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Alexandre Valance - One of the best experts on this subject based on the ideXlab platform.
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three dimensional analysis of the Collision Process of a bead on a granular packing
Physical Review E, 2009Co-Authors: M Ammi, Luc Oger, Djaoued Beladjine, Alexandre ValanceAbstract:We present results of the Collision Process of a bead onto a static granular packing. We provide, in particular, a three-dimensional (3D) extensive characterization of this Process from a model experiment that allows us to propel a spherical bead onto a granular packing with a well-controlled velocity and impact angle. A Collision typically produces a high-energy particle (rebound particle) and several low-energy grains (ejected particles). The Collision Process is recorded by means of two fast video cameras. The sequence of images from both cameras are then analyzed via image Processing and the trajectories of all particles are reconstructed in 3D space. We show that the incident particle does not remain in the vertical incident plane after the rebound and that the deviation angle increases with increasing impact angle. Concerning the ejected particles, we demonstrated that the ejection angle (measured with respect to the horizontal plane) is surprisingly independent of both the impact angle and velocity of the incident particle, and is very close to 60\ifmmode^\circ\else\textdegree\fi{}. The horizontal component of the ejection speed of the splashed particles is found to be weakly dependent on the incident speed and impact angle, and is relatively isotropic (no particular horizontal direction is favored). This last feature suggests that the bead packing acts as a perfect diffusive medium with respect to energy propagation.
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Collision Process between an incident bead and a three dimensional granular packing
Physical Review E, 2007Co-Authors: Djaoued Beladjine, M Ammi, Luc Oger, Alexandre ValanceAbstract:We report on experimental studies of the Collision Process between an incident bead and a three-dimensional granular packing (made of particles identical to the impacting one). The understanding of such a Process and the resulting ejection of particles is, in particular, crucial to describe eolian sand transport. We present here an extensive experimental analysis of the Collision and ejection Process. The analysis is two dimensional in the sense that we determined only the vertical component V{z} of the ejection velocity of the splashed particles and the horizontal component V{x} lying in the incident plane. We extracted in particular the distribution of the ejection velocities for a wide range of impact angles theta{i} and incident velocity V{i} . We show that the mean quadratic horizontal velocity of the splashed particles is almost insensitive to changes in the impact angle and velocity, while the mean quadratic vertical velocity slightly increases with increasing impact velocity (as V{i}{1/2}). Moreover, the mean number of splashed particles per Collision is found to be dependent on both the impact angle and velocity, and to scale with the impact speed as V{i}{3/2}. A consequence of these outcomes is that the sum of the kinetic energy of the splashed particles is directly proportional to the kinetic energy of the incident particle. Finally, we provide the bivariate probability distribution function P(V{x},V{z}) of the ejection velocities and show that it can be approximated by the product of a log-normal distribution and a circular normal one.
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experimental study of the Collision Process of a grain on a two dimensional granular bed
Physical Review E, 2000Co-Authors: Francois Rioual, Alexandre Valance, D BideauAbstract:We report an experimental study on the Collision of a bead on a two-dimensional hexagonal granular packing. This Collision Process is of crucial importance in aeolian transport of grains. We have investigated the kinematic properties of the incident bead before and after the Collision, and the resulting deformation of the packing. A typical Collision is characterized by the rebound of the impacting bead and the ejection of a few beads of the packing. We have shown that the properties of the rebound bead depend weakly on the impact speed and that the rebound Process involves only a few bead layers of the packing. On the contrary, the ejection mechanism depends strongly on the impact speed. In particular, it is found that the number of ejected grains increases with the impact speed whereas the most likely value of their energy is practically independent of the impact speed. Furthermore, we have given evidences that the ejection Process involves a great number of packing layers and therefore is extremely sensitive to the height of the packing. For small packing heights, one observes additional ejected grains which can be interpreted as being produced by the reflection of the shock wave on the bottom of the pile.
David Demille - One of the best experts on this subject based on the ideXlab platform.
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inelastic Collisions of ultracold heteronuclear molecules in an optical trap
Physical Review Letters, 2008Co-Authors: Eric R Hudson, Nathan Gilfoy, Svetlana Kotochigova, Jeremy M Sage, David DemilleAbstract:Ultracold RbCs molecules in high-lying vibrational levels of the a 3 Σ + ground electronic state are confined in an optical trap. Inelastic Collision rates of these molecules with both Rb and Cs atoms are determined for individual vibrational levels, across an order of magnitude of binding energies. The long-range dispersion coefficients for the Collision Process are calculated and used in a model that accurately reproduce the observed scattering rates.
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inelastic Collisions of ultracold heteronuclear molecules in an optical trap
Physical Review Letters, 2008Co-Authors: Eric R Hudson, Nathan Gilfoy, Svetlana Kotochigova, Jeremy M Sage, David DemilleAbstract:Ultracold RbCs molecules in high-lying vibrational levels of the ${a}^{3}{\ensuremath{\Sigma}}^{+}$ ground electronic state are confined in an optical trap. Inelastic Collision rates of these molecules with both Rb and Cs atoms are determined for individual vibrational levels, across an order of magnitude of binding energies. The long-range dispersion coefficients for the Collision Process are calculated and used in a model that accurately reproduce the observed scattering rates.
Jun Taniguchi - One of the best experts on this subject based on the ideXlab platform.
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molecular dynamics simulation of ga ion Collision Process
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2013Co-Authors: Shin-ichi Satake, Masahiko Shibahara, K Ono, Jun TaniguchiAbstract:Molecular dynamics (MD) simulations of 30 keV accelerated Ga ions has been carried out, colliding with a Si surface. Using this procedure the amorphous structural region of the Si was found to expand with the progression of the interface region, that lie between the amorphous structure and the crystalline structure, as fluence increased in the depth direction. The height of the structure is increased and has a peak value around 1.6 × 1015 ion/cm2, the height becomes the negative value beyond the peak, that is, the phenomenon changes from a deformation to a remove. The tendency of distribution for height and depth is a good agreement with an experimental data.
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molecular dynamics simulation of surface deformation via ar ion Collision Process
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2012Co-Authors: Shin-ichi Satake, Masahiko Shibahara, S Momota, A Fukushige, S Yamashina, Jun TaniguchiAbstract:Abstract We have carried out molecular dynamics (MD) simulations of 50 keV accelerated Ar ions, colliding with a Si surface. Using this procedure the amorphous structural region of the Si was found to expand with the progression of the interface region, that lie between the amorphous structure and the crystalline structure, as fluence increased in the depth direction. There has been considerable interest in studying the time development of the behavior of sputtered silicon atoms after being subjected to Collisions with the Ar ions. Here, by tracking the atoms in the computational domain, clusters formed during sputtering are classified under various kinds. In this Process small cluster of atoms e.g., monomer and dimer, and large cluster of atoms in forms of hillocks are formed where the smaller cluster have their energy higher than that of the large cluster.
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surface deformation of ar ion Collision Process via molecular dynamics simulation with comparison to experiment
Journal of Applied Physics, 2009Co-Authors: Shin-ichi Satake, Masahiko Shibahara, S Momota, S Yamashina, Jun TaniguchiAbstract:Molecular dynamics simulations of Ar ion Collision on a Si surface using an optimized potential function were carried out in the case of the acceleration voltages of 50keV for Ar ions. A hillock structure was formed by the Ar ion impact on the Si surface. The height of the structure calculated by the simulations corresponded to those of the experiments. The height of the structure was found to be proportional to the fluence of Ar ions. The amorphous structural region was expanded by the progress of the interface region between the amorphous structure and the crystalline structure with increasing the fluence in the depth direction.
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Quantum molecular dynamics study on energy transfer to the secondary electron in surface Collision Process of an ion
Journal of Physics: Conference Series, 2008Co-Authors: Masahiko Shibahara, Shin-ichi Satake, Jun TaniguchiAbstract:In the present study the quantum molecular dynamics method was applied to an energy transfer problem to an electron during ionic surface Collision Process in order to elucidate how energy of ionic Collision transfers to the emitted electrons. Effects of various physical parameters, such as the Collision velocity and interaction strength between the observed electron and the classical particles on the energy transfer to the electron were investigated by the quantum molecular dynamics method when the potassium ion was collided with the surface so as to elucidate the energy path to the electron and the predominant factor of energy transfer to the electron. Effects of potential energy between the ion and the electron and that between the surface molecule and the electron on the electronic energy transfer were shown in the present paper. The energy transfer to the observed secondary electron through the potential energy term between the ion and the electron was much dependent on the ion Collision energy although the energy increase to the observed secondary electron was not monotonous through the potential energy between the ion and surface molecules with the change of the ion Collision energy.
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Quantum Molecular Dynamics Study on Energy Transfer to the Secondary Electron in Surface Collision Process of an Ion
ASME JSME 2007 Thermal Engineering Heat Transfer Summer Conference Volume 1, 2007Co-Authors: Masahiko Shibahara, Shin-ichi Satake, Jun TaniguchiAbstract:It is well known that an emission of secondary electrons is observed in an ion Collision Process to a surface, such as the focused ion beam (FIB) Process. However, the physical effect of secondary electron emission to energy and mass transfer is seldom considered and there are few examples of analysis of the secondary electron emission. It is one of interesting problems as an extreme small scale energy transfer problem how energy is transferred to the electron emitted from the surface by ionic Collisions. In the present study the quantum molecular dynamics method was applied to an energy transfer problem to an electron during ionic surface Collision Process in order to elucidate how energy of ionic Collision transfers to the emitted electrons. The energy transfer paths to the electron was discussed during the Collision Process of an ion with changing the interaction between the electron and ions and that between the electron and surface molecules by the quantum molecular dynamics method. Effects of various physical parameters, such as the Collision velocity and interaction strength between the observed electron and the classical particles to the energy transfer to the electron were investigated by the quantum molecular dynamics method when the potassium ion was collided with the surface so as to elucidate the energy path to the electron and the predominant factor of energy transfer to the electron. Effects of potential energy between the ion and the electron and that between the surface molecule and the electron to the electronic energy transfer were shown in the present paper. The energy transfer to the observed secondary electron through the potential energy term between the ion and the electron was much dependent on the ion Collision energy although the energy increase to the observed secondary electron was not monotonous through the potential energy between the ion and surface molecules with the change of the ion Collision energy.Copyright © 2007 by ASME
Kei Ichi Maeda - One of the best experts on this subject based on the ideXlab platform.
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Collision of domain walls in asympotically anti de sitter spacetime
Albert Einstein Century International Conference, 2006Co-Authors: Yu Ichi Takamizu, Kei Ichi MaedaAbstract:We study Collision of two domain walls in 5‐dimensional asymptotically Anti de Sitter spacetime. This may provide the reheating mechanism of an ekpyrotic brane universe, in which two BPS branes collide and evolve into a hot big bang universe. We evaluate a change of scalar field making the domain wall and can investigate the effect of a negative cosmological term in the bulk to the Collision Process and the evolution of our universe.
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Collision of domain walls in asymptotically anti de sitter spacetime
Physical Review D, 2006Co-Authors: Yu Ichi Takamizu, Kei Ichi MaedaAbstract:We study Collision of two domain walls in five-dimensional asymptotically anti--de Sitter spacetime. This may provide the reheating mechanism of an ekpyrotic (or cyclic) brane universe, in which two Bogomol'nyi-Prasad-Sommerfield branes collide and evolve into a hot big bang universe. We evaluate a change of scalar field making the domain wall and can investigate the effect of a negative cosmological term in the bulk to the Collision Process and the evolution of our universe.
P Limaovieira - One of the best experts on this subject based on the ideXlab platform.
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electron transfer induced decomposition in potassium nitroimidazoles Collisions an experimental and theoretical work
International Journal of Molecular Sciences, 2019Co-Authors: M Mendes, Gustavo Garcia, M C Bacchusmontabonel, P LimaovieiraAbstract:Electron transfer induced decomposition mechanism of nitroimidazole and a selection of analogue molecules in Collisions with neutral potassium (K) atoms from 10 to 1000 eV have been thoroughly investigated. In this laboratory Collision regime, the formation of negative ions was time-of-flight mass analyzed and the fragmentation patterns and branching ratios have been obtained. The most abundant anions have been assigned to the parent molecule and the nitrogen oxide anion (NO2–) and the electron transfer mechanisms are comprehensively discussed. This work focuses on the analysis of all fragment anions produced and it is complementary of our recent work on selective hydrogen loss from the transient negative ions produced in these Collisions. Ab initio theoretical calculations were performed for 4-nitroimidazole (4NI), 2-nitroimidazole (2NI), 1-methyl-4- (Me4NI) and 1-methyl-5-nitroimidazole (Me5NI), and imidazole (IMI) in the presence of a potassium atom and provided a strong basis for the assignment of the lowest unoccupied molecular orbitals accessed in the Collision Process.