. In particular we study the role of shear deformations on polarity pattern and show that the polarity of the tissue reorients during shear flow. Our simple mechanisms for ordering can account for the processes observed during development of the Drosophila wing.
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Jefcoate, Barry J. E. "A 3D discrete element model of packing, entrainment and saltation of sediment mixtures." Thesis, University of Aberdeen, 1996. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU094037.
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It is believed that the behaviour of the bed-load fraction of transported sediment as a whole is influenced by the behaviour of the individual grain. At this micro-scale spatial resolution it is difficult to make field and laboratory observations. For this reason, numerical models have found a particular niche. A model has been developed to investigate the interaction between the surface of a bed of multi-sized spherical particles (from a continuous size distribution) and a logarithmic flow velocity profile. The model is based upon the cycle of erosion, transport and deposition. The first phase of operation involves depositing a layer of particles to the pre-determined size distribution. This packing is shown to behave as expected, on evidence from experiments undertaken in the investigation of powders and particulate materials. The surface is exposed to the bottom boundary of a multi-slab flow model with superimposed random fluctuations, the reaction to the sum of the drag forces acting upon the surface particles acts to retard the bottom flow layer. Thus the flow model and the bed model are linked. Particle entrainment is determined from a three dimensional moment analysis of a surface particle about its nearest contacts, subject to fluid and body forces. Once entrained the particle follows a nearly ballistic trajectory until it collides with the bed, from where it can either be deposited or rebound into successive trajectories. In this way the bed is modified. The packing of spheres onto a regular foundation layer shows three distinct regions; an interface layer, an homogeneous region, and a rough surface. Calculated properties or particle size distribution, porosity, a number of particle contacts are reasonably constant in the homogeneous region, diverging towards the foundation and the surface.
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Hilgenfeld, Jonathan. "Anwendungsorientierte Mischungsentwicklung und Ökobilanz eines zementreduzierten Ökobetons." Hochschule für Technik, Wirtschaft und Kultur Leipzig, 2020. https://htwk-leipzig.qucosa.de/id/qucosa%3A73721.
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Die vorliegende Thesis befasst sich mit der Mischungsentwicklung eines zementreduzierten Ökobetons für die Verwendung in einem ökologisch verbesserten Deckensystem. Dafür wurden mithilfe eines in Microsoft Excel aufgestellten physikalischen Analysemodells – dem Compaction-Interaction Packing Model nach FENNIS – Rezepturen entwickelt, die durch eine optimierte Packungsdichte einen geringeren Zementleimbedarf aufweisen. Dabei gelang es, Zement teilweise durch feine Kalksteinmehle zu ersetzen und eine CO2-sparende Mischung mit einem reduzierten Zementgehalt von 150 kg je Kubikmeter Beton herzustellen, welche die an sie gestellten Anforderungen erfüllt – u. a. bezogen auf Festigkeit (Festigkeitsklasse C 20/25), Verarbeitbarkeit (Konsistenzklasse C3) und Alkalität (pH-Wert > 10). Diese Eigenschaften wurden experimentell geprüft. Zwar wurden bei der auf empirischen Daten beruhenden Prognose von Festigkeit und Konsistenz im Modell nur teilweise realitätsnahe Werte ermittelt, das Modell stellte sich insgesamt jedoch als zielführendes Instrument bei der Mischungsentwicklung von Ökobetonen heraus.:1 Einleitung
2 Verringerung der Umwelteinwirkungen bei der Betonherstellung
3 Methodik der Mischungsentwicklung zementreduzierter Ökobetone
4 Packungsdichteberechnung mit dem Compaction-Interaction Packing Model
nach FENNIS
5 Mischungsentwicklung eines Ökobetons im Rahmen des Forschungsvorhabens
GRO-COCE
6 Herstellung der Auswahlmischungen und experimentelle Ermittlung von
Betoneigenschaften
7 Eingrenzung einer Zielmischung
8 Diskussion der Ergebnisse
9 Zusammenfassung und AusblickThe present thesis deals with the mix development of a cement-reduced eco-concrete for the use in an ecologically improved ceiling system. For this purpose, a physical analysis model built in Microsoft Excel – the Compaction-Interaction Packing Model according to FENNIS – was used to develop recipes which, due to an optimised packing density, have a low cement paste requirement. It was possible to partially replace cement with fine limestone powders and to produce a CO2-saving mixture with a reduced cement content of 150 kg per cubic metre of concrete, which meets the requirements placed on it – among other things with regard to strength (strength class C 20/25), workability (consistency class C3) and alkalinity (pH-value > 10). These properties were tested experimentally. Although only partially realistic values were determined in the model for the prediction of strength and consistency based on empirical data, the model turned out to be a suitable instrument for mix developments of eco-concretes.:1 Einleitung 2 Verringerung der Umwelteinwirkungen bei der Betonherstellung 3 Methodik der Mischungsentwicklung zementreduzierter Ökobetone 4 Packungsdichteberechnung mit dem Compaction-Interaction Packing Model nach FENNIS 5 Mischungsentwicklung eines Ökobetons im Rahmen des Forschungsvorhabens GRO-COCE 6 Herstellung der Auswahlmischungen und experimentelle Ermittlung von Betoneigenschaften 7 Eingrenzung einer Zielmischung 8 Diskussion der Ergebnisse 9 Zusammenfassung und Ausblick
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Chao, Chien-Wei. "An Improved Dynamic Particle Packing Model for Prediction of the Microstructure in Porous Electrodes." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5632.
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The goal of this work is to develop a model to predict the microstructure of Li-ion batteries, specifically focusing on the cathode component of the batteries. This kind of model has the potential to assist researchers and battery manufacturers who are trying to optimize the capacity, cycle life, and safety of batteries. Two dynamic particle packing (DPP) microstructure models were developed in this work. The first is the DPP1 model, which simulates the final or dried electrode structure by moving spherical particles under periodic boundaries using Newton's laws of motion. The experience derived from developing DPP1 model was beneficial in making the final model, called DPP2. DPP2 is an improved version of DPP1 that includes solvent effects and is used to simulate the slurry-coating, drying, and calendering processes. Two type of properties were used to validate the DPP1 and DPP2 models in this work, although not every property was used with the DPP1 model. First are the structural properties, which include volume fraction, and electronic and ionic conductivities. Experimental structural properties were determined by analyzing 2D cross sectional images of the battery cathodes. These images were taken through focused ion beam (FIB) planarization and scanning electron microscopy (SEM). The second category are the mechanical properties, which include film elasticity and slurry viscosity. These properties were measured through experiments executed by our group. The DPP2 model was divided into two submodels : active-free and active-composite. The 2D cross sectional images of the simulated structure of the models have a similar particle arrangements as the experimental structures. The submodels show reasonable agreement with the experimental values for liquid and solid mass density, shrink ratio, and elasticity. For the viscosity, both models show shear-thinning behavior, which is a characteristic of slurries. The volume fractions of the simulated structures of the active-free and active-composite models have better agreement with the experimental values, which is also reflected in the 2D cross sectional images of the structure.
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Obeng, George Boakye. "A Game Theoretical Model For Prevention of Meat Contamination at A Meat Packing House." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1302800451.
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Brown, Eric L. "A quadratic partial assignment and packing model and algorithm for the airline gate assignment problem." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-07212009-040541/.
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Pauchet, Morgan. "Application of the derived crystal packing model to molecular crstals grown in solutions or in gels." Rouen, 2007. http://www.theses.fr/2007ROUES056.
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The Derived Crystal Packing (DCP) model has been partly automated. The docking step can be handled by two computer program. They are tested on two couples of enantiomer / racemic compound to underline their structural similarities. The limits of the model are also discussed. A second part of the study is devoted to the experimentation of the crystallization in gel. This technique is tested with the gel precursor Tetramethoxysilane on several organic compounds. Different methods for the crystallization are described. In addition, a theoretical as well as experimental study is carried out on (±) modafinil and covers the two aforementioned themes. The first experimental data allowed the DCP model to predict the crystal structure of the form III, starting from that of form I. Subsequent structural comparisons pointed toward the extensive similarities between the two forms: they share common (001) slices. The possibility of defaults such as twinning is thus suggested. The application of the crystallization in gel to (±) modafinil yielded single crystals of form III and allowed the confirmation of the predicted structure. Careful examination of other grown crystals showed the occurrence of twinning among (±) modafinil form I crystals. The twin law was solved: a stacking fault of (001)form I leading to a form III like interface. Additional experiments on twin crystals raised the question of the structural purity of (±) modafinil form I: several twinned crystals underwent a partial dissolution of lamellar domains which could account for the presence of form III (metastable) into form I (stable), or multitwinningLe modèle appelé "Derived Crystal Packing" a été en partie automatisé. L'étape de docking peut être traitée grâce à deux programmes informatiques. Ils sont testés sur deux couples d'énantiomère / composé racémique afin de souligner leur similitudes structurales. Les limites du modèle sont également discutées. Une seconde partie de l'étude est consacrée à l'expérimentation de la cristallisation en gel. Cette technique est testée avec le précurseur Tétraméthoxysilane sur plusieurs composés organiques. Différentes méthodes de cristallisation sont décrites. Par ailleurs, une étude structurale et expérimentale est conduite sur le (±) modafinil. Les données expérimentales initiales ont permis l'application du modèle DCP et la prédiction de la structure cristalline de la forme III à partir de celle de la forme I. La comparaison des structures révèle les nombreuses similitudes structurales des deux formes: elles présentent des tranches (001) communes. La possibilité de défauts tels que le maclage est mise en avant. L'application de la cristallisation en gel au (±) modafinil a conduit à l'obtention de cristaux de forme III et a ainsi permis de confirmer la structure prédite. L'observation minutieuse des autres cristaux obtenus montre la présence de macles parmi les monocristaux de forme I. La loi de macle a été résolue: il s'agit d'une faute d'empilement de tranches (001)forme I conduisant à une interface de forme III. D'autres expériences sur les cristaux maclés ont soulevé la question de la pureté structurale du (±) modafinil forme I: plusieurs cristaux maclés ont subi une dissolution partielle de domaines lamellaires qui pourraient s'expliquer par la présence de forme III (métastable) dans la forme I (stable), ou de multi-maclage
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Mellor, David W. "Random close packing (RCP) of equal spheres : structure and implications for use as a model porous medium." Thesis, Open University, 1989. http://oro.open.ac.uk/57280/.
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The structure of the Finney Random Close Packing (RCP) of equal spheres has been analysed, together with the influence which such structure exerts over the capillary pressure characteristics of geometrically similar sphere packings. The analysis is centred on the simplicial, or Delaunay cell, which is an irregular tetrahedron with apices defined by four immediate neighbour sphere-centres. In terms of using RCP as a model porous medium, an individual simplicial cell is equivalent to an individual pore. A number of measured pore-size distribution parameters are presented for the Finney packing, from which it is shown from first principles that drainage-imbibition hysteresis is not an intrinsic property of the individual pore. The nature and degree of randomness which characterises the Finney packing is evaluated on two levels. First, by classifying edgelengths as either short or long, seven mutually exclusive cell classes are defined. Using the binomial theorem it is shown that cells (pores) are not random on the level of the individual cell. There are less of the extreme cells (with 6 long edges, or with 6 short edges) and more of the bland cells (with 3 short and 3 long edges) in the Finney packing than predicted on the basis of simple random expectations. Second, the distribution of cell classes within the packing is shown to be essentially homogeneously random. Evidence for extremely slight cell class clustering is found. The drainage and imbibition processes within the packing are simulated using pore-level algorithms. The algorithms utilise both the Haines' insphere approximation and the MS-P approximation for critical drainage meniscus curvature, and the cell cavity insphere radius approximation for critical imbibition meniscus curvature. Good agreement with experimental data is obtained, and the results confirm that drainage-imbibition hysteresis is a direct consequence of the connectivity between cells (pores), and is not an intrinsic property of the individual pore. Finally, the drainage and imbibition algorithms are adapted to emulate percolation theory models. The results prove that the classical bond problem of percolation theory does not adequately describe the drainage process for RCP, and that the classical site problem does not adequately describe the imbibition process for RCP.
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Hofmann, Andreas, Nils Menager, Stephan Schweig, and Lars Mikelsons. "Model-Based Engineering mit Industriesteuerungen." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-163626.
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Das durchgängige Engineering über den gesamten Lebenszyklus ist neben der horizontalen und vertikalen Vernetzung die dritte Säule von Industrie 4.0. Durchgängigkeit im Engineering bedeutet dabei insbesondere Wiederverwendung von Modellen aus vorherigen Entwicklungsphasen. Beispiele hierfür sind die virtuelle Inbetriebnahme sowie die Codegenerierung. Dieser Beitrag stellt dar, wie diese modernen Engineering-Methoden bei der Verwendung von Rexroth Komponenten angewendet werden können. Die Kosten für die Inbetriebnahme neuer technischer Systeme beanspruchen heute einen erheblichen Anteil des Projektbudgets. Insbesondere die Optimierung des Steuerungscodes der Anlage erfordert einen hohen Zeitaufwand. So werden bis zu 70% der Zeit, die für die Inbetriebnahme der Steuerungstechnik benötigt wird, für das Finden und Beheben von Softwarefehlern aufgewendet. Um die Anzahl der Prozessdurchläufe beim Kunden zu reduzieren, kann heute ein großer Anteil dieser Aufgaben virtuell gelöst werden. In diesem Beitrag wird ein Software-Framework für die virtuelle Inbetriebnahme vorgestellt. Dieses Framework kann für mechatronische Systeme, die von Rexroth Komponenten angetrieben werden, eingesetzt werden. Exemplarisch wird dies am Beispiel eines Deltaroboters aus dem Packaging-Bereich präsentiert. Dafür wird die reale SPS-Steuerung der Anlage mit einem Simulationsmodell des Deltaroboters gekoppelt. Zur einfacheren Interpretation der Simulationsergebnisse werden diese mittels einer 3D-Visualisierung graphisch dargestellt. Die Modellierung des Deltaroboters erfolgt in der Modellierungssprache Modelica. Diese eignet sich besonders für domänenübergreifende Systeme. Außerdem erlaubt der objektorientierte Ansatz eine hohe Wiederverwendbarkeit der verwendeten Modelle. Die Kopplung von Rexroth Industriesteuergeräten und der Simulation wurde mit Hilfe des OpenCore-Interfaces realisiert. Die entwickelten Modelle wurden durch Messungen mit verschiedenen Bewegungsabläufen des Deltaroboters bestätigt. Somit ist es möglich, zukünftige Anlagen dieses Typs virtuell in Betrieb zu nehmen und die Anzahl der Iterationen, während der Inbetriebnahme, deutlich zu reduzieren. Dies setzt voraus, dass das imulationsmodell das dynamische Verhalten der Anlage ausreichend genau abbildet. Neben der virtuellen Inbetriebnahme ist die Codegenerierung eine wichtige Technologie, um vorhandene Modelle in weitere Entwicklungsphasen zu übernehmen. Insbesondere erlaubt die Codegenerierung die Übernahme von Modellen in die Betriebsphase des Systems. Der wohl bekannteste Anwendungsfall der Codegenerierung ist das Rapid Control Prototyping. Neben der Möglichkeit zur Generierung von Steuerungscode gibt es jedoch auch Use-Cases, die die Simulation eines physikalischen Systems auf dem Steuergerät voraussetzen. Hierzu zählt beispielsweise die modellbasierte Diagnose, die modellbasierte Regelung oder die virtuelle Inbetriebnahme auf Basis einer Simulation auf dem Steuergerät. In diesem Beitrag wird eine Toolchain zur Generierung von Code aus Modelica, der auf Rexroth Steuergeräten ausgeführt werden kann, vorgestellt.
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Yideti, Tatek Fekadu. "Performance model for unbound grnular materials pavements." Licentiate thesis, KTH, Väg- och banteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-97752.
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Recently, there has been growing interest on the behaviour of unbound granular material in road base layers. Researchers have studied that the design of a new pavement and prediction of service life need proper characterization of unbound granular materials, which is one of the requirements for a new mechanistic design method in flexible pavement. Adequate knowledge of the strength and deformation characteristics of unbound layer in pavements is a prerequisite for proper thickness design, residual life determination, and overall economic optimization of the pavement structure. The current knowledge concerning the granular materials employed in pavement structures is limited. In addition, to date, no general framework has been established to explain satisfactorily the behaviour of unbound granular materials under the complex repeated loading which they experience. In this study, a conceptual method, packing theory-based model is introduced; this framework evaluates the stability and performance of granular materials based on their packing arrangement. In the framework two basic aggregate structures named as Primary Structure (PS), and Secondary Structure (SS). The Primary Structure (PS) is a range of interactive grain sizes that forms the network of unbound granular materials. The Secondary Structure (SS) includes granular materials smaller than the primary structure. The Secondary Structures fill the gaps between the particles in the Primary Structure and larger particles essentially float in the skeleton. In this particular packing theory-based model; the Primary Structure porosity, the average contact points (coordination number) of Primary Structure, and a new parameter named Disruption Potential are the key parameters that determine whether or not a particular gradation results in a suitable aggregate structure. Parameters mentioned above play major role in the aggregate skeleton to perform well in terms of resistance to permanent deformation as well as load carrying capacity (resilient modulus). The skeleton of the materials must be composed of both coarse enough and a limited amount of fine granular materials to effectively resist deformation and carry traffic loads.QC 20120601
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Fernandez, Martinez Pablo Enrique. "THE MAKE-OR-BUY DECISIONS IN ITALCEMENTI PACKING SOLUTIONS : A quantitative approach in the global purchasing strategy context." Thesis, KTH, Industriell ekonomi och organisation (Inst.), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-102835.
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Many multinational corporations find themselves frequently in the dichotomous question of whether to make or buy a given component; but when those companies are operating with a global purchasing strategy, oriented to high levels of centralization and dealing simultaneously with the implications of purchasing and producing the same item, the approach to take the decision becomes difficult to find, even with the current literature and practitioners knowledge This master thesis addresses in a comprehensive proposal the way to undertake this kind of make-or-buy decisions. Through the literature review done, regarding global purchasing strategy, purchasing models, supplier selection methods and make-or-buy frameworks; it was found a convenient model to merge those concepts with the empirical experiences of a single case study in the Italcementi Group, one of the largest Cement producers in the world. The model proposed considers both strategic and economic elements and is designed as an iterative algorithm that evaluates several alternatives in order to arrive to the best make-or-buy approach. The methodologies selected and combined to solve the problem are mostly quantitative, but keeping the importance of qualitative elements within the analysis. The outcome of the thesis is a contribution to academicians and practitioners aiming to turn the existing knowledge about make-or-buy decisions into practical solutions for business management.
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Silva, Everton Fernandes da. "Modelos matemáticos para um problema de caminho de corte." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-04102016-162035/.
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Os problemas de corte e empacotamento são frequentes em diferentes processos produtivos, por exemplo, na produção de roupas, de calçados, de peças metálicas e de móveis. Seu objetivo mais frequente e a minimização do desperdício de matéria-prima. No entanto, em algumas situações, o problema de determinação do caminho de corte e fundamental para eciência do planejamento da produção. Este problema consiste em determinar a trajetória de corte que minimize, por exemplo, o tempo total de corte de um plano de corte previamente estabelecido. Devido a existência de poucas abordagens para este problema, nosso objetivo e propor modelos matemáticos para resolver o problema de determinação do caminho de corte. Além disso, uma variação do problema que considera a utilização de grafos dinâmicos também é abordada. Os resultados obtidos são comparados com resultados da literatura.Cutting and packing problems are frequent in dierent productive process, for example, in the garment, shoe, metallic pieces and furniture production. Its most common objective is the minimization of the raw material waste. However, in some situations, the cutting path determination problem is fundamental to the eciency of the production planning. This problem consists in determining the cutting trajectory that minimizes, for example, the total cutting time of a previously established cutting plane. Due to the few existing approaches to this problem, our objective is to propose mathematical models to solve the cutting path determination problem. Furthermore, a variation of the problem that considers the use of dynamic graphs is also adressed. The obtained results are compared with those from the literature.
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Ladewig, Leon [Verfasser], Susanne [Akademischer Betreuer] Albers, Thomas [Gutachter] Kesselheim, and Susanne [Gutachter] Albers. "Online Algorithms for Packing Problems in the Random-Order Model / Leon Ladewig ; Gutachter: Thomas Kesselheim, Susanne Albers ; Betreuer: Susanne Albers." München : Universitätsbibliothek der TU München, 2021. http://d-nb.info/1237815789/34.
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Nikiema, Sompassaté Josiane. "Attenuation of greenhouse gas emissions by means of methane biofiltration optimization of the operating parameters." Thèse, Université de Sherbrooke, 2008. http://savoirs.usherbrooke.ca/handle/11143/1911.
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The main goal of this work has been that of optimizing the operating conditions of a biofilter, intended for the control of methane, an important greenhouse gas widely emitted by older or smaller landfill installations.The specific objectives were: (1) to select a suitable packing material (of organic or inorganic type); (2) to optimize the concentrations of input nutrients, mainly consisting of nitrogen, phosphorus, potassium and copper, which are intended to be introduced via the nutrient solution; (3) to determine the optimized values of the most important design parameters, such as the methane inlet load (which depends on the air flow rate and the inlet methane concentration); and (4) to model the biofilter performance. Firstly, the comparison of the two packing materials, one of organic type, and the other of inorganic type, has revealed that the latter was the more appropriate material for the methane biofiltration. Then, through the use of the selected packing material, the influence of each individual nutrient on the efficiency of the process has been investigated.The results obtained have shown that both nitrogen and phosphorus concentrations have to be controlled, while potassium and copper were revealed as being nutrients of only minor importance. Secondly, the optimization of the inlet gas flow rate and of the inlet methane concentration (and consequently, of the methane inlet load also), has been performed. According to the results of the studies, these parameters require good control during methane biofiltration because a limitation in biofilter performance could otherwise be induced. In addition, it was noted that the increase in the inlet gas flow rate led generally to a greater decrease of the methane conversion than the one induced by the inlet methane concentration. Finally, a new method, based on the use of solid extracts sampled from the methane biofilter, has been applied to the determination of methane biofilter kinetic parameters. Following this study, a steady state model of the methane biofiltration, taking into consideration the important operational parameters, as identified previously, has been developed. One particular feature of this model is that it takes into consideration the influence of the biofilter average temperature.The prediction results, obtained with the use of the model, have been successfully compared with the experimental results.
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Sohail, Raveed, and Sai Anuroop Nimmagadda Bhavani. "Calculation Method and Tool to Visualize Cable Harness Usage in Trucks." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-17754.
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Cable harness is an integral part of a modern-day automobile. The design of many mechanical components is based on the cable harness and hence it is important to accurately calculate the space occupied by cable harness. In this thesis, a theoretical model representing n arbitrarily sized cables was used to generate a packing of the cable harness, and the space occupied by them was calculated. The model was used to develop an algorithm that generated a feasible configuration and a container around that packing. The optimisation toolbox in MATLAB was also used to calculate the space and optimise the container size. A customised standalone tool was developed in MATLAB by utilising the established methods, that enables calculation of space occupied by cables at various points of interest along the truck chassis for Scania CV.
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Dury, Olivier. "Organic pollutants in unsaturated soils : effect of butanol as a model contaminant on phase saturation and flow characteristics of a quartz sand packing /." [S.l.] : [s.n.], 1997. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=12270.
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Antomarchi, Anne-Lise. "Conception et pilotage d'un atelier intégrant la fabrication additive." Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC035/document.
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La fabrication additive est un domaine en plein essor. Cependant, les industriels sont aujourd’hui dans une phase d’interrogation sur l’utilisation de ce procédé dans le cadre d’une production de masse. La problématique posée dans le cadre de ces travaux de recherche est : Comment rendre viable, industriellement, le procédé de fusion sur lit de poudre ? Nos travaux abordent la conception et le pilotage d’ateliers intégrant la fabrication additive et le processus complet d’obtention de la pièce selon les trois niveaux de décision : stratégique, tactique et opérationnel. D’un point du vue stratégique, des décisions fortes d’investissement, de sélection de machines et de choix d’organisation sont à prendre avec des enjeux économiques importants. L’objectif est de définir une méthode d’optimisation multicritère pour la conception modulaire d’un système de production intégrant la fabrication additive en présence de données incertaines, optimale sur le long terme et sur le court terme. D’un point de vue tactique, toutes les pièces ne sont pas forcément des candidates pertinentes pour la fabrication additive. Dans ces travaux, nous avons développé un outil d’aide à la décision qui évalue la pertinence ou non de la fabrication additive pour l’obtention des pièces dans une approche globale des coûts. Au niveau opérationnel, nous proposons un outil basé sur la simulation de flux qui permet de passer des commandes aux ordres de fabrication et leur ordonnancement de manière à garantir l’efficience de l’atelier. Ces travaux de recherche sont développés en lien avec des acteurs du monde industriel : AddUp, MBDA et Dassault qui alimentent nos travaux et nous permettent de confronter nos outils à une réalité industrielleThe additive manufacturing is a field on the rise. However, companies wonder about the use of additive manufacturing for mass production. The problem raised in the context of this thesis is: How to make the process of sintering laser melting industrially viable? Our work focuses on the design and on the management of workshops integrating the additive manufacturing and of the complete process to obtain part according to three levels of decision: strategic, tactic and operational. About the strategic level, strong decisions of investment, machines selection and organization choice are taken with important economic issues. The aim is to define a multicriteria optimization method for the modular design of a production system integrating the additive manufacturing in the presence of uncertain data, optimal in the long term and the short term. From a tactical point of view, not all parts are necessarily relevant candidates for additive manufacturing. In this work, we developed a decision support tool that evaluates the relevance or not of additive manufacturing to obtain parts in a global cost approach. At the operational level, we offer a tool based on flow simulation that allows orders to be placed to production orders and their scheduling in order to guarantee the efficiency of the workshop. This research work is developed in collaboration with companies: AddUp, MBDA and Dassault, who contribute to our work and enable us to compare our tools with an industrial reality
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Tagliaferri, de Grazia Mayra. "Contribution to the Understanding of Fresh and Hardened State Properties of Low Cement Concrete." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38109.
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Concrete, the major construction material used in the civil industry worldwide, displays remarkable performance and economic benefits. Yet, it also presents a huge environmental impact producing about 7% of the global carbon dioxide (CO2). Given the rise of global warming concerns, studies have been focusing on alternatives to reduce the amount of Portland cement (PC), which is the least sustainable ingredient of the mixture, for example by adopting particle packing model (PPM) techniques. Although a promising alternative, there is currently a lack of studies regarding the efficiently use of PPMs to reduce PC without compromising the fresh and hardened properties of the material. This work appraises the influence of PPMs and advanced mix-design techniques on the fresh (rheological behaviour) and hardened (compressive strength, modulus of elasticity, porosity, and permeability) state behaviours of systems with reduced amount of PC, the so-called low cement content (LCC) concrete. Results show that is possible to produce eco-efficient concrete maintaining and/or enhancing fresh and hardened properties of the material. Nevertheless, further durability and long-term behaviour must be performed on LCC systems.
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Mackura, Mark. "Nano-confinement Effects of Crystalline Walls on the Glass Transition of a Model Polymer." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1366815752.
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De, Freitas Macedo Hian. "Concrete Made with Fine Recycled Concrete Aggregate (FRCA): A Feasibility Study." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39619.
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In the process of crushing concrete waste, significant amounts of fine by-products, the so called fine recycled concrete aggregates (FRCA), are generated and excluded from potential use. Limited research has thoroughly investigated the performance of concrete mixes with FRCA, very likely due to the complexity in analysing non-negligible amounts of adhered residual cement paste (RCP). Although some studies have proposed promising sustainable mix-design procedures accounting for the different microstructure when using coarse recycled concrete aggregates (CRCA), no similar approach exists for FRCA concrete. In this work, two promising procedures for mix-designing eco-efficient concrete with 100% FRCA are proposed accounting for the presence of RCP to reduce cement content in new mixtures. First, built on top of the existing procedure for CRCA mix-design, modifications to the Equivalent Volume (EV) method were introduced toconsider full replacement of fine natural sand by FRCA. Second, based on the concept of continuous Particle Packing Models (PPM), an optimized procedure was proposed to allow maximum packing density of FRCA mix linked to a given level of measured RCP content. Results verified the feasibility of producing eco-efficient concrete mixes with 100% FRCA, emphasizing the PPM mixes to report superior rheological and mechanical performance along with suitable durability-related properties. Yet, results also indicated the influence of simple or multistage crushed FRCA on the overall performance of mixes.
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Fraga, Keith Jeffrey. "Explorations into protein structure with the knob-socket model." Scholarly Commons, 2016. https://scholarlycommons.pacific.edu/uop_etds/264.
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Protein sequences contain the information in order for a protein to fold to a unique compact, three-dimensional native structure. The forces that drive protein structures to form compact folds are largely dominated by burial of hydrophobic amino acids, which results in non-specific packing of amino acid side-chains. The knob-socket model attempts to organize side-chain packing into tetrahedral packing motifs. This tetrahedral motif is characterized with a three residues on the same secondary structure forming the base of the tetrahedron packing with a side-chain from a separate secondary structure. The base of the motif is termed the socket, and the other side-chain is called the knob. Here, we focus on extending the knob-socket model to understand tertiary and quaternary structure. First, single knobs sometimes pack into more than one socket in real structures. We focus on understanding the topology and amino acid preferences of these tertiary packing surfaces. The main results from the study of tertiary packing surfaces is that they have a preferred handedness, some interactions are ancillary to the packing interaction, there are specific amino preferences for specific positions in packing surfaces, and there is no relationship between side-chain rotamer of the knob packing into the tertiary packing surface. Next, we examine the application of the knob-socket to irregular and mixed packing in protein structure. The main conclusions from these efforts show canonical packing modes between secondary structures and highlight the important of coil secondary structure in providing many of the knobs for packing. Third, we investigate protein quaternary structure with a clique analysis of side-chain interactions. We identify a possible pseudo knob-socket interaction, and compare knob-socket interactions between tertiary and quaternary structure. Lastly, we discuss the workflow used in CASP12 to predict side-chain contacts and atomic coordinates of proteins.
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Bartlok, Guido. "Untersuchungen zur Neuverteilung der Rücklaufflüssigkeit in Packungskolonnen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2002. http://nbn-resolving.de/urn:nbn:de:swb:14-1038918418015-57600.
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Bei der Rektifikation werden heute zunehmend Füllkörperkolonnen mit geordneten Packungen eingesetzt. Die Maldistribution, ein bislang ungelöstes Problem in Füllkörperkolonnen, wirkt sich negativ auf die Stoffaustauschleistung aus. Zur Verringerung der Maldistribution wird zwischen den Packungssektionen mehrfach die Rücklaufflüssigkeit gesammelt und erneut gleichmäßig über den Kolonnenquerschnitt verteilt. Diese Neuverteilung realisieren Zwischenverteiler, die somit einen Großteil der Kolonnenhöhe beanspruchen und damit die Investitions- und Betriebskosten erheblich erhöhen. Hauptursache für die Bauhöhe der Zwischenverteiler ist der Wunsch nach einem vollständigen Konzentrationsausgleich vor der Neuverteilung. Um die Kolonnenhöhe zu verringern und dennoch die gleiche Trennleistung zu erreichen, mangelt es den Anlagenbauern bislang an einer praktikablen Lösung. Entgegen der bisherigen Lehrbuchmeinung wird in dieser Arbeit die Bedeutung des vollständigen Konzentrationsausgleich grundsätzlich in Frage gestellt. Es erfolgen deshalb theoretische und experimentelle Untersuchungen für ein besseres Verständnis der Neuverteilung der Rücklaufflüssigkeit und deren Auswirkung auf die Trennleistung. Durch Modifizierung des klassischen Zwei-Kolonnen-Modells gelingt es, den Einfluss der Maldistribution, der Dampfquervermischung und der hydraulisch gleichmäßigen Flüssigkeitsneuverteilung mit und ohne vollständigen Konzentrationsausgleich numerisch zu simulieren. Die Überprüfung der Simulationsmodelle erfolgt an einer Pilotkolonne mit einem inneren Durchmesser von 1 m. Die Kolonne ist mit Sulzer MellapakPlus 752.Y ausgerüstet und als Testgemisch dient trans-/cis-Dekalin. Im Ergebnis zeigt sich, dass vor allem der hydraulische Ausgleich erforderlich ist und es praktisch keinen Unterschied zwischen vollständigen und unvollständigen Konzentrationsausgleich bei sonst gleichen Betriebsbedingungen gibt. Überlegungen für deutlich flachere Verteilerkonstruktionen werden vorgestellt.
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Lobato, Rafael Durbano. "Ellipsoid packing." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/45/45134/tde-24022017-134632/.
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The problem of packing ellipsoids consists in arranging a given collection of ellipsoids within a particular set. The ellipsoids can be freely rotated and translated, and must not overlap each other. A particular case of this problem arises when the ellipsoids are balls. The problem of packing balls has been the subject of intense theoretical and empirical research. In particular, many works have tackled the problem with optimization tools. On the other hand, the problem of packing ellipsoids has received more attention only in the past few years. This problem appears in a large number of practical applications, such as the design of high-density ceramic materials, the formation and growth of crystals, the structure of liquids, crystals and glasses, the flow and compression of granular materials, the thermodynamics of liquid to crystal transition, and, in biological sciences, in the chromosome organization in human cell nuclei. In this work, we deal with the problem of packing ellipsoids within compact sets from an optimization perspective. We introduce continuous and differentiable nonlinear programming models and algorithms for packing ellipsoids in the n-dimensional space. We present two different models for the non-overlapping of ellipsoids. As these models have quadratic numbers of variables and constraints, we also propose an implicit variables models that has a linear number of variables and constraints. We also present models for the inclusion of ellipsoids within half-spaces and ellipsoids. By applying a simple multi-start strategy combined with a clever choice of starting guesses and a nonlinear programming local solver, we present illustrative numerical experiments that show the capabilities of the proposed models.O problema de empacotamento de elipsoides consiste em arranjar uma dada coleção de elipsoides dentro de um determinado conjunto. Os elipsoides podem ser rotacionados e transladados e não podem se sobrepor. Um caso particular desse problema surge quando os elipsoides são bolas. O problema de empacotamento de bolas tem sido alvo de intensa pesquisa teórica e experimental. Em particular, muitos trabalhos têm abordado esse problema com ferramentas de otimização. O problema de empacotamento de elipsoides, por outro lado, começou a receber mais atenção apenas recentemente. Esse problema aparece em um grande número de aplicações práticas, como o projeto de materiais cerâmicos de alta densidade, na formação e crescimento de cristais, na estrutura de líquidos, cristais e vidros, no fluxo e compressão de materiais granulares e vidros, na termodinâmica e cinética da transição de líquido para cristal e em ciências biológicas, na organização de cromossomos no núcleo de células humanas. Neste trabalho, tratamos do problema de empacotamento de elipsoides dentro de conjuntos compactos do ponto de vista de otimização. Introduzimos modelos de programação não-linear contínuos e diferenciáveis e algoritmos para o empacotamento de elipsoides no espaço n-dimensional. Apresentamos dois modelos diferentes para a não-sobreposição de elipsoides. Como esses modelos têm números quadráticos de variáveis e restrições em função do número de elipsoides a serem empacotados, também propomos um modelo com variáveis implícitas que possui uma quantidade linear de variáveis e restrições. Também apresentamos modelos para a inclusão de elipsoides em semi-espaços e dentro de elipsoides. Através da aplicação de uma estratégia multi-start simples combinada com uma escolha inteligente de pontos iniciais e um resolvedor para otimização local de programas não-lineares, apresentamos experimentos numéricos que mostram as capacidades dos modelos propostos.
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Giang, Anh Tuan. "Capacity of vehicular Ad-hoc NETwork." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-00989836.
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In recent years, Inter Vehicle Communication (IVC) has become an intensive research area, as part of Intelligent Transportation Systems. It supposes that all, or a subset of the vehicles is equipped with radio devices, enabling communication between them. IEEE 802.11p (standardized for vehicular communication) shows a great deal of promise. By using ad hoc mode, this radio technology allows vehicles to extend their scopes of communication and thus forming a Multi-hop wireless Ad-hoc NETwork, also called Vehicular Ad-hoc NETwork (VANET). This thesis addresses a fundamental problem of VANET: the network capacity. Two simple theoretical models to estimate this capacity have been proposed: a packing model and a Markovian point process model. They offer simple and closed formulae on the maximum number of simultaneous transmitters, and on the distribution of the distance between them. An accurate upper bound on the maximum capacity had been derived. An analytical formula on distribution of the transmitters had been presented. This distribution allows us to optimize Clear Channel Assessment (CCA) parameters that leads to an optimization of the network capacity.In order to validate the approach of this thesis, results from the analytical models are compared to simulations performed with the network simulator NS-3. Simulation parameters was estimated from real experimentation. Impact of different traffic distributions (traffic of vehicles) on the network capacity is also studied. This thesis also focuses on extended perception map applications, which use information from local and distant sensors to offer driving assistance (autonomous driving, collision warning, etc.). Extended perception requires a high bandwidth that might not be available in practice in classical IEEE 802.11p ad hoc networks. Therefore, this thesis proposes an adaptive power control algorithm optimized for this particular application. It shows through an analytical model and a large set of simulations that the network capacity is then significantly increased.
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Roquier, Gérard. "Etude de la compacité optimale des mélanges granulaires binaires : classe granulaire dominante, effet de paroi, effet de desserrement." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1001/document.
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La compacité des matériaux granulaires est une grandeur qui intéresse un grand nombre de secteurs, notamment les bétons hydrauliques. Lorsque les fractions granulaires ne possèdent pas des rapports de tailles infinis, deux interactions géométriques se développent : l’effet de paroi et l’effet de desserrement. La première peut se décrire ainsi : une grosse particule isolée constitue un « intrus » contre lequel viennent se ranger les petites particules, créant un supplément de vides à l’interface. La seconde se produit lorsque les petits grains sont insuffisamment fins pour se glisser entre les gros. Nous analysons comment elles sont prises en compte dans un certain nombre de modèles d’empilement en nous fixant finalement sur celui de de Larrard et al. : le modèle d’empilement compressible (MEC), l’un des plus efficaces. Dans celui-ci, les effets de paroi et de desserrement sont quantifiés par l’intermédiaire de deux coefficients dont les expressions sont obtenues par lissage de données expérimentales en fonction du rapport des diamètres fins/gros. Cependant, il n’existe aucune théorie pleinement satisfaisante permettant de les obtenir. Cette thèse vise à combler ce chaînon manquant. Nous avons conduit notre étude dans le cadre des empilements ordonnés et compacts de particules afin d’être en adéquation avec les hypothèses de constitution du MEC qui propose, comme préalable à l’obtention de la compacité réelle, la détermination d’une compacité virtuelle définie comme la compacité maximale susceptible d’être atteinte si l’on pouvait déposer, un à un, chaque grain à son emplacement idéal. Cette façon de procéder permet la création de cellules élémentaires juxtaposées. Dans ce cadre, l’interaction exercée par une espèce granulaire sur une autre de taille différente est menée à partir d’une étude localisée autour d’une particule « intruse » de la classe dominée, entourée de particules de la classe dominante. La simulation numérique apporte une confirmation de la validité du modèle. En plus de fournir des coefficients d’effets de paroi et de desserrement très proches de ceux prédits théoriquement, elle a permis l’étude d’empilements désordonnés de compacité maximale pour des billes bidispersées sans frottement dont les rapports de tailles valent 0,2 et 0,4. Le concept de « pressions partielles », qui tient compte à la fois des aspects géométrique et mécanique, a permis d’affiner la notion de classe dominante et de mieux appréhender la constitution du squelette porteur de l’édifice granulaire. En plus des zones constituées par les « fins dominants » et par les « gros dominants », il existe une zone mixte que nous avons dénommée « zone de synergie du squelette porteur » où les « pressions partielles » fines-grosses sont les plus importantes. En tenant compte de la nouvelle théorie développée pour les interactions géométriques, le modèle d’empilement compressible (MEC) subit une évolution et devient le MEC 4-paramètres, qui sont : les coefficients d’effet de paroi et d’effet de desserrement, le rapport de tailles de caverne critique et l’indice de compaction du mélange. Ce dernier ayant subi un nouvel étalonnage, le MEC 4-paramètres montre son efficacité quant à la prédiction de compacités sur mélanges binaires à partir de l’analyse de 780 résultats obtenus sur différents types de matériaux. Enfin, un modèle visant à prédire la viscosité d’une suspension concentrée de particules sphériques multidimensionnelles suspendues dans un fluide visqueux est présenté. Compatible avec la relation d’Einstein, il fait appel au concept de changement d’échelle de Farris et à une loi de viscosité de type Krieger-Dougherty. Lorsque la fraction volumique de solide atteint sa valeur critique, la suspension devient empilement et le mélange atteint la compacité du squelette solide déterminée par le MEC 4-paramètresPacking density of granular materials is a quantity which interests many sectors, in particular hydraulic concrete. When two monodimensional grain classes have no very different sizes, two geometrical interactions develop : the wall effect and the loosening effect. The first one express the perturbation of the packing of the small grains at the interface between large and small grains. The second one occurs when small grains are not enough fine to insert into small cavities created by the touching larger grains. We analyze how they are taken into account in existing packing models. We select finally the compressible packing model (CPM) of de Larrard et al., one of the most effective. In this one, wall effect and loosening effect are quantified by two coefficients. They can, of course, be calculated from experimental results on binary mixtures, as a function of fine/coarse diameter ratios. However, there is no satisfactory theory allowing to calculate them. This doctoral thesis is done to fill this missing link. Ordered and very packed piles of particles are used as a reference frame to be in adequation with the CPM assumptions which require, before the calculation of the real packing density, the determination of a virtual packing density. The latter is defined as the maximum packing density attainable if each particle could be positioned in its ideal location. This approach allows the creation of elementary juxtaposed cells. In that context, the effect of a smaller grain (loosening effect) or a larger grain (wall effect) on the packed class is based on the study of a foreign sphere surrounded by dominant class neighbours. The numerical simulation confirms the validity of the model. In addition to predict wall effect and loosening effect coefficients close to those determined theoretically, numerical simulation was used to predict the solid fraction of maximally dense disordered packings of bidisperse spherical frictionless particles with 0,2 and 0,4 size ratios. The « partial pressures » concept, that includes both geometrical and mechanical aspects, allows to complete and improve the notion of dominant class and to better understand the build-up of the granular skeleton. In addition with « small grains packed » and « large grains packed » zones, the numerical simulation has highlighted a joint zone, called « synergism zone of the granular skeleton » where « partial pressures » fine-large particles are the most important. With this new theory developed for geometrical interactions, the compressible packing model (CPM) is evolving to the new 4-parameter CPM which are : the wall effect coefficient, the loosening effect coefficient, the critical cavity size ratio and the compaction index of the mixing, which requires a new recalibration. The 4-parameter CPM demonstrates its efficiency to predict the packing density of binary mixtures from the analysis of 780 results obtained on different types of materials. Finally, a model intended to predict the viscosity of a multimodal concentrated suspension with spherical particles suspended in a viscous fluid is presented. We resort to the iterative approach advocated by Farris and to a power-law relation (Krieger-Dougherty type) for the relative viscosity, compatible with the Einstein relation appropriate for a dilute suspension. When the solid volume fraction reaches its critical value, the suspension is jammed and the mixture reaches the packing density of the solid skeleton calculated with the 4-parameter CPM
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Zheng, Xiao-Qin Materials Science & Engineering Faculty of Science UNSW. "Packing of particles during softening and melting process." Awarded by:University of New South Wales. School of Materials Science & Engineering, 2007. http://handle.unsw.edu.au/1959.4/31517.
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Softening deformation of iron ore in the form of sinter, pellet, and lump ore in the cohesive zone of an ironmaking blast furnace is an important phenomenon that has a significant effect on gas permeability and consequently blast furnace production efficiency. The macroscopic softening deformation behavior of the bed and the microscopic deformation behavior of the individual particles in the packed bed are investigated in this study using wax balls to simulate the fused layer behavior of the cohesive zone. The effects of softening temperature, load pressure, and bed composition (mono - single melting particles, including pure or blend particles vs binary ??? two different melting point particles) on softening deformation are examined. The principal findings of this study are: 1. At low softening temperatures, an increase in load pressure increases the deformation rate almost linearly. 2. At higher softening temperatures, an increase in load pressure dramatically increases the deformation rate, and after a certain time there is no more significant change in deformation rate. 3. The bed deformation rate of a mono bed is much greater than that of a binary one. 4. In a binary system, the softening deformation rate increases almost proportionally with the increase in the amount of lower melting point wax balls. 5. In a mono system with blend particles, the content of the lower melting point material has a more significant effect on overall bed deformation than the higher melting point one. 6. The macro softening deformation of the bed behaves the theory of creep deformation. 7. A mathematical model for predicting bed porosity change due to softening deformation based on creep deformation theory has been developed. 8. Increase in load pressure also reduces the peak contact face number of the distribution curves, and this is more prominent with higher porosity values. 9. The contribution of contact face number to bed porosity reduction is more pronounced in a mono system than in a binary system. 10. The porosity reduction in a binary bed is more due to the contact face area increase, presumably of the lower melting point particles. 11. The mono system has a single peak contact face number distribution pattern while the binary system exhibits a bimodal distribution pattern once the higher melting point material starts to deform. 12. In a binary system, an increase in deformation condition severity tends to reduce the contact face number of the higher melting point material without having to increase the contact face number of the lower melting point material accordingly to achieve a given porosity.
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Kim, Injoong. "Development of a knowledge model for the computer-aided design for reliability of electronic packaging systems." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22708.
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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2008.Committee Co-Chair: Peak, Russell; Committee Co-Chair: Sitaraman, Suresh; Committee Member: Paredis, Christiaan; Committee Member: Pucha, Raghuram; Committee Member: Wong, C.
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Weyers, Megan. "Optimised mix composition and structural behaviour of Ultra-High-Performance Fibre Reinforced Concrete." Diss., University of Pretoria, 2020. http://hdl.handle.net/2263/73097.
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The overall objective of this study was to develop an optimised Ultra-High-Performance Concrete (UHPC) matrix based on the modified Andreasen and Andersen optimum particle packing model by using available South African materials. The focus of this study was to determine the optimum combined fibre and superplasticiser content for UHPC by using a response surface design.
The UHPC was appropriately designed, produced and tested. Various changes in mechanical properties resulting from different combinations of steel fibre and superplasticiser contents was investigated. The flowability, density and mechanical properties of the designed UHPC were measured and analysed. Both the fibre and superplasticiser content play a significant role in the flowability of the fresh concrete. The addition of fibres significantly improved the strength of the concrete. The results show that the superplasticiser content can be increased if a more workable mix is required without decreasing the strength significantly. The statistical analysis of the response surface methodology confirms that the designed models can be used to navigate the design space defined by the Central Composite Design. The optimum combined fibre and superplasticiser content depend on the required mechanical properties and cost. Using the modified Andreasen and Andersen particle packing model and surface response design methodology, it is possible to efficiently produce a dense Ultra-High-Performance Fibre Reinforced Concrete (UHPFRC) with a relatively low binder amount, low fibre content and good workability.
The effect of heat curing on the mechanical properties was investigated. It was concluded that heat curing is not recommended when considering the long-term strength development. The estimated strength development of concrete obtained by using the fib Model Code 2010 (2013) does not incorporate the detrimental effect of high curing temperatures on long-term strength and therefore overestimate the long-term strengths. The strength estimates for both early and long-term ages can be improved by considering this effect in the strength development functions obtained from fib Model Code 2010 (2013).
The effect of specimen size on the compressive and flexural tensile strength of UHPFRC members were established. It was found that the specimen size has a significant effect on the measured cube compressive strength. Smaller beam specimens showed higher ductility compared to those of the larger beam specimens. The crack width decreased as the beam’s depth decreased. A lower variability was experienced in the beams with limited depth (< 45 mm). Further testing is required to determine whether a span-to-depth ratio of 10 would yield optimum results.
The utilisation of by-products, such as undensified silica fume and fly ash, as cement replacement materials makes UHPFRC sustainable, leading to a reduced life-cycle cost. The calculated Embodied Energy per unit strength (EE/unit strength) and Embodied Carbon per unit strength (EC/unit strength) values for the UHPFRC mixture yield lower values compared to that of the 30 MPa concrete mixture, indicating that UHPFRC can be used to reduce the environmental footprint of the concrete industry.
The inverse analysis method used was successful in providing an improved simplified stress-strain response for the UHPFRC. The analysis provided valuable information into the stress-strain, load-deflection and moment-curvature responses of the UHPFRC. Standard material test results were used to theoretically calculate moment-curvature responses and were then compared to the experimental results obtained.
The study demonstrated that it is possible to efficiently produce a dense and workable UHPFRC with relatively low binder amount and low fibre content. This can result in more cost-effective UHPFRC, thus improving the practical application thereof.Dissertation (MEng)--University of Pretoria, 2020.
Civil Engineering
MEng (Structural engineering)
Unrestricted
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Wong, Chun Chuen. "Graph approach modeling and optimal heuristics for the one-dimensional cutting and packing problems." HKBU Institutional Repository, 2002. http://repository.hkbu.edu.hk/etd_ra/444.
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Jasek, Megan Cathleen. "Building an interactive occupant packaging model with human figure." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/37778.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (p. 91-93).
by Megan Cathleen Jasek.
M.Eng.
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Huang, Kuo-Li. "A conceptual model of packaging design for E-commerce." Thesis, Sheffield Hallam University, 2005. http://shura.shu.ac.uk/19839/.
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Packaging is a "salesman" which is used as a marketing tool to assist product sales and deliver product information and attract consumers in conventional marketplaces. It also gives producers a voice in the retail environment. Since the introduction of E-commerce in the 1990's, these functions of packaging have not yet been reproduced in the virtual environment for products sold online. This research explores the meaning by which "online packaging" can be designed and implemented. Many researchers have identified that consumers find it difficult to buy online, due to poor product presentation and insufficient product information. They can easily obtain these functional advantages from physical packaging. Thus, the aim of this research is to explore a design guideline of online packaging for designers to better apply packaging thinking for products sold online. This research starts with practical work which contains five tentative studies and a final "laboratory online shop" providing a continuing process of development and evaluation of the research questions and engaging design principles. Rapid ethnographic methods were employed for the data collection. The data analysis and the practical design of online packaging were informed by the theory of Elaboration Likelihood Model (ELM). The result of the "laboratory online shop" is mainly consistent with the ELM's prediction and the research has resulted in design guidelines for online packaging, providing a framework for designers of online packaging. The guidelines integrate packaging thinking, the rapid ethnographic approaches and applications of the ELM theory, offering an opportunity for designers to apply the functions of packaging to products sold online. The approach helps designers to collect relevant background information before they design and evaluate developing designs. The guidelines influence designers to have a dual consideration of messages for consumers informed by the ELM's concept of "involvement" during the development of online packaging. Finally, a successful design of online packaging will not only depend on the designers, but retailers and manufacturers will also need to establish the infrastructure of an online shop, so that designers can apply online packaging to eCommerce.
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Tsukruk, Vladimir, Nikolay Mischenko, Peter Köberle, and André Laschewsky. "The structural order of some novel ionic polymers; 2. : Models of molecular packing." Universität Potsdam, 1992. http://opus.kobv.de/ubp/volltexte/2009/1725/.
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The molecular packing and spatial correlations of two isomeric zwitterionic polymethacrylates and one polyacrylate analog are studied by means of X-ray analysis and conformational calculations. The analysis of the correlation functions and density distribution profiles suggest a double-layered molecular packing which is discussed for the three polymers investigated, with respect to their different chemical structures. Whereas the zwitterionic polymethacrylates studied exhibit liquid-like short-range order, the polyacrylate analog exhibits an ordered double-layered superstructure.
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Wilks, Elizabeth. "A new international food packaging hygiene model : a model of compliance for self-regulation." Thesis, Cardiff Metropolitan University, 2012. http://hdl.handle.net/10369/6481.
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This research is the first of its kind in not only reviewing how the UK food packaging industry introduced a voluntary code of practice for packaging hygiene but also in developing a set of guiding principles for companies to adopt it. Given the context of operating within the food supply where hygiene remains paramount, the challenge for the food packaging industry in the UK was to meet the high hygiene expectations of the food manufacturers and retailers. Prior to the Global Packaging Hygiene Standard, many audits were carried out by food manufacturer and retailer visits measuring against their own individual hygiene criteria. The food and packaging manufacturers spent a great deal of time and money preparing for each audit. They were also faced with rising costs caused by the need to audit a global supply chain. The need for a universal hygiene standard for food packaging was escalated by these rising costs and the need to demonstrate and defend the process in place, beyond reasonable doubt for the food packaging hygiene risk. The BRC (British Retail Consortium), an association representing the British retailer, had already used a working group method for the development of a common UK food hygiene standard (BRC Food standard). It was therefore a logical extension of this to also address the quality and hygiene levels of the packaging being used in food manufacture, storage and distribution. The first universal Global food packaging hygiene standard was launched together with the Institute of Packaging (the UK Packaging Association) in 2001 (BRC & IOP, 2001). The key principles for a model of compliance for companies seeking to adopt this standard are achieved through a variety of research methods: - surveys, audit reports and case studies. Two specific models are used to determine the readiness and evolution of the culture of selected paper and board companies, in implementing this standard. The models used are Cameron and Quinn's competing values framework and Kotter's eight stages of implementation. This research brings together the food and packaging industry, in demonstrating how collaboration throughout the supply chain can provide an effective system for self regulation as well as: - • providing guidelines for other sectors/industries developing self regulatory standards. These will aid other sectors also having to develop voluntary standards to comply with government regulations. • establishing key principles for a model of compliance for packaging companies based on the BRC/IOP Global Packaging standard. These principles will support the required growth of the Global Packaging standard worldwide.
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Beselin, Hallberg Jacob, and Per Uhrbom. "Volvo Logistics Corporation Returnable Packaging System : a model for analysing cost savings when switching packaging system." Thesis, Jönköping University, JTH, Industrial Engineering and Management, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-1360.
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This thesis is a study for analysing costs affected by packaging in a producing industry. The purpose is to develop a model that will calculate and present possible cost savings for the customer by using Volvo Logistics Corporations, VLC’s, returnable packaging instead of other packaging solutions.
The thesis is based on qualitative data gained from both theoretical and empirical studies. The methodology for gaining information has been to study theoretical sources such as course literature and articles, as well as through interviews and consolidation with staff at Volvo Logistics Corporations office in Gothenburg.
The model is constructed in Microsoft Excel and consists of six different sheets. The first sheet is a front page that summarises the costs calculated in the other sheets and presents the possible cost savings. After the front page there are three sheets with calculations for the costs in different scenarios, Today’s Situation, VLC Packaging Solution (Pre implementation) and VLC Packaging Solution (Post implementation). The first sheet, Today’s Situation, presents the result of the model that will calculate the customers’ current costs that are associated with packaging. The different costs presented in the model are costs for unloading, repacking, today’s cost for an internal packaging solution, quality related costs, one-way packaging costs and the costs for other packaging solutions. The next sheet, VLC Packaging Solution (Pre), presents an estimation of the cost for thecustomer when using VLC’s returnable packaging system. The estimation will serve as an investment tool, for calculating possible cost savings compared to the present situation. The different costs that will be discussed are handling costs, quality related costs, distribution cost, transaction cost, and investment cost. The third and final calculation sheet, VLC Packaging Solution (Post), presents the actual costs for the customer after the implementation. When the costs have been calculated they will be used to evaluate the actual cost savings for the customer. The last two sheets are a data sheet, which consists of data needed for the calculations in the previous sheets, and an instruction sheet where there are instructions to the different calculations in the model.
The conclusion shows that the objective to create a model for calculating the costs for different packaging systems and present possible cost savings is fulfilled.
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Kurian, Akshay. "The environmental assessment of reusable packaging for Unwrapped's business model and prospects of zero packaging for food stores." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-284239.
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Packaging for food products has impacts on the environment. In particular, single-use packaging have been criticized for the environmental and social impact created along recycling supply-chains in Asia. As a result, reusable packaging for food products started to reappear in Europe. This paper evaluates the environmental impacts of reusable packaging for Unwrapped’s business model using the organisational lifecycle assessment framework. The overall impacts of the organisation and hotspots of reusable packa ging are identified and compared with a reference retail activity using single-use packaging. The upstream processes of production of food products resulted in being the most significant impacts. However, reusable packaging performed worse and better than single-use packaging depending on the number of uses. The identified improvements for reusable packaging materials are proposed by increasing the number of uses. Changes in the upstream mode of transportation are other adopted improvement options for Unwra pped’s business model. The organisational lifecycle assessment framework highlighted issues in the current supply chain system that affect the niche business model in achieving the positive environmental benefits of reusable packaging. However, the reusable packaging business model shows promising aspects in a move towards sustainable businesses.Matförpackningar påverkar miljön. Särskilt blev engångsförpackningar kritiserad för dessa miljö och sociala påverkan i återvinningsbranschen i Asien. och möjligheter. Återanvändbara förpackningar reintroducerades till marknaden i Europa. Den här avhandlingen kommer att granska och diskutera användning av återvinningsbara förpackningar i Unwrappeds affärsmodell med hjälp av organisationens livscykelanalys. Unwrappeds miljöpåverkan fastställs och jämförs med liknande affärsmodeller för engångsförpackning. Matproduktion innan förpackningen har den mest betydande påverkan. Återvinningsbara förpackningar visade sig vara bättre eller sämre beroende på antal gånger dem används. De fastställda förbättringarna för återanvändbara förpackningsmaterial är att återanvända dem så många gånger som möjligt. Förändringar i transportering är en annan förbättringsalternativ för Unwrappeds affärsmodell. Ramen för organisationens livscykelanalys påpekade problemen i nuvarande försörjningskedjans system som påverkar nischverksamhet för att uppnå miljövänligare återvinnin gsbara förpackningar. Dock, återvinningsbara förpackningars affärsmodeller visar lovande perspektiv på steg mot hållbara affären.
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Lakhanpal, Chetan. "Mathematical modelling of applied heat transfer in temperature sensitive packaging systems. Design, development and validation of a heat transfer model using lumped system approach that predicts the performance of cold chain packaging systems under dynamically changing environmental thermal conditions." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/5776.
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Development of temperature controlled packaging (TCP) systems involves a significant lead-time and cost as a result of the large number of tests that are carried out to understand system performance in different internal and external conditions.
This MPhil project aims at solving this problem through the development of a transient spreadsheet based model using lumped system approach that predicts the performance of packaging systems under a wide range of internal configurations and dynamically changing environmental thermal conditions.
Experimental tests are conducted with the aim of validating the predictive model. Testing includes monitoring system temperature in a wide range of internal configurations and external thermal environments.
A good comparison is seen between experimental and model predicted results; increasing the mass of the chilled phase change material (PCM) in a system reduces the damping in product performance thereby reducing the product fluctuations or amplitude of the product performance curve. Results show that the thermal mathematical model predicts duration to failure within an accuracy of +/- 15% for all conditions considered.
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Dunne, Rajiv Carl. "An integrated process modeling methodology and module for sequential multilayered high-density substrate fabrication for microelectronic packages." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17379.
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Pierce, Daniel W. "Toward a comprehensive cost model for multichip module (MCM) manufacturing." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/11113.
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Choi, Kwang Lim. "Modeling and simulation of embedded passives using rational functions in multi-layered substrates." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/14858.
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Biswas, Debabrata Misra Anil. "An application of modal analysis approach for 2D regular imperfect granular packings." Diss., UMK access, 2004.
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Thesis (M.S.)--School of Computing and Engineering. University of Missouri--Kansas City, 2004."A thesis in civil engineering." Typescript. Advisor: Anil Misra. Vita. Title from "catalog record" of the print edition Description based on contents viewed Feb. 22, 2006. Includes bibliographical references (leaves 82-89). Online version of the print edition.
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Daniel, Aang. "Routing and Scheduling with Time Windows: Models and Algorithms for Tramp Sea Cargos and Rail Car-Blocks." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/19698.
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Thesis (Ph.D)--Industrial and Systems Engineering, Georgia Institute of Technology, 2007.Committee Chair: Al-Khayyal, Faiz; Committee Member: Barnes, Earl; Committee Member: Johnson, Ellis; Committee Member: Karimi, IA; Committee Member: Sokol, Joel.
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Kodavati, Venkata Seshank, and Devi Prasad Buraga. "Study of Numerical Model Parameters and Crack Tip of a Packaging Materials." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13840.
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Packaging industries widely use Low-Density Polyethylene (LDPE) in manufacturing different types of containers to store the food products. They are difficult to model numerically in order to have similar experimental response. This research deals with the study of numerical material model parameters of continuum LDPE. It is carried out with the help of experiments along with the numerical simulation of LDPE. Study of stress-strain distribution at crack tip and elements close to the tip is carried out in the LDPE material with the pre-existing center crack with varying lengths. By implementing an optimization algorithm and automating the simulation with the help of python code, we obtain a set of parameters. This obtained data for the material can be used directly for numerical simulation in the future without carrying out additional experimental studies. After implementing the optimization algorithm is also validated, against the results that were close to the experimental response.
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MADDALA, PRANAY RAJ REDDY. "Investigation of Polymer packaging films behavior subjected to tension and tearing." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-15002.
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The course of polymer film functioning has been a crucial concern in the advent of packaging technology. The thesis project aims towards obtaining an understanding of mechanical properties for a class of these materials, namely LDPE and PET. A constitutive understanding of this behavior in the case of LDPE is acquired through incorporating a plastic stress strain relationship in an iterative approach with focus put on the sensitivity of a few parameters by following a simple linear curve-fit technique in a way that the global as well as the local response are predictable. FE-models also developed in this way are validated with experimental data. An inverse analysis testing validity or usefulness of DIC technique in identifying a material model is done and some discussions are drawn towards this area. A relative numerical study with respect to experimentally obtained global response for tearing of these polymers is done through use of a similar material model developed from tensile tests and the challenges faced in this area have been addressed.
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Moussaoui, Hamza. "Microstructural optimization of Solid Oxide Cells : a coupled stochastic geometrical and electrochemical modeling approach applied to LSCF-CGO electrode." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI028/document.
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Ce travail porte sur la compréhension de l’impact de la microstructure sur les performances des Cellules à Oxyde Solide (SOC), avec une illustration sur l’électrode à oxygène en LSCF-CGO. Une approche couplant de la modélisation géométrique et électrochimique a été adoptée pour cet effet. Le modèle des champs aléatoires plurigaussiens et un autre basé sur des empilements de sphères ont été développés et adaptés pour les microstructures des SOCs. Ces modèles 3D de géométrie stochastique ont été ensuite validés sur différentes électrodes reconstruites par nano-holotomographie aux rayons X au synchrotron ou par tomographie avec un microscope électronique à balayage couplé à une sonde ionique focalisée. Ensuite, des corrélations semi-analytiques ont été proposées et validées sur une large base de microstructures synthétiques. Ces relations permettent de relier les paramètres ‘primaires’ de l’électrode (la composition, la porosité et les diamètres des phases) aux paramètres qui pilotent les réactions électrochimiques (la densité de points triples, les surfaces spécifiques interphases) et sont particulièrement pertinents pour les équipes de mise-en-forme des électrodes qui ont plus de contrôle sur ce premier ensemble de paramètres. Concernant la partie portant sur l’électrochimie, des tests sur une cellule symétrique en LSCF-CGO ont permis de valider un modèle déjà développé au sein du laboratoire, et qui permet de simuler la réponse électrochimique d’une électrode à oxygène à partir des données thermodynamiques et de microstructure. Finalement, le couplage des deux modèles validés a permis d’étudier l’impact de la composition des électrodes, leur porosité ou encore taille des grains sur leurs performances. Ces résultats pourront guider les équipes de mise-en-forme des électrodes vers des électrodes plus optimiséesThis work aims at better understanding the impact of Solid Oxide Cells (SOC) microstructure on their performance, with an illustration on an LSCF-CGO electrode. A coupled 3D stochastic geometrical and electrochemical modeling approach has been adopted. In this frame, a plurigaussian random field model and an in-house sphere packing algorithm have been adapted to simulate the microstructure of SOCs. The geometrical models have been validated on different electrodes reconstructed by synchrotron X-ray nano-holotomography or focused ion-beam tomography. Afterwards, semi-analytical microstructural correlations have been proposed and validated on a large dataset of representative synthetic microstructures. These relationships allow establishing the link between the electrode ‘basic’ parameters (composition, porosity and grain size), to the ‘key’ electrochemical parameters (Triple Phase Boundary length density and Specific surface areas), and are particularly useful for cell manufacturers who can easily control the first set of parameters. Concerning the electrochemical part, a reference symmetrical cell made of LSCF-CGO has been tested in a three-electrode setup. This enabled the validation of an oxygen electrode model that links the electrode morphological parameters to its polarization resistance, taking into account the thermodynamic data. Finally, the coupling of the validated models has enabled the investigation of the impact of electrode composition, porosity and grain size on the cell electrochemical performance, and thus providing useful insights to cell manufacturers
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Laird, Mark. "Logistics Management: A Firm’s Efficiency Performance Model." Ohio University Honors Tutorial College / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1338575775.
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Yousuf, Saif. "Structural Low Cement Content (LCC) Concrete: An Eco-friendly Alternative for Construction Industry." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37590.
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Pressure is mounting in the construction industry to adopt more environmentally sustainable methods to reduce CO2 emissions. Portland cement (PC) often constitutes to more than two-thirds of the embodied energy of concrete, and its production generates 5% of global greenhouse gas emissions. One efficient strategy to reduce the cement content without sacrificing performance is the use of particle packing models (PPM) to mix- proportion concrete mixtures with low cement content, the so-called low cement content (LCC) concrete. If on the one hand LCC was seen to be an effective sustainable alternative to the construction industry, its mechanical behaviour, durability and long-term performance are still under debate and thus further research is needed in the area. In this project, continuous PPM theories were used to mix- design structural concrete mixes presenting distinct mechanical properties (i.e. 25 & 35 MPa) and cement contents. Their performance was evaluated in the fresh and hardened states, and gaps, recommendations, and further needs were highlighted. Results show that the use of PPM enables the development of LCC systems, showing impressive hardened state performance (i.e. higher compressive strength and modulus of elasticity and lower electrical resistivity) and low carbon footprint. However, challenges in the fresh state were faced, which may be potentially solved with the use of chemical admixtures, fillers and/or supplementary cementing materials (SCMs).