Academic literature on the topic 'Micro deposits'
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Journal articles on the topic "Micro deposits":
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Zhu, Feng, Jiujun Xu, Xiaoguang Han, Yan Shen, and Mei Jin. "Deposit formation on chromium-plated cylinder liner in a fully formulated oil." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 230, no. 12 (November 12, 2016): 1415–22. http://dx.doi.org/10.1177/1350650116636508.
Abstract:
Chromium plated cylinder has been wildly used in large bore diesel engines due to its light weight, good durability, and low induced liner wear. Deposits accumulated in the grooves and micro-crack on chromium plated cylinder could smooth the running surface, reduce the oil retention capability, and increase the engine’s oil consumption. In the present research, deposit formation on chromium-plated cylinder in fully formulated oil under different loads and temperatures was investigated by using a reciprocating sliding tester. Surface analytical techniques such as SEM, EDX, and XPS have been used to gain the knowledge about deposits’ origin, distribution, and factors affecting the deposit formation. The deposits are mainly derived from C, O, and S in the lubricating oil and anti-wear additive ZDDP (Zn and P). Deposits only accumulated in the depression (honing grooves and micro-cracks) on chromium plated cylinder surface, and there were no deposits found on the plateaus. The deposit formation increased with the increasing of load and temperature, and increased sharply over 60 MPa and 150℃. The deposit formation on liner surface was significantly different between chromium-plated coating and cast iron in component and distribution.
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Leonova, L. V., A. A. Galeev, and A. A. Galeev. "Microfossils in bottom-hydrothermal sediments of the Saf'yanovskoe Cu-Zn deposit (Middle Urals)." LITHOSPHERE (Russia) 22, no. 3 (July 2, 2022): 376–90. http://dx.doi.org/10.24930/1681-9004-2022-22-3-376-390.
Abstract:
Research subject. Framboidal pyrites and sulfide micro-concretions in carbonaceous-siliceous and ore rocks of the Safyanovskoye deposit (Middle Urals). Aim. To identify the signs of vital activity of microbial communities in bottomhydrothermal deposits using the example of the Safyanovskoye sulfide deposit. The methods. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). Results. TThe analyzed ore and carbonaceous-siliceous rock samples showed the presence of mineralized silicon dioxide films covering framboidal pyrites. Micro-concretions were found to consist of microfossils of filamentous organisms and framboids. Pyrite samples included the remains of tubular casts of sulfidized vestimentifera and polychaetes, associated with framboids. The possibility of using fossilized remains of microbial communities for distinguishing bottom-hydrothermal facies among pyrite deposits was confirmed. Conclusions. Hydrothermal-sedimentary deposits are characterized by the traces of specific microbial communities, since prokaryotic organisms were pioneers in hydrothermal oases. Their long active existence created a basis for the second trophic link, i.e. filter feeding macrofauna and endosymbiotrophs. These organisms, in turn, formed another level in the food chain of the trophic pyramid. It is believed that micro-concretions and framboidal pyrites are indicators of the vital activity of microbial communities.
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Jhavar, S., C. P. Paul, and N. K. Jain. "Experimental investigation on geometrical aspects of micro-plasma deposited tool steel for repair applications." International Journal of Modern Physics: Conference Series 32 (January 2014): 1460347. http://dx.doi.org/10.1142/s2010194514603470.
Abstract:
Recent advancement in direct material deposition processes found wide applications in rapid prototyping, manufacturing and tooling industry. Micro-plasma deposition is one of the recent developments in this domain. This paper reports the deployment of newly integrated micro-plasma deposition system for the deposition of AISI P-20 tool steel on the AISI P20 tool steel substrate. A number of test tracks for single track deposition were deposited at the various combination of processing parameters. The sets of parameters yielding good deposits were selected to deposit overlap tracks. The geometry of single and overlapped tracks was evaluated to understand the parametric dependence. The study indicates that the aspect ratio of track geometry (ratio of width to height of track) is dependent on the processing parameters and the discharge current is identified as the most dominating parameters (contribution = 44%), followed by scan speed (contribution = 26.68%) and wire feed rate (contribution = 26.98%) with almost same effect. The microscopic study of the deposits indicates that the material deposited at the optimum processing parameters is free from surface and bulk defects. The estimated material properties are found to be at par with conventional processed material. This feasibility study proved that the micro-plasma deposition can be used for the generation of surfaces and multi-featured material deposition. It paved a way for the application of the process in die/mold repairs.
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Renna, Gilda, Paola Leo, and Caterina Casavola. "Effect of ElectroSpark Process Parameters on the WE43 Magnesium Alloy Deposition Quality." Applied Sciences 9, no. 20 (October 17, 2019): 4383. http://dx.doi.org/10.3390/app9204383.
Abstract:
This research aims to investigate the effects of process parameters on the quality of WE43 coatings deposited on homologue substrate by ElectroSpark Deposition (ESD) technology. ESD is new technology used to apply coatings or for the restoration and refurbishment of worn or damaged high valued parts. The depositions were processed using five different levels of Energy input (Es, Spark Energy). The microstructure of both the base material and deposits cross-section were characterized by optical and scanning electron microscopies. Also, X-ray diffraction technique was used. In addition, stereological studies of the through-thickness heterogeneities of the deposits (e.g., voids) were performed. The mechanical properties were evaluated by Vickers micro-hardness. The results show that the deposits exhibited a fine grained microstructure due to the rapid solidification. The average micro-hardness values of the deposits are lower than that of the substrate and distributed in a small range (49–60 HV). The lower hardness of the deposits respect to the base material is due to the presence of defectiveness such as spherical, laminar and random shaped voids. The defects area percentage inside the deposits remains well below than 11%. All the deposits were mainly affected by laminar morphology defects. The results indicate that the deposits defectiveness decreases as the energy input increases.
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Bhat, Ramesh Sooryanarayana, Manjunatha Krishna Balakrishna, Poornesh Parthasarathy, and Ampar Chitharanjan Hegde. "Structural Properties of Zn-Fe Alloy Coatings and Their Corrosion Resistance." Coatings 13, no. 4 (April 15, 2023): 772. http://dx.doi.org/10.3390/coatings13040772.
Abstract:
Single-layer and multilayer alloy deposits were coated onto a mild steel substrate by a single-bath electroplating process. The developed coating consists of Zn and Fe alloys having different compositions with different layers. The anticorrosion behavior of single-layer and multilayer deposits was evaluated by the potentiodynamic polarization method. The surface morphology of the deposits was studied with a scanning electron microscope. The crystal structure of the deposits was analyzed with the X-ray diffraction technique. The Fe content in the deposit was analyzed by a colorimeter and verified with energy-dispersive X-ray spectroscopy. The micro-hardness tester with a Vickers indenter was used to evaluate the microhardness of the developed single-layer and multilayer coatings. It was found that the microhardness increased with applied current densities. The Zn-Fe multilayer coatings with 300 layers deposited with square and triangular pulses at the applied current density of 2.0/3.0 A dm−2 were five and four times more corrosion-resistant, respectively, than the single-layer coating of the same thickness. The development of Zn-Fe coatings that are resistant to corrosion is particularly important for the automotive industry and steel-based vehicle parts.
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Macuda, Jan, Paweł Baran, and Marian Wagner. "Evaluation of the Presence of Methane in Złoczew Lignite: Comparison with Other Lignite Deposits in Poland." Natural Resources Research 29, no. 6 (May 16, 2020): 3841–56. http://dx.doi.org/10.1007/s11053-020-09691-7.
Abstract:
Abstract Catastrophic cases of methane explosion during exploratory drilling within the Bełchatów ortholignite deposit have led to testing for methane in other Polish ortholignite mining areas, as well as in the Złoczew deposit, where it is planned to begin mining operations. Initial tests have shown Złoczew lignite to have the highest methane content among the Polish deposits so far studied, comparable with lignite from the Bełchatów deposit, with a methane capacity in excess of 2.5 dcm3/kg at a pressure of 10 bar. Based on the computed values of the Langmuir constant, a determination was made of the quantity of methane that can be desorbed from a pressure of 10 bar to 1 bar, as well as the residual methane content. For all of the tested samples, the residual methane content is between 30 and 50% of the sorption capacity at a pressure of 10 bar. The thermal sorption equations were used to compute values of the limiting isosteric heat of adsorption. Higher values of the heat of adsorption at zero surface capacity may indicate the presence of a small quantity of micro-pores. In the case of the samples with the highest sorption capacity, the limiting isosteric heats of adsorption are low, indicating a low proportion of micro-pores in the lignite. This was confirmed by tests of nitrogen adsorption at 77 K. The proportion of micro-pores in the studied lignites is 2–3%, while the dominant pore fraction is the meso-pores, which in lignite from the Złoczew and Bełchatów deposits account for 50–66% of total pores. It is concluded that the significant adsorption of methane in the ortholignite occurs chiefly in meso-pores because of compression of the gas under increased orogenic pressure. A link is made between the higher methane-bearing capacity of the ortholignite deposits and the degree of gelification of the huminite components, based on simple statistical correlations between the methane sorption capacity and the content of humic gelified maceral. The results concerning methane sorption in lignite from the Złoczew deposit have enabled a preliminary classification of the methane-bearing capacity of Polish ortholignite deposits, which may also be of significance for similar deposits in other countries.
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Zhang, Chun Hua, Chao Wang, Song Zhang, Ming Sheng Wang, Yu Jiang Xie, and Jun Zhe Tan. "Growth Mechanism of Micro-Arc Spark Deposited Stellite Alloy Coatings." Applied Mechanics and Materials 455 (November 2013): 83–87. http://dx.doi.org/10.4028/www.scientific.net/amm.455.83.
Abstract:
Micro-arc spark deposition with Stellite6 alloy as the coating material on SCH13 steel substrates was carried out using high-energy micro-arc process with different processing parameters. The microstructure, chemical compositions and phase identification of the deposition layers were examined by using scanning electron microscopy (SEM), energy dispersive Xray spectroscopy (EDS) and X-ray diffraction (XRD), respectively. Meanwhile the form and growth mechanism of a single pulse deposit were focused on. The results show that the morphology of the single pulse deposit is splashshape. A large number of single pulse deposits deposited and superimposed continuously and then deposition layers with a certain thickness were formed. The epitaxial growth coating with columnar grains was then achieved by the micro-arc spark deposition. The prepared Stellite6 alloy coating has a good metallurgical combination with the SCH13 steel substrate and the elements at the interface are smooth transition. Because of the effects of the temperature gradient and the solidification rate, the microstructure of the deposition layer is slightly coarser with the increasing of the processing voltage. The coatings are consisted of γ-Co solid solution and chromium carbides.
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Aldunate, Felipe. "Deposit Insurance, Bank Risk-Taking, and Failures: Evidence from Early Twentieth-Century State Deposit Insurance Systems." Review of Corporate Finance Studies 8, no. 2 (April 15, 2019): 260–301. http://dx.doi.org/10.1093/rcfs/cfz001.
Abstract:
Abstract I use the introduction of deposit insurance in eight U.S. states in the early twentieth-century to study the effects of deposit insurance on the banking system. Using a triple difference approach exploiting regulatory differences between national and state banks and between states, I find that insured banks experienced higher deposit growth and decreased funding costs. I also observe a replacement of demand deposits by riskier time deposits. However, I find no aggregate effects on failure rates or risk-taking. Using hand-collected micro-level data, I show that small and large banks reacted differently and that banks facing funding problems especially benefited. Received July 20, 2017; editorial decision November 12, 2018 by Editor Efraim Benmelech.
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Wang, Xi Ran, Hui Lu, Ying Wei Zhang, Xin Gang Hu, and Jing Wu. "The Influence of Plating Temperature on the Properties of Electroless Ni-Cu-P Alloys on Aluminum." Advanced Materials Research 189-193 (February 2011): 1096–99. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.1096.
Abstract:
In this work, the effect of plating temperature on the electroless plating rate and the properties of the electroless Ni-Cu-P deposits was studied. The corrosion resistance, hardness, surface morphology and components of the coating were studied by using electrochemical workstation, digital micro-hardness SEM and EDS. The results show that the optimum plating temperature is 75°C. The deposition rate, hardness and corrosion resistance are all good when the optimal temperature is 75°C. The adhesion between the deposits and the matrix is better. The deposits is smooth and uniformity, smooth by SEM. The deposit contains Ni 77.80%, Cu 7.68%, P 14.52% by the analyses of energy disperse X-ray.
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Jiang, Yiming, Chun-Yi Chen, Tso-Fu Mark Chang, Xun Luo, Daisuke Yamane, and Masato Sone. "Electrodeposition of Ni-Co Alloys and Their Mechanical Properties by Micro-Vickers Hardness Test." Electrochem 2, no. 1 (December 24, 2020): 1–9. http://dx.doi.org/10.3390/electrochem2010001.
Abstract:
Nanocrystalline Ni-Co alloy deposits with grain sizes less than 30 nm were produced by electrodeposition with a direct current in a sulfamate bath. Surfaces of the Ni-Co alloy deposits showed granular morphology. The size of the granular particles and the Co content decreased when a lower current density was applied. Addition of NiBr2 and a surface brightener (NSF-E) into the bath resulted in the grain refinement effect and an increase of Co content in the deposit. The grain size reached roughly 14 nm and 60 at.% of Co content in Ni-Co alloys electrodeposited with the bath containing the two additives. Ni-Co alloys obtained in this study showed higher microhardnesses than those of pure Ni and Co deposits prepared under the same condition, which revealed the solid solution strengthening effect. With a decrease in the grain size, the microhardness further increased, and this trend followed the Hall–Petch relationship well. The maximum microhardness value of 862.2 Hv was obtained owing to both the grain boundary and solid solution strengthening effects.
Dissertations / Theses on the topic "Micro deposits":
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Young, Thomas. "Dépôts micro structurés pour la réalisation de capteurs d’activité hydrolytique." Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILN062.
Abstract:
La phytase, une enzyme capable d'hydrolyser séquentiellement l'acide phytique en formant des inositols moins phosphorylés et du phosphate, est de plus en plus souvent ajoutée aux régimes alimentaires des animaux afin d'optimiser l'absorption du phosphore par les animaux monogastriques et de réduire sa présence dans les fèces et les sols. À cet égard, la possibilité de mesurer son activité est évidemment d'un intérêt primordial. Cependant, à ce jour, il existe très peu de méthodes permettant de mesurer facilement l'activité de la phytase dans l'industrie. Les principales raisons sont que les techniques actuelles sont chronophages, ne sont pas adaptées aux échantillons d'aliments complexes et utilisent des réactifs dangereux.Dans ce projet de thèse, nous avons proposé de développer un capteur enzymatique innovant dédié à la détection de l'activité de la phytase dans des échantillons complexes en utilisant une méthode de détection directe grâce à la technologie de Zymoptiq. L'acide phytique, substrat de la phytase, possède de nombreuses charges négatives qui peuvent interagir avec des polymères chargés positivement comme le chitosan pour former des complexes. Ce phénomène est bien connu et documenté dans la littérature et constitue la pierre angulaire de notre capteur. Notre capteur est basé sur la dégradation de micro dépôts basés sur une structure en réseau de chaînes de chitosan insensibles à l'enzyme et réticulées avec de l'acide phytique lorsqu'ils sont incubés en présence d'activité phytase (FTU/mL).Cependant, pour assurer la stabilité du micro dépôt, une étude systématique a été menée pour mieux contrôler et comprendre tous les phénomènes sous-jacents liés à son assemblage. Cela a aussi permis d'améliorer la sensibilité du capteur développé. Grâce à des versions intermédiaires, nous avons démontré la capacité de notre méthode à mesurer l'activité d'un échantillon de phytase pure de 100 FTU/mL et d'un échantillon d'aliment complexe simulé avec des activités aussi faibles que 20 mFTU/mL. Enfin, après avoir caractérisé le mécanisme d'hydrolyse de l'acide phytique complexé avec le chitosan par la phytase, cette étude nous a permis de proposer une méthode de mesure innovante, sûre et rapidePhytase, an enzyme capable of sequential hydrolysis of phytic acid to lower phosphorylated inositols and phosphate, has been increasingly added to animal diets to optimize phosphorus uptake by monogastric animals and to reduce its presence in faeces and soils. In this respect, the ability to measure its activity is obviously of primary interest. However, to date there are very few methods available to easily measure phytase activity in industry. The main reasons are that current techniques are time consuming, not suitable for complex feed samples and use hazardous reagents.In this thesis project, we proposed to develop an innovative enzymatic sensor dedicated to the detection of phytase activities in complex samples using a label-free approach thanks to Zymoptiq's technology. Phytic acid, the substrate of phytase, possesses numerous negative charges that can interact with positively charged polymers such as chitosan to form complexes. This phenomenon is well known and documented in the literature and is the cornerstone of our sensor. Our sensor is based on the degradation of micro deposits-based on a network structure of enzyme-insensitive chitosan chains cross-linked with phytic acid- when incubated in the presence of phytase activity (FTU/mL).However, to ensure the stability of the micro deposit, a systematic study was carried out to better control and understand all the underlying phenomena related to the complexes assembly. This also allows us to tailor our sensor's sensitivity. Through intermediate versions, we have demonstrated the ability to measure the activity of both a pure phytase sample of 100 FTU/mL and a simulated complex feed sample with activities as low as 20 mFTU/mL. Finally, after characterizing the hydrolysis mechanism of phytic acid complexed with chitosan by phytase, this study has enabled us to propose an innovative, safe and time-saving method of measurement
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Barron, Lance W. "High-reflectance, sputter-deposited aluminum alloy thin films for micro-electro-mechanical systems /." Online version of thesis, 2005. http://hdl.handle.net/1850/5195.
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Perry, Richard. "Towards environmentally friendly electrodeposition : using citrate based electrolytes to deposit nickel and nickel-iron." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/16184.
Abstract:
The production of magnetic materials is of great interest for use in the micro-fabrication industry. In particular, Permalloy (Ni80Fe20) is used in the production of micro-electromechanical systems (MEMS) due to its favourable magnetic properties (high relative permeability, low coercivity and high magnetic saturation). This leads to applications in devices such as inductors, transformers and micro-actuators. The electrodeposition of NiFe is also of fundamental electrochemical interest, as there is anomalous thermodynamic behaviour, with the less noble (iron) metal depositing preferentially to the more noble (nickel) metal. To enable consistent alloy deposition nickel and nickel-iron baths are currently almost exclusively based on boric acid. Boric acid has an important role in the deposition of NiFe films but its role(s) in the electro-deposition mechanism is (are) not wholly understood. Recently (2011) boric acid has been identified as a “substance of very high concern” based on the criteria established by EU chemical regulation, REACH. In anticipation of increased regulation an alternative was sought to provide a benign alternative to boric acid in the NiFe plating bath suitable for use in micro-fabrication. Initial work was performed to benchmark the performance of existing boric acid based electro-deposition baths. Cyclic voltammetry was performed, which demonstrated the deposition of nickel and nickel-iron from boric acid baths. Coulombic efficiencies up to 93 % were measured for the deposition of nickel using the electrochemical quartz crystal microbalance (EQCM) on platinum electrodes. For nickel-iron deposition control of the film composition was demonstrated on copper electrodes through varying the iron (II) concentration, current density and temperature. A citrate bath for the deposition of nickel-iron was then developed and characterised. Cyclic voltammetry was performed in these citrate baths demonstrating the deposition of nickel and nickel-iron. Optimal conditions for depositing Ni80Fe20 were demonstrated to be an elevated temperature (60 °C) with a current density of 20 mA cm-2 and a pH of 3. Using the EQCM the efficiency for nickel deposition was measured to be > 80 %. The effects of sodium saccharin and sodium dodecyl sulfate as additives were investigated; these were shown to influence morphology but not the coulombic efficiency. Decreasing the pH was shown to lower the efficiency of nickel deposition from the citrate bath. Comparisons of key properties were made between NiFe films deposited from a boric acid bath and the citrate bath developed in this work. Test structures were used to compare the strain in the films; no significant difference was found. For 2.2 μm thick Ni80Fe20 films the sheet resistance was measured using Greek cross structures as 0.078 ± 0.004 Ω/square for films deposited from the boric acid bath and 0.090 ± 0.006 Ω/square from the citrate bath. The magnetic saturation, Ms, was measured as 895 ± 66 emu cm-3 for deposits from the boric acid bath and 923 ± 111 emu cm-3 from the citrate bath. These again show no significant difference in these values within experimental error. Coercivities for these films were measured to be between 20 and 120 A m-1. In combination, this work demonstrates the development and characterisation of a new citrate based electrodeposition bath for nickel and nickel-iron. Similar chemical, electrical, mechanical and magnetic properties were found from films deposited from both baths, thus demonstrating the suitability of the citrate bath for the deposition of nickel-iron films in microfabrication.
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Jaber, Wassim. "Phonon heat conduction probed by means of an electro-thermal method involving deposited micro and nanowires." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI109/document.
Abstract:
The context of this PhD is the reduction of sizes involved in material development and the confinement of heat in modern devices, which are known to lead to the apparition of hot spots. The goal is to investigate heat conduction from micro- to nanoscale wide Joule-heated wires standing on flat layered materials. A particular focus is given to the analysis of phonon heat dissipation when departing from the well-known Fourier diffusive conduction and entering the ballistic regime. The manuscript starts with a summary of the main observed effects on the effective thermal conductivity in nanoscale materials, especially in light of the values of thermallyaveraged phonon mean free paths and the associated Knudsen number. Then the advantages and drawbacks of various measurement techniques are discussed. The analysis of the experimental configuration requires 2D analytical and 3D finite-element method based numerical studies of diffusive heat conduction from a finite source into a medium. Limitations of the 3! method due to wire length, substrate geometry and thin oxide layers are highlighted. The electro-thermal setup developed and the procedure used to deposit the devices on top of the samples are then detailed. A set of well-known materials with mean free path ranging from few nanometers to hundreds of nanometers is characterized with microwires. The thermal conduction properties of multilayer materials are investigated. Heat dissipation from finite sources on top of silicon substrates is then measured as a function of temperature. The mean free path is known to become large when temperature decreases. As a result, this configuration provides clues for understanding heat conduction from ballistic sources. The observed behavior is very different from the one predicted by Fourier’s law and shows a strong reduction of the dissipation. It is found that the results are comparable to earlier measurements involving ridges. They are analyzed with various levels of approximations of predictions using the Boltzmann transport equation. The results obtained may be useful in many fields, in particular for electronics and thermoelectric designsLe contexte de ce doctorat est la réduction des tailles impliquées dans le développement des matériaux et le confinement de la chaleur dans les dispositifs modernes, qui sont connus pour conduire à l'apparition de points chauds. L'objectif est d'étudier la conduction de la chaleur à partir de fils chauffés par Joule à l'échelle nanométrique et à l'échelle nanométrique, reposant sur des matériaux à couches planes. Une attention particulière est accordée à l'analyse de la dissipation thermique des phonons en partant de la conduction de Fourier bien connue et en entrant dans le régime balistique. Le manuscrit commence par un résumé des principaux effets observés sur la conductivité thermique effective dans les matériaux à l'échelle nanométrique, en particulier à la lumière des valeurs des voies libres moyennes des phonons et du nombre de Knudsen associé. Ensuite, les avantages et les inconvénients des différentes techniques de mesure sont discutés. L'analyse de la configuration expérimentale nécessite des études numériques 2D basées sur la méthode des éléments finis et des éléments finis de la conduction de chaleur par diffusion à partir d'une source finie dans un milieu. Limitations du 3! méthode en raison de la longueur du fil, de la géométrie du substrat et des couches minces d'oxyde sont mises en évidence. La configuration électro-thermique développée et la procédure utilisée pour déposer les dispositifs sur les échantillons sont ensuite détaillées. Un ensemble de matériaux bien connus avec un chemin libre moyen allant de quelques nanomètres à des centaines de nanomètres est caractérisé par des microfils. Les propriétés de conduction thermique des matériaux multicouches sont étudiées. La dissipation thermique des sources finies sur les substrats de silicium est ensuite mesurée en fonction de la température. Le libre parcours moyen est connu pour devenir important lorsque la température diminue. En conséquence, cette configuration fournit des indices pour comprendre la conduction de la chaleur à partir de sources balistiques. Le comportement observé est très différent de celui prédit par la loi de Fourier et montre une forte réduction de la dissipation. On trouve que les résultats sont comparables à des mesures antérieures impliquant des crêtes. Ils sont analysés avec différents niveaux d'approximations de prédictions en utilisant l'équation de transport de Boltzmann. Les résultats obtenus peuvent être utiles dans de nombreux domaines, en particulier pour les conceptions électroniques et thermoélectriques
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Lawson, Thomas Ryan. "Micro-Raman spectroscopy and dry turning evaluations of nanostructured diamond films deposited on tungsten-carbide lathe inserts." Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2008m/lawson.pdf.
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Tripp, Marie K. "Atomic layer deposited thin films for micro- and nano-electromechanical systems with applications in short-wavelength adaptive optics." Diss., Connect to online resource, 2005. http://wwwlib.umi.com/dissertations/fullcit/3165821.
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Steinhauer, Tim [Verfasser]. "On the Micro- and Ultrafiltration of Dairy Fluids - Molecular Mechanisms of Membrane Fouling and Elucidation of Deposit Layer Structures / Tim Steinhauer." München : Verlag Dr. Hut, 2016. http://d-nb.info/1113335769/34.
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Barbosa, Leo. "EXAMINATION OF MICRO-SCALE SULFIDE DISTRIBUTION FOR THE GOLD MINERALIZATION IN THE LAPPBERGET DEPOSIT, GARPENBERG MINE, SWEDEN: TOWARDS A GEOMETALLURGICAL APPROACH." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-87022.
Abstract:
Ore characterization studies are of great importance to the mining industry, especially when dealing with precious metals by-products. It is a way towards increasing mining efficiency. The Swedish Boliden’s Zn–Pb–Ag–(Cu–Au) Lappberget Deposit is the main ore body at the Garpenberg Mine producing concentrates of zinc, lead, copper, and a gravity concentrate of silver and gold, which accounts for a significant revenue for the mine. Garpenberg Mine is an ancient and traditional mining site in Sweden, nonetheless the Lappberget deposit is a relatively recent discovery and there are still on-going studies on this ore body. More recently detailed ore investigations have been carried out on the sulfides and silver mineralization in different geological domains within the Lappberget deposit. In this context, the present work is focused on investigating the gold mineralization of the deposit, aiming to study the occurrence and distribution of gold minerals, characterize the gold in the ore and how its characteristics affect gold recoveries during its processing. To achieve these goals, different investigative methods were applied on drill core samples of the footwall disseminated to semi-massive mineralization (FWD), and on samples from the gravity concentrator at Boliden’s processing plant. The techniques applied were optical microscopy, scanning electron microscopy, energy dispersive x-ray spectrometry, electron probe microanalysis, laser ablation inductively couple plasma mass spectrometry, and bulk chemical analysis. The main findings pointed electrum as the main gold mineral, occurring with a strong sulfide association, in a variety of textures and grain sizes. The study also identified the occurrence of Au-Bi alloy, not previously described in literature of the Garpenberg region. The potential of invisible gold in the sulfide carriers was also a subject of investigation, as well as the evaluation of the characteristics of the samples from the gravity concentrator.
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Barbakadze, Nato. "Micro-, nanomechanical measurements on insect and plant cuticles." Stuttgart Max-Planck-Inst. für Metallforschung, 2005. http://deposit.d-nb.de/cgi-bin/dokserv?idn=979181348.
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McWilliam, Lyn. "Combined hydrogen diesel combustion : an experimental investigation into the effects of hydrogen addition on the exhaust gas emissions, particulate matter size distribution and chemical composition." Thesis, Brunel University, 2008. http://bura.brunel.ac.uk/handle/2438/3611.
Abstract:
This investigation examines the effects of load, speed, exhaust gas recirculation (EGR) level and hydrogen addition level on the exhaust gas emissions, particulate matter size distribution and chemical composition. The experiments were performed on a 2.0 litre, 4 cylinder, direct injection engine. EGR levels were then varied from 0% to 40%. Hydrogen induction was varied between 0 and 10% vol. of the inlet charge. In the case of using hydrogen and EGR, the hydrogen replaced air. The load was varied from 0 to 5.4 bar BMEP at two engine speeds, 1500 rpm and 2500 rpm. For this investigation the carbon monoxide (CO), total unburnt hydrocarbons (THC), nitrogen oxides (NOX) and the filter smoke number (FSN) were all measured. The in-cylinder pressure was also captured to allow the heat release rate to be calculated and, therefore, the combustion to be analysed. A gravimetric analysis of the particulate matter size distribution was conducted using a nano-MOUDI. Finally, a GC-MS was used to determine the chemical composition of the THC emissions. The experimental data showed that although CO, FSN and THC increase with EGR, NOX emissions decrease. Inversely, CO, FSN and THC emissions decrease with hydrogen, but NOX increases. When hydrogen was introduced the peak cylinder pressure was increased, as was the maximum rate of in-cylinder pressure rise. The position of the peak cylinder pressure was delayed as hydrogen addition increased. This together with the obtained heat release patterns shows an increase in ignition delay, and a higher proportion of premixed combustion. The experimental work showed that the particulate matter size distribution was not dramatically altered by the addition of EGR, but the main peak was slightly shifted towards the nucleation mode with the addition of hydrogen. Hydrogen addition does not appear to have a large effect on the chemical composition of the THC, but does dramatically decrease the emissions.
Books on the topic "Micro deposits":
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Liang, Yayun. Mineral Micro-Geochemistry Constraints on Petrogenesis and Genesis of Gold Deposit. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1022-6.
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Liang, Yayun. Mineral Micro-Geochemistry Constraints on Petrogenesis and Genesis of Gold Deposit. Springer, 2022.
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Liang, Yayun. Mineral Micro-Geochemistry Constraints on Petrogenesis and Genesis of Gold Deposit. Springer Singapore Pte. Limited, 2021.
Book chapters on the topic "Micro deposits":
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Liang, Yayun. "Micro-Geochemistry of Pyrite and Gold Mineral in Jiaodong Gold Deposits: Implications for Genesis of Gold Deposit." In Mineral Micro-Geochemistry Constraints on Petrogenesis and Genesis of Gold Deposit, 135–203. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1022-6_4.
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Williams, Neil. "Light-Element Stable Isotope Studies of the Clastic-Dominated Lead–Zinc Mineral Systems of Northern Australia and the North American Cordillera: Implications for Ore Genesis and Exploration." In Isotopes in Economic Geology, Metallogenesis and Exploration, 329–72. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27897-6_11.
Abstract:
AbstractClastic-dominated lead–zinc (CD Pb–Zn) deposits are an important source of the world’s Pb and Zn supply. Their genesis is contentious due to uncertainties regarding the time of ore formation relative to the deposition of the fine-grained carbonaceous strata that host CD Pb–Zn mineralization. Sulfur-isotopic studies are playing an important role in determining if ore minerals precipitated when hydrothermal fluids exhaled into the water column from which the host strata were being deposited, or when hydrothermal fluids entered the host strata during diagenesis or even later after lithification. Older conventional S-isotopic studies, based on analyses of bulk mineral-separate samples obtained by either physical or chemical separation methods, provided data that has been widely used to support a syngenetic-exhalative origin for CD Pb–Zn mineralization. However, with the advent in the late 1980’s of in situ S-isotopic studies using micro-analytical methods, it soon became apparent that detailed S-isotopic variations of genetic importance are blurred in conventional analytical data sets because of averaging during sample preparation. Clastic-dominated Pb–Zn mineralization in the North Australian Proterozoic metallogenic province and the North American Paleozoic Cordilleran province has been the subject of many stable isotope studies based on both bulk and in situ analytical methods. Together with detailed mineral texture observations, the studies have revealed a similar sulfide mineral paragenesis in both provinces. The earliest sulfide phase in the paragenesis is fine-grained pyrite that sometimes has a framboidal texture. This pyrite typically has a wide range of δ34S values that are more than 15‰ lower than the value of coeval seawater sulfate. These features are typical of, and very strong evidence for, pyrite formation by bacterial sulfate reduction (BSR) either syngenetically in an anoxic water column or during early diagenesis in anoxic muds. The formation of this early pyrite is followed by one or more later generations of pyrite that often occur as overgrowths around the early pyrite generation. The later pyrite generations have δ34S values that are much higher than the early pyrite, often approaching the value of coeval seawater sulfate. Later pyrite formation has been variously attributed to BSR in a more restricted diagenetic environment, to sulfate driven-anaerobic oxidation of methane (SD-AOM) and to abiotic thermal sulfate reduction (TSR), with all three mechanisms again involving coeval seawater sulfate. The main sulfide ore minerals, galena and sphalerite, either overlap with or postdate later pyrite generations and are most often attributed to TSR of seawater sulfate. However, in comparison with pyrite, there is a dearth of in situ δ34S data for galena and sphalerite that needs to be rectified to better understand ore forming processes. Importantly, the available data do not support a simple sedimentary-exhalative model for the formation of all but part of one of the Northern American and Australian deposits. The exception is the giant Red Dog deposit group in Alaska where various lines of evidence, including stable isotopic data, indicate that ore formation was protracted, ranging from early syn-sedimentary to early diagenetic sulfide formation through to late sulfide deposition in veins and breccias. The Red Dog deposits are the only example with early sphalerite with extremely low negative δ34S values typical of a BSR-driven precipitation mechanism. By contrast, later stages of pyrite, sphalerite and galena have higher positive δ34S values indicative of a TSR-driven precipitation mechanism. In CD Pb–Zn deposits in carbonate-bearing strata, carbon and oxygen isotope studies of the carbonates provide evidence that the dominant carbonate species in the ore-forming hydrothermal fluids was H2CO3, and that the fluids were initially warm (≥ 150 °C) and neutral to acid. The δ18O values of the hydrothermal fluids are ≥ 6‰, suggesting these fluids were basinal fluids that evolved through exchange with the basinal sedimentary rocks. Known CD Pb–Zn deposits all occur at or near current land surfaces and their discovery involved traditional prospecting, geophysical and geochemical exploration techniques. Light stable isotopes are unlikely to play a significant role in the future search for new CD Pb–Zn deposits deep beneath current land surfaces, but are likely to prove useful in identifying ore-forming hydrothermal fluid pathways in buried CD Pb–Zn systems and be a vector to new mineralization.
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Yépez-Pérez, Luis, Rogelio Bustamante-Bello, Ricardo A. Ramírez-Mendoza, and Jorge de J. Lozoya-Santos. "Fault Tolerance Methodology for Micro-volume Deposit System." In Properties and Characterization of Modern Materials, 333–44. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-10-1602-8_28.
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Tseng, F. G., H. M. Huang, C. Y. Huang, S. C. Lin, and C. C. Chieng. "Dual-Protein Micro Arrays Deposited by µ-Stamps and µ-Wells." In Micro Total Analysis Systems 2001, 591–92. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-010-1015-3_258.
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Romer, R. L., and R. Thomas. "U-Pb dating of micro-inclusions: The age of the Ehrenfriedersdorf tin deposit (Erzgebirge, Germany)." In Mineral Deposit Research: Meeting the Global Challenge, 817–20. Berlin, Heidelberg: Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/3-540-27946-6_208.
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Laskou, M., and M. Economou-Eliopoulos. "Micro-organisms as fossils and present-day development in Ni-laterites and bauxites of the Balkan peninsula." In Mineral Deposit Research: Meeting the Global Challenge, 1003–6. Berlin, Heidelberg: Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/3-540-27946-6_256.
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Liang, Yayun. "Micro-Geochemistry of Clinopyroxene of the Mafic Dykes in the Jiaodong Peninsula: Implications for Petrogenesis and Geodynamic." In Mineral Micro-Geochemistry Constraints on Petrogenesis and Genesis of Gold Deposit, 25–134. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1022-6_3.
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Liang, Yayun. "Introduction." In Mineral Micro-Geochemistry Constraints on Petrogenesis and Genesis of Gold Deposit, 1–9. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1022-6_1.
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Liang, Yayun. "Geological Setting." In Mineral Micro-Geochemistry Constraints on Petrogenesis and Genesis of Gold Deposit, 11–23. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1022-6_2.
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Ikhmayies, Shadia J. "A Comparison Between ZnO Hexagonal Micro/Nanoprisms Deposited on Aluminum and Glass Substrates." In The Minerals, Metals & Materials Series, 321–28. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05749-7_32.
Conference papers on the topic "Micro deposits":
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Watanabe, Yusuke, Yuji Ichikawa, Kazuhiro Ogawa, and Hideo Miura. "Microtexture and Electrical and Mechanical Properties of the Cold-Sprayed Copper Deposit." In ASME 2013 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ipack2013-73150.
Abstract:
Cold-spray (CS) technique is a new coating technology that is based on the high-velocity impinging of small solid particles on a substrate. The CS technique can make a thick deposit with less heat influence. Recently, this CS technique has been applied to the formation of an electrically conductive copper layer on dielectric materials such as polymers or ceramics. Previous researches show that the deposits made by the CS technique have high strength and residual stress comparing with bulk copper. However, since the deposits show brittle fracture and cracks propagate along the interfaces of the deposited particles, the deposits can not be applied to the products for which high reliability is indispensable. Therefore, it is very important to clarify the dominant factors which change the crystallinity of the deposits comparing with that of bulk copper in order to improve the quality of the deposits. One of the important factors should be the integrity of the interfaces between the deposited fine particles. This study is to evaluate the micro-texture and physical properties of the cold-sprayed copper deposit. Electron back-scatter diffraction method was applied to the evaluation of the crystallinity of the deposits. In addition, the relationship between the crystallinity with both mechanical and electrical properties of the deposits was clarified quantitatively.
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Ichikawa, Y., R. Tokoro, and K. Ogawa. "Microscale Adhesion Strength Evaluation of Cold Sprayed Copper Deposit." In ITSC2017, edited by A. Agarwal, G. Bolelli, A. Concustell, Y. C. Lau, A. McDonald, F. L. Toma, E. Turunen, and C. A. Widener. DVS Media GmbH, 2017. http://dx.doi.org/10.31399/asm.cp.itsc2017p0328.
Abstract:
Abstract Adhesion strength is one of the most important characteristics when discussing the reliability of a cold spray. A focused ion beam (FIB) was used to conduct ultra-micro tensile tests for micro-scale adhesive strength evaluations of high-pressure type cold-sprayed copper deposition on an aluminum substrate. It was also used to determine the essential factor of adhesion strength and the coating formation mechanism. The micro-scale local adhesion strength of cold-sprayed copper deposits on an aluminum substrate was successfully evaluated by FIB microtensile tests. The average local adhesion strength of this deposit was 223 MPa. The variations in adhesion strength between deposit and substrate were smaller than the interfacial strength of cold-sprayed deposits. This was caused by the repeated collision of these subsequent particles.
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Zeghal, Mourad, and Claudia Medina. "Dynamic Response of Unsaturated Granular Soil Deposits: A Micro-Mechanical Study." In Fourth International Conference on Unsaturated Soils. Reston, VA: American Society of Civil Engineers, 2006. http://dx.doi.org/10.1061/40802(189)39.
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Chizhova, S. "Formation Micro Imager (FMI) Processing and Interpretation in the Paleozoic Deposits." In GeoBaikal 2018. Netherlands: EAGE Publications BV, 2018. http://dx.doi.org/10.3997/2214-4609.201802056.
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Varadaraj, Ramesh, and Kristina Fontenot. "Micro-Heterogeneous Solvent Mixtures for Removal of Organic Deposits from Various Surfaces." In SPE International Conference on Oilfield Chemistry. SPE, 2023. http://dx.doi.org/10.2118/213794-ms.
Abstract:
Abstract The technical feasibility of using oxygenated solvent mixtures as an environmental and ecological friendly alternative to aromatic hydrocarbon and terpene solvents for removal of organic deposits from surfaces has been demonstrated. Micro-heterogeneous solvents were prepared using mixtures of di-alkyl ethers and 2-alkyl alkanols. These micro-heterogeneous solvents exhibit unique properties and are effective in solubilizing and removing organic asphaltenic hydrocarbon deposits from surfaces. The main applications of micro-heterogeneous solvents are in organic deposits removal from wellbores and near wellbore regions, heavy oil recovery from oil sands and oily sludges, and heavy oil processing equipment cleaning.
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Akisin, Cletus J., Chris J. Bennett, Federico Venturi, and Tanvir Hussain. "Effect of Heat-Treatment on the Microstructure and Mechanical Properties of CoCrFeNiMn High Entropy Alloy Additively Manufactured via Cold Spray." In ITSC 2023. ASM International, 2023. http://dx.doi.org/10.31399/asm.cp.itsc2023p0400.
Abstract:
Abstract The application of cold spray (CS) for additive manufacturing (CSAM) of structural components using metallic materials has recently attracted much attention. However, there are limited reports on developing thick deposits or components with high entropy alloys (HEAs) via CSAM and investigating the microstructural evolution and mechanical properties after deposition and subsequent annealing heat-treatment. This work investigated the microstructure and mechanical properties of asdeposited and heat-treated thick CoCrFeNiMn HEA deposit fabricated via CSAM. The microstructure of the HEA deposit and after heat-treatment were characterised using scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), and x-ray diffraction (XRD). The microstructural analysis reveals heterogeneous grain size distribution with ultrafine grains at the particle-particle interfacial regions and coarse grains at the particle interiors in the as-deposited sample. The as-deposited sample, characterised by moderate porosity, was consolidated following the heat treatment at different temperatures. Additionally, increasing the temperature increases grain sizes resulting from static recovery and recrystallisation, with annealing twin formed at higher temperatures. Most notably, phase decomposition of the deposit microstructure occurs at 600 ºC, with Cr-rich phase particles formed at regions of high dislocations and grain boundaries. Nano-and micro-hardness and tensile testing of micro-flat dogbones samples were performed on the as-deposited and heattreated samples. The effect of heat-treatment on the microstructure and mechanical properties of the cold-sprayed HEA deposit were analysed and discussed.
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Hao, S., C. J. Li, G. J. Yang, and Y. Z. Xing. "Influence of Substrate Surface Temperature on the Microstructure and Properties of Plasma-Sprayed Al2O3 Coatings." In ITSC2010, edited by B. R. Marple, A. Agarwal, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima, and G. Montavon. DVS Media GmbH, 2010. http://dx.doi.org/10.31399/asm.cp.itsc2010p0259.
Abstract:
Abstract Thermally sprayed ceramic coatings have a layered structure with a limited interface bonding. Substrate surface temperature prior to droplets impact during deposition significantly influences the microstructure and properties of the coatings. Through the controlling of substrate surface temperature, the lamellar interface bonding of the deposits could be possibly improved. Al2O3 coatings were deposited by atmospheric plasma spraying at the surface temperatures of 100, 275, 375, 480, 530 and 660°C. The fractured cross-section morphology was characterized by scanning electron microscopy. X-ray diffraction was used to analyse the phase contents. Micro-hardness, Young’s modulus and thermal conductivity of the deposits were measured. It was observed that the interface area with columnar grain growth across splat-splat interfaces was increased with increasing deposition temperature. Consequently, micro-hardness, Young’s modulus and thermal conductivity were increased with the increase of deposition temperature. The improvement of properties suggest that the lamellar interface bonding in the deposits was improved as the substrate surface temperature is increased.
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Mizernaya, M., B. Dyachkov, A. Miroshnikova, and A. Mizerny. "INDUSTRIAL TYPES OF GOLD DEPOSITS OF THE EAST KAZAKHSTAN." In GEOLINKS International Conference. SAIMA Consult Ltd, 2020. http://dx.doi.org/10.32008/geolinks2020/b1/v2/14.
Abstract:
The East Kazakhstan territory is the unique geologic province where a number of large-scale non-ferrous and gold deposits are concentrated [1]. Gold base metals (gold-containing) type is represented by gold containing sulphide complex deposits. It is characterized by many large-scale commercial deposits of copper, lead and zinc where gold as well as silver, cadmium, platinum, selenium and other elements are the associate component of copper-sulphide and sulphide complex deposits [2]. There are following ore types are distinguished: gold-listvenite type occurs in the Irtysh zone (Maraliha deposit); the gold-sulphide vein-disseminated type associated with island-arc, volcanogenic-carbonate-terrigenous formation С1v2-3 (Suzdalskoye, Baibura, Mirazh, Zhaima); gold-quartzite type is characterized by gold-quartzite-vein deposits in West Kalba zone (Kuludzhun, Sentash, Kazan-Chunkur and others); gold-arsenic-carbon-bearing type is presented by large, middle and small deposits of Bakyrchik’s group (Bakyrchik, Bolshevik, Gluboky Log and others). Last one is formed on middle-Hercynian collision ore-bearing level (С2-С3) [3]. Multiple-stage concentration of gold contributed to formation of very large deposits. Gold content ranges from is 0.2 to 60 g/t, average is 8-9 g/t. Considerable part of gold is found in micro- and nanoparticles, nanotubes containing Au, Ag, Pt, Pd, W, Mo, Sn, Y, Yb, Ta and other elements [
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Wei, Ying-Kang, Xiao-Tao Luo, and Chang-Jiu Li. "The Mechanisms of Enhancement of Inter-Particle Bonding in In-Situ Micro-Forging Assisted Cold Spray." In ITSC2019, edited by F. Azarmi, K. Balani, H. Koivuluoto, Y. Lau, H. Li, K. Shinoda, F. Toma, J. Veilleux, and C. Widener. ASM International, 2019. http://dx.doi.org/10.31399/asm.cp.itsc2019p0450.
Abstract:
Abstract In this study, high-strength aluminum alloy AA7055 deposits are prepared using a recently developed cold spray process that employs in-situ microforging. The in-situ hammering effect is achieved by mixing large shot-peening particles into the spray powder and is shown to enhance interparticle bonding along with the plastic deformation of deposited particles. The underlying mechanisms are discussed based on the characterization of interface microstructure and the distribution of oxide film at the interparticle interface.
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Gao, P. H., G. J. Yang, C. J. Li, and C. X. Li. "Influence of Powder Structure on the Micro-Hardness and Fracture Toughness of Cold-Sprayed WC-12Co Deposit." In ITSC2009, edited by B. R. Marple, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima, and G. Montavon. ASM International, 2009. http://dx.doi.org/10.31399/asm.cp.itsc2009p0986.
Abstract:
Abstract In this study, WC-12Co powders with multimodal-sized WC particles were prepared by ball milling and deposited onto stainless steel substrates by cold spraying. Microhardness and fracture toughness were measured on cross-sections by the indentation approach. Coatings produced from powders with small carbide particles, resulting from long milling times, were found to exhibit high microhardness and high fracture toughness. Deposits sprayed with high porosity powders produced by cold compaction had low microhardness, but high fracture toughness.
Reports on the topic "Micro deposits":
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Pinet, N., O. H. Ardakani, J. Cesar, D. C. Petts, C. Debuhr, and P J Sack. Exploring the link between organic matter and Carlin-type gold mineralization: new insights from Yukon deposits. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/330086.
Abstract:
The link between organic matter and gold in sediment-hosted Carlin-type deposits is controversial. This study aims to tackle this potential link by documenting the occurrence of organic matter in a single borehole from a Carlin-type gold deposit in Yukon and by considering, in a preliminary way, the spatial and/or temporal relationship between organic matter and gold mineralization. The sedimentary succession hosting the Conrad deposit was relatively rich in organic matter, possibly related to Archea. Despite the high maturation of samples, the total organic carbon (TOC) content of the limestone unit averages 1.31 wt. % (maximum = 3.18 wt. %). Petrographic observations indicate that pore and fracture filling pyrobitumen is the dominant organic matter maceral in the studied samples. This type of pyrobitumen was matured after its emplacement, indicating that hydrocarbon fluids cannot have served as an agent for gold transport. Pyrobitumen disseminated in the rock or associated with stylolites are also documented. The correlation between TOC and Tl (the best proxy for Au) for selected samples and the high As content of pyrobitumen filling pores may suggest a link between organic matter content and gold deposition, but this was not demonstrated by LA-ICP-MS micro-scale mapping. This study also highlights the challenges of establishing a direct spatial relationship between 'invisible' gold and very small (< 10 µm) pyrobitumen particles.
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Cruces, Juan José. Argentina's Residential Real Estate Sector: A Magnet for Savings amidst Mistrust in Traditional Investment Vehicles. Inter-American Development Bank, March 2016. http://dx.doi.org/10.18235/0009277.
Abstract:
This paper measures the flow of funds into the real estate sector for the city of Buenos Aires since 1992 and compares it to traditional savings instruments. For each dollar that went into the city's real estate from 1992 until 2000, about six dollars went into deposits in the national banking system. From 2003 until 2012, for each dollar that went into real estate, only 99 cents went to bank deposits. While the 2010 census reports a vacancy rate of 24 percent for the city, analysis of a micro data set on individual house electricity consumption suggests that the rate is only about 6 percent, in line with international standards. Increased supply, however, has resulted in a dramatic reduction of real rental values and rental yields. The paper concludes by estimating the welfare loss from allocating society's scarce capital to such a low-return activity, which is interpreted as a lower bound of the flow cost of mistrust in traditional savings instruments.
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Chriscoe, Mackenzie, Rowan Lockwood, Justin Tweet, and Vincent Santucci. Colonial National Historical Park: Paleontological resource inventory (public version). National Park Service, February 2022. http://dx.doi.org/10.36967/nrr-2291851.
Abstract:
Colonial National Historical Park (COLO) in eastern Virginia was established for its historical significance, but significant paleontological resources are also found within its boundaries. The bluffs around Yorktown are composed of sedimentary rocks and deposits of the Yorktown Formation, a marine unit deposited approximately 4.9 to 2.8 million years ago. When the Yorktown Formation was being deposited, the shallow seas were populated by many species of invertebrates, vertebrates, and micro-organisms which have left body fossils and trace fossils behind. Corals, bryozoans, bivalves, gastropods, scaphopods, worms, crabs, ostracodes, echinoids, sharks, bony fishes, whales, and others were abundant. People have long known about the fossils of the Yorktown area. Beginning in the British colonial era, fossiliferous deposits were used to make lime and construct roads, while more consolidated intervals furnished building stone. Large shells were used as plates and dippers. Collection of specimens for study began in the late 17th century, before they were even recognized as fossils. The oldest image of a fossil from North America is of a typical Yorktown Formation shell now known as Chesapecten jeffersonius, probably collected from the Yorktown area and very likely from within what is now COLO. Fossil shells were observed by participants of the 1781 siege of Yorktown, and the landmark known as “Cornwallis Cave” is carved into rock made of shell fragments. Scientific description of Yorktown Formation fossils began in the early 19th century. At least 25 fossil species have been named from specimens known to have been discovered within COLO boundaries, and at least another 96 have been named from specimens potentially discovered within COLO, but with insufficient locality information to be certain. At least a dozen external repositories and probably many more have fossils collected from lands now within COLO, but again limited locality information makes it difficult to be sure. This paleontological resource inventory is the first of its kind for Colonial National Historical Park (COLO). Although COLO fossils have been studied as part of the Northeast Coastal Barrier Network (NCBN; Tweet et al. 2014) and, to a lesser extent, as part of a thematic inventory of caves (Santucci et al. 2001), the park had not received a comprehensive paleontological inventory before this report. This inventory allows for a deeper understanding of the park’s paleontological resources and compiles information from historical papers as well as recently completed field work. In summer 2020, researchers went into the field and collected eight bulk samples from three different localities within COLO. These samples will be added to COLO’s museum collections, making their overall collection more robust. In the future, these samples may be used for educational purposes, both for the general public and for employees of the park.
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Lever, James, Susan Taylor, Arnold Song, Zoe Courville, Ross Lieblappen, and Jason Weale. The mechanics of snow friction as revealed by micro-scale interface observations. Engineer Research and Development Center (U.S.), December 2021. http://dx.doi.org/10.21079/11681/42761.
Abstract:
The mechanics of snow friction are central to competitive skiing, safe winter driving and efficient polar sleds. For nearly 80 years, prevailing theory has postulated that self-lubrication accounts for low kinetic friction on snow: dry-contact sliding warms snow grains to the melting point, and further sliding produces meltwater layers that lubricate the interface. We sought to verify that self-lubrication occurs at the grain scale and to quantify the evolution of real contact area to aid modeling. We used high-resolution (15 μm) infrared thermography to observe the warming of stationary snow under a rotating polyethylene slider. Surprisingly, we did not observe melting at contacting snow grains despite low friction values. In some cases, slider shear failed inter-granular bonds and produced widespread snow movement with no persistent contacts to melt (μ < 0.03). When the snow grains did not move and persistent contacts evolved, the slider abraded rather than melted the grains at low resistance (μ < 0.05). Optical microscopy revealed that the abraded particles deposited in air pockets between grains and thereby carried heat away from the interface, a process not included in current models. Overall, our results challenge whether self-lubrication is indeed the dominant mechanism underlying low snow kinetic friction.
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Rogg, Christian S. The Impact of Access to Credit on the Saving Behavior of Microentrepreneurs: Evidence from 3 Latin American Countries. Inter-American Development Bank, April 2000. http://dx.doi.org/10.18235/0011211.
Abstract:
This paper aims to shed light on changes in the saving behavior of microentrepreneurs in response to improved access to credit. This paper argues that it is necessary to extend the analysis to the shifting of assets between different forms of savings. The econometric analysis in this paper, which is based on data from IDB evaluations of its Micro and Small Enterprise Global Programs in Ecuador, El Salvador and Paraguay, concludes that increased access to credit induces borrowers to shift their savings from livestock, jewelry and other assets with low or negative returns into deposit accounts with positive returns. This shift takes place as microentrepreneurs develop an understanding of, and confidence in, the various operations and services of the financial sector. As a result of this shift, borrowers tend to achieve a better return on their savings.
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Tan, Peng, and Nicholas Sitar. Parallel Level-Set DEM (LS-DEM) Development and Application to the Study of Deformation and Flow of Granular Media. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, March 2023. http://dx.doi.org/10.55461/kmiz5819.
Abstract:
We present a systematic investigation of computational approaches to the modeling of granular materials. Granular materials are ubiquitous in everyday life and in a variety of engineering and industrial applications. Despite the apparent simplicity of the laws governing particle-scale interactions, predicting the continuum mechanical response of granular materials still poses extraordinary challenges. This is largely due to the complex history dependence resulting from continuous rearrangement of the microstructure of granular material, as well as the mechanical interlocking due to grain morphology and surface roughness. X-Ray Computed Tomography (XRCT) is used to characterize the grain morphology and the fabric of the granular media, naturally deposited sand in this study. The Level-Set based Discrete Element Method (LS-DEM) is then used to bridge the granular behavior gap between the micro and macro scale. The LS-DEM establishes a one-to-one correspondence between granular objects and numerical avatars and captures the details of grain morphology and surface roughness. However, the high-fidelity representation significantly increases the demands on computational resources. To this end a parallel version of LS-DEM is introduced to significantly decrease the computational demands. The code employs a binning algorithm, which reduces the search complexity of contact detection from O(n2) to O(n), and a domain decomposition strategy is used to elicit parallel computing in a memory- and communication-efficient manner. The parallel implementation shows good scalability and efficiency. High fidelity LS avatars obtained from XRCT images of naturally deposited sand are then used to replicate the results of triaxial tests using the new, parallel LS-DEM code. The result show that both micro- and macro-mechanical behavior of natural material is well captured and is consistent with experimental data, confirming experimental observation that the primary source of peak strength of sand is the mechanical interlocking between irregularly shaped grains. Specifically, triaxial test simulations with a flexible membrane produce a very good match to experimentally observed relationships between deviatoric stress and mobilized friction angle for naturally deposited sand. We then explore the viability of modeling dynamic problems with a new formulation of an impulse based LS-DEM. The new formulation is stable, fast, and energy conservative. However, it can be numerically stiff when the assembly has substantial mass differences between particles. We also demonstrate the feasibility of modeling deformable structures in the rigid body framework and propose several enhancements to improve the convergence of collision resolution, including a hybrid time integration scheme to separately handle at rest contacts and dynamic collisions. Finally, we extend the impulse-based LS-DEM to include arbitrarily shaped topographic surfaces and exploit its algorithmic advantages to demonstrate the feasibility of modeling realistic behavior of granular flows. The novel formulation significantly improves performance of dynamic simulations by allowing larger time steps, which is advantageous for observing the full development of physical phenomena such as rock avalanches, which we present as an illustrative example.