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1
Naidoo, Dhesigen P. "Metals and the conformation of fibrin". Master's thesis, University of Cape Town, 1992. http://hdl.handle.net/11427/26555.
Testo completoAbstract (sommario):
The carboxy terminal of the γ-chain of human fibrinogen contains at least three biologically. important functional domains: (i) the fibrinogen γ-chain polymerisation centre, (ii) the platelet receptor domain and (iii) the site for staphyloccocal clumping. The nature of the site specificity of these interactions necessitates the existence of a preferred conformation for this region, the nature of which has yet to be clearly established. A novel zinc metalloproteinase isolated from puff adder venom (PAV protease) capable of specifically cleaving the di-γ-chain of transglutaminase (Factor XIIIa) catalysed crosslinked plasmin derived D-dimer into apparently symmetrical monomers has been described. The activity is fibrin specific and displays an unusual site specificity for the γ-carboxy terminal domains within the crosslink region. The activity was reported to be potentiated by zinc. The effect of zinc on the digestion of D-dimer by PAV protease was evaluated by SDS-PAGE and by a fluorimetric technique utilising a fluorescent dansylcadaverine conjugate of the substrate (f-D-dimer). A differential zinc binding study determined that the potentiation of activity by zinc was due to a zinc-substrate rather than a zinc-enzyme interaction. The binding constant for zinc to D-dimer was determined by Scatchard analysis of zinc titration data. The interaction of zinc and f-D-dimer was confirmed by fluorescence anisotropy determinations. The nature of the coordination capsule around the metal cation was determined by examining a cobalt-fibrin-D-dimer complex and characterising the difference visible absorption spectrum thereof. The donor ligands from the D-dimer fragment for the metal ion were determined as histidines by examining zinc(II) and cobalt(II) binding to diethylpyrocarbonate modified fibrin-D-dimer and hydroxylamine treated DEPC-fibrin-D-dimer. Through this study it has been established that the PAV protease cleavage of the di-γ-chain of the plasmin derived D-dimer fragment is potentiated by zinc(II) ions through the formation of a novel zinc determined conformation of fibrin-D-dimer. This presents the possibility of a fibrinspecific neo-epitope being manifested in the presence of zinc ions that could provide a means to determine fibrin degradation products more specifically. A model for the neo-epitope has been proposed.
2
Kocak, Ozgur. "Analysis Of The Formability Of Metals". Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1178714/index.pdf.
Testo completoAbstract (sommario):
Workpieces during cold forging fail basically due to ductile fracture. Ductile fracture can be predicted by damage models. In this study, various damage models such as Cockcroft &Latham, McClintock, Freudenthal, Rice &
Tracy, Oyane, Ayada, Brozzo are investigated for their applicability to three workpiece materials: bearing steel (100Cr6), stainless steel (X5CrNiMo1810) and brass (CuZn39). The damage material parameters have been obtained by various tests such as tensile, standard compression, ring compression, compression with flanges and conical compression tests. The characterization has been assisted by finite element simulation of the various tests. It has been shown that the available damage models can predict the location of failure satisfactorily but are no able to predict the onset of failure quantitatively. Keywords: Formability Limit, Failure Criteria, Cold Forming, Surface Cracks, Finite Element Analysis
3
Thuramalla, Naveen. "Multiscale modeling and analysis of failure and stability during super plastic deformation -- under different loading conditions". Lexington, Ky. : [University of Kentucky Libraries], 2004. http://lib.uky.edu/ETD/ukymeen2004t00171/NAVEEN.pdf.
Testo completoAbstract (sommario):
Thesis (m.s.)--University of Kentucky, 2004.Title from document title page (viewed Jan. 5, 2005). Document formatted into pages; contains x, 112p. : ill. Includes abstract and vita. Includes bibliographical references.
4
Dangolle, Champa D. P. "Some aspects of trace analysis of metals". Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318885.
Testo completo
5
Mirmasoudi, Sara. "High Temperature Transient Creep Analysis of Metals". Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1452693927.
Testo completo
6
Lambidis, Elisavet. "Synthesis and photophysical studies of metal complexes for biological applications /Lambidis Elisavet". HKBU Institutional Repository, 2017. http://repository.hkbu.edu.hk/etd_oa/346.
Testo completoAbstract (sommario):
Nowadays the necessity for designing and synthesizing novel imaging agents increases rapidly. The long wavelength, and thus, low energy, of excitation and emission, and the good specificity and stability are examples of essential characteristics of ideal diagnostic and therapeutic agents. In this work, the synthesis and photophysical studies of metal complexes for biological applications were performed and evaluated, and it contained the development of (a) a porphyrin probe for imaging and treatment and (b) a tripodal thermal sensor for imaging. The research and study of the two cases of complex is analyzed in the second and third chapters, respectively, which follow the introduction or literature review to the diagnostic and/ or therapeutic agents which is given with examples in the first chapter. The scope of the main project, which is analysed in the second chapter, was the development and synthesis of a porphyrin-based bio-probe capable of bacterial fluorescence imaging. The porphyrin moiety of a complex is also able to generate singlet oxygen and this effect can be used for treatment purposes (PDT, Photodynamic Therapy). Thus, the complex can act as a diagnostic and therapeutic (anti-bacterial in this case) agent simultaneously. A probe with such a dual capability is known as theranostic agent. A theranostic agent is crucial for the enhancement and expansion of personalised medicine. The studies and physical measurements of the proposed, synthesised porphyrin complex have proved its capability to be used as a theranostic probe. Furthermore, after coupling the porphyrin moiety firstly with a small protein part (ampetoid: antimicrobial peptoid) and secondly with a radionuclide (Gallium-68), the in vitro and in vivo studies have to be performed. The aim of the project analysed in the third chapter was the development of a thermal sensor. Coordination of a tripodal ligand with a mixture of two lanthanides in various ratios was achieved and the photophysical measurements of the resulted complexes were evaluated. Lanthanide metals were chosen due to their unique photophysical properties that they offer when they are connected to an organic chomophoric ligand. Additionally, the preferred final luminophore product would obey a thermostable structure over a wide temperature range and it would be capable of effectively sensing the alterations in temperature. These properties were true for the ratio 99.5:0.5 for Terbium: Europium, and thus, the complex with such a consistency clarified the final product. Furthermore, the highly promising results after repeatedly photophysical (especially emission) measurements could conclude that the complex can be served as an ideal thermal sensor. Additional emission measurements at higher temperatures have to be done in order to confirm the ability of the proposed thermal sensor to be used for bio-imaging purposes. In conclusion, two-kind of metal complexes for biological applications were synthesized and their photophysical properties were assessed. Both the bulky porphyrin complex and the smaller tripodal ligand have shown promising results for their proposed applications. Of course, a more detailed assessment is required to verify their capability.
7
Al-Attar, A. F. "Selenium and trace metals as pollutants". Thesis, University of Bristol, 1987. http://hdl.handle.net/1983/1858b91b-362e-422f-b91c-84aa44e23e90.
Testo completo
8
Sadjadi, Seyedabdolreza. "Ab initio relativistic-consistent calculations and charge density and experimental mass-spectroscopic analysis of mono and poly-nuclearclusters of group 11 and 12 transition metals and metal chlorides: ySeyedabdolreza Sadjadi". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hub.hku.hk/bib/B5060577X.
Testo completoAbstract (sommario):
The electron density function of molecular systems supplies a package of information. Quantum mechanical methods of producing and analyzing this function have been significantly improved during the past few years. The advent of accurate pseudopotentials and corresponding basis sets for Kohn-Sham density functional and for post-Hartree-Fock electron-correlated approaches have enabled the inclusion of scalar relativistic and spin-orbit coupling effects as well as electron correlation effects into the electron density function. The unpacking of the information embedded in such a function via the quantum theory of atoms in molecules (QTAIM) became possible by utilizing the very new subshell fitting method of reconstructing the density distribution of core electrons that had been replaced by the pseudopotentials.
These theoretical advances were applied in this thesis to characterize and explore the topological features of metal-metal bonding as one of the fundamental types of bonds formed between two elements. Group 11 and 12 transition metals which include gold and mercury as the most relativistic elements were the main focus of this work. Mono and poly-nuclear compounds (with up to 4 metal atoms) in both pure metal clusters and chloro-complexes were studied by ab initio MØller-Plesset perturbation calculations followed by QTAIM analysis on the relaxed density. Some of these chloro-complexes of copper, gold, zinc and cadmium metals were identified in the gas phase by mass spectrometric experiments. The general formulas of the set of molecules studied in group 11 were : M2, MCl, MCl+, MCl2, MCl2+, M2Cl+, M2Cl2^(s+), M2Cl3+, M3Cl2+, M3Cl3+, M3Cl5+, M4Cl5+ and M4Cl7+ and in group 12 were : M2, MCl, MCl+, MCl2, M2Cl3+, M3Cl5+, M4Cl7+ and M2^(s+). The topological features of metal-metal bonding were calculated along with atomic properties for each individual local minimum isomer found. The comparison of
the metal-metal bonding within the complexes and with the dimers revealed new
features of metal-metal bonding in 3d, 4d and 5d transition metal elements of
groups 11 and 12. With the aid of strong correlation between bond dissociation
energy and electron density at the location of the bond critical points found in the
case of dimers, the strength of the metal-metal bonding in the complexes was
estimated. The electron density’s basin properties calculated accurately for all the
clusters and their isomers in this thesis provided more insight also into the nature
of M-Cl bondings in the group 11 and 12 chloride clusters. Ultimately the bonding
information was used to predict the viability of these clusters in the gas phase.published_or_final_version
Chemistry
Doctoral
Doctor of Philosophy
9
Jones, Matthew Kenneth. "Multiscale Analysis of Void Coalescence in Ductile Metals". MSSTATE, 2004. http://sun.library.msstate.edu/ETD-db/theses/available/etd-11112004-165827/.
Testo completoAbstract (sommario):
A mulitscale approach is used to model the coalescence of voids. At the microscale, cylindrical and spherical voids in nickel and the magnesium alloy AM60 are simulated through finite element analyses. The nickel cylindrical void simulations are compared to a set of experiments to validate this micromechanical finite element approach used to study void coalescence. At the macroscale, the coalescence portion of a microstructure-property material model is modified to reflect the behavior of three-dimensional spherical voids using results from the micromechanical simulations. An analysis of an automotive component illustrates the influence of void coalescence at the structural scale.
10
Bond, Philip Harvey. "Analysis of flexible interlayers between metals and ceramics". Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282713.
Testo completo
11
Auer, Derek. "Flow-injection analysis of the platinum-group metals". Doctoral thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/17511.
Testo completoAbstract (sommario):
Includes bibliographical references.To date the principle methods for the determination of the platinum-group metals (PGMs) use an "off-line" assay with flame-atomic absorption spectrometry and visible spectrometry. Both suffer numerous interferences and involve time-consuming and arduous laboratory separation methods prior to analysis. An "on-line" method for the rapid assay of the PGMs is indeed a lacking component in the analysts' repertoire of methods. This study describes the development of spectrophotometric methods for the determination of the PGMs using flow-injection analysis (FIA). The principle of exploiting the remarkably specific and selective reaction of stannous halides with the PGMs to yield a series of intensely coloured complexes in acidic solutions forms the basis of these methods. The reaction is subject to relatively few interferences from other transition metals. A high speed scanning spectrophotometer is employed to obtain second order data. The successful manipulation of the data enables the determination of PGMs as single components and also simultaneously in mixtures. Attention is focused on the establishment of principles for successful multi-component analysis of PGMs. The development of a software program for multi-wavelength data manipulation was mandatory and is described. Criteria for successful selection of analytical wavelengths are discussed. The usefulness of multi-dimensional graphical data representation is demonstrated in a stop-flow study of the palladium reaction with tin (II) chloride. Qualitative information is provided regarding the nature of complexes and their interactions. Correlation of spectrophotometric data with complex solution colour changes is made. The requirements for future progress in multi-component FIA determinations as well as the direction for future research conclude the study.
12
Bian, Lichun, e 卞立春. "Fatigue crack growth analysis of metallic plates with an inclinedsemi-elliptical crack". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31242844.
Testo completo
13
Meuli, Reto Meuli Reto Giulio Meuli Reto Giulio Meuli Reto Giulio. "Geostatistical analysis of regional soil contamination by heavy metals /". [S.l.] : [s.n.], 1997. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=12121.
Testo completo
14
Colombo, Carlo Maurizio. "Flow analysis of trace metals in seawater by voltammetry". Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338581.
Testo completo
15
Kucz, Daniel Allen. "Analysis of distortion-induced fatigue cracking in a steel trapezoidal box girder bridge". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 177 p, 2009. http://proquest.umi.com/pqdweb?did=1885755701&sid=9&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Testo completo
16
Limson, Janice Leigh. "Electrochemical studies of metal-ligand interactions and of metal binding proteins". Thesis, Rhodes University, 1999. http://hdl.handle.net/10962/d1018239.
Testo completoAbstract (sommario):
Electrochemical methods were researched for the analysis of metals, proteins and the identification of metal binding proteins. Adsorptive cathodic stripping voltamrnetry for metal analysis combines the inherent sensitivity of electrochemical techniques with the specificity of ligands for the nonfaradaic preconcentration of analytes at the electrode. The utility of catechol, resorcinol, 4-methylcatechol and 4-t-butylcatechol as ligands was explored for the sensitive analysis of copper, bismuth, cadmium and lead on a mercury film glassy carbon electrode. Metal complexes of lead, copper and bismuth with resorcinol showed the largest increase in current with increase in metal concentration, whereas complexes of these metals with 4-t-butylcatechol showed the lowest current response. Cadmium showed the highest current responses with 4-methylcatechol. The four metals could be determined simultaneously in the presence of resorcinol, although considerable interference was observed between bismuth and copper. The electroanalysis of cysteine and cysteine containing proteins at carbon electrodes are impaired by slow electron transfer rates at carbon electrodes, exhibiting high overpotentials, greater than 1 V vs Ag! Agel. Metallophthalocyanines have been shown to promote the electrocatalysis of cysteine at lowered potentials. Chemical modification of electrodes with appropriate modifiers is a means of incorporating specificity into electroanalysis, with applications in electrocatalysis. A glassy carbon electrode was modified by electrodeposition of cobalt (II) tetrasulphophthalocyanine [Co(II)TSPct to produce a chemically modified glassy carbon electrode (CMGCE). The CoTSPc-CMGCE catalysed the oxidation of cysteine in the pH range 1 to 10. The significance of this electrode is an application for analysis of proteins at biological pH's. A biscyanoruthenium(II) phthalocyanine CMGCE catalysed the oxidation of cysteine at 0.43 V vs Ag/AgCl a significant lowering in the overpotential for the oxidation of cysteine. Metallothionein, a metal binding protein, is believed to be involved in metal homeostasis and detoxification in the peripheral organs of living systems. A method for the quantitative determination of this protein utilising its high cysteine content was presented. At pH 8.4 Tris-HCl buffer, and using a CoTSPc-CMGCE modified by electrodeposition of the modifier, the anodic peaks for the oxidation of metallothionein was observed at 0. 90 V vs Ag/ AgCI. Ferredoxin is a simple iron-sulphur protein. One tenth of its residues are cysteine. Ferredoxin is involved in simple electron transfer processes during photosynthesis and respiration. Electrochemical studies of spinach ferredoxin were conducted at a CoTSPc-CMGCE. Anodic currents for the oxidation of the cysteine fragment of ferredoxin was observed at 0.85 V vs Ag/AgCl in HEPES buffer at pH 7.4, representing a new method for analysis of this protein. Voltammetric studies of its ferric/ferrous transition have shown quasi-reversible waves atE~ -0.62 V vs Ag/AgCl only in the presence of promoters. At a CoTSPc-CMGCE, a cathodic wave attributed to the reduction of Fe(III)/Fe(II) was observed at Epc -0.34 V vs Ag/AgCl. This represents an alternative method for voltammetric studies of the ferric/ferrous transition at significantly lowered potentials. Melatonin, a pineal gland hormone functions m setting and entraining circadian rhythms and in neuroprotection as a free radical scavenger and general antioxidant. Using adsorptive cathodic stripping voltammetry, the binding affinities of melatonin, serotonin and tryptophan for metals, were measured. The results showed that the following metal complexes were formed: aluminium with melatonin, serotonin and tryptophan; cadmium with melatonin and tryptophan; copper with melatonin and serotonin; iron (III) with melatonin and serotonin; lead with melatonin, tryptophan and serotonin, zinc with melatonin and tryptophan and iron (II) with tryptophan. The studies suggest a further role for melatonin in the reduction of free radical generation and in metal detoxification and may explain the accumulation of aluminium in Alzheimer's disease.
17
Wang, Jin 1954. "Extraction of heavy metals with supercritical carbon dioxide : a novel approach to heavy metal analysis and decontamination". Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39890.
Testo completoAbstract (sommario):
The technique of extraction with supercritical carbon dioxide (SC-CO$ sb2$), which is now used routinely for the recovery of non-polar analytes from a variety of liquid and semipermeable solid media, was extended to the efficient extraction of metal ions. Measurements of the solubilities in SC-CO$ sb2$ corroborated the hypothesis that the non-polar character of a series of tetraalkylammoniun dialkyldithiocarbamates ion pairs was influenced (i) primarily by the chain length of the alkyl substituent(s) on the carbamate nitrogen and (ii) to a lesser extent, by the chain length of the alkyl substituent(s) on the ammonium counter ion. In operation, analyte metal(s) in aqueous medium was derivatized by in situ complexation with the dithiocarbamate complexing reagent and the product complex(es) was partitioned into the SC-CO$ sb2$ mobile phase then purged from the extractor by replacing the headspace with fresh solvent. A novel silica flame-in-tube interface was developed for the sensitive detection, by atomic absorption spectrometry (AAS), of As, Cd, Cu, Mn, Pb, Se, or Zn in SC-CO$ sb2$ extractor eluate. For different analyte elements, the limits of detection (LODs) ranged from sub-nanogram to low picogram if standard was flow injected into the mobile phase. These sensitivities permitted differences in the rates of mobilization of different forms of the analyte metal from various media to be explored as a technique for probing the interaction of the analyte metal with the matrix. A portion of the Zn burden in fresh bovine liver was mobilized rapidly in the absence of complexing agent and the remainder was solubilized more rapidly than the Zn in a freeze-dried reference material of this tissue. The nebulizer assembly of a conventional flame-AAS was modified to extend the range of metals amenable to on-line detection. Supplemental heating of the inlet air to 200$ sp circ$C resulted in an on line detector which provided approximately a ten-fold improvement over convention
18
Heydenrych, Greta. "New amino- and titanoxycarbene complexes of group 6 metals". Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52355.
Testo completo
19
Soffiati, João Emanuel. "Analise numerica e experimental do cravamento de componentes mecanicos tubulares em haste com ponta esferica". [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264408.
Testo completoAbstract (sommario):
Orientador: Sergio Tonini ButtonDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-08-09T22:04:57Z (GMT). No. of bitstreams: 1 Soffiati_JoaoEmanuel_M.pdf: 11880628 bytes, checksum: 29a510c6bed00d4a1a53fe4897d4cc0f (MD5) Previous issue date: 2007
Resumo: Cravamento é um processo de conformação de metais a frio que apresenta baixo custo na utilização de fixação de componentes tubulares. O tipo de cravamento estudado é aplicado em projetos de componentes que necessitem transmitir movimento de rotação, similar às articulações de pedais de freios automotivos. Se a folga da articulação, neste caso, for menor que 0,02mm causará restrições no movimento da articulação, podendo não fechar a válvula de vácuo do sistema de frenagem causando a diminuição da eficiência, em contra partida, se a folga for maior que 0,15mm o acionamento do freio poderá apresentar ruídos. Outro problema é a presença de trincas passantes geradas pela escolha de parâmetros de processos inadequados no cravamento. Usualmente estes parâmetros não são especificados no projeto do sistema de frenagem, causando alta variabilidade no processo de manufatura. Este trabalho apresenta a análise de cravamento considerando seis fatores que foram escolhidos para iniciar a análise: geometria do punção, rugosidade do punção, diâmetro da ponta da haste a ser cravada, espessura da parede do componente tubular, profundidade da indentação e folga entre esfera e diâmetro do tubo para indentação. O processo de manufatura foi simulado experimentalmente através de um dispositivo especialmente projetado e montado para este trabalho e comparado com os resultados obtidos com o software MSC Superforge 2005
Abstract: Crimping is a cold metal forming process that presents low costs for use in holding tubular components. The type of crimping analyzed is used in projects of components that transmit rotating motion, such as joining systems of brake pedals. If the joining clearance, in this case, is less than 0,02mm the brake movement will be restrained and may not close the vacuum valve of the break system what could cause reduction of efficiency; however, if that clearance is greater than 0,15mm may cause excessive noisy. Another problem is the presence of cracks or fissures generated by the choice of inappropriate process parameters. These parameters are not usually specified in the product design leading to high process variability. This work presents six factors that were chosen to start the analysis: punch geometry, roughness of the punch, diameter of the rod end, thickness of the tubular component, indentation depth, and position of indentation load. The crimping manufacturing process was simulated experimentally through the fixture specially projected and built to this work and compared with the results obtained with the software MSC Superforge 2005
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
20
Kiani, Ahmed. "Analysis of metal oxide thin film transistors with high-k dielectrics and source/drain contact metals". Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648586.
Testo completo
21
Williams, Timothy Paul. "Determination of trace metals by ion-chromatography with chemiluminescence detection". Thesis, University of Plymouth, 1990. http://hdl.handle.net/10026.1/2182.
Testo completo
22
Ahuja, Vishal. "Analysis of novel transition metals as catalysts for oxygen delignification". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ62909.pdf.
Testo completo
23
Wang, Z. P. "Analysis and palliation of contact stresses between ceramics and metals". Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.352926.
Testo completo
24
Dallmeier, Johannes. "Experimental analysis and numerical fatigue modeling for magnesium sheet metals". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2016. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-209124.
Testo completoAbstract (sommario):
The desire for energy and resource savings brings magnesium alloys as lightweight materials with high specific strength more and more into the focus. Most structural components are subjected to cyclic loading. In the course of computer aided product development, a numerical prediction of the fatigue life under these conditions must be provided. For this reason, the mechanical properties of the considered material must be examined in detail. Wrought magnesium semifinished products, e.g. magnesium sheet metals, typically reveal strong basal textures and thus, the mechanical behavior considerably differs from that of the well-established magnesium die castings. Magnesium sheet metals reveal a distinct difference in the tensile and compressive yield stress, leading to non-symmetric sigmoidal hysteresis loops within the elasto-plastic load range. These unusual hysteresis shapes are caused by cyclic twinning and detwinning. Furthermore, wrought magnesium alloys reveal pseudoelastic behavior, leading to nonlinear unloading curves. Another interesting effect is the formation of local twin bands during compressive loading. Nevertheless, only little information can be found on the numerical fatigue analysis of wrought magnesium alloys up to now.
The aim of this thesis is the investigation of the mechanical properties of wrought magnesium alloys and the development of an appropriate fatigue model. For this purpose, twin roll cast AM50 as well as AZ31B sheet metals and extruded ME21 sheet metals were used. Mechanical tests were carried out to present a comprehensive overview of the quasi-static and cyclic material behavior. The microstructure was captured on sheet metals before and after loading to evaluate the correlation between the microstructure, the texture, and the mechanical properties. Stress- and strain-controlled loading ratios and strain-controlled experiments with variable amplitudes were performed. Tests were carried out along and transverse to the manufacturing direction to consider the influence of the anisotropy. Special focus was given to sigmoidal hysteresis loops and their influence on the fatigue life. A detailed numerical description of hysteresis loops is necessary for numerical fatigue analyses. For this, a one-dimensional phenomenological model was developed for elasto-plastic strain-controlled constant and variable amplitude loading. This model consists of a three-component equation, which considers elastic, plastic, and pseudoelastic strain components. Considering different magnesium alloys, good correlation is reached between numerically and experimentally determined hysteresis loops by means of different constant and variable amplitude load-time functions.
For a numerical fatigue life analysis, an energy based fatigue parameter has been developed. It is denoted by “combined strain energy density per cycle” and consists of a summation of the plastic strain energy density per cycle and the 25 % weighted tensile elastic strain energy density per cycle. The weighting represents the material specific mean stress sensitivity. Applying the energy based fatigue parameter on modeled hysteresis loops, the fatigue life is predicted adequately for constant and variable amplitude loading including mean strain and mean stress effects. The combined strain energy density per cycle achieves significantly better results in comparison to conventional fatigue models such as the Smith-Watson-Topper model. The developed phenomenological model in combination with the combined strain energy density per cycle is able to carry out numerical fatigue life analyses on magnesium sheet metals.
25
Parker, Gavin James. "Analysis of metals in airborne particulate matter in eastern Iowa". Thesis, University of Iowa, 2019. https://ir.uiowa.edu/etd/7010.
Testo completoAbstract (sommario):
Airborne particulate matter (PM) consists of solid and liquid particles suspended in air. PM causes many negative health effects when inhaled like exacerbations of asthma, chronic obstructive pulmonary disease (COPD), and premature death. The health impacts of PM depend on the physical size and chemical composition of the inhaled particles. Particles less than 2.5 micrometers can penetrate the deep lung and enter the bloodstream. Understanding the composition of PM helps study human exposures and evaluate PM sources to support control and mitigation strategies. This thesis examines PM in power plant emissions, in ambient air, and in homes, with an emphasis on characterizing hazardous metals.
PM emissions from the University of Iowa power plant were examined during a transition away from coal. Biomass is a renewable fuel and when used in place of or co-fired alongside coal it directly reduces emissions of fossil CO2 and PM to the atmosphere. PM emissions were examined under two scenarios: the first was a stoker boiler that fired 100% renewable energy pellets. PM and metal emissions reduced by 59 and 80% respectively despite increases to polycyclic aromatic hydrocarbons (PAHs) that was attributed to emission of unburned carbon fuel. The second test was done in a circulating fluidized bed boiler firing 78% oat hulls, 17% coal, and 5% energy pellets. Decreases in PM, PAHs, and metal emissions were 32, 33, and 50%, respectively. Reductions in PM, PAHs, and metals when firing renewable fuels provide environmental advantages to local air quality while trying to eliminate the use of coal.
Ambient air quality was examined downwind of the power plant. The levels of PM2.5 in Iowa City in 2016 ranged from 1.4-32.1 µg m-3 with an annual mean of 7.5 µg m-3. These levels are below the National Ambient Air Quality Standards (NAAQS) for 24-hours (35 µg m-3) and the annual average (12 µg m-3). On average, the analyzed metals accounted for 10.7 ± 5.3% of PM2.5. Potassium, calcium, and zinc were the most abundant metals (averaging 250 ± 10, 170 ± 40, and 11.2 ± 0.5 ng m-3, respectively) and are associated with geological sources and biomass burning. Metals associated with fossil fuel combustion such as arsenic, lead, or vanadium were observed at low levels (averaging 0.58 ± 0.01, 1.32 ± 0.03, and 0.19 ± 0.01 ng m 3, respectively). Harmful metals were at least an order of magnitude lower than the World Health Organization’s guideline concentrations in Iowa City PM2.5. Overall, the hazardous metals in ambient PM2.5 observed in Iowa City were not at concerning levels. The work in this chapter helps provide a metal speciation profile for future studies and these measurements can be used to assess future changes in PM2.5 metal concentrations.
Indoor PM collected in homes of Eastern Iowa COPD patients was characterized for its metal content. COPD patients are at higher risk of developing respiratory infections, which cause acute exacerbations of COPD—the leading cause of mortality in COPD patients—and airborne PM increases risk of infection. From the 21 homes studied 6-87 mg of indoor PM was collected over 30 days in winter. Crustal metals such as magnesium, iron, and aluminum were the most concentrated in indoor PM, having mass fractions from 3000-25,000 ng mg-1. Toxic metals like vanadium and arsenic were at lower levels from 3-65 ng mg-1. Between homes the relative abundance of metals was similar, but the absolute abundance was highly variable. Analyzing indoor PM is essential since Americans on average spend 80% of their day indoors making it a significant environment for PM exposure. This chapter provides a chemical profile for different homes when studying the impact PM has on respiratory health.
This thesis also provides new measurements of the chemical composition of PM at the point of emission, in ambient air, and within homes. Advancing knowledge of PM composition in different environments is vital in understanding its impacts on human health. Improvements to local air quality with reductions to PM and metal emissions were observed when firing alternative fuels. Ambient PM2.5 concentrations in Iowa City were lower than NAAQS levels and the composition of both ambient and indoor PM was evaluated. With greater understanding of PM composition, better control strategies can be studied and employed to improve local air quality.
26
Merriman, Colin Clarke. "Orientation dependence of dislocation structure evolution of aluminum alloys in 2-D and 3-D". Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Summer2007/C_Merriman_072507.pdf.
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27
Li, Ching-Chang. "Use of iterative techniques for the rigid-viscoplastic finite element analysis". Ohio : Ohio University, 1986. http://www.ohiolink.edu/etd/view.cgi?ohiou1183139974.
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28
Tappin, Alan David. "Studies of trace metals in shelf waters of the British Isles". Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330182.
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29
Banerji, Kingshuk. "Quantitative analysis of fracture surfaces using computer aided fractography". Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/15381.
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30
KJERENGTROEN, LIDVIN. "RELIABILITY ANALYSIS OF SERIES STRUCTURAL SYSTEMS (PROBABILITY, DESIGN, FATIGUE)". Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187909.
Testo completoAbstract (sommario):
Reliability analysis of series structural systems with emphasis on problems typical for metal fatigue is addressed. Specific goals include the following: (1) Given the distribution of strength of the components and the distribution of external loads on the system what is the probability of failure of the system? (2) Given the target safety index for the system, what would be the target safety index for the components? Exact solutions in the analysis of series structural systems only exists for some special problems. Some of these special problems are investigated. In particular some special cases of the problem of unequal element reliabilities are considered and some interesting observations are made. Numerical integration is in general required even when an exact solution exists. A correction or adjustment factor is developed for an important class of problems. This factor makes it possible to relate element and system probabilities of failure without numerical integration. However in most cases no exact solution to the structural series system problem exists. Approximations by for instance bounds on the probability of failure or Monte Carlo simulation has been the only way of approximating solutions. These two methods are generally not good approximation schemes since they are either too crude or too expensive. In this dissertation an approximation scheme for analysis of series systems where no exact solution exists is developed. The method only requires a simple numerical integration if the component safety index and the correlation coefficient between failure modes is known. Numerous examples are used to verify the method against known exact results and excellent estimates are obtained. Applications by practical examples is also given. In the appendix the problem of convergence of fatigue life distribution is also summarized.
31
Feinberg-Ringel, Karen Stacey. "Quantitative fractographic analysis of Al[subscript]2O[subscript]3/Al-25%Li metal martrix composite". Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/19987.
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32
Julião, Fabiana Cristina. "Avaliação das condições microbiológicas e físico-químicas da água de reservatório domiciliar e predial: importância da qualidade dessa água no contexto da saúde pública". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/22/22133/tde-18072011-105108/.
Testo completoAbstract (sommario):
Na atualidade, as questões relacionadas ao monitoramento da qualidade da água destinada ao consumo humano, têm sido motivo de preocupação nos países de todos os continentes. No Brasil, no início do século XIX, houve uma melhoria da infraestrutura das redes de abastecimento público de água, no entanto, diante das intermitências do fornecimento surgiu a necessidade da utilização de reservatórios de água para suprir a demanda diária de consumo, principalmente nas áreas urbanas. Os reservatórios podem garantir a quantidade de água necessária diariamente, porém a ausência de cuidados mínimos com a limpeza e manutenção destes recipientes podem prejudicar a qualidade da água a ser consumida. Este trabalho objetivou avaliar as condições microbiológicas e físico-químicas da água do reservatório de 217 domicílios e de 23 Unidades Básicas de Saúde no município de Ribeirão Preto-SP, a fim de se obter informações sobre a condição sanitária da água consumida após o armazenamento, bem como as ações da população relacionadas à manutenção dos reservatórios domésticos. Foram realizadas análises bacteriológicas, utilizando-se a Técnica de Tubos Múltiplos com substrato cromogênico; análise parasitológica a partir da sedimentação espontânea e análise para metais através de Espectroscopia com Plasma Induzido-Espectroscopia de Massa. A partir da coleta de dados foi evidenciado que a população tem informações sobre a necessidade da limpeza do reservatório domiciliar, porém não a realiza no período recomendado, apesar da água armazenada neste local ser comumente utilizada para atividades de higiene pessoal e limpeza doméstica. Os resultados das análises e os testes estatísticos revelaram valores que se enquadram aos parâmetros recomendados pela Portaria 518/2004 do Ministério da Saúde. A água do município é proveniente de um manancial subterrâneo e o monitoramento de suas características é realizado periodicamente pela instituição municipal responsável pelo abastecimento público e esses fatores têm colaborado para a manutenção da qualidade da água fornecida em Ribeirão Preto-SP. O uso rotineiro da água do reservatório diminui o tempo de armazenamento, mantendo condições sanitárias adequadas, no entanto, a população necessita ser sensibilizada sobre a importância da limpeza e manutenção dos recipientes para garantir o consumo de água segura, evitando riscos à saúde da população.Issues related to the monitoring of the quality of water destined for human consumption have been a concern around the world. The public water supply infrastructure was improved in Brazil at the beginning of the 19th century, however intermittent water supply requires the use of water reservoirs to meet the demand of daily consumption, especially in urban areas. Reservoirs can ensure the quantity of daily water requirements, but a lack of minimum care concerning cleaning and maintenance of such reservoirs may threaten the quality of water to be consumed. This study evaluated the microbiological and physiochemical conditions of water in the reservoirs of 217 houses and 23 Primary Health Units in Ribeirão Preto, SP, Brazil to obtain information concerning the sanitary condition of water consumed after storage, as well as actions on the part of the population related to the maintenance of domestic reservoirs. Bacteriological analyses were performed using the Multiple Tube method with a chromogenic substrate; parasitological analysis based on spontaneous sedimentation and analysis of metals through Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS). The data collections revealed that the population is aware of the need to clean house reservoirs. However, they do not perform it within the recommended period, even though they use the water stored for personal hygiene and domestic cleansing. The results of the analyses and statistical tests revealed values that fall within the parameters recommended by Ministry of Health Decree 518/2004. The water in the city comes from an underground spring and the company responsible for the city\'s public supply monitors its characteristics periodically; factors that collaborate in the maintenance of the quality of the water supplied in Ribeirão Preto, SP, Brazil. The routine use of water from the reservoir reduces the storage time keeping appropriate sanitary conditions. The population, though, needs to be regularly sensitized of the importance of cleaning and maintaining this reservoir to ensure safe water consumption and to avoid risks to the health of population.
33
Minnaar, Karel. "Comparison and analysis of dynamic shear failure behavior of structural metals". Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/16340.
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34
Mattisson, Emmy. "Increased leaching of metals as a result of foundation work". Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232049.
Testo completoAbstract (sommario):
Heavy metal contamination in the environment is a global issue that is likely to increase in the future. This report investigates a construction area in which increased concentrations of the heavy metals cadmium, cobalt, copper, nickel and zinc and a decreased pH-value has been observed in the surface water recipient. The focus is on assessing contamination characteristics and identifying suitable remediation methods to avoid a river protected by environmental quality standards further downstream from getting contaminated. The bedrock in the area is sulphide containing and releases acidic leachate when oxidising, which is assumed to have occurred due to plane blasting and filling of residual rock. The contamination characteristics were assessed with the statistical methods modified double mass analysis and principal components analysis. A water balance was established to obtain the flowrates, discharge volumes and to determine the masses of the released metals in the surface water. Identification of suitable remediation methods was performed through a literature study of available remediation methods and using the findings of the assessments as basis. The results showed that there was a significant increase in metal concentrations and decrease in pH-value roughly around the same time as blasting and filling of residual rocks in the area was begun and that there were elevated levels of sulphide and sulphur, but they could not be specifically linked to any media. The yearly masses of metals released from the area into the surface water were between 77-98 % higher than allowed by the established guidelines. By separating the water assumed to carry the majority of the contaminants from the remaining natural water in the watershed, the volume that needs to be treated can be halved. As the contamination is so extensive, a mixture of remediation methods was proposed, including installing green roofs to decrease the runoff from the area, confining the crushed rock with bentonite and installing a filter for fast, efficient reduction. For long-term remediation, it is suggested to optimise the existing sedimentation basins and wetlands. The conclusions were that it will be very expensive to remediate the contamination, due to the extent and magnitude, and that handling sulphide containing bedrock for construction purposes should be legally regulated in order to avoid negative environmental and economic impacts.Förorening av tungmetaller i naturen är ett globalt problem som troligtvis kommer öka i framtiden. Den här rapporten undersöker en byggarbetsplats där ökade koncentrationer av metallerna kadmium, kobolt, koppar, nickel och zink samt ett minskat pH-värde har observerats i ytvattenrecipienten. Fokus ligger på att analysera föroreningskaraktärer och identifiera lämpliga åtgärdsmetoder för att undvika att en å nedströms som är skyddad av miljökvalitetsnormer ska förorenas. Berggrunden i området är sulfidförande och släpper ut surt lakvatten när den oxiderar, vilket är antaget har hänt till följd av plansprängning och utfyllnad av överblivet bergmaterial. Föroreningskaraktärerna analyserades med de statistiska metoderna modified double mass analysis och principalkomponentsanalys. En vattenbalans etablerades för att ta fram flöden, volymer och för att bestämma massorna av de frigjorda metallerna i ytvattnet. Identifiering av lämpliga åtgärdsmetoder gjordes med en litteraturstudie av tillgängliga metoder som grund. Resultaten visade att det är en signifikant ökning av metallkoncentrationer och minskning i pH-värde runt samma tid som sprängning och utfyllning av bergmaterial påbörjades samt att det är förhöjda halter av sulfid och svavel, men de kunde inte bli associerade med ett specifikt media. De årliga massorna av frigjorda metaller som släpps ut från området i ytvattnet är mellan 77-98 % högre än tillåtet av de etablerade riktlinjerna. Genom att separera vattnet som kan antas innehålla majoriteten av föroreningarna från det naturliga vattenflödet i avrinningsområdet kan volymen som behöver renas halveras. Eftersom föroreningen är så omfattande föreslås en kombination av åtgärdsmetoder; installation av gröna tak för att minska avrinningen från området, inneslutning av utfyllnadsmaterialet med bentonit och installation av ett filter för snabb, effektiv reduktion. För mer långsiktig rening föreslås det att optimera de existerande sedimentationsdammarna och våtmarken. Slutsatsen är att det kommer bli väldigt dyrt att åtgärda föroreningen på grund av dess omfattning, och hantering av sulfidförande berg för exploateringssyfte borde vara lagstadgat för att undvika miljömässiga och ekonomiska kostnader.
35
Hewitt, C. D. "The development and application of trace metals analysis in clinical chemistry". Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377737.
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36
Bi, Zhaoshun. "Speciation analysis of trace metals in natural waters using vibrating electrodes". Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/9375/.
Testo completoAbstract (sommario):
The speciation of trace metals plays a very important role in conditioning their biogeochemical cycles in the marine system. Their species are found to be strongly related to organic matters such as humic acids (HA) and fulvic acids (FA). This thesis aims to develop appropriate techniques to improve our understanding of the speciation of some trace metals, mainly in marine waters. Lead (Pb), cadmium (Cd) and chromium (Cr) which are widely used in industry were analytzed. The concentration of lead in uncontaminated seawater is between 10 and 100 pM, whilst in coastal waters it is higher at up to low nanomolar levels. Little is known about the chemical speciation of lead since it is difficult to be determined at picomolar levels. The work in this dissertation was to develop a suitable electrode and procedure to determine lead in seawater, with the objective that the electrode could be applied for in-situ measurement (without reagents) and for speciation. Several electrodes and materials were tested, including a solid bismuth rod and different microwire materials. Vibration was used to enhance mass transport, instead of solution stirring, to decrease detection limits and facilitate in-situ monitoring. The bismuth electrode was found to be suitable for monitoring lead in coastal waters: it is mercury-free and therefore environmentally friendly, but insufficiently sensitive for oceanic lead concentrations. Comparison of microwires of carbon, gold and silver showed that all of these bare electrodes give a signal for lead, but they suffer variable interference from cadmium, although this is minor if the cadmium concentration is lower than lead. A large improvement was obtained by coating the electrodes with mercury, which gave good peak resolution between cadmium and lead, and good sensitivity. The carbon and gold electrodes had good reproducibility and sensitivity when the mercury was renewed for each measurement. Once coated with mercury, the silver electrode formed amalgam with the silver which could not be completely removed. This electrode was thus not suitable to be used as a renewable mercury film electrode. However, as a permanently amalgamated silver electrode, it was found to have good sensitivity for lead, good separation from cadmium, and was stable for long time usage. This electrode, the silver amalgam microwire (SAM) electrode, was selected for further speciation study of Pb in oceanic waters. Optimum conditions for using the SAM electrode for trace lead detection in seawater involve the use of conditioning potentials. The limit of detection for lead was 4 pM lead in acidified seawater and 12 pM lead in seawater of pH 8. The higher limit of detection at pH 8 is due to the inorganic speciation at that pH. The SAM electrode was successfully used for pseudopolarography of lead to determine its organic complexation. This method was calibrated using model compounds and applied for the first time to estuarine, coastal and oceanic samples at natural concentrations of Pb. It was found that lead occurs mostly as a labile (reactive, organic) species, with a smaller fraction as a strongly organically bound species. The SAM electrode was also tested for chromium analysis using cathodic stripping voltammetry (CSV) in natural waters. Its detection limit is as good as the mercury drop electrode but reduces consumption of mercury.
37
Zhou, Yan. "Synthesis, photophysical and biological studies of lanthanide complexes for photodynamic therapy". HKBU Institutional Repository, 2017. https://repository.hkbu.edu.hk/etd_oa/467.
Testo completoAbstract (sommario):
1.2\xPrior to the PDT, we have also synthesized a series of water-soluble homoleptic lanthanides (Ln3+ = Gd, Er, and Yb) sandwich (DD) di-PEGylated porphyrin complexes. The Yb complex (YbDD) has shown the same NIR emission quantum yield as the highest record Yb complex in the literature (Yb-RhB), yet, the emission intensity is double compared to the Yb-N. This implies a new thinking about the quantity measurement for biological imaging. The brightness might be the prime factor for the development of luminescence in vitro/in vivo imaging agent rather than the emission quantum yield.
38
Watkins, Gareth Mostyn. "Ligand isotope vibrational studies of metal(II) complexes with particular reference to heterocyclic N-oxides". Doctoral thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/17042.
Testo completoAbstract (sommario):
Includes bibliographical references.A critical examination of the characteristic N-O vibrational frequencies of aromatic N-oxides questions the widely held assignment of αN-O (840cm⁻¹) and YN-O (47oon- 1). The present investigation supports the assignments of αN-O (470cm⁻¹) and γN-O (280cm⁻¹), with the assignment of the band at 840cm⁻¹ as being vring coupled with νN-O.
39
Roy, Ajay K. Payton Lewis Nathaniel. "Finite element analysis and life estimation of a permanent cylidrical mold with Ansys and Coffin-Manson approach". Auburn, Ala., 2005. http://hdl.handle.net/10415/1283.
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40
Tanha, Ariana, e Daniel Zarate. "Landfill Mining: Prospecting metal in Gärstad landfill". Thesis, Linköpings universitet, Industriell miljöteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-86427.
Testo completoAbstract (sommario):
All processes in society produce waste. In nature, the waste is normally used as a resource for another process, but in human societies waste is often discarded. These discarded materials end up in places for depositing waste known as landfills. The increase in population, and humans’ tendency to improve their quality of life, has led to an increase in consumption of material. More material consumption means generating more waste, and more waste means bigger landfills. The increasing size of landfills has brought some other issues, such as increased land use and higher environmental impact. However in these landfills a lot of valuable materials are discarded and the concept of landfill mining (LFM) has been proposed in order to solve these issues and use landfills as a possible source of materials. Landfill mining is not yet a common practice, and the first barrier for this is the uncertainty of the amount and value of materials within landfills. The purpose of this study is to prospect the amount of metals in one specific landfill, in this case Gärstad landfill in Linköping, Sweden. This is a first step to show the feasibility of landfill mining as an alternative way of extracting materials. The study is limited only to metals because they are one of the most important resources in today’s society. The theoretical background of the study is based on material flow analysis (MFA). Two approaches are used to study the materials in the landfill. The first is top-down which studies the flows of materials and the second is bottom-up which studies the stocks of material in the landfill. Based on these approaches the method was developed. First the system boundaries in time and space were defined. Then the amount of waste in landfill was estimated from the two mentioned approaches. In the end the metal content of the waste was estimated. Some criteria are also defined to compare the accessibility of the metals in the landfill. The results of this study show that there is a considerable amount of metals in the landfill, and that ash deposits resulting from incineration are the most interesting source of metals; with iron, aluminium, copper and zinc being the most abundant. The results are presented by type of waste, area of the landfill and accessibility in order to identify the hotspots. Later it is discussed that the method is cheap and fast but highly depends on previous data and available information. Also the metal content of the landfill is compared with natural ores. In the end the metal content of the landfill is evaluated and estimated to be around 3 billion SEK. It shows that aluminium, titanium and copper have the highest value money wise. As conclusion it was shown material flow analysis is a valid way to prospect landfills. But further cost-benefit analysis must be carried out to determine if landfill mining is justifiable. Also some recommendations are proposed to Tekniska Verken in order to facilitate future studies. The first is to develop a systematic way for landfilling different kind of waste and document them. Second is to include metals which have economic potential in the regular sampling from landfill.Många processer i samhället generar avfall. I naturen används avfallet normalt som en resurs i en annan process, men i människliga samhällen kastas avfallet oftast bort. Bortkastat material hamnar förr eller senare oftast i deponier. Befolkningsökningen och människans tendens till att försöka förbättra sin livskvalitet har lett till en ökad materialkonsumtion. Högre konsumtion genererar mer avfall, och mer avfall kräver större deponier. Växande avfallsanläggningar leder i sin tur till ökad markanvändning och högre miljöpåverkan. I dessa anläggningar finns det emellertid stora mängder värdefullt material deponerat, och från dessa läcker både tungmetaller och metan ut, vilket är skadligt för miljön. Landfill Mining (LFM) har föreslagits som en lösning på dessa problem och avfallsanläggningarna används då även som en möjlig källa till material. Landfill mining är idag inte vanligt förekommande och det huvudsakliga hindret är de många osäkerheterna kring ett sådant projekt, till exempel; hur mycket material finns i deponierna och hur mycket är det värt? Syftet med den här studien är att uppskatta metallinnehållet i en specifik avfallsanläggning, i det här fallet Gärstad avfallsanläggning i Linköping. Detta är ett första steg i att utröna genomförbarheten av LFM som en alternativ resursbas. Studien är begränsad till metaller eftersom dessa håller på att ta slut i jordskorpan och det vore därför intressant att finna nya materialkällor till dessa. Den teoretiska bakgrunden till den här studien är baserad på materialflödesanalys (MFA). Två metoder har använts för att prospektera Gärstad. Dels top-down, som studerar flödet av material, dels bottom-up, som studerar materialförrådet i avfallsanläggningen. Avfallens totalmängd var uppskattad genom att beräkna flödet in och ut från anläggningen. Sedan använde vi tidigare gjorda provtagningar av avfallets metallmängder för att uppskatta metallinnehållet. Slutligen analyserades metallernas tillgänglighet baserad på typ av avfall, och om deponi delområdet var sluttäckt. Resultatet visar att det finns mycket metaller deponerat i Gärstad. Askan från avfallsförbränningen visade sig vara den avfallstyp med rikast metallinnehåll. Järn, aluminium, koppar och zink är de vanligaste förkommande metallerna. Metallkoncentrationen av avfallsanläggningen kan jämföras med naturliga malmer. Värdet av metallerna i Gärstad uppgår till cirka 3 miljarder. Dock är endast 30 % av metallerna tillgängliga med dagens teknik. De största värdena finns enligt följd i aluminium, titan och koppar. För att identifiera hotspots, redovisas resultatet enligt avfallstyp, lokalisering och tillgänglighet. MFA är ett fungerande prospekteringsverktyg för deponier. Metod är billig och snabb men beroende av att det finns tillgänglig data. Innan deponin transformeras till en gruva bör emellertid först en kostnad och nyttoanalys genomföras för att undersöka genomförbarheten vidare. Rekommendationer för att underlätta framtida utgrävningar är att utveckla ett systematiskt sätt att deponera olika typer av avfall och att dokumentera dem. De metaller som har ekonomisk potential bör dessutom inkluderas vid den normala provtagningen av deponerat avfall.
41
Mukunthan, Kannappar. "Properties of ultra fine grain [beta]-CuAlNi strain memory alloys". Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26724.
Testo completoAbstract (sommario):
A method has been developed to produce grain sizes as low as 5µm in β-CuAlNi alloys and the effect of grain size on mechanical and strain-memory properties was studied. The thermomechanical treatment procedure involved two. sequential warm working and recrystallization steps at 600° C and 800° C respectively on eutectoid alloys. Three different eutectoid alloys, two with Ms temperature of around 0°C and one with Ms = 220° C were used for the present studies. Even at fine grain sizes, the specimens produced were of single β- phase type without any second phases.
Two-stage characteristic stress-strain curves were obtained for most of the specimens in both the strain memory and pseudoelastic states. It was found that the ultimate tensile strength and strain to failure increased with decreasing grain size according to a Hall-Petch relationship down to a grain size of 5µm with the exception of one alloy. Fracture strengths of 1,200 MPa and fracture strains of 10% could be obtained.
It was found that the major recovery mode, whether pseudoelastic or strain memory, did not have any significant effect on the total recovery obtained. Recovery properties were not affected significantly by decreasing grain size. Approximately 86% recovery could be obtained for an initial applied strain of 5% at a grain size of around 10µm.
Grain refinement increased the fatigue life considerably, possibly due to high ultimate fracture strength and ductile fracture mode. Fatigue life of 275,000 cycles could be obtained for an applied stress of 330 MPa and a steady state strain of 0.6%.
Most of the fractures are due to intergranular-type brittle fracture. At fine grain sizes, transgranular-type brittle fracture and microvoid coalescence-type ductile fracture dominated the fracture mode. Oxygen segregation at grain boundaries is the possible explanation for the different mechanical properties shown by different alloys in the present work by being a major factor in causing intergranular-type fracture.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
42
Mason, Christopher James. "The use of microwave flow-through digestion in the analysis of trace metals and total nitrogen in soils". Thesis, University of Greenwich, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325665.
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43
Smith, Debbie A. "Analytical Methods for Toxic Metals and Proteins and Synthesis of Perovskites". Youngstown State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1289923061.
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44
Rossin, Joseph A. "Synthesis, characterization and reactivity of transition metal containing zeolites". Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/76271.
Testo completoAbstract (sommario):
Transition metal containing zeolites (zeolite A and ZSM-5) were prepared by addition of various transition metal containing substrates to zeolite synthesis gels. Crystal growth data were recorded in order to determine the influence of the transition metal species on the rate of crystal growth. X-ray diffraction, oxygen adsorption, FTIR and SEM were utilized to evaluate crystal purity. X-ray photoelectron spectroscopy (XPS), chemical analysis and electron microprobe analysis were performed in order to ascertain the position (intrazeolitic versus surface) and homogeneity of the transition metal. It was concluded that intrazeolitic transition metals were produced by the novel procedure presented in this work.
1-Hexene hydroformylation by rhodium zeolite A showed intrazeolitic rhodium to migrate to the external surface of the zeolite. However, in the presence of a solution and surface rhodium poison, intrazeolitic rhodium was found to hydroformylate 1-hexene exclusively to heptanal.
Ruthenium containing zeolite A was evaluated under CO-hydrogenation conditions. No migration of intrazeolitic ruthenium to the external surface of the zeolite was observed over the course of the reaction. The product distribution obtained for this catalyst did not follow a log normal behavior. Also, loss of zeolite crystallinity was observed following the reaction.
Cobalt ZSM-5 was evaluated under CO-hydrogenation conditions. No migration of cobalt to the external surface of the zeolite occurred. XPS analysis of the catalyst following various stages of the reaction indicated that intrazeolitic cobalt was not reduced to the zero valent state. Consequently, the non-zero valent cobalt was not capable of hydrogenating carbon monoxide.Ph. D.
45
Cho, Hyunjoong. "Development of advanced techniques for identification of flow stress and friction parameters for metal forming analysis". Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1167699938.
Testo completo
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Vähäoja, P. (Pekka). "Oil analysis in machine diagnostics". Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514280768.
Testo completoAbstract (sommario):
Abstract
This study concentrates on developing and tuning various oil analysis methods to meet the requirements of modern industry and environmental analytics. Oil analysis methods form a vital part of techniques used to monitor the condition of machines and may help to improve the overall equipment effectiveness value of a factory in a significant manner.
Worm gears are used in various production machines, and their breakdowns may cause significant production losses. Wearing of these gears is relatively difficult to monitor with vibration analysis. Analysis of two indicator metals, copper and iron, may reveal wearing phenomena of worm gears effectively, and savings can be significant.
Effective wear metal analysis requires good tools. ICP-OES with kerosene dilution is widely used in wear metal analysis, but purchasing and using of ICP-OES is expensive. A cheaper FAAS technique with similar pre-treatment of oil samples was tested and it proved to be useful especially in analyzing small amounts of samples. The accuracy of FAAS was sufficient for quantitative work in machine diagnostics and waste oil characterization. Solid debris analyses are useful in oil contamination control as well as in detection of wearing mechanisms. Membrane filtration, optical microscopy, SEM and automatic particle counting were applied in analysis of rolling and gear oils. Particle counting is an effective way to detect oil contamination, but in the studied cases even larger particles than those detected in normal ISO classes would be informative. However, membrane filtration and optical microscopy may reveal the wearing machine element exactly. Additives provide oils with desired properties thus they should be monitored intensively. A FTIR method for quantitative analysis of fatty alcohols and fatty acid esters in machinery oils was developed during this work. It has already been used successfully in quantitative and qualitative analysis of machinery oil samples.
Various kinds of oils may be spilled into the soil during use and in accident situations, and they can migrate to groundwater layers. Biodegradation of oils can remove them from the soil or water completely or at least diminish the amount of harmful substances. An automatic, respirometric BOD OxiTop method was used to evaluate the biodegradability of various oils in water and soil media. The biodegradation of certain bio and mineral hydraulic oils was evaluated in groundwater, where bio oils usually biodegraded more effectively than mineral oils. The use of oils in machines weakened especially the biodegradability of bio oils. Biodegradability of bio oils was also studied in standard conditions of OECD 301 F and bio oils usually biodegraded moderately good in these conditions. The biodegradation of forestry chain oils and wood preservative oils was evaluated in forest soils. Linseed oil biodegraded moderately, but certain experimental wood preservatives biodegraded more effectively. Widely used creosote oil biodegraded in a lesser degree. Rapeseed oil-based chain oils biodegraded more effectively than corresponding tall oil.
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Jones, Brittany Laurél. "Econometric analysis of the historical growth and volatility trends of various metals". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76124.
Testo completoAbstract (sommario):
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 58-59).
Post Malthusian economics, there is growing recognition of the impact technological change and advance has on market activity. By studying historical production and price trends, boundaries of feasible growth can be determined and, dependent on a firm's goals, materials that may require added recyclability, substitution, or engineering efficiency identified. Therefore, a contextual understanding of growth and volatility can mitigate negative economic impacts. This study involved the econometric analysis of a 16-metal survey. Various analysis techniques were used to determine historical growth and volatility trends of both industrial and precious metals. For this data set, a typical sustained annualized growth rate of production was between 0.0% and 5.0% based on 20-year CAGR data. Price growth tended to range between -2.5% and 2.5% for 20-year time frames but was much more volatile in the short-term. From 1979 to 2009, 56% of all annual value growth rates were greater than +10.0% or less than -10.0%. Additionally, several metals had coefficients of variation greater than unity thereby being classified as hyper-variant. While the premise of a commodities exchange is to heighten the predictability of value, little difference of price volatility was found between metals on (0.28) and off (0.31) open exchanges. Aside from the survey, case studies of tantalum and niobium were completed. These co-mined materials appeared to have a strong correlation with their price growth as well as their production trends.
by Brittany Laurél Jones.
S.B.
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Abbas, Naseeba. "Analysis of phase transformations in hydrogenated titanium metals by non-isothermal dilatometry". Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/12339.
Testo completoAbstract (sommario):
Includes bibliographical references (leaves 124-127).Hydrogen was used as a temporary alloying element in CP Ti and Ti-6AI-4V. The microstructural evolution and phase transformations were monitored, before, during and after hydrogenation with in-situ dilatometric testing. Wrought CP Ti and Ti-6AI-4V specimens were pre-annealed and experienced four consecutive thermal cycles (Cycles 1-4) i.e. hydrogenation, post-hydrogenation, dehydrogenation and post-dehydrogenation, during dilatometric testing. The specimen in each thermal cycle was heated to 1000°C, heating rate 1°C/min (with an isothermal hold at 1000°C for three hours for hydrogenation and dehydrogenation cycles) and then cooled to room temperature at cooling rate of 1°C/min.
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Mitchell, Linda. "Fluorescent sensor arrays to monitor heavy metals and therapeutic drugs in biological systems". Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/26168.
Testo completoAbstract (sommario):
Sensitive and rapid detection of chemical analytes is a widespread challenge, particularly in areas with limited access to technical facilities. Optical sensor arrays are a promising technique to address this challenge as they can detect chemical analytes in environmental and biological fluids. There are many analytes with no suitable on-site detection methods, and to address this gap, this work outlines the development of several new systems.
A set of coumarin sensors were investigated to determine a candidate for heavy metal sensing. Of the four sensors and solvents investigated, a thiocoumarin sensor was identified as the best candidate, enabling the sensitive detection of seven heavy metals in a multi-solvent system.
Platinum chemotherapy treatment is often limited by side effects and varied patient tolerance. Therapeutic drug monitoring offers an opportunity to address the potential issue of ineffective dosing protocols. A fluorescent sensor array was designed to distinguish between platinum complexes with diverse coordination environments. The array system was able to monitor platinum levels in clinical samples from patients undertaking platinum-based chemotherapy.
Polymer materials are also promising candidates for sensor array applications. Six polymers with various functionality were synthesised, and one polymer modified with a coumarin fluorophore. The fluorescent polymer was investigated using a variety of analytes and solution conditions. Upon testing with a library of antibiotics, the polymer displayed a unique fluorescence response to each antibiotic, a promising result for future sensor array applications.
This work has contributed significant progress towards the detection of chemical analytes in complex fluids and outlines the importance of developing new strategies for monitoring chemical analytes in environmental and clinical applications.
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Mahenthirarajah, Thushitha. "Synthesis and characterisation of electronically active species". Thesis, University of St Andrews, 2009. http://hdl.handle.net/10023/954.
Testo completoAbstract (sommario):
An exploration of some early transition metal (oxy) fluoride systems using solvothermal techniques has been carried out. 30 novel materials have been synthesised, which fall into three classes based on different metal centres; vanadium (21), molybdenum (5) and niobium (4). Some of these also contain secondary metal centres, namely copper (22) and zinc (1). Simultaneously, the relationship between the SHG values and the crystal structures of the hilgardites family members Pb₂B₅O₉Cl, Pb₂B₅O₉Br, Sr₂B₅O₉Cl and Ba₂B₅O₉Cl was investigated. In particular, the Pb–containing members of the hilgardite family of borate halides exhibit an abnormally large non–linear optical response, which was analysed based on neutron powder diffraction. Using solvothermal synthesis in HF–containing media, 21 novel vanadium oxyfluorides containing interesting structural features, were synthesised at 160˚C using a range of organo-amine compounds as a ligand, template, linker or structure directing agent. The architectures of the crystal structures may be categorised into; four clusters including monomeric vanadium units, five clusters including vanadium dimers, eight 1–D chains, two 2–D layers and two 3–D networks. ‘Composition–space’ diagrams with three components were used to study the effect of stoichiometry changes of reactants and to map out the crystallisation fields. The combination of early (Nb⁵⁺, Mo⁶⁺) and late (Cu²⁺) transition metals with different organo-amines produced nine novel compounds incorporating monomers, chains and 2– D interpenetrated networks. The chains and layers were synthesised from a systematic series of reactions at 160˚C and can be subdivided into four pairs, the topologies of which are essentially unique to each ligand, containing in each case a Cu–based cationic species, but alternately either [MoO₂F₄]²⁻ or [NbOF₅]²⁻, in an isomorphous manner, as the anionic moiety. The overall structures of these materials reflect the influence of the organo–amine ligands. The materials have been studied for their magnetic properties and characterised by thermogravimetric analysis, Rietveld refinement and elemental analysis where relevant.