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Breslavsky, D. V., V. O. Mietielov, O. K. Morachkovsky, S. O. Pashchenko, and О. А. Tatarinova. "Asymptotic methods and finite element method in cyclic creep-damage problems." Thesis, Львівський національний університет ім. І. Франка, 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/19395.
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Du, Bing. "Hydrodynamics and flow structure, gas and solids mixing behavior, and choking phenomena in gas-solid fluidization." Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1110208922.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xxvii, 334 p.; also includes graphics (some col). Includes bibliographical references (p. 322-334). Available online via OhioLINK's ETD Center
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Mostoufi, Navid. "Solids behaviour in fluidized beds." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0017/NQ53540.pdf.
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Abdel-Fattah, Mohamed Thabit. "Nonlinear behaviour of cylindrical shells containing elastic solids." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ58196.pdf.
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Lu, Xia. "Nonequilibrium thermodynamic models for the dynamic behavior of polycrystalline solids." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/12549.
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Mohammed, Malik Ahmed. "NMR studies of quantum molecular motions in solids." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329802.
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Li, Qin. "Simulations of dynamic behaviour of packed particulate systems : applications of discrete element methods /." [St. Lucia, Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16731.pdf.
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Zhen, Tiejun. "Compressive behavior of kinking nonlinear elastic solids - Ti3SiC2, graphite, mica and BN /." Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/312.
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Lashkari, Omid. "The rheological behavior of semi-solid A356 alloy." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2006. http://theses.uqac.ca.
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Thèse (D.Eng.) -- Université du Québec à Chicoutimi, 2006.La p. de t. porte en outre: Dissertation presented to the University of Quebec at Chicoutimi in partial fulfilment of the requirement for the degree of doctor of philosophy in engineering. CaQCU Bibliogr.: f. 177-184. Document électronique également accessible en format PDF. CaQCU
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Milligan, Walter W. Jr. "Yielding and deformation behavior of the single crystal superalloy PWA 1480." Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/20152.
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Fletcher, Patrick Alan. "High pressure vibrational and EXAFS spectroscopy." Thesis, University of Leicester, 1987. http://hdl.handle.net/2381/33673.
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Chattoraj, Joyjit. "Effect of finite temperatures on the elementary mechanisms of plastic deformation in amorphous materials." Thesis, Paris Est, 2011. http://www.theses.fr/2011PEST1074/document.
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Par la mise en œuvre de simulations numériques d'un modèle bidimensionnel de verre de Lennard-Jones, nous étudions l'effet de la température sur les mécanismes élémentaires de la déformation dans les matériaux amorphes. Nous présentons un ensemble très complet de données couvrant plusieurs décades de taux de cisaillement à différentes températures en dessous et jusqu'à la transition vitreuse. Les mesures, qui portent sur la diffusion transverse, la contrainte macroscopique ainsi que sur des champs mésoscopiques (déformation, contrainte) et leurs corrélations spatiales, conduisent à proposer que la dynamique des avalanches identifiée précédemment dans les simulations athermiques continue d'être à l'œuvre - en restant presque inchangée - jusqu'à la transition vitreuse. Nous arguons que dans la gamme de paramètres utilisée l'effet des fluctuations thermiques revient à déplacer les seuils auxquels les événements dissipatifs se produisent, ce qui se traduit par une forte baisse du niveau de contrainte macroscopique aux températures les plus bassesUsing numerical simulations of a model two-dimensional Lennard-Jones glass, we study the effect of small temperatures on the elementary mechanisms of deformation in amorphous materials. A very extensive data set covering several decades of shear rate at various temperatures below and up to the glass transition was compiled. Measurements, which include transverse diffusion, macroscopic stress, and coarse-grained fields (strain, stress) and their spatial correlations, lead us to propose that the avalanche dynamics previously identified in athermal simulations continues to be at work -- and nearly unchanged -- up to the glass transition. It is then argued that in this range, thermal fluctuation essentially shift the strains at which dissipative events take place, which results in a sharp drop of the macroscopic stress level at the lowest temperatures
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Ashwood, Lori-Anne. "Switching behavior in ferromagnetic nanorings /." Connect to online version, 2009. http://ada.mtholyoke.edu/setr/websrc/pdfs/www/2009/382.pdf.
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Paunovic, Irena. "Solid-liquid phase behavior of mixtures of n-alkanes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0021/MQ48067.pdf.
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McCrorie, J. David. "Particle behavior in solid propellant rocket motors and plumes." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/24002.
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Racine, John A. "Subscale solid rocket motor infrared signature and particle behavior." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/26801.
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Panagiotidou, Andriani Ioanna. "Adaptation of granular solid hydrodynamics for modeling sand behavior." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/113480.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017Cataloged from PDF version of thesis.
Includes bibliographical references (pages 399-408).
The development of constitutive models that can realistically represent the effective stress-strain-strength of the soil properties is essential for making accurate predictions using finite element analysis. Currently, most of the existing constitutive models are based on the framework of incrementally-linearized elasto-plasticity. However, most of these models do not typically consider energy conservation and are also phenomenological. This means that they can only be used to predict the behavior/ loading conditions for which they have been developed and that they often employ artificial mathematical formulations. This research proposes an improved constitutive model for sands based on the framework of Granular Solid Hydrodynamics [GSHJ. The GSH framework considers energy and momentum conservation simultaneously and, by combining them with thermodynamic considerations, develops constitutive relations for a given energy expression.
This thesis offers a detailed study of the element level behavior of the Tsinghua-Thermosoil model [TTSI (Zhang and Cheng, 2016) based on the GSH. Through this study, we identify and propose a series of modifications to the original formulation in order to improve predictions of well-established soil behavior. The proposed formulation, MIT-GH, introduces a new expression of the free energy and modifies the evolution laws and the steady state values for the internal variables. The model can successfully predict phenomena such as a unique compression response at high confining pressures (Limiting Compression Curve [LCC]) and at large shear strain conditions (Critical State Line [CSL]), and a State Boundary Surface [SBS] that limits the peak shear resistance measured in drained shear tests. The LCC and CSL conditions are defined solely from the evolution of elastic strains while the SBS is defined from the free energy expression.
Finally, our work also offers a novel use of the "double" failure mechanism -- inherent in the GSH framework. Using these mechanisms, MIT-GH can model not only Critical State conditions but also localization phenomena. The proposed criterion for the localization is the maximum expected peak friction angle that a specimen can develop at different void ratios and stress levels. This study also includes a detailed parametric analysis of the model and a proposal for the calibration of the model. The proposed MIT-GH model should be considered as a first generation formulation based on the principles of granular solid hydrodynamics and how it ties to classic knowledge of soil behavior and prior elasto-plastic models. Further research is now needed to extend the framework to address more complex features of sand behavior including the cyclic response and liquefaction.
by Andriani-loanna Panagiotidou.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering
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Arabgol, Raheleh. "MBBR Produced Solids: Particle Characteristics, Settling Behaviour and Investigation of Influencing Factors." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/41919.
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The separation of solids from biological wastewater treatment is an important step in the treatment process, as it has a significant impact on effluent water quality. The moving bed biofilm reactor (MBBR) technology is a proven upgrade or replacement wastewater treatment system for carbon and nitrogen removal. However, a challenge of this technology is the characteristics of the effluent solids that results in their poor settlement; with settling being the common method of solids removal. The main objective of this research is to understand and expand the current knowledge on the settling characteristics of MBBR produced solids and the parameters that influence them. In particular, in this dissertation, the impacts are studied of carrier types, biofilm thickness restraint design of carriers, and varying carbonaceous loading rates on MBBR performance, biofilm morphology, biofilm thickness, biofilm mass, biofilm density, biofilm detachment rate, solids production, particle size distribution (PSD) and particle settling velocity distribution (PSVD).
With this aim, three MBBR reactors housing three different carrier types were operated with varying loading rates. In order to investigate the effect of carrier geometrical properties on the MBBR system, the conventional, cylindrically-shaped, flat AnoxK™ K5 carrier with protected voids was compared to two newly-designed, saddle-shaped Z-carriers with the fully exposed surface area. Moreover, the AnoxK™ Z-200 carrier was compared to the AnoxK™ Z-400 carrier to evaluate the biofilm thickness restraint design of these carriers, where the Z-200 carrier is designed for greater biofilm thickness-restraint. The Z-200 carrier is designed to limit the biofilm thickness to the level of 200 µm as opposed to 400 µm for the Z-400 carrier. Finally, to investigate the effects of varying carbonaceous loading rates on system removal performance, biofilm characteristics and solids characteristics, further analyses were performed at three different loading rates of 1.5 to 2.5 and 6.0 g-sBOD/m2·d in steady-state conditions. The PSD and the PSVD analyses were combined to relate these two properties. A settling velocity distribution analytical method, the ViCAs, was applied in combination with microscopy imaging and micro-flow imaging to investigate the relation of PSD and settling behaviour of MBBR produced particles.
The obtained results have indicated that the carrier type significantly impacted the MBBR performance, biofilm, and particle characteristics. As such, the K5 carrier MBBR system demonstrated a statistically significantly higher carbonaceous removal rate and efficiency (3.8 ± 0.3 g-sBOD/m2·d and 59.9 ± 3.0% sBOD removal), higher biofilm thickness (281.1 ± 8.7 μm), higher biofilm mass per carrier (43.9 ± 1.0 mg), lower biofilm density (65.0 ± 1.5 kg/m3), lower biofilm detachment rate (1.7 ± 0.7 g-TSS/ m2·d) and hence lower solids production (0.7 ± 0.3 g-TSS/d) compared to the two Z-carriers. The Z-carriers' different shape exposes the biofilm to additional shear stress, which could explain why the Z-carriers have thinner and denser biofilm, resulting in higher solids production and lower system performance in comparison with K5. Moreover, the carrier type was also observed to impact the particle characteristics significantly. PSD analysis demonstrated a higher percentage of small particles in the Z-carrier system effluent and hence a significantly lower solids settling efficiency. Therefore, the solids produced in the K5 reactor have shown enhanced settling behaviour, consisting of larger particles with faster settling velocities compared to Z-carriers.
This dissertation also investigated the effects of restraint biofilm thickness on MBBR performance by comparing the Z-200 biofilm thickness-restraint carrier to the Z-400 carrier. No significant difference was observed in removal efficiency, biofilm morphology, biofilm density, biofilm detachment rate, and solids production between the Z-200 to the Z-400 carriers. The PSD and the PSVD analyses did not illustrate any significant difference in the particles’ settling behaviour for these two biofilm thickness restraint carriers, indicating that the biofilm thickness-restraint carrier design was not a controlling factor in the settling potential of MBBR produced solids.
Finally, this research studied the effect of varying loading rates and demonstrated a positive, strong linear correlation between the measured sBOD loading rate and the removal rate, indicating first-order BOD removal kinetics. The biofilm thickness, biofilm density and biofilm mass decreased when the surface area loading rate (SALR) was increased from 2.5 to 6.0 g-sBOD/m2·d. The solids retention time (SRT) was also shown to decrease by increasing the SALR, where the lowest SRT (1.7 ± 0.1 days) was observed at the highest SALR, with the highest cell viability (81.8 ± 1.7%). Significantly higher biofilm detachment rate and yield were observed at SALR 2.5, with the thickest biofilm and a higher percentage of dead cells. Consequently, a higher fraction of larger and rapidly settling particles was observed at SALR of 2.5 g-sBOD/m2·d, which leads to a significantly better settling behaviour of the MBBR effluent solids.
This study expands the current knowledge of MBBR-produced particle characteristics and settling behaviour. A comprehensive understanding of the MBBR system performance and the potential influencing factors on the MBBR produced solids, particle characteristics, and their settleability will lead to optimized MBBR design for future pilot- and full-scale applications of the MBBR.
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Bakhurji, Alhussain. "Hydrodynamics and solids mixing behaviour of fluidized beds with inclined-hole distributor." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62101.
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Most research on the hydrodynamics and solids mixing of swirling fluidized beds has targeted applications relate to drying and combustion processes, with large mean particle
diameters. A potential use of such reactors is in the area of catalyst regeneration to improve mixing. In the present study, the hydrodynamics and solids mixing behaviour of swirling fluidized beds were investigated for particles in Groups A and B of the Geldart classification. Three distributors were designed and fabricated in-house. They shared the same specifications, but differed in the orifice inclination angle (30, 45 and 90 to the horizontal).
The effect of orifice angle on the hydrodynamics of a fluidized bed of glass beads was investigated. The study showed that, in an empty bed, the distributor pressure drop was
lower for the inclined-hole distributors compared to the 90-hole distributor by a factor of 10%. In addition, bed pressure drop increased with the inclined-hole distributors as well with
static bed height. Bed expansion was also investigated and found that in a shallow bed, the inclined-hole distributor led to less expansion compared to the 90-hole distributor. However,
in a deep bed, the orifice angle had negligible influence on bed expansion. The minimum fluidization velocity was found to change with static bed height for the inclined-hole distributors, and it was also higher for steeper angles.
Solids mixing was also explored, axial mixing for the 90-hole distributor and tangential
mixing for all three distributors. Residence time distribution studies were conducted using
phosphorescent tracer particles belonging to Group A, activated by ultraviolet light. The
turnover time was estimated using the bubbling bed model and found to match the experimental results well. It was found that the probes installed at the walls of the fluidization column reduced the dense phase downward velocity. The tangential particle
velocity was also estimated and was found to be highest for the 30-hole distributor,
decreasing with increasing orifice angle. A dispersion model was used to describe tangential mixing for all three distributors which showed that the dispersion coefficient for the inclined-hole distributors was twice that for the 90-hole in a shallow bed.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
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Lopez, G. F. G. "Convective drying and solid-moisture interactions." Thesis, University of Reading, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234903.
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Ruiz, De Sotto Miguel. "Characterization and modeling of the thermo-mechanical behavior of a Ti-6Al-4V alloy under dynamic complex loading." Thesis, Toulouse, ISAE, 2020. http://depozit.isae.fr/theses/2020/2020_Ruiz_De_Sotto_Miguel_D.pdf.
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Lors de la certification des moteurs d’avion, certains composants sont testés vis-à-vis de phénomènes balistiques. La soufflante doit ainsi résister à l’ingestion d’oiseaux et à la perte d’aubes sans compromettre les performances globales du réacteur. Les aubes de soufflante, et particulièrement leur bord d’attaque, subissent des déformations élevées à grande vitesse, des chargements non proportionnels et un auto-échauffement induit parla dissipation plastique. Compte tenu de leurs bonnes propriétés mécaniques spécifiques,les alliages de titane Ti-6Al-4V sont considérés comme des candidats prometteurs pour le bord d’attaque d’aubes de soufflante multi-composants. Dans ce travail, une campagne expérimentale a été menée sur un alliage de Ti-6Al-4V laminé comprenant des essais de traction, compression et cisaillement à plusieurs températures et vitesses de déformation(lentes et rapides), sous des trajets de chargements monotones et alternés. A partir des résultats obtenus, un modèle constitutif a été développé rendant compte des effets combinés de l’orthotropie, de l’asymétrie traction-compression, des écrouissages cinématique et isotrope non linéaires, de la vitesse et de l’adoucissement thermique. Les constantes ont été identifiées au moyen du logiciel Zset. Le modèle a ensuite été implémenté entant que procédure matériau utilisateur (Fortran) dans le code de calculs commercial par élément finis LS-DYNA. Les performances du modèle numérique ont alors été évaluées en menant des simulations numériques sur un élément de volume soumis à différents trajets de chargement ainsi que sur des éprouvettes utilisées pour la campagne expérimentaleDuring the aircraft engine certification, various components are tested against ballisticphenomena. The engine fan must accordingly resist bird strike and blade loss withoutcompromising the whole engine thrust performance. Fan blades, and particularly theirleading edge, undergo large deformation under high strain rate, non-proportional loadingpaths and plastic dissipation induced self-heating. Due to their high specific mechanicalproperties, Ti-6Al-4V titanium alloys are promising candidates for fan multi-componentblade leading edge. In this work, an experimental campaign has been carried out on acold rolled Ti-6Al-4V alloy comprising tension, compression and shear tests performed atvarious temperatures and (low and high) strain rates, under monotonic and alternatedloading paths. Based on these results, a constitutive model has been developed accountingfor the combined effects of orthotropy, strength differential, nonlinear kinematic andisotropic hardenings, strain rate hardening as well as thermal softening. Material constantshave been identified using Zset software. The model has been implemented asuser material (Fortran) subroutine into the commercial finite element computation codeLS-DYNA. The performances of the numerical model have then been estimated by conductingnumerical simulations considering a volume element under various loading pathsas well as the specimens used for the experimental campaign
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Bracikowski, Christopher. "Fluctuations and chaos in a multimode solid state laser system." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/30658.
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Chen, Kezheng. "Origin of Polarization Behavior in All-Solid-State Lithium-Ion Battery Using Sulfide Solid Electrolyte." Kyoto University, 2018. http://hdl.handle.net/2433/235998.
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Wang, Fei, and 王飞. "Behavior of perfluorochemicals on solid surfaces: sorption and mineralization processes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hub.hku.hk/bib/B50899892.
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The study evaluated the sorption behavior of PFOS and PFOA on γ-alumina and boehmite. The results of adsorption kinetics on γ-alumina and boehmite show that it takes 48 h to reach equilibrium. The adsorption isotherms reveal the maximum adsorption capacities of PFOS and PFOA are different due to their different functional groups. An increase in pH leads to a decrease in PFOS and PFOA adsorption on alumina, which may be attributed to the reduction in electrostatic interaction. The adsorption of both PFOS and PFOA decreases with an increase in ionic strength due to the compression of the electrical double layer. The different sorption level of PFC on γ-alumina and boehmite indicated that the crystal phase of mineral also affected the sorption process. The sorption of PFOS and PFBuS on boehmite was significantly retarded by the competitive sorption of humic acid (HA), implying that PFOS and PFBuS are likely more mobile in water and groundwater systems enriched with HA. The sorption behavior of PFOS and PFBuS on the HA-modified boehmite surface was also found to differ due to their different chain lengths. In addition, the results revealed that the sorption of PFOS and PFBuS on HA-modified boehmite is pH-dependent.
The isotherm study of FOSA on three types of microplastics indicated that hydrophobic interaction plays a dominant role in the sorption process and the molecule structure of different microplastics can affect its sorption level. The PFOS sorption isotherm indicated that electrostatic interaction plays an important role in the PFOS sorption process on PE and PS while its sorption on PVC was electrostatic interaction independent. The effects of pH and ionic strength indicated that electrostatic interaction plays an important role in PFOS sorption process. The kinetic study showed that the PCMAs had a rapid sorption towards PFAS species and the isotherm study indicated that hydrophobic interaction played an important role in the sorption process. The sorption of PFOS by the PCMAs was not significantly affected by the pH and slightly decreased with an increase in ionic strength. Moreover, the sorbent had showed excellent regeneration performance.
Two main fluorine mineralization mechanisms leading to the substantial formation of CaF2 and Ca5(PO4)3F phases were observed. They had a close relationship with the thermal treatment condition and the PFOS content of the sludge. At low temperatures (300C -600C), CaF2 dominated in the product and increases in treatment time and temperature generally enhanced the fluorine transformation. However, at higher temperatures (700C -900C), increases in treatment time and temperature had a negative effect on the overall efficiency of the fluorine crystallization. The results suggest that in the high temperature environment there were greater losses of gaseous products such as HF and SiF4 in the transformation of CaF2 to Ca5(PO4)3F, the hydrolysis of CaF2, and the reaction with SiO2. The quantitative analysis also showed that when treating sludge with low PFOS content at high temperatures, the formation of Ca5(PO4)3F may be the primary mechanism for the mineralization of the fluorine in PFOS.published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy
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Smith, Michael J. "An experimental investigation of the behavior of metallized solid propellants." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/41935.
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Approved for public release, distribution unlimitedNo PDF currently available.
The combustion behavior of metallized solid propellants at pressures between 100 and 750 psi was investigated using high speed motion pictures together with scanning electron microscope and light diffraction examinations of collected residue. A reduced smoke ZrC propellant and two propellants with low aluminum loadings were utilized. ZrC was observed to agglomerate and ignite on the propellant surface before being ejected. The aluminum did not agglomerate but did ignite on the propellant surface. ZrC was found to burn in part with a detached flame and the flame moved closer to the particle surface as pressure increased. Aluminum particles were observed to burn with similar behavior, but with flames more detached from the particle surface. Increased aluminum loading resulted in smaller particles above the propellant surface, but the flames were further from particle surfaces.
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Anaredy, Radhika Sudhakar. "The study of ionic liquid behavior at solid-liquid interfaces." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6540.
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Ionic liquids are organic salts with room temperature melting points. Their unique physicochemical properties make them popular choices in the fields of tribology, energy storage and production, and extractions. Previous studies show that IL’s interfacial volume, extending some nanometers from an adjacent surface, is characterized by the self-assembly of IL molecules into ordered structures. This ordering imparts unique properties which often govern the properties of ILs and affect their application in the aforementioned areas. This thesis describes research conducted to understand the behaviors and interactions of ILs at interfaces, along with investigations of bulk IL structures and transitions in the presence of water. The findings reported will help the scientific community by giving insight into the physical and chemical processes surrounding IL behavior, allowing ILs’ physicochemical properties to be more accurately tailored, via judicious synthesis, to a desired application.
Major findings of this work show that the ordered interfacial region may extend up to two orders of magnitude further from the interface than previously thought. Specifically, this thesis shows several examples of reversible IL self-assembly into long-range ordered films that extend up to ~ 2 μm from a surface. This is approximately twelve times the thickness of interfacial region previously reported.
Temperature controlled studies on the bulk structure of an IL at its phase transition temperatures aid in understanding the structural arrangement of molecules in the bulk fluid as a function of temperature. Spectroscopic analyses of these bulk studies and the above interfacial systems showed no similarities, indicating that the self-assembled interfacial structures are, in fact, unique.
Being hygroscopic in nature, water is the most common impurity found in ILs. Water can affect IL intermolecular forces and the resulting structures in bulk fluids as well as at the interface. One of the chapter of this thesis describes these interactions, and the variably hydrated IL structures for two classes of ILs via spectroscopic and electrochemical techniques.
The outcomes of this thesis will aid the community in understanding interfacial and bulk structures of ILs, as well as influences of temperature and water on these structures. The description of extended IL structures provides valuable insights into new design principles for truly task-specific ILs.
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Sarpal, Kanika. "PHASE BEHAVIOR OF AMORPHOUS SOLID DISPERSIONS: MISCIBILITY AND MOLECULAR INTERACTIONS." UKnowledge, 2019. https://uknowledge.uky.edu/pharmacy_etds/98.
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Over the past few decades, amorphous solid dispersions (ASDs) have been of great interest to pharmaceutical scientists to address bioavailability issues associated with poorly water-soluble drugs. ASDs consist of an active pharmaceutical ingredient (API) that is typically dispersed in an inert polymeric matrix. Despite promising advantages, a major concern that has resulted in limited marketed formulations is the physical instability of these complex formulations. Physical instability is often manifested as phase heterogeneity, where the drug and carrier migrate and generate distinct phases, which can be a prelude to recrystallization. One important factor that dictates the physical stability of ASDs is the spatial distribution of API in the polymeric matrix. It is generally agreed that intimate mixing of the drug and polymer is necessary to achieve maximum stabilization, and thus understanding the factors controlling phase mixing and nano-domain structure of ASDs is crucial to rational formulation design. The focus of this thesis work is to better understand the factors involved in phase mixing on the nanometric level and get insights on the role of excipients on overall stabilization of these systems. The central hypothesis of this research is that an intimately mixed ASD will have better physical stability as compared to a partially homogeneous or a non-homogeneous system. Our approach is to probe and correlate phase homogeneity and intermolecular drug-excipient interactions to better understand the physical stability of ASDs primarily using solid-state nuclear magnetic resonance (SSNMR) spectroscopy and other solid-state characterization tools. A detailed investigation was carried out to understand the role of hydrogen bonding on compositional homogeneity on different model systems. A comprehensive characterization of ternary ASDs in terms of molecular interactions and physical stability was studied. Finally, long-term physical stability studies were conducted in order to understand the impact of different grades of a cellulosic polymer on phase homogeneity for two sets of samples prepared via different methods. Overall, through this research an attempt has been made to address some relevant questions pertaining to nano-phase heterogeneity in ASDs and provide a molecular level understanding of these complex systems to enable rational formulation design.
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Wu, Yi. "Release behavior of alkyl-p-aminobenzoate ester–PVP solid dispersions." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/2024.
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Solid polymer-drug dispersions are used to prepare and stabilize amorphous forms of poorly soluble drugs as a means of improving drug solubility, dissolution and bioavailability. Despite many reports on this subject, solid dispersion dissolution mechanisms have not been well understood. An early study was reported by Simonelli, Mehta and Higuchi (SMH) in 1969 and has served as a model for dispersion dissolution behavior. These authors proposed a dissolution model (SMH) which gave good agreement between their experimental results and model predictions for one drug and one type of PVP.
Few researchers have applied this traditional approach (SMH) in a systematic fashion to solid dispersion systems. One difficulty is obtaining parameters needed for predictions such as polymer diffusion coefficient, diffusion layer thickness or other pertinent parameters. In this work, a general model has been developed based on the concepts in the traditional approach (SMH) and simulations with this model were performed to show how dispersion dissolution rates change with system variables. Such simulations showed underestimation of dissolution rates resulted when compounds had low solubility.
In this work, solid dispersion dissolution behavior was studied systematically with a homologous compound series (alkyl-p-aminobenzoate esters, or PABA esters) and three polyvinylpyrrolidone (PVP) molecular weights (K15, K30 and K90). The PABA esters with varying solubility used in this study were methyl PABA (MePABA), ethyl PABA (EtPABA), propyl PABA (PrPABA) and butyl PABA (BuPABA). Six solid dispersions for each PABA ester and PVP (weight ratios of PVP:PABA ester 20:1, 10:1, 6:1, 3:1, 4:1 and 2:1) were prepared by a solvent evaporation method. Solid dispersions were obtained and their amorphous character confirmed by powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC). Intrinsic dissolution rates for these dispersions were obtained in water with a rotating disc dissolution system. Both dissolution rate of drug (PABA ester) and carrier (PVP) were measured to obtain more information on which to evaluate the release behavior. Measuring the dissolution of the polymer (dispersion agent) and drug is unique in this work and has not been done in most other reported studies.
For the more soluble PABA esters (i.e., MePABA, EtPABA and PrPABA), as drug loading increased, PABA ester dissolution rates first increased and then decreased to that of the pure drug for PVP K15 and K30 dispersions. For K90 systems, drug dissolution rates were below pure drug rates and increased steadily as drug loading increased, eventually reaching that of the pure drug. On the other hand, PVP dissolution rates decreased constantly as drug content increased for all three PVP grades. However, the decrease in polymer dissolution was more pronounced for the lower molecular weight PVPs (K15 and K30) than the higher molecular weight PVP (K90). Comparison of drug and polymer dissolution behavior indicated that congruent release of both components occurred when drug loading was low (< 15%). As drug loading increased, more deviation from congruent release behavior was observed. For BuPABA, the least soluble PABA ester, precipitated BuPABA solid accumulated on the disc surface during dissolution.
PABA ester relative dissolution rates were calculated and compared with the predictions from the developed general model (based on assumptions in the traditional approach). Such predictions correlated well with experimental results at high drug loadings (i.e., >25%) but at low drug loadings (i.e.,
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Agarwal, Gaurav. "Solid Fuel Blend Pyrolysis-Combustion Behavior and Fluidized Bed Hydrodynamics." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/51677.
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As a carbon neutral and renewable source of energy, biomass carries a high potential to help sustain the future energy demand. The co-firing of coal and biomass mixtures is an alternative fuel route for the existing coal based reactors. The main challenges associated with co-firing involves proper understanding of the co-firing behavior of blended coal-biomass fuels, and proper understanding of advanced gasification systems used for converting such blended fuels to energy.
The pyrolysis and combustion behavior of coal-biomass mixtures was quantified by devising laboratory experiments and mathematical models. The pyrolysis-combustion behavior of blended fuels was quantified on the basis of their physicochemical, kinetic, energetic and evolved gas behavior during pyrolysis/combustion. The energetic behavior of fuels was quantified by applying mathematical models onto the experimental data to obtain heat of pyrolysis and heat of combustion. Fuel performance models were developed to compare the pyrolysis and combustion performance of non-blended and blended fuels. The effect of blended fuel briquetting was also analyzed to find solutions related to coal and biomass co-firing by developing a bench scale fuel combustion setup. The collected data was analyzed to identify the effects of fuel blending and briquetting on fuel combustion performance, ignitability, flammability and evolved pollutant gases.
A further effort was made in this research to develop the understanding of fluidized bed hydrodynamics. A lab scale cold-flow fluidized bed setup was developed and novel non-intrusive techniques were applied to quantify the hydrodynamics behavior. Particle Image Velocimetry and Digital Image Analysis algorithms were used to investigate the evolution of multiple inlet gas jets located at its distributor base. Results were used to develop a comprehensive grid-zone phenomenological model and determine hydrodynamics parameters such as jet particle entrainment velocities and void fraction among others. The results were further used to study the effect of fluidization velocity, particle diameter, particle density, distributor orifice diameter and orifice pitch on the solid circulation in fluidized beds.Ph. D.
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Picquart, Marion. "Développement d’une loi de comportement pour les méthodes de dimensionnement des chargements en propergol solide composite." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASC019.
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Ces travaux de thèse portent sur le développement d’une loi de comportement viscoélastique non-linéaire pour les propergols solides composites. Une base expérimentale mettant en évidence le comportement à modéliser est construite à l’aide du propergol d’étude. Puis, les origines microscopiques de ce comportement macroscopique sont investiguées, au moyen d’éprouvettes spécialement conçues à cet effet. Les résultats de l’étude montrent que le frottement et la cavitation sont deux mécanismes prépondérants. Les relations mathématiques entre ces micromecanismes et les propriétés mécaniques du matériau sont déterminées par homogénéisation, puis introduites dans un cadre viscoélastique isotrope tridimensionnel. Les paramètres du modèle ainsi obtenu sont identifiés sur la base expérimentale, suite à quoi la loi est capable de restituer la majeure partie des non-linéarités du comportement exprimées sous sollicitations cycliques. Après intégration dans un code de calcul par éléments finis, la loi est finalement validée sur des cas d’application réels. Les résultats montrent qu’une meilleure restitution du comportement du propergol au cours de son cycle de vie permet d’améliorer le dimensionnement des chargements de manière significativeThis work describes the development of a viscoelastic nonlinear constitutive law for solid composite propellants. An experimental basis showing the nonlinear behavior expressed by solid propellants is constructed. Then, microscopic sources of this macroscopic behavior are investigated using new samples specifically designed. Results show that friction and cavitation are responsible for the major parts of the nonlinearities. Homogenization is used to determine mathematical relations between these two mechanisms and the mechanical properties of the material. The relations are then integrated in a viscoelastic, isotropic, tridimensional model. Parameters are identified using the experimental basis. The model shows a good ability to reproduce and predict the propellant behavior nonlinearities expressed under cyclic loads. After completion of the development, the model is used into a design method and finite element calculation are performed on real objects. Results validate the new method and show that improving the behavior prediction also improves the design method and generates profits
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Hao, Bin. "The effects of inserts on flow behavior of cohesive bulk solids in a model bin." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ32124.pdf.
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Haghighat, Siavash. "Melt and solid state behaviour of polyolefin blends." Thesis, Loughborough University, 1990. https://dspace.lboro.ac.uk/2134/28165.
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Polymer–polymer blends are rapidly growing as an important resource for obtaining new and improved polymeric materials; and polyolefins are among the most widely used thermoplastics in the polymer industries due to their low cost, desirable physical properties and wide range of applications. For this reason several polyolefin polymers were melt blended and different experimental techniques were used to investigate their characteristics and their properties. The blends under investigation are reported in four chapters, following a literature survey and a description of experimental techniques.
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G??n, B??lent Materials Science & Engineering Faculty of Science UNSW. "Crystallization behaviour and rheological properties of a Mg-Cu-Y bulk metallic glass." Awarded by:University of New South Wales. Materials Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/43352.
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A repetitive low-pressure die casting technique has been developed for casting high quality Mg6SCU2SY10 bulk metallic glass (BMG) samples. Using these as-cast samples, the thermal and mechanical behaviour of the BMG in the supercooled liquid (SCL) region was investigated principally by uniaxial tensile testing, differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Using the die casting facility, charge temperature, injection pressure and injection velocity were found to be important parameters for controlling the length, porosity and degree of crystallinity in the as-cast samples. A processing map was generated which showed that a melt temperature and casting pressure in the range 560-580°C and 0.4-0.5 bar, respectively, generated the highest quality samples. The static crystallization behaviour of the as-cast BMG was investigated in detail. It was found that the kinetics of both anisothermal and isothermal crystallization were adequately represented by a number of transformation models. Using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) relation in conjunction with isothermal DSC, the Avrami exponent was found to vary from 2.2 to 2.5 with increasing annealing temperature which implies that, at high annealing temperatures, nucleation occurs at a constant rate accompanied by diffusion-controlled growth of spherical grains. A comparable Avrami exponent of 2.34 was also calculated by anisothermal DSC using the Ozawa method. The tensile flow behaviour of the BMG was investigated over a range of strain rates (10.3to 10.1S•1) and deformation temperatures (150 to 170 QC) in the SCL region using standardized tensile test samples. It was found that, the flow stress increased rapidly to a maximum value followed by a decrease to a very low steady-state value. In the SCL region, the relationship between peak flow stress, strain rate and absolute deformation temperature was described adequately by the classic Sellars-Tegart constitutive relationship. There was also a good correlation between the Zener-Hollomon parameter, Z, and the flow characteristics of the BMG such as the transition from Newtonian to non-Newtonian flow at Z>1 031 S•1 and optimum superplasticity for Z-values in the range 5 x 1030 to 5 x 1031 S•1 where tensile elongations in excess of 1400% were achieved.
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Deyirmenjian, Vatche Berj. "Quantum mechanical simulation of the mechanical behaviour and metallic bonding of defective aluminium." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338279.
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Ning, Wang. "Convective drying : modelling and water-solid interactions." Thesis, University of Reading, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317297.
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Mouille, Hervé. "Influence of strain rate and temperature upon the mechanical and fracture behavior of a simulated solid propellant /." This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07212009-040252/.
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Chamberlain, Debra K. "Materials behaviour in liquid potassium and rubidium." Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280314.
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Zhang, Bo. "Constitutive modelling of municipal solid waste." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/7984.
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Design of landfills must consider both stability and integrity of the lining system. Therefore, stresses and strains in both mineral and geosynthetic lining materials must be controlled. Interaction between waste and barrier system is of particular importance for assessing the stability and structural integrity of steep non-self supporting barrier systems. The most appropriate approach to assess the interaction is the use of numerical modelling techniques, and therefore an appropriate constitutive model for waste material is required to represent its mechanical behaviour. In a literature review the key aspects of mechanical behaviour of municipal solid waste (MSW) were investigated, including the influence of compressible and reinforcing particles on compression and shear behaviour of MSW were identified. Constitutive modelling of both MSW and soil material were reviewed, based on which the methodology for this study have been developed. In addition, requirements of an appropriate constitutive model for MSW have been suggested from the numerical modelling experience, and a framework to develop a constitutive model for MSW was produced. A one-dimensional compression model was developed by including the influence of compressible particles on MSW compression behaviour. One-dimensional compression tests on both real and synthetic waste samples were modelled and the results have shown that the compression model can reproduce the measured behaviour. A fibre reinforcing model was developed by including the influence of reinforcing particles on MSW shear behaviour. A triaxial compression test on fibre reinforced sand was modelled and the results have shown that the reinforcing model can predict its shear strength. A constitutive model for MSW has been developed by combining the Modified Cam-Clay with the one-dimensional compression and the fibre reinforcing models. Typical MSW triaxial compression tests have been modelled and the results have shown that the MSW model can reproduce the stress-strain behaviour in specific strain ranges. The constitutive model for MSW has been coded into a non-linear elasto-plastic finite element method program. Comparisons between the finite element analysis results and the analytical solutions have been performed and good agreements have been obtained.
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Leung, Janet (Janet H. ). "Effect of volume fraction of solids on the compressive stress-strain behavior of collagen-glycosaminoglycan scaffolds." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35062.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.Includes bibliographical references (leaf 35).
This thesis aims to examine the effect of volume fraction of solids in collagen-glycosaminoglycan (GAG) scaffolds on the compressive-strain behavior of the structure and compare these results to the open-cell foam model. Collagen-GAG (CG) scaffolds have been used for regenerating skin, conjunctiva, and peripheral nerves with varying levels of success. In these uses, the temporary scaffolds are often deployed with a non-degradable support structure such as a waterproof film or a silicone neural tube which are removed after healing is complete if it is outside the body (for skin regeneration) or are expected to remain permanently in the body (for nerve regeneration). Unfortunately, leaving non-degradable implants in the body could provoke immune responses. At the same time, to remove supports that have been implanted in the body after healing has been completed would result in more injury to the site and other medical complications. For a truly temporary implant, the scaffold must in its entirety be degradable. Thus, the bulk mechanical properties of the scaffold are important to study. Previous research has concentrated on the effects of cells on the scaffolds on a microlevel. However, the scaffold must also be able to bear mechanical stress from surrounding tissues to keep the wound open and provide mechanical support for the body, if, for example, collagen or bone is being regenerated. Here, the bulk mechanical properties of the scaffold are tested under uniaxial, unconfined compression. The Young's modulus and critical stress are calculated from the experimental data and compared to the values predicted by the open-celled foam model. There is very good agreement between the low density scaffolds, with variability in the results increasing with increasing density and with hydration of the specimens. Further research should focus on the
(cont.) However, the scaffold must also be able to bear mechanical stress from surrounding tissues to keep the wound open and provide mechanical support for the body, if, for example, collagen or bone is being regenerated. Here, the bulk mechanical properties of the scaffold are tested under uniaxial, unconfined compression. The Young's modulus and critical stress are calculated from the experimental data and compared to the values predicted by the open-celled foam model. There is very good agreement between the low density scaffolds, with variability in the results increasing with increasing density and with hydration of the specimens. Further research should focus on the origins and the effects of heterogeneities observed in the scaffold structures on the mechanical behavior.
by Janet Leung.
S.B.
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Paoletti, Francesca. "Behavior of oxyanions forming heavy metals in municipal solid waste incineration." Karlsruhe : FZKA, 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=967951496.
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Yakin, Bülent. "Combustor and nozzle effects on particulate behavior in solid rocket motors /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA277304.
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Yakin, Bulent. "Combustor and nozzle effects on particulate behavior in solid rocket motors." Thesis, Monterey, California. Naval Postgraduate School, 1993. http://hdl.handle.net/10945/39764.
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Approved for public release; distribution is unlimited.An investigation was conducted using a subscale solid rocket motor to measure the effect of nozzle residence time on the behavior of Al203 particles to assess the applicability of subscale motor data to full-scale motors and to measure the effects of nozzle entrance particle size distribution on the slag accumulated with submerged nozzles. Although particles as large as 140 micrometers were present at the nozzle entrance, most of the particulate mass was contained in much smaller particles. This observation is in good agreement with the small mass that accumulated above the submerged nozzle. It was found that both particle breakup and collision coalescence occurred across the exhaust nozzle, with a significant increase in the mass fraction of small (<2 micrometers) particles. Increasing the nozzle residence time enhanced particle breakup but did not affect the maximum plume particle size. Thus, full-scale motors are expected to have a higher percentage of mass in particles less than 2 micrometers than subscale motors but with similar diameters of the largest particles.
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Chan, Yik Chung. "Solubility measurement apparatus for rapid determination of solid-liquid equilibrium behavior /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CBME%202008%20CHANY.
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Yurko, James Andrew 1975. "Fluid flow behavior of semi-solid aluminum at high shear rates." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8451.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2001."June 2001."
Includes bibliographical references (leaves 119-127).
The rheological behavior and microstructure of semi-solid aluminum alloys were studied using a novel apparatus, the Drop Forge Viscometer (DFV). The viscometer determines force from the curvature of displacement data allowing calculations of viscosities at shear rates in excess of 1000 s-1. Alternatively, the DFV can be operated like a conventional parallel-plate compression viscometer, attaining shear rates as low as 10-5 s-1. Durations of an experiment range between approximately 5 ms and 24 hours. Most rapid compression tests resulted in periods of first rapidly increasing shear rate followed by rapidly decreasing shear rate. Viscosity during the increasing shear rate period decreased by 1-2 orders of magnitude. The viscosity during the decreasing shear rate was an order of magnitude smaller (relative to another experiment) when it achieved a 75% greater maximum shear rate. The DFV was used to calculate viscosity as a function of shear rate for Al-Si and Al-Cu alloys that were rheocast with the commercial SIMA and MHD processes, as well as the recently developed MIT method. Experiments were conducted between fractions solid of 0.44 and 0.67. Viscosity of A357 produced by the three processing routes all had similar viscosities, ranging from 300 Pas at 120 s-1 to 2.2 Pas at 1500 s-1. The final height of compressed Al-Cu was always greater than Al-Si for a given set of experimental conditions. Segregation was not observed in rapid compression experiments shorter than 10 ms, either visually or with EDS characterization. At low compression velocities, segregation was observed and increased with the amount of strain.
by James Andrew Yurko.
Ph.D.
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Tesfaye, Alexander Teklit. "Study and improve the electrochemical behaviour of new negative electrodes for li-ion batteries." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0346/document.
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Les accumulateurs commerciaux à base de lithium-ion (LIB) utilisent des matériaux à base de carbone (graphite) comme électrode négative; cependant, la technologie atteint sa limite en raison de la faible capacité spécifique théorique. L'objectif de cette thèse est d'étudier le comportement électrochimique de trois nouvelles anodes à haute capacité (SnSb microsturé, Ti3SiC2 anodisé et nanotubes de Si poreux) comme alternatives au graphite, d'identifier les principaux paramètres responsables de la perte de capacité et de proposer une solution commune pour améliorer leurs performances électrochimiques. Ces matériaux d'électrode présentent une bonne performance électrochimique qui les rend prometteurs pour remplacer le carbone en tant qu'électrode négative pour batteries au Li-ion. Cependant, ils présentent une perte de capacité initiale importante qui doit être résolue avant la commercialisation. Les limitations observées sont attribuées à de nombreux facteurs, et en particulier à la formation et la croissance d’une SEI à la surface des matériaux. En raison de la forte perte de la capacité et du manque d’études détaillées sur les matériaux à base d’étain, en particulier le SnSb, nous avons concentré la suite du travail à la formation et la croissance de la SEI sur cette électrode négative. L'évolution des propriétés électriques, de la composition chimique et de la morphologie du SnSb microstructuré a été étudiée en détail pour comprendre son comportement électrochimique. Pour limiter l’effet de la SEI, nous avons proposé d’appliquer un film protecteur à la surface de l'électrodeCurrently, commercial lithium ion batteries (LIBs) use carbon based materials as negative electrode; however the technology is reaching its limit because of the low theoretical specific capacity. The objective of this thesis is to study the electrochemical behaviour of three different new high capacity anodes (SnSb alloy, anodized Ti3SiC2, and Si nanotubes) as alternative to graphite, identify the main parameters responsible for the capacity fading, and propose a versatile solution to improve their electrochemical performance. These electrode materials exhibit good electrochemical performance which makes them promising candidates to replace carbon as a negative electrode for LIBs. However, their limitation due to capacity fading and the large initial irreversible capacity loss must be resolved before commercialization. The observed limitations are attributed to many factors, and particularly, to the formation and growth of SEI layer which is the common factor for all the three electrode materials. Because of the strong capacity fade and lack of many detailed studies on the Sn-based materials, specifically SnSb, we focus our study to investigate the formation and growth of SEI layer on SnSb electrode. The evolution of the electrical, compositional, and morphological properties have been investigated in detail to understand the electrochemical behavior of micron-sized SnSb. To limit the capacity fade, we propose the use of a protective film on the electrode surface. The electrochemical performance of micron-sized SnSb electrode coated with thermoplastic elastomer protective film, namely poly(styrene-b-2-hydroxyethyl acrylate) PS-b-PHEA has been achieved
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Gustafsson, Christina. "Solid state characterisation and compaction behaviour of pharmaceutical materials." Doctoral thesis, Uppsala University, Department of Pharmacy, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-509.
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In this thesis, factors important in tableting operations and for tablet properties have been studied and characterised by different spectroscopic techniques as well as by some more conventionally used particle characterisation techniques. The spectroscopic techniques solid-state NMR, FT-IR and NIR spectroscopy, proved to be valuable tools in the estimation of particle and tablet properties, offering both specificity and sensitivity in the measurements. Because of the large amount of information obtained in a spectrum, multivariate data analysis was in some cases used in the processing of the spectral data. Correlations between the solid state structure measured by spectroscopy and the particle and tablet properties could be obtained including useful prediction models.
The surface area obtained using different principles has in this thesis been shown to reflect different properties and tableting behaviour of a collection of pharmaceutical materials. The particle shape and the external surface area of the powders measured by permeametry, were found to be important factors for the tensile strength of tablets made of hydroxypropyl methylcellulose. Furthermore, the external surface area could be used to access dominating interparticulate bonding mechanisms in compacts of different materials by normalising the tablet tensile strength for the tablet surface area. It was also shown that for materials prone to develop solid bridges, the actual surface area participating in the bonding was more important than the average interparticulate distance.
When studying the properties of microcrystalline cellulose and cellulose powder from the alga Cladophora sp., the cellulose fibril surface area estimated by solid-state NMR resulted in better correlations to the tableting behaviour and to tablet disintegration than the external permeametric surface area did. It was suggested that the difference in fibril surface area of the two celluloses was the primary factor responsible for properties like the crystallinity and the disintegration of the tablets.
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Kim, Hee-Soo. "Microstructure and deformation behaviour of semi-solid aluminium alloys." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400141.
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Langer, Ulrich. "Shear and compression behaviour of undegraded municipal solid waste." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/3203.
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To ensure stability of a construction the physical properties of its components have tobe well known. In a landfill, waste presents the largest structural element and controlsboth the stability and integrity of the lining system. In spite of this critical role there is adearth of knowledge on behaviour of waste as an engineering material. Wastevariability and changes in waste stream aggravate the assessment of wastemechanical properties.In a literature review the main influences on shear behaviour of municipal solid waste(MSW) were identified. Design values and recommendation for shear parameter weresummarised. To assess mechanical behaviour in a systematic way the use of aclassification system was deemed crucial for a comparison of different findings fromliterature and a categorisation of waste in regard to its composition. A framework for aclassification system was introduced. Main elements of a comprehensive classificationsystem were identified in a literature review and discussed, and data from literaturewas applied to the classification framework. For the validation of a classificationsystem, municipal solid waste was examined in an in-situ waste sorting analysis andalso applied to the framework.The findings from the waste sorting and the classification system were also used todevelop a family of synthetic waste to gradually examine the influencing factors onwaste mechanical behaviour. For this, the materials, size ranges and shapes of wastecomponents identified in the waste sorting analysis were reduced to a minimum butstill representative amount. A range of synthetic waste compositions was engineeredand tested in a large-scale shear device. Compression tests were also conducted in alarge compression cell. The results from the laboratory testing were compared tovalues from the literature and MSW mechanical behaviour was subsequentlydiscussed in view to potential changes from changing waste streams.The results from shear and compression tests (constrained and shear modulus) onsynthetic waste were linked to the classification system and trends of the mechanicalbehaviour in relation to the tested synthetic waste compositions were identified.A framework for classifying MSW and comparing waste mechanical behaviour waspresented and demonstrated. A family of synthetic wastes was engineered and testedin shear and compression tests. The results were comparable to values from theliterature. Further research is recommended to refine the synthetic waste and theclassification.
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Westberg, Stig-Björn. "Sintering behaviour of α and β solid solution sialons." Doctoral thesis, Luleå tekniska universitet, 1992. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16900.
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Some ceramics have the ability to form solid solutions. One such group are the sialons, which contain silicon, aluminium, oxygen and nitrogen in specific proportions. Through a stabilizing process with yttrium, not only beta-sialons but also alfa-sialons can be produced. The basic difference between these two is in the two different crystal structures of the silicon nitride. This type of ceramic is usually produced by the sintering of powder mixtures at temperatures up to 1850ºC, during which complicated chemical reactions take place through a liquid phase. During sintering, the material is densified to a pore free body, characterized by high hardness, chemical inertness, high oxidation resistance and high strength at elevated temperature. Alfa- and beta-sialons with four different compositions were studied by means of high temperature sintering dilatometry. This allowed in situ studies of the densification process to be made during sintering. The compositions used werebeta-10 = Si5.23Al0.77O0.68N7.23, beta-60 = Si2Al4O4N4, alfa-33 = Y0.33Si10.51Al1.49O0.5 N15.51 and alfa-45 = Y0.45Si9.98Al2.02O0.68N15.32 .Reaction routes were determined by interrupted sintering with specimens cooled from different temperatures as well as the influence of the heating rate on the material phase composition and densification. In addition, the extent to which it is possible to control the densification by the heating rate profile was also established. Experiments were carried out in which specimens sintered with constant rate of heating were compared with specimens from sintering cycles established from a predetermined profile for the densification rate. The transient liquid which occures during the earliest stage of densification exists for only a short period of time during which only minor densification takes place. Instead, a sialon with specific composition apparently independent of the powder composition was precipitated from the liquid. This process largly absorbes the transient liquid. The composition of this first formed sialon is Si2.5Al3.5O3.5N4.5 for beta-sialon, and between Y0.40Si10.20Al1.80O0.6ON15.4 0 and Y0.50Si9.75Al2.25O0.75N15.25 for alfa-sialon. After this, the process continues by solution of the first formed sialon and alfa-Si3N4 from the powder, together with precipitation of a sialon with lower amount of additives. During this part of the reaction the main densification takes place. The densification behaviour of the high alloyed beta-60 composition differs from that of the others. Instead of densifying when the first liquid was formed, the greenbody started to expand. This is explained by the entrapment of gasses, evolved due to chemical reactions. The chemical composition of the phases formed contribute to the formation of a large amount of liquid during the early stages of sintering. The expansion continues until the material is completely transformed to beta-ss, whereafter it densifies rapidly. The densification is made possible by the completion of the transformation to beta-ss which reduces the amount of liquid phase and lets the evolved gas pass through the porous structure. The reactions taking place during sintering results in different phases being dissolved and precipitated which causes the composition of the liquid phase to change during densification. These different processes results in characteristic changes of the densification rate during sintering. Application of rate controlled sintering showed that it was possible to obtain a predetermined densification rate profile. However, depending on the composition, the densification rate profile which increases the bending strength of the beta-10 composition failed to do so for the beta-60 composition. Fractography revealed large pores to be the strength limiting defect. The results show that more than just the densification rate determine the optimum sintering programme. Depending on the composition, which leads to different reactions and structure during sintering, different sialons must be sintered with different sintering programmes to achieve optimum properties.Godkänd; 1992; 20070429 (ysko)
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Huang, Zhi. "Structure and phase behaviour of phosphatidylcholine-amphiphile mixtures." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283416.
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