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1
Norfleet, David Matthew. "Sample size effects related to nickel, titanium and nickel-titanium at the micron size scale." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1187038020.
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Tavana-Roudsari, Aria 1962. "FEEDBACK CONTROL OF CRYSTAL-SIZE DISTRIBUTION IN A POTASSIUM-CHLORIDE CRYSTALLIZER BY ESTIMATION OF NUCLEI DENSITY." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/291283.
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El-Awady, Jaafar Abbas. "Size effects on plasticity and fatigue microstructure evolution in FCC single crystals." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1693067871&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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4
Kok, Mei Yeng. "Orientation of molecular solutes in nematic liquid crystals : size and shape effects." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/25911.
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An understanding of the mechanisms of orientation of solutes in anisotropic solvents is of fundamental importance in the theory of liquid crystalline systems. A systematic study of these mechanisms is presently being conducted in this and other laboratories. As part of this investigation, the orientational order of a series of C[sub 2v] solutes in the liquid crystal mixture 55 wt% 1132 (Merck ZLI 1132) and 45 wt% partially deuterated EBBA (N-(4-ethoxybenzylidene)-2,6-dideutero-4-n-butylaniline) was studied using NMR spectroscopy. This technique provides a description of the average orientation of a solute in terms of the order parameters. The results obtained indicate a good correlation between order parameters and the size and shape of the solutes. A model based on short range hard body interactions, which depend on the dimensions of the solute, was used to predict orientational ordering. Excellent agreement was obtained between observed and calculated order parameters. These results provide supportive evidence that the mechanism responsible for orientation in the 55 wt% 1132 system is short range hard body interactions.
A side study was conducted on the ordering of furan and thiophene in the liquid crystalline solvents 1132 and EBBA. Temperature dependence of order parameters in 55 wt% 1132 were examined. Orientation in 1132 and EBBA and temperature dependence in 55 wt% 1132 can be explained in terms of:
(i) the short range interactions dependent on the dimensions of the solute, and
(ii) the interaction between the molecular quadrupole moment of the solute and the average electric field gradient which is due to the solvent.Science, Faculty of
Chemistry, Department of
Graduate
5
Becker, Martin. "Incompatibility and instability based size effects in crystals and composites at finite elastoplastic strains." Stuttgart Inst. für Mechanik (Bauwesen), 2006. http://deposit.d-nb.de/cgi-bin/dokserv?idn=980579732.
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Hutt, James. "The origin of equiaxed crystals and the grain size transition in aluminium-silicon alloys /." St. Lucia, Qld, 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16244.pdf.
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Chang, Li-Wu. "Revealing fundamental aspects of size effects in ferroelectrics through experiments on fiber single crystals." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527668.
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8
Demir, Eralp [Verfasser]. "Constitutive modeling of fcc single crystals and experimental study of mechanical size effects / Eralp Demir." Aachen : Shaker, 2010. http://d-nb.info/1104047683/34.
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9
Pessina, Florent. "Toward particle size reduction by spray flash evaporation : the case of organic energetic crystals and cocrystals." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAE031/document.
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La cristallisation en continu de nanoparticules énergétiques est un défi de longue date. Le Spray Flash Evaporation (SFE) est une technique majeure développée et brevetée en interne, pour la production en continu de matériaux énergétiques submicroniques ou nanométriques ; la technologie se base sur la surchauffe d’un solvant pulvérisé dans le vide et s’évaporant de manière flash. Ce présent travail de recherche a pour but de comprendre et contrôler la cristallisation au sein du procédé SFE. Le RDX et le cocristal CL-20:HMX 2:1 sont étudiés. La sursaturation, concernant le SFE, est une fonction du temps et de l’espace liée aux tailles et vitesses de gouttes : elle fut variée par un anti-solvant et par l’amélioration du SFE avec un système double buse. Ensuite, PVP 40K et PEG 400 ont été utilisés afin de contrôler la nucléation et la croissance. Les particules ont pu être ajustées d’une taille de 160 nm à 5 µm, avec des morphologies facettées ou sphériques et avec des sensibilités moindresThe continuous formation of nanosized energetic material is a long-standing challenge. Spray Flash Evaporation (SFE) is a major technique, internally developed and patented, for continuously producing energetic materials at submicron or nano scale; it relies on the superheating of a solvent sprayed into vacuum and thus flashing. This present research project aims to understand and control the crystallisation occurring in the SFE process. RDX and the cocrystal CL-20:HMX 2:1 was studied overcome the limited in situ characterizations also. The supersaturation is a function of time and space in SFE, linked to the size distribution and velocity of droplets. Supersaturation was raised with an anti-solvent and by the enhancement of the SFE with a dual nozzle system. Then PVP 40K and PEG 400 were successfully used to alter the nucleation and the growth. The particles were subsequently tuned from 160 nm spheres to 5 µm grains and were less sensitive, especially toward electrostatic discharge
10
Synnatschke, Kevin [Verfasser], and Claudia [Akademischer Betreuer] Backes. "Liquid phase exfoliation and size dependent properties of van der Waals crystals / Kevin Synnatschke ; Betreuer: Claudia Backes." Heidelberg : Universitätsbibliothek Heidelberg, 2021. http://d-nb.info/1229695400/34.
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11
Kim, Gyu Seok. "Small volume investigation of slip and twinning in magnesium single crystals." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENI072/document.
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XA combined experimental and computational investigation of the deformation behavior of pure magnesium single crystal at the micron length scale has been carried out. Employing the recently exploited method of microcompression testing, uniaxial microcompression experiments have been performed on magnesium single crystals with [0001], [2-1-12], [10-11], [11-20] and [10-10] compression axes. The advantage of the microcompression method over conventional mechanical testing techniques is the ability to localize a single crystalline volume which is characterizable after deformation. The stress-strain relations resulting from microcompression experiments are presented and discussed in terms of orientation dependent slip activity, twinning mechanisms and an anisotropic size effect. Such a mechanistic picture of the deformation behavior is revealed through SEM, EBSD and TEM characterization of the deformation structures, and further supported by 3D discrete dislocation dynamics simulations. The [0001], [2-1-12], and [10-11] compression axes results show dislocation plasticity. Specifically, the deformation due to [0001] compression is governed by pyramidal slip and displays significant hardening and massive unstable shear at stresses above 500MPa. In the case of the two orientations with compression along an axis 45 degrees to the basal plane, unsurpringly it is found that basal slip dominates the deformation. In contrast, compression along the [11-20] and [10-10] directions show deformation twinning in addition to dislocation plasticity. In the case of compression along [11-20], the twinning leads to easy basal slip, while the twin resultant during compression along [10-10] does not lead to easy basal slip. In all cases, a size effect in the stress-strain behavior is observed; the flow stress increases with decreasing column diameter. Furthermore, the extent of the size effect is shown to depend strongly on the number of active slip systems; compression along the [0001] axis is associated with 12 slips systems and displays a saturation of the size effect at a diameter of 10μm, while the other orientations still show a significant size effect at this diameter. The experimental evidence of an orientation-dependent deformation behavior in flow stress has been investigated by 3D discrete dislocation dynamics simulations. Here, the code TRIDIS was modified for hcp structure and c/a ratio of Mg. By matching the simulation results to experimental results, some proper constitutive material parameters such as initial dislocation density, dislocation source length, the critical resolved shear stress were suggested. For the case of [0001] and [2-1-12] orientation, dislocation feature in the pillar during the deformation was exhibited and strain burst was discussed
12
Shariare, Mohammad Hossain. "The rational design of drug crystals to facilitate particle size reduction : investigation of crystallisation conditions and crystal properties to enable optimised particle processing and comminution." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5395.
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Micronisation of active pharmaceutical ingredients (APIs) to achieve desirable quality attributes for formulation preparation and drug delivery remains a major challenge in the pharmaceutical sciences. It is therefore important that the relationships between crystal structure, the mechanical properties of powders and their subsequent influence on processing behaviour are well understood. The aim of this project was therefore to determine the relative importance of particle attributes including size, crystal quality and morphology on processing behaviour and the characteristics of micronised materials. It was then subsequently intended to link this behaviour back to crystal structure and the nature of molecular packing and intermolecular interactions within the crystal lattice enabling the identification of some generic rules which govern the quality of size reduced powders. In this regard, different sieve fractions of lactose monohydrate and crystal variants of ibuprofen and salbutamol sulphate (size, morphology and crystal quality) were investigated in order to determine those factors with greatest impact on post-micronisation measures of particle quality including particle size, degree of crystallinity and surface energy. The results showed that smaller sized feedstock should typically be used to achieve ultrafine powders with high crystallinity. This finding is attributed to the reduced number of fracture events necessary to reduce the size of the particles leading to decreases in milling residence time. However the frequency of crystal cracks is also important, with these imperfections being implicated in crack propagation and brittle fracture. Ibuprofen crystals with a greater number of cracks showed a greater propensity for comminution. Salbutamol sulphate with a high degree of crystal dislocations however gave highly energetic powders, with reduced degree of crystallinity owing to the role dislocations play in facilitating plastic deformation, minimising fragmentation and extending the residence of particles in the microniser. Throughout these studies, morphology was also shown to be critical, with needle like morphology giving increased propensity for size reduction for both ibuprofen and salbutamol sulphate, which is related to the small crack propagation length of these crystals. This behaviour is also attributed to differences in the relative facet areas for the different morphologies of particles, with associated alternative deformation behaviour and slip direction influencing the size reduction process. Molecular modelling demonstrated a general relationship between low energy slip planes, d-spacing and brittleness for a range of materials, with finer particle size distributions achieved for APIs with low value of highest d-spacings for identified slip planes. The highest d-spacing for any material can be readily determined by PXRD (powder x-ray diffraction) which can potentially be used to rank the milling behaviour of pharmaceutical materials and provides a rapid assessment tool to aid process and formulation design. These studies have shown that a range of crystal properties of feedstock can be controlled in order to provide micronised powders with desirable attributes. These include the size, morphology and the density of defects and dislocations in the crystals of the feedstock. Further studies are however required to identify strategies to ensure inter-batch consistency in these attributes following crystallisation of organic molecules.
13
Shariare, Mohammad H. "The rational design of drug crystals to facilitate particle size reduction. Investigation of crystallisation conditions and crystal properties to enable optimised particle processing and comminution." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5395.
Full textAbstract:
Micronisation of active pharmaceutical ingredients (APIs) to achieve desirable quality attributes for formulation preparation and drug delivery remains a major challenge in the pharmaceutical sciences. It is therefore important that the relationships between crystal structure, the mechanical properties of powders and their subsequent influence on processing behaviour are well understood. The aim of this project was therefore to determine the relative importance of particle attributes including size, crystal quality and morphology on processing behaviour and the characteristics of micronised materials. It was then subsequently intended to link this behaviour back to crystal structure and the nature of molecular packing and intermolecular interactions within the crystal lattice enabling the identification of some generic rules which govern the quality of size reduced powders. In this regard, different sieve fractions of lactose monohydrate and crystal variants of ibuprofen and salbutamol sulphate (size, morphology and crystal quality) were investigated in order to determine those factors with greatest impact on post-micronisation measures of particle quality including particle size, degree of crystallinity and surface energy.
The results showed that smaller sized feedstock should typically be used to achieve ultrafine powders with high crystallinity. This finding is attributed to the reduced number of fracture events necessary to reduce the size of the particles leading to decreases in milling residence time. However the frequency of crystal cracks is also important, with these imperfections being implicated in crack propagation and brittle fracture. Ibuprofen crystals with a greater number of cracks showed a greater propensity for comminution. Salbutamol sulphate with a high degree of crystal dislocations however gave highly energetic powders, with reduced degree of crystallinity owing to the role dislocations play in facilitating plastic deformation, minimising fragmentation and extending the residence of particles in the microniser. Throughout these studies, morphology was also shown to be critical, with needle like morphology giving increased propensity for size reduction for both ibuprofen and salbutamol sulphate, which is related to the small crack propagation length of these crystals. This behaviour is also attributed to differences in the relative facet areas for the different morphologies of particles, with associated alternative deformation behaviour and slip direction influencing the size reduction process. Molecular modelling demonstrated a general relationship between low energy slip planes, d-spacing and brittleness for a range of materials, with finer particle size distributions achieved for APIs with low value of highest d-spacings for identified slip planes. The highest d-spacing for any material can be readily determined by PXRD (powder x-ray diffraction) which can potentially be used to rank the milling behaviour of pharmaceutical materials and provides a rapid assessment tool to aid process and formulation design.
These studies have shown that a range of crystal properties of feedstock can be controlled in order to provide micronised powders with desirable attributes. These include the size, morphology and the density of defects and dislocations in the crystals of the feedstock. Further studies are however required to identify strategies to ensure inter-batch consistency in these attributes following crystallisation of organic molecules.
14
Charmolue, Herve. "The effects of process variables on purity, size, and habit of L-serine crystals recovered by batch crystallization." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/11163.
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15
Zhou, Meijuan. "Development of novel nanostructured polymer membranes based on polymerizable lyotropic liquid crystals for aqueous molecular-size selective separations." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3239419.
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16
Kim, Gyu seok. "Small volume investigation of slip and twinning in magnesium single crystals." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00721838.
Full textAbstract:
A combined experimental and computational investigation of the deformation behavior of pure magnesium single crystal at the micron length scale has been carried out. Employing the recently exploited method of microcompression testing, uniaxial microcompression experiments have been performed on magnesium single crystals with [0001], [2-1-12], [10-11], [11-20] and [10-10] compression axes. The advantage of the microcompression method over conventional mechanical testing techniques is the ability to localize a single crystalline volume which is characterizable after deformation. The stress-strain relations resulting from microcompression experiments are presented and discussed in terms of orientation dependent slip activity, twinning mechanisms and an anisotropic size effect. Such a mechanistic picture of the deformation behavior is revealed through SEM, EBSD and TEM characterization of the deformation structures, and further supported by 3D discrete dislocation dynamics simulations. The [0001], [2-1-12], and [10-11] compression axes results show dislocation plasticity. Specifically, the deformation due to [0001] compression is governed by pyramidal slip and displays significant hardening and massive unstable shear at stresses above 500MPa. In the case of the two orientations with compression along an axis 45 degrees to the basal plane, unsurpringly it is found that basal slip dominates the deformation. In contrast, compression along the [11-20] and [10-10] directions show deformation twinning in addition to dislocation plasticity. In the case of compression along [11-20], the twinning leads to easy basal slip, while the twin resultant during compression along [10-10] does not lead to easy basal slip. In all cases, a size effect in the stress-strain behavior is observed; the flow stress increases with decreasing column diameter. Furthermore, the extent of the size effect is shown to depend strongly on the number of active slip systems; compression along the [0001] axis is associated with 12 slips systems and displays a saturation of the size effect at a diameter of 10μm, while the other orientations still show a significant size effect at this diameter. The experimental evidence of an orientation-dependent deformation behavior in flow stress has been investigated by 3D discrete dislocation dynamics simulations. Here, the code TRIDIS was modified for hcp structure and c/a ratio of Mg. By matching the simulation results to experimental results, some proper constitutive material parameters such as initial dislocation density, dislocation source length, the critical resolved shear stress were suggested. For the case of [0001] and [2-1-12] orientation, dislocation feature in the pillar during the deformation was exhibited and strain burst was discussed.
17
Kimble, Walter Lee. "Effect of mineral substrates on nucleation, size, morphology, and purity of chicken egg-white lysozyme crystals obtained from vapor diffusion." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/11267.
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Becker, Martin [Verfasser]. "Incompatibility and instability based size effects in crystals and composites at finite elastoplastic strains / Institut für Mechanik (Bauwesen) der Universität Stuttgart. Vorgelegt von Martin Becker." Stuttgart : Inst. für Mechanik (Bauwesen), 2006. http://d-nb.info/980579732/34.
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PERIGO, ELIO A. "Estudo das correlacoes entre microestrutura propriedades magneticas e fator de quadratura em imas sinterizadas de PrFeB e NdFeB processados com hidrogenio." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9423.
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Made available in DSpace on 2014-10-09T12:26:42Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:06:28Z (GMT). No. of bitstreams: 1 14042.pdf: 6705801 bytes, checksum: 3dbb089e18c9947629283f47af921286 (MD5)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
FAPESP:05/04711-2
20
Park, Jun Gwan. "Characteristic behavior of a side branch in a dendritic crystal growth." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1187198212.
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Simon, Darren, and s3027589@student rmit edu au. "Chemistry and Morphology of Polymer Thin Films for Electro-Optical Application." RMIT University. Applied Sciences, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070123.122707.
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Thin polymer films and their properties have been investigated. The characteristics of crystalline polymers according to film thickness have been improved using polycaprolactone (PCL). The melting enthalpy of PCL has increased when the film thickness decreased and the peak melting temperature showed no significant changes with film thickness. Film thickness variation influenced surface roughness and crystal size. Optical microscope images showed the rougher surface of thicker films. The spinning time has shown no influence on film thickness and no significant changes to surface roughness. Thin films of block copolymers were used in the surface modification study; films studied included poly(styrene-b-butadiene-b-styrene) (SBS) and poly(styrene-b-isoprene-b-styrene) (SIS) and their surface modifications have been controlled using different methods of treatment. Films of SIS heated at different temperatures have shown different surface texture and roughness. Films treated at low temperature (45 °C) had smooth surfaces when compared with films heated at high temperature (120 °C and 160 °C). Phase separation of SIS heated at (120 °C and 160 °C) caused bulges of different sizes to cover the surface. The height and width of the bulges showed variation with film thickness and heating. Substrate interaction with SBS and SIS block copolymer films showed different surface texture when using the same type of substrate and different texture were obtained when SBS solutions were spun onto different substrates. It has been demonstrated that using different solvents in copolymer preparation caused different texture. Thermal and surface property variations with film thickness have been improved using amorphous polymers. Surface roughness of poly(methyl methacrylate) PMMA and disperse red 1-poly(methyl methacrylate) DR1-PMMA, PMMA has improved using thickness variation. Glass transition temperature measurement has increased when film thickness was increased. The glass transition temperature (Tg) and surface roughness of UV15 UV - curable coating polymer has been modified using UV curing and heating methods. Tg variation was observed when curing time and curing intensity were changed causing the optical properties of the polymer to be more variable. A plasma etcher caused wrinkles to occur on the surface of unheated UV15. Tg of UV15 increased when curing time increased. The Fourier Transform Infrared Spectroscopy (FTIR) spectra of cured UV15 film have shown peak variations of the ester and carbon double bond regions over the range of 1850-1700 cm-1. Urethane-Urea (UU) Polymer thin films were used to investigate optical properties and develop an optical waveguide. Absorption and transmission properties of light using non-linear optical (NLO) polymer was investigated and used in optical waveguide fabrication. Refractive indices were measured to examine UU films at two different wavelengths. A UU film of 1 µm thickness caused a maximum absorption at max = 471 nm also obtained at 810 nm wavelength. Many methods of fabrication were used; photolithography, plasma etching in a barrel reactor and thin film deposition using sputtering and evaporation. Etched depths from 1 μm to 100 μm were obtained. An optical waveguide has been prepared using plasma etching of a cured UV15 as a cladding layer on a silicon substrate.
22
Pandey, Rajiv 1967. "Crystal size manipulation of acetaminophen via recrystallization." Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/278344.
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The crystal size distribution (CSD) of any material determines its end use. Consequently, comminution processes are used to transform material from one size distribution to another. Often, recrystallization from solution is one of the processes used. Recently, a novel recrystallization process named the GAS process was developed to mill compounds that were thermally labile and insoluble in supercritical fluids. CSD could be manipulated using this process. To further illustrate the applicability of this process, size manipulation studies of acetaminophen (a widely available drug) were performed. The aim of this work was to produce crystals in the mass mean size range from 5mum to 50mum, and identify the conditions for producing the desired size distribution. A modified GAS process and a liquid anti-solvent (LAS) process were also investigated. Together with acetaminophen-butanol, other systems studied were aspirin-methanol and benzoic acid-methanol.
23
Kuylenstierna, Elin. "The Crystal Size Distribution of Cerro Bayo." Thesis, Uppsala universitet, Mineralogi, petrologi och tektonik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-354154.
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To understand the complex structure of magmatic plumbing systems beneath volcanoes, one needs to study the different textures shown in the igneous rocks produced by the volcano in question. By doing this, one can get a clue of the processes that resulted in the final rock. One of the most important methods to use for studying rock samples is the Crystal Size Distribution (CSD), which can reveal a great amount of information about the history of the rock and give an insight in the journey of the crystals during their time in the magma. An extinct volcano named Chachahuén, located in Argentina, South America, was chosen for this study. Samples of rock were collected from one of its laccoliths named Cerro Bayo and was identified as hornblende-bearing dacite. The difference in crystal size was very significant in these samples, with both larger and smaller crystals embedded in the same matrix. This is interesting considering the fact that large crystals form by slow cooling of the magma while smaller crystals form as the magma cools rapidly. By studying the CSD and interpreting other textures found in samples of igneous rock, one may interpret different processes which affected the crystals, indicating what the structure of the magma chamber once looked like.För att kunna förstå den komplexa strukturen hos magmatiska system under vulkaner måste man studera olika texturer som påträffas i de magmatiska bergarter producerade av vulkanen i fråga. Genom att göra detta kan man få en inblick i de processer som resulterade i den slutgiltiga bergarten. En av de viktigaste metoderna att använda sig av för att studera stenprov är kristallstorleksfördelningen (CSD), som kan avslöja en mängd viktig information om bergarten och kristallernas historia under sin färd i magman. En slocknad vulkan vid namn Chachahuén belägen i Argentina, Sydamerika, valdes ut för denna studie. Stenprover samlades från en av dess lakkoliter med namnet Cerro Bayo, och identifierades som hornblände-bärande dacit. Skillnaden i kristallstorleken var mycket markant, med både större och mindre kristaller inbäddade i samma matrix. Detta är intressant med tanke på att stora kristaller bildas under en långsam nedkylning av magma medan mindre kristaller bildas när magma kyls ner snabbt. Genom att studera CSD och tolka andra texturer som finns hos magmatiska stenprover kan man tolka olika processer som har påverkat kristallerna, vilket i sin tur indikerar hur strukturen av magmakammaren en gång såg ut.
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Fromm, Bradley S. "Incorporating grain size effects in Taylor crystal plasticity /." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2261.pdf.
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Fromm, Bradley S. "Incorporating Grain Size Effects in Taylor Crystal Plasticity." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1275.
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A method to incorporate grain size effects into crystal plasticity is presented. The classical Hall-Petch equation inaccurately predicts the macroscopic yield strength for materials with non-equiaxed grains or materials that contain unequal grain size distributions. These deficiencies can be overcome by incorporating both grain size and orientation characteristics into crystal plasticity theory. Homogenization relationships based on a viscoplastic Taylor-like approach are introduced along with a new function, the grain size and orientation distribution function (GSODF). Estimates of the GSODF for high purity α-titanium are recovered through orientation imaging microscopy coupled with the chord length distribution. A comparison between the new method and the traditional viscoplastic Taylor approach is made by evaluating yield surface plots.
26
TSURUOKA, SYUJI. "DYNAMICS AND FEEDBACK CONTROL OF CRYSTAL SIZE DISTRIBUTION IN A CONTINUOUS CRYSTALLIZER." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183847.
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A simulation algorithm for crystal size distribution dynamics in a continuous crystallizer was developed using the method of lines. Dimensionless crystal sizes, in vector form, were used as state variables. Simulation results using this algorithm satisfied stability criteria for continuous crystallizers, which had been developed previously using different methods. The use of a state space representation of the algorithm permits the use of well-known theoretical and numerical approaches to the modeling of an experimental R-z crystallizer and for design of a proportional controller for a continuous crystallizer system. Boundary conditions defined by the nucleation/growth rate kinetics were separately written as an auxiliary function so that other kinetics can be substituted without any change of the main algorithm. This implies that the algorithm is applicable for any growth-type particulate system. CSD dynamics from an experimental crystallizer were satisfactorily modelled using this algorithm with reasonable parameters: e.g. the recycle ratios of the fines dissolver and the product classifier, crystal sizes at the upper cut size of the dissolver and at the lower cut size of the classifier, initial CSD, and the form of the upset. Algorithms for controller design using pole placement and optimization techniques were applied to develop a proportional matrix controller for an R-z crystallizer. It was evident that pole placement is a better method than optimization to design a controller for this crystallizer system. The system poles are concentrated at a point and it is necessary to assign the controller poles further apart to obtain appropriate control. To summarize controller design using the pole placement method, a schematic flow diagram of a system controller using the minimum order Luenberger observer was illustrated. In this example, only a few population densities need to be measured to drive the controller.
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Lee, Michael Siew Khay. "Side chain liquid crystal polysiloxanes." Thesis, University of Hull, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384846.
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Christie, David W. "Alternating copolymers containing side-chain liquid crystal groups." Thesis, University of Aberdeen, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311158.
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The copolymerisation of N-ethyl maleimide (NEM) with ethyl vinyl ether (EVE) in benzene (Bz) was investigated. The copolymerisation displays a tendency towards alternation but is not alternating and propagation involves the formation of a 1:1 NEM/EVE charge-transfer complex. This complex and the monomer/solvent complexes were investigated by 1H NMR spectroscopic methods. The equilibria were combined mathematically to model the NEM/EVE/Bz system. The copolymerisations of functionalised N-substituted maleimides, N-4-[6-(4'-methoxy-4-azobenzoxy) hexoxycarbonyl] phenylmaleimide (NMeAz6PM) and N-4-[6-(4'-nitro-4-azobenzoxy)hexoxycarbonyl] phenylmaleimide (NNitAz6PM), with styrene (St), 4-vinyl pyridine (4VP), or EVE as the comonomer were studied and the reactivity ratios calculated. The monomer pairs NMeAz6PM/St, NMeAz6PM/4VP and NNitAz6PM/St produce alternating copolymers but NMeAz6PM/EVE does not. The absence of liquid crystallinity in these materials was attributed to the rigidity of the polymer backbone coupled with the low mesogen content arising from the alternating backbone. Blends of amorphous maleimide based copolymers with 6-(4-methoxy-4'-azobenzoxy)hexanoic acid, 4.2, were investigated. The copolymers chosen were believed to be alternating and are the product of the copolymerisation of N-phenyl, N-(4-methoxy) phenyl, or N-(4-hydroxy) phenyl maleimide with St or 4VP. 4.2 is essentially immiscible with the St based copolymers. However 4.2 is miscible with the 4VP based copolymers and liquid crystallinity is induced. This behaviour is attributed to the formation of hydrogen bonds between 4.2 and the pyridyl units of the copolymer backbone. Blends of 4.2 or 6-(4-nitro-4'azobenzoxy)hexanoic acid, 5.2, with copoly(NMeAz6PM-alt-St) or copoly(NMeAz6PM-alt-4VP) were investigated. The limited miscibility and liquid crystalline behaviour of the acid/styrene copolymer blends was attributed to interactions between the mesogens on the copolymer and the acid. However, the enhanced miscibility and liquid crystalline behaviour seen in the pyridine blends can be attributed to the formation of hydrogen bonds between the acids and the pyridyl units of the backbone, in addition to the acid/copolymer mesogen interactions.
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Elliott, Alice Margaret Sophie. "The physical structure of a system of mesogenic side chain polymers." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388435.
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Yoo, Hyun Seung. "Color Illusions on Liquid Crystal Displays and Design Guidelines for Information Visualization." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/36372.
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The influence of color on size and depth perception has been explored for a century, but there is very limited research on interventions that can reduce the color illusions. This study was motivated to identify interventions and propose design guidelines for information visualization, especially where size judgment is critical.
This study replicated the color size illusion and color depth illusion on an LCD monitor and it was found that yellow is the smallest and farthest color among red, yellow, green, and blue on a white background. Three types of interventions (background brightness, border color, and background grid brightness) were tested to identify the conditions that reduce the color illusions, but all of them were not statistically significant.
Based on the experiment results and literature survey, design guidelines were proposed. To extend the guidelines to the bioinformatics field, design recommendations were proposed and implementation examples were illustrated. Evaluations on design implementations were evaluated by interviewing domain experts.
Additionally, the relationship between the color size illusion and the color depth illusion was explored.
Master of Science
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Sharnez, Rizwan 1960. "Dynamic simulation and control of crystal-size distribution in a continuous crystallizer." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/558079.
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Johnson, Jeffrey L. "Multivariable control of the crystal size distribution in an MSMPR crystallizer." Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/11245.
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Hartman, R. M. "Pyrolitic graphite films : Their preparation, crystal size, orientation and other properties." Thesis, Lancaster University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377389.
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Demiral, Murat. "Enhanced gradient crystal-plasticity study of size effects in B.C.C. metal." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/11634.
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Owing to continuous miniaturization, many modern high-technology applications such as medical and optical devices, thermal barrier coatings, electronics, micro- and nano-electro mechanical systems (MEMS and NEMS), gems industry and semiconductors increasingly use components with sizes down to a few micrometers and even smaller. Understanding their deformation mechanisms and assessing their mechanical performance help to achieve new insights or design new material systems with superior properties through controlled microstructure at the appropriate scales. However, a fundamental understanding of mechanical response in surface-dominated structures, different than their bulk behaviours, is still elusive. In this thesis, the size effect in a single-crystal Ti alloy (Ti15V3Cr3Al3Sn) is investigated. To achieve this, nanoindentation and micropillar (with a square cross-section) compression tests were carried out in collaboration with Swiss Federal Laboratories for Materials Testing and Research (EMPA), Switzerland. Three-dimensional finite element models of compression and indentation with an implicit time-integration scheme incorporating a strain-gradient crystal-plasticity (SGCP) theory were developed to accurately represent deformation of the studied body-centered cubic metallic material. An appropriate hardening model was implemented to account for strain-hardening of the active slip systems, determined experimentally. The optimized set of parameters characterizing the deformation behaviour of Ti alloy was obtained based on a direct comparison of simulations and the experiments. An enhanced model based on the SGCP theory (EMSGCP), accounting for an initial microstructure of samples in terms of different types of dislocations (statistically stored and geometrically necessary dislocations), was suggested and used in the numerical analysis. This meso-scale continuum theory bridges the gap between the discrete-dislocation dynamics theory, where simulations are performed at strain rates several orders of magnitude higher than those in experiments, and the classical continuum-plasticity theory, which cannot explain the dependence of mechanical response on a specimen s size since there is no length scale in its constitutive description. A case study was performed using a cylindrical pillar to examine, on the one hand, accuracy of the proposed EMSGCP theory and, on the other hand, its universality for different pillar geometries. An extensive numerical study of the size effect in micron-size pillars was also implemented. On the other hand, an anisotropic character of surface topographies around indents along different crystallographic orientations of single crystals obtained in numerical simulations was compared to experimental findings. The size effect in nano-indentation was studied numerically. The differences in the observed hardness values for various indenter types were investigated using the developed EMSGCP theory.
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Liu, Xiao-Hua. "Calamitic octahedral manganese(I) and rhenium(I) metallomesogens and side chain liquid crystalline poly(ferrocenylsilanes)." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264433.
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Waigh, Thomas Andrew. "The structure and side-chain liquid-crystalline polymeric properties of starch." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284951.
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Patchigolla, Kumar. "Particle process measurements : shape and size with crystal growth and nucleation kinetics." Thesis, Heriot-Watt University, 2007. http://hdl.handle.net/10399/2088.
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To deduce particle size information, the majority of particle sizing techniques assume that the particles are spheres. For industrial materials, particles are rarely spherical. Non-sphericity causes discrepancies in different measurement technologies so results vary from the real characteristics of the sample. Applications like crystallisation require .shape information in addition to the size of the particles. The majority of this thesis describes results that have demonstrated that particle shape has a strong influence on particle size distribution measured by different techniques. The effect of shape on measured particle size distribution was investigated by ultrasonic attenuation spectroscopy (VAS) compared with other widely used techniques such as laser diffraction spectroscopy (LDS), microscopic image analysis (MIA) and focused beam reflectance measurement (FBRM). A strategy was applied using different chemical systems to monitor the importance of shape to measured size distribution using different techniques; fragile and non-fragile, .sp-pericaC'crystalline and irregular materials were tested. The measurements were successfully applied to laboratory crystallisation processes of different organic and inorganic chemicals In-situ monitoring of particle size evolution during crystallisation using FBRM has aroused much interest. Therefore it was important to demonstrate the dependence of measured particle size on different operating conditions and more particularly on the hydrodynamic conditions, solvent, temperature and other physical and chemical , properties of the system. In-situ measurement of maximum supersaturation during batch crystallisation and dissolution processes of different chemical systems is presented, through which nucleation kinetics of the crystallisation was retrieved. This was clemonstrated for different organic and inorganic chemical systems using FBRM as a process analytical technique (PAT). Based on crystallisation behaviour and with process analytical techniques, notably FBRM to retrieve the nucleation kinetics, the growth kinetics of different chemical systems are presented based on seeded batch cooling crystallisation. Finally future developments within this area of research are presented.
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Rostron, Paul. "Synthesis of novel side chain liquid crystal polymers." Thesis, Northumbria University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245238.
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Talari, Kiran. "LIQUID CRYSTAL THERMOGRAPHY STUDIES IN WATER POOL BOILING AT SUBATMOSPHERIC PRESSURES." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3388.
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A pool boiling experimental facility has been designed and built to investigate nucleate pool boiling in water under sub atmospheric pressure. Liquid crystal thermography, a non intrusive technique, is used for the determination of surface temperature distributions. This technique uses encapsulated liquid crystals that reflect definite colors at specific temperatures and viewing angle. Design of the test section is important in this experimental study. Since a new TLC is required for every new set of test conditions, a permanently sealed test section is not an option. The real challenge is to design a leak proof test section which is flexible so that it can be taken apart easily. A plexiglass test section, including a top chamber with an internal volume of 60.9 x 60.9 x 66.4 mm and a bottom plate of 5.5mm thickness is designed and assembled together using quick grips. In the test section, water is boiled using 85.0mm x 16.0mm and 0.050mm thick Fecralloy® as the heating element. The TLC sheet is attached to the bottom plate and the heating element is placed on top of TLC so that the temperature distribution of the heating element during boiling can be interpreted from TLC. A camera system fast enough to capture the thermal response of the TLC and an arrangement to capture both hue of the TLC and growth of the bubble on the same frame has been designed and successfully used. This system allowed recording of position, size and shape of the bubble with synchronized surface temperature. In order to get hue vs. temperature relation, in-situ calibration of the TLC is performed for each test condition with the present experimental setup and lighting conditions. It is found that the calibration curve of the TLC at atmospheric pressure is different from the calibration curve of the same TLC at subatmospheric pressures. The maximum temperature difference between the two curves for the same hue is found to be only 0.6°C. The experiment is run at four different test conditions of subatmospheric pressure and low heat flux. It is run at system pressures of 6.2kPa (0.89Psi) and 8.0kPa (1.16Psi) with a constant heat flux of 1.88kW/m2 and 2.70kW/m2, and a constant heat flux of 2.70kW/m2, 3.662kW/m2 and 4.50 kW/m2 respectively. Analysis of nucleating surface temperatures using thermochromic liquid crystal technique is performed for these test conditions and the bubble dynamics is studied. The temperature distribution is quite varied in each case and the temperature is at its maximum value at the center of the bubble and it decreases radially from the center. The dry spot observed during the experiments indicates that the process of evaporation of the microlayer is dominant at subatmospheric pressures. It is observed that at very low pressure and heat flux the bubble growth is accompanied by the neck formation. Boiling parameters such as bubble frequency, bubble size and contact are also analyzed and a summary of these results for four different test conditions is presented and the relevant differences between the cases are discussed and the effect of increase in pressure and heat flux is noted.M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering
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Park, Kyoungweon. "Synthesis, Characterization, and Self-Assembly of Size Tunable Gold Nanorods." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14035.
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The successful applications of nanoparticles require the ability to tune their properties by controlling size and shape at the nanoscale. In metal nanomaterial research, the optical properties have been of interest especially because of the applications to medical diagnostics and nanooptics. It is important to prepare nanoparticles of well-defined shape and size for properly characterizing the optical properties.
We describe improved seed mediated synthesis of gold nanorods (GNRs) producing a high yield of NRs with low polydispersity and few byproducts. The efficient separation of GNRs from mixture of shapes is achieved by understanding the hydrodynamics of nanoparticles undergoing centrifugation. The optical properties of resulting refined GNRs are compared to predictions of existing theories, and the main parameters affecting them are discussed.
GNRs with well defined aspect ratios are introduced into a polyvinyl alcohol matrix by means of solution-casting techniques. The film is drawn to induce the uniaxial alignment of GNRs to be used as color polarizing filters. We prepare GNR polarizing filter with different peak positions ranging from visible to near infra red by using different aspect ratio of NRs.
To utilize GNRs to make nanoscale devices, spatial organization is required. We characterize the self-assembly of GNRs observed on a TEM grid. The drying process is accompanied by complex hydrodynamic and thermodynamic events, which create rich range of patterns observed. Being anisotropic in shape, the rods can form liquid crystal (LC) assemblies above a certain concentration. We observed LC phase of GNRs by resorting to an evaporation of aqueous NR solution. The convective flow caused by the solvent evaporation carries NRs from the bulk solution to solid-liquid-air interface, which makes the solution locally very concentrated driving the phase transition of NRs. We calculate the order parameter from various assemblies observed, and compare the observed phase behavior to the one expected on the basis of theory.
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Sinangil, Mehmet Selcuk. "Estimation of crystal size and inhomogeneous strain in polymers using single peak analysis." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/19096.
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Li, Jicong Ph D. Massachusetts Institute of Technology. "Novel continuous crystallization configurations for improved yield, purity and controlled crystal size distribution." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104210.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references.
Continuous crystallization process has potential advantages such as lower cost and improved flexibility in pharmaceutical production when compared to batch crystallization. A good continuous crystallization process should achieve a high product yield and purity comparable to current batch crystallization processes. The aim of this thesis is to develop novel continuous crystallization process to enhance the final yield while control the quality of the crystal product. Three different approaches were studied: (1) the use of continuous solids recycle to enhance the yield by increasing the crystal surface area and total crystal mass deposition; (2) the optimization of multistage continuous mixed-suspension, mixed-product removal (MSMPR) crystallization to minimize the number of stages and total residence time; (3) the combination of impurity complexation and organic solvent nanofiltration to remove the impurity that has similar molecular weight and structure to the active pharmaceutical ingredient (API). For the first two approaches, continuous crystallization processes of cyclosporine were developed. The first method, solids recycle, successfully increased the surface area of crystals in the crystallizer thus increasing the mass deposition rate. With solids recycle to the second stage and both stages, 75.3% and 79.8% in yield were achieved, respectively. The product purity remained the same while the yield was enhanced. The second method proved that optimization of stage conditions could help obtain high yield and purity within short residence time. Different behaviors of the impurities were investigated and the impurity distribution model helped estimate the highest product purity achievable of the process. The results showed that optimization in stage number and stage temperatures could improve the yield close to the batch yield at equilibrium. In the third method, fenofibrate and fenofibric acid system with 1,3-di-otolylguanidine (DOTG) as complexing agent was studied. Complexing agent firstly formed hydrogen bonds with the impurity specifically, thus reduced the structure similarity of the API and impurity. It became more difficult for the impurity molecules to incorporate into the API crystal lattice. Then organic solvent nanofiltration membrane separated the API and complex in the mother liquor. By recycling the purified mother liquor back to the crystallizer, the final yield of the process was improved.
by Jicong Li.
Ph. D.
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Lupica, Spagnolo Lucia. "Supramolecular templating agents and metal organic frameworks : control over crystal size and assembly." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/401110/.
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Metal organic frameworks(MOFs) are an interesting class of microcrystalline materials constituted by metal ions or clusters connected by organic linkers characterised by their high porosity and tunable structures. Due to their chemical variability and numerous applications they have received great attention during the last few decades. Recently also the control of their physical form or macroscopic structure, such as crystal size, morphology and the aggregation of the crystals into superstructures, have received more attention since it would further develop and enhance properties and applications of these materials. Indeed beside all the inherent properties derived from the chemical composition and microporosity of MOFs the higher level of order or the control over the dimensionality or shape of the particles should enrich their overall performance and open new fields of application, such as drug delivery or integration into electronic sensor devices. In this context three prototypical MOFs were investigated, namely HKUST-1, ZIF-8 and ZIF-61; at first an overview of the behavior of HKUST-1 in presence of templating agents was performed, which involved the use of Pluronic-P123 (HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H, EO20PO70EO20, EO=ethylene oxide, PO=propylene oxide) and two carboxylic acids, namely octanoic acid and dodecanoic acid, on the synthesis of HKUST-1. As a proof of concept, this chapter underlined the importance of the synthetic conditions and of the interactions between MOF precursors and templating agents in directing the macroscopic structure of the MOF Thereafter the directional self-assembly properties of ZIF-8 in aqueous media with the templating agents SPAN-80 and/or dodecane for the formation of hollow capsule and colloidosomes was investigated, again in relation to optimize the synthetic conditions and understand the mechanism behind the hollow structure formation, which finally depended on the nature of the templating agent and the MOF precursors-templating agent interactions. Furthermore the etching effect of imidazole on the hollow capsule, which led to flower-like microcapsules was analyzed. Furthermore the optimization of the synthesis of zni phase in aqueous media and the topological and morphological conversion from zni phase (ZIF-61) to sod phase (SALEM-2) promoted by the surfactant SPAN-80 was studied. The role of SPAN-80 was further investigated also in light of the variation of the composition of the two ZIFs and the thermodynamic of the system. Finally the thesis was an attempt to rationalized the mechanism of MOF macroscopic structures formation, considering the structural features of the starting MOF, the synthetic conditions and the choice of the templating agents, envisioning a design a priori of the macroscopic structure of MOFs.
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Borsos, Akos. "Modelling and control of crystal purity, size and shape distributions in crystallization processes." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/25478.
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Crystallization is a key unit operation used for obtaining purified products by many process industries. The key properties of the crystalline products, such as size and shape distribution, purity and polymorphic form are controlled by the crystallization process. All these properties impact significantly the downstream operations such as drying or filtration. Therefore, monitoring and controlling this process is fundamental to ensure the quality of the final product. Process analytical technology (PAT) brings numerous new methods and opportunities in the process analytics and real time process monitoring systems, which can be integrated into the control algorithm and provide high level optimal control strategies as well as deeper understanding of the process. Process monitoring helps develop mathematical models which can, in one hand, help in better understanding the processes and consecvently the development and application of advanced control methods in order to achieve better product quality. In this work, image processing and image analysis based direct nucleation control (IA-DNC) is developed in order to investigate the evolution of the crystal properties, such as crystal size, and crystal shape distribution. The IA-DNC approach is also compared to alternative DNC techniques, in which particle number were measured by Focused Beam Reflectance Measurement (FBRM) in order to control crystal size. A control approach is introduced that control the nucleation and disappearance of crystals during cooling and heating segments related to the changes of the number of counts (measured by Particle Vision Measurment, so called PVM or combination of FBRM and PVM). The approach was applied to investigate crystallization of compounds with different behavior: potassium dihydrogen phosphate (KDP) water, contaminated KDP -water and Ascorbic acid water systems. The results demonstrate the application of imaging technique for model-free feedback control for tailoring crystal product properties. The second main aim of the thesis is to investigate and control crystallization processes in impure media in the presence of multiple impurities, with an impact on the crystal shape via growth kinetics. The broad impact of the crystal growth modifiers (impurities) on the growth kinetics is observed in real time by using in situ video imaging probe and real-time image analysis. A morphological population balance model is developed, which incorporates a multi-site, competitive adsorption mechanism of the impurities on the crystal faces. The kinetic parameters of primary nucleation, growth and impurity adsorption for a model system of potassium dihydrogen phosphate crystallization in water in the presence of two impurities, were estimated and validated with experimental results. It was demonstrated that the model can be used to describe the dynamic evolution of crystal properties, such as size and aspect ratio during crystallization for different impurity profiles in the system. Manual, feedback and hybrid feedback-feedforward control techniques are developed and investigated numerically for continuous processes, while model-based and model-free control approach for crystal shape are developed for batch processes. The developed morphological population balance model is implemented and applied in the model-based control approaches, which are suitable to describe multicomponent adsorption processes and their influence on the crystal shape. Case studies show the effectiveness of crystal growth modifiers based shape control techniques. Comparison of different control approaches shows the effectiveness of the techniques. The third part of the thesis deals with purification of crystals when adsorption of impurities on crystal surfaces and its incorporation into crystals are considered. A purification method, called competitive purity control (CPC) is proposed and investigated. A morphological population balance model, including nucleation, growth and competitive impurity adsorption kinetics is developed to describe the case when multiple impurities can adsorb competitively on the crystal surface. The model is also combined with liquid phase chemical reaction model, in order to investigate the purity control case when an additive is introduced in the system that reacts with the impurity forming a non-adsorbing reaction product. Both competitive purity control approaches proposed: the adsorption based competitive purity control (A-CPC) and the reaction based competitive purity control (R-CPC); are investigated using detailed numerical simulations then compared with the alternative widely used purification method, called recrystallization. In the last contribution chapter, an integrated process optimization of a continuous chemical reactor and crystallizer is performed and studied numerically. The purpose of this study is to show the way in which the byproduct produced in the chemical reactor may affect the crystallization process and how its negative effect can be reduced by applying integrated process optimization. Sensitivity analysis of the system was performed by considering the flow rate and the concentration of substances in the input stream of the chemical reactor as manipulated process variables. Model based integrated process optimization and the sensitivity analysis in order to obtain improved quality product in terms of crystal size, shape and purity.
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Chang, Hyung-Jun. "Analysis of nano indentation size effect based on dislocation dynamics and crystal plasticity." Grenoble INPG, 2009. http://www.theses.fr/2009INPG0134.
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Ce mémoire de thèse concerne une étude expérimentale et numérique de l'essai d'indentation dans des monocristaux de cuivre. Des essais d'indentation sont réalisés sur différentes orientations du monocristal. L'effet de l'orientation de l'axe d'indentation est quantifié sur la modification de la courbe de charge et sur la forme de l'empreinte résiduelle observée par microscopie à force atomique. On observe un effet de taille pour de faibles profondeurs de pénétration de l'indenteur. Les simulations sont réalisées en utilisant un modèle de plasticité cristalline à variables internes qui prend en compte la densité de dislocations sur les différents systèmes de glissement. Le modèle est implémenté dans le logiciel ABAQUS à la fois en mode explicite et implicite. La valeur de certains paramètres du modèle est déterminée en comparant les résultats de simulations 3D d'indentations avec les expériences. L'effet de taille en indentation est reproduit en utilisant un modèle simplifié de plasticité à gradient. Finalement, le cas de l'indentation suivant l'axe (111) est simulée en utilisant une approche multiéchelle fondée sur la dynamique de dislocations dicrètes. Cette modélisation utilise des résultats de dynamique moléculaire spécifiant le procédé de germination de dislocations sous indenteurThis thesis deals with experiments and simulations of nanoindentation in copper single crystals. Indentation experiments are performed with different orientations of the indentation axis and both the load-displacement curve and the surface imprint observed by atomic force microscopy are analysed and compared. Indentation size effect is observed for low penetration of the indenter. Simulations are then performed using crystal plasticity finite element modelling. ABAQUS user subroutines are specially developed in order to account for the physics of dislocation activity in the twelve glide systems of copper crystals. 3D simulations are then performed and comparisons with the experiments give access to key parameters of the constitutive equations. The indentation size effect is reproduced using a simplified size effect theory implanted in the finite element modelling. Finally, a multiscale approach based on discrete dislocation dynamics is used to reproduce (111) indentations of copper single crystals. Molecular dynamics simulations give details of dislocation nucleation beneath the indenter. Dislocation dynamics simulations are then performed and the indentation size effect is addressed
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Parulekar, Sumedh. "A novel approach to manipulate cavity size In resorcinarenes." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001810.
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Buxton, Peter. "Synthesis of side-chain liquid crystal polymers by cyclopolymerisation." Thesis, University of Hull, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297391.
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Al-Ammar, Khalid Hassan Bader. "Electro-optic phenomena in side-chain liquid crystal polymers." Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279707.
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Craig, Aileen A. "Structure-property relationships in side chain liquid crystal polymers." Thesis, University of Aberdeen, 1996. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU551561.
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Knowledge-based rules relating polymer structure to thermal behaviour for side chain liquid crystal polymers are established and tested by the syntheses and characterisation of carefully selected homologous series of homo- and copolymers. The effects of the length and parity of the flexible spacer and the flexibility of the polymer backbone on thermal behaviour are considered in detail. The mesogenic properties of the poly-(4-methoxbipheny1-4'-yloxy)alkyl methacrylates are described; the clearing temperatures (Tcl) show a distinct odd-even effect while the glass transition temperatures (T g) decrease without alternation. Structural investigations of this series show that SA1 phases are exhibited. The transitional behaviour of the poly-4'-cyanobiphenyl-4'- yloxy)alkyl methacrylates shows that increasing backbone flexibility results in decreased Tgs but enhanced T cls. These trends are rationalised in terms of the ability of the anisotropic environment to confine the backbone. These empirical rules are tested using the poly-(4-methoxybiphenyl-4'-yloxy)alkyl acrylates. It is expected that the polyacrylate-based series will exhibit higher Tcls than the corresponding polymethacrylate-based series. The odd members of this series, however, display anomalously low T cls. This behaviour suggests that for the polyacrylates, the clearing transition is entropically driven whereas for the polymethacrylates it is enthalpically driven. The thermal and mechanical behaviour of the poly-(4-cyanoazaobenzene-4'-oxy)alkyl methacrylates are studied. The Tgs lie intermediate between those of the analogous methoxybiphenyl- and cyanobiphenyl-bases series. This is rationalised in terms of the smectic phase structure and the interaction strength parameter between mesogens. Dynamic mechanical thermal analysis detects a weak relaxation for members of this series which is considered to be associated with 180° reorientational jumps of the long axis of the mesogenic unit about the polymer backbone.
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Shade, Paul A. "Small Scale Mechanical Testing Techniques and Application to Evaluate a Single Crystal Nickel Superalloy." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1228103042.
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