Littérature scientifique sur le sujet « Thermal Evolution Comets »
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Articles de revues sur le sujet "Thermal Evolution Comets"
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Blum, Jürgen, Dorothea Bischoff et Bastian Gundlach. « Formation of Comets ». Universe 8, no 7 (15 juillet 2022) : 381. http://dx.doi.org/10.3390/universe8070381.
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Questions regarding how primordial or pristine the comets of the solar system are have been an ongoing controversy. In this review, we describe comets’ physical evolution from dust and ice grains in the solar nebula to the contemporary small bodies in the outer solar system. This includes the phases of dust agglomeration, the formation of planetesimals, their thermal evolution and the outcomes of collisional processes. We use empirical evidence about comets, in particular from the Rosetta Mission to comet 67P/Churyumov–Gerasimenko, to draw conclusions about the possible thermal and collisional evolution of comets.
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Seiferlin, K., T. Spohn et J. Benkhoff. « Cometary ice texture and the thermal evolution of comets ». Advances in Space Research 15, no 10 (janvier 1995) : 35–38. http://dx.doi.org/10.1016/0273-1177(94)00148-t.
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Gkotsinas, Anastasios, Aurélie Guilbert-Lepoutre, Sean N. Raymond et David Nesvorny. « Thermal Processing of Jupiter-family Comets during Their Chaotic Orbital Evolution ». Astrophysical Journal 928, no 1 (1 mars 2022) : 43. http://dx.doi.org/10.3847/1538-4357/ac54ac.
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Abstract Evidence for cometary activity beyond Jupiter’s and Saturn’s orbits—such as that observed for Centaurs and long-period comets—suggests that the thermal processing of comet nuclei starts long before they enter the inner solar system, where they are typically observed and monitored. Such observations raise questions as to the depth of unprocessed material and whether the activity of Jupiter-family comets (JFCs) can be representative of any primitive material. Here we model the coupled thermal and dynamical evolution of JFCs, from the moment they leave their outer solar system reservoirs until their ejection into interstellar space. We apply a thermal evolution model to a sample of simulated JFCs obtained from dynamical simulations that successfully reproduce the orbital distribution of observed JFCs. We show that due to the stochastic nature of comet trajectories toward the inner solar system, all simulated JFCs undergo multiple heating episodes resulting in significant modifications of their initial volatile contents. A statistical analysis constrains the extent of such processing. We suggest that primordial condensed hypervolatile ices should be entirely lost from the layers that contribute to cometary activity observed today. Our results demonstrate that understanding the orbital (and thus, heating) history of JFCs is essential when putting observations in a broader context.
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Rigley, Jessica K., et Mark C. Wyatt. « Comet fragmentation as a source of the zodiacal cloud ». Monthly Notices of the Royal Astronomical Society 510, no 1 (1 décembre 2021) : 834–57. http://dx.doi.org/10.1093/mnras/stab3482.
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ABSTRACT Models of the zodiacal cloud’s thermal emission and sporadic meteoroids suggest Jupiter-family comets (JFCs) as the dominant source of interplanetary dust. However, comet sublimation is insufficient to sustain the quantity of dust presently in the inner Solar system, suggesting that spontaneous disruptions of JFCs may supply the zodiacal cloud. We present a model for the dust produced in comet fragmentations and its evolution. Using results from dynamical simulations, the model follows individual comets drawn from a size distribution as they evolve and undergo recurrent splitting events. The resulting dust is followed with a kinetic model which accounts for the effects of collisional evolution, Poynting–Robertson drag, and radiation pressure. This allows to model the evolution of both the size distribution and radial profile of dust, and we demonstrate the importance of including collisions (both as a source and sink of dust) in zodiacal cloud models. With physically motivated free parameters this model provides a good fit to zodiacal cloud observables, supporting comet fragmentation as the plausibly dominant dust source. The model implies that dust in the present zodiacal cloud likely originated primarily from disruptions of ∼50-km comets, since larger comets are ejected before losing all their mass. Thus much of the dust seen today was likely deposited as larger grains ∼0.1 Myr in the past. The model also finds the dust level to vary stochastically; e.g. every ∼50 Myr large (>100 km) comets with long dynamical lifetimes inside Jupiter cause dust spikes with order of magnitude increases in zodiacal light brightness lasting ∼1 Myr. If exozodiacal dust is cometary in origin, our model suggests it should be similarly variable.
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Mumma, Michael J. « Organics In Comets ». International Astronomical Union Colloquium 161 (janvier 1997) : 121–42. http://dx.doi.org/10.1017/s0252921100014640.
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AbstractThe birth-endowed organic fraction of the newly formed (hot) Earth was destroyed by thermal decomposition during the cooling epoch. After Earth cooled sufficiently, an early organic inventory was likely replenished by the impact of comets and asteroids — a process which continues even today. The present organic composition of comets and asteroids can provide information relevant to this secondary organic seeding of the planets, for comparison with scenarios leading to self-replicating organic entities. Although impacts no longer deliver organics in significant quantities, compared with the existing terrestrial inventory, small bodies can deliver their organics intact to Earth‘s surface while giant impacts may cause punctuated extinction of living species (and create opportunities for renewed speciation). Hence, the exogenous organic flux has great importance for life’s origins and terminations. Current knowledge of the organic composition of comets is reviewed, and recent progress in our understanding of the chemical evolution of organic material from its formation to its incorporation into comets and later into planets is outlined. The need for detailed quantitative chemical analysis of material obtained directly from the cometary nucleus is indicated.
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Gkotsinas, Anastasios, Aurélie Guilbert-Lepoutre et Sean N. Raymond. « On Averaging Eccentric Orbits : Implications for the Long-term Thermal Evolution of Comets ». Astronomical Journal 165, no 2 (24 janvier 2023) : 67. http://dx.doi.org/10.3847/1538-3881/acaafd.
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Abstract One of the common approximations in long-term evolution studies of small bodies is the use of circular orbits averaging the actual eccentric ones, facilitating the coupling of processes with very different timescales, such as the orbital changes and the thermal processing. Here we test a number of averaging schemes for elliptic orbits in the context of the long-term evolution of comets, aiming to identify the one that best reproduces the elliptic orbits’ heating patterns and the surface and subsurface temperature distributions. We use a simplified thermal evolution model applied on simulated comets both on elliptic and on their equivalent averaged circular orbits, in a range of orbital parameter space relevant to the inner solar system. We find that time-averaging schemes are more adequate than spatial-averaging ones. Circular orbits created by means of a time average of the equilibrium temperature approximate efficiently the subsurface temperature distributions of elliptic orbits in a large area of the orbital parameter space, rendering them a powerful tool for averaging elliptic orbits.
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Guilbert-Lepoutre, Aurélie, Anastasios Gkotsinas, Sean N. Raymond et David Nesvorny. « The Gateway from Centaurs to Jupiter-family Comets : Thermal and Dynamical Evolution ». Astrophysical Journal 942, no 2 (1 janvier 2023) : 92. http://dx.doi.org/10.3847/1538-4357/acaa3a.
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Abstract It was recently proposed that there exists a “gateway” in the orbital parameter space through which Centaurs transition to Jupiter-family comets (JFCs). Further studies have implied that the majority of objects that eventually evolve into JFCs should leave the Centaur population through this gateway. This may be naively interpreted as gateway Centaurs being pristine progenitors of JFCs. This is the point we want to address in this work. We show that the opposite is true: gateway Centaurs are, on average, more thermally processed than the rest of the population of Centaurs crossing Jupiter’s orbit. Using a dynamically validated JFC population, we find that only ∼20% of Centaurs pass through the gateway prior to becoming JFCs, in accordance with previous studies. We show that more than half of JFC dynamical clones entering the gateway for the first time have already been JFCs—they simply avoided the gateway on their first pass into the inner solar system. By coupling a thermal evolution model to the orbital evolution of JFC dynamical clones, we find a higher than 50% chance that the layer currently contributing to the observed activity of gateway objects has been physically and chemically altered, due to previously sustained thermal processing. We further illustrate this effect by examining dynamical clones that match the present-day orbits of 29P/Schwassmann-Wachmann 1, P/2019 LD2 (ATLAS), and P/2008 CL94 (Lemmon).
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Kwon, Yuna G., Ludmilla Kolokolova, Jessica Agarwal et Johannes Markkanen. « An update of the correlation between polarimetric and thermal properties of cometary dust ». Astronomy & ; Astrophysics 650 (juin 2021) : L7. http://dx.doi.org/10.1051/0004-6361/202141199.
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Context. Comets are conglomerates of ice and dust particles, the latter of which encode information on changes in the radiative and thermal environments. Dust displays distinctive scattered and thermal radiation in the visible and mid-infrared (MIR) wavelengths, respectively, based on its inherent characteristics. Aims. We aim to identify a possible correlation between the properties of scattered and thermal radiation from dust and the principal dust characteristics responsible for this relationship, and therefrom gain insights into comet evolution. Methods. We use the NASA/PDS archival polarimetric data on cometary dust in the red (0.62−0.73 μm) and K (2.00−2.39 μm) domains to leverage the relative excess of the polarisation degree of a comet to the average trend at the given phase angle (Pexcess) as a metric of the dust’s scattered light characteristics. The flux excess of silicate emissions to the continuum around 10 μm (FSi/Fcont) is adopted from previous studies as a metric of the dust’s MIR feature. Results. The two observables – Pexcess and FSi/Fcont – show a positive correlation when Pexcess is measured in the K domain (Spearman’s rank correlation coefficient ρ = 0.71−0.19+0.10). No significant correlation was identified in the red domain (ρ = 0.13−0.15+0.16). The gas-rich comets have systematically weaker FSi/Fcont than the dust-rich ones, and yet both groups retain the same overall tendency with different slope values. Conclusions. The observed positive correlation between the two metrics indicates that composition is a peripheral factor in characterising the dust’s polarimetric and silicate emission properties. The systematic difference in FSi/Fcont for gas-rich versus dust-rich comets would instead correspond to the difference in their dust size distribution. Hence, our results suggest that the current MIR spectral models of cometary dust, which search for a minimum χ2 fit by considering various dust properties simultaneously, should prioritise the dust size and porosity over the composition. With light scattering being sensitive to different size scales in two wavebands, we expect the K-domain polarimetry to be sensitive to the properties of dust aggregates, such as size and porosity, which might have been influenced by evolutionary processes. On the other hand, the red-domain polarimetry reflects the characteristics of sub-micrometre constituents in the aggregate.
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Klinger, J. « Physical Properties of Frozen Volatiles–Their Relevance to the Study of Comet Nuclei ». International Astronomical Union Colloquium 116, no 1 (1989) : 227–41. http://dx.doi.org/10.1017/s0252921100109704.
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AbstractThe structural and thermodynamical properties of water ice and ice mixtures containing CO, CO2, CH4, and NH3 are thought to be important for the evolution of cometary nuclei. Based on recent laboratory studies performed by several groups, an overview is given of the properties of various ices condensed at low temperatures and of their evolution during heating up to a temperature of about 200 K, typical of the perihelion temperature of a comet such as P/Halley. It is shown that the porous surface of amorphous water ice plays an important role in the retention of other volatiles. The kinetics of formation and of decomposition of clathrate hydrates are discussed. The molecular hydrates formed by NH3 are briefly presented, and the possibility of their occurrence in comet nuclei is discussed. With special attention drawn to amorphous ices and clathrate hydrates, a qualitative discussion of the influence of the physical properties of various types of ices on the thermal behavior of comet nuclei and on gas production rates of comets is presented.
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Heggy, Essam, Elizabeth M. Palmer, Alain Hérique, Wlodek Kofman et M. Ramy El-Maarry. « Post-rendezvous radar properties of comet 67P/CG from the Rosetta Mission : understanding future Earth-based radar observations and the dynamical evolution of comets ». Monthly Notices of the Royal Astronomical Society 489, no 2 (12 août 2019) : 1667–83. http://dx.doi.org/10.1093/mnras/stz2174.
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ABSTRACT Radar observations provide crucial insights into the formation and dynamical evolution of comets. This ability is constrained by our knowledge of the dielectric and textural properties of these small-bodies. Using several observations by Rosetta as well as results from the Earth-based Arecibo radio telescope, we provide an updated and comprehensive dielectric and roughness description of Comet 67P/CG, which can provide new constraints on the radar properties of other nuclei. Furthermore, contrary to previous assumptions of cometary surfaces being dielectrically homogeneous and smooth, we find that cometary surfaces are dielectrically heterogeneous ( εr′≈1.6–3.2), and are rough at X- and S-band frequencies, which are widely used in characterization of small-bodies. We also investigate the lack of signal broadening in CONSERT observations through the comet head. Our results suggest that primordial building blocks in the subsurface are either absent, smaller than the radar wavelength, or have a weak dielectric contrast (Δ εr′). To constrain this ambiguity, we use optical albedo measurements by the OSIRIS camera of the freshly exposed subsurface after the Aswan cliff collapse. We find that the hypothetical subsurface blocks should have |Δ εr′|≳0.15, setting an upper limit of ∼ 1 m on the size of 67P/CG's primordial building blocks if they exist. Our analysis is consistent with a purely thermal origin for the ∼ 3 m surface bumps on pit walls and cliff-faces, hypothesized to be high-centred polygons formed from fracturing of the sintered shallow ice-bearing subsurface due to seasonal thermal expansion and contraction. Potential changes in 67P/CG's radar reflectivity at these at X- and S-bands can be associated with large-scale structural changes of the nucleus rather than small-scale textural ones. Monitoring changes in 67P/CG's radar properties during repeated close-approaches via Earth-based observations can constrain the dynamical evolution of its cometary nucleus.
Thèses sur le sujet "Thermal Evolution Comets"
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Gkotsinas, Anastasios. « On the pristine nature of cometary nuclei : coupled modeling of their thermal and dynamical evolution ». Electronic Thesis or Diss., Lyon 1, 2023. http://www.theses.fr/2023LYO10144.
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Les comètes sont une population de petits corps du Système Solaire souvent décrits comme les objets les plus primitifs de notre Système Solaire, détenant des informations précieuses sur sa formation et son évolution. Formées tôt, au même temps que les planètes géantes, dans les parties externes du disque protoplanétaire et dispersées vers l'extérieur peu après leur formation pour être stockées dans des réservoirs lointains et froids, elles sont considérées comme ayant largement conservé leurs propriétés et composition primordiales. Cependant, le niveau de leur nature primitive a commencé à être revu, car un nombre croissant d'observables et d'études théoriques suggèrent la possibilité d'altérations thermiques avant leur retour dans les parties internes du Système Solaire où elles sont généralement étudiées et observées. Dans ce contexte, ce travail vise à examiner le niveau de cette nature primitive pour les différentes familles cométaires de notre Système Solaire. Dans ce but, nous avons développé un modèle d'évolution thermique dédié, conçu pour un couplage efficace aux simulations N-corps qui suivent l'évolution orbitale à long terme des planétésimaux, provenant des parties externes du disque protoplanétaire et évoluant vers des orbites dans la région planétaire, après un séjour prolongé dans les réservoirs extérieurs du système solaire. Nos résultats révèlent la possibilité d'altérations thermiques, affectant principalement le contenu condensé primordial d'hyper-volatiles et dans un second lieu le contenu primordial modérément volatile et la glace d'eau amorphe, au cours des premières phases de la vie des comètes. Une étude comparative indique que les comètes à longue période devraient être la population la moins altérée. Une activité intense, mais sporadique, est également enregistrée dans la région des planètes géantes, alors que les comètes reviennent dans le Système Solaire interne, compatible avec les observables actuelles concernant la population de Centaures. Ces résultats indiquent que l'évolution thermique des noyaux cométaires est inextricablement liée à leur évolution orbitale. Ils indiquent également que l'activité cométaire observée dans les parties internes du Système Solaire provient très probablement de couches déjà altérées, soulignant la nécessité de prendre en compte l'histoire dynamique des comètes lors de l'interprétation des observations actuellesComets are a population of small Solar System bodies, often described as the most primitive population in our Solar System, holding valuable information on its formation and evolution. Formed early, at the same time as the giant planets, in the outer parts of the protoplanetary disk and scattered outwards shortly after their formation towards distant and cold reservoirs, they are considered to have preserved their primordial composition and properties to a great extent. However, the level of this primitive nature has started to be reevaluated recently, as a growing body of observational evidence and an important number of theoretical studies are suggesting the possibility of thermally-induced alterations before their return to the inner parts of the Solar System, where they are usually studied and observed. In this context, our work aims to examine the level of the primitive nature of different cometary families in our Solar System. To do so, we developed a dedicated thermal evolution model, designed for an efficient coupling to N-body simulations, tracking the long-term orbital evolution of planetesimals, originating in the outer parts of the protoplanetary disk and evolving into planetary-crossing orbits after a prolonged stay in outer Solar System reservoirs. Our results reveal the possibility of thermal processing, affecting mainly the primordial condensed hyper-volatile content and on a lesser extent the primordial moderately-volatile and amorphous water ice content, during the early phases of a comet's lifetime. A comparative study is indicating that long-period comets are expected to be the least altered population. Intense, yet sporadic, activity is also recorded in the planetary region, as comets return in the inner Solar System, compatible with the current observables on the Centaur population. These results indicate that the thermal evolution of cometary nuclei is inextricably related to their orbital evolution. They are also indicating that the cometary activity observed in the inner parts of the Solar System is very likely triggered from thermally processed subsurface layers, highlighting the necessity of considering the past evolutionary history of comets when interpreting the current observations in a broader context
Livres sur le sujet "Thermal Evolution Comets"
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Stern, S. Alan. A semi-annual report for studies of extra-solar oort clouds and the Kuiper disk. San Antonio, Tex : Southwest Research Institute, Instrumentation and Space Research Division, 1992.
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Stern, S. Alan. A semi-annual report for studies of extra-solar Oort Clouds and the Kuiper Disk. San Antonio, Texas : Southwest Research Institute, Instrumentation and Space Research Division, 1993.
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Stern, S. Alan. A semi-annual report for studies of extra-solar Oort clouds and the Kuiper disk. San Antonio, Tex : Southwest Research Institute, Instrumentation and Space Research Division, 1995.
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United States. National Aeronautics and Space Administration., dir. A semi-annual report for studies of extra-solar Oort Clouds and the Kuiper Disk. San Antonio, Texas : Southwest Research Institute, Instrumentation and Space Research Division, 1994.
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United States. National Aeronautics and Space Administration., dir. A semi-annual report for studies of extra-solar Oort clouds and the Kuiper disk. San Antonio, Tex : Southwest Research Institute, Instrumentation and Space Research Division, 1995.
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Stern, S. Alan. A semi-annual report for studies of extra-solar Oort Clouds and the Kuiper Disk. San Antonio, Texas : Southwest Research Institute, Instrumentation and Space Research Division, 1993.
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Stern, S. Alan. A semi-annual report for studies of extra-solaʹr oort clouds and the Kuiper disk. San Antonio, Tex : Southwest Research Institute, Instrumentation and Space Research Division, 1992.
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United States. National Aeronautics and Space Administration., dir. A semi-annual report for studies of extra-solar Oort clouds and the Kuiper disk. San Antonio, Tex : Southwest Research Institute, Instrumentation and Space Research Division, 1995.
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Stern, S. Alan. A semi-annual report for studies of extra-solar Oort Clouds and the Kuiper Disk. San Antonio, Texas : Southwest Research Institute, Instrumentation and Space Research Division, 1993.
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A semi-annual report for studies of extra-solaʹr oort clouds and the Kuiper disk. San Antonio, Tex : Southwest Research Institute, Instrumentation and Space Research Division, 1992.
Trouver le texte intégralChapitres de livres sur le sujet "Thermal Evolution Comets"
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Prialnik, Dina, Gal Sarid, Eric D. Rosenberg et Rainer Merk. « Thermal and Chemical Evolution of Comet Nuclei and Kuiper Belt Objects ». Dans Space Sciences Series of ISSI, 147–64. New York, NY : Springer New York, 2008. http://dx.doi.org/10.1007/978-0-387-85455-7_9.
Texte intégralActes de conférences sur le sujet "Thermal Evolution Comets"
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Karaivanov, Ventzislav G., Danny W. Mazzotta, Minking K. Chyu, William S. Slaughter et Mary Anne Alvin. « Three-Dimensional Modeling of Creep Damage in Airfoils for Advanced Turbine Systems ». Dans ASME Turbo Expo 2008 : Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-51278.
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Future oxy-fuel and hydrogen-fired turbines promise increased efficiency and low emissions. However, this comes at the expense of increased thermal load from higher inlet temperatures and a change in the working fluid in the gas path, leading to aero-thermal characteristics that are significantly different than those in traditional gas turbines. A computational methodology, based on three-dimensional finite element analysis (FEA) and damage mechanics is presented for predicting the evolution of creep in airfoils in these advanced turbine systems. Information revealed from three-dimensional computational fluid dynamics (CFD) simulations of external heat transfer and thermal loading over a generic airfoil provides detailed local distributions of pressure, surface temperature, and heat flux penetrating through the thermal barrier coated layer. There is an additional mechanical loading due to the centrifugal acceleration of the airfoil. Finite element analysis is then used to predict temperature and stress fields over the domain of the airfoil. The damage mechanics-based creep model uses a scalar damage parameter. This creep model is coupled with finite element analysis to predict the evolution of stress and creep damage over the entire airfoil. Visualization of the creep damage evolution over the airfoil shows the regions that are most susceptible to failure by creep.
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Poignand, Gaelle, Emmanuel Jondeau et Philippe Blanc-Benon. « Aerodynamic and Thermal Measurements in a Standing Wave Thermoacoustic Refrigerator ». Dans ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30672.
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Thermoacoustic refrigerators produce a cooling power from an acoustic energy. Over the last decades, these devices have been extensively studied since they are environment-friendly, robust and miniaturizable. Despite all these advantages, their commercialization is limited by their low efficiency. One reason for this limitation comes from the complex thermo-fluid process between the stack and the two heat exchangers which is still not sufficiently understood to allow for optimization. In particular, at high acoustic pressure level, vortex shedding can occur behind the stack as highlight by [Berson & al., Heat Mass Trans, 44, 10151023 (2008)]. The created vortex can affect heat transfer between the stack and the heat exchangers and thus, they can reduce the system performance. In this work, aerodynamic and thermal measurements are both conducted in a standing wave thermoacoustic refrigerator allowing investigation of vortex influence on the system performance. The proposed device consists on a resonator operated at frequency of 200 Hz, with hot and cold heat exchangers placed at the stack extremities. The working fluid is air at ambient temperature and atmospheric pressure. The aerodynamic field behind the stack is described using high-speed Particle Image Velocimetry. This technique allows the acoustic velocity field measurement at a frequency up to 3000 Hz. Thermal measurements consist on the acquisition of both the temperature evolution along the stack and the heat fluxes extracted at the cold heat exchanger. These measurements are performed by specific micro-sensors developed by MEMS technology. The combination of these two measurements should be helpful for the further understanding of the heat transfer between the stack and the heat exchangers.
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Govindaraju, N., et B. Q. Li. « Parallel Computing of Magnetically-Induced Flows and Microstructure Formation During Solidification Processing ». Dans ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/fed-24968.
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Abstract Solidification starts with nucleation that comes from the clustering of molecules, followed by deposition of molecules upon the nuclei or grain growth. In materials dynamics, these events are modeled at a spatial scale of microns and a temporal scale of micro seconds. On the other hand, the electrodynamic, fluid flow and heat transfer phenomena in solidifying metals are observable and thus modeled at a scale of millimeters (or sometimes centimeters) and a fraction of a second. An integrated macro/micro model is developed to represent the evolution of complex electrodynamic and transport phenomena and microstructure formation in solidifying metals with electromagnetic stirring applied to affect the solidification micrstructures. The model development is based on the hybrid boundary/finite element solution of the Maxwell equations and the finite element solution of the momentum and thermal transport equations, in combination with the Monte-Carlo-Cellular-Automaton representation of the evolution of solidification microstructure formation. Parallel computing has been applied to speed up the microstruture formation simulation, which is the most time consuming part of the calculations. The model should be useful to further our fundamental understanding of flow and microstructure formation in electromagnetically-assisted processes such as electromagnetic casting, arc welding, and vacuum refining.
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Natarajan, Manikandan, Thejasree Pasupuleti, Lakshmi Narasimhamu Katta, Jothi Kiruthika, R. Silambarasan et Gowthami Kotapati. « Evolution of Regression and Neural Network Models on Wire Electrical Discharge Machining of Nickel Based Superalloy ». Dans International Conference on Advances in Design, Materials, Manufacturing and Surface Engineering for Mobility. 400 Commonwealth Drive, Warrendale, PA, United States : SAE International, 2023. http://dx.doi.org/10.4271/2023-28-0078.
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<div class="section abstract"><div class="htmlview paragraph">In addition to traditional methods, there are also non-traditional techniques that can be used to overcome the challenges of conventional metal working. One such technique is wire electrical discharge (WEDM). This type of advanced manufacturing process involves making complex shapes using materials. Utilizing intelligent tools can help a company meet its goals. Nickel is a hard metal to machine for various applications such as nuclear, automobile and aerospace. Due its high thermal conductivity and strength, traditional methods are not ideal when it comes to producing components using this material. This paper aims to provide a comprehensive analysis of the various steps in the development of a neural network model for the manufacturing of Inconel 625 alloy which is used for specific applications such as exhaust couplings in sports motor vehicle engines. The study was conducted using a combination of computational and experimental methods. It was then used to develop an index that measures the correlation between various process variables. After analyzing the results of the study, a set of equations was then created to forecast the future performance of a manufacturing process. The parameters used in the study were then updated to create a new multi-performance index prediction model. The results of the study were then used to develop an equation set that can be utilized to forecast the future performance. A comparative analysis was performed between the two sets of equations. After analyzing the results, the neural network model was found to perform better than the multi-performance index.</div></div>
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Lall, Pradeep, Shantanu Deshpande et Luu Nguyen. « Copper, Silver, and PCC Wirebonds Reliability in Automotive Underhood Environments ». Dans ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/ipack2018-8358.
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Wire bonding is popular first-level interconnect method used in the semiconductor device packaging. Gold (Ag) wire is often used in high-reliability applications. Typical wire diameters vary between 0.8mil to 2mil. Recent increases in the gold-price have motivated the industry to search for alternate materials candidates for use in wirebonding. Three of the leading candidates are Silver (Ag), Copper (Cu), and Palladium Coated Copper (PCC). The new material candidates are inexpensive in comparison with gold and may have better electrical, and thermal properties, which is advantageous for fine pitch-high density electronics. The transition, however, comes along with few trade-offs such as narrow process window, higher wire-hardness, increased propensity for chip-cratering, lack of reliability knowledge base of when deployed in harsh environment applications. Relationship between mechanical degradation of the wirebond and the change in electric response needs to be established for better understanding of the failure modes and their respective mechanisms. Understanding the physics of damage progression may provide insights into the process parameters for manufacture of more robust interconnects. In this paper, a detailed study of the electrical and mechanical degradation of wirebonds under high temperature exposure is presented. Four wirebond candidates (Au, Ag, Cu and PCC) bonded onto Aluminum (Al) pad were subjected to high temperature storage life until failure to study the degradation of the bond-wire interface. Same package architecture and electronic molding compound (EMC) were used for all four candidates. Detailed analysis of intermetallic (IMC) phase evolution is presented along with quantification of the phases and their evolution over time. Ball shear strength was measured after decapsulation. Measurements of shear strength, shear failure modes, and IMC composition have been correlated with the change in the electrical response. Change in shear strength and different shear failure modes for different wirebond systems are discussed in the paper.
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Natarajan, Manikandan, Thejasree Pasupuleti, Jothi Kiruthika, V. Kumar, Palanisamy D et Vamsinath Polanki. « Optimization of Spark Erosion Machining of Monel 400 Alloy for Automobile Applications ». Dans International Conference on Advances in Design, Materials, Manufacturing and Surface Engineering for Mobility. 400 Commonwealth Drive, Warrendale, PA, United States : SAE International, 2023. http://dx.doi.org/10.4271/2023-28-0140.
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<div class="section abstract"><div class="htmlview paragraph">Monel 400, a type of nickel alloy which is adopted in numerous engineering fields, such as high-temperature devices. Owing to its better strength and thermal diffusion, it can be difficult to machine with conventional methods. In order to avoid the disadvantages of conventional methods, various advanced material removal techniques have been developed. One of these is Wire Electro Discharge Machining (WEDM). This process is an evolution of the electrical discharge method. In the process of WEDM, difficult materials with intricate forms are usually machined. In this study, the performance of this method on Monel 400 has been analyzed. The three independent variables that are considered when it comes to analyzing the performance of this process are the pulse on, the applied current, and the pulse off. The experiments were performed using the design approach of Taguchi, which involves using an L27 orthogonal array. The single response analysis performed by Taguchi revealed that the process parameters can influence the output variables that are desired by the users. Through the use of the Taguchi-grey relational analysis method, the multiple aspects optimization of the process was performed. The results of the exploration divulged that the proposed method can improve the effectiveness of this process.</div></div>
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Aranha, Pedro Esteves, Eduardo Schnitzler, Nelson Moreira, Luis Eduardo Duccini, André Leibsohn Martins, Alexandre Brambilla Falchetto et Jorel Lopes Dos Anjos. « Field Life Extension : Real Time Well Integrity Management ». Dans Offshore Technology Conference. OTC, 2022. http://dx.doi.org/10.4043/31816-ms.
Texte intégralRésumé :
Abstract This article aims to present the evolution of well design and well integrity monitoring throughout their life cycle and life extension analysis. The motivation comes from the need to make a decision to extend the life of wells, accounting both for Green and Brown Fields. PETROBRAS design practices were updated to meet the Well Integrity National Regulatory requirements and to support the life extension analysis. In order to assess the well integrity during production lifetime, a Digital Twin of the well was developed and is capable of modelling the physics of permanent and transient fluid flow and corresponding behavior of trapped annuli with thermo-structural coupling to the mechanical structure. Also, as part of the monitoring process, additional information will be provided by new sensors to be installed in the A and B annuli, aiming to improve monitoring capability. This paper will present the results of the new well design and life extension analysis practices for retrofit projects. Besides that, a discussion on new challenging scenarios faced by the company is included. The well integrity case study of a deep-water field in Brazilian offshore, through a real time digital twin approach, will highlight the main technological solutions developed to ensure well operation within the envelope during its lifetime. The adoption of this strategy allows the optimization of procedures with the goal of maximizing production or injection rates, still according to safety requirements. The availability of additional annuli sensors can improve the system capability. With the well integrity surveillance digital twin, PETROBRAS successfully implemented a unique monitoring integrity system for offshore production units in Brazil, increasing the understanding of the well structure behavior and, consequentially, the assets operational safety during its lifetime. In addition, this initiative aims to push the industry towards the development of wet X-mas tree according to API RP 17V requirements.
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Aranha, Pedro Esteves, Eduardo Schnitzler, Nelson Moreira, Luis Eduardo Duccini, André Leibsohn Martins, Alexandre Brambilla Falchetto et Jorel Lopes Dos Anjos. « Field Life Extension : Real Time Well Integrity Management ». Dans Offshore Technology Conference. OTC, 2022. http://dx.doi.org/10.4043/31816-ms.
Texte intégralRésumé :
Abstract This article aims to present the evolution of well design and well integrity monitoring throughout their life cycle and life extension analysis. The motivation comes from the need to make a decision to extend the life of wells, accounting both for Green and Brown Fields. PETROBRAS design practices were updated to meet the Well Integrity National Regulatory requirements and to support the life extension analysis. In order to assess the well integrity during production lifetime, a Digital Twin of the well was developed and is capable of modelling the physics of permanent and transient fluid flow and corresponding behavior of trapped annuli with thermo-structural coupling to the mechanical structure. Also, as part of the monitoring process, additional information will be provided by new sensors to be installed in the A and B annuli, aiming to improve monitoring capability. This paper will present the results of the new well design and life extension analysis practices for retrofit projects. Besides that, a discussion on new challenging scenarios faced by the company is included. The well integrity case study of a deep-water field in Brazilian offshore, through a real time digital twin approach, will highlight the main technological solutions developed to ensure well operation within the envelope during its lifetime. The adoption of this strategy allows the optimization of procedures with the goal of maximizing production or injection rates, still according to safety requirements. The availability of additional annuli sensors can improve the system capability. With the well integrity surveillance digital twin, PETROBRAS successfully implemented a unique monitoring integrity system for offshore production units in Brazil, increasing the understanding of the well structure behavior and, consequentially, the assets operational safety during its lifetime. In addition, this initiative aims to push the industry towards the development of wet X-mas tree according to API RP 17V requirements.
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Farley, Daniel, Abhijit Dasgupta et J. F. J. M. Caers. « Characterization of Non-Conductive Adhesives ». Dans ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems collocated with the ASME 2005 Heat Transfer Summer Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/ipack2005-73021.
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This study aims to establish a global-local modeling methodology for determining the residual contact stress developed during fabrication of flip-chip-on-flex (FCOF) microelectronics systems. The assembly consists of a silicon die with gold bumps bonded with a non-conductive adhesive (NCA) on to gold-plated copper bumps on a flex substrate. Manufacturing variabilities cause a nonuniformity in the bump heights, leading to some bumps that are “tall” and some that are “short.” The fabrication process needs to achieve a significant amount of compressive initial contact stress in all the bumps, to achieve an acceptable level of electrical contact resistance. Furthermore, this stress level forms the initial condition for cyclic relaxation of the stress (and corresponding progressive loss of contact resistance) due to temperature cycling throughout the life cycle of the assembly. A key issue to be investigated is the nonuniformity of the contact stresses due to the variabilities in the height of the metal contact bumps. The method is demonstrated for a selected NCA. The fabrication process consists of mechanical compression to bring all the bumps into contact, thermal curing of the adhesive during which it undergoes chemical shrinkage, removal of the mechanical compressive force and cool-down to room temperature. The modeling complexities include the geometric complexity, as well as nonlinearities due to elastic-plastic properties and large deformations of the metal bumps, evolution of contact surfaces between the two bumps, and nonlinear thermomechanical properties of the adhesive as it cures. Modeling strategies used to capture the nonlinearities include “contact elements” to prevent interpenetration at the contact surfaces, elastic-plastic models to account for metal plasticity, “element birth and death” to account for the solidification of the polymer NCA. The entire bonding process is modeled with a global-local model to reduce the computational complexity. The results of the global model serve as the input for the local model. Key findings include: the accuracy of the simulation is very sensitive to the accuracy of the gold and flex constitutive models used; the inclusion of viscoelastic properties for the epoxy has a significant effect on simulations; and better stress development comes from a higher concentration of short bumps than tall bumps.
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Shrivastava, Sourabh, Ishan Verma, Rakesh Yadav et Pravin Nakod. « Solution-Based Mesh Adaption Criteria Development for Accelerating Flame Tracking Simulations ». Dans ASME Turbo Expo 2022 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-82620.
Texte intégralRésumé :
Abstract Accurate flame tracking plays a vital role in predicting the combustion characteristics of a system. This is even more critical for systems that evolve over time. Predicting relight performance of an aero combustor, predicting flame propagation due to gas leakage from a storage tank or during the thermal runaway of batteries, are some examples of such dynamic systems. Predicting accurate flame position also plays an important role in deriving the correct pollutant formation rate from a combustion system. The challenge with flame tracking through a 3D computational fluid dynamics (CFD) simulation comes from the requirement to have a good resolution of gradients along the flame front. This requirement can push the overall mesh count of any industrial cases to a very large value (several million-mesh count). Further, the global drive towards using hydrogen or hydrogen blended fuels for different combustion applications pushes the limits on having even finer cells since hydrogen is a fast-burning fuel and has a much thinner flame front compared to hydrocarbons. Solution-based mesh adaption approaches have been widely studied and tested by different research groups to generate the required finer meshes in the critical regions on the fly while keeping the overall mesh count to a manageable level. However, these approaches are typically applicable for a set of problems, and therefore, there is a need for a generic approach suitable for a broader range of problems. This work explores various parameters and specific weightage factors to predict correct flame-tracking outcomes for different types of flames. The selections of flow quantities (flow-variables, their gradients, curvatures) are performed using simple flames and flow configurations. The functions based on selected flow-quantities derived from these studies are then tested to predict the results for the more complex set of published flames like the Engine Combustion Network (ECN) spray flame and Knowledge for Ignition, Acoustics and Instabilities (KIAI) five-burner configuration (liquid and gas fuel). Derived adaption criteria are found to predict the correct flame tracking behavior in terms of transient evolution of flame front, flame propagation, and ignition timing of burners. The parameters used for the study are identified keeping genericity as the key point, and thus making sure that the derived adaption functions can be applied across different types of fuel blends, combustion systems (gaseous or liquid fuel-based systems) and combustion models, for example species transport or mixture fraction-based models.