Dissertations / Theses on the topic 'Physicl properties'
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1
Noh, Tae Won. "Optical properties of some metal-insulator composites /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487266362336089.
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Khammang, Alex. "Investigating Mechanical Properties of Metallic Nanowires using Molecular Dynamics." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3409.
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Metallic nanowires have useful applications in scanning tunneling microscopes and atomic force microscopes due to their unique sensitivity to force and electricity. These unique properties arise because of the large surface area to volume ratio. One of these properties is that introducing twinning planes the mechanical properties of metallic nanowires can be altered. The effects of twinning planes on metallic nanowires were studied using molecular dynamics simulations. Silver, copper, and nickel nanowires with and without twinning planes were simulated with engineering strain until the first yielding stress was obtained. The radial simulations showed that as the radius of twinned nanowires increased, the strength gained by introducing the twinning planes increased. The temperature simulations showed that nanowires with twinning planes were stronger than their un-twinned counterparts as temperature increased. The purpose of this investigation was to better understand the effect twinning planes had on metallic nanowires, so that future technological advances would benefit from the results.
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Adams, Alyssa M. "Exploring the Properties of Mira-Type Stars with Spectropolarimetry." Digital Commons @ East Tennessee State University, 2013. https://dc.etsu.edu/honors/118.
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Mira-type stars are luminous red giants that have pulsation periods that last anywhere between 100 and 700 days. The irregular behavior of their periods and atmospheric properties flag them as excellent candidates for astrophysical studies of non-spherical stars. This paper focuses on the linear polarization of light emitted from three Mira- type stars: Mira itself, R Leo, and V CVn. Polarimetric data from the University of Wisconsin’s Half-Wave Spectropolarimeter (HPOL) database, as well as other archives of polarimetric data, provide us with insight into the atmospheric and geometrical prop- erties of these three stars. We were able to study the net polarizations and position angles alongside light curves provided by AAVSO. The observed variable polarization is a clear signature of evolving aspherical geometries for these stars. However, we found a major surprise concerning the polarimetric characteristics in V CVn, which suggest that V CVn is unlike a traditional Mira-type variable star. We end with an exploration of new possibilities regarding the atmospheric properties of V CVn.
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Behera, Swayamprabha. "STABILITY AND SPECTROSCOPIC PROPERTIES OF NEGATIVE IONS." VCU Scholars Compass, 2011. http://scholarscompass.vcu.edu/etd/210.
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Negative ions play an important role in chemistry as building blocks of salts and oxidizing agents. Halogen atoms, due to their ability to attract electrons, readily form negative ions. Considerable interest exists in the design and synthesis of new negative ions called superhaogens whose electron affinities are much higher than those of halogen atoms. This thesis deals with the design of such species. Using density functional theory I have studied two classes of superhalogens. First one involves d1 transition metal (Sc, Y, La) atoms surrounded by Cl while the second one involves simple metals (Na, Mg, Al) surrounded by pseudohalogens such as CN. Geometry, electronic structure, and electron affinity of these species containing up to 5 ligands have been calculated. Studies reveal a fundamental difference between the interaction of transition and metal atoms with electronegative ligands. In addition, pseudohalogens can be used to synthesize a new class of superhalogens.
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Nielbock, Markus. "Physical properties of protostars." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=962916951.
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Amado, Pedro J. "Physical properties of starspots." Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387975.
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Nilsson, Frederik. "Alkylglucosides physical-chemical properties /." Lund : Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/39761789.html.
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Neglur, Rekha R. "Physical properties of solid-state erythromycin derived compounds." Thesis, Nelson Mandela Metropolitan University, 2016. http://hdl.handle.net/10948/7228.
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This thesis investigated the physical properties of the macrolide antibiotics: Erythromycin dihydrate (EM-DH), Roxithromycin monohydrate (RM-MH) and Azithromycin dihydrate (AZM-DH). The abovementioned hydrate compounds were investigated in terms of the hydrate-anhydrate crystal structure stability, dehydration and observed polymorphism under controlled temperature heating programs. Identified hydrate and anhydrate polymorphs were subjected to physical stability testing during controlled storage. EM-DH was characterized by thermal analysis (DSC, TGA), X-ray diffraction, FTIR and microscopy. Dehydration of EM-DH at temperatures of 100, 157 and 200°C (followed by supercooling to 25°C) produced the form (I) anhydrate (Tm =142.9°C), form (II) anhydrate (Tm = 184.7°C ) and amorph (II) (Tg = 118°C) respectively. The attempts to produce amorph (I) from melting (in vicinity of form (I) melt over temperature range 133°C to 144°C) and supercooling was unsuccessful due to the high crystallization tendency of the form (I) melt. Brief humidity exposure and controlled temperature (40°C)/ humidity storage for 4 days (0-96% RH) revealed hygroscopic behaviour for the anhydrate crystal (forms (I) and (II)) and amorph (II) forms. Form (II) converted to a nonstoichiometric hydrate where extent of water vapour absorption increased with increased storage humidity (2.1% absorbed moisture from recorded TGA at 96% RH). Amorph (II) exhibited similar trends but with greater water absorption of 4.7% (recorded with TGA) at 96% RH. The pulverization and sieving process of amorph (II) (at normal environmental conditions) was accompanied by some water vapour absorption (1.1%). A slightly lower absorbed moisture content of 3.3% (from TGA) after controlled 4 days storage at 40°C/ 96% RH was recorded. This suggested some physical instability (crystallization tendency) of amorph (II) after pulverization. The thermally induced dehydration of RM-MH by DSC-TG was evaluated structurally (SCXRD), morphologically (microscopy) and by kinetic analysis. Various kinetic analysis approaches were employed (advanced, approximation based integral and differential kinetic analysis methods) in order to obtain reliable dehydration kinetic parameters. The crystal structure was little affected by dehydration as most H-bonds were intramolecular and not integral to the crystal structure stability. Kinetic parameters from thermally stimulated dehydration indicated a multidimensional diffusion based mechanism, due to the escape of water from interlinked voids in crystal. The hygroscopicity of the forms RM-MH, Roxithromycin-anhydrate and amorph glass (Tg = 81.4°C) were investigated. Roxithromycinanhydrate (crystalline) converted readily to RM-MH which were found to be compositionally stable over the humidity range 43-96%RH. Amorphous glass exhibited increased water vapour absorption with increasing storage humidity (40°C/ 0-96% RH). TG analysis suggested a moisture content of 3.5% at 96% RH after 4 storage days. DSC and powder XRD analysis of stored pulverised amorphous glass indicated some physical instability due to water induced crystallization. Commercial AZM-DH and its modifications were characterized by thermal analysis (DSC, TGA), SC-XRD and microscopy. Thermally stimulated dehydration of AZM-DH occurred in a two-step process over different temperature ranges. This was attributed to different bonding environments for coordinated waters which were also verified from the crystal structure. Dehydration activation energies for thermally stimulated dehydration were however similar for both loss steps. This was attributed to similarities in the mode of H- bonding. Different forms of AZM were prepared by programmed temperature heating and cooling of AZM-DH. The prepared forms included amorphous glass (melt supercooling), amorphous powder (prepared below crystalline melting temperature), crystalline anhydrate and crystalline partial dehydrate. Humidity exposure indicated hygroscopic behaviour for the amorphous, crystalline anhydrate and crystalline partial dehydrate modifications. Both the crystalline anhydrate and partial dehydrate modifications converted to the stoichiometric dihydrate form (AZM-DH) at normal environmental conditions at ambient temperature. Both the amorph glass and amorph powder exhibited increased moisture absorption with increased humidity exposure. TG analysis of the pulverised amorph glass indicated a moisture content of 5.1% at 96% RH after 4 storage days. The absence of crystalline melt in DSC and presence of Tg (106.9°C) indicated the sample remained amorphous after pulverisation and storage for 4 days at 40°C/ 96% RH.
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Le, Brun Virginie. "Physical Properties of Protein Formulations." Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-109666.
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Livings, Simon John. "Physical properties of starch wafers." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321480.
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Micciche, Salvatore. "Physical properties of gravitational solitons." Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/33196.
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Soliton solutions of Einstein's field equations for space–times with two non-null, commuting Killing Vectors are exact solutions obtained using the solution-generating techniques that resemble the well-known Inverse Scattering Methods that have been widely used m the solution of certain nonlinear PDE's such as Korteweg–de Vries, Sine–Gordon, non-linear Schrödinger. There exist two main soliton techniques in General Relativity. The Belinski–Zakharov technique allows for purely gravitational solutions. The Alekseev technique allows for solutions of the Einstein–Maxwell equations. In both techniques, solitons arise in connection with the poles of a certain so-called "dressing matrix".
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Tang, Xiaoli Dong Jianjun. "Theoretical study of thermal properties and thermal conductivities of crystals." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SUMMER/Physics/Dissertation/Tang_Xiaoli_9.pdf.
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Sheung-kei, Winnie S. "Cooking quality: physical and biochemical properties of lentils (Lens culinaris)." Thesis, Curtin University, 2000. http://hdl.handle.net/20.500.11937/2528.
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Lentils, one of the cool-season pulses, are consumed as a staple food in most developing countries. The demand for pulses in western societies is increasing because of its valuable nutritional quality and an increased awareness of health issues. Australia has a good reputation for producing clean low moisture legume products and could increase as market share of lentil production by identifying, developing and promoting good quality varieties.Lentils which are graded as good quality varieties must have a short and uniform cooking time, without 'hard to cook' seed, have the hull stay attached to the seed during cooking, and have a final acceptable taste, texture, flavour and appearance after cooking (Bhatty 1990). Cooking quality in this study is defined as the maximum force (N) that is required to compress the whole seed cooked product after cooking for a standard period of time. This study aims to develop an objective measurement to determine the cooking quality of lentils and thereby evaluates the relationships between lentil cooking quality and some of its physical and biochemical properties. Four cultivars used (Cassab, Digger, ILL 7180 and Matilda) were grown during 1999 at Mullewa and Pingaring, Western Australia. The relationship between the cooking quality of lentil and water absorption, seed size, seed coat thickness, phytic acid, mineral composition and initial moisture content was investigated.Texture measurement was carried out using the TA.XT2i meter as an alternative to the subjective method "Cooking time test". By comparing the cooking time determined by 'Cooking time test, 220 N was established and suggested as an optimal peak compression force to determine the adequate cooking time for lentils. Both methods showed that 35 minutes cooking time was adequate for red lentils (Cassab, Digger, and ILL 7180), and 45 minutes for green lentils (Matilda).Cooking significantly reduced the hardness of the seeds (R= - 0.752 to - 0.89) and promoted mineral leaching (P < 0.05). The interaction between environment and genotype had a significant effect on seed size, seed coat thickness, mineral composition (Phytic acid, Ne, K+, Mg2+, Ca2+ M+, Fe2+ and CU2+) and hardness (P< 0.05). Seed coat thickness did not correlated with this rate of water uptake and cooking quality. Growing environments had a greater influence on the cooking quality than genotypes. Lentils grown at Pingaring are generally had a higher in Phyti acid content, better mineral retention and were harder in texture than those grown at Mullewa.The results of this study implicated that the peak compression force (220 N) was identified as an indicator to determine the cooking time of lentil cultivars. Texture Profile Analysis (TPA) is a useful method to evaluate various texture characteristics (hardness, cohesiveness, chewiness, springiness, gumminess and adhesiveness) of lentil cultivars. Cooking quality of lentil is significantly affected by the effect of varieties and growing locations. However, not the various biochemical compositions (phytic acid and minerals) and the thickness of seed coat have no significant effect on the cooking quality of lentil.
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McCoy, James Martin. "The physical properties of magnetic inks." Thesis, Durham University, 1988. http://etheses.dur.ac.uk/6646/.
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The magnetic particle inspection (MPI) method is a widely used non destructive testing (NDT) technique for ferrous structures. Magnetic inks used in MPI are suspensions of fine ferro/ferrimagnetic particles which, when applied to a magnetized test specimen, delineate surface flaws. This work is an investigation of some of the properties of magnetic ink systems and some aspects of their interaction with defect leakage flux. Reviews of magnetism, the MPI method and leakage flux at defects are given. The construction, characterization and automation of a 1.2 T electromagnet vibrating sample magnetometer, used for magnetic measurements on the inks, is described. The instrument has a resolution of better than l0(^-9) JT(^-1) . A 2D model of indication formation in MPI, based upon the simulation of many particles in the neighbourhood of a defect, is presented. Results of the role of several of the model parameters are given. Results indicate that carrier coefficients of viscosity at the lower end of the range investigated (η = 0.3 mPas) are optimum. The size and contrast of an indication increases with defect size. The contrast and rate of formation of contrast increase with defect aspect ratio. The effect of the contrast paint layer thickness indicates that the recommendation of the British Standard, BS 5044 (1973), is qualitatively correct. Experimental observations of particles in field gradients reveals a discrepancy between theoretical and observed behaviour which is attributed, in particular, to unobservable voids in the particles. Detailed characterization of the particles shows them to be aggregates of 20 - 200 nm crystallites which are probably single domain particles. The morphology of larger aggregates is related to measurements of the low field susceptibility. Evidence from intensive magnetic measurements supports the relationship between magnetic properties and aggregate characteristics. A 'In t' magnetic viscosity effect is reported. At 77 K, the coefficient of magnetic viscosity has a maximum near the coercivity field.
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Gauthier, Sylvie 1955. "Synthesis and physical properties of styrene-vinylpyridinium ionomers of various architectures." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=72029.
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Styrene-4-vinylpyridinium ionomers of different architectures, random and ABA blocks, were synthesized and their thermal and dynamic mechanical properties investigated.The Tg's of the random ionomers were found to increase regularly with increasing ion content, at a rate of about 3.5(DEGREES)C per mole % of ions. In contrast with other ionomeric systems studied before, however, these materials showed only one peak in their tan delta curves, associated with the Tg of the matrix. The absence of a second, high temperature peak suggests the absence of clusters in these vinylpyridinium ionomers, at least at temperatures above their Tg. The storage modulus curves were in agreement with this conclusion.
An elaborate polymerization line was constructed for the production of the block copolymers by living anionic polymerization; a basic design was modified considerably and two new units were completely designed in this laboratory. Only one Tg, associated with the Tg of the polystyrene phase, was observed in DSC measurements for the resulting ionomers. The glass transition of the ionic domains was detected in dynamic mechanical measurements as a shoulder on the low temperature side of the polystyrene transition. This unexpected low value for the Tg of the ionic domains was attributed to plasticization by water.
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Sheung-kei, Winnie S. "Cooking quality: physical and biochemical properties of lentils (Lens culinaris)." Curtin University of Technology, School of Public Health, 2000. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=10354.
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Lentils, one of the cool-season pulses, are consumed as a staple food in most developing countries. The demand for pulses in western societies is increasing because of its valuable nutritional quality and an increased awareness of health issues. Australia has a good reputation for producing clean low moisture legume products and could increase as market share of lentil production by identifying, developing and promoting good quality varieties.Lentils which are graded as good quality varieties must have a short and uniform cooking time, without 'hard to cook' seed, have the hull stay attached to the seed during cooking, and have a final acceptable taste, texture, flavour and appearance after cooking (Bhatty 1990). Cooking quality in this study is defined as the maximum force (N) that is required to compress the whole seed cooked product after cooking for a standard period of time. This study aims to develop an objective measurement to determine the cooking quality of lentils and thereby evaluates the relationships between lentil cooking quality and some of its physical and biochemical properties. Four cultivars used (Cassab, Digger, ILL 7180 and Matilda) were grown during 1999 at Mullewa and Pingaring, Western Australia. The relationship between the cooking quality of lentil and water absorption, seed size, seed coat thickness, phytic acid, mineral composition and initial moisture content was investigated.Texture measurement was carried out using the TA.XT2i meter as an alternative to the subjective method "Cooking time test". By comparing the cooking time determined by 'Cooking time test, 220 N was established and suggested as an optimal peak compression force to determine the adequate cooking time for lentils. Both methods showed that 35 minutes cooking time was adequate for red lentils (Cassab, Digger, and ILL 7180), and 45 minutes for green lentils ++(Matilda).Cooking significantly reduced the hardness of the seeds (R= - 0.752 to - 0.89) and promoted mineral leaching (P < 0.05). The interaction between environment and genotype had a significant effect on seed size, seed coat thickness, mineral composition (Phytic acid, Ne, K+, Mg2+, Ca2+ M+, Fe2+ and CU2+) and hardness (P< 0.05). Seed coat thickness did not correlated with this rate of water uptake and cooking quality. Growing environments had a greater influence on the cooking quality than genotypes. Lentils grown at Pingaring are generally had a higher in Phyti acid content, better mineral retention and were harder in texture than those grown at Mullewa.The results of this study implicated that the peak compression force (220 N) was identified as an indicator to determine the cooking time of lentil cultivars. Texture Profile Analysis (TPA) is a useful method to evaluate various texture characteristics (hardness, cohesiveness, chewiness, springiness, gumminess and adhesiveness) of lentil cultivars. Cooking quality of lentil is significantly affected by the effect of varieties and growing locations. However, not the various biochemical compositions (phytic acid and minerals) and the thickness of seed coat have no significant effect on the cooking quality of lentil.
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Skedung, Lisa. "Tactile perception : role of physical properties." Licentiate thesis, Stockholm : Skolan för kemivetenskap, Kungliga Tekniska högskolan, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11891.
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Potužák, Marcel. "Physico-Chemical Properties of Silicate Melts." Diss., lmu, 2006. http://nbn-resolving.de/urn:nbn:de:bvb:19-55228.
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Mitsch, Carsten. "Structure and physical properties of Inovirus." Thesis, University of Cambridge, 1998. https://www.repository.cam.ac.uk/handle/1810/251636.
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顧若愚 and Ruoyu Gu. "Physical properties of some magnetic systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31240173.
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Lim, Wen Huei. "Physico-chemical properties of ultraflexible vesicles." Thesis, King's College London (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417109.
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Kefaleas, Christos. "Physical properties of molecules in polyolefins." Thesis, University of Sussex, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391878.
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Gilchrist, H. E. M. "Physical properties of continuous random networks." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38330.
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Rogers, Salman Samson. "Some physical properties of amyloid fibrils." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613906.
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Gupta, Saloni. "Physico-chemical properties of polypropylene glycols." Thesis, University of Greenwich, 2015. http://gala.gre.ac.uk/21538/.
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Poly(propylene glycol) (PPG) samples of different molecular mass were characterized using differential scanning calorimetry, modulated differential scanning calorimetry, thermogravimetry and thermally stimulated current (TSC) spectroscopy. It was shown, by TSC, that the glass transition temperature and the degree of molecular mobility increased with increasing molecular mass of PPG. Additional experiments showed that PPGs of molecular mass 425, 1000 and 2000 Da undergo one global relaxation process; however, PPG 2700 (Da) undergoes an additional relaxation process after the glass transition which has been attributed either to the release of the excess charge delocalised in the polymer structure or a liquid-liquid transition. Thermally induced phase separation in aqueous solutions of PPG has been examined using a variety of techniques including high sensitivity scanning calorimetry (HSDSC), hot stage microscopy, small angle neutron scattering, and turbidity measurements. The data suggest that phase separation is a consequence of PPG aggregation (droplets); the aggregates grow in size, as the temperature is raised further. It is postulated that phase separation occurs via nucleation and growth, which is corroborated by model fitting the calorimetric data using a mass action aggregation model. It is concluded that phase separation of PPG occurs as a result of the disruption of a hydrogen bonded network between water and PPG. The effect of five sugars (mannitol, maltose, raffinose, sucrose and trehalose) on the Tm (transition temperature) of aqueous PPG 1000 solutions was studied by HSDSC and turbidity measurements. All the sugars decreased the phase separation temperature of the PPG solutions, with trehalose and maltose showing the greatest effect. A series of experiments, using HPLC, showed that phase separated PPG (1000 Da) increased the apparent aqueous solubility of naphthalene.
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Wu, Jiajun Ph D. Massachusetts Institute of Technology. "Computational perception of physical object properties." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103736.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 49-50).
We study the problem of learning physical object properties from visual data. Inspired by findings in cognitive science that even infants are able to perceive a physical world full of dynamic content at a early age, we aim to build models to characterize object properties from synthetic and real-world scenes. We build a novel dataset containing over 17, 000 videos with 101 objects in a set of visually simple but physically rich scenarios. We further propose two novel models for learning physical object properties by incorporating physics simulators, either a symbolic interpreter or a mature physics engine, with deep neural nets. Our extensive evaluations demonstrate that these models can learn physical object properties well and, with a physic engine, the responses of the model positively correlate with human responses. Future research directions include incorporating the knowledge of physical object properties into the understanding of interactions among objects, scenes, and agents.
by Jiajun Wu.
S.M.
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Nico, Cláudio Miguel Silva. "Niobium oxides and niobates physical properties." Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/14851.
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Doutoramento em Nanociências e NanotecnologiaNiobium oxides have been pointed as an alternative to tantalum in the production of solid electrolytic capacitors, with advantages regarding the dielectric constant, density and price. In this work, it is intended to create a new family of niobium oxides based capacitors, adapting the technology and production line currently used with tantalum. Despite the known potentialities of niobium oxides, and many types of niobates, in several technological applications, the understanding of these oxide systems is still noticeably insufficient. Hence, a careful bibliographic review is shown, which evidences the complexity of these materials, the difficulty in identifying of their different phases and polymorphs, as well as in the interpretation of their properties. In this context, several fundamental studies on niobium oxides are presented, namely structural, microstructural, optical and electrical characterizations, which allow not only to contribute in an important way for the general knowledge of the physical properties of these materials, but also to advance to a sustained development of the niobium oxides based solid electrolytic capacitors. Several processing parameters were studied, clearing the way towards the creation of a prototype. It was also decided to perform a preliminary study on the synthesis and characterization of other oxide systems based in niobium, namely rare-earth orthoniobates (RENbO4), which interest has been related to their optical properties and protonic conductivity. Hence, single and polycrystalline samples of RENbO4 were synthesized and characterized structural, optical and electrically, leaving open an interesting future work.
Os óxidos de nióbio têm sido apontados como uma alternativa ao tântalo na produção de condensadores eletrolíticos sólidos, com vantagens relativamente à constante dielétrica, densidade e preço. Neste trabalho, pretende-se criar uma nova família de condensadores de óxidos de nióbio, adaptando a tecnologia e linha de produção atualmente utilizada com o tântalo. Apesar das já conhecidas potencialidades dos óxidos de nióbio, e vários tipos de niobatos, em diversas aplicações tecnológicas, o conhecimento destes sistemas óxidos é ainda manifestamente insuficiente. Assim, é apresentada uma cuidadosa revisão bibliográfica que evidencia a complexidade destes materiais, as dificuldades na identificação das suas várias fases e polimorfos, assim como na interpretação das suas propriedades. Neste contexto, são apresentados vários estudos fundamentais em óxidos de nióbio, nomeadamente caracterização estrutural, microestrutural, ótica e elétrica, que permitem não só contribuir de uma forma importante para o conhecimento geral das propriedades físicas destes materiais, como avançar para o desenvolvimento sustentado dos condensadores eletrolíticos sólidos à base de óxidos de nióbio. Estudaram-se vários parâmetros de processamento abrindo caminho para a criação de um protótipo. Avançou-se também para um estudo preliminar da síntese e caracterização de outros sistemas óxidos à base de nióbio, nomeadamente ortoniobatos de terras-raras (RENbO4), cujo interesse tem sido manifestado relativamente às suas propriedades óticas e de condutividade protónica. Assim, amostras mono e policristalinas de RENbO4 foram sintetizadas e caracterizadas estrutural, ótica e eletricamente, deixando em aberto um interessante trabalho futuro.
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Hills, Romilly D. Y. "Physical properties of graphene nano-devices." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/17993.
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In this doctoral thesis the two dimensional material graphene has been studied in depth with particular respect to Zener tunnelling devices. From the hexagonal structure the Hamiltonian at a Dirac point was derived with the option of including an energy gap. This Hamiltonian was then used to obtain the tunnelling properties of various graphene nano-devices; the devices studied include Zener tunnelling potential barriers such as single and double graphene potential steps. A form of the Landauer formalism was obtained for graphene devices. Combined with the scattering properties of potential barriers the current and conductance was found for a wide range of graphene nano-devices. These results were then compared to recently obtained experimental results for graphene nano-ribbons, showing many similarities between nano-ribbons and infinite sheet graphene. The methods studied were then applied to materials which have been shown to possess three dimensional Dirac cones known as topological insulators. In the case of Cd3As2 the Dirac cone is asymmetrical with respect to the z-direction, the effect of this asymmetry has been discussed with comparison to the symmetrical case.
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Gu, Ruoyu. "Physical properties of some magnetic systems /." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21981942.
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André, Tomas. "Benchmarking Physical Properties of Water Models." Thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388336.
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Water is a fundamental part of life as we know it, and by that also a fundamental for biology, chemistry, and parts of physics. Understanding how water behaves and interacts is key in many fields of all these three branches of science. Numerical simulation using molecular dynamics can aid in building insight in the behavior and interactions of water. In this thesis molecular dynamics is used to simulate common rigid 3 point water models to see how well they replicate certain physical and chemical properties as functions of temperature. This is done with molecular dynamics program GROMACS which offers a complete set of tools to run simulations and analyze results. Everything has been automated to work with a python script and a file of input parameters. Most of the models follow the same trends and are valid within a limited temperature range.Vatten är en av de fundamentala byggstenarna för liv, därmed är det även fundamentalt för biologi, kemi och delar av fysiken. Att förstå hur vatten beter sig och interagerar är en stor fråga inom dessa tre grenar av vetenskap. Med molekyldynamik går det att utföra numeriska simuleringar som kan användas som hjälpmedel för att bygga en djupare förståelse för riktigt vatten. I den här uppsatsen så har molekyldynamik använts till att simulera vanliga rigida 3 punkts parametiseringar av vatten för att se hur bra de kan replikera vissa egenskaper som funktioner av temperatur. Simuleringen är gjord med hjälp av molekyldynamik programet GROMACS som ger en fullständig uppsättning verktyg för att simulera och analysera molekylsystem. Alla simuleringar och analys är automatiserat med ett pythonprogram och en fil för parametrar. De allra flesta modeller följer liknande trender och är giltiga inom små temperaturintervall.
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Maruatona, Gaamangwe Nehemiah. "Physico-chemical, nutritional and functional properties of defatted marama bean flour." Diss., Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-06112009-142412/.
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Orrah, D. J. "Physical properties of cyclic and linear poly(dimethylsiloxanes)." Thesis, University of York, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381327.
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Hu, Zhonghan. "Transport properties, optical response and slow dynamics of ionic liquids." Diss., University of Iowa, 2007. http://ir.uiowa.edu/etd/160.
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Malec, Christopher Evan. "Transport in graphene tunnel junctions." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41140.
Full textAbstract:
It has been predicted that gold, aluminum, and copper do not fundamentally change the graphene band structure when they are in close proximity to graphene, but merely increase the doping. My data confirms this prediction, as well as explores other consequences of the metal/graphene interface. First, I present a technique to fabricate thin oxide barriers between graphene and aluminum and copper to create tunnel junctions and directly probe graphene in close proximity to a metal. I map the differential conductance of the junctions versus tunnel probe and back gate voltage, and observe mesoscopic fluctuations in the conductance that are directly related to the graphene density of states. I develop a simple theory of tunneling into graphene to extract experimental numbers, such as the doping level of the graphene, and take into account the electrostatic gating of graphene by the tunneling probe. Next, results of measurements in magnetic fields will also be discussed, including evidence for incompressible states in the Quantum Hall regime wherein an electron is forced to tunnel between a localized state and an extended state that is connected to the lead. The physics of this system is similar to that encountered in Single Electron Transistors, and some work in this area will be reviewed. Finally, another possible method of understanding the interface between a metal and graphene through transport is presented. By depositing disconnected gold islands on graphene, I am able to measure resonances in the bias dependent differential resistance, that I connect to interactions between the graphene and gold islands.
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Eppell, Steven Joseph. "Platinum on graphite (0001): A model system for the study of physical and chemical properties of small metal islands." Case Western Reserve University School of Graduate Studies / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1055523982.
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Ghorai, Suman. "Chemical, physical and mechanical properties of nanomaterials and its applications." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/2501.
Full textAbstract:
The contribution of atmospheric aerosols towards radiative forcing has a very high uncertainty due to their short atmospheric lifetime. The aerosol effects are largely controlled by the density, elemental composition, and hygroscopic properties of the aerosol particles. Therefore, we have performed designed new methodology using Scanning Transmission X-ray Microscopy (STXM), Atomic force spectroscopy (AFM), micro-FTIR spectroscopy and Scanning Electron Microscopy (SEM) to quantify these important aerosol properties. Hygroscopic properties are quantified by plotting the mass of water on a single particle basis, calculated from STXM, as a function of relative humidity. Alternatively, micro-FTIR spectra have been used to study the effect of composition of aerosol particles on the hygroscopic properties of NaCl. Moreover, a unique combination of STXM and AFM has been utilized to quantify density and elemental composition of micrometer dimensional particles. This method has also been extended towards exploring mixing state of particles, consisting of heterogeneously mixed inorganic and organic compounds. In addition to these above mentioned properties, the fate of an atmospheric particle is often altered by chemical transformation and that in turn is influenced by the atmospheric RH. Therefore, we have studied an unusual keto-enol tautomerism in malonic acid particles at high RH, which is not observed in bulk. This observation could potentially be utilized to significantly improve the models to estimate Secondary Organic Aerosols (SOA). Using STXM and micro-FTIR technique, RH dependent equilibrium constant of the tautomerism reaction has been quantified as well.
Organic nanocrystals capable of undergoing solid state photochemical changes in a single-crystal-to-single-crystal (SCSC) manner have been particularly important in fabricating molecular switches, data storage devices etc. Mechanical properties of these nanomaterials may control its SCSC reactivity. In addition, investigation of mechanical stiffness is important to define allowable limit of stiffness towards device application. Therefore, we studied mechanical properties of series organic nano cocrystals primarily consisting of trans-1,2-bis(4-pyridyl)ethylene and substituted resorcinol using AFM nanoindentation technique. Dependence of mechanical properties and SCSC reactivity on the resorcinol structure is also investigated as well. Moreover, photolithography on the thin film of these organic cocrystals has been performed to demonstrate its applicability as a photoresist.
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Brown, Dawn Gayatri. "Physical characterisation of a commercial magnesium stearate powder." Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307588.
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Rhyner, Jakob. "Physical and mathematical properties of quasiperiodic structures /." [S.l.] : [s.n.], 1987. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=8451.
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Díez, Orrite Silvia. "Physico-chemical properties of polymers at interfaces." Doctoral thesis, Universitat Rovira i Virgili, 2002. http://hdl.handle.net/10803/8511.
Full textAbstract:
A polymer is a large molecule constructed from many smaller structural units calledmonomers joined together by covalent bonds. Polymers have existed in natural form
since life began and those such as DNA, RNA, proteins and polysaccharides are some
of the most important macromolecules found in plant and animal life. From the earliest
times, the man has used many of these polymers as materials for providing clothing,
decoration, tools, weapons and other requirements. However, the origins of today's
polymer industry commonly are accepted as being in the nineteenth century when
important discoveries were made concerning to the modification of certain natural
polymers, as cellulose. The use of synthetic and natural polymers as stabilisers for
colloid systems (sols, dispersions, microemulsions, etc.) is becoming more important
everyday in contemporary life. Polymer additives can be applied in preconcentrations
and dehydration of suspensions in mineral processing, purification of wastewater and
even in nutritional and pharmaceutical emulsions being their importance related to the
characteristics of the process and the properties that they show. The present work aims
to develop appropriate numerical and analytical modelling techniques, which can
describe (considering the formation of loops and tails) the structure of a polymeric layer
adsorbed on heterogeneous surfaces; this adsorbed layer is an relevant factor in the
properties showed by this kind of materials. Taking into account this, the methodology
known as Single Chain Mean Field (SCMF) (originally used to study micellar
aggregates and grafted polymers) was modified to apply on polymer adsorption
problems. In this way, it was possible to calculate numerically properties that can be
experimentally measured, such as total monomer volume fraction profiles, loop and tail
volume fraction profiles, adsorbance or the thickness of the adsorbed layer. The
structure of the polymeric layer was examined both for flat and spherical (colloidal
particles) surface geometries. When compared with other well established
methodologies for the numerical simulation of polymeric systems, this new version of
SCMF was found to be more efficient due to the improved sampling of the polymer
chain configuration space.
Thus, SCMF method results, in the case of the adsorption on flat surfaces, compare well
with those obtained either with Monte Carlo simulations or with the method developed
in the 80s by Scheutjens and Fleer (SCF). Due to the lack of studies focusing to polymer
adsorption on colloidal particles, our results have been the first to present quantitative
predictions of the structure of the polymeric layer adsorbed on a spherical surface. Thus,
we have demonstrated the dependence of the adsorbed polymer layer with the size of
the colloidal particle as well as the characteristic lengths that influence on it. Finally, in
this work an analytical approach for the description of polymer-colloidal mixtures has
been developed which compares well with the numerical results obtained from the
SCMF methodology. Furthermore, the analytical approach is able to predict system
behaviours, as for example the formation of gels.
Un polímero es una molécula de grandes dimensiones formada de pequeñas unidades
llamadas monómeros, los cuales se encuentran unidos por medio de enlaces covalentes.
Los polímeros han existido de forma natural desde el comienzo de la vida, y aquellos
como el DNA, RNA o las proteínas son algunos de los polímeros más importantes
encontrados tanto en la vida animal como en la vegetal. Desde siempre el hombre ha
utilizado muchos de estos polímeros como materiales para hacer ropa, decoración,
herramientas, etc. Sin embargo, el origen de la industria de polímeros que conocemos
hoy en día se produjo en el siglo 19, gracias a importantes descubrimientos dentro de la
modificación de ciertos polímeros naturales, como la celulosa. El uso de polímeros
sintéticos y naturales como estabilizadores de sistemas coloidales (dispersiones,
microemulsiones, etc.) juega en nuestros días un papel importante. Los polímeros
utilizados como aditivos, pueden ser aplicados en preconcentraciones y deshidratación
de suspensiones dentro de procesos minerales, tratamiento de aguas residuales e incluso
los podemos encontrar dentro de la industria farmacéutica y alimentaria, donde su
importancia es debida a la procesabilidad y propiedades que ellos exhiben. El trabajo
que se presenta es orientado al desarrollo de técnicas de modelización, tanto analíticas
como computacionales, y su aplicación en la descripción (por medio de la formación de
bucles y colas) de la estructura de la capa de polímeros adsorbida en superficies
heterogéneas, siendo dicha capa de polímeros un factor importante en las propiedades
que este tipo de materiales presentan. Con este propósito, la metodología conocida
como Single Chain Mean Field, utilizada anteriormente tanto para el estudio de
agregados micelares como de polímeros anclados en superficies, ha sido modificada
para describir la adsorción de polímeros en superficies. Así se han podido calcular
numéricamente propiedades medibles experimentalmente como los perfiles de la
fracción en volumen de monómeros totales, además de los pertenecientes a los bucles y
colas, adsorbancia o el espesor de la capa adsorbida, para geometrías de la superficie
absorbente tanto plana como esférica (partículas coloidales). En su comparación con
otras metodologías, ya establecidas para la simulación numérica dentro de la física de
polímeros, la aplicación de esta nueva versión del Single Chain Mean Field (SCMF)
ha resultado ser más eficiente debido a un mejor muestreo del espacio de
configuraciones de las cadenas poliméricas. De este modo, comparando los resultados
obtenidos a partir del SCMF, con aquellos obtenidos mediante técnicas de simulación
Monte Carlo o la teoría desarrollada en los años 80 por Scheutjens y Fleer (SCF), se ha
podido encontrar un buen acuerdo en las propiedades calculadas para el caso de la
adsorción en superficies planas. Debido a la dificultad intrínseca del estudio de la
adsorción en superficies curvadas, nuestros resultados son los primeros que presentan
predicciones cuantitativas sobre la estructura de la capa que se forma sobre una
partícula coloidal. Así hemos podido comprobar la dependencia de la estructura de la
capa de polímeros adsorbidos con el tamaño de la partícula sobre la que se encuentran
adsorbidos además de las longitudes características de las cuales depende. Finalmente,
en este trabajo se ha desarrollado, también, una teoría analítica para la descripción de la
mezcla polímero-coloide. De este modo, los resultados numéricos obtenidos con el
SCMF han podido ser comparados con dicha teoría, obteniendo, de nuevo, un buen
acuerdo y predecir, además, comportamientos colectivos como la formación de geles.
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Churakov, Sergey. "Physical-chemical properties of complex natural fluids." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=962849723.
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Haynes, Kaaren K. "Physical properties of laccase-mediator delignified pulps." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/5884.
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Zysman-Colman, Eli. "The chemical and physical properties of polychalcogens." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84864.
Full textAbstract:
The optimized synthesis of acyclic dialkoxy disulfides and aromatic polysulfides is described and their physical properties probed. A theoretical survey of dialkoxy disulfides and thionosulfites was undertaken in order to determine the most efficacious method for accurately modeling these compounds. In particular, the origin of the high barrier to rotation in the dialkoxy disulfides was determined to be due to a generalized anomeric effect resulting from two lone pair donations of each sulfur atom into each of their respective sulfur-oxygen antibonding orbitals. The origin of the high rotational barrier was also verified experimentally, in particular with respect to solvent and substituent effects. Complimentary to this thermal process, the decomposition of dialkoxy disulfides was also investigated. It was determined that these compounds decompose under first order kinetics via an initial asymmetric S-O homolytic cleavage. Activation parameters for both of these processes were determined.Theoretical modeling on the relative ground state energies of dialkoxy disulfides is also described. It has been ascertained that the equilibrium position between the two isomers can be influenced by the ring size of the molecule; larger rings promote the dialkoxy disulfide isomer. These modeling studies were successfully corroborated experimentally. Of note is the synthesis of a new 8-membered ring dialkoxy disulfides as well as novel 7-membered ring thionosulfites. These compounds were also confirmed by single X-ray crystallography.
The kinetics of desulfurization of acyclic aromatic tri- and tetrasulfides is described. Tetrasulfides were found to transfer a sulfur atom to triphenylphosphine over ten times faster than their trisulfide analogues.
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Le, Van Lich. "Multi-physics Properties in Topologically Nanostructured Ferroelectrics." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/217166.
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Pforr, Janine. "Galaxy physical properties from population model fitting." Thesis, University of Portsmouth, 2011. https://researchportal.port.ac.uk/portal/en/theses/galaxy-physical-properties-from-population-model-fitting(c5eab7e4-a52f-4071-bb28-ff990b2496eb).html.
Full textAbstract:
In the last two decades astronomers carried out a large number of galaxy surveys tuned towards the study of galaxy formation and evolution. With the ever improving technology, increasing telescope sizes of ground-based telescopes and the development of space-based telescopes it has become possible to detect galaxies at a time when the Universe was only a few hundred million years old. However, for the majority of galaxies a detailed spectroscopic analysis is not possible due to their distance and limited telescope time. Thus, many surveys rely on photometric data alone to help unveil the properties of galaxies. One of the most important areas of study within galaxy formation and evolution is the analysis of the galaxy stellar population parameters as these can provide us with information about the star formation histories of galaxies and when and possibly how they assembled their mass. A popular approach in the literature is the fitting of synthetic spectral energy distributions inferred from stellar population modelling to the multi-wavelength photometry of galaxies. However, this approach comes with a large number of fitting parameters all of which are essentially user-dependent and will bias the result in one way or another. The aim of this thesis is to investigate the accuracy and efficiency of spectral energy distribution fitting as derivation technique for the galaxy physical properties, such as age, stellar mass, dust reddening, etc., as a function of the fitting parameters, such as star formation histories, age grids, metallicity, initial mass function, dust reddening, reddening law, filter setup and wavelength coverage and stellar population model, and to find the setup of parameters that recovers the properties best. In particular, we investigate in detail the dependence of the derived properties on the assumed wavelength coverage and exact filter setups. Mock galaxies with known properties serve as test particles for this exercise. The synthetic spectral energy distributions used in this thesis are based on the Maraston (2005) stellar population models. Literature results which investigate similar problems are obtained using the models of Bruzual & Charlot (2003). Firstly, the fitting is carried out under the assumption that galaxy redshifts are known mimicking surveys for which galaxy redshifts are derived spectroscopically. Then we study the case in which the redshift is not known and needs to be determined alongside the galaxy physical properties which is the case for most photometric surveys. In general, we find that - using normal template star formation histories as widely used in the literature - ages and stellar masses of star-forming galaxies are underestimated, reddening and star formation rates are overestimated. This is due to a mismatch in star formation history and the overshining effect. The addition of the rest-frame near-IR appears to be crucial for the derivation of robust results. For aged galaxies with little or no on-going star formation we find that a setup covering a wide range of star formation histories and metallicities works best when the fit is carried out excluding dust reddening. For high redshift star-forming galaxies we find that a new type of star formation history (inverted-� models which start forming stars at high redshift) recovers stellar masses and star formation rates best. The parameters of truly passive galaxies are much better determined. In order to ease the comparison of literature data that was analysed with different fitting parameter setups we provide scaling relations for the transformation of stellar masses between different setups. Our results concerning the importance of the wavelength coverage in the fitting are particularly useful for the planning of future surveys and observation proposals. We apply our findings from the study of mock galaxies to various samples of real galaxies which cover different redshift ranges and galaxy types. We derive the stellar population properties for a sample of star-forming galaxies at z ∼ 2 from the GOODS-S survey using inverted-� models (with high formation redshifts) and show that the obtained dust reddening and star formation histories are in excellent agreement with those derived from other methods. We also show how the wrong set of fitting parameters can lead to unrealistically young ages, low stellar masses and high star formation rates which are a pure artefact from the fit. Furthermore, we study a sample of low redshift, predominantly passive galaxies from the SDSS-III/BOSS survey for which we use the spectral model of Maraston et al. (2009) that is tuned to the needs of this particular type of galaxies. We find that BOSS galaxies are mostly passive, old and massive at each redshift in the range 0 < z < 0.7. Finally, we complement the study of SDSS-III/BOSS galaxies by deriving stellar masses for the SDSS-I/II galaxies in a similar fashion. We conclude that the simultaneous derivation of stellar population properties of galaxies from spectral energy distribution fitting is difficult but that these properties can be very well derived provided the right setup and wavelength coverage are used in the fitting. We also conclude that more work is needed to better match star formation histories of aged galaxies with little on-going star formation in order to improve estimates of stellar population parameters.
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Roach, Steven John. "Determination of the physical properties of melts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ60491.pdf.
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Zhang, Shu. "Mechanical and physical properties of electrospun nanofibers." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-07102009-165411/.
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The process of electrospinning was utilized to fabricate randomly aigned nylon6 nanofibers and aligned nylon6 nanofibers. Polymer concentration affecting electrospinning was investigated. This parameter was evaluated using degree of crystallinity by differential scanning calorimetry (DSC) as well as visual images produced by scanning electron microscopy (SEM). DSC data demonstrated that more crystals were formed with lower polymer concentrations; SEM images revealed that slimmer fibers were produced by lower concentrations. The mechanical properties of unoriented fibers and aligned fibers were tested on Instron 5544. The result of tensile tests indicated higher Youngâs modulus and tensile strength of aligned nanofibers than that of unaligned fibers. The SEM images at broken edges of fibers illustrated different broken mechanisms of these two forms of nanofibers. The broken mechanism of aligned nanofibers was further confirmed by crystallinity parameters obtained from DSC and fiber diameter shown from SEM images.
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Ghassemi, Ali. "Nonparametric geostatistical estimation of soil physical properties." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63904.
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Alves, Luis. "Physical and chemical properties of gold nitride." Thesis, University of Newcastle Upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512027.
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Alcock, Joseph Patrick. "Mechanical and physical properties of orthodontic archwires." Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492645.
Full textAbstract:
The aim of this study was to investigate the nanomechanical properties of as received, autoclaved and clinically exposed orthodontic archwires. This study was prospective. The clinical component took place in the Orthodontic department of a district general hospital in Bath. Laboratory tests were performed at Bristol Dental School.
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Astafyeva, Ksenia. "Physical and acoustical properties of fluorocarbon nanoparticles." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2014. http://tel.archives-ouvertes.fr/tel-00960290.
Full textAbstract:
In this thesis, acoustical and other physical properties of soft submicron suspensions were investigated in order to provide invaluable clues for their adaptation in theragnostic applications. Two types of dispersions were studied: fluorocarbon droplets stabilised with a polymeric (PLGA, PLGA-PEG) shell or a semifluorinated surfactant (called FTAC) shell. Since preparation of polymeric particles had been already developed, we first studied factors affecting mean diameter, size distribution, and coarsening of emulsions made of FTAC stabilising droplets of various fluorocarbons. Mechanical parameters used for emulsion synthesis and surfactants length were optimised to get the smallest droplets (~200 nm in diameter) that stay mainly submicrometric for several weeks. In addition, a full characterisation of surfactant properties was conducted. Next, for ultrasonic theragnostic purpose, it was necessary to improve our understanding in the mechanisms underlying interactions between ultrasonic waves and particles of a suspension. To do so, ultrasound propagation studies through dilute suspensions were carried out in a large frequency range (3-90 MHz) with subsequent modelling. The model could fit with a good accuracy our experimental data on polymeric particles and reveals information about unknown parameters of the shell: the geometrical parameters (shell thickness) and the viscoelastic parameters of the shell (speed of sound, shear moduli at infinite and zero frequencies, and the relaxation frequency). Therefore, such a model provides the required feedback for tuning the physicochemical parameters of nanoparticles in order to optimize their design.