Bibliographies thématiques / Comets Dynamics

Littérature scientifique sur le sujet « Comets Dynamics »

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Publié le 25 mai 2024

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Articles de revues sur le sujet "Comets Dynamics"

Carusi, A., et G. B. Valsecchi. « Dynamics of Comets ». Symposium - International Astronomical Union 152 (1992) : 255–68. http://dx.doi.org/10.1017/s0074180900091245.

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The gravitational processes affecting the dynamics of comets are reviewed. At great distances from the Sun the motion of comets is primarily affected by the vertical component of the galactic field, as well as by encounters with stars and giant molecular clouds. When comets move in the region of the planets, encounters with these can strongly affect their motion. A good fraction of all periodic comets spend some time in temporary libration about mean motion resonances with Jupiter; some comets can be captured by this planet as temporary satellites. Finally, there is a small number of objects with orbital characteristics quite different from those of all other short-period comets.

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Zheng, J. Q., M. J. Valtonen, S. Mikkola et H. Rickman. « Dynamics and orbital evolution of Oort cloud comets ». Symposium - International Astronomical Union 172 (1996) : 209–12. http://dx.doi.org/10.1017/s007418090012738x.

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Investigators generally conjecture a steady flux of new comets from the Oort cloud through the inner Solar system. Due to gravitational perturbations by major planets these objects may escape, become long period comets (LPCs) if their orbital periods P are larger than 200yr or become short period comets (SPCs) when their period is less than 200yr. SPCs are further divided in two types: the Halley type comets (HT, for P > 20yr) and the Jupiter family comets (JF, for P < 20yr).

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Fernández, Julio A. « Dynamics of Comets : Recent Developments and New Challenges ». Symposium - International Astronomical Union 160 (1994) : 223–40. http://dx.doi.org/10.1017/s0074180900046568.

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There is a broad consensus that long-period comets come from a huge reservoir surrounding the solar system, as proposed originally by Oort. Yet, the classical picture of the Oort cloud has substantially changed during the last decade. In addition to passing stars, the tidal force of the galactic disk and giant molecular clouds have also been identified as major perturbers of the Oort cloud. In particular, the latter may be responsible for limiting the size of the stable Oort cloud to no more than ≈ 104AU, i.e. about one tenth of the classical Oort's radius.Most comets are injected into the planetary region by the quasi-steady action of the tidal force of the galactic disk. The concentration of aphelion points of dynamically young comets toward mid-galactic latitudes is a consequence of its dominant influence. The frequency of comet passages into the inner planetary region could experience significant fluctuations with time as the Oort cloud meets random strong perturbers. The observed ordered pattern of most comet aphelia, associated with the galactic structure, argues against a recent strong perturbation of the Oort cloud.The origin of the Jupiter family has become another point of intense debate. Jupiter family comets may come from a transneptunian comet belt -the Kuiper belt- from where they can reach the planetary region through chaotic motion. The Kuiper belt has become accessible to large telescopes, as shown by the recent discoveries of 1992QB1 and 1993FW, possibly belt members. The major challenge will be to explore the region usually inaccessible to external perturbers that goes from ~30 AU to a few thousand AU. A significant mass may have been locked there from the beginnings of the solar system, giving rise to an inner core that feeds the outer or classical Oort cloud. Our aim will be to briefly discuss some of the topics summarized here.

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Neslušan, L. « Dynamics of comets in the collapsing protosolar nebula ». International Astronomical Union Colloquium 173 (1999) : 45–50. http://dx.doi.org/10.1017/s0252921100031225.

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AbstractComets are created in the cool, dense regions of interstellar clouds. These macroscopic bodies take place in the collapse of protostar cloud as mechanically moving bodies in contrast to the gas and miscroscopic dust holding the laws of hydrodynamics. In the presented contribution, there is given an evidence concerning the Solar system comets: if the velocity distribution of comets before the collapse was similar to that in the Oort cloud at the present, then the comets remained at large cloud-centric distances. Hence, the comets in the solar Oort cloud represent a relict of the nebular stage of the Solar system.

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Borinskaya, Sofya, Katrina B. Velle, Kenneth G. Campellone, Arthur Talman, Diego Alvarez, Hervé Agaisse, Yi I. Wu, Leslie M. Loew et Bruce J. Mayer. « Integration of linear and dendritic actin nucleation in Nck-induced actin comets ». Molecular Biology of the Cell 27, n^o 2 (15 janvier 2016) : 247–59. http://dx.doi.org/10.1091/mbc.e14-11-1555.

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The Nck adaptor protein recruits cytosolic effectors such as N-WASP that induce localized actin polymerization. Experimental aggregation of Nck SH3 domains at the membrane induces actin comet tails—dynamic, elongated filamentous actin structures similar to those that drive the movement of microbial pathogens such as vaccinia virus. Here we show that experimental manipulation of the balance between unbranched/branched nucleation altered the morphology and dynamics of Nck-induced actin comets. Inhibition of linear, formin-based nucleation with the small-molecule inhibitor SMIFH2 or overexpression of the formin FH1 domain resulted in formation of predominantly circular-shaped actin structures with low mobility (actin blobs). These results indicate that formin-based linear actin polymerization is critical for the formation and maintenance of Nck-dependent actin comet tails. Consistent with this, aggregation of an exclusively branched nucleation-promoting factor (the VCA domain of N-WASP), with density and turnover similar to those of N-WASP in Nck comets, did not reconstitute dynamic, elongated actin comets. Furthermore, enhancement of branched Arp2/3-mediated nucleation by N-WASP overexpression caused loss of the typical actin comet tail shape induced by Nck aggregation. Thus the ratio of linear to dendritic nucleation activity may serve to distinguish the properties of actin structures induced by various viral and bacterial pathogens.

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S. Najm, Rasha, Salman Z. Khalaf et Khaleel I. Abood. « X-Ray Emission Spectroscopy Analysis for Near-Asteroid Belt of Atmospheric of the Comets ». Iraqi Journal of Physics 20, n^o 3 (1 septembre 2022) : 86–97. http://dx.doi.org/10.30723/ijp.v20i3.1006.

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According to Chandra Survey Observatory Near-Asteroid Belt Comets, the solar wind's contact with the comet produces a variety of spectral characteristics. The study of X-ray spectra produced by charge exchange is presented here. The spectrum of a comet can reveal a lot about its composition. This study has concentrated on the elemental abundance in six different comets, including 17P/Holmes, C/1999T1, C/2013A1, 9p/Temple1, and 103p/Hartley2 (NEAT). Numerous aspects of the comet's dynamics allow it to behave in a unique manner as it gets closer to the Near-Asteroid Belt. These characteristics are being examined, and some studies are still ongoing. The computations allow us to observe, for instance, how the composition of a comet's upper atmosphere affects how much gas it produces. For several comet morphologies, both linear and nonlinear, bow shock, contact surface, and stagnation point are investigated in relation to gas production rate. Our results shed light on the complex interactions between cometary ions and the solar wind. An increase in gas production rate was shown to be significantly correlated with sharp drops in average molecular weight.

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Mysen, Eirik. « Rotational dynamics of subsolar sublimating triaxial comets ». Planetary and Space Science 52, n^o 10 (août 2004) : 897–907. http://dx.doi.org/10.1016/j.pss.2004.04.001.

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Emel'yanenko, V. V. « Dynamics of periodic comets and meteor streams ». Celestial Mechanics and Dynamical Astronomy 54, n^o 1-3 (1992) : 91–110. http://dx.doi.org/10.1007/bf00049546.

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Haghighipour, N., T. I. Maindl, C. Schäfer, R. Speith et R. Dvorak. « Triggering Comet-Like Activity of Main Belt Comets ». Proceedings of the International Astronomical Union 10, S318 (août 2015) : 135–41. http://dx.doi.org/10.1017/s1743921315009680.

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AbstractMain Belt Comets (MBCs) have attracted a great deal of interest since their identification as a new class of bodies by Hsieh and Jewitt in 2006. Much of this interest is due to the implication that MBC activity is driven by the sublimation of volatile material (presumed to be water-ice) presenting these bodies as probable candidates for the delivery of a significant fraction of Earth's water. Results of the studies of the dynamics of MBCs suggest that these objects might have formed in-situ as the remnants of the break-up of large icy asteroids. Simulations also show that collisions among MBCs and small objects could have played an important role in triggering the cometary activity of these bodies. Such collisions might have exposed sub-surface water-ice which sublimated and created thin atmospheres and tails around MBCs. In order to drive the effort of understanding the nature of the activation of MBCs, we have investigated these collision processes by simulating the impacts in detail using a smooth particle hydrodynamics (SPH) approach that includes material strength and fracture models. We have carried out simulations for a range of impact velocities and angles, allowing m-sized impactors to erode enough of an MBC's surface to expose volatiles and trigger its activation. Impact velocities were varied between 0.5 km/s and 5.3 km/s, and the projectile radius was chosen to be 1 m. As expected, we observe significantly different crater depths depending on the impact energy, impact angle, and MBC's material strength. Results show that for all values of impact velocity and angle, crater depths are only a few meters, implying that if the activity of MBCs is due to the sublimation of water-ice, ice has to exist in no deeper than a few meters from the surface. We present details of our simulations and discuss the implications of their results.

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Fernández, J. A., et T. Gallardo. « From the Oort cloud to Halley-type comets ». International Astronomical Union Colloquium 173 (1999) : 327–38. http://dx.doi.org/10.1017/s0252921100031638.

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AbstractThe Oort cloud probably is the source of Halley-type (HT) comets and perhaps of some Jupiter-family (JF) comets. The process of capture of Oort cloud comets into HT comets by planetary perturbations and its efficiency are very important problems in comet ary dynamics. A small fraction of comets coming from the Oort cloud − of about 10−2− are found to become HT comets (orbital periods < 200 yr). The steady-state population of HT comets is a complex function of the influx rate of new comets, the probability of capture and their physical lifetimes. From the discovery rate of active HT comets, their total population can be estimated to be of a few hundreds for perihelion distancesq <2 AU. Randomly-oriented LP comets captured into short-period orbits (orbital periods < 20 yr) show dynamical properties that do not match the observed properties of JF comets, in particular the distribution of their orbital inclinations, so Oort cloud comets can be ruled out as a suitable source for most JF comets. The scope of this presentation is to review the capture process of new comets into HT and short-period orbits, including the possibility that some of them may become sungrazers during their dynamical evolution.

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Thèses sur le sujet "Comets Dynamics"

De, Biasi Alice. « Tidal Effects on the Oort Cloud Comets and Dynamics of the Sun in the Spiral Arms of the Galaxy ». Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423732.

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The Solar System presents a complex dynamical structure and is not isolated from the Galaxy. In particular the comet reservoir of our planetary system, the Oort cloud, is extremely sensitive to the the galactic environment due to its peripheral collocation inside the Solar System. In this framework, the growing evidences about a possible migration of the Sun open new research scenarios relative to the effects that such kind of migration might induce on the cometary motion. Following several previous studied, we identified the spiral arm structure as the main perturbation that is able to produce an efficient solar migration through the disk. Widening the classical model for the spiral arms, provided by Lin& Shu to a 3D formalism, we verified the compatibility between the presence of the spiral perturbation and a significant solar motion for an inner Galactic position to the current one, in agreement with the constrains in position, velocity and metallicity due to the present conditions of our star. The main perturbers of the Oort cloud, the close stellar passages and the tidal field of the Galaxy, might be both affected by the variation of Galactic environment that the solar migration entails. Despite that, in order to isolate the effects to the two different perturbators, we decided to focus our attention only on the Galactic tide. The perturbation due to the spiral structure was included in the study on the cometary motion, introducing the solar migration and adding the direct presence of the non-axisymmetric component in the Galactic potential of the tidal field. The results show a significant influence of the spiral arm in particular on cometary objects belonged to the outer shell of the Oort cloud, for which provides an injection rate three times bigger than the integration performed without the spiral arms. The introduction of the spiral perturbation seems to bolster the planar component of the tide, indeed it produces the most significant variation of the perihelion distance for moderate inclination orbits with respect to the plane. The peak for the cometary injections has been registered between 6 and 7 kpc. If this evidence will be confirmed by more realistic cometary sample, it might involve a redefinition of the habitability edges in the Galaxy (GHZ). In particular regions not precluded to the formation of life, may compromise the development of the life with a high cometary impact risk
Il Sistema Solare è una struttura con una dinamica complessa e non isolata da quella galattica. In particolare la riserva cometaria del nostro sistema planetario, la nube di Oort, a causa della sua periferica collocazione all’interno del Sistema Solare, risulta estremamente sensibile all'ambiente galattico circostante. In questo contesto, le crescenti evidenze di una possibile migrazione del Sole, aprono un nuovo scenario di indagine relativo ai cambiamenti che tale migrazione potrebbe indurre sul moto cometario. Seguendo un filone di ricerca già tracciato, abbiamo identificato nella struttura a spirale la principale perturbazione in grado di produrre un efficace effetto migratorio per il Sole. Ampliando il classico modello di Lin & Shu con una modellizzazione 3D per i bracci a spirale considerati in regime transiente, siamo stati in grado di verificare la compatibilità tra tale perturbazione e un moto solare attraverso il disco, in accordo con i vincoli di posizione, velocità e metallicità imposti dalla attuale condizione della nostra stella. Malgrado i maggiori perturbatori della nube di Oort, i passaggi stellari ravvicinati e il campo mareale della Galassia, siano entrambi potenzialmente sensibili alla variazione di ambiente galattico che una migrazione solare comporta, abbiamo concentrato il nostro studio unicamente sulla marea galattica. La perturbazione dovuta alla spirale, è stata incorporata nello studio dei moti cometari, sia attraverso l’introduzione della migrazione solare, che come effetto diretto sulle comete grazie alla presenza della componente non assisimmetrica nel campo mareale. I risultati mostrano un’influenza significativa della spirale, in particolar modo sulla popolazione cometaria del guscio più esterno della nube, per la quale si sono registrati tassi di immissione cometaria 3 volte maggiori rispetto al caso senza tale perturbazione. La spirale sembra rinforzare l’azione della componente piana della marea, producendo infatti le maggiori variazioni sui perieli cometari in corrispondenza di orbite con inclinazioni moderate rispetto al piano galattico. Si è inoltre rilevato che il picco di immissione cometaria si trova in corrispondenza di distanze galattiche per il Sole comprese tra 6 e 7 kpc. Se tale evidenza fosse confermata anche da campioni cometari più realistici, potrebbe comportare un vincolo ulteriore alla definizione della zona di abitabilità galattica (GHZ). In particolare, regioni del disco non attualmente precluse alla formazione della vita, potrebbero risultare inadatte allo sviluppo della stessa per un rischio di impatto cometario troppo elevato

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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 actuelles
Comets 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

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Volk, Kathryn Margaret. « Dynamical studies of the Kuiper belt and the Centaurs ». Thesis, The University of Arizona, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3560868.

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The Kuiper belt is a population of small bodies located outside Neptune's orbit. The observed Kuiper belt objects (KBOs) can be divided into several subclasses based on their dynamical structure. I construct models for these subclasses and use numerical integrations to investigate their long-term evolution. I use these models to quantify the connection between the Kuiper belt and the Centaurs (objects whose orbits cross the orbits of the giant planets) and the short-period comets in the inner solar system. I discuss how these connections could be used to determine the physical properties of KBOs and what future observations could conclusively link the comets and Centaurs to specific Kuiper belt subclasses.

The Kuiper belt's structure is determined by a combination of long-term evolution and its formation history. The large eccentricities and inclinations of some KBOs and the prevalence of KBOs in mean motion resonances with Neptune are evidence that much of the Kuiper belt's structure originated during the solar system's epoch of giant planet migration; planet migration can sculpt the Kuiper belt's scattered disk, capture objects into mean motion resonances, and dynamically excite KBOs. Different models for planet migration predict different formation locations for the subclasses of the Kuiper belt, which might result in different size distributions and compositions between the subclasses; the high-inclination portion of the classical Kuiper belt is hypothesized to have formed closer to the Sun than the low-inclination classical Kuiper belt. I use my model of the classical Kuiper belt to show that these two populations remain largely dynamically separate over long timescales, so primordial physical differences could be maintained until the present day.

The current Kuiper belt is much less massive than the total mass required to form its largest members. It must have undergone a mass depletion event, which is likely related to planet migration. The Haumea collisional family dates from the end of this process. I apply long-term evolution to family formation models and determine how they can be observationally tested. Understanding the Haumea family's formation could shed light on the nature of the mass depletion event.

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Heisler, Julia. « Dynamical influences on the comets of the Oort Cloud ». Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/15186.

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Hu, Hongyao. « Atmospheres of comets : Gas dynamic models and inference of kinematic parameters ». Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185429.

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Cometary nuclei may be our best available probes of the physical and chemical nature of the presolar nebula. However, in situ sampling of cometary nuclei to determine their composition is generally not feasible. Instead, remote spectroscopic observations of cometary comae are used to infer cometary composition. This approach relies on one's ability to model accurately the density distributions of gas and dust in the comae and a complex network of photochemical and molecular processes. Previously, a variety of theoretical models had been developed and, unfortunately, they are applicable only to a portion of the coma or to specific problems. In the first part of this thesis we introduce a preliminary version of a gas model built upon the concepts of dilute gas theory. This model is valid over the whole coma and it incorporates all previous models as its special cases, thus providing a new theoretical foundation for future cometary studies. In the second part of the thesis we discuss a spectral outflow model. This model is a special case of the dilute gas model and is tailored specifically to retrieve kinematic properties of cometary comae from velocity-resolved spectral line profiles. We review the formation of cometary spectral line profiles and we develop an analytic expression that maps three dimensional number density distributions into synthetic spectral line profiles. After discussing simplifications and Monte Carlo computational procedures, we apply the spectral outflow model to interpret infrared observations of H₂O in comets Halley and Wilson.

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Conrad, Michael Curt. « COMET : CONSTRAINED OPTIMIZATION OF MULTIPLE-DIMENSIONS FOR EFFICIENT TRAJECTORIES ». DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/666.

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The paper describes the background and concepts behind a master’s thesis platform known as COMET (Constrained Optimization of Multiple-dimensions for Efficient Trajectories) created for mission designers to determine and evaluate suitable interplanetary trajectories. This includes an examination of the improvements to the global optimization algorithm, Differential Evolution, through a cascading search space pruning method and decomposition of optimization parameters. Results are compared to those produced by the European Space Agency’s Advanced Concept Team’s Multiple Gravity Assist Program. It was found that while discrepancies in the calculation of ΔV’s for flyby maneuvers exist between the two programs, COMET showed a noticeable improvement in its ability to avoid premature convergence and find highly isolated solutions.

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Pujolàs, Fons Pau Salvador. « Essays on International Trade and Firm Dynamics ». Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/120540.

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El primer capítol d’aquesta Tesis porta per Títol “Trade Patterns, Income Differences and Gains From Trade” i ha estat elaborada conjuntament amb el meu col·lega Wyatt J. Brooks. Quantificar els guanys provinents de comerç internacional és una àrea de recerca que ha estat estudiada usant una gran varietat de models de comerç. Al mateix temps, s’ha mostrat com les no-homoteticitats són molt útils per explicar patrons de comerç observats en dades molt desagregades. Posem ambdues literatures juntes per preguntar com les no-homoteticitats afecten les prediccions de guanys de comerç. A tal fi, desenvolupem un model de comerç amb N països amb els mateixos volums de comerç internacional, població, PIB per càpita i desigualtat dins de cada país que a les dades. Incloem les no-homoteticitats per tal que el comerç entre països rics i països pobres sigui igual al que observem a les dades. Amb aquest model, podem comparar els resultats en benestar obtinguts amb els que impliquen Arkolakis, Costinot, and Rodriguez-Clare (2012) – que dóna una fórmula senzilla de guanys comercials per part d’un gran nombre de models homotètics (també la versió d’aquest model quan les preferències són homotètiques). El principal resultat és que els models homotètics esbiaixen a la baixa els guanys comercials en països amb poca població i baixa productivitat, i a l’alça el dels països molt poblats i molt productius. El model homotètic esbiaixa a l’alça els guanys comercials dels EE.UU. i de Japó en 14% i 22%, mentre que ho fa a la baixa per Espanya i Itàlia en un 24% i un 14%. El segon capitol d’aquesta Tesis porta per títol “Measured Productivity and International Trade: An Unresolved Puzzle”. Utilitzar models de dinàmica d’empreses correctes quan s’analitza l’impacte del comerç és clau a fi d’entendre completament quins són els efectes a la part productiva de l’economia quan aquesta es dedica a comerciar més. Hi ha diversos models de comerç que intenten entendre la relació entre comerç i dinàmica d’empreses, però un d’ells és sens dubte el més utilitzat per economistes de comerç: el de Melitz (2003). Aquest model explica algunes característiques de les dades. En particular, vol explicar per què les empreses més productives exporten. És de comú parer entre els economistes que aquest model explica bé les característiques de productivitat de les empreses. En aquest capítol ens preguntem: ho és? Concretament, mostrem que si hom mesura la productivitat als resultats del model tal i com es fa a les dades, ens trobem amb resultats sorprenents sobre quines són les empreses més productives: poden ser les que no exporten. El tercer capítol de la Tesis es titula “Distortions, Productivity, and Idiosyncratic Shocks” i és escrita conjuntament amb el meu professor José María Da Rocha. Considerem distorsions en un model on les plantes tenen xocs idiosincràtics a la productivitat que evolucionen amb una moció Browniana. Introduir els xocs en el model implica que les plantes tenen beneficis no constants i com a resultat el marge de sortida es torna exogen, i les plantes han de decidir en cada període si es queden o no produint. Utilitzem l’equació de Kolmogorov per tal de caracteritzar l’equilibri estacionari. La contribució de l’estudi consisteix en mostrar que si un model es calibra/s’estima sense xocs idiosincràtics, les plantes tenen productivitat constant en el temps i la rati de sortida és exògena a fi d’obtenir els moments generats pel model amb xocs i sortida endògena, les distorsions en PTF són esbiaixades a l’alça.
The first chapter of this Thesis is entitled Trade Patterns, Income Differences and Gains From Trade and is coauthored with my colleague Wyatt J. Brooks. Quantifying the gains from international trade is an area of research that has been widely studied using a variety of trade models. At the same time, it has been shown that nonhomotheticities are useful for matching the systematic patterns of trade present in disaggregated trade data. We bring these two literatures together to ask how nonhomotheticities affect our predictions for gains from trade. To do so, we develop a N-country trade model that exactly matches bilateral trade, population, GDP per capita and within country income inequality for many countries. We include nonhomotheticities to match patterns of trade between rich and poor countries that we observe in highly disaggregated trade data. We then make use of the results from Arkolakis, Costinot, and Rodriguez-Clare (2012), which gives a simple formula for gains from trade in a large class of homothetic models, including a version of our model with the nonhomotheticity removed. Our main finding is that homothetic models underestimate gains from trade in countries with small populations and low productivities, and overestimate gains in countries with large populations and high productivities. The homothetic model overestimates the gains from being open to trade in the U.S. and Japan by 14% and 22%, and underestimates them in Spain and Italy by 24% and 14%. The second chapter of this Thesis is entitled Measured Productivity and International Trade: An Unresolved Puzzle. Using correct models of firm dynamics when analyzing the impact of trade is key in order to fully understand what are the effects to the supply side of the economy when it engages into trade. There are several models of trade that try to understand the role of trade and firm dynamics, but there is one that is most used by trade economists: the Melitz model (2003). This model explains several features of the data. In particular, it aims to explain why more productive firms export. It is a common agreement among economists that the model is well suited in order to explain these patterns. In this chapter we ask: is it? In particular, we show that measuring productivity in the model's outcome as it is done in the data may lead to some surprising results regarding what more productive firms do: they may be the non-exporters. The third chapter of this Thesis is entitled Distortions, Productivity, and Idiosyncratic Shocks and is coauthored with my professor José María Da Rocha. We consider policy distortions in a model where plants face idiosyncratic productivity shocks that evolve following a Brownian motion. Introducing idiosyncratic shocks into the model implies that plants have non-constant operating profits and as a result there is an endogenous exit margin and incumbent plants must decide in each period whether or not to remain in the industry. By using the forward Kolmogorov equation, we analytically characterize the Stationary Equilibrium. Our main contribution is to show that if a model is being calibrated/estimated without idiosyncratic shocks, where plants face constant productivity over time and the exit rate is exogenous to fit data generated from a model with shocks and endogenous entry, TFP distortions will be overestimated.

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Beaver, David Ian. « Presupposition and assertion in dynamic semantics : Part (I) The presupposition : a critical review of presupposition theory ; Part (II) The assertion : what comes first in dynamic semantics ». Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/10767.

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The Context Change Potential (CCP) model of presupposition, due primarily to Kartunnen and Heim, is formally elaborated and modified within a propositional dynamic logic, a first-order dynamic logic, and within a three sorted type theory. It is shown that the definitions of connectives and quantifiers can be motivated independently of the phenomenon of presupposition by consideration of the semantics of anaphora and epistemic modality (cf. the work of Groenendijk & Stokhof and Veltman), and that these independently motivated definitions provide a solution to the projection problem for presupposition. It is argued that with regard to the interaction between presupposition and quantification the solution is empirically superior to those in competing accounts. The treatment of epistemic modality is also shown to be superior to existing dynamic accounts, combining solutions to traditional model identity problems with an adequate treatment of presuppositions in quantified contexts. A compositional semantics which integrates dynamic treatments of quantification, anaphora, modality and presupposition is then specified for a fragment of English. Finally, a formal modal of global accommodation (cf. Lewis, Heim, van der Sandt) is defined, this model differing from previous accounts in being non-structural. This means that the accommodated material cannot be deduced from formal properties of the utterance alone, but is essentially dependent on world-knowledge and common sense reasoning. Thus the model provides an essentially pragmatic account in the style of Stalnaker. It is shown that the formal model provides both a general solution to the problem of the in-formativeness of presuppositions, and a specific solution to a problem within the CCP model, namely its tendency to yield innapropriately weak conditionalised presuppositions. It argued that a pragmatic model can provide superior predictions to any purely semantic theory of presupposition, and to any theory based on a purely structural account of accommodation or cancellation (cf. Gazdar).

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DUVET, LUDOVIC. « Instrumentation pour l'etude in-situ des atmospheres neutres et ionises planetaires et cometaires : idm (ion dynamics monitor) et cops (comet pressure sensor) ». Paris 6, 2001. http://www.theses.fr/2001PA066296.

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Le travail realise durant cette these a consiste en le developpement, la realisation et les tests de deux instruments destines a l'etude des environnements neutres et ionises planetaires et cometaires. Le premier instrument, idm (ion dynamics monitor), est un spectrometre a plasma thermique et suprathermique (< 200 ev) developpe initialement lors de la phase de consolidation du projet cometaire europeen rosetta. Une version amelioree a ensuite ete adaptee pour l'etude de l'ionosphere et de la couche limite de mars dans le cadre du projet dynamo. Les deux versions du spectrometre ont ete testees en laboratoire et les resultats, en tres bon accord avec la simulation, ont montre le respect des specifications necessaires a la mesure. Le second instrument est destine a la mesure des parametres dynamiques d'une atmosphere neutre. Une etude detaillee des techniques de mesures actuelles de la dynamique d'un gaz neutre est tout d'abord presentee et montre l'interet de l'utilisation d'un concept instrumental reposant sur des jauges de densite a impact electronique et des chambres d'equilibre. L'instrument cops (comet pressure sensor), premiere realisation de ce concept, sera embarque a bord de la sonde rosetta et permettra l'evaluation de la vitesse d'expansion et de la densite du gaz cometaire. Le developpement de l'instrument a necessite la mise au point de techniques de modelisation de l'interaction d'un gaz et d'un solide en regime moleculaire et a conduit a la realisation de tests sous faisceau moleculaire. Les resultats montrent que les principaux objectifs sont atteints. Une seconde application de ce concept instrumental destinee a l'etude de la haute atmosphere martienne est aussi presentee.

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Tsoumpra, Natalia. « Comic leadership and power dynamics in Aristophanes ». Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:1b3d4779-609e-4638-81f2-2e7f0d410477.

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This thesis investigates the concept of leadership in four comedies of Aristophanes. In the first chapter (Lysistrata) I focus on the relationship of the female leadership with religious rituals and medical pathology, and I show that the power of women lies in their important biological role and their ability to conceive and (re)produce life in the context of marriage. In chapter two (Knights) I examine the operation of leadership through the alimentary and sacrificial codes of the play. I argue that the Sausage-seller gradually manifests himself as the sacrificial cook Agorakritos who sacrifices Demos. In this way he puts an end to the politics of savage, raw consumption as they were employed by Paphlagon (and, occasionally, by Demos himself), and saves the day by inaugurating a new era of political practice. In chapter three (Birds) I focus on the political competition between the former leader of the Birds, Tereus, and the newcomer Peisetairos. I argue that Peisetairos captivates his audience through the abuse of rhetoric and sophistry, and gradually adopts more brutal ways, by perverting the ritual of hospitality, committing cannibalism, and becoming sexually aggressive. In this respect, Peisetairos is assimilated to the tragic Tereus of the Sophoclean tragedy, but finally emerges as a more successful version of both the comic and the tragic Tereus. In the fourth and last chapter (Ecclesiazusae) I discuss the women’s disruption and overturn of the normal social order by focusing on the practice of cross-dressing and on love-magic rituals: the exchange of costume between the two sexes, as well as the control of magic practices by the women over men, empower women and, by contrast, disempower and ridicule men, who are finally reduced to a state of impotence, infertility and almost death.

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Livres sur le sujet "Comets Dynamics"

The dynamics of Halley-type comets. Manchester : University of Manchester, 1994.

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Chambers, John Eric. The dynamics of Halley-type comets. Manchester : University of Manchester, 1994.

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Carusi, Andrea, et Giovanni B. Valsecchi, dir. Dynamics of Comets : Their Origin and Evolution. Dordrecht : Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5400-7.

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Fernández, J. A. Comets : Nature, dynamics, origin, and their cosmogonical relevance. Dordrecht, The Netherlands : Springer, 2005.

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Comets : Nature, dynamics, origin, and their cosmogonical relevance. Dordrecht, Netherlands : Springer, 2005.

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Yabushita, Shin, et Jacques Henrard, dir. Dynamics of Comets and Asteroids and Their Role in Earth History. Dordrecht : Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-017-1321-4.

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1946-, Carusi Andrea, et Valsecchi Giovanni B. 1951-, dir. Dynamics of comets : Their origin and evolution : proceedings of the 83rd Colloquium of the International Astronomical Union, held in Rome, Italy, 11-15 June 1984. Dordrecht, Holland : D. Reidel Pub. Co., 1985.

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International Astronomical Symposium (1992 Pléneuf-Val-André, France). Interactions between physics and dynamics of solar system bodies : Proceedings of the International Astronomical Symposium held in Pléneuf-Val-André (France) from June 21 to June 28, 1992. Dordrecht : Kluwer Academic Publishers, 1993.

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1936-, Yabushita Shin, et Henrard J, dir. Dynamics of comets and asteroids and their role in earth history : Proceedings of a workshop held at the Dynic Astropark 'Ten-Kyu-Kan', August 14-18, 1997. Dordrecht, The Netherlands : Kluwer Academic, 1998.

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United States. National Aeronautics and Space Administration., dir. The kinetics and dynamics of Halley's comet. Ann Arbor, MI : Space Physics Research Laboratory, Dept. of Atmospheric, Oceanic and Space Sciences, University of Michigan, 1994.

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Chapitres de livres sur le sujet "Comets Dynamics"

Milani, Andrea. « The Dynamics of the Trojan Asteroids ». Dans Asteroids, Comets, Meteors 1993, 159–74. Dordrecht : Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1148-5_12.

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Remy, F., et F. Mignard. « Stellar Perturbations on Comets ». Dans Dynamics of Comets : Their Origin and Evolution, 97–104. Dordrecht : Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5400-7_8.

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Fernández, Julio A. « Dynamics of Comets : Recent Developments and New Challenges ». Dans Asteroids, Comets, Meteors 1993, 223–40. Dordrecht : Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1148-5_16.

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Nakamura, Tsuko, et Makoto Yoshikawa. « Invisible Comets On Evolutionary Track Of Short-Period Comets ». Dans Dynamics and Evolution of Minor Bodies with Galactic and Geological Implications, 261–66. Dordrecht : Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2743-1_22.

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Hughes, David W. « The Transition Between Long Period Comets, Short Period Comets and Meteoroid Streams ». Dans Dynamics of Comets : Their Origin and Evolution, 129–42. Dordrecht : Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5400-7_11.

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Rickman, Hans. « Interrelations between Comets and Asteroids ». Dans Dynamics of Comets : Their Origin and Evolution, 149–72. Dordrecht : Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5400-7_13.

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Yeomans, D. K. « Cometary Orbital Dynamics and Astrometry ». Dans Comets in the Post-Halley Era, 3–17. Dordrecht : Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3378-4_1.

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Koon, W. S., M. W. Lo, J. E. Marsden et S. D. Ross. « Resonance and Capture of Jupiter Comets ». Dans Dynamics of Natural and Artificial Celestial Bodies, 27–38. Dordrecht : Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-017-1327-6_3.

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Kresák, Ľubor. « The Aging and Lifetimes of Comets ». Dans Dynamics of Comets : Their Origin and Evolution, 279–302. Dordrecht : Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5400-7_24.

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Emel’yanenko, V. V. « Dynamics Of Periodic Comets And Meteor Streams ». Dans Dynamics and Evolution of Minor Bodies with Galactic and Geological Implications, 91–110. Dordrecht : Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2743-1_7.

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Actes de conférences sur le sujet "Comets Dynamics"

Nishio, M., M. Yoshihara, A. Nakashima et M. Sasaki. « Development of the COMETS structure (Communications and Broadcasting Engineering Test Satellite) ». Dans 36th Structures, Structural Dynamics and Materials Conference. Reston, Virigina : American Institute of Aeronautics and Astronautics, 1995. http://dx.doi.org/10.2514/6.1995-1511.

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Finklenburg, Susanne, Nicolas Thomas, Jörg Knollenberg et Ekkehard Kührt. « Comparison of DSMC and Euler Equations Solutions for Inhomogeneous Sources on Comets ». Dans 27TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS. AIP, 2011. http://dx.doi.org/10.1063/1.3562799.

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HILL, STEVEN, et TODD MCCUSKER. « COMET Recovery System flight dynamics ». Dans Flight Simulation and Technologies. Reston, Virigina : American Institute of Aeronautics and Astronautics, 1993. http://dx.doi.org/10.2514/6.1993-3693.

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Byram, Sharyl, Daniel Scheeres et Michael Combi. « Realistic Models for the Comet Dynamical Environment ». Dans AIAA/AAS Astrodynamics Specialist Conference and Exhibit. Reston, Virigina : American Institute of Aeronautics and Astronautics, 2006. http://dx.doi.org/10.2514/6.2006-6288.

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Costa, Marc, Miguel Pérez, Miguel Almeida, Mike Ashman, Raymond Hoofs, Steve Chien, Federico Nespoli, Juan José García et Michael Kueppers. « Rosetta : rapid science operations for a dynamic comet ». Dans SpaceOps 2016 Conference. Reston, Virginia : American Institute of Aeronautics and Astronautics, 2016. http://dx.doi.org/10.2514/6.2016-2538.

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van der Mark, Martin B. « Electrifying catheters by fiber optics, MRI compatibility and everything else that comes for free (Conference Presentation) ». Dans Dynamics and Fluctuations in Biomedical Photonics XV, sous la direction de Valery V. Tuchin, Kirill V. Larin, Martin J. Leahy et Ruikang K. Wang. SPIE, 2018. http://dx.doi.org/10.1117/12.2302364.

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Wang, Haowei, Yicheng Pan, Meng Ma et Ping Wang. « When Dynamic Causality Comes to Graph-Temporal Neural Network ». Dans 2022 International Joint Conference on Neural Networks (IJCNN). IEEE, 2022. http://dx.doi.org/10.1109/ijcnn55064.2022.9892477.

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Williamsen, Joel, William Bohl, Jeremy Stober, Tim Flora et H. Evans. « Flying Through a Comet : Designing Structural Protection for the Deep Impact Spacecraft ». Dans 43rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference. Reston, Virigina : American Institute of Aeronautics and Astronautics, 2002. http://dx.doi.org/10.2514/6.2002-1608.

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Tenishev, Valeriy, Martin Rubin et Michael R. Combi. « Kinetic simulation of neutral∕ionized gas and electrically charged dust in the coma of comet 67P∕Churyumov-Gerasimenko ». Dans 27TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS. AIP, 2011. http://dx.doi.org/10.1063/1.3562802.

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Badescu, M., R. Bonitz, A. Ganino, N. Haddad, P. Walkemeyer, P. Backes, L. Shiraishi et al. « Dynamic acquisition and Retrieval Tool (DART) for comet sample return ». Dans 2013 IEEE Aerospace Conference. IEEE, 2013. http://dx.doi.org/10.1109/aero.2013.6496920.

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Rapports d'organisations sur le sujet "Comets Dynamics"

Perdigão, Rui A. P. Earth System Dynamic Intelligence - ESDI. Meteoceanics, avril 2021. http://dx.doi.org/10.46337/esdi.210414.

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Earth System Dynamic Intelligence (ESDI) entails developing and making innovative use of emerging concepts and pathways in mathematical geophysics, Earth System Dynamics, and information technologies to sense, monitor, harness, analyze, model and fundamentally unveil dynamic understanding across the natural, social and technical geosciences, including the associated manifold multiscale multidomain processes, interactions and complexity, along with the associated predictability and uncertainty dynamics. The ESDI Flagship initiative ignites the development, discussion and cross-fertilization of novel theoretical insights, methodological developments and geophysical applications across interdisciplinary mathematical, geophysical and information technological approaches towards a cross-cutting, mathematically sound, physically consistent, socially conscious and operationally effective Earth System Dynamic Intelligence. Going beyond the well established stochastic-dynamic, information-theoretic, artificial intelligence, mechanistic and hybrid techniques, ESDI paves the way to exploratory and disruptive developments along emerging information physical intelligence pathways, and bridges fundamental and operational complex problem solving across frontier natural, social and technical geosciences. Overall, the ESDI Flagship breeds a nascent field and community where methodological ingenuity and natural process understanding come together to shed light onto fundamental theoretical aspects to build innovative methodologies, products and services to tackle real-world challenges facing our planet.

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Behr, Marek, Daniel M. Pressel, Walter B. Sturek et Sr. Comments on Computational Fluid Dynamics (CFD) Code Performance on Scalable Architectures. Fort Belvoir, VA : Defense Technical Information Center, décembre 2002. http://dx.doi.org/10.21236/ada409739.

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Fabio Morales, Leonardo, Eleonora Dávalos et Raquel Zapata. Estimating Vacancy Stocks from Aggregated Data on Hires : A Methodology to Study Frictions in the Labor Market. Banco de la República de Colombia, avril 2023. http://dx.doi.org/10.32468/be.1228.

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We develop a methodology that recovers an estimate of the average stock of vacancies using the information on aggregated hires. We show that our prediction of the vacancy stock is unbiased, and it captures well the level and the dynamics of the United States job opening positions reported in the Job Openings and Labor Turnover Survey. We use the methodology to predict vacancies in Colombia for formal and informal salaried workers; together with unemployment, we estimate Beveridge curves and matching functions by occupations, which allows us to study the nature of the efficiency, frictions, and mismatches for different occupations. We find that the formal labor market of technicians is the most inefficient of them all; this inefficiency comes from the mismatch between the abilities of the workers and the requirement of the vacancies. Reducing friction in this occupation will require education and job-oriented training policies. In contrast, the frictions in the market for unskilled workers come from informational lacks. The reductions of friction, in this case, will come from better intermediation and active search policies.

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Scollay, Robert. Asia's Infrastructure, Trade Costs and Regional Co-operation : Comments. Inter-American Development Bank, juin 2008. http://dx.doi.org/10.18235/0006850.

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This presentation comments on Douglas H. Brooks' paper Asia's infrastructure, trade costs and regional co-operation which discusses topics of trade dynamics within developing Asia. After highlighting Brooks' key points, it covers issues on trade costs, namely, avoidable versus unavoidable "Non-Tariff" trade costs and the reduction of "Non-Tariff" trade costs as a policy objective. Then it presents the implications of a world where each economy achieves "optimal" reductions in "non-tariff" trade costs. This presentation was prepared for the Latin America/Caribbean and Asia/Pacific Economics and Business Association (LAEBA)'s 4th Annual Meeting held in Lima, Peru on June 17th, 2008.

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Tacsir, Ezequiel. Innovation in Services : The Hard Case for Latin America and the Caribbean. Inter-American Development Bank, novembre 2011. http://dx.doi.org/10.18235/0006897.

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Recent research conducted by the IDB shows that innovation positively affects productivity growth in the Latin American and Caribbean region, although the evidence comes almost exclusively from the manufacturing sector. The dearth of evidence regarding innovation in services is related, at least in part, to uncertainty with respect to how innovation in services actually works, how it can best be measured and whether or not old measurement tools (biased toward manufacturing and R&D) are really applicable to innovation in service sector environments. This paper aims to provide a deeper understanding of the dynamics at play in the service sector in the region and the relationship between productivity and innovation in services (as well as specific sub-sectors of services) represents a policy making opportunity that, if ignored, could contribute to prolonged productivity lags in the region, while, if well designed and implemented, could have large economic payoffs. This paper was presented at the Fifth Americas Competiveness Forum for the Inter-American Development Bank and Compete Caribbean Santo Domingo, Dominican Republic, October 5-7, 2011.

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Ajzenman, Nicolás, et Laura Jaitman. Crime Concentration and Hot Spot Dynamics in Latin America. Inter-American Development Bank, juin 2016. http://dx.doi.org/10.18235/0011745.

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Latin America and the Caribbean is the most violent region in the world, with an annual homicide rate of more than 20 per 100,000 population and with an increasing trend. Yet most evidence of crime concentration, geo-temporal patterns, and event dependence comes from cities in high-income countries. Understanding crime patterns in the region and how they compare to those in high-income countries is of first-order importance to formulate crime reduction policies. This paper is the first to analyze crime patterns of cities in five Latin American countries. Using micro-geographic units of analysis, the paper finds, first, that crime in Latin America is highly concentrated in a small proportion of blocks: 50 percent of crimes are concentrated in 3 to 7.5 percent of street segments, and 25 percent of crimes are concentrated in 0.5 to 2.9 percent of street segments. This validates Weisburd's "law of crime concentration at place" (Weisburd, 2105). These figures are fairly constant over time but sensitive to major police reforms. The second finding is that hot spots of crime are not always persistent. Crime is constantly prevalent in certain areas, but in other areas hot spots either appear or disappear, suggesting a possible rational adaptation from criminals to police actions that cause crime displacement in the medium run to other areas. Finally, the paper finds a significant pattern of repeated crime victimization in location and time for property crimes. There are striking similarities with the developed world in crime concentration, although crime levels are much higher and usually increasing. There are also some differences in terms of the persistence of hot spots that pose interesting policy implications and avenues for future research.

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Campbell, John, et Jianping Mei. Where do Betas Come From ? Asset Price Dynamics and the Sources of Systematic Risk. Cambridge, MA : National Bureau of Economic Research, avril 1993. http://dx.doi.org/10.3386/w4329.

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Alvaredo, Facundo, François Bourguignon, Francisco H. G. Ferreira et Nora Lustig. Seventy-five Years of Measuring Income Inequality in Latin America. Inter-American Development Bank, octobre 2023. http://dx.doi.org/10.18235/0005211.

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Drawing on a comprehensive compilation of quantile shares and inequality measures for 34 countries, including over 5,600 estimated Gini coefficient, we review the measurement of income inequality in Latin America and the Caribbean over the last seven decades. Although the evidence from the first quarter century roughly until the 1970s is too fragmentary and difficult to compare, clearer patterns emerge for last fifty years. The central feature of these patterns is a broad inverted U curve, with inequality rising in most countries prior to the 1990s, and falling during the early 21st Century, at least until the mid-2010s, when trends appear to diverge across countries. This broad pattern is modified by country specificities, with considerable variation in timing and magnitude. Whereas this broad picture emerges for income inequality dynamics, there is much more uncertainty about the exact levels of inequality in the region. The uncertainty arises from the disparity in estimates for the same country/year combinations, depending on whether they come from household surveys exclusively; from some combination of surveys and administrative tax data; and on whether they attempt to scale income aggregates to achieve consistency with National Accounts estimates. Since no single method is fully convincing at present, we are left with (often wide) ranges, or bands, of inequality as our best summaries of inequality levels. Reassuringly, however, the dynamic patterns are generally robust across the bands.

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Chen. PR-224-03158-R01 Static and Cyclic Surface Loading on the Performance of Welds in Pre-1970 Pipelines. Chantilly, Virginia : Pipeline Research Council International, Inc. (PRCI), août 2009. http://dx.doi.org/10.55274/r0010973.

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These are the notes and comments summarizing the incomplete work to assess stresses on vintage pipelines due to soil loadings. The work was performed by C-FER Technologies, Battelle Memorial Institute, and Marina Smith. The overall objective was to develop an assessment tool that would allow pipeline engineers to evaluate the safety of shallowly buried pre-1970 pipelines under static and cyclic surface loads. The work completed includes the development of a dynamic model. However, the weld capacity models were never completed. Related documents (attachments can be found in the links below).

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Muhyiddin, Muhyiddin. Indonesia Employment Report 2023. Pusat Pengembangan Kebijakan Ketenagakerjaan Kementerian Ketenagakerjaan, décembre 2023. http://dx.doi.org/10.47198/report.2023.

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In 2023, Indonesia experienced economic recovery amidst challenges posed by the uncertain global economic slowdown. This is attributed to various factors such as the Russia-Ukraine war, high inflation, and supply chain disruptions. According to the latest report from the International Monetary Fund (IMF), global economic growth in 2023 is projected to reach only 3.6%, own from the previous projection of 3.7%. This figure is lower than the global economic growth in 2022, which reached 6.1%. One of the primary factors causing the global economic slowdown is the Russia-Ukraine war. This war has led to disruptions in global trade and energy supplies, resulting in price increases. Indonesia's response to global challenges reflects its resilience and adaptation in facing the dynamics of the global economy. Employment is closely linked to economic development in Indonesia. The presence of high-quality labor can accelerate the development process and enable Indonesia to compete with other countries.

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