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1
Caputo, Antonella <1978>. « Erosioni dentali nei bambini affetti da GERD ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/4088/1/Caputo_Antonella_tesi.pdf.
Texte intégralRésumé :
L’erosione dentale è definita come una perdita progressiva e irreversibile dei tessuti duri del dente, a causa di un processo chimico che non coinvolge i batteri.
La sua prevalenza è accresciuta negli ultimi anni nella popolazione generale, particolarmente nei bambini e negli adolescenti e rappresenta attualmente un’enorme sfida per la cura della salute orale.
L'eziologia delle erosioni è difficile da diagnosticare perché può essere il risultato di una varietà di fattori e si può manifestare in maniera differente in base alla causa che l’ha determinata. L’eziologia può essere intrinseca, cioè derivante dal contenuto acido dello stomaco associato a disordini alimentari come l’anoressia, la bulimia nervosa, il reflusso gastro-esofageo e il regurgito, o estrinseca, derivante dal contenuto acido proveniente dall’ambiente esterno (cibi dietetici, bevande analcoliche, succhi di frutta, ecc).
L’erosione è particolarmente frequente nei bambini e poiché i soggetti che presentano erosioni in dentizione decidua hanno un rischio aumentato di manifestare erosioni in dentizione permanente, una diagnosi precoce e una prevenzione attuata in tenera età, aiuterà a prevenire il danno a carico dei denti permanenti. Inoltre se l’erosione dentale non è controllata e stabilizzata, il bambino potrebbe soffrire di severe perdite di superfici dentali, sensibilità dentale, malocclusione, inestetismi o anche ascessi dentali dei denti affetti.
Lo studio caso-controllo è stato condotto dalla Sezione di Odontostomatologia del Dipartimento Testa - Collo, in collaborazione con l’Unità Operativa Complessa di Gastroenterologia Pediatrica dell’Azienda Ospedaliera-Univesitaria di Parma.
Il gruppo di studio comprende 60 pazienti di età compresa tra i 4 e i 13 anni.
Dei 60 bambini arruolati, 30 presentano sintomi e storia clinica di GERD, mentre gli altri 30 sono bambini sani senza alcun sintomo di GERD o di altri disturbi gastrointestinali.
Il gruppo campione A include anche soggetti affetti, oltre che dal reflusso gastro-esofageo, da varie forme di disabilità, in alcune delle quali il GERD sembra essere parte del quadro sindromico.
I risultati ottenuti dallo studio hanno dimostrato una prevalenza maggiore di erosioni dentali nel gruppo di bambini affetti da GERD, rispetto ai bambini sani, in accordo con quanto riportato dalla letteratura.
2
Caputo, Antonella <1978>. « Erosioni dentali nei bambini affetti da GERD ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/4088/.
Texte intégralRésumé :
L’erosione dentale è definita come una perdita progressiva e irreversibile dei tessuti duri del dente, a causa di un processo chimico che non coinvolge i batteri.
La sua prevalenza è accresciuta negli ultimi anni nella popolazione generale, particolarmente nei bambini e negli adolescenti e rappresenta attualmente un’enorme sfida per la cura della salute orale.
L'eziologia delle erosioni è difficile da diagnosticare perché può essere il risultato di una varietà di fattori e si può manifestare in maniera differente in base alla causa che l’ha determinata. L’eziologia può essere intrinseca, cioè derivante dal contenuto acido dello stomaco associato a disordini alimentari come l’anoressia, la bulimia nervosa, il reflusso gastro-esofageo e il regurgito, o estrinseca, derivante dal contenuto acido proveniente dall’ambiente esterno (cibi dietetici, bevande analcoliche, succhi di frutta, ecc).
L’erosione è particolarmente frequente nei bambini e poiché i soggetti che presentano erosioni in dentizione decidua hanno un rischio aumentato di manifestare erosioni in dentizione permanente, una diagnosi precoce e una prevenzione attuata in tenera età, aiuterà a prevenire il danno a carico dei denti permanenti. Inoltre se l’erosione dentale non è controllata e stabilizzata, il bambino potrebbe soffrire di severe perdite di superfici dentali, sensibilità dentale, malocclusione, inestetismi o anche ascessi dentali dei denti affetti.
Lo studio caso-controllo è stato condotto dalla Sezione di Odontostomatologia del Dipartimento Testa - Collo, in collaborazione con l’Unità Operativa Complessa di Gastroenterologia Pediatrica dell’Azienda Ospedaliera-Univesitaria di Parma.
Il gruppo di studio comprende 60 pazienti di età compresa tra i 4 e i 13 anni.
Dei 60 bambini arruolati, 30 presentano sintomi e storia clinica di GERD, mentre gli altri 30 sono bambini sani senza alcun sintomo di GERD o di altri disturbi gastrointestinali.
Il gruppo campione A include anche soggetti affetti, oltre che dal reflusso gastro-esofageo, da varie forme di disabilità, in alcune delle quali il GERD sembra essere parte del quadro sindromico.
I risultati ottenuti dallo studio hanno dimostrato una prevalenza maggiore di erosioni dentali nel gruppo di bambini affetti da GERD, rispetto ai bambini sani, in accordo con quanto riportato dalla letteratura.
3
Garcia-Chevesich, Pablo Andres. « Erosion Processes and Control ». Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/195844.
Texte intégralRésumé :
This dissertation represents a unique contribution to the Spanish literature of soil erosion. The author of this document has written and published "Procesos y control de la erosion", a textbook about the engineering of soil erosion processes and the design of the most up-to-date methods and products used for erosion control. The text has been presented in Appendix A.Besides the above, the author of this dissertation is an active committee member at the International Erosion Control Association (IECA), specifically the International Development and the SOIL Fund programs. IECA members are drawn from individuals and erosion control business of different sizes. However, there was a lack of knowledge within IECA members about the formation of post-fire water repellent layers. For instance, Appendix B is represented by an article written by the author of this document, published in Environmental Connection (Volume 2, Issue 3), on July of 2008. The article gives a general description of what post-fire water repellency is, how is it formed, what factors affect it, its consequences on soil erosion, and how to control soil erosion on an efficient way when such a layer has been formed as a consequence of fire.Finally, Appendix C is a research paper in process of submission to the International Journal of Wildland Fire, about the formation of post-fire water repellent layers on Chilean Monterrey pine plantations. Since water repellent layers following wildfires have never been documented on Chilean soils, the need for such a publication is urgent, because Chilean land managers have been ignorant of such phenomenon.
4
Hamlin, Lauren Kearns. « Erosion ». The University of Montana, 2009. http://etd.lib.umt.edu/theses/available/etd-05282009-130629/.
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5
Lönnborg, Pernilla. « Erosion ». Thesis, KTH, Arkitektur, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-168677.
Texte intégralRésumé :
Byggnader är under ständig förändring. Den omkringliggande miljön orsakar en nedbrytning i form av vittring. Material som bryts ner. Vi vet att en byggnad inte kommer att finns för alltid så vad händer om vi låter nedbrytningen vara en tillgång. Naturens processer ger oss perspektiv på tid. Årstider som följer varandra. Berg som eroderar och formeras. Hur kan man förstärka upplevelsen av tid och rum genom en byggnad som tillåts interagera med den omkringliggande miljön och vara under ständig förändring?Buildings are constantly changing. The surrounding environment partly causes a breakdown through weathering. Materials that breaks down. We know that a building won’t stand forever so what happens if we turn the decomposition to an asset? The process of nature gives us perspective of time. Seasons that follows each other. Rocks that erodes and forms. How can we enhance the experience of time through a building that allows integrating with the surrounding environment and being in constant change?
6
Slotte, Mikael. « Erosion ». Thesis, KTH, Arkitektur, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-146183.
Texte intégralRésumé :
Rosenlunds sandbankar är ett naturskyddsområde mellan Jönköping och Huskvarna som rasar med ungefär 30 cm per år. Platsen tillåts att årligen krympa men inte att användas. Det görs inga större ansatser för att dokumentera den för framtida generationer eller synliggöra den för nu levande generationer. I detta examensarbete undersöks ett naturligt fenomen som kommer att påverka civilisationer i tusentals år. Examensarbetet syftar i första hand till att återintroducera en bortglömd plats och beskriva hur den förändras i tid och rum. Med hjälp av studier om erosion, landhöjning, istid och med hjälp av fältstudier tolkas platsens förgänglighet i fotografier och i en serie ritningar. Därefter föreslås ett promenadstråk där det direkt går att beskåda de geologiska processer som omformar platsen. Stråket knyts ihop över tre terränger – sandbank, strandkant och sjö. Den enkla konstruktionen består av balkar och trädäck som placeras på träpålar och gabioner. Konstruktionens livstid är i ett idealfall detsamma som platsens – pelare kommer att ruttna, delar av platsen kommer att växa igen och i ett längre tidsperspektiv kommer branten att flackas ut. Under hela konstruktionens livstid kommer den att kunna användas för att tolka de processer som pågår på platsen och spegla platsens unika förgänglighet.Rosenlunds sandbankar is a nature reserve between Jönköping and Huskvarna eroding about 30 cm per year. It is allowed to annually shrink but not to be used. There are no major attempts to document it for future generations or to make it visible for the present. This thesis examines a natural phenomenon that will affect civilizations for thousands of years. The work is primarily aimed at reintroducing a forgotten site and describe how it changes in time and space. Using studies of erosion, land uplift, ice age and with the help of field studies the site's transformation is interpreted in photographs and a series of drawings. I propose a promenade where the geological processes that transform the site can be observed and followed. The footpath connects three terrains - sand bluff, shore and lake. The structure consists of beams and decking placed on wooden piles and gabions. In an ideal case it will exist as long as the site itself. Pillars will rot, parts of the site will be overgrown, and in the longer term, the slope will flatten out. During its life span, the structure can be used to interpret the processes and reflect the site's unique transience.
7
Dotson, Matthew. « Erosion ». Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/490.
Texte intégralRésumé :
In my work I am often drawn to relatively simple systems that unfold before the listener. In Erosion, there are several of these processes which unfold simultaneously. The piece begins with a pitch cluster that gradually spreads into total chromatic saturation (about half-way through the piece) before shrinking back into clusters. As this is happening there is, on a macro level, a gradual speeding of events throughout the entire duration of the work. The interactions between this linear progression in the time domain and the (relatively) cyclical progression in the frequency domain form the main dialogue of the work.
8
Lucchese, Antonio. « Analisi dei fenomeni di erosione interna nei rilevati arginali del fiume Panaro ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Trouver le texte intégralRésumé :
Il lavoro di tesi ha come oggetto di studio i fenomeni di erosione interna che possono interessare le opere in materiali sciolti, facendo particolare riferimento ai rilevati arginali.
Si inquadrano le generalità degli argini, i possibili meccanismi di rottura e quali sono i differenti meccanismi di erosione interna che possono interessare una sezione arginale.
Inoltre, il lavoro illustra le varie categorie di test che permettono di stimare l’erodibilità di un terreno, dedicando maggiore attenzione all’Hole Erosion Test (HET): si descrive il funzionamento e la teoria della prova standard (UNSW); viene illustrata la riproduzione dell’Hole Erosion Test presente in Boretto (RE) con annessa analisi critica.
Infine, vengono illustrati i risultati ottenuti dalle analisi di filtrazione e di stabilità applicate ad un caso reale: la sezione trasversale, in sinistra idraulica, dello stante uno a valle della cassa di espansione del fiume Panaro. La sezione oggetto di verifiche è stata ipotizzata sia intatta, ma anche caratterizzata dalla presenza di tana in modo da poter commentare l’influenza che questa genera sul fenomeno di erosione interna e sulla stabilità.
Infine, è stato applicato un modello analitico semplificato (Bezzazi et al., 2010) alla sezione oggetto di studio. Tale modello ha consentito di stimare la vulnerabilità della sezione al fenomeno di erosione interna, sotto l’ipotesi di lavoro che il cunicolo della tana comunicasse il petto con la schiena dell’argine.
9
Laqui, Calizaya Fernando Ramiro. « Estimación de la erosión y transporte potencial de sedimentos hasta el eje de la futura represa Callazas en sub-cuenca del río Callazas en la región Tacna-Perú ». Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2019. http://hdl.handle.net/10757/626410.
Texte intégralRésumé :
La investigación consiste en la estimación de la tasa potencial media de erosión hídrica (ton/ha. año) y el volumen promedio del transporte potencial de sedimentos en millones de metros cúbicos (MMC) en proyección a 50 años hasta el eje de la futura represa Callazas. La delimitación del área de estudio se ubica desde aguas abajo de la laguna Suches hasta el eje de la futura represa Callazas denominada subcuenca Callazas Zona 1. Se estima que la tasa de erosión hídrica promedio con la metodología de USLE a nivel conceptual es 108.9 (ton/ha. Año) y con herramienta GIS un valor de 64.3 (ton/ha. año), el cual se considera una erosión ligera/moderada.
Asimismo, se estima el volumen de sedimentos del vaso proyectado de la represa Callazas con el valor de 0.372 MMC del registro histórico de 50 años con USLE y con la fórmula de transporte total de sedimentos de Englund-Hansen la estimación de 0.485 MMC en proyección a 50 años de operación. Por tanto, por un factor de seguridad de resultados se complementan las 2 metodologías con un volumen muerto de 0.857 MMC. El resultado preliminar se podría considerar aceptable ya que el estudio de factibilidad de la represa Callazas estima 11.5 MMC de volumen de almacenamiento y 1 MMC de volumen muerto, el cual resulta menor al volumen muerto proyectado.The research consists in estimating the average potential rate of water erosion (ton / ha. Year) and the average volume of potential sediment transport in millions of cubic meters (MMC) in projection at 50 years to the axis of the future dam Callazas. The delimitation of the study area is located from downstream of the Suches lagoon to the axis of the future Callazas dam called Callazas sub-basin Zone 1. It is estimated that the average water erosion rate with the USLE methodology at the average conceptual level is 108.9 (ton / ha. year) and with GIS tool an average of 64.3 (ton / ha. year), which is considered a light / moderate erosion. Likewise, the volume of sediments of the projected vessel of the Callazas dam is estimated with the value of 0.372 MMC of the historical record of 50 years with USLE and with the formula of total transport of sediments of Englund-Hansen the estimate of 0.485 MMC in projection to 50 years of operation. Therefore, the 2 methodologies area complemented by a safety factor of results with a dead volume of 0.857 MMC. The preliminary result could be considered acceptable since the feasibility study of the Callazas dam estimates 11.5 MMC of storage volume and 1 MMC of dead volume, which is less than the projected dead volume.
Tesis
10
Schmidt, Walter, et Marcus Schindewolf. « Erosion 3D Sachsen ». Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-38172.
Texte intégralRésumé :
Für die Erstellung von Bewirtschaftungs- und Maßnahmenplänen (FFH, EU-WRRL) ist es erforderlich, den bislang noch sehr hohen Aufwand für die Datenbeschaffung und -generierung im Rahmen der Modellierung mit EROSION 3D zu senken. Erreicht werden soll eine schnellere sowie effizientere Abschätzung von Landnutzungsänderungen, Landschaftseingriffen, des Klimawandels usw. auf Oberflächenabfluss, Bodenabtrag sowie Sedimenteintrag in Gewässer mit EROSION 3D.
Im vorliegenden Projekt ist es gelungen, Parametrisierung und Modellanwendung so zu kombinieren, dass eine Bodenabtragssimulation mit dem Modell EROSION 3D flächendeckend für Sachsen mit vertretbarem Zeitaufwand durchführbar ist.
Der korrigierte und angepasste Geo-Basisdatensatz liefert die Primärinformationen zur Datenbankabfrage der Parametrisierungssoftware DPROC. Durch eine interaktive Flächenauswahl, kombiniert mit einem Flächendatenzuschnitt, können Landnutzungs- und Bearbeitungsszenarien für hydrologische Einzugsgebiete oder Oberflächenwasserkörper schnell parametrisiert werden. Die grundlegend korrigierte und erweiterte Datenbank des DPROC erlaubt die verbesserte Abschätzung erosionsrelevanter Bodenparameter, besonders für die dauerhaft konservierende Bodenbearbeitung und die Direktsaat. Die umfangreiche Dokumentation der Arbeitsschritte und die Transparenz der Datenbank ermöglichen es, jederzeit Aktualisierungen (Geo-Basisdaten) und Erweiterungen (DPROC-Datenbank) vorzunehmen.
Von den Projektergebnissen profitieren vor allem die Anwender des Programms EROSION 3D.
Beim Druck des Dokumentes ist zu beachten, dass die Karten im Format DIN A3 erstellt wurden.
11
Dormoy, Thomas Gerard. « Arctic Coastal Erosion ». Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bygg, anlegg og transport, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-27046.
Texte intégralRésumé :
With the recent increase of interest in Arctic, the need rises for new tools for understanding the typical mechanisms of this very unique and so vulnerable area. The coast, which concentrates nearly all of the human activities, is in the front line and probably the most critical part of the system. Trough the past decades, mappings of the Arctic’s shorelines point out huge erosion rates and show the threat of a climate change upon the coast. Recent studies seem to link those tremendous moves to the annual thermal variations within the soil. However, the mechanisms of thermal abrasion that are suggested to be at the hearth of the process are not yet completely understood.In answer for the need of numerical models for thermal analysis of the erosion process, this thesis proposes a toolbox specially designed, based on literature review and fieldwork data. Trough the chapters, the reader shall find essential tools for estimations of the heat transfer into a soil and complete understanding of the physical mechanisms behind. Critical parameters that influence the erosion process are highlighted. To assess the operational deployment of those tools, a thermal analysis of a site has been performed. The conclusions demonstrate the capacity of numerical models to underline the critical gears of the heat transfers, and hopefully will help understanding the erosion processes of this particular place.
12
Dun, Shuhui. « Adapting WEPP (Water Erosion Prediction Project) for forest watershed erosion modeling ». Online access for everyone, 2006. http://www.dissertations.wsu.edu/Thesis/Summer2006/S%5FDun%5F073106.pdf.
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13
Ferdos, Farzad. « Internal Erosion Phenomena in Embankment Dams : Throughflow and internal erosion mechanisms ». Doctoral thesis, KTH, Byggvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-193627.
Texte intégralRésumé :
In this study, two major internal erosion initiation processes, suffusion and concentrated leak mechanisms, which lead to both defect formation in a dam’s body and its foundation and high throughflow in dams subjected to internal erosion were studied. This understanding has the potential to facilitate numerical modelling and expedite dam safety assessment studies. The throughflow properties of coarse rockfill material were studied by; analysing filed pump test data, performing extensive laboratory experiments with a large-scale apparatus and numerically simulating the three-dimensional flow through coarse rock materials, replicating the material used in the laboratory experiments. Results from the tests demonstrate that the parameters of the nonlinear momentum equation of the flow depend on the Reynolds number for pore Reynolds numbers lower than 60000. Numerical studies were also carried out to conduct numerical experiments. By applying a Lagrangian particle tracking method, a model for estimating the lengths of the flow channels in the porous media was developed. The shear forces exerted on the coarse particles in the porous media were found to be significantly dependent on the inertial forces of the flow. Suffusion and concentrated leak mechanisms were also studied by means of laboratory experiments to develop a theoretical framework for continuum-based numerical modelling. An erosion apparatus was designed and constructed with the capability of applying hydraulic and mechanical loading. Results were then used to develop constitutive laws of the soil erosion as a function of the applied hydromechanical load for both suffusion and concentrated leak mechanisms. Both the initiation and mass removal rate of were found to be dependent on the soil in-situ stresses. A three-dimensional electrical-resistivity-based tomography method was also adopted for the internal erosion apparatus and was found to be successful in visualising the porosity evolution due to suffusion.QC 20161006
14
Boden, Wiebke. « Prediction of erosion damages in hydraulic machines for hydro-abrasive erosion ». Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC034/document.
Texte intégralRésumé :
L’énergie hydraulique, où l’énergie cinétique de l’eau est transformée en énergie électrique, représente une contribution importante aux énergies renouvelables. L’eau qui passe par les turbines hydrauliques contient toujours une partie solide, par exemple du sable et de l’argile. Ces sédiments peuvent atteindre des niveaux de concentration élevés, ce qui nuit considérablement à la structure de la turbine par un mécanisme d’endommagement appelé érosion hydro-abrasive. Des types de turbine impliquant des vitesses d’écoulement très élevées, comme les turbines Pelton, sont particulièrement sensibles à l’érosion hydro-abrasive. Les simulations numériques présentent un moyen efficace d’étudier le sujet de l’érosion hydro-abrasive dans les turbines Pelton car elles permettent facilement la variation des nombreux paramètres. Ainsi, une réponse immédiate aux questions opérationnelles, de conception ou d’optimisation peut être obtenue. Cependant, il a été démontré que l’application des modèles d’érosion généraux et souvent utilisés ne fournit pas de résultats corrects en raison des propriétés particulières du matériel et de l’écoulement des turbines Pelton. Par conséquent, ce travail étudie le potentiel de la modélisation de l’érosion directe basée sur des principes fondamentaux. Cela implique que le mouvement des sédiments dans le fluide est simulé, leurs paramètres au moment de l’impact enregistrés et ensuite l’endommagement macroscopique global du matériel calculé sur la base des simulations de structure en microéchelle. Une formulation très appropriée pour les simulations fluides dans les turbines Pelton est une méthode sans maillage, plutôt nouvelle, qui s’appelle Smoothed Particle Hydrodynamics (SPH). Par conséquent, la première partie de ce travail aborde la mise en oeuvre et l’évaluation d’un modèle Lagrangien de transport des sédiments dans le cadre de cette méthode où les sédiments sont transportés par une équation de mouvement. L’effet du bruit inhérent à la méthode SPH sur le mouvement des sédiments est évalué par rapport à l’effet de la dispersion turbulente des sédiments, qui a été introduite par un modèle basé sur l’équation de Langevin. En outre, les termes liés aux différentes forces dans l’équation du mouvement sont étudiés dans le cadre de la méthode SPH. Une deuxième partie de ce travail développe une approche efficace et généralement applicable pour obtenir l’endommagement globale sans adopter des modèles d’érosion. Pour obtenir cet endommagement global en macroéchelle, l’endommagement causé par un seul impact de sédiment, qui est calculé par des simulations de structure en microéchelle, est combiné avec les statistiques d’impact des simulations du fluideHydraulic energy represents one important contribution to the growing source of renewable energies where the kinetic energy of water is transformed into electric energy. The water flowing through the hydraulic turbines always contains a solid part, for example sand and clay. Those sediments can reach high concentrations, harming importantly the turbine structure by a mechanism called hydro-abrasive erosion. Turbine types implying very high flow velocities, like Pelton turbines, are in particular sensitive to hydro-abrasive erosion. Numerical simulations present an efficient way to study the topic of hydro-abrasive erosion in Pelton turbines as they allow the variation of numerous parameters. Thus an immediate response to operational, design or optimization questions can be obtained. However it has been shown that the application of general, widely used erosion models do not deliver physical correct results due to the particular material and flow properties of Pelton turbines. Consequently this work investigates the potential of erosion modeling based on first principals. That means the sediment movement in the fluid is simulated, their state at impact tracked and then the overall macroscopic material damage calculated based on microscale structural simulations. A convenient formulation for fluid simulations in Pelton turbines is the rather novel, meshless method Smoothed Particle Hydrodynamics (SPH). Therefore the first part of this work addresses the implementation and evaluation of a Lagrangian sediment transport model in the framework of this method where sediments are transported by a particle equation of motion. The effect of the SPH method inherent noise on the sediment movement is evaluated against the effect of the turbulent dispersion of the sediments, which has been introduced via an ad-hoc model based on the Langevin equation. Furthermore the different force terms in the particle equation of motion are investigated with respect to the SPH method. A second part develops an efficient and general applicable approach to obtain the overall erosion damage without adopting erosion models. Therefore the damage caused by a single sediment impact is calculated by structural simulations on the microscale in a first step. In a second step that isolated damage is combined with impact statistics from the fluid simulations and hence gives the overall damage profile on the macroscale
15
Bertrand, Fabienne. « Fluvial erosion measurements of streambank using Photo-Electronic Erosion Pins (PEEP) ». Thesis, University of Iowa, 2010. https://ir.uiowa.edu/etd/642.
Texte intégralRésumé :
Fluvial erosion incites significant bridge scour and large-scale bank erosion causing estimated $1.1 billion damage in the Midwest. Conventional, manual, field monitoring methods, typically erosion pins, cross-section resurveys or terrestrial photogrammetry, used to monitor fluvial erosion rates merely provide a net change in bank surface retreat since the previous measurement. If mass wasting has occurred, the ongoing fluvial erosion would be masked. Erosion event timing, and the precise bank response to individual flow or flow hydrograph changes, is generally uncertain. Thus, a technique that automatically quantifies bank erosion on a continuous basis is needed. This study will monitor the bank response to individual flow (i.e., fluvial erosion) using the Photo-Electronic Erosion Pin (PEEP) sensors in Clear Creek Iowa. It attends to monitor a full episode of bank change, including event timings and magnitude information for specific erosion and deposition events, which can be compared to flow discharges and hydrographs. If exploited, this method can lead to more detailed analysis of bank erosion related to temporal fluctuations in the suspected hydraulic forces.
16
Smith, Jennifer Lynn. « The use of rolled erosion control products (RECPs) for minimizing soil erosion ». Related electronic resource : Current Research at SU : database of SU dissertations, recent titles available, full text:, 2007. http://wwwlib.umi.com/cr/syr/main.
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Pickles, Matthew Jonathan. « Hydrodynamic erosion of coatings ». Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243503.
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Duncan, Helen. « Erosion corrosion by minerals ». Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278290.
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Feng, Zheng, et Zheng Feng. « The erosion of materials ». Doctoral thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/23076.
Texte intégralRésumé :
Solid particle erosion tests of glass, stainless steel, WC-Co and sintered alumina, have been performed with seven erodents using a range of particle diameters D (63 μm - 1000 μm), velocities V (33 m.s⁻¹ - 131 m.s⁻¹ ) and impact angles α (30° - 90°). The seven erodents are steel shot, glass beads, silica, alumina, tungsten carbide, silicon carbide and diamond· particles. In addition, the target materials have been subjected to cavitation erosion using a conventional ultrasonic horn in distilled water. Systematic studies of the influence of the impact variables on the erosion rate have been made. Scanning electron microscopy of the eroded surfaces and the erodents after impact has been performed. Empirical correlations between erosion rate and the parameters of erosion and the erodents were obtained and are discussed in terms of the modes and mechanisms of erosion. A semi-quantitative theoretical model has been developed to explain the empirical correlations for brittle and ductile materials. The mode of erosion of glass impacted by irregularly shaped particles is associated with the formation and interaction of lateral cracks over all impact velocities and angles used in this study. The erosion of glass by spherical particles is determined by particle size, impingement velocity and angle. An erosion map, in which the erosion of glass is mapped against velocity and particle size, has been constructed to categorise the types of damage observed in glass for impingement angles between 90° and 30°. The erosion. behaviour of 304 stainless steel is associated with cutting or ploughing and plastic accumulation processes. The erosion of WC-Co is associated with a combination of ductile and brittle modes of erosion. The erosion of alumina is brittle and associated with intergranular spallation and grain-crushing. An analysis of the results reveals that for the brittle materials, glass and alumina, the erosion rate is determined by kinetic energy, particle size and the relative hardness and toughness of the erodents. However, for ductile materials, the shape and kinetic energy of erodents are the most important factors determining the erosion rate. There is no significant effect of hardness and toughness of erodents on erosion. Surprisingly, the erosion resistance of the softer 304 stainless steel is better than that of alumina and WC-Co when hard erodents are used at impact angle greater than 40°. On the other hand the erosion resistance of the harder WC-Co and alumina is better than that of 304 stainless steel for softer erodents like silica erodents. Glass always exhibits poor erosion resistance. In cavitation erosion, stainless steel exhibits better cavitation erosion resistance than glass, alumina and WC-Co. The cavitation erosion resistance of WC-Co is dependent upon the cobalt content. An attempt to rationalise the results in terms of mechanisms has been made. Both solid particle and cavitation erosion rate for the as received glass is higher than that for the tempered glass due to introduction of residual compressive stresses into the surface by the tempering process. Particularly, it reveals that compressive stresses are more efficient in preventing the formation and propagation of Hertzian cracks. These findings will assist in the choice and design of materials that undergo both particle and cavitation erosion under specified conditions.
20
Mahoney, Erin Kathleen. « Erosion Of Primary Teeth ». Thesis, Faculty of Dentistry, 2009. http://hdl.handle.net/2123/4612.
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21
Lüthi, Marcel. « A modified hole erosion test (HET-P) to study erosion characteristics of soil ». Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/36999.
Texte intégralRésumé :
Today’s increasing demand for energy and natural resources requires safe and reliable infrastructure. This includes hydraulic earth structures like dikes, levees, or dams. Such structures are susceptible to piping, a fundamental type of internal soil erosion. Piping is one of the principal causes of failures and accidents affecting embankment dams. The Hole Erosion Test (HET) is based on soil piping, and is used to determine the erodibility and critical shear stress of a soil. A soil specimen with a preformed axial hole is subjected to a constant-head pressure flow, and the rate of enlargement of the soil pipe is determined indirectly from flow rate and hydraulic gradient. This study presents a Modified Hole Erosion Test (HET-P) that introduces a conventional Pitot-static tube to measure total energy head and flow velocity of the exiting jet, which is correlated to a mean velocity within the axial hole. A series of Modified Hole Erosion Tests (HET-P) was performed on non-erodible PVC specimens with axial holes of constant, but different diameter, followed by HET-P tests on two types of soil, namely glacial till material of a dam core and natural clay deposits from Ontario river banks. Results confirmed that sidewall hydraulic head measurements to determine hydraulic gradients in the standard HET overestimate the resulting axial wall shear stress by as much as an order of magnitude. Furthermore, velocity measurements increase the confidence in test results as they allow for a more direct estimate of the axial hole diameter at any time during a test. A Pitot-static tube used in the HET-P for velocity and pressure measurement can easily be incorporated, and yields more transparent and reliable results by eliminating or amending some of the limiting assumptions of the standard test. It is an easy, fast, and economical approach that can be applied to soils in both constructed earth structures including dams and embankments, and to natural river banks to determine their susceptibility to internal and surface erosion.
22
Choi, Daniel Mintae. « Rainfall intensity and soil erosion by water : limitations of current erosion models and implications for erosion model-based studies under future climates ». Thesis, University of Oxford, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604890.
Texte intégralRésumé :
Existing simulation studies of the effects of future climate change upon erosion indicate that, under land usages that leave the soil unprotected, even minor increases in rainfall amounts are likely to result in disproportionately large increases in erosion, but commonly make the simplifying assumption that distributions of future rainfall intensities remain unchanged from the present. This research aims to determine implications of rainfall -intensity changes on soil erosion using computerised models. Thus, this thesis is a step towards the ultimate goal of predicting future rates of soil erosion caused by future rainfall intensity changes. Three soil erosion models, WEPP, EUROSEM, and RillGrow are employed to investigate impacts of various rainfall intensities on runoff and soil loss rates. Two extreme daily rainfall events in summer and autumn are subjectively selected from the tipping-bucket rainfall data, and runoff and soil losses are simulated using three erosion models. Estimated runoff and soil loss rates with high resolution rainfall data are greater than those with low temporal resolution rainfall data. Within-Storm Intensity Patterns (WSIPs) affect soil erosion amount, although runoff was not much affected. An additional daily rainfall event with Within-Storm Gaps (WSGs) is also selected to investigate effects of WSG removals on soil erosion. For a given amount of rainfall, events with constant low intensity (constant WSIP) produced dramatically less erosion: thus it appears that assuming a constant (or averaged) intensity throughout a storm does not provide a good representation of a real rainfall with its continuously varying intensity. Analyses of outputs from WEPP simulations revealed a problem that WEPP modifies original rainfall intensity and, thus, simulates erroneous runoff and erosion rates. Future soil erosion rates are estimated using WEPP and CLIGEN data. 30 year-long weather is generated by CLIGEN. Likely future rainfall frequency and intensity are anticipated by changing the mean maximum 30 minutes peak intensity also known as MX.SP. No fu ture rainfall amount change is assumed. WEPP simulation results suggest that where mean maximum 30-min peak intensity of the wet months increases soil erosion increases at a greater rate than runoff. This research assists in improving the performance of erosion models with respect to changes of rainfall intensity by highlighting where current problem exists. In conclusion, greater knowledge found here will, once future changes in rainfall intensity become better known and appropriate rainfall data become available, improve our ability to estimate future rates of erosion.
23
Sutarto, Tommy Ekamitra. « Bank erosion processes in streams in the U.S. Midwest ». Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/6648.
Texte intégralRésumé :
Rivers in the U.S. Midwest are dynamic systems that can be natural laboratories for understanding the different modes of bank erosion, namely fluvial erosion, mass erosion, and mass failure. Fluvial and mass erosion are hydraulically driven and semicontinuous, whereas mass failure is episodic and often catastrophic. Being catastrophic, mass failure and its driving mechanisms have received considerable attention comparatively to mass and fluvial erosion. However, the linkage between hydraulically driven erosion and mass failure has not been examined fully. We hypothesize that fluvial and mass erosion affect the memory and response of the system by creating favorable hydrogeomorphic conditions for mass failure.
This dissertation addresses three major shortcomings in the bank erosion literature, including the confusion surrounding critical erosional strength values for mass and fluvial erosion (τc,m and τc,f, respectively). The herein results clearly show that these two parameters are different, with τc,m being three to five times greater than τc,m. Therefore, excluding mass erosion estimates from sediment budgets or stability analyses can lead to significant errors in quantifying or predicting bank retreat and channel geometry. In addition, this study offered a methodological improvement for measuring the τc,m in-situ using Photo-Electric Erosion Pins, which semi-automatically measure mass erosion to generate erosional strength and erodibility values that are currently missing in the literature. This study also addressed the preconceived notion in morphodynamic modeling that bank soil profiles are homogeneous and universal strength/ cohesion parameters adequately represent the bank soil profile. This study shows that bank soil heterogeneity is present and significantly affects bank stability.
Therefore, heterogeneity along a bank face must be assessed in at least three locations to provide adequate input data for bank erosion models. Finally, this study suggests that Factors of Safety for mass failure must be complemented with those for fluvial and mass erosion to avoid underestimating mass failure by as much as 30%. Hence, this study provides agencies like the U.S. Department of Agriculture key data regarding the total contributions from the different modes of bank erosion and channel, itself, to the stream sediment load for strategic targeting of Best Management Practices and in-streams stabilization structures.
24
Thapa, Bhola. « Sand Erosion in Hydraulic Machinery ». Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-302.
Texte intégralRésumé :
The topic of this thesis is damage of hydraulic machinery due to sand erosion. This is a very broad topic in which all the aspects of design of hydraulic machinery namely material selection; mechanics of material and hydraulics are involved. The issue of sand erosion is equally important for operation and maintenance of hydropower plants.
The erosion damage of turbines of hydropower plants in Himalayan Rivers, in particular in Nepal, due to high sediment contents in river is a motivating factor for this research. The findings of this study are believed to help to reduce erosion of turbine components, increase their life time and improve maintenance procedure.
The objectives of this study are to:
1. Study the erosion process on different materials and compare lifetime of turbine material with hard surface coating.
2. Study the flow in the turbine and identify the region of highest velocity and acceleration where most serious sand erosion occurs.
3. Study erosion rate of turbine as a function of operating parameters (head and speed), particle characteristics and turbine material.
4. Assess loss of efficiency and to analyze repair method and repair interval that gives optimal economy of the hydropower plants.
The goals laid out in the objectives are achieved by understanding the theory of erosion of material through literature, investigating the nature of turbine damage from field observation and finally by experiments to study effect of variables of erosion rate and investigation of particle separation process in rotational flow.
25
Schindewolf, Marcus. « Phosphoreinträge durch Erosion in Sachsen ». Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-85270.
Texte intégralRésumé :
Im Projekt wurde eine Methodik entwickelt, um mit dem Modell EROSION 3D sachsenweit für erosionsauslösende Starkniederschlagsszenarien den partikelgebundene Phosphoreintrag in Oberflächenwasserkörper abzuschätzen.
Mit dieser Abschätzung und der Identifikation wassererosionsgefährdeter Ackerflächen bzw. Feststoffeintragspfade in Gewässer lassen sich zur erfolgreichen Umsetzung der EU-Wasserrahmenrichtlinie zielgerichtete Maßnahmen zum Erosionsschutz ableiten.
Die Modellierungen mit EROSION 3D zeigen, dass eine konsequente Umstellung auf konservierende Bodenbearbeitung die P-Austräge in Sachsen signifikant um 80-90 % senken würde. Die Projektergebnisse liefern wichtige Grundlagen zur P-Anreicherung im Feinbodenanteil von Ackerböden und geben einen Einblick in das Prozessverständnis der partikelgebundenen P-Austragsdynamik.
26
Zhu, Jingxu (Jesse). « Tube erosion in fluidized beds ». Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29225.
Texte intégralRésumé :
Heat transfer tubes suffer erosion when immersed in fluidized beds. This has caused problems, especially in fluidized bed combustors. The mechanism of erosion for horizontal tubes in fluidized beds is not well understood. The purpose of this study was to investigate the erosion mechanism in fluidized beds and to investigate the influence of operating parameters and the mechanical properties of the particles and tube materials.
Horizontal tube erosion tests were carried out in a room temperature three-dimensional fluidized bed with a cross-section of 216 mm by 203 mm and height of 1.52 m. Sample rings of ten different materials were mounted on a solid bar and were weighed before and after each test to determine the erosion rate. The parameters tested were particle size (0.30 to 1.51 mm), particle sphericity (0.84 to 1.0), particle density, particle hardness, superficial air velocity (0.88 to 2.52 m/s), tube diameter (15 mm to 32 mm), tube configuration and material mechanical properties. Two additional types of experiments were also conducted to help understand the mechanism of erosion. In one particles were dropped freely in an empty column to impact on test specimens at different velocities determined by the dropping distance, in order to investigate erosion due to solid particle impact under known conditions. In the other the particle movement was filmed in the vicinity of a horizontal tube in a two-dimensional fluidized bed in order to investigate the particle flow pattern around a tube. A small number of tests were also conducted at high temperatures.
The erosion of a horizontal tube in fluidized beds was found to be caused mainly by the impact of solid particles on the lower surface. Erosion was found to be strongly dependent on the particle impact velocity, which is closely related to the void (bubble or slug) rise velocity. The void rise velocity, in turn, is determined by the mean void size which depends on the superficial air velocity, column size and other fluidizing conditions. Particle diameter also has a strong influence on erosion. The target material Young's modulus appears to be the major mechanical property which is closely related to the erosion rate caused by solid impact erosion. Of the materials tested, all non-ferrous metals suffer much more erosion than ferrous metals. Localized high particle velocities due to jets and at bends or near feed points can be extremely harmful.
The mechanism of erosion caused by low velocity (< 6m/s) solid particle impacts appears to be different than that caused by high velocity (> 30m/s) impacts reported in the literature, although there are some similarities in trends. The erosion at low impact velocities appears to be mainly due to a surface fatigue process, which, instead of plastically deforming a small amount of target material for every impact, deforms the target materials in the elastic range and causes them to crack on or underneath the surface leading to removal of materials.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
27
Duncan, S. « Ion erosion in surface analysis ». Thesis, Loughborough University, 1985. https://dspace.lboro.ac.uk/2134/28023.
Texte intégralRésumé :
Low energy ion bombardment is a process used in surface analysis and in the electronics and telecommunications industries. Techniques such as Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS) and Secondary Ion Mass Spectroscopy (SIMS) employ ion bombardment for surface cleaning and for the provision of composition-depth profiles.
28
Zhang, Yu 1965. « Erosion behaviour of engineering ceramics ». Monash University, School of Physics and Materials Engineering, 2002. http://arrow.monash.edu.au/hdl/1959.1/8404.
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29
Godwin, Ian Chandler Paterson. « Physiographic Components of Trail Erosion ». Thesis, Montana State University, 2000. http://etd.lib.montana.edu/etd/2000/godwin/GodwinI_00.pdf.
Texte intégralRésumé :
No previous study has sought to discriminate between soil erosion and soil compaction when explaining the "missing" cross-sectional areas of incised trails, assuming instead that erosion was the dominant process. Separating the two processes of erosion and compaction is critical to understanding the relationship between physiographic variables and the structure of trails. The purposes of this project are to estimate the relative effects of compaction and erosion on trail cross sectional area along the New World Gulch Trail, Montana, and to better understand the relationship between erosion, compaction, local topography, vegetation, soil bulk density, and soil texture. The following hypotheses were addressed: 1) adjusting the incised cross sectional area of a trail, by removing the effects of soil compaction, will increase the amount of variance in erosion explained by collected physiographic variables; and 2) inclusion of soil bulk density and soil texture as physiographic variables will increase the amount of variance in cross-sectional area explained along the trail. The goals of this study required the collection of field data, analysis of soil samples, and statistical analysis of data. Soil samples and other field measurements were collected over several months during the summer and fall of 1994. Some of the topographic information used in the statistical analysis originated in Urie's (1994) study of recreational trails. The determination of trail slope as one of the primary components of trail incision is consistent with previous studies. Soil water content is the second most significant independent variable when the percentage of particle sizes are not considered. Percent vegetative cover is also significant in the stepwise regression, although it is not significantly correlated to cross-sectional area. The most significant variable added to those already studied was soil bulk density. When individual variables were regressed against the measured cross-sectional area, off-trail soil bulk density accounted for the second greatest amount of variance (r² = 0.12) after trail slope (r² = 0.35). The ratio of on-trail soil bulk density to off-trail soil bulk density, which could be considered a measure of compaction, accounted for even more variance (r² = 0.18) than soil bulk density.
30
Eltvik, Mette. « Sediment erosion in Francis turbines ». Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22755.
Texte intégralRésumé :
Sediment erosion is a major challenge for run-of-river power plants, especially during flood periods. Due to the high content of hard minerals such as quartz and feldspar carried in the river, substantial damage is observed on the turbine components. Material is gradually removed, thus the efficiency of the turbine decreases and the operating time of the turbine reduces. Hydro power plants situated in areas with high sediment concentration suffer under hard conditions, where turbine components could be worn out after only a short period of three months. This short life expectation causes trouble for energy production since the replacement of new turbine parts is a time consuming and costly procedure. It is desirable to design a Francis runner which will withstand sediment erosion better than the traditional designs. The literature states that an expression for erosion is velocity to the power of three. By reducing the relative velocities in the runner by 10%, the erosion will decrease almost 30%. The objective is to improve the design of a Francis turbine which operates in rivers with high sediment concentration, by looking at the design parameters in order to reduce erosion wear. A Francis turbine design tool was developed to accomplish the parameter study. In the search for an optimized Francis runner, several design proposals were compared against a reference design by evaluating the turbine’s performance. The hydraulic flow conditions and the prediction of erosion on the turbine components are simulated by analyzing the models with a Computational Fluid Dynamic (CFD) tool. A Fluid Structure Interaction (FSI) analysis ensures that the structural integrity of the design is within a desired value. Results from this research show that it is feasible to design a runner with an extended lifetime, without affecting the main dimensions and hydraulic efficiency.
31
Szente, Roberto Nunes. « Erosion of plasma torch electrodes ». Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74256.
Texte intégralRésumé :
The erosion of copper electrodes in a concentric cylinder geometry with magnetically driven arcs was studied at steady state for currents up to 250 A in a variety of gases and gas mixtures, magnetic field strengths and gas flow rates. The effects of arc velocity, gas composition, current density and heat transfer to the cathode on erosion rates were examined.The arc velocity varied with the magnetic field strength and arc current accordingly to a newly developed equation, V $ alpha$ B$ sp{0.60}$ I$ sp{0.56}$, when the cathode surface was slightly contaminated with C, Cl, O or N. The composition of the surfaces was found using Auger and ESCA spectroscopy. A surface drag force, a new force opposing to the arc motion was proposed. In the case of clean and heavily contaminated surfaces (contaminant layers thicker than 10 microns), the surface drag becomes the major force opposing the arc movement. Work function measurements showed that surface drag increased as electron emission became more difficult.
A novel technique was developed to determine the current distribution of the arc foot on the electrodes. A correlation between the arc foot current density and erosion rate was proposed. The effects of the surface composition, magnetic field and arc velocity on the arc current distribution were also examined.
A conceptual model was developed for electrode erosion; the model was supported by experimental results and by the results of simulations using macroscopic and microscopic heat transfer models.
32
Ewunkem, Asoumu Emmanuel. « Cavitation erosion of engineering materials ». Thesis, City University London, 1993. http://openaccess.city.ac.uk/8358/.
Texte intégralRésumé :
The work presented in this thesis is concerned with evaluating the erosion resistance or behaviour of various engineering materials to cavitation erosion in a through flow device. A wide range of engineering materials have been utilized, from metal alloys, plastics, ceramics to composiles. These were procured from various industrial and research establishments. The metal alloys which were supplied in various condition of heat treatments, ranged from aluminium alloy to nitrided and tool steels. The plastic employed were epoxy resins. These were supplied in two different formulations the "Novalac" and the Bisphenol" systems. They were produced in as cast and machined conditions. Thus the influence of both the formulation and the production processes on their cavitation erosion behaviour have been analysed. Silicon carbide arid silicon nitride were the ceramic materials employed in this project. Both were produced under three surface finish conditions. These were fired or sintered, ground and lapped respectively. The performances of all three surface finishes have been elucidated and the cavitation erosion resistance of both silicon carbide and silicon nitride have been ascertained. Glass reinforced plastic (GRP) and Fybroc were the composites utilized. They both employed glass fibre as the reinforcing element. Their cavitation erosion behaviour and resistance have been evaluated. Detailed observation of damage progression in the above three classes of materials have been made. A comprehensive cavitation erosion test data base has been obtained. An appraisal on a comparative basis of the different erosion rates of the various material tested is presented.
33
Scullion, I. M. « Erosion by solid particle impact ». Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234058.
Texte intégralRésumé :
Basic single particle impact studies were carried out on copper, steel and dural. By calculating the coefficient of restitution without employing the usual small indentation approximations, closer agreement was found with experimental data. The experimentally determined dynamic hardness was found to be between 1.3 and 1.4 times the quasi-static indentation hardness. A notable feature of these experiments was the formation of surface rings in the bottom of the impact crater. These impacts were analysed in a manner analogous to that used for the impact of a liquid drop on a rigid substrate where damage is caused by the detachment of the shock wave from the contact periphery. An extension of the single particle impact studies was an investigation into the chipping car paint. The failure mechanism was found to be primarily shear debonding at the coating/substrate interface which facilitated the formation of chips and subsequent corrosion of the metal substrate. Suggestions were made to improve the performance of the paint system. In the area of multiple particle impact, considerable improvements were made to the existing erosion apparatus and associated instrumentation, particularly in the area of particle velocity measurement. This was then used to investigate the behaviour of a range of materials including pure metals, nimonic alloys and polymer specimens. The nimonic alloys were found to have an angular response more typical of a brittle material than of a ductile metal. Most of the materials studied exhibited incubation times which were shown to correspond to between ten and several hundred impacts on the same target area. Study of titanium metal (which emits sparks during erosion) at normal incidence showed that some mass loss is actually occurring throughout the incubation period, although the specimen may be exhibiting a net mass gain. This mass loss is thought to be due to a single impact mechanism such as cutting or ploughing, which is then swamped by a co-operative mechanism to produce a linear erosion rate. The incubation period cannot therefore be due solely to the superposition of a linear mass loss and a saturating rate of embeddment.
34
Harris, P. K. « Erosion in centrifugal compressor impellers ». Thesis, Cranfield University, 1996. http://dspace.lib.cranfield.ac.uk/handle/1826/10622.
Texte intégralRésumé :
An experimental and theoretical study of erosion in centrifugal compressor impellers is
presented. An experimental rig using laser anemometry techniques was employed to create
a database of particle restitution ratios for a range of materials. This data was unique in
that the particle rebound was measured in a quiescent condition where the aerodynamic
effects had been minimised, and also parametric factors not previously available were
included. These values were incorporated into the existing Particle Trajectory Code
developed by Cranfield University and Rolls Royce PLC. The code is used to calculate
the trajectories of discrete particles in three dimensional gas turbine geometries, and the
ensuing erosion. It was modified to include the effects of the periodic boundary
conditions, particle fragmentation, splitter blades, and variations in inlet dust concentration
profile. Flowfield calculations were performed on a Rolls Royce GEM-2 and splittered
GEM-60 impeller, which both represent the high pressure stage of the axial + centrifugal
compression system of GEM engines. A procedure developed by Tourlidakis, for the
analysis of steady viscous flow in high speed centrifugal compressors with tip leakage,
was used to generate the flowfields. The GEM-2 impeller flowfield was analysed at 1009c
speed, and validated with calculations and measurements which had been taken for
previous projects. Simulated erosion data under the same conditions was checked using
practical results obtained in a Rolls Royce PLC Helicopter Engine Environmental
Protection Programme, and good agreement was achieved. In order to provide a qualitative,
experimental assessment of erosion, a GEM-60 impeller was coated with four layers of
paint of different colours. Two sizes of quartz particle, each at three different vane
heights, were then seeded into the impeller while it was run cold at (the maximum) 70%
speed. The erosion patterns generated compared well with the results generated by the
Particle Trajectory Code.
35
Hankey, S. E. « Cavitation erosion of WC-Co ». Master's thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/21135.
Texte intégralRésumé :
Bibliography: pages 68-70.An investigation involving the vibratory cavitation erosion of WC-Co alloys was undertaken in order to determine the mechanisms of material removal. Nineteen grades of WC-Co alloys were studied. These alloys had been previously characterised according to microstructural and mechanical properties. Further characterisation by way of Young's modulus and density of the materials was undertaken. An investigation of the i nfluence of various parameters on cavitation erosion established a binder content dependence on erosion. For two grain sizes, erosion was found to increase to a maximum at 12 vo1-% binder content (1.8 μm grain size) and 23 vol-% binder (2.8 μm grain size). The main mode of material removal was found to be cobalt removal followed by WC grain pull-out. In high binder content alloys, cobalt removal was predominant with little loss of WC grains. X-ray diffraction showed that the allotropic phase transformation of the binder under cavitational attack was beneficial to the erosion resistance of these alloys. The erosion of low binder content alloys was controlled by the contiguity of the WC skeleton. Maximum erosion occurred at binder contents which corresponded to the combination of a fragile WC skeleton and a small volume of available cobalt for strain induced transformation.
36
Wellman, R. G. « Solid particle erosion of ceramics ». Master's thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/18219.
Texte intégralRésumé :
The zeolite ZSM-5 is well-known for its unique intersecting channel system. This channel system has a great bearing on the shape-selective properties and the long life-times of ZSM-5. In this study, ZSM-5 was modified in various ways to eliminate the external acidity of the catalyst to further improve these properties, and the success and effects of these modifications were investigated primarily using temperature programmed desorption techniques. The internal surface of ZSM-5, a medium pore zeolite, plays a major role in the shape selective properties of this catalyst, due to the diffusional restrictions imposed by the channel system on bulky molecules. Even though the number of acid sites on the external surface is small compared to the total number of acid sites, these easily accessible and non-shape selective acid sites may provide a high turnover rate for non-shape selective reactions. Furthermore, the main cause of deactivation of ZSM-5 is thought to be the formation of polyaromatic molecules on the external surface, which block access to the channels of the catalyst.
37
Conforto, Sesto Juan R. « Erosion in Southern Monterey Bay ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Mar%5FConfortoSesto.pdf.
Texte intégralRésumé :
Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, March 2004.Thesis advisor(s): Edward B. Thornton, James MacMahan. Includes bibliographical references (p. 37). Also available online.
38
Pilippu, Hewage Eranga Dulanjalee. « Erosion and entrainment during landslides ». Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/28901.
Texte intégralRésumé :
The main focus of this thesis is to experimentally investigate the effect of grain size on the mechanism of erosion during landslides using small-scale laboratory experiments. Specifically, we have focused on the effect of the grain size of the flowing and erodible bed materials on the erosion rate. We experimentally investigated a flow of particles over an erodible base in a laboratory-scale inclined flume with different particle size combinations for the flow and the erodible substrate. The dynamics of the flow-erodible bed interface was captured with X-ray radiography. The evolving erosion depths were estimated from the well-established critical velocity-based method and a novel particle size-based method.
The erosion rates estimated from the two techniques gave contradictory conclusions. The normalized erosion rate increases with the flow to bed grain size ratio in the critical-velocity-based erosion rate estimation, whereas the erosion rates estimated from the particle-size-based approach encounter the opposite trend. To further investigate this behaviour, we have developed a one-dimensional continuum model which incorporates the kinematics of the flowing system. The observed erosion behaviour interpreted from the bidisperse calibration method is reproduced with this model reasonably well. The effect of size-based segregation in these flows is found to be minimal, however overall, we observed reverse segregation in the flow system.
In this research, we successfully captured the internal micromechanics of the flow field with X-ray radiography. This imaging methodology allows us to probe deeply within the flowing material, avoiding limitations in data capturing only near sidewalls that are prevalent with other imaging methods. In contrast to the critical velocity-based technique, the newly developed bidisperse calibration technique precisely determined the flow-erodible bed interface.
39
Chun, Wang. « Erosion-corrosion mitigation using chemicals ». Thesis, University of Leeds, 2007. http://etheses.whiterose.ac.uk/747/.
Texte intégralRésumé :
The presence of entrained sand in oil and gas production is becoming increasingly prevalent as wells age and this is leading to erosion-corrosion in C02-saturated conditions becoming a major mechanism of material attack. Its understanding, prediction and control are key challenges to sound facilities design. The use of carbon steel in conjunction with corrosion inhibitors in preventing erosioncorrosion has been observed as an economically viable solution for oil and gas piping systems. In order to produce highly effective corrosion inhibitors, it is important to understand how inhibitors act on each of the components of erosion-corrosion. Although research into corrosion inhibition has been extensively conducted, there is less documentation of inhibitors in retarding erosion-corrosion. This thesis has attempted to construct a quantitative structure relationship between erosion, corrosion and their synergistic effects to investigate erosion-corrosion and inhibition mechanisms with four fully formulated CO2 inhibitors (CGO, CRO, CRW8 and CRW9) along with some mechanistic studies involving single components from inhibitor formulations. Two experimental set-ups were used: a rotating cylinder electrode (RCE) and a submerged impinging jet (SIJ). In both experimental methodologies, gravimetric measurement, cathodic polarisation, Linear Polarisation and AC impedance techniques were used to ascertain the extent of corrosion as a function of conditions and inhibitor dosing/type. Both RCE and SIJ test samples were studied using surface analysis techniques such as scanning electron microscope (SEM), Light microscope, Energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS). In this thesis, through integration of electrochemical analysis and gravimetric measurements the damage has been identified as being associated with mechanical erosion, electrochemical corrosion or interactive electrochemical/mechanical processes. The role that inhibitors can play in reducing damage in addition to that caused by corrosion, namely by erosion and their synergistic action has been shown. Under both configurations. erosion-corrosion interactions play a major role in damage with corrosion being a controlling parameter. The thesis has made substantial advances in the understanding of the extent to which corrosion inhibitors could be used to control erosion-corrosion damage and in understanding the mechanisms of how this can be achieved.
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Meng, Hang. « Erosion-corrosion of marine alloys ». Thesis, University of Leeds, 2009. http://etheses.whiterose.ac.uk/12739/.
Texte intégralRésumé :
Marine alloys such as stainless steels, copper-base alloys and cast iron have a long history of applications over a wide range of industries. They always are exposed to aggressive erosion-corrosion environments to support or transmit forces during the service, where more than millions of pounds are involved to repair the material degradation every year. In order to minimize this cost, lots of money and research have been put into practice, from which more and more erosion-corrosion behaviour and mechanisms of marine alloys were understood, however, downtime of marine systems still happens, moreover it is still a fact that it is quite difficult to choose the optimum material for the specific working environment. In this project, erosion-corrosion performance of eight marine alloys which include three different grade stainless steels, four copper-base alloys and one Niresist cast iron has been assessed under liquid-solid jet impingement over eight sets of test conditions in 3.5% sodium chloride solution. Firstly, the weight loss of different marine alloys ranks the priority of their corrosion, erosion and erosion-corrosion resistance over the range of the test conditions, furthermore the total weight loss test, in conjunction with in-situ electrochemistry measurements, enable the relative contribution of the different mechanisms interacting in the degradation to be quantified, meanwhile the aspects of erosion-corrosion mechanisms of different marine alloys have been detailed. Even erosion-corrosion is a complex process, but microhardness has been found to be the controlling factor in severe erosion-dominated conditions. More importantly, primary concerns have been brought on the factorial contributions of individual environmental parameters and their interactions to the overall material degradations. A full two-level factorial experimental design method combined with following analysis of variance was applied to qualify these factorial contributions, which shows effects of the individual environmental parameters and their interactions on the weight loss during the erosion-corrosion processes, and the prominent factors are velocity, sand loading and their interaction. Fluid temperature has the smallest effect compared with other environmental parameters.
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Deneke, Fred. « Soil Erosion Control after Wildfire ». College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2002. http://hdl.handle.net/10150/146945.
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DeGomez, Tom. « Soil Erosion Control after Wildfire ». College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2011. http://hdl.handle.net/10150/239603.
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Pineda, Rondon Saira Freda. « Numerical prediction of cavitation erosion ». Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC031/document.
Texte intégralRésumé :
La cavitation peut avoir lieu dans les turbines hydrauliques. Ce phénomène se produit lorsque les bulles de vapeur s’effondrent à proximité de la surface de la machine. Ceci entraîne des conséquences négatives, telles que l’érosion, affectant ainsi les performances de la machine. L’effondrement d’une bulle de gaz non-condensable dans l’eau est simulé en utilisant la méthode sans maillage SPH-ALE, qui intègre un modèle pour simuler les écoulements compressibles et multiphases. Le modèle résout les équations de conservation de masse, de quantité de mouvement et d’énergie du système d’Euler, en utilisant l’équation d’état de Stiffened Gas pour l’eau et l’équation d’état de gaz parfait pour le gaz non-condensable à l´ıntérieur de la bulle. Les deux phases sont modélisées comme compressibles et le changement de phase n’est pas considéré. La caractéristique sans maillage de la méthode SPH-ALE permet le calcul des écoulements diphasiques où l’interface est nettement définie. Pour les applications de cavitation, où le nombre de Mach atteint des valeurs de 0.5, la distribution de particules doit être corrigée. Cela est réalisé grâce à la fonctionnalité ALE. Le modèle compressible a été validé à l’aide de configurations monodimensionnelles, comme le cas du tube à choc pour des écoulements monophase et multiphases. L’effondrement de la bulle près d´une paroi a été abordé comme le mécanisme fondamental qui produit des dégâts. Son comportement général se caractérise par la formation d’un micro jet d’eau et par l’effondrement de la bulle sur elle-même. Le phénomène est analysé en tenant compte des principaux paramètres qui le régissent, comme la distance initiale entre le centre de la bulle et la paroi (H0), la taille de la bulle (R0) et le taux de pression qui entraîne l’effondrement (pw/pb). Il est démontré que l’intensité de l’effondrement dépend principalement du rapport de pression entre le liquide et la bulle (pw/pb). De plus, quatre indicateurs, comme la pression en paroi, l’impulsion, la pression du coup de bélier et la vitesse du micro jet d’eau, servent à déterminer le chargement. Cette analyse indique qu’une bulle initialement située à une distance inférieure à H0/R0 = 2 présente un haut potentiel d’endommagement. Afin de prédire cet endommagement, la mécanique du solide est analysée à l’aide de simulations d’interaction fluide-structure. On obtient que le matériau réagit aux charges hydrauliques en ayant des zones de compression et de traction. Ceci suggère qu’un mécanisme de fatigue entraîne le phénomène d’endommagement. En plus, on constate que les contraintes les plus importantes sont situées sous la surface du matériau, indiquant que cette zone peut être sujette à une déformation plastiqueHydraulic turbines can experience cavitation, which is a phenomenon occurring when vapor bubbles collapse in the vicinity of the machine’s surface. This phenomenon can lead to negative consequences, such as erosion, that affect the machine’s performance. The compression of a non-condensable gas bubble in water is simulated with the Smoothed Particle Hydrodynamics method following the Arbitrary Lagrange Euler approach (SPHALE), where a compressible and multiphase model has been developed. The model solves the mass, momentum and energy conservation equations of the Euler system using the Stiffened Gas EOS for water and the ideal gas EOS for the non-condensable gas inside the bubble. Both phases are modeled as compressible and the phase change is not considered. The meshless feature of the SPH-ALE method allows the calculation of multiphase flows where the interface is sharply defined. For cavitation applications, where the Mach number reaches values of 0.5, the distribution of particles must be corrected, which is achieved by the ALE feature. The compressible model was validated through monodimensional configurations, such as shock tube test cases for monophase and multiphase flows. The bubble compression close to the wall has been addressed as the fundamental mechanism producing damage. Its general behavior is characterized by the formation of a water jet and by the collapse of the bubble by itself. The phenomenon is analyzed by considering the major parameters that govern the bubble collapse dynamics, such as the initial distance between the bubble center and the wall (H0), the bubble size (R0), and the collapse driven pressure ratio (pw/pb). It is shown that the intensity of the collapse depends mainly on the pressure ratio between the liquid and the bubble (pw/pb). As well, four indicators, such as the pressure at the wall, the impulse, the water-hammer pressure and the water jet velocity, are used to determine the loading. This analysis gives that the bubble initially located at a distance lower than H0/R0 = 2 presents high potential to cause damage. In order to predict the damage due to the bubble collapse, the solid mechanics is analyzed through fluid-structure interaction simulations. It is obtained that the material reacts to the hydraulic loads by having compression and traction zones, suggesting that a fatigue mechanism drives the damage phenomenon. Additionally, it is found that the highest stresses are located below the material surface, indicating that this zone may reach plastic deformation
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Sigby, Albin. « Förändringsanalys av erosion längs Klarälven ». Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-74725.
Texte intégralRésumé :
Klarälven är en av Sveriges längsta älvar och är unik i Skandinavien för sitt karaktäristiska meanderlopp. Det unika i Klarälvens fall är att älvfåran är instängd mellan två bergssidor. Klarälvens meanderlopp innebär erosion och förändringar i älvens lopp. Syftet med studien är att jämföra och analysera hur erosionen längs en sträcka av Klarälven har förändrats över tid. Underlaget består av en historisk karta från 1883 samt ortofoton från 1961 och 2014. Studien är avgränsad till en 25 km lång sträcka norr om Ekshärad i Värmland. Metoder som används omfattar georeferering av den historiska kartan samt skärmdigitalisering av samtliga data. Därefter granskades och jämfördes resultaten genom överlagringsanalys uppdelat i två perioder samt alla perioder på en gång. Resultatet visar att omfattande erosion och avlagring har skett. I älvens ytterkurvor där vattnets hastighet är som högst har störst erosion skett och i innerkurvorna där vattnet rinner långsammare har det eroderade materialet avlagrats. De största skillnaderna är uppmätta mellan åren 1883 och 1961. Men erosionsförändring i mindre skala har skett även mellan 1961 och 2014.River Klarälven is one of Sweden's longest rivers and is unique in Scandinavia because of its characteristic meander course. The uniqueness in the case of Klarälven is that the riverbed is trapped between two mountain sides. The meandering course of Klarälven means major changes in its path due to extensive erosion along some reaches. The purpose of this study is to compare and analyze how some reaches of River Klarälven have changed over time. The data consists of a historical map from 1883 as well as orthophotos from 1961 and 2014. The study is limited to a 25 km meandering reach north of the town Ekshärad in northern Värmland. Methods involved are georeferencing of the historical map and screen digitizing of all data. Subsequently, the results were reviewed and compared by overlay analysis divided into two periods and all periods at once. The result shows that extensive erosion and deposit have taken place. In the river's outer curves where the velocity of the water is highest is also the place where most erosion occurs. In the inner curves where the water velocity is slower, the eroded material is deposited. The largest differences were measured between the years 1883 and 1961. However, erosion changes on a smaller scale also occurred between 1961 and 2014.
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PIGAZZINI, ILARIA. « Evaluating and Detecting Architecture Erosion ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/365009.
Texte intégralRésumé :
Un'architettura software è erosa (o degradata) se mostra una progressiva perdita di integrità strutturale a causa di violazioni dei principi di progettazione. I sistemi erosi soffrono di Architectural Technical Debt (ATD), lo sforzo aggiuntivo richiesto agli sviluppatori per gestire i difetti causati dall'erosione. Un sintomo dell'accumulo di ATD è la presenza di Architectural Smells (AS), decisioni di software design che hanno un impatto negativo sulla qualità interna del sistema software. I sistemi affetti da AS soffrono di maggiori costi di manutenzione e sono più difficili da evolvere. Questa tesi indaga sei diversi tipi di AS che violano diversi principi di design in progetti Java monolitici Open-Source e industriali. Identifichiamo gli AS con il nostro strumento, Arcan, e introduciamo la sua nuova estensione per la rappresentazione dei software concerns. Discutiamo poi gli AS dal punto di vista dei professionisti, cercando di riassumere come gli AS sono percepiti e validando i risultati di Arcan. Riportiamo anche i risultati dei nostri studi empirici riguardanti l'evoluzione e la correlazione di AS e ATD. Infine, presentiamo i nostri primi risultati riguardanti la migrazione e la manutenzione di architetture a microservizi, con particolare attenzione al rilevamento degli odori dei microservizi.A software architecture is eroded (or degraded) if it shows a progressive loss of structural integrity due to design principle violations which leads to the deviation of the implemented architecture from the intended architecture. Eroded systems suffer from Architectural Technical Debt (ATD), the additional effort required by developers to manage the shortcomings caused by the erosion. A symptom of the accumulation of ATD is the presence of Architectural Smells (AS), design decisions that impact negatively on the internal system quality. Systems affected by AS suffer from higher maintenance costs and are harder to evolve. This thesis investigates six different types of AS violating different design principles in Open-Source and industrial monolithic Java projects. We identify AS with our tool, Arcan, and introduce its new extension for the representation of software concerns. We then discuss AS from the point of view of practitioners, trying to summarise how AS are perceived and validating Arcan results. We also report the results of our empirical studies concerning AS and ATD evolution and correlation. Finally, we present our first results concerning the migration and maintenance of microservices architectures, with a focus on the detection of microservices smells.
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Van, der Poel Petrus W. « Plunge pool erosion in cohesive channels below a free overfall / ». Connect to resource, 1985. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1202403267.
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Fernandes, Leila Posser. « AVALIAÇÃO DA ERODIBILIDADE DE UM PERFIL DE SOLO TÍPICO DA ÁREA DO CAMPO DE INSTRUÇÃO DE SANTA MARIA RS ». Universidade Federal de Santa Maria, 2015. http://repositorio.ufsm.br/handle/1/7895.
Texte intégralRésumé :
Fundação de Amparo a Pesquisa no Estado do Rio Grande do SulThe research that resulted in this master thesis was developed on a dirt road Instruction Campo de Santa Maria, RS. The main objective was to study the erodibility of the surface soil horizons A, B and C. The methodology consisted in the literature; field investigations and laboratory stage. In the latter were carried out tests of physical and chemical characterization, direct shear strength tests, cone penetrometer dynamic test, testing for indirect evaluation (breakdown, laboratory cone, infiltration rate and loss by immersion) and direct (Inderbitzen) erodibility . The results were compared with the proposed Bastos (1999) to estimate the soil erodibility unsaturated located in Porto Alegre.A road evaluated this on a probable fluvial terrace. Based on results of direct shear tests showed greater susceptibility to erosion to the horizon C. The test of dynamic cone penetrometer confirmed the results found by Pittelkow (2013) and Santos (2014) showing greater penetration resistance for the crust layer. In indirect evaluation of erodibility - by estimating the erodibility factor (KUSLE) soil horizons A, B and C, was between 0.24 and 0.40, making sure it can not separate these materials on the erodibility. The breakdown test showed increased susceptibility to erosion for the B and C horizons, regardless of the moisture condition. The results of the laboratory test cone was unsatisfactory with the results observed in the field. The MCT methodology presented a good relationship of correspondence between the results of the tests and the behavior of soils in the studied sites, primarily for the air condition to dry moisture, proving their applicability to the materials. Direct evaluation made through the tests Inderbitzen confirmed that the loss of soil generally is greater the larger the slope of the ramp and flow test. According to this assessment to the horizon samples B and C there was a tendency of higher values of erodibility in dry condition the air. It was also found lower values of erodibility of the horizon, standing from about 0 to 13.8 g / cm2 / min / Pa, for natural moisture condition and dry air, respectively. B horizon values stood at an intermediate level, for samples in natural moisture condition. The values for K for the C horizon stood at 65.8 g / cm2 / min / Pa for the natural moisture. Did not establish critical hydraulic stresses for the A and B horizons, the natural moisture condition, but for the other conditions ranged between 0.94 and 1.29 Pa for the horizon and 0.95 and 1.17 Pa for the B horizon to horizon C values were between 0.90 and 1.19 Pa. The B and C horizons were the materials most potentially erodible. The criteria had better correlation with geotechnical proposed Bastos (1999) were the erodibility coefficient obtained in Inderbitzen test and the erodibility criteria MCT methodology.
A pesquisa que resultou nesta dissertação de mestrado foi desenvolvida em um perfil de solo típico do Campo de Instrução de Santa Maria, RS. O objetivo principal é a avaliação da erodibilidade dos solos superficiais dos horizontes A, B e C que compõem esse perfil de solo. A metodologia aplicada consistiu no levantamento bibliográfico; investigações de campo e na etapa de laboratório. Nesta última foram realizados os ensaios de caracterização física e química, ensaios de resistência ao cisalhamento direto, ensaio do penetrômetro dinâmico de cone, ensaios para avaliação indireta (desagregação, cone de laboratório, infiltrabilidade e perda por imersão) e direta (Inderbitzen) da erodibilidade. Os resultados foram classificados segundo a proposta geotécnica de Bastos (1999) para a estimativa da erodibilidade de solos não saturados na região de Porto Alegre. O perfil de solo esta situado próxima a jazida de empréstimo que esta sobre um provável terraço fluvial. Os resultados obtidos nos ensaios de cisalhamento direto demonstraram maior susceptibilidade à erosão para o horizonte C. O ensaio do penetrômetro dinâmico de cone confirmou os resultados encontrados por Pittelkow (2013) e Santos (2014) demonstrando maior resistência à penetração para a camada de crosta. Na avaliação indireta da erodibilidade através da estimativa do fator erodibilidade (KUSLE) os solos dos horizontes A, B e C, situou-se entre 0,24 e 0,40, verificando que não se consegue separar estes materiais quanto à erodibilidade. O ensaio de desagregação demonstrou maior susceptibilidade à erosão para os horizontes B e C, independente da condição de umidade. Os resultados do ensaio de cone de laboratório não foram satisfatórios com os resultados observados em campo. A metodologia MCT apresentou uma boa relação de correspondência entre os resultados dos ensaios e o comportamento dos solos nos locais estudados, principalmente para a condição de umidade seca ao ar, comprovando sua aplicabilidade a estes materiais. A avaliação direta, feita através dos ensaios de Inderbitzen, confirmou que geralmente a perda de solo é tanto maior quanto maior for à inclinação da rampa e a vazão de ensaio. Segundo esta avaliação, para as amostras dos horizontes B e C verificou-se certa tendência de valores mais elevados de erodibilidade na condição seca ao ar. Também se verificou valores mais baixos de erodibilidade do horizonte A, situando-se de aproximadamente 0 a 13,8 g/cm2/min/Pa, para a condição de umidade natural e seca ao ar, respectivamente. No horizonte B os valores situaram-se em um patamar intermediário, para as amostras na condição de umidade natural. O valore de K para o horizonte C situou-se em 65,8 g/cm2/ min/ Pa, para a umidade natural. Não se conseguiu determinar as tensões hidráulicas críticas para os horizontes A e B, na condição de umidade natural, mas para as demais condições situaram entre 0,94 e 1,29 Pa para o horizonte A e 0,95 e 1,17 Pa para o horizonte B. Para o horizonte C os valores situaram-se entre 0,90 e 1,19 Pa. Os horizontes B e C foram os materiais mais potencialmente erodíveis. Os critérios que obtiveram melhor correlação com a proposta geotécnica de Bastos (1999) foram o coeficiente de erodibilidade obtido no ensaio Inderbitzen e o critério de erodibilidade da metodologia MCT.
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Martínez, Casasnovas José Antonio. « Suelo-paisaje-erosión. Erosión por cárcavas y barrancos en el Alt Penedès - Anoia (Catalunya). Un enfoque de estudio mediante tecnologías de la información espacial : bases de datos, Sistemas de Información Geográfica y teledetección = Soil-landscape-erosion. Gully erosion in the Alt Penedès - Anoia (Catalonia) : a spatial information technology approach : spatial databases, Geographical Information Systems and remote sensing ». Doctoral thesis, Universitat de Lleida, 1998. http://hdl.handle.net/10803/8244.
Texte intégralRésumé :
Aquesta investigació suposa una contribució al desenvolupament de metodologies queamplien l'aplicabilitat dels sistemes d'informació geogràfica (SIG), la teledetecció i les
bases de dades en l'anàlisi del territori. En concret, la investigació es centra en l'anàlisi de
les relacions sòl-paisatge, de les propietats dels sòls y dels processos d'erosió hídrica,
particularment els processos d'erosió per xaragalls i barrancs. La investigació se porta a
terme en les comarques de l'Alt Penedès y l'Anoia (Catalunya), una àrea on la vinya per a
la producció de vins d'alta qualitat i caves és el principal cultiu, però on la forma actual de
l'ús i maneig del sòl, amb escasses mesures de conservació, condiciona la sostenibilitat
futura dels usos agrícolas presents.
Un dels resultats principals de la investigació és el sistema d'informació de sòls (SIS),
desenvolupat a una escala semidetallada a nivell de tota l'àrea d'estudi. Aquest SIS ha
permès analitzar la distribució espacial dels principals tipus de sòl, les seves propietats i el
seu comportament davant l'acció dels processos erosius i de les actuacions antròpiques.
També constitueix l'estructura sobre la qual es poden desenvolupar bases de dades
espacials de sòls més detallades.
Una altra aportació és el conjunt de metodologies basades en l'anàlisi multitemporal de
fotografies aèries, de models digitals d'elevacions (MDE), i també en la classificació
multiespectral d'imatges de satèl·lit i en les operacions d'anàlisi espacial mitjançant SIG,
que conduexen a l'anàlisi de processos d'erosió per xaragalls i barrancs. L'aplicació
d'aquestes metodologies a l'àrea de l'Alt Penedès - Anoia confirma la important influència
de l'acció antròpica en l'acceleració dels processos d'erosió actual. Aquesta acceleració
dels processos erosius es reflecteix principalment en:
a) les propietats dels sòls, amb la posada en superfície de materials d'horitzonts
subjacents, rics en carbonat càlcic, calcilutites o arenisques,
b) 1' anàlisi morfomètric i morfogràfic de les geoformes, que mostra un modelat del
paisatge amb vessants complexes i barrancs, i una alta densitat de xaragalls
incipients,
c) l'anàlisi de les taxes d'erosió per xaragalls i barrancs, que han estat particularment
elevades des de la deforestació generalitzada amb roturació de terres per a la
plantació de vinya, a partir del segle XVI, sobretot, a partir de la mecanització dels
cultius.
La investigació realitzada confirma la importancia de combinar tècniques de camp i
laboratori amb tècniques de teledetecció per a l'adquisició de dades i coneixement dels
processos d'erosió, i amb tècniques de SIG amb finalitat de modelització.
La presente investigación supone una contribución al desarrollo de metodologías que
amplíen la aplicabilidad de los sistemas de información geográfica (SIG), la teledetección
y las bases de datos al análisis del territorio. En concreto, la investigación se centra en el
análisis de las relaciones suelo-paisaje, de las propiedades de los suelos y de los procesos
de erosión hídrica, particularmente los procesos de erosión por cárcavas y barrancos. La
investigación se desarrolla en las comarcas de l'Alt Penedès y l'Anoia (Cataluña), un área
donde la viña para producción de vinos de alta calidad y cavas es el principal cultivo, pero
donde la forma actual de los usos y manejo del suelo, con escasas medidas de
conservación, condiciona la sostenibilidad futura de los presentes usos agrícolas.
Uno de los resultados principales de la investigación es el sistema de información de suelos
(SIS), desarrollado a una escala semidetallada a nivel de toda el área de estudio. Este SIS
ha permitido analizar la distribución espacial de los principales tipos de suelo, sus
propiedades y su comportamiento frente a la acción de los procesos erosivos y actuaciones
antrópicas. También, constituye la estructura sobre la cual poder desarrollar bases de datos
espaciales de suelos más detalladas.
Otra de las aportaciones es el conjunto de metodologías, basadas en el análisis
multitemporal de fotografías aéreas y de modelos digitales de elevaciones (MDE), en la
clasificación multiespectral de imágenes de satélite y en operaciones de análisis espacial
mediante SIG, conducentes al análisis de procesos de erosión por cárcavas y barrancos. La
aplicación de estas metodologías al área del Alt Penedès - Anoia ha permitido confirmar la
importante influencia de la acción antrópica en la aceleración de los procesos de erosión
actual, que se ve reflejada principalmente en:
a) las propiedades de los suelos, con la puesta en superficie de materiales de
horizontes subyacentes ricos en carbonato calcico, calcilutitas o areniscas,
b) el análisis morfométrico y morfográfico de las geoformas, que muestra un
modelado del paisaje con vertientes complejas y barrancos, y una alta densidad de
cárcavas,
c) el análisis de las tasas de erosión por cárcavas y barrancos, que han sido
particularmente elevadas a partir de la deforestación generalizada con roturación de
tierras para la plantación de viña a partir del siglo XVI, y sobre todo a partir de la
mecanización de los cultivos.
La investigación realizada confirma la importancia de combinar técnicas de campo y
laboratorio con las técnicas de teledetección para la adquisición de datos y conocimiento
de los procesos de erosión, y con las técnicas de SIG con fines de modelización.
This research represents a contribution to the development of methodologies to extend the
applicability of geographical information systems (GIS), remote sensing and spatial
databases to terrain analysis, particularly soil-landscape relationships, soil properties and
hydric erosion processes, and more specifically gully erosion processes. The research is
carried out in the l'Alt Penedès y l'Anoia (Catalonia), an area where vineyards for high
quality and "cava" production are the main crop, but where the present manner of soil use
and management, with few control measures, determines the future sustainability of the
present agricultural uses.
One of the main results of the present research is the soil information system (SIS), that
contains semi-detailed scale information about the soils of the study area. It allowed the
analysis of the spatial distribution of the main soil types, their properties and their
behaviour in front of the actuation of erosion processes and anthropic transformations.
Also, it constitutes the basic structure from which more detailed soil spatial databases can
be developed.
Another contribution is the set of methodologies, based on the multitemporal analysis of
aerial photographs and digital elevation models (DEM), multispectral classification of
satellite images and GIS spatial analysis, that is addressed to the analysis of gully erosion
processes. The application of those methodologies to the Alt Penedès - Anoia area
revealed the important influence of the anthropic factor in the acceleration of the present
erosion processes, that is observed through:
a) the soil properties, with the presence on surface of materials that are rich in calcium
carbonate, calcilutites or sandstones from subsurface layers,
b) the morphometric and morphographic analysis of the geoforms, which shows a
shape of the landscape with complex slopes and large gullies, and a high density of
gullies,
c) the analysis of the rates of gully erosion, that have been particularly high since the
generalised deforestation to plant vineyards in the XVI Century and, above all,
since the advent of mechanisation.
This research confirms the importance of combining field and laboratory techniques with
remote sensing techniques for data acquisition and knowledge concerning the occuring
erosion processes, and with GIS techniques for modelling.
49
Olivetti, Valerio <1976>. « Erosione e sollevamento nell'arco calabro-peloritano ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/2197/1/Olivetti_Valerio_tesi.pdf.
Texte intégralRésumé :
The Calabrian-Peloritani arc represents key site to unravel evolution of surface processes on top of subducting lithosphere. During the Pleistocene, in fact the arc uplifted at rate of the order of about 1mm/yr, forming high-standing low-relief upland (figure 2). Our study is focused on the relationship between tectonic and land evolution in the Sila Massif, Messina strait and Peloritani Mts. Landforms reflect a competition between tectonic, climatic, and surficial processes. Many landscape evolution models that explore feedbacks between these competing processes,
given steady forcing, predict a state of erosional equilibrium, where the rates of river incision and hillslope erosion balance rock uplift. It has been suggested that this may be the final constructive stage of orogenic systems. Assumptions of steady erosion and incision are used in the interpretation of exhumation and uplift rates from different geologic data, and in the
formulation of fluvial incision and hillslope evolution models. In the Sila massif we carried out cosmogenic isotopes analysis on 24 samples of modern fluvial sediments to constrain long-term (~103 yr) erosion rate averaged on the catchment area. 35 longitudinal rivers profiles have been analyzed to study the tectonic signal on the landscape evolution. The rivers analyzed exhibit a wide variety of profile forms, diverging from equilibrium state form. Generally the river profiles show at least 2 and often 3
distinct concave-up knickpoint-bounded segments, characterized by different value of concavity and steepness indices. River profiles suggest three main stages of incision. The values of ks and θ in the lower segments evidence a decrease in river incision, due probably to
increasing uplift rate. The cosmogenic erosion rates pointed out that old landscape upland is eroding slowly
at ~0.1 mm/yr. In the contrary, the flanks of the massif is eroding faster with value from 0.4 to 0.5 mm/yr due to river incision and hillslope processes. Cosmogenic erosion rates mach linearly with steepness indices and with average hillslope gradient.
In the Messina area the long term erosion rate from low-T thermochronometry are of the same order than millennium scale cosmogenic erosion rate (1-2 mm/yr). In this part of the chain the fast erosion is active since several million years, probably controlled by extensional tectonic
regime.
In the Peloritani Mts apatite fission-track and (U-Th)/He thermochronometry are applied to constraint the thermal history of the basement rock. Apatite fission-track ages range between 29.0±5.5 and 5.5±0.9 Ma while apatite (U-Th)/He ages vary from 19.4 to 1.0 Ma.
Most of the AFT ages are younger than the overlying terrigenous sequence that in turn postdates the main orogenic phase. Through the coupling of the thermal modelling with the stratigraphic record, a Middle Miocene thermal event due to tectonic burial is unravel. This
event affected a inner-intermediate portion of the Peloritani belt confined by young AFT data (<15 Ma) distribution. We interpret this thermal event as due to an out-of–sequence thrusting occurring in the inner portion of the belt. Young (U-Th)/He ages (c. 5 Ma) record a final
exhumation stage with increasing rates of denudation since the Pliocene times due to postorogenic extensional tectonics and regional uplift.
In the final chapter we change the spatial scale to insert digital topography analysis and field data within a geodynamic model that can explain surface evidence produced by subduction process.
50
Olivetti, Valerio <1976>. « Erosione e sollevamento nell'arco calabro-peloritano ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/2197/.
Texte intégralRésumé :
The Calabrian-Peloritani arc represents key site to unravel evolution of surface processes on top of subducting lithosphere. During the Pleistocene, in fact the arc uplifted at rate of the order of about 1mm/yr, forming high-standing low-relief upland (figure 2). Our study is focused on the relationship between tectonic and land evolution in the Sila Massif, Messina strait and Peloritani Mts. Landforms reflect a competition between tectonic, climatic, and surficial processes. Many landscape evolution models that explore feedbacks between these competing processes,
given steady forcing, predict a state of erosional equilibrium, where the rates of river incision and hillslope erosion balance rock uplift. It has been suggested that this may be the final constructive stage of orogenic systems. Assumptions of steady erosion and incision are used in the interpretation of exhumation and uplift rates from different geologic data, and in the
formulation of fluvial incision and hillslope evolution models. In the Sila massif we carried out cosmogenic isotopes analysis on 24 samples of modern fluvial sediments to constrain long-term (~103 yr) erosion rate averaged on the catchment area. 35 longitudinal rivers profiles have been analyzed to study the tectonic signal on the landscape evolution. The rivers analyzed exhibit a wide variety of profile forms, diverging from equilibrium state form. Generally the river profiles show at least 2 and often 3
distinct concave-up knickpoint-bounded segments, characterized by different value of concavity and steepness indices. River profiles suggest three main stages of incision. The values of ks and θ in the lower segments evidence a decrease in river incision, due probably to
increasing uplift rate. The cosmogenic erosion rates pointed out that old landscape upland is eroding slowly
at ~0.1 mm/yr. In the contrary, the flanks of the massif is eroding faster with value from 0.4 to 0.5 mm/yr due to river incision and hillslope processes. Cosmogenic erosion rates mach linearly with steepness indices and with average hillslope gradient.
In the Messina area the long term erosion rate from low-T thermochronometry are of the same order than millennium scale cosmogenic erosion rate (1-2 mm/yr). In this part of the chain the fast erosion is active since several million years, probably controlled by extensional tectonic
regime.
In the Peloritani Mts apatite fission-track and (U-Th)/He thermochronometry are applied to constraint the thermal history of the basement rock. Apatite fission-track ages range between 29.0±5.5 and 5.5±0.9 Ma while apatite (U-Th)/He ages vary from 19.4 to 1.0 Ma.
Most of the AFT ages are younger than the overlying terrigenous sequence that in turn postdates the main orogenic phase. Through the coupling of the thermal modelling with the stratigraphic record, a Middle Miocene thermal event due to tectonic burial is unravel. This
event affected a inner-intermediate portion of the Peloritani belt confined by young AFT data (<15 Ma) distribution. We interpret this thermal event as due to an out-of–sequence thrusting occurring in the inner portion of the belt. Young (U-Th)/He ages (c. 5 Ma) record a final
exhumation stage with increasing rates of denudation since the Pliocene times due to postorogenic extensional tectonics and regional uplift.
In the final chapter we change the spatial scale to insert digital topography analysis and field data within a geodynamic model that can explain surface evidence produced by subduction process.