Dissertationen zum Thema „Natural and technogenic materials“
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Hostyn, Guillaume. „Contribution des fractions granulométriques grossières au fonctionnement des sols très anthropisés“. Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0088.
Der volle Inhalt der QuelleThe approaches of requalification of degraded sites increasingly answer the double challenge of depollution and valorization. The soils of these sites, known as "highly anthropized soils", are often characterized by a disturbed functioning due to anthropogenetic impacts. In particular, anthropic actives are responsible for the presence in these soils of exogenous materials, from both technogenic or natural origins, in varying quantities and natures. In this context, all the diagnoses and considerations regarding their management are carried out on the fine fraction, obtained after sieving at 2 mm, and ignore the so-called "coarse" fraction, which is often overrepresented (up to 50-60% by mass). This fraction, considered as inert, may not necessarily be so and its presence may have important consequences on the functioning of ecosystems and their future management.A dedicated methodological approach was developed. First, the dimensions and nature of the objects to be studied were precisely defined using an appropriate granulometric scale and the construction of a typology. This approach coupled to physico-chemical characterizations confirmed the efficiency of the tested screening strategy and fully enabled a precise and meaningful discrimination among coarse materials. The typology was thus implemented with composition characteristics of the material categories. On this basis, five reference materials (anthracite, brick, limestone, petroleum coke and blast furnace slag) were selected in order to allow for the generalization of the results. An adaptation process of standard soil analysis methods was then developed in order to assess the reactivity of coarse granulometric fractions. Results showed that coarse fractions are not inert. Their reactivity, although reduced compared to the fine fraction from a mass point of view, is only dependent on the type of material and the surface of the particles. Taken alone, the selected model materials present an insufficient level of fertility for plant development and are only marginally at the origin of toxicity. In an overall soil system, the coarse fraction constitutes a perennial stock of elements of interest that can be mobilized over time through the weathering processes generated by pedogenesis. The direct contribution of coarse fractions to plant nutrition was confirmed both under controlled conditions in the laboratory and in lysimeters at the pilot field scale. They also significantly contribute to water retention and storage. The type of material is the main factor governing the intensity of these effects.This thesis work has thus positioned the coarse granulometric fractions as being an active part of the functioning of highly anthropized soils. The results obtained provide new knowledge for stakeholders involved in soil engineering and highly anthropized soils management. To this end, a systematic procedure of diagnosis of coarse granulometric fractions has been proposed, the effects of which should serve two purposes, i) to enrich the knowledge related to the constituents of coarse fractions and ii) to allow an insightful decision-making process, based on a complete knowledge of the reality of a highly anthropized soil, authorizing an optimal and sensible management according to the targeted type of renaturation
Huang, Weichun. „Acoustic properties of natural materials“. Thesis, Le Mans, 2018. http://www.theses.fr/2018LEMA1031/document.
Der volle Inhalt der QuelleStraw-inspired metamaterials for sound absorption are investigated in this Thesis. A straw stack is idealized as a highly concentratedresonant anisotropic porous medium constituted of a periodic arrangement of densely packed cylindrical hollow tubes. The approach tothis metamaterial relies on the two-scale asymptotic homogenization of a permeable array of perfectly rigid resonators, where the physicsis further enriched by tailoring inner resonances. The main features of such sound absorbing medium are the possibility for the effectivecompressibility to become negative around the tube resonance and the drastic reduction of the effective sound speed (slow sound) at verylow frequency in the system. Moreover, an optimal configuration for sound absorption is designed, based on the critical couplingcondition, in which the energy leakage out of the open resonant system is perfectly compensated by the intrinsic losses induced by thevisco-thermal losses both in the anisotropic matrix and in the resonators. Impedance tube measurements are performed on 3-D printedsamples with controlled parameters to validate the theoretical results. This metamaterial is a sub-wavelength absorber that can achievetotal absorption at a very low frequency and possesses a quasi-band-gap around the tube resonance. Furthermore, the anisotropic nature ofthe configuration gives rise to high absorption at low-frequency range for all incidences and diffuse field excitation. It paves the way tothe design of angular and frequency selective sound absorber. To conclude, the results of this Thesis show that straw is a good candidatefor perfect sound absorption
Kozii, Ivan, und Іван Козій. „Using a highly efficient gas cleaning equipment for reduction technogenic impact on the environment“. Thesis, National Aviation University, 2021. https://er.nau.edu.ua/handle/NAU/50966.
Der volle Inhalt der QuelleGrowth in the scale of economic activity leads to increased human impacts and disturbance of equilibrium in the environment. Along with the depletion of natural resources increases environmental pollution, in particular water and air. This significantly undermines the natural resource potential of the state’s development, negatively affects the welfare and health of the population, and poses a threat to environmental safety. Consuming natural resources, industrial enterprises are sources of complex environmental contamination. Activities of industrial enterprises has a negative impact on the state of ecosystems surrounding areas. Deposition of contaminants from the waste gases results in contamination of the soil and migration of heavy metals in the groundwater and surface water. The problem is compounded by the fact that the exhaust gases contain different by dispersion of the solid particles. This poses the problem of the development of environmental protection measures for air protection from emissions of industrial enterprises. One way to reduce the amount of pollutants released into the air with the flue gases is the selection of highly efficient gas-cleaning equipment, which must take into account several factors: physical and chemical characteristics of the carrier gas, the characteristics of chemical and particulate contaminants.
Зростання масштабів економічної діяльності призводить до посилення людського впливу та порушення рівноваги в навколишньому середовищі. Разом з виснаженням природних ресурсів збільшується забруднення навколишнього середовища, зокрема води та повітря. Це суттєво підриває природно-ресурсний потенціал розвитку держави, негативно впливає на добробут та здоров’я населення та створює загрозу екологічній безпеці. Споживаючи природні ресурси, промислові підприємства є джерелами складного забруднення навколишнього середовища. Діяльність промислових підприємств негативно впливає на стан екосистем навколишніх територій. Відкладення забруднень із відпрацьованих газів призводить до забруднення ґрунту та міграції важких металів у підземні та поверхневі води. Проблема ускладнюється тим, що вихлопні гази містять різні за рахунок дисперсії твердих частинок. Це ставить проблему розробки природоохоронних заходів щодо захисту повітря від викидів промислових підприємств. Одним із способів зменшити кількість забруднюючих речовин, що викидаються в повітря з димовими газами, є підбір високоефективного газоочисного обладнання, яке повинно враховувати декілька факторів: фізичні та хімічні характеристики газу-носія, характеристики хімічних та твердих частинок забруднювачі.
Wegst, Ulrike G. K. „The mechanical performance of natural materials“. Thesis, University of Cambridge, 1996. https://www.repository.cam.ac.uk/handle/1810/272820.
Der volle Inhalt der QuelleKim, Edward Soo. „Data-mining natural language materials syntheses“. Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122075.
Der volle Inhalt der QuelleThesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
Discovering, designing, and developing a novel material is an arduous task, involving countless hours of human effort and ingenuity. While some aspects of this process have been vastly accelerated by the advent of first-principles-based computational techniques and high throughput experimental methods, a vast ocean of untapped historical knowledge lies dormant in the scientific literature. Namely, the precise methods by which many inorganic compounds are synthesized are recorded only as text within journal articles. This thesis aims to realize the potential of this data for informing the syntheses of inorganic materials through the use of data-mining algorithms. Critically, the methods used and produced in this thesis are fully automated, thus maximizing the impact for accelerated synthesis planning by human researchers.
There are three primary objectives of this thesis: 1) aggregate and codify synthesis knowledge contained within scientific literature, 2) identify synthesis "driving factors" for different synthesis outcomes (e.g., phase selection) and 3) autonomously learn synthesis hypotheses from the literature and extend these hypotheses to predicted syntheses for novel materials. Towards the first goal of this thesis, a pipeline of algorithms is developed in order to extract and codify materials synthesis information from journal articles into a structured, machine readable format, analogous to existing databases for materials structures and properties. To efficiently guide the extraction of materials data, this pipeline leverages domain knowledge regarding the allowable relations between different types of information (e.g., concentrations often correspond to solutions).
Both unsupervised and supervised machine learning algorithms are also used to rapidly extract synthesis information from the literature. To examine the autonomous learning of driving factors for morphology selection during hydrothermal syntheses, TiO₂ nanotube formation is found to be correlated with NaOH concentrations and reaction temperatures, using models that are given no internal chemistry knowledge. Additionally, the capacity for transfer learning is shown by predicting phase symmetry in materials systems unseen by models during training, outperforming heuristic physically-motivated baseline stratgies, and again with chemistry-agnostic models. These results suggest that synthesis parameters possess some intrinsic capability for predicting synthesis outcomes. The nature of this linkage between synthesis parameters and synthesis outcomes is then further explored by performing virtual synthesis parameter screening using generative models.
Deep neural networks (variational autoencoders) are trained to learn low-dimensional representations of synthesis routes on augmented datasets, created by aggregated synthesis information across materials with high structural similarity. This technique is validated by predicting ion-mediated polymorph selection effects in MnO₂, using only data from the literature (i.e., without knowledge of competing free energies). This method of synthesis parameter screening is then applied to suggest a new hypothesis for solvent-driven formation of the rare TiO₂ phase, brookite. To extend the capability of synthesis planning with literature-based generative models, a sequence-based conditional variational autoencoder (CVAE) neural network is developed. The CVAE allows a materials scientist to query the model for synthesis suggestions of arbitrary materials, including those that the model has not observed before.
In a demonstrative experiment, the CVAE suggests the correct precursors for literature-reported syntheses of two perovskite materials using training data published more than a decade prior to the target syntheses. Thus, the CVAE is used as an additional materials synthesis screening utility that is complementary to techniques driven by density functional theory calculations. Finally, this thesis provides a broad commentary on the status quo for the reporting of written materials synthesis methods, and suggests a new format which improves both human and machine readability. The thesis concludes with comments on promising future directions which may build upon the work described in this document.
by Edward Soo Kim.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering
Lowe, David James. „Natural rubber/organoclay nanocomposites“. Thesis, Queen Mary, University of London, 2012. http://qmro.qmul.ac.uk/xmlui/handle/123456789/2971.
Der volle Inhalt der QuelleHolcroft, Neal. „Natural fibre insulation materials for retrofit applications“. Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707590.
Der volle Inhalt der QuelleBrakus, Josko. „Mechanical properties of natural materials : an overview“. Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11553.
Der volle Inhalt der QuelleFlores, Ramírez Eleonora [Verfasser], Martin [Akademischer Betreuer] Kaupenjohann, Martin [Gutachter] Kaupenjohann, Grabach Christina [Gutachter] Siebe und Jean Louis [Gutachter] Morel. „Purpose-designed technogenic materials for sustainable urban greening / Eleonora Flores Ramírez ; Gutachter: Martin Kaupenjohann, Christina Siebe Grabach, Jean Louis Morel ; Betreuer: Martin Kaupenjohann“. Berlin : Technische Universität Berlin, 2018. http://d-nb.info/1169210341/34.
Der volle Inhalt der QuelleTurvill, Michael W. „The synthesis of natural and synthetic colouring materials“. Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280103.
Der volle Inhalt der QuelleFILHO, ROMILDO DIAS TOLEDO. „COMPOSITE MATERIALS REINFORCED WITH NATURAL FIBRES: EXPERIMENTAL CHARACTERIZATION“. PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1997. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=2144@1.
Der volle Inhalt der QuelleBRITISH COUNCIL
UNIVERSIDADE FEDERAL DA PARAÍBA
A presente tese estuda as propriedades de curta e londa duração de argamassas de cimento reforçadas com fibras de coco e sisal. O trabalho experimental visou a determinação das propriedades físicas e mecânicas do reforço e o estudo da influência do tipo, fração volumétrica e tamanho de fibra, orientação e composição da matriz nas propriedades mecânicas do compósito. Estudos foram executados com o objetivo de se determinar a influência do reforço na retração plástica, com e sem restrições, das matrizes de argamassa. Fissurações resultantes da imposição das restrições e o fenômeno de cicatrização das fissuras foram também investigados. O modo de ruptura e as propriedades de aderência interfacial fibra-matriz foram determinados através de ensaios de arrancamento. As propriedades de longa duração dos compósitos foram determinadas através dos ensaios de fluência, retração e durabilidade. A influência da adição de várias frações volumétricas e tamanhos de fibras na fluência das matrizes de argamassa foi determinada usando-se corpos de prova, selados e não selados, submetidos a uma pressão de 14,4 MPa durante um período de 210-350 dias. Recuperações das deformações elásticas foram monitoradas por um período de 56-180 dias. A influência dos tipos de fibra, fração volumétrica, tamanho de fibra, tipo de cura, traço da argamassa e substituição parcial do cimento Portland por micro-sílica e escória de alto forno na estabilidade dimensional das matrizes de argamassa foi determinada com o uso de ensaios de retração por um período de 320 dias. A durabilidade das fibras de coco e sisal, imersas em soluções alcalinas de hidróxido de cálcio e de sódio e em água de torneira, foi determinada através da realização de ensaios de resistência à tração em idades variando de 30-420 dias. A durabilidade das argamassas reforçadas com fibras naturais após 320-360 dias imersas em água, expostas a ciclos de molhagem e secagem bem como ao ambiente natural foi determinada através de resultados de ensaios de flexão e de observações de imagens obtidas com o uso de microscopia eletrônica. Um mapeamento de elementos químicos foi realizado com o objetivo de se verificar possíveis migrações de produtos da matriz de cimento Portland para o lúmen e paredes das fibras. Tratamentos para garantir a durabilidade dos compósitos foram estudados, a saber: (a) modificações na matriz através da substituição parcial do cimento Portland por micro-sílica e escória de alto orno; (b) carbonatação da matriz de cimento Portland; (c) imersão das fibras em micro-sílica líquida antes de serem incorporadas à matriz de cimento Portand.
This thesis studies both the short-term and long- term behaviour of sisal and coconut fibre reinforced mortar composites.The experimental work involved extensive laboratory testing to determine the physical and mechanical properties of the fibre reinforcement and to study the influence of fibre type, volume fraction, fibre length, fibre arrangement and matrix composition on the mechanical properties of the composite.Studies were also made to determine the influence of fibre reinforcement in controlling free and restrained shrinkage during the early age of mortar mixes. Cracking due to restraint and the phenomenon of crack self-healing were also investigated. The mode of failure and the properties of the resistance to fibre-matrix interfacial bonding were determined using the single fibre pull-out test.The long-term properties of the sisal and coconut fibre reinforced-mortar composites were assessed throughout creep, shrinkage and durability tests. The influence of the addition of sisal and coconut fibres, of various volume fraction and lengths, on the creep of a mortar matrix was determined using sealed and unsealed specimens subjected to a pressure of 14.4 MPa over a period of 210-350 days. Recovery strains were recorded for a period of 56-180 days.The influence of fibre types, volume fraction, fibre lengths, cure types, mix proportions and replacement of OPC by slag and silica fume on the dimensional stability of mortar matrices was determined using drying shrinkage tests for a period of 320 days. The durability of sisal and coconut fibres exposed to alkaline solutions of calcium and sodium hydroxide and stored in tap water was measured as strength loss over a period of 420 days. The durability of fibre-reinforced mortars after 320 to 360 days, stored under water, exposed to cycles of wetting and drying as well as to the natural weather,was assessed from results of flexural tests and from observations of the photomicrographs obtained using backscattered imaging and secondary electron imaging. Dotting maps of chemical elements were obtained in order to verify possible migration of cement products from the matrix to the lumen and voids within of the fibres. Treatments to enhance the durability performance of the composites were studied,including: (a) modifications to the matrix through the replacement of Portland cement by undensified silica fume and by blast-furnace slag; (b) carbonation of the cementitious matrix and (c) immersion of the fibres in slurry silica fume prior to being incorporated into the Portland cement matrix.
Song, Juha. „Multiscale materials design of natural exoskeletons : fish armor“. Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/69670.
Der volle Inhalt der QuelleThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 261-282).
Biological materials have developed hierarchical and heterogeneous material nanostructures and microstructures to provide protection against various environmental threats that, in turn, provide bioinspired clues to man-made, protective material designs. In particular, designs of dermal fish armor are a tradeoff between protection and mobility. A comprehensive knowledge base of the materials and mechanical design principles of fish armor has broad applicability to the development of synthetic engineered protective/flexible materials. In this thesis, two fish armor model systems have been investigated by means of structure-property-function relationships, ultimately answering how the armor systems have been designed in response to their environmental threats. The first model system, Polypterus senegalus are descendants of ancient fish and their body is covered by a natural armor consisting of small bony scales. The quadlayered armor scales are composed of ganoine, dentin, isopedine and bone, to protect against predatory biting attacks. First of all, multilayer design principles of P. senegalus scales were understood with respect to penetration resistance by the multiscale experimental and computational study. The quad-layered scales exhibit mechanical gradient within and between material layers and have geometrically corrugated junctions with an undetectable gradation; all of which lead to effective penetration resistance including load-dependent effective material properties, circumferential surface cracking, plastic dissipation in the underlying dentin layer, stress redistribution around the interfaces with suppression of interfacial failure. Secondly, since the outmost ganoine is structurally anisotropic, the roles of anisotropy of ganoine in the entire system have been investigated by combining orientation-dependant indentation and mechanical modeling. The elastic-plastic anisotropy of the ganoine layer enhances the load-dependent penetration resistance of the multilayered armor compared with the isotropic ganoine layer mainly by (i) enhancing the transmission of stress and dissipation to the underlying dentin layer, (ii) lowering the ganoine/dentin interfacial stresses and hence reducing any propensity toward delamination, and (iii) providing discrete structural pathways for cracks to propagate normal to the surface for easy arrest by the underlying dentin layer. Inspired by P. senegalus scales, threat-protection interaction and structurefunction relationships among various layered armor systems have been investigated using parametric studies with finite element (FE) models. Geometry, microstructure and mechanical properties of a threat system significantly influence its ability to effectively penetrate into the armor system or to be defeated by the armor. Simultaneously, three structure parameters of multilayered armor designs are mainly considered: (i) the thickness of the outmost layer; (ii) the quad-layered vs. bilayer structure; and (iii) the sequence of the outer two layers. The role of the armor microstructure in defeating threats as well as providing avenues of energy dissipation to withstand biting attacks is identified. Microstructural length scale and material property matching between the threat and armor is clearly observed. Bilayered and quadlayred models are mechanically comparable, but the quad-layer model achieves a weight reduction. Studies of predatorprey threat-protection interactions may lead to insights into tunability in mechanical functionality of each system in conjunction with adaptive phenotypic plasticity of the tooth and scale microstructure and geometry, "adaptive stalemates," and the so-called evolutionary "arms race." The second model system, Gasterosteus aculeatus, is well-known for light-weight and morphologically varied armor structure among different G. aculeatus populations. Marine and freshwater G. aculeatus armor structures have been assessed quantitatively by micro-computed tomography ([mu]CT) technique. The convolution of plate geometry in conjunction with plate-to-plate overlap allows a relatively constant armor thickness to be maintained throughout the assembly, promoting spatially homogeneous protection and thereby avoiding weakness at the armor unit interconnections. Plate-to-plate junctures act to register and join the plates while permitting compliance in sliding and rotation in selected directions. SEM and [mu]CT revealed a porous, sandwich-like cross-section of lateral plates beneficial for bending stiffness and strength at minimum weight. Moreover, the structural parameters of the pelvic assemblies were also quantified via pCT, which include the spatial dependence of the suture amplitude and frequency, the suture plate inclination angle, and the suture gap. Significant differences in these structural parameters were observed between the different G. aculeatus populations. Composite analytical and finite element computational models were developed and used in conjunction with the pCT data to simulate the mechanical behavior of the pelvic assembly, to predict the effective suture stiffness and to understand the conformational change of the pelvic assembly from the "rest" to "offensive" states. This study elucidates the structural and functional differences between different divergent populations of G. aculeatus and serves as a model for other systems of interest in evolutionary biology.
by Juha Song.
Ph.D.
Ghidan, Osama Yousef Ali. „The isotopic composition of Zn in natural materials“. Thesis, Curtin University, 2008. http://hdl.handle.net/20.500.11937/1215.
Der volle Inhalt der QuelleGhidan, Osama Yousef Ali. „The isotopic composition of Zn in natural materials“. Curtin University of Technology, School of Science and Computing, Department of Imaging and Applied Physics, 2008. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=116055.
Der volle Inhalt der QuelleThe isotopic composition of the Zn minerals and igneous rocks agreed with that of the absolute reference material, which makes it possible to consider this reference material as being representative of “bulk Earth” Zn. Significant and consistent fractionation of ~+0.3 ‰ per amu were found in 5 sediments from a range of localities. The consistency of this is attributed to conveyor type oceanic circulations effects. The results from the two metamorphic samples indicate that the fractionation of Zn in these rocks is the same as found in igneous rocks but are different from the Zn found in sedimentary rocks. This supports the widely held assumption that high temperature and pressure processes do not fractionate the isotopic composition of chalcophile elements, such as has been found for Cd. Clay sample TILL-3 appears to exhibit a consistently slightly positive Zn fractionation of +0.12 ± 0.10 ‰ amu-1, although inside the uncertainties of both igneous and sedimentary rocks, which is not surprising since Till is thought to be a formed from a range of mixed glacial sediments The isotopic composition of Zn was measured in two plants and one animal sample. The fractionation of (-0.088 ± 0.070 ‰ amu-1) of Zn in the Rice (a C3 type plant material) sample suggested that Zn may be used to study Zn systematics in plants. The result obtained for MURST-Iss-A2 (Antarctic Krill) was +0.21 ± 0.11 ‰ amu-1 relative to the laboratory standard which is similar to the average Zn fractionation results of +0.281 ± 0.083 ‰ amu-1 obtained for marine sediments.
In this work, the isotopic composition of Zn was measured in five stone and two iron meteorites. The range of Zn fractionation in stone meteorites was between -0.287 ± 0.098 and + 0.38 ± 0.16 ‰ amu-1, and was consistent with previous work, although more measurements would be needed to generalize this to all stone meteorites. In iron meteorites; Canyon Diablo was found to have the greatest fractionation of +1.11 ± 0.11 ‰ amu-1 relative to the laboratory standard. Of all the meteorites studied, Redfields clearly showed an anomalous isotopic composition indicating that this meteorite possesses a significantly different Zn isotopic composition compared to all of the other natural materials measured. Using 64Zn as a reference isotope, significant differences relative to the laboratory standard were found of +5.6 ± 0.4‰, +4.4 ± 3.6 ‰, and +21.0± 0.9 ‰ and +27.4 ± 18.8 ‰ on 66Zn and 67Zn, 68Zn and 70Zn respectively. These significant “Redfields anomalies” can be interpreted in a number of ways in relation to their nucleosynthetic production. Whether Redfields is a primitive type of iron meteorite or not, the Redfields anomaly strongly suggests wide spread isotopic heterogeneity of at least one part of the Solar System and does not support the suggestion that “Zn was derived from an initially single homogeneous reservoir in the early Solar System”. A pilot study to determine the concentration and the isotopic composition of Zn in River and tap water was performed.
The concentration of Zn in River water averaged 6.9 ± 0.8 ngg-1, while for tap water it ranged from 13.1 ngg-1 to 5.2 μgg-1. River water was fractionated by -1.09 ± 0.70 ‰ amu-1, while restrained tap water yielded the maximum fractionation of -6.39 ± 0.62 ‰ amu-1 relative to the laboratory standard. The Zn fractionation of tap water is much larger than all other natural samples, although the uncertainty is also significantly greater due to the use of the less precise Daly detector used for these preliminary experimental measurements. The fractionation of Zn in seven ultra pure Zn standard materials was measured relative to the laboratory standard and found to range from -5.11 ± 0.36 ‰ amu-1 for AE 10760 to +0.12 ± 0.16 ‰ amu-1 for Zn IRMM 10440. There appears to be some evidence for a relationship between Zn fractionation and its purity. As well as natural materials, the fractionation of Zn was measured in a number of processed materials. None of these results or those obtained for natural materials impact on the currently IUPAC accepted value for the atomic weight of Zn. Along with fractionation determinations, the concentration of Zn was also measured by Isotope Dilution Mass Spectrometry in all of the samples. The concentration of Zn in five stony meteorites ranged from 26 ± 13 to 302 ± 14 μgg-1 for Plainview and Orgueil respectively. For ordinary Chondrites, the concentration of Zn in the three samples analysed ranged from 26 ± 13 to 64 ± 34 μgg-1 for Plainview and Brownfield 1937 respectively.
The concentration of Zn was measured in two metamorphic rocks standard materials; the maximum concentration was 101.5 ± 1.7 µgg-1 in SDC-1. The concentration of Zn present in plant samples studied in this research was 22.15 ± 0.42, 14.62 ± 0.27 µgg-1 for Rice IMEP-19 and Sargasso NIES-Number 9 respectively which is within the normal range of Zn concentrations. Except for meteorites, the final uncertainties consistently cover the ranges of individual concentration measurements and indicate the homogeneity of the samples, including samples from different bottles where available. The final fractional uncertainties obtained for SRMs were all less than 2.8 %, demonstrating the high level of precision possible using IDMS.
Buchholt, Kristina. „Nanostructured materials for gas sensing applications“. Doctoral thesis, Linköpings universitet, Tillämpad Fysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-69641.
Der volle Inhalt der QuelleEspert, Ana. „Natural fibres/polypropylene composites from residual and recycled materials“. Licentiate thesis, KTH, Fibre and Polymer Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1667.
Der volle Inhalt der QuelleNatural fibres fulfil all the requirements in order toreplace inorganic fillers in thermoplastic composites. Naturalfibres are inexpensive, renewable, biodegradable, present lowerdensity and their mechanical properties can be compared tothose of inorganic fillers. However, several disadvantagesappear when natural fibres are used for composites. First ofall, the poor compatibility between the hydrophilic fibres withthe hydrophobic thermoplastic matrix leads to a weak interface,which results in poor mechanical properties. On the other hand,the hydrophilic nature of the fibres makes them very sensitivetowards water absorption, which leads also to the loss ofproperties and the swelling and dimensional instability.
In order to enhance the compatibility fibre-matrix, thefibres were chemically surface modified by five differentmethods: a) graft copolymerisation withpolypropylene-graftedmaleic anhydride copolymer (PPgMA), b)modification by PPgMA during processing, c) modification byorganosilanes, d) acetylation, e) modification with peroxideoligomers. Modified fibres led to improved mechanicalproperties and thermal behaviour when used in composites withpost-industrial polypropylene (PP) containing ethylene vinylacetate copolymer (EVA). Modification with peroxide oligomersshowed very promising results, but modification with PPgMA waschosen for further preparation of composites due to itssimplicity.
Two sets of composites were prepared using two differentpolypropylene types as matrix: virgin polypropylene (PP) andthe above mentioned post-industrial polypropylene (PP/EVA).Four different types of cellulosic fibres were used as fillers:cellulose fibres from pulping, sisal fibres, coir fibres andLuffa sponge fibres. The mechanical properties of thecomposites were dependent mostly on the fibre loading andslightly on the type of fibre. The fibers changed thecharacteristics of the material leading a higher stiffness buta lower toughness.
Water absorption of composites was studied at threedifferent temperatures: 23°C, 50°C and 70°C. Thewater absorption kinetics were studied and it was found thatwater is absorbed in composites following the kineticsdescribed by the Fickian diffusion theory. After absorption, animportant loss of properties was observed, due to thedestruction of the fibre structure due to the waterabsorbed.
Zhao, Wen. „The Control of Water Contaminants Assisted by Natural Materials“. Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/7114.
Der volle Inhalt der QuelleMahony, Oliver. „Silica-Natural Polymer Hybrid Materials for Human Tissue Regeneration“. Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526370.
Der volle Inhalt der QuelleLees, Joan Anne. „Modelling the magnetic properties of natural and environmental materials“. Thesis, Coventry University, 1994. http://curve.coventry.ac.uk/open/items/aa273a60-0c0d-a613-81b9-b95cc2ec3fdd/1.
Der volle Inhalt der QuelleFerreira, Pinto Da Silva Carla Florbela. „Interactions between volatile organic compounds and natural building materials“. Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760948.
Der volle Inhalt der QuelleKarlsson, Oskar. „Ferulic Acid – A Valuable Natural Compound for Sustainable Materials“. Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290233.
Der volle Inhalt der QuelleEtt av de största problemen som vi står inför i modern tid är hur vi ska ersätta material som är producerade från fossila bränslen. Dessa material finns överallt i vårt moderna samhälle och spelar en betydelserik roll i vår infrastruktur. Detta har tvingat oss att undersöka andra miljövänligare källor för att se om dessa kan ersätta de fossila. Polymera material är ett exempel på material som tidigare har haft en fossil bas. På grund av detta har dessa material och hur dem kan producerats undersökt för att se om det finns en alternativ biobaserad källa. Ferulsyra är en aromatisk kanelsyra som är mest känd för att ha antioxidatiova egenskaper. Utöver detta innehåller ferulsyra en dubbelbindning mellan två kol och dessutom fler än två funktionella grupper vilket indikerar att den kan vara en möjlig monomer för polymersyntes. Ferulsyra kan produceras från sidoströmmar från jordbruksindustrin så som till exemper sockerbetsmassa, linhår och vete, både genom enzymatiska reaktioner eller med hjälp av extraktion med ett lösningsmedel. En av de största användningsområdena gällande ferulsyra är inom biologiska applikationer. Den kan bland annat användas som solskydd, både inom hudvårdsindustrin och som ytbeläggning i textilier. Ferulsyra har också uppvisat medicinska egenskaper som visar på att det kan användas mot allergier, inflammationer, diabetes, canser och virussjukdomar. De två vanligaste metoderna för polymersyntes är fri radikalpolymerisation och stegvis polymerisation. Ferulsyra uppvisar stor potential för att kunna användas som monomer i båda metoderna då den innehåller en dubbelbindning mellan två kol och fler än två funktionella grupper. Syntes av ferulsyra genom stegvis polymerisation har genomförts. Resultatet var att de producerade materialen uppvisade termostabila och biologiskt nedbrytbara egenskaper. För att fri radikalpolymerisation ska vara möjligt med ferulsyra som monomer krävs det att dubbelbindningen inte är steriskt hindrad. Detta innebär att ferulsyra först måste modifieras innan polymerisationen är möjlig. Dessa modifieringar har genomförts på labbskala och den producerade monomeren är teoretiskt sätt möjlig att polymerisera genom fri radikalpolymerisation.
Hasbach, Ximena. „Natural carbonaceous materials for use in transparent Joule heaters“. Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122181.
Der volle Inhalt der QuelleCataloged from PDF version of thesis.
Includes bibliographical references (page 35).
Natural carbonaceous materials have the potential to be used in a new class of more economically and environmentally sound electronic devices due to their tunable conductivity as well as robust mechanical and thermal properties. This study aims to explore the potential of steam cracker tar (SCT), a byproduct of ethylene production, for use in conductive applications, specifically transparent Joule heaters. The SCT was made into thin films using both rod-rolling and spray-coating methods. After the superior uniformity of the rod-rolled films was observed, a 2 laser cutter was used to anneal the rod-rolled films with the intention of increasing their sp² content and thus improving their conductivity. First the power and then the z-defocusing of the laser were varied, and the ability of the resulting films to heat was tested with an applied voltage. To test the conductivity and heating capabilities of the annealed SCT films, 60 volts were applied, the current measured, and the number of degrees heated measured with a thermal camera software. A combination of Raman spectroscopy and profilometry was used to characterize the films. The film with the best heating capabilities was found to be the one annealed with 8% laser power and 0.2 inch z-defocus. This film was observed to heat to 35 degrees Celsius, and was demonstrated to efficiently de-ice a frozen sheet of tempered glass. Future work in this study will focus on finding ways to improve conductivity in SCT films with better transparency.
by Ximena Hasbach.
S.B.
S.B. Massachusetts Institute of Technology, Department of Materials Science and Engineering
Garkhail, Sanjeev Kumar. „Composites based on natural fibres and thermoplastic matrices“. Thesis, Queen Mary, University of London, 2002. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1700.
Der volle Inhalt der QuelleMontoya, Armisén Pedro. „Characterization of 2D materials“. Thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-416436.
Der volle Inhalt der QuelleCochrane, Emma Louise. „Natural biosorbent materials for the remediation of copper contaminated wastewaters“. Thesis, University of Aberdeen, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540478.
Der volle Inhalt der QuelleZhao, Shengjie. „Natural frequency based damage identification of beams using piezoelectric materials“. ASME 2015 International Mechanical Engineering Congress and Exposition, 2015. http://hdl.handle.net/1993/31652.
Der volle Inhalt der QuelleOctober 2016
Escalera, Edwin. „Characterization of some natural and synthetic materials with silicate structures“. Licentiate thesis, Luleå tekniska universitet, Materialvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25679.
Der volle Inhalt der QuelleGodkänd; 2013; 20130118 (edwesc); Tillkännagivande licentiatseminarium 2013-01-30 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Edwin Escalera Mejia Ämne: Konstruktionsmaterial/Engineering Materials Uppsats: Characterization of Some Natural and Synthetic Materials With Silicate Structures Examinator: Docent Marta-Lena Antti, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Dr Farid Akhtar, Dept of Materials and Environmental Chemistry, Stockholm University Tid: Onsdag den 20 februari 2013 kl 10.15 Plats: E246, Luleå tekniska universitet
Guidetti, Giulia. „Cellulose photonics : designing functionality and optical appearance of natural materials“. Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/277918.
Der volle Inhalt der QuelleBarrera, Martinez Cindy Sofia. „Novel Renewable Materials from Natural Rubber and Agro-Industrial Residues“. The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480540955796333.
Der volle Inhalt der QuelleO'Neill-Williams, Barrie. „The use of natural site derived materials as concrete aggregate“. Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/12178.
Der volle Inhalt der QuelleIncludes bibliographical references.
This thesis focuses on the use of site-derived fine material, in its natural form, as aggregate in concrete construction. It is proposed that the utilisation of this type of concrete aggregate will lead to; the preservation of natural materials that would otherwise have to be beneficiated off site, the reduction of waste material produced on a construction site, and an overall energy saving.
Connell, Louise Stephanie. „Natural and synthetic polymer-based hybrid materials for tissue regeneration“. Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/24820.
Der volle Inhalt der QuelleYang, Hong-Seok. „Outdoor noise control by natural/sustainable materials in urban areas“. Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/4484/.
Der volle Inhalt der QuellePoompradub, Sirilux. „Structure and physical properties of natural rubber based composite materials“. 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144559.
Der volle Inhalt der QuelleLotfi, Amirhossein. „Study on the Machinability of Natural Fiber Reinforced Composite Materials“. Thesis, Griffith University, 2020. http://hdl.handle.net/10072/396146.
Der volle Inhalt der QuelleThesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
Full Text
Buraglio, Nadia. „Accelerator mass spectrometry of 129I and its applications in natural water systems“. Doctoral thesis, Uppsala universitet, Institutionen för materialvetenskap, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1077.
Der volle Inhalt der QuelleDahlqvist, Martin. „Materials Design from First Principles : stability and magnetism of nanolaminates“. Doctoral thesis, Linköpings universitet, Tunnfilmsfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-104764.
Der volle Inhalt der QuelleKopec, Grant Michael. „Examining natural resource futures with material flow analysis“. Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709409.
Der volle Inhalt der QuelleBoglaienko, Daria. „Capture and Densification of Floating Hydrophobic Liquids by Natural Granular Materials“. FIU Digital Commons, 2017. http://digitalcommons.fiu.edu/etd/3261.
Der volle Inhalt der QuelleRoy, Debashish. „Natural-synthetic hybrid functional materials from cellulose via the RAFT process“. Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441327.
Der volle Inhalt der QuelleAbbas, Shah Rukh. „Preliminary investigation of natural materials for use in ultrasound contrast agents“. Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708316.
Der volle Inhalt der QuelleMatsuo, Miyuki. „Color Change of Lignocellulosic Materials during Natural Aging and Heat Treatment“. Kyoto University, 2012. http://hdl.handle.net/2433/157700.
Der volle Inhalt der Quelle0048
新制・課程博士
博士(農学)
甲第16909号
農博第1925号
新制||農||999(附属図書館)
学位論文||H24||N4670(農学部図書室)
29584
京都大学大学院農学研究科森林科学専攻
(主査)教授 川井 秀一, 教授 杉山 淳司, 准教授 仲村 匡司
学位規則第4条第1項該当
Nelson, Andrew Wyatt. „Naturally occurring radioactive materials associated with unconventional drilling for natural gas“. Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/5579.
Der volle Inhalt der QuelleKalyankar, Rahul R. „Natural fiber reinforced structural insulated panels for panelized construction“. Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2010r/kalyankar.pdf.
Der volle Inhalt der QuelleMital, D., J. Zajac, F. Botko, M. Hatala, Z. Mitalova, S. Radchenko, Віталій Олександрович Іванов, Виталий Александрович Иванов und Vitalii Oleksandrovych Ivanov. „Measuring of roundness of WPC materials after turning“. Thesis, Sumy State University, 2016. http://essuir.sumdu.edu.ua/handle/123456789/48030.
Der volle Inhalt der QuelleLi, Weiyao. „Understanding UV Protection Mechanism of Natural and Synthetic Eumelanin“. University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1491930546268438.
Der volle Inhalt der QuelleСкиданенко, Юлія Павлівна, Юлия Павловна Скиданенко und Yuliia Pavlivna Skydanenko. „Науково-методичні підходи до визначення економічної сутності наслідків надзвичайних ситуацій природного характеру“. Thesis, Видавництво СумДУ, 2012. http://essuir.sumdu.edu.ua/handle/123456789/26759.
Der volle Inhalt der QuelleRahman, Muhammad Ziaur. „Mechanical Performance of Natural / Natural Fiber Reinforced Hybrid Composite Materials Using Finite Element Method Based Micromechanics and Experiments“. DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6482.
Der volle Inhalt der QuelleBurström, Karin. „Metal Oxide Composites with Carbon Materials : Synthesis, Characterisation and Preliminary Catalytic Applications“. Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75791.
Der volle Inhalt der QuelleBuraglio, Nadia. „Accelerator mass spectrometry of 129I and its applications in natural water systems“. Doctoral thesis, Uppsala University, Department of Materials Science, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1077.
Der volle Inhalt der QuelleDuring recent decades, huge amount of radioactive waste has been dumped into the earth's surface environments. 129I (T1/2 = 15.6 My) is one of the radioactive products that has been produced through a variety of processes, including atomic weapon testing, reprocessing of nuclear fuel and nuclear accidents. This thesis describes development of the Accelerator Mass Spectrometry (AMS) ultra-sensitive atom counting technique at Uppsala Tandem Laboratory to measure 129I and discusses investigations of its distribution in the hydrosphere (marine and fresh water) and precipitation. The AMS technique provides a method for measuring long-lived radioactive isotopes in small samples, relative to other conventional techniques, and thus opens a new line of research. The optimization of the AMS system at Uppsala included testing a time of flight detector, evaluation of the most appropriate charge-state, reduction of molecular interference and imporvement of the detection limit. Furthermore, development of a chemical procedure for separation of iodine from natural water samples has been accomplished.
The second part of the thesis reports investigations of 129I in natural waters and indicates that high concentrations of 129I (3-4 orders of magnitude higher than in the pre-nuclear era) are found in most of the considered natural waters. Inventory calculations and results of measurements suggest that the major sources of radioactive iodine are the two main European nuclear reprocessing facilities at Sellafield (U.K.) and La Hague (France). This information provides estimates of the transit time and vertical mixing of water masses in the central Arctic Ocean. Results from precipitation, lakes and runoff are used to elucidate mechanisms of transport of 129I from the point sources and its pathways in the hydrological environment. This study also shows the need for continuous monitoring of the 129I level in the hydrosphere and of its future variability.
Santim, Ricardo Hidalgo [UNESP]. „Síntese e caracterização de blendas borracha natural/polianilina e borracha natural/polipirrol obtidas por polimerização in situ“. Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/126367.
Der volle Inhalt der QuelleOs polímeros geralmente são muito conhecidos por serem materiais leves, flexíveis e de fácil processamento. Cada vez mais a área tecnológica tem a demanda dessas propriedades associadas a condutividade elétrica ajustável. Nessa perspectiva, há trabalhos que se empenham em associar Polímeros Condutores Intrínsecos (PCI) com matrizes de boa propriedade mecânica. Entre os PCI, o polipirrol (PPy) e a polianilina (PAni) têm se destacado devido à fácil síntese, alta estabilidade ambiental, alta condutividade (10 2 S/cm) e baixo custo dos monômeros. Uma das limitações nas aplicações tecnológica desses polímeros condutores está na sua pobre propriedade mecânica e baixa solubilidade. Uma das alternativas para contornar esses problemas é fazer a polimerizão in situ dos polímeros condutores na presença de um polímero com boas propriedades mecânicas. Dessa forma, o objetivo desse trabalho foi preparar blendas de borracha natural (BN) com PAni e BN com PPy através da polimerização in situ da anilina e do pirrol, respectivamente, no látex de seringueira, natural e prevulcanizado. Foram estudadas as propriedades morfológicas, estruturais, elétricas, mecânicas e térmicas dessas amostras. As análises dos espectros de infravermelho e UV-Vis- NIR evidenciaram a síntese, em meio látex, da polianilina no estado sal de esmeraldina (dopada) e do polipirrol no estado dopado. As blendas apresentaram condutividade elétrica na faixa de 10 -14 a 10 -2 S/cm que variou em função da razão borracha/monômero. Na maioria dos casos, obteve-se maior condutividade elétrica quando utilizou-se o látex prevulcanizado. A tensão na ruptura aumentou com a diminuição da razão de BN/monômero para as blendas obtidas a partir de látex natural e também de látex prevulcanizado. Para a mesma condição de síntese, a tensão de ruptura foi superior para as blendas obtidas a partir do látex...
The polymers are generally known to be very lightweight materials, flexible and easy processing. Each year, more and more the technology area has the demand for these properties associated with adjustable electrical conductivity. From this perspective, there are studies that seek to associate intrinsically conducting polymers (ICP) with polymer matrices that has good mechanical property. Among those ICP, polypyrrole (PPy) and polyaniline (PAni) has received much attention due to easy of synthesis, high environmental stability, high conductivity (10 2 S/cm) and low cost of monomers. However, they have poor mechanical property and low solubility. An alternative to overcome these problems is to make in situ polymerization of the conductive polymer in the presence of another polymer that possesses good mechanical properties. In this way, the aim of this study was to obtain natural rubber (NR) composites with PAni and NR with PPY by in situ polymerization of aniline and pyrrole, respectively, in the natural and prevulcanized natural rubber latex. Morphological, structural, electrical, mechanical and thermal properties these samples were studied. Analysis of infrared and UV-Vis-NIR spectra showed the polyaniline and polypyrrole are in doped state. The electrical conductivity of the composites showed to be dependent on the ratio rubber/ monomer, staying in the range of 10 -14 to 10 -2 S/cm. In most cases, higher conductivity occurred when prevulcanized latex was used. The strain at break of the composites increases with decreasing rubber/monomer ratio. For the same synthesis conditions the strain at break was higher to the composites obtained from prevulcanized latex. In some polymerization condition it was evident the occurrence of encapsulation of prevulcanized rubber particles with the conducting polymers mainly to low rubber/monomer ratio