Thematische Bibliographien / Collisional parameters

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Auswahl der wissenschaftlichen Literatur zum Thema „Collisional parameters“

Autor: Grafiati

Veröffentlicht am 25. Mai 2024

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Zeitschriftenartikel zum Thema "Collisional parameters"

Chatterjee, A., and A. Ruina. "A New Algebraic Rigid-Body Collision Law Based on Impulse Space Considerations." Journal of Applied Mechanics 65, no. 4 (1998): 939–51. http://dx.doi.org/10.1115/1.2791938.

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We present a geometric representation of the set of three-dimensional rigid-body collisional impulses that are reasonably permissible by the combination of non-negative post-collision separation rate, non-negative collisional compression impulse, non-negative energy dissipation and the Coulomb friction inequality. The construction is presented for a variety of special collisional situations involving special symmetry or extremes in the mass distribution, the friction coefficient, or the initial conditions. We review a variety of known friction laws and show how they do and do not fit in the permissible region in impulse space as well as comment on other attributes of these laws. We present a few parameterizations of the full permissible region of impulse space. We present a simple generalization to arbitrary three-dimensional point contact collisions of a simple law previously only applicable to objects with contact-inertia eigenvectors aligned with the surface normal and initial relative tangential velocity component (e.g., spheres and disks). This new algebraic collision law has two restitution parameters for general three-dimensional frictional single-point rigid-body collisions. The new law generates a collisional impulse that is a weighted sum of the impulses from a frictionless but nonrebounding collision and from a perfectly sticking, nonrebounding collision. We describe useful properties of our law; show geometrically the set of impulses it can predict for several collisional situations; and compare it with existing laws. For simultaneous collisions we propose that the new algebraic law be used by recursively breaking these collisions into a sequence ordered by the normal approach velocities of potential contact pairs.

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Arakawa, Sota, Hidekazu Tanaka, and Eiichiro Kokubo. "Impacts of Viscous Dissipation on Collisional Growth and Fragmentation of Dust Aggregates." Astrophysical Journal 933, no. 2 (2022): 144. http://dx.doi.org/10.3847/1538-4357/ac7460.

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Abstract Understanding the collisional behavior of dust aggregates consisting of submicron-sized grains is essential to unveiling how planetesimals formed in protoplanetary disks. It is known that the collisional behavior of individual dust particles strongly depends on the strength of viscous dissipation force; however, impacts of viscous dissipation on the collisional behavior of dust aggregates have not been studied in detail, especially for the cases of oblique collisions. Here we investigated the impacts of viscous dissipation on the collisional behavior of dust aggregates. We performed numerical simulations of collisions between two equal-mass dust aggregates with various collision velocities and impact parameters. We also changed the strength of viscous dissipation force systematically. We found that the threshold collision velocity for the fragmentation of dust aggregates barely depends on the strength of viscous dissipation force when we consider oblique collisions. In contrast, the size distribution of fragments changes significantly when the viscous dissipation force is considered. We obtained the empirical fitting formulae for the size distribution of fragments for the case of strong dissipation, which would be useful to study the evolution of size and spatial distributions of dust aggregates in protoplanetary disks.

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Arakawa, Sota, Hidekazu Tanaka, and Eiichiro Kokubo. "Collisional Growth Efficiency of Dust Aggregates and Its Independence of the Strength of Interparticle Rolling Friction." Astrophysical Journal 939, no. 2 (2022): 100. http://dx.doi.org/10.3847/1538-4357/ac96e1.

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Abstract The pairwise collisional growth of dust aggregates consisting of submicron-sized grains is the first step of planet formation, and understanding the collisional behavior of dust aggregates is therefore essential. It is known that the main energy dissipation mechanisms are the tangential frictions between particles in contact, namely, rolling, sliding, and twisting. However, there is great uncertainty for the strength of rolling friction, and the dependence of the collisional growth condition on the strength of rolling friction was poorly understood. Here we performed numerical simulations of collisions between two equal-mass porous aggregates with various collision velocities and impact parameters, and we also changed the strength of rolling friction systematically. We found that the threshold of the collision velocity for the fragmentation of dust aggregates is nearly independent of the strength of rolling friction. This is because the total amount of the energy dissipation by the tangential frictions is nearly constant even though the strength of rolling friction is varied.

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Seaton, M. J. "New Atomic Data for Astronomy: An Introductory Review." Highlights of Astronomy 10 (1995): 570–71. http://dx.doi.org/10.1017/s1539299600012065.

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Astronomers require the following basic atomic data: energy levels and wavelengths’, radiative transition probabilities; cross sections for photo-ionisation and for collisional processes; and line profile parameters. They also require processed data such as: level populations; opacities; radiation forces; line emissivities; and collisional rate-coefficients.Many of the data used by astronomers come from theoretical work. Experimental work is of importance in determining accurate wavelengths, in providing essential checks on theory for radiative probabilities and collision rates, and in the determination of line-profile parameters. Experimental studies are particularly important for processes of collisional ionisation.

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Jesus, Antônio D. C., Rafael S. Ribeiro, Alessandro Rossi, and Ernesto Veira Neto. "Evasive Maneuvers in Space Debris Environment and Technological Parameters." Mathematical Problems in Engineering 2012 (2012): 1–15. http://dx.doi.org/10.1155/2012/126521.

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We present a study of collisional dynamics between space debris and an operational vehicle in LEO. We adopted an approach based on the relative dynamics between the objects on a collisional course and with a short warning time and established a semianalytical solution for the final trajectories of these objects. Our results show that there are angular ranges in 3D, in addition to the initial conditions, that favor the collisions. These results allowed the investigation of a range of technological parameters for the spacecraft (e.g., fuel reserve) that allow a safe evasive maneuver (e.g., time available for the maneuver). The numerical model was tested for different values of the impact velocity and relative distance between the approaching objects.

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Ngo, N. H., H. Tran, R. R. Gamache, and J. M. Hartmann. "Pressure effects on water vapour lines: beyond the Voigt profile." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, no. 1968 (2012): 2495–508. http://dx.doi.org/10.1098/rsta.2011.0272.

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A short overview of recent results on the effects of pressure (collisions) regarding the shape of isolated infrared lines of water vapour is presented. The first part of this study considers the basic collisional quantities, which are the pressure-broadening and -shifting coefficients, central parameters of the Lorentzian (and Voigt) profile and thus of any sophisticated line-shape model. Through comparisons of measured values with semi-classical calculations, the influences of the molecular states (both rotational and vibrational) involved and of the temperature are analysed. This shows the relatively unusual behaviour of H 2 O broadening, with evidence of a significant vibrational dependence and the fact that the broadening coefficient (in cm −1 atm −1 ) of some lines increases with temperature. In the second part of this study, line shapes beyond the Voigt model are considered, thus now taking ‘velocity effects’ into account. These include both the influence of collisionally induced velocity changes that lead to the so-called Dicke narrowing and the influence of the dependence of collisional parameters on the speed of the radiating molecule. Experimental evidence of deviations from the Voigt shape is presented and analysed. The interest of classical molecular dynamics simulations, to model velocity changes, together with semi-classical calculations of the speed-dependent collisional parameters for line-shape predictions from ‘first principles’, are discussed.

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Chernoff, David F., and Xiaolan Huang. "Frequency of Stellar Collisions in Three-Body Heating." Symposium - International Astronomical Union 174 (1996): 263–72. http://dx.doi.org/10.1017/s0074180900001601.

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The probability for collisional interaction of three body binaries is calculated as a function of the physical radius and mass of the stellar objects and the depth of the cluster potential well. For typical cluster parameters, there is a significant chance of physical collision for objects as small as white dwarfs. One consequence of the collisions is to lower the amount of heat produced from hardening a binary, thereby diminishing the efficiency of the three-body heating mechanism.

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Campo Bagatin, A., and P. Farinella. "Collisional reaccumulation of asteroids." International Astronomical Union Colloquium 173 (1999): 145–52. http://dx.doi.org/10.1017/s0252921100031341.

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AbstractWe have developed a new version of the code developed by Campo Bagatin (1994a, b) to model the collisional evolution of the asteroid size distribution. The new code distinguishes between “intact”, unfractured asteroids and asteroids converted by energetic collisions into “piles of rubble”. We have run a number of simulations of the collisional evolution process to assess the size range where reaccumulated bodies should be expected to be abundant in the main asteroid belt. We find that this diameter range ranges from about 10 to 100 km, but may extend to smaller or larger bodies depending on the prevailing collisional response parameters.

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FIORE, M., F. FIÚZA, M. MARTI, R. A. FONSECA, and L. O. SILVA. "Relativistic effects on the collisionless–collisional transition of the filamentation instability in fast ignition." Journal of Plasma Physics 76, no. 6 (2010): 813–32. http://dx.doi.org/10.1017/s0022377810000413.

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AbstractRelativistic collisional effects on the filamentation instability are analytically and numerically investigated by comparing collisionless and collisional scenarios for a fast ignition (FI) configuration. The theoretical kinetic model, including warm species and space charge effects, predicts the preferential formation of larger filaments and the inhibition/enhancement of the instability when collisions are accounted for. These collisional effects are qualitatively and quantitatively confirmed by 1D and 2D particle-in-cell (PIC) simulations, also providing a physical picture for the inhibition/enhancement regime due to collisions, based on the electron beam slowdown. By plugging typical FI parameters in the dispersion relation, the theoretical model predicts significant growth rates of the instability deep inside the FI target, thus showing the potential role of the filamentation instability as a mechanism for energy deposition into the pellet core.

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Mohammed, A. I., and C. S. Adams. "Ion shock layer formation during multi-ion-species plasma jet stagnation events." Physics of Plasmas 29, no. 7 (2022): 072307. http://dx.doi.org/10.1063/5.0087509.

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We report the characteristics of collisional plasma shocks formed during interactions between low density ([Formula: see text] cm−3), low temperature ([Formula: see text] eV), high velocity (30 km s−1), plasma jets and stagnant plasma of similar parameters. This investigation seeks to probe the structure of shocks in multi-ion-species plasmas, in particular, the presence of gradient-driven ion species separation at the shock front. The railgun-accelerated jets utilized here have previously been shown to exist in a collisional regime with intra-jet collisional mean-free-path substantially smaller than jet size [Schneider et al., Plasma Sources Sci. Technol. 29, 045013 (2020)]. To induce collisions, a dielectric barrier is located downstream of the railgun to stagnate an initially supersonic plasma jet. Around the time of stagnation, the railgun emits a second jet which shortly collides with the stagnant plasma. The presence of a structure emitting in the UV-visible band is evident in high-speed photographs of the moments immediately following the arrival of the second jet at the stagnant plasma. Analysis of interferometric and spectroscopic data suggests that the observed increase in density from the jet to the post-collision plasma is consistent with the formation of a bow shock structure with a multi-millimeter-scale ion shock layer.

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