Collision Properties Research Articles

The influence of self-assembled particle layer on particle collision properties

Interactions between particle and particle layers are fundamental in modeling deposition processes. The complex mechanical behaviors of these layers pose significant challenges in precisely predicting the rebound characteristics of incident particle, especially at the micron and nanoscale. Very few related experimental studies have been reported in this area. To better control the structure of particle layers and offer a path to more systematic research, this study introduces the particle self-assembly method, combined with high-speed imaging technology, to investigate the influence of particle monolayer, their diameters, and impact velocity on critical capture velocity (vcr), normal coefficient of restitution (COR), and angle deflection of incident particles. Results indicate that self-assembled particle layers remain stable within an impact velocity range and experimental data within this stable range exhibit good repeatability. These layers significantly enhance kinetic energy dissipation. A semi-logarithmic plot revealed a negative linear relationship between vcr and particle size ratio. The effect of particle layer on COR depends on particle layer diameter and impact velocity. Specifically, the dissipation of particle layer diminishes and approaches zero for smaller layer particles (0.5 μm), but increases and stabilizes for larger particles (2 μm). Moreover, statistical results indicate that angle deflection decreases as particle size ratio increases, aligning with a power-law relationship predicted by Monte Carlo simulations. Overall, this study presents a novel method for understanding micro and nano particle layers' influence on incident particle dynamics.

Bulk medium properties of heavy-ion collisions from the beam energy scan with a multistage hydrodynamic model

I introduce a method to reconstruct full rapidity distributions of charged particle multiplicity and net proton yields, crucial for constraining the longitudinal dynamics of nuclear matter created in the beam energy scan program. Employing rapidity distributions within a multistage hydrodynamic model calibrated for Au+Au collisions at sNN=7.7–200GeV, I estimate the total energy and baryon number deposited into the collision fireball, offering insights into initial dynamics and the identification of nuclear remnants. I explore the potential of rapidity-dependent measurements in probing equations of state at finite chemical potentials. Furthermore, I compare the freeze-out parameters derived from both hydrodynamics and thermal models, highlighting that the parameters extracted via thermal models represent averaged properties across rapidities. Published by the American Physical Society 2024

Constraining nucleon effective masses with flow and stopping observables from the SπRIT experiment

Properties of the nuclear equation of state (EoS) can be probed by measuring the dynamical properties of nucleus-nucleus collisions. In this study, we present the directed flow (v1), elliptic flow (v2) and stopping (VarXZ) measured in fixed target Sn + Sn collisions at ▪ with the SπRIT Time Projection Chamber. We perform Bayesian analyses in which EoS parameters are varied simultaneously within the Improved Quantum Molecular Dynamics-Skyrme (ImQMD-Sky) transport code to obtain a multivariate correlated constraint. The varied parameters include symmetry energy, S0, and slope of the symmetry energy, L, at saturation density, isoscalar effective mass, ms⁎/mN, isovector effective mass, mv⁎/mN and the in-medium cross-section enhancement factor η. We find that the flow and VarXZ observables are sensitive to the splitting of proton and neutron effective masses and the in-medium cross-section. Comparisons of ImQMD-Sky predictions to the SπRIT data suggest a narrow range of preferred values for ms⁎/mN, mv⁎/mN and η.

Modulation instability and collision dynamics of solitons in birefringence optical fibers

In this paper, we investigate soliton modulation instability and collision dynamics in the birefringence optical fibers. Soliton transmission in the picosecond or femtosecond range in optical fibers is described by the coupled hybrid nonlinear Schrödinger equations. We focus on the modulation instability of the plane wave solutions and the gain spectrum under different parameters. The three-soliton solutions are used to analyze soliton collisions, and the asymptotic analysis is provided to reveal the properties of soliton collisions. The elastic and inelastic collisions of three-soliton are presented, and there exists the possibility of shape restoration of one or two solitons during the three-soliton inelastic collisions. The relevant results provide not only a new perspective for the realization of optical logic gates, but also theoretical value for the experimental observation of soliton collisions.

Collision properties of overtaking magnetosonic solitary waves in the ionospheric multi-ion plasmas

Collision properties of overtaking magnetosonic solitary waves in the ionospheric multi-ion plasmas

Effect of finite volume on thermodynamics of quark-hadron matter

The effects of a finite system volume on thermodynamic quantities, such as the pressure, energy density, specific heat, speed of sound, conserved charge susceptibilities, and correlations, in hot and dense strongly interacting matter are studied within the parity-doublet chiral mean field model. Such an investigation is motivated by relativistic heavy-ion collisions, which create a blob of hot QCD matter of a finite volume, consisting of strongly interacting hadrons and potentially deconfined quarks and gluons. The effect of the finite volume of the system is incorporated by introducing lower momentum cutoffs in the momentum integrals appearing in the model, the numerical value of the momentum cutoff being related to the de Broglie wavelength of the given particle species. It is found that some of these quantities show a significant volume dependence, in particular, those sensitive to pion degrees of freedom, and the crossover transition is generally observed to become smoother in finite volume. These findings are relevant for the effective equation of state used in fluid dynamical simulations of heavy-ion collisions and efforts to extract the freeze-out properties of heavy-ion collisions with susceptibilities involving electric charge and strangeness. Published by the American Physical Society 2024

Microscopic derivation of the collision properties of molecules in two systems at thermal equilibrium

The mean relative speed and relative speed distribution function of molecules play important roles in kinetics and related topics. College textbooks frequently present a simplified derivation of these quantities that, while yielding the correct result, are not well justified. This paper presents a detailed physical picture of collision-related processes based on the microscopic kinetic theory. Formulas for the mean relative speed and mean collision rate along with the relative speed distribution function and the distribution function of relative speed of the paired particles in collisions (collision possible distribution function) are derived for molecules from two different systems that are each at thermal equilibrium.

Looking for QGP signatures in ultraperipheral PbPb collisions

Ultraperipheral collisions of relativistic heavy ion beams lead to a diverse set of photon-nucleus (photonuclear) interactions. The measurements of particles and their interaction produced in photonuclear reactions can shed light on the QCD dynamics of these novel, extremely asymmetric colliding systems, with energies between those available at RHIC and the LHC. Previous studies by ATLAS indicate significant elliptic and triangular flow coefficients in these events [1]. Thus, it is imperative to check these events for other potential QGP signatures including radial flow, strangeness enhancement, and enhanced baryon/meson production. This proceeding presents the measurement of charged hadron yields in photonuclear collisions using 5.02 TeV Pb+Pb data collected in 2018 by ATLAS, with a dedicated photo-nuclear event trigger. The charged hadron yields are presented as a function of pseudorapidity and transverse momentum in different categories of event multiplicity. The results are compared with 5.02 TeV p+Pb data collected in 2016 by ATLAS, at the same event multiplicities. The results are also compared with calculations from DPMJET and hydrodynamic-based models. These comparisons enable detailed characterizations of photonuclear collision properties, including the photon energy distribution, and whether small QGP droplets may be formed.

CoTree: A Side-Channel Collision Tool to Push the Limits of Conquerable Space

By introducing collision information into divide-and-conquer distinguishers, the existing collision-optimized side-channel attacks transform the given candidate space into a significantly smaller collision space, thus achieving more efficient key recovery. However, the candidates of the first several sub-keys shared by collision chains are still repeatedly detected, which happens very frequently and brings huge computational overhead. To alleviate this, we propose a highly-efficient collision-optimized attack named Collision Tree (CoTree). This collision detection tool exploits tree structure to store the chains created from the same sub-chain on the same branch, thus significantly reducing the storage requirements. It then benefits from the properties of both tree and collisions, and exploits a top-down tree building procedure and traverses each node only once when detecting their collisions with a candidate of the sub-key currently under consideration. Finally, unlike the traditional top-down node removal, CoTree launches a bottom-up branch removal procedure to remove the chains unsatisfying the collision conditions from the tree after traversing all the considered candidates of this sub-key, thus avoiding the traversal of the branches satisfying the collision condition. These strategies make our CoTree significantly alleviate the repetitive collision detection, and our experiments verify that it significantly outperforms the existing works.

Infinite collision property for the three-dimensional uniform spanning tree

Let [Formula: see text] be the three-dimensional uniform spanning tree, whose probability law is denoted by [Formula: see text]. For [Formula: see text]-a.s. realization of [Formula: see text], the recurrence of the simple random walk on [Formula: see text] is proved in Benjamini et al. (2001) [I. Benjamini, R. Lyons, Y. Peres and O. Schramm, Uniform spanning forests, Ann. Probab. 29(1) (2001) 1–65] and it is also demonstrated in Hutchcroft and Peres (2015) [T. Hutchcroft and Y. Peres, Collisions of random walks in reversible random graphs, Electron. Commun. Probab. 20(63) (2015) 1–6] that two independent simple random walks on [Formula: see text] collide infinitely often. In this paper, we will give a quantitative estimate on the number of collisions of two independent simple random walks on [Formula: see text], which provides another proof of the infinite collision property of [Formula: see text].

The coupled modified Yajima–Oikawa system: Model derivation and soliton solutions

In this paper, we consider a coupled modified Yajima–Oikawa (YO) system which describes the nonlinear resonant interaction between one long wave (LW) and two short waves (SWs). It is shown that this coupled system can be derived from a three-component modified nonlinear Schrödinger equations through asymptotic reductions. Furthermore, the bright, dark multi-soliton and multi-breather solutions in terms of determinants are obtained respectively by virtue of the bilinear Kadomtsev–Petviashvili-hierarchy reduction technique. The detailed analysis of dynamical properties for one- and two-solitons and breathers is performed, which show the interesting collision properties for the bright and dark solitons. Particularly, differing from the modified YO system with the single SW component, two bright solitons can undergo inelastic collisions and two dark solitons can generate the bound state in the coupled modified YO system. Finally, general bright, dark multi-soliton and multi-breather solutions are presented for the multi-component modified YO system with multi short waves.

Interaction Solutions of the (2+1)-Dimensional Sawada-Kotera Equation

The N-soliton solution of the (2+1)-dimensional Sawada-Kotera equation is given by using the Hirota bilinear method, and then, the conjugate parameter method and the long-wave limit method are used to get the breather solution and the lump solution, as well as the interaction solution of the elastic collision properties between them. In addition, according to the expression of the lump-type soliton solution and the striped soliton solution, the completely inelastic collision, rebound, absorption, splitting, and other particle characteristics of the two solitons in the interaction process are directly studied with the simulation method, which reveals the laws of physics reflected behind the phenomenon.

Properties of synchronous collisions of solitons in the Korteweg–de Vries equation

Synchronous collisions of solitons of the Korteweg–de Vries equation are considered as a representative example of the interaction of a large number of solitons in a soliton gas. Statistical properties of the soliton field are examined for a model distribution of soliton amplitudes according to a power law. N-soliton solutions (N≤50) are constructed with the help of a numerical procedure using the Darboux transformation and 100-digits arithmetic. It is shown that there exist qualitatively different patterns of evolving multisoliton solutions depending on the amplitude distribution. Collisions of a large number of solitons lead to the decrease of values of statistical moments (the orders from 3 to 7 have been considered). The statistical moments are shown to exhibit long intervals of quasi-stationary behavior in the case of a sufficiently large number of interacting solitons with close amplitudes. These intervals can be characterized by the maximum value of the soliton gas density and by “smoothing” of the wave fields in integral sense. The analytical estimates describing these degenerate states of interacting solitons are obtained.

Some anomalous exact solutions for the four-component coupled nonlinear Schrödinger equations on complex wave backgrounds

The coupled nonlinear Schrödinger (CNLS) equations are the important models for the study of the multicomponent Bose-Einstein condensates (BECs). In this paper, we study the four-components CNLS equations via Darboux transformation and obtain the N-soliton solutions with zero seed and non-zero seed solutions(q_i=0 or q_i=e^{-2it}). The 1-soliton solution and 2-soliton solution are calculated on complex wave backgrounds, the dark-bright-bright-bright soliton solutions and dark-dark-bright-bright soliton solutions are constructed. We can obtain a new class of dark-bright-bright-bright soliton solutions, which admit one-valley dark soliton in component q_1 and triple-hump bright solitons in the other three components. The collision properties between dark-dark-bright-bright solitons are considered, and the vector solitons are expected to be much more abundant than those of previously reported vector soliton collisions.

Phase characters of optical dark solitons with third-order dispersion and delayed nonlinear response.

Dark soliton is usually seen as one of the simplest topological solitons, due to phase shift across its intensity dip. We investigate phase characters of single-valley dark soliton (SVDS) and double-valley dark soliton (DVDS) in a single-mode optical fiber with third-order dispersion and delayed nonlinear response. Notably, two different phase shifts can produce an SVDS with the same velocity under some conditions, which is not admitted for a dark soliton with only the second-order dispersion and self-phase modulation, whose phase shift and velocity is a one-to-one match. This phase property of SVDS can be used to explain the generation of previously reported DVDS in Hirota equationand make DVDSs show two types of phase profiles. Moreover, the different topological vector potentials underlying the distinct phase profiles have been uncovered. We further explore the collision properties of the DVDSs by analyzing their topological phases. Strikingly, the inelastic collision can lead to the conversion between the two types of phase profiles for DVDS. The results reveal that inelastic or elastic collision can be judged by analyzing virtual topological magnetic fields.

Investigation of ion collision effect on electrostatic sheath formation in weakly ionized and weakly collisional plasma

The effects of ion collisions on plasma–sheath formation are investigated experimentally for a low-density and low-pressure discharge. The space potential and ion velocity distribution measurements at high spatial resolution show that the ion collision properties observed in the presheath are maintained in the plasma–sheath transition region. The potential drop in the transition region indicates the existence of ionization as an effect of ion collisions in the transition region owing to the non-negligible density of the electrons penetrating the sheath. Based on comparisons between the space potential measurements and Riemann’s presheath–sheath transition solution, the ion collision length λ i was determined as a key parameter in the presheath and transition region. And it represents that the thermal properties of ions and neutral gases affects space potential by the charge exchange and ionization collisions. The existence of the ion collision effect in the transition region suggests possible influence on the incident conditions of ions and electrons near the sheath edge. Consequently, the energy distributions of ions and electrons incident on the material surface facing the sheath are sensitive to the collisionality and operating conditions.

Super rogue waves: Collision of rogue waves in Bose-Einstein condensate.

An important and incompletely answered question is whether a high-order rogue wave (RW) can be excited by the collision of first-order RWs, especially for its generation and propagation mechanisms. In this paper, the evolution properties of collisions between RWs are studied numerically for two-component coupled Bose-Einstein condensates. We find that whether a second-order RW can be successfully excited strongly depends on the location and time of the first-order RWs encountered. Only when the highest peaks of two RWs meet at the same position at the same time, can the standard second-order RW be triggered and its structure is in good agreement with the exact solution. Further, we demonstrate that such results are also applicable to the collision of subordinate RWs. This paper not only reveals the collision properties of RWs, but also provides a feasible scheme to generate higher-order RWs for experimental realization.

CFD-DEM-based Numerical Simulation of Erosion Characteristic of Multistage Pressure Relief String Regulating Valve

The regulating valve applied in coal liquefaction systems becomes seriously worn and its service life decreases because of a significant difference in pressure and solid–liquid flow. This study proposes a wear-resistant multistage pressure relief string-regulating valve, and examines the characteristics of depressurization of flow and the erosion of its throttle element by using computational fluid dynamics (CFD) simulations and the discrete element method (DEM) combined with the E/CRC (Erosion/Corrosion Center) erosion model of the WC-Co coating. The influence of different sizes of the opening of the valve and varying differences in pressure on the characteristics of erosion is analyzed. Moreover, properties of collisions between particles (such as the particle impact velocity and mass per second) are used to represent and analyze the characteristics of erosion. The numerical results show that the cylinder, flat, and bevel of the valve are at high risk of erosion. The characteristics of erosion of the multistage pressure relief string-regulating valve studied in this paper can provide a reference for optimizing methods of erosion prevention.

Vector multi-pole solutions in the [formula omitted]-coupled Hirota equation

In this paper, we study the vector multi-pole (MP) solutions of the r-coupled Hirota equation (RCHE). First of all, based on the Darboux transformation and the N-soliton solution, we derive the explicit formulas of the arbitrary-order vector MP solutions. Then, through the balance between exponential and algebraic terms, we give all asymptotic solitons in the vector double- and triple-pole solutions via an asymptotic analysis method. Furthermore, we analyze the soliton interactions in vector MP solutions. By comparing with the scalar Hirota equation, we find that the RCHE has richer collision properties: the position shift of each component soliton grows logarithmically with r, the asymptotic solitons have the same shape in each component, and their amplitudes are proportional among the components.

Initiation of Alfvénic turbulence by Alfvén wave collisions: A numerical study

In the framework of compressional magnetohydrodynamics (MHD), we numerically studied the commonly accepted presumption that the Alfvénic turbulence is generated by the collisions between counter-propagating Alfvén waves (AWs). In the conditions typical for the low-beta solar corona and inner solar wind, we launched two counter-propagating AWs in the three-dimensional simulation box and analyzed polarization and spectral properties of perturbations generated before and after AW collisions. The observed post-collisional perturbations have different polarizations and smaller cross-field scales than the original waves, which supports theoretical scenarios with direct turbulent cascades. However, contrary to theoretical expectations, the spectral transport is strongly suppressed at the scales satisfying the classic critical balance of incompressional MHD. Instead, a modified critical balance can be established by colliding AWs with significantly shorter perpendicular scales. We discuss consequences of these effects for the turbulence dynamics and turbulent heating of compressional plasmas. In particular, solar coronal loops can be heated by the strong turbulent cascade if the characteristic widths of the loop substructures are more than ten times smaller than the loop width. The revealed new properties of AW collisions have to be incorporated in the theoretical models of AW turbulence and related applications.