scholarly journals Dynamical evolution of massive perturbers in realistic multicomponent galaxy models I: implementation and validation

2021 ◽  
Vol 502 (3) ◽  
pp. 3554-3568
Author(s):  
Matteo Bonetti ◽  
Elisa Bortolas ◽  
Alessandro Lupi ◽  
Massimo Dotti
Keyword(s):  
Dynamical Evolution ◽  
Analytical Framework ◽  
Dynamical Friction ◽  
Large Parameter ◽  
Galactic Disc ◽  
Physical Processes ◽  
Rotating Disc ◽  
The Individual ◽  
Analytical Approaches ◽  
Large Parameter Space

ABSTRACT Galaxies are self-gravitating structures composed by several components encompassing spherical, axial, and triaxial symmetry. Although real systems feature heterogeneous components whose properties are intimately connected, semi-analytical approaches often exploit the linearity of the Poisson’s equation to represent the potential and mass distribution of a multicomponent galaxy as the sum of the individual components. In this work, we expand the semi-analytical framework developed in Bonetti et al. (2020) by including both a detailed implementation of the gravitational potential of exponential disc (modelled with a sech2 and an exponential vertical profile) and an accurate prescription for the dynamical friction experienced by massive perturbers (MP) in composite galaxy models featuring rotating disc structures. Such improvements allow us to evolve arbitrary orbits either within or outside the galactic disc plane. We validate the results obtained by our numerical model against public semi-analytical codes as well as full N-body simulations, finding that our model is in excellent agreement to the codes it is compared with. The ability to reproduce the relevant physical processes responsible for the evolution of MP orbits and its computational efficiency make our framework perfectly suited for large parameter-space exploration studies.

Academic Events: An Empirically Grounded Typology and Their Academic Impact

2020 ◽  
Vol 24 (4) ◽  
pp. 481-497 ◽  
Author(s):  
Thomas Trøst Hansen ◽  
David Budtz Pedersen ◽  
Carmel Foley
Keyword(s):  
Analytical Framework ◽  
Future Research ◽  
Academic Impact ◽  
Future Research Agenda ◽  
Tourism Studies ◽  
Academic Events ◽  
Business Events ◽  
The Individual ◽  
Analytical Frameworks ◽  
Academic Sector

The meetings industry, government bodies, and scholars within tourism studies have identified the need to understand the broader impact of business events. To succeed in this endeavor, we consider it necessary to develop analytical frameworks that are sensitive to the particularities of the analyzed event, sector, and stakeholder group. In this article we focus on the academic sector and offer two connected analyses. First is an empirically grounded typology of academic events. We identify four differentiating dimensions of academic events: size, academic focus, participants, and tradition, and based on these dimensions we develop a typology of academic events that includes: congress, specialty conference, symposium, and practitioners' meeting. Secondly, we outline the academic impact of attending these four types of events. For this purpose, the concept of credibility cycles is used as an analytical framework for examining academic impact. We suggest that academic events should be conceptualized and evaluated as open marketplaces that facilitate conversion of credibility. Data were obtained from interviews with 22 researchers at three Danish universities. The study concludes that there are significant differences between the events in terms of their academic impact. Moreover, the outcome for the individual scholar depends on the investment being made. Finally, the study calls for a future research agenda on beyond tourism benefits based on interdisciplinary collaborations.

scholarly journals A SIGHT OVER THE HEALTH OF WASTE PICKERS: AN ANALYTICAL FRAMEWORK PROPOSITION

2018 ◽  
Vol 21 (0) ◽  
Author(s):  
LAYSCE ROCHA DE MOURA ◽  
SYLMARA LOPES FRANCELINO GONÇALVES DIAS ◽  
LUCIANO ANTONIO PRATES JUNQUEIRA
Keyword(s):  
Systematic Review ◽  
Empirical Studies ◽  
Analytical Framework ◽  
Review Of Literature ◽  
Individual Activity ◽  
The Individual ◽  
Waste Pickers

Abstract This study aims to identify articles focused on the waste picker’s health to support the construction of an analytical framework that considers the individual and the environment in the scope of their labor activity. For this purpose, it is intended to answer the following question: which aspects can be considered in the analysis of the waste picker’s health in their labor activity? Methodologically, it has an exploratory nature and use the Systematic Review of Literature. The results pointed out to four categories of analysis grouped into the following aspects: meanings, individual, activity and environment. The analytical framework proposed presents contributions for an extended understanding of waste picker’s health, its aspects and interrelationships. Finally, it is suggested that empirical studies could be carried out to validate the proposed structure.

scholarly journals Comets (Existing Populations)

1994 ◽  
Vol 160 ◽  
pp. 77-94
Author(s):  
Ľ. Kresák
Keyword(s):  
Kuiper Belt ◽  
Dynamical Evolution ◽  
Oort Cloud ◽  
Survival Times ◽  
Evolutionary Time ◽  
Origin And Evolution ◽  
History Of ◽  
The Individual ◽  
Evolutionary Paths

The definition, population, extent, origin and evolution of the individual subsystems of comets and transitions between them are discussed, together with presentation of the relevant statistical data and their changes with time. The largest outer subsystems are unobservable, but their existence is documented by the necessity of progressive replenishment of the observable populations, with limited survival times. There is persuasive evidence for two different evolutionary paths, one from the Oort cloud and another from the Kuiper belt. While the extent and accuracy of the data available is increasing rapidly, the Jupiter family of comets is the only one for which the evolutionary time scales do not exceed by many orders of magnitude the history of astronomical observations. The individual comet populations differ from one another not only by the distribution of orbits, but also by the size distribution and aging rate of their members. Their dynamical evolution is coupled with disintegration processes, which make it questionable whether the present state can be interpreted as a long-term average.

scholarly journals Postsocialistiske svar: Skolelærere og „moderniseringen” af grundskolen i Brčko, Bosnien- Hercegovina

2010 ◽  
Author(s):  
Marie Larsen Ryberg
Keyword(s):  
Civic Education ◽  
Teaching Methods ◽  
Analytical Framework ◽  
Gift Giving ◽  
International Organisations ◽  
Teaching Methodologies ◽  
Socialist System ◽  
Modern Development ◽  
Nuanced Understanding ◽  
Analytical Approaches

Marie Larsen Ryberg: Post Socialistic Answers: Schoolteachers and the “Modernising” of Elementary School in Brcko, Bosnia-Hercegovina Since the disintegration of Yugoslavia, international organisations and scholars have stressed the problems of primary education in Bosnia-Herzegovina, pointing to the “legacy” from socialist times and a need to “modernise” the school system. The aim of this article is to analyse the ways in which schoolteachers in Brčko, Bosnia-Herzegovina relate to the two most prominent NGOs present in Brčko and their efforts to “modernise” the teaching methodologies and implement “democracy” and “civic education”. The article argues that an understanding of the teachers’ practices should include a broader analytical framework than conceptualising them as a “legacy” or “backward.” For a more nuanced understanding, the article takes three analytical approaches. First, it argues that the teachers’ practices and ideas in relation to knowledge should be viewed as connected to a socialist narrative of modern development. Second, it points to gift-giving as a way of understanding how the teachers draw on teaching methods such as lectures and learning by heart. Third, the article points to a model of the socialist system, and suggests that an appreciation of the teachers’ exclusive role as bureaucrats in a socialist system of allocation is central to an understanding of their practices today. The article thus unfolds the different ideas, motives and structures that shape the teachers’ practices as a post-socialist respond rather than as a “legacy.” Keywords: Post-socialism, Bosnia-Herzegovina, education, modernization, knowledge, gift-giving. 

Fog forecasting for Schiphol airport at sub-kilometre scale.  

2021 ◽  
Author(s):  
Gert-Jan Steeneveld ◽  
Roosmarijn Knol
Keyword(s):  
Spatial Resolution ◽  
Numerical Models ◽  
Wrf Model ◽  
Horizontal Resolution ◽  
Physical Processes ◽  
Radiation Fog ◽  
Fog Forecasting ◽  
Elevation Data ◽  
The Individual ◽  
The Impact

<p>Fog is a critical weather phenomenon for safety and operations in aviation. Unfortunately, the forecasting of radiation fog remains challenging due to the numerous physical processes that play a role and their complex interactions, in addition to the vertical and horizontal resolution of the numerical models. In this study we evaluate the performance of the Weather Research and Forecasting (WRF) model for a radiation fog event at Schiphol Amsterdam Airport (The Netherlands) and further develop the model towards a 100 m grid spacing. Hence we introduce high resolution land use and land elevation data. In addition we study the role of gravitational droplet settling, advection of TKE, top-down diffusion caused by strong radiative cooling at the fog top. Finally the impact of heat released by the terminal areas on the fog formation is studied. The model outcomes are evaluated against 1-min weather observations near multiple runways at the airport.</p><p>Overall we find the WRF model shows an reasonable timing of the fog onset and is well able to reproduce the visibility and meteorological conditions as observed during the case study. The model appears to be relatively insensitive to the activation of the individual physical processes. An increased spatial resolution to 100 m generally results in a better timing of the fog onset differences up to three hours, though not for all runways. The effect of the refined landuse dominates over the effect of refined elevation data. The modelled fog dissipation systematically occurs 3-4 h hours too early, regardless of physical processes or spatial resolution. Finally, the introduction of heat from terminal buildings delays the fog onset with a maximum of two hours, an overestimated visibility of 100-200 m and a decrease of the LWC with 0.10-0.15 g/kg compared to the reference.</p>

scholarly journals Global torques and stochasticity as the drivers of massive black hole pairing in the young Universe

2020 ◽  
Vol 498 (3) ◽  
pp. 3601-3615 ◽  
Author(s):  
Elisa Bortolas ◽  
Pedro R Capelo ◽  
Tommaso Zana ◽  
Lucio Mayer ◽  
Matteo Bonetti ◽  
...  
Keyword(s):  
Black Hole ◽  
Large Scale ◽  
High Redshift ◽  
Dynamical Evolution ◽  
Dynamical Friction ◽  
Massive Black Hole ◽  
Orbital Decay ◽  
Orbital Phase ◽  
Order Of Magnitude ◽  
Statistical Sample

ABSTRACT The forthcoming Laser Interferometer Space Antenna (LISA) will probe the population of coalescing massive black hole (MBH) binaries up to the onset of structure formation. Here, we simulate the galactic-scale pairing of ∼106 M⊙ MBHs in a typical, non-clumpy main-sequence galaxy embedded in a cosmological environment at z = 7–6. In order to increase our statistical sample, we adopt a strategy that allows us to follow the evolution of six secondary MBHs concomitantly. We find that the magnitude of the dynamical-friction-induced torques is significantly smaller than that of the large-scale, stochastic gravitational torques arising from the perturbed and morphologically evolving galactic disc, suggesting that the standard dynamical friction treatment is inadequate for realistic galaxies at high redshift. The dynamical evolution of MBHs is very stochastic, and a variation in the initial orbital phase can lead to a drastically different time-scale for the inspiral. Most remarkably, the development of a galactic bar in the host system either significantly accelerates the inspiral by dragging a secondary MBH into the centre, or ultimately hinders the orbital decay by scattering the MBH in the galaxy outskirts. The latter occurs more rarely, suggesting that galactic bars overall promote MBH inspiral and binary coalescence. The orbital decay time can be an order of magnitude shorter than what would be predicted relying on dynamical friction alone. The stochasticity and the important role of global torques have crucial implications for the rates of MBH coalescences in the early Universe: both have to be accounted for when making predictions for the upcoming LISA observatory.

scholarly journals Water worlds in N-body simulations with fragmentation in systems without gaseous giants

2020 ◽  
Vol 641 ◽  
pp. A139
Author(s):  
A. Dugaro ◽  
G. C. de Elía ◽  
L. A. Darriba
Keyword(s):  
Realistic Model ◽  
Habitable Zone ◽  
Minimum Mass ◽  
Dynamical Friction ◽  
Solar Type ◽  
Formation And Evolution ◽  
Hit And Run ◽  
The Individual ◽  
Very High ◽  
Water Contents

Aims. We analyze the formation and evolution of terrestrial-like planets around solar-type stars in the absence of gaseous giants. In particular, we focus on the physical and dynamical properties of those that survive in the system’s habitable zone (HZ). This investigation is based on a comparative study between N-body simulations that include fragmentation and others that consider all collisions as perfect mergers. Methods. We use an N-body code, presented in a previous paper, that allows planetary fragmentation. We carry out three sets of 24 simulations for 400 Myr. Two sets are developed adopting a model that includes hit-and-run collisions and planetary fragmentation, each one with different values of the individual minimum mass allowed for the fragments. For the third set, we considered that all collisions lead to perfect mergers. Results. The planetary systems produced in N-body simulations with and without fragmentation are broadly similar, though with some differences. In simulations with fragmentation, the formed planets have lower masses since part of them is distributed among collisional fragments. Additionally, those planets presented lower eccentricities, presumably due to dynamical friction with the generated fragments. Lastly, perfect mergers and hit-and-run collisions are the most common outcome. Regardless of the collisional treatment adopted, most of the planets that survive in the HZ start the simulation beyond the snow line, having very high final water contents. Such planets are called water worlds. The fragments’ contribution to their final mass and water content is negligible. Finally, the individual minimum mass for fragments may play an important role in the planets’ collisional history. Conclusions. Collisional models that incorporate fragmentation and hit-and-run collisions lead to a more detailed description of the physical properties of the terrestrial-like planets formed. We conclude that planetary fragmentation is not a barrier to the formation of water worlds in the HZ. The results shown in this work suggest that further refinement is necessary to have a more realistic model of planetary formation.

scholarly journals On the survival of resonant and non-resonant planetary systems in star clusters

2020 ◽  
Vol 497 (2) ◽  
pp. 1807-1825
Author(s):  
Katja Stock ◽  
Maxwell X Cai ◽  
Rainer Spurzem ◽  
M B N Kouwenhoven ◽  
Simon Portegies Zwart
Keyword(s):  
Solar System ◽  
Star Clusters ◽  
Planetary Systems ◽  
Dynamical Evolution ◽  
Giant Planets ◽  
Mean Motion Resonances ◽  
Orbital Parameters ◽  
Eccentric Orbits ◽  
The Individual ◽  
Exoplanet Systems

ABSTRACT Despite the discovery of thousands of exoplanets in recent years, the number of known exoplanets in star clusters remains tiny. This may be a consequence of close stellar encounters perturbing the dynamical evolution of planetary systems in these clusters. Here, we present the results from direct N-body simulations of multiplanetary systems embedded in star clusters containing N = 8k, 16k, 32k, and 64k stars. The planetary systems, which consist of the four Solar system giant planets Jupiter, Saturn, Uranus, and Neptune, are initialized in different orbital configurations, to study the effect of the system architecture on the dynamical evolution of the entire planetary system, and on the escape rate of the individual planets. We find that the current orbital parameters of the Solar system giants (with initially circular orbits, as well as with present-day eccentricities) and a slightly more compact configuration, have a high resilience against stellar perturbations. A configuration with initial mean-motion resonances of 3:2, 3:2, and 5:4 between the planets, which is inspired by the Nice model, and for which the two outermost planets are usually ejected within the first 105 yr, is in many cases stabilized due to the removal of the resonances by external stellar perturbation and by the rapid ejection of at least one planet. Assigning all planets the same mass of 1 MJup almost equalizes the survival fractions. Our simulations reproduce the broad diversity amongst observed exoplanet systems. We find not only many very wide and/or eccentric orbits, but also a significant number of (stable) retrograde orbits.

Globular cluster tidal interactions and mergers in the Galactic disc

2019 ◽  
Vol 14 (S351) ◽  
pp. 442-446
Author(s):  
Alessandra Mastrobuono-Battisti ◽  
Sergey Khoperskov ◽  
Paola Di Matteo ◽  
Misha Haywood
Keyword(s):  
Globular Cluster ◽  
Iron Content ◽  
Globular Clusters ◽  
Dynamical Evolution ◽  
Stellar Populations ◽  
Cluster System ◽  
Galactic Disc ◽  
Tidal Interactions ◽  
Globular Cluster System ◽  
Shed Light

AbstractThe Galactic globular cluster system went and is still going through dynamical processes that require to be explored in detail. Here we illustrate how primordial massive globular clusters born in the Milky Way’s disc evolved by stripping material from each other or even merging very early during their lives. These processes might explain the puzzling presence of star-by-star spreads in iron content observed in massive globular clusters and should be taken into account when studying globular cluster stellar populations. In this context, we show how the direct comparison between the predictions provided by our direct N-body simulations and observations can shed light on the origin and chemo-dynamical evolution of globular clusters.

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