Littérature scientifique sur le sujet « Erosione arch »
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Articles de revues sur le sujet "Erosione arch"
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Ricketts, B. D. « Princess Margaret Arch : re-evaluation of an element of the Eurekan Orogen, Axel Heiberg Island, Arctic Archipelago ». Canadian Journal of Earth Sciences 24, no 12 (1 décembre 1987) : 2499–505. http://dx.doi.org/10.1139/e87-234.
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It is argued on the basis of structural, stratigraphic, and sedimentologic criteria that Princess Margaret Arch developed during the principal phase of Eurekan thrusting and folding and therefore is no older than Middle Eocene. Sub-Eureka Sound Group unconformities on eastern Axel Heiberg Island are not associated with uplift on the eastern flank of this arch but are related to erosion of Mesozoic Sverdrup Basin strata over local evaporite diapir domes and ridges. Considerable disparity exists between levels of erosion on the flanks of the arch and the level of erosion along its axis, which cannot be explained by pre-Eocene uplift. Sedimentary facies and textural and petrographic characterisitics of Eureka Sound Group strata do not reflect proximity to an arch. Palynomorph assemblages in the west-derived, syntectonic Buchanan Lake Formation (Middle Eocene) contain reworked latest Cretaceous spores and pollen that were derived from Eureka Sound Group strata originally located on or close to the arch axis.Eureka Sound Group sedimentation in the Axel Heiberg Island – west Ellesmere Island region took place in a single, contiguous basin, rather than in smaller basins that were separated by ancestral Princess Margaret Arch.
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Groom, Robert C., Aaron G. Hill, Bechara F. Akl, Alan M. Speir, Paul S. Massimiano, Edward A. Lefrak, Derek D. Muehrcke et Delos M. Cosgrove. « Cannula length and arch flow erosion ». Annals of Thoracic Surgery 61, no 2 (février 1996) : 773–74. http://dx.doi.org/10.1016/0003-4975(96)89379-9.
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Feinstein, S., G. K. Williams, L. R. Snowdon, F. Goodarzi et T. Gentzis. « Thermal maturation of organic matter in the Middle Devonian to Tertiary section, Fort Norman area (central Mackenzie Plain) ». Canadian Journal of Earth Sciences 28, no 7 (1 juillet 1991) : 1009–18. http://dx.doi.org/10.1139/e91-092.
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The Fort Norman area is marked by a complex structural and depositional history with temporally and spatially variable temperature and maturity gradients. Maturity of the Middle Devonian Canol – Hare Indian unit indicates two terrains of markedly different paleotemperatures and thermal gradients, roughly coinciding with the Palaeozoic Keele Arch (north) and Root Basin (south), with a sharp transition (lateral discontinuity) between them. Maturity of the unconformably overlying Cretaceous to early tertiary section is lower and laterally continuous across the entire study area, showing no relation to the sub-Cretaceous structures. The vertical maturity profile in the southern terrain is unique in that two discontinuous segments record markedly different thermal histories, neither of which is related to present burial conditions. Maturity of the Devonian formations was established some time prior to the sub-Cretaceous erosion, whereas that in the Cretaceous to Tertiary section postdates Palaeocene but predates a major part of the later Tertiary deformation and erosion. In contrast, the continuous maturity profile recorded in the northern terrain reflects a significant effect of the Tertiary thermal conditions, indicating much lower thermal gradients in the Keele Arch than in the Root Basin during the early phase of maturation. Along with the structural pattern and sedimentary history, the striking differences indicated in the thermal gradients between the Root Basin and the Keele Arch suggest a strike-slip-related pull-apart or another stretching mechanism for the Root Basin in contrast to the compression in the Keele Arch. In addition to the characterization of the regional thermal history and its variation with time, the maturity pattern obtained allows some estimate to be made of the thickness of the eroded section and timing of the major erosional phases.
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Hannon, Chris J., et Ben J. Evans. « Solid particle erosion protection for the BLOODHOUND SSC front wheel arches ». Proceedings of the Institution of Mechanical Engineers, Part L : Journal of Materials : Design and Applications 232, no 12 (13 juillet 2016) : 1012–22. http://dx.doi.org/10.1177/1464420716659777.
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BLOODHOUND SSC is a World Land Speed Record Vehicle designed to travel at speeds of up to 1050 mph (469 m·s−1), with the lower chassis and suspension extremely close to the ground. The shockwave from the nose of the car is expected to fluidise the desert surface of the track in Hakskeen Pan, South Africa. Sacrificial materials must be added to the exterior of the car to limit erosive wear. An open loop gas blast erosion rig was used to test materials at velocities predicted by computational fluid dynamics in the front wheel arches, an area highlighted by the BLOODHOUND SSC engineers as requiring extensive protection. Tests of potential erosion protection materials were performed at 15° and 90° Impact angle using alumina as a substitute for Hakskeen Pan soil. Testing resulted in the use of a 2-mm thick Kevlar 49 laminate and 1.2 mm thick titanium Ti 15 V-3Cr-3Sn-3Al sheet for the wheel arch liner, with titanium Ti 6Al-4V used for the wheel arch lip. The erodent mass flow rate for the application was an unknown variable during testing; the test rig used a specific erodent mass flow rate of approximately 300 kg·m−2·s−1. Depending on in-service erosion rates, the titanium liner may be replaced with either a more durable liner made from Stellite 6B or a less dense liner made from aluminium Al 6082-T6.
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Benedetti, Alice, Alvise Del Monte, Maurizio Rubino et Daniela Mancuso. « 506 Uneventful pseudoaneurysm of the ascending aorta with sternal erosion in pregnancy ». European Heart Journal Supplements 22, Supplement_N (1 décembre 2020) : N142—N145. http://dx.doi.org/10.1093/eurheartj/suaa210.
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Abstract A 36-year-old woman at 31 weeks’ gestation presented with exertional dyspnoea and palpitations. She had a history of bicuspid aortic valve treated with surgical aortic valvotomy for severe stenosis, followed by ascending aorta replacement for type A acute aortic dissection and Bentall operation with a mechanical valve for severe aortic regurgitation. Eight years after the last surgery, magnetic resonance angiography showed aortic arch aneurysm (49 mm) with a small intimal flap. Thereafter, the patient was lost to follow-up until the current admission. She was hemodynamically stable on presentation and physical examination was unremarkable apart from a mechanical second heart sound. The electrocardiogram showed sinus rhythm with left bundle branch block (Panel A). Transthoracic echocardiography revealed severe left ventricular dilation (EDV 90 ml/m2) with mild dysfunction (EF 50%), normal prosthetic aortic valve function, and aortic arch dilation (50 mm) (Panel B and C). After a multidisciplinary evaluation, elective cesarean section was performed at 34 weeks’ gestation. A post-delivery aortic computed tomography angiography revealed aortic arch aneurysm (52 mm) with intimal flap and two pseudoaneurysms of the anterior aortic wall causing sternal erosion (Panel D, E, F and G). Subsequently, the patient underwent ascending aorta and aortic arch replacement by Frozen Elephant Trunk technique with a 24 x130 mm prosthesis between the aortic root and the descending aorta. The postoperative course was uneventful, and the patient was discharged to a cardiac rehabilitation centre.
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Li, Yaohuang. « Namtso Ancient Lagoon and Ancient Sea Erosion Landform ». E3S Web of Conferences 206 (2020) : 01015. http://dx.doi.org/10.1051/e3sconf/202020601015.
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During a certain geological period, the sea surface is at the current elevation of about 4746-4755 meters. When the sea surface is about 4746-4755 meters above sea level, the Namtso region of Tibet is a lagoon in the sea. The sea surface was kept stable at the above location for a long time, and a lot of sea erosion landforms were generated on the coast. The ancient sea erosion caves, sea erosion pillars, sea erosion arch bridges, sea erosion headlands, sea erosion headlands, sea erosion cliffs, sea erosion platforms and other various ancient sea erosion micro-landforms are well preserved on the banks of Namtso Lake. It is a unique and natural ancient coastal landscape park in the world
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Chidsey, Thomas, Jr, et Grant Willis. « Landscape Arch, Delicate Arch, and Double Arch in Arches National Park, Southeastern Utah ». Geosites 1 (11 mars 2020) : 1–12. http://dx.doi.org/10.31711/geosites.v1i1.54.
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Arches National Park in southeastern Utah has the greatest concentration of natural rock arches in the world. The park is located in a geologic region called the Paradox fold and fault belt in the northern Paradox Basin and showcases spectacular and classic Colorado Plateau geology with its colorful sedimentary rocks, ancient sand dunes, cliffs, domes, fins, and pinnacles, as well as the arches. The arches in the park and the surrounding region were formed by a unique set of circumstances involving Middle Pennsylvanian (about 308 million years ago [Ma]) to Late Triassic (200 Ma) movement of subsurface salt layers, Middle Pennsylvanian to Late Cretaceous (about 70 Ma) deposition, and Tertiary and Quaternary (23 Ma to the present) folding, faulting, erosion, and salt dissolution. Massive, hard, brittle sandstones jointed by folding, resting on or containing soft layers or partings, and located near fold structures such as salt-cored anticlines undergoing dissolution, and a dry climate, all favor the formation of arches. Rarely do all these phenomena occur in one place, but they do in Arches National Park.The Natural Arch and Bridge Society (NABS) stated, “A natural arch is a rock exposure that has a hole completely through it formed by the natural, selective removal of rock, leaving a relatively intact frame.” They also make it clear that a natural bridge (which is at least partially formed by flowing water) is one type of natural arch (NABS website) (see A Bit of Perspective, below, for more explanation). Using their own criteria, Stevens and McCarrick (1988) catalogued over 2000 natural arches in Arches National Park; most have unique characteristics that could qualify them as geosites. However, the three most famous arches in the park, and perhaps the world, are Landscape Arch, Delicate Arch, and Double Arch, and thus these were selected as the geosites for this paper.
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Rukosujew, Andreas, Raluca Weber, Bernd Kasprzak et Angelo Maria Dell’Aquila. « Stent erosion after treatment of coarctation of right-sided aorta and successful surgical management ». European Journal of Cardio-Thoracic Surgery 57, no 5 (21 octobre 2019) : 1007–8. http://dx.doi.org/10.1093/ejcts/ezz281.
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Abstract We present a case of surgical treatment of a pseudoaneurysm of the right-sided aortic arch after stent implantation for primary coarctation in a 36-year-old woman with a previous history of ventricle septal defect closure in early childhood. As a first step, she underwent a left carotid to subclavian artery bypass for an aberrant left subclavian artery and as a second step a ‘beating heart’ aortic arch and descending aorta replacement via resternotomy. The postoperative course was uneventful.
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Caputo, Mario Vicente, et Emilio Alberto Amaral Soares. « Eustatic and tectonic change effects in the reversion of the transcontinental Amazon River drainage system ». Brazilian Journal of Geology 46, no 2 (juin 2016) : 301–28. http://dx.doi.org/10.1590/2317-4889201620160066.
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ABSTRACT: The development of the transcontinental Amazon River System involved geological events in the Andes Chain; Vaupés, Purus and Gurupá arches; sedimentary basins of the region and sea level changes. The origin and age of this river have been discussed for decades, and many ideas have been proposed, including those pertaining to it having originated in the Holocene, Pleistocene, Pliocene, Late Miocene, or even earlier times. Under this context, the geology of the sedimentary basins of northern Brazil has been analyzed from the Mesozoic time on, and some clarifications are placed on its stratigraphy. Vaupés Arch, in Colombia, was uplifted together with the Andean Mountains in the Middle Miocene time. In the Cenozoic Era, the Purus Arch has not blocked this drainage system westward to marine basins of Western South America or eastward to the Atlantic Ocean. Also the Gurupá Arch remained high up to the end of Middle Miocene, directing this drainage system westward. With the late subsidence and breaching of the Gurupá Arch and a major fall in sea level, at the beginning of the Late Miocene, the Amazon River quickly opened its pathway to the west, from the Marajó Basin, through deep headward erosion, capturing a vast drainage network from cratonic and Andean areas, which had previously been diverted towards the Caribbean Sea. During this time, the large siliciclastic influx to the Amazon Mouth (Foz do Amazonas) Basin and its fan increased, due to erosion of large tracts of South America, linking the Amazon drainage network to that of the Marajó Basin. This extensive exposure originated the Late Miocene (Tortonian) unconformity, which marks the onset of the transcontinental Amazon River flowing into the Atlantic Ocean.
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Ruocci, Gianluca, Rosario Ceravolo et Alessandro de Stefano. « Modal Identification of an Experimental Model of Masonry Arch Bridge ». Key Engineering Materials 413-414 (juin 2009) : 707–14. http://dx.doi.org/10.4028/www.scientific.net/kem.413-414.707.
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The erosion of the river bed material at bridge pier foundation produced by scour events is one of the main causes of the observed masonry bridges failures and collapses. Foundation settlements and rotations derived from the reduction of the footprint under the piers threaten masonry arch bridges integrity more than any gravity load. The resulting effect on the structure is the development of cracking mechanisms on the arches which may affect the dynamic behaviour of the whole bridge. A scaled experimental model of a masonry arch bridge has been built in the laboratory of the Dep. of Structural Engineering at the Politecnico di Torino. The aim was to better understand scour damage scenario and to identify early structural symptoms of pier erosion. A preliminary dynamic identification is carried out on the intact structure and a comparison with the FEM results is performed. The set of identified modal parameters is adopted as the reference system that will be compared with those acquired after the application of damage of increasing extent.
Thèses sur le sujet "Erosione arch"
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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.
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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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Seon, Hongsun 1965. « Electrode erosion and arc stability in transferred arcs with graphite electrodes ». Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=108637.
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Arc stability and erosion behavior were studied on a hollow graphite DC cathode in an argon atmosphere at atmospheric pressure. It was found that the arc stability is associated with the electron emission mode transition of the cathode operation. Estimation of current densities, SEM pictures, Fast Fourier Transform (FFT) of total voltage, and measurement of cathode surface temperature supported this. Stable arcs are in the thermionic emission regime while unstable arcs in the thermofield emission regime. Higher argon gas flow rate is believed to cause the shift of the mode from the thermofield emission to the thermionic emission by increasing the arc root temperature through steepening the thermal gradient at the arc root and increasing ionization phenomena inside the arc. Sharp cathode tip geometry usually leads to the thermionic emission while a rounded tip geometry encourages the thermofield emission. For the unstable arcs, the high voltage fluctuation resulted from the jumping of the arc root between different cathode spots and changes in the arc length. In the stable arcs, however, the voltage was almost constant because of the absence of arc jumping. The standard deviation of the voltage was used as the arc stability indicator and was less than 3 V for the stable arc in this transferred arc system.The erosion rate of the cathode in this work ranged from 0.41 to 2.61 mug/C. At 150 A runs the arc stability strongly influenced the erosion rate; as the arc stability increased, the erosion rate decreased. Higher currents runs (300 and 400 A), however, showed the opposite trend because of the carbon vapor redeposition. The total erosion rates of 150 A runs were separated into the stable (Es) and the unstable (Eu) erosion rate. The Eu was more than 3 times higher in this work. It is believed that the thermofield emission of the unstable arcs produced more erosion because of the higher local heat flux to the cathode spots.
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Schneider, Wolfgang. « Studies on arcing phenomena at high current discharges ». Thesis, University of Essex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310044.
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Szente, Roberto Nunes. « Cathode erosion in magnetically rotated arces ». Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65438.
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Cunha, Matheus Araújo da. « Influência do tipo de erodente à base de alumina na incrustação em um revestimento de FeCr, aspergido por arco elétrico, empregado em ensaios de desgaste erosivo, à temperatura ambiente e a 400ºC ». reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/115272.
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Este trabalho investigou a influência do tipo de erodente à base de alumina na incrustação em um revestimento metálico à base de FeCr, aspergido por arco elétrico, empregados em ensaios de desgaste erosivo, tanto à temperatura ambiente como a 400°C, com ângulo de incidência entre o erodente e a superfície de 30° e 90° e velocidade de projeção de 25 m/s. Como erodente, utilizou-se alumina eletrofundida com faces anguladas e irregulares e também alumina calcinada com formando aglomerados esferoides. O revestimento dos corpos-de-prova foi caracterizado quanto à morfologia (MEV), porosidade, densidade aparente, análise térmica, espessura da camada depositada, taxa de erosão e mapeamento de elementos por espectrometria de energia dispersiva (EDS). Os erodentes foram caracterizados quanto a sua morfologia (MEV), distribuição granulométrica e área superficial (BET). Os resultados mostraram que à temperatura ambiente os ensaios realizados com alumina calcinada com ângulo de 30° e alumina eletrofundida a 90° foram os que apresentaram maiores quantidades de alumínio incrustado no revestimento para uma mesma área de análise. Os ensaios realizados com a alumina eletrofundida com ângulo de 30° foi a que apresentou a maior taxa de erosão. Já a distribuição granulométrica e área superficial dos erodentes após ensaio de erosão apresentaram uma diminuição em relação aos valores de antes do ensaio. Os ensaios realizados a 400°C de temperatura mostraram que a alumina calcinada, para os dois ângulos de ensaio, resultou em maior incrustação no revestimento ensaiado, sendo maior para o ângulo de 90° do que para o ângulo de 30°. Para essa temperatura de ensaio, a maior taxa de erosão ocorreu para o ensaio conduzido com ângulo de 30°, utilizando alumina calcinada. Ainda para os ensaios a 400°C, os resultados para o tamanho médio de partícula na distribuição granulométrica indicaram uma redução nos valores iniciais para todos os ensaios realizados. No entanto, a área superficial de ambos erodentes permaneceu com valores muito próximos ao de antes do ensaio.This work investigated the influence of the kind of erodent based on alumina embedded in a metallic coating based on FeCr, sprayed by arc electric technique, used in erosive wear test at room temperature and 400°C with angle of incidence between the erodent and the surface of 30° and 90° and erodent velocity of 25 m/s. As erodent was used fused alumina that showed angled and irregular surfaces and also calcined alumina forming spheroids agglomerates. The coating of the samples was characterized morphology (SEM), porosity, density, thermal analysis, the layer thickness, erosion rate and mapping of elements by energy dispersive spectrometry (EDS). The erodent was characterized by their morphology (SEM), particle size distribution and surface area (BET). The results showed that the room temperature tests performed with alumina calcined with angle of 30° and fused alumina with angle of 90° were those with larger amounts of aluminum embedded in the coating to the same area of analysis. Tests performed with the electro alumina with angle of 30° were presented the highest rate of erosion. Already the particle size distribution and surface area of erodent after testing erosion showed a decrease compared to the values before the test. The tests performed at 400°C temperature showed that the calcined alumina for the both angles test resulted in greater embedded of aluminum in the tested coating, being higher for the 90° angle than the angle of 30°. For this test temperature, the higher erosion rate occurred for the experiment with 30° angle using calcined alumina. Also for the tests at 400°C, the results for the average particle size in the particle size distribution showed a reduction in initial values for all tests. However, the surface area of erodent remained with both values very close to that of before the test.
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Pons, Frédéric. « Electrical contact material arc erosion : experiments and modeling towards the design of an AgCdO substitute ». Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33816.
Texte intégralRésumé :
AgCdO is one of the most widely used contact materials in the world because of its outstanding performance. Nevertheless, due to environmental considerations, it will soon be completely forbidden by European environmental directives. Therefore, finding a good substitute is of crucial importance.
Electrical arc erosion plays a crucial role in the reliability and life of power switching devices. Depending on the contact material's behavior in response to an electrical arc, surface damage can induce severe changes in contact material properties that will impact the power switching device's functioning. Consequently, electrical arc effects and consequences on the contact material surface are of first importance.
In this context, we have focused our research activities on the following axes.
First of all, in order to better understand AgCdO (Current contact material in aerospace industry) and AgSnO₂(Potential candidate to AgCdO substitution) arc erosion behaviors, arc erosion experiments, where the power switching devices have been subjected to different numbers of arc discharges, have been realized.
Further, a general macroscopic electrical contact arc erosion model valid for low and high currents was developed. To compare model results to experimental data, this model describes the complete breaking process of electrical contacts and gives the total amount of material removed after one breaking operation. In parallel, arc erosion experiments on AgCdO power switching devices have been conducted at high currents (0
-> 1000 A) in order to validate the arc erosion model.
Next, using the general arc erosion model, the properties having the greatest
influence on the electrical arc erosion process have been determined through simulations
on silver contact material. At this stage, ab initio calculations were needed to obtain
ranges of variation of certain silver contact material properties.
Finally, an investigation of the trends of changing local contact material on these identified material properties was performed. This study composition of AgSnO₂was based on ab initio calculations for two different oxide compositions of AgSnO₂.
These will allow us to give directions to aid the design of a good substitute for AgCdO, and therefore, to complete the main objective of this research work.
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Sumption, Alan. « The evolution of break arc erosion from arc initiation to extinction on silver alloy electrical contacts in low voltage DC switches ». Thesis, University of Southampton, 2005. https://eprints.soton.ac.uk/47499/.
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This study concerns the evolution of electrical contact erosion in low voltage 42V DC (24A) applications. The aim is to describe the erosion mechanisms of a single arc discharge at both contact surfaces during operation. To this end the experiments conducted are designed to produce results that enable close examination of the surface profile changes, volumetric contact material movements, and relative quantities of metallic and gaseous species in the arc discharge. The experimental procedure is arranged so that the contacts undergo a low number of operation cycles in order to limit the cumulative effects of arc erosion. To obtain results portraying the evolution of arc erosion in a 42V system the apparatus allows for interruption of the arc at any desired voltage level. A series of tests are conducted at specified voltage steps from arc initiation to extinction. The samples collected are analysed using a non-contact laser profile apparatus giving 2D and 3D surface scans. During each arc discharge a record of spectral emissions is collected by a spectrometer and later analysed to show the constituents of the arc. The data is represented with reference to voltage level and shows how the erosion evolution from a low number of operation cycles is related to arc phenomena. In addition the voltage profiles of the arc are recorded and represented by amplitude modulation. It has been found that the erosion site dimensions are related to the arc voltage fluctuations. In these tests a marked change of voltage slope is seen but is not found to be related to the metallic to gaseous phase transition as often thought. It is determined that the anodic to cathodic arc transition is not due to a metallic to gaseous phase transition. Changes in surface profile at the cathode occurring during the cathodic arc phase, and before gaseous phase initiation, are affected by density per unit area of ions impacting the surface. The vaporization of the cathode requires a critical ion density. This determines the anodic to cathodic transition point. Conversely the anode is thought to endure intense electron sputtering throughout the arc lifetime and its volumetric loss is greater than that of the cathode.
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Pons, Frédéric. « Erosion suite à l'impact d'un arc électrique : modélisation et campagnes expérimentales en vue du développement d'un matériau de substitution à l'alliage AgCdO ». Thesis, Metz, 2010. http://www.theses.fr/2010METZ039S/document.
Texte intégralRésumé :
L’AgCdO est l’un des matériaux de contact parmi les plus répandus dans le monde du fait de ses excellentes propriétés. Cependant, étant donné la présence de Cadmium dans celui-ci, il sera bientôt totalement interdit par des directives européennes d’ordre environnementales. Trouver un matériau ne contenant pas de Cadmium et ayant au moins d’aussi bonnes propriétés est donc la clé du projet. Le phénomène d’érosion du matériau de contact suite à l’impact d’un arc électrique joue un rôle de premier ordre dans la fiabilité et la durée de vie des dispositifs de commutation de puissance. Celui-ci influe en effet sur les propriétés du matériau et affecte ainsi le fonctionnement du dispositif de commutation de puissance. Dans ce contexte, nos axes de recherche ont été les suivants. Avant tout, et ce afin de mieux comprendre le comportement à l’érosion suite à l’impact d’un arc électrique de l’AgCdO (matériau de contact utilisé actuellement dans l’industrie aérospatiale) et celui de l’AgSnO2 (candidat potentiel au remplacement de l’AgCdO), des essais ont été réalisés en soumettant les dispositifs de commutation de puissance à différents nombres de décharges. Ensuite, un modèle macroscopique permettant de prédire l’érosion d’un matériau suite à l’impact d’un arc électrique, valable pour faibles et forts courants, a été développé. Ce modèle décrit le processus complet de coupure et donne la quantité totale de matériau érodé suite à une opération de commutation. En parallèle, des essais ont été réalisés sur des dispositifs de commutation de puissance AgCdO à forts courants (0 -> 1000 A) afin de valider ce modèle d’érosion. Les propriétés matériau les plus influentes sur le processus d’érosion ont ensuite été déterminées à l’aide de ce modèle. Enfin, une étude ab initio portant sur les effets d’un changement de composition locale du matériau sur ses propriétés identifiées comme influentes sur le processus d’érosion a été réalisée. Ainsi, l’ensemble de ces travaux permettront de conclure sur des directives dans l’élaboration du matériau de contact qui remplacera l’AgCdO, objectif principal de ces travaux de rechercheAgCdO is one of the most widely used contact materials in the world because of its outstanding performance. Nevertheless, due to environmental considerations, it will soon be completely forbidden by European environmental directives. Therefore, finding a good substitute is of crucial importance. Electrical arc erosion plays a crucial role in the reliability and life of power switching devices. Depending on the contact material’s behavior in response to an electrical arc, surface damage can induce severe changes in contact material properties that will impact the power switching device’s functioning. Consequently, electrical arc effects and consequences on the contact material surface are of first importance. In this context, we have focused our research activities on the following axes. First of all, in order to better understand AgCdO (Current contact material in aerospace industry) and AgSnO2 (Potential candidate to AgCdO substitution) arc erosion behaviors, arc erosion experiments, where the power switching devices have been subjected to different numbers of arc discharges, have been realized. Further, a general macroscopic electrical contact arc erosion model valid for low and high currents was developed. To compare model results to experimental data, this model describes the complete breaking process of electrical contacts and gives the total amount of material removed after one breaking operation. In parallel, arc erosion experiments on AgCdO power switching devices have been conducted at high currents (0 -> 1000 A) in order to validate the arc erosion model. Next, using the general arc erosion model, the properties having the greatest influence on the electrical arc erosion process have been determined through simulations on silver contact material. At this stage, ab initio calculations were needed to obtain ranges of variation of certain silver contact material properties. Finally, an investigation of the trends of changing local contact material composition of AgSnO2 on these identified material properties was performed. This study was based on ab initio calculations for two different oxide compositions of AgSnO2. These will allow us to give directions to aid the design of a good substitute for AgCdO, and therefore, to complete the main objective of this research work
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Collot, Jean-Yves. « Obduction et collision : exemples de la Nouvelle-Calédonie et de la zone de subduction des Nouvelles-Hébrides ». Paris 11, 1989. http://www.theses.fr/1989PA112401.
Texte intégralRésumé :
Deux cas particuliers d'évolution de la lithosphère océanique aux frontières de plaques sont examinés en utilisant les méthodes modernes de la géophysique marine. Le premier est celui de l'abduction d'une nappe ophiolitique sur un fragment continental en Nouvelle-Calédonie et le second celui de la déformation de la lithosphère de l'arc insulaire des Nouvelles-Hébrides en réponse à la collision d'aspérités topographiques portées par la plaque plongeante. La nappe ophiolitique de Nouvelle-Calédonie s'est mise en place tectoniquement à l'Eocène supérieur sur un substratum permien à éocène supérieur. Notre étude montre que cette ophiolite, épaisse au maximum de 10 km, résulte de l'obduction d'un fragment de lithosphère océanique du bassin des Loyauté adjacent à la Nouvelle-Calédonie. Cette abduction se serait accomplie sur environ 800 km, le long de la ride de Nouvelle-Calédonie, sans faire intervenir de collision continent-arc ou continent-continent. Nous discutons du contexte géodynamique de l'ophiolite au moment de sa rupture et de son abduction. La Zone d'Entrecasteaux (DEZ) et le Massif Ouest Torres sont deux aspérités topographiques sous-marines hautes de 1000 à 3000 rn qui entrent en collision et subductent sous l'arc insulaire des Nouvelles-Hébrides à 10 cm/an. La DEZ est légèrement oblique à la direction de convergence des plaques de telle façon qu'elle balaye l'arc vers le Nord à environ 2. 5 cm/an. L'analyse des structures de la plaque plongeante et de l'arc des Nouvelles-Hébrides centrales suggère que la déformation résultant d'une collision peut se développer dans des directions opposées. Dans le cas de la subduction/collision de la DEZ, la déformation se développe sur l'arc et affecte la marge qui s'épaissit et se soulève de 3 à 4 mm/an depuis le Pliocène terminal, le bassin intra-arc qui se fracture et subside et la zone arrière-arc qui se comprime et tend à chevaucher la bassin marginal adjacent. A l'opposé au sud de cette zone de collision, dans une région précédemment balayée par la DEZ, la déformation se développe vers l'océan depuis la marge qui s'effondre, jusque sur la plaque plongeante qui subit un raccourcissement. Bien que des indices d'accrétion sous la marge soient discutés, l'érosion tectonique de cette marge semble être un des phénomènes majeurs résultant de la collision et du balayage d'une aspérité topographique le long de l'arc.
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Nuber, Eduardo. « Evolução morfológica e sedimentológica do Arco Praial de Massaguaçú, litoral norte de São Paulo ». Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/21/21133/tde-30062009-145019/.
Texte intégralRésumé :
Nesta dissertação apresenta-se a evolução morfológica e sedimentológica no Arco Praial de Massaguaçú, Litoral Norte do Estado de São Paulo, em uma escala espaço-temporal histórica e de eventos. O Arco Praial de Massaguaçú localiza-se ao norte da Baia de Caraguatatuba e tem uma extensão de aproximadamente 7,5km. A metodologia consistiu na determinação da variação da linha de costa através da análise de fotografias aéreas de 1962, 1977, 1994 e 2001 e GPS para 2006. Foram obtidos 174 perfis bidimensionais e 16 perfis tridimensionais coletados em cinco levantamentos de campos entre os meses de novembro de 2006 e março de 2008 utilizando o método de DGPS. Foram coletadas ainda 176 amostras sedimentares na zona de espraiamento do Arco Praial, junto ao último ponto de cada perfil bidimensional, sendo uma coleta por perfil. Os resultados demonstraram que a maior parte da praia sofreu progradação entre os anos de 1962 e 1994, sendo observada mudança nesta tendência entre 1994 e 2006. Os dados de morfologia e sedimentologia mostraram grande variabilidade espaço temporal, sendo que estas parecem estar relacionadas a variações anuais de energia de onda. Foi identificada uma Zona de Erosão Acentuada (ZEA) na Parte Central do Arco Praial e dividiu-se a praia em cinco áreas de risco, onde este é menor nas extremidades do Arco Praial e aumenta em direção a região central.This dissertation characterize the morphological and sedimentological evolution of Massaguaçú Bay Beach, São Paulo State, Northeast Brazil, in a Historical and events spatial-temporal scale. Massaguaçú Bay Beach is localized northward of Caraguatatuba Bay and has approximately 7.5Km length. The methodology consisted on the determination of the shoreline changes with Aerophotographic analyses of 1962, 1977, 1994 and 2001, 2006 shoreline was taken with GPS. The DGPS Method was used to obtain 174 two-dimensional profiles and 16 tri-dimensional profiles in 5 field campaigns conducted between November, 2006 and March, 2008. 176 sand samples were collect in the swash zone, next to the last position of each two-dimensional profile. Data showed that almost all beach demonstrated shoreline progradation between 1962 and 1994, this tendency change between 1994 and 2006 with the possibility of increase of the retraction processes. It was observed a great variability in morphological and sedimentological data, this appear to be related with variations on the wave height pattern during the year. It has identified an Erosional Hotspot in the central area of the beach and the beach has divided in five risck areas where the risck increase from the extremities to the center of the beach.
Livres sur le sujet "Erosione arch"
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M, Curran Francis, et United States. National Aeronautics and Space Administration., dir. A low-erosion starting technique for high-performance arcjets. Washington, DC : National Aeronautics and Space Administration, 1994.
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M, Curran Francis, et United States. National Aeronautics and Space Administration., dir. A low-erosion starting technique for high-performance arcjets. Washington, DC : National Aeronautics and Space Administration, 1994.
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M, Curran Francis, et United States. National Aeronautics and Space Administration., dir. A low-erosion starting technique for high-performance arcjets. Washington, DC : National Aeronautics and Space Administration, 1994.
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M, Curran Francis, et United States. National Aeronautics and Space Administration., dir. A low-erosion starting technique for high-performance arcjets. Washington, DC : National Aeronautics and Space Administration, 1994.
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Electrode erosion in arc discharges at atmospheric pressure. [Washington, D.C : National Aeronautics and Space Administration, 1985.
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Woodson, Steven Wayne. An investigation of unipolar arcing at atmospheric pressure in Aluminum 2024 and aluminum coated glass slides. 1987.
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Booth, Adam M., et Anita L. Grunder, dir. From Terranes to Terrains : Geologic Field Guides on the Construction and Destruction of the Pacific Northwest. Geological Society of America, 2021. http://dx.doi.org/10.1130/fld062.
Texte intégralRésumé :
The eight field trips in this volume, associated with GSA Connects 2021 held in Portland, Oregon, USA, reflect the rich and varied geological legacy of the Pacific Northwest. The western margin of North America has had a complex subduction and transform history throughout the Phanerozoic, building a collage of terranes. The terrain has been modified by Cenozoic sedimentation, magmatism, and faulting related to Cascadia subduction, passage of the Yellowstone hot spot, and north and westward propagation of the Basin and Range province. The youngest flood basalt province on Earth also inundated the landscape, while the mighty Columbia watershed kept pace with arc construction and funneled epic ice-age floods from the craton to the coast. Additional erosive processes such as landslides continue to shape this dynamic geological wonderland.
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Vargas Simón, Georgina, et Reinaldo Pire. Inga jinicuil Schild. Árbol Multiuso. Universidad Juárez Autónoma de Tabasco, 2017. http://dx.doi.org/10.19136/book.13.
Texte intégralRésumé :
"Este libro presenta una revisión comprensiva de un árbol multiuso, Inga jinicuil, y representa una referencia básica para el conocimiento de la planta; es adecuado para estudiantes, agrónomos, forestales técnicos y ecólogos. Esta contribución nos familiariza desde la morfología más completa hasta los servicios de ecosistema que esta especie nos brinda. El libro se encuentra ilustrado con excelentes imágenes en color, especialmente las anatómicas y de morfología foliar". "La obra hace una reseña académica de fácil lectura en la que se exponen datos de los experimentos llevados a cabo en germinación y propagación de la especie. Con las preocupaciones actuales del cambio climático y la reducción de gases en la atmósfera, los autores proponen a Inga jinicuil como una buena especie de valor ambiental así como adecuada para recuperar áreas degradadas por la erosión y mal manejo de la tierra". "Para mí es un placer recomendar este libro que es un compendio de investigación y recopilación de información realizada por varios años por ambos autores, quienes tienen la experiencia práctica y académica con sus trabajos en México y Venezuela". Lourdes Rico Arce Systematics Groups; Leguminosae Team Herbarium, Library, Art & Archives Royal Botanic Gardens Kew, RichmondSurrey, TW9 3AB, UK
Chapitres de livres sur le sujet "Erosione arch"
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Behrisch, R. « Surface Erosion by Electrical Arcs ». Dans Physics of Plasma-Wall Interactions in Controlled Fusion, 495–513. Boston, MA : Springer US, 1986. http://dx.doi.org/10.1007/978-1-4757-0067-1_12.
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Beilis, Isak. « Electrode Erosion. Macroparticle Generation ». Dans Plasma and Spot Phenomena in Electrical Arcs, 255–83. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44747-2_9.
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Beilis, Isak. « Electrode Erosion. Total Mass Losses ». Dans Plasma and Spot Phenomena in Electrical Arcs, 213–54. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44747-2_8.
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Gorokhovsky, V., J. Wallace, C. Bowman, P. E. Gannon, J. O'Keefe, V. Champagne et M. Pepi. « Large Area Filtered Arc and Hybrid Coating Deposition Technologies for Erosion and Corrosion Protection of Aircraft Components ». Dans Advanced Ceramic Coatings and Interfaces III, 55–66. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2009. http://dx.doi.org/10.1002/9780470456323.ch4.
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Cui, Yu Sheng, Liang Zhen, Y. Wang, Wen Zhu Shao et V. V. Ivanov. « The Contact Resistance and Arc Erosion Behavior of Separable CP-Nb-Cr/Cu-Cd Electrical Contact Material ». Dans Key Engineering Materials, 886–89. Stafa : Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-456-1.886.
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Luca, Mihail. « Simulation of Permanent Movement in Collectors Non-Standardized Sewerage ». Dans Sustainable Development. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.109256.
Texte intégralRésumé :
Sewage collectors for domestic waste water and rainwater have flow sections that are standardized in shape and size. The collector with vertical dimension H > 1.50 m is admitted to be visitable and for H ≤ 0.80 m it is not visitable. Sewage collectors can be made in demanding situations with non standardized flow sections. A series of natural and anthropogenic action can change the geometric and hydraulic parameters of the flow section over time. Thus, the flow section no longer respects the initial geometric and hydraulic parameters and becomes a non-standardized section. Knowing the hydraulic parameters at such a flow section becomes difficult for monitoring the mining process. The circular, ovoid, circular bell, parabolic bell type flow section transforms into sections consisting of straight lines and circular arcs or only circular arcs. The factors that produce are erosion, siltation and cementation of transported material, repair and rehabilitation works and others. The erosion phenomenon also causes a change in the roughness on the watered perimeter of the section. In order to obtain the hydraulic operating parameters of the visitable sever collectors with non-standard flow section, several calculation programs have been elaborated on the forms of permanent water movement.
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Alexander, Earl B., Roger G. Coleman, Todd Keeler-Wolfe et Susan P. Harrison. « Klamath Mountains, Domain 5 ». Dans Serpentine Geoecology of Western North America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195165081.003.0023.
Texte intégralRésumé :
Domain 5 has mountains on the west aligned in broad arcs; in the eastern Klamath Mountains this arcuate pattern is not as evident. The outer arc curves from the triple junction of the California Coast Ranges, Great Valley, and Klamath Mountains in western Tehama County around through Del Norte County, where it is within a few kilometers of the Pacific Ocean, to Douglas County in Oregon. This western edge of the Klamath Mountains marks a boundary with the California Coast Ranges. The eastern edge of the Klamath Mountains forms a boundary with the Cascade Mountains. The southern, or southeast, boundary is where sediments of the Great Valley lap over the Klamath Mountains in Shasta and western Tehama counties. Serpentine rocks are more extensive in the Klamath Mountains than in any other domain or physiographic province in North America. Through the middle of the Tertiary, the Klamath Mountains were eroded to a nearly level plain called the Klamath peneplain (Diller 1902). According to Diller, the Klamath peneplain and the submerged coastal area that had been accumulating sediments were uplifted slightly during the Miocene, and erosion reduced the northern California Coast Ranges to a nearly level plain which he called the Bellsprings peneplain, noting that it is practically continuous with the Klamath peneplain. Subsequently discovered sediments of the Weaverville formation were deposited in a depression, or graben, in the Klamath Mountains during the Oligocene, indicating that uplift of the Klamath peneplain must have begun during the Paleogene, before the Miocene. Uplift was intermittent, allowing time for the erosion of broad valleys in less resistant rocks between episodes of uplift. Concordant summits, or mountains with summits of nearly equal elevation, are the evidence that led Diller (1902) to suspect a former peneplain. Although the mountain summits in any particular area are nearly equal or subequal, there is a general increase in summit elevation from the coast inland to 2.5–2.7 km. The altitude of Mt. Eddy on the eastern edge of the Klamath Mountains is 2751 m and that of Mt.
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Sa\'ad ZA Kader, Al-Mashaikie. « Abnormal Ophiolite (Olivine/Pyroxene Rich) Sandstone NE Iraq : An Approach to the Origin and Tectonosedimentary Evolution of Zagros Foreland Basin ». Dans New Insights in Sedimentary Rocks [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.108333.
Texte intégralRésumé :
Unusual Paleocene ophiolite sandstone rich in olivine/pyroxene identified in Zagros Thrust Belt (NZTB) in NE Iraq. NZTB is regionally extended from Iran to Alpen Belt. Kolosh sandstones are controlled by progressive thrusting during late Cretaceous-Paleocene. Zagros thrust sheets composed of ophiolites, oceanic crust, basaltic flows, and ash sequences. Kolosh sandstones reveal high percentages of fresh olivine-pyroxene grains accompanied by igneous intrusive and volcanic ultrabasic-basic fragments, which are reported for the first time in NE Iraq and along ZTB. Olivine, pyroxene, ultrabasic igneous altered, serpentine and chlorite fragments, heavy minerals (includes chrome spinal), anorthite, and labradorite all together composed about 70% of the mineralogical composition. Sanidine, anorthoclase, quartz and cristobalite, argillaceous, carbonate and chert fragments all together composed (12.25%), supported by argillaceous matrix (16.53%), which are derived from mantle and oceanic crust/ophiolite sequences from NE Iraq, emplaced during late Cretaceous with arc volcanism, which subjected to rapid submarine erosion and deposition. Intense wave action accelerated the erosion of beach rocks, and concentrate the heavy minerals insitue that slumped to deeper margins. Identified lithofacies types, grouped in four associations, slope/submarine channel, inner, outer fan, and hemipelagic/pelagic, respectively, represented progressive upward transgression from slope to basin plain systems controlled by progressive thrusting.
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Alexander, Earl B., Roger G. Coleman, Todd Keeler-Wolfe et Susan P. Harrison. « Blue Mountains, Domain 6 ». Dans Serpentine Geoecology of Western North America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195165081.003.0024.
Texte intégralRésumé :
The Blue Mountains domain is mostly in northeastern Oregon. It is the name that we and others (Orr and Orr 1996) have adopted for the Central Highlands subprovince of the Columbia Intermountain province (Freeman et al. 1945). Small areas of Blue Mountains ultramafic rocks are exposed in an arcuate trend from central Oregon through northeastern Oregon into western Idaho. They are in the Baker and Wallowa terranes (Vallier and Brooks 1995). These terranes with the ultramafic rocks are covered or surrounded by Tertiary volcanic flows, largely Columbia River basalt. The ultramafic rocks are exposed in the Canyon Mountain and Sparta complexes and in smaller areas from the edge of the Idaho Batholith near Riggins in Idaho south–southwest across northeastern Oregon to the Aldrich Mountains south of Dayville. The Snake River has cut a deep gorge through the Blue Mountains domain. At Hells Canyon it is >2000 m deep. Strawberry Mountain southeast of John Day rises to 2755 m. Ultramafic rocks are exposed from about 975 m at the foot of the Strawberry Range, near Canyon City, to 2243 m on Baldy Mountain in the Strawberry Range and a bit higher on Vinegar Hill, which is about 45 km northeast of the Strawberry Range, although the summit of Vinegar Hill (2478 m above sea level) is not composed of ultramafic rocks. Summers are hot and dry and winters are cold, with snow that persists through winters at the higher elevations. Mean annual temperatures are mostly in the 3°C–9oC range, and mean annual precipitation ranges from 25 to 100 cm. The frost-free period is about 150 days at lower elevations and <60 days at higher elevations. The ultramafic rocks were exposed by late Tertiary uplift and erosion of the overlying volcanic sequence. The older rocks are composed of a volcanic island arc complex that contains marine sediments interlayered with mafic volcanic flows. Deep erosion of this area has exposed the roots of the volcanic arc. The roots contain gabbro and peridotite–serpentine at their lowest levels. Seven-thousand-year-old volcanic ash from Mt.
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Grove, M., G. E. Bebout, C. E. Jacobson, A. P. Barth, D. L. Kimbrough, R. L. King, Haibo Zou, O. M. Lovera, B. J. Mahoney et G. E. Gehrels. « The Catalina Schist : Evidence for middle Cretaceous subduction erosion of southwestern North America ». Dans Special Paper 436 : Formation and Applications of the Sedimentary Record in Arc Collision Zones, 335–61. Geological Society of America, 2008. http://dx.doi.org/10.1130/2008.2436(15).
Texte intégralActes de conférences sur le sujet "Erosione arch"
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Levy, C., M. Perl et Q. Ma. « The Influence of Finite Three Dimensional Multiple Axial Erosions on the Fatigue Life of Partially Autofrettaged Pressurized Cylinders ». Dans ASME 2002 Pressure Vessels and Piping Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/pvp2002-1160.
Texte intégralRésumé :
Erosion geometry effects on the mode I stress intensity factor (SIF) for a crack emanating from the farthest erosion’s deepest point in a finitely or fully multiply eroded, partially autofrettaged, pressurized, thick-walled cylinder is investigated. The problem is solved via the FEM method. Autofrettage, based on von Mises yield criterion, is simulated by thermal loading and SIFs are determined by the nodal displacement method. SIFs were evaluated for a variety of relative crack depths, a/t = 0.01 – 0.30 and crack ellipticities, a/c = 0.5 – 1.5 emanating from the tip of the erosion of various geometries, namely, a) semi-circular erosions of relative depths of 1–10% of the cylinder’s wall thickness, t; b) arc erosions for several dimensionless radii of curvature, r′/t = 0.05 – 0.3; and C) semi-elliptical erosions with ellipticities of d/h = 0.5 – 1.5. In the cases of finite erosions, the semi-erosion length to the semicrack length, Le/c, was between 2 and 10, erosion angular spacing, α, was between 7 and 120 degrees, whereas autofrettage effects investigated were for 30%, 60% and 100% autofrettage. The normalized SIFs and the normalized effective SIFs of a crack emanating from the farthest finite erosion are found to rise sharply for values of Le/c < 3. Both the normalized SIF and normalized effective SIF values are mitigated as the amount of partial autofrettage increases with the most rapid decrease occurring between 0–60% autofrettage. The purpose of this study is to detail these findings.
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Ma, Q., C. Levy et M. Perl. « Stress Concentration and Stress Intensity for Pressurized Eroded Autofrettaged Thick Cylinders With Bauschinger Effect ». Dans ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/pvp2010-25607.
Texte intégralRésumé :
Our previous studies have shown that stress intensity factors (SIFs) are influenced considerably from the presence of the Bauschinger Effect (BE) in thick-walled pressurized cracked cylinders. For some types of pressure vessels, such as gun barrels, working in corrosive environment, in addition to acute temperature gradients and repetitive high-pressure impulses, erosions can be practically induced. Those erosions cause stress concentration at the bore, where cracks can readily initiate and propagate. In this study, The BE on the SIFs will be investigated for a crack emanating from an erosion’s deepest point in a multiply eroded autofrettaged, pressurized thick-walled cylinder. A commercial finite element package, ANSYS, was employed to perform this type of analysis. A two-dimensional model, analogous to the authors’ previous studies, has been adopted for this new investigation. Autofrettage with and without BE, based on von Mises yield criterion, is simulated by thermal loading and the SIFs are determined by the nodal displacement method. The SIFs are evaluated for a variety of relative crack lengths, a0/t = 0.01–0.45 emanating from the tip of the erosion of different geometries including (a) semi-circular erosions of relative depths of 1–10 percent of the cylinder’s wall thickness, t; (b) arc erosions for several dimensionless radii of curvature, r′/t = 0.05–0.4; and (c) semi-elliptical erosions with ellipticities of d/h = 0.5–1.5, and erosion span angle, α, from 6 deg to 360 deg. The effective SIFs for relatively short cracks are found to be increased by the presence of the erosion and further increased due to the BE, which may result in a significant decrease in the vessel’s fatigue life. Deep cracks are found to be almost unaffected by the erosion, but are considerably affected by BE.
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Ma, Q., C. Levy et M. Perl. « The Combined Effect of a Finite Axial Erosion With Bauschinger Modified Autofrettage on the 3D SIFs of Pressurized Cylinders ». Dans ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28033.
Texte intégralRésumé :
Autofrettage is the process to introduce favorable residual compressive hoop stresses on the bore of a pressurized cylinder to enhance its strength and durability. For certain type of pressurized vessels under certain severe operating conditions, erosions and cracks often occur causing significant reduction in pressure vessel fatigue life. Those erosions and cracks are in general 3D geometrical configurations. The Stress Intensity Factors (SIFs) of the cracks are often the key to estimate the fatigue life. However the SIFs are largely dependent on not only the crack geometrical configurations but also the geometrical configurations of the erosions introduced during its operation. The Bauschinger effect on the SIFs further complicates the analysis. In this study, a closer look is taken at how a finite axial erosion in combination with the Bauschinger modified autofrettage properties affect the 3D SIFs. The problem is solved via the finite element method (FEM). The SIFs are evaluated for a variety of relative crack depth, different crack configurations and erosion geometrical configurations including arc erosion, semi-circular and semi-elliptical erosions. We show that the effective SIFs can be increased significantly by any of these factors but the combined effect often worsens the situation.
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Lapointe, F., et S. Dallaire. « Erosion and Abrasion Resistance of Boride and Carbide-Based Weld Overlays ». Dans ITSC2003, sous la direction de Basil R. Marple et Christian Moreau. ASM International, 2003. http://dx.doi.org/10.31399/asm.cp.itsc2003p0421.
Texte intégralRésumé :
Abstract WELD OVERLAYS, more specifically chromium carbide weld overlays, have been widely used as thick coatings to protect critical plant components from abrasion wear. These thick coatings have been also considered in applications involving severe erosion, their thickness being synonymous with long life protection. Recently, boride-based arc-sprayed coatings have been developed especially for erosion control. They have demonstrated their superiority in erosion resistance over various coatings including chromium carbide submerged arc overlays. This work was undertaken to produce dense boride-based coatings comparable in thickness with carbide-based overlays. A GMAW (Gas Metal Arc Welding) welding procedure was developed for depositing boride-based overlays from cored wires. A comparative evaluation of the hardness, erosive and abrasive wear resistance of these boride-based overlays with regards to chromium and tungsten carbide overlays was carried out. Abrasion and erosion wear testing demonstrated that boride-based overlays showed higher abrasion and erosion resistance than chromium and tungsten carbide-based overlays. Overlays with higher wear resistance can be obtained if appropriate welding procedure is used to decrease weld bead dilution and therefore increase coating hardness. Results also showed that boride-based coatings deposited by arc spraying posses higher erosion resistance than those produced by the welding process.
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Sekikawa, Junya, et Takayoshi Kubono. « Effects of Rotational Motion of Break Arcs on Arc Duration and Contact Erosion ». Dans 2011 IEEE 57th Holm Conference on Electrical Contacts (Holm 2011). IEEE, 2011. http://dx.doi.org/10.1109/holm.2011.6034808.
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Legoux, J. G., B. Arsenault, J. P. Immarigeon, V. R. Parameswaran et H. Hawthorne. « Slurry and Dry Erosion of Arc-Sprayed Metal and Composite Coatings ». Dans ITSC 1999, sous la direction de E. Lugscheider et P. A. Kammer. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 1999. http://dx.doi.org/10.31399/asm.cp.itsc1999p0422.
Texte intégralRésumé :
Abstract Arc spraying can be used to produce coatings to protect against wear and tear against erosion. This paper presents some results obtained within the core research program of the NRC Technology Group in Surface Engineering on the development of erosion-resistant coatings. A relationship is established between the volume loss of the material (performance) under different erosion conditions and the coating properties or the microstructure. The results show that the wear behavior of the arc-sprayed materials depends on the type, size and impact strength of the impacting eroding particles. It is observed that for soft materials, even if ductile tearing is an active mode of degradation, the brittle behavior of intersplat oxides also plays an important role. For harder materials, this brittle delamination of splats becomes the dominant erosive mechanism, as can be observed on the worn surfaces. Paper includes a German-language abstract.
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Ma, Q., C. Levy et M. Perl. « The Bauschinger Effect’s Influence on the SIFs of a Semi-Elliptical Crack Emanating From an Erosion at the Bore of a Fully Autofrettaged Pressurized Cylinder ». Dans ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78012.
Texte intégralRésumé :
The benefits of autofrettage for thick-walled cylindrical vessels as a means of improving the vessel’s durability and sustainability have been addressed in the published literature. However the presence of the Bauschinger effect complicates the overall effect of autofrettage, especially when complex three-dimensional crack geometries emanating from erosions at the cylinder bore are considered. In this paper, the Bauschinger effect’s impact on the stress intensity factors (SIFs) on such cracks is investigated. The effect of various erosion geometrical configurations on the mode I stress intensity factor distribution along the front of a semi-elliptical crack, emanating from the deepest line of the erosion surface (DLES) at the bore of an autofrettaged, pressurized thick-walled cylinder of outer-to-inner radius ratio, R0/Ri = 2, is investigated. Both autofrettage with Bauschinger effect (BEDA) and Hill’s ideal autofrettage residual stress field (BEIA) are considered and simulated by an equivalent thermal load. The SIFs are determined for the semi-elliptical cracks of various crack depths to wall thickness ratio, a/t = 0.05 to 0.25, and ellipticities, a/c, ranging from 0.5 to 1.5, emanating from the DLES via ANSYS software and the nodal displacement method. Three groups of erosion geometries are considered: (a) arc erosions of constant relative depth, d/t, equal to 5% and with relative radii of curvature, r′/t, between 5% and 30%; (b) semi-elliptic erosions of constant relative depth, d/t, of 5% with erosion ellipticity, d/h, varying from 0.3 to 2.0; and (c) semi-circular erosions of relative depth, d/t, between 1 and 10% of the wall thickness. KIP, the SIF due to pressurization, is highly dependent on the stress concentration ahead of the DLES which directly relates to the erosion geometry. It is found that the absolute value of KIA, the SIF due to autofrettage, is just slightly reduced by the presence of the erosion. Its change solely depends on, and is directly proportional to, the erosion depth. Thus, the combined SIFs of deep cracks are found to be significantly enhanced by the presence of autofrettage and might result in a shortening of the vessel’s fatigue life by up to an order of magnitude. Counteracting this, the combined SIFs are found to be significantly higher for BEDA cases than for BEIA cases. Therefore the vessel’s fatigue life can be profoundly influenced by the presence of the Bauschinger effect.
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Modica, F., G. Guadagno, V. Marrocco et I. Fassi. « Evaluation of Micro-EDM Milling Performance Using Pulse Discrimination ». Dans ASME 2014 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/detc2014-34373.
Texte intégralRésumé :
In this paper, the pulse discrimination of gap voltage and discharge current waveforms occurring during micro-EDM milling of micro-channels is analyzed in relation to process parameters variation and machining performance. The pulse classification algorithm discriminates voltage and current waveforms into four defined pulse types: short, arc, delayed and normal. The micro-channels are manufactured in hardened steel using an energy level corresponding to the finishing regime and varying pulse width, frequency, gain and gap. The analysis shows that when the erosion process is stable, normal discharges are predominant. Delayed and short pulses are very sporadic. A major number of arcs can be detected when the gap is decreased and gain increased, i.e. erosion speed and feed rate are increased and affect in particular tool wear. Also the increase of the pulse width has an effect on tool wear, though the percentage of the arcs remains small. On the contrary, material removal rate does not seem to be apparently related to the percentage of arcs as the process parameters are varied, since these values are spread in a constant range for all parameter combinations. The evaluation of the depth errors does not provide any significant insights about the erosion process in relation to the considered process parameters.
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Miranda, Javier, Lorena Bejarano et Alfredo Valarezo. « High Temperature Erosion Mechanisms and Erosion Rate of Hard Coatings for Surface Recovery of Heavy-Fuel Engines ». Dans ITSC2018, sous la direction de F. Azarmi, K. Balani, H. Li, T. Eden, K. Shinoda, T. Hussain, F. L. Toma, Y. C. Lau et J. Veilleux. ASM International, 2018. http://dx.doi.org/10.31399/asm.cp.itsc2018p0561.
Texte intégralRésumé :
Abstract This study aims at evaluating the erosion resistance at temperature of several hard coatings, including: CrC-NiCr by HVOF, Fe-based alloy by Arc Spray, NiCrBSiFe by powder flame spraying. These coatings are to be used for the recovery of highly eroded walls (above 10 mm thickness) of gray cast iron in the exhaust ducts in heavy-fuel engines. The erosion test consists of erosive particles thrown through a high temperature gas jet, for 5 cycles of 5 minutes, according to ASTM G211-14 (modified). Coated samples are subjected to a fuel gas-torch reaching a front temperature of 450ºC and a back temperature of 90ºC (water cooled), simulating the actual application. The eroded samples are characterized using EDS, and SEM. The results show the erosion rate of each material/system, and their corresponding erosion mechanisms. Thus, the results allows for the selection of an optimum coating for this surface recovery application.
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Kirschner, M., T. Wobst, B. Rittmeister et Ch Mundt. « Erosion Testing of Thermal Barrier Coatings in a High Enthalpy Wind Tunnel ». Dans ASME Turbo Expo 2014 : Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25523.
Texte intégralRésumé :
One of the major problems facing the users of aircraft engines and stationary gas turbines in dusty and dirty environments is erosion, causing engine performance deterioration. Thermal barrier coatings (TBCs) are often applied on metal engine components as combustor heat shields or tiles as well as turbine blades allowing enhanced operating temperatures and resulting in increased thermal efficiency of the turbine and also reduced fuel consumption and gaseous emission. Erosive attack by airborne dust or fly ash, coarse particles causes coating degradation resulting in lifing issues of engine components. In the present study an erosion test facility was used to simulate the mechanisms of coating degradation expected in gas turbines in a more realistic way closer to real engine conditions. A loading situation combining thermal gradient cycling and erosive media was used. The experiments has been performed with an arc heated plasma wind tunnel (total enthalpy up to 20 MJ/kg), which is available at the Institute for Thermodynamics at the University of the Federal Armed Forces in Munich, Germany. The experimental setup and the integration of the air jet erosion test rig into the existing plasma wind tunnel will be elucidated. Different plasma sprayed thermal barrier coating materials, including the standard TBC material yttria-stabilised zirconia, were investigated regarding their erosion resistance. For validation and verification, samples of nickel-based Mar-M 247 and INCO 718 alloys have been used.
Rapports d'organisations sur le sujet "Erosione arch"
1
Rosa, R. J., et R. J. Pollina. Corrosion and arc erosion in MHD channels. Office of Scientific and Technical Information (OSTI), août 1992. http://dx.doi.org/10.2172/7185088.
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Rosa, R. J., et R. J. Pollina. Corrosion and arc erosion in MHD channels. Office of Scientific and Technical Information (OSTI), octobre 1991. http://dx.doi.org/10.2172/5910319.
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Rosa, R. J., et R. J. Pollina. Corrosion and arc erosion in MHD channels. Final report. Office of Scientific and Technical Information (OSTI), août 1992. http://dx.doi.org/10.2172/10178671.
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Rosa, R. J., et R. J. Pollina. Corrosion and arc erosion in MHD channels. Quarterly progress report, July--September 1991. Office of Scientific and Technical Information (OSTI), octobre 1991. http://dx.doi.org/10.2172/10110099.
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Corrosion and arc erosion in MHD channels. Office of Scientific and Technical Information (OSTI), janvier 1989. http://dx.doi.org/10.2172/6676311.
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Corrosion and arc erosion in MHD channels. Quarterly progress report, April--June 1989. Office of Scientific and Technical Information (OSTI), décembre 1989. http://dx.doi.org/10.2172/10140198.
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