Academic literature on the topic 'ISM: kinematics and dynamics'
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Journal articles on the topic "ISM: kinematics and dynamics"
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Steffen, Wolfgang. "Dynamical modeling and the interactions with the ISM." Proceedings of the International Astronomical Union 7, S283 (2011): 168–75. http://dx.doi.org/10.1017/s1743921312010897.
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AbstractThis paper is a review of some of the recent modeling efforts to improve our understanding of structure formation and evolution of planetary nebulae including their interaction with the interstellar medium. New propositions have been made for the formation mechanism of multi-polar PNe and PPNe. These mechanisms are based on the central engine with interacting binary stars or hole producing instabilities in expanding shock waves leading to illumination effects from the central star that change the appearance of the nebula. Furthermore, there has been a lot of progress in the observation and 3D modeling of the kinematics, which is key to the understanding of the dynamics. Extensive observational catalogs are coming online for the kinematics, as well as some very detailed proper motion measurements have been made. New techniques for morpho–kinematic 3D modeling help to make the interpretation of kinematic data more reliable and detailed. In addition to individual pointed observations, new surveys have lead to the discovery of many PNe that show clear signs of interaction with the interstellar medium. Systematic hydrodynamic models of the interaction have produced a general scheme for the observed structure that results from the interaction of an evolving planetary nebula with the ISM. Detailed modeling of the dust-gas dynamics during the interaction with the ISM have produced interesting predictions for future IR observations. Detailed models were worked out for the structure of the bowshock and tail of Mira that was recently discovered in the UV.
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Crotts, Arlin P. S., and Jun Xu. "The ISM near SN 1987A: Kinematics and 3-D Structure." Symposium - International Astronomical Union 190 (1999): 162–64. http://dx.doi.org/10.1017/s0074180900117772.
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We present two views of the region around SN 1987A: a three-dimensional map of structure revealed by light echoes, and a multicomponent velocity map at 10 km s−1 resolution in [N II], correlating the various superbubble structures found in both, with implications for their age and dynamics, as well as the history of the SN progenitor.
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Molina, Juan, Edo Ibar, Nicolás Godoy, et al. "VALES." Astronomy & Astrophysics 643 (November 2020): A78. http://dx.doi.org/10.1051/0004-6361/202039008.
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Context. Spatially resolved observations of the ionized and molecular gas are critical for understanding the physical processes that govern the interstellar medium (ISM) in galaxies. The observation of starburst systems is also important as they present extreme gas conditions that may help to test different ISM models. However, matched resolution imaging at ∼kpc scales for both ISM gas phases are usually scarce, and the ISM properties of starbursts still remain poorly understood. Aims. We aim to study the morpho-kinematic properties of the ionized and molecular gas in three dusty starburst galaxies at z = 0.12−0.17 to explore the relation between molecular ISM gas phase dynamics and the star-formation activity. Methods. We employ two-dimensional dynamical modelling to analyse Atacama Large Millimeter/submillimiter Array CO(1–0) and seeing-limited Spectrograph for INtegral Field Observations in the Near Infrared Paschen-α (Paα) observations, tracing the molecular and ionized gas morpho-kinematics at ∼kpc-scales. We use a dynamical mass model, which accounts for beam-smearing effects, to constrain the CO-to-H2 conversion factor and estimate the molecular gas mass content. Results. One starburst galaxy shows irregular morphology, which may indicate a major merger, while the other two systems show disc-like morpho-kinematics. The two disc-like starbursts show molecular gas velocity dispersion values comparable with those seen in local luminous and ultra luminous infrared galaxies but in an ISM with molecular gas fraction and surface density values in the range of the estimates reported for local star-forming galaxies. We find that these molecular gas velocity dispersion values can be explained by assuming vertical pressure equilibrium. We also find that the star-formation activity, traced by the Paα emission line, is well correlated with the molecular gas content, suggesting an enhanced star-formation efficiency and depletion times of the order of ∼0.1−1 Gyr. We find that the star-formation rate surface density (ΣSFR) correlates with the ISM pressure set by self-gravity (Pgrav) following a power law with an exponent close to 0.8. Conclusions. In dusty disc-like starburst galaxies, our data support the scenario in which the molecular gas velocity dispersion values are driven by the ISM pressure set by self-gravity and are responsible for maintaining the vertical pressure balance. The correlation between ΣSFR and Pgrav suggests that, in these dusty starbursts galaxies, the star-formation activity arises as a consequence of the ISM pressure balance.
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Fei, Qinyue, Ran Wang, Juan Molina, et al. "Dynamics of Molecular Gas in the Central Region of the Quasar I Zwicky 1." Astrophysical Journal 946, no. 1 (2023): 45. http://dx.doi.org/10.3847/1538-4357/acbb05.
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Abstract We present a study of the molecular gas distribution and kinematics in the cicumnuclear region (radii ≲2 kpc) of the z ≈ 0.061 quasar I Zwicky 1 using a collection of available Atacama Large Millimeter/submillimeter Array observations of the carbon monoxide (CO) emission. With an angular resolution of ∼0.″36 (corresponding to ∼400 pc), the host-galaxy substructures including the nuclear molecular gas disk, spiral arms, and a compact bar-like component are resolved. We analyzed the gas kinematics based on the CO image cube and obtained the rotation curve and radial distribution of velocity dispersion. The velocity dispersion is about 30 km s−1 in the outer CO disk region and rises up to ≳100 km s−1 at radius ≲1 kpc, suggesting that the central region of the disk is dynamically hot. We constrain the CO-to-H2 conversion factor, α CO, by modeling the cold gas disk dynamics. We find that, with prior knowledge about the stellar and dark matter components, the α CO value in the circumnuclear region of this quasar host galaxy is 1.55 − 0.49 + 0.47 M ⊙ K km s − 1 pc 2 − 1 , which is between the value reported in ultraluminous infrared galaxies and in the Milky Way. The central 1 kpc region of this quasar host galaxy has significant star formation activity, which can be identified as a nuclear starburst. We further investigate the high-velocity dispersion in the central region. We find that the interstellar medium (ISM) turbulent pressure derived from the gas velocity dispersion is in equilibrium with the weight of the ISM. This argues against extra power from active galactic nuclei feedback that significantly affects the kinematics of the cold molecular gas.
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Fei, Qinyue, Ran Wang, Juan Molina, et al. "Constraining Quasar Feedback from Analysis of the Hydrostatic Equilibrium of the Molecular Gas in Their Host Galaxies." Astrophysical Journal 976, no. 2 (2024): 201. http://dx.doi.org/10.3847/1538-4357/ad7e26.
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Abstract We investigate the kinematics and dynamics of the molecular and ionized gas in the host galaxies of three Palomar-Green quasars at low redshifts, benefiting from the archival millimeter-wave interferometric and optical integral field unit data. We study the kinematics of both cold molecular and hot ionized gas by analyzing the CO and Hα data cubes, and construct the mass distributions of our sample through gas dynamics, utilizing a priori knowledge regarding the galaxy light distribution. We find no systematic offset between the stellar mass derived from our dynamical method and that from the broadband photometry and mass-to-light ratio, suggesting the consistency of both methods. We then study the kinetic pressure and the weight of the interstellar medium (ISM) using our dynamical mass model. By studying the relationship between kinetic pressure and gravitational pressure of the quasar host galaxies, we find an equivalence in the hydrostatic equilibrium states of ISM in the quasar host galaxies, similar to the result of gas equilibrium in normal star-forming galaxies, suggesting minimal quasar feedback. Regarding noncircular motion as indicative of quasar-driven outflows, we observe an exceptionally low coupling efficiency between molecular gas outflow and active galactic nucleus bolometric luminosities. These results demonstrate the marginal influence of the central engine on the properties of cold molecular gas in quasar host galaxies.
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Murray, Claire E., Sten Hasselquist, Joshua E. G. Peek, et al. "A Galactic Eclipse: The Small Magellanic Cloud Is Forming Stars in Two Superimposed Systems." Astrophysical Journal 962, no. 2 (2024): 120. http://dx.doi.org/10.3847/1538-4357/ad1591.
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Abstract The structure and dynamics of the star-forming disk of the Small Magellanic Cloud (SMC) have long confounded us. The SMC is widely used as a prototype for galactic physics at low metallicity, and yet we fundamentally lack an understanding of the structure of its interstellar medium (ISM). In this work, we present a new model for the SMC by comparing the kinematics of young, massive stars with the structure of the ISM traced by high-resolution observations of neutral atomic hydrogen (H i) from the Galactic Australian Square Kilometre Array Pathfinder survey. Specifically, we identify thousands of young, massive stars with precise radial velocity constraints from the Gaia and APOGEE surveys and match these stars to the ISM structures in which they likely formed. By comparing the average dust extinction toward these stars, we find evidence that the SMC is composed of two structures with distinct stellar and gaseous chemical compositions. We construct a simple model that successfully reproduces the observations and shows that the ISM of the SMC is arranged into two superimposed, star-forming systems with similar gas mass separated by ∼5 kpc along the line of sight.
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Izquierdo, Andrés F., Rowan J. Smith, Simon C. O. Glover, et al. "The Cloud Factory II: gravoturbulent kinematics of resolved molecular clouds in a galactic potential." Monthly Notices of the Royal Astronomical Society 500, no. 4 (2020): 5268–96. http://dx.doi.org/10.1093/mnras/staa3470.
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ABSTRACT We present a statistical analysis of the gravoturbulent velocity fluctuations in molecular cloud complexes extracted from our ‘Cloud Factory’ Galactic-scale interstellar medium (ISM) simulation suite. For this purpose, we produce non-local thermodynamic equilibrium 12CO J = 1 − 0 synthetic observations and apply the principal component analysis (PCA) reduction technique on a representative sample of cloud complexes. The velocity fluctuations are self-consistently generated by different physical mechanisms at play in our simulations, which include Galactic-scale forces, gas self-gravity, and supernova feedback. The statistical analysis suggests that, even though purely gravitational effects are necessary to reproduce standard observational laws, they are not sufficient in most cases. We show that the extra injection of energy from supernova explosions plays a key role in establishing the global turbulent field and the local dynamics and morphology of molecular clouds. Additionally, we characterize structure function scaling parameters as a result of cloud environmental conditions: some of the complexes are immersed in diffuse (interarm) or dense (spiral-arm) environments, and others are influenced by embedded or external supernovae. In quiescent regions, we obtain time-evolving trajectories of scaling parameters driven by gravitational collapse and supersonic turbulent flows. Our findings suggest that a PCA-based statistical study is a robust method to diagnose the physical mechanisms that drive the gravoturbulent properties of molecular clouds. Also, we present a new open source module, the pcafactory, which smartly performs PCA to extract velocity structure functions from simulated or real data of the ISM in a user-friendly way.
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Vayner, Andrey. "Distant quasar host galaxies and their environments with multi-wavelength 3D spectroscopy." Proceedings of the International Astronomical Union 15, S359 (2020): 78–81. http://dx.doi.org/10.1017/s1743921320004329.
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AbstractWe have conducted a multi-wavelength survey of distant (1.3 < z < 2.6) luminous quasars host galaxies using the Keck integral field spectrograph (IFS) OSIRIS and laser guide star adaptive optics (LGS-AO) system, ALMA, HST and VLA. Studying distant quasar host galaxies is essential for understanding the role of active galactic nuclei (AGN) feedback on the interstellar medium (ISM), and its capability of regulating the growth of massive galaxies and their supermassive black holes (SMBH). The combination of LGS-AO and OSIRIS affords the necessary spatial resolution and contrast to disentangle the bright quasar emission from that of its faint host galaxy. We resolve the nebular emission lines, [OIII], [NII],, and [SII] at a sub-kiloparsec resolution to study the distribution, kinematics, and dynamics of the warm-ionized ISM in each quasar host galaxy. The goal of the survey was to search for ionized outflows and relate their spatial extent and energetics to the star-forming properties of the host galaxy. Combining ALMA and OSIRIS, we directly test whether outflows detected with OSIRIS are affecting the molecular ISM. We find that several mechanisms are responsible for driving the outflows within our systems, including radiation pressure in low and high column density environments as well as adiabatic and isothermal shocks driven by the quasar. From line ratio diagnostics, we obtain resolved measurements of the photoionization mechanisms and the gas-phase metallicity. We find that the quasars are responsible for photoionizing the majority of the ISM with metalicities lower than that of gas photoionized by AGN in the low redshift systems. We are now obtaining detailed observations of the circumgalactic medium (CGM) of these systems with the Keck Cosmic Web Imager (KCWI). The gas in the CGM may play an essential role in the evolution of these galaxies.
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Wellons, Sarah, Claude-André Faucher-Giguère, Daniel Anglés-Alcázar, et al. "Measuring dynamical masses from gas kinematics in simulated high-redshift galaxies." Monthly Notices of the Royal Astronomical Society 497, no. 4 (2020): 4051–65. http://dx.doi.org/10.1093/mnras/staa2229.
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ABSTRACT Advances in instrumentation have recently extended detailed measurements of gas kinematics to large samples of high-redshift galaxies. Relative to most nearby, thin disc galaxies, in which gas rotation accurately traces the gravitational potential, the interstellar medium (ISM) of $z$ ≳ 1 galaxies is typically more dynamic and exhibits elevated turbulence. If not properly modelled, these effects can strongly bias dynamical mass measurements. We use high-resolution FIRE-2 cosmological zoom-in simulations to analyse the physical effects that must be considered to correctly infer dynamical masses from gas kinematics. Our analysis covers a range of galaxy properties from low-redshift Milky-Way-mass galaxies to massive high-redshift galaxies (M⋆ &gt; 1011 M⊙ at $z$ = 1). Selecting only snapshots where a disc is present, we calculate the rotational profile $\bar{v}_\phi (r)$ of the cool ($10^{3.5}\,\lt {\it T}\lt 10^{4.5}~\rm {K}$) gas and compare it to the circular velocity $v_{\rm c}=\sqrt{GM_{\rm enc}/r}$. In the simulated galaxies, the gas rotation traces the circular velocity at intermediate radii, but the two quantities diverge significantly in the centre and in the outer disc. Our simulations appear to over-predict observed rotational velocities in the centres of massive galaxies (likely from a lack of black hole feedback), so we focus on larger radii. Gradients in the turbulent pressure at these radii can provide additional radial support and bias dynamical mass measurements low by up to 40 per cent. In both the interior and exterior, the gas’ motion can be significantly non-circular due to e.g. bars, satellites, and inflows/outflows. We discuss the accuracy of commonly used analytic models for pressure gradients (or ‘asymmetric drift’) in the ISM of high-redshift galaxies.
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Jenkins, Edward B., and Todd M. Tripp. "New results on the distribution of thermal pressures in the diffuse ISM." Proceedings of the International Astronomical Union 2, S237 (2006): 53–56. http://dx.doi.org/10.1017/s1743921307001214.
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AbstractThe ground electronic state of neutral atomic carbon has three fine-structure levels. In the interstellar medium, the relative populations of the upper two levels are established by collisional excitations (and de-excitations) balanced against spontaneous radiative decay. Consequently, the fractions of C I in the upper two levels indicate acceptable combinations of local temperature and density, which in turn indicate the approximate thermal pressures of the medium. We can measure the values of these fractions and how they vary from one location to the next by observing the multiplets of C I seen in absorption in the ultraviolet spectra of hot stars.We have identified 102 stars for which the HST MAST archive has E140H STIS spectra that are suitable for measuring the absorption features of C I at velocity resolutions of 3 kms−1(or better). A special analysis method developed by Jenkins & Tripp (2001) permits determinations of the amounts of C I in each of the three levels as a function of radial velocity over a wide dynamic range in column density, since several multiplets of vastly different strengths can be considered simultaneously.The C I data reveal that the much of the diffuse, cold, neutral medium has pressures that are distributed in an approximately log-normal fashion, spread over a range 1000 < p/k < 104 cm−3 K (FWHM), but with low level tails outside this range. The dispersion of pressures increases slightly for gases that have radial velocities outside the expected range for quiescent material along each line of sight. This link to the kinematics of the gas is consistent with the picture that pressure fluctuations are driven by the dynamics of a turbulent medium. If the gas is a single medium that is being driven by turbulent forces, its barytropic index (slope of log p vs. log n) is more than 0.9, which is inconsistent with the value 0.72 for material that is expected to be in thermal equilibrium. Slightly less than one part in a thousand of the gas is at pressures of order or greater than ~105cm−3 K and seems to nearly always accompany the gas at normal pressures.
Dissertations / Theses on the topic "ISM: kinematics and dynamics"
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Seo, Young Min, and Andrew N. Youdin. "The role of non-ionizing radiation pressure in star formation: the stability of cores and filaments." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/621725.
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Stars form when filaments and dense cores in molecular clouds fragment and collapse due to self-gravity. In the most basic analyses of gravitational stability, the competition between self-gravity and thermal pressure sets the critical (i.e. maximum stable) mass of spheres and the critical line density of cylinders. Previous work has considered additional support from magnetic fields and turbulence. Here, we consider the effects of non-ionizing radiation, specifically the inward radiation pressure force that acts on dense structures embedded in an isotropic radiation field. Using hydrostatic, isothermal models, we find that irradiation lowers the critical mass and line density for gravitational collapse, and can thus act as a trigger for star formation. For structures with moderate central densities, similar to 10(3) cm(-3), the interstellar radiation field in the Solar vicinity has an order unity effect on stability thresholds. For more evolved objects with higher central densities, a significant lowering of stability thresholds requires stronger irradiation, as can be found closer to the Galactic centre or near stellar associations. Even when strong sources of ionizing radiation are absent or extincted, our study shows that interstellar irradiation can significantly influence the star formation process.
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Cabral, Ana Isabel Duarte. "Kinematics and physical properties of young proto-clusters." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/kinematics-and-physical-properties-of-young-protoclusters(8eb34d15-b343-4aab-b4b0-ede4bba903be).html.
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The formation of stars begins with the fragmentation of molecular clouds and the formation of dense cores. This fragmentation process can either be the result of classical gravitational instabilities or triggered by some external event. The gas and dust of young protoclusters often hold the imprints of the initial conditions and triggers of that specific star forming episode. In this context, my thesis work is a study of the gas properties of young protoclus- ters within the Gould Belt. The first part of my work consists of a detailed study of the young Serpens star forming region with CO isotopologues. This study has revealed a complex temperature, column density and velocity structure. I proposed a scenario where a collision between two filamentary clouds or flows is responsible for the observed complex structure and the most recent burst of star formation in Serpens. This hypothesis was tested with SPH simulations and provides a plausible scenario. I am currently extending this work to other regions with a variety of star formation efficiencies, in search of the particular physical properties and dynamics of a molecular cloud that allow or prevent clouds to be in the verge of forming stars. As such, I have included in this manuscript my study of the gas in the B59 star forming region, the only active clump in the Pipe Nebula. The results from this study have shown it to be very different from Serpens, even though further studies are needed to provide a complete picture of the region. B59 was taken as the starting point for a larger study of the entire Pipe Nebula, driven by the peculiarly low star formation efficiency in the cloud and a test to the physical properties of cores prior to star formation.
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Bieging, John H., Saahil Patel, William L. Peters, L. Viktor Toth, Gábor Marton, and Sarolta Zahorecz. "THE ARIZONA RADIO OBSERVATORY CO MAPPING SURVEY OF GALACTIC MOLECULAR CLOUDS. V. THE SH2-235 CLOUD IN CO J = 2 − 1, 13 CO J = 2 − 1, AND CO J = 3 − 2." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621984.
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We present the results of a program to map the Sh2-235 molecular cloud complex in the CO and (CO)-C-13 J = 2 - 1 transitions using the Heinrich Hertz Submillimeter Telescope. The map resolution is 38 '' (FWHM), with an rms noise of 0.12K brightness temperature, for a velocity resolution of 0.34 km s(-1). With the same telescope, we also mapped the CO J = 3 - 2 line at a frequency of 345 GHz, using a 64 beam focal plane array of heterodyne mixers, achieving a typical rms noise of 0.5 K brightness temperature with a velocity resolution of 0.23 km s(-1). The three spectral line data cubes are available for download. Much of the cloud appears to be slightly sub-thermally excited in the J = 3 level, except for in the vicinity of the warmest and highest column density areas, which are currently forming stars. Using the CO and (CO)-C-13. J = 2 - 1 lines, we employ an LTE model to derive the gas column density over the entire mapped region. Examining a 125 pc(2). region centered on the most active star formation in the vicinity of Sh2-235, we find that the young stellar object surface density scales as approximately the 1.6-power of the gas column density. The area distribution function of the gas is a steeply declining exponential function of gas column density. Comparison of the morphology of ionized and molecular gas suggests that the cloud is being substantially disrupted by expansion of the H II regions, which may be triggering current star formation.
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Imara, Nia, Charles Lada, John Lewis, et al. "X Marks the Spot: Nexus of Filaments, Cores, and Outflows in a Young Star-forming Region." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624336.
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We present a multiwavelength investigation of a region of a nearby giant molecular cloud that is distinguished by a minimal level of star formation activity. With our new (CO)-C-12(J = 2-1) and (CO)-C-13(J = 2-1) observations of a remote region within the middle of the California molecular cloud, we aim to investigate the relationship between filaments, cores, and a molecular outflow in a relatively pristine environment. An extinction map of the region from Herschel Space Observatory observations reveals the presence of two 2 pc long filaments radiating from a highextinction clump. Using the (CO)-C-13 observations, we show that the filaments have coherent velocity gradients and that their mass-per-unit-lengths may exceed the critical value above which filaments are gravitationally unstable. The region exhibits structure with eight cores, at least one of which is a starless, prestellar core. We identify a low-velocity, low-mass molecular outflow that may be driven by a flat spectrum protostar. The outflow does not appear to be responsible for driving the turbulence in the core with which it is associated, nor does it provide significant support against gravitational collapse.
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Reiter, Megan, Megan M. Kiminki, Nathan Smith, and John Bally. "Proper motions of collimated jets from intermediate-mass protostars in the Carina Nebula." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/625733.
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We present proper motion measurements of 37 jets and HH objects in the Carina Nebula measured in two epochs of H alpha images obtained similar to 10 yr apart with Hubble Space Telescope/Advanced Camera for Surveys (ACS). Transverse velocities in all but one jet are faster than greater than or similar to 25 km s(-1), confirming that the jet-like H alpha features identified in the first epoch images trace outflowing gas. Proper motions constrain the location of the jet-driving source and provide kinematic confirmation of the intermediate-mass protostars that we identify for 20/37 jets. Jet velocities do not correlate with the estimated protostar mass and embedded driving sources do not have slower jets. Instead, transverse velocities (median similar to 75 km s(-1)) are similar to those in jets from low-mass stars. Assuming a constant velocity since launch, we compute jet dynamical ages (median similar to 10(4) yr). If continuous emission from inner jets traces the duration of the most recent accretion bursts, then these episodes are sustained longer (median similar to 700 yr) than the typical decay time of an FU Orionis outburst. These jets can carry appreciable momentum that may be injected into the surrounding environment. The resulting outflow force, dp/dt, lies between that measured in low- and high-mass sources, despite the very different observational tracers used. Smooth scaling of the outflow force argues for a common physical process underlying outflows from protostars of all masses. This latest kinematic result adds to a growing body of evidence that intermediate-mass star formation proceeds like a scaled-up version of the formation of low-mass stars.
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Battersby, Cara, John Bally, and Brian Svoboda. "The Lifetimes of Phases in High-mass Star-forming Regions." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624382.
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High-mass stars form within star clusters from dense, molecular regions (DMRs), but is the process of cluster formation slow and hydrostatic or quick and dynamic? We link the physical properties of high-mass star-forming regions with their evolutionary stage in a systematic way, using Herschel and Spitzer data. In order to produce a robust estimate of the relative lifetimes of these regions, we compare the fraction of DMRs above a column density associated with high-mass star formation, N(H-2) > 0.4-2.5 x 10(22) cm(-2), in the "starless" (no signature of stars >= 10 M circle dot forming) and star-forming phases in a 2 degrees x 2(degrees) region of the Galactic Plane centered at l = 30 degrees. Of regions capable of forming high-mass stars on similar to 1 pc scales, the starless (or embedded beyond detection) phase occupies about 60%-70% of the DMR lifetime, and the star-forming phase occupies about 30%-40%. These relative lifetimes are robust over a wide range of thresholds. We outline a method by which relative lifetimes can be anchored to absolute lifetimes from large-scale surveys of methanol masers and UCHII regions. A simplistic application of this method estimates the absolute lifetime of the starless phase to be 0.2-1.7 Myr (about 0.6-4.1 fiducial cloud free-fall times) and the star-forming phase to be 0.1-0.7 Myr (about 0.4-2.4 free-fall times), but these are highly uncertain. This work uniquely investigates the star-forming nature of high column density gas pixel by pixel, and our results demonstrate that the majority of high column density gas is in a starless or embedded phase.
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Drabek-Maunder, Emily Rae. "A submillimetre study of nearby star formation using molecular line data." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/14587.
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This thesis primarily uses submillimetre molecular line data from HARP, a heterodyne array on the James Clerk Maxwell Telescope (JCMT), to further investigate star formation in the Ophiuchus L1688 cloud. HARP was used to observe CO J = 3-2 isotopologues: 12CO, 13CO and C18O; and the dense gas tracer HCO+ J = 4-3. A method for calculating molecular line contamination in the SCUBA-2 450 and 850 μm dust continuum data was developed, which can be used to convert 12CO J =6-5and J =3-2 maps of integrated intensity (K km s−1) to molecular line flux (mJy beam−1) contaminating the continuum emission. Using HARP maps of 12CO J = 3-2, I quantified the amount of molecular line contamination found in the SCUBA-2 850 μm maps of three different regions, including NGC 1333 of Perseus and NGC 2071 and NGC 2024 of Orion B. Regions with ‘significant’ (i.e. > 20%) molecular line contamination correspond to molecular outflows. This method is now being used to remove molecular line contamination from regions with both SCUBA-2 dust continuum and HARP 12CO map coverage in the Gould Belt Legacy Survey (GBS). The Ophiuchus L1688 cloud was observed in all three CO J = 3-2 isotopologues. I carried out a molecular outflow analysis in the region on a list of 30 sources from the Spitzer ‘c2d’ survey [Evans et al., 2009]. Out of the 30 sources, 8 had confirmed bipolar outflows, 20 sources had ‘confused’ outflow detections and 2 sources did not have outflow detections. The Ophiuchus cloud was found to be gravitationally bound with the turbulent kinetic energy a factor of 7 lower than the gravitational binding energy. The high-velocity outflowing gas was found to be only 21% of the turbulence in the cloud, suggesting outflows are significant but not the dominant source of turbulence in the region. Other factors were found to influence the global high-velocity outflowing gas in addition to molecular outflows, including hot dust from nearby B-type stars, outflow remnants from less embedded sources and stellar winds from the Upper Scorpius OB association. To trace high density gas in the Ophiuchus L1688 cloud, HCO+ J = 4-3 was observed to further investigate the relationship between high column density and high density in the molecular cloud. Non-LTE codes RADEX and TORUS were used to develop density models corresponding to the HCO+ emission. The models involved both constant density and peaked density profiles. RADEX [van der Tak et al., 2007] models used a constant density model along the line-of-sight and indicated the HCO+ traced densities that were predominantly subthermally excited with den- sities ranging from 10^3–10^5 cm^−3. Line-of-sight estimates ranged from several parsecs to 90 pc, which was unrealistic for the Ophiuchus cloud. This lead to the implementation of peaked density profiles using the TORUS non-LTE radiative transfer code. Initial models used a ‘triangle’ density profile and a more complicated log-normal density probability density function (PDF) profile was subsequently implemented. Peaked density models were relatively successful at fitting the HCO+ data. Triangle models had density fits ranging from 0.2–2.0×10^6 cm^−3 and 0.1–0.3×10^6 cm^−3 for the 0.2 and 0.3 pc cloud length models re- spectively. Log-normal density models with constant-σ had peak density ranges from 0.2–1.0 ×10^5 cm^−3 and 0.6–2.0×10^5 cm^−3 for 0.2 and 0.3 pc models respectively. Similarly, log-normal models with varying-σ had lower and upper density limits corresponding to the range of FWHM velocities. Densities (lower and upper limits) ranged from 0.1–1.0 ×10^6 and 0.5–3.0 ×10^5 cm^-3 for the 0.2 and 0.3 pc models respectively. The result of the HCO+ density modelling indicated the distributions of starless, prestellar and protostellar cores do not have a preference for higher densities with respect to the rest of the cloud. This is contrary to past research suggesting the probability of finding a submillimetre core steeply rises as a function of column density (i.e. density; Belloche et al. 2011; Hatchell et al. 2005). Since the majority of sources are less embedded (i.e Class II/III), it is possible the evolutionary state of Ophiuchus is the main reason the small sample of Class 0/I protostars do not appear to have a preference for higher densities in the cloud.
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Zhang, Huanian, Dennis Zaritsky, Guangtun Zhu, Brice Ménard, and David W. Hogg. "HYDROGEN EMISSION FROM THE IONIZED GASEOUS HALOS OF LOW-REDSHIFT GALAXIES." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622684.
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Using a sample of nearly half a million galaxies, intersected by over 7 million lines of sight from the Sloan Digital Sky Survey Data Release 12, we trace H alpha + [N II] emission from a galactocentric projected radius, r(p), of 5 kpc to more than 100 kpc. The emission flux surface brightness is alpha r(p) 1.9 +/- 0.4. We obtain consistent results using only the Ha or [N II] flux. We measure a stronger signal for the bluer half of the target sample than for the redder half on small scales, r(p) < 20 kpc. We obtain a 3 sigma detection of H alpha + [N II] emission in the 50-100 kpc r(p) bin. The mean emission flux within this bin is (1.10 +/- 0.35) x 10(-20) erg cm(-2) s(-1) angstrom(-1), which corresponds to 1.87 x 10(-20) erg cm(-2) s(-1) arcsec(-2) or 0.0033 Rayleigh. This detection is 34 times fainter than a previous strict limit obtained using deep narrow-band imaging. The faintness of the signal demonstrates why it has been so difficult to trace recombination radiation out to large radii around galaxies. This signal, combined with published estimates of n(H), leads us to estimate the temperature of the gas to be 12,000 K, consistent with independent empirical estimates based on metal ion absorption lines and expectations from numerical simulations.
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Sabatini, Giovanni. "Unveiling the inner morphology and gas kinematics of NGC 5135 with ALMA." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14062/.
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Active galactic nuclei are thought to play a major role in the formation and evolution of galaxies, providing mechanisms for feedback from the supermassive black hole (SMBH) to its hosting galaxy and the intergalactic medium. In co-evolutionary scenarios, the SMBH properties are strictly connected to those of the host galaxy, in either high redshift quasars and in local Seyfert nuclei. Local Seyfert galaxies hosting both SMBHs and star forming regions, can be considered as the nearest counterparts of high redshift sub-mm heavily dust obscured star forming galaxies, where a significant fraction of the optical and UV photons are absorbed by dust are re-emitted in the IR and sub-mm bands. In the absence of major merging events and companions, the mechanisms that link the star formation (SF) and the accretion onto the black hole (BH) lie in the inner galactic regions (within ~1 kpc from the BH) and are responsible for the feeding of the BH and the quenching of the SF through feedback mechanisms from the BH itself. On the one hand, high resolution observations in the sub-mm band suggest that feeding might happen through the formation of bars at the inner end of the spiral galactic arms. On the other hand, outflows from the SMBHs have been observed and seem to be responsible for halting the gas infall and the SF in the inner galactic regions.
Fuelling and outflows seem to constitute a self-regulating combination of processes on the small scales that determine the galaxy morphology and dynamics. How the small scales dynamics influences the overall galaxy morphology, what is the timescale on which different processes happen, and if the different evolutionary stages justify the different observed morphologies, are still open questions.
This thesis project develops within the above astrophysical context, with the main goal of studying the morphology, the kinematics and the physical processes at play in the inner regions of the nearby Seyfert 2 galaxy NGC 5135 with ALMA.
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Marchal, Antoine. "On the multiphase structure of the turbulent neutral interstellar medium." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS249.
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La formation des étoiles dans les galaxies est intimement liée aux processus physiques qui régissent l'évolution du milieu interstellaire. Les étoiles se forment dans les nuages moléculaires par effondrement gravitationnel de structures denses et froides, mais le processus qui mène à la formation de ces surdensités est encore relativement mal compris. Un des élément clé semble être lié à l'efficacité de la formation de nuages froids d'hydrogène neutre (HI), également appelé "Cold neutral Medium" (CNM).Plusieurs études ont visé à comprendre la production du CNM par condensation du "Warm Neutral Medium" (WNM) dans un écoulement turbulent et thermiquement instable à l'aide de simulations numériques. De façon générale, ces études indiquent la présence d'une fraction significative de la masse dans le régime instable (c'est-à-dire avec une température à mi-chemin entre les états stables CNM et WNM). Cependant, les conditions thermodynamiques du gaz restent largement inexplorées du point de vue de l'observation : pour aller plus loin, et comparer réellement avec les simulations numériques, il est nécessaire de cartographier la structure de densité des colonnes de chaque phase et d'étudier les variations spatiales de leurs champs de vitesse et de dispersion des vitesses. Par nature, cela nécessite le développement de méthodes pouvant extraire ces informations de données entièrement échantillonnées spatialement: l'émission de la raie à 21 cm.Un nouvel algorithme de décomposition en Gaussiènne, appelé ROHSA, est présenté dans cette thèse. Basée sur un processus multi-résolution, et utilisant un critère de moindres carrés non-linéaires régularisés prenant en compte simultanément la cohérence spatiale de l'émission et la nature multiphase du gaz, cette méthode nous permet d'inférer une vision spatialement cohérente des phases milieu interstellaire neutre.Une analyse détaillée est ensuite présentée sur un champ à haute latitude centré sur le pôle nord écliptique. En particulier, nous apportons de nouvelles contraintes sur les propriétés thermodynamiques du WNM, ainsi que sur les propriétés statistiques de la cascade turbulente agissant dans le fluide. Enfin, nous discutons dans quelles conditions l'instabilité thermique peut se développer dans ce milieu et converger vers la phase froide du milieu interstellaire neutre, le CNM<br>Star formation in galaxies is strongly linked to the physical processes that govern the evolution of the interstellar medium. Stars form by gravitational collapse of dense and cold structures in molecular clouds but the process that leads to the formation of these over-densities is still unclear. One key element seems to be related to the efficiency of the formation of cold clouds of neutral hydrogen (HI) also called the Cold Neutral Medium (CNM).Several studies have aimed at understanding the production of the CNM through the condensation of the Warm Neutral Medium (WNM) in a turbulent and thermally unstable flow using numerical simulations. In general, these studies indicate the presence of a significant fraction of the mass being in the thermally unstable regime, (i.e., with a temperature mid-way between the CNM and WNM stable states). However, the thermodynamical conditions of the gas remain largely unexplored from the observational point of view.To go further, and really compare with numerical simulation that are, for now, under-constrained by observation, it is mandatory to map the column density structure of each phase and study the spatial variations of their centroid velocity and velocity dispersion. This calls for methods that can extract the information of each HI phase from fully sampled 21 cm emission data only.An original Gaussian decomposition algorithm, named ROHSA, is presented is this thesis. Based on a multi-resolution process from coarse to fine grid, and using a regularized non-linear least-square criterion to take into account simultaneously the spatial coherence of the emission and the multiphase nature of the gas, this method allows us to infer a spatially coherent vision of the three-phase neutral ISM.A detailed analysis is then presented on a high latitude HI field centred on the North Ecliptic Pole. In particular we provide new constraints on the thermodynamical properties of the WNM, and the statistical properties of the turbulent cascade acting in the fluid. Finally, we discuss under which condition the condensation mode of the thermal instability can grow in this medium and converge toward the cold phase of the neutral ISM, the CNM
Books on the topic "ISM: kinematics and dynamics"
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Vallejo Maldonado, Pablo Ramon, and Nikolay Chaynov. Kinematics and dynamics of automobile piston engines. INFRA-M Academic Publishing LLC., 2019. http://dx.doi.org/10.12737/989072.
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The fundamentals of kinematics and dynamics of transport piston internal combustion engines made using different layout schemes are presented. Along with the traditional in-line, V-shaped, including oppositional, arrangement of cylinders, schemes with "staggered" arrangement of cylinders in the block at the displaced connecting rod necks of the crankshaft of the engine are considered. The kinematics of the coaxial crank mechanism is considered in detail. The questions of dynamics with reduction of calculated dependences of forces, moments, a choice of a rational order of work of cylinders in relation to the considered kinematic schemes are in detail stated. Considerable attention is paid to the unevenness of the crankshaft rotation speed and engine balancing. The loads on the main and connecting rod bearings of the crankshaft, the knowledge of which is necessary in determining the bearing capacity of bearing units, are also considered.
 Meets the requirements of the Federal state educational standards of higher education of the last generation.
 For students of higher educational institutions studying in the direction of training 23.03.03 "Operation of transport and technological machines and complexes" and related areas.
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Val'eho, Mal'donado, and Nikolay Chaynov. Calculation of kinematics and dynamics of inline piston engines. INFRA-M Academic Publishing LLC., 2021. http://dx.doi.org/10.12737/1058850.
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The textbook discusses the kinematics and dynamics of inline piston internal combustion engines with axial and deaxial crank mechanism. The necessary material for calculating the forces and moments acting in the engine is given, the balancing of engines, the construction of vector diagrams of pressure on the crankshaft bearings are considered, examples of calculations are given.
 Meets the requirements of the federal state educational standards of higher education of the latest generation.
 For students of higher educational institutions studying in the field of training "Energy engineering".
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Norton, Robert L. Cam design and manufacturing handbook. 2nd ed. Industrial Press, 2009.
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Schwinger, Julian Seymour. Quantum Kinematics and Dynamics. Advanced Book Program, Perseus Pub., 2000.
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Schwinger, Julian Seymour. Quantum kinematics and dynamics. Addison-Wesley Pub. Co. Advanced Book Program, 1991.
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Peter, Sadler J., ed. Kinematics and dynamics of machinery. 3rd ed. Pearson Education, 2003.
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Peter, Sadler J., ed. Kinematics and dynamics of machinery. 2nd ed. HarperCollinsCollegePublishers, 1993.
Find full textBook chapters on the topic "ISM: kinematics and dynamics"
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Wittenburg, Jens. "Dynamics of Mechanisms." In Kinematics. Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-48487-6_19.
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Fabien, Brian. "Kinematics." In Analytical System Dynamics. Springer US, 2008. http://dx.doi.org/10.1007/978-0-387-85605-6_2.
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Jazar, Reza N. "⋆ Applied Kinematics." In Vehicle Dynamics. Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4614-8544-5_5.
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Schiehlen, Werner, and Peter Eberhard. "Basic Kinematics." In Applied Dynamics. Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-07335-4_2.
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Roberson, Robert E., and Richard Schwertassek. "Kinematics." In Dynamics of Multibody Systems. Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-86464-3_10.
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Billingsley, John. "Kinematics." In Essentials of Dynamics and Vibrations. Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-56517-0_8.
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Billingsley, John. "Kinematics." In Essentials of Dynamics and Vibrations. Springer Nature Switzerland, 2025. https://doi.org/10.1007/978-3-031-79047-8_8.
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Drabble, G. E. "Kinematics of Mechanisms: Analysis." In Dynamics. Macmillan Education UK, 1990. http://dx.doi.org/10.1007/978-1-349-10448-2_4.
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Jazar, Reza N. "⋆ $$\star$$ Applied Kinematics." In Vehicle Dynamics. Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-53441-1_4.
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To, Cho W. S. "Kinematics of Particles." In Engineering Dynamics. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-031-79617-3_2.
Full textConference papers on the topic "ISM: kinematics and dynamics"
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Lou, Huanhuan, Qingxiang Wu, Hai Wang, Tong Yang, Huawang Liu, and Ning Sun. "Kinematics and Dynamics Modeling of Bionic Variable Structure UAVs." In 2024 IEEE International Conference on Real-time Computing and Robotics (RCAR). IEEE, 2024. http://dx.doi.org/10.1109/rcar61438.2024.10670985.
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Liu, Yongchen, and Wenzhi Zhang. "Modeling and simulation of kinematics and dynamics of wire-driven robots." In Fourth International Conference on Testing Technology and Automation Engineering (TTAE 2024), edited by Sumeet S. Aphale and Ajit Jha. SPIE, 2024. https://doi.org/10.1117/12.3055356.
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Wang, Chunbao, Zhengdi Sun, Jianjun Wei, et al. "Kinematics and Dynamics Analysis of a Two- Arms Rehabilitation Robot." In 2018 IEEE International Conference on Intelligence and Safety for Robotics (ISR). IEEE, 2018. http://dx.doi.org/10.1109/iisr.2018.8535985.
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Ahmad, Aftab, Suleman Khan, and Kjell Anderson. "Kinematics and dynamics of a novel 6-DoF TAU haptic device." In 2011 IEEE International Conference on Mechatronics (ICM). IEEE, 2011. http://dx.doi.org/10.1109/icmech.2011.5971209.
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Wang, Junshi, Huy Tran, Martha Christino, et al. "Hydrodynamics and Flow Characterization of Tuna-Inspired Propulsion in Forward Swimming." In ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ajkfluids2019-5472.
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Abstract A combined experimental and numerical approach is employed to study the hydrodynamic performance and characterize the flow features of thunniform swimming by using a tuna-inspired underwater vehicle in forward swimming. The three-dimensional, time-dependent kinematics of the body-fin system of the underwater vehicle is obtained via a stereo-videographic technique. A high-fidelity computational model is then directly reconstructed based on the experimental data. A sharp-interface immersed-boundary-method (IBM) based incompressible flow solver is employed to compute the flow. The primary objective of the computational effort is to quantify the thrust performance of the model. The body kinematics and hydrodynamic performances are quantified and the dynamics of the vortex wake are analyzed. Results have shown significant leading-edge vortex at the caudal fin and unique vortex ring structures in the wake. The results from this work help to bring insight into understanding the thrust producing mechanism of thunniform swimming and to provide potential suggestions in improving the hydrodynamic performance of swimming underwater vehicles.
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Wang, Junshi, Pan Han, Yaselly Sanchez, Jinxiang Xi, and Haibo Dong. "Computational Analysis on Aerodynamics and Vortex Formation of Sleep Apnea." In ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/fedsm2018-83257.
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The fluid dynamics of air flow in the pharynx is critical to the vibration of the uvula and to the generation of the snoring sound. In this work, a combined experimental and computational approach was conducted to study the aerodynamics of the flow field in the human airway. An anatomically accurate pharynx model associated with different uvula kinematics was reconstructed from human magnetic resonance images (MRI) and high-speed photography. An immersed-boundary-method (IBM)-based direct numerical simulation (DNS) flow solver was used to simulate the corresponding unsteady flows in all their complexity. Analysis has been performed on vortex dynamics and pressure oscillation at various points of interest. Computations with varying airway obstructions, uvula kinematics, and vibrating frequencies were conducted to study the effect of the three factors on the vortex formation and pressure oscillation, respectively. It is found that the vortex formation is significantly affected by the airway width. The fast Fourier transformation (FFT) analysis of the pressure time history revealed the existence of higher order harmonics of the base frequency at significant amplitudes. It was also found that the pressure tended to oscillate more violently at higher uvula vibrating frequencies. Results from this work are expected to bring novel understanding on the sound producing in patients with sleep apnea and provide guidance for surgical interventions.
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Arthur, S. Jane, Randall K. Smith, Steven L. Snowden, and K. D. Kuntz. "Dynamics of Bubbles in the ISM." In THE LOCAL BUBBLE AND BEYOND II: Proceedings of the International Conference. AIP, 2009. http://dx.doi.org/10.1063/1.3211828.
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Wagnerberger, Larissa, Detlef Runde, Mustafa Tevfik Lafci, David Przewozny, Sebastian Bosse, and Paul Chojecki. "Inverse kinematics for full-body self representation in VR-based cognitive rehabilitation." In 2021 IEEE International Symposium on Multimedia (ISM). IEEE, 2021. http://dx.doi.org/10.1109/ism52913.2021.00029.
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Patterson, Rita M., Manuel F. DaSilva, Steven F. Viegas, and J. C. Goslings. "Carpal Kinematics During Radial Ulnar Deviation." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0467.
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Abstract This study investigates carpal kinematics during a wrist Radial/Ulnar deviation motion using high speed video data acquisition. A cadaver forearm was stabilized allowing unconstrained excursion of the wrist for passive range of motion. Capitate/radius and 3rd metacarpal/radius angles were calculated to determine which measurement would be best for determining global wrist angle. The average difference in angle between the capitate and third metacarpal was 1.3 ± 1.3 degrees with a maximum difference of 5.0 degrees. Hence, the capitate-third metacarpal joint can be considered ridged. The proximal wrist joint (R/L angle) contributed 15.1 degrees to global wrist radial ulnar deviation and the midcarpal joint (C/L angle) contributed 20.6 degrees to global wrist radial ulnar deviation (43.0% and 55.8%, respectively, of the 36.4° total wrist ROM). Radio-scaphoid angles averaged 16.8 degrees (46.5% of the 36.4° total wrist ROM). The radio-lunate joint and the capito-lunate joint contribute equally to global wrist radial ulnar deviation. This new combination of motion analysis and 3D reconstructions of CT images affords a high speed, dynamic analysis of kinematics. It shows that normal carpal kinematics, during wrist radial/ulnar deviation, does not have an instantaneous screw axis (ISA) fixed in or limited to the capitate. In addition, the ISA data provides evidence that translational motion is a real and measurable component of normal carpal motion. This would change the understanding of carpal kinematics from previous studies, which suggested that the center of rotation was fixed in the capitate.
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El-Khasawneh, Bashar, and Anas Alazzam. "Kinematics, Dynamics and Vibration Models for 3RPR Parallel Kinematics Manipulator." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-64525.
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Parallel link manipulators are the type of mechanisms that have closed kinematics chains. Some of their advantages over open kinematics chains (called also serial kinematics manipulators) are their high stiffness and accuracy. This paper carries out forward and inverse kinematic and dynamic analysis on a certain type of parallel kinematic mechanisms. This is needed to conduct vibration analysis on the same platform. The type of mechanism is planar 3 RPR manipulator. This entails identifying the modes of the manipulator. A simplified vibration theoretical model is derived. This derivation helps in the optimization of parallel kinematics machine design for improved/optimized dynamic performance. The implications of dynamic stiffness modeling should reflect on better noise rejection, less chatter during machining, and increasing the bandwidth of such mechanisms to admit running at higher speeds.
Reports on the topic "ISM: kinematics and dynamics"
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Nasr, Jonathan. DEVELOPMENT OF A DESIGN GUIDELINE FOR BRIDGE PILE FOUNDATIONS SUBJECTED TO LIQUEFACTION-INDUCED LATERAL SPREADING. Deep Foundations Institute, 2018. http://dx.doi.org/10.37308/cpf-2016-ssmc-1.
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Effective-stress nonlinear dynamic analyses (NDA) were performed for piles in liquefiable sloped ground to assess how inertia and liquefaction-induced lateral spreading combine in long-duration vs. short-duration earthquakes. A parametric study was performed using input motions from subduction and crustal earthquakes covering a wide range of earthquake durations. The NDA results were used to evaluate the accuracy of the equivalent static analysis (ESA) recommended by Caltrans/ODOT for estimating pile demands. Finally, the NDA results were used to develop new ESA methods to combine inertial and lateral spreading loads for estimating elastic and inelastic pile demands. The NDA results showed that pile demands increase in liquefied conditions compared to nonliquefied conditions due to the interaction of inertia (from superstructure) and kinematics (from liquefaction-induced lateral spreading). Comparing pile demands estimated from ESA recommended by Caltrans/ODOT with those computed from NDA showed that the guidelines by Caltrans/ODOT (100% kinematic combined with 50% inertia) slightly underestimates demands for subduction earthquakes with long durations. A revised ESA method was developed to extend the application of the Caltrans/ODOT method to subduction earthquakes. The inertia multiplier was back-calculated from the NDA results and new multipliers were proposed: 100% Kinematic + 60% Inertia for crustal earthquakes and 100% Kinematic + 75% Inertia for subduction earthquakes. The proposed ESA compared reasonably well against the NDA results for elastic piles. The revised method also made possible to estimate demands in piles that performed well in the dynamic analyses but could not be analyzed using Caltrans/ODOT method (i.e. inelastic piles that remained below Fult on the liq pushover curve). However, it was observed that the pile demands became unpredictable for cases where the pile head displacement exceeded the displacement corresponding to the ultimate pushover force in liquefied conditions. Nonlinear dynamic analysis is required for these cases to adequately estimate pile demands.
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Aardema, James. Robotic Refueler Arm Kinematics, Dynamics and Global Position Control. Defense Technical Information Center, 1989. http://dx.doi.org/10.21236/ada396690.
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Perdigão, Rui A. P., and Julia Hall. Spatiotemporal Causality and Predictability Beyond Recurrence Collapse in Complex Coevolutionary Systems. Meteoceanics, 2020. http://dx.doi.org/10.46337/201111.
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Causality and Predictability of Complex Systems pose fundamental challenges even under well-defined structural stochastic-dynamic conditions where the laws of motion and system symmetries are known. However, the edifice of complexity can be profoundly transformed by structural-functional coevolution and non-recurrent elusive mechanisms changing the very same invariants of motion that had been taken for granted. This leads to recurrence collapse and memory loss, precluding the ability of traditional stochastic-dynamic and information-theoretic metrics to provide reliable information about the non-recurrent emergence of fundamental new properties absent from the a priori kinematic geometric and statistical features. Unveiling causal mechanisms and eliciting system dynamic predictability under such challenging conditions is not only a fundamental problem in mathematical and statistical physics, but also one of critical importance to dynamic modelling, risk assessment and decision support e.g. regarding non-recurrent critical transitions and extreme events. In order to address these challenges, generalized metrics in non-ergodic information physics are hereby introduced for unveiling elusive dynamics, causality and predictability of complex dynamical systems undergoing far-from-equilibrium structural-functional coevolution. With these methodological developments at hand, hidden dynamic information is hereby brought out and explicitly quantified even beyond post-critical regime collapse, long after statistical information is lost. The added causal insights and operational predictive value are further highlighted by evaluating the new information metrics among statistically independent variables, where traditional techniques therefore find no information links. Notwithstanding the factorability of the distributions associated to the aforementioned independent variables, synergistic and redundant information are found to emerge from microphysical, event-scale codependencies in far-from-equilibrium nonlinear statistical mechanics. The findings are illustrated to shed light onto fundamental causal mechanisms and unveil elusive dynamic predictability of non-recurrent critical transitions and extreme events across multiscale hydro-climatic problems.
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Keyser, Daniel. Diagnosis of the Kinematics and Dynamics of Rapidly Developing Maritime Cyclones. Defense Technical Information Center, 1992. http://dx.doi.org/10.21236/ada267008.
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Khosravifar, Arash. COMBINED EFFECTS OF LATERAL SPREADING AND SUPERSTRUCTURE INERTIA. Deep Foundations Institute, 2023. http://dx.doi.org/10.37308/cpf-2020-drsh-2.
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The seismic behavior of a RC pile with a diameter of 0.25 m subjected to liquefaction-induced lateral spreading was investigated using a shake table experiment that was conducted at the University of California, San Diego by Professor Ahmed Elgamal and Dr. Ahmed Ebeido (Ebeido and Elgamal 2019). A sinusoidal motion was applied at the base of a model that was inclined by 4 degrees. The loose and dense sand layers liquefied during the test, resulting in a permanent lateral spreading displacement of approximately 0.4 m (Figure E1). The pile was subjected to the combined effects of inertial loads from the acceleration of the superstructure mass and kinematic loads from the overlying nonliquefiable, dry crust. The dynamic responses of the soil and pile were analyzed to evaluate the relative contributions of inertial and kinematic loads during critical cycles (i.e., at the time of maximum inertia and the time of maximum pile strains). It was found that large pile strains developed after liquefaction was triggered. Large pile strains (and curvature) were recorded at a shallow depth within the crust (0.49 m) and a deeper location below the loose liquefiable sand (1.89 m). Large pile strains at shallow depth were found to be correlated with the inertial loads applied in the upslope direction. These upslope inertial loads were resisted by downslope crust loads, indicating an out-of-phase interaction. In contrast, large pile strains that occurred at deeper locations were correlated with downslope inertial loads and were accompanied by zero crust load, indicating that there was no lateral spreading force during the downslope inertial cycles. A gap at the downslope area in front of the pile formed because the soil displacements exceeded the pile displacements during the cyclic phase after liquefaction was triggered. The lack of crust load during the downslope inertial cycles is attributed to the pile head outrunning the crust displacement and causing the pile to be pushed into the gap at the downslope area in front of the pile. The interaction of inertia and kinematics appears to be a site- and project-specific phenomena. Therefore,the findings of this study—and, specifically, the lack of lateral spreading crust load during downslope inertial cycles—should be considered in design as one possible scenario in addition to the scenarios from several other studies that suggest combining the inertial loads with a lateral spreading force (e.g., Boulanger et al. 2007, Turner et al. 2016, Souri et al. 2022, Tokimatsu et al. 2005, Cubrinovski et al 2017).
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Lai, Chin-Ta, and Joel Conte. Dynamic Modeling of the UC San Diego NHERI Six-Degree-of-Freedom Large High-Performance Outdoor Shake Table. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, 2024. http://dx.doi.org/10.55461/jsds5228.
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The UC San Diego Large High-Performance Outdoor Shake Table (LHPOST), which was commissioned on October 1, 2004 as a shared-use experimental facility of the National Science Foundation (NSF) Network for Earthquake Engineering Simulation (NEES) program, was upgraded from its original one degree-of-freedom (LHPOST) to a six degree-of-freedom configuration (LHPOST6) between October 2019 and April 2022. The LHPOST6 is a shared-use experimental facility of the NSF Natural Hazard Engineering Research Infrastructure (NHERI) program. A mechanics-based numerical model of the LHPOST6 able to capture the dynamics of the upgraded 6-DOF shake table system under bare table condition is presented in this report. The model includes: (i) a rigid body kinematic model that relates the platen motion to the motions of components attached to the platen, (ii) a hydraulic dynamic model that calculates the hydraulic actuator forces based on all fourth-stage servovalve spool positions, (iii) a hold-down strut model that determines the pull-down forces produced by the three hold-down struts, (iv) a 2-D and various 1-D Bouc-Wen models utilized to represent the dissipative forces in the shake table system, and (v) a 6-DOF rigid body dynamic model governing the translational and rotational motions of the platen subjected to the forces from the various components attached to the platen. In this report, the rigid body dynamics is studied utilizing the platen twist (combination of platen translational and rotational velocities) and wrench (combination of force and moment resultants acting on the platen) following principles from the robotic analysis literature. The numerical model of the LHPOST6 is validated extensively using experimental data from the acceptance tests performed following the shake table upgrade, and the model predictions of the shake table system response are found to be consistently in very good agreement with the experimental results for tri-axial and six-axial earthquake shake table tests. The validated mechanics-based numerical model of the LHPOST6 presented in this study can be coupled with finite element models of shake table test specimens installed on the rigid platen to study the dynamic interaction between the shake table system and the specimens. Another important potential use of the model is to improve the motion tracking performance of the LHPOST6 through either off-line tuning of the shake table controller and/or development of more advanced shake table controllers.
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Melville, W. K., and Eric Terrill. Airborne Measurements of Whitecap Kinematics and Dynamics in the High-Wind Regime: Source Functions for Marine Aerosols, Surface Currents and Turbulence. Defense Technical Information Center, 2003. http://dx.doi.org/10.21236/ada630299.
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Khan, Asad, Angeli Jayme, Imad Al-Qadi, and Gregary Renshaw. Embedded Energy Harvesting Modules in Flexible Pavements. Illinois Center for Transportation, 2024. http://dx.doi.org/10.36501/0197-9191/24-008.
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Energy from pavements can be harvested in multiple ways to produce clean energy. One of the techniques is electromagnetic energy harvesting, in which mechanical energy from vehicles is captured in the form of input displacement to produce electricity. In this study, a rack-and-pinion electromagnetic energy harvester proposed in the literature as a speed bump is optimized for highway-speed vehicles. A displacement transfer plate is also proposed, with a minimum depth of embedment in the pavement to carry input displacements from passing vehicles and excite the energy harvester. The energy harvester was designed, and kinematic modeling was carried out to establish power–output relations as a function of rack velocity. Sensitivity analysis of various parameters indicated that, for high-speed applications where rack velocities are relatively high, small input excitations could be harnessed to achieve the rated revolutions per minute (RPM) of the generator. A set of laboratory tests was conducted to validate the kinematic model, and a good correlation was observed between measured and predicted voltages. Dynamic modeling of the plate was done for both recovery and compression to obtain the plate and rack velocities. Using Monte Carlo simulation, the plate was designed for a class-9 truck with wide-base tires moving at 128 km/h. Design and layout of the energy harvester with a displacement transfer plate was proposed for field validation. The energy harvester with the displacement plate could be integrated with transverse rumble strips in construction zones and near diversions. Hence, it could be used as a standalone system to power roadside applications such as safety signs, road lights, speed cameras, and vehicle-to-infrastructure (V2I) systems.
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Kozlovsky, Evgen O., та Hennadiy M. Kravtsov. Мультимедийная виртуальная лаборатория по физике в системе дистанционного обучения. [б. в.], 2018. http://dx.doi.org/10.31812/0564/2455.
Full textAbstract:
Research goals: the description of technology of software development in Physics Virtual Laboratory for Distance Learning System. Research objectives: the architecture of client and server parts of the lab, the functionality of the system modules, user roles, as well as the principles of virtual laboratory use on a personal computer. Object of research: the distance learning system “Kherson Virtual University”. Subject of research: virtual laboratory for physics in the distance learning. Research methods used: analysis of statistics and publications. Results of the research. The development of the software module “Virtual Lab” in distance learning system “Kherson Virtual University” (DLS KVU) applied to the problems of physics on topics kinematics and dynamics. The information technology design and development, the structure of the virtual laboratory, and its place in the DLS KVU are described. The principal modes of the program module operation in the system and methods for its use in the educational process are described. The main conclusions and recommendations. The use of this software interface allows teachers to create labs and use them in their distance courses. Students, in turn, will be able to conduct research, carrying out virtual laboratory work.