Insight into collision zone dynamics from topography: numerical modelling results and observations
A. D. Bottrill; J. van Hunen; M. B. Allen
2012-01-01
Dynamic models of subduction and continental collision are used to predict dynamic topography changes on the overriding plate. The modelling results show a distinct evolution of topography on the overriding plate, during subduction, continental collision and slab break-off. A prominent topographic feature is a temporary (few Myrs) deepening in the area of the back arc-basin after initial collision. This collisional mantle dynamic basin (CMDB) is caused by slab steepening drawing material away...
Molecular dynamics and binary collisions modeling of the primary damage state of collision cascades
International Nuclear Information System (INIS)
Heinisch, H.L.; Singh, B.N.
1992-01-01
The objective of this work is to determine the spectral dependence of defect production and microstructure evolution for the development of fission-fusion correlations. Quantitative information on defect production in cascades in copper obtained from recent molecular dynamics (MD) simulations is compared to defect production information determined earlier with a model based on the binary collision approximation (BCA). The total numbers of residual defects, the fractions of them that are mobile, and the sizes of immobile clusters compare favorably, especially when the termination conditions of the two simulations are taken into account. A strategy is laid out for integrating the details of the cascade quenching phase determined by MD into a BCA-based model that is practical for simulating much higher energies and longer times than MD alone can achieve. The extraction of collisional phase information from MD simulations and the correspondence of MD and BCA versions of the collisional phase demonstrated at low energy
Molecular dynamics and binary collision modeling of the primary damage state of collision cascades
DEFF Research Database (Denmark)
Heinisch, H.L.; Singh, B.N.
1992-01-01
Quantitative information on defect production in cascades in copper obtained from recent molecular dynamics simulations is compared to defect production information determined earlier with a model based on the binary collision approximation (BCA). The total numbers of residual defects......, the fractions of them that are mobile, and the sizes of immobile clusters compare favorably, especially when the termination conditions of the two simulations are taken into account. A strategy is laid out for integrating the details of the cascade quenching phase determined by MD into a BCA-based model...... that is practical for simulating much higher energies and longer times than MD alone can achieve. The extraction of collisional phase information from MD simulations and the correspondence of MD and BCA versions of the collisional phase is demonstrated at low energy....
Energy Technology Data Exchange (ETDEWEB)
Jung, Byung Jin; Koo, Ja Choon; Choi, Hyouk Ryeol; Moon, Hyung Pil [Sungkyunkwan University, Suwon (Korea, Republic of)
2014-11-15
This paper presents the development and experimental evaluation of a collision detection method for robotic manipulators sharing a workspace with humans. Fast and robust collision detection is important for guaranteeing safety and preventing false alarms. The main cause of a false alarm is modeling error. We use the characteristic of the maximum frequency boundary of the manipulator's dynamic model. The tendency of the frequency boundary's location in the frequency domain is applied to the collision detection algorithm using a band pass filter (band designed disturbance observer, BdDOB) with changing frequency windows. Thanks to the band pass filter, which considers the frequency boundary of the dynamic model, our collision detection algorithm can extract the collision caused by the disturbance from the mixed estimation signal. As a result, the collision was successfully detected under the usage conditions of faulty sensors and uncertain model data. The experimental result of a collision between a 7-DOF serial manipulator and a human body is reported.
A collision dynamics model of a multi-level train
2006-11-05
In train collisions, multi-level rail passenger vehicles can deform in modes that are different from the behavior of single level cars. The deformation in single level cars usually occurs at the front end during a collision. In one particular inciden...
Border Collision Bifurcations in a Generalized Model of Population Dynamics
Directory of Open Access Journals (Sweden)
Lilia M. Ladino
2016-01-01
Full Text Available We analyze the dynamics of a generalized discrete time population model of a two-stage species with recruitment and capture. This generalization, which is inspired by other approaches and real data that one can find in literature, consists in considering no restriction for the value of the two key parameters appearing in the model, that is, the natural death rate and the mortality rate due to fishing activity. In the more general case the feasibility of the system has been preserved by posing opportune formulas for the piecewise map defining the model. The resulting two-dimensional nonlinear map is not smooth, though continuous, as its definition changes as any border is crossed in the phase plane. Hence, techniques from the mathematical theory of piecewise smooth dynamical systems must be applied to show that, due to the existence of borders, abrupt changes in the dynamic behavior of population sizes and multistability emerge. The main novelty of the present contribution with respect to the previous ones is that, while using real data, richer dynamics are produced, such as fluctuations and multistability. Such new evidences are of great interest in biology since new strategies to preserve the survival of the species can be suggested.
Collision dynamics of the coherent Jaynes-Cummings model
International Nuclear Information System (INIS)
Rabello, M.L.C.; Toledo Piza, A.F.R. de.
1985-01-01
The anatomy of the dynamics of quantum correlations of two interacting subsystems described by the Jaynes-Cummings Model is studied, making use of a natural states decomposition, following an old suggestion by Schroedinger. The amplitude modulation of the fast Rabi oscillations which occur for a strong, coherent initial field is obtained from the spin intrinsic depolarization resulting from corrections to the mean field approximation. (Author) [pt
Collision dynamics of the coherent Jaynes-Cumminings model
International Nuclear Information System (INIS)
Rabello, M.L.C.; Toledo Piza, A.F.R. de
1984-01-01
The anatomy of the dynamics of quantum correlations of two interacting subsystems described by the Jaynes-Cummings Model is studied, making use of a natural states decomposition, following an old suggestion by Schroedinger. The amplitude modulation of the fast Rabi oscillations which occur for a strong, coherent initial field is obtained from the spin intrinsic depolarization resulting from corrections to the mean field approximation. (Author) [pt
Insight into collision zone dynamics from topography: numerical modelling results and observations
Directory of Open Access Journals (Sweden)
A. D. Bottrill
2012-11-01
Full Text Available Dynamic models of subduction and continental collision are used to predict dynamic topography changes on the overriding plate. The modelling results show a distinct evolution of topography on the overriding plate, during subduction, continental collision and slab break-off. A prominent topographic feature is a temporary (few Myrs basin on the overriding plate after initial collision. This "collisional mantle dynamic basin" (CMDB is caused by slab steepening drawing, material away from the base of the overriding plate. Also, during this initial collision phase, surface uplift is predicted on the overriding plate between the suture zone and the CMDB, due to the subduction of buoyant continental material and its isostatic compensation. After slab detachment, redistribution of stresses and underplating of the overriding plate cause the uplift to spread further into the overriding plate. This topographic evolution fits the stratigraphy found on the overriding plate of the Arabia-Eurasia collision zone in Iran and south east Turkey. The sedimentary record from the overriding plate contains Upper Oligocene-Lower Miocene marine carbonates deposited between terrestrial clastic sedimentary rocks, in units such as the Qom Formation and its lateral equivalents. This stratigraphy shows that during the Late Oligocene–Early Miocene the surface of the overriding plate sank below sea level before rising back above sea level, without major compressional deformation recorded in the same area. Our modelled topography changes fit well with this observed uplift and subsidence.
Fluid dynamics of moving fish in a two-dimensional multiparticle collision dynamics model
Reid, Daniel A. P.; Hildenbrandt, H.; Padding, J. T.; Hemelrijk, C. K.
2012-02-01
The fluid dynamics of animal locomotion, such as that of an undulating fish, are of great interest to both biologists and engineers. However, experimentally studying these fluid dynamics is difficult and time consuming. Model studies can be of great help because of their simpler and more detailed analysis. Their insights may guide empirical work. Particularly the recently introduced multiparticle collision dynamics method may be suitable for the study of moving organisms because it is computationally fast, simple to implement, and has a continuous representation of space. As regards the study of hydrodynamics of moving organisms, the method has only been applied at low Reynolds numbers (below 120) for soft, permeable bodies, and static fishlike shapes. In the present paper we use it to study the hydrodynamics of an undulating fish at Reynolds numbers 1100-1500, after confirming its performance for a moving insect wing at Reynolds number 75. We measure (1) drag, thrust, and lift forces, (2) swimming efficiency and spatial structure of the wake, and (3) distribution of forces along the fish body. We confirm the resemblance between the simulated undulating fish and empirical data. In contrast to theoretical predictions, our model shows that for steadily undulating fish, thrust is produced by the rear 2/3 of the body and that the slip ratio U/V (with U the forward swimming speed and V the rearward speed of the body wave) correlates negatively (instead of positively) with the actual Froude efficiency of swimming. Besides, we show that the common practice of modeling individuals while constraining their sideways acceleration causes them to resemble unconstrained fish with a higher tailbeat frequency.
Composite quantum collision models
Lorenzo, Salvatore; Ciccarello, Francesco; Palma, G. Massimo
2017-09-01
A collision model (CM) is a framework to describe open quantum dynamics. In its memoryless version, it models the reservoir R as consisting of a large collection of elementary ancillas: the dynamics of the open system S results from successive collisions of S with the ancillas of R . Here, we present a general formulation of memoryless composite CMs, where S is partitioned into the very open system under study S coupled to one or more auxiliary systems {Si} . Their composite dynamics occurs through internal S -{Si} collisions interspersed with external ones involving {Si} and the reservoir R . We show that important known instances of quantum non-Markovian dynamics of S —such as the emission of an atom into a reservoir featuring a Lorentzian, or multi-Lorentzian, spectral density or a qubit subject to random telegraph noise—can be mapped on to such memoryless composite CMs.
SMACK: A New Algorithm for Modeling Collisions and Dynamics of Planetesimals in Debris Disks
Nesvold, Erika Rose; Kuchner, Marc J.; Rein, Hanno; Pan, Margaret
2013-01-01
We present the Superparticle Model/Algorithm for Collisions in Kuiper belts and debris disks (SMACK), a new method for simultaneously modeling, in 3-D, the collisional and dynamical evolution of planetesimals in a debris disk with planets. SMACK can simulate azimuthal asymmetries and how these asymmetries evolve over time. We show that SMACK is stable to numerical viscosity and numerical heating over 10(exp 7) yr, and that it can reproduce analytic models of disk evolution. We use SMACK to model the evolution of a debris ring containing a planet on an eccentric orbit. Differential precession creates a spiral structure as the ring evolves, but collisions subsequently break up the spiral, leaving a narrower eccentric ring.
Energy Technology Data Exchange (ETDEWEB)
Abe, M; Morisawa, M [Musashi Institute of Technology, Tokyo (Japan); Sato, T [Keio University, Tokyo (Japan); Kobayashi, K [Molex-Japan Co. Ltd., Tokyo (Japan)
1997-10-01
The past study of safety at vehicle collision pays attention to phenomena within the short time from starting collision, and the behavior of rollover is studied separating from that at collision. Most simulations of traffic accident are two-dimensional simulations. Therefore, it is indispensable for vehicle design to the analyze three-dimensional and continuous behavior from crash till stopping. Accordingly, in this study, the three-dimensional behavior of two vehicles at collision was simulated by computer using dynamic models. Then, by comparison of the calculated results with real vehicles` collision test data, it was confirmed that dynamic model of this study was reliable. 10 refs., 6 figs., 3 tabs.
2000-11-01
In an effort to study occupant survivability in train collisions, analyses and tests were conducted to understand and improve the crashworthiness of rail vehicles. A collision dynamics model was developed in order to estimate the rigid body motion of...
Modelling the many-body dynamics of heavy ion collisions. Present status and future perspective
International Nuclear Information System (INIS)
Hartnack, Ch.; Puri, R.K.; Aichelin, J.; Konopka, J.; Bass, S.A.; Stoecker, H.; Greiner, W.
1996-01-01
Basic problems of the semiclassical microscopic modelling of strongly interacting systems are discussed within the framework of Quantum Molecular Dynamics (QMD). It is shown that the same predictions can be obtained with several - numerically completely different and independently written -programs as far as the same model parameters are employed and the same basic approximations are made. Some of the physical results, however, depend also on rather technical parameters like the preparation of the initial configuration in phase space. This crucial problem is connected with the description of the ground state of single nuclei, which differs among the various approaches. An outlook to an improved molecular dynamics scheme for heavy ion collisions is given. (author)
Modelling the many-body dynamics of heavy ion collisions. Present status and future perspective
Energy Technology Data Exchange (ETDEWEB)
Hartnack, Ch.; Puri, R.K.; Aichelin, J. [Centre National de la Recherche Scientifique, 44 - Nantes (France). Lab. de Physique Subatomique et des Technologies Associees; Konopka, J.; Bass, S.A.; Stoecker, H.; Greiner, W. [Johann Wolfgang Goethe Univ., Frankfurt am Main (Germany). Inst. fuer Theoretische Physik
1996-12-31
Basic problems of the semiclassical microscopic modelling of strongly interacting systems are discussed within the framework of Quantum Molecular Dynamics (QMD). It is shown that the same predictions can be obtained with several - numerically completely different and independently written -programs as far as the same model parameters are employed and the same basic approximations are made. Some of the physical results, however, depend also on rather technical parameters like the preparation of the initial configuration in phase space. This crucial problem is connected with the description of the ground state of single nuclei, which differs among the various approaches. An outlook to an improved molecular dynamics scheme for heavy ion collisions is given. (author). 86 refs.
Dynamical initial-state model for relativistic heavy-ion collisions
Shen, Chun; Schenke, Björn
2018-02-01
We present a fully three-dimensional model providing initial conditions for energy and net-baryon density distributions in heavy-ion collisions at arbitrary collision energy. The model includes the dynamical deceleration of participating nucleons or valence quarks, depending on the implementation. The duration of the deceleration continues until the string spanned between colliding participants is assumed to thermalize, which is either after a fixed proper time, or a fluctuating time depending on sampled final rapidities. Energy is deposited in space time along the string, which in general will span a range of space-time rapidities and proper times. We study various observables obtained directly from the initial-state model, including net-baryon rapidity distributions, two-particle rapidity correlations, as well as the rapidity decorrelation of the transverse geometry. Their dependence on the model implementation and parameter values is investigated. We also present the implementation of the model with 3+1-dimensional hydrodynamics, which involves the addition of source terms that deposit energy and net-baryon densities produced by the initial-state model at proper times greater than the initial time for the hydrodynamic simulation.
Fluid dynamics of moving fish in a two-dimensional multiparticle collision dynamics model
Reid, Daniel A. P.; Hildenbrandt, H.; Hemelrijk, C. K.; Padding, J.T.
2012-01-01
The fluid dynamics of animal locomotion, such as that of an undulating fish, are of great interest to both biologists and engineers. However, experimentally studying these fluid dynamics is difficult and time consuming. Model studies can be of great help because of their simpler and more detailed
Modeling the locomotion of the African trypanosome using multi-particle collision dynamics
International Nuclear Information System (INIS)
Babu, Sujin B; Stark, Holger
2012-01-01
The African trypanosome is a single flagellated micro-organism that causes the deadly sleeping sickness in humans and animals. We study the locomotion of a model trypanosome by modeling the spindle-shaped cell body using an elastic network of vertices with additional bending rigidity. The flagellum firmly attached to the model cell body is either straight or helical. A bending wave propagates along the flagellum and pushes the trypanosome forward in its viscous environment, which we simulate with the method of multi-particle collision dynamics. The relaxation dynamics of the model cell body due to a static bending wave reveals the sperm number from elastohydrodynamics as the relevant parameter. Characteristic cell body conformations for the helically attached flagellum resemble experimental observations. We show that the swimming velocity scales as the root of the angular frequency of the bending wave reminiscent of predictions for an actuated slender rod attached to a large viscous load. The swimming velocity for one geometry collapses on a single master curve when plotted versus the sperm number. The helically attached flagellum leads to a helical swimming path and a rotation of the model trypanosome about its long axis as observed in experiments. The simulated swimming velocity agrees with the experimental value. (paper)
From many body wee partons dynamics to perfect fluid: a standard model for heavy ion collisions
Energy Technology Data Exchange (ETDEWEB)
Venugopalan, R.
2010-07-22
We discuss a standard model of heavy ion collisions that has emerged both from experimental results of the RHIC program and associated theoretical developments. We comment briefly on the impact of early results of the LHC program on this picture. We consider how this standard model of heavy ion collisions could be solidified or falsified in future experiments at RHIC, the LHC and a future Electro-Ion Collider.
International Nuclear Information System (INIS)
Santos, Ivan; Marques, Luis A.; Pelaz, Lourdes; Lopez, Pedro
2007-01-01
In this paper, we present classical molecular dynamics results about the formation of amorphous pockets in silicon for energy transfers below the displacement threshold. While in binary collision simulations ions with different masses generate the same number of Frenkel pairs for the same deposited nuclear energy, in molecular dynamics simulations the amount of damage and its complexity increase with ion mass. We demonstrate that low-energy transfers to target atoms are able to generate complex damage structures. We have determined the conditions that have to be fulfilled to produce amorphous pockets, showing that the order-disorder transition depends on the particular competition between melting and heat diffusion processes. We have incorporated these molecular dynamics results in an improved binary collision model that is able to provide a good description of damage with a very low computational cost
Development of FB-MultiPier dynamic vessel-collision analysis models, phase 2 : [summary].
2014-07-01
When collisions between large vessels and bridge : supports occur, they can result in significant : damage to bridge and vessel. These collisions : are extremely hazardous, often taking lives on : the vessel and the bridge. Direct costs of repair : a...
DEFF Research Database (Denmark)
Granados, Alba; Brunskog, Jonas; Misztal, M. K.
2015-01-01
When vocal folds vibrate at normal speaking frequencies, collisions occurs. The numerics and formulations behind a position-based continuum model of contact is an active field of research in the contact mechanics community. In this paper, a frictionless three-dimensional finite element model...
Fluid dynamics of moving fish in a two-dimensional multiparticle collision dynamics model in 2D
Reid, D.A.P.; Hildenbrandt, H.; Padding, J.T.; Hemelrijk, C.K.
2012-01-01
The fluid dynamics of animal locomotion, such as that of an undulating fish, are of great interest to both biologists and engineers. However, experimentally studying these fluid dynamics is difficult and time consuming. Model studies can be of great help because of their simpler and more detailed
Stability of nuclei in peripheral collisions in the JAERI quantum molecular dynamics model
International Nuclear Information System (INIS)
Mancusi, Davide; Niita, Koji; Maruyama, Tomoyuki; Sihver, Lembit
2009-01-01
The JAERI quantum molecular dynamics (JQMD) model has been successfully used for a long time now to describe many different aspects of nuclear reactions in a unified way. In some cases, however, the JQMD model cannot produce consistent results: First, it lacks a fully relativistically covariant approach to the problem of molecular dynamics; second, the quantum-mechanical ground state of nuclei cannot be faithfully reproduced in a semiclassical framework. Therefore, we introduce R-JQMD, an improved version of JQMD that also features a new ground-state initialization algorithm for nuclei. We compare the structure of the two codes and discuss whether R-JQMD can be adjusted to improve JQMD's agreement with measured heavy-ion fragmentation cross sections
Collision avoidance for multiple Lagrangian dynamical systems with gyroscopic forces
Directory of Open Access Journals (Sweden)
Lorenzo Sabattini
2017-01-01
Full Text Available This article introduces a novel methodology for dealing with collision avoidance for groups of mobile robots. In particular, full dynamics are considered, since each robot is modeled as a Lagrangian dynamical system moving in a three-dimensional environment. Gyroscopic forces are utilized for defining the collision avoidance control strategy: This kind of forces leads to avoiding collisions, without interfering with the convergence properties of the multi-robot system’s desired control law. Collision avoidance introduces, in fact, a perturbation on the nominal behavior of the system: We define a method for choosing the direction of the gyroscopic force in an optimal manner, in such a way that perturbation is minimized. Collision avoidance and convergence properties are analytically demonstrated, and simulation results are provided for validation purpose.
Outer Dynamics of Ship Collisions
DEFF Research Database (Denmark)
Pedersen, Preben Terndrup
1996-01-01
The purpose is to present analysis procedures for the motion of ships during ship-ship collisions and for ship collisions with offshore structures. The aim is to estimate that part of the lost kinetic energy which will have to be absorbed by rupture and plastic damage of the colliding structures....
Outer Dynamics of Ship Collisions
DEFF Research Database (Denmark)
Pedersen, Preben Terndrup
1996-01-01
The purpose of these notes is to present analysis procedures for the motion of ships during ship-ship collisions and for ship collisons with offshore structures. The aim is to estimate that part of the lost kinetic energy which will have to be absorbed by rupture and plastic damage of the colliding...
Chirality in molecular collision dynamics
Lombardi, Andrea; Palazzetti, Federico
2018-02-01
Chirality is a phenomenon that permeates the natural world, with implications for atomic and molecular physics, for fundamental forces and for the mechanisms at the origin of the early evolution of life and biomolecular homochirality. The manifestations of chirality in chemistry and biochemistry are numerous, the striking ones being chiral recognition and asymmetric synthesis with important applications in molecular sciences and in industrial and pharmaceutical chemistry. Chiral discrimination phenomena, due to the existence of two enantiomeric forms, very well known in the case of interaction with light, but still nearly disregarded in molecular collision studies. Here we review some ideas and recent advances about the role of chirality in molecular collisions, designing and illustrating molecular beam experiments for the demonstration of chiral effects and suggesting a scenario for a stereo-directional origin of chiral selection.
The 2011 Dynamics of Molecular Collisions Conference
Energy Technology Data Exchange (ETDEWEB)
Nesbitt, David J. [JILA, NIST
2011-07-11
The Dynamics of Molecular Collisions Conference focuses on all aspects of molecular collisions--experimental & theoretical studies of elastic, inelastic, & reactive encounters involving atoms, molecules, ions, clusters, & surfaces--as well as half collisions--photodissociation, photo-induced reaction, & photodesorption. The scientific program for the meeting in 2011 included exciting advances in both the core & multidisciplinary forefronts of the study of molecular collision processes. Following the format of the 2009 meeting, we also invited sessions in special topics that involve interfacial dynamics, novel emerging spectroscopies, chemical dynamics in atmospheric, combustion & interstellar environments, as well as a session devoted to theoretical & experimental advances in ultracold molecular samples. Researchers working inside & outside the traditional core topics of the meeting are encouraged to join the conference. We invite contributions of work that seeks understanding of how inter & intra-molecular forces determine the dynamics of the phenomena under study. In addition to invited oral sessions & contributed poster sessions, the scientific program included a formal session consisting of five contributed talks selected from the submitted poster abstracts. The DMC has distinguished itself by having the Herschbach Medal Symposium as part of the meeting format. This tradition of the Herschbach Medal was first started in the 2007 meeting chaired by David Chandler, based on a generous donation of funds & artwork design by Professor Dudley Herschbach himself. There are two such awards made, one for experimental & one for theoretical contributions to the field of Molecular Collision Dynamics, broadly defined. The symposium is always held on the last night of the meeting & has the awardees are asked to deliver an invited lecture on their work. The 2011 Herschbach Medal was dedicated to the contributions of two long standing leaders in Chemical Physics, Professor
Ghatage, Dhairyasheel; Chatterji, Apratim
2013-10-01
We introduce a method to obtain steady-state uniaxial exponential-stretching flow of a fluid (akin to extensional flow) in the incompressible limit, which enables us to study the response of suspended macromolecules to the flow by computer simulations. The flow field in this flow is defined by v(x) = εx, where v(x) is the velocity of the fluid and ε is the stretch flow gradient. To eliminate the effect of confining boundaries, we produce the flow in a channel of uniform square cross section with periodic boundary conditions in directions perpendicular to the flow, but simultaneously maintain uniform density of fluid along the length of the tube. In experiments a perfect elongational flow is obtained only along the axis of symmetry in a four-roll geometry or a filament-stretching rheometer. We can reproduce flow conditions very similar to extensional flow near the axis of symmetry by exponential-stretching flow; we do this by adding the right amounts of fluid along the length of the flow in our simulations. The fluid particles added along the length of the tube are the same fluid particles which exit the channel due to the flow; thus mass conservation is maintained in our model by default. We also suggest a scheme for possible realization of exponential-stretching flow in experiments. To establish our method as a useful tool to study various soft matter systems in extensional flow, we embed (i) spherical colloids with excluded volume interactions (modeled by the Weeks-Chandler potential) as well as (ii) a bead-spring model of star polymers in the fluid to study their responses to the exponential-stretched flow and show that the responses of macromolecules in the two flows are very similar. We demonstrate that the variation of number density of the suspended colloids along the direction of flow is in tune with our expectations. We also conclude from our study of the deformation of star polymers with different numbers of arms f that the critical flow gradient ε
The Concept of Collision-Free Motion Planning Using a Dynamic Collision Map
Directory of Open Access Journals (Sweden)
Keum-Bae Cho
2014-09-01
Full Text Available In this paper, we address a new method for the collision-free motion planning of a mobile robot in dynamic environments. The motion planner is based on the concept of a conventional collision map (CCM, represented on the L(travel length-T(time plane. We extend the CCM with dynamic information about obstacles, such as linear acceleration and angular velocity, providing useful information for estimating variation in the collision map. We first analyse the effect of the dynamic motion of an obstacle in the collision region. We then define the measure of collision dispersion (MOCD. The dynamic collision map (DCM is generated by drawing the MOCD on the CCM. To evaluate a collision-free motion planner using the DCM, we extend the DCM with MOCD, then draw the unreachable region and deadlocked regions. Finally, we construct a collision-free motion planner using the information from the extended DCM.
Modeling collisions in circumstellar debris disks
Nesvold, Erika
2015-10-01
Observations of resolved debris disks show a spectacular variety of features and asymmetries, including inner cavities and gaps, inclined secondary disks or warps, and eccentric, sharp-edged rings. Embedded exoplanets could create many of these features via gravitational perturbations, which sculpt the disk directly and by generating planetesimal collisions. In this thesis, I present the Superparticle Model/Algorithm for Collisions in Kuiper belts and debris disks (SMACK), a new method for simultaneously modeling, in 3-D, the collisional and dynamical evolution of planetesimals in a debris disk with planets. SMACK can simulate azimuthal asymmetries and how these asymmetries evolve over time. I show that SMACK is stable to numerical viscosity and numerical heating over 107 yr, and that it can reproduce analytic models of disk evolution. As an example of the algorithm's capabilities, I use SMACK to model the evolution of a debris ring containing a planet on an eccentric orbit and demonstrate that differential precession creates a spiral structure as the ring evolves, but collisions subsequently break up the spiral, leaving a narrower eccentric ring. To demonstrate SMACK's utility in studying debris disk physics, I apply SMACK to simulate a planet on a circular orbit near a ring of planetesimals that are experiencing destructive collisions. Previous simulations of a planet opening a gap in a collisionless debris disk have found that the width of the gap scales as the planet mass to the 2/7th power (alpha = 2/7). I find that gap sizes in a collisional disk still obey a power law scaling with planet mass, but that the index alpha of the power law depends on the age of the system t relative to the collisional timescale t coll of the disk by alpha = 0.32(t/ tcoll)-0.04, with inferred planet masses up to five times smaller than those predicted by the classical gap law. The increased gap sizes likely stem from the interaction between collisions and the mean motion
The dynamics of milk droplet-droplet collisions
Finotello, Giulia; Kooiman, Roeland F.; Padding, Johan T.; Buist, Kay A.; Jongsma, Alfred; Innings, Fredrik; Kuipers, J. A. M.
2018-01-01
Spray drying is an important industrial process to produce powdered milk, in which concentrated milk is atomized into small droplets and dried with hot gas. The characteristics of the produced milk powder are largely affected by agglomeration, combination of dry and partially dry particles, which in turn depends on the outcome of a collision between droplets. The high total solids (TS) content and the presence of milk proteins cause a relatively high viscosity of the fed milk concentrates, which is expected to largely influence the collision outcomes of drops inside the spray. It is therefore of paramount importance to predict and control the outcomes of binary droplet collisions. Only a few studies report on droplet collisions of high viscous liquids and no work is available on droplet collisions of milk concentrates. The current study therefore aims to obtain insight into the effect of viscosity on the outcome of binary collisions between droplets of milk concentrates. To cover a wide range of viscosity values, three milk concentrates (20, 30 and 46% TS content) are investigated. An experimental set-up is used to generate two colliding droplet streams with consistent droplet size and spacing. A high-speed camera is used to record the trajectories of the droplets. The recordings are processed by Droplet Image Analysis in MATLAB to determine the relative velocities and the impact geometries for each individual collision. The collision outcomes are presented in a regime map dependent on the dimensionless impact parameter and Weber ( We) number. The Ohnesorge ( Oh) number is introduced to describe the effect of viscosity from one liquid to another and is maintained constant for each regime map by using a constant droplet diameter ( d ˜ 700 μ m). In this work, a phenomenological model is proposed to describe the boundaries demarcating the coalescence-separation regimes. The collision dynamics and outcome of milk concentrates are compared with aqueous glycerol
Popa, Vlad; Trecroce, Danielle A; McAllister, Robert G; Konermann, Lars
2016-06-16
Electrospray ionization mass spectrometry (ESI-MS) has become an indispensable technique for examining noncovalent protein complexes. Collision-induced dissociation (CID) of these multiply protonated gaseous ions usually culminates in ejection of a single subunit with a disproportionately large amount of charge. Experiments suggest that this process involves subunit unfolding prior to separation from the residual complex, as well as H(+) migration onto the unravelling chain. Molecular dynamics (MD) simulations are a promising avenue for gaining detailed insights into these CID events. Unfortunately, typical MD algorithms do not allow for mobile protons. Here we address this limitation by implementing a strategy that combines atomistic force fields (such as OPLS/AA and CHARMM36) with a proton hopping algorithm, focusing on the tetrameric complexes transthyretin and streptavidin. Protons are redistributed over all acidic and basic sites in 20 ps intervals, subject to an energy function that reflects electrostatic interactions and proton affinities. Our simulations predict that nativelike conformers at the onset of collisional heating contain multiple salt bridges. Collisional heating initially causes subtle structural changes that lead to a gradual decline of these zwitterionic patterns. Many of the MD runs show gradual unfolding of a single subunit in conjunction with H(+) migration, culminating in subunit separation from the complex. However, there are also instances where two or more chains start to unfold simultaneously, giving rise to charge competition. The scission point where the "winning" subunit separates from the complex can be attained for different degrees of unfolding, giving rise to product ions in various charge states. The simulated product ion distributions are in close agreement with experimental CID data. Proton enrichment in the departing subunit is driven by charge-charge repulsion, but the combination of salt bridge depletion, charge migration
Fermionic molecular dynamics for ground states and collisions of nuclei
International Nuclear Information System (INIS)
Feldmeier, H.; Bieler, K.; Schnack, J.
1994-08-01
The antisymmetric many-body trial state which describes a system of interacting fermions is parametrized in terms of localized wave packets. The equations of motion are derived from the time-dependent quantum variational principle. The resulting Fermionic Molecular Dynamics (FMD) equations include a wide range of semi-quantal to classical physics extending from deformed Hartree-Fock theory to Newtonian molecular dynamics. Conservation laws are discussed in connection with the choice of the trial state. The model is applied to heavy-ion collisions with which its basic features are illustrated. The results show a great variety of phenomena including deeply inelastic collisions, fusion, incomplete fusion, fragmentation, neck emission, promptly emitted nucleons and evaporation. (orig.)
Dynamical evolution of hadronic matter in relativistic collisions
International Nuclear Information System (INIS)
Dean, D.J.; Umar, A.S.; Strayer, M.R.
1993-01-01
We use the (3+1)-dimensional string-parton model to study relativistic collisions of heavy ions at CERN energies. Various inclusive hadronic observables, such as transverse energy, dE T /dη, and rapidity distributions, are calculated and compared with WA80 and NA35 data. We study secondary interactions that occur during the dynamical evolution, and show that these interactions tend to fill the midrapidity region. The dynamical evolution of the energy density of produced mesons and their thermodynamic properties are also studied
Collision models in quantum optics
Ciccarello, Francesco
2017-12-01
Quantum collision models (CMs) provide advantageous case studies for investigating major issues in open quantum systems theory, and especially quantum non-Markovianity. After reviewing their general definition and distinctive features, we illustrate the emergence of a CM in a familiar quantum optics scenario. This task is carried out by highlighting the close connection between the well-known input-output formalism and CMs. Within this quantum optics framework, usual assumptions in the CMs' literature - such as considering a bath of noninteracting yet initially correlated ancillas - have a clear physical origin.
Phase transition dynamics in ultrarelativistic heavy ion collisions
International Nuclear Information System (INIS)
Csernai, L.P.; Zabrodin, E.E.; Moscow State Univ.
1993-01-01
We investigate various problems related to the dynamics of a first-order phase transition from quarkgluon plasma to hadronic matter in ultra-relativistic heavy ion collisions. These include nucleation, growth and fusion of hadronic bubbles in either the Bjorken longitudinal hydrodynamic expansion model or the Cooper-Frye-Schonberg spherical hydrodynamic expansion model. With reasonable input parameters the conversion of one phase into the other is relatively close to the idealized adiabatic Maxwell construction, although one can choose parameters such that the conversion is strongly out of equilibrium. (orig.)
Phase transition dynamics in ultrarelativistic heavy ion collisions
International Nuclear Information System (INIS)
Csernai, L.P.; Kapusta, J.I.; Kluge, Gy.; Hungarian Academy of Sciences, Budapest; Zabrodin, E.E.; Moskovskij Gosudarstvennyj Univ., Moscow
1992-12-01
Various problems were investigated concerning the dynamics of a first-order phase transition from quark-gluon plasma to hadronic matter in ultra-relativistic heavy ion collisions. These include nucleation, growth and fusion of hadronic bubbles in either the Bjorken longitudinal hydrodynamic expansion model or the Cooper-Frye-Schonberg spherical hydrodynamic expansion model. With reasonable input parameters the conversion of one phase into the other is relatively close to the idealized adiabatic Maxwell construction, although one can choose parameters such that the conversion is strongly out of equilibrium. (author) 10 refs.; 7 figs
Models of high energy nuclear collisions
International Nuclear Information System (INIS)
Glendenning, N.K.
1978-06-01
The discussion covers nuclear collisions at relativistic energies including classes of high energy nucleus--nucleus collisions, and the kinetics of a central collision; and the asymptotic hadron spectrum including known and unknown hadrons, the relevance of the spectrum and the means of its study, thermodynamics of hadronic matter, examples of hadronic spectra, the temperature, composition of the initial fireball and its expansion, isoergic expansion with no pre-freezeout radiation, isentropic expansion of the fireball, the quasi-dynamical expansion, and finally antinuclei, hypernuclei, and the quark phase. 28 references
Binary collisions in popovici’s photogravitational model
Directory of Open Access Journals (Sweden)
Mioc V.
2002-01-01
Full Text Available The dynamics of bodies under the combined action of the gravitational attraction and the radiative repelling force has large and deep implications in astronomy. In the 1920s, the Romanian astronomer Constantin Popovici proposed a modified photogravitational law (considered by other scientists too. This paper deals with the collisions of the two-body problem associated with Popovici’s model. Resorting to McGehee-type transformations of the second kind, we obtain regular equations of motion and define the collision manifold. The flow on this boundary manifold is wholly described. This allows to point out some important qualitative features of the collisional motion: existence of the black-hole effect, gradientlikeness of the flow on the collision manifold, regularizability of collisions under certain conditions. Some questions, coming from the comparison of Levi-Civita’s regularizing transformations and McGehee’s ones, are formulated.
Baryon-antibaryon dynamics in relativistic heavy-ion collisions
Seifert, E.; Cassing, W.
2018-04-01
The dynamics of baryon-antibaryon annihilation and reproduction (B B ¯↔3 M ) is studied within the Parton-Hadron-String Dynamics (PHSD) transport approach for Pb+Pb and Au+Au collisions as a function of centrality from lower Super Proton Synchrotron (SPS) up to Large Hadron Collider (LHC) energies on the basis of the quark rearrangement model. At Relativistic Heavy-Ion Collider (RHIC) energies we find a small net reduction of baryon-antibaryon (B B ¯ ) pairs while for the LHC energy of √{sN N}=2.76 TeV a small net enhancement is found relative to calculations without annihilation (and reproduction) channels. Accordingly, the sizable difference between data and statistical calculations in Pb+Pb collisions at √{sN N}=2.76 TeV for proton and antiproton yields [ALICE Collaboration, B. Abelev et al., Phys. Rev. C 88, 044910 (2013), 10.1103/PhysRevC.88.044910], where a deviation of 2.7 σ was claimed by the ALICE Collaboration, should not be attributed to a net antiproton annihilation. This is in line with the observation that no substantial deviation between the data and statistical hadronization model (SHM) calculations is seen for antihyperons, since according to the PHSD analysis the antihyperons should be modified by the same amount as antiprotons. As the PHSD results for particle ratios are in line with the ALICE data (within error bars) this might point towards a deviation from statistical equilibrium in the hadronization (at least for protons and antiprotons). Furthermore, we find that the B B ¯↔3 M reactions are more effective at lower SPS energies where a net suppression for antiprotons and antihyperons up to a factor of 2-2.5 can be extracted from the PHSD calculations for central Au+Au collisions.
Multifragmentation and dynamics in heavy ion collisions
Indian Academy of Sciences (India)
like structure is most likely to appear in those events. Since a ... one, an exclusive analysis has been based on the heaviest particle of each event. .... component behaves in a way independent of impact parameter, or violence of the collision,.
Hard photons a probe of the heavy ion collision dynamics
International Nuclear Information System (INIS)
Schutz, Y.
1994-01-01
Heavy-ion collisions have proven to be a unique tool to study the nucleus in extreme states, with values of energy, spin and isospin far away from those encountered in the nucleus in its ground state. Heavy-ion collisions provide also the only mean to form and study in the laboratory nuclear matter under conditions of density and temperature which could otherwise only be found in stellar objects like neutron stars and super-novae. the goal of such studies is to establish the equation of state of nuclear matter and the method consist in searching the collective behaviour in which heavy-ion collisions differ from a superposition of many nucleon-nucleon collisions. Among the various probes of collective effects, like flow, multifragmentation, or subthreshold particles, we have selected hard photons because they provide, together with dileptons, the only unperturbed probe of a phase of the collision well localized in space and time. The origin of hard photons, defined as the photons building up the spectrum beyond the energy of the giant dipole resonance (E γ > 30∼MeV), is attributed predominantly to the bremsstrahlung radiation emitted incoherently in individual neutron-proton collisions. Their energy reflects the combination of the beam momentum and the momenta induced by the Fermi motion of the nucleons within the collision zone. Therefore, at intermediate energies, hard photons probe the dynamical phase space distribution of participant nucleons and they convey information on the densities reached in heavy-ion collisions, the size and life time of the dense photon source and the compressibility of nuclear matter. The techniques we have developed include intensity interferometry and exclusive measurements scanning with high resolution the whole range of impact parameters. The interpretation of our data is guided by dynamical phase space calculations of the BUU type
On the quantum dynamical foundations of collision terms
International Nuclear Information System (INIS)
Nemes, M.C.; Toledo Piza, A.F.R. de
1981-08-01
Collision terms are non-unitary corrections usually added to mean field descriptions in order to describe dissipative effects. Derivations of collision terms usually include assumptions which lack an explicit connection with a fully quantum dynamical description. Quantum dynamical foundations of collision terms are examined: they are shown to reflect the dynamics of quantum correlations. A careful study of the non-unitary aspects of the evolution of quantum correlations leads naturally to an unambiguous definition of a collision term. This collision term is shown to obey a non-linear pre-master equation, whose derivation is fully quantum-mechanical. Moreover, it is shown that quantum correlations also yield an unitary correction to the mean field description, which could be absorbed in a suitable redefinition of the mean field. Formal expressions for these corrections are derived and their connection with memory effects exhibited explicitely. The typical time of evaluation of quantum correlations allows for an analytical expression for the 'lifetime of mean field descriptions'. Finally, a quantum mechanical point of view for 'irreversibility' in deep inelastic is discussed. (Author) [pt
Collision dynamics of gap solitons in Kerr media
International Nuclear Information System (INIS)
Royston Neill, D.; Atai, Javid
2006-01-01
The collision dynamics of counterpropagating gap solitons in a fiber Bragg grating are investigated. In the case of initially in-phase solitons, it is found that the dynamics are more complex and richer than previously reported. An important finding is that, in general, the outcome of the collisions is dependent upon gap soliton parameters (θ, V) and the initial separation of solitons. However, if the solitons are initially very far apart the dependence on the initial separation is negligible. In the case of π-out-of-phase solitons, we find that they generally bounce off each other with negligible radiation as long as the solitons are stable (i.e., 0 π/1.98) the collision strongly catalyzes the onset of instability and results in the destruction of solitons
Collision dynamics probed by convoy electron emission
International Nuclear Information System (INIS)
Seliger, M.; Burgdoerfer, J.; Toekesi, K.; Reinhold, C.O.; Takabayashi, Y.; Ito, T.; Komaki, K.; Azuma, T.; Yamazaki, Y.; RIKEN, Saitama
2002-01-01
The description of the collision mechanisms was examined by the emission of convoy electrons as a result of the transport of an Ar 17+ ion with an energy of 390 MeV/amu through self-supporting amorphous carbon foils of thickness varying from 25 to 9190 μg/cm 2 . A classical trajectory Monte Carlo (CTMC) simulation of the random walk of the electron initially attached to the relativistic hydrogenic Argon ion was performed. Measurements were made of the final kinetic energy of the emitted convoy electrons at the Heavy Ion Medical Accelerator in Chiba (HIMAC). (R.P.)
Evolution of collision numbers for a chaotic gas dynamics.
Vidgop, Alexander Jonathan; Fouxon, Itzhak
2011-11-01
We put forward a conjecture of recurrence for a gas of hard spheres that collide elastically in a finite volume. The dynamics consists of a sequence of instantaneous binary collisions. We study how the numbers of collisions of different pairs of particles grow as functions of time. We observe that these numbers can be represented as a time integral of a function on the phase space. Assuming the results of the ergodic theory apply, we describe the evolution of the numbers by an effective Langevin dynamics. We use the facts that hold for these dynamics with probability one, in order to establish properties of a single trajectory of the system. We find that for any triplet of particles there will be an infinite sequence of moments of time, when the numbers of collisions of all three different pairs of the triplet will be equal. Moreover, any value of difference of collision numbers of pairs in the triplet will repeat indefinitely. On the other hand, for larger numbers of pairs there is but a finite number of repetitions. Thus the ergodic theory produces a limitation on the dynamics.
Fan Affinity Laws from a Collision Model
Bhattacharjee, Shayak
2012-01-01
The performance of a fan is usually estimated using hydrodynamical considerations. The calculations are long and involved and the results are expressed in terms of three affinity laws. In this paper we use kinetic theory to attack this problem. A hard sphere collision model is used, and subsequently a correction to account for the flow behaviour…
Collision dynamics and particle production in relativistic nucleus- nucleus collisions at CERN
International Nuclear Information System (INIS)
Harris, J.W.
1990-03-01
The possibility of forming a quark-gluon plasma is the primary motivation for studying nucleus-nucleus collisions at very high energies. Various ''signatures'' for the existence of a quark-gluon plasma in these collisions have been proposed. These include an enhancement in the production of strange particles, suppression of J/Ψ production, observation of direct photons from the plasma, event-by-event fluctuations in the rapidity distributions of produced particles, and various other observables. However, the system will evolve dynamically from a pure plasma or mixed phase through expansion, cooling, hadronization and freezeout into the final state particles. Therefore, to be able to determine that a new, transient state of matter has been formed it will be necessary to understand the space-time evolution of the collision process and the microscopic structure of hadronic interactions, at the level of quarks and gluons, at high temperatures and densities. In this talk I will review briefly the present state of our understanding of the dynamics of these collisions and, in addition, present a few recent results on particle production from the NA35 experiment at CERN. 21 refs., 5 figs
Dynamics in ion-molecule collisions at high velocities: One- and two-electron processes
International Nuclear Information System (INIS)
Wang, Yudong.
1992-01-01
This dissertation addresses the dynamic interactions in ion-molecule collisions. Theoretical methods are developed for single and multiple electron transitions in fast collisions with diatomic molecules by heavy-ion projectiles. Various theories and models are developed to treat the three basic inelastic processes (excitation, ionization and charge transfer) involving one and more electrons. The development, incorporating the understanding of ion-atom collision theories with some unique characteristics for molecular targets, provides new insights into phenomena that are absent from collisions with atomic targets. The influence from the multiple scattering centers on collision dynamics is assessed. For diatomic molecules, effects due to a fixed molecular orientation or alignment are calculated and compared with available experimental observations. Compared with excitation and ionization, electron capture, which probes deeper into the target, presents significant two-center interference and strong orientation dependence. Attention has been given in this dissertation to exploring mechanisms for two-and multiple electron transitions. Application of independent electron approximation to transfer excitation from molecular hydrogen is studied. Electron-electron interaction originated from projectile and target nuclear centers is studied in conjunction with the molecular nature of target. Limitations of the present theories and models as well as possible new areas for future theoretical and experimental applications are also discussed. This is the first attempt to describe multi-electron processes in molecular dynamics involving fast highly charged ions
A numerical 4D Collision Risk Model
Schmitt, Pal; Culloch, Ross; Lieber, Lilian; Kregting, Louise
2017-04-01
With the growing number of marine renewable energy (MRE) devices being installed across the world, some concern has been raised about the possibility of harming mobile, marine fauna by collision. Although physical contact between a MRE device and an organism has not been reported to date, these novel sub-sea structures pose a challenge for accurately estimating collision risks as part of environmental impact assessments. Even if the animal motion is simplified to linear translation, ignoring likely evasive behaviour, the mathematical problem of establishing an impact probability is not trivial. We present a numerical algorithm to obtain such probability distributions using transient, four-dimensional simulations of a novel marine renewable device concept, Deep Green, Minesto's power plant and hereafter referred to as the 'kite' that flies in a figure-of-eight configuration. Simulations were carried out altering several configurations including kite depth, kite speed and kite trajectory while keeping the speed of the moving object constant. Since the kite assembly is defined as two parts in the model, a tether (attached to the seabed) and the kite, collision risk of each part is reported independently. By comparing the number of collisions with the number of collision-free simulations, a probability of impact for each simulated position in the cross- section of the area is considered. Results suggest that close to the bottom, where the tether amplitude is small, the path is always blocked and the impact probability is 100% as expected. However, higher up in the water column, the collision probability is twice as high in the mid line, where the tether passes twice per period than at the extremes of its trajectory. The collision probability distribution is much more complex in the upper end of the water column, where the kite and tether can simultaneously collide with the object. Results demonstrate the viability of such models, which can also incorporate empirical
Dynamic simulation of collisions of heavy high-speed trucks with concrete barriers
International Nuclear Information System (INIS)
Itoh, Yoshito; Liu, Chunlu; Kusama, Ryuichi
2007-01-01
Real vehicle collision experiments on full-scale road safety barriers are important to determine the outcome of a vehicle versus barrier impact accident. However, such experiments require large investment of time and money. Numerical simulation has therefore been imperative as an alternative method for testing concrete barriers. In this research, spring subgrade models were first developed to simulate the ground boundary of concrete barriers. Both heavy trucks and concrete barriers were modeled using finite element methods (FEM) to simulate dynamic collision performances. Comparison of the results generated from computer simulations and on-site full-scale experiments demonstrated that the developed models could be applied to simulate the collision of heavy trucks with concrete barriers to provide the data to design new road safety barriers and analyze existing ones
Energy Technology Data Exchange (ETDEWEB)
Swaminathan-Gopalan, Krishnan; Stephani, Kelly A., E-mail: ksteph@illinois.edu [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)
2016-02-15
A systematic approach for calibrating the direct simulation Monte Carlo (DSMC) collision model parameters to achieve consistency in the transport processes is presented. The DSMC collision cross section model parameters are calibrated for high temperature atmospheric conditions by matching the collision integrals from DSMC against ab initio based collision integrals that are currently employed in the Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) and Data Parallel Line Relaxation (DPLR) high temperature computational fluid dynamics solvers. The DSMC parameter values are computed for the widely used Variable Hard Sphere (VHS) and the Variable Soft Sphere (VSS) models using the collision-specific pairing approach. The recommended best-fit VHS/VSS parameter values are provided over a temperature range of 1000-20 000 K for a thirteen-species ionized air mixture. Use of the VSS model is necessary to achieve consistency in transport processes of ionized gases. The agreement of the VSS model transport properties with the transport properties as determined by the ab initio collision integral fits was found to be within 6% in the entire temperature range, regardless of the composition of the mixture. The recommended model parameter values can be readily applied to any gas mixture involving binary collisional interactions between the chemical species presented for the specified temperature range.
Dynamical and statistical aspects of intermediate energy heavy ion collisions
International Nuclear Information System (INIS)
Knoll, J.
1987-01-01
The lectures presented deal with three different topics relevant for the discussion of nuclear collisions at medium to high energies. The first lecture concerns a subject of general interest, the description of statistical systems and their dynamics by the concept of missing information. If presents an excellent scope to formulate statistical theories in such a way that they carefully keep track of the known (relevant) information while maximizing the ignorance about the irrelevant, unknown information. The last two lectures deal with quite actual questions of intermediate energy heavy-ion collisions. These are the multi-fragmentation dynamics of highly excited nuclear systems, and the so called subthreshold particle production. All three subjects are self-contained, and can be read without the knowledge about the other ones. (orig.)
Collision dynamics of two-dimensional non-Abelian vortices
Mawson, Thomas; Petersen, Timothy C.; Simula, Tapio
2017-09-01
We study computationally the collision dynamics of vortices in a two-dimensional spin-2 Bose-Einstein condensate. In contrast to Abelian vortex pairs, which annihilate or pass through each other, we observe non-Abelian vortex pairs to undergo rungihilation—an event that converts the colliding vortices into a rung vortex. The resulting rung defect subsequently decays to another pair of non-Abelian vortices of different type, accompanied by a magnetization reversal.
Binary cluster collision dynamics and minimum energy conformations
Energy Technology Data Exchange (ETDEWEB)
Muñoz, Francisco [Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Germany); Departamento de Física, Facultad de Ciencias, Universidad de Chile, Santiago (Chile); Centro para el Desarrollo de la Nanociencia y Nanotecnología, CEDENNA, Avenida Ecuador 3493, Santiago (Chile); Rogan, José; Valdivia, J.A. [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Santiago (Chile); Centro para el Desarrollo de la Nanociencia y Nanotecnología, CEDENNA, Avenida Ecuador 3493, Santiago (Chile); Varas, A. [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Santiago (Chile); Nano-Bio Spectroscopy Group, ETSF Scientific Development Centre, Departamento de Física de Materiales, Universidad del País Vasco UPV/EHU, Av. Tolosa 72, E-20018 San Sebastián (Spain); Kiwi, Miguel, E-mail: m.kiwi.t@gmail.com [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Santiago (Chile); Centro para el Desarrollo de la Nanociencia y Nanotecnología, CEDENNA, Avenida Ecuador 3493, Santiago (Chile)
2013-10-15
The collision dynamics of one Ag or Cu atom impinging on a Au{sub 12} cluster is investigated by means of DFT molecular dynamics. Our results show that the experimentally confirmed 2D to 3D transition of Au{sub 12}→Au{sub 13} is mostly preserved by the resulting planar Au{sub 12}Ag and Au{sub 12}Cu minimum energy clusters, which is quite remarkable in view of the excess energy, well larger than the 2D–3D potential barrier height. The process is accompanied by a large s−d hybridization and charge transfer from Au to Ag or Cu. The dynamics of the collision process mainly yields fusion of projectile and target, however scattering and cluster fragmentation also occur for large energies and large impact parameters. While Ag projectiles favor fragmentation, Cu favors scattering due to its smaller mass. The projectile size does not play a major role in favoring the fragmentation or scattering channels. By comparing our collision results with those obtained by an unbiased minimum energy search of 4483 Au{sub 12}Ag and 4483 Au{sub 12}Cu configurations obtained phenomenologically, we find that there is an extra bonus: without increase of computer time collisions yield the planar lower energy structures that are not feasible to obtain using semi-classical potentials. In fact, we conclude that phenomenological potentials do not even provide adequate seeds for the search of global energy minima for planar structures. Since the fabrication of nanoclusters is mainly achieved by synthesis or laser ablation, the set of local minima configurations we provide here, and their distribution as a function of energy, are more relevant than the global minimum to analyze experimental results obtained at finite temperatures, and is consistent with the dynamical coexistence of 2D and 3D liquid Au clusters conformations obtained previously.
Dynamic processes in heavy-ion collisions at intermediate energies
Prendergast, E. P.
1999-03-01
This thesis describes the study of the reaction dynamics in heavy-ion collisions of small nuclear systems at intermediate energies. For this, experiments were performed of 24Mg+27A1 at 45 and 95 AMeV. The experiments described in this thesis were performed at the GANIL accelerator facility in Caeri (France) using the Huygens detectors in conjunction with the ‘MUR’. The Huygens detectors consist of the CsI(Tl)-Wall (CIW) covering the backward hemisphere and, located at mid-rapidity, the central trigger detector (CTD), a gas chamber with microstrip read-out backed by 48 plastic scintillators. The forward region is covered by 16 of the plastic scintillators of the CTD and by the MUR, a time-of-flight wall consisting of 96 plastic scintillator sheets. In earlier experiments only fragments with atomic number, Z, greater then two could be identifled in the CTD. Therefore, an investigation was done into the properties of different drift gases. The use of freon (CF4) in the drift chamber, combined with an increase of the gas pressure to 150 mbar, makes it possible to identify all particles with Z ≥ 2. Under these conditions particles with Z = 1 can only be identifled to approximately 25 AMeV. The Isospin Quantum Molecular Dynamics (IQMD) model has been used, to interpret the measured data. This model gives a microscopical description of heavy-ion collisions and simulates collisions on an event by event basis. In IQMD all protons and neutrons are represented as individual Gaussian wave packets. After initialisation the path of each nucleon is calculated for 200 fm/c, after which the simulation is stopped. At this time, nucleons which are close in space are clustered into fragments. The events generated by IQMD can then be processed by a GEANT detector simulation. This calculation takes into account the effects of the detector on the incoming particles. By using the GEANT simulation it is possible to give a direct comparison between the results of IQMD and the
Firetube model and hadron-hadron collisions
International Nuclear Information System (INIS)
Nazareth, R.A.M.S.; Kodama, T.; Portes Junior, D.A.
1992-01-01
A new version of the fire tube model is developed to describe hadron-hadron collisions at ultrarelativistic energies. Several improvements are introduced in order to include the longitudinal expansion of intermediate fireballs, which remedies the overestimates of the transverse momenta in the previous version. It is found that, within a wide range of incident energies, the model describes well the experimental data for the single particle rapidity distribution, two-body correlations in the pseudo-rapidity, transverse momentum spectra of pions and kaons, the leading particle spectra and the K/π ratio. (author)
Traffic simulation based ship collision probability modeling
Energy Technology Data Exchange (ETDEWEB)
Goerlandt, Floris, E-mail: floris.goerlandt@tkk.f [Aalto University, School of Science and Technology, Department of Applied Mechanics, Marine Technology, P.O. Box 15300, FI-00076 AALTO, Espoo (Finland); Kujala, Pentti [Aalto University, School of Science and Technology, Department of Applied Mechanics, Marine Technology, P.O. Box 15300, FI-00076 AALTO, Espoo (Finland)
2011-01-15
Maritime traffic poses various risks in terms of human, environmental and economic loss. In a risk analysis of ship collisions, it is important to get a reasonable estimate for the probability of such accidents and the consequences they lead to. In this paper, a method is proposed to assess the probability of vessels colliding with each other. The method is capable of determining the expected number of accidents, the locations where and the time when they are most likely to occur, while providing input for models concerned with the expected consequences. At the basis of the collision detection algorithm lays an extensive time domain micro-simulation of vessel traffic in the given area. The Monte Carlo simulation technique is applied to obtain a meaningful prediction of the relevant factors of the collision events. Data obtained through the Automatic Identification System is analyzed in detail to obtain realistic input data for the traffic simulation: traffic routes, the number of vessels on each route, the ship departure times, main dimensions and sailing speed. The results obtained by the proposed method for the studied case of the Gulf of Finland are presented, showing reasonable agreement with registered accident and near-miss data.
Sensor Fusion Based Model for Collision Free Mobile Robot Navigation
Almasri, Marwah; Elleithy, Khaled; Alajlan, Abrar
2015-01-01
Autonomous mobile robots have become a very popular and interesting topic in the last decade. Each of them are equipped with various types of sensors such as GPS, camera, infrared and ultrasonic sensors. These sensors are used to observe the surrounding environment. However, these sensors sometimes fail and have inaccurate readings. Therefore, the integration of sensor fusion will help to solve this dilemma and enhance the overall performance. This paper presents a collision free mobile robot navigation based on the fuzzy logic fusion model. Eight distance sensors and a range finder camera are used for the collision avoidance approach where three ground sensors are used for the line or path following approach. The fuzzy system is composed of nine inputs which are the eight distance sensors and the camera, two outputs which are the left and right velocities of the mobile robot’s wheels, and 24 fuzzy rules for the robot’s movement. Webots Pro simulator is used for modeling the environment and the robot. The proposed methodology, which includes the collision avoidance based on fuzzy logic fusion model and line following robot, has been implemented and tested through simulation and real time experiments. Various scenarios have been presented with static and dynamic obstacles using one robot and two robots while avoiding obstacles in different shapes and sizes. PMID:26712766
Sensor Fusion Based Model for Collision Free Mobile Robot Navigation
Directory of Open Access Journals (Sweden)
Marwah Almasri
2015-12-01
Full Text Available Autonomous mobile robots have become a very popular and interesting topic in the last decade. Each of them are equipped with various types of sensors such as GPS, camera, infrared and ultrasonic sensors. These sensors are used to observe the surrounding environment. However, these sensors sometimes fail and have inaccurate readings. Therefore, the integration of sensor fusion will help to solve this dilemma and enhance the overall performance. This paper presents a collision free mobile robot navigation based on the fuzzy logic fusion model. Eight distance sensors and a range finder camera are used for the collision avoidance approach where three ground sensors are used for the line or path following approach. The fuzzy system is composed of nine inputs which are the eight distance sensors and the camera, two outputs which are the left and right velocities of the mobile robot’s wheels, and 24 fuzzy rules for the robot’s movement. Webots Pro simulator is used for modeling the environment and the robot. The proposed methodology, which includes the collision avoidance based on fuzzy logic fusion model and line following robot, has been implemented and tested through simulation and real time experiments. Various scenarios have been presented with static and dynamic obstacles using one robot and two robots while avoiding obstacles in different shapes and sizes.
Fluid-solid boundary conditions for multiparticle collision dynamics
International Nuclear Information System (INIS)
Whitmer, Jonathan K; Luijten, Erik
2010-01-01
The simulation of colloidal particles suspended in solvent requires an accurate representation of the interactions between the colloids and the solvent molecules. Using the multiparticle collision dynamics method, we examine several proposals for stick boundary conditions, studying their properties in both plane Poiseuille flow (where fluid interacts with the boundary of a stationary macroscopic solid) and particle-based colloid simulations (where the boundaries are thermally affected and in motion). In addition, our simulations compare various collision rules designed to remove spurious slip near solid surfaces, and the effects of these rules on the thermal motion of colloidal particles. Furthermore, we demonstrate that stochastic reflection of the fluid at solid boundaries fails to faithfully represent stick boundary conditions, and conclude that bounce-back conditions should be applied at both mobile and stationary surfaces. Finally, we generalize these ideas to create partial slip boundary conditions at both stationary and mobile surfaces.
Dynamical scenario of intermediary mass fragments formation in heavy ion collisions
International Nuclear Information System (INIS)
Ayik, S.; Belkacem, M.; Gregoire, C.; Stryjewski, J.; Suraud, E.
1989-01-01
We briefly remind the possible dynamical scenario of fragments formation in heavy-ion collisions at some tens fo MeV/A. We discuss how present day dynamical models can describe fragment formation. We next turn to the Boltzmann-Langevin formalism which provides a well defined theoretical framework for the understanding of the growing of the dynamical instabilities leading to multifragmentation. We present a first numerical solution of the Boltzmann-Langevin equation and we apply the formalism to the onset of multifragmentation of the 40 Ca + 40 Ca system between 20 and 60 MeV/A beam energy [fr
Single nucleon-nucleon collision model for subthreshold pion production in heavy ion collisions
International Nuclear Information System (INIS)
Bellini, V.; Di Toro, M.; Bonasera, A.
1985-01-01
We show that inclusive experimental data on subthreshold pion production in 12 C + 12 C and 16 O + 12 C collisions can be reproduced using a first chance Nucleon-Nucleon (NN) collision mechanism. Pauli blocking effects are extremely important while π-resorption can be safely neglected for these light systems. We apply our method at various beam energies. The possible importance of collective dynamical effects around the physical threshold is finally suggested
Molecular dynamics of coalescence and collisions of silver nanoparticles
Energy Technology Data Exchange (ETDEWEB)
Guevara-Chapa, Enrique, E-mail: enrique_guevara@hotmail.com [Universidad Autónoma de Nuevo León, Facultad de Ciencias Físico Matemáticas (Mexico); Mejía-Rosales, Sergio [Universidad Autónoma de Nuevo León, Center for Innovation, Research and Development in Engineering and Technology (CIIDIT), and CICFIM-Facultad de Ciencias Físico Matemáticas (Mexico)
2014-12-15
We study how different relative orientations and impact velocity on the collision of two silver nanoparticles affect the first stages of the formation of a new, larger nanoparticle. In order to do this, we implemented a set of molecular dynamics simulations on the NVE ensemble on pairs of silver icosahedral nanoparticles at several relative orientations, that allowed us to follow the dynamics of the first nanoseconds of the coalescence processes. Using bond angle analysis, we found that the initial relative orientation of the twin planes has a critical role on the final stability of the resulting particle, and on the details of the dynamics itself. When the original particles have their closest twins aligned to each other, the formed nanoparticle will likely stabilize its structure onto a particle with a defined center and a low surface-to-volume ratio, while nanoparticles with misaligned twins will promote the formation of highly defective particles with a high inner energy.
Molecular dynamics of coalescence and collisions of silver nanoparticles
International Nuclear Information System (INIS)
Guevara-Chapa, Enrique; Mejía-Rosales, Sergio
2014-01-01
We study how different relative orientations and impact velocity on the collision of two silver nanoparticles affect the first stages of the formation of a new, larger nanoparticle. In order to do this, we implemented a set of molecular dynamics simulations on the NVE ensemble on pairs of silver icosahedral nanoparticles at several relative orientations, that allowed us to follow the dynamics of the first nanoseconds of the coalescence processes. Using bond angle analysis, we found that the initial relative orientation of the twin planes has a critical role on the final stability of the resulting particle, and on the details of the dynamics itself. When the original particles have their closest twins aligned to each other, the formed nanoparticle will likely stabilize its structure onto a particle with a defined center and a low surface-to-volume ratio, while nanoparticles with misaligned twins will promote the formation of highly defective particles with a high inner energy
Microscopic model of nucleus-nucleus collisions
International Nuclear Information System (INIS)
Harvey, B.G.
1986-04-01
The collision of two nuclei is treated as a collection of collisions between the nucleons of the projectile and those of the target nucleus. The primary projectile fragments contain only those nucleons that did not undergo a collision. The inclusive and coincidence cross sections result from the decay of the excited primary fragments. 15 refs., 5 figs
Studies on the dynamics of heavy ion collisions at intermediate energies
International Nuclear Information System (INIS)
David, C.; Hartnack, C; Aichelin, J.
1997-01-01
We use the Quantum Molecular Dynamics model for the investigation of the dynamics of heavy ion collisions at intermediate energies. A detailed comparison between different versions of the models demonstrate the influence of not exactly known parameters in the description of nuclei like interaction range or initial densities and thus describes the limits of predictive power. The dynamics of the reaction are discussed quite similarly in the different models. A radial expansion with a linear velocity profile is found at central collisions. A strong interaction of pions with nuclear matter is reported. This interaction is strongly influenced by the lifetime of baryonic resonances in nuclear matter. These lifetimes depend strongly on the mass distribution of the resonances. These mass distributions are influenced by the momentum distribution in the nuclei. Here the inclusion of the spectral function shows visible effects. These effects influence the energy dissipation in nuclei and thus enter e.g. into the analysis of p + A collisions for the GEDEON project. (author)
Review of quantum collision dynamics in Debye plasmas
Directory of Open Access Journals (Sweden)
R.K. Janev
2016-09-01
Full Text Available Hot, dense plasmas exhibit screened Coulomb interactions, resulting from the collective effects of correlated many-particle interactions. In the lowest particle correlation order (pair-wise correlations, the interaction between charged plasma particles reduces to the Debye–Hückel (Yukawa-type potential, characterized by the Debye screening length. Due to the importance of Coulomb interaction screening in dense laboratory and astrophysical plasmas, hundreds of theoretical investigations have been carried out in the past few decades on the plasma screening effects on the electronic structure of atoms and their collision processes employing the Debye–Hückel screening model. The present article aims at providing a comprehensive review of the recent studies in atomic physics in Debye plasmas. Specifically, the work on atomic electronic structure, photon excitation and ionization, electron/positron impact excitation and ionization, and excitation, ionization and charge transfer of ion-atom/ion collisions will be reviewed.
Hydrodynamics in adaptive resolution particle simulations: Multiparticle collision dynamics
Energy Technology Data Exchange (ETDEWEB)
Alekseeva, Uliana, E-mail: Alekseeva@itc.rwth-aachen.de [Jülich Supercomputing Centre (JSC), Institute for Advanced Simulation (IAS), Forschungszentrum Jülich, D-52425 Jülich (Germany); German Research School for Simulation Sciences (GRS), Forschungszentrum Jülich, D-52425 Jülich (Germany); Winkler, Roland G., E-mail: r.winkler@fz-juelich.de [Theoretical Soft Matter and Biophysics, Institute for Advanced Simulation (IAS), Forschungszentrum Jülich, D-52425 Jülich (Germany); Sutmann, Godehard, E-mail: g.sutmann@fz-juelich.de [Jülich Supercomputing Centre (JSC), Institute for Advanced Simulation (IAS), Forschungszentrum Jülich, D-52425 Jülich (Germany); ICAMS, Ruhr-University Bochum, D-44801 Bochum (Germany)
2016-06-01
A new adaptive resolution technique for particle-based multi-level simulations of fluids is presented. In the approach, the representation of fluid and solvent particles is changed on the fly between an atomistic and a coarse-grained description. The present approach is based on a hybrid coupling of the multiparticle collision dynamics (MPC) method and molecular dynamics (MD), thereby coupling stochastic and deterministic particle-based methods. Hydrodynamics is examined by calculating velocity and current correlation functions for various mixed and coupled systems. We demonstrate that hydrodynamic properties of the mixed fluid are conserved by a suitable coupling of the two particle methods, and that the simulation results agree well with theoretical expectations.
Ahu Akin, F; Ree, Jongbaik; Ervin, Kent M; Kyu Shin, Hyung
2005-08-08
The energetics and dynamics of collision-induced dissociation of O2- with Ar and Xe targets are studied experimentally using guided ion-beam tandem mass spectrometry. The cross sections and the collision dynamics are modeled theoretically by classical trajectory calculations. Experimental apparent threshold energies are 2.1 and 1.1 eV in excess of the thermochemical O2- bond dissociation energy for argon and xenon, respectively. Classical trajectory calculations confirm the observed threshold behavior and the dependence of cross sections on the relative kinetic energy. Representative trajectories reveal that the bond dissociation takes place on a short time scale of about 50 fs in strong direct collisions. Collision-induced dissociation is found to be remarkably restricted to the perpendicular approach of ArXe to the molecular axis of O2-, while collinear collisions do not result in dissociation. The higher collisional energy-transfer efficiency of xenon compared with argon is attributed to both mass and polarizability effects.
International Nuclear Information System (INIS)
Ahu Akin, F.; Ree, Jongbaik; Ervin, Kent M.; Hyung, Kyu Shin
2005-01-01
The energetics and dynamics of collision-induced dissociation of O 2 - with Ar and Xe targets are studied experimentally using guided ion-beam tandem mass spectrometry. The cross sections and the collision dynamics are modeled theoretically by classical trajectory calculations. Experimental apparent threshold energies are 2.1 and 1.1 eV in excess of the thermochemical O 2 - bond dissociation energy for argon and xenon, respectively. Classical trajectory calculations confirm the observed threshold behavior and the dependence of cross sections on the relative kinetic energy. Representative trajectories reveal that the bond dissociation takes place on a short time scale of about 50 fs in strong direct collisions. Collision-induced dissociation is found to be remarkably restricted to the perpendicular approach of Ar/Xe to the molecular axis of O 2 - , while collinear collisions do not result in dissociation. The higher collisional energy-transfer efficiency of xenon compared with argon is attributed to both mass and polarizability effects
Modelling early stages of relativistic heavy-ion collisions
Directory of Open Access Journals (Sweden)
Ruggieri M.
2016-01-01
Full Text Available In this study we model early time dynamics of relativistic heavy ion collisions by an initial color-electric field which then decays to a plasma by the Schwinger mechanism. The dynamics of the many particles system produced by the decay is described by relativistic kinetic theory, taking into account the backreaction on the color field by solving self-consistently the kinetic and the field equations. Our main results concern isotropization and thermalization for a 1+1D expanding geometry. In case of small η/s (η/s ≲ 0.3 we find τisotropization ≈ 0.8 fm/c and τthermalization ≈ 1 fm/c in agreement with the common lore of hydrodynamics.
A classical statistical model of heavy ion collisions
International Nuclear Information System (INIS)
Schmidt, R.; Teichert, J.
1980-01-01
The use of the computer code TRAJEC which represents the numerical realization of a classical statistical model for heavy ion collisions is described. The code calculates the results of a classical friction model as well as various multi-differential cross sections for heavy ion collisions. INPUT and OUTPUT information of the code are described. Two examples of data sets are given [ru
Comparison of models of high energy nuclear collisions
International Nuclear Information System (INIS)
Gyulassy, M.
1978-01-01
The treatment of high energy nuclear reaction models covers goals of such collisions, the choice of theoretical framework, the zoo of models (p inclusive), light composites, models versus experiment, conclusions drawn, needed experiments, and pion production. 30 diagrams
Hässig, Marc; Rolland, Yann; Sosson, Marc; Hassani, Riad; Topuz, Gultekin; Faruk Çelik, Ömer; Gerbault, Muriel; Galoyan, Ghazar; Müller, Carla; Sahakyan, Lilit; Avagyan, Ara
2013-04-01
In the Lesser Caucasus three main domains are distinguished from SW to NE: (1) the South Armenian Block (SAB), a Gondwanian-derived continental terrane; (2) scattered outcrops of ophiolites coming up against the Sevan-Akera suture zone; and (3) the Eurasian plate. The Armenian ophiolites represent remnants of an oceanic domain which disappeared during Eurasia-Arabia convergence. Previous works using geochemical whole-rock analyses, 40Ar/39Ar and paleontological dating have shown that the ophiolite outcrops throughout this area were emplaced during the Late Cretaceous as one non-metamorphic preserved ophiolitic nappe of back-arc origin that formed during Middle to Late Jurassic. From these works, tectonic reconstructions include two clearly identified subductions, one related to the Neotethys subduction beneath the Eurasian margin and another to intra-oceanic subduction responsible for the opening of the back-arc basin corresponding to the ophiolites of the Lesser Caucasus. The analysis of the two stages of metamorphism of the garnet amphibolites of the ophiolite obduction sole at Amasia (M1: HT-LP peak of P = 6-7 kbar and T > 630°C; M2; MP-MT peak at P = 8-10 kbar and T = 600°C) has allowed us to deduce the onset of subduction of the SAB at 90 Ma for this locality, which age coincides with other paleontological ages at the obduction front. A preliminary paleomagnetic survey has also brought quantification to the amount of oceanic domain which disappeared by subduction between the SAB and Eurasia before collision. We propose a dynamic finite element model using ADELI to test the incidence of parameters such as the density of the different domains (or the interval between the densities), closing speed (or speeds if sporadic), the importance and interactions of mantle discontinuities with the subducting lithosphere and set a lithospheric model. Our field observations and analyses are used to validate combinations of factors. The aim is to better qualify the
Dynamics of particles accelerated by head-on collisions of two magnetized plasma shocks
Takeuchi, Satoshi
2018-02-01
A kinetic model of the head-on collision of two magnetized plasma shocks is analyzed theoretically and in numerical calculations. When two plasmas with anti-parallel magnetic fields collide, they generate magnetic reconnection and form a motional electric field at the front of the collision region. This field accelerates the particles sandwiched between both shock fronts to extremely high energy. As they accelerate, the particles are bent by the transverse magnetic field crossing the magnetic neutral sheet, and their energy gains are reduced. In the numerical calculations, the dynamics of many test particles were modeled through the relativistic equations of motion. The attainable energy gain was obtained by multiplying three parameters: the propagation speed of the shock, the magnitude of the magnetic field, and the acceleration time of the test particle. This mechanism for generating high-energy particles is applicable over a wide range of spatial scales, from laboratory to interstellar plasmas.
Dynamical Evolution of the Scalar Condensate in Heavy Ion Collisions
Csernai, Laszlo P.; Jeon, Sangyong; Kapusta, Joseph I.; Csernai, Laszlo P.; Ellis, Paul J.; Jeon, Sangyong; Kapusta, Joseph I.
2000-01-01
We derive the effective coarse-grained field equation for the scalar condensate of the linear sigma model in a simple and straightforward manner using linear response theory. In general, the necessary response functions cannot be obtained in perturbation theory but require a summation of ladder diagrams. We estimate these response functions using direct physical reasoning. The field equation is solved for hot matter undergoing either one or three dimensional expansion and cooling in the aftermath of a high energy nuclear collision. The results show that the time constant for returning the scalar condensate to thermal equilibrium is of order 2 fm/c.
Spectroscopy and reaction dynamics of collision complexes containing hydroxyl radicals
Energy Technology Data Exchange (ETDEWEB)
Lester, M.I. [Univ. of Pennsylvania, Philadelphia (United States)
1993-12-01
The DOE supported work in this laboratory has focused on the spectroscopic characterization of the interaction potential between an argon atom and a hydroxyl radical in the ground X{sup 2}II and excited A {sup 2}{summation}{sup +} electronic states. The OH-Ar system has proven to be a test case for examining the interaction potential in an open-shell system since it is amenable to experimental investigation and theoretically tractable from first principles. Experimental identification of the bound states supported by the Ar + OH (X {sup 2}II) and Ar + OH(A {sup 2}{summation}{sup +}) potentials makes it feasible to derive realistic potential energy surfaces for these systems. The experimentally derived intermolecular potentials provide a rigorous test of ab initio theory and a basis for understanding the dramatically different collision dynamics taking place on the ground and excited electronic state surfaces.
Modelling seabird collision risk with off-shore wind farms
Energy Technology Data Exchange (ETDEWEB)
Mateos, Maria; Arroyo, Gonzalo Munoz; Rosario, Jose Juan Alonso del
2011-07-01
Full text: Recent concern about the adverse effects of collision mortality of avian migrants at wind farms has highlighted the need to understand bird-wind turbine interactions. Here, a stochastic collision model, based on data of seabird behaviour collected on- site, is presented, as a flexible and easy to take tool to assess the collisions probabilities of off-shore wind farms in a pre-construction phase. The collision prediction model considering the wind farm area as a risk window has been constructed as a stochastic model for avian migrants, based on Monte Carlo simulation. The model calculates the probable number of birds collided per time unit. Migration volume, wind farm dimensions, vertical and horizontal distribution of the migratory passage, flight direction and avoidance rates, between other variables, are taken into account in different steps of the model as the input variables. In order to assess the weighted importance of these factors on collision probability predictions, collision probabilities obtained from the set of scenarios resulting from the different combinations of the input variables were modelled by using Generalised Additive Models. The application of this model to a hypothetical project for erecting a wind farm at the Strait of Gibraltar showed that collision probability, and consequently mortality rates, strongly depend on the values of the avoidance rates taken into account, and the distribution of birds into the different altitude layers. These parameters should be considered as priorities to be addressed in post-construction studies. (Author)
Modeling defect production in high energy collision cascades
International Nuclear Information System (INIS)
Heinisch, H.L.; Singh, B.N.
1993-01-01
A multi-model approach roach (MMA) to simulating defect production processes at the atomic scale is described that incorporates molecular dynamics (MD), binary collision approximation (BCA) calculations and stochastic annealing simulations. The central hypothesis of the MMA is that the simple, fast computer codes capable of simulating large numbers of high energy cascades (e.g., BCA codes) can be made to yield the correct defect configurations when their parameters are calibrated using the results of the more physically realistic MD simulations. The calibration procedure is investigated using results of MD simulations of 25 keV cascades in copper. The configurations of point defects are extracted from the MD cascade simulations at the end of the collisional phase, similar to the information obtained with a binary collision model. The MD collisional phase defect configurations are used as input to the ALSOME annealing simulation code, and values of the ALSOME quenching parameters are determined that yield the best fit to the post-quenching defect configurations of the MD simulations
Border-Collision Bifurcations and Chaotic Oscillations in a Piecewise-Smooth Dynamical System
DEFF Research Database (Denmark)
Zhusubaliyev, Z.T.; Soukhoterin, E.A.; Mosekilde, Erik
2002-01-01
Many problems of engineering and applied science result in the consideration of piecewise-smooth dynamical systems. Examples are relay and pulse-width control systems, impact oscillators, power converters, and various electronic circuits with piecewise-smooth characteristics. The subject...... of investigation in the present paper is the dynamical model of a constant voltage converter which represents a three-dimensional piecewise-smooth system of nonautonomous differential equations. A specific type of phenomena that arise in the dynamics of piecewise-smooth systems are the so-called border......-collision bifurcations. The paper contains a detailed analysis of this type of bifurcational transition in the dynamics of the voltage converter, in particular, the merging and subsequent disappearance of cycles of different types, change of solution type, and period-doubling, -tripling, -quadrupling and -quintupling...
Phase transition dynamics in ultra-relativistic heavy-ion collisions
International Nuclear Information System (INIS)
Csernai, L.P.; Kapusta, J.I.; Kluge, G.Y.; Zabrodin, E.E.
1992-11-01
The authors investigate various problems related to the dynamics of a first-order phase transition from quark-gluon plasma to hadronic matter in ultra-relativistic heavy ion collisions. These include nucleation, growth and fusion of hadronic bubbles in either the Bjorken longitudinal hydrodynamic expansion model or the Cooper-Frye-Schonberg spherical hydrodynamic expansion model. With reasonable input parameters the conversion of one phase into the other is relatively close to the idealized adiabatic Maxwell construction, although one can choose parameters such that the conversion is strongly out of equilibrium. 10 refs., 7 figs
Scaling of multiplicity distribution in hadron collisions and diffractive-excitation like models
International Nuclear Information System (INIS)
Buras, A.J.; Dethlefsen, J.M.; Koba, Z.
1974-01-01
Multiplicity distribution of secondary particles in inelastic hadron collision at high energy is studied in the semiclassical impact parameter representation. The scaling function is shown to consist of two factors: one geometrical and the other dynamical. We propose a specific choice of these factors, which describe satisfactorily the elastic scattering, the ratio of elastic to total cross-section and the simple scaling behaviour of multiplicity distribution in p-p collisions. Two versions of diffractive-excitation like models (global and local excitation) are presented as interpretation of our choice of dynamical factor. (author)
International Nuclear Information System (INIS)
Lewis, J.C.
2011-01-01
In a recent paper (Lewis, 2008) a class of models suitable for application to collision-sequence interference was introduced. In these models velocities are assumed to be completely randomized in each collision. The distribution of velocities was assumed to be Gaussian. The integrated induced dipole moment μk, for vector interference, or the scalar modulation μk, for scalar interference, was assumed to be a function of the impulse (integrated force) fk, or its magnitude fk, experienced by the molecule in a collision. For most of (Lewis, 2008) it was assumed that μk fk and μk fk, but it proved to be possible to extend the models, so that the magnitude of the induced dipole moment is equal to an arbitrary power or sum of powers of the intermolecular force. This allows estimates of the in filling of the interference dip by the dis proportionality of the induced dipole moment and force. One particular such model, using data from (Herman and Lewis, 2006), leads to the most realistic estimate for the in filling of the vector interference dip yet obtained. In (Lewis, 2008) the drastic assumption was made that collision times occurred at equal intervals. In the present paper that assumption is removed: the collision times are taken to form a Poisson process. This is much more realistic than the equal-intervals assumption. The interference dip is found to be a Lorentzian in this model
On the balance energy and nuclear dynamics in peripheral heavy-ion collisions
International Nuclear Information System (INIS)
Chugh, Rajiv; Puri, Rajeev K.
2010-01-01
We present here the system size dependence of balance energy for semi-central and peripheral collisions using quantum molecular dynamics model. For this study, the reactions of Ne 20 +Ne 20 , Ca 40 +Ca 40 , Ni 58 + Ni 58 , Nb 93 +Nb 93 , Xe 131 +Xe 131 , and Au 197 +Au 197 are simulated at different incident energies and impact parameters. A hard equation of state along with nucleon–nucleon cross-sections between 40 and 55 mb explains the data nicely. Interestingly, balance energy follows a power law ∝A τ for the mass dependence at all colliding geometries. The power factor τ is close to –1/3 in central collisions, whereas it is –2/3 for peripheral collisions suggesting stronger system size dependence at peripheral geometries. This also suggests that in the absence of momentum dependent interactions, Coulomb's interaction plays an exceedingly significant role. These results are further analyzed for nuclear dynamics at the balance point. (author)
Insights from 3D numerical simulations on the dynamics of the India-Asia collision zone
Pusok, A. E.; Kaus, B.; Popov, A.
2013-12-01
The dynamics of the India-Asia collision zone remains one of the most remarkable topics of the current research interest: the transition from subduction to collision and uplift, followed by the rise of the abnormally thick Tibetan plateau, and the deformation at its Eastern and Western syntaxes, are processes still not fully understood. Models that have addressed this topic include wholescale underthrusting of Indian lithospheric mantle under Tibet, distributed homogeneous shortening or the thin-sheet model, slip-line field model for lateral extrusion or lower crustal flow models for the exhumation of the Himalayan units and lateral spreading of the Tibetan plateau. Of these, the thin-sheet model has successfully illustrated some of the basic physics of continental collision and has the advantage of a 3D model being reduced to 2D, but one of its major shortcomings is that it cannot simultaneously represent channel flow and gravitational collapse of the mantle lithosphere, since these mechanisms require the lithosphere to interact with the underlying mantle, or to have a vertically non-homogeneous rheology. As a consequence, 3D models are emerging as powerful tools to understand the dynamics of coupled systems. However, because of yet recent developments and various complexities, the current 3D models simulating the dynamics of continent collision zones have relied on certain explicit assumptions, such as replacing part of the asthenosphere with various types of boundary conditions that mimic the effect of mantle flow, in order to focus on the lithospheric/crustal deformation. Here, we employ the parallel 3D code LaMEM (Lithosphere and Mantle Evolution Model), with a finite difference staggered grid solver, which is capable of simulating lithospheric deformation while simultaneously taking mantle flow and a free surface into account. We present qualitative results on lithospheric and upper-mantle scale simulations in which the Indian lithosphere is subducted and
A quantal toy model for heavy-ion collisions
International Nuclear Information System (INIS)
Cassing, W.
1987-01-01
A one-dimensional toy model of moving finite boxes is analysed with respect to quantal phenomena associated with heavy-ion dynamics at low and intermediate energies. Special attention is payed to the relation between energy and momentum of the nucleons inside and outside the time-dependent mean field. A Wigner transformation of the one-body density matrix in space and time allows for a unique comparison with classical phase-space dynamics. It is found that high momentum components of the nuclear groundstate wave function approximately become on-shell during the heavy-ion reaction. This leads to the emission of energetic nucleons which do not appear classically. It is furthermore shown, that the low lying eigenstates of the dinuclear system for fixed time are only partly occupied throughout the reaction at intermediate energies. This opens up final phase space for nucleons after producing e.g. a pion or energetic photon. Through the present model does not allow for a reliable calculation of double differential nucleon spectra, pion or photon cross sections, it transparently shows the peculiar features of quantum dynamics in heavy-ion collisions. (orig.)
Nuclear quantum many-body dynamics: from collective vibrations to heavy-ion collisions
International Nuclear Information System (INIS)
Simenel, Cedric
2012-01-01
This report gives a summary of my research on nuclear dynamics during the past ten years. The choice of this field has been motivated by the desire to understand the physics of complex systems obeying quantum mechanics. In particular, the interplay between collective motion and single-particle degrees of freedom is a source of complex and fascinating behaviours. For instance, giant resonances are characterised by a collective vibration of many nucleons, but their decay may occur by the emission of a single nucleon. Another example could be taken from the collision of nuclei where the transfer of few nucleons may have a strong impact on the formation of a compound system is non trivial. To describe these complex systems, one needs to solve the quantum many-body problem. The description of the dynamics of composite systems can be very challenging, especially when two such systems interact. An important goal of nuclear physics is to find a unified way to describe the dynamics of nuclear systems. Ultimately, the same theoretical model should be able to describe vibrations, rotations, fission, all the possible outcomes of heavy-ion collisions (elastic and inelastic scattering, particle transfer, fusion, and multifragmentation), and even the dynamics of neutron star crust. This desire for a global approach to nuclear dynamics has strongly influenced my research activities. In particular, all the numerical applications presented in this report have been obtained from few numerical codes solving equations derived from the same variational principle. Beside the quest for a unified model of nuclear dynamics, possible applications of heavy-ion collisions such as the formation of new nuclei is also a strong motivation for the experimental and theoretical studies of reaction mechanisms. This report is not a review article, but should be considered as a reading guide of the main papers my collaborators and myself have published. It also gives the opportunity to detail some
Modelling of the Internal Mechanics in Ship Collisions
DEFF Research Database (Denmark)
Paik, Jeom Kee; Pedersen, Preben Terndrup
1996-01-01
A method for analysis of the structural damage due to ship collisions is developed. The method is based on the idealized structural unit method (ISUM). Longitudinal/transverse webs which connect the outer and the inner hulls are modelled by rectangular plate units. The responses are determined...... on the stiffness and the strength is considered as well. In order to include the coupling effects between local and global failure of the structure, the usual non-linear finite-element technique is applied. In order to deal with the gap and contact conditions between the striking and the struck ships, gap......-skin plated structures in collision/grounding situations with the present solutions. As an illustrative example the procedure has been used for analyses of a side collision of a double-hull tanker. Several factors affecting ship collision response, namely the collision speed and the scantlings/ arrangements...
Modeling and simulation of cars in frontal collision
Deac, S. C.; Perescu, A.; Simoiu, D.; Nyaguly, E.; Crâştiu, I.; Bereteu, L.
2018-01-01
Protection of cars, mainly drivers and passengers in a collision are very important issues worldwide. Statistics given by “World Health Organization” are alarming rate of increase in the number of road accidents, most claiming with serious injury, human and material loss. For these reasons has been a continuous development of protection systems, especially car causing three quarters of all accidents. Mathematical modeling and simulation of a car behavior during a frontal collision leads to new solutions in the development of protective systems. This paper presents several structural models of a vehicle during a frontal collision and its behavior is analyzed by numerical simulation using Simulink.
Some remarks on the statistical model of heavy ion collisions
International Nuclear Information System (INIS)
Koch, V.
2003-01-01
This contribution is an attempt to assess what can be learned from the remarkable success of this statistical model in describing ratios of particle abundances in ultra-relativistic heavy ion collisions
Toy model for pion production in nucleon-nucleon collisions
International Nuclear Information System (INIS)
Hanhart, C.; Miller, G. A.; Myhrer, F.; Sato, T.; Kolck, U. van
2001-01-01
We develop a toy model for pion production in nucleon-nucleon collisions that reproduces some of the features of the chiral Lagrangian calculations. We calculate the production amplitude and examine some common approximations
Collision dynamics of H+ + N2 at low energies based on time-dependent density-functional theory
Yu, W.; Zhang, Y.; Zhang, F. S.; Hutton, R.; Zou, Y.; Gao, C.-Z.; Wei, B.
2018-02-01
Using time-dependent density-functional theory at the level of local density approximation augmented by a self-interaction correction and coupled non-adiabatically to molecular dynamics, we study, from a theoretical perspective, scattering dynamics of the proton in collisions with the N2 molecule at 30 eV. Nine different collision configurations are employed to analyze the proton energy loss spectra, electron depletion, scattering angles and self-interaction effects. Our results agree qualitatively with the experimental data and previous theoretical calculations. The discrepancies are ascribed to the limitation of the theoretical models in use. We find that self-interaction effects can significantly influence the electron capture and the excited diatomic vibrational motion, which is in consistent with other calculations. In addition, it is found that the molecular structure can be readily retrieved from the proton energy loss spectra due to a significant momentum transfer in head-on collisions.
Modelling of a collision between two smartphones
de Jesus, V. L. B.; Sasaki, D. G. G.
2016-09-01
In the predominant approach in physics textbooks, the collision between particles is treated as a black box, where no physical quantity can be measured. This approach becomes even more evident in experimental classes where collisions are the simplest and most common way of applying the theorem of conservation of linear momentum in the asymptotic behavior. In this paper we develop and analyse an experiment on collisions using only two smartphones. The experimental setup is amazingly simple; the two devices are aligned on a horizontal table of lacquered wood, in order to slide more easily. At the edge of one of them a piece of common sponge is glued using double-sided tape. By using a free smartphone application, the values generated by the accelerometer of the two devices in full motion are measured and tabulated. Through numerical iteration, the speed graphs of the smartphones before, during, and after the collision are obtained. The main conclusions were: (i) the demonstration of the feasibility of using smartphones as an alternative to air tracks and electronic sensors employed in a teaching lab, (ii) the possibility of investigating the collision itself, its characteristics and effects; this is the great advantage of the use of smartphones over traditional experiments, (iii) the compatibility of the results with the impulse-momentum theorem, within the margin of uncertainty.
Recent advances in vibro-impact dynamics and collision of ocean vessels
Ibrahim, Raouf A.
2014-11-01
The treatment of ship impacts and collisions takes different approaches depending on the emphasis of each discipline. For example, dynamicists, physicist, and mathematicians are dealing with developing analytical models and mappings of vibro-impact systems. On the other hand, naval architects and ship designers are interested in developing design codes and structural assessments due to slamming loads, liquid sloshing impact loads in liquefied natural gas tanks and ship grounding accidents. The purpose of this review is to highlight the main differences of the two disciplines. It begins with a brief account of the theory of vibro-impact dynamics based on modeling and mapping of systems experiencing discontinuous changes in their state of motion due to collision. The main techniques used in modeling include power-law phenomenological modeling, Hertzian modeling, and non-smooth coordinate transformations originally developed by Zhuravlev and Ivanov. In view of their effectiveness, both Zhuravlev and Ivanov non-smooth coordinate transformations will be described and assessed for the case of ship roll dynamics experiencing impact with rigid barriers. These transformations have the advantage of converting the vibro-impact oscillator into an oscillator without barriers such that the corresponding equation of motion does not contain any impact term. One of the recent results dealing with the coefficient of restitution is that its value monotonically decreases with the impact velocity and not unique but random in nature. Slamming loads and grounding events of ocean waves acting on the bottom of high speed vessels will be assessed with reference to the ship structural damage. It will be noticed that naval architects and marine engineers are treating these problems using different approaches from those used by dynamicists. The problem of sloshing impact in liquefied natural gas cargo and related problems will be assessed based on the numerical and experimental results. It is
Bravina, L V; Korotkikh, V L; Lokhtin, I P; Malinina, L V; Nazarova, E N; Petrushanko, S V; Snigirev, A M; Zabrodin, E E
2015-01-01
The possible mechanisms contributing to anisotropic flow fluctuations in relativistic heavy ion collisions are discussed. The LHC data on event-by-event harmonic flow coefficients measured in PbPb collisions at center-of-mass energy 2.76 TeV per nucleon pair are analyzed and interpreted within the HYDJET++ model. To compare the model results with the experimental data the unfolding procedure is employed. It is shown that HYDJET++ correctly reproduces dynamical fluctuations of elliptic and triangular flows and related to it eccentricity fluctuations of the initial state.
Avian collision risk models for wind energy impact assessments
Energy Technology Data Exchange (ETDEWEB)
Masden, E.A., E-mail: elizabeth.masden@uhi.ac.uk [Environmental Research Institute, North Highland College-UHI, University of the Highlands and Islands, Ormlie Road, Thurso, Caithness KW14 7EE (United Kingdom); Cook, A.S.C.P. [British Trust for Ornithology, The Nunnery, Thetford IP24 2PU (United Kingdom)
2016-01-15
With the increasing global development of wind energy, collision risk models (CRMs) are routinely used to assess the potential impacts of wind turbines on birds. We reviewed and compared the avian collision risk models currently available in the scientific literature, exploring aspects such as the calculation of a collision probability, inclusion of stationary components e.g. the tower, angle of approach and uncertainty. 10 models were cited in the literature and of these, all included a probability of collision of a single bird colliding with a wind turbine during passage through the rotor swept area, and the majority included a measure of the number of birds at risk. 7 out of the 10 models calculated the probability of birds colliding, whilst the remainder used a constant. We identified four approaches to calculate the probability of collision and these were used by others. 6 of the 10 models were deterministic and included the most frequently used models in the UK, with only 4 including variation or uncertainty in some way, the most recent using Bayesian methods. Despite their appeal, CRMs have their limitations and can be ‘data hungry’ as well as assuming much about bird movement and behaviour. As data become available, these assumptions should be tested to ensure that CRMs are functioning to adequately answer the questions posed by the wind energy sector. - Highlights: • We highlighted ten models available to assess avian collision risk. • Only 4 of the models included variability or uncertainty. • Collision risk models have limitations and can be ‘data hungry’. • It is vital that the most appropriate model is used for a given task.
Avian collision risk models for wind energy impact assessments
International Nuclear Information System (INIS)
Masden, E.A.; Cook, A.S.C.P.
2016-01-01
With the increasing global development of wind energy, collision risk models (CRMs) are routinely used to assess the potential impacts of wind turbines on birds. We reviewed and compared the avian collision risk models currently available in the scientific literature, exploring aspects such as the calculation of a collision probability, inclusion of stationary components e.g. the tower, angle of approach and uncertainty. 10 models were cited in the literature and of these, all included a probability of collision of a single bird colliding with a wind turbine during passage through the rotor swept area, and the majority included a measure of the number of birds at risk. 7 out of the 10 models calculated the probability of birds colliding, whilst the remainder used a constant. We identified four approaches to calculate the probability of collision and these were used by others. 6 of the 10 models were deterministic and included the most frequently used models in the UK, with only 4 including variation or uncertainty in some way, the most recent using Bayesian methods. Despite their appeal, CRMs have their limitations and can be ‘data hungry’ as well as assuming much about bird movement and behaviour. As data become available, these assumptions should be tested to ensure that CRMs are functioning to adequately answer the questions posed by the wind energy sector. - Highlights: • We highlighted ten models available to assess avian collision risk. • Only 4 of the models included variability or uncertainty. • Collision risk models have limitations and can be ‘data hungry’. • It is vital that the most appropriate model is used for a given task.
Theory of collective dynamics: flow, fluctuations and correlations in heavy ion collisions
Energy Technology Data Exchange (ETDEWEB)
Denicol, Gabriel S. [Physics Department, Brookhaven National Lab, Building 510A, Upton, NY, 11973 (United States); Department of Physics, McGill University, 3600 University Street, Montreal, Quebec, H3A 2T8 (Canada)
2016-12-15
I review recent developments in the hydrodynamic modeling of ultra-relativistic heavy ion collisions and the extraction of the properties of bulk QCD matter from heavy ion collision measurements. I briefly summarize the current framework used for the theoretical modeling of heavy ion collisions and report the recent progress on the extraction of the temperature dependence of the shear and bulk viscosity coefficients, the development of statistical tools for data-to-model comparison, and anisotropic hydrodynamics. All these recent developments in our field pave the way for more quantitative determination of the transport properties of bulk QCD matter from the experimental heavy ion collision program.
Linking spatial and dynamic models for traffic maneuvers
DEFF Research Database (Denmark)
Olderog, Ernst-Rüdiger; Ravn, Anders Peter; Wisniewski, Rafal
2015-01-01
For traffic maneuvers of multiple vehicles on highways we build an abstract spatial and a concrete dynamic model. In the spatial model we show the safety (collision freedom) of lane-change maneuvers. By linking the spatial and dynamic model via suitable refinements of the spatial atoms to distance...
Dynamics of the single and double ionization of helium in fast proton collisions
International Nuclear Information System (INIS)
Doerner, R.; Schmidt-Boecking, H.
1991-08-01
A new experimental approach, designed to measure differential ionisation and electron capture cross sections for relativistic heavy ion beams, has been developed and was used to investigate dynamic mechanisms of Helium single and double ionisation in collisions with fast protons. Detailed insight into the dynamics of the ionisation process has been obtained. The experimental results prove, that the many-body momentum exchange between all particles involved, the projectile and target nucleus as well as the emitted electrons, has to be incorporated in order to correctly describe the ionisation collision dynamics. For the proton on Helium collision system the transverse momenta of projectile and recoil-ion were found to be of comparable magnitude only for very close collisions and large scattering angles above 1 mrad, which contribute less than 3% to the total ionisation cross section. (orig./HSI) [de
Electron capture in ion-molecule collisions at intermediate energy
International Nuclear Information System (INIS)
Kumura, M.
1986-01-01
Recent progress of theoretical charge transfer study in ion-molecule collisions at the intermediate energy is reviewed. Concept of close and distant collisions obtained from extensive ion-atom collision studies is identified so that it can be utilized to model two distinct collision processes. For a close collision, explicit representation of the whole collision complex is necessary to describe collision dynamics correctly, while a model potential approach for molecule is appropriate for a distant collision. It is shown that these two distinct models are indeed capable of reproducing experimental charge transfer cross sections. Some remarks for further theoretical study of ion-molecule collisions are also given. 21 refs., 8 figs
Semiclassical calculation for collision induced dissociation. II. Morse oscillator model
International Nuclear Information System (INIS)
Rusinek, I.; Roberts, R.E.
1978-01-01
A recently developed semiclassical procedure for calculating collision induced dissociation probabilities P/sup diss/ is applied to the collinear collision between a particle and a Morse oscillator diatomic. The particle--diatom interaction is described with a repulsive exponential potential function. P/sup diss/ is reported for a system of three identical particles, as a function of collision energy E/sub t/ and initial vibrational state of the diatomic n 1 . The results are compared with the previously reported values for the collision between a particle and a truncated harmonic oscillator. The two studies show similar features, namely: (a) there is an oscillatory structure in the P/sup diss/ energy profiles, which is directly related to n 1 ; (b) P/sup diss/ becomes noticeable (> or approx. =10 -3 ) for E/sub t/ values appreciably higher than the energetic threshold; (c) vibrational enhancement (inhibition) of collision induced dissociation persists at low (high) energies; and (d) good agreement between the classical and semiclassical results is found above the classical dynamic threshold. Finally, the convergence of P/sup diss/ for increasing box length is shown to be rapid and satisfactory
Csörgő, Tamás Hegyi, Sándor Kittel, Wolfram
The Table of Contents for the book is as follows: * Preface * QCD IN MULTIPARTICLE PRODUCTION * QCD and multiparticle production - The status of the perturbative cascade * Test of QCD predictions for multiparticle production at LEP * Multijet final states in e+e- annihilation * Tests of QCD in two photon physics at LEP * Interplay between perturbative and non-perturbative QCD in three-jet events * QCD and hadronic final states at the LHC * Transverse energy and minijets in high energy collisions * Multiparticle production at RHIC and LHC: A classical point of view * High energy interaction with the nucleus in the perturbative QCD with Nc → ∞ * DIFFRACTIVE PRODUCTION AND SMALL-x * Introduction to low-x physics and diffraction * Low-x physics at HERA * Diffractive structure functions at the Tevatron * What is the experimental evidence for the BFKL Pomeron? * Self-organized criticality in gluon systems and its consequences * Scale anomaly and dipole scattering in QCD * Pomeron and AdS/CFT correspondence for QCD * INTERPLAY BETWEEN SOFT AND HARD PHENOMENA * Inclusive jet cross sections and BFKL dynamics searches in dijet cross sections * Soft and hard interactions in p bar{p} Collisions at √ s = 1800 and 630 GeV * Recent results on particle production from OPAL * New results on αs and optimized scales * Preliminary results of the standard model Higgs boson search at LEP 2 in 2000 * Ways to go between hard and soft QCD * Alternative scenarios for fragmentation of a gluonic Lund String * A simultaneous measurement of the QCD colour charges and the strong coupling from LEP multijet data * Branching processes and Koenigs function * Soft and hard QCD dynamics in J/ψ hadroproduction * HADRONIC FINAL STATES IN 1+1, 1+h AND h+h REACTIONS * Universality in hadron production in electron-positron, lepton-hadron and hadron-hadron reactions * Search for gluonic mesons in gluon jets * Vector-to-pseudoscalar and meson-to-baryon ratios in hadronic Z decays at LEP
Molecular dynamics simulation of structural changes during the collision of copper nanoparticles
International Nuclear Information System (INIS)
Rojas T, Justo; Instituto Peruano de Energia Nuclear, Lima; Copa, Betty
2009-01-01
Molecular dynamics simulations with embedded-atom potential (EAM) have been performed to study the energetic and structural changes during the collision and coalescence of two Cu n nanoparticles. We simulated collision of nanoparticles at several temperatures below the melting point and with different impact energy. Analyzing the potential energy change during the collision we identify three clearly defined stages. The pair correlation function and the pair analysis technique are used to reveal the structural changes in the collision process. The variation in the time of the population of different pairs has been quantified, being observed diverse structural transformations. During the collision of two equal icosahedral nanoparticles ( Cu 55 ) has been observed different behavior of 1551 pairs depending on the impact velocity. (author).
TRIDYN - binary collision simulation of atomic collisions dynamic composition changes in solids
International Nuclear Information System (INIS)
Moeller, W.; Eckstein, W.
1988-05-01
The report deals with the computerized simulation of the following problem: a beam of fast ions entering a solid substance is slowed down and scattered due to electronic interaction and nuclear collisions. Together with created recoil atoms local compositional changes are produced. For large fluences collisional mixing is caused in layered substances. (BHO)
Non-Markovianity in the collision model with environmental block
Jin, Jiasen; Yu, Chang-shui
2018-05-01
We present an extended collision model to simulate the dynamics of an open quantum system. In our model, the unit to represent the environment is, instead of a single particle, a block which consists of a number of environment particles. The introduced blocks enable us to study the effects of different strategies of system–environment interactions and states of the blocks on the non-Markovianities. We demonstrate our idea in the Gaussian channels of an all-optical system and derive a necessary and sufficient condition of non-Markovianity for such channels. Moreover, we show the equivalence of our criterion to the non-Markovian quantum jump in the simulation of the pure damping process of a single-mode field. We also show that the non-Markovianity of the channel working in the strategy that the system collides with environmental particles in each block in a certain order will be affected by the size of the block and the embedded entanglement and the effects of heating and squeezing the vacuum environmental state will quantitatively enhance the non-Markovianity.
Hydrodynamic modelling for relativistic heavy-ion collisions at RHIC ...
Indian Academy of Sciences (India)
model, to describe the microscopic evolution and decoupling of the hadronic ... progress on hydrodynamic modelling, investigation on the flow data and the ... and to describe and predict the soft particle physics in relativistic heavy-ion collisions [4]. It is based on the conservation laws of energy, momentum and net charge ...
A Mathematical Model for Analysis on Ships Collision Avoidance ...
African Journals Online (AJOL)
This study develops a mathematical model for analysis on collision avoidance of ships. The obtained model provides information on the quantitative effect of the ship's engine's response and the applied reversing force on separation distance and stopping abilities of the ships. Appropriate evasive maneuvers require the ...
Ghanem, Bernard; Ahuja, Narendra
2013-01-01
This paper proposes the problem of modeling video sequences of dynamic swarms (DSs). We define a DS as a large layout of stochastically repetitive spatial configurations of dynamic objects (swarm elements) whose motions exhibit local spatiotemporal
Dynamics of the water dimer + nitric oxide collision
Energy Technology Data Exchange (ETDEWEB)
Ree, Jong Baik [Dept. of Chemistry Education, Chonnam National University, Gwangju (Korea, Republic of); Kim, Yoo Hang [Dept. of Chemistry, Inha University, Incheon (Korea, Republic of); Shin, Hyung Kyu [Dept. of Chemistry, University of Nevada, Nevada (Korea, Republic of)
2017-02-15
Collision-induced intermolecular energy transfer and intramolecular vibrational redistribution in the collision of a water dimer and nitric oxide are studied by use of quasiclassical procedures. Intermolecular energy flow is shown to occur mainly through a direct-mode mechanism transferring relatively large amounts in strong collisions. About a quarter of the energy initially deposited in the dimer transfers to the ground state NO, while the rest redistributes among internal motions of the collision system. The main portion of initial energy deposited in the dimer redistributes in the stretches of the donor monomer through the 1:1 resonance followed by in the bend through the 1:2 resonance. Energy transfer from the excited NO to the ground-state dimer is equally efficient, transferring more than half the initial excitation to the donor monomer, the efficiency that is attributed to the internal modes operating as energy reservoirs. The hydrogen bond shares about 15% of the initial excitation stored in both dimer-to-NO and NO-to-dimer processes as a result of strong coupling of the hydrogen bond with the proton-donor OH bond of the monomer. A small fraction of collisions proceeds through a complex-mode mechanism and lead to NO dissociation, the dissociated O atom showing a propensity to form a new hydrogen bond.
A mathematical model of bird collisions with wind turbine rotors
International Nuclear Information System (INIS)
Tucker, V.A.
1996-01-01
When a bird flies through the disk swept out by the blades of a wind turbine rotor, the probability of collision depends on the motions and dimensions of the bird and the blades. The collision model in this paper predicts the probability for birds that glide upwind, downwind, an across the wind past simple one-dimensional blades represented by straight lines, and upwind and downwind past more realistic three-dimensional blades with chord and twist. Probabilities vary over the surface of the disk, and in most cases, the tip of the blade is less likely to collide with a bird than parts of the blade nearer the hub. The mean probability may be found by integration over the disk area. The collision model identifies the rotor characteristics that could be altered to make turbines safer for birds
Discrete Velocity Models for Polyatomic Molecules Without Nonphysical Collision Invariants
Bernhoff, Niclas
2018-05-01
An important aspect of constructing discrete velocity models (DVMs) for the Boltzmann equation is to obtain the right number of collision invariants. Unlike for the Boltzmann equation, for DVMs there can appear extra collision invariants, so called spurious collision invariants, in plus to the physical ones. A DVM with only physical collision invariants, and hence, without spurious ones, is called normal. The construction of such normal DVMs has been studied a lot in the literature for single species, but also for binary mixtures and recently extensively for multicomponent mixtures. In this paper, we address ways of constructing normal DVMs for polyatomic molecules (here represented by that each molecule has an internal energy, to account for non-translational energies, which can change during collisions), under the assumption that the set of allowed internal energies are finite. We present general algorithms for constructing such models, but we also give concrete examples of such constructions. This approach can also be combined with similar constructions of multicomponent mixtures to obtain multicomponent mixtures with polyatomic molecules, which is also briefly outlined. Then also, chemical reactions can be added.
Realistic modelling of jets in heavy-ion collisions
International Nuclear Information System (INIS)
Young, Clint; Schenke, Björn; Jeon, Sangyong; Gale, Charles
2013-01-01
The reconstruction of jets in heavy-ion collisions provides insight into the dynamics of hard partons in media. Unlike the spectrum of single hadrons, the spectrum of jets is highly sensitive to q -hat ⊥ , as well as being sensitive to partonic energy loss and radiative processes. We use martini, an event generator, to study how finite-temperature processes at leading order affect dijets
Time-based collision risk modeling for air traffic management
Bell, Alan E.
Since the emergence of commercial aviation in the early part of last century, economic forces have driven a steadily increasing demand for air transportation. Increasing density of aircraft operating in a finite volume of airspace is accompanied by a corresponding increase in the risk of collision, and in response to a growing number of incidents and accidents involving collisions between aircraft, governments worldwide have developed air traffic control systems and procedures to mitigate this risk. The objective of any collision risk management system is to project conflicts and provide operators with sufficient opportunity to recognize potential collisions and take necessary actions to avoid them. It is therefore the assertion of this research that the currency of collision risk management is time. Future Air Traffic Management Systems are being designed around the foundational principle of four dimensional trajectory based operations, a method that replaces legacy first-come, first-served sequencing priorities with time-based reservations throughout the airspace system. This research will demonstrate that if aircraft are to be sequenced in four dimensions, they must also be separated in four dimensions. In order to separate aircraft in four dimensions, time must emerge as the primary tool by which air traffic is managed. A functional relationship exists between the time-based performance of aircraft, the interval between aircraft scheduled to cross some three dimensional point in space, and the risk of collision. This research models that relationship and presents two key findings. First, a method is developed by which the ability of an aircraft to meet a required time of arrival may be expressed as a robust standard for both industry and operations. Second, a method by which airspace system capacity may be increased while maintaining an acceptable level of collision risk is presented and demonstrated for the purpose of formulating recommendations for procedures
Dynamic Latent Classification Model
DEFF Research Database (Denmark)
Zhong, Shengtong; Martínez, Ana M.; Nielsen, Thomas Dyhre
as possible. Motivated by this problem setting, we propose a generative model for dynamic classification in continuous domains. At each time point the model can be seen as combining a naive Bayes model with a mixture of factor analyzers (FA). The latent variables of the FA are used to capture the dynamics...
Collision prediction models using multivariate Poisson-lognormal regression.
El-Basyouny, Karim; Sayed, Tarek
2009-07-01
This paper advocates the use of multivariate Poisson-lognormal (MVPLN) regression to develop models for collision count data. The MVPLN approach presents an opportunity to incorporate the correlations across collision severity levels and their influence on safety analyses. The paper introduces a new multivariate hazardous location identification technique, which generalizes the univariate posterior probability of excess that has been commonly proposed and applied in the literature. In addition, the paper presents an alternative approach for quantifying the effect of the multivariate structure on the precision of expected collision frequency. The MVPLN approach is compared with the independent (separate) univariate Poisson-lognormal (PLN) models with respect to model inference, goodness-of-fit, identification of hot spots and precision of expected collision frequency. The MVPLN is modeled using the WinBUGS platform which facilitates computation of posterior distributions as well as providing a goodness-of-fit measure for model comparisons. The results indicate that the estimates of the extra Poisson variation parameters were considerably smaller under MVPLN leading to higher precision. The improvement in precision is due mainly to the fact that MVPLN accounts for the correlation between the latent variables representing property damage only (PDO) and injuries plus fatalities (I+F). This correlation was estimated at 0.758, which is highly significant, suggesting that higher PDO rates are associated with higher I+F rates, as the collision likelihood for both types is likely to rise due to similar deficiencies in roadway design and/or other unobserved factors. In terms of goodness-of-fit, the MVPLN model provided a superior fit than the independent univariate models. The multivariate hazardous location identification results demonstrated that some hazardous locations could be overlooked if the analysis was restricted to the univariate models.
2011-09-01
This report presents the test results and finite element correlations of a full-scale dynamic collision test with rail vehicles as part of the Federal Railroad Administrations research program on improved crashworthiness of locomotive structures. ...
Modeling of driver's collision avoidance maneuver based on controller switching model.
Kim, Jong-Hae; Hayakawa, Soichiro; Suzuki, Tatsuya; Hayashi, Koji; Okuma, Shigeru; Tsuchida, Nuio; Shimizu, Masayuki; Kido, Shigeyuki
2005-12-01
This paper presents a modeling strategy of human driving behavior based on the controller switching model focusing on the driver's collision avoidance maneuver. The driving data are collected by using the three-dimensional (3-D) driving simulator based on the CAVE Automatic Virtual Environment (CAVE), which provides stereoscopic immersive virtual environment. In our modeling, the control scenario of the human driver, that is, the mapping from the driver's sensory information to the operation of the driver such as acceleration, braking, and steering, is expressed by Piecewise Polynomial (PWP) model. Since the PWP model includes both continuous behaviors given by polynomials and discrete logical conditions, it can be regarded as a class of Hybrid Dynamical System (HDS). The identification problem for the PWP model is formulated as the Mixed Integer Linear Programming (MILP) by transforming the switching conditions into binary variables. From the obtained results, it is found that the driver appropriately switches the "control law" according to the sensory information. In addition, the driving characteristics of the beginner driver and the expert driver are compared and discussed. These results enable us to capture not only the physical meaning of the driving skill but the decision-making aspect (switching conditions) in the driver's collision avoidance maneuver as well.
Molenaar, Peter C M
2017-01-01
Equivalences of two classes of dynamic models for weakly stationary multivariate time series are discussed: dynamic factor models and autoregressive models. It is shown that exploratory dynamic factor models can be rotated, yielding an infinite set of equivalent solutions for any observed series. It also is shown that dynamic factor models with lagged factor loadings are not equivalent to the currently popular state-space models, and that restriction of attention to the latter type of models may yield invalid results. The known equivalent vector autoregressive model types, standard and structural, are given a new interpretation in which they are conceived of as the extremes of an innovating type of hybrid vector autoregressive models. It is shown that consideration of hybrid models solves many problems, in particular with Granger causality testing.
Czech Academy of Sciences Publication Activity Database
Lukerchenko, Nikolay
2012-01-01
Roč. 50, č. 2 (2012), s. 251-252 ISSN 0022-1686 Institutional research plan: CEZ:AV0Z20600510 Keywords : saltation * spherical particle * particle-particle collision * numerical model Subject RIV: BK - Fluid Dynamics
Transport models for relativistic heavy-ion collisions at Relativistic ...
Indian Academy of Sciences (India)
While the free-streaming of particles in the kinetic theory drive the system out of equi- ... For collisions at RHIC and LHC, a transport model may involve four main com- ...... Further, there are many important conceptual issues such as imple-.
Pseudo potentials and model potentials in atomic collisions
International Nuclear Information System (INIS)
Reyes, O.; Jouin, H.; Fuentealba, P.
1988-01-01
In this work, it is discussed the main differences between the use of pseudo-potentials and model potentials in collision problems . It is shown the potential energy curves for distinct systems obtained with both kinds of potentials. (A.C.A.S.) [pt
Parsons, Neal; Levin, Deborah A; van Duin, Adri C T; Zhu, Tong
2014-12-21
The Direct Simulation Monte Carlo (DSMC) method typically used for simulating hypersonic Earth re-entry flows requires accurate total collision cross sections and reaction probabilities. However, total cross sections are often determined from extrapolations of relatively low-temperature viscosity data, so their reliability is unknown for the high temperatures observed in hypersonic flows. Existing DSMC reaction models accurately reproduce experimental equilibrium reaction rates, but the applicability of these rates to the strong thermal nonequilibrium observed in hypersonic shocks is unknown. For hypersonic flows, these modeling issues are particularly relevant for nitrogen, the dominant species of air. To rectify this deficiency, the Molecular Dynamics/Quasi-Classical Trajectories (MD/QCT) method is used to accurately compute collision and reaction cross sections for the N2(Σg+1)-N2(Σg+1) collision pair for conditions expected in hypersonic shocks using a new potential energy surface developed using a ReaxFF fit to recent advanced ab initio calculations. The MD/QCT-computed reaction probabilities were found to exhibit better physical behavior and predict less dissociation than the baseline total collision energy reaction model for strong nonequilibrium conditions expected in a shock. The MD/QCT reaction model compared well with computed equilibrium reaction rates and shock-tube data. In addition, the MD/QCT-computed total cross sections were found to agree well with established variable hard sphere total cross sections.
International Nuclear Information System (INIS)
Parsons, Neal; Levin, Deborah A.; Duin, Adri C. T. van; Zhu, Tong
2014-01-01
The Direct Simulation Monte Carlo (DSMC) method typically used for simulating hypersonic Earth re-entry flows requires accurate total collision cross sections and reaction probabilities. However, total cross sections are often determined from extrapolations of relatively low-temperature viscosity data, so their reliability is unknown for the high temperatures observed in hypersonic flows. Existing DSMC reaction models accurately reproduce experimental equilibrium reaction rates, but the applicability of these rates to the strong thermal nonequilibrium observed in hypersonic shocks is unknown. For hypersonic flows, these modeling issues are particularly relevant for nitrogen, the dominant species of air. To rectify this deficiency, the Molecular Dynamics/Quasi-Classical Trajectories (MD/QCT) method is used to accurately compute collision and reaction cross sections for the N 2 ( 1 Σ g + )-N 2 ( 1 Σ g + ) collision pair for conditions expected in hypersonic shocks using a new potential energy surface developed using a ReaxFF fit to recent advanced ab initio calculations. The MD/QCT-computed reaction probabilities were found to exhibit better physical behavior and predict less dissociation than the baseline total collision energy reaction model for strong nonequilibrium conditions expected in a shock. The MD/QCT reaction model compared well with computed equilibrium reaction rates and shock-tube data. In addition, the MD/QCT-computed total cross sections were found to agree well with established variable hard sphere total cross sections
Cascade statistics in the binary collision approximation and in full molecular dynamics
International Nuclear Information System (INIS)
Hou, M.; Pan, Z.Y.
1995-01-01
The Binary Collision Approximation (BCA) and Molecular Dynamics (MD) are used to simulate low energy atomic collision cascades in solids. Results are compared and discussed on the example of copper and gold self irradiation. For MD, long range N-body potentials are built, similar to those deduced from the second moment semi-empirical tight binding model. The pair interaction contribution is splined to a Moliere screened Coulomb potential at small separation distances. The BCA calculations are performed with the MARLOWE program, using the same Moliere potential as for MD, and modelling the N-body contribution by a binding of the atoms to their equilibrium lattice sites. The scattering integrals are estimated by means of a 4 points Gauss-Mehler quadrature. In MD, the NVT equations of motion are integrated with a constant time step of 2 fs. For the NVE cascade simulations, the Newton equations of motion are solved with a dynamically adjusted time step, kept lower than 2 fs. The influence of the time step on the simulated trajectories is discussed. The mean number of moving atoms with total energy above threshold values ranging from 1 to 100 eV is estimated as a function of time over 300 fs both with MARLOWE and by MD. This estimate is repeated for external primary energies ranging from 250 eV to 1 keV. In the case of copper, the BCA results are found to be in remarkable agreement with MD over about 200 fs cascade development, provided the size of the crystallite used in MD is sufficiently large in order to account for the early mechanical response of the close environment. This agreement between the two methods is found to be the best when the binding energy of the target atoms as modelled in the BCA is adjusted to a value close to the cohesive energy. In the case of gold, the agreement between BCA and MD is reasonable and the results suggest the need of an accurate modelling of linear collision sequences in the BCA. (orig.)
The multistring model VENUS for ultrarelativistic heavy ion collisions
International Nuclear Information System (INIS)
Werner, K.
1988-02-01
The event generator VENUS is based on a multistring model for heavy ion collisions at ultrarelativistic energies. The model is a straightforward extension of a successful model for soft proton-proton scattering, the latter one being consistent with e/sup /plus//e/sup /minus// annihilation and deep inelastic lepton scattering. Comparisons of VENUS results with pA and recent AA data alow some statements about intranuclear cascading. 18 refs., 7 figs
Inclusion of the diffuseness in the schematic model of heavy ion collisions
International Nuclear Information System (INIS)
Marta, H.D.
1989-01-01
The schematic model of central heavy ion collisions developed by Swiatecki includes the Coulomb and surface contributions to the potential energy of the system and one-body dissipation. This model is extended by considering the diffuseness of the nuclear surface; this has the implication that we must consider the proximity forces in the dynamics of the collisions. For the sake of simplicity we work with symmetrical systems. The results of the model studied are compared with experimental data and with other theoretical calculations. We conclude that the detailed consideration of the diffuseness of the nuclear surfaces does not substantially change the results of the schematic model for sharp surfaces in which the diffuseness is considered only through the parameters. (author) [pt
International Nuclear Information System (INIS)
Adebayo, G.A.; Anusionwu, B.C.; Njah, A.N.; Adeniran, O.J.; Mathew, B.; Sunmonu, R.S.
2009-01-01
Arising from the inability of theoretical calculations to give accurate descriptions of (shear) viscosity in rare gases at high densities, we investigated the likely cause of discrepancy between theory and experiments. Molecular Dynamics simulations were performed to calculate transport coefficients and collision frequency of rare gases at high densities and different temperatures using a Lennard-Jones modelled pair potential. The results, when compared with experiments show an underestimation of the viscosity calculated through the Green-Kubo formalism, but in agreement with some other calculations performed by other groups. In the present work the origin of the underestimation is considered. Analyses of the transport coefficients show a very high collision frequency which suggests an atom may spend much less time in the neighbourhood of the fields of force of another atom and that the distribution in the systems studied adjusts itself to a nearly Maxwellian type which resulted in a locally and temporarily slowly varying temperature. We show that the time spent in the fields of force is so small compared with relaxation time thereby leading to a possible reduction in local velocity auto-correlation between atoms. (author)
International Nuclear Information System (INIS)
Oliva, L; Plumari, S; Scardina, F; Greco, V; Ruggieri, M
2017-01-01
In this study we discuss our results on the spectrum of photons emitted from the quark-gluon plasma produced in heavy ion collisions at RHIC energies. Simulating the space-time evolution of the fireball by solving the relativistic Boltzmann transport equation and including two-particle scattering processes with photon emission allows us to make a first step in the description of thermal photons from the QGP as well as of those produced in the pre-equilibrium stage. Indeed, we consider not only a standard Glauber initial condition but also a model in which quarks and gluons are produced in the very early stage through the Schwinger mechanism by the decay of an initial color-electric field. In the latter approach relativistic kinetic equations are coupled in a self-consistent way to field equations. We aim at spotting the impact of early stage non-equilibrium dynamics on the photon production. (paper)
How to combine binary collision approximation and multi-body potential for molecular dynamics
International Nuclear Information System (INIS)
Saito, Seiki; Nakamura, Hiroaki; Takayama, Arimichi; Ito, Atsushi M.; Kenmotsu, Takahiro
2010-01-01
Our group has been developing a hybrid simulation of the molecular dynamics (MD) and the binary collision approximation (BCA) simulation. One of the main problems of this hybridization model is that the multi-body potential suddenly appears at the moment when the simulation method switches from the BCA to the MD. This instantaneously emerged multi-body potential causes the acceleration or deceleration of atoms of the system. To solve this problem, the kinetic energy of atoms should be corrected to conserve the total energy in the system. This paper gives the solution. The hybrid simulation for hydrogen atom injection into a graphite material is executed in order to demonstrate the solution. (author)
Towards a Collision-Free WLAN: Dynamic Parameter Adjustment in CSMA/E2CA
Directory of Open Access Journals (Sweden)
Bellalta Boris
2011-01-01
Full Text Available Carrier sense multiple access with enhanced collision avoidance (CSMA/ECA is a distributed MAC protocol that allows collision-free access to the medium in WLANs. The only difference between CSMA/ECA and the well-known CSMA/CA is that the former uses a deterministic backoff after successful transmissions. Collision-free operation is reached after a transient state during which some collisions may occur. This paper shows that the duration of the transient state can be shortened by appropriately setting the contention parameters. Standard absorbing Markov chain theory is used to describe the behaviour of the system in the transient state and to predict the expected number of slots to reach the collision-free operation. The paper also introduces CSMA/E2CA, in which a deterministic backoff is used two consecutive times after a successful transmission. CSMA/E2CA converges quicker to collision-free operation and delivers higher performance than CSMA/ECA, specially in harsh wireless scenarios with high frame-error rates. The last part of the paper addresses scenarios with a large number of contenders. We suggest dynamic parameter adjustment techniques to accommodate a varying (and potentially high number of contenders. The effectiveness of these adjustments in preventing collisions is validated by means of simulation.
A numerical strategy for finite element modeling of frictionless asymmetric vocal fold collision.
Granados, Alba; Misztal, Marek Krzysztof; Brunskog, Jonas; Visseq, Vincent; Erleben, Kenny
2017-02-01
Analysis of voice pathologies may require vocal fold models that include relevant features such as vocal fold asymmetric collision. The present study numerically addresses the problem of frictionless asymmetric collision in a self-sustained three-dimensional continuum model of the vocal folds. Theoretical background and numerical analysis of the finite-element position-based contact model are presented, along with validation. A novel contact detection mechanism capable to detect collision in asymmetric oscillations is developed. The effect of inexact contact constraint enforcement on vocal fold dynamics is examined by different variational methods for inequality constrained minimization problems, namely, the Lagrange multiplier method and the penalty method. In contrast to the penalty solution, which is related to classical spring-like contact forces, numerical examples show that the parameter-independent Lagrange multiplier solution is more robust and accurate in the estimation of dynamical and mechanical features at vocal fold contact. Furthermore, special attention is paid to the temporal integration schemes in relation to the contact problem, the results suggesting an advantage of highly diffusive schemes. Finally, vocal fold contact enforcement is shown to affect asymmetric oscillations. The present model may be adapted to existing vocal fold models, which may contribute to a better understanding of the effect of the nonlinear contact phenomenon on phonation. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Comparison of many bodied and binary collision cascade models up to 1 keV
International Nuclear Information System (INIS)
Schwartz, D.M.; Schiffgens, J.D.; Doran, D.G.; Odette, G.R.; Ariyasu, R.G.
1976-01-01
A quasi-dynamical code ADDES has been developed to model displacement cascades in copper for primary knockon atom energies up to several keV. ADDES is like a dynamical code in that it employs a many body treatment, yet similar to a binary collision code in that it incorporates the basic assumption that energy transfers below several eV can be ignored in describing cascade evolution. This paper is primarily concerned with (1) a continuing effort to validate the assumptions and specific parameters in the code by the comparison of ADDES results with experiment and with results from a dynamical code, and (2) comparisons of ADDES results with those from a binary collision code. The directional dependence of the displacement threshold is in reasonable agreement with the measurements of Jung et al. The behavior of focused replacement sequences is very similar to that obtained with the dynamical codes GRAPE and COMENT. Qualitative agreement was found between ADDES and COMENT for a higher energy (500 eV) defocused event while differences, still under study, are apparent in a 250 eV high index event. Comparisons of ADDES with the binary collision code MARLOWE show surprisingly good agreement in the 250 to 1000 eV range for both number and separation of Frenkel pairs. A preliminary observation, perhaps significant to displacement calculations utilizing the concept of a mean displacement energy, is the dissipation of 300 to 400 eV in a replacement sequence producing a single interstitial
Time-dependent shell-model theory of dissipative heavy-ion collisions
International Nuclear Information System (INIS)
Ayik, S.; Noerenberg, W.
1982-01-01
A transport theory is formulated within a time-dependent shell-model approach. Time averaging of the equations for macroscopic quantities lead to irreversibility and justifies weak-coupling limit and Markov approximation for the (energy-conserving) one- and two-body collision terms. Two coupled equations for the occupation probabilities of dynamical single-particle states and for the collective variable are derived and explicit formulas for transition rates, dynamical forces, mass parameters and friction coefficients are given. The applicability of the formulation in terms of characteristic quantities of nuclear systems is considered in detail and some peculiarities due to memory effects in the initial equilibration process of heavy-ion collisions are discussed. (orig.)
Studies of collision dynamics in electron capture processes
International Nuclear Information System (INIS)
Hansen, J.P.
1990-12-01
This thesis presents some recent development in time-dependent coupled channel methods for one- and two-electron systems. The methods have been applied to detailed studies on several different aspects of charge transfer processes in ion-atom collisions at intermediate to low energies. Measurable quantities, such as partial and total cross sections, partial cross sections in projectile energy gain, orientation and alignment fractions, have been calculated. Confrontation with experiments has in general given good agreement. 29 refs
Studies of collision dynamics in electron capture processes
International Nuclear Information System (INIS)
Hansen, J.P.
1989-12-01
The thesis presents some recent development in time-dependent coupled channel methods for one- and two-electron systems. The methods have been applied to detailed studies on several different aspects of charge transfer processes in ion-atom collisions at intermediate to low energies. Measurable quantities, such as partial and total cross sections, partial cross sections in projectile energy gain, orientation and alignment fractions, have been calculated. Confrontation with experiments has in general given good agreement. 14 refs., 2 figs
NASA Lewis Launch Collision Probability Model Developed and Analyzed
Bollenbacher, Gary; Guptill, James D
1999-01-01
There are nearly 10,000 tracked objects orbiting the earth. These objects encompass manned objects, active and decommissioned satellites, spent rocket bodies, and debris. They range from a few centimeters across to the size of the MIR space station. Anytime a new satellite is launched, the launch vehicle with its payload attached passes through an area of space in which these objects orbit. Although the population density of these objects is low, there always is a small but finite probability of collision between the launch vehicle and one or more of these space objects. Even though the probability of collision is very low, for some payloads even this small risk is unacceptable. To mitigate the small risk of collision associated with launching at an arbitrary time within the daily launch window, NASA performs a prelaunch mission assurance Collision Avoidance Analysis (or COLA). For the COLA of the Cassini spacecraft, the NASA Lewis Research Center conducted an in-house development and analysis of a model for launch collision probability. The model allows a minimum clearance criteria to be used with the COLA analysis to ensure an acceptably low probability of collision. If, for any given liftoff time, the nominal launch vehicle trajectory would pass a space object with less than the minimum required clearance, launch would not be attempted at that time. The model assumes that the nominal positions of the orbiting objects and of the launch vehicle can be predicted as a function of time, and therefore, that any tracked object that comes within close proximity of the launch vehicle can be identified. For any such pair, these nominal positions can be used to calculate a nominal miss distance. The actual miss distances may differ substantially from the nominal miss distance, due, in part, to the statistical uncertainty of the knowledge of the objects positions. The model further assumes that these position uncertainties can be described with position covariance matrices
On the dynamical fluctuations in the multiparticle final states of e+e- collisions
International Nuclear Information System (INIS)
Liu Fuming; Liu Feng; Liu Lianshou
1999-01-01
The scaling property of factorial moments in the multiparticle final-states of e + e - collisions is studied in both the laboratory and the thrust-axis coordinate systems by using the Jetset generator. It turns out that in both of the two cases, the 3-dimensional lnF 2 -lnM are approximately straight lines when the phase space are divided isotropically in different directions, showing that the dynamical fluctuations in the multiparticle final-state of e + e - collisions are approximately isotropic. In the lab system, the three γ parameters obtained by fitting F 2 -M of p x , p y , p z to Ochs formula respectively are approximately equal. In the thrust system, the three γ values obtained by fitting F 2 (y)-M, F 2 (p t )-M and F 2 (φ)-M are also close to each other provided the starting point in fitting F 2 (φ)-M is chosen appropriately. All of these provide further evidence for the above assertion. The results show that the essential feature, i.e. anisotropy of approximate) isotropy, of the dynamical fluctuations in soft and hard processes can be revealed by studying the scaling property of factorial moments in the collisions. Therefore, further investigation of the scaling properties of factorial moments in various kinds of collisions processes is significant for the understanding of the essential characteristics of collision dynamics
International Nuclear Information System (INIS)
Verkhovtsev, A.; Korol, A.V.; Solovyov, A.V.
2017-01-01
We present the results of classical molecular dynamics simulations of collision-induced fusion and fragmentation of C 60 fullerenes, performed by means of the MBN Explorer software package. The simulations provide information on structural differences of the fused compound depending on kinematics of the collision process. The analysis of fragmentation dynamics at different initial conditions shows that the size distributions of produced molecular fragments are peaked for dimers, which is in agreement with a well-established mechanism of C 60 fragmentation via preferential C 2 emission. Atomic trajectories of the colliding particles are analyzed and different fragmentation patterns are observed and discussed. On the basis of the performed simulations, characteristic time of C 2 emission is estimated as a function of collision energy. The results are compared with experimental time-of-flight distributions of molecular fragments and with earlier theoretical studies. Considering the widely explored case study of C 60 -C 60 collisions, we demonstrate broad capabilities of the MBN Explorer software, which can be utilized for studying collisions of a broad variety of nano-scale and bio-molecular systems by means of classical molecular dynamics. (authors)
Multiple-collision model for pion production in relativistic nucleus-nucleus collisions
International Nuclear Information System (INIS)
Vary, J.P.
1978-01-01
A simple model for pion production in relativistic heavy-ion collisions is developed based on nucleon-nucleon data, nuclear density distribution, and the assumption of straight-line trajectories. Multiplicity distributions for total pion production and for negative-pion production are predicted for 40 Ar incident on a Pb 3 O 4 target at 1.8 GeV/nucleon. Production through intermediate baryon resonances reduces the high-multiplicity region but insufficiently to yield agreement with data. This implies the need for a coherent production mechanism
Dynamics of complete and incomplete fusion in heavy ion collisions
Bao, Xiao Jun; Guo, Shu Qing; Zhang, Hong Fei; Li, Jun Qing
2018-02-01
In order to study the influence of the strong Coulomb and nuclear interactions on the dynamics of complete and incomplete fusion, we construct a new four-variable master equation (ME) so that the deformations as well as the nucleon transfer are viewed as consistently governed by MEs in the potential energy surface of the system. The calculated yields of quasifission fragments and evaporation residue cross section (ERCS) are in agreement with experimental data of hot fusion reactions. Comparing cross sections by theoretical results and experimental data, we find the improved dinuclear sysytem model also describes the transfer cross sections reasonably. The production cross sections of new neutron-rich isotopes are estimated by the multinucleon transfer reactions.
Special dynamic behavior of an aluminum alloy and effects on energy absorption in train collisions
Directory of Open Access Journals (Sweden)
Chao Yang
2016-05-01
Full Text Available Dynamic tension tests and compression tests were carried out for 5083-H111 aluminum alloy to investigate the dynamic mechanical behavior and its effect on energy absorption characteristics of an energy-absorbing device. The material constitutive relations were obtained at various levels of strain rates by means of tests. Three material models were performed on the energy-absorbing device of railway vehicles. We investigated the influence of the material dynamic behavior on the energy absorption capability. The results indicate that 5083-H111 aluminum alloy is endowed with negative strain rate sensitivity at medium–low strain rates and possesses the feature of negative and then positive strain rate sensitivity in the range of medium strain rates. The material presents obvious strain rate strengthening effect at high strain rates. Moreover, the order of magnitudes of the strain rate in the train collision is 0–2. It belongs to the medium strain rate. The practical absorbed energy of the structure made of 5083-H111 alloy is less than that of the same structure without regard to the strain rate effect in design phases.
Models for Dynamic Applications
DEFF Research Database (Denmark)
Sales-Cruz, Mauricio; Morales Rodriguez, Ricardo; Heitzig, Martina
2011-01-01
This chapter covers aspects of the dynamic modelling and simulation of several complex operations that include a controlled blending tank, a direct methanol fuel cell that incorporates a multiscale model, a fluidised bed reactor, a standard chemical reactor and finally a polymerisation reactor...... be applied to formulate, analyse and solve these dynamic problems and how in the case of the fuel cell problem the model consists of coupledmeso and micro scale models. It is shown how data flows are handled between the models and how the solution is obtained within the modelling environment....
Modelling MIZ dynamics in a global model
Rynders, Stefanie; Aksenov, Yevgeny; Feltham, Daniel; Nurser, George; Naveira Garabato, Alberto
2016-04-01
Exposure of large, previously ice-covered areas of the Arctic Ocean to the wind and surface ocean waves results in the Arctic pack ice cover becoming more fragmented and mobile, with large regions of ice cover evolving into the Marginal Ice Zone (MIZ). The need for better climate predictions, along with growing economic activity in the Polar Oceans, necessitates climate and forecasting models that can simulate fragmented sea ice with a greater fidelity. Current models are not fully fit for the purpose, since they neither model surface ocean waves in the MIZ, nor account for the effect of floe fragmentation on drag, nor include sea ice rheology that represents both the now thinner pack ice and MIZ ice dynamics. All these processes affect the momentum transfer to the ocean. We present initial results from a global ocean model NEMO (Nucleus for European Modelling of the Ocean) coupled to the Los Alamos sea ice model CICE. The model setup implements a novel rheological formulation for sea ice dynamics, accounting for ice floe collisions, thus offering a seamless framework for pack ice and MIZ simulations. The effect of surface waves on ice motion is included through wave pressure and the turbulent kinetic energy of ice floes. In the multidecadal model integrations we examine MIZ and basin scale sea ice and oceanic responses to the changes in ice dynamics. We analyse model sensitivities and attribute them to key sea ice and ocean dynamical mechanisms. The results suggest that the effect of the new ice rheology is confined to the MIZ. However with the current increase in summer MIZ area, which is projected to continue and may become the dominant type of sea ice in the Arctic, we argue that the effects of the combined sea ice rheology will be noticeable in large areas of the Arctic Ocean, affecting sea ice and ocean. With this study we assert that to make more accurate sea ice predictions in the changing Arctic, models need to include MIZ dynamics and physics.
Dynamic Test of a Collision Post of a State-of-the-Art End Frame Design
2008-09-24
In support of the Federal Railroad Administration's (FRA) : Railroad Equipment Safety Program, a full-scale dynamic test : of a collision post of a state-of-the-art (SOA) end frame was : conducted on April 16, 2008. The purpose of the test was to : e...
New Development on Modelling Fluctuations and Fragmentation in Heavy-Ion Collisions
Lin, Hao; Danielewicz, Pawel
2017-09-01
During heavy-ion collisions (HIC), colliding nuclei form an excited composite system. Instabilities present in the system may deform the shape of the system exotically, leading to a break-up into fragments. Many experimental efforts have been devoted to the nuclear multifragmentation phenomenon, while traditional HIC models, lacking in proper treatment of fluctuations, fall short in explaining it. In view of this, we are developing a new model to implement realistic fluctuations into transport simulation. The new model is motivated by the Brownian motion description of colliding particles. The effects of two-body collisions are recast in one-body diffusion processes. Vastly different dynamical paths are sampled by solving Langevin equations in momentum space. It is the stochastic sampling of dynamical paths that leads to a wide spread of exit channels. In addition, the nucleon degree of freedom is used to enhance the fluctuations. The model has been tested in reactions such as 112Sn + 112Sn and 58Ni + 58Ni, where reasonable results are yielded. An exploratory comparison on the 112Sn + 112Sn reaction at 50 MeV/nucleon with two other models, the stochastic mean-field (SMF) and the antisymmetrized molecular dynamics (AMD) models, has also been conducted. Work supported by the NSF Grant No. PHY-1403906.
DEFF Research Database (Denmark)
Andreasen, Martin Møller; Meldrum, Andrew
This paper studies whether dynamic term structure models for US nominal bond yields should enforce the zero lower bound by a quadratic policy rate or a shadow rate specification. We address the question by estimating quadratic term structure models (QTSMs) and shadow rate models with at most four...
A model for high-energy heavy-ion collisions
International Nuclear Information System (INIS)
Myers, W.D.
1978-01-01
A model is developed for high-energy heavy-ion collisions that treats the variation across the overlap region of the target and projectile in the amount of energy and momentum that is deposited. The expression for calculating any observable takes the form of a sum over a series of terms, each one of which consists of a geometric, a kinematic, and a statistical factor. The geometrical factors for a number of target projectile systems are tabulated. (Auth.)
Comparison of models of high energy heavy ion collision
International Nuclear Information System (INIS)
Gyulassy, M.
1977-01-01
Some of the main theoretical developments on heavy ion collisions at energies (0.1 to 2.0) GeV/nuc are reviewed. The fireball, firestreak, hydrodynamic (1-fluid, 2-fluids), ''row on row'', hard sphere and intranuclear cascades, and classical equations of motion models are discussed in detail. Results are compared to each other and to measured Ne + U → p + X reactions
Global variables and the dynamics or relativistic nucleus-nucleus collisions
International Nuclear Information System (INIS)
Cugnon, J.; L'Hote, D.
1983-01-01
Various global variables providing a simple description of high multiplicity events are reviewed. Many of them are calculated in the framework of an intra-nuclear cascade model, which describes the collision process as a series of binary on-shell relativistic baryon-baryon collisions and which includes inelasticity through the production of δ-resonances. The calculations are first made for the Ar+KCl system at 0.8 GeV/A, with global variables including either all the nucleons or only the participant nucleons. The shape and the orientation of the ellipsoid of sphericity are particularly investigated. For both cases, on the average, the large axis of the ellipsoid is found to point in the beam direction. This result is discussed in comparison with hydrodynamics predictions and in relation with the mean free path. A kind of small 'bounce-off effect' is detected for intermediate impact parameters. The possibility of extracting the value of the impact parameter b from the value of a global variable is shown to depend upon the variation of this variable with b and upon the fluctuation of the global variable for a given impact parameter. A quality factor is defined to quantify this possibility. No current global variable seems to be more appropriate than the number of participant nucleons for the impact parameter selection. The physical origin of the fluctuations inside the intranuclear cascade model is discussed and the possibility of extracting useful information on the dynamics of the system from the fluctuations is pointed out. The energy dependence of our results is discussed. Some results of the calculations at 250 and 400 MeV/A are also presented for the same system Ar+KCl. (orig.)
Study of the dynamical potential barriers in heavy ion collisions
International Nuclear Information System (INIS)
Zhu, Long; Su, Jun; Xie, Wen-Jie; Zhang, Feng-Shou
2013-01-01
The nucleus–nucleus interaction potentials for the fusion reactions 16 O + 208 Pb, 64 Ni + 64 Ni, 58 Ni + 58 Ni and 16 O + 154 Sm are extracted from the improved isospin-dependent quantum molecular dynamics model. The shell correction effects are discussed. The negative shell correction energies lower potential barriers of a certain reaction. The incident energy dependence of the potential barrier is investigated for each system. A complex phenomenon of energy dependence is observed. It is also found that incident energy dependence of the barrier radius and barrier height shows opposite behaviors. The Coulomb potential shows weak energy dependence when distance of two colliding nuclei is lower than the touching distance. The isospin effects of the potential barrier are investigated. The orientation effects of the potential barrier is also discussed for the system 16 O + 154 Sm. The fusion cross sections that correspond to the equatorial orientation of 154 Sm are very low in sub-barrier region because of the high fusion barriers and the shallow potential pockets
Thin sheet numerical modelling of continental collision
Jimenez-Munt, I.; Garcia-Gastellanos, D.; Fernandez, M.
2005-01-01
We study the effects of incorporating surface mass transport and the gravitational potential energy of both crust and lithospheric mantle to the viscous thin sheet approach. Recent 2D (cross-section) numerical models show that surface erosion and sediment transport can play a major role in shaping
Simple model of surface roughness for binary collision sputtering simulations
Energy Technology Data Exchange (ETDEWEB)
Lindsey, Sloan J. [Institute of Solid-State Electronics, TU Wien, Floragasse 7, A-1040 Wien (Austria); Hobler, Gerhard, E-mail: gerhard.hobler@tuwien.ac.at [Institute of Solid-State Electronics, TU Wien, Floragasse 7, A-1040 Wien (Austria); Maciążek, Dawid; Postawa, Zbigniew [Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30348 Kraków (Poland)
2017-02-15
Highlights: • A simple model of surface roughness is proposed. • Its key feature is a linearly varying target density at the surface. • The model can be used in 1D/2D/3D Monte Carlo binary collision simulations. • The model fits well experimental glancing incidence sputtering yield data. - Abstract: It has been shown that surface roughness can strongly influence the sputtering yield – especially at glancing incidence angles where the inclusion of surface roughness leads to an increase in sputtering yields. In this work, we propose a simple one-parameter model (the “density gradient model”) which imitates surface roughness effects. In the model, the target’s atomic density is assumed to vary linearly between the actual material density and zero. The layer width is the sole model parameter. The model has been implemented in the binary collision simulator IMSIL and has been evaluated against various geometric surface models for 5 keV Ga ions impinging an amorphous Si target. To aid the construction of a realistic rough surface topography, we have performed MD simulations of sequential 5 keV Ga impacts on an initially crystalline Si target. We show that our new model effectively reproduces the sputtering yield, with only minor variations in the energy and angular distributions of sputtered particles. The success of the density gradient model is attributed to a reduction of the reflection coefficient – leading to increased sputtering yields, similar in effect to surface roughness.
Simple model of surface roughness for binary collision sputtering simulations
International Nuclear Information System (INIS)
Lindsey, Sloan J.; Hobler, Gerhard; Maciążek, Dawid; Postawa, Zbigniew
2017-01-01
Highlights: • A simple model of surface roughness is proposed. • Its key feature is a linearly varying target density at the surface. • The model can be used in 1D/2D/3D Monte Carlo binary collision simulations. • The model fits well experimental glancing incidence sputtering yield data. - Abstract: It has been shown that surface roughness can strongly influence the sputtering yield – especially at glancing incidence angles where the inclusion of surface roughness leads to an increase in sputtering yields. In this work, we propose a simple one-parameter model (the “density gradient model”) which imitates surface roughness effects. In the model, the target’s atomic density is assumed to vary linearly between the actual material density and zero. The layer width is the sole model parameter. The model has been implemented in the binary collision simulator IMSIL and has been evaluated against various geometric surface models for 5 keV Ga ions impinging an amorphous Si target. To aid the construction of a realistic rough surface topography, we have performed MD simulations of sequential 5 keV Ga impacts on an initially crystalline Si target. We show that our new model effectively reproduces the sputtering yield, with only minor variations in the energy and angular distributions of sputtered particles. The success of the density gradient model is attributed to a reduction of the reflection coefficient – leading to increased sputtering yields, similar in effect to surface roughness.
A collision model in plasma particle simulations
International Nuclear Information System (INIS)
Ma Yanyun; Chang Wenwei; Yin Yan; Yue Zongwu; Cao Lihua; Liu Daqing
2000-01-01
In order to offset the collisional effects reduced by using finite-size particles, β particle clouds are used in particle simulation codes (β is the ratio of charge or mass of modeling particles to real ones). The method of impulse approximation (strait line orbit approximation) is used to analyze the scattering cross section of β particle clouds plasmas. The authors can obtain the relation of the value of a and β and scattering cross section (a is the radius of β particle cloud). By using this relation the authors can determine the value of a and β so that the collisional effects of the modeling system is correspondent with the real one. The authors can also adjust the values of a and β so that the authors can enhance or reduce the collisional effects fictitiously. The results of simulation are in good agreement with the theoretical ones
Quark model and high energy collisions
International Nuclear Information System (INIS)
Nyiri, J.; Kobrinsky, M.N.
1982-06-01
The aim of the present review is to show that the additive quark model describes well not only the static features of hadrons but also the interaction processes at high energies. Considerations of the hadron-hadron and hadron-nucleus interactions and of the hadron production in multiparticle production processes suggest serious arguments in favour of the nucleus-like hadron structure and show the possibility to apply the rules of quark statistics to the description of the secondary particle production. (author)
Pauli blocking and laser manipulation of the electron dynamics in atomic collisions
International Nuclear Information System (INIS)
Kirchner, T.
2004-01-01
Full text: The dynamics of ion-atom collisions are governed primarily by the Coulomb interactions between the active electrons and the projectile and target nuclei. This contribution is devoted to the question whether and how other phenomena can modify the outcome of atomic scattering experiments. Firstly, the role of the Pauli exclusion principle on electronic transitions will be considered. Supported by experimental data it will be argued that Pauli blocking may have an important influence on electron transfer processes if collision systems with electrons on target and projectile in the initial channel are addressed [1]. Secondly, it will be discussed to which extent the electron dynamics can be modified and manipulated by an external interaction, namely by a suitable laser field [2]. The prototype scattering system He 2+ -H will be considered in the framework of the semiclassical approximation, i.e., projectile and laser interactions are described in terms of time-dependent external potentials which govern the quantum dynamics of the electron. The focus will be on slow collisions, in which electron transfer dominates, and on relatively short wavelengths such that both time dependent potentials vary on comparable time scales. A strong enhancement of laser-assisted electron transfer is found at collision energies below 1 keV/amu [3]. Its origin and its disappearance at higher energies as well as implications for planned experiments will be discussed
Artificial neural network modelling in heavy ion collisions
International Nuclear Information System (INIS)
El-dahshan, E.; Radi, A.; El-Bakry, M.Y.; El Mashad, M.
2008-01-01
The neural network (NN) model and parton two fireball model (PTFM) have been used to study the pseudo-rapidity distribution of the shower particles for C 12, O 16, Si 28 and S 32 on nuclear emulsion. The trained NN shows a better fitting with experimental data than the PTFM calculations. The NN is then used to predict the distributions that are not present in the training set and matched them effectively. The NN simulation results prove a strong presence modeling in heavy ion collisions
Quark model and high energy collisions
Anisovich, V V; Nyíri, J; Shabelski, Yu M
2004-01-01
This is an updated version of the book published in 1985. QCD-motivated, it gives a detailed description of hadron structure and soft interactions in the additive quark model, where hadrons are regarded as composite systems of dressed quarks. In the past decade it has become clear that nonperturbative QCD, responsible for soft hadronic processes, may differ rather drastically from perturbative QCD. The understanding of nonperturbative QCD requires a detailed investigation of the experiments and the theoretical approaches. Bearing this in mind, the book has been rewritten paying special attenti
International Nuclear Information System (INIS)
Eudes, Ph.; Basrak, Z.; Sebille, F.
1997-01-01
Characteristics of charged-particle emission in heavy-ion reactions have been studied in the framework of the semiclassical Landau-Vlasov approach for the 40 Ar + 27 Al collisions at 65 MeV/u. The reaction mechanism is dominated by binary dissipative collisions. After an abundant prompt emission coming from the overlapping region between the target and the projectile, two excited nuclei, the quasi-target and the quasi-projectile, emerge from the collision. To shed some light on the role played by dynamical effects, light-charged particle observables, which are currently used as an experimental signature a of hot equilibrated nucleus, have been carefully investigated. (K.A.)
Interactive collision detection for deformable models using streaming AABBs.
Zhang, Xinyu; Kim, Young J
2007-01-01
We present an interactive and accurate collision detection algorithm for deformable, polygonal objects based on the streaming computational model. Our algorithm can detect all possible pairwise primitive-level intersections between two severely deforming models at highly interactive rates. In our streaming computational model, we consider a set of axis aligned bounding boxes (AABBs) that bound each of the given deformable objects as an input stream and perform massively-parallel pairwise, overlapping tests onto the incoming streams. As a result, we are able to prevent performance stalls in the streaming pipeline that can be caused by expensive indexing mechanism required by bounding volume hierarchy-based streaming algorithms. At runtime, as the underlying models deform over time, we employ a novel, streaming algorithm to update the geometric changes in the AABB streams. Moreover, in order to get only the computed result (i.e., collision results between AABBs) without reading back the entire output streams, we propose a streaming en/decoding strategy that can be performed in a hierarchical fashion. After determining overlapped AABBs, we perform a primitive-level (e.g., triangle) intersection checking on a serial computational model such as CPUs. We implemented the entire pipeline of our algorithm using off-the-shelf graphics processors (GPUs), such as nVIDIA GeForce 7800 GTX, for streaming computations, and Intel Dual Core 3.4G processors for serial computations. We benchmarked our algorithm with different models of varying complexities, ranging from 15K up to 50K triangles, under various deformation motions, and the timings were obtained as 30 approximately 100 FPS depending on the complexity of models and their relative configurations. Finally, we made comparisons with a well-known GPU-based collision detection algorithm, CULLIDE [4] and observed about three times performance improvement over the earlier approach. We also made comparisons with a SW-based AABB
Dynamic plasma screening effects on atomic collisions in dense plasmas
International Nuclear Information System (INIS)
Young-Dae Jung
1999-01-01
Dynamic plasma screening effects are investigated on electron-ion collisional excitation and Coulomb Bremsstrahlung processes in dense plasmas. The electron-ion interaction potential is considered by introduction of the plasma dielectric function. The straight-ling trajectory method is applied to the path of the projectile electron. The transition probability including the dynamic plasma screening effect is found to be always greater than that including the static plasma screening effects. It is found that the differential Bremsstrahlung radiation cross section including the dynamic plasma screening effect is also greater than that including the static plasma screening effect. When the projectile velocity is smaller than the electron thermal velocity, the dynamic polarization screening effect becomes the static plasma screening effect. However, when the projectile velocity is greater than the electron thermal velocity, the interaction potential is almost unshielded
3-D Numerical Modelling of Oblique Continental Collisions with ASPECT
Karatun, L.; Pysklywec, R.
2017-12-01
Among the fundamental types of tectonic plate boundaries, continent-continent collision is least well understood. Deformation of the upper and middle crustal layers can be inferred from surface structures and geophysical imaging, but the fate of lower crustal rocks and mantle lithosphere is not well resolved. Previous research suggests that shortening of mantle lithosphere generally may be occurring by either: 1) a distributed thickening with a formation of a Raleigh-Tailor (RT) type instability (possibly accompanied with lithospheric folding); or 2) plate-like subduction, which can be one- or two-sided, with or without delamination and slab break-off; a combination of both could be taking place too. 3-D features of the orogens such as along-trench material transfer, bounding subduction zones can influence the evolution of the collision zone significantly. The current study was inspired by South Island of New Zealand - a young collision system where a block of continental crust is being shortened by the relative Australian-Pacific plate motion. The collision segment of the plate boundary is relatively small ( 800 km), and is bounded by oppositely verging subduction zones to the North and South. Here, we present results of 3-D forward numerical modelling of continental collision to investigate some of these processes. To conduct the simulations, we used ASPECT - a highly parallel community-developed code based on the Finite Element method. Model setup for three different sets of models featured 2-D vertical across strike, 3-D with periodic front and back walls, and 3-D with open front and back walls, with velocities prescribed on the left and right faces. We explored the importance of values of convergent velocity, strike-slip velocity and their ratio, which defines the resulting velocity direction relative to the plate boundary (obliquity). We found that higher strike-slip motion promotes strain localization, weakens the lithosphere close to the plate boundary and
International Nuclear Information System (INIS)
Nishimura, Hiroshi.
1993-05-01
Object-Oriented Programming has been used extensively to model the LBL Advanced Light Source 1.5 GeV electron storage ring. This paper is on the present status of the class library construction with emphasis on a dynamic modeling
Bun, M.J.G.; Sarafidis, V.
2013-01-01
This Chapter reviews the recent literature on dynamic panel data models with a short time span and a large cross-section. Throughout the discussion we considerlinear models with additional endogenous covariates. First we give a broad overview of available inference methods placing emphasis on GMM.
Ghanem, Bernard
2013-01-01
This paper proposes the problem of modeling video sequences of dynamic swarms (DSs). We define a DS as a large layout of stochastically repetitive spatial configurations of dynamic objects (swarm elements) whose motions exhibit local spatiotemporal interdependency and stationarity, i.e., the motions are similar in any small spatiotemporal neighborhood. Examples of DS abound in nature, e.g., herds of animals and flocks of birds. To capture the local spatiotemporal properties of the DS, we present a probabilistic model that learns both the spatial layout of swarm elements (based on low-level image segmentation) and their joint dynamics that are modeled as linear transformations. To this end, a spatiotemporal neighborhood is associated with each swarm element, in which local stationarity is enforced both spatially and temporally. We assume that the prior on the swarm dynamics is distributed according to an MRF in both space and time. Embedding this model in a MAP framework, we iterate between learning the spatial layout of the swarm and its dynamics. We learn the swarm transformations using ICM, which iterates between estimating these transformations and updating their distribution in the spatiotemporal neighborhoods. We demonstrate the validity of our method by conducting experiments on real and synthetic video sequences. Real sequences of birds, geese, robot swarms, and pedestrians evaluate the applicability of our model to real world data. © 2012 Elsevier Inc. All rights reserved.
The study of hadron dynamics in relativistic heavy ion collisions
International Nuclear Information System (INIS)
Venema, L.B.
1994-01-01
In this thesis, pion emission patterns were studied in two reaction systems Ar + Ca and Au + Au at 1 GeV/u, with the aim to improve the understanding of the pion production in relativistic heavy ion collisions. The study of the high energy tail of the π 0 -momentum spectrum was regarded as promising because of its sensitivity to compression since it did not appear in small reaction systems. Experiments were performed with TAPS together with the Forward Wall of the FoPi-collaboration at GSI. The combined measurement of charged particle multiplicities in the Forward Wall and the particles entering TAPS enabled an exclusive study of the pion production. TAPS was tested in separate experiments and its capabilities were demonstrated by measuring different reaction products, like photons, charged particles and neutrons. The data analysis involved new methods to treat the background contamination below the invariant mass peak of the π 0 -meson due to the geometry of the detector and to perform particle identification in a high particle multiplicity environment. (orig.)
Modeling of Ship Collision Risk Index Based on Complex Plane and Its Realization
Xiaoqin Xu; Xiaoqiao Geng; Yuanqiao Wen
2016-01-01
Ship collision risk index is the basic and important concept in the domain of ship collision avoidance. In this paper, the advantages and deficiencies of the various calculation methods of ship collision risk index are pointed out. Then the ship collision risk model based on complex plane, which can well make up for the deficiencies of the widely-used evaluation model proposed by Kearon.J and Liu ruru is proposed. On this basis, the calculation method of collision risk index under the encount...
Ultrafast spectral dynamics of dual-color-soliton intracavity collision in a mode-locked fiber laser
Wei, Yuan; Li, Bowen; Wei, Xiaoming; Yu, Ying; Wong, Kenneth K. Y.
2018-02-01
The single-shot spectral dynamics of dual-color-soliton collisions inside a mode-locked laser is experimentally and numerically investigated. By using the all-optically dispersive Fourier transform, we spectrally unveil the collision-induced soliton self-reshaping process, which features dynamic spectral fringes over the soliton main lobe, and the rebuilding of Kelly sidebands with wavelength drifting. Meanwhile, the numerical simulations validate the experimental observation and provide additional insights into the physical mechanism of the collision-induced spectral dynamics from the temporal domain perspective. It is verified that the dynamic interference between the soliton and the dispersive waves is responsible for the observed collision-induced spectral evolution. These dynamic phenomena not only demonstrate the role of dispersive waves in the sophisticated soliton interaction inside the laser cavity, but also facilitate a deeper understanding of the soliton's inherent stability.
International Nuclear Information System (INIS)
Frankland, J.D.; Chbihi, A.; Hudan, S.
2002-01-01
Fragment production in central collisions of Xe+Sn has been systematically studied with the INDRA multidetector from 25 to 150 AMeV. The predominant role of collision dynamics is evidenced in multiple intermediate mass fragment production even at the lowest energies, around the so-called multifragmentation threshold. For beam energies 50 AMeV and above, a promising agreement with suitably modified Anti-symmetrized Molecular Dynamics calculations has been achieved. Intriguingly the same reactions have recently been interpreted as evidence for a liquid-gas phase transition in thermodynamically equilibrated systems. The universal fluctuation theory, thanks to its lack of any equilibrium hypothesis, shows clearly that in all but a tiny minority of carefully-selected central collisions fragment production is incompatible with either critical or phase coexistence behaviour. On the other hand, it does not exclude some similarity with aggregation scenarios such as the lattice-gas or Fisher droplet models. (authors)
Energy Technology Data Exchange (ETDEWEB)
Frankland, J.D.; Chbihi, A.; Hudan, S. [and others
2002-07-01
Fragment production in central collisions of Xe+Sn has been systematically studied with the INDRA multidetector from 25 to 150 AMeV. The predominant role of collision dynamics is evidenced in multiple intermediate mass fragment production even at the lowest energies, around the so-called multifragmentation threshold. For beam energies 50 AMeV and above, a promising agreement with suitably modified Anti-symmetrized Molecular Dynamics calculations has been achieved. Intriguingly the same reactions have recently been interpreted as evidence for a liquid-gas phase transition in thermodynamically equilibrated systems. The universal fluctuation theory, thanks to its lack of any equilibrium hypothesis, shows clearly that in all but a tiny minority of carefully-selected central collisions fragment production is incompatible with either critical or phase coexistence behaviour. On the other hand, it does not exclude some similarity with aggregation scenarios such as the lattice-gas or Fisher droplet models. (authors)
Advances in molecular vibrations and collision dynamics molecular clusters
Bacic, Zatko
1998-01-01
This volume focuses on molecular clusters, bound by van der Waals interactions and hydrogen bonds. Twelve chapters review a wide range of recent theoretical and experimental advances in the areas of cluster vibrations, spectroscopy, and reaction dynamics. The authors are leading experts, who have made significant contributions to these topics.The first chapter describes exciting results and new insights in the solvent effects on the short-time photo fragmentation dynamics of small molecules, obtained by combining heteroclusters with femtosecond laser excitation. The second is on theoretical work on effects of single solvent (argon) atom on the photodissociation dynamics of the solute H2O molecule. The next two chapters cover experimental and theoretical aspects of the energetics and vibrations of small clusters. Chapter 5 describes diffusion quantum Monte Carlo calculations and non additive three-body potential terms in molecular clusters. The next six chapters deal with hydrogen-bonded clusters, refle...
International Nuclear Information System (INIS)
Benlliure, J.; Armbruster, P.; Bernas, M.
2001-09-01
197 Au(800 A MeV)-on-proton collisions are used to investigate the fission dynamics at high excitation energy. The kinematic properties together with the isotopic identification of the fission fragments allow to determine the mass, charge and excitation energy of the fissioning nucleus at saddle. The comparison of these observables and the measured total fission cross section with model calculations evidences a clear hindrance of fission at high excitation energy that can be explained in terms of nuclear dissipation. Assuming a statistical evaporation for other de-excitation channels than fission, an estimated value of the transient time of fission of (3 ± 1) . 10 -21 s is obtained. (orig.)
Dynamical effects in heavy ion collisions: neck emission in the Pb + Au system at 29 A.MeV
International Nuclear Information System (INIS)
Aboufirassi, M; Bizard, G.; Bougault, R.; Brou, R.; Buta, A.; Colin, J.; Cussol, D.; Durand, D.; Genoux-Lubain, A.; Horn, D.; Kerambrun, A.; Laville, J.L.; Le Brun, C.; Lecolley, J.F.; Lefebvres, F.; Lopez, O.; Louvel, M.; Meslin, C.; Metivier, V.; Nakagawa, T.; Peter, J.; Popescu, R.; Regimbart, R.; Steckmeyer, J.C.; Tamain, B.; Vient, E.; Wieloch, A.; Yuasa-Nakagawa, K.
1998-01-01
In the study of the Pb + Au system with the assembly NAUTILUS a special class of events were made evident. Three body complete events have allowed observing a dynamical behavior in the fragment emission. A plot of the correlation between the emission angle and the charges Z 1 and Z 2 of the two fragments associated to the event shows a contribution of an intermediate mass third fragment reflecting a dynamical emission subsequent to the interaction phase between the two partners of the deep inelastic scattering (a phenomenon featuring the neck emission). Such a process has been observed in the Kr + Au at 60 MeV/nucleon and Xe + Cu at 50 MeV/nucleon. The on-going analysis of the Xe + Sn at 50 MeV/nucleon reveals the existence of a similar mechanism. A complete kinematical analysis of this class of events has permitted making evident the impact parameter window, here implied; it is situated for the associated collisions to an reduced impact parameter around 0.8 b max , corresponding to an excitation energy for the bi-nucleus system of the order of 2 MeV/nucleon. This phenomenon may allow to constrain more strongly the models describing the dynamics of the heavy ion collisions, particularly the kinetic models of Landau-Vlasov type. Then, the different mean field potential prescriptions my be tested by comparison with the experimental data
Deterministic Role of Collision Cascade Density in Radiation Defect Dynamics in Si
Wallace, J. B.; Aji, L. B. Bayu; Shao, L.; Kucheyev, S. O.
2018-05-01
The formation of stable radiation damage in solids often proceeds via complex dynamic annealing (DA) processes, involving point defect migration and interaction. The dependence of DA on irradiation conditions remains poorly understood even for Si. Here, we use a pulsed ion beam method to study defect interaction dynamics in Si bombarded in the temperature range from ˜-30 ° C to 210 °C with ions in a wide range of masses, from Ne to Xe, creating collision cascades with different densities. We demonstrate that the complexity of the influence of irradiation conditions on defect dynamics can be reduced to a deterministic effect of a single parameter, the average cascade density, calculated by taking into account the fractal nature of collision cascades. For each ion species, the DA rate exhibits two well-defined Arrhenius regions where different DA mechanisms dominate. These two regions intersect at a critical temperature, which depends linearly on the cascade density. The low-temperature DA regime is characterized by an activation energy of ˜0.1 eV , independent of the cascade density. The high-temperature regime, however, exhibits a change in the dominant DA process for cascade densities above ˜0.04 at.%, evidenced by an increase in the activation energy. These results clearly demonstrate a crucial role of the collision cascade density and can be used to predict radiation defect dynamics in Si.
Particle production at large transverse momentum and hard collision models
International Nuclear Information System (INIS)
Ranft, G.; Ranft, J.
1977-04-01
The majority of the presently available experimental data is consistent with hard scattering models. Therefore the hard scattering model seems to be well established. There is good evidence for jets in large transverse momentum reactions as predicted by these models. The overall picture is however not yet well enough understood. We mention only the empirical hard scattering cross section introduced in most of the models, the lack of a deep theoretical understanding of the interplay between quark confinement and jet production, and the fact that we are not yet able to discriminate conclusively between the many proposed hard scattering models. The status of different hard collision models discussed in this paper is summarized. (author)
International Nuclear Information System (INIS)
Papa, Massimo; Cardella, Giuseppe; Bonanno, Antonio; Pappalardo, Giuseppe; Rizzo, Francesca; Amorini, Francesca; Bonasera, Aldo; Di Pietro, Alessia; Figuera, Pier Paolo; Tudisco, Salvatore; Maruyama, Toshiki
2003-01-01
Coherent and incoherent dipolar γ-ray emission is studied in a fully dynamical approach by means of the constrained molecular dynamics model. The study is focused on the system 40 Ca+ 48 Ca for which recently experimental data have been collected at 25 MeV/nucleon. The approach allows us to explain the experimental results in a self-consistent way without using statistical or hybrid models. Moreover, calculations performed at higher energy show interesting correlations between the fragment formation process, the degree of collectivity, and the coherence degree of the γ-ray emission process
Dynamical simulation of heavy ion collisions; VUU and QMD method
International Nuclear Information System (INIS)
Niita, Koji
1992-01-01
We review two simulation methods based on the Vlasov-Uehling-Uhlenbeck (VUU) equation and Quantum Molecular Dynamics (QMD), which are the most widely accepted theoretical framework for the description of intermediate-energy heavy-ion reactions. We show some results of the calculations and compare them with the experimental data. (author)
International Nuclear Information System (INIS)
Sotiralis, P.; Ventikos, N.P.; Hamann, R.; Golyshev, P.; Teixeira, A.P.
2016-01-01
This paper presents an approach that more adequately incorporates human factor considerations into quantitative risk analysis of ship operation. The focus is on the collision accident category, which is one of the main risk contributors in ship operation. The approach is based on the development of a Bayesian Network (BN) model that integrates elements from the Technique for Retrospective and Predictive Analysis of Cognitive Errors (TRACEr) and focuses on the calculation of the collision accident probability due to human error. The model takes into account the human performance in normal, abnormal and critical operational conditions and implements specific tasks derived from the analysis of the task errors leading to the collision accident category. A sensitivity analysis is performed to identify the most important contributors to human performance and ship collision. Finally, the model developed is applied to assess the collision risk of a feeder operating in Dover strait using the collision probability estimated by the developed BN model and an Event tree model for calculation of human, economic and environmental risks. - Highlights: • A collision risk model for the incorporation of human factors into quantitative risk analysis is proposed. • The model takes into account the human performance in different operational conditions leading to the collision. • The most important contributors to human performance and ship collision are identified. • The model developed is applied to assess the collision risk of a feeder operating in Dover strait.
Peck, Louis; Billiar, Kristen; Ray, Malcolm
2010-01-01
The goal of this study was to model the dynamic failure properties of ligaments and their attachment sites to facilitate the development of more realistic dynamic finite element models of the human lower extremities for use in automotive collision simulations. Porcine medial collateral ligaments were chosen as a test model due to their similarities in size and geometry with human ligaments. Each porcine medial collateral ligament-bone complex (n = 12) was held in a custom test fixture placed in a drop tower to apply an axial impulsive impact load, applying strain rates ranging from 0.005 s-1 to 145 s-1. The data from the impact tests were analyzed using nonlinear regression to construct model equations for predicting the failure load of ligament-bone complexes subjected to specific strain rates as calculated from finite element knee, thigh, and hip impact simulations. The majority of the ligaments tested failed by tibial avulsion (75%) while the remaining ligaments failed via mid-substance tearing. The failure load ranged from 384 N to 1184 N and was found to increase with the applied strain rate and the product of ligament length and cross-sectional area. The findings of this study indicate the force required to rupture the porcine MCL increases with the applied bone-to-bone strain rate in the range expected from high speed frontal automotive collisions. PMID:20461229
2D numerical model of particle-bed collision in fluid-particle flows over bed
Czech Academy of Sciences Publication Activity Database
Lukerchenko, Nikolay; Chára, Zdeněk; Vlasák, Pavel
2006-01-01
Roč. 44, č. 1 (2006), s. 70-78 ISSN 0022-1686 R&D Projects: GA AV ČR IAA2060201 Institutional research plan: CEZ:AV0Z20600510 Keywords : saltation * particle-bed collision * collision angle * bed roughness Subject RIV: BK - Fluid Dynamics Impact factor: 0.527, year: 2006
Malafeyev, O. A.; Nemnyugin, S. A.; Rylow, D.; Kolpak, E. P.; Awasthi, Achal
2017-07-01
The corruption dynamics is analyzed by means of the lattice model which is similar to the three-dimensional Ising model. Agents placed at nodes of the corrupt network periodically choose to perfom or not to perform the act of corruption at gain or loss while making decisions based on the process history. The gain value and its dynamics are defined by means of the Markov stochastic process modelling with parameters established in accordance with the influence of external and individual factors on the agent's gain. The model is formulated algorithmically and is studied by means of the computer simulation. Numerical results are obtained which demonstrate asymptotic behaviour of the corruption network under various conditions.
Quantum State-Resolved Collision Dynamics of Nitric Oxide at Ionic Liquid and Molten Metal Surfaces
Zutz, Amelia Marie
Detailed molecular scale interactions at the gas-liquid interface are explored with quantum state-to-state resolved scattering of a jet-cooled beam of NO(2pi1/2; N = 0) from ionic liquid and molten metal surfaces. The scattered distributions are probed via laser-induced fluorescence methods, which yield rotational and spin-orbit state populations that elucidate the dynamics of energy transfer at the gas-liquid interface. These collision dynamics are explored as a function of incident collision energy, surface temperature, scattering angle, and liquid identity, all of which are found to substantially affect the degree of rotational, electronic and vibrational excitation of NO via collisions at the liquid surface. Rotational distributions observed reveal two distinct scattering pathways, (i) molecules that trap, thermalize and eventually desorb from the surface (trapping-desorption, TD), and (ii) those that undergo prompt recoil (impulsive scattering, IS) prior to complete equilibration with the liquid surface. Thermally desorbing NO molecules are found to have rotational temperatures close to, but slightly cooler than the surface temperature, indicative of rotational dependent sticking probabilities on liquid surfaces. Nitric oxide is a radical with multiple low-lying electronic states that serves as an ideal candidate for exploring nonadiabatic state-changing collision dynamics at the gas-liquid interface, which induce significant excitation from ground (2pi1/2) to excited (2pi 3/2) spin-orbit states. Molecular beam scattering of supersonically cooled NO from hot molten metals (Ga and Au, Ts = 300 - 1400 K) is also explored, which provide preliminary evidence for vibrational excitation of NO mediated by thermally populated electron-hole pairs in the hot, conducting liquid metals. The results highlight the presence of electronically nonadiabatic effects and build toward a more complete characterization of energy transfer dynamics at gas-liquid interfaces.
Directory of Open Access Journals (Sweden)
Omar I. Abdelkarim
2016-12-01
Full Text Available This paper presents the difference in behavior between hollow-core fiber reinforced polymer-concrete-steel (HC-FCS columns and conventional reinforced concrete (RC columns under vehicle collision in terms of dynamic and static forces. The HC-FCS column consisted of an outer FRP tube, an inner steel tube, and a concrete shell sandwiched between the two tubes. The steel tube was hollow inside and embedded into the concrete footing with a length of 1.5 times the tube diameter while the FRP tube stopped at the top of footing. The RC column had a solid cross-section. The study was conducted through extensive finite element impact analyses using LS-DYNA software. Nine parameters were studied including the concrete material model, unconfined concrete compressive strength, material strain rate, column height-to-diameter ratio, column diameter, column top boundary condition, axial load level, vehicle velocity, and vehicle mass. Generally, the HC-FCS columns had lower dynamic forces and higher static forces than the RC columns when changing the values of the different parameters. During vehicle collision with either the RC or the HC-FCS columns, the imposed dynamic forces and their equivalent static forces were affected mainly by the vehicle velocity and vehicle mass.
A Simple Model of Wings in Heavy-Ion Collisions
Parikh, Aditya
2015-01-01
We create a simple model of heavy ion collisions independent of any generators as a way of investigating a possible source of the wings seen in data. As a first test, we reproduce a standard correlations plot to verify the integrity of the model. We then proceed to test whether an η dependent v2 could be a source of the wings and take projections along multiple Δφ intervals and compare with data. Other variations of the model are tested by having dN/dφ and v2 depend on η as well as including pions and protons into the model to make it more realistic. Comparisons with data seem to indicate that an η dependent v2 is not the main source of the wings.
Directory of Open Access Journals (Sweden)
Loktev Aleksey Alekseevich
2013-01-01
Full Text Available The authors present their findings associated with their modeling of a dynamic load damper. According to the authors, the damper is to be installed onto a structure or its element that may be exposed to impact, vibration or any other dynamic loading. The damper is composed of paralleled or consecutively connected viscous and elastic elements. The authors study the influence of viscosity and elasticity parameters of the damper produced onto the regular displacement of points of the structure to be protected and onto the regular acceleration transmitted immediately from the damper to the elements positioned below it.
Effect of collision cascades on dislocations in tungsten: A molecular dynamics study
Energy Technology Data Exchange (ETDEWEB)
Fu, B.Q., E-mail: bqfu@scu.edu.cn [Key Laboratory for Radiation Physics and Technology, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610065 (China); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Fitzgerald, S.P. [Department of Applied Mathematics, University of Leeds, Leeds LS2 9JT (United Kingdom); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Hou, Q.; Wang, J.; Li, M. [Key Laboratory for Radiation Physics and Technology, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610065 (China)
2017-02-15
Highlights: • A cascde near a dislocation promotes climb motion. • Kinks induced by cascade facilitate the dipoles motion toward the cascade. • Shearing of dipole is dependent on PKA energy, position, direction, and dipole width. - Abstract: Tungsten (W) is the prime candidate material for the divertor and other plasma-facing components in DEMO. The point defects (i.e. vacancies and self-interstitials) produced in collision cascades caused by incident neutrons aggregate into dislocation loops (and voids), which strongly affect the mechanical properties. The point defects also interact with existing microstructural features, and understanding these processes is crucial for modelling the long term microstructural evolution of the material under fusion conditions. In this work, we performed molecular dynamics simulations of cascades interacting with initially straight edge dislocation dipoles. It was found that the residual vacancy number usually exceeds the residual interstitial number for cascades interacting with vacancy type dipoles, but for interstitial type dipoles these are close. We observed that a cascade near a dislocation promotes climb, i.e. it facilitates the movement of point defects along the climb direction. We also observed that the dislocations move easily along the glide direction, and that kinks are formed near the centre of the cascade, which then facilitate the movement of the dipoles. Some dipoles are sheared off by the cascade, and this is dependent on PKA energy, position, direction, and the width of dipole.
International Nuclear Information System (INIS)
Pustovit, A.N.
2006-01-01
A new approach to the theoretical description of energy losses of atomic particle of medium energy during their interaction with the substance is proposed. The corner-stone of this approach is the supposition that all of the collision processes have inelastic nature during particle movement through the substance, while the calculation of the atomic particles braking is based on the law of their dispersion and the laws of energy and momentum conservation at the inelastic collisions. It is shown that inelastic atomic collision there are three dispersion zones for the only potential interaction with different laws, which characterize energy losses. The application conditions of this approach are determined [ru
Investigation of the dynamics of dissipative U+Au collisions with δ-electron spectroscopy
International Nuclear Information System (INIS)
Stroth, J.; Dahlinger, M.; Konen, W.; Stiebing, K.
1997-01-01
δ-electron emission in elastic and dissipative collisions of U+Au at E/A=8.65 MeV has been investigated. The velocity vectors of the reaction products were measured in coincidence with electrons of energies up to 3.2 MeV. The δ-electron yield measured for elastic collisions is in good agreement with coupled-channel calculations. The δ-electron spectra of dissipative reactions show a clear dependence on the violence of the collision, i.e. the total kinetic energy loss (TKEL). The shape of the spectra are analysed with an atomic model by a fitting procedure using phenomenological trajectories. The results indicate an increasing contact time of the united system with increasing total kinetic energy loss reaching 1.16(4) x 10 -21 s at left angle TKEL right angle =375 MeV. (orig.). With 2 figs
Study regarding seat’s rigidity during rear end collisions using a MADYMO occupant model
Ionut Radu, Alexandru; Cofaru, Corneliu; Tolea, Bogan; Popescu, Mihaela
2017-10-01
The aim of this paper is to study the effects of different front occupant backseat’s rigidities in the case of a rear end collision using a multibody virtual model of an occupant. Simulation will be conducted in PC Crash, the most common accident reconstruction software using a MADYMO multibody occupant to simulate kinematics and dynamic of the passenger. Different backseat torques will be used to see how this will influence the acceleration in the head and torso of the occupant. Also, a real crash test is made to analyze the kinematics of the occupant. We believe that the softer seat’s rigidity will reduce not only the head’s acceleration but also reduces the effect of „whiplash” upon the neck due to the fact that the backseat will rotate backwards increasing its displacement and absorb some of the energy generated by the collision. Although a softer seat could reduce the head’s acceleration, a broken seat will increase it due to the fact that the impact of the backseat with the vehicle’s rear seats will generate a second collision. So, in order to achieve a lower acceleration, a controlled torque is recommended and a controlled angular displacement of the backseat is to be used.
International Nuclear Information System (INIS)
Colin, J.; Bocage, F.; Louvel, M.; Bellaize, N.; Bougault, R.; Brou, R.; Cussol, D.; Durand, D.; Genouin-Duhamel, E.; Lecolley, J.F.; Le Neindre, N.; Lopez, O.; Nguyen, A.D.; Peter, J.; Steckmeyer, J.C.; Tamain, B.; Vient, E.; Brun, C. le; Genoux-Lubain, A.
1999-01-01
Recent experimental results concerning heavy systems (Pb+Au, Pb+Ag, Pb+Al, Gd+U, Gd+C, Ta+Au, U+U, U+C, Xe+Sn... o btained at Ganil by the Indra and Nautilus collaborations will be presented. A study of reaction mechanisms has shown the dominant binary and highly dissipative character of the process. The two heavy and excited fragments produced after the first stage of the interaction can experience various decay modes: evaporation, fission, multifragmentation. However, deviations from this simple picture have been found by analysing angular and velocity distributions of light charge particles, IMF's (Intermediate Mass Fragment) and fragments. Indeed, there is an amount of matter in excess emitted in-between the two primary sources suggesting either the existence of a mid-rapidity source similar to the one observed in the relativistic regime (participants) or a strong deformation induced by the dynamics of the collision (neck instability). This last scenario is explored by analysing in details the angular distributions of the fission fragments. More precisely, authors observed two components: The first one is isotropic and consistent with the predictions of a statistical model, the second is aligned along the velocity direction of the fissioning nuclei and has to be compared with the predictions of dynamical calculations. In this talk, authors present the probability associated to each component as a function of the system size, the charge asymmetry of the fission fragments, the incident energy and the impact parameter. From the statistical component authors extract the temperature, the charge and the angular momentum of the fissioning nuclei. From the second component authors propose a scenario to explain such process and authors discuss the physical parameters which can be extracted
International Nuclear Information System (INIS)
Colin, J.; Bocage, F.; Louvel, M.
1999-10-01
Recent experimental results concerning heavy systems (Pb+Au, Pb+Ag, Pb+Al, Gd+U, Gd+C, Ta+Au, U+U, U+C, Xe+Sn...) obtained at Ganil by the Indra and Nautilus collaborations will be presented. A study of reaction mechanisms has shown the dominant binary and highly dissipative character of the process. The two heavy and excited fragments produced after the first stage of the interaction can experience various decay modes: evaporation, fission, multifragmentation. However, deviations from this simple picture have been found by analysing angular and velocity distribution of light charge particles, IMF's (Intermediate Mass Fragment) and fragments. Indeed, there is an amount of matter in excess emitted in-between the two primary sources suggesting either the existence of a mi-rapidity source similar to the one observed in the relativistic regime (participants) or a strong deformation induced by the dynamics of the collision (neck instability). This last scenario is explored by analysing in details the angular distributions of the fission fragments. More precisely, we observed two components: the first one is isotropic and consistent with the predictions of a statistical model, the second is aligned along the velocity direction of the fissioning nuclei and has to be compared with the predictions of dynamical calculations. In this talk, we present the probability associated to each component as a function of the system size, the charge asymmetry of the fission fragments, the incident energy and the impact parameter. From the statistical component we extract the temperature, the charge and the angular momentum of the fissioning nuclei. From the second component we propose a scenario to explain such process and we discuss the physical parameters which can be extracted. (authors)
Dynamic wake meandering modeling
Energy Technology Data Exchange (ETDEWEB)
Larsen, Gunner C.; Aagaard Madsen, H.; Bingoel, F. (and others)
2007-06-15
We present a consistent, physically based theory for the wake meandering phenomenon, which we consider of crucial importance for the overall description of wind turbine loadings in wind farms. In its present version the model is confined to single wake situations. The model philosophy does, however, have the potential to include also mutual wake interaction phenomenons. The basic conjecture behind the dynamic wake meandering model is that wake transportation in the atmospheric boundary layer is driven by the large scale lateral- and vertical turbulence components. Based on this conjecture a stochastic model of the downstream wake meandering is formulated. In addition to the kinematic formulation of the dynamics of the 'meandering frame of reference', models characterizing the mean wake deficit as well as the added wake turbulence, described in the meandering frame of reference, are an integrated part the model complex. For design applications, the computational efficiency of wake deficit prediction is a key issue. Two computationally low cost models are developed for this purpose. The character of the added wake turbulence, generated by the up-stream turbine in the form of shed and trailed vorticity, has been approached by analytical as well as by numerical studies. The dynamic wake meandering philosophy has been verified by comparing model predictions with extensive full-scale measurements. These comparisons have demonstrated good agreement, both qualitatively and quantitatively, concerning both flow characteristics and turbine load characteristics. Contrary to previous attempts to model wake loading, the dynamic wake meandering approach opens for a unifying description in the sense that turbine power and load aspects can be treated simultaneously. This capability is a direct and attractive consequence of the model being based on the underlying physical process, and it potentially opens for optimization of wind farm topology, of wind farm operation as
International Nuclear Information System (INIS)
Colanero, K.; Chu, M.-C.
2002-01-01
We study a dynamical chiral bag model, in which massless fermions are confined within an impenetrable but movable bag coupled to meson fields. The self-consistent motion of the bag is obtained by solving the equations of motion exactly assuming spherical symmetry. When the bag interacts with an external meson wave we find three different kinds of resonances: fermionic, geometric, and σ resonances. We discuss the phenomenological implications of our results
Model for macroevolutionary dynamics.
Maruvka, Yosef E; Shnerb, Nadav M; Kessler, David A; Ricklefs, Robert E
2013-07-02
The highly skewed distribution of species among genera, although challenging to macroevolutionists, provides an opportunity to understand the dynamics of diversification, including species formation, extinction, and morphological evolution. Early models were based on either the work by Yule [Yule GU (1925) Philos Trans R Soc Lond B Biol Sci 213:21-87], which neglects extinction, or a simple birth-death (speciation-extinction) process. Here, we extend the more recent development of a generic, neutral speciation-extinction (of species)-origination (of genera; SEO) model for macroevolutionary dynamics of taxon diversification. Simulations show that deviations from the homogeneity assumptions in the model can be detected in species-per-genus distributions. The SEO model fits observed species-per-genus distributions well for class-to-kingdom-sized taxonomic groups. The model's predictions for the appearance times (the time of the first existing species) of the taxonomic groups also approximately match estimates based on molecular inference and fossil records. Unlike estimates based on analyses of phylogenetic reconstruction, fitted extinction rates for large clades are close to speciation rates, consistent with high rates of species turnover and the relatively slow change in diversity observed in the fossil record. Finally, the SEO model generally supports the consistency of generic boundaries based on morphological differences between species and provides a comparator for rates of lineage splitting and morphological evolution.
International Nuclear Information System (INIS)
McFadden, J.H.; Paulsen, M.P.; Gose, G.C.
1981-01-01
Thermal-hydraulic codes in general use for system calculations are based on extensive analyses of loss-of-coolant accidents following the postulated rupture of a large coolant pipe. In this study, time-dependent equation for the slip velocity in a two-phase flow condition has been incorporated into the RETRAN-02 computer code. This model addition was undertaken to remove a limitation in RETRAN-01 associated with the homogeneous equilibrium mixture model. The dynamic slip equation was derived from a set of two-fluid conservation equations. 18 refs
Proton nucleus collisions in the Landau hydrodynamical model
International Nuclear Information System (INIS)
Andersson, B.
1976-01-01
The dependence upon energy and the atomic number A for the multiplicities and the angular distributions of the relativistic secondaries is computed according to the hydrodynamic model for proton-nucleus collisions. Some different ways of converting the dependence upon tunnellength in nuclear matter into A dependence are discussed and a phenomenological model employed to exhibit the correlations to the fragmentation of the nucleus. The treatment is valid for arbitrary values of the velocity of sound c 0 in nuclear matter inside the range 0.2 0 0 around c 0 approximately 0.5 is preferred in a comparison to the presently available experimental data. This is the same range of values of the parameter for which the best agreement between theory and experiment occurs in the ISR range. (Auth.)
Heavy ion collision evolution modeling with ECHO-QGP
Rolando, V.; Inghirami, G.; Beraudo, A.; Del Zanna, L.; Becattini, F.; Chandra, V.; De Pace, A.; Nardi, M.
2014-11-01
We present a numerical code modeling the evolution of the medium formed in relativistic heavy ion collisions, ECHO-QGP. The code solves relativistic hydrodynamics in (3 + 1)D, with dissipative terms included within the framework of Israel-Stewart theory; it can work both in Minkowskian and in Bjorken coordinates. Initial conditions are provided through an implementation of the Glauber model (both Optical and Monte Carlo), while freezeout and particle generation are based on the Cooper-Frye prescription. The code is validated against several test problems and shows remarkable stability and accuracy with the combination of a conservative (shock-capturing) approach and the high-order methods employed. In particular it beautifully agrees with the semi-analytic solution known as Gubser flow, both in the ideal and in the viscous Israel-Stewart case, up to very large times and without any ad hoc tuning of the algorithm.
Langevin dynamics of heavy flavors in relativistic heavy-ion collisions
Alberico, W M; De Pace, A; Molinari, A; Monteno, M; Nardi, M; Prino, F
2011-01-01
We study the stochastic dynamics of c and b quarks, produced in hard initial processes, in the hot medium created after the collision of two relativistic heavy ions. This is done through the numerical solution of the relativistic Langevin equation. The latter requires the knowledge of the friction and diffusion coefficients, whose microscopic evaluation is performed treating separately the contribution of soft and hard collisions. The evolution of the background medium is described by ideal/viscous hydrodynamics. Below the critical temperature the heavy quarks are converted into hadrons, whose semileptonic decays provide single-electron spectra to be compared with the current experimental data measured at RHIC. We focus on the nuclear modification factor R_AA and on the elliptic-flow coefficient v_2, getting, for sufficiently large p_T, a reasonable agreement.
Dynamical aspects of intermediate-energy nucleus-nucleus collisions. Pt. 1
International Nuclear Information System (INIS)
Cassing, W.
1987-01-01
Central collisions of heavy nuclei are investigated within the limit of selfconsistent independent single-particle motion in terms of the Wigner transform of the one-body density matrix in space and time. The energy regime considered extends from roughly 15 MeV/u to 150 MeV/u. Special attention is devoted to the relation between energy and momentum of the nucleons in the collision zone of the two nuclei. An initial average energy-momentum distribution f(k; E) is determined within the fully quantal approach which proves to be vital for our understanding of energetic particle production in the very early stage of the heavy-ion reaction. A comparison with related classical quantities shows the peculiar features of quantum dynamics for finite size fermion systems far from equilibrium. (orig.)
Glaese, John R.; Tobbe, Patrick A.
1986-01-01
The Space Station Mechanism Test Bed consists of a hydraulically driven, computer controlled six degree of freedom (DOF) motion system with which docking, berthing, and other mechanisms can be evaluated. Measured contact forces and moments are provided to the simulation host computer to enable representation of orbital contact dynamics. This report describes the development of a generalized math model which represents the relative motion between two rigid orbiting vehicles. The model allows motion in six DOF for each body, with no vehicle size limitation. The rotational and translational equations of motion are derived. The method used to transform the forces and moments from the sensor location to the vehicles' centers of mass is also explained. Two math models of docking mechanisms, a simple translational spring and the Remote Manipulator System end effector, are presented along with simulation results. The translational spring model is used in an attempt to verify the simulation with compensated hardware in the loop results.
Simple model of surface roughness for binary collision sputtering simulations
Lindsey, Sloan J.; Hobler, Gerhard; Maciążek, Dawid; Postawa, Zbigniew
2017-02-01
It has been shown that surface roughness can strongly influence the sputtering yield - especially at glancing incidence angles where the inclusion of surface roughness leads to an increase in sputtering yields. In this work, we propose a simple one-parameter model (the "density gradient model") which imitates surface roughness effects. In the model, the target's atomic density is assumed to vary linearly between the actual material density and zero. The layer width is the sole model parameter. The model has been implemented in the binary collision simulator IMSIL and has been evaluated against various geometric surface models for 5 keV Ga ions impinging an amorphous Si target. To aid the construction of a realistic rough surface topography, we have performed MD simulations of sequential 5 keV Ga impacts on an initially crystalline Si target. We show that our new model effectively reproduces the sputtering yield, with only minor variations in the energy and angular distributions of sputtered particles. The success of the density gradient model is attributed to a reduction of the reflection coefficient - leading to increased sputtering yields, similar in effect to surface roughness.
International Nuclear Information System (INIS)
Suraud, E.
1990-01-01
We briefly remind the possible dynamical scenario of fragments formation in central heavy-ion collisions at some tens of MeV/A. We discuss how present day dynamical models can describe fragment formation. We show that particle methods provide a reasonable solution of Boltzman-like equations. We next turn to the Boltzmann-Langevin formalism which gives a well defined framework for the understanding of Intermediate Mass Fragments formation. We present a first numerical solution of this equation and show the importance of fluctuations in the dynamics of the collision. We finally apply the formalism to the onset of multifragmentation in the 40 Ca + 40 Ca system between 20 and 60 MeV/A beam energy
Revisiting directed flow in relativistic heavy-ion collisions from a multiphase transport model
Guo, Chong-Qiang; Zhang, Chun-Jian; Xu, Jun
2017-12-01
We have revisited several interesting questions on how the rapidity-odd directed flow is developed in relativistic 197Au+197Au collisions at √{s_{NN}} = 200 and 39 GeV based on a multiphase transport model. As the partonic phase evolves with time, the slope of the parton directed flow at midrapidity region changes from negative to positive as a result of the later dynamics at 200 GeV, while it remains negative at 39 GeV due to the shorter life time of the partonic phase. The directed flow splitting for various quark species due to their different initial eccentricities is observed at 39 GeV, while the splitting is very small at 200GeV. From a dynamical coalescence algorithm with Wigner functions, we found that the directed flow of hadrons is a result of competition between the coalescence in momentum and coordinate space as well as further modifications by the hadronic rescatterings.
A collision model for safety evaluation of autonomous intelligent cruise control.
Touran, A; Brackstone, M A; McDonald, M
1999-09-01
This paper describes a general framework for safety evaluation of autonomous intelligent cruise control in rear-end collisions. Using data and specifications from prototype devices, two collision models are developed. One model considers a train of four cars, one of which is equipped with autonomous intelligent cruise control. This model considers the car in front and two cars following the equipped car. In the second model, none of the cars is equipped with the device. Each model can predict the possibility of rear-end collision between cars under various conditions by calculating the remaining distance between cars after the front car brakes. Comparing the two collision models allows one to evaluate the effectiveness of autonomous intelligent cruise control in preventing collisions. The models are then subjected to Monte Carlo simulation to calculate the probability of collision. Based on crash probabilities, an expected value is calculated for the number of cars involved in any collision. It is found that given the model assumptions, while equipping a car with autonomous intelligent cruise control can significantly reduce the probability of the collision with the car ahead, it may adversely affect the situation for the following cars.
Basic Modelling principles and Validation of Software for Prediction of Collision Damage
DEFF Research Database (Denmark)
Simonsen, Bo Cerup
2000-01-01
This report describes basic modelling principles, the theoretical background and validation examples for the collision damage prediction module in the ISESO stand-alone software.......This report describes basic modelling principles, the theoretical background and validation examples for the collision damage prediction module in the ISESO stand-alone software....
Direct modeling for computational fluid dynamics
Xu, Kun
2015-06-01
All fluid dynamic equations are valid under their modeling scales, such as the particle mean free path and mean collision time scale of the Boltzmann equation and the hydrodynamic scale of the Navier-Stokes (NS) equations. The current computational fluid dynamics (CFD) focuses on the numerical solution of partial differential equations (PDEs), and its aim is to get the accurate solution of these governing equations. Under such a CFD practice, it is hard to develop a unified scheme that covers flow physics from kinetic to hydrodynamic scales continuously because there is no such governing equation which could make a smooth transition from the Boltzmann to the NS modeling. The study of fluid dynamics needs to go beyond the traditional numerical partial differential equations. The emerging engineering applications, such as air-vehicle design for near-space flight and flow and heat transfer in micro-devices, do require further expansion of the concept of gas dynamics to a larger domain of physical reality, rather than the traditional distinguishable governing equations. At the current stage, the non-equilibrium flow physics has not yet been well explored or clearly understood due to the lack of appropriate tools. Unfortunately, under the current numerical PDE approach, it is hard to develop such a meaningful tool due to the absence of valid PDEs. In order to construct multiscale and multiphysics simulation methods similar to the modeling process of constructing the Boltzmann or the NS governing equations, the development of a numerical algorithm should be based on the first principle of physical modeling. In this paper, instead of following the traditional numerical PDE path, we introduce direct modeling as a principle for CFD algorithm development. Since all computations are conducted in a discretized space with limited cell resolution, the flow physics to be modeled has to be done in the mesh size and time step scales. Here, the CFD is more or less a direct
Comparison of string models for heavy ion collisions
International Nuclear Information System (INIS)
Werner, K.
1990-01-01
An important method to explore new domains in physics is to compare new results with extrapolations from known areas. For heavy ion collision this can be done with string models, which extrapolate from light to heavy systems and which also may be used to extrapolate to higher energies. That does not mean that these string models are only background models, one may easily implement new ideas on top of the known aspects, providing much more reliable models than those formed from scratch. All the models to be considered in this paper have in common that they consist of three independent building blocks: (a) geometry, (b) string formation and (c) string fragmentation. The geometry aspect is treated quite similar in all models: nucleons are distributed inside each nucleus according to some standard parameterization of nuclear densities. The nuclei move through each other on a straight line trajectory, with all the nucleon positions being fixed. Whenever a projectile and a target nucleon come close, they interact. Such an interaction results in string formation. In the last step these strings decay into observable hadrons according to some string fragmentation procedure. The three building blocks are independent, so one can combine different methods in an arbitrary manner. Therefore rather than treating the models one after the other, the author discusses the procedures for string formation and string fragmentation as used by the models. He considers string models in a very general sense, so he includes models where the authors never use the word string, but which may be most naturally interpreted as string models and show strong similarities with real string models. Although very important he does not discuss - for time and space reasons - recent developments concerning secondary scattering
Energy Technology Data Exchange (ETDEWEB)
Sharma, Subash L., E-mail: sharma55@purdue.edu [School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907-1290 (United States); Hibiki, Takashi; Ishii, Mamoru [School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907-1290 (United States); Brooks, Caleb S. [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois, Urbana, IL 61801 (United States); Schlegel, Joshua P. [Nuclear Engineering Program, Missouri University of Science and Technology, Rolla, MO 65409 (United States); Liu, Yang [Nuclear Engineering Program, Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 (United States); Buchanan, John R. [Bechtel Marine Propulsion Corporation, Bettis Laboratory, West Mifflin, PA 15122 (United States)
2017-02-15
Highlights: • Void distribution in narrow rectangular channel with various non-uniform inlet conditions. • Modeling of void diffusion due to bubble collision force. • Validation of new modeling in adiabatic air–water two-phase flow in a narrow channel. - Abstract: The prediction capability of the two-fluid model for gas–liquid dispersed two-phase flow depends on the accuracy of the closure relations for the interfacial forces. In previous studies of two-phase flow Computational Fluid Dynamics (CFD), interfacial force models for a single isolated bubble has been extended to disperse two-phase flow assuming the effect in a swarm of bubbles is similar. Limited studies have been performed investigating the effect of the bubble concentration on the lateral phase distribution. Bubbles, while moving through the liquid phase, may undergo turbulence-driven random collision with neighboring bubbles without significant coalescence. The rate of these collisions depends upon the bubble approach velocity and bubble spacing. The bubble collision frequency is expected to be higher in locations with higher bubble concentrations, i.e., volume fraction. This turbulence-driven random collision causes the diffusion of the bubbles from high concentration to low concentration. Based on experimental observations, a phenomenological model has been developed for a “turbulence-induced bubble collision force” for use in the two-fluid model. For testing the validity of the model, two-phase flow data measured at Purdue University are utilized. The geometry is a 10 mm × 200 mm cross section channel. Experimentally, non-uniform inlet boundary conditions are applied with different sparger combinations to vary the volume fraction distribution across the wider dimension. Examining uniform and non-uniform inlet data allows for the influence of the volume fraction to be studied as a separate effect. The turbulence-induced bubble collision force has been implemented in ANSYS CFX. The
Modeling Vehicle Collision Angle in Traffic Crashes Based on Three-Dimensional Laser Scanning Data
Directory of Open Access Journals (Sweden)
Nengchao Lyu
2017-02-01
Full Text Available In road traffic accidents, the analysis of a vehicle’s collision angle plays a key role in identifying a traffic accident’s form and cause. However, because accurate estimation of vehicle collision angle involves many factors, it is difficult to accurately determine it in cases in which less physical evidence is available and there is a lack of monitoring. This paper establishes the mathematical relation model between collision angle, deformation, and normal vector in the collision region according to the equations of particle deformation and force in Hooke’s law of classical mechanics. At the same time, the surface reconstruction method suitable for a normal vector solution is studied. Finally, the estimation model of vehicle collision angle is presented. In order to verify the correctness of the model, verification of multi-angle collision experiments and sensitivity analysis of laser scanning precision for the angle have been carried out using three-dimensional (3D data obtained by a 3D laser scanner in the collision deformation zone. Under the conditions with which the model has been defined, validation results show that the collision angle is a result of the weighted synthesis of the normal vector of the collision point and the weight value is the deformation of the collision point corresponding to normal vectors. These conclusions prove the applicability of the model. The collision angle model proposed in this paper can be used as the theoretical basis for traffic accident identification and cause analysis. It can also be used as a theoretical reference for the study of the impact deformation of elastic materials.
A rigorous test for a new conceptual model for collisions
International Nuclear Information System (INIS)
Peixoto, E.M.A.; Mu-Tao, L.
1979-01-01
A rigorous theoretical foundation for the previously proposed model is formulated and applied to electron scattering by H 2 in the gas phase. An rigorous treatment of the interaction potential between the incident electron and the Hydrogen molecule is carried out to calculate Differential Cross Sections for 1 KeV electrons, using Glauber's approximation Wang's molecular wave function for the ground electronic state of H 2 . Moreover, it is shown for the first time that, when adequately done, the omission of two center terms does not adversely influence the results of molecular calculations. It is shown that the new model is far superior to the Independent Atom Model (or Independent Particle Model). The accuracy and simplicity of the new model suggest that it may be fruitfully applied to the description of other collision phenomena (e.g., in molecular beam experiments and nuclear physics). A new techniques is presented for calculations involving two center integrals within the frame work of the Glauber's approximation for scattering. (Author) [pt
Vehicle-pedestrian collisions - Aspects regarding pedestrian kinematics, dynamics and biomechanics
Petrescu, L.; Petrescu, Al
2017-10-01
Vehicle-pedestrian collisions result in a substantial number of pedestrian fatalities and injuries worldwide. Concern continues to limit and reduce the tragic consequences suffered by pedestrians involved in road accidents, caused the vehicle-pedestrian accident reconstruction become an important area and distinctly outlined in the reconstruction of road incidents involving vehicle. This paper analyzes the dynamics of vehicle-pedestrian impact influence over pedestrian biomechanics, which is directly connected with the severity of injury after contact with the vehicle profile and with the place where the pedestrian is projected. The main goal of this paper is to highlight some features of reconstruction of road accidents involving pedestrian, looking at the kinematics and dynamics of pedestrian impact for a better understanding of the phenomena that occur. The study on the dynamics and biomechanics of the pedestrian hit by the vehicle is useful in order to understand how the injuries, including the lethal ones, are generated in the collision, what is essential in road accidents reconstruction.
International Nuclear Information System (INIS)
Ono, A.; Horiuchi, H.
1995-01-01
Collective transverse momentum flow of nucleons and fragments in intermediate energy 40 Ar+ 27 Al collisions is calculated with the antisymmetrized molecular dynamics (AMD). The observed flow and its balance energy are reproduced well by calculation with the Gogny force which corresponds to the soft equation of state (EOS) of nuclear matter. The calculated absolute value of the fragment flow is larger than that of the nucleon flow in the negative flow region, which can be explained by the existence of two components of flow. In addition to many similarities, the difference in the deuteron flow is found between 12 C+ 12 C and 40 Ar+ 27 Al collisions, and its origin is investigated by studying the production mechanism of light fragments. We also investigate the dependence of the flow of nucleons and fragments on the stochastic collision cross section and the effective interaction, and conclude that the stiff EOS without momentum dependence of the mean field is not consistent with the experimental data
A parallel Discrete Element Method to model collisions between non-convex particles
Directory of Open Access Journals (Sweden)
Rakotonirina Andriarimina Daniel
2017-01-01
Full Text Available In many dry granular and suspension flow configurations, particles can be highly non-spherical. It is now well established in the literature that particle shape affects the flow dynamics or the microstructure of the particles assembly in assorted ways as e.g. compacity of packed bed or heap, dilation under shear, resistance to shear, momentum transfer between translational and angular motions, ability to form arches and block the flow. In this talk, we suggest an accurate and efficient way to model collisions between particles of (almost arbitrary shape. For that purpose, we develop a Discrete Element Method (DEM combined with a soft particle contact model. The collision detection algorithm handles contacts between bodies of various shape and size. For nonconvex bodies, our strategy is based on decomposing a non-convex body into a set of convex ones. Therefore, our novel method can be called “glued-convex method” (in the sense clumping convex bodies together, as an extension of the popular “glued-spheres” method, and is implemented in our own granular dynamics code Grains3D. Since the whole problem is solved explicitly, our fully-MPI parallelized code Grains3D exhibits a very high scalability when dynamic load balancing is not required. In particular, simulations on up to a few thousands cores in configurations involving up to a few tens of millions of particles can readily be performed. We apply our enhanced numerical model to (i the collapse of a granular column made of convex particles and (i the microstructure of a heap of non-convex particles in a cylindrical reactor.
International Nuclear Information System (INIS)
Deladerriere, N.; Delaye, J.-M.; Peuget, S.; Bureau, G.
2008-01-01
A novel method based on classical molecular dynamics was used to measure acoustic velocities in simplified glasses and in pure silica. The method was then applied to observe the acoustic velocity variation in a simple glass subjected to displacement cascades. The Rayleigh velocity and Young's modulus were observed to decrease; this behavior is consistent with experimental results obtained for the same glass irradiated by heavy ions. The increasing disorder and reduction in atomic density resulting from elastic collisions are thus directly related to the drop in the Rayleigh velocities and Young's modulus
DEFF Research Database (Denmark)
Borregaard, Michael K.; Matthews, Thomas J.; Whittaker, Robert James
2016-01-01
Aim: Island biogeography focuses on understanding the processes that underlie a set of well-described patterns on islands, but it lacks a unified theoretical framework for integrating these processes. The recently proposed general dynamic model (GDM) of oceanic island biogeography offers a step...... towards this goal. Here, we present an analysis of causality within the GDM and investigate its potential for the further development of island biogeographical theory. Further, we extend the GDM to include subduction-based island arcs and continental fragment islands. Location: A conceptual analysis...... of evolutionary processes in simulations derived from the mechanistic assumptions of the GDM corresponded broadly to those initially suggested, with the exception of trends in extinction rates. Expanding the model to incorporate different scenarios of island ontogeny and isolation revealed a sensitivity...
Stochastic approaches to dynamics of heavy ion collisions, the case of thermal fission
International Nuclear Information System (INIS)
Boilley, D.; Abe, Y.
1994-01-01
In order to study the influence of fluctuations on various phenomena linked to heavy ion collisions, a Langevin equation has been derived from a microscopic model. Parameters entering this equation are completely determined from microscopic quantities characterizing nuclear matter. This equation has been applied to various phenomena at intermediate energies. This paper focuses on large amplitude motions and especially thermal fission. Fission rate is calculated and compared to experimental results
Collisional model for granular impact dynamics.
Clark, Abram H; Petersen, Alec J; Behringer, Robert P
2014-01-01
When an intruder strikes a granular material from above, the grains exert a stopping force which decelerates and stops the intruder. Many previous studies have used a macroscopic force law, including a drag force which is quadratic in velocity, to characterize the decelerating force on the intruder. However, the microscopic origins of the force-law terms are still a subject of debate. Here, drawing from previous experiments with photoelastic particles, we present a model which describes the velocity-squared force in terms of repeated collisions with clusters of grains. From our high speed photoelastic data, we infer that "clusters" correspond to segments of the strong force network that are excited by the advancing intruder. The model predicts a scaling relation for the velocity-squared drag force that accounts for the intruder shape. Additionally, we show that the collisional model predicts an instability to rotations, which depends on the intruder shape. To test this model, we perform a comprehensive experimental study of the dynamics of two-dimensional granular impacts on beds of photoelastic disks, with different profiles for the leading edge of the intruder. We particularly focus on a simple and useful case for testing shape effects by using triangular-nosed intruders. We show that the collisional model effectively captures the dynamics of intruder deceleration and rotation; i.e., these two dynamical effects can be described as two different manifestations of the same grain-scale physical processes.
Modeling of Ship Collision Risk Index Based on Complex Plane and Its Realization
Directory of Open Access Journals (Sweden)
Xiaoqin Xu
2016-07-01
Full Text Available Ship collision risk index is the basic and important concept in the domain of ship collision avoidance. In this paper, the advantages and deficiencies of the various calculation methods of ship collision risk index are pointed out. Then the ship collision risk model based on complex plane, which can well make up for the deficiencies of the widely-used evaluation model proposed by Kearon.J and Liu ruru is proposed. On this basis, the calculation method of collision risk index under the encountering situation of multi-ships is constructed, then the three-dimensional image and spatial curve of the risk index are figured out. Finally, single chip microcomputer is used to realize the model. And attaching this single chip microcomputer to ARPA is helpful to the decision-making of the marine navigators.
Statistical model predictions for p+p and Pb+Pb collisions at LHC
Kraus, I.; Cleymans, J.; Oeschler, H.; Redlich, K.; Wheaton, S.
2009-01-01
Particle production in p+p and central collisions at LHC is discussed in the context of the statistical thermal model. For heavy-ion collisions, predictions of various particle ratios are presented. The sensitivity of several ratios on the temperature and the baryon chemical potential is studied in
Modeling and Analysis of Ultrarelativistic Heavy Ion Collisions
McCormack, William; Pratt, Scott
2014-09-01
High-energy collisions of heavy ions, such as gold, copper, or uranium serve as an important means of studying quantum chromodynamic matter. When relativistic nuclei collide, a hot, energetic fireball of dissociated partonic matter is created; this super-hadronic matter is believed to be the quark gluon plasma (QGP), which is theorized to have comprised the universe immediately following the big bang. As the fireball expands and cools, it reaches freeze-out temperatures, and quarks hadronize into baryons and mesons. To characterize this super-hadronic matter, one can use balance functions, a means of studying correlations due to local charge conservation. In particular, the simple model used in this research assumed two waves of localized charge-anticharge production, with an abrupt transition from the QGP stage to hadronization. Balance functions were constructed as the sum of these two charge production components, and four parameters were manipulated to match the model's output with experimental data taken from the STAR Collaboration at RHIC. Results show that the chemical composition of the super-hadronic matter are consistent with that of a thermally equilibrated QGP. High-energy collisions of heavy ions, such as gold, copper, or uranium serve as an important means of studying quantum chromodynamic matter. When relativistic nuclei collide, a hot, energetic fireball of dissociated partonic matter is created; this super-hadronic matter is believed to be the quark gluon plasma (QGP), which is theorized to have comprised the universe immediately following the big bang. As the fireball expands and cools, it reaches freeze-out temperatures, and quarks hadronize into baryons and mesons. To characterize this super-hadronic matter, one can use balance functions, a means of studying correlations due to local charge conservation. In particular, the simple model used in this research assumed two waves of localized charge-anticharge production, with an abrupt transition
Account of the effect of nuclear collision cascades in model of radiation damage of RPV steels
International Nuclear Information System (INIS)
Kevorkyan, Yu.R.; Nikolaev, Yu.A.
1997-01-01
A kinetic model is proposed for describing the effect of collision cascades in model of radiation damage of reactor pressure vessel steels. This is a closed system of equations which can be solved only by numerical methods in general case
Campagnoli, Patrizia; Petris, Giovanni
2009-01-01
State space models have gained tremendous popularity in as disparate fields as engineering, economics, genetics and ecology. Introducing general state space models, this book focuses on dynamic linear models, emphasizing their Bayesian analysis. It illustrates the fundamental steps needed to use dynamic linear models in practice, using R package.
GIS and dynamic phenomena modeling
Czech Academy of Sciences Publication Activity Database
Klimešová, Dana
2006-01-01
Roč. 4, č. 4 (2006), s. 11-15 ISSN 0139-570X Institutional research plan: CEZ:AV0Z10750506 Keywords : dynamic modelling * temporal analysis * dynamics evaluation * temporal space Subject RIV: BC - Control Systems Theory
Calibrating a multi-model approach to defect production in high energy collision cascades
International Nuclear Information System (INIS)
Heinisch, H.L.; Singh, B.N.; Diaz de la Rubia, T.
1994-01-01
A multi-model approach to simulating defect production processes at the atomic scale is described that incorporates molecular dynamics (MD), binary collision approximation (BCA) calculations and stochastic annealing simulations. The central hypothesis is that the simple, fast computer codes capable of simulating large numbers of high energy cascades (e.g., BCA codes) can be made to yield the correct defect configurations when their parameters are calibrated using the results of the more physically realistic MD simulations. The calibration procedure is investigated using results of MD simulations of 25 keV cascades in copper. The configurations of point defects are extracted from the MD cascade simulations at the end of the collisional phase, thus providing information similar to that obtained with a binary collision model. The MD collisional phase defect configurations are used as input to the ALSOME annealing simulation code, and values of the ALSOME quenching parameters are determined that yield the best fit to the post-quenching defect configurations of the MD simulations. ((orig.))
DEFF Research Database (Denmark)
Pedersen, Preben Terndrup; Servis, D.P.; Zhang, Shengming
1999-01-01
The first section of the present report describes the procedures that are being programmed at DTU for evaluation of the external collision dynamics. Then follows a detailed description of a comprehensive finite element analysis of one collision scenario for MS Dextra carried out at NTUA. The last...
Gas phase collision dynamics by means of pulse-radiolysis methods
International Nuclear Information System (INIS)
Hatano, Yoshihiko
1989-01-01
After a brief survey of recent advances in gas-phase collision dynamics studies using pulse radiolysis methods, the following two topics in our research programs are presented with emphasis on the superior advantages of the pulse radiolysis methods over the various methods of gas-phase collision dynamics, such as beam methods, swarm methods and flow methods. One of the topics is electron attachment to van der Waals molecules. The attachment rates of thermal electrons to O 2 and other molecules in dense gases have been measured in wide ranges of both gas temperatures and pressures, from which experimental evidence has been obtained for electron attachment to van der Waals molecules. The results have been compared with theories and discussed in terms of the effect of van der Waals interaction on the electron attachment resonance. The obtained conclusions have been related with investigations of electron attachment, solvation and localization in the condensed phase. The other is Penning ionization and its related processes. The rate constants for the de-excitation of He(2 1 P), He(2 3 S), Ne( 3 P 0 ), Ne( 3 P 1 ), Ne( 3 P 2 ), Ar( 1 P 1 ), Ar( 3 P 1 ), by atoms and molecules have been measured in the temperature range from 100 to 300 K, thus obtaining the collisional energy dependence of the de-excitation cross sections. The results are compared in detail with theories classified according to the excited rare gas atoms in the metastable and resonance states. (author)
Dynamical and statistical aspects in nucleus-nucleus collisions around the Fermi energy
Energy Technology Data Exchange (ETDEWEB)
Tamain, B.; Bocage, F.; Bougault, R.; Brou, R. [Caen Univ., 14 (France). Lab. de Physique Corpusculaire; Assenard, M. [Centre National de la Recherche Scientifique, 44 - Nantes (France). Lab. de Physique Subatomique et des Technologies Associees; Auger, G.; Benlliure, J. [Grand Accelerateur National d`Ions Lourds (GANIL), 14 - Caen (France); Bacri, C.O.; Borderie, B. [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire; Bisquer, E. [Lyon-1 Univ., 69 - Villeurbanne (France). Inst. de Physique Nucleaire] [and others
1997-12-31
Nucleus-nucleus collisions at low incident energy are mainly governed by statistical dissipative processes, fusion and deep inelastic reactions being the most important ones. Conversely, in the relativistic energy regime, dynamical effects play a dominant role and one should apply a participant-spectator picture in order to understand the data. In between, the intermediate energy region is a transition one in which it is necessary to disentangle dynamics from statistical effects. Moreover, the Fermi energy region corresponds to available energies comparable with nuclear binding energies and one may except to observe phase transition effects. Experiments performed recently with 4{pi} devices have given quite new data and a much better insight into involved mechanisms and hot nuclear matter properties. INDRA data related to reaction mechanisms and multifragmentation are presented. (author) 53 refs.
Dynamical and statistical aspects in nucleus-nucleus collisions around the Fermi energy
International Nuclear Information System (INIS)
Tamain, B.; Bocage, F.; Bougault, R.; Brou, R.; Bacri, C.O.; Borderie, B.; Bisquer, E.
1997-01-01
Nucleus-nucleus collisions at low incident energy are mainly governed by statistical dissipative processes, fusion and deep inelastic reactions being the most important ones. Conversely, in the relativistic energy regime, dynamical effects play a dominant role and one should apply a participant-spectator picture in order to understand the data. In between, the intermediate energy region is a transition one in which it is necessary to disentangle dynamics from statistical effects. Moreover, the Fermi energy region corresponds to available energies comparable with nuclear binding energies and one may except to observe phase transition effects. Experiments performed recently with 4π devices have given quite new data and a much better insight into involved mechanisms and hot nuclear matter properties. INDRA data related to reaction mechanisms and multifragmentation are presented. (author)
International Nuclear Information System (INIS)
Sun Zhongguo; Xi Guang; Chen Xi
2009-01-01
The binary collision of liquid droplets is of both practical importance and fundamental value in computational fluid mechanics. We present a modified surface tension model within the moving particle semi-implicit (MPS) method, and carry out two-dimensional simulations to investigate the mechanisms of coalescence and separation of the droplets during binary collision. The modified surface tension model improves accuracy and convergence. A mechanism map is established for various possible deformation pathways encountered during binary collision, as the impact speed is varied; a new pathway is reported when the collision speed is critical. In addition, eccentric collisions are simulated and the effect of the rotation of coalesced particle is explored. The results qualitatively agree with experiments and the numerical protocol may find applications in studying free surface flows and interface deformation
New dynamics information from experimental results obtained in d-Au collisions at RHIC-BNL energies
International Nuclear Information System (INIS)
Jipa, Alexandru
2004-01-01
During the last runs d-Au collisions at √s NN = 200 GeV have been investigated at RHIC-BNL using the BRAHMS Experiment. Some interesting experimental results on charged particle multiplicities, rapidity distributions, transverse momentum spectra, antiparticle to particle ratios, participant spectator evolution have been obtained. In this work the most interesting results are presented for different rapidity and collision centrality ranges. Taking into account the importance of the collision geometry and collision symmetry in the collision dynamics, comparisons with the similar experimental results obtained in Au-Au collisions have been done. New interesting results can be reported. The most significant are related to the evolution of the nuclear modification factor with rapidity and collision centrality. The high transverse momentum suppression and the behaviours in different rapidity and centrality ranges suggest strong initial state effects. These effects could be related to the gluonic structure of the colliding nuclei. Some insights on the Color Glass Condensate formation are possible. (author)
International Nuclear Information System (INIS)
Roberts, W.W. Jr.; Stewart, G.R.
1987-01-01
The different roles played by orbital dynamics and dissipative cloud-cloud collisions in the formation of giant molecular clouds (GMCs) in a global spiral structure are investigated. The interstellar medium (ISM) is simulated by a system of particles, representing clouds, which orbit in a spiral-perturbed, galactic gravitational field. The overall magnitude and width of the global cloud density distribution in spiral arms is very similar in the collisional and collisionless simulations. The results suggest that the assumed number density and size distribution of clouds and the details of individual cloud-cloud collisions have relatively little effect on these features. Dissipative cloud-cloud collisions play an important steadying role for the cloud system's global spiral structure. Dissipative cloud-cloud collisions also damp the relative velocity dispersion of clouds in massive associations and thereby aid in the effective assembling of GMC-like complexes
Modelling dynamic roughness during floods
Paarlberg, Andries; Dohmen-Janssen, Catarine M.; Hulscher, Suzanne J.M.H.; Termes, A.P.P.
2007-01-01
In this paper, we present a dynamic roughness model to predict water levels during floods. Hysteresis effects of dune development are explicitly included. It is shown that differences between the new dynamic roughness model, and models where the roughness coefficient is calibrated, are most
Model unspecific search for new physics in pp collisions
International Nuclear Information System (INIS)
Malhotra, Shivali
2013-01-01
The model-independent analysis systematically scans the data taken by Compact Muon Solenoid - CMS detector for deviations from the Standard Model (SM) predictions. This approach is sensitive to a variety of models for new physics due to the minimal theoretical bias i.e. without assumptions on specific models of new physics and covering a large phase space. Possible causes of the significant deviations could be insufficient understanding of the collision event generation or detector simulation, or indeed genuine new physics in the data. Thus the output of MUSiC must be seen as only the first, but important step in the potential discovery of new physics. To get the distinctive final states, events with at least one electron or muon are classified according to their content of reconstructed objects (muons, electrons, photons, jets and missing transverse energy) and sorted into event classes. A broad scan of three kinematic distributions (scalar sum of the transverse momentum, invariant mass of reconstructed objects and missing transverse energy) in those event classes is performed by identifying deviations from SM expectations, accounting for systematic uncertainties. A scanning algorithm determines the regions in the considered distributions where the measured data deviates most from the SM predictions. This search is sensitive to an excess as well as a deficit in the comparison of data and SM background. This approach has been applied to the CMS data and we have obtained the preliminary results. I will talk about the details of the analysis techniques, its implementation in analyzing CMS data, results obtained and the discussion on the discrepancy observed
Modeling of Inelastic Collisions in a Multifluid Plasma: Excitation and Deexcitation
2016-05-31
DATES COVERED (From - To) 4. TITLE AND SUBTITLE Modeling of Inelastic Collisions in a Multifluid Plasma: Excitation and 5a. CONTRACT NUMBER...describe here a model for inelastic collisions for electronic excitation and deexcitation processes in a general, multifluid plasma. The model is derived... Excitation and Deexcitationa) Hai P. Le1, b) and Jean-Luc Cambier2, c) 1)Department of Mathematics, University of California, Los Angeles, California
Ionic wave propagation and collision in an excitable circuit model of microtubules
Guemkam Ghomsi, P.; Tameh Berinyoh, J. T.; Moukam Kakmeni, F. M.
2018-02-01
In this paper, we report the propensity to excitability of the internal structure of cellular microtubules, modelled as a relatively large one-dimensional spatial array of electrical units with nonlinear resistive features. We propose a model mimicking the dynamics of a large set of such intracellular dynamical entities as an excitable medium. We show that the behavior of such lattices can be described by a complex Ginzburg-Landau equation, which admits several wave solutions, including the plane waves paradigm. A stability analysis of the plane waves solutions of our dynamical system is conducted both analytically and numerically. It is observed that perturbed plane waves will always evolve toward promoting the generation of localized periodic waves trains. These modes include both stationary and travelling spatial excitations. They encompass, on one hand, localized structures such as solitary waves embracing bright solitons, dark solitons, and bisolitonic impulses with head-on collisions phenomena, and on the other hand, the appearance of both spatially homogeneous and spatially inhomogeneous stationary patterns. This ability exhibited by our array of proteinic elements to display several states of excitability exposes their stunning biological and physical complexity and is of high relevance in the description of the developmental and informative processes occurring on the subcellular scale.
A Cross-Domain Survey of Metrics for Modelling and Evaluating Collisions
Directory of Open Access Journals (Sweden)
Jeremy A. Marvel
2014-09-01
Full Text Available This paper provides a brief survey of the metrics for measuring probability, degree, and severity of collisions as applied to autonomous and intelligent systems. Though not exhaustive, this survey evaluates the state-of-the-art of collision metrics, and assesses which are likely to aid in the establishment and support of autonomous system collision modelling. The survey includes metrics for 1 robot arms; 2 mobile robot platforms; 3 nonholonomic physical systems such as ground vehicles, aircraft, and naval vessels, and; 4 virtual and mathematical models.
de Carvalho, Paulo Victor R; Ferreira, Bemildo
2012-01-01
In this article we present a model of some functions and activities of the Brazilian Air traffic Control System (ATS) in the period in which occurred a mid-air collision between flight GLO1907, a commercial aircraft Boeing 737-800, and flight N600XL, an executive jet EMBRAER E-145, to investigate key resilience characteristics of the ATM. Modeling in some detail activities during the collision and related them to overall behavior and antecedents that stress the organization uncover some drift into failure mechanisms that erode safety defenses provided by the Air Navigation Service Provider (ANSP), enabling a mid-air collision to be happen.
Li, Tianlong; Chang, Xiaocong; Wu, Zhiguang; Li, Jinxing; Shao, Guangbin; Deng, Xinghong; Qiu, Jianbin; Guo, Bin; Zhang, Guangyu; He, Qiang; Li, Longqiu; Wang, Joseph
2017-09-26
Self-propelled micro- and nanoscale robots represent a rapidly emerging and fascinating robotics research area. However, designing autonomous and adaptive control systems for operating micro/nanorobotics in complex and dynamically changing environments, which is a highly demanding feature, is still an unmet challenge. Here we describe a smart microvehicle for precise autonomous navigation in complicated environments and traffic scenarios. The fully autonomous navigation system of the smart microvehicle is composed of a microscope-coupled CCD camera, an artificial intelligence planner, and a magnetic field generator. The microscope-coupled CCD camera provides real-time localization of the chemically powered Janus microsphere vehicle and environmental detection for path planning to generate optimal collision-free routes, while the moving direction of the microrobot toward a reference position is determined by the external electromagnetic torque. Real-time object detection offers adaptive path planning in response to dynamically changing environments. We demonstrate that the autonomous navigation system can guide the vehicle movement in complex patterns, in the presence of dynamically changing obstacles, and in complex biological environments. Such a navigation system for micro/nanoscale vehicles, relying on vision-based close-loop control and path planning, is highly promising for their autonomous operation in complex dynamic settings and unpredictable scenarios expected in a variety of realistic nanoscale scenarios.
Dynamics of violent collisions induced by Ar on Ag between 27 and 60 MeV/nucleon
International Nuclear Information System (INIS)
Rivet, M.F.; Borderie, B.; Box, P.; Dakowski, M; Cabot, C.; Gardes, D.; Hanappe, F.; Sebille, F.; Haddad, F.
1993-01-01
The dynamics of violent collisions were studied for the 40 Ar + nat Ag system between 27 and 57 MeV/u. The persistence of binary dissipative collisions over this energy range was demonstrated. They are accompanied by preequilibrium emission, the abundance of which increases with the violence of the collision, and with the incident energy. The evolution of the damping of the relative motion with the emission angle of the light partner is compared with the predictions of dynamical calculations, which brings information on the nucleon-nucleon cross section in the nuclear medium. Finally a limitation of the thermal excitation energy is observed, through the saturation of both the temperature (7 MeV) of the heavy partner and the multiplicity of light charged particles that it emits. (author) 13 refs.; 7 figs.; 2 tabs
Impulsive Collision Dynamics of CO Super Rotors from an Optical Centrifuge.
Murray, Matthew J; Ogden, Hannah M; Toro, Carlos; Liu, Qingnan; Mullin, Amy S
2016-11-18
We report state-resolved collision dynamics for CO molecules prepared in an optical centrifuge and measured with high-resolution transient IR absorption spectroscopy. Time-resolved polarization-sensitive measurements of excited CO molecules in the J=29 rotational state reveal that the oriented angular momentum of CO rotors is relaxed by impulsive collisions. The translational energy gains for molecules in the initial plane of rotation are threefold larger than for randomized angular momentum orientations, indicating the presence of anisotropic kinetic energy. The transient data show enhanced population for CO molecules in the initial plane of rotation immediately following the optical centrifuge pulse. A comparison with previous CO 2 super rotor studies illustrates the behavior of molecular gyroscopes; spatial reorientation of CO 2 J=76 rotors takes substantially longer than that for CO J=29 rotors, despite similarities in classical rotational period and rotational energy gap. High-resolution transient IR absorption measurements of the CO J=29-39 rotational states show that the collisional depopulation rates increase with J quantum number. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
On the dynamical fluctuations in the multiparticle final states of $e^{+}e^{-}$ collisions
Liu, F; Liu, L
1999-01-01
The scaling property of factorial moments in the multiparticle final- states of e/sup +/e/sup -/ collisions is studied in both the laboratory and the thrust-axis coordinate systems by using the Jetset generator. It turns out that in both of the two cases, the 3- dimensional lnF/sub 2/~lnM are approximately straight lines when the phase space are divided isotropically in different directions, showing that the dynamical fluctuations in the multiparticle final- state of e/sup +/e/sup $/collisions are approximately isotropic. In the lab system, the three gamma parameters obtained by fitting F/sub 2/~M of p/sub x/, p/sub y/, p/sub z/ to Ochs formula respectively are approximately equal. In the thrust system, the three gamma values obtained by fitting F/sub 2/(y)~M, F/sub 2/(p/sub t/)~M and F/sub 2/( phi )~M are also close to each other provided the starting point in fitting F/sub 2/( phi )~M is chosen appropriately. All of these provide further evidence for the above assertion. Our results show that the essential ...
Bourbakis, N G
1997-01-01
This paper presents a generic traffic priority language, called KYKLOFORTA, used by autonomous robots for collision-free navigation in a dynamic unknown or known navigation space. In a previous work by X. Grossmman (1988), a set of traffic control rules was developed for the navigation of the robots on the lines of a two-dimensional (2-D) grid and a control center coordinated and synchronized their movements. In this work, the robots are considered autonomous: they are moving anywhere and in any direction inside the free space, and there is no need of a central control to coordinate and synchronize them. The requirements for each robot are i) visual perception, ii) range sensors, and iii) the ability of each robot to detect other moving objects in the same free navigation space, define the other objects perceived size, their velocity and their directions. Based on these assumptions, a traffic priority language is needed for each robot, making it able to decide during the navigation and avoid possible collision with other moving objects. The traffic priority language proposed here is based on a set of primitive traffic priority alphabet and rules which compose pattern of corridors for the application of the traffic priority rules.
Energy Technology Data Exchange (ETDEWEB)
Picard, Y
1999-04-15
The goal of this work is the complete analysis of the fragmentation of alkali clusters (Na{sub n}{sup +} (n < 10), NaK{sup +} and K{sub 2}{sup +}) induced by collision with light atomic (He) or molecular (H{sub 2}) targets. The main point is to study how the energy is transmitted to the cluster during the collision and how this energy is shared among the various degrees of freedom of the system and leads to its fragmentation. Two types of interactions govern the collision induced dissociation processes: on one hand, the electronic mechanisms where the target perturbs the electronic cloud and brings the molecule into a dissociative state, and on the other hand, the impulsive mechanisms where the momentum transferred to the atomic cores leads to the rotational-vibrational dissociation of the molecule. The experimental procedure is based on the measurement of the velocity vectors of the outgoing fragments detected in coincidence. This allows to reconstruct the full kinematics of the fragmentation and to separate and characterize for the first time the two types of interactions. The two basic mechanisms of collision induced dissociation are then clearly resolved for the diatomic molecule Na{sub 2}{sup +}. For the heteronuclear molecular ion NaK{sup +}, it is shown that the dissociation process is due to a combination of electronic and impulsive mechanisms in some of the dissociation pathways. The extension to the study of metallic clusters Na{sub n}{sup +} (n < 10) fragmentation shows the role and the relative importance of the electronic and impulsive mechanisms and their evolution with the cluster size. The complete analysis of Na{sub 3}{sup +} multi-fragmentation is also presented. (author)
Dynamics of hadronization in ultra-relativistic nucleus-nucleus collisions
International Nuclear Information System (INIS)
Friman, B.L.
1986-01-01
One of the main problems in the search for quark-gluon plasma in ultra-relativistic nucleus-nucleus collisions is finding a reliable signature for deconfinement. Several signatures have been suggested, e.g., dileptons with a spectrum characteristic of the plasma, an increase in the number of strange particles and effects due to the hadronization of the plasma. In this talk I will describe some recent work on the effects of the hadronization transition in the central rapidity region within the hydrodynamic model of Bjorken, Kajantie and McLerran. (orig.)
Incident energy dependence of collision dynamics in A+A reactions from AGS to SPS
International Nuclear Information System (INIS)
Nara, Yasushi
2000-01-01
Based on the hadronic transport model of JAM, I calculate the time evolution of particles, density, temperature and energy density for the heavy ion collision at the incident energies of AGS(11A GeV), JHF(25A GeV) and SPS(158A GeV). Microscopic calculations show that resonance matter with extremely large baryon density is created at AGS energy, while at JHF energy, quark matter with extremely large baryon density is suggested. At SPS energy, quark matter with large baryon density might be created. (author)
Modeling the Dynamical Structure of the Haumea Family
Proudfoot, Benjamin; Ragozzine, Darin
2018-04-01
Collisions are known to be critical in explaining the full story of the outer Solar System. The dwarf planet Haumea provides a unique empirical view into this, as Haumea is the only known example of a collisional family in the Kuiper Belt. Although there have been many Haumea formation hypotheses presented in the literature, none are fully self-consistent. In particular, it is challenging to explain the low ejection velocity of the family. With the addition of many new Haumea family members (Maggard & Ragozzine 2018, in prep.), we further investigate how we can use collision models to recreate the current dynamical distribution of Haumea family members in (proper) a-e-i-dv-H space. Using synthetic families created using different collision models, we use a Bayesian methodology to infer the posterior distribution of our model parameters that best matches the current family. Our newest results continue to exclude the planar distribution of family members that would result from a ‘graze-and-merge’ type collision (e.g., Leinhardt et al. 2010) based on a lack of a-e-i correlation (Proudfoot & Ragozzine, DPS 2017, DDA 2017). We present here our results from more models. We have also validated a statistical method for automatically and self-consistently identifying interlopers from the background population.
Hybrid dynamics for currency modeling
Theodosopoulos, Ted; Trifunovic, Alex
2006-01-01
We present a simple hybrid dynamical model as a tool to investigate behavioral strategies based on trend following. The multiplicative symbolic dynamics are generated using a lognormal diffusion model for the at-the-money implied volatility term structure. Thus, are model exploits information from derivative markets to obtain qualititative properties of the return distribution for the underlier. We apply our model to the JPY-USD exchange rate and the corresponding 1mo., 3mo., 6mo. and 1yr. im...
Explosion-evaporation model for fragment production in intermediate-energy nuclear collisions
International Nuclear Information System (INIS)
Fai, G.; Randrup, J.
1981-01-01
Nuclear collisions at intermediate energies may create transient systems of hot nuclear matter that decay into many nuclear fragments. The disassembly of such a nuclear fireball is described as a two-stage process. In the primary explosion stage the system quickly fragments into nucleons and composite nuclei according to the available phase space. The explosion produces excited nuclei with half-lives longer than the time associated with the breakup. In the secondary evaporation stage, these nuclei decay, first by sequential emission of light particles (neutrons, protons, alphas), later by electromagnetic radiation. The secondary stage in general changes the relative abundancies of the various fragment species. This general feature makes it essential to take account of the composite fragments before using d/p as a measure of the entropy of the initial source. The formation of unbound nuclei at the explosion stage also has the desirable effect of enhancing the final abundancies of particularly stable nuclei, e.g., 4 He. For neutron-excessive sources the presence of composite nuclei amplifies the ratio of observed neutrons and protons; this effect persists for heavier mirror systems. Predictions of the model are qualitatively compared to available experimental data. The model offers a convenient way to augment existing dynamical models, such as intra-nuclear cascade and nuclear fluid dynamics, to yield actual nuclear fragments rather than merely matter distributions
Galilean invariance in the exponential model of atomic collisions
International Nuclear Information System (INIS)
del Pozo, A.; Riera, A.; Yaez, M.
1986-01-01
Using the X/sup n/ + (1s 2 )+He/sup 2+/ colliding systems as specific examples, we study the origin dependence of results in the application of the two-state exponential model, and we show the relevance of polarization effects in that study. Our analysis shows that polarization effects of the He + (1s) orbital due to interaction with X/sup (//sup n//sup +1)+/ ion in the exit channel yield a very small contribution to the energy difference and render the dynamical coupling so strongly origin dependent that it invalidates the basic premises of the model. Further study, incorporating translation factors in the formalism, is needed
Energy Technology Data Exchange (ETDEWEB)
Bauge, E
1994-07-01
In heavy ion collisions at intermediate energies, reaction processes are ranging from slow processes where equilibrium is achieved between every emission, up to direct processes where nucleon nucleon scattering and phase space availability are the deciding factors. In order to investigate this transition, both the emission dynamics and the characteristics of the emitter have been studied, both theoretically and experimentally in the AMPHORA detector, for the systems 7, 17, 27 and 34 AMeV, {sup 40}Ar+Al, {sup 40}Ar+Cu and {sup 40}Ar+Ag. First, the linear momentum transfer of the most central collisions has been evaluated for these systems, by measuring the velocity of heavy residues. Then, by measuring azimuthal angle correlations functions, and by comparing them with statistical model predictions, the average angular momentum of the emitter has been evaluated. To study the charged particles emission dynamics, experimental azimuthal angle and relative momentum correlation functions have been compared with simulations based on a classical trajectory model. Finally, predictions of an advanced BUU model have been studied for the system 34 AMeV 40 Ar+Al. (authors). 69 refs., 52 figs., 5 tabs.
Dynamics of solid inner-shell electrons in collisions with bare and dressed swift ions
International Nuclear Information System (INIS)
Montanari, C.C.; Miraglia, J. E.; Arista, N.R.
2002-01-01
We analyze the dynamical interactions of swift heavy projectiles and solid inner-shell electrons. The dielectric formalism employed to deal with the free-electron gas is extended to account for the core electrons, by using the local plasma approximation. Results for stopping power, energy straggling, and inner-shell ionization in collisions of bare ions with metals are displayed, showing very good accord with the experimental data. Simultaneous excitations of projectile and target electrons are also analyzed. In the high-energy range we find a similar contribution of target core and valence electrons to the probability of projectile-electron loss. The problem of no excitation threshold within the local plasma approximation and the possibility of collective excitations of the shells are discussed
Hadronic Expansion Dynamics in Central Pb+Pb Collisions at 158 GeV per Nucleon
Appelshäuser, H; Bailey, S J; Barnby, L S; Bartke, Jerzy; Barton, R A; Bialkowska, H; Billmeier, A; Blyth, C O; Bock, R; Bormann, C; Brady, F P; Brockmann, R; Brun, R; Buncic, P; Caines, H L; Cebra, D; Cooper, G E; Cramer, J G; Csató, P; Dunn, J; Eckardt, V; Eckhardt, F; Ferguson, M I; Ferenc, D; Fischer, H G; Flierl, D; Fodor, Z; Foka, P Y; Freund, P; Friese, V; Fuchs, M; Gabler, F; Gál, J; Gazdzicki, M; Gladysz-Dziadus, E; Grebieszkow, J; Günther, J; Harris, J W; Hegyi, S; Henkel, T; Hill, L A; Huang, I; Hümmler, H; Igo, G; Irmscher, D; Jacobs, P; Jones, P G; Kadija, K; Kolesnikov, V I; Kowalski, M; Lasiuk, B; Lévai, Peter; Malakhov, A I; Margetis, S; Markert, C; Melkumov, G L; Mock, A; Molnár, J; Nelson, J M; Oldenburg, M; Odyniec, Grazyna Janina; Pálla, G; Panagiotou, A D; Petridis, A; Piper, A; Porter, R J; Poskanzer, A M; Poziombka, S; Prindle, D J; Pühlhofer, F; Rauch, W; Reid, J G; Renfordt, R E; Retyk, W; Ritter, H G; Röhrich, D; Roland, C; Roland, G; Rudolph, H; Rybicki, A; Sandoval, A; Sann, H; Semenov, A Yu; Schäfer, E; Schmischke, D; Schmitz, N; Schönfelder, S; Seyboth, P; Seyerlein, J; Siklér, F; Skrzypczak, E; Squier, G T A; Stock, Reinhard; Ströbele, H; Struck, C; Szentpétery, I; Sziklai, J; Toy, M; Trainor, T A; Trentalange, S; Ullrich, T S; Vassiliou, Maria; Vesztergombi, G; Vranic, D; Wang, F; Weerasundara, D D; Wenig, S; Whitten, C; Wienold, T; Wood, L; Yates, T A; Xu, N; Zimányi, J; Zhu, X Z; Zybert, R
1998-01-01
Two-particle correlation functions of negative hadrons over wide phase space, and transverse mass spectra of negative hadrons and deuterons near mid-rapidity have been measured in central Pb+Pb collisions at 158 GeV per nucleon by the NA49 experiment at the CERN SPS. A novel Coulomb correction procedure for the negative two-particle correlations is employed making use of the measured oppositely charged particle correlation. Within an expanding source scenario these results are used to extract the dynamic characteristics of the hadronic source, resolving the ambiguities between the temperature and transverse expansion velocity of the source, that are unavoidable when single and two particle spectra are analysed separately. The source shape, the total duration of the source expansion, the duration of particle emission, the freeze-out temperature and the longitudinal and transverse expansion velocities are deduced.
Directory of Open Access Journals (Sweden)
A. Campanile
2018-01-01
Full Text Available The incidence of collision damage models on oil tanker and bulk carrier reliability is investigated considering the IACS deterministic model against GOALDS/IMO database statistics for collision events, substantiating the probabilistic model. Statistical properties of hull girder residual strength are determined by Monte Carlo simulation, based on random generation of damage dimensions and a modified form of incremental-iterative method, to account for neutral axis rotation and equilibrium of horizontal bending moment, due to cross-section asymmetry after collision events. Reliability analysis is performed, to investigate the incidence of collision penetration depth and height statistical properties on hull girder sagging/hogging failure probabilities. Besides, the incidence of corrosion on hull girder residual strength and reliability is also discussed, focussing on gross, hull girder net and local net scantlings, respectively. The ISSC double hull oil tanker and single side bulk carrier, assumed as test cases in the ISSC 2012 report, are taken as reference ships.
International Nuclear Information System (INIS)
Shibahara, M; Satake, S; Taniguchi, J
2008-01-01
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
Directory of Open Access Journals (Sweden)
LIU Junfeng
2017-03-01
Full Text Available The analytical method for predicting the dynamic responses of a ship in a collision scenario features speed and accuracy,and the external dynamics constitute an important part. A 3D simplified analytical method is implemented by MATLAB and used to calculate the energy dissipation of ship-ship collisions. The results obtained by the proposed method are then compared with those of a 2D simplified analytical method. The total dissipated energy can be obtained through the proposed analytical method, and the influence of the collision heights,angles and locations on the dissipated energy is discussed on that basis. Furthermore,the effects of restitution on the conservative coefficients and the effects of conservative coefficients on energy dissipation are discussed. It is concluded that the proposed 3D analysis yields a lesser energy dissipation than that of the 2D analysis,and the collision height has a significant influence on the dissipated energy. In using the proposed simplified method,it is not safe to simplify the conservative coefficient as zero when the collision angle is greater than 90 degrees. In the future research, to get more accurate energy dissipation, it is a good way to adopt the 3D simplified analytical method instead of the 2D method.
Final Report. The 2015 Conference on the Dynamics of Molecular Collisions
Energy Technology Data Exchange (ETDEWEB)
Suits, Arthur G. [Wayne State Univ., Detroit, MI (United States)
2015-08-31
The 25th The Conference on the Dynamics of Molecular Collisions (DMC) was held from July 12-17, 2015. The Conference provides a unique platform and focal point for the gathering of experimentalists and theoreticians in the field of chemical dynamics. Since its inauguration in 1965, it has played an irreplaceable role in the development of this field and of many distinguished careers. This 25th meeting was highly successful. We held ten oral sessions and four poster sessions. Nobel Laureate Yuan T. Lee presented the keynote lecture. At this meeting, celebrating 50 years of chemical reaction dynamics, one hundred thirty-seven attendees participated, forty-two talks were presented as well as fifty-nine posters.Many attendees remarked that it was the “best meeting of the year.” Results from the meeting and other contributions were collected in a special issue of the Journal of Physical Chemistry A, published December 17, 2015. With this proposal we sought support for students, post-doctoral researchers and junior scientists who needed financial support. The Department of Energy has a large program in gas phase chemistry and many of the speakers and session chairs at the meeting are presently supported by DOE, including Professor Millard Alexander and Carl Lineberger, the recipents of the 2015 Herschbach Prizes that were awarded at the meeting. Funds were used to supplement registration fees for students and post-docs and to cover registration fees for the six selected “hot topic” presentations.
Model of Optimal Collision Avoidance Manoeuvre on the Basis of Electronic Data Collection
Directory of Open Access Journals (Sweden)
Jelenko Švetak
2005-11-01
Full Text Available The results of the data analyses show that accidents mostlyinclude damages to the ship's hull and collisions. Generally allaccidents of ships can be divided into two basic categories.First, accidents in which measures for damage control shouldbe taken immediately, and second, those which require a littlemore patient reaction. The very fact that collisions belong to thefirst category provided the incentive for writing the current paper.The proposed model of optimal collision avoidance manoeuvreof ships on the basis of electronic data collection wasmade by means of the navigation simulator NTPRO- 1000,Transas manufacturer, Russian Federation.
Large-scale model-based assessment of deer-vehicle collision risk.
Directory of Open Access Journals (Sweden)
Torsten Hothorn
Full Text Available Ungulates, in particular the Central European roe deer Capreolus capreolus and the North American white-tailed deer Odocoileus virginianus, are economically and ecologically important. The two species are risk factors for deer-vehicle collisions and as browsers of palatable trees have implications for forest regeneration. However, no large-scale management systems for ungulates have been implemented, mainly because of the high efforts and costs associated with attempts to estimate population sizes of free-living ungulates living in a complex landscape. Attempts to directly estimate population sizes of deer are problematic owing to poor data quality and lack of spatial representation on larger scales. We used data on >74,000 deer-vehicle collisions observed in 2006 and 2009 in Bavaria, Germany, to model the local risk of deer-vehicle collisions and to investigate the relationship between deer-vehicle collisions and both environmental conditions and browsing intensities. An innovative modelling approach for the number of deer-vehicle collisions, which allows nonlinear environment-deer relationships and assessment of spatial heterogeneity, was the basis for estimating the local risk of collisions for specific road types on the scale of Bavarian municipalities. Based on this risk model, we propose a new "deer-vehicle collision index" for deer management. We show that the risk of deer-vehicle collisions is positively correlated to browsing intensity and to harvest numbers. Overall, our results demonstrate that the number of deer-vehicle collisions can be predicted with high precision on the scale of municipalities. In the densely populated and intensively used landscapes of Central Europe and North America, a model-based risk assessment for deer-vehicle collisions provides a cost-efficient instrument for deer management on the landscape scale. The measures derived from our model provide valuable information for planning road protection and defining
Characteristics of particle production in high energy nuclear collisions a model-based analysis
Guptaroy, P; Bhattacharya, S; Bhattacharya, D P
2002-01-01
The present work pertains to the production of some very important negatively charged secondaries in lead-lead and gold-gold collisions at AGS, SPS and RHIC energies. We would like to examine here the role of the particular version of sequential chain model (SCM), which was applied widely in the past in analysing data on various high-energy hadronic collisions, in explaining now the latest findings on the features of particle production in the relativistic nucleus-nucleus collisions. The agreement between the model of our choice and the measured data is found to be modestly satisfactory in cases of the most prominent and abundantly produced varieties of the secondaries in the above-stated two nuclear collisions. (25 refs).
Diffractive ''semioptical'' model for nucleus-nucleus collisions
International Nuclear Information System (INIS)
Barashenkov, V.S.; Musulmanbekov, Zh.Zh.
1979-01-01
Diffraction Glauber theory for nucleus-nucleus collisions is considered in approximation when the initial nucleus interacts as a whole with nucleons of the target nucleus. Such an approach, being intermediate between precise Glauber theory and its optical limit, essentially simplifies numerical calculations and gives a good agreement with experiments as well. (author)
Computer Modelling of Dynamic Processes
Directory of Open Access Journals (Sweden)
B. Rybakin
2000-10-01
Full Text Available Results of numerical modeling of dynamic problems are summed in the article up. These problems are characteristic for various areas of human activity, in particular for problem solving in ecology. The following problems are considered in the present work: computer modeling of dynamic effects on elastic-plastic bodies, calculation and determination of performances of gas streams in gas cleaning equipment, modeling of biogas formation processes.
International Nuclear Information System (INIS)
Errea, L.F.; Mendez, L.; Riera, A.
1991-01-01
To offset the defective behavior of the molecular method of atomic collisions at intermediate energies, we propose a method to approximate the probability flux towards continuum and discrete states not included in the molecular basis. We check the degree of accuracy and limitations of the method for a model case where transition probabilities can be calculated exactly. An application to the benchmark case of He + +H + collisions is also presented, and yields complementary information on the properties of this approach
Inelasticity in hadron-nucleus collisions in the geometrical two-chain model
International Nuclear Information System (INIS)
Wibig, T.; Sobczynska, D.
1995-01-01
Two features of great importance registered in experiments on hadron-nucleus collisions are the decreased inelasticity and multiplicity in intranucleus collisions. In this paper we show that such behaviour is a natural consequence of the geometrical two-chain model of multi-particle production processes: only the forward-going chain can undergo secondary interactions in the nucleus. A quantitative comparison with the data is presented. (author)
International Nuclear Information System (INIS)
Altsybeev, Igor
2016-01-01
In the present work, Monte-Carlo toy model with repulsing quark-gluon strings in hadron-hadron collisions is described. String repulsion creates transverse boosts for the string decay products, giving modifications of observables. As an example, long-range correlations between mean transverse momenta of particles in two observation windows are studied in MC toy simulation of the heavy-ion collisions
Ultra-relativistic heavy ion collisions in a multi-string model
International Nuclear Information System (INIS)
Werner, K.
1987-01-01
We present a model for ultra-relativistic heavy ion collisions based on color string formation and subsequent independent string fragmentation. Strings are formed due to color exchange between quarks at each individual nucleon nucleon collision. The fragmentation is treated as in e + e - or lepton nucleon scattering. Calculation for pp, pA, and AA were carried out using the Monte Carlo code VENUS for Very Energetic Nuclear Scattering (version 1.0). 20 refs., 6 figs
Galilean invariance in the exponential model of atomic collisions
Energy Technology Data Exchange (ETDEWEB)
del Pozo, A.; Riera, A.; Yaez, M.
1986-11-01
Using the X/sup n//sup +/(1s/sup 2/)+He/sup 2+/ colliding systems as specific examples, we study the origin dependence of results in the application of the two-state exponential model, and we show the relevance of polarization effects in that study. Our analysis shows that polarization effects of the He/sup +/(1s) orbital due to interaction with X/sup (//sup n//sup +1)+/ ion in the exit channel yield a very small contribution to the energy difference and render the dynamical coupling so strongly origin dependent that it invalidates the basic premises of the model. Further study, incorporating translation factors in the formalism, is needed.
Structural dynamic modifications via models
Indian Academy of Sciences (India)
The study shows that as many as half of the matrix ... the dynamicist's analytical modelling skill which would appear both in the numerator as. Figure 2. ..... Brandon J A 1990 Strategies for structural dynamic modification (New York: John Wiley).
Dynamic programming models and applications
Denardo, Eric V
2003-01-01
Introduction to sequential decision processes covers use of dynamic programming in studying models of resource allocation, methods for approximating solutions of control problems in continuous time, production control, more. 1982 edition.
Dynamical models of the Galaxy
Directory of Open Access Journals (Sweden)
McMillan P.J.
2012-02-01
Full Text Available I discuss the importance of dynamical models for exploiting survey data, focusing on the advantages of “torus” models. I summarize a number of applications of these models to the study of the Milky Way, including the determination of the peculiar Solar velocity and investigation of the Hyades moving group.
Neural network model for proton-proton collision at high energy
International Nuclear Information System (INIS)
El-Bakry, M.Y.; El-Metwally, K.A.
2003-01-01
Developments in artificial intelligence (AI) techniques and their applications to physics have made it feasible to develop and implement new modeling techniques for high-energy interactions. In particular, AI techniques of artificial neural networks (ANN) have recently been used to design and implement more effective models. The primary purpose of this paper is to model the proton-proton (p-p) collision using the ANN technique. Following a review of the conventional techniques and an introduction to the neural network, the paper presents simulation test results using an p-p based ANN model trained with experimental data. The p-p based ANN model calculates the multiplicity distribution of charged particles and the inelastic cross section of the p-p collision at high energies. The results amply demonstrate the feasibility of such new technique in extracting the collision features and prove its effectiveness
Revisiting directed flow in relativistic heavy-ion collisions from a multiphase transport model
Energy Technology Data Exchange (ETDEWEB)
Guo, Chong-Qiang; Zhang, Chun-Jian [Chinese Academy of Sciences, Shanghai Institute of Applied Physics, Shanghai (China); University of Chinese Academy of Sciences, Beijing (China); Xu, Jun [Chinese Academy of Sciences, Shanghai Institute of Applied Physics, Shanghai (China)
2017-12-15
We have revisited several interesting questions on how the rapidity-odd directed flow is developed in relativistic {sup 197}Au + {sup 197}Au collisions at √(s{sub NN}) = 200 and 39 GeV based on a multiphase transport model. As the partonic phase evolves with time, the slope of the parton directed flow at midrapidity region changes from negative to positive as a result of the later dynamics at 200 GeV, while it remains negative at 39 GeV due to the shorter life time of the partonic phase. The directed flow splitting for various quark species due to their different initial eccentricities is observed at 39 GeV, while the splitting is very small at 200 GeV. From a dynamical coalescence algorithm with Wigner functions, we found that the directed flow of hadrons is a result of competition between the coalescence in momentum and coordinate space as well as further modifications by the hadronic rescatterings. (orig.)
Colour rope model for extreme relativistic heavy ion collisions
International Nuclear Information System (INIS)
Biro, T.S.; Nielsen, H.B.; Knoll, J.
1984-04-01
Our goal is to investigate the possible cumulative effects of the colour fields of the observable meson multiplicity distribution in the central rapidity region in extreme relativistic heavy ion collisions. In the first Chapter we overview the space-time picture of the string formation in a central heavy ion collision. We take into account trivial geometrical factors in a straight line geometry. In the second Chapter we consider the colour chargation process of heavy ions as a random walk. We calculate the expectation value and the relative standard deviation of the total effective charge square. In the third Chapter we consider the stochastic decay of a K-fold string-rope to mesons by the Schwinger-mechanism. We calculate the expected lifetime of a K-fold string and the time for the first quark antiquark pair creation. In the fourth Chapter we deal with the meson production of a K-fold rope relative to that of a single string and hence we look for a scaling between A + A and p + p collisions. (orig./HSI)
Li, Xiaomeng; Yan, Xuedong; Wu, Jiawei; Radwan, Essam; Zhang, Yuting
2016-12-01
Driver's collision avoidance performance has a direct link to the collision risk and crash severity. Previous studies demonstrated that the distracted driving, such as using a cell phone while driving, disrupted the driver's performance on road. This study aimed to investigate the manner and extent to which cell phone use and driver's gender affected driving performance and collision risk in a rear-end collision avoidance process. Forty-two licensed drivers completed the driving simulation experiment in three phone use conditions: no phone use, hands-free, and hand-held, in which the drivers drove in a car-following situation with potential rear-end collision risks caused by the leading vehicle's sudden deceleration. Based on the experiment data, a rear-end collision risk assessment model was developed to assess the influence of cell phone use and driver's gender. The cell phone use and driver's gender were found to be significant factors that affected the braking performances in the rear-end collision avoidance process, including the brake reaction time, the deceleration adjusting time and the maximum deceleration rate. The minimum headway distance between the leading vehicle and the simulator during the rear-end collision avoidance process was the final output variable, which could be used to measure the rear-end collision risk and judge whether a collision occurred. The results showed that although cell phone use drivers took some compensatory behaviors in the collision avoidance process to reduce the mental workload, the collision risk in cell phone use conditions was still higher than that without the phone use. More importantly, the results proved that the hands-free condition did not eliminate the safety problem associated with distracted driving because it impaired the driving performance in the same way as much as the use of hand-held phones. In addition, the gender effect indicated that although female drivers had longer reaction time than male drivers in
Model of the humanoid body for self collision detection based on elliptical capsules
CSIR Research Space (South Africa)
Dube, C
2011-12-01
Full Text Available . The humanoid body is modeled using elliptical capsules, while the moving segments, i.e. arms and legs, of the humanoid are modeled using circular capsules. This collision detection model provides a good fit to the humanoid body shape while being simple...
Kral, Q.; Thebault, P.; Charnoz, S.
2014-01-01
The first attempt at developing a fully self-consistent code coupling dynamics and collisions to study debris discs (Kral et al. 2013) is presented. So far, these two crucial mechanisms were studied separately, with N-body and statistical collisional codes respectively, because of stringent computational constraints. We present a new model named LIDT-DD which is able to follow over long timescales the coupled evolution of dynamics (including radiation forces) and collisions in a self-consistent way.
International Nuclear Information System (INIS)
McFadden, J.H.; Paulsen, M.P.; Gose, G.C.
1981-01-01
A time dependent equation for the slip velocity in a two-phase flow condition has been incorporated into a developmental version of the RETRAN computer code. This model addition has been undertaken to remove a limitation in RETRAN-01 associated with the homogeneous equilibrium mixture model. In this paper, the development of the slip model is summarized and the corresponding constitutive equations are discussed. Comparisons of RETRAN analyses with steady-state void fraction data and data from the Semiscale S-02-6 small break test are also presented
Electron collisions in the trapped gyro-Landau fluid transport model
International Nuclear Information System (INIS)
Staebler, G. M.; Kinsey, J. E.
2010-01-01
Accurately modeling electron collisions in the trapped gyro-Landau fluid (TGLF) equations has been a major challenge. Insights gained from numerically solving the gyrokinetic equation have lead to a significant improvement of the low order TGLF model. The theoretical motivation and verification of this model with the velocity-space gyrokinetic code GYRO[J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] will be presented. The improvement in the fidelity of TGLF to GYRO is shown to also lead to better prediction of experimental temperature profiles by TGLF for a dedicated collision frequency scan.
Using a collision model to design safer wind turbine rotors for birds
International Nuclear Information System (INIS)
Tucker, V.A.
1996-01-01
A mathematical model for collisions between birds and propeller-type turbine rotors identifies the variables that can be manipulated to reduce the probability that birds will collide with the rotor. This study defines a safety index--the clearance power density--that allows rotors of different sizes and designs to be compared in terms of the amount of wind energy converted to electrical energy per bird collision. The collision model accounts for variations in wind speed during the year and shows that for model rotors with simple, one-dimensional blades, the safety index increases in proportion to rotor diameter, and variable speed rotors have higher safety indexes than constant speed rotors. The safety index can also be increased by enlarging the region near the center of the rotor hub where the blades move slowly enough for birds to avoid them. Painting the blades to make them more visible might have this effect. Model rotors with practical designs can have safety indexes an order of magnitude higher than those for model rotors typical of the constant speeds rotors in common use today. This finding suggests that redesigned rotors could have collision rates with birds perhaps an order of magnitude lower than today's rotors, with no reduction in the production of wind power. The empirical data that exist for collisions between raptors, such as hawks and eagles, and rotors are consistent with the model: the numbers of raptor carcasses found beneath large variable speed rotors, relative to the numbers found under small constant speed rotors, are in the proportions predicted by the collision model rather than in proportion to the areas swept by the rotor blades. However, uncontrolled variables associated with these data prevent a stronger claim of support for the model
Modeling Propellant Tank Dynamics
National Aeronautics and Space Administration — The main objective of my work will be to develop accurate models of self-pressurizing propellant tanks for use in designing hybrid rockets. The first key goal is to...
Bryon, Jacob
2017-09-01
The chiral magnetic effect (CME) arises from the chirality imbalance of quarks and its interaction to the strong magnetic field generated in non-central heavy-ion collisions. Possible formation of domains of quarks with chirality imbalances is an intrinsic property of the Quantum ChromoDynamics (QCD), which describes the fundamental strong interactions among quarks and gluons. Azimuthal-angle correlations have been used to measure the magnitude of charge- separation across the reaction plane, which was predicted to arise from the CME. However, backgrounds from collective motion (flow) of the collision system can also contribute to the correlation observable. In this poster, we investigate the magnitude of the background utilizing the AMPT model, which contains no CME signals. We demonstrate, for Au +Au collisions at 200 and 39 GeV, a scheme to remove the flow background via the event-shape engineering with the vanishing magnitude of the flow vector. We also calculate the ensemble average of the charge-separation observable, and provide a background baseline for the experimental data.
Modelling group dynamic animal movement
DEFF Research Database (Denmark)
Langrock, Roland; Hopcraft, J. Grant C.; Blackwell, Paul G.
2014-01-01
makes its movement decisions relative to the group centroid. The basic idea is framed within the flexible class of hidden Markov models, extending previous work on modelling animal movement by means of multi-state random walks. While in simulation experiments parameter estimators exhibit some bias......, to date, practical statistical methods which can include group dynamics in animal movement models have been lacking. We consider a flexible modelling framework that distinguishes a group-level model, describing the movement of the group's centre, and an individual-level model, such that each individual......Group dynamic movement is a fundamental aspect of many species' movements. The need to adequately model individuals' interactions with other group members has been recognised, particularly in order to differentiate the role of social forces in individual movement from environmental factors. However...
Modeling Internet Topology Dynamics
Haddadi, H.; Uhlig, S.; Moore, A.; Mortier, R.; Rio, M.
Despite the large number of papers on network topology modeling and inference, there still exists ambiguity about the real nature of the Internet AS and router level topology. While recent findings have illustrated the inaccuracies in maps inferred from BGP peering and traceroute measurements,
Generative Models of Conformational Dynamics
Langmead, Christopher James
2014-01-01
Atomistic simulations of the conformational dynamics of proteins can be performed using either Molecular Dynamics or Monte Carlo procedures. The ensembles of three-dimensional structures produced during simulation can be analyzed in a number of ways to elucidate the thermodynamic and kinetic properties of the system. The goal of this chapter is to review both traditional and emerging methods for learning generative models from atomistic simulation data. Here, the term ‘generative’ refers to a...
The Dynamics of Multiple Pair-Wise Collisions in a Chain for Designing Optimal Shock Amplifiers
Directory of Open Access Journals (Sweden)
Bryan Rodgers
2009-01-01
Full Text Available The major focus of this work is to examine the dynamics of velocity amplification through pair-wise collisions between multiple masses in a chain, in order to develop useful machines. For instance low-cost machines based on this principle could be used for detailed, very-high acceleration shock-testing of MEMS devices. A theoretical basis for determining the number and mass of intermediate stages in such a velocity amplifier, based on simple rigid body mechanics, is proposed. The influence of mass ratios and the coefficient of restitution on the optimisation of the system is identified and investigated. In particular, two cases are examined: in the first, the velocity of the final mass in the chain (that would have the object under test mounted on it is maximised by defining the ratio of adjacent masses according to a power law relationship; in the second, the energy transfer efficiency of the system is maximised by choosing the mass ratios such that all masses except the final mass come to rest following impact. Comparisons are drawn between both cases and the results are used in proposing design guidelines for optimal shock amplifiers. It is shown that for most practical systems, a shock amplifier with mass ratios based on a power law relationship is optimal and can easily yield velocity amplifications of a factor 5–8 times. A prototype shock testing machine that was made using above principles is briefly introduced.
Three-body dynamical interference in electron and positron collision with positronium atom
Directory of Open Access Journals (Sweden)
E Ghanbari Adivi
2010-12-01
Full Text Available In this project, the Faddeev-Watson-Lovelace (FWL formalism is generalized to large scattering angles. The angular range includes 0-180 degrees. Using this method, the charge transfer differential cross-sections are calculated, in a second-order approximation, for collision of energetic positrons and electrons with neutral positronium atoms. In this approximation, the rearrangement amplitude contains two first-order and three second-order partial amplitudes. The first first-order term is the Born amplitude in a first-order approximation. The second one corresponds to capturing the transferred particle without perturbing the state of this particle. This term, in fact, describes a knock-on process. Since the masses of the particles and the absolute values of their charges are equal, one expects that the second-order terms be similar in magnitude. This aspect causes the instructive interference of the partial amplitudes in some angles and destructive interference in some others. However, it is predicted that these amplitudes have local maxima in direction of the recoiling of the projectile. In order to investigate this situation, the second-order partial amplitudes are calculated and their relations with the parity of the initial and final states of the scattering system are analyzed. In particular, the role of dynamical interference of these partial amplitudes in creation of the kinematical peak and the peak corresponding to the knock-on scattering in angular distribution of the differential cross sections is investigated.
International Nuclear Information System (INIS)
Choi, B.H.; Poe, R.T.
1985-01-01
We present a systematic formulation of the atom--surface scattering dynamics which includes the vibrational states of the atoms in the solid (phonons). The properties of the total scattering wave function of the system, a representation of the interaction potential matrix, and the characteristics of the independent physical solutions are all derived from the translational invariance of the full Hamiltonian. The scattering equations in the integral forms as well as the related Green functions were also obtained. The configurational representations of the Green functions, in particular, are quite different from those of the conventional scattering theory where the collision partners are spatially localized. Various versions of the integral expression of scattering, transition, and reactance matrices were also obtained. They are useful for introducing approximation schemes. From the present formulation, some specific theoretical schemes which are more realistic compared to those that have been employed so far and at the same time capable of yielding effective ab initio computation are derived in the following paper. The time reversal invariance and the microscopic reversibility of the atom--surface scattering were discussed. The relations between the in and outgoing scattering wave functions which are satisfied in the atom--surface system and important in the transition matrix methods were presented. The phonon annihilation and creation, and the adsorption and desorption of the atom are related through the time reversal invariance, and thus the microscopic reversibility can be tested by the experiment
Lei, Hong; Jiang, Jimin; Yang, Bin; Zhao, Yan; Zhang, Hongwei; Wang, Weixian; Dong, Guiwen
2018-04-01
Mathematical simulation is an effective tool to analyze the fluid flow and the inclusion behavior in the bloom continuous caster with mold electromagnetic stirring (M-EMS). The mathematical model is applied to the modeling of magnetic field, flow field, and inclusion field. Due to the introduction of Archimedes force, the collision mechanism and inclusion's slipping velocity should be modified in the inclusion mass and population conservation model. Numerically predicted magnetic field, flow field, and the inclusion spatial distribution conform to the experimental results in the existing literature. Lorentz force plays an important role in the fluid flow, and Archimedes force plays an important role in the inclusion distribution in the continuous caster. Due to Brownian collision, Stokes collision, Archimedes collision, and turbulent collision, the coalescence among inclusions occurs in the bloom continuous caster with M-EMS. Among the four types of collisions, turbulent collision occurs most frequently, followed by Archimedes collision and Stokes collision. The frequency of Brownian collision is several orders of magnitudes smaller and is therefore negligible. The inclusion volume concentration, number density, and characteristic radius exhibit a U-shape in the continuous caster without M-EMS. However, with M-EMS, they exhibit an inverted U-shape.
Pacheco, Alexander B.; Reyes, Andrés; Micha, David A.
2006-12-01
Collision-induced light emission during the interaction of an alkali-metal atom and a noble-gas atom is treated within a first-principles, or direct, dynamics approach that calculates a time-dependent electric dipole for the whole system, and spectral emission cross sections from its Fourier transform. These cross sections are very sensitive to excited diatomic potentials and a source of information on their shape. The coupling between electronic transitions and nuclear motions is treated with atomic pseudopotentials and an electronic density matrix coupled to trajectories for the nuclei. A recently implemented pseudopotential parametrization scheme is used here for the ground and excited states of the LiHe system, and to calculate state-to-state dipole moments. To verify the accuracy of our new parameters, we recalculate the integral cross sections for the LiHe system in the keV energy regime and obtain agreement with other results from theory and experiment. We further present results for the emission spectrum from 10keV Li(2s)+He collisions, and compare them to experimental values available in the region of light emitted at 300-900nm .
Statistical modeling of competitive threshold collision-induced dissociation
Rodgers, M. T.; Armentrout, P. B.
1998-08-01
Collision-induced dissociation of (R1OH)Li+(R2OH) with xenon is studied using guided ion beam mass spectrometry. R1OH and R2OH include the following molecules: water, methanol, ethanol, 1-propanol, 2-propanol, and 1-butanol. In all cases, the primary products formed correspond to endothermic loss of one of the neutral alcohols, with minor products that include those formed by ligand exchange and loss of both ligands. The cross-section thresholds are interpreted to yield 0 and 298 K bond energies for (R1OH)Li+-R2OH and relative Li+ binding affinities of the R1OH and R2OH ligands after accounting for the effects of multiple ion-molecule collisions, internal energy of the reactant ions, and dissociation lifetimes. We introduce a means to simultaneously analyze the cross sections for these competitive dissociations using statistical theories to predict the energy dependent branching ratio. Thermochemistry in good agreement with previous work is obtained in all cases. In essence, this statistical approach provides a detailed means of correcting for the "competitive shift" inherent in multichannel processes.
Collisions with Springs: A Useful Context for the Study of Analytical Dynamics
Twomey, Patrick; O'Sullivan, Colm; O'Riordan, John; Fahy, Stephen
2012-01-01
A recent paper in this journal describes an experimental demonstration of the conservation of total momentum before, during, and after an elastic collision between two bodies. The experiment also appears to show that total kinetic energy is conserved in the process, including "during" the collision. There is a danger that this may give rise to…
Ekpyrosis and inflationary dynamics in heavy ion collisions: the role of quantum fluctuations
Energy Technology Data Exchange (ETDEWEB)
Dusling, K.; Venugopalan, R.; Gelis, F.
2011-05-23
We summarize recent significant progress in the development of a first-principles formalism to describe the formation and evolution of matter in very high energy heavy ion collisions. The key role of quantum fluctuations both before and after a collision is emphasized. Systematic computations are now feasible to address early time isotropization, flow, parton energy loss and the Chiral Magnetic Effect.
High-speed collision of copper nanoparticle with aluminum surface: Molecular dynamics simulation
Pogorelko, Victor V.; Mayer, Alexander E.; Krasnikov, Vasiliy S.
2016-12-01
We investigate the effect of the high-speed collision of copper nanoparticles with aluminum surface by means of molecular dynamic simulations. Studied diameter of nanoparticles is varied within the range 7.2-22 nm and the velocity of impact is equal to 500 or 1000 m/s. Dislocation analysis shows that a large quantity of dislocations is formed within the impact area. Overall length of dislocations is determined, first of all, by the impact velocity and by the size of incident copper nanoparticle, in other words, by the kinetic energy of the nanoparticle. Dislocations occupy the total volume of the impacted aluminum single crystal layer (40.5 nm in thickness) in the form of intertwined structure in the case of large kinetic energy of the incident nanoparticle. Decrease in the initial kinetic energy or increase in the layer thickness lead to restriction of the penetration depth of the dislocation net; formation of separate dislocation loops is observed in this case. Increase in the initial system temperature slightly raises the dislocation density inside the bombarded layer and considerably decreases the dislocation density inside the nanoparticle. The temperature increase also leads to a deeper penetration of the copper atoms inside the aluminum. Additional molecular dynamic simulations show that the deposited particles demonstrate a very good adhesion even in the case of the considered relatively large nanoparticles. Medium energy of the nanoparticles corresponding to velocity of about 500 m/s and elevated temperature of the system about 700-900 K are optimal parameters for production of high-quality layers of copper on the aluminum surface. These conditions provide both a good adhesion and a less degree of the plastic deformation. At the same time, higher impact velocities can be used for combined treatment consisting of both the plastic deformation and the coating.
Moreno, P. A.; Bombardelli, F. A.
2012-12-01
Particles laying motionless at the bed of rivers, lakes and estuaries can be put into motion when the shear stress exerted by the flow on the particles exceeds the critical shear stress. When these particles start their motion they can either remain suspended by long periods of time (suspended load) or move close to the bed (bed load). Particles are transported as bed load in three different modes: Sliding, rolling and saltation. Saltation is usually described as the bouncing motion of sediment particles in a layer a few particle diameters thick. The amount of particles and the bed-load mode in which they move depend on the particle size and density, and the flow intensity, usually quantified by the shear velocity. The bottom shear stress in natural streams will most likely be large enough to set saltation as the most important bed-load transport mechanism among all three modes. Thus, studying the saltation process is crucial for the overall understanding of bed-load transport. Particularly, numerical simulations of this process have been providing important insight regarding the relative importance of the physical mechanisms involved in it. Several processes occur when particles are saltating near the bed: i) Particles collide with the bed, ii) they "fly" between collisions with the bed, as a result of their interaction with the fluid flow, iii) and they collide among themselves. These processes can be simulated using a three-dimensional Eulerian-Lagrangian model. In order to mimic these processes we have experimented with an averaged turbulent flow field represented by the logarithmic law of the wall, and with a more involved approach in which a computed turbulent velocity field for a flat plate was used as a surrogate of the three-dimensional turbulent conditions present close to stream beds. Since flat-plate and open-channel boundary layers are essentially different, a dynamic similarity analysis was performed showing that the highly-resolved three
Vehicle dynamics modeling and simulation
Schramm, Dieter; Bardini, Roberto
2014-01-01
The authors examine in detail the fundamentals and mathematical descriptions of the dynamics of automobiles. In this context different levels of complexity will be presented, starting with basic single-track models up to complex three-dimensional multi-body models. A particular focus is on the process of establishing mathematical models on the basis of real cars and the validation of simulation results. The methods presented are explained in detail by means of selected application scenarios.
Research on The Construction of Flexible Multi-body Dynamics Model based on Virtual Components
Dong, Z. H.; Ye, X.; Yang, F.
2018-05-01
Focus on the harsh operation condition of space manipulator, which cannot afford relative large collision momentum, this paper proposes a new concept and technology, called soft-contact technology. In order to solve the problem of collision dynamics of flexible multi-body system caused by this technology, this paper also proposes the concepts of virtual components and virtual hinges, and constructs flexible dynamic model based on virtual components, and also studies on its solutions. On this basis, this paper uses NX to carry out model and comparison simulation for space manipulator in 3 different modes. The results show that using the model of multi-rigid body + flexible body hinge + controllable damping can make effective control on amplitude for the force and torque caused by target satellite collision.
Statistical Model Predictions for p+p and Pb+Pb Collisions at LHC
Kraus, I; Oeschler, H; Redlich, K; Wheaton, S
2009-01-01
Particle production in p+p and central Pb+Pb collisions at LHC is discussed in the context of the statistical thermal model. For heavy-ion collisions, predictions of various particle ratios are presented. The sensitivity of several ratios on the temperature and the baryon chemical potential is studied in detail, and some of them, which are particularly appropriate to determine the chemical freeze-out point experimentally, are indicated. Considering elementary interactions on the other hand, we focus on strangeness production and its possible suppression. Extrapolating the thermal parameters to LHC energy, we present predictions of the statistical model for particle yields in p+p collisions. We quantify the strangeness suppression by the correlation volume parameter and discuss its influence on particle production. We propose observables that can provide deeper insight into the mechanism of strangeness production and suppression at LHC.
Constituent quark model for nuclear stopping in high energy nuclear collisions
International Nuclear Information System (INIS)
Choi, T.K.; Maruyama, M.; Takagi, F.
1997-01-01
We study nuclear stopping in high energy nuclear collisions using the constituent quark model. It is assumed that wounded nucleons with a different number of interacted quarks hadronize in different ways. The probabilities of having such wounded nucleons are evaluated for proton-proton, proton-nucleus, and nucleus-nucleus collisions. After examining our model in proton-proton and proton-nucleus collisions and fixing the hadronization functions, it is extended to nucleus-nucleus collisions. It is used to calculate the rapidity distribution and the rapidity shift of final-state protons in nucleus-nucleus collisions. The computed results are in good agreement with the experimental data on 32 S+ 32 S at E lab =200A GeV and 208 Pb+ 208 Pb at E lab =160A GeV. Theoretical predictions are also given for proton rapidity distribution in 197 Au+ 197 Au at √(s)=200A GeV (BNL-RHIC). We predict that the nearly baryon-free region will appear in the midrapidity region and the rapidity shift is left-angle Δy right-angle=2.24
Containing Terrorism: A Dynamic Model
Directory of Open Access Journals (Sweden)
Giti Zahedzadeh
2017-06-01
Full Text Available The strategic interplay between counterterror measures and terror activity is complex. Herein, we propose a dynamic model to depict this interaction. The model generates stylized prognoses: (i under conditions of inefficient counterterror measures, terror groups enjoy longer period of activity but only if recruitment into terror groups remains low; high recruitment shortens the period of terror activity (ii highly efficient counterterror measures effectively contain terror activity, but only if recruitment remains low. Thus, highly efficient counterterror measures can effectively contain terrorism if recruitment remains restrained. We conclude that the trajectory of the dynamics between counterterror measures and terror activity is heavily altered by recruitment.
High-Performance Computer Modeling of the Cosmos-Iridium Collision
Energy Technology Data Exchange (ETDEWEB)
Olivier, S; Cook, K; Fasenfest, B; Jefferson, D; Jiang, M; Leek, J; Levatin, J; Nikolaev, S; Pertica, A; Phillion, D; Springer, K; De Vries, W
2009-08-28
This paper describes the application of a new, integrated modeling and simulation framework, encompassing the space situational awareness (SSA) enterprise, to the recent Cosmos-Iridium collision. This framework is based on a flexible, scalable architecture to enable efficient simulation of the current SSA enterprise, and to accommodate future advancements in SSA systems. In particular, the code is designed to take advantage of massively parallel, high-performance computer systems available, for example, at Lawrence Livermore National Laboratory. We will describe the application of this framework to the recent collision of the Cosmos and Iridium satellites, including (1) detailed hydrodynamic modeling of the satellite collision and resulting debris generation, (2) orbital propagation of the simulated debris and analysis of the increased risk to other satellites (3) calculation of the radar and optical signatures of the simulated debris and modeling of debris detection with space surveillance radar and optical systems (4) determination of simulated debris orbits from modeled space surveillance observations and analysis of the resulting orbital accuracy, (5) comparison of these modeling and simulation results with Space Surveillance Network observations. We will also discuss the use of this integrated modeling and simulation framework to analyze the risks and consequences of future satellite collisions and to assess strategies for mitigating or avoiding future incidents, including the addition of new sensor systems, used in conjunction with the Space Surveillance Network, for improving space situational awareness.
Line-shape theory and molecular dynamics in collision-induced light scattering
International Nuclear Information System (INIS)
Balucani, U.; Tognetti, V.; Vallauri, R.
1979-01-01
Molecular-dynamics studies in argon at 148 amagats are presented for gaining information on the dynamical properties responsible for the depolarized light scattering from simple fluids. The total and pair-correlation functions are computed within the simple dipole--induced-dipole model of polarizability anisotropy. The pair spectral shape is derived. These results are compared with a theoretical analysis based on a continued-fraction approach. The necessary frequency moments are calculated both in the low-density limit and taking into account first-order density corrections, and compared with the molecular-dynamics data. The agreement between the theoretical spectra and molecular-dynamics data shows the validity of the memory-function approach. The comparison with the real experimental results allows one to test the relevant physical contributions to the polarizability anisotropy
A dynamical model of terrorism
Directory of Open Access Journals (Sweden)
Firdaus Udwadia
2006-01-01
Full Text Available This paper develops a dynamical model of terrorism. We consider the population in a given region as being made up of three primary components: terrorists, those susceptible to both terrorist and pacifist propaganda, and nonsusceptibles, or pacifists. The dynamical behavior of these three populations is studied using a model that incorporates the effects of both direct military/police intervention to reduce the terrorist population, and nonviolent, persuasive intervention to influence the susceptibles to become pacifists. The paper proposes a new paradigm for studying terrorism, and looks at the long-term dynamical evolution in time of these three population components when such interventions are carried out. Many important features—some intuitive, others not nearly so—of the nature of terrorism emerge from the dynamical model proposed, and they lead to several important policy implications for the management of terrorism. The different circumstances in which nonviolent intervention and/or military/police intervention may be beneficial, and the specific conditions under which each mode of intervention, or a combination of both, may be useful, are obtained. The novelty of the model presented herein is that it deals with the time evolution of terrorist activity. It appears to be one of the few models that can be tested, evaluated, and improved upon, through the use of actual field data.
Models of nanoparticles movement, collision, and friction in chemical mechanical polishing (CMP)
Energy Technology Data Exchange (ETDEWEB)
Ilie, Filip, E-mail: filip@meca.omtr.pub.ro [Polytechnic University of Bucharest, Department of Machine Elements and Tribology (Romania)
2012-03-15
Nanoparticles have been widely used in polishing slurry such as chemical mechanical polishing (CMP) process. The movement of nanoparticles in polishing slurry and the interaction between nanoparticles and solid surface are very important to obtain an atomic smooth surface in CMP process. Polishing slurry contains abrasive nanoparticles (with the size range of about 10-100 nm) and chemical reagents. Abrasive nanoparticles and hydrodynamic pressure are considered to cause the polishing effect. Nanoparticles behavior in the slurry with power-law viscosity shows great effect on the wafer surface in polishing process. CMP is now a standard process of integrated circuit manufacturing at nanoscale. Various models can dynamically predict the evolution of surface topography for any time point during CMP. To research, using a combination of individual nanoscale friction measurements for CMP of SiO{sub 2}, in an analytical model, to sum these effects, and the results scale CMP experiments, can guide the research and validate the model. CMP endpoint measurements, such as those from motor current traces, enable verification of model predictions, relating to friction and wear in CMP and surface topography evolution for different types of CMP processes and patterned chips. In this article, we explore models of the microscopic frictional force based on the surface topography and present both experimental and theoretical studies on the movement of nanoparticles in polishing slurry and collision between nanoparticles, as well as between the particles and solid surfaces in time of process CMP. Experimental results have proved that the nanoparticle size and slurry properties have great effects on the polishing results. The effects of the nanoparticle size and the slurry film thickness are also discussed.
TDHF-motivated macroscopic model for heavy ion collisions: a comparative study
International Nuclear Information System (INIS)
Biedermann, M.; Reif, R.; Maedler, P.
1984-01-01
A detailed investigation of Bertshc's classical TDHF-motivated model for the description of heavy ion collisions is performed. The model agrees well with TDHF and phenomenological models which include deformation degrees of freedom as well as with experimental data. Some quantitative deviations from experiment and/or TDHF can be removed to a large extent if the standard model parameters are considered as adjustable parameters in physically reasonable regions of variation
A probabilistic model for hydrokinetic turbine collision risks: exploring impacts on fish.
Hammar, Linus; Eggertsen, Linda; Andersson, Sandra; Ehnberg, Jimmy; Arvidsson, Rickard; Gullström, Martin; Molander, Sverker
2015-01-01
A variety of hydrokinetic turbines are currently under development for power generation in rivers, tidal straits and ocean currents. Because some of these turbines are large, with rapidly moving rotor blades, the risk of collision with aquatic animals has been brought to attention. The behavior and fate of animals that approach such large hydrokinetic turbines have not yet been monitored at any detail. In this paper, we conduct a synthesis of the current knowledge and understanding of hydrokinetic turbine collision risks. The outcome is a generic fault tree based probabilistic model suitable for estimating population-level ecological risks. New video-based data on fish behavior in strong currents are provided and models describing fish avoidance behaviors are presented. The findings indicate low risk for small-sized fish. However, at large turbines (≥5 m), bigger fish seem to have high probability of collision, mostly because rotor detection and avoidance is difficult in low visibility. Risks can therefore be substantial for vulnerable populations of large-sized fish, which thrive in strong currents. The suggested collision risk model can be applied to different turbine designs and at a variety of locations as basis for case-specific risk assessments. The structure of the model facilitates successive model validation, refinement and application to other organism groups such as marine mammals.
A probabilistic model for hydrokinetic turbine collision risks: exploring impacts on fish.
Directory of Open Access Journals (Sweden)
Linus Hammar
Full Text Available A variety of hydrokinetic turbines are currently under development for power generation in rivers, tidal straits and ocean currents. Because some of these turbines are large, with rapidly moving rotor blades, the risk of collision with aquatic animals has been brought to attention. The behavior and fate of animals that approach such large hydrokinetic turbines have not yet been monitored at any detail. In this paper, we conduct a synthesis of the current knowledge and understanding of hydrokinetic turbine collision risks. The outcome is a generic fault tree based probabilistic model suitable for estimating population-level ecological risks. New video-based data on fish behavior in strong currents are provided and models describing fish avoidance behaviors are presented. The findings indicate low risk for small-sized fish. However, at large turbines (≥5 m, bigger fish seem to have high probability of collision, mostly because rotor detection and avoidance is difficult in low visibility. Risks can therefore be substantial for vulnerable populations of large-sized fish, which thrive in strong currents. The suggested collision risk model can be applied to different turbine designs and at a variety of locations as basis for case-specific risk assessments. The structure of the model facilitates successive model validation, refinement and application to other organism groups such as marine mammals.
Generative Models of Conformational Dynamics
Langmead, Christopher James
2014-01-01
Atomistic simulations of the conformational dynamics of proteins can be performed using either Molecular Dynamics or Monte Carlo procedures. The ensembles of three-dimensional structures produced during simulation can be analyzed in a number of ways to elucidate the thermodynamic and kinetic properties of the system. The goal of this chapter is to review both traditional and emerging methods for learning generative models from atomistic simulation data. Here, the term ‘generative’ refers to a model of the joint probability distribution over the behaviors of the constituent atoms. In the context of molecular modeling, generative models reveal the correlation structure between the atoms, and may be used to predict how the system will respond to structural perturbations. We begin by discussing traditional methods, which produce multivariate Gaussian models. We then discuss GAMELAN (GrAphical Models of Energy LANdscapes), which produces generative models of complex, non-Gaussian conformational dynamics (e.g., allostery, binding, folding, etc) from long timescale simulation data. PMID:24446358
Dynamic effect of collision failure of phase in gas of cold dark atoms
International Nuclear Information System (INIS)
Il'ichev, L.V.
2005-01-01
In a gas of slow atoms exhibiting the effect of coherent population trapping (CPT) on the sublevels of the ground state in a spatially nonuniform light field, rare collisions destroying the CPT state initiate the irreversible exchange of momentum between radiation and atoms. This exchange is manifested as an additional force that acts on the particles. The force is of geometric origin, being determined only by the structure of the field of local CPT states. When this force is not masked by the standard collision change in atomic momentum, the observation of the kinetics of the particles may provide information on the physics of the collisions [ru
Experimental Modeling of Dynamic Systems
DEFF Research Database (Denmark)
Knudsen, Morten Haack
2006-01-01
An engineering course, Simulation and Experimental Modeling, has been developed that is based on a method for direct estimation of physical parameters in dynamic systems. Compared with classical system identification, the method appears to be easier to understand, apply, and combine with physical...
Double pendulum model for a tennis stroke including a collision process
Youn, Sun-Hyun
2015-10-01
By means of adding a collision process between the ball and racket in the double pendulum model, we analyzed the tennis stroke. The ball and the racket system may be accelerated during the collision time; thus, the speed of the rebound ball does not simply depend on the angular velocity of the racket. A higher angular velocity sometimes gives a lower rebound ball speed. We numerically showed that the proper time-lagged racket rotation increased the speed of the rebound ball by 20%. We also showed that the elbow should move in the proper direction in order to add the angular velocity of the racket.
A model of fast radio bursts: collisions between episodic magnetic blobs
Li, Long-Biao; Huang, Yong-Feng; Geng, Jin-Jun; Li, Bing
2018-06-01
Fast radio bursts (FRBs) are bright radio pulses from the sky with millisecond durations and Jansky-level flux densities. Their origins are still largely uncertain. Here we suggest a new model for FRBs. We argue that the collision of a white dwarf with a black hole can generate a transient accretion disk, from which powerful episodicmagnetic blobs will be launched. The collision between two consecutive magnetic blobs can result in a catastrophic magnetic reconnection, which releases a large amount of free magnetic energy and forms a forward shock. The shock propagates through the cold magnetized plasma within the blob in the collision region, radiating through the synchrotron maser mechanism, which is responsible for a non-repeating FRB signal. Our calculations show that the theoretical energetics, radiation frequency, duration timescale and event rate can be very consistent with the observational characteristics of FRBs.
H(D) → D(H) + Cu(111) collision system: molecular dynamics study of surface temperature effects.
Vurdu, Can D; Güvenç, Ziya B
2011-04-28
All the channels of the reaction dynamics of gas-phase H (or D) atoms with D (or H) atoms adsorbed onto a Cu(111) surface have been studied by quasiclassical constant energy molecular dynamics simulations. The surface is flexible and is prepared at different temperature values, such as 30 K, 94 K, and 160 K. The adsorbates were distributed randomly on the surface to create 0.18 ML, 0.28 ML, and 0.50 ML of coverages. The multi-layer slab is mimicked by a many-body embedded-atom potential energy function. The slab atoms can move according to the exerted external forces. Treating the slab atoms non-rigid has an important effect on the dynamics of the projectile atom and adsorbates. Significant energy transfer from the projectile atom to the surface lattice atoms takes place especially during the first impact that modifies significantly the details of the dynamics of the collisions. Effects of the different temperatures of the slab are investigated in this study. Interaction between the surface atoms and the adsorbates is modeled by a modified London-Eyring-Polanyi-Sato (LEPS) function. The LEPS parameters are determined by using the total energy values which were calculated by a density functional theory and a generalized gradient approximation for an exchange-correlation energy for many different orientations, and locations of one- and two-hydrogen atoms on the Cu(111) surface. The rms value of the fitting procedure is about 0.16 eV. Many different channels of the processes on the surface have been examined, such as inelastic reflection of the incident hydrogen, subsurface penetration of the incident projectile and adsorbates, sticking of the incident atom on the surface. In addition, hot-atom and Eley-Rideal direct processes are investigated. The hot-atom process is found to be more significant than the Eley-Rideal process. Furthermore, the rate of subsurface penetration is larger than the sticking rate on the surface. In addition, these results are compared and
Andrić, N.; Vogt, K.; Matenco, L.; Cvetković, V.; Cloetingh, S.; Gerya, T.
The relationship between magma generation and the tectonic evolution of orogens during subduction and subsequent collision requires self-consistent numerical modelling approaches predicting volumes and compositions of the produced magmatic rocks. Here, we use a 2D magmatic-thermomechanical numerical
Application of a distorted wave model to electron capture in atomic collisions
International Nuclear Information System (INIS)
Deco, G.R.; Martinez, A.E.; Rivarola, R.D.
1988-01-01
In this work, it is presented the CDW-EIS approximation applied to the description of processes of electron capture in ion-atom collisions. Differential and total cross sections are compared to results obtained by other theoretical models, as well as, to experimental data. (A.C.A.S.) [pt
Riaz, Faisal; Niazi, Muaz A
2017-01-01
This paper presents the concept of a social autonomous agent to conceptualize such Autonomous Vehicles (AVs), which interacts with other AVs using social manners similar to human behavior. The presented AVs also have the capability of predicting intentions, i.e. mentalizing and copying the actions of each other, i.e. mirroring. Exploratory Agent Based Modeling (EABM) level of the Cognitive Agent Based Computing (CABC) framework has been utilized to design the proposed social agent. Furthermore, to emulate the functionality of mentalizing and mirroring modules of proposed social agent, a tailored mathematical model of the Richardson's arms race model has also been presented. The performance of the proposed social agent has been validated at two levels-firstly it has been simulated using NetLogo, a standard agent-based modeling tool and also, at a practical level using a prototype AV. The simulation results have confirmed that the proposed social agent-based collision avoidance strategy is 78.52% more efficient than Random walk based collision avoidance strategy in congested flock-like topologies. Whereas practical results have confirmed that the proposed scheme can avoid rear end and lateral collisions with the efficiency of 99.876% as compared with the IEEE 802.11n-based existing state of the art mirroring neuron-based collision avoidance scheme.
Niazi, Muaz A.
2017-01-01
This paper presents the concept of a social autonomous agent to conceptualize such Autonomous Vehicles (AVs), which interacts with other AVs using social manners similar to human behavior. The presented AVs also have the capability of predicting intentions, i.e. mentalizing and copying the actions of each other, i.e. mirroring. Exploratory Agent Based Modeling (EABM) level of the Cognitive Agent Based Computing (CABC) framework has been utilized to design the proposed social agent. Furthermore, to emulate the functionality of mentalizing and mirroring modules of proposed social agent, a tailored mathematical model of the Richardson’s arms race model has also been presented. The performance of the proposed social agent has been validated at two levels–firstly it has been simulated using NetLogo, a standard agent-based modeling tool and also, at a practical level using a prototype AV. The simulation results have confirmed that the proposed social agent-based collision avoidance strategy is 78.52% more efficient than Random walk based collision avoidance strategy in congested flock-like topologies. Whereas practical results have confirmed that the proposed scheme can avoid rear end and lateral collisions with the efficiency of 99.876% as compared with the IEEE 802.11n-based existing state of the art mirroring neuron-based collision avoidance scheme. PMID:29040294
A numerical strategy for finite element modeling of frictionless asymmetric vocal fold collision
DEFF Research Database (Denmark)
Granados, Alba; Misztal, Marek Krzysztof; Brunskog, Jonas
2016-01-01
. Theoretical background and numerical analysis of the finite-element position-based contact model are presented, along with validation. A novel contact detection mechanism capable to detect collision in asymmetric oscillations is developed. The effect of inexact contact constraint enforcement on vocal fold...
Recombination model and baryon production by pp and πp collisions
International Nuclear Information System (INIS)
Takasugi, E.; Tata, X.
1979-12-01
The recombination model predictions for baryon production, using modified Kuti-Weisskopf structure functions, are in good agreement with the pp and πp collision data. The indistinguishability of sea quarks naturally accounts for the difference in the p and anti p spectra in the pion fragmentation region. 4 figures, 2 tables
Directory of Open Access Journals (Sweden)
Faisal Riaz
Full Text Available This paper presents the concept of a social autonomous agent to conceptualize such Autonomous Vehicles (AVs, which interacts with other AVs using social manners similar to human behavior. The presented AVs also have the capability of predicting intentions, i.e. mentalizing and copying the actions of each other, i.e. mirroring. Exploratory Agent Based Modeling (EABM level of the Cognitive Agent Based Computing (CABC framework has been utilized to design the proposed social agent. Furthermore, to emulate the functionality of mentalizing and mirroring modules of proposed social agent, a tailored mathematical model of the Richardson's arms race model has also been presented. The performance of the proposed social agent has been validated at two levels-firstly it has been simulated using NetLogo, a standard agent-based modeling tool and also, at a practical level using a prototype AV. The simulation results have confirmed that the proposed social agent-based collision avoidance strategy is 78.52% more efficient than Random walk based collision avoidance strategy in congested flock-like topologies. Whereas practical results have confirmed that the proposed scheme can avoid rear end and lateral collisions with the efficiency of 99.876% as compared with the IEEE 802.11n-based existing state of the art mirroring neuron-based collision avoidance scheme.
Study of proton-nucleus collisions at high energies based on the hydrodynamical model
International Nuclear Information System (INIS)
Masuda, N.; Weiner, R.M.
1978-01-01
We study proton-nucleus collisions at high energies using the one-dimensional hydrodynamical model of Landau with special emphasis on the effect of the size of the target nucleus and of the magnitude of velocity of sound of excited hadronic matter. We convert a collision problem of a proton and a nucleus with a spherical shape into that of a proton and a one-dimensional nuclear tunnel whose length is determined from the average impact parameter. By extending the methods developed by Milekhin and Emelyanov, we obtain the solutions of the hydrodynamical equations of proton-nucleus collisions for arbitrary target tunnel length and arbitrary velocity of sound. The connection between these solutions and observable physical quantities is established as in the work of Cooper, Frye, and Schonberg. Extensive numerical analyses are made at E/sub lab/ = 200 GeV and for the velocity of sound u = 1/√3 of a relativistic ideal Bose gas and u = 1/(7.5)/sup 1/2/ of an interacting Bose gas. In order to compare proton-nucleus collisions with proton-proton collisions, all the analyses are made in the equal-velocity frame. We find the following results. (1) In comparing the number of secondary particles produced in p-A collisions N/sub p/A with those in p-p collisions N/sub p/p, while most of the excess of N/sub p/A over N/sub p/p is concentrated in the backward rapidity region, there exists also an increase of N/sub p/A with A in the forward rapidity region. This result is at variance with the predictions of the energy-flux-cascade model and of the coherent-production model. (2) The excess energies are contained exclusively in the backward region. We also find evidence for new phenomena in proton-nucleus collisions. (3) The existence of an asymmetry of average energies of secondary particles between forward and backward regions, in particular, >> for larger nuclear targets. Thus, energetic particles are predominantly produced in the backward region
Solov'yov, Andrey; ISACC 2007; Latest advances in atomic cluster collisions
2008-01-01
This book presents a 'snapshot' of the most recent and significant advances in the field of cluster physics. It is a comprehensive review based on contributions by the participants of the 2nd International Symposium on Atomic Cluster Collisions (ISACC 2007) held in July 19-23, 2007 at GSI, Darmstadt, Germany. The purpose of the Symposium is to promote the growth and exchange of scientific information on the structure and properties of nuclear, atomic, molecular, biological and complex cluster systems studied by means of photonic, electronic, heavy particle and atomic collisions. Particular attention is devoted to dynamic phenomena, many-body effects taking place in cluster systems of a different nature - these include problems of fusion and fission, fragmentation, collective electron excitations, phase transitions, etc.Both the experimental and theoretical aspects of cluster physics, uniquely placed between nuclear physics on the one hand and atomic, molecular and solid state physics on the other, are discuss...
Flesch, L.; Bendick, R.; Bischoff, S.
2018-02-01
Surface velocities derived from Global Positioning System observations and Quaternary fault slip rates measured throughout an extended region of high topography in South Asia vary smoothly over thousands of kilometers and are broadly symmetrical, with components of both north-south shortening and east-west extension relative to stable Eurasia. The observed velocity field does not contain discontinuities or steep gradients attributable to along-strike differences in collision architecture, despite the well-documented presence of a lithospheric slab beneath the Pamir but not the Tibetan Plateau. We use a modified Akaike information criterion (AICc) to show that surface velocities do not efficiently constrain 3D rheology, geometry, or force balance. Therefore, although other geophysical and geological observations may indicate the presence of mechanical or dynamic heterogeneities within the Indian-Asian collision, the surface Global Positioning System velocities contain little or no usable information about them.
International Nuclear Information System (INIS)
Gonzalez, J. A; Guzman, F. S.
2011-01-01
In order to explore nonlinear effects on the distribution of matter during collisions within the Bose-Einstein condensate (BEC) dark matter model driven by the Schroedinger-Poisson system of equations, we study the head-on collision of structures and focus on the interference pattern formation in the density of matter during the collision process. We explore the possibility that the collision of two structures of fluid matter modeled with an ideal gas equation of state also forms interference patterns and found a negative result. Given that a fluid is the most common flavor of dark matter models, we conclude that one fingerprint of the BEC dark matter model is the pattern formation in the density during a collision of structures.
Charge distributions and correlations in fragmentation models for soft hadron collisions
International Nuclear Information System (INIS)
Wolf, E.A. de
1984-01-01
Data on charge distributions and charge correlations in pp and meson-proton interactions at PS and SPS energies are successfully compared with the Lund fragmentation model for low-psub(T) hadron collisions. It is argued that local conservation of quantum numbers and resonance production, as implemented in fragmentation models, are sufficient ingredients to explain most of the available experimental results at these energies. No necessity is found for dual-sheet contributions considered in DTU-based parton models. (orig.)
High-speed collision of copper nanoparticle with aluminum surface: Molecular dynamics simulation
Energy Technology Data Exchange (ETDEWEB)
Pogorelko, Victor V., E-mail: vik_ko83@mail.ru [Chelyabinsk State University, Bratiev Kashirinykh 129, 454001 Chelyabinsk (Russian Federation); South Ural State University (National Research University), Lenin Prospect 76, 454080 Chelyabinsk (Russian Federation); Mayer, Alexander E., E-mail: mayer@csu.ru [Chelyabinsk State University, Bratiev Kashirinykh 129, 454001 Chelyabinsk (Russian Federation); South Ural State University (National Research University), Lenin Prospect 76, 454080 Chelyabinsk (Russian Federation); Krasnikov, Vasiliy S., E-mail: vas.krasnikov@gmail.com [Chelyabinsk State University, Bratiev Kashirinykh 129, 454001 Chelyabinsk (Russian Federation); South Ural State University (National Research University), Lenin Prospect 76, 454080 Chelyabinsk (Russian Federation)
2016-12-30
Highlights: • High-speed nanoparticle impact induces shock waves and intensive plastic deformation. • Lattice orientation strongly influences on the deformation degree. • Plastic deformation goes through nucleation, growth and separation of semi-loops. • Medium impact energy and elevated temperature are optimal for high-quality coating. • High impact velocity and room temperature lead to plastic deformation and coating. - Abstract: We investigate the effect of the high-speed collision of copper nanoparticles with aluminum surface by means of molecular dynamic simulations. Studied diameter of nanoparticles is varied within the range 7.2–22 nm and the velocity of impact is equal to 500 or 1000 m/s. Dislocation analysis shows that a large quantity of dislocations is formed within the impact area. Overall length of dislocations is determined, first of all, by the impact velocity and by the size of incident copper nanoparticle, in other words, by the kinetic energy of the nanoparticle. Dislocations occupy the total volume of the impacted aluminum single crystal layer (40.5 nm in thickness) in the form of intertwined structure in the case of large kinetic energy of the incident nanoparticle. Decrease in the initial kinetic energy or increase in the layer thickness lead to restriction of the penetration depth of the dislocation net; formation of separate dislocation loops is observed in this case. Increase in the initial system temperature slightly raises the dislocation density inside the bombarded layer and considerably decreases the dislocation density inside the nanoparticle. The temperature increase also leads to a deeper penetration of the copper atoms inside the aluminum. Additional molecular dynamic simulations show that the deposited particles demonstrate a very good adhesion even in the case of the considered relatively large nanoparticles. Medium energy of the nanoparticles corresponding to velocity of about 500 m/s and elevated temperature of the
High-speed collision of copper nanoparticle with aluminum surface: Molecular dynamics simulation
International Nuclear Information System (INIS)
Pogorelko, Victor V.; Mayer, Alexander E.; Krasnikov, Vasiliy S.
2016-01-01
Highlights: • High-speed nanoparticle impact induces shock waves and intensive plastic deformation. • Lattice orientation strongly influences on the deformation degree. • Plastic deformation goes through nucleation, growth and separation of semi-loops. • Medium impact energy and elevated temperature are optimal for high-quality coating. • High impact velocity and room temperature lead to plastic deformation and coating. - Abstract: We investigate the effect of the high-speed collision of copper nanoparticles with aluminum surface by means of molecular dynamic simulations. Studied diameter of nanoparticles is varied within the range 7.2–22 nm and the velocity of impact is equal to 500 or 1000 m/s. Dislocation analysis shows that a large quantity of dislocations is formed within the impact area. Overall length of dislocations is determined, first of all, by the impact velocity and by the size of incident copper nanoparticle, in other words, by the kinetic energy of the nanoparticle. Dislocations occupy the total volume of the impacted aluminum single crystal layer (40.5 nm in thickness) in the form of intertwined structure in the case of large kinetic energy of the incident nanoparticle. Decrease in the initial kinetic energy or increase in the layer thickness lead to restriction of the penetration depth of the dislocation net; formation of separate dislocation loops is observed in this case. Increase in the initial system temperature slightly raises the dislocation density inside the bombarded layer and considerably decreases the dislocation density inside the nanoparticle. The temperature increase also leads to a deeper penetration of the copper atoms inside the aluminum. Additional molecular dynamic simulations show that the deposited particles demonstrate a very good adhesion even in the case of the considered relatively large nanoparticles. Medium energy of the nanoparticles corresponding to velocity of about 500 m/s and elevated temperature of the
Wanginingastuti Mutmainnah; Masao Furusho
2016-01-01
4M Overturned Pyramid (MOP) model is a new model, proposed by authors, to characterized MTS which is adopting epidemiological model that determines causes of accidents, including not only active failures but also latent failures and barriers. This model is still being developed. One of utilization of MOP model is characterizing accidents in MTS, i.e. collision in Indonesia and Japan that is written in this paper. The aim of this paper is to show the characteristics of ship collision accidents...
International Nuclear Information System (INIS)
De Backer, A; Sand, A; Ortiz, C J; Domain, C; Olsson, P; Berthod, E; Becquart, C S
2016-01-01
The damage produced by primary knock-on atoms (PKA) in W has been investigated from the threshold displacement energy (TDE) where it produces one self interstitial atom–vacancy pair to larger energies, up to 100 keV, where a large molten volume is formed. The TDE has been determined in different crystal directions using the Born–Oppenheimer density functional molecular dynamics (DFT-MD). A significant difference has been observed without and with the semi-core electrons. Classical MD has been used with two different empirical potentials characterized as ‘soft’ and ‘hard’ to obtain statistics on TDEs. Cascades of larger energy have been calculated, with these potentials, using a model that accounts for electronic losses (Sand et al 2013 Europhys. Lett. 103 46003). Two other sets of cascades have been produced using the binary collision approximation (BCA): a Monte Carlo BCA using SDTrimSP (Eckstein et al 2011 SDTrimSP: Version 5.00. Report IPP 12/8) (similar to SRIM www.srim.org) and MARLOWE (RSICC Home Page. (https://rsicc.ornl.gov/codes/psr/psr1/psr-137.html) (accessed May, 2014)). The comparison of these sets of cascades gave a recombination distance equal to 12 Å which is significantly larger from the one we reported in Hou et al (2010 J. Nucl. Mater. 403 89) because, here, we used bulk cascades rather than surface cascades which produce more defects (Stoller 2002 J. Nucl. Mater. 307 935, Nordlund et al 1999 Nature 398 49). Investigations on the defect clustering aspect showed that the difference between BCA and MD cascades is considerably reduced after the annealing of the cascade debris at 473 K using our Object Kinetic Monte Carlo model, LAKIMOCA (Domain et al 2004 J. Nucl. Mater. 335 121). (paper)
Trending in Probability of Collision Measurements via a Bayesian Zero-Inflated Beta Mixed Model
Vallejo, Jonathon; Hejduk, Matt; Stamey, James
2015-01-01
We investigate the performance of a generalized linear mixed model in predicting the Probabilities of Collision (Pc) for conjunction events. Specifically, we apply this model to the log(sub 10) transformation of these probabilities and argue that this transformation yields values that can be considered bounded in practice. Additionally, this bounded random variable, after scaling, is zero-inflated. Consequently, we model these values using the zero-inflated Beta distribution, and utilize the Bayesian paradigm and the mixed model framework to borrow information from past and current events. This provides a natural way to model the data and provides a basis for answering questions of interest, such as what is the likelihood of observing a probability of collision equal to the effective value of zero on a subsequent observation.
Business model dynamics and innovation
DEFF Research Database (Denmark)
Cavalcante, Sergio Andre; Kesting, Peter; Ulhøi, John Parm
2011-01-01
the impact of specific changes to a firm's business model. Such a tool would be particularly useful in identifying path dependencies and resistance at the process level, and would therefore allow a firm's management to take focused action on this in advance. Originality/value – The paper makes two main...... and specifies four different types of business model change: business model creation, extension, revision, and termination. Each type of business model change is associated with specific challenges. Practical implications – The proposed typology can serve as a basis for developing a management tool to evaluate......Purpose – This paper aims to discuss the need to dynamize the existing conceptualization of business model, and proposes a new typology to distinguish different types of business model change. Design/methodology/approach – The paper integrates basic insights of innovation, business process...
On whole Abelian model dynamics
Energy Technology Data Exchange (ETDEWEB)
Chauca, J.; Doria, R. [CBPF, Rio de Janeiro (Brazil); Aprendanet, Petropolis, 25600 (Brazil)
2012-09-24
Physics challenge is to determine the objects dynamics. However, there are two ways for deciphering the part. The first one is to search for the ultimate constituents; the second one is to understand its behaviour in whole terms. Therefore, the parts can be defined either from elementary constituents or as whole functions. Historically, science has been moving through the first aspect, however, quarks confinement and complexity are interrupting this usual approach. These relevant facts are supporting for a systemic vision be introduced. Our effort here is to study on the whole meaning through gauge theory. Consider a systemic dynamics oriented through the U(1) - systemic gauge parameter which function is to collect a fields set {l_brace}A{sub {mu}I}{r_brace}. Derive the corresponding whole gauge invariant Lagrangian, equations of motion, Bianchi identities, Noether relationships, charges and Ward-Takahashi equations. Whole Lorentz force and BRST symmetry are also studied. These expressions bring new interpretations further than the usual abelian model. They are generating a systemic system governed by 2N+ 10 classical equations plus Ward-Takahashi identities. A whole dynamics based on the notions of directive and circumstance is producing a set determinism where the parts dynamics are inserted in the whole evolution. A dynamics based on state, collective and individual equations with a systemic interdependence.
Relating structure and dynamics in organisation models
Jonkers, C.M.; Treur, J.
2002-01-01
To understand how an organisational structure relates to dynamics is an interesting fundamental challenge in the area of social modelling. Specifications of organisational structure usually have a diagrammatic form that abstracts from more detailed dynamics. Dynamic properties of agent systems,
Energy Technology Data Exchange (ETDEWEB)
May, Roel; Nygaard, Torgeir; Dahl, Espen Lie; Reitan, Ole; Bevanger, Kjetil
2011-05-15
Large soaring birds of prey, such as the white-tailed eagle, are recognized to be perhaps the most vulnerable bird group regarding risk of collisions with turbines in wind-power plants. Their mortalities have called for methods capable of modelling collision risks in connection with the planning of new wind-power developments. The so-called 'Band model' estimates collision risk based on the number of birds flying through the rotor swept zone and the probability of being hit by the passing rotor blades. In the calculations for the expected collision mortality a correction factor for avoidance behaviour is included. The overarching objective of this study was to use satellite telemetry data and recorded mortality to back-calculate the correction factor for white-tailed eagles. The Smoela wind-power plant consists of 68 turbines, over an area of approximately 18 km2. Since autumn 2006 the number of collisions has been recorded on a weekly basis. The analyses were based on satellite telemetry data from 28 white-tailed eagles equipped with backpack transmitters since 2005. The correction factor (i.e. 'avoidance rate') including uncertainty levels used within the Band collision risk model for white-tailed eagles was 99% (94-100%) for spring and 100% for the other seasons. The year-round estimate, irrespective of season, was 98% (95-99%). Although the year-round estimate was similar, the correction factor for spring was higher than the correction factor of 95% derived earlier from vantage point data. The satellite telemetry data may provide an alternative way to provide insight into relative risk among seasons, and help identify periods or areas with increased risk either in a pre- or post construction situation. (Author)
Collision-produced atomic states
International Nuclear Information System (INIS)
Andersen, N.; Copenhagen Univ.
1988-01-01
The last 10-15 years have witnessed the development of a new, powerful class of experimental techniques for atomic collision studies, allowing partial or complete determination of the state of the atoms after a collision event, i.e. the full set of quantum-mechanical scattering amplitudes or - more generally - the density matrix describing the system. Evidently, such studies, involving determination of alignment and orientation parameters, provide much more severe tests of state-of-the-art scattering theories than do total or differential cross section measurements which depend on diagonal elements of the density matrix. The off-diagonal elements give us detailed information about the shape and dynamics of the atomic states. Therefore, close studies of collision-produced atomic states are currently leading to deeper insights into the fundamental physical mechanisms governing the dynamics of atomic collision events. The first part of the lectures deals with the language used to describe atomic states, while the second part presents a selection of recent results for model systems which display fundamental aspects of the collision physics in particularly instructive ways. I shall here restrict myself to atom-atom collisions. The discussion will be focused on states decaying by photon emission though most of the ideas can be easily modified to include electron emission as well. (orig./AH)
SU-E-T-754: Three-Dimensional Patient Modeling Using Photogrammetry for Collision Avoidance
Energy Technology Data Exchange (ETDEWEB)
Popple, R; Cardan, R [Univ Alabama Birmingham, Birmingham, AL (United States)
2015-06-15
Purpose: To evaluate photogrammetry for creating a three-dimensional patient model. Methods: A mannequin was configured on the couch of a CT scanner to simulate a patient setup using an indexed positioning device. A CT fiducial was placed on the indexed CT table-overlay at the reference index position. Two dimensional photogrammetry targets were placed on the table in known positions. A digital SLR camera was used to obtain 27 images from different positions around the CT table. The images were imported into a commercial photogrammetry package and a 3D model constructed. Each photogrammetry target was identified on 2 to 5 images. The CT DICOM metadata and the position of the CT fiducial were used to calculate the coordinates of the photogrammetry targets in the CT image frame of reference. The coordinates were transferred to the photogrammetry software to orient the 3D model. The mannequin setup was transferred to the treatment couch of a linear accelerator and positioned at isocenter using in-room lasers. The treatment couch coordinates were noted and compared with prediction. The collision free regions were measured over the full range of gantry and table motion and were compared with predictions obtained using a general purpose polygon interference algorithm. Results: The reconstructed 3D model consisted of 180000 triangles. The difference between the predicted and measured couch positions were 5 mm, 1 mm, and 1 mm for longitudinal, lateral, and vertical, respectively. The collision prediction tested 64620 gantry table combinations in 11.1 seconds. The accuracy was 96.5%, with false positive and negative results occurring at the boundaries of the collision space. Conclusion: Photogrammetry can be used as a tool for collision avoidance during treatment planning. The results indicate that a buffer zone is necessary to avoid false negatives at the boundary of the collision-free zone. Testing with human patients is underway. Research partially supported by a grant
International Nuclear Information System (INIS)
Fowler, G.N.; Navarra, F.S.; Plumer, M.; Lawrence Berkeley Laboratory, Nuclear Science Division, Berkeley, California 94720); Vourdas, A.; Weiner, R.M.
1989-01-01
The interacting gluon model developed to describe the inelasticity distribution in hadron-nucleon collisions has been generalized and applied to hadron-nucleus and nucleus-nucleus interactions. Leading particle spectra and energy distributions in hadron-nucleus and nucleus-nucleus collisions are calculated
Hydrodynamic modeling of 3He–Au collisions at sNN=200 GeV
Directory of Open Access Journals (Sweden)
Piotr Bożek
2015-07-01
Full Text Available Collective flow and femtoscopy in ultrarelativistic 3He–Au collisions are investigated within the 3+1-dimensional (3+1D viscous event-by-event hydrodynamics. We evaluate elliptic and triangular flow coefficients as functions of the transverse momentum. We find the typical long-range ridge structures in the two-particle correlations in the relative azimuth and pseudorapidity, in the pseudorapidity directions of both Au and 3He. We also make predictions for the pionic interferometric radii, which decrease with the transverse momentum of the pion pair. All features found hint on collectivity of the dynamics of the system formed in 3He–Au collisions, with hydrodynamics leading to quantitative agreement with the up-to-now released data.
Social Dynamics Modeling and Inference
2018-03-29
the experiment(s)/ theory and equipment or analyses. Development of innovative theoretical model and methodologies with experimental verifications...information. The methodology based on communication and information theory (thanks to leave at MIT supported by this research) is described in [J1], [C2...a dynamic system [C1] and as a social learning mechanism in details [J4]. Furthermore, by incentive seeding and rewiring connections, information
Sirmas, Nick; Radulescu, Matei I.
2016-01-01
The problem of thermal ignition in a homogeneous gas is revisited from a molecular dynamics perspective. A two-dimensional model is adopted, which assumes reactive disks of type A and B in a fixed area that react to form type C products if an activation threshold for impact is surpassed. Such a reaction liberates kinetic energy to the product particles, representative of the heat release. The results for the ignition delay are compared with those obtained from the continuum description assumi...
International Nuclear Information System (INIS)
Rosa, Bogdan; Parishani, Hossein; Ayala, Orlando; Wang, Lian-Ping; Grabowski, Wojciech W
2011-01-01
In recent years, direct numerical simulation (DNS) approach has become a reliable tool for studying turbulent collision-coalescence of cloud droplets relevant to warm rain development. It has been shown that small-scale turbulent motion can enhance the collision rate of droplets by either enhancing the relative velocity and collision efficiency or by inertia-induced droplet clustering. A hybrid DNS approach incorporating DNS of air turbulence, disturbance flows due to droplets, and droplet equation of motion has been developed to quantify these effects of air turbulence. Due to the computational complexity of the approach, a major challenge is to increase the range of scales or size of the computation domain so that all scales affecting droplet pair statistics are simulated. Here we discuss our on-going work in this direction by improving the parallel scalability of the code, and by studying the effect of large-scale forcing on pair statistics relevant to turbulent collision. New results at higher grid resolutions show a saturation of pair and collision statistics with increasing flow Reynolds number, for given Kolmogorov scales and small droplet sizes. Furthermore, we examine the orientation dependence of pair statistics which reflects an interesting coupling of gravity and droplet clustering.
Model-Based Estimation of Collision Risks of Predatory Birds with Wind Turbines
Directory of Open Access Journals (Sweden)
Marcus Eichhorn
2012-06-01
Full Text Available The expansion of renewable energies, such as wind power, is a promising way of mitigating climate change. Because of the risk of collision with rotor blades, wind turbines have negative effects on local bird populations, particularly on raptors such as the Red Kite (Milvus milvus. Appropriate assessment tools for these effects have been lacking. To close this gap, we have developed an agent-based, spatially explicit model that simulates the foraging behavior of the Red Kite around its aerie in a landscape consisting of different land-use types. We determined the collision risk of the Red Kite with the turbine as a function of the distance between the wind turbine and the aerie and other parameters. The impact function comprises the synergistic effects of species-specific foraging behavior and landscape structure. The collision risk declines exponentially with increasing distance. The strength of this decline depends on the raptor's foraging behavior, its ability to avoid wind turbines, and the mean wind speed in the region. The collision risks, which are estimated by the simulation model, are in the range of values observed in the field. The derived impact function shows that the collision risk can be described as an aggregated function of distance between the wind turbine and the raptor's aerie. This allows an easy and rapid assessment of the ecological impacts of (existing or planned wind turbines in relation to their spatial location. Furthermore, it implies that minimum buffer zones for different landscapes can be determined in a defensible way. This modeling approach can be extended to other bird species with central-place foraging behavior. It provides a helpful tool for landscape planning aimed at minimizing the impacts of wind power on biodiversity.
Dynamics of density fluctuations in a non-Markovian Boltzmann- Langevin model
International Nuclear Information System (INIS)
Ayik, S.
1996-01-01
In the course of the past few years, the nuclear Boltzmann-Langevin (BL)model has emerged as a promising microscopic model for nuclear dynamics at intermediate energies. The BL model goes beyond the much employed Boltzmann-Uehling-Uhlenbeck (BUU) model, and hence it provides a basis for describing dynamics of density fluctuations and addressing processes exhibiting spontaneous symmetry breaking and catastrophic transformations in nuclear collisions, such as induced fission and multifragmentation. In these standard models, the collision term is treated in a Markovian approximation by assuming that two-body collisions are local in both space and time, in accordance with Boltzmann's original treatment. This simplification is usually justified by the fact that the duration of a two-body collision is short on the time scale characteristic of the macroscopic evolution of the system. As a result, transport properties of the collective motion has then a classical character. However, when the system possesses fast collective modes with characteristic energies that are not small in comparision with the temperature, then the quantum-statistical effects are important and the standard Markovian treatment is inadequate. In this case, it is necessary to improve the one-body transport model by including the memory effect due to the finite duration of two-body collisions. First we briefly describe the non-Markovian extension of the BL model by including the finite memory time associated with two-body collisions. Then, using this non-Markovian model in a linear response framework, we investigate the effect of the memory time on the agitation of unstable modes in nuclear matter in the spinodal zone, and calculate the collisional relaxation rates of nuclear collective vibrations
Directory of Open Access Journals (Sweden)
Kwang Cheol Shin
2009-02-01
Full Text Available In the fields of production, manufacturing and supply chain management, Radio Frequency Identification (RFID is regarded as one of the most important technologies. Nowadays, Mobile RFID, which is often installed in carts or forklift trucks, is increasingly being applied to the search for and checkout of items in warehouses, supermarkets, libraries and other industrial fields. In using Mobile RFID, since the readers are continuously moving, they can interfere with each other when they attempt to read the tags. In this study, we suggest a Time Division Multiple Access (TDMA based anti-collision algorithm for Mobile RFID readers. Our algorithm automatically adjusts the frame size of each reader without using manual parameters by adopting the dynamic frame size adjustment strategy when collisions occur at a reader. Through experiments on a simulated environment for Mobile RFID readers, we show that the proposed method improves the number of successful transmissions by about 228% on average, compared with Colorwave, a representative TDMA based anti-collision algorithm.
Shin, Kwang Cheol; Park, Seung Bo; Jo, Geun Sik
2009-01-01
In the fields of production, manufacturing and supply chain management, Radio Frequency Identification (RFID) is regarded as one of the most important technologies. Nowadays, Mobile RFID, which is often installed in carts or forklift trucks, is increasingly being applied to the search for and checkout of items in warehouses, supermarkets, libraries and other industrial fields. In using Mobile RFID, since the readers are continuously moving, they can interfere with each other when they attempt to read the tags. In this study, we suggest a Time Division Multiple Access (TDMA) based anti-collision algorithm for Mobile RFID readers. Our algorithm automatically adjusts the frame size of each reader without using manual parameters by adopting the dynamic frame size adjustment strategy when collisions occur at a reader. Through experiments on a simulated environment for Mobile RFID readers, we show that the proposed method improves the number of successful transmissions by about 228% on average, compared with Colorwave, a representative TDMA based anti-collision algorithm.
International Nuclear Information System (INIS)
Jung, Y.
1997-01-01
In dense plasmas, dynamic plasma screening effects are investigated on 1s→2p dipole transition probabilities for electron-impact excitation of hydrogenic ions. The electron endash ion interaction potential is considered by introduction of the plasma dielectric function. A semiclassical straight-line trajectory method is applied to the path of the projectile electron in order to visualize the semiclassical transition probability as a function of the impact parameter, projectile energy, and plasma parameters. The transition probability including the dynamic plasma screening effect is always greater than that including the static plasma screening effect. When the projectile velocity is smaller than the electron thermal velocity, the dynamic polarization screening effect becomes the static plasma screening effect. When the projectile velocity is greater than the electron thermal velocity, then the interaction potential is almost unshielded. The difference between the dynamic and static plasma screening effects is more significant for low-energy projectiles. It is also found that the static plasma screening formula obtained by the Debye endash Hueckel model overestimates the plasma screening effects on the atomic excitation processes in dense plasmas. copyright 1997 American Institute of Physics
International Nuclear Information System (INIS)
Yakimenko, I.P.; Zagorodny, A.G.
1980-01-01
The kinetic theory of fluctuations is used to investigate the influence of the collisions of charged particles with atoms and molecules on the dynamic form-factors of semi-infinite weakly ionized plasma. It is shown that the collisions between the electrons and neutral particles and the diffuse processes connected with them lead to a much increased influence of the boundary on correlations in a plasma [ru
International Nuclear Information System (INIS)
Romanova, M.M.
1985-01-01
The dynamics of a gas--star disk embedded in a dense, mildly oblate (flattening epsilon-c or approx. =0.2--0.3 the stable disk will survive for at least half the cluster evolution time. The possibility of a thin disk of stars existing inside a dense star cluster is considered. For small epsilon-c and for disk member stars having > or approx. =0.04 the mass of the cluster members, collisions between cluster and disk stars will have no effect on the disk evolution prior to instability
Bleicher, M; Liu, F M; Keränen, A; Aichelin, J; Bass, S A; Becattini, F; Redlich, K; Werner, K
2002-05-20
The Omega/Omega ratio originating from string decays is predicted to be larger than unity in proton-proton interactions at SPS energies ( E(lab) = 160 GeV). The antiomega dominance increases with decreasing beam energy. This surprising behavior is caused by the combinatorics of quark-antiquark production in small and low-mass strings. Since this behavior is not found in a statistical description of hadron production in proton-proton collisions, it may serve as a key observable to probe the hadronization mechanism in such collisions.
Bleicher, M; Keränen, A; Aichelin, Jörg; Bass, S A; Becattini, F; Redlich, Krzysztof; Werner, K
2002-01-01
The $\\bar{\\Omega}/\\Omega$ ratio originating from string decays is predicted to be larger than unity in proton proton interactions at SPS energies ($E_{\\rm lab}$=160 GeV). The anti-omega dominance increases with decreasing beam energy. This surprising behavior is caused by the combinatorics of quark-antiquark production in small and low-mass strings. Since this behavior is not found in a statistical description of hadron production in proton proton collisions, it may serve as a key observable to probe the hadronization mechanism in such collisions.
Hard photons and mesons as probes of heavy ion collision dynamics
International Nuclear Information System (INIS)
Metag, V.
1991-01-01
Hard photon production in heavy ion collisions has been studied by a large number of groups at various laboratory and a large body of data has been collected. Recent results reviewed are summarized here in a systematics for photon emission. A brief discussion of π 0 -production in heavy ion collisions will be given including first results with the Two Arm Photon spectrometer TAPS obtained at SIS. Furthermore, the new perspectives for the study of compressed nuclear matter by meson emission will be outlined. (orig.)
International Nuclear Information System (INIS)
Bleicher, M.; Liu, F. M.; Aichelin, J.; Werner, K.; Keraenen, A.; Bass, S. A.; Becattini, F.; Redlich, K.
2002-01-01
The Ω/Ω ratio originating from string decays is predicted to be larger than unity in proton-proton interactions at SPS energies (E lab =160 GeV ). The antiomega dominance increases with decreasing beam energy. This surprising behavior is caused by the combinatorics of quark-antiquark production in small and low-mass strings. Since this behavior is not found in a statistical description of hadron production in proton-proton collisions, it may serve as a key observable to probe the hadronization mechanism in such collisions
Modeling chiral criticality and its consequences for heavy-ion collisions
Energy Technology Data Exchange (ETDEWEB)
Almási, Gábor András, E-mail: g.almasi@gsi.de [Gesellschaft für Schwerionenforschung, GSI, D-64291 Darmstadt (Germany); Friman, Bengt, E-mail: b.friman@gsi.de [Gesellschaft für Schwerionenforschung, GSI, D-64291 Darmstadt (Germany); ExtreMe Matter Institute (EMMI), D-64291 Darmstadt (Germany); Redlich, Krzysztof, E-mail: krzysztof.redlich@ift.uni.wroc.pl [ExtreMe Matter Institute (EMMI), D-64291 Darmstadt (Germany); University of Wrocław - Faculty of Physics and Astronomy, PL-50-204 Wrocław (Poland); Department of Physics, Duke University, Durham, NC 27708 (United States)
2016-12-15
We explore the critical fluctuations near the chiral critical endpoint (CEP) in a chiral effective model and discuss possible signals of the CEP, recently explored experimentally in nuclear collision. Particular attention is paid to the dependence of such signals on the location of the phase boundary and the CEP relative to the chemical freeze-out conditions in nuclear collisions. We argue that in effective models, standard freeze-out fits to heavy-ion data should not be used directly. Instead, the relevant quantities should be examined on lines in the phase diagram that are defined self-consistently, within the framework of the model. We discuss possible choices for such an approach.
Modeling chiral criticality and its consequences for heavy-ion collisions
Energy Technology Data Exchange (ETDEWEB)
Almasi, Gabor [Gesellschaft fuer Schwerionenforschung, GSI, Darmstadt (Germany); Friman, Bengt [Gesellschaft fuer Schwerionenforschung, GSI, Darmstadt (Germany); ExtreMe Matter Institute (EMMI), Darmstadt (Germany); Redlich, Krzysztof [ExtreMe Matter Institute (EMMI), Darmstadt (Germany); University of Wroclaw, Faculty of Physics and Astronomy, Wroclaw (Poland); Department of Physics, Duke University, Durham, NC (United States)
2016-07-01
We explore the critical fluctuations near the chiral critical endpoint (CEP), which belongs to the Z(2) universality class, in a chiral effective model and discuss possible signals of the CEP, recently explored in nuclear collision experiments. Particular attention is attributed to the dependence of such signals on the location of the phase boundary and the CEP relative to the hypothetical freeze-out conditions in nuclear collisions. We argue that in effective models freeze-out fits to heavy-ion results should not be used directly, and relevant quantities should be investigated on lines of the phase diagram, that are defined self-consistently in the framework of the model. We discuss possible choices for such an approach. Additionally we discuss the effect of the repulsive vector interaction of quarks on the location of the CEP and on the structure of the baryon number cumulant ratios.
Modeling detour behavior of pedestrian dynamics under different conditions
Qu, Yunchao; Xiao, Yao; Wu, Jianjun; Tang, Tao; Gao, Ziyou
2018-02-01
Pedestrian simulation approach has been widely used to reveal the human behavior and evaluate the performance of crowd evacuation. In the existing pedestrian simulation models, the social force model is capable of predicting many collective phenomena. Detour behavior occurs in many cases, and the important behavior is a dominate factor of the crowd evacuation efficiency. However, limited attention has been attracted for analyzing and modeling the characteristics of detour behavior. In this paper, a modified social force model integrated by Voronoi diagram is proposed to calculate the detour direction and preferred velocity. Besides, with the consideration of locations and velocities of neighbor pedestrians, a Logit-based choice model is built to describe the detour direction choice. The proposed model is applied to analyze pedestrian dynamics in a corridor scenario with either unidirectional or bidirectional flow, and a building scenario in real-world. Simulation results show that the modified social force model including detour behavior could reduce the frequency of collision and deadlock, increase the average speed of the crowd, and predict more practical crowd dynamics with detour behavior. This model can also be potentially applied to understand the pedestrian dynamics and design emergent management strategies for crowd evacuations.
International Nuclear Information System (INIS)
Beck, W.A.
2000-01-01
The semiclassical model of atomic collisions, especially in different areas of the maximum stopping, when proton collides at the velocity of the boron order velocity, providing as the result for interactions of many bodies with an electron target, enabling application of the model with high degree of confidence to a clearly expressed experimental problem, such the antiproton capture on helium, is presented. The semiclassical collision model and stopping energy are considered. The stopping and capture of negatively-charged particles are investigated. The capture and angular moments of antiprotons, captures at the end of the collision cascade, are presented [ru
Modelling and Analysis of a Collision Avoidance Protocol using SPIN and UPPAAL
DEFF Research Database (Denmark)
Skou, Arne; Larsen, Kim Guldstrand; Jensen, Henrik Ejersbo
1997-01-01
, the modelling of the media becomes ackward due to the lack of broadcast communication in the PROMELA language. On the other hand we find it easy to model the timed aspects using the UPPAAL tool. Especially, the notion of committed locations supports the modelling of broadcast communication. However......This paper compares the tools SPIN and UPPAAL by modelling and verifying a Collision Avoidance Protocol for an Ethernet-like medium. We find that SPIN is well suited for modelling the untimed aspects of the protocol processes and for expressing the relevant (untimed) properties. However...
Introduction to fluid model for RHIC heavy ion collisions
International Nuclear Information System (INIS)
Muraya, Shin
2007-01-01
An introductory review of the fluid model which has been looked upon as the promising phenomenological model for the heavy ion scattering experiments at RHIC is presented here. Subjects are especially focused on the fundamental assumptions of the model and the decision process of the phenomenological parameters considering newcomers to hadron physics. Introduction of thermodynamical quantities, 1+1 dimension model, time-space evolution of fluid, correspondence of fluid to particles, initial condition, boundary condition and comparison of the equation of state of fluid model and that of hadron model are described. Limitation of fluid picture and the validity of the model are discussed finally. It is summarized that the present fluid model does not predict much about results in advance but gives interpretation after the event, nevertheless it reproduces much of the experimental results in natural form. It is expected that the parameter of the fluid model is to be used as the intermediate theory to relate experimental results with theory. (S. Funahashi)
International Nuclear Information System (INIS)
Hou, M.; Ortiz, C.J.; Becquart, C.S.; Domain, C.; Sarkar, U.; Debacker, A.
2010-01-01
It is important to develop an understanding of the evolution of W microstructure the conditions the International Thermonuclear Experimental Reactor (ITER) as well as the DEMOnstration Power Plan (DEMO), and modelling techniques can be very helpful. In this paper, the Binary Collision Approximation of Molecular Dynamics as implemented in the Marlowe code is used to model the slowing down of atomic helium and hydrogen on tungsten in the 1-100 keV range. The computed helium and Frenkel Pairs (FP) distributions are then used as input for the simulation of isochronal annealing experiments with an Object Kinetic Monte Carlo (OKMC) model. Parameterisation is discussed in a companion paper to this one. To model inelastic energy losses beyond the Lindhard regime, a new module has been implemented in the Marlowe code which is presented here, along with a discussion on various parameters of the model important in the modelling of channelled trajectories. For a given total inelastic stopping cross section, large differences in low energy channelling ranges are identified depending on whether inelastic energy loss is considered to be purely continuous or to also occur during the atomic collisions. In polycrystals, the channelling probability is shown to be significant over the whole range of slowing down energies considered. Channelling together with short replacement sequences has the effect of reducing the FP production efficiency by more than a factor two in polycrystalline as compared with an hypothetical structureless tungsten. This has a crucial effect on the helium isochronal desorption spectra predicted by the OKMC simulations. Those predicted with structureless tungsten are at variance with experiment, due to the overestimation of He trapping on the radiation induced defects.
Energy Technology Data Exchange (ETDEWEB)
Hou, M., E-mail: mhou@ulb.ac.b [Physique des Solides Irradies et des Nanostructures CP234, Universite Libre de Bruxelles, Bd du Triomphe, B-1050 Brussels (Belgium); Ortiz, C.J. [Laboratorio Nacional de Fusion por Confinamiento Magnetico, CIEMAT, E-28040 Madrid (Spain); Becquart, C.S. [Unite Materiaux Et Transformations (UMET), UMR 8207, Universite de Lille 1, F-59655 Villeneuve d' Ascq Cedex (France); Domain, C. [EDF-R and D Departement MMC, Les Renardieres, F-77818 Moret sur Loing Cedex (France); Sarkar, U. [Physics Department, Assam University, Silchar (India); Debacker, A. [Unite Materiaux Et Transformations (UMET), UMR 8207, Universite de Lille 1, F-59655 Villeneuve d' Ascq Cedex (France)
2010-08-15
It is important to develop an understanding of the evolution of W microstructure the conditions the International Thermonuclear Experimental Reactor (ITER) as well as the DEMOnstration Power Plan (DEMO), and modelling techniques can be very helpful. In this paper, the Binary Collision Approximation of Molecular Dynamics as implemented in the Marlowe code is used to model the slowing down of atomic helium and hydrogen on tungsten in the 1-100 keV range. The computed helium and Frenkel Pairs (FP) distributions are then used as input for the simulation of isochronal annealing experiments with an Object Kinetic Monte Carlo (OKMC) model. Parameterisation is discussed in a companion paper to this one. To model inelastic energy losses beyond the Lindhard regime, a new module has been implemented in the Marlowe code which is presented here, along with a discussion on various parameters of the model important in the modelling of channelled trajectories. For a given total inelastic stopping cross section, large differences in low energy channelling ranges are identified depending on whether inelastic energy loss is considered to be purely continuous or to also occur during the atomic collisions. In polycrystals, the channelling probability is shown to be significant over the whole range of slowing down energies considered. Channelling together with short replacement sequences has the effect of reducing the FP production efficiency by more than a factor two in polycrystalline as compared with an hypothetical structureless tungsten. This has a crucial effect on the helium isochronal desorption spectra predicted by the OKMC simulations. Those predicted with structureless tungsten are at variance with experiment, due to the overestimation of He trapping on the radiation induced defects.
An analysis of urban collisions using an artificial intelligence model.
Mussone, L; Ferrari, A; Oneta, M
1999-11-01
Traditional studies on road accidents estimate the effect of variables (such as vehicular flows, road geometry, vehicular characteristics), and the calculation of the number of accidents. A descriptive statistical analysis of the accidents (those used in the model) over the period 1992-1995 is proposed. The paper describes an alternative method based on the use of artificial neural networks (ANN) in order to work out a model that relates to the analysis of vehicular accidents in Milan. The degree of danger of urban intersections using different scenarios is quantified by the ANN model. Methodology is the first result, which allows us to tackle the modelling of urban vehicular accidents by the innovative use of ANN. Other results deal with model outputs: intersection complexity may determine a higher accident index depending on the regulation of intersection. The highest index for running over of pedestrian occurs at non-signalised intersections at night-time.
International Nuclear Information System (INIS)
Yu, Victoria Y.; Tran, Angelia; Nguyen, Dan; Cao, Minsong; Ruan, Dan; Low, Daniel A.; Sheng, Ke
2015-01-01
Purpose: Significant dosimetric benefits had been previously demonstrated in highly noncoplanar treatment plans. In this study, the authors developed and verified an individualized collision model for the purpose of delivering highly noncoplanar radiotherapy and tested the feasibility of total delivery automation with Varian TrueBeam developer mode. Methods: A hand-held 3D scanner was used to capture the surfaces of an anthropomorphic phantom and a human subject, which were positioned with a computer-aided design model of a TrueBeam machine to create a detailed virtual geometrical collision model. The collision model included gantry, collimator, and couch motion degrees of freedom. The accuracy of the 3D scanner was validated by scanning a rigid cubical phantom with known dimensions. The collision model was then validated by generating 300 linear accelerator orientations corresponding to 300 gantry-to-couch and gantry-to-phantom distances, and comparing the corresponding distance measurements to their corresponding models. The linear accelerator orientations reflected uniformly sampled noncoplanar beam angles to the head, lung, and prostate. The distance discrepancies between measurements on the physical and virtual systems were used to estimate treatment-site-specific safety buffer distances with 0.1%, 0.01%, and 0.001% probability of collision between the gantry and couch or phantom. Plans containing 20 noncoplanar beams to the brain, lung, and prostate optimized via an in-house noncoplanar radiotherapy platform were converted into XML script for automated delivery and the entire delivery was recorded and timed to demonstrate the feasibility of automated delivery. Results: The 3D scanner measured the dimension of the 14 cm cubic phantom within 0.5 mm. The maximal absolute discrepancy between machine and model measurements for gantry-to-couch and gantry-to-phantom was 0.95 and 2.97 cm, respectively. The reduced accuracy of gantry-to-phantom measurements was
Energy Technology Data Exchange (ETDEWEB)
Yu, Victoria Y.; Tran, Angelia; Nguyen, Dan; Cao, Minsong; Ruan, Dan; Low, Daniel A.; Sheng, Ke, E-mail: ksheng@mednet.ucla.edu [Department of Radiation Oncology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California 90024 (United States)
2015-11-15
Purpose: Significant dosimetric benefits had been previously demonstrated in highly noncoplanar treatment plans. In this study, the authors developed and verified an individualized collision model for the purpose of delivering highly noncoplanar radiotherapy and tested the feasibility of total delivery automation with Varian TrueBeam developer mode. Methods: A hand-held 3D scanner was used to capture the surfaces of an anthropomorphic phantom and a human subject, which were positioned with a computer-aided design model of a TrueBeam machine to create a detailed virtual geometrical collision model. The collision model included gantry, collimator, and couch motion degrees of freedom. The accuracy of the 3D scanner was validated by scanning a rigid cubical phantom with known dimensions. The collision model was then validated by generating 300 linear accelerator orientations corresponding to 300 gantry-to-couch and gantry-to-phantom distances, and comparing the corresponding distance measurements to their corresponding models. The linear accelerator orientations reflected uniformly sampled noncoplanar beam angles to the head, lung, and prostate. The distance discrepancies between measurements on the physical and virtual systems were used to estimate treatment-site-specific safety buffer distances with 0.1%, 0.01%, and 0.001% probability of collision between the gantry and couch or phantom. Plans containing 20 noncoplanar beams to the brain, lung, and prostate optimized via an in-house noncoplanar radiotherapy platform were converted into XML script for automated delivery and the entire delivery was recorded and timed to demonstrate the feasibility of automated delivery. Results: The 3D scanner measured the dimension of the 14 cm cubic phantom within 0.5 mm. The maximal absolute discrepancy between machine and model measurements for gantry-to-couch and gantry-to-phantom was 0.95 and 2.97 cm, respectively. The reduced accuracy of gantry-to-phantom measurements was
Yu, Victoria Y; Tran, Angelia; Nguyen, Dan; Cao, Minsong; Ruan, Dan; Low, Daniel A; Sheng, Ke
2015-11-01
Significant dosimetric benefits had been previously demonstrated in highly noncoplanar treatment plans. In this study, the authors developed and verified an individualized collision model for the purpose of delivering highly noncoplanar radiotherapy and tested the feasibility of total delivery automation with Varian TrueBeam developer mode. A hand-held 3D scanner was used to capture the surfaces of an anthropomorphic phantom and a human subject, which were positioned with a computer-aided design model of a TrueBeam machine to create a detailed virtual geometrical collision model. The collision model included gantry, collimator, and couch motion degrees of freedom. The accuracy of the 3D scanner was validated by scanning a rigid cubical phantom with known dimensions. The collision model was then validated by generating 300 linear accelerator orientations corresponding to 300 gantry-to-couch and gantry-to-phantom distances, and comparing the corresponding distance measurements to their corresponding models. The linear accelerator orientations reflected uniformly sampled noncoplanar beam angles to the head, lung, and prostate. The distance discrepancies between measurements on the physical and virtual systems were used to estimate treatment-site-specific safety buffer distances with 0.1%, 0.01%, and 0.001% probability of collision between the gantry and couch or phantom. Plans containing 20 noncoplanar beams to the brain, lung, and prostate optimized via an in-house noncoplanar radiotherapy platform were converted into XML script for automated delivery and the entire delivery was recorded and timed to demonstrate the feasibility of automated delivery. The 3D scanner measured the dimension of the 14 cm cubic phantom within 0.5 mm. The maximal absolute discrepancy between machine and model measurements for gantry-to-couch and gantry-to-phantom was 0.95 and 2.97 cm, respectively. The reduced accuracy of gantry-to-phantom measurements was attributed to phantom setup
Multiscale modeling of pedestrian dynamics
Cristiani, Emiliano; Tosin, Andrea
2014-01-01
This book presents mathematical models and numerical simulations of crowd dynamics. The core topic is the development of a new multiscale paradigm, which bridges the microscopic and macroscopic scales taking the most from each of them for capturing the relevant clues of complexity of crowds. The background idea is indeed that most of the complex trends exhibited by crowds are due to an intrinsic interplay between individual and collective behaviors. The modeling approach promoted in this book pursues actively this intuition and profits from it for designing general mathematical structures susceptible of application also in fields different from the inspiring original one. The book considers also the two most traditional points of view: the microscopic one, in which pedestrians are tracked individually, and the macroscopic one, in which pedestrians are assimilated to a continuum. Selected existing models are critically analyzed. The work is addressed to researchers and graduate students.
Relativistic nuclear collisions: theory
International Nuclear Information System (INIS)
Gyulassy, M.
1980-07-01
Some of the recent theoretical developments in relativistic (0.5 to 2.0-GeV/nucleon) nuclear collisions are reviewed. The statistical model, hydrodynamic model, classical equation of motion calculations, billiard ball dynamics, and intranuclear cascade models are discussed in detail. Inclusive proton and pion spectra are analyzed for a variety of reactions. Particular attention is focused on how the complex interplay of the basic reaction mechanism hinders attempts to deduce the nuclear matter equation of state from data. 102 references, 19 figures
International Nuclear Information System (INIS)
Merdeev, A. V.; Satarov, L. M.; Mishustin, I. N.
2011-01-01
We use (3 + 1) dimensional ideal hydrodynamics to describe the space-time evolution of strongly interacting matter created in Au + Au and Pb + Pb collisions. The model is applied for the domain of bombarding energies 1-160 GeV/nucleon which includes future NICA (Dubna) and FAIR (Darmstadt) experiments. Two equations of state are used, the first one corresponding to resonance hadron gas and the second one including the deconfinement phase transition. The initial state is represented by two Lorentz-boosted nuclei. Dynamic trajectories of matter in the central box of the system are analyzed. They can be well represented by a fast shock-wave compression followed by a relatively slow isentropic expansion. The parameters of collective flows and hadronic spectra are calculated under assumption of the isochronous freeze-out. It is shown that the deconfinement phase transition leads to broadening of proton rapidity distributions, increase of elliptic flows, and formation of the directed antiflow in the central rapidity region. These effects are most pronounced at bombarding energies around 10 GeV/nucleon, when the system spends the longest time in the mixed phase. From the comparison with three-fluid calculations we conclude that the transparency effects are not so important in central collisions at NICA-FAIR energies (below 30 GeV/nucleon).
Strangeness production in hadronic and nuclear collisions in the dual parton model
International Nuclear Information System (INIS)
Capella, A.; Tran Thanh Van, J.; Ranft, J.
1993-01-01
Λ, antiΛ and K s 0 production is studied in a Monte Carlo Dual Parton model for hadron-hadron, hadron-nucleus and nucleus-nucleus collisions with a SU(3) symmetric sea for chain formation (chain ends) but strangeness suppression in the chain fragmentation. Additionally, (qq)-(antiqantiq) production from the sea was introduced into the chain formation process with the same probability as for the q → qq branching within the chain decay process. This together with the popcorn mechanism of diquark fragmentation result in a new central component of hyperon production, which was not present in previous versions of the model. With these assumptions rapidity distributions and multiplicity ratios for strange particles in hadron-hadron, hadron-nucleus and nucleus-nucleus collisions are compared to a comprehensive collection of experimental data. 5 figs., 2 tabs., 15 refs
International Nuclear Information System (INIS)
Springer, H.K.; Miller, W.O.; Levatin, J.L.; Pertica, A.J.; Olivier, S.S.
2010-01-01
Satellite collision debris poses risks to existing space assets and future space missions. Predictive models of debris generated from these hypervelocity collisions are critical for developing accurate space situational awareness tools and effective mitigation strategies. Hypervelocity collisions involve complex phenomenon that spans several time- and length-scales. We have developed a satellite collision debris modeling approach consisting of a Lagrangian hydrocode enriched with smooth particle hydrodynamics (SPH), advanced material failure models, detailed satellite mesh models, and massively parallel computers. These computational studies enable us to investigate the influence of satellite center-of-mass (CM) overlap and orientation, relative velocity, and material composition on the size, velocity, and material type distributions of collision debris. We have applied our debris modeling capability to the recent Iridium 33-Cosmos 2251 collision event. While the relative velocity was well understood in this event, the degree of satellite CM overlap and orientation was ill-defined. In our simulations, we varied the collision CM overlap and orientation of the satellites from nearly maximum overlap to partial overlap on the outermost extents of the satellites (i.e, solar panels and gravity boom). As expected, we found that with increased satellite overlap, the overall debris cloud mass and momentum (transfer) increases, the average debris size decreases, and the debris velocity increases. The largest predicted debris can also provide insight into which satellite components were further removed from the impact location. A significant fraction of the momentum transfer is imparted to the smallest debris (< 1-5mm, dependent on mesh resolution), especially in large CM overlap simulations. While the inclusion of the smallest debris is critical to enforcing mass and momentum conservation in hydrocode simulations, there seems to be relatively little interest in their
Energy Technology Data Exchange (ETDEWEB)
Kumar, Rohit [Department of Physics, Panjab University, Chandigarh-160014 (India)
2016-05-06
We discuss the stability of fragments identified by secondary algorithms used to construct fragments within quantum molecular dynamics model. For this purpose we employ three different algorithms for fragment identification. 1) The conventional minimum spanning tree (MST) method based on the spatial correlations, 2) an improved version of MST with additional binding energy constraints of cold nuclear matter, 3) and that of hot matter. We find significant role of thermal binding energies over cold matter binding energies. Significant role is observed for fragment multiplicities and stopping of fragments. Whereas insignificant effect is observed on fragment’s flow.
Mass exchange and angular distribution in a dynamical treatment of heavy ion collisions
International Nuclear Information System (INIS)
Ngo, C.; Hofmann, H.
1977-01-01
One presents a first numerical computation of the absolute value of the double differential cross section as a function of mass asymmetry and detection angle including a dynamical coupling between relative motion and mass asymmetry. One applies it to the 63 Cu+ 197 Au experiment at two different energies. The equation of motion used is a Fokker-Planck equation for distribution function in classical phase space. The coefficients needed are those known from classical model calculations, besides a friction coefficient introduced for the mass asymmetry degree. Encouraging agreement between the calculated and experimental curves is found
On transient effects in violent nuclear collisions
International Nuclear Information System (INIS)
Suraud, E.; Belkacem, M.; Feng-Shou Zhang; Academia Sinica, Lanzhou, GS
1993-01-01
It is shown that the numerical simulations of the recently developed Boltzmann-Langevin model exhibit large dynamical fluctuations in momentum space during the early stages of heavy-ion collisions, which arise from an interplay between the nuclear meanfield and binary collisions. It is pointed out that this transient behaviour provides an initial seed for the development of density fluctuations, and could strongly influence the particle production cross-sections at subthreshold energies. (author) 13 refs.; 3 figs
Geometric branching model of high-energy hadron-hadron collisions
International Nuclear Information System (INIS)
Chen, W.
1988-01-01
A phenomenological model is proposed to describe collisions between hadrons at high energies. In the context of the eikonal formalism, the model consists of two components: soft and hard. The former only involves the production of particles with small transverse momenta; the latter is characterized by jet production. Geometrical scaling is taken as an essential input to describe the geometrical properties of hadrons as extended objects on the one hand, and on the other to define the soft component in both regions below and above the jet threshold. A stochastical Furry branching process is adopted as the mechanism of soft particle production, while the jet fragmentation and gluon initial-state bremsstrahlung are for the production of hadrons in hard collisions. Impact parameter and virtuality are smeared to describe the statistical averaging effects of hadron-hadron collisions. Many otherwise separated issues, ranging from elastic scattering to parton decay function, are connected together in the framework of this model. The descriptions of many prominent features of hadronic collisions are in good agreement with the observed experimental data at all available energies. Multiplicity distributions at all energies are discussed as a major issue in this paper. KNO scaling is achieved for energies within ISR range. The emergence of jets is found to be responsible not only for the violation of both geometrical scaling and KNO scaling, but also for the continuous broadening of the multiplicity distribution with ever increasing energy. It is also shown that the geometrical size of a hadron reaches an asymptote in the energy region of CERN-SppS. A Monte Carlo version of the model for soft production is constructed
Correlations in simple multi-string models of pp collisions at ISR energies
International Nuclear Information System (INIS)
Lugovoj, V.V.; Chudakov, V.M.
1989-01-01
Simple statistical simulation algorithms are suggested for formation and breaking of a few quark-gluon strings in inelastic pp collisions. Theoretical multiplicity distributions, semi-inclusive quasirapidity spectra, forward-backward correlations of charged secondaries and seagull effect agree well with the experimental data at ISR energies. In the framework of the model, the semi-inclusive two-particle correlations of quasirapidities depend upon the fraction of the spherical chains. The seagull effect is qualitatively interpretated
Simple quantal model for collision-induced dissociation: An Airy basis calculation
International Nuclear Information System (INIS)
Hunt, P.M.; Sridharan, S.
1982-01-01
New matrix elements for the Airy continuum basis are employed to find quantum mechanical dissociation probabilities for the the forced Morse oscillator. The calculations performed illustrate the ease with which the continuously infinite Airy basis can be manipulated, and they illustrate the transition from vibrational enhancement to vibrational inhibition of diatomic breakup. The forced Morse oscillator model thus reproduces the behavior of more complicated collinear collision-induced dissociation systems
International Nuclear Information System (INIS)
Evans, G.T.
1987-01-01
The differential orientational cross section, obtainable from molecular beam experiments on aligned molecules, is calculated using the line-of-normals model for reactive collisions involving hard convex bodies. By means of kinetic theory methods, the dependence of the cross section on the angle of attack γ 0 is expressed in a Legendre function expansion. Each of the Legendre expansion coefficients is given by an integral over the molecule-fixed cross section and functions of the orientation dependent threshold energy
International Nuclear Information System (INIS)
Gao Chongshou; Wang Chengshing
1993-01-01
A macroscopic damping model is proposed to calculate the zero degree energy distribution in ultra-relativistic heavy ion collisions. The main features of the measured distributions are reproduced, good agreement is obtained in the middle energy region while overestimation results on the high energy side. The average energy loss coefficient of incident nucleons, varying in the reasonable region 0.2-0.6, depends on beam energy and target size
Sazhin, Sergei S.; Xie, Jianfei; Shishkova, Irina N.; Elwardani, Ahmed Elsaid; Heikal, Morgan Raymond
2013-01-01
The previously developed kinetic model for droplet heating and evaporation into a high pressure air is generalised to take into account the combined effects of inelastic collisions between molecules in the kinetic region, a non-unity evaporation
Pradhan, Aniruddhe; Akhavan, Rayhaneh
2017-11-01
Effect of collision model, subgrid-scale model and grid resolution in Large Eddy Simulation (LES) of wall-bounded turbulent flows with the Lattice Boltzmann Method (LBM) is investigated in turbulent channel flow. The Single Relaxation Time (SRT) collision model is found to be more accurate than Multi-Relaxation Time (MRT) collision model in well-resolved LES. Accurate LES requires grid resolutions of Δ+ LBM requires either grid-embedding in the near-wall region, with grid resolutions comparable to DNS, or a wall model. Results of LES with grid-embedding and wall models will be discussed.
Full-dimensional quantum dynamics of CO in collision with H{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Yang, Benhui; Stancil, P. C. [Department of Physics and Astronomy and the Center for Simulational Physics, The University of Georgia, Athens, Georgia 30602 (United States); Balakrishnan, N. [Department of Chemistry, University of Nevada, Las Vegas, Nevada 89154 (United States); Zhang, P. [Department of Chemistry, Duke University, Durham, North Carolina 27708 (United States); Wang, X.; Bowman, J. M. [Department of Chemistry, Emory University, Atlanta, Georgia 30322 (United States); Forrey, R. C. [Department of Physics, Penn State University, Berks Campus, Reading, Pennsylvania 19610 (United States)
2016-07-21
Inelastic scattering computations are presented for collisions of vibrationally and rotationally excited CO with H{sub 2} in full dimension. The computations utilize a newly developed six-dimensional potential energy surface (PES) and the previously reported four-dimensional V12 PES [P. Jankowski et al., J. Chem. Phys. 138, 084307 (2013)] and incorporate full angular-momentum coupling. At low collision energies, pure rotational excitation cross sections of CO by para-, ortho-, and normal-H{sub 2} are calculated and convolved to compare with recent measurements. Good agreement with the measured data is shown except for j{sub 1} = 0 → 1 excitation of CO for very low-energy para-H{sub 2} collisions. Rovibrational quenching results are presented for initially excited CO(v{sub 1}j{sub 1}) levels with v{sub 1} = 1, j{sub 1} = 1–5 and v{sub 1} = 2, j{sub 1} = 0 for collisions with para-H{sub 2} (v{sub 2} = 0, j{sub 2} = 0) and ortho-H{sub 2} (v{sub 2} = 0, j{sub 2} = 1) over the kinetic energy range 0.1–1000 cm{sup −1}. The total quenching cross sections are found to have similar magnitudes, but increase (decrease) with j{sub 1} for collision energies above ∼300 cm{sup −1} (below ∼10 cm{sup −1}). Only minor differences are found between para- and ortho-H{sub 2} colliders for rovibrational and pure rotational transitions, except at very low collision energies. Likewise, pure rotational deexcitation of CO yields similar cross sections for the v{sub 1} = 0 and v{sub 1} = 1 vibrational levels, while rovibrational quenching from v{sub 1} = 2, j{sub 1} = 0 is a factor of ∼5 larger than that from v{sub 1} = 1, j{sub 1} = 0. Details on the PES, computed at the CCSD(T)/aug-cc-pV5Z level, and fitted with an invariant polynomial method, are also presented.
Characterizing and Modeling Citation Dynamics
Eom, Young-Ho; Fortunato, Santo
2011-01-01
Citation distributions are crucial for the analysis and modeling of the activity of scientists. We investigated bibliometric data of papers published in journals of the American Physical Society, searching for the type of function which best describes the observed citation distributions. We used the goodness of fit with Kolmogorov-Smirnov statistics for three classes of functions: log-normal, simple power law and shifted power law. The shifted power law turns out to be the most reliable hypothesis for all citation networks we derived, which correspond to different time spans. We find that citation dynamics is characterized by bursts, usually occurring within a few years since publication of a paper, and the burst size spans several orders of magnitude. We also investigated the microscopic mechanisms for the evolution of citation networks, by proposing a linear preferential attachment with time dependent initial attractiveness. The model successfully reproduces the empirical citation distributions and accounts for the presence of citation bursts as well. PMID:21966387
MATHEMATICAL MODEL FOR RIVERBOAT DYNAMICS
Directory of Open Access Journals (Sweden)
Aleksander Grm
2017-01-01
Full Text Available Present work describes a simple dynamical model for riverboat motion based on the square drag law. Air and water interactions with the boat are determined from aerodynamic coefficients. CFX simulations were performed with fully developed turbulent flow to determine boat aerodynamic coefficients for an arbitrary angle of attack for the air and water portions separately. The effect of wave resistance is negligible compared to other forces. Boat movement analysis considers only two-dimensional motion, therefore only six aerodynamics coefficients are required. The proposed model is solved and used to determine the critical environmental parameters (wind and current under which river navigation can be conducted safely. Boat simulator was tested in a single area on the Ljubljanica river and estimated critical wind velocity.
Energy Technology Data Exchange (ETDEWEB)
Cipiti, Benjamin B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2017-03-01
The Co-Decontamination (CoDCon) Demonstration project is designed to test the separation of a mixed U and Pu product from dissolved spent nuclear fuel. The primary purpose of the project is to quantify the accuracy and precision to which a U/Pu mass ratio can be achieved without removing a pure Pu product. The system includes an on-line monitoring system using spectroscopy to monitor the ratios throughout the process. A dynamic model of the CoDCon flowsheet and on-line monitoring system was developed in order to expand the range of scenarios that can be examined for process control and determine overall measurement uncertainty. The model development and initial results are presented here.
Modeling the dynamics of choice.
Baum, William M; Davison, Michael
2009-06-01
A simple linear-operator model both describes and predicts the dynamics of choice that may underlie the matching relation. We measured inter-food choice within components of a schedule that presented seven different pairs of concurrent variable-interval schedules for 12 food deliveries each with no signals indicating which pair was in force. This measure of local choice was accurately described and predicted as obtained reinforcer sequences shifted it to favor one alternative or the other. The effect of a changeover delay was reflected in one parameter, the asymptote, whereas the effect of a difference in overall rate of food delivery was reflected in the other parameter, rate of approach to the asymptote. The model takes choice as a primary dependent variable, not derived by comparison between alternatives-an approach that agrees with the molar view of behaviour.
Dynamical modeling of tidal streams
International Nuclear Information System (INIS)
Bovy, Jo
2014-01-01
I present a new framework for modeling the dynamics of tidal streams. The framework consists of simple models for the initial action-angle distribution of tidal debris, which can be straightforwardly evolved forward in time. Taking advantage of the essentially one-dimensional nature of tidal streams, the transformation to position-velocity coordinates can be linearized and interpolated near a small number of points along the stream, thus allowing for efficient computations of a stream's properties in observable quantities. I illustrate how to calculate the stream's average location (its 'track') in different coordinate systems, how to quickly estimate the dispersion around its track, and how to draw mock stream data. As a generative model, this framework allows one to compute the full probability distribution function and marginalize over or condition it on certain phase-space dimensions as well as convolve it with observational uncertainties. This will be instrumental in proper data analysis of stream data. In addition to providing a computationally efficient practical tool for modeling the dynamics of tidal streams, the action-angle nature of the framework helps elucidate how the observed width of the stream relates to the velocity dispersion or mass of the progenitor, and how the progenitors of 'orphan' streams could be located. The practical usefulness of the proposed framework crucially depends on the ability to calculate action-angle variables for any orbit in any gravitational potential. A novel method for calculating actions, frequencies, and angles in any static potential using a single orbit integration is described in the Appendix.
Adiabatic analysis of collisions. III. Remarks on the spin model
International Nuclear Information System (INIS)
Fano, U.
1979-01-01
Analysis of a spin-rotation model illustrates how transitions between adiabatic channel states stem from the second, rather than from the first, rate of change of these states, provided that appropriate identification of channels and scaling of the independent variable are used. These remarks, like the earlier development of a post-adiabatic approach, aim at elucidating the surprising success of approximate separation of variables in the treatment of complex mechanical systems
Nonequilibrium models of relativistic heavy-ion collisions
International Nuclear Information System (INIS)
Stoecker, H; Bratkovskaya, E L; Bleicher, M; Soff, S; Zhu, X
2005-01-01
We review the results from the various hydrodynamical and transport models on the collective flow observables from AGS to RHIC energies. A critical discussion of the present status of the CERN experiments on hadron collective flow is given. We emphasize the importance of the flow excitation function from 1 to 50 A GeV: here the hydrodynamic model has predicted the collapse of the v 1 -flow and of the v 2 -flow at ∼10 A GeV; at 40 A GeV it has been recently observed by the NA49 collaboration. Since hadronic rescattering models predict much larger flow than observed at this energy we interpret this observation as evidence for a first-order phase transition at high baryon density ρ B . Moreover, the connection of the elliptic flow v 2 to jet suppression is examined. It is proven experimentally that the collective flow is not faked by minijet fragmentation. Additionally, detailed transport studies show that the away-side jet suppression can only partially ( 1 , v 2 closer to beam rapidity is related to the occurrence of a high density first order phase transition in the RHIC data at 62.5, 130 and 200 A GeV
International Nuclear Information System (INIS)
Singh, Vishal; Modi, Swati; Arumugam, P.
2017-01-01
Recent advancements in accelerator technology and polarized beams have created opportunities to study oriented collisions of deformed targets. We extend the Glauber model to calculate the interaction cross section for a spherical projectile and a deformed target at different orientation angles of the target. It has been found that the observed reaction cross sections of various systems at high energies can be reproduced with this model. We have used the relativistic mean field (RMF) theory to find the density distribution of nucleons in the projectile and target which are utilised in the Glauber model. We present the variation of interaction cross section of target and projectile with the orientation of deformed target
A phenomenological model of deep-inelastic collisions between complex nuclei
International Nuclear Information System (INIS)
Siwek-Wilczynska, K.; Wilczynski, J.
1976-01-01
A simple model of heavy-ion collisions is proposed. Classical equations of motion with inclusion of a phenomenological two-body friction force are integrated numerically along trajectories. The nucleus-nucleus interaction potential which is used in the calculations includes deformation degrees of freedom in the exit channel. Both entrance and exit-channel potentials are based on the boundary conditions following the liquid-drop model. The existing data on fusion cross sections, and also the energy-angle distributions of deep-inelastic reactions are very well reproduced by the model. (author)
Non-Abellian field dynamics in the early stage of ultrarelativistic nuclear collisions
International Nuclear Information System (INIS)
Rischke, D.H.
1997-01-01
It was argued that the gluon field of a large, ultrarelativistic nucleus can be considered as a classical field for small values of the longitudinal momentum fraction x and on transverse momentum scales Λ 2 QCD 2 perpendicular 2 , where μ 2 is the transverse area density of color charges. The authors estimated μ ∼ 0.4 GeV for collisions of Au-nuclei at RHIC energies. Based on this argument, the gluon field produced in a collision of two ultrarelativistic nuclei is computed perturbatively by solving the classical Yang-Mills equations order by order in the strong coupling constant g. It is shown that to first order in g, the spectrum of produced gluons is identical to that obtained in a perturbative quantum calculation of gluon Bremsstrahlung. It is also identical with that of a coherent quantum state generated by independent collisions between the (classical) color charges in the two nuclei. The perturbative solution is unstable under perturbations. The instabilities arise from the non-Abelian terms in the equations of motion for the gluon field, which enter only at higher order in the perturbative solution scheme. The decay rate of the perturbative solution is shown to be of order μ. Since the non-Abelian terms describe the self-interaction of the produced gluon field, and since such interactions lead to thermalization, the decay rate provides an estimate for the thermalization time scale of classical color fields in ultrarelativistic nuclear collisions. For Au-nuclei, this time scale is therefore of order 0.5 fm/c, in agreement with results for the kinetic thermalization time scale
Non-Abellian field dynamics in the early stage of ultrarelativistic nuclear collisions
Energy Technology Data Exchange (ETDEWEB)
Rischke, D.H. [Brookhaven National Lab., Upton, NY (United States)
1997-09-22
It was argued that the gluon field of a large, ultrarelativistic nucleus can be considered as a classical field for small values of the longitudinal momentum fraction x and on transverse momentum scales {Lambda}{sup 2}{sub QCD} << k{sup 2}{perpendicular} << {mu}{sup 2}, where {mu}{sup 2} is the transverse area density of color charges. The authors estimated {mu} {approx} 0.4 GeV for collisions of Au-nuclei at RHIC energies. Based on this argument, the gluon field produced in a collision of two ultrarelativistic nuclei is computed perturbatively by solving the classical Yang-Mills equations order by order in the strong coupling constant g. It is shown that to first order in g, the spectrum of produced gluons is identical to that obtained in a perturbative quantum calculation of gluon Bremsstrahlung. It is also identical with that of a coherent quantum state generated by independent collisions between the (classical) color charges in the two nuclei. The perturbative solution is unstable under perturbations. The instabilities arise from the non-Abelian terms in the equations of motion for the gluon field, which enter only at higher order in the perturbative solution scheme. The decay rate of the perturbative solution is shown to be of order {mu}. Since the non-Abelian terms describe the self-interaction of the produced gluon field, and since such interactions lead to thermalization, the decay rate provides an estimate for the thermalization time scale of classical color fields in ultrarelativistic nuclear collisions. For Au-nuclei, this time scale is therefore of order 0.5 fm/c, in agreement with results for the kinetic thermalization time scale.
Multichannel approach to the Glauber model for heavy-ion collisions
International Nuclear Information System (INIS)
Lenzi, S.M.; Zardi, F.; Vitturi, A.
1990-01-01
A formalism is developed in order to describe, within the Glauber model, the scattering processes between heavy ions in situations involving several coupled channels. The approach is based on a suitable truncation of the number of nuclear states which can be excited at each microscopic nucleon-nucleon collision. The set of coupled equations for the S-matrix elements of the conventional reaction theory is replaced by simple matrix relations, only involving the nucleon-nucleon scattering amplitude and the nuclear densities and transition densities. This method avoids the difficulties arising from the combinatorial aspects of the multiple scattering theories, the slow convergence of the series, and the problems of center-of-mass correlations. We discuss some specific examples of multichannel collisions where the multiple-scattering series can be summed to give analytic expressions for the scattering amplitude. We finally explicate the formalism for the perturbative treatment of mutual excitation and charge-exchange processes
Studying the collision energy dependence of elliptic and triangular flow with a hybrid model
Energy Technology Data Exchange (ETDEWEB)
Auvinen, Jussi [Frankfurt Institute for Advanced Studies, Frankfurt am Main (Germany); Petersen, Hannah [Frankfurt Institute for Advanced Studies, Frankfurt am Main (Germany); Institut fuer Theoretische Physik, Goethe Universitaet, Frankfurt am Main (Germany)
2014-07-01
Elliptic flow has been one of the key observables for establishing the finding of the quark-gluon plasma (QGP) at the highest energies of Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). As a sign of collectively behaving matter, the elliptic flow is expected to decrease at lower beam energies, where the QGP is not produced. However, in the recent RHIC beam energy scan, it has been found that the inclusive charged hadron elliptic flow changes relatively little in magnitude within the energy range 7.7-39 GeV per nucleon-nucleon collision. We study the collision energy dependence of the elliptic and triangular flow utilizing a Boltzmann+hydrodynamics hybrid model. Such a hybrid model provides a natural framework for the transition from high collision energies, where the hydrodynamical description is essential, to smaller energies, where the hadron transport dominates. This approach is thus suitable for investigating the relative importance of these two mechanisms for the production of the collective flow at different beam energies.
A particle-in-cell method for modeling small angle Coulomb collisions in plasmas
International Nuclear Information System (INIS)
Parker, S.E.
1989-01-01
We propose a computational method to self-consistently model small angle collisional effects. This method may be added to standard Particle-In-Cell (PIC) plasma simulations to include collisions, or as an alternative to solving the Fokker-Planck (FP) equation using finite difference methods. The distribution function is represented by a large number of particles. The particle velocities change due to the drag force, and the diffusion in velocity is represented by a random process. This is similar to previous Monte-Carlo methods except we calculate the drag force and diffusion tensor self- consistently. The particles are weighted to a grid in velocity space and associated ''Poisson equations'' are solved for the Rosenbluth potentials. The motivation is to avoid the very time consuming method of Coulomb scattering pair by pair. First the approximation for small angle Coulomb collisions is discussed. Next, the FP-PIC collision method is outlined. Then we show a test of the particle advance modeling an electron beam scattering off a fixed ion background. 4 refs
The Mathematical Model High Energy Collisions Process Hadron-Nucleus
International Nuclear Information System (INIS)
Wojciechowski, A.; Strugalska-Gola, E.; Strugalski, Z.
2002-01-01
During the passage high energy hadron by the heavy nucleus emitted are nucleons and many other particles from which most more group are nucleons and mesons π + π - π 0 . in this work we will present the mathematical model which is a simplified description of basic processes in the interior of the nucleus during passing of the hadron by the nucleus. Result of calculations we will compare with experimental results. Experimental data are based on photographs of 180 litre xenon bubble chambers (180 1 KKP) of Institute of Theoretical and Experimental Physics in Moscow (ITEF, Moscow) irradiated with the beam of mesons π - with momentum 3.5 GeV/c. (author)
Many-electron model for multiple ionization in atomic collisions
International Nuclear Information System (INIS)
Archubi, C D; Montanari, C C; Miraglia, J E
2007-01-01
We have developed a many-electron model for multiple ionization of heavy atoms bombarded by bare ions. It is based on the transport equation for an ion in an inhomogeneous electronic density. Ionization probabilities are obtained by employing the shell-to-shell local plasma approximation with the Levine and Louie dielectric function to take into account the binding energy of each shell. Post-collisional contributions due to Auger-like processes are taken into account by employing recent photoemission data. Results for single-to-quadruple ionization of Ne, Ar, Kr and Xe by protons are presented showing a very good agreement with experimental data
Many-electron model for multiple ionization in atomic collisions
Energy Technology Data Exchange (ETDEWEB)
Archubi, C D [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina); Montanari, C C [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina); Miraglia, J E [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina)
2007-03-14
We have developed a many-electron model for multiple ionization of heavy atoms bombarded by bare ions. It is based on the transport equation for an ion in an inhomogeneous electronic density. Ionization probabilities are obtained by employing the shell-to-shell local plasma approximation with the Levine and Louie dielectric function to take into account the binding energy of each shell. Post-collisional contributions due to Auger-like processes are taken into account by employing recent photoemission data. Results for single-to-quadruple ionization of Ne, Ar, Kr and Xe by protons are presented showing a very good agreement with experimental data.
Accurate Treatment of Collisions and Water-Delivery in Models of Terrestrial Planet Formation
Haghighipour, Nader; Maindl, Thomas; Schaefer, Christoph
2017-10-01
It is widely accepted that collisions among solid bodies, ignited by their interactions with planetary embryos is the key process in the formation of terrestrial planets and transport of volatiles and chemical compounds to their accretion zones. Unfortunately, due to computational complexities, these collisions are often treated in a rudimentary way. Impacts are considered to be perfectly inelastic and volatiles are considered to be fully transferred from one object to the other. This perfect-merging assumption has profound effects on the mass and composition of final planetary bodies as it grossly overestimates the masses of these objects and the amounts of volatiles and chemical elements transferred to them. It also entirely neglects collisional-loss of volatiles (e.g., water) and draws an unrealistic connection between these properties and the chemical structure of the protoplanetary disk (i.e., the location of their original carriers). We have developed a new and comprehensive methodology to simulate growth of embryos to planetary bodies where we use a combination of SPH and N-body codes to accurately model collisions as well as the transport/transfer of chemical compounds. Our methodology accounts for the loss of volatiles (e.g., ice sublimation) during the orbital evolution of their careers and accurately tracks their transfer from one body to another. Results of our simulations show that traditional N-body modeling of terrestrial planet formation overestimates the amount of the mass and water contents of the final planets by over 60% implying that not only the amount of water they suggest is far from being realistic, small planets such as Mars can also form in these simulations when collisions are treated properly. We will present details of our methodology and discuss its implications for terrestrial planet formation and water delivery to Earth.
System Dynamics Modelling for a Balanced Scorecard
DEFF Research Database (Denmark)
Nielsen, Steen; Nielsen, Erland Hejn
2008-01-01
/methodology/approach - We use a case study model to develop time or dynamic dimensions by using a System Dynamics modelling (SDM) approach. The model includes five perspectives and a number of financial and non-financial measures. All indicators are defined and related to a coherent number of different cause...... have a major influence on other indicators and profit and may be impossible to predict without using a dynamic model. Practical implications - The model may be used as the first step in quantifying the cause-and-effect relationships of an integrated BSC model. Using the System Dynamics model provides......Purpose - To construct a dynamic model/framework inspired by a case study based on an international company. As described by the theory, one of the main difficulties of BSC is to foresee the time lag dimension of different types of indicators and their combined dynamic effects. Design...
Quistberg, D Alex; Howard, Eric J; Ebel, Beth E; Moudon, Anne V; Saelens, Brian E; Hurvitz, Philip M; Curtin, James E; Rivara, Frederick P
2015-11-01
Walking is a popular form of physical activity associated with clear health benefits. Promoting safe walking for pedestrians requires evaluating the risk of pedestrian-motor vehicle collisions at specific roadway locations in order to identify where road improvements and other interventions may be needed. The objective of this analysis was to estimate the risk of pedestrian collisions at intersections and mid-blocks in Seattle, WA. The study used 2007-2013 pedestrian-motor vehicle collision data from police reports and detailed characteristics of the microenvironment and macroenvironment at intersection and mid-block locations. The primary outcome was the number of pedestrian-motor vehicle collisions over time at each location (incident rate ratio [IRR] and 95% confidence interval [95% CI]). Multilevel mixed effects Poisson models accounted for correlation within and between locations and census blocks over time. Analysis accounted for pedestrian and vehicle activity (e.g., residential density and road classification). In the final multivariable model, intersections with 4 segments or 5 or more segments had higher pedestrian collision rates compared to mid-blocks. Non-residential roads had significantly higher rates than residential roads, with principal arterials having the highest collision rate. The pedestrian collision rate was higher by 9% per 10 feet of street width. Locations with traffic signals had twice the collision rate of locations without a signal and those with marked crosswalks also had a higher rate. Locations with a marked crosswalk also had higher risk of collision. Locations with a one-way road or those with signs encouraging motorists to cede the right-of-way to pedestrians had fewer pedestrian collisions. Collision rates were higher in locations that encourage greater pedestrian activity (more bus use, more fast food restaurants, higher employment, residential, and population densities). Locations with higher intersection density had a lower
Heavy ion collision dynamics of 10,11B+10,11B reactions
Directory of Open Access Journals (Sweden)
Singh BirBikram
2015-01-01
Full Text Available The dynamical cluster-decay model (DCM of Gupta and collaborators has been applied successfully to the decay of very-light (A ∼ 30, light (A ∼ 40−80, medium, heavy and super-heavy mass compound nuclei for their decay to light particles (evaporation residues, ER, fusion-fission (ff, and quasi-fission (qf depending on the reaction conditions. We intend to extend here the application of DCM to study the extreme case of decay of very-light nuclear systems 20,21,22Ne∗ formed in 10,11B+10,11B reactions, for which experimental data is available for their binary symmetric decay (BSD cross sections, i.e., σBSD. For the systems under study, the calculations are presented for the σBSD in terms of their preformation and barrier penetration probabilities P0 and P. Interesting results are that in the decay of such lighter systems there is a competing reaction mechanism (specifically, the deep inelastic orbiting of non-compound nucleus (nCN origin together with ff. We have emipirically estimated the contribution of σnCN. Moreover, the important role of nuclear structure characteristics via P0 as well as angular momentum ℓ in the reaction dynamics are explored in the study.
Heavy ion collisions at intermediate energy
International Nuclear Information System (INIS)
Bertsch, G.; Amsden, A.A.
1978-01-01
Two types of measurement are proposed for the analysis of heavy ion collisions in the range of energy of 20--200 MeV/A. First, measurement of the longitudinal component of the kinetic energy of the collision products characterizes the impact parameter of the collision. The distribution in this quantity allows the dissipation in the theoretical models to be determined. A second kind of measurement is that of the coefficients of a spherical harmonic expansion of the angular distribution of the products. Besides giving independent information on the impact parameter and reaction dynamics, measurement of these coefficients offers the possibility of measuring the stiffness of the equation of state of nuclear matter. These ideas are explored in the context of a hydrodynamic model for the collision. In the purely hydrodynamic model there is a large measurable asymmetry in the angular distribution, but the dependence on the equation of state is small
Directory of Open Access Journals (Sweden)
S Hadji
2008-09-01
Full Text Available This study deals with the simulation of transport and interaction betweenbodies considered as a rectangular shape particles, in urban flow. We usedan hydrodynamic two-dimensional finite elements model coupled to theparticles model based on Maxey-Riley equations, and taking into accountof contact between bodies. The finite element discretization is based onthe velocity field richer than pressure field, and the particles displacementsare computed by using a rigid body motion method. A collision strategy isalso developed to handle cases in which bodies touch.
New space--time model for hadron--nucleus collisions at high energies
International Nuclear Information System (INIS)
Bialkowski, G.; Chiu, C.B.; Tow, D.M.
1976-12-01
A new space-time model for hadron-nucleus collisions is proposed, where particles at the instant of creation are immature and their maturity rate is enhanced in the presence of other hadronic matter, as in a nucleus. With only one free parameter, the model can explain dn/sub A//sup p//d eta, dn/sub A//sup pi//d eta, R/sub A//sup p/(E/sub L/), and the A-dependences of sigma/sub in/sup pA/ and sigma/sub in/sup pi A/
International Nuclear Information System (INIS)
Kunz, J.
1982-01-01
In this thesis the classical model is extended in order to regard the inelastic processes important in the heavy ion collisions of the considered energy range. For this a classical pion field was coupled to the nucleons via the pseudo-scalar #betta# 5 -interactions. Nucleon and pion fields were treated in a completely relativistic way. The equations of motion were analytically studied for the one-nucleon system. From the statical solution the bare mass of the nucleon was determined, and its dependence on both parameters of this modell, the coupling constant and the cut-off momentum of the form factor, was considered. (orig./HSI) [de
Transport theory for deeply inelastic heavy-ion collisions within the statistical model
International Nuclear Information System (INIS)
Shlomo, S.
1978-01-01
The theory I am going to describe has been developed recently by Agassi, Ko and Weidenmueller. It is based on a random-matrix model for the form factor (FF) which couples a collective degree of freedom, taken to be the distance anti r between the two ions, with the intrinsic degrees of freedom. This study of dissipative phenomena in a microsystem was triggered by the success of the simple friction and diffusion models in describing experimental data on deeply inelastic collisions. I plan to describe the underlying physical assumptions, to outline the theoretical developments and to show some very recent results. (orig.) [de
International Nuclear Information System (INIS)
Shin, Seung Ki; Seong, Poong Hyun
2008-01-01
Conventional static reliability analysis methods are inadequate for modeling dynamic interactions between components of a system. Various techniques such as dynamic fault tree, dynamic Bayesian networks, and dynamic reliability block diagrams have been proposed for modeling dynamic systems based on improvement of the conventional modeling methods. In this paper, we review these methods briefly and introduce dynamic nodes to the existing Reliability Graph with General Gates (RGGG) as an intuitive modeling method to model dynamic systems. For a quantitative analysis, we use a discrete-time method to convert an RGGG to an equivalent Bayesian network and develop a software tool for generation of probability tables
E917 experiment: Probing the dynamics of HI collisions + searching for the QGP
International Nuclear Information System (INIS)
Ogilvie, C.A.
1996-01-01
Experiment E917 has two main goals: to understand and probe the detailed mechanism of hadronic rescattering in HI collisions and to systematically search for a small volume of QGP. Correlated, discrete changes in sensitive QGP signatures as a function of both centrality and beam energy could indicate the presence of new physics. A precursor to the QGP is the possible change of hadronic properties in a dense medium. We will measure the φ and K * effective mass as a function of centrality to search for any change in the width or mass of these particles
Characterizing and modeling citation dynamics.
Directory of Open Access Journals (Sweden)
Young-Ho Eom
Full Text Available Citation distributions are crucial for the analysis and modeling of the activity of scientists. We investigated bibliometric data of papers published in journals of the American Physical Society, searching for the type of function which best describes the observed citation distributions. We used the goodness of fit with Kolmogorov-Smirnov statistics for three classes of functions: log-normal, simple power law and shifted power law. The shifted power law turns out to be the most reliable hypothesis for all citation networks we derived, which correspond to different time spans. We find that citation dynamics is characterized by bursts, usually occurring within a few years since publication of a paper, and the burst size spans several orders of magnitude. We also investigated the microscopic mechanisms for the evolution of citation networks, by proposing a linear preferential attachment with time dependent initial attractiveness. The model successfully reproduces the empirical citation distributions and accounts for the presence of citation bursts as well.
Supply based on demand dynamical model
Levi, Asaf; Sabuco, Juan; Sanjuán, Miguel A. F.
2018-04-01
We propose and numerically analyze a simple dynamical model that describes the firm behaviors under uncertainty of demand. Iterating this simple model and varying some parameter values, we observe a wide variety of market dynamics such as equilibria, periodic, and chaotic behaviors. Interestingly, the model is also able to reproduce market collapses.
Opinion dynamics model based on quantum formalism
Energy Technology Data Exchange (ETDEWEB)
Artawan, I. Nengah, E-mail: nengahartawan@gmail.com [Theoretical Physics Division, Department of Physics, Udayana University (Indonesia); Trisnawati, N. L. P., E-mail: nlptrisnawati@gmail.com [Biophysics, Department of Physics, Udayana University (Indonesia)
2016-03-11
Opinion dynamics model based on quantum formalism is proposed. The core of the quantum formalism is on the half spin dynamics system. In this research the implicit time evolution operators are derived. The analogy between the model with Deffuant dan Sznajd models is discussed.
Eichelberger, Angela H; McCartt, Anne T
2016-02-01
Advanced crash avoidance and driver assistance technologies potentially can prevent or mitigate many crashes. Previous surveys with drivers have found favorable opinions for many advanced technologies; however, these surveys are not necessarily representative of all drivers or all systems. As the technologies spread throughout the vehicle fleet, it is important to continue studying driver acceptance and use of them. This study focused on 2010-2013 Toyota Sienna and Prius models that were equipped with adaptive cruise control, forward collision avoidance, and lane departure warning and prevention (Prius models only). Telephone interviews were conducted in summer 2013 with 183 owners of vehicles with these technologies. About 9 in 10 respondents wanted adaptive cruise control and forward collision avoidance on their next vehicle, and 71% wanted lane departure warning/prevention again. Males and females reported some differences in their experiences with the systems; for example, males were more likely to have turned on lane departure warning/prevention than females, and when using this system, males reported more frequent warnings than did females. Relative to older drivers, drivers age 40 and younger were more likely to have seen or heard a forward collision warning. Consistent with the results in previous surveys of owners of luxury vehicles, the present survey found that driver acceptance of the technologies was high, although less so for lane departure warning/prevention. Experiences with the Toyota systems differed by driver age and gender to a greater degree than in previous surveys, suggesting that the responses of drivers may begin to differ as crash avoidance technology becomes available on a wider variety of vehicles. Crash avoidance technologies potentially can prevent or mitigate many crashes, but their success depends in part on driver acceptance. These systems will be effective only to the extent that drivers use them. Copyright © 2015 Elsevier Ltd and
Relating structure and dynamics in organisation models
Jonker, C.M.; Treur, J.
2003-01-01
To understand how an organisational structure relates to dynamics is an interesting fundamental challenge in the area of social modelling. Specifications of organisational structure usually have a diagrammatic form that abstracts from more detailed dynamics. Dynamic properties of agent systems, on
Directory of Open Access Journals (Sweden)
Wanginingastuti Mutmainnah
2016-07-01
Full Text Available 4M Overturned Pyramid (MOP model is a new model, proposed by authors, to characterized MTS which is adopting epidemiological model that determines causes of accidents, including not only active failures but also latent failures and barriers. This model is still being developed. One of utilization of MOP model is characterizing accidents in MTS, i.e. collision in Indonesia and Japan that is written in this paper. The aim of this paper is to show the characteristics of ship collision accidents that occur both in Indonesian and Japanese maritime traffic systems. There were 22 collision cases in 2008–2012 (8 cases in Indonesia and 14 cases in Japan. The characteristics presented in this paper show failure events at every stage of the three accident development stages (the beginning of an accident, the accident itself, and the evacuation process.
Diffusion model analyses of the experimental data of 12C+27Al, 40Ca dissipative collisions
International Nuclear Information System (INIS)
SHEN Wen-qing; QIAO Wei-min; ZHU Yong-tai; ZHAN Wen-long
1985-01-01
Assuming that the intermediate system decays with a statistical lifetime, the general behavior of the threefold differential cross section d 3 tau/dZdEdtheta in the dissipative collisions of 68 MeV 12 C+ 27 Al and 68.6 MeV 12 C+ 40 Ca system is analyzed in the diffusion model framework. The lifetime of the intermediate system and the separation distance for the completely damped deep-inelastic component are obtained. The calculated results and the experimental data of the angular distributions and Wilczynski plots are compared. The probable reasons for the differences between them are briefly discussed
International Nuclear Information System (INIS)
Lehaut, G.
2009-10-01
The properties of the fragments produced in heavy-ion collisions around the Fermi energy have been studied through the isospin degree of freedom. First, a theoretical approach based on a lattice gas model with two types of particles (neutron,proton) interacting by an isospin dependent and Coulomb interactions was developed. The study of the phase diagram shows that this system presents three different phases (liquid, gas, fission). In the liquid and gas phases, the energy of the system was described by a density functional, where the temperature dependence acts only on the density. The symmetry term of this functional was related to the isotopic content of the biggest fragment via an iso-scaling analysis. Secondly a systematic study of the stopping power of the nuclear matter and isospin equilibration of light particles in the most violent collisions was carried out using the experimental data taken by the INDRA multidetector at GANIL and GSI. Two stopping power regimes appear; at low energy (< 40 MeV/A) the stopping power decreases with increasing beam energy, whereas at high energy the stopping power is governed by the quantity of matter along the beam direction. An other study has been focused on the Xe+Sn reaction at 32 and 45 MeV/A with different isospin systems. The separation of three different reaction mechanisms by use of a principal component analysis allowed us to observe that the isospin content of light particles seems to be independent on the mechanism, but depends on the violence of the collision (i.e. impact parameter). (author)
An evaluation of collision models in the Method of Moments for rarefied gas problems
Emerson, David; Gu, Xiao-Jun
2014-11-01
The Method of Moments offers an attractive approach for solving gaseous transport problems that are beyond the limit of validity of the Navier-Stokes-Fourier equations. Recent work has demonstrated the capability of the regularized 13 and 26 moment equations for solving problems when the Knudsen number, Kn (where Kn is the ratio of the mean free path of a gas to a typical length scale of interest), is in the range 0.1 and 1.0-the so-called transition regime. In comparison to numerical solutions of the Boltzmann equation, the Method of Moments has captured both qualitatively, and quantitatively, results of classical test problems in kinetic theory, e.g. velocity slip in Kramers' problem, temperature jump in Knudsen layers, the Knudsen minimum etc. However, most of these results have been obtained for Maxwell molecules, where molecules repel each other according to an inverse fifth-power rule. Recent work has incorporated more traditional collision models such as BGK, S-model, and ES-BGK, the latter being important for thermal problems where the Prandtl number can vary. We are currently investigating the impact of these collision models on fundamental low-speed problems of particular interest to micro-scale flows that will be discussed and evaluated in the presentation. Engineering and Physical Sciences Research Council under Grant EP/I011927/1 and CCP12.
Bimodality emerges from transport model calculations of heavy ion collisions at intermediate energy
Mallik, S.; Das Gupta, S.; Chaudhuri, G.
2016-04-01
This work is a continuation of our effort [S. Mallik, S. Das Gupta, and G. Chaudhuri, Phys. Rev. C 91, 034616 (2015)], 10.1103/PhysRevC.91.034616 to examine if signatures of a phase transition can be extracted from transport model calculations of heavy ion collisions at intermediate energy. A signature of first-order phase transition is the appearance of a bimodal distribution in Pm(k ) in finite systems. Here Pm(k ) is the probability that the maximum of the multiplicity distribution occurs at mass number k . Using a well-known model for event generation [Botzmann-Uehling-Uhlenbeck (BUU) plus fluctuation], we study two cases of central collision: mass 40 on mass 40 and mass 120 on mass 120. Bimodality is seen in both the cases. The results are quite similar to those obtained in statistical model calculations. An intriguing feature is seen. We observe that at the energy where bimodality occurs, other phase-transition-like signatures appear. There are breaks in certain first-order derivatives. We then examine if such breaks appear in standard BUU calculations without fluctuations. They do. The implication is interesting. If first-order phase transition occurs, it may be possible to recognize that from ordinary BUU calculations. Probably the reason this has not been seen already is because this aspect was not investigated before.
Band-structure-based collisional model for electronic excitations in ion-surface collisions
International Nuclear Information System (INIS)
Faraggi, M.N.; Gravielle, M.S.; Alducin, M.; Silkin, V.M.; Juaristi, J.I.
2005-01-01
Energy loss per unit path in grazing collisions with metal surfaces is studied by using the collisional and dielectric formalisms. Within both theories we make use of the band-structure-based (BSB) model to represent the surface interaction. The BSB approach is based on a model potential and provides a precise description of the one-electron states and the surface-induced potential. The method is applied to evaluate the energy lost by 100 keV protons impinging on aluminum surfaces at glancing angles. We found that when the realistic BSB description of the surface is used, the energy loss obtained from the collisional formalism agrees with the dielectric one, which includes not only binary but also plasmon excitations. The distance-dependent stopping power derived from the BSB model is in good agreement with available experimental data. We have also investigated the influence of the surface band structure in collisions with the Al(100) surface. Surface-state contributions to the energy loss and electron emission probability are analyzed
Scherr, Rachel E.; Robertson, Amy D.
2015-06-01
We observe teachers in professional development courses about energy constructing mechanistic accounts of energy transformations. We analyze a case in which teachers investigating adiabatic compression develop a model of the transformation of kinetic energy to thermal energy. Among their ideas is the idea that thermal energy is generated as a byproduct of individual particle collisions, which is represented in science education research literature as an obstacle to learning. We demonstrate that in this instructional context, the idea that individual particle collisions generate thermal energy is not an obstacle to learning, but instead is productive: it initiates intellectual progress. Specifically, this idea initiates the reconciliation of the teachers' energy model with mechanistic reasoning about adiabatic compression, and leads to a canonically correct model of the transformation of kinetic energy into thermal energy. We claim that the idea's productivity is influenced by features of our particular instructional context, including the instructional goals of the course, the culture of collaborative sense making, and the use of certain representations of energy.
Directory of Open Access Journals (Sweden)
Luz A. Melo Varela
2013-01-01
Full Text Available This paper shows a study, both analytical and numerical, of a continuous-time dynamical system associated with a simple model of a wastewater biorreactor. Nonsmooth phenomena and border-collision local bifurcations appear when the main parameters (dilution and biomass concentration at the inflow are varied. We apply the Filippov methods following Kuznetsov’s work.
The dynamics of the nuclear disassembly in a field-theoretical model at finite entropies
International Nuclear Information System (INIS)
Knoll, J.; Strack, B.
1984-10-01
The expansion phase of a hot nuclear system as created in an energetic heavy-ion collision is calculated and discussed by a selfconsistent field-theoretical model. Dynamical instabilities arising during the expansion from strong fluctuations of the one-body density are included explicitely. First multiplicity distributions and mass spectra resulting from a series of numerical runs in a 2+1 dimensional model world are presented. The dependence of break-up dynamics both on the properties of the binding force and possible correlations in the initially compressed hot state are discussed. (orig.)
Dynamic modelling of nuclear steam generators
International Nuclear Information System (INIS)
Kerlin, T.W.; Katz, E.M.; Freels, J.; Thakkar, J.
1980-01-01
Moving boundary, nodal models with dynamic energy balances, dynamic mass balances, quasi-static momentum balances, and an equivalent single channel approach have been developed for steam generators used in nuclear power plants. The model for the U-tube recirculation type steam generator is described and comparisons are made of responses from models of different complexity; non-linear versus linear, high-order versus low order, detailed modeling of the control system versus a simple control assumption. The results of dynamic tests on nuclear power systems show that when this steam generator model is included in a system simulation there is good agreement with actual plant performance. (author)
Dynamic Airspace Managment - Models and Algorithms
Cheng, Peng; Geng, Rui
2010-01-01
This chapter investigates the models and algorithms for implementing the concept of Dynamic Airspace Management. Three models are discussed. First two models are about how to use or adjust air route dynamically in order to speed up air trafï¬c ï¬‚ow and reduce delay. The third model gives a way to dynamically generate the optimal sector conï¬guration for an air trafï¬c control center to both balance the controllerâ€™s workload and save control resources. The ï¬rst model, called the Dynami...
Wind Farm Decentralized Dynamic Modeling With Parameters
DEFF Research Database (Denmark)
Soltani, Mohsen; Shakeri, Sayyed Mojtaba; Grunnet, Jacob Deleuran
2010-01-01
Development of dynamic wind flow models for wind farms is part of the research in European research FP7 project AEOLUS. The objective of this report is to provide decentralized dynamic wind flow models with parameters. The report presents a structure for decentralized flow models with inputs from...... local models. The results of this report are especially useful, but not limited, to design a decentralized wind farm controller, since in centralized controller design one can also use the model and update it in a central computing node.......Development of dynamic wind flow models for wind farms is part of the research in European research FP7 project AEOLUS. The objective of this report is to provide decentralized dynamic wind flow models with parameters. The report presents a structure for decentralized flow models with inputs from...
System dynamics modelling of situation awareness
CSIR Research Space (South Africa)
Oosthuizen, R
2015-11-01
Full Text Available . The feedback loops and delays in the Command and Control system also contribute to the complex dynamic behavior. This paper will build on existing situation awareness models to develop a System Dynamics model to support a qualitative investigation through...
An Agent Model Integrating an Adaptive Model for Environmental Dynamics
Treur, J.; Umair, M.
2011-01-01
The environments in which agents are used often may be described by dynamical models, e.g., in the form of a set of differential equations. In this paper, an agent model is proposed that can perform model-based reasoning about the environment, based on a numerical (dynamical system) model of the
Hydration dynamics near a model protein surface
International Nuclear Information System (INIS)
Russo, Daniela; Hura, Greg; Head-Gordon, Teresa
2003-01-01
The evolution of water dynamics from dilute to very high concentration solutions of a prototypical hydrophobic amino acid with its polar backbone, N-acetyl-leucine-methylamide (NALMA), is studied by quasi-elastic neutron scattering and molecular dynamics simulation for both the completely deuterated and completely hydrogenated leucine monomer. We observe several unexpected features in the dynamics of these biological solutions under ambient conditions. The NALMA dynamics shows evidence of de Gennes narrowing, an indication of coherent long timescale structural relaxation dynamics. The translational water dynamics are analyzed in a first approximation with a jump diffusion model. At the highest solute concentrations, the hydration water dynamics is significantly suppressed and characterized by a long residential time and a slow diffusion coefficient. The analysis of the more dilute concentration solutions takes into account the results of the 2.0M solution as a model of the first hydration shell. Subtracting the first hydration layer based on the 2.0M spectra, the translational diffusion dynamics is still suppressed, although the rotational relaxation time and residential time are converged to bulk-water values. Molecular dynamics analysis shows spatially heterogeneous dynamics at high concentration that becomes homogeneous at more dilute concentrations. We discuss the hydration dynamics results of this model protein system in the context of glassy systems, protein function, and protein-protein interfaces
Directory of Open Access Journals (Sweden)
TengFei Wang
2017-03-01
Full Text Available A multi-ship collision avoidance decision-making and path planning formulation is studied in a distributed way. This paper proposes a complete set of solutions for multi-ship collision avoidance in intelligent navigation, by using a top-to-bottom organization to structure the system. The system is designed with two layers: the collision avoidance decision-making and the path planning. Under the general requirements of the International Regulations for Preventing Collisions at Sea (COLREGs, the performance of distributed path planning decision-making for anti-collision is analyzed for both give-way and stand-on ships situations, including the emergency actions taken by the stand-on ship in case of the give-way ship’s fault of collision avoidance measures. The Artificial Potential Field method(APF is used for the path planning in details. The developed APF method combined with the model of ship domain takes the target ships’ speed and course in-to account, so that it can judge the moving characteristics of obstacles more accurately. Simulation results indicate that the system proposed can work effectiveness.
Quantum approaches for the insertion dynamics of the H++D2 and D++H2 reactive collisions
International Nuclear Information System (INIS)
Gonzalez-Lezana, Tomas; Aguado, Alfredo; Paniagua, Miguel; Roncero, O.
2005-01-01
The H + +D 2 and D + +H 2 reactive collisions are studied using a recently proposed adiabatic potential energy surface of spectroscopic accuracy. The dynamics is studied using an exact wave packet method on the adiabatic surface at energies below the curve crossing occurring at ≅1.5 eV above the threshold. It is found that the reaction is very well described by a statistical quantum method for a zero total angular momentum (J) as compared with the exact ones, while for higher J some discrepancies are found. For J>0 different centrifugal sudden approximations are proposed and compared with the exact and statistical quantum treatments. The usual centrifugal sudden approach fails by considering too high reaction barriers and too low reaction probabilities. A new statistically modified centrifugal sudden approach is considered which corrects these two failures to a rather good extent. It is also found that an adiabatic approximation for the helicities provides results in very good agreement with the statistical method, placing the reaction barrier properly. However, both statistical and adiabatic centrifugal treatments overestimate the reaction probabilities. The reaction cross sections thus obtained with the new approaches are in rather good agreement with the exact results. In spite of these deficiencies, the quantum statistical method is well adapted for describing the insertion dynamics, and it is then used to evaluate the differential cross sections
Forecasting house prices in the 50 states using Dynamic Model Averaging and Dynamic Model Selection
DEFF Research Database (Denmark)
Bork, Lasse; Møller, Stig Vinther
2015-01-01
We examine house price forecastability across the 50 states using Dynamic Model Averaging and Dynamic Model Selection, which allow for model change and parameter shifts. By allowing the entire forecasting model to change over time and across locations, the forecasting accuracy improves substantia......We examine house price forecastability across the 50 states using Dynamic Model Averaging and Dynamic Model Selection, which allow for model change and parameter shifts. By allowing the entire forecasting model to change over time and across locations, the forecasting accuracy improves...
Various models for pion probability distributions from heavy-ion collisions
International Nuclear Information System (INIS)
Mekjian, A.Z.; Mekjian, A.Z.; Schlei, B.R.; Strottman, D.; Schlei, B.R.
1998-01-01
Various models for pion multiplicity distributions produced in relativistic heavy ion collisions are discussed. The models include a relativistic hydrodynamic model, a thermodynamic description, an emitting source pion laser model, and a description which generates a negative binomial description. The approach developed can be used to discuss other cases which will be mentioned. The pion probability distributions for these various cases are compared. Comparison of the pion laser model and Bose-Einstein condensation in a laser trap and with the thermal model are made. The thermal model and hydrodynamic model are also used to illustrate why the number of pions never diverges and why the Bose-Einstein correction effects are relatively small. The pion emission strength η of a Poisson emitter and a critical density η c are connected in a thermal model by η/n c =e -m/T <1, and this fact reduces any Bose-Einstein correction effects in the number and number fluctuation of pions. Fluctuations can be much larger than Poisson in the pion laser model and for a negative binomial description. The clan representation of the negative binomial distribution due to Van Hove and Giovannini is discussed using the present description. Applications to CERN/NA44 and CERN/NA49 data are discussed in terms of the relativistic hydrodynamic model. copyright 1998 The American Physical Society
MODELING DISPERSION FROM CHEMICALS RELEASED AFTER A TRAIN COLLISION IN GRANITEVILLE, SOUTH CAROLINA
Energy Technology Data Exchange (ETDEWEB)
Buckley, R; Chuck Hunter, C; Robert Addis, R; Matt Parker, M
2006-08-07
The Savannah River National Laboratory's (SRNL) Weather INformation and Display (WIND) System was used to provide meteorological and atmospheric modeling/consequence assessment support to state and local agencies following the collision of two Norfolk Southern freight trains on the morning of January 6, 2005. This collision resulted in the release of several toxic chemicals to the environment, including chlorine. The dense and highly toxic cloud of chlorine gas that formed in the vicinity of the accident was responsible for nine fatalities, and caused injuries to more than five hundred others. Transport model results depicting the forecast path of the ongoing release were made available to emergency managers in the county's Unified Command Center shortly after SRNL received a request for assistance. Support continued over the ensuing two days of the active response. The SRNL also provided weather briefings and transport/consequence assessment model results to responders from South Carolina Department of Health and Environmental Control (SCDHEC), the Savannah River Site's (SRS) Emergency Operations Center (EOC), Department of Energy Headquarters, and hazmat teams dispatched from the SRS. Although model-generated forecast winds used in consequence assessments conducted during the incident were provided at 2-km horizontal grid spacing during the accident response, a high-resolution Regional Atmospheric Modeling System (RAMS, version 4.3.0) simulation was later performed to examine potential influences of local topography on plume migration. The detailed RAMS simulation was used to determine meteorology using multiple grids with an innermost grid spacing of 125 meters. Results from the two simulations are shown to generally agree with meteorological observations at the time; consequently, local topography did not significantly affect wind in the area. Use of a dense gas dispersion model to simulate localized plume behavior using the higher resolution
Improved elastic collision modeling in DEGAS 2 for low-temperature plasmas
International Nuclear Information System (INIS)
Kanzleiter, Randall J.; Stotler, Daren P.; Karney, Charles F. F.; Steiner, Don
2000-01-01
Recent emphasis on low-temperature divertor operations has focused attention on proper treatment of neutral-elastic collisions in low-temperature environments. For like species collisions, as in D + +D, quantum mechanical indistinguishability precludes differentiation of small-angle elastic scattering from resonant charge exchange for collision energies + +D 2 are included for the first time. An integration technique is utilized that reduces the total collision cross section while keeping the other transport cross sections invariant. The inclusion of ion-molecular elastic collisions results in significant increases in energy exchange between background ions and neutral test species
Directory of Open Access Journals (Sweden)
Panagiota Foka
2016-11-01
Full Text Available The first collisions of lead nuclei, delivered by the CERN Large Hadron Collider (LHC at the end of 2010, at a centre-of-mass energy per nucleon pair sNN= 2.76 TeV, marked the beginning of a new era in ultra-relativistic heavy-ion physics. Following the Run 1 period, LHC also successfully delivered Pb–Pb collisions at the collision energy sNN= 5.02 TeV at the end of 2015. The study of the properties of the produced hot and dense strongly-interacting matter at these unprecedented energies is experimentally pursued by all four big LHC experiments, ALICE, ATLAS, CMS, and LHCb. This review presents selected experimental results from heavy-ion collisions delivered during the first three years of the LHC operation focusing on the bulk matter properties and the dynamical evolution of the created system. It also presents the first results from Run 2 heavy-ion data at the highest energy, as well as from the studies of the reference pp and p–Pb systems, which are an integral part of the heavy-ion programme. Keywords: Large hadron collider, Heavy-ion collisions, High energy physics
Directory of Open Access Journals (Sweden)
Rulin Huang
2017-04-01
Full Text Available Existing collision avoidance methods for autonomous vehicles, which ignore the driving intent of detected vehicles, thus, cannot satisfy the requirements for autonomous driving in urban environments because of their high false detection rates of collisions with vehicles on winding roads and the missed detection rate of collisions with maneuvering vehicles. This study introduces an intent-estimation- and motion-model-based (IEMMB method to address these disadvantages. First, a state vector is constructed by combining the road structure and the moving state of detected vehicles. A Gaussian mixture model is used to learn the maneuvering patterns of vehicles from collected data, and the patterns are used to estimate the driving intent of the detected vehicles. Then, a desirable long-term trajectory is obtained by weighting time and comfort. The long-term trajectory and the short-term trajectory, which are predicted using a constant yaw rate motion model, are fused to achieve an accurate trajectory. Finally, considering the moving state of the autonomous vehicle, collisions can be detected and avoided. Experiments have shown that the intent estimation method performed well, achieving an accuracy of 91.7% on straight roads and an accuracy of 90.5% on winding roads, which is much higher than that achieved by the method that ignores the road structure. The average collision detection distance is increased by more than 8 m. In addition, the maximum yaw rate and acceleration during an evasive maneuver are decreased, indicating an improvement in the driving comfort.
Directory of Open Access Journals (Sweden)
Shanjin Wang
2016-01-01
Full Text Available Radio frequency identification, that is, RFID, is one of important technologies in Internet of Things. Reader collision does impair the tag identification efficiency of an RFID system. Many developed methods, for example, the scheduling-based series, that are used to avoid RFID reader collision, have been developed. For scheduling-based methods, communication resources, that is, time slots, channels, and power, are optimally assigned to readers. In this case, reader collision avoidance is equivalent to an optimization problem related to resource allocation. However, the existing methods neglect the overlap between the interrogation regions of readers, which reduces the tag identification rate (TIR. To resolve this shortage, this paper attempts to build a reader-to-reader collision avoidance model considering the interrogation region overlaps (R2RCAM-IRO. In addition, an artificial immune network for resource allocation (RA-IRO-aiNet is designed to optimize the proposed model. For comparison, some comparative numerical simulations are arranged. The simulation results show that the proposed R2RCAM-IRO is an effective model where TIR is improved significantly. And especially in the application of reader-to-reader collision avoidance, the proposed RA-IRO-aiNet outperforms GA, opt-aiNet, and PSO in the total coverage area of readers.
Adaptive numerical modeling of dynamic crack propagation
International Nuclear Information System (INIS)
Adouani, H.; Tie, B.; Berdin, C.; Aubry, D.
2006-01-01
We propose an adaptive numerical strategy that aims at developing reliable and efficient numerical tools to model dynamic crack propagation and crack arrest. We use the cohesive zone theory as behavior of interface-type elements to model crack. Since the crack path is generally unknown beforehand, adaptive meshing is proposed to model the dynamic crack propagation. The dynamic study requires the development of specific solvers for time integration. As both geometry and finite element mesh of the studied structure evolve in time during transient analysis, the stability behavior of dynamic solver becomes a major concern. For this purpose, we use the space-time discontinuous Galerkin finite element method, well-known to provide a natural framework to manage meshes that evolve in time. As an important result, we prove that the space-time discontinuous Galerkin solver is unconditionally stable, when the dynamic crack propagation is modeled by the cohesive zone theory, which is highly non-linear. (authors)
International Nuclear Information System (INIS)
Chu, P.M.Y.
1991-10-01
The vibrational to translational (V→T) energy transfer in collisions between large highly vibrationally excited polyatomics and rare gases was investigated by time-of-flight techniques. Two different methods, UV excitation followed by intemal conversion and infrared multiphoton excitation (IRMPE), were used to form vibrationally excited molecular beams of hexafluorobenzene and sulfur hexafluoride, respectively. The product translational energy was found to be independent of the vibrational excitation. These results indicate that the probability distribution function for V→T energy transfer is peaked at zero. The collisional relaxation of large polyatomic molecules with rare gases most likely occurs through a rotationally mediated process. Photodissociation of nitrobenzene in a molecular beam was studied at 266 nm. Two primary dissociation channels were identified including simple bond rupture to produce nitrogen dioxide and phenyl radical and isomerization to form nitric oxide and phenoxy radical. The time-of-flight spectra indicate that simple bond rupture and isomerization occurs via two different mechanisms. Secondary dissociation of the phenoxy radicals to carbon monoxide and cyclopentadienyl radicals was observed as well as secondary photodissociation of phenyl radical to give H atom and benzyne. A supersonic methyl radical beam source is developed. The beam source configuration and conditions were optimized for CH 3 production from the thermal decomposition of azomethane. Elastic scattering of methyl radical and neon was used to differentiate between the methyl radicals and the residual azomethane in the molecular beam
Dynamics of nucleus-nucleus collisions up to 100 MeV/u and caloric curve
International Nuclear Information System (INIS)
Peter, J.; Angelique, J.C.; Auger, G.
1997-01-01
Using the 4π multidetector array Mur + Tonneau at GANIL made it possible to determine that, at incidence energy 35-95 MeV/u, the fusion (or one main source) cross section is very small in nearly symmetrical light and medium systems. Dissipative binary collisions accompanied by mid-rapidity (participant) emission were found to dominate at all impact parameters. The excitation energy of the reconstructed quasi-projectile was obtained via calorimetry and reaches high values. Using the 4π array INDRA several new features of mid-rapidity emission were revealed: the isotopic composition, mean transverse momentum and apparent temperature do not vary with the impact parameter, whereas the number of emitted nucleons increases with decreasing impact parameter. Mid-rapidity products are more n-rich than quasi-projectile products. Hot quasi-projectiles formed in two reactions were used to study the caloric curve. The apparent temperatures were obtained from several double isotopic yield ratios and slopes of kinetic energy spectra at excitation energy per nucleon ranging up to 24 MeV. Different thermometers give different values, but all of them increase steadily with excitation energy. These data can be explained by calculations assuming a steady increase of the initial temperature with excitation energy, without a plateau which was claimed as evidence for a liquid-gas phase transition. (authors)
A collision avoidance model for two-pedestrian groups: Considering random avoidance patterns
Zhou, Zhuping; Cai, Yifei; Ke, Ruimin; Yang, Jiwei
2017-06-01
Grouping is a common phenomenon in pedestrian crowds and group modeling is still an open challenging problem. When grouping pedestrians avoid each other, different patterns can be observed. Pedestrians can keep close with group members and avoid other groups in cluster. Also, they can avoid other groups separately. Considering this randomness in avoidance patterns, we propose a collision avoidance model for two-pedestrian groups. In our model, the avoidance model is proposed based on velocity obstacle method at first. Then grouping model is established using Distance constrained line (DCL), by transforming DCL into the framework of velocity obstacle, the avoidance model and grouping model are successfully put into one unified calculation structure. Within this structure, an algorithm is developed to solve the problem when solutions of the two models conflict with each other. Two groups of bidirectional pedestrian experiments are designed to verify the model. The accuracy of avoidance behavior and grouping behavior is validated in the microscopic level, while the lane formation phenomenon and fundamental diagrams is validated in the macroscopic level. The experiments results show our model is convincing and has a good expansibility to describe three or more pedestrian groups.
Studies of nucleus-nucleus collisions with a schematic liquid-drop model and one-body dissipation
Energy Technology Data Exchange (ETDEWEB)
Donangelo, R; Canto, L F
1986-03-24
The inclusion of an asymmetry friction term into the dissipation function of the schematic model of nuclear collisions due to WJ Swiatecki is found to change some of the earlier predictions of the model, in particular the scaling relation for the extra-push and extra-extra-push energies and the existence of a cliff phenomenon. (orig.).
Modeling Gas Dynamics in California Sea Lions
2015-09-30
W. and Fahlman, A. (2009). Could beaked whales get the bends?. Effect of diving behaviour and physiology on modelled gas exchange for three species...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Modeling Gas Dynamics in California Sea Lions Andreas...to update a current gas dynamics model with recently acquired data for respiratory compliance (P-V), and body compartment size estimates in
A Dynamic Model of Sustainment Investment
2015-02-01
Sustainment System Dynamics Model 11 Figure 7: Core Structure of Sustainment Work 12 Figure 8: Bandwagon Effect Loop 13 Figure 9: Limits to Growth Loop 14...Dynamics Model sustainment capacity sustainment performance gap Bandwagon Effect R1 Limits to Growth B1 S Work Smarter B3 Work Bigger B2 desired...which is of concern primarily when using the model as a vehicle for research. Figure 8 depicts a reinforcing loop called the “ Bandwagon Effect
Modeling the Dynamic Digestive System Microbiome†
Estes, Anne M.
2015-01-01
“Modeling the Dynamic Digestive System Microbiome” is a hands-on activity designed to demonstrate the dynamics of microbiome ecology using dried pasta and beans to model disturbance events in the human digestive system microbiome. This exercise demonstrates how microbiome diversity is influenced by: 1) niche availability and habitat space and 2) a major disturbance event, such as antibiotic use. Students use a pictorial key to examine prepared models of digestive system microbiomes to determi...
Dynamical vs. geometric anisotropy in relativistic heavy-ion collisions. Which one prevails?
Energy Technology Data Exchange (ETDEWEB)
Bravina, L.V. [University of Oslo, Department of Physics, Oslo (Norway); National Research Nuclear University ' ' MEPhI' ' (Moscow Engineering Physics Institute), Moscow (Russian Federation); Lokhtin, I.P.; Malinina, L.V.; Petrushanko, S.V.; Snigirev, A.M. [Lomonosov Moscow State University, Skobeltsyn Institute of Nuclear Physics, Moscow (Russian Federation); Zabrodin, E.E. [Lomonosov Moscow State University, Skobeltsyn Institute of Nuclear Physics, Moscow (Russian Federation); University of Oslo, Department of Physics, Oslo (Norway); National Research Nuclear University ' ' MEPhI' ' (Moscow Engineering Physics Institute), Moscow (Russian Federation)
2017-11-15
We study the influence of geometric and dynamical anisotropies on the development of flow harmonics and, simultaneously, on the second- and third-order oscillations of femtoscopy radii. The analysis is done within the Monte Carlo event generator HYDJET++, which was extended to dynamical triangular deformations. It is shown that the merely geometric anisotropy provides the results which anticorrelate with the experimental observations of either v{sub 2} (or v{sub 3}) or second-order (or third-order) oscillations of the femtoscopy radii. Decays of resonances significantly increase the emitting areas but do not change the phases of the radii oscillations. In contrast to the spatial deformations, the dynamical anisotropy alone provides the correct qualitative description of the flow and the femtoscopy observables simultaneously. However, one needs both types of the anisotropy to match quantitatively the experimental data. (orig.)
The collision of a strong shock with a gas cloud: a model for Cassiopeia A
International Nuclear Information System (INIS)
Sgro, A.G.
1975-01-01
The result of the collision of the shock with the cloud is a shock traveling around the cloud, a shock transmitted into the cloud, and a shock reflected from the cloud. By equating the cooling time of the posttransmitted shock gas to the time required for the transmitted shock to travel the length of the cloud, a critical cloud density n/subc/ /sup prime/ is defined. For clouds with density greater than n/subc/ /sup prime/, the posttransmitted shock gas cools rapidly and then emits the lines of the lower ionization stages of its constituent elements. The structure of such and its expected appearance to an observer are discussed and compared with the quasi-stationary condensations of Cas A. Conversely, clouds with density less than n/subc//sup prime/ remain hot for several thousand years, and are sources of X-radiation whose temperatures are much less than that of the intercloud gas. After the transmitted shock passes, the cloud pressure is greater than the pressure in the surrounding gas, causing the cloud to expand and the emission to decrease from its value just after the collision. A model in which the soft X-radiation of Cas A is due to a collection of such clouds is discussed. The faint emission patches to the north of Cas A are interpreted as preshocked clouds which will probably become quasi-stationary condensations after being hit by the shock
Arzeliès, Henri
1972-01-01
Relativistic Point Dynamics focuses on the principles of relativistic dynamics. The book first discusses fundamental equations. The impulse postulate and its consequences and the kinetic energy theorem are then explained. The text also touches on the transformation of main quantities and relativistic decomposition of force, and then discusses fields of force derivable from scalar potentials; fields of force derivable from a scalar potential and a vector potential; and equations of motion. Other concerns include equations for fields; transfer of the equations obtained by variational methods int
Exploring QCD dynamics in medium energy γA semiexclusive collisions
Directory of Open Access Journals (Sweden)
A.B. Larionov
2016-09-01
Full Text Available We demonstrate that studies of the semiexclusive large angle photon–nucleus reactions: γ+A→h1+h2+(A−1⁎ with tagged photon beams of energies 6÷10 GeV which can be performed in Hall D at Thomas Jefferson National Acceleration Facility (TJNAF would allow to probe several aspects of the QCD dynamics: establish the t-range in which transition from soft to hard dynamics occurs, compare the strength of the interaction of various mesons and baryons with nucleons at the energies of few GeV, as well as look for the color transparency effects.
Production of excitons in grazing collisions of protons with LiF surfaces: An onion model
Energy Technology Data Exchange (ETDEWEB)
Miraglia, J. E.; Gravielle, M. S. [Instituto de Astronomia y Fisica del Espacio, Consejo Nacional de Investigaciones Cientificas y Tecnicas and Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Casilla de Correo 67, Sucursal 28, (C1428EGA) Buenos Aires (Argentina)
2011-12-15
In this work we evaluate the production of excitons of a lithium fluoride crystal induced by proton impact in the intermediate and high energy regime (from 100 keV to 1 MeV). A simple model is proposed to account for the influence of the Coulomb grid of the target by dressing crystal ions to transform them in what we call onions. The excited states of these onions can be interpreted as excitons. Within this model, total cross section and stopping power are calculated by using the first Born and the continuum distorted-wave (CDW) eikonal initial-state (EIS) approximations. We found that between 7 and 30 excitons per incident proton are produced in grazing collisions with LiF surfaces, becoming a relevant mechanism of inelastic transitions.
Classical model for nuclear collisions including the meson degree of freedom
International Nuclear Information System (INIS)
Babinet, R.; Kunz, J.; Mosel, U.; Wilets, L.
1980-01-01
Many different approaches have been taken to describe high energy heavy ion collisions. L. Wilets et al proposed a classical treatment of the problem. In his model non-relativistic nucleons move on classical trajectories. However, the Pauli-principle is simulated by a momentum dependent potential acting between the nucleons. This model is extended in two ways. The nucleons are coupled to a pionfield, which enables us to describe inelastic processes. Nucleons and pionfiled are treated completely relativistically, this also assures Lorentz invariance. We aim at a set of classical equations of motion describing the interacting system of nucleons and pionfield. These classical equations should have a quantum mechanical basis. Further, they should contain such fundamental properties of the pion-nucleon system as the Δ(3,3)-resonance, at least in a qualitative manner. (orig./FKS)
Directory of Open Access Journals (Sweden)
Yan Gao
2014-01-01
Full Text Available The increasing marine activities in Arctic area have brought growing interest in ship-iceberg collision study. The purpose of this paper is to study the iceberg geometry shape effect on the collision process. In order to estimate the sensitivity parameter, five different geometry iceberg models and two iceberg material models are adopted in the analysis. The FEM numerical simulation is used to predict the scenario and the related responses. The simulation results including energy dissipation and impact force are investigated and compared. It is shown that the collision process and energy dissipation are more sensitive to iceberg local shape than other factors when the elastic-plastic iceberg material model is applied. The blunt iceberg models act rigidly while the sharp ones crush easily during the simulation process. With respect to the crushable foam iceberg material model, the iceberg geometry has relatively small influence on the collision process. The spherical iceberg model shows the most rigidity for both iceberg material models and should be paid the most attention for ice-resist design for ships.
Conceptual model for collision detection and avoidance for runway incursion prevention
Latimer, Bridgette A.
The Federal Aviation Administration (FAA), National Transportation and Safety Board (NTSB), National Aeronautics and Space Administration (NASA), numerous corporate entities, and research facilities have each come together to determine ways to make air travel safer and more efficient. These efforts have resulted in the development of a concept known as the Next Generation (Next Gen) of Aircraft or Next Gen. The Next Gen concept promises to be a clear departure from the way in which aircraft operations are performed today. The Next Gen initiatives require that modifications are made to the existing National Airspace System (NAS) concept of operations, system level requirements, software (SW) and hardware (HW) requirements, SW and HW designs and implementations. A second example of the changes in the NAS is the shift away from air traffic controllers having the responsibility for separation assurance. In the proposed new scheme of free flight, each aircraft would be responsible for assuring that it is safely separated from surrounding aircraft. Free flight would allow the separation minima for enroute aircraft to be reduced from 2000 nautical miles (nm) to 1000 nm. Simply put "Free Flight is a concept of air traffic management that permits pilots and controllers to share information and work together to manage air traffic from pre-flight through arrival without compromising safety [107]." The primary goal of this research project was to create a conceptual model that embodies the essential ingredients needed for a collision detection and avoidance system. This system was required to operate in two modes: air traffic controller's perspective and pilot's perspective. The secondary goal was to demonstrate that the technologies, procedures, and decision logic embedded in the conceptual model were able to effectively detect and avoid collision risks from both perspectives. Embodied in the conceptual model are five distinct software modules: Data Acquisition, State
A Habitat-based Wind-Wildlife Collision Model with Application to the Upper Great Plains Region
Energy Technology Data Exchange (ETDEWEB)
Forcey, Greg, M.
2012-08-28
Most previous studies on collision impacts at wind facilities have taken place at the site-specific level and have only examined small-scale influences on mortality. In this study, we examine landscape-level influences using a hierarchical spatial model combined with existing datasets and life history knowledge for: Horned Lark, Red-eyed Vireo, Mallard, American Avocet, Golden Eagle, Whooping Crane, red bat, silver-haired bat, and hoary bat. These species were modeled in the central United States within Bird Conservation Regions 11, 17, 18, and 19. For the bird species, we modeled bird abundance from existing datasets as a function of habitat variables known to be preferred by each species to develop a relative abundance prediction for each species. For bats, there are no existing abundance datasets so we identified preferred habitat in the landscape for each species and assumed that greater amounts of preferred habitat would equate to greater abundance of bats. The abundance predictions for bird and bats were modeled with additional exposure factors known to influence collisions such as visibility, wind, temperature, precipitation, topography, and behavior to form a final mapped output of predicted collision risk within the study region. We reviewed published mortality studies from wind farms in our study region and collected data on reported mortality of our focal species to compare to our modeled predictions. We performed a sensitivity analysis evaluating model performance of 6 different scenarios where habitat and exposure factors were weighted differently. We compared the model performance in each scenario by evaluating observed data vs. our model predictions using spearmans rank correlations. Horned Lark collision risk was predicted to be highest in the northwestern and west-central portions of the study region with lower risk predicted elsewhere. Red-eyed Vireo collision risk was predicted to be the highest in the eastern portions of the study region and in
Differential equation models for sharp threshold dynamics.
Schramm, Harrison C; Dimitrov, Nedialko B
2014-01-01
We develop an extension to differential equation models of dynamical systems to allow us to analyze probabilistic threshold dynamics that fundamentally and globally change system behavior. We apply our novel modeling approach to two cases of interest: a model of infectious disease modified for malware where a detection event drastically changes dynamics by introducing a new class in competition with the original infection; and the Lanchester model of armed conflict, where the loss of a key capability drastically changes the effectiveness of one of the sides. We derive and demonstrate a step-by-step, repeatable method for applying our novel modeling approach to an arbitrary system, and we compare the resulting differential equations to simulations of the system's random progression. Our work leads to a simple and easily implemented method for analyzing probabilistic threshold dynamics using differential equations. Published by Elsevier Inc.
Freeze-out dynamics in heavy-ion collisions: Recent advances
Indian Academy of Sciences (India)
2015-05-01
May 1, 2015 ... a renewed interest in the dynamics of the bulk hadron production, revived old ideas and .... that these numbers are crude approximations and only have an illustrative purpose. ... the order of 5 pm, mostly due to the large molecular mass. ... apparent full chemical equilibrium of strange particle abundances.
DEFF Research Database (Denmark)
Damkjær, Jesper; Erleben, Kenny
2009-01-01
and a simultaneous descend in the tandem traversal. The data structure design and traversal are highly specialized for exploiting the parallel threads in the NVIDIA GPUs. As proof-of-concept we demonstrate a GPU implementation for a multibody dynamics simulation, showing an approximate speedup factor of up to 8...
Dynamics and thermalization in violent collisions around 30 MeV/u
International Nuclear Information System (INIS)
Borderie, B.; Jouan, D.; Rivet, M.F.; Cabot, C.; Fuchs, H.; Gardes, D.; Gauvin, H.; Jacquet, D.; Monnet, F.; Montoya, M.
1990-01-01
In this paper, through exclusive measurements between heavy residues and light charged particles or intermediate-mass fragments, the dynamics of the different mechanisms involved in the Ar + nat Ag system at 27 MeV/u are described. Balances are presented. Finally the thermalization stage is discussed
International Nuclear Information System (INIS)
Schlingemann, D.
1996-10-01
Several two dimensional quantum field theory models have more than one vacuum state. An investigation of super selection sectors in two dimensions from an axiomatic point of view suggests that there should be also states, called soliton or kink states, which interpolate different vacua. Familiar quantum field theory models, for which the existence of kink states have been proven, are the Sine-Gordon and the φ 4 2 -model. In order to establish the existence of kink states for a larger class of models, we investigate the following question: Which are sufficient conditions a pair of vacuum states has to fulfill, such that an interpolating kink state can be constructed? We discuss the problem in the framework of algebraic quantum field theory which includes, for example, the P(φ) 2 -models. We identify a large class of vacuum states, including the vacua of the P(φ) 2 -models, the Yukawa 2 -like models and special types of Wess-Zumino models, for which there is a natural way to construct an interpolating kink state. In two space-time dimensions, massive particle states are kink states. We apply the Haag-Ruelle collision theory to kink sectors in order to analyze the asymptotic scattering states. We show that for special configurations of n kinks the scattering states describe n freely moving non interacting particles. (orig.)
Nonlinear dynamic phenomena in the beer model
DEFF Research Database (Denmark)
Mosekilde, Erik; Laugesen, Jakob Lund
2007-01-01
The production-distribution system or "beer game" is one of the most well-known system dynamics models. Notorious for the complex dynamics it produces, the beer game has been used for nearly five decades to illustrate how structure generates behavior and to explore human decision making. Here we...
Phone Routing using the Dynamic Memory Model
DEFF Research Database (Denmark)
Bendtsen, Claus Nicolaj; Krink, Thiemo
2002-01-01
In earlier studies a genetic algorithm (GA) extended with the dynamic memory model has shown remarkable performance on real-world-like problems. In this paper we experiment with routing in communication networks and show that the dynamic memory GA performs remarkable well compared to ant colony...
Bayesian model comparison for one-dimensional azimuthal correlations in 200GeV AuAu collisions
Directory of Open Access Journals (Sweden)
Eggers Hans C.
2016-01-01
Full Text Available In the context of data modeling and comparisons between different fit models, Bayesian analysis calls that model best which has the largest evidence, the prior-weighted integral over model parameters of the likelihood function. Evidence calculations automatically take into account both the usual chi-squared measure and an Occam factor which quantifies the price for adding extra parameters. Applying Bayesian analysis to projections onto azimuth of 2D angular correlations from 200 GeV AuAu collisions, we consider typical model choices including Fourier series and a Gaussian plus combinations of individual cosine components. We find that models including a Gaussian component are consistently preferred over pure Fourier-series parametrizations, sometimes strongly so. For 0–5% central collisions the Gaussian-plus-dipole model performs better than Fourier Series models or any other combination of Gaussian-plus-multipoles.
A dynamic neutral fluid model for the PIC scheme
Wu, Alan; Lieberman, Michael; Verboncoeur, John
2010-11-01
Fluid diffusion is an important aspect of plasma simulation. A new dynamic model is implemented using the continuity and boundary equations in OOPD1, an object oriented one-dimensional particle-in-cell code developed at UC Berkeley. The model is described and compared with analytical methods given in [1]. A boundary absorption parameter can be adjusted from ideal absorption to ideal reflection. Simulations exhibit good agreement with analytic time dependent solutions for the two ideal cases, as well as steady state solutions for mixed cases. For the next step, fluid sources and sinks due to particle-particle or particle-fluid collisions within the simulation volume and to surface reactions resulting in emission or absorption of fluid species will be implemented. The resulting dynamic interaction between particle and fluid species will be an improvement to the static fluid in the existing code. As the final step in the development, diffusion for multiple fluid species will be implemented. [4pt] [1] M.A. Lieberman and A.J. Lichtenberg, Principles of Plasma Discharges and Materials Processing, 2nd Ed, Wiley, 2005.
Dynamic queuing transmission model for dynamic network loading
DEFF Research Database (Denmark)
Raovic, Nevena; Nielsen, Otto Anker; Prato, Carlo Giacomo
2017-01-01
and allowing for the representation of multiple vehicle classes, queue spillbacks and shock waves. The model assumes that a link is split into a moving part plus a queuing part, and p that traffic dynamics are given by a triangular fundamental diagram. A case-study is investigated and the DQTM is compared...
DEFF Research Database (Denmark)
Loukonen, Ville; Bork, Nicolai; Vehkamaki, Hanna
2014-01-01
-principles molecular dynamics collision simulations of (sulphuric acid)1(water)0, 1 + (dimethylamine) → (sulphuric acid)1(dimethylamine)1(water)0, 1 cluster formation processes. The simulations indicate that the sticking factor in the collisions is unity: the interaction between the molecules is strong enough...... control. As a consequence, the clusters show very dynamic ion pair structure, which differs from both the static structure optimisation calculations and the equilibrium first-principles molecular dynamics simulations. In some of the simulation runs, water mediates the proton transfer by acting as a proton...... to overcome the possible initial non-optimal collision orientations. No post-collisional cluster break up is observed. The reasons for the efficient clustering are (i) the proton transfer reaction which takes place in each of the collision simulations and (ii) the subsequent competition over the proton...
International Nuclear Information System (INIS)
Aker, P.M.; Germann, G.J.; Tabor, K.D.; Valentini, J.J.
1989-01-01
We report measurement of product state distributions for the rotationally and/or vibrationally excited HX formed in collisions of translationally hot H atoms with HX (X = Cl, Br, and I) at 1.6 eV collision energy. The product state distributions are probed after only one collision of the fast H atom, using coherent anti-Stokes Raman scattering spectroscopy. Whether proceeding by inelastic collisions or reactive exchange, the transfer of translational energy to vibrational and rotational energy is quite inefficient in H+HX collisions at 1.6 eV. For all three hydrogen halides only 2--3% of the initial translational energy appears as HX vibration. For H+HCl only 6% of the initial energy is converted to HCl rotational energy, while for H+HBr and H+HI, this percentage is twice as large, 11--12%, but still small. The indistinguishability of the two H atoms involved makes it impossible to distinguish reactive exchange from inelastic energy transfer in these H+HX collisions. However, the difference in rotational energy partitioning for H+HBr and H+HI as compared with H+HCl, suggests that reactive exchange is dominant in the former and inelastic energy transfer dominates in the latter. The total cross sections for the combined energy transfer/reactive exchange do not change much with the identity of X, being 13 +- 3, 11 +- 2, and 11 +- 2 A 2 , for H+HCl, H+HBr, and H+HI, respectively
Source dimensions in ultrarelativistic heavy ion collisions
International Nuclear Information System (INIS)
Herrmann, M.; Bertsch, G.F.
1994-01-01
Recent experiments on pion correlations, interpreted as interferometric measurements of the collision zone, are compared with models that distinguish a prehadronic phase and a hadronic phase. The models include prehadronic longitudinal expansion, conversion to hadrons in local kinetic equilibrium, and rescattering of the produced hadrons. The longitudinal radius measured in collisions of 200 GeV/u sulfur nuclei on a heavy target require the existence of a prehadronic phase which converts to the hadronic phase at densities around 0.8 GeV/fm 3 . The transverse radii cannot be reproduced without introducing more complex dynamics into the transverse expansion
Dynamics and thermalization in argon induced collisions around 30 MeV / nucleon
International Nuclear Information System (INIS)
Rivet, M.F.; Borderie, B.; Jouan, D.; Cabot, C.; Fuchs, H.; Gauvin, H.; Gardes, D.; Montoya, M.
1991-01-01
Through exclusive measurements between heavy residues and light charged particles or intermediate mass fragments, the dynamics of the different mechanisms involved in the 40 Ar + nat Ag at 27 MeV/nucleon are described. Primary masses of the fragments can then be calculated. The excitation energy partition between the two fragments is derived from the number of particles evaporated by each fragment, and thermalization times are deduced. Finally linear momentum, mass and Z balances are presented. (authors)
Some dynamical aspects of interacting quintessence model
Indian Academy of Sciences (India)
Binayak S Choudhury
2018-03-16
Mar 16, 2018 ... Accelerated expansion of the Universe; quintessence; dynamical system; Friedmann–Lemaitre–. Robertson–Walker ... accepted theoretical model. One of the .... Thus, quintessence loses its self-strength and gives dark matter.
Modeling of truck's braking dynamics with ABS
Directory of Open Access Journals (Sweden)
Maxym DYACHUK
2014-09-01
Full Text Available In the article some questions of ABS simulation on the basis of plane vehicle's dynamics and automatic modeling are considered. The author's algorithm of ABS modulators control is presented.
Kotte, Jens; Schmeichel, Carsten; Zlocki, Adrian; Gathmann, Hauke; Eckstein, Lutz
2017-05-29
State-of-the-art collision avoidance and collision mitigation systems predict the behavior of pedestrians based on trivial models that assume a constant acceleration or velocity. New sources of sensor information-for example, smart devices such as smartphones, tablets, smartwatches, etc.-can support enhanced pedestrian behavior models. The objective of this article is the development and implementation of a V2Xpedestrian collision avoidance system that uses new information sources. A literature review of existing state-of-the-art pedestrian collision avoidance systems, pedestrian behavior models in advanced driver assistance systems (ADAS), and traffic simulations is conducted together with an analysis of existing studies on typical pedestrian patterns in traffic. Based on this analysis, possible parameters for predicting pedestrian behavior were investigated. The results led to new requirements from which a concept was developed and implemented. The analysis of typical pedestrian behavior patterns in traffic situations showed the complexity of predicting pedestrian behavior. Requirements for an improved behavior prediction were derived. A concept for a V2X collision avoidance system, based on a cost function that predicts pedestrian near future presence, and its implementation is presented. The concept presented considers several challenges such as information privacy, inaccuracies of the localization, and inaccuracies of the prediction. A concept for an enhanced V2X pedestrian collision avoidance system was developed and introduced. The concept uses new information sources such as smart devices to improve the prediction of the pedestrian's presence in the near future and considers challenges that come along with the usage of these information sources.
Dynamic Models of Insurgent Activity
2014-05-19
one dimension that has recently been studied in the computer science community. The model involves movement with a speed proportional to a “fear...more realistic model of human locomotion. The movement of the criminal agents follows a biased Levy flight with step sizes distributed according to a...power-law distribution. The biased Brownian motion of the original model is then derived as a special case. Starting with an agent-based model, we
International Nuclear Information System (INIS)
Knoll, J.
1985-10-01
A quantum dynamical model is suggested which describes the expansion and disassembly phase of highly excited compounds formed in energetic heavy-ion collisions. First applications in two space and one time dimensional model world are discussed and qualitatively compared to standard freeze-out concepts. (orig.)
Stochastic population dynamic models as probability networks
M.E. and D.C. Lee. Borsuk
2009-01-01
The dynamics of a population and its response to environmental change depend on the balance of birth, death and age-at-maturity, and there have been many attempts to mathematically model populations based on these characteristics. Historically, most of these models were deterministic, meaning that the results were strictly determined by the equations of the model and...
A neural computational model for animal's time-to-collision estimation.
Wang, Ling; Yao, Dezhong
2013-04-17
The time-to-collision (TTC) is the time elapsed before a looming object hits the subject. An accurate estimation of TTC plays a critical role in the survival of animals in nature and acts as an important factor in artificial intelligence systems that depend on judging and avoiding potential dangers. The theoretic formula for TTC is 1/τ≈θ'/sin θ, where θ and θ' are the visual angle and its variation, respectively, and the widely used approximation computational model is θ'/θ. However, both of these measures are too complex to be implemented by a biological neuronal model. We propose a new simple computational model: 1/τ≈Mθ-P/(θ+Q)+N, where M, P, Q, and N are constants that depend on a predefined visual angle. This model, weighted summation of visual angle model (WSVAM), can achieve perfect implementation through a widely accepted biological neuronal model. WSVAM has additional merits, including a natural minimum consumption and simplicity. Thus, it yields a precise and neuronal-implemented estimation for TTC, which provides a simple and convenient implementation for artificial vision, and represents a potential visual brain mechanism.
Efficient solution of three-body quantum collision problems: Application to the Temkin-Poet model
International Nuclear Information System (INIS)
Jones, S.; Stelbovics, Andris T.
2002-01-01
We have developed a variable-spacing finite-difference algorithm that rapidly propagates the general solution of Schroedinger's equation to large distances (whereupon it can be matched to asymptotic solutions, including the ionization channel, to extract the desired scattering quantities). The present algorithm, when compared to Poet's corresponding fixed-spacing algorithm [R. Poet, J. Phys. B 13, 2995 (1980); S. Jones and A. T. Stelbovics, Phys. Rev. Lett. 84, 1878 (2000)], reduces storage by 98% and computation time by 99.98%. The method is applied to the Temkin-Poet electron-hydrogen model collision problem. Complete results (elastic, inelastic, and ionization) are obtained for low (17.6 eV), intermediate (27.2, 40.8, and 54.4 eV), and high (150 eV) impact energies
Collision-model approach to steering of an open driven qubit
Beyer, Konstantin; Luoma, Kimmo; Strunz, Walter T.
2018-03-01
We investigate quantum steering of an open quantum system by measurements on its environment in the framework of collision models. As an example we consider a coherently driven qubit dissipatively coupled to a bath. We construct local nonadaptive and adaptive as well as nonlocal measurement scenarios specifying explicitly the measured observable on the environment. Our approach shows transparently how the conditional evolution of the open system depends on the type of the measurement scenario and the measured observables. These can then be optimized for steering. The nonlocal measurement scenario leads to maximal violation of the used steering inequality at zero temperature. Further, we investigate the robustness of the constructed scenarios against thermal noise. We find generally that steering becomes harder at higher temperatures. Surprisingly, the system can be steered even when bipartite entanglement between the system and individual subenvironments vanishes.
Born term for high-energy meson-hadron collisions from QCD and chiral quark model
International Nuclear Information System (INIS)
Ochs, W.; Shimada, T.
1988-01-01
Various experimental observations reveal a sizeable hard component in the high-energy 'soft' hadronic collisions. For primary meson beams we propose a QCD Born term which describes the dissociation of the primary meson into a quark-antiquark pair in the gluon field of the target. A pointlike effective pion-quark coupling is assumed as in the chiral quark model by Manohar and Georgi. We derive the total cross sections which for pion beams, for example, are given in terms of f π -2 and some properties of the hadronic final states. In particular, we stress the importance of studying three-jet events in meson-nucleon scattering and discuss the seagull effect. (orig.)
Standard-model predictions for W-pair production in electron-positron collisions
International Nuclear Information System (INIS)
Beenakker, W.; Denner, A.
1994-03-01
We review the status of the theoretical predictions for W-pair production in e + e - collisions within the electroweak standard model (SM). We first consider for on-shell W-bosons the lowest-order cross-section within the SM, the general effects of anomalous couplings, the radiative corrections within the SM, and approximations for them. Then we discuss the inclusion of finite-width effects in lowest order and the existing results for radiative corrections to off-shell W-pair production, and we outline the general strategy to calculate radiative corrections within the pole scheme. We summarize the theoretical predictions for the total and partial W-boson widths including radiative corrections and discuss the quality of an improved Born approximation. Finally we provide a general discussion of the structure-function method to calculate large logarithmic higher-order corrections associated with collinear photon radiation. (orig.)
Yamaguchi, Satoshi; Yamada, Yuya; Yoshida, Yoshinori; Noborio, Hiroshi; Imazato, Satoshi
2012-01-01
The virtual reality (VR) simulator is a useful tool to develop dental hand skill. However, VR simulations with reactions of patients have limited computational time to reproduce a face model. Our aim was to develop a patient face model that enables real-time collision detection and cutting operation by using stereolithography (STL) and deterministic finite automaton (DFA) data files. We evaluated dependence of computational cost and constructed the patient face model using the optimum condition for combining STL and DFA data files, and assessed the computational costs for operation in do-nothing, collision, cutting, and combination of collision and cutting. The face model was successfully constructed with low computational costs of 11.3, 18.3, 30.3, and 33.5 ms for do-nothing, collision, cutting, and collision and cutting, respectively. The patient face model could be useful for developing dental hand skill with VR.
Bond graph modeling of nuclear reactor dynamics
International Nuclear Information System (INIS)
Tylee, J.L.
1981-01-01
A tenth-order linear model of a pressurized water reactor (PWR) is developed using bond graph techniques. The model describes the nuclear heat generation process and the transfer of this heat to the reactor coolant. Comparisons between the calculated model response and test data from a small-scale PWR show the model to be an adequate representation of the actual plant dynamics. Possible application of the model in an advanced plant diagnostic system is discussed
International Nuclear Information System (INIS)
Moehring, H.; Ranft, J.; Capella, A.; Tran Thanh Van, J.
1993-01-01
Λ, bar Λ, and K S 0 production is studied in a Monte Carlo dual parton model for hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions with an SU(3) symmetric sea for chain formation (chain ends) but strangeness suppression in the chain fragmentation process. Additionally, (qq)-(bar q bar q) production from the sea was introduced into the chain formation process with the same probability as for the q→qq branching within the chain decay process. With these assumptions, multiplicity ratios and Feynman-x distributions for strange particles in h-h and multiplicity ratios in heavy ion collisions are reasonably well reproduced
Swarm Intelligence for Urban Dynamics Modelling
International Nuclear Information System (INIS)
Ghnemat, Rawan; Bertelle, Cyrille; Duchamp, Gerard H. E.
2009-01-01
In this paper, we propose swarm intelligence algorithms to deal with dynamical and spatial organization emergence. The goal is to model and simulate the developement of spatial centers using multi-criteria. We combine a decentralized approach based on emergent clustering mixed with spatial constraints or attractions. We propose an extension of the ant nest building algorithm with multi-center and adaptive process. Typically, this model is suitable to analyse and simulate urban dynamics like gentrification or the dynamics of the cultural equipment in urban area.
Swarm Intelligence for Urban Dynamics Modelling
Ghnemat, Rawan; Bertelle, Cyrille; Duchamp, Gérard H. E.
2009-04-01
In this paper, we propose swarm intelligence algorithms to deal with dynamical and spatial organization emergence. The goal is to model and simulate the developement of spatial centers using multi-criteria. We combine a decentralized approach based on emergent clustering mixed with spatial constraints or attractions. We propose an extension of the ant nest building algorithm with multi-center and adaptive process. Typically, this model is suitable to analyse and simulate urban dynamics like gentrification or the dynamics of the cultural equipment in urban area.
Understanding and Modeling Teams As Dynamical Systems
Gorman, Jamie C.; Dunbar, Terri A.; Grimm, David; Gipson, Christina L.
2017-01-01
By its very nature, much of teamwork is distributed across, and not stored within, interdependent people working toward a common goal. In this light, we advocate a systems perspective on teamwork that is based on general coordination principles that are not limited to cognitive, motor, and physiological levels of explanation within the individual. In this article, we present a framework for understanding and modeling teams as dynamical systems and review our empirical findings on teams as dynamical systems. We proceed by (a) considering the question of why study teams as dynamical systems, (b) considering the meaning of dynamical systems concepts (attractors; perturbation; synchronization; fractals) in the context of teams, (c) describe empirical studies of team coordination dynamics at the perceptual-motor, cognitive-behavioral, and cognitive-neurophysiological levels of analysis, and (d) consider the theoretical and practical implications of this approach, including new kinds of explanations of human performance and real-time analysis and performance modeling. Throughout our discussion of the topics we consider how to describe teamwork using equations and/or modeling techniques that describe the dynamics. Finally, we consider what dynamical equations and models do and do not tell us about human performance in teams and suggest future research directions in this area. PMID:28744231
Finite element simulation of lower limb injuries to the driver in minibus frontal collisions.
Shi, Liang-Liang; Lei, Chen; Li, Kui; Fu, Shuo-Zhen; Wu, Zheng-Wei; Yin, Zhi-Yong
2016-06-01
This study aims to explore the biomechanical mechanism of lower limb injuries to the driver by establishing a finite element (FE) simulation model of collisions. First a minibus FE model was integrated with a seat belt system. Then it was used to rebuild two collisions together with the total human model for safety (THUMS) provided by Toyota Motor Corporation: a rear-end collision between a minibus and a truck and a head-on collision of a minibus to a rigid wall. The impact velocities of both collisions were set at 56 km/h. The vehicle dynamic response, vehicle deceleration, and dashboard intrusion in the two collisions were compared. In the minibus rear-end truck collision, the peak values of the von Mises equivalent stress at the tibia and the femur were 133 MPa and 126 MPa respectively; while in the minibus head-on rigid wall collision, the data were 139 MPa and 99 MPa. Compared with the minibus head-on rigid wall collision, the vehicle deceleration was smaller and the dashboard intrusion was larger in the minibus rear-end truck collision. The results illustrate that a longer dashboard incursion distance corresponds to a higher von Mises equivalent stress at the femur. The simulation results are consistent with the driver's autopsy report on lower limbs injuries. These findings verify that FE simulation method is reliable and useful to analyze the mechanisms of lower limb injuries to the driver in minibus frontal collisions.
Sornborger, Andrew T.; Stancil, Phillip; Geller, Michael R.
2018-05-01
One of the most promising applications of an error-corrected universal quantum computer is the efficient simulation of complex quantum systems such as large molecular systems. In this application, one is interested in both the electronic structure such as the ground state energy and dynamical properties such as the scattering cross section and chemical reaction rates. However, most theoretical work and experimental demonstrations have focused on the quantum computation of energies and energy surfaces. In this work, we attempt to make the prethreshold (not error-corrected) quantum simulation of dynamical properties practical as well. We show that the use of precomputed potential energy surfaces and couplings enables the gate-based simulation of few-channel but otherwise realistic molecular collisions. Our approach is based on the widely used Born-Oppenheimer approximation for the structure problem coupled with a semiclassical method for the dynamics. In the latter the electrons are treated quantum mechanically but the nuclei are classical, which restricts the collisions to high energy or temperature (typically above ≈ 10 eV). By using operator splitting techniques optimized for the resulting time-dependent Hamiltonian simulation problem, we give several physically realistic collision examples, with 3-8 channels and circuit depths < 1000.
Dynamics and thermalization in argon induced collisions around 30 MeV/nucleon
International Nuclear Information System (INIS)
Rivet, M.F.; Borderie, B.; Jouan, D.; Cabot, C.; Fuchs, H.; Gauvin, H.; Gardes, D.; Montoya, M.
1991-01-01
Through exclusive measurements between heavy residues and light charged particles or intermediate mass fragments, the dynamics of the different mechanisms involved in the 40 Ar + nat Ag at 27 MeV/nucleon are described. Primary masses of the fragments can then be calculated. The excitation energy partition between the two fragments is derived from the number of particles evaporated by each fragment, and thermalization times are deduced. Finally, linear momentum, mass and Z-balances are presented. (author) 21 refs., 8 figs., 1 tab
Dynamical models of spiral galaxies
International Nuclear Information System (INIS)
Grosbol, P.
1990-01-01
The effects of changing the basic parameters of rotation curve steepness, amount of bulge, and pitch angle of the imposed spiral pattern in the galactic model of Contoupolos and Grosbel (1986) are investigated. The general conclusions of the model are confirmed and shown to be insensitive to the specific choice of parameters for the galactic potential. The exact amplitude at which the nonlinear effects at the 4:1 resonance become important do, however, depend on the model
Kang, Dongdong; Dai, Jiayu
2018-02-01
The structural, thermodynamic and transport properties of warm dense matter (WDM) are crucial to the fields of astrophysics and planet science, as well as inertial confinement fusion. WDM refers to the states of matter in a regime of temperature and density between cold condensed matter and hot ideal plasmas, where the density is from near-solid up to ten times solid density, and the temperature between 0.1 and 100 eV. In the WDM regime, matter exhibits moderately or strongly coupled, partially degenerate properties. Therefore, the methods used to deal with condensed matter and isolated atoms need to be properly validated for WDM. It is therefore a big challenge to understand WDM within a unified theoretical description with reliable accuracy. Here, we review the progress in the theoretical study of WDM with state-of-the-art simulations, i.e. quantum Langevin molecular dynamics and first principles path integral molecular dynamics. The related applications for WDM are also included.
Energy Balance Models and Planetary Dynamics
Domagal-Goldman, Shawn
2012-01-01
We know that planetary dynamics can have a significant affect on the climate of planets. Planetary dynamics dominate the glacial-interglacial periods on Earth, leaving a significant imprint on the geological record. They have also been demonstrated to have a driving influence on the climates of other planets in our solar system. We should therefore expect th.ere to be similar relationships on extrasolar planets. Here we describe a simple energy balance model that can predict the growth and thickness of glaciers, and their feedbacks on climate. We will also describe model changes that we have made to include planetary dynamics effects. This is the model we will use at the start of our collaboration to handle the influence of dynamics on climate.
Stirling Engine Dynamic System Modeling
Nakis, Christopher G.
2004-01-01
The Thermo-Mechanical systems branch at the Glenn Research Center focuses a large amount time on Stirling engines. These engines will be used on missions where solar power is inefficient, especially in deep space. I work with Tim Regan and Ed Lewandowski who are currently developing and validating a mathematical model for the Stirling engines. This model incorporates all aspects of the system including, mechanical, electrical and thermodynamic components. Modeling is done through Simplorer, a program capable of running simulations of the model. Once created and then proven to be accurate, a model is used for developing new ideas for engine design. My largest specific project involves varying key parameters in the model and quantifying the results. This can all be done relatively trouble-free with the help of Simplorer. Once the model is complete, Simplorer will do all the necessary calculations. The more complicated part of this project is determining which parameters to vary. Finding key parameters depends on the potential for a value to be independently altered in the design. For example, a change in one dimension may lead to a proportional change to the rest of the model, and no real progress is made. Also, the ability for a changed value to have a substantial impact on the outputs of the system is important. Results will be condensed into graphs and tables with the purpose of better communication and understanding of the data. With the changing of these parameters, a more optimal design can be created without having to purchase or build any models. Also, hours and hours of results can be simulated in minutes. In the long run, using mathematical models can save time and money. Along with this project, I have many other smaller assignments throughout the summer. My main goal is to assist in the processes of model development, validation and testing.
Pion production in relativistic collisions of nuclear drops
International Nuclear Information System (INIS)
Alonso, C.T.; Wilson, J.R.; McAbee, T.L.; Zingman, J.A.
1988-09-01
In a continuation of the long-standing effort of the nuclear physics community to model atomic nuclei as droplets of a specialized nuclear fluid, we have developed a hydrodynamic model for simulating the collisions of heavy nuclei at relativistic speeds. Our model couples ideal relativistic hydrodynamics with a new Monte Carlo treatment of dynamic pion production and tracking. The collective flow for low-energy (200 MeV/N) collisions predicted by this model compares favorably with results from earlier hydrodynamic calculations which used quite different numerical techniques. Our pion predictions at these lower energies appear to differ, however, from the experimental data on pion multiplicities. In this case of ultra-relativistic (200 GeV/N) collisions, our hydrodynamic model has produced baryonic matter distributions which are in reasonable agreement with recent experimental data. These results may shed some light on the sensitivity of relativistic collision data to the nuclear equation of state. 20 refs., 12 figs
Brand Equity Evolution: a System Dynamics Model
Directory of Open Access Journals (Sweden)
Edson Crescitelli
2009-04-01
Full Text Available One of the greatest challenges in brand management lies in monitoring brand equity over time. This paper aimsto present a simulation model able to represent this evolution. The model was drawn on brand equity concepts developed by Aaker and Joachimsthaler (2000, using the system dynamics methodology. The use ofcomputational dynamic models aims to create new sources of information able to sensitize academics and managers alike to the dynamic implications of their brand management. As a result, an easily implementable model was generated, capable of executing continuous scenario simulations by surveying casual relations among the variables that explain brand equity. Moreover, the existence of a number of system modeling tools will allow extensive application of the concepts used in this study in practical situations, both in professional and educational settings
Discrete dynamic modeling of cellular signaling networks.
Albert, Réka; Wang, Rui-Sheng
2009-01-01
Understanding signal transduction in cellular systems is a central issue in systems biology. Numerous experiments from different laboratories generate an abundance of individual components and causal interactions mediating environmental and developmental signals. However, for many signal transduction systems there is insufficient information on the overall structure and the molecular mechanisms involved in the signaling network. Moreover, lack of kinetic and temporal information makes it difficult to construct quantitative models of signal transduction pathways. Discrete dynamic modeling, combined with network analysis, provides an effective way to integrate fragmentary knowledge of regulatory interactions into a predictive mathematical model which is able to describe the time evolution of the system without the requirement for kinetic parameters. This chapter introduces the fundamental concepts of discrete dynamic modeling, particularly focusing on Boolean dynamic models. We describe this method step-by-step in the context of cellular signaling networks. Several variants of Boolean dynamic models including threshold Boolean networks and piecewise linear systems are also covered, followed by two examples of successful application of discrete dynamic modeling in cell biology.
Energy Technology Data Exchange (ETDEWEB)
Lombardi, A., E-mail: ebiu2005@gmail.com; Faginas-Lago, N.; Pacifici, L.; Grossi, G. [Dipartimento di Chimica, Università di Perugia, via Elce di Sotto 8, 06123 Perugia (Italy)
2015-07-21
Carbon dioxide molecules can store and release tens of kcal/mol upon collisions, and such an energy transfer strongly influences the energy disposal and the chemical processes in gases under the extreme conditions typical of plasmas and hypersonic flows. Moreover, the energy transfer involving CO{sub 2} characterizes the global dynamics of the Earth-atmosphere system and the energy balance of other planetary atmospheres. Contemporary developments in kinetic modeling of gaseous mixtures are connected to progress in the description of the energy transfer, and, in particular, the attempts to include non-equilibrium effects require to consider state-specific energy exchanges. A systematic study of the state-to-state vibrational energy transfer in CO{sub 2} + CO{sub 2} collisions is the focus of the present work, aided by a theoretical and computational tool based on quasiclassical trajectory simulations and an accurate full-dimension model of the intermolecular interactions. In this model, the accuracy of the description of the intermolecular forces (that determine the probability of energy transfer in molecular collisions) is enhanced by explicit account of the specific effects of the distortion of the CO{sub 2} structure due to vibrations. Results show that these effects are important for the energy transfer probabilities. Moreover, the role of rotational and vibrational degrees of freedom is found to be dominant in the energy exchange, while the average contribution of translations, under the temperature and energy conditions considered, is negligible. Remarkable is the fact that the intramolecular energy transfer only involves stretching and bending, unless one of the colliding molecules has an initial symmetric stretching quantum number greater than a threshold value estimated to be equal to 7.
Lombardi, A; Faginas-Lago, N; Pacifici, L; Grossi, G
2015-07-21
Carbon dioxide molecules can store and release tens of kcal/mol upon collisions, and such an energy transfer strongly influences the energy disposal and the chemical processes in gases under the extreme conditions typical of plasmas and hypersonic flows. Moreover, the energy transfer involving CO2 characterizes the global dynamics of the Earth-atmosphere system and the energy balance of other planetary atmospheres. Contemporary developments in kinetic modeling of gaseous mixtures are connected to progress in the description of the energy transfer, and, in particular, the attempts to include non-equilibrium effects require to consider state-specific energy exchanges. A systematic study of the state-to-state vibrational energy transfer in CO2 + CO2 collisions is the focus of the present work, aided by a theoretical and computational tool based on quasiclassical trajectory simulations and an accurate full-dimension model of the intermolecular interactions. In this model, the accuracy of the description of the intermolecular forces (that determine the probability of energy transfer in molecular collisions) is enhanced by explicit account of the specific effects of the distortion of the CO2 structure due to vibrations. Results show that these effects are important for the energy transfer probabilities. Moreover, the role of rotational and vibrational degrees of freedom is found to be dominant in the energy exchange, while the average contribution of translations, under the temperature and energy conditions considered, is negligible. Remarkable is the fact that the intramolecular energy transfer only involves stretching and bending, unless one of the colliding molecules has an initial symmetric stretching quantum number greater than a threshold value estimated to be equal to 7.