Дисертації: "High functional properties"

1

Liu, Xiaoming. "Effect of high hydrostatic pressure on whey protein concentrate functional properties." Online access for everyone, 2004. http://www.dissertations.wsu.edu/Dissertations/Spring2004/X%5Fliu%5F050504.pdf.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

2

Zhang, Xi. "Empirical Properties of Functional Regression Models and Application to High-Frequency Financial Data." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1973.

Повний текст джерела

Анотація:

Functional data analysis (FDA) has grown into a substantial field of statistical research, with new methodology, numerous useful applications and interesting novel theoretical developments. My dissertation focuses on the empirical properties of functional regression models and their application to financial data. We start from testing the empirical properties of forecasts with the functional autoregressive models based on simulated and real data. We define intraday returns and consider their prediction from such returns on a market index. This is an extension to intraday data of the Capital Asset Pricing model. Finally we investigate multifactor functional models and assess their suitability for the prediction of intraday returns for various financial assets, including stock and commodity futures.

Стилі APA, Harvard, Vancouver, ISO та ін.

3

ye, Yubin. "Effect of High Intensity Ultrasound on Crystallization Behavior and Functional Properties of Lipids." DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4281.

Повний текст джерела

Анотація:

The effects of high intensity ultrasound (HIU) on the crystallization behavior and functional properties of shortenings were evaluated. HIU was applied to different shortenings such as interesterified soybean oil (IESBO), multi-purpose commercial shortening, palm oil, and palm stearin. The functional properties measured include crystal morphology, solid fat content, melting profile, viscoelastic properties, hardness, and polymorphism. Different experimental set-ups were evaluated including a static batch system, a temperature cycling design, and flow cell system. Results showed that HIU generated harder material on IESBO, commercial shortening, and palm oil with more uniform and smaller crystal size, sharper melting profile, and higher elasticity. No chemical changes on triacylglycerol (TAG) and fatty acids were observed on IESBO under the sonication conditions used in this dissertation. Application of HIU maintained the texture of the commercial shortening that was subjected to temperature fluctuations, especially when HIU was applied before changes in temperature occurred. When sonication was applied in a flow-cell system lower power levels applied in a continuous manner was proved to be the most effective at inducing crystallization of palm oil. Research also showed that pulse irradiation of sonication and higher flow rates could be used to decrease the thermal effects generated by higher power levels of HIU. In addition, HIU was used in a highly saturated fat (palm stearin) at low power levels with long durations to delay lipid crystallization and generate a softer material. All the research findings suggest the great potential use of HIU in shortening production and food processing to improve the texture and its stability, as well as other functional properties.

Стилі APA, Harvard, Vancouver, ISO та ін.

4

Alreshidi, Abdulrahman Nassar. "A generic high-level specification language for non-functional properties of component-based systems." Thesis, King's College London (University of London), 2016. https://kclpure.kcl.ac.uk/portal/en/theses/a-generic-highlevel-specification-language-for-nonfunctional-properties-of-componentbased-systems(c818019a-5483-4a69-b3c3-d37d74f6851e).html.

Повний текст джерела

Анотація:

The component-based software development is helpful in providing reuse of the components and reducing complexity of software systems. Different components work together to produce a complete system that needs a good understanding of the way the components interact with each other. The components' reuse requires a high level specification, among other things for non-functional properties (NFPs) as these properties control the way these components co-ordinate with each other. The complexity of modern software systems demands a generic and flexible language for formal specification of the functional and NFPs of the system so that the different components in a system can have a well-defined behaviour expectation. The non-functional properties of component-based system are important part of specification because they highlight the non-functional perspective of the system. They also help in implementation of functional elements with constraints on the NFPs in consideration. The absence of specification of NFPs can render the system not usable because the functional implementation may not have considered the constraints for working environment of the system. This is because the component developer will have no clearly defined non-functional objectives of the system. The formal specification of NFPs for components and their interaction with each other can help implement reliable systems. Incorporating these design concepts in the language specification would describe the usage context of language features in clear and precise manner. In this thesis, we developed a novel generic specification language (QML/CS) for NFPs of component-based systems. Defining such a high level specication language using a standard meta-modelling approach is challenging because its definition requires multi levels modelling. We employed deep meta-modelling technique to address this complex problem. We begin by discussing the key concepts used, then show how our meta-model is defined. In addition, we show how our meta-model for QML/CS overcame the issues of the standard meta-modelling language like UML and the mapping of a measurement to a concrete application. Finally, we show a prototype for QML/CS and discuss how the mapping of QML/CS expressions into TLA+ specications can dene the QML/CS semantics.

Стилі APA, Harvard, Vancouver, ISO та ін.

5

Ramzan, Muhammad. "Structural, Electronic and Mechanical Properties of Advanced Functional Materials." Doctoral thesis, Uppsala universitet, Materialteori, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-205243.

Повний текст джерела

Анотація:

The search for alternate and renewable energy resources as well as the efficient use of energy and development of such systems that can help to save the energy consumption is needed because of exponential growth in world population, limited conventional fossil fuel resources, and to meet the increasing demand of clean and environment friendly substitutes. Hydrogen being the simplest, most abundant and clean energy carrier has the potential to fulfill some of these requirements provided the development of efficient, safe and durable systems for its production, storage and usage. Chemical hydrides, complex hydrides and nanomaterials, where the hydrogen is either chemically bonded to the metal ions or physiosorbed, are the possible means to overcome the difficulties associated with the storage and usage of hydrogen at favorable conditions. We have studied the structural and electronic properties of some of the chemical hydrides, complex hydrides and functionalized nanostructures to understand the kinetics and thermodynamics of these materials. Another active field relating to energy storage is rechargeable batteries. We have studied the detailed crystal and electronic structures of Li and Mg based cathode materials and calculated the average intercalation voltage of the corresponding batteries. We found that transition metal doped MgH2 nanocluster is a material to use efficiently not only in batteries but also in fuel-cell technologies. MAX phases can be used to develop the systems to save the energy consumption. We have chosen one compound from each of all known types of MAX phases and analyzed the structural, electronic, and mechanical properties using the hybrid functional. We suggest that the proper treatment of correlation effects is important for the correct description of Cr2AlC and Cr2GeC by the good choice of Hubbard 'U' in DFT+U method. Hydrogen is fascinating to physicists due to predicted possibility of metallization and high temperature superconductivity. On the basis of our ab initio molecular dynamics studies, we propose that the recent claim of conductive hydrogen by experiments might be explained by the diffusion of hydrogen at relevant pressure and temperature. In this thesis we also present the studies of phase change memory materials, oxides and amorphization of oxide materials, spintronics and sulfide materials.

Стилі APA, Harvard, Vancouver, ISO та ін.

6

Souza, de Almeida Jailton. "Designing and Tuning the Properties of Materials by Quantum Mechanical Calculations." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6923.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

7

Osorio, Guillén Jorge Mario. "Density Functional Theory in Computational Materials Science." Doctoral thesis, Uppsala University, Department of Physics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4496.

Повний текст джерела

Анотація:

The present thesis is concerned to the application of first-principles self-consistent total-energy calculations within the density functional theory on different topics in materials science.

Crystallographic phase-transitions under high-pressure has been study for TiO2, FeI2, Fe3O4, Ti, the heavy alkali metals Cs and Rb, and C3N4. A new high-pressure polymorph of TiO2 has been discovered, this new polymorph has an orthorhombic OI (Pbca) crystal structure, which is predicted theoretically for the pressure range 50 to 100 GPa. Also, the crystal structures of Cs and Rb metals have been studied under high compressions. Our results confirm the recent high-pressure experimental observations of new complex crystal structures for the Cs-III and Rb-III phases. Thus, it is now certain that the famous isostructural phase transition in Cs is rather a new crystallographic phase transition.

The elastic properties of the new superconductor MgB2 and Al-doped MgB2 have been investigated. Values of all independent elastic constants (c11, c12, c13, c33, and c55) as well as bulk moduli in the a and c directions (Ba and Bc respectively) are predicted. Our analysis suggests that the high anisotropy of the calculated elastic moduli is a strong indication that MgB2 should be rather brittle. Al doping decreases the elastic anisotropy of MgB2 in the a and c directions, but, it will not change the brittle behaviour of the material considerably.

The three most relevant battery properties, namely average voltage, energy density and specific energy, as well as the electronic structure of the Li/LixMPO4 systems, where M is either Fe, Mn, or Co have been calculated. The mixing between Fe and Mn in these materials is also examined. Our calculated values for these properties are in good agreement with recent experimental values. Further insight is gained from the electronic density of states of these materials, through which conclusions about the physical properties of the various phases are made.

The electronic and magnetic properties of the dilute magnetic semiconductor Mn-doped ZnO has been calculated. We have found that for an Mn concentration of 5.6%, the ferromagnetic configuration is energetically stable in comparison to the antiferromgnetic one. A half-metallic electronic structure is calculated by the GGA approximation, where Mn ions are in a divalent state leading to a total magnetic moment of 5 μB per Mn atom.

Стилі APA, Harvard, Vancouver, ISO та ін.

8

Pandolfi, Silvia. "High-pressure pathways towards new functional Si-based materials with tailored optoelectronic properties and their characterization." Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS459.pdf.

Повний текст джерела

Анотація:

Dans cet ouvrage, le traitement à haute température et haute pression est utilisé pour développer et optimiser la synthèse de nouvelles formes exotiques du silicium. La synthèse de nouvelles phases de silicium est un point clé dans le développement de technologies à base de Si, en particulier l'énergie solaire. Le développement de nouveaux matériaux à base de silicium à haut rendement pourrait faire face à la fois à l'optimisation des performances et à la réduction des coûts. Au niveau industriel, la haute pression a été principalement utilisée pour la synthèse des diamants et des matériaux super-durs, mais des études récentes ont prouvé qu’elle est également efficace pour la synthèse de nouveaux matériaux à base de silicium à propriétés remarquables pour les applications. Nous abordons ce défi sous tous ses aspects, à partir de l'étude des mécanismes de transition à haute pression jusqu’à la synthèse et à la caractérisation d'un nouveau matériau de silicium. Nous utilisons la diffraction in situ de rayons X à haute-pression haute-température pour observer et caractériser des transitions de phase du silicium et leur dynamique. Grâce à nos résultats, nous donnons de nouvelles perspectives capables de clarifier certains aspects du diagramme de phase du silicium qui étaient encore en discussion. Nous obtenons la première synthèse de silicium hexagonal pur, un défi de longue date dans le domaine. Grâce à notre échantillon de phase pure, nous caractérisons ses propriétés physiques et structurales. Nous prouvons que le silicium hexagonal obtenu à partir du traitement haute pression est sous forme du polytype 4H (séquence d'empilement ABCB). D'autres caractérisations structurelles révèlent une nanostructure hiérarchique dans la morphologie de l'échantillon. La découverte et la caractérisation de nanoparticules quasi-2D accessibles à la manipulation ouvrent de nouvelles perspectives pour le développement de nouveaux dispositifs optoélectroniques
In this work, high-pressure high-temperature treatment is used to develop and optimize synthetic pathways to new and exotic forms of silicon. The synthesis of new phases of silicon is a key point in the future development of Si-based technology, especially for solar energy. Development of new Si-based materials with high-efficiency could both optimise the performances and reduce the costs. At an industrial level, high-pressure has been mainly used for the synthesis of diamonds and super-hard materials, but recent studies have proven it also efficient in the synthesis of new silicon-based materials with enhanced properties for applications. We tackle this challenge in all its aspects, starting from the study of transition mechanisms at high-pressure and arriving to the synthesis and characterization of a new silicon material. We use in-situ x-ray diffraction at high-pressure high-temperature conditions to monitor and characterize silicon phase transitions and their dynamics. Our results give new insights that clarify some aspects of the silicon phase diagram that were still a matter of debate. We obtain the first synthesis of pure hexagonal silicon, a longstanding challenge in the field. Thanks to our pure-phase sample, we characterize its physical and structural properties. We prove that hexagonal silicon obtained from high-pressure is in the form of 4H polytype (ABCB stacking sequence). Further structural characterizations reveal a hierarchical nanostructure in the pristine morphology of the sample. Discovery and characterization of discrete quasi-2D nanoparticles accessible for manipulation opens new perspectives for the design of new optoelectronic devices

Стилі APA, Harvard, Vancouver, ISO та ін.

9

Kamath, Ganesh K. "Micro-structural and functional properties of TiAlCN/VCN coating produced by High Power Impulse Magnetron Sputtering Technology." Thesis, Sheffield Hallam University, 2011. http://shura.shu.ac.uk/20171/.

Повний текст джерела

Анотація:

Nanoscale TiAlCN/VCN multilayer coating was deposited in an industrial size 1000x4 Hauzer Techno Coating machine capable to operate with both unbalanced magnetron sputtering (UBMS) and high power impulse magnetron sputtering (HIPIMS) mode. The work was directed to study the impact of HIPIMS on the microstructure of the nanoscale TiAlCN/VCN coating, in relation to its properties at both room and elevated temperatures. TiAlCN/VCN coatings were deposited by three different ways in combination of reactive UBM and HIPIMS technique. These are (i) reactive pure UBMS, (ii) reactive combined UBMS and HIPIMS, (iii) reactive pure HIPIMS. The microstructure and mechanical properties of the nanoscale TiAlCN/VCN coatings deposited in all the above combination of deposition have been studied. In all three cases, coatings were deposited in three major steps: (a) HIPIMS etching by Ar[+] + V[+] ions (b) a 300 nm thick TiAIN base layer deposition in Ar + N[2] atmosphere followed by 2.5 pm thick TiAlCN/VCN coating deposition in mixed Ar+N[2]+CH[4] reactive atmosphere. PVD chamber furnished with two pairs of opposing magnetrons with TiAl and V targets were utilised deposit this coating. During the second case of combined deposition, two opposing magnetrons were enabled to operate in HIPIMS mode and other two magnetrons were operated in UBMS mode, where as in third case only two opposing targets with HIPIMS power supply were utilised to deposit the TiAlCN/VCN coating respectively. In all the three cases, deposition parameters such as bias voltage (U[b] = -75V), deposition temperature (T[s]= 450 °C) and total pressure of reactive gas mixture (Ar+N[2]+CH[4]; P = 4 X 10[-3] mbar) were maintained at similar conditions. The V+ HIPIMS etching used in all three processes has shown excellent adhesion (Lc > 50) of the coating to the substrate. The plasma compositional analysis of V+ HIPIMS etching has shown high metal-to-gas ion ratio with ionization states of V up to 5+. The ionic composition of the HIPIMS plasma as a function of discharge current was analysed by plasma sampling using energy-resolved mass spectrometery. During the coating of TiAlCN/VCN, the plasma analysis has confirmed the higher production rate of metal ions and free carbon in case of HIPIMS-UBM in contrast to pure UBM. This has resulted to a denser closed columnar microstructure of the coating during the HDPIMS-UBM technique than UBM. The formation of graded like microstructure achieved during reactive pure HIPIMS case, further plants the importance of HIPIMS in producing advanced nanostructured coatings for high technology applications.

Стилі APA, Harvard, Vancouver, ISO та ін.

10

Ganesh, Kamath K. "Micro-structural and functional properties of TiA1CN/VCN coating produced by high power impulse magnetron sputtering technology." Thesis, Sheffield Hallam University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.548497.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

11

Tabanelli, Giulia <1982&gt. "Use of sub-lethal high pressure homogenization (HPH) treatments to enhance functional properties of lactic acid bacteria probiotic strains." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3598/.

Повний текст джерела

Анотація:

The aim of this PhD thesis was to evaluate the effect of a sub-lethal HPH treatment on some probiotic properties and on cell response mechanisms of already-known functional strains, isolated from Argentinean dairy products. The results achieved showed that HPH treatments, performed at a sub-lethal level of 50 MPa, increased some important functional and technological characteristics of the considered non intestinal probiotic strains. In particular, HPH could modify cell hydrophobicity, autoaggregation and resistance to acid gastric conditions (tested in in vitro model), cell viability and cell production of positive aroma compounds, during a refrigerate storage in a simulated dairy product. In addition, HPH process was able to increase also some probiotic properties exerted in vivo and tested for two of the considered strains. In fact, HPH-treated cells were able to enhance the number of IgA+ cells more than other not treated cells, although this capacity was time dependent. On the other hand, HPH treatment was able to modify some important characteristics that are linked to the cell wall and, consequently, could alter the adhesion capacity in vivo and the interaction with the intestinal cells. These modifications, involving cell outermost structures, were highlighted also by Trasmission Electron Microscopy (TEM) analysis. In fact, the micrographs obtained showed a significant effect of the pressure treatment on the cell morphology and particularly on the cell wall. Moreover, the results achieved showed that composition of plasma membranes and their level of unsaturation are involved in response mechanisms adopted by cells exposed to the sub-lethal HPH treatment. Although the response to the treatment varied according to the characteristics of individual strains, time of storage and suspension media employed, the results of present study, could be exploited to enhance the quality of functional products and to improve their organoleptic properties.

Стилі APA, Harvard, Vancouver, ISO та ін.

12

Tzounis, Lazaros. "Glass and Jute fibers modified with CNT-based functional coatings for high performance composites." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-144493.

Повний текст джерела

Анотація:

Carbon nanotubes are known as one of the strongest materials in nature and since their discovery; they have triggered the scientific interest for fabricating multi-functional polymer composites. However, a well-known problem associated to the incorporation of nanoparticulate materials in polymer matrices is their tendency to agglomerate in order to reduce their surface energy, and the extreme increase of the polymer viscosities (i.e melts, solutions, etc), which makes it very difficult to process them. Polymers can be efficiently reinforced by fibers for applications where high strength and stiffness are required. Micro-scale short fiber reinforced polymer composites have been an alternative way to obtain fiber reinforced composites since the long fiber incorporation is a painful job and not always feasible and easy to produce composites in big scale. Therefore, use of long glass fibers as the support for depositing CNTs as well as CNTs+other kind of nanoparticles was made, and the resulting interfaces were investigated in detail by single fiber model composites. This approach can bring the CNT functionality, fiber strength and toughness to the final composite, and simultaneously alleviate the manufacturing process from increase of the polymer high viscosities. Finally, very logically the question of whether to improve or destroy the interface integrity comes before implementing the hybrid hierarchical reinforcements in bigger scales, and an output out of this work will be given. Furthermore, several information and functionalities arising from the CNTs at the interphase region will be elucidated like cure monitoring of the epoxy resin matrix, UV-sensing ability, and thermoelectric energy harvesting, giving rise to multi-functional structural composites. CNT-modified natural fibers also have been utillised to fabricate short fiber reinforced composites, and have shown a promising reinforcement effect due to the CNT nanostructured interfaces. The ‘interface’ in fiber reinforced polymer composites (FRPCs) is known as a very crucial parameter that has to be considered in the design of a composite with desired properties. Interfaces are often considered as surfaces however, they are in fact zones or areas with compositional, structural, and property gradients, typically varying from that of the fiber and the matrix material. Characterization of the mechanical properties of interfaces is necessary for understanding the mechanical behavior of scaled-up composites. In fact, the mechanical characteristics of a fiber/resin composite depend mainly on i) the mechanical properties of the component materials, ii) the surface of the fiber, and iii) the nature of the fiber/resin bonding as well as the mode of stress transfer at the interface. Among the many factors that govern the characteristics of composites involving a glass, carbon, natural or ceramic fiber, and a macromolecular matrix, the adhesion between fiber and matrix plays a predominant role. In specific, the stress transfer at the interface requires an efficient coupling between fiber and matrix. Therefore, it is important to optimize the interfacial bonding since a direct linkage between fiber and matrix gives rise to a rigid, low impact resistance composite material.

Стилі APA, Harvard, Vancouver, ISO та ін.

13

Kargén, Ulf. "First-Principles Study of Elastic Properties of Fe-Mg alloy at Earth’s core pressure." Thesis, Linköping University, The Department of Physics, Chemistry and Biology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-15742.

Повний текст джерела

Анотація:

The purpose of this thesis has been to investigate the elastic properties of an fcc FeMg alloy with 10 at.% magnesium under high pressure. Recent research has shown that magnesium can be a possible candidate for light element impurities in the Earth’s inner core, something that was previously not considered possible because of the low miscibility of magnesium in iron at ambient pressure. Gaining knowledge about the composition of the Earth’s core can help us better understand such phenomena as seismic activity and the fluctuations of the Earth’s magnetic field.

The elastic constants of the FeMg alloy was calculated using ab-initio methods based on Density Functional Theory. The Exact Muffin-Tin Orbitals method was used in conjunction with the Coherent Potential Approximation.

The FeMg alloy was found to be overall considerably softer than pure iron, and the softening effect on the elastic constants was also found to increase with pressure. The results also showed that 10% Mg alloying increased the anisotropy with about 40% compared to pure iron.

Стилі APA, Harvard, Vancouver, ISO та ін.

14

Paar, Susanne Adelgunde Monica [Verfasser], and Fritz [Akademischer Betreuer] Schick. "Assessment of morphological and functional properties of the genitourinary system using high resolution MRI / Susanne Adelgunde Monica Paar ; Betreuer: Fritz Schick." Tübingen : Universitätsbibliothek Tübingen, 2016. http://d-nb.info/1199615722/34.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

15

Karki, Bishnu. "Use of high-power ultrasound during soy protein production and study of its effect on functional properties of soy protein isolate." [Ames, Iowa : Iowa State University], 2009. 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:3389112.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

16

Paar, Susanne [Verfasser], and Fritz [Akademischer Betreuer] Schick. "Assessment of morphological and functional properties of the genitourinary system using high resolution MRI / Susanne Adelgunde Monica Paar ; Betreuer: Fritz Schick." Tübingen : Universitätsbibliothek Tübingen, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:21-dspace-734382.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

17

White, Thomas G. "Study of high energy density matter through quantum molecular dynamics and time resolved X-ray scattering." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:ec7d9bd3-5b94-4466-9276-6f5d6edfc710.

Повний текст джерела

Анотація:

The warm dense matter regime (WDM), defined by temperatures of a few electron volts and densities comparable with solids, is a complex state of matter where multi-body particle correlations and quantum effects play an important role in determining the overall structure and equation of state. The study of WDM states represents the laboratory analogue of the astrophysical environments found in the cores of planets and in the crusts of old stars, but also has practical applications for controlled thermonuclear fusion. Time resolved X-ray diffraction is used to study the temporal evolution of a sample from solid state towards WDM, either after irradiation with an intense proton/electron beam, in carbon samples, or direct laser illumination, in thin gold nanofoils. The electron-ion equilibration time is extracted through the use of the two-temperature model and in highly excited carbon shown to be longer than previously thought, this is attributed to strong ion-ion coupling screening the interaction (coupled mode theory). Calculation of the dynamic ion-ion structure factor is performed using orbital-free density functional theory (OF-DFT) and shown to compare well with Kohn-Sham DFT in both the static and dynamic cases. Experimental verification of these results is vital and measurement of the microscopic dynamics of warm dense aluminium have been successfully demonstrated through inelastic X-ray scattering. Using the self-seeded beam at the linear coherent light source (LCLS) scattering at a small momentum exchange allowed the first direct measurement of ion acoustic waves in WDM. This data provides the basis for a direct experimental test of many dense plasma theories through direct comparison with the ion-ion dynamic structure factor.

Стилі APA, Harvard, Vancouver, ISO та ін.

18

Pedras, Marcelo Monteiro. "Avaliação de propriedades fisico-quimicas e funcionais de leite processado por tecnologia de homogeneização a ultra alta pressão." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/254835.

Повний текст джерела

Анотація:

Orientador: Marcelo Cristianini
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-08T04:19:13Z (GMT). No. of bitstreams: 1 Pedras_MarceloMonteiro_M.pdf: 951624 bytes, checksum: 118f33f7311ebd4a32deb6f15dc8a20a (MD5) Previous issue date: 2007
Resumo: O tratamento de homogeneização a ultra alta pressão (HUAP) é uma tecnologia que vem sendo utilizada tanto para inibir o crescimento de microorganismos, como para alterar as propriedades físico-químicas e funcionais do leite e de sua fração proteica. O objetivo deste estudo foi avaliar algumas das principais alterações físico-químicas de leite desnatado submetido a diferentes níveis de HUAP. Além disso, avaliar solubilidade, propriedades de aeração e emulsificação de caseína e proteínas de soro isoladas de leite processado por HUAP. Leite cru desnatado foi submetido a 3 níveis de pressão de homogeneização (100 MPa, 200 MPa e 300 MPa) onde foram avaliadas as alterações físico-químicas do leite (pH, composição centesimal, estabilidade ao álcool, luminosidade, desnaturação de proteínas do soro, hidrofobicidade e viscosidade) e as propriedades funcionais da caseína e proteínas do soro (solubilidade, aeração e emulsificação). O processo apresentou boa repetibilidade e aumento de temperatura de no máximo 55°C. As medidas de pH e nitrogênio não proteico (NNP) foram as únicas variáveis que não apresentaram alteração estatisticamente significativa para nenhum dos níveis de pressão. Estabilidade a precipitação com álcool, luminosidade e hidrofobicidade apresentaram aumento a partir de 100 MPa. A desnaturação de proteínas do soro ocorreu somente a partir de 200 MPa, aumentando ainda mais com uso de 300 MPa. A única variável que apresentou alteração somente no nível de 300 MPa foi a viscosidade. A caseína e as proteínas do soro foram isoladas por acidificação a pH 4,6 e centrifugação, o sobrenadante e precipitado foram neutralizados e liofilizados. Foram avaliadas as seguintes propriedades: solubilidade, capacidade de formação de espuma, estabilidade de espuma, capacidade emulsificante e estabilidade de emulsão. A caseína não sofreu alteração de solubilidade, já as propriedades de aeração e emulsificação apresentaram melhora de performance, sendo estatisticamente significativas a partir de diferentes níveis de pressão de acordo com a propriedade avaliada. As proteínas do soro apresentaram diminuição da solubilidade nos níveis de 100 MPa e 200 MPa, as propriedades de aeração foram melhoradas em 300 MPa, e as propriedades de emulsificação não foram influenciadas. O tratamento de leite fluido por tecnologia de HUAP promove alterações significativas em propriedades funcionais de caseína e proteínas do soro. As alterações estão relacionadas à desestruturação das micelas de caseína, desnaturação de proteínas do soro, interação das micelas entre si e com as proteínas do soro, e com o aumento da hidrofobicidade e capacidade de hidratação das mesmas
Abstract: The ultra high-pressure homogenisation (UHPH) is a recent technology used to inhibit microorganisms¿ growth, as to modify the physical-chemical properties of milk and its protein fraction. The purpose of this study was to evaluate the main physical-chemical characteristics caused by different levels of high-pressure homogenisation in skim milk. Besides to evaluate solubility, foaming properties and emulsifying properties of casein and whey proteins isolated from milk processed by UHPH. Raw skimmed milk was submitted to 3 pressure levels (100 MPa, 200 MPa e 300 MPa), the processing parameters and the modifications on milk physical-chemical properties has been evaluated. The process presented good repeatability and the maximum temperature increase was 55°C. The measurements of pH and non-protein nitrogen (NPN) were the only variables that did not present any statistically significant change. Ethanol stability, lightness (L*) and hydrophobicity showed an improvement or increment from 100 MPa to 300 MPa. Whey protein denaturation occurred only from 200 MPa to 300 MPa. The only variable that presented changes only at 300 MPa was viscosity. Casein and whey proteins were isolated by acidification at pH 4.6 and centrifugation, further they were neutralized and freeze-dried. The following properties were evaluated: solubility, foaming capacity, foam stability, emulsifying capacity and emulsion stability. The freeze-dried casein did not show any modification on solubility, however all foaming and emulsifying characteristics presented improved performance, being statistically significant for different pressure levels according to each analysed property. UHPH decreased the solubility of the whey proteins obtained from milk treated at 100 MPa and 200 MPa, foaming properties increased for the freeze-dried protein obtained from milk treated at 300 MPa, and no influence were noted on the emulsifying properties. The treatment of fluid milk by UHPH was able to promote significant alterations on the functional properties of casein and whey proteins. The modifications were related to casein micelles disruption, whey proteins denaturation, interaction among the micelles and with denaturated whey proteins, and also with increase of molecular hydrophobicty and water retention
Mestrado
Mestre em Tecnologia de Alimentos

Стилі APA, Harvard, Vancouver, ISO та ін.

19

Cebulska, Aleksandra. "Jakość mięsa świń polskich ras rodzimych i mieszańców wysokoprodukcyjnych oraz jego przydatność do pozyskiwania żywności o właściwościach funkcjonalnych." Rozprawa doktorska, Uniwersytet Technologiczno-Przyrodniczy w Bydgoszczy, 2015. http://dlibra.utp.edu.pl/Content/817.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

20

Drain, John Frederick. "Development of magnetic bond-order potentials for Mn and Fe-Mn." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:68a01493-4a20-4d78-ad4a-6c3c2fe072d6.

Повний текст джерела

Анотація:

While group VII 4d Tc and 5d Re have hexagonally close-packed (hcp) ground states, 3d Mn adopts the complex chi-phase which exhibits non-collinear magnetism. Density functional theory (DFT) calculations have shown that without magnetism the chi-phase remains the ground state of Mn implying that magnetism is not the critical factor, as is commonly believed, in driving the anomalous stability of the chi-phase over hcp. Using a tight-binding (TB) model it is found that while harder potentials stabilise close-packed hcp, a softer potential stabilises the more open chi-phase. By analogy with the structural trend from open to close-packed phases down the group IV elements, the anomalous stability of the chi-phase in Mn is shown to be due to 3d valent Mn lacking d states in the core which leads to an effectively softer atomic repulsion between the atoms than in 4d Tc and 5d Re. Subsequently an analytic Bond-Order Potential (BOP) is developed to investigate the structural and magnetic properties of elemental Mn at 0 K. It is derived within BOP theory directly from a new short-ranged orthogonal d-valent TB model of Mn, the parameters of which are fitted to reproduce the DFT binding energy curves of the five experimentally observed phases of Mn, alpha, beta, gamma, delta, and epsilon-Mn. Not only does the BOP reproduce qualitatively DFT binding energy curves of the five different structure types, it also predicts the complex collinear antiferromagnetic (AFM) ordering in alpha-Mn, the ferrimagnetic (FiM) ordering in beta-Mn and the AFM ordering in the other phases that are found by DFT. A BOP expansion including 14 moments is sufficiently converged to reproduce most of the properties of the TB model with the exception of the elastic shear constants which require further moments. Magnetic analytic BOPs are also developed for Fe and Fe-Mn. The Fe model correctly reproduces trends in the structural stabilities of the common metallic structures except that AFM hcp is overstabilised. Reproduction of the elastic constants with a 9-moment BOP is reasonable although as is found for the Mn BOP the elastic shear constants require more moments to converge. Vacancy formation energies are close to those determined by experiment and DFT and the relative stabilities of self-interstitial atom (SIA) defects in ferromagnetic bcc Fe are correctly reproduced. The SIA formation energies are found to be better than those calculated with existing BOP models. The Fe-Mn TB and BOP models were challenging to fit and nonmagnetic face-centred cubic (fcc) structures are overstabilised. Furthermore within BOP an incorrect magnetic solution is predicted for one fcc structure resulting in poor reproduction of the DFT stacking fault energies. Refitting the bond integrals might help to better reproduce the nonmagnetic hcp-fcc energy differences while an environment-dependent Stoner parameter could help provide the flexibility needed to correctly capture the magnetic energy differences.

Стилі APA, Harvard, Vancouver, ISO та ін.

21

Hylla, Kai [Verfasser], Wolfgang [Akademischer Betreuer] Nebel, and Wolfgang [Akademischer Betreuer] Rosenstiel. "Bridging the gap between precise RT-level power/timing estimation and fast high-level simulation : a method for automatically identifying and characterising combinational macros in synchronous sequential systems at register-transfer level and subsequent executable high-level model generation with respect to non-functional properties / Kai Hylla. Betreuer: Wolfgang Nebel ; Wolfgang Rosenstiel." Oldenburg : BIS der Universität Oldenburg, 2014. http://d-nb.info/1050816560/34.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

22

Макаренко, Виктория Васильевна. "Теплоэлектроизоляционный материал и изделия из него с повышенной стойкостью в потоках ионизованного газа". Thesis, НТУ "ХПИ", 2017. http://repository.kpi.kharkov.ua/handle/KhPI-Press/29350.

Повний текст джерела

Анотація:

Диссертация на соискание ученой степени кандидата технических наук по специальности 05.17.11 – технология тугоплавких неметаллических материалов. – Национальный технический университет "Харьковский политехнический институт", Харьков, 2017. Диссертация посвящена разработке технологии корундовых композиционных материалов и изделий из них сложной конфигурации для эксплуатации в потоках ионизированного газа, вместо дорогих ГП аналогов, которые используются в новой технике. При проектировании составов КМ на основе системы Аl₂O₃–SiO₂ использован золь-гель процесс, спекающие добавки и модифицирование наполнителя и волокон алкоксидом кремния. Установлены температура появления расплава в корундовой матрице, закономерности муллитообразования и спекания смесей электрокорунда с золь-гель связующим с добавкой В₂O₃. Показано, что управление количеством синтезированного муллита может осуществляться за счет изменения количества образованного расплава путем варьирования концентраций В₂O₃ в золе и плотности золь-гель связующего. Установлен механохимический синтез муллита в процессе измельчения электрокорунда с добавкой алкоксида кремния. Исследованы физико-химические и эксплуатационные свойства материала с муллитокремнеземистым и поликристаллическим корундовым волокном. Установлено, что благодаря присутствию наночастиц муллита и высокой однородности структуры с введенным поликристаллическим волокном обеспечивается повышение твердости и трещиностойкости материала СМД, что обеспечивает более высокую стойкость в потоках ионизованного газа, чем ГП материалов новой техники. Показано, что управление количеством синтезированного муллита может осуществляться за счет изменения количества образованного расплава. При обжиге электрокорунда модифицированного алкоксидом кремния с 1 % поликристаллического волокна, образуется однородная мелкокристаллическая структура из матрицы α-Аl₂O₃, армированной частицами и нитевидными кристаллами муллита и поликристаллическим волокном, которые равномерно распределяются между собой. При обжиге в азотной среде на поверхности материала образуется оксинитридная пленка, которая уплотняет поверхность изделия и улучшает стойкость его к износу в потоках ионизированных газов. Установлено, что разработанная технология с использованием модифицированного алкоксидом кремния поликристаллического волокна, обеспечивает замедление начала кристаллизации структуры волокна, а комплексное связующее ускоряет муллитизацию корундовой матрицы и интенсифицирует ее спекание, создается фрагментальная структура материала, обеспечивающая повышение его физико-механических свойств и трещиностойкости. Трещиностойкость составляет 12,0-12,7 МПа·м⁰ˈ⁵, диаграммы деформирования материала СМД подобны слоистым металокерамическим материалам. Разработанный КМ СМД имеет однородную структуру, характеризуется пределом прочности при сжатии выше 900 МПа, электросопротивлением 3·10¹¹ Ом, термостойкостью – выше 50 термосмен 1000 ⁰С – вода. Ключевые слова: композиционный материал, Аl₂O₃–SiO₂, электрокорунд, волокно муллитокремнеземистое, волокно поликристаллическое корундовое, механоактивация, алко-ксид кремния, золь-гель, синтез новообразований, муллит, SiC, оксинитрид кремния, функциональные свойства, стойкость в потоках ионизированного газа
Polytechnic Institute", Kharkov, 2017. The thesis is devoted to the development of technology for alumina composite materials and products of complex configuration for use in streams of ionized gas instead of expensive GP analogues used in the new technique. When designing the warehouses of CM based on the system Аl₂O₃–SiO₂ is used the possibilities of mechanochemical activation processes of synthesis of refractory compounds in the modification of corundum filler alkoxide silicon and when using the Sol-gel binder, in particular with the addition of boric acid to intensify multitorrent, coating a surface of a polycrystalline fiber alkoxide silicon to prevent its crystallization during heating and compaction during the pressing masses on the basis of electrocorundum and ceramic fibers through the use of complex binder paraffin–Sol with ethylsilicate. The physical and chemical processes during heating of modified components, their mixtures with different swatowski, the conditions of heat treatment of the masses using various media. The developed compositions and technological parameters of manufacturing a KM with multitransistor and polycrystalline fibre products for the manufacture of various purposes with a complex of high mechanical properties. Developed KM of SMD homogeneous structure for the flow of ionized gas is characterized by the limit of compressive strength of above 900 MPa, fracture toughness 12,0-12,8 MPa∙м⁰ˈ⁵, the resistivity of 3·10¹¹ Om, resistance – above 50 thermo-changes 1000 °C – water.

Стилі APA, Harvard, Vancouver, ISO та ін.

23

Макаренко, Вікторія Василівна. "Теплоелектроізоляційний матеріал та вироби з нього з підвищеною стійкістю в потоках іонізованого газу". Thesis, НТУ "ХПІ", 2017. http://repository.kpi.kharkov.ua/handle/KhPI-Press/29347.

Повний текст джерела

Анотація:

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.17.11 – технологія тугоплавких неметалічних матеріалів. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2017 р. Дисертацію присвячено розробці технології корундових композиційних матеріалів і виробів із них складної конфігурації для експлуатації в потоках іонізованого газу замість дорогих ГП аналогів, що використовуються в новій техніці. При проектуванні складів КМ на основі системи Аl₂O₃–SiO₂ використано можливості механохімічної активації процесів синтезу тугоплавких сполук при модифікації корундового наповнювача алкоксидом кремнію та при використанні золь-гель зв'язуючих, в тому числі з добавкою борної кислоти, для інтенсифікації мулітоутворення, покриття поверхні полікристалічного волокна алкоксидом кремнію для запобігання його кристалізації при нагріванні та ущільнення при пресуванні мас на основі електрокорунду та керамічного волокна за рахунок використання комплексного звязуючого парафін–золь із етилсилікату. Встановлено фізико-хімічні процеси при нагріванні модифікованих компонентів, їх сумішей із різними зв'язуючими, встановлено режими термообробки мас при використанні різних середовищ. Розроблено склади та технологічні пара-метри виготовлення КМ з використанням мулітокремнеземного та полікристалічного волокна для виготовлення виробів різного призначення з комплексом високих механічних властивостей. Розроблений композиційний матеріал одно-рідної структури для служби в потоках іонізованого газу характеризується межею міцності при стиску вище, ніж 900 МПа, тріщиностійкістю 12,0 МПа·м⁰ˈ⁵, електроопором 3·10¹¹ Ом, термостійкістю – більш, ніж 50 термозмін 1000 ⁰С–вода.
The dissertation on competition of a scientific degree of candidate of technical Sciences in specialty 05.17.11 – technology of refractory nonmetallic materials. – National technical University "Kharkiv Polytechnic Institute", Kharkov, 2017. The thesis is devoted to the development of technology for alumina composite materials and products of complex configuration for use in streams of ionized gas instead of expensive GP analogues used in the new technique. When designing the warehouses of CM based on the system Аl₂O₃–SiO₂ is used the possibilities of mechanochemical activation processes of synthesis of refractory compounds in the modification of corundum filler alkoxide silicon and when using the Sol-gel binder, in particular with the addition of boric acid to intensify multitorrent, coating a surface of a polycrystalline fiber alkoxide silicon to prevent its crystallization during heating and compaction during the pressing masses on the basis of electrocorundum and ceramic fibers through the use of complex binder paraffin–Sol with ethylsilicate. The physical and chemical processes during heating of modified components, their mixtures with different swatowski, the conditions of heat treatment of the masses using various media. The developed compositions and technological parameters of manufacturing a KM with multitransistor and polycrystalline fibre products for the manufacture of various purposes with a complex of high mechanical properties. Developed KM of SMD homogeneous structure for the flow of ionized gas is characterized by the limit of compressive strength of above 900 MPa, fracture toughness 12,0-12,8 MPa∙м⁰ˈ⁵, the resistivity of 3·10¹¹ Om, resistance – above 50 thermo-changes 1000 °C – water.

Стилі APA, Harvard, Vancouver, ISO та ін.

24

Ivanenko, Yevhen. "Estimation of electromagnetic material properties with application to high-voltage power cables." Licentiate thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-64265.

Повний текст джерела

Анотація:

Efficient design of high-voltage power cables is important to achieve an economical delivery of electric power from wind farms and power plants over the very long distances as well as the overseas electric power. The main focus of this thesis is the investigation of electromagnetic losses in components of high-voltage power cables. The objective of the ongoing research is to develop the theory and optimization techniques as tools to make material choices and geometry designs to minimize the high-frequency attenuation and dispersion for HVDC power cables and the power losses associated with HVAC cables. Physical limitations, dispersion relationships and the application of sum rules as well as convex optimization will be investigated to obtain adequate physical insight and a priori modeling information for these problems. For HVAC power cables, the objectives are addressed by performing measurements and estimation of complex valued permeability of cable armour steel in Papers I and II. Efficient analytical solutions for the electromagnetic field generated by helical structures with applications for HVAC power cables have been obtained in Paper III. For HVDC power cables, estimation of insulation characteristics from dielectric spectroscopy data using Herglotz functions, convex optimization and B-splines, has been investigated in Papers V and VI. The unique solution requirements in waveguide problems have been reviewed in Paper IV.

Стилі APA, Harvard, Vancouver, ISO та ін.

25

Fukumoto, Yoshihiro. "Effects of high-velocity resistance training on muscle function, muscle properties, and physical performance in individuals with hip osteoarthritis." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/185208.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

26

Madungandaba, Pam Mana. "Microstructure and mechanical properties as a function of process parameters for Ti6Al4V produced by high power laser powder bed fusion." Diss., University of Pretoria, 2019. http://hdl.handle.net/2263/79274.

Повний текст джерела

Анотація:

Laser-powder bed fusion (L-PBF) processing finds its application in various metal forming industries such as aerospace, automotive and medical industries. Ti6Al4V alloy is widely used in aerospace applications. The main interest of studies on additive manufacturing of Ti6Al4V is to investigate the material properties (strength, toughness and corrosion resistance) with regards to applications in the aerospace industry. The L-PBF process allows great flexibility with regards to process control and process design, and therefore control over microstructure and properties. The aim of the project was to study the effect of process parameters (laser power, scanning speed, hatch spacing, spot size and energy density) on Ti6Al4V microstructure and hardness of samples produced by L-PBF processing. The main objective was to analyse, and statistically predict part properties based on selected process parameters in order to enhance process understanding. The equipment that was used to manufacture the samples is a prototype powder bed fusion setup, with an Ytterbium laser system housed in a LENS (laser engineering net shaping) chamber. Experiments were carried out using a laser power of 1 to 3 kW, 2 to 4 m/s scanning speed, 0.10 to 0.24 mm hatch spacing, 250 to 450 μm spot size, and laser energy density of 33 to 200 J/mm3. Porosity analysis was conducted using the OHAUS Explore® balance precision weighing equipment. Optical microscope (OM) and EBSD analysis scanning electron microscope (SEM) was used to analyse microstructures of the samples. Porosity was found to be a function of laser power, scanning speed, hatch spacing and energy density. Linear regression relationships were developed to predict porosity of Ti6Al4V under the set of parameters used in the study. The lowest level of fraction porosity obtained from the built parts was 0.6% (2 kW laser power, 2 m/s scanning speed, 0.24 μm hatch spacing and 450 μm spot size). The amount of porosity varied with laser power. A higher laser power resulted in increased micro round porosity. A microstructure of acicular  martensite within columnar prior  grains was obtained for all energy density values used. Changes in process parameters used in the project scope were found to have a significant effect on the microstructure and not so much on the hardness range. However, through electron backscatter diffraction analysis a change in β content of (0.2 to 5.5%) was found with increasing energy densities, whilst content decreased with increasing energy densities. The hardness was between 326 and 418 HV (300 g).
Dissertation (MSc)--University of Pretoria, 2019.
Metallurgy
MSc
Unrestricted

Стилі APA, Harvard, Vancouver, ISO та ін.

27

Mora, Anne-Sophie. "Élaboration de revêtements époxy pour contact alimentaire à empreinte environnementale réduite A perspective approach on the amine reactivity and the hydrogen bonds effect on epoxy-amine systems vanillin-derived amines for bio-based thermosets synthesis of biobased reactive hydroxyl amines by amination reaction of cardanol-based epoxy monomers synthesis of pluri-functional amine hardeners from bio-based aromatic aldehydes for epoxy amine thermosets cardanol-based epoxy monomers for high thermal properties thermosets." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2019. http://www.theses.fr/2019ENCM0012.

Повний текст джерела

Анотація:

Les travaux de thèse présentés sont issus d’une collaboration industrielle avec la société Nouvelle Sogatra, spécialisée dans la conception, la fabrication et la commercialisation de revêtements de protection bi-composants répondant aux normes d’alimentarité. L’objectif principal de ce projet est de proposer de nouveaux revêtements époxydiques performants en utilisant des produits biosourcés et, dans l’idéal, moins dangereux pour l’Homme et pour l’environnement. Ces travaux de thèse s’axent autour de l’identification de nouvelles méthodologies de synthèse de durcisseurs aminés biosourcés qui soient facilement applicables industriellement.L’amination directe des groupements époxy par ouverture de cycle en présence d’ammoniaque ainsi que l’amination réductrice via la synthèse d’imine ont été sélectionnées comme voies de synthèse pour leur facilité d’application et leur caractère respectueux de l’environnement. Pour cela, des précurseurs commerciaux biosourcés et/ou à toxicité réduite ont été sélectionnés. De nouveaux durcisseurs aminés ont été synthétisés à partir de bio ressources telles que la vanilline, le cardanol et le benzaldéhyde. Ces durcisseurs ont ensuite été utilisés pour la synthèse de système époxy-amine thermodurcissables dont les propriétés physico-chimiques et thermodynamiques ont été caractérisées
The presented PhD works were initiated by an industrial collaboration with the company Nouvelle Sogatra, specialized in the design, manufacturing and marketing of two component protective coatings for food contact. The aim of this project is to offer new high-performance epoxy thermosets from bio based reactants and, ideally with a low impact on the health and the environment. This PhD works focus on the identification of new synthesis methodologies of bio-based amine hardeners, which could be easily industrialized.The direct epoxy amination by ring opening using ammonia and the reductive amination via imine synthesis were selected as synthesis routes for their simple utilization and their eco friendly character. Hence, bio based and/or reduced toxicity commercial precursors were selected. New amine hardeners were synthesized from bio resources, such as vanillin, cardanol and benzaldehyde. These hardeners were then used to synthesize epoxy-amine thermosets, whose thermomechanical and physicochemical properties were characterized

Стилі APA, Harvard, Vancouver, ISO та ін.

28

Kasimoglu, Ismail Hakki. "Estimation of a Coronary Vessel Wall Deformation with High-Frequency Ultrasound Elastography." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19762.

Повний текст джерела

Анотація:

Elastography, which is based on applying pressure and estimating the resulting deformation, involves the forward problem to obtain the strain distributions and inverse problem to construct the elastic distributions consistent with the obtained strains on observation points. This thesis focuses on the former problem whose solution is used as an input to the latter problem. The aim is to provide the inverse problem community with accurate strain estimates of a coronary artery vessel wall. In doing so, a new ultrasonic image-based elastography approach is developed. Because the accuracy and quality of the estimated strain fields depend on the resolution level of the ultrasound image and to date best resolution levels obtained in the literature are not enough to clearly see all boundaries of the artery, one of the main goals is to acquire high-resolution coronary vessel wall ultrasound images at different pressures. For this purpose, first an experimental setup is designed to collect radio frequency (RF) signals, and then image formation algorithm is developed to obtain ultrasound images from the collected signals. To segment the noisy ultrasound images formed, a geodesic active contour-based segmentation algorithm with a novel stopping function that includes local phase of the image is developed. Then, region-based information is added to make the segmentation more robust to noise. Finally, elliptical deformable template is applied so that a priori information regarding the shape of the arteries could be taken into account, resulting in more stable and accurate results. The use of this template also implicitly provides boundary point correspondences from which high-resolution, size-independent, non-rigid and local strain fields of the coronary vessel wall are obtained.

Стилі APA, Harvard, Vancouver, ISO та ін.

29

Pelteku, Altin E. "Development of an electromagnetic glottal waveform sensor for applications in high acoustic noise environments." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0114104-142855/.

Повний текст джерела

Анотація:

Thesis (M.S.)--Worcester Polytechnic Institute.
Keywords: basis functions; perfectly matched layers; PML; neck model; parallel plate resonator; finite element; circulator; glottal waveform; multi-transmission line; dielectric properties of human tissues; radiation currents; weighted residuals; non-acoustic sensor. Includes bibliographical references (p. 104-107).

Стилі APA, Harvard, Vancouver, ISO та ін.

30

Erman, Marko. "L'éllipsométrie spectroscopique à haute résolution latérale : modélisation, application aux surfaces, interfaces et puits quantiques dans le matériaux semi-conducteur III-V." Paris 6, 1986. http://www.theses.fr/1986PA066400.

Повний текст джерела

Анотація:

Etude théorique et expérimentale de l'application de la méthode aux semi-conducteurs III-V et en particulier à l'analyse des interfaces. Etude des systèmes GaAlAs/GaAs et GaInAs/InP. Détermination simultanée de l'épaisseur des couches et de l'énergie de localisation pour les différentes transitions optiques, dans le cas de puits quantiques et de super-réseaux; effets dus au couplage entre les puits quantiques. Obtention de cartographies avec une résolution optique de 10mu m. Le traitement théorique des images ellipsométriques est base sur le concept de trajectoires.

Стилі APA, Harvard, Vancouver, ISO та ін.

31

Garcia, Lyda G. "Functional Properties and Utilization of High pH Beef." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-08-7185.

Повний текст джерела

Анотація:

Two Texas fed beef and cow/bull packing plants were surveyed for high pH beef carcasses as well as the evaluation of functional properties of high pH beef in whole muscle beef jerky, frankfurters, and snack stick production. An estimated 42% of cow carcasses were of 6.0 muscle pH or greater as well as exhibiting darker, less red colored lean. Jerky high in pH from cow inside rounds resulted in the greatest percent moisture and least percent protein compared to other treatments. High pH cooked jerky were higher in (P < 0.05) pH and water activity and lower in percent fat and shear force values. In cooked jerky slices, fed-high resulted in the highest percent MPR and cook yield, but was the most tender. In contrast, fed-normal resulted in the least water activity, MPR and toughest jerky slices. In frankfurter production, emulsion stability and hydration values was highest for C (1.98mL) followed by 100H (3.37mL) that decreased as percent high pH decreased. As storage day increased, frankfurter pH decreased, especially by day 56 (5.67) where LAB and APC counts had reached a log of 6.0 indicative of spoilage by day 28 and became lighter and less red in color with minimal lipid oxidation. 100H was harder and less cohesive with trained panelists reported containing at least 50% high pH meat was harder. The pH and internal color of cooked snack sticks significantly increased and became lighter and redder as percent high pH meat increased. Even though water activity compared to a whole muscle dry product or an emulsified, water added product ranged from 0.85 to 0.86 (P > 0.05), minimal (P greater than 0.05) lipid oxidation occurred. 100N resulted in the least percentage of fat but 3% more (P less than 0.05) protein and highest shear force values. Overall, beef raw materials high in pH may be better suited in a semi-dry fermented product.

Стилі APA, Harvard, Vancouver, ISO та ін.

32

"Prediction of structures and properties of high-pressure solid materials using first principles methods." Thesis, 2016. http://hdl.handle.net/10388/ETD-2016-02-2441.

Повний текст джерела

Анотація:

The purpose of the research contained in this thesis is to allow for the prediction of new structures and properties of crystalline structures due to the application of external pressure by using first-principles numerical computations. The body of the thesis is separated into two primary research projects. The properties of cupric oxide (CuO) have been studied at pressures below 70 GPa, and it has been suggested that it may show room-temperature multiferroics at pressure of 20 to 40 GPa. However, at pressures above these ranges, the properties of CuO have yet to be examined thoroughly. The changes in crystal structure of CuO were examined in these high-pressure ranges. It was predicted that the ambient pressure monoclinic structure changes to a rocksalt structure and CsCl structure at high pressure. Changes in the magnetic ordering were also suggested to occur due to superexchange interactions and Jahn-Teller instabilities arising from the d-orbital electrons. Barium chloride (BaCl) has also been observed, which undergoes a similar structural change due to an s – d transition, and whose structural changes can offer further insight into the transitions observed in CuO. Ammonia borane (NH3BH3) is known to have a crystal structure which contains the molecules in staggered conformation at low pressure. The crystalline structure of NH3BH3 was examined at high pressure, which revealed that the staggered configuration transforms to an eclipsed conformation stabilized by homopolar B–Hδ-∙∙∙ δ-H–B dihydrogen bonds. These bonds are shown to be covalent in nature, comparable in bond strength to conventional hydrogen bonds, and may allow for easier molecular hydrogen formation in hydrogen fuel storage.

Стилі APA, Harvard, Vancouver, ISO та ін.

33

Xuan-WeiLiue and 劉軒瑋. "Characterization of Thermoelastic and Fracture Properties for Functional Graded High Heat Risistance Materials via Meshless Radial Point Interpolation." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/81893181734571190084.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

34

Chan, Jacky Tin Yan. "Protein functionality in turkey meat." Master's thesis, 2011. http://hdl.handle.net/10048/1803.

Повний текст джерела

Анотація:

Turkey with pale, soft, exudative (PSE)-like condition is one of the growing concerns in the poultry industry as it affects meat quality due to low ultimate pH at 24 h post mortem (pH24). Hence, there is a need for better utilization of PSE-like meat for the preparation of further processed products. In the first two studies, the biochemical, functional, rheological, and textural properties of proteins in turkey breast meat with different pH24 in fresh and frozen conditions were investigated. These studies revealed that low and normal pH meat had similar properties indicating similar extent of protein denaturation, except for lower water holding capacity (WHC) in low pH meat. High pH meat had similar or better functional properties than normal pH meat. In the third study, improvements in WHC, protein solubility, and gel forming ability of low pH meat was achieved by the application of high pressure processing (HPP).
Food Science and Technology

Стилі APA, Harvard, Vancouver, ISO та ін.

35

Tzounis, Lazaros. "Glass and Jute fibers modified with CNT-based functional coatings for high performance composites." Doctoral thesis, 2011. https://tud.qucosa.de/id/qucosa%3A28116.

Повний текст джерела

Анотація:

Carbon nanotubes are known as one of the strongest materials in nature and since their discovery; they have triggered the scientific interest for fabricating multi-functional polymer composites. However, a well-known problem associated to the incorporation of nanoparticulate materials in polymer matrices is their tendency to agglomerate in order to reduce their surface energy, and the extreme increase of the polymer viscosities (i.e melts, solutions, etc), which makes it very difficult to process them. Polymers can be efficiently reinforced by fibers for applications where high strength and stiffness are required. Micro-scale short fiber reinforced polymer composites have been an alternative way to obtain fiber reinforced composites since the long fiber incorporation is a painful job and not always feasible and easy to produce composites in big scale. Therefore, use of long glass fibers as the support for depositing CNTs as well as CNTs+other kind of nanoparticles was made, and the resulting interfaces were investigated in detail by single fiber model composites. This approach can bring the CNT functionality, fiber strength and toughness to the final composite, and simultaneously alleviate the manufacturing process from increase of the polymer high viscosities. Finally, very logically the question of whether to improve or destroy the interface integrity comes before implementing the hybrid hierarchical reinforcements in bigger scales, and an output out of this work will be given. Furthermore, several information and functionalities arising from the CNTs at the interphase region will be elucidated like cure monitoring of the epoxy resin matrix, UV-sensing ability, and thermoelectric energy harvesting, giving rise to multi-functional structural composites. CNT-modified natural fibers also have been utillised to fabricate short fiber reinforced composites, and have shown a promising reinforcement effect due to the CNT nanostructured interfaces. The ‘interface’ in fiber reinforced polymer composites (FRPCs) is known as a very crucial parameter that has to be considered in the design of a composite with desired properties. Interfaces are often considered as surfaces however, they are in fact zones or areas with compositional, structural, and property gradients, typically varying from that of the fiber and the matrix material. Characterization of the mechanical properties of interfaces is necessary for understanding the mechanical behavior of scaled-up composites. In fact, the mechanical characteristics of a fiber/resin composite depend mainly on i) the mechanical properties of the component materials, ii) the surface of the fiber, and iii) the nature of the fiber/resin bonding as well as the mode of stress transfer at the interface. Among the many factors that govern the characteristics of composites involving a glass, carbon, natural or ceramic fiber, and a macromolecular matrix, the adhesion between fiber and matrix plays a predominant role. In specific, the stress transfer at the interface requires an efficient coupling between fiber and matrix. Therefore, it is important to optimize the interfacial bonding since a direct linkage between fiber and matrix gives rise to a rigid, low impact resistance composite material.

Стилі APA, Harvard, Vancouver, ISO та ін.

36

Lai, Yueh-Chun, and 賴岳軍. "Realizing multi-functional plasmonic biosensor/bio-imaging and artificial electromagnetic response with low-loss and high-symmetry properties by metamaterials." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/54585353959939755630.

Повний текст джерела

Анотація:

博士
國立清華大學
材料科學工程學系
100
Metamaterials are artificial electromagnetic materials in which the size of building elements is smaller than the wavelength of illuminating light. Based on the collective resonances in internal designed structures, metamaterials enable physical and optical properties that have not been achieved in naturally existing materials. Among diverse metamaterials, it is the split-ring resonator (SRR) structure a pioneering design proposed by Pendry et al. as magnetic meta-atoms to achieve negative magnetic permeability and high-frequency magnetism. The fundamental resonant behaviors of SRRs are conventionally understood by the equivalent LC circuit model and the multiple resonant reflectance peaks under normal incidence can be elucidated by model of standing-wave plasmonic resonances. More importantly, such a resonance condition depends on the local dielectric environment so sensitively that the SRRs can be readily employed as refractive-index (RI) sensors, especially for real-time, label-free and cell-level bimolecular detections by monitoring the shifts of reflectance peaks as analytes binding to molecular receptors immobilized on the SRR surface. Thus, we present a comprehensive understanding of the relative sensitivity and the detection length about the multi-mode plasmonic resonances in the planar SRR structure. By applying thin dielectric layers with different thicknesses on the SRR array, we demonstrate a quantitative interpretation to the distinct sensing behaviors (including sensitivity and detection length) of each resonance mode in the multi-resonance reflectance spectra based on both simulation and experimental results, present a coupler-free, scalable and multi-mode refractive index sensor based on nano-structured split ring resonators. Next, we develop a compact plasmonic bioimages based on SRRs. Owning advantages such as label-free, coupler-free, tunable spectrum range (from MIR to VIS) and longer detection length, the SRR microscopy (SRRM) is a strong competitor compared to the surface plasmon resonance microscopy (SPRM) for observing bio-target. Our experimental results has successfully demonstrated its capability of constructing the refractive index distribution images of human bone marrow-derived mesenchymal stem cells (hMSCs) and meanwhile, obtaining the information of functional groups from the target cells. Therefore, we expect that the SRR microscopy (SRRM) delivers much simple optical configuration and better penetration depth for truly whole-cell imaging applications. In addition, we utilize high dielectric constant ceramic materials such as zirconia, alumina to design negative refractive index media (NRIM) in the microwave region that have attracted significant attention for their potential to revise conventional electromagnetic rules involving refractive indices such as inverse optical rules. From a periodic array of commercially available zirconia (Alumina) cubes, we demonstrate artificial magnetic and electric dipoles due to the combination of displacement currents and Mie resonance. By scaling the size and periodicity of these dielectric resonators, the corresponding magnetic and electric responses are shifted to the desired frequencies. To further overlap the magnetic and electric resonances in the same frequency, we create a negative refractive index medium from single-dielectric resonators. On the other hand, we hybridize commercially available zirconia and alumina structures to harvest their individual artificial magnetic and electric response simultaneously, presenting a negative refractive index medium. Finally, we introduce the coupling of Mie resonances in the dielectric resonator pairs, especially in the asymmetric case that supports an extraordinary electromagnetic response such as metamaterials-induced transparency (MIT) phenomena. Using two hybrid structures of identical-dielectric-constant resonators (IDRs) and distinct-dielectric-constant resonators (DDRs), we demonstrate a larger group index (ng~354), better bandwidth-delay product (BDP~0.9) than metallic-type metamaterials. The keys to enable these properties are to excite either the trapped mode or the suppressed mode resonances, which can be managed by controlling the contrast of dielectric constants between the dielectric resonators in the hybrid metamaterials. Comparing with the conventional metamaterials-based applications constructed by metallic elements, the demonstrated all-dielectric metamaterials possesses low-loss and high-symmetry advantages, thus benefiting practical applications in communication components, perfect lenses, invisible cloaking and other novel electromagnetic devices.

Стилі APA, Harvard, Vancouver, ISO та ін.

37

Tsai, Hui-Ling, and 蔡惠玲. "Study on the functional properties of micronized soybean by-product and the technology of preparing noodle with high dietary fiber." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/59170418363524677755.

Повний текст джерела

Анотація:

碩士
國立中興大學
食品暨應用生物科技學系所
99
This study uses soybean residue a by-product of soybean processing as the raw materials to produce micronized soybean residue powder through drying, grinding, sieving, etc. Their physicochemical and functional properties are determined. Soybean by-product powder were added in the place of some parts of the flour in noodle to examine the effects of various particle sizes and additives ratio on the quality of the noodles. The soybean by-products were divided into five groups of different sizes after freeze drying (FD), hot drying (HD), and sieving of the ground micronized powder. The total dietary fiber contents were around 66.99-78.60%, which showed the by-products can be a good source of dietary fiber. The experimental results were as follows: in the color analysis, there was a negative correlation between the L values and particle sizes. The a and b values had a positive correlation with particle sizes. The physicochemical properties analysis show that there was a positive correlation between bulk density, water-holding capacity, swelling capacity and particle size. There was a gradual increase in oil-holding capacity along with a decrease in particle sizes after the degreasing treatment. There was a distinctive increasement in cation-exchange capacity when the particle size decreased. The water-holding capacity, oil-holding capacity and swelling capacity were higher in the freeze-dried samples than in the hot-dried samples. In the section of functional composition analysis, the functional dietary fiber contents were mainly consisted of insoluble dietary fiber, ranging from 63.34 to 75.84 %. The soy flavonoid contents were 26.38 ~ 82.19 μg/g, which increased as particle size decreased. The micronized soybean by-product powder of big particle size (316.72 μm), medium particle size (126.85 μm), and small particle size (35.25 μm) ,treated with hot drying, were used to replace 5 %, 10 %, and 15 % of the flour respectively, and effects of them on the quality of the noodles were examined. Analysis of the pasting properties of the noodles showed that there was a gradual decrease in the peak viscosity, breakdown viscosity, final viscosity and setback viscosity when the replacement amount increased. The swelling power, water soluble index and water absorption index have a positive correlation with temperature and particle size. The quality characteristics of the noodles showed that there was a decreasing trend in the L value , b value, W.I. and B.I. values when the replacement amount increased. There was a negative correlation between the L value, a value, W.I .value and particle size. The b value and B.I. value have a positive correlation with particle sizes. Hardness (HD), adhesiveness (AS), and tensile strength (TS) of the noodles decreased when the replacement amount increased, but they increased when the particle size decreased.. The cooking properties showed that there was an increase in the cooking loss, cooked weight gain, and cooked volume gain when the replacement amount increased, but they decreased when the particle size became smaller. The experimental results showed that there was an increasing trend in the quality characteristics, cooking properties and the sensory evaluation analysis of the noodles when the particle size and the replacement amount decreased.. The addition of micronized soybean by-product powder of 35.25 μm particle size to replace 5 - 10 % of the flour had a similar result with the noodles made from pure flour. This result showed that other ingredients besides flour can be used to develop nutritious and tasty noodles.

Стилі APA, Harvard, Vancouver, ISO та ін.

38

Chang, Kai-Chi, and 張凱期. "Prediction on structural, mechanical, thermodynamic, and electronic properties of AlNbTaTiZrMo high-entropy alloy by molecular dynamics simulation and density functional theory calculation." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/qkg92y.

Повний текст джерела

Анотація:

碩士
國立中山大學
機械與機電工程學系研究所
107
This study combined density functional theory (DFT), particle swarm optimization (PSO), maximum entropy method and molecular dynamics (MD) simulation to develop and design a complete simulation program for new high entropy alloys (HEA). The second nearest neighbor modified embedding atomic method (2NN MEAM) is applied to MD method. Through this program, the most stable HEA structure composed of different elements is predicted. Detailed HEA structures and mechanical properties, including young''s modulus, bulk modulus and strength, can be predicted by using the advantages of MD simulation. Tensile simulation is applied systematically to HEA with different elements to observe the fracture mechanism of HEA and understand the relationship between mechanical properties and HEA element composition. According to the stress-strain curve, young''s modulus is about 146.28 GPa, which is very close to the experimental value of 122 GPa, and it can predict the trend of material properties of elements with different proportions. But local analysis high entropy alloys by the deformation and stress, because of the defects of potential energy parameters that can accurately predict AlMo0.5 NbTa0.5 TiZr HEA linear elastic stage performance, but not the right to predict the formation of the slip, nucleation and destruction, we speculated that the reason is that too little fitting parameters of sliding data as a reference structure, leading to HEA simulate tensile test to yield stage after poor performance, in the final analysis shows AlMo0.5 NbTa0.5 TiZr charge distribution of the six elements, affecting the situation of the electronic exchange and corrosion resistant properties.

Стилі APA, Harvard, Vancouver, ISO та ін.

39

Chao, Dongfang. "Effects of thermal and high pressure treatments on structural and functional properties of pea seed (Pisum sativum L.) proteins and enzymatic protein hydrolysates." 2012. http://hdl.handle.net/1993/8103.

Повний текст джерела

Анотація:

The effects of heat or high pressure treatment on the physicochemical and functional properties of pea proteins were evaluated by measuring polypeptide composition, hydrophobicity, solubility, gelation, emulsification, foaming, water-holding capacity and oil-holding capacity. Heat processing (≥ 70 °C) and high pressure treatment (≥ 200 MPa) led to significant increase (from 1.41 to 2.42) in hydrophobicity of native pea proteins. Native gel electrophoresis showed that the content of 11S protein decreased (increased aggregation) as intensity of pressure treatment was increased. In contrast the 7S protein was resistant to pressure-induced protein aggregation. The solubility and emulsifying capacity of pea proteins processed under higher pressure or heat at neutral pH had slight decreases probably due to the formation of aggregates. High pressure treatment of pea proteins led to reductions in the amount of protease required to produce renin-inhibitory peptides.

Стилі APA, Harvard, Vancouver, ISO та ін.

40

Roberts, Mokone Joseph. "The molecular structure of selected South African coal-chars to elucidate fundamental principles of coal gasification / Mokone Joseph Roberts." Thesis, 2015. http://hdl.handle.net/10394/16014.

Повний текст джерела

Анотація:

Advances in the knowledge of chemical structure of coal and development of high performance computational techniques led to more than hundred and thirty four proposed molecular level representations (models) of coal between 1942 and 2010. These models were virtually on the carboniferous coals from the northern hemisphere. There are only two molecular models based on the inertinite- and vitrinite-rich coals from the southern hemisphere. The current investigation is based on the chars derived from the Permian-aged coals in two major South African coalfields, Witbank #4 seam and Waterberg Upper Ecca. The two coals were upgraded to 85 and 93% inertinite- and vitrinite-rich concentrates, on visible mineral matter free basis. The coals were slow heated in inert atmosphere at 20 ℃ min-1 to 450, 700 and 1000 ℃ and held at that temperature for an hour. After the HCl-HF treatment technique at ambient temperatures, the characteristics of the coals and chars were examined with proximate, ultimate, helium density, porosity, surface area, petrographic, solid-state 13C NMR, XRD and HRTEM analytical techniques. The results largely showed that substantial transitions occurred at 700-1000 ℃, where the chars became physically different but chemically similar. Consequently, the chars at the highest temperature (1000 ℃) drew attention to the detailed study of the atomistic properties that may give rise to different reactivity behaviours with CO2 gas. The H/C atomic ratios for the inertinite- and vitrinite-rich chars were respectively 0.31 and 0.49 at 450 ℃ and 0.10 and 0.12 at 1000 ℃. The true density was respectively 1.48 and 1.38 g.cm-3 at 450 ℃ and 1.87 and 1.81 g.cm-3 at 1000 ℃. The char form results from the petrographic analysis technique indicated that the 700-1000 ℃ inertinite-rich chars have lower proportions of thick-walled isotropic coke derived from pure vitrinites (5-8%) compared with the vitrinite-rich chars (91-95%). This property leads to the creation of pores and increases of volume and surface area as the softening walls expand. It was found that the average crystallite diameter, La, and the mean length of the aromatic carbon fringes from the XRD and HRTEM techniques, respectively, were in good agreement and made a definite distinction between the 1000 ℃ inertinite- and vitrinite-rich chars. The crystallite diameter on peak (10) approximations, La(10), of 37.6Å for the 1000 ℃ inertinite-rich chars fell within the HRTEM’s range of minimummaximum length boundary of 11x11 aromatic fringes (27-45Å). The La (10) of 30.7Å for the vitrinite-rich chars fell nearly on the minimum-maximum length range of 7x7 aromatic fringes (17-28Å.) The HRTEM results showed that the 1000 ℃ inertinite-rich chars comprised a higher distribution of larger aromatic fringes (11x11 parallelogram catenations) compared with a higher distribution of smaller aromatic fringes (7x7 parallelogram catenations). The mechanism for the similarity between the 700-1000 ℃ inertinite- and vitrinite-rich chars was the greater transition occurring in the vitrinite-rich coal to match the more resistant inertinite-rich coal. This emphasised that the transitions in the properties of vitrinite-rich coals were more thermally accelerated than those of the inertinite-rich coals. The similarity between the inertinite- and vitrinite-rich chars was shown by the total maceral reflectance, proximate, ultimate, skeletal density and aromaticity results. Evidence for this was the carbon content by mass for the inertinite- and vitrinite-rich chars of respectively 90.5 and 85.3% at 450 ℃ and 95.9 and 94.1% at 1000 ℃. The aromaticity from the XRD technique was respectively 87 and 77% at 450 ℃ and 98 and 96% at 1000 ℃. A similar pattern was found in the hydrogen and oxygen contents, the atomic O/C ratios and the aromaticity from the NMR technique. The subsequent construction of large-scale molecular structures for the 1000 ℃ inertinite-rich chars comprised 106 molecules constructed from a total of 42929 atoms, while the vitrinite-rich char model was made up of 185 molecules consisting of a total of 44315 atoms. The difference between the number of molecules was due to the inertinite-rich char model comprising a higher distribution of larger molecules compared with the vitrinite-rich char model, in agreement with the XRD and HRTEM results. These char structures were used to examine the behaviour on the basis of gasification reactivity with CO2. The density functional theory (DFT) was used to evaluate the interactions between CO2 and the atomistic representations of coal char derived from the inertinite- and vitrinite rich South African coals. The construction of char models used the modal aromatic fringes (fringes of highest frequencies in size distributions) from the HRTEM, for the inertinite- and vitrinite-rich chars, respectively (11x11 and 7x7 parallelogram-shaped aromatic carbon rings). The structures were DFT geometrically optimized and used to measure reactivity with the Fukui function, f+(r) and to depict a representative reactive carbon edge for the simulations of coal gasification reaction mechanism with CO2 gas. The f+(r) reactivity indices of the reactive edge follows the sequence: zigzag C remote from the tip C (Czi = 0.266) > first armchair C (Cr1 = 0.087) > tip C (Ct = 0.075) > second armchair C (Cr2 = 0.029) > zigzag C proximate to the tip C (Cz = 0.027). The DFT simulated mean activation energy, ΔEb, for the gasification reaction mechanism (formation of second CO gas molecule) was 233 kJ mol-1. The reaction for the formation of second CO molecule is defines gasification in essence. The experimental activation energy determined with the TGA and random pore model to account essentially for the pore variation in addition to the gasification chemical reaction were found to be very similar: 191 ± 25 kJ mol-1 and 210 ± 8 kJ mol-1; and in good agreement with the atomistic results. The investigation gave promise towards the utility of molecular representations of coal char within the context of fundamental coal gasification reaction mechanism with CO2.
PhD (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

Стилі APA, Harvard, Vancouver, ISO та ін.

41

Matara, Kankanamge Indika. "Optoelectronic and Structural Properties of Group III-Nitride Semiconductors Grown by High Pressure MOCVD and Migration Enhanced Plasma Assisted MOCVD." 2016. http://scholarworks.gsu.edu/phy_astr_diss/89.

Повний текст джерела

Анотація:

The objective of this dissertation is to understand the structural and optoelectronic properties of group III-nitride materials grown by High-Pressure Metal Organic Chemical Vapor Deposition (HP-MOCVD) and Migration Enhanced Plasma Assisted MOCVD by FTIR reflectance spectroscopy, Raman spectroscopy, X-ray diffraction, and Atomic Force Microscopy. The influence of the substrates/templates (Sapphire, AlN, Ga-polar GaN, N-polar GaN, n-GaN, and p-GaN) on the free carrier concentration, carrier mobility, short-range crystalline ordering, and surface morphology of the InN layers grown on HP-MOCVD were investigated using those techniques. The lowest carrier concentration of 7.1×1018 cm-3 with mobility of 660 cm2V-1s-1 was found in the InN film on AlN template, by FTIR reflectance spectra analysis. Furthermore, in addition to the bulk layer, an intermediate InN layers with different optoelectronic properties were identified in these samples. The best local crystalline order was observed in the InN/AlN/Sapphire by the Raman E2 high analysis. The smoothest InN surface was observed on the InN film on p-GaN template. The influence of reactor pressures (2.5–18.5 bar) on the long-range crystalline order, in plane structural quality, local crystalline order, free carrier concentration, and carrier mobility of the InN epilayers deposited on GaN/sapphire by HP-MOCVD has also been studied using those methods. Within the studied process parameter space, the best material properties were achieved at a reactor pressure of 12.5 bar and a group-V/III ratio of 2500 with a free carrier concentration of 1.5x1018 cm-3, a mobility in the bulk InN layer of 270 cm2 V-1s-1 and the Raman (E2 high) FWHM of 10.3 cm-1. The crystalline properties, probed by XRD 2θ–ω scans have shown an improvement with the increasing reactor pressure. The effect of an AlN buffer layer on the free carrier concentration, carrier mobility, local crystalline order, and surface morphology of InN layers grown by Migration-Enhanced Plasma Assisted MOCVD were also investigated. Here, the AlN nucleation layer was varied to assess the physical properties of the InN layers. This study was focused on optimization of the AlN nucleation layer (e.g. temporal precursor exposure, nitrogen plasma exposure, and plasma power) and its effect on the InN layer properties.

Стилі APA, Harvard, Vancouver, ISO та ін.

42

Amorim, Carlos de Oliveira. "Experimental and modeling studies of magnetoelectric multiferroic heterostructured materials." Doctoral thesis, 2019. http://hdl.handle.net/10773/27751.

Повний текст джерела

Анотація:

Multiferroic materials are a very exotic type of materials which present simultaneously two or more ferroic properties. Magnetoelectric multiferroics, in particular, are a very prominent class of materials, mainly due to their outstanding foreseen applications such as magnetic sensors, energy harvester/conversion devices, and high efficiency memories. However, intrinsic magnetoelectric materials are quite rare and do not have, yet, the adequate properties to the everyday applications. One of the reasons for this to occur is due to the requirements for magnetism and ferroelectricity in matter being a priori contradictory, since the former needs unfilled dn orbitals, while the latter favours d0 orbitals. Nevertheless, extrinsic magnetoelectric multiferroics do not suffer from this problem because they do not share the same phase, hence being a very promising approach to engineer adequate magnetoelectric multiferroics. This thesis focus on the study of Fe and BaTiO3 systems as a means of achieving novel magnetoelectric effects. It is shown that a peculiar type of BaTiO3:Fe auto-composite presents an ordered magnetic behaviour, despite the concentration of Fe being as low as 113 atomic ppm. The Fe magnetization displays two abrupt changes in its spontaneous value, one with M/M ≈ 32% and the other with M/M ≈ 14%. These magnetic transitions are correlated the BaTiO3 orthorhombic↔tetragonal and tetragonal↔cubic ferroelectric phase transitions. This magnetoelectric auto-composite was the motivation to resort to Density Functional Theory (DFT) modeling as a means to discover the microscopic mechanism(s) behind such a strong magnetoelectric effect. The study of an iron monolayer placed upon several possible BaTiO3 unit cells lead to the discovery of several interfaces with abrupt changes in their spontaneous magnetization, either through the enhancement and reduction of the Fe magnetic moments, or through the change between antiferromagnetic and ferromagnetic order of the Fe monolayer. However, the highlight of these DFT studies lies in the discovery of a particular kind of interfaces, namely in the BTO221_2ndFe and BTO99_2ndFe supercells, where there is a High-Spin–Low-Spin state transition which can quench completely the atomic magnetic moment of each of Fe atom, depending on the local crystal field felt by the Fe atoms. Based on this specific effect, where it is possible to turn on and off the magnetic moments of the Fe atoms, a magnetoelectric multiferroic device was proposed. Knowing the importance of the crystal field for the High-Spin–Low-Spin state transition, a thorough study regarding the Electric Field Gradient (EFG) of each possible BaTiO3 site was performed, resorting to a combined study of DFT and Perturbed Angular Correlations (PAC) spectroscopy. In this study, it was concluded that the PAC spectroscopy is not the most adequate hyperfine technique to be used in a quantitative study of the BaTiO3/Fe interfaces EFG tensor, due to the non-negligible effects of the radioactive probe on the BaTiO3 matrix. Finally, the deposition of BTO/Fe heterostructures on LaAlO3, MgO, Al2O3 and SrTiO3 substrates using RF-Sputtering, and the Molecular Beam Epitaxy (MBE) deposition of Fe layers on BaTiO3 cut at the (100), (110) and (111) planes were performed as an attempt to recreate the interfaces with the most appealing magnetoelectric effects predicted in the DFT modeling. The thin films deposited using sputtering showed the growth of many Fe, Ba-Ti-O and Fe-Ti-O oxides depending strongly on their substrate, as well as in the deposition and annealing conditions. Still no magnetoelectric coupling was observed in such thin films. On the other hand the Fe thin films deposited on BaTiO3 substrates showed large magnetoelectric couplings between the BaTiO3 ferroelectric phase transitions and the magnetization of the Fe layers (similarly to what happened in the BaTiO3:Fe auto-composite). The magnitude of this magnetoelectric couplings is strongly correlated with the BTO interface where the Fe was deposited, showing a huge change in spontaneous magnetization and coercivity for the rhombohedral↔orthorhombic ferroelectric phase transition up to M/M ≈ 148% and HC/HC ≈ 183% respectively for the (110) case.
Materiais Multiferróicos são um tipo de materiais bastante exótico que apresentam simultaneamente dois ou mais tipos de propriedades ferróicas. Multiferróicos magnetoelétricos, em particular, são uma classe de materiais muito proeminente, principalmente devido às suas espantosas aplicações tecnológicas, tais como sensores magnéticos, dispositivos de conversão/colheita de energia, e memórias the alta eficiência. Todavia, materiais magnetoelétricos intrínsecos são verdadeiramente raros e ainda não possuem propriedades adequadas ao uso do dia-a-dia. Uma das razões para que isto aconteça prende-se com o facto dos requisitos para existência de magnetismo e ferroeletricidade na matéria serem a priori contraditórios, uma vez que enquanto os primeiros necessitam de orbitais dn semipreenchidas, os últimos tendem a favorecer orbitais d0. Porém, Multiferróicos magnetoelétricos extrínsecos não sofrem desta limitação pois não partilham a mesma fase sendo portanto uma abordagem promissora para a construção de um bom Multiferróico magnetoelétrico. Esta tese focar-se-á no estudo de sistemas contendo Fe e BaTiO3 como meio de se alcançarem novos efeitos magnetoelétricos. Um auto-compósito de BaTiO3:Fe é apresentado, que apesar da sua diminuta concentração de Fe (apenas 113 ppm atómicas), ainda assim apresenta um comportamento magnético ordenado. A magnetização do Fe apresenta duas variações bruscas no seu valor espontâneo, uma com M/M ≈ 32% e outra com M/M ≈ 14%. Estas transições magnéticas estão correlacionadas com as transições de fase ferroelétricas do BaTiO3 (ortorrômbica↔tetragonal e tetragonal↔cúbica). Este auto-compósito magnetoelétrico foi a motivação par ao uso da Teoria de Densidade Funcional (DFT) como meio para descobrir os mecanismos microscópicos por trás deste acoplamento magnetoelétrico tão intenso. O estudo de uma mono-camada de Fe colocada sobre várias células unitárias de BaTiO3 levaram à descoberta de várias interfaces com mudanças abruptas na sua magnetização espontânea, ora através do aumento ou diminuição dos momentos magnéticos do Fe, ora através da mudança entre a natureza antiferromagnética ou ferromagnética da camada de Fe. Contudo, o destaque dos estudos de DFT reside na descoberta de um tipo particular de interfaces onde ocorre uma transição de estado High-Spin–Low-Spin que consegue colapsar completamente o momento magnético atómico dos átomos de Fe, dependendo do campo cristalino local sentido por esses mesmos átomos. Baseado neste efeito, um dispositivo Multiferróico magnetoelétrico foi proposto. Sabendo a importância do campo cristalino para as transições de estado High-Spin–Low-Spin state, um estudo minucioso foi feito relativo ao gradiente de campo elétrico (EFG) nos sítios possíveis do BaTiO3, usando um estudo combinado entre Correlações Angulares Perturbadas (PAC) e DFT. Neste estudo, concluiu-se que PAC não é uma técnica hiperfina adequada para o estudo quantitativo do tensor EFG de interfaces de BaTiO3/Fe, dados os efeitos não desprezáveis das sondas radioativas na matriz de BaTiO3. Finalmente, foi feita a deposição de Heteroestruturas de BTO/Fe em substratos de LaAlO3, MgO, Al2O3 e SrTiO3 usando RF-Sputtering, assim como deposição de camadas de Fe em substratos de BaTiO3 cortados nos planos (100), (110) e (111) planes, usando Molecular Beam Epitaxy (MBE), numa tentativa de recrear as interfaces com efeitos magnetoelétricos mais apelativos, previstos pela modelação DFT. Os filmes finos depositados por sputtering mostraram o crescimento de múltiplos óxidos de Fe, Ba-Ti-O e Fe-Ti-O dependendo fortemente do substrato onde foram crescidos, assim como das condições de deposição e tratamentos térmicos. Porém, nenhum efeito magnetoelétrico foi observado nestes filmes. Por outro lado, os filmes depositados nos substratos de BaTiO3 mostraram grandes acoplamentos magnetoelétricos entre as fases ferroelétricas do BTO e a magnetização das camadas de Fe (à semelhança do que aconteceu no auto-compósito de BaTiO3:Fe). A ordem de grandeza destes acoplamentos está fortemente correlacionada com a interface do BTO onde o Fe foi depositado, apresentando uma enorme variação na magnetização espontânea e na coercividade para o caso da transição romboédrica↔ortorrômbica, até M/M ≈ 148% e HC/HC ≈ 183% respetivamente para o caso da orientação (110).
Tese realizada com apoio financeiro da FCT através da bolsa SFRH/BD/93336/2013.
Programa Doutoral em Física

Стилі APA, Harvard, Vancouver, ISO та ін.

43

Vamadevan, Varatharajan. "Organization of Glucan Chains in Starch Granules as Revealed by Hydrothermal Treatment." Thesis, 2013. http://hdl.handle.net/10214/7240.

Повний текст джерела

Анотація:

Regular starches contain two principal types of glucan polymers: amylopectin and amylose. The structure of amylopectin is characterized according to the unit chain length profile and the nature of the branching pattern, which determine the alignment of glucan chains during biosynthesis. The organization of glucan chains in amylopectin and their impact on the structure of starch are still open to debate. The location of amylose and its exact contribution to the assembly of crystalline lamellae in regular and high-amylose starch granules also remain unknown. The primary focus of this thesis is the organization and flexibility of glucan chains in crystalline lamellae. The organization and flexibility of glucan chains in native, annealed (ANN), and heat-moisture treated (HMT) normal, waxy, hylon V, hylon VII, and hylon VIII corn starches were examined. This study has shown for the first time that increased amounts of apparent amylose in B-type starches hinder the polymorphic transition (from B to A+B) during HMT. The research has also demonstrated that an iodine-glucan complex transformed the B-type polymorphic pattern of hylon starches into a V-type pattern. The differential scanning calorimetry (DSC) results showed that ANN- and HMT-induced changes were most pronounced in hylon starches. These findings suggest that the glucan tie chains influences the assembly of crystalline lamellae in high-amylose starches. The relationship between the internal unit chain composition of amylopectin, and the thermal properties and annealing of starches from four different structural types of amylopectin was investigated by DSC. The onset gelatinization temperature (To) correlated negatively with the number of building blocks in clusters (NBbl) and positively with the inter-block chain length (IB-CL). The enthalpy of gelatinization (∆H) correlated positively with the external chain length of amylopectin. Annealing results showed that starches with a short IB-CL were most susceptible to ANN, as evidenced by a greater increase in the To and Tm. The increase in enthalpy was greater in starches with long external chains and IB-CLs. These data suggest that the internal organization of glucan chains in amylopectin determines the alignment of chains within the crystalline lamellae and thereby the thermal properties and annealing of the starch granules.

Стилі APA, Harvard, Vancouver, ISO та ін.

Дисертації з теми "High functional properties"

Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями