Surface modeling with oriented particle systems

A new approach to surface modeling and reconstruction is developed which overcomes some important limitations of existing surface representations methods. The approach features two components. The first is a dynamic self-organizing oriented particle system which discovers topological and geometric surface structure implicit in visual data. The oriented particles evolve according to Newtonian mechanics and interact through long-range attraction forces, short-range repulsion forces, and coplanarity, conormality, and cocircularity forces. The second component is an efficient triangulation scheme that connects the particles into a continuous global surface model that is consistent with the inferred structure. A flexible surface reconstruction algorithm is developed that can compute complete, detailed, viewpoint-invariant geometric surface descriptions of objects with arbitrary topology. The algorithms are applied to 3-D medical image segmentation and to surface reconstruction from object silhouettes. >

Chapter 7 - Tribological experiments with friction force microscopy

Particle systems have many applications, with the most popular being to produce special effects in video games and films. To permit particle systems to be created quickly and easily, Particle System Interfaces (PSIs) have been developed. A PSI is a piece of software designed to perform common tasks related to particle systems for clients, while providing them with a set of parameters whose values can be adjusted to create different particle systems. Most PSIs are inflexible, and when clients require functionality that is not supported by the PSI they are using, they are forced to either find another PSI that meets their requirements or, more commonly, create their own particle system or PSI from scratch. This paper presents three original contributions. First, it identifies 18 features that a PSI should provide in order to be capable of creating diverse effects. If these features are implemented in a PSI, clients will be more likely to be able to accomplish all desired effects related to particle systems with one PSI. Secondly, it introduces a novel use of events to determine, at run time, which particle system code to execute in each frame. Thirdly, it describes a software architecture called the Dynamic Particle System Framework (DPSF). Simulation results show that DPSF possesses all 18 desirable features.

Statistical mechanics of a lipid monolayer

Modeling the C. elegans nematode and its environment using a particle system

It may sound absurd to believe that a traffic jam model, eigenvalues of random matrices, and the length of the longest increasing subsequence of random permutations have a connection.Mathematicians say otherwise.Surprising results show that some fluctuations of these and many other models have the same asymptotic behavior.The development of integrable probability, a branch of representation theory applied to probability, is crucial for such findings.The totally asymmetric simple exclusion process (TASEP) is an interacting particle system that simulates traffic.We find the TASEP in a particular parametrization of a more general object, the Schur process, which is the main object of this study.

Particles may be removed from a lattice by murder, coalescence, mutual annihilation and simple death. If the particle system is not to die out, the removed particles must be replaced by births. This letter shows that coalescence can be counteracted by arbitrarily small birth-rates and contrasts this with the situations for annihilation and pure death where there are critical phenomena. The problem is unresolved for murder.

Consider the system of particles onℤ d where particles are of two types—A andB—and execute simple random walks in continuous time. Particles do not interact with their own type, but when anA-particle meets aB-particle, both disappear, i.e., are annihilated. This system serves as a model for the chemical reactionA+B→ inert. We analyze the limiting behavior of the densitiesρ A (t) andρ B (t) when the initial state is given by homogeneous Poisson random fields. We prove that for equal initial densitiesρ A (0)=ρ B (0) there is a change in behavior fromd⩽4, whereρ A (t)=ρ B (t)∼C/t d /4, tod⩾4, whereρ A (t)=ρ B (t)∼C/tast→∞. For unequal initial densitiesρ A (0)<ρ B (0),ρ A (t)∼e−c√l ind=1,ρ A (t)∼e−Ct/logt ind=2, andρ A (t)∼e−Ct ind⩾3. The termC depends on the initial densities and changes withd. Techniques are from interacting particle systems. The behavior for this two-particle annihilation process has similarities to those for coalescing random walks (A+A→A) and annihilating random walks (A+A→inert). The analysis of the present process is made considerably more difficult by the lack of comparison with an attractive particle system.

The transport properties of excess electrons in non polar gases or liquids give important information on the electronic states in a disordered medium and on the relationship among the electron-atom interactions and the properties of the fluid. Anomalous density effects on electron mobilities were discovered in a number of compressed gases1. A negative density effect, i. e., the density-normalized zero-field mobility μ 0 N of electrons decreases with increasing the gas density N, is shown by gases such as He and Ne, whose interaction with electrons is dominated by short-range repulsive exchange forces and whose scattering length a is positive. On the other hand, a positive density effect, i. e., μ 0 N increases with N, is shown by Ar, Kr, and Xe, whose scattering length is negative owing to the overwhelming contribution of the long-range attractive polarization forces to the atom-electron interaction.

A system of particles in a double well potential is a widely studied and useful example for understanding quantum mechanics. This simple system has recently been used in theoretical proposals and related experiments as a way to make quantum logic gates for ultracold atoms confined in optical lattices. Such quantum gates are the fundamental building blocks for quantum information processing; in these proposals, a regular array of cold atoms in an optical lattice serves as the quantum register. We explain how this research can be understood in terms of well-known principles for systems of identical particles.

We examine rotational transitions of HCl in collisions with H2 by carrying out quantum mechanical close-coupling and quasi-classical trajectory (QCT) calculations on a recently developed globally accurate full-dimensional ab initio potential energy surface for the H3Cl system. Signatures of rainbow scattering in rotationally inelastic collisions are found in the state resolved integral and differential cross sections as functions of the impact parameter (initial orbital angular momentum) and final rotational quantum number. We show the coexistence of distinct dynamical regimes for the HCl rotational transition driven by the short-range repulsive and long-range attractive forces whose relative importance depends on the collision energy and final rotational state, suggesting that the classification of rainbow scattering into rotational and l-type rainbows is effective for H2 + HCl collisions. While the QCT method satisfactorily predicts the overall behavior of the rotationally inelastic cross sections, its capability to accurately describe signatures of rainbow scattering appears to be limited for the present system.

The van Kampen analysis of condensation in a fluid of hard spheres with long-range attractions is extended to investigate the statistical mechanics of a fluid of rigid rod-like molecules which interact through both short-range repulsive and long-range attractive forces and which assume only a restricted set of three mutually orthogonal orientations. The thermodynamic properties are derived for the fluid near the liquid-gas critical point and at the nematic-isotropic transition. The model predicts that both isotropic and anisotropic attractive and repulsive interactions contribute to the stabilization of the nematically ordered fluid when a density change accompanies the transition. However, when the transition occurs at constant density, only the anisotropic contributions of the long-range dispersion energy and short-range repulsions are found to stabilize the transition in partial accord with the Maier-Saupe theory. Numerical results for a rigid-rod fluid with length-to-breadth ratio 3 at various packing...

Non-linear elasto-plastic shock waves in particle systems at high-velocity compaction are simulated by the discrete element method. The contact laws applied between the spherical metal particles include non-linear elastic and plastic loading, adhesion and elastic unloading. Of particular interest is to study the transmission and reflection of non-linear shock waves through a particle system with and without voids between the particles. Interesting results are presented in the paper including the particle deformation at incident and reflected shocks and particle velocity oscillations as a result of voids. The study of non-linear elasto-plastic shock waves in particle systems has a strong practical relevance including high-velocity compaction of metal powder.

Simulation purposes are to create an event in the world as real as possible, and by using Virtual Reality Technologies, it can achieve a higher level of realism and immersion. By using particle Systems from Unity can be used to producing a phenomenon that involving a small moving object on a big scale such as smoke, fire, or rain. However, when trying to use the particle system, sometimes the performance got reduced because there are too many particles working at the same time and result in a frame rate drop that causing discomfort to the player. For this reason, it's essential to optimize the performance by limiting objects that are needed to draw to lighten up the GPU process. In this paper, we discussed how to produces rain using the particle system in unity and find the best way to simulating rain with the best frame rate. We will show how the lifetime of the particle affecting the cycle of the particle system and the impact on the particle emission. We concluded that it's essential for developers to focus on the balance for creating realistic and detailed simulation and the stability of the simulation performance so the player can be more comfortable and immersive.

Granular particles systems under vertical vibration exhibit Brazilian Nut separation (BN), Reversed BN (RBN) separation or transitional phases at different vibrating conditions. In the present work, we investigate the influence of rotation on the BN separation of a binary granular particle system by changing rotational speed. 13X molecular sieve particles with diameter 6.00 mm and 0.60 mm are used. Vibration frequency f is 30 Hz and dimensionless acceleration Γ is 1.52 or 1.75, in which the particle system mainly exhibits BN separation tendency. Rotational speed ω varies from 0 to 150rpm, while the upper surface of the particle system maintains flat. We took the pictures of the particles distribution and measured the particles mass layer by layer to obtain the 3-D distribution of the particles. The results show that rotation enhances the BN separation tendency at slow rotational speed. The BN separation becomes strongest when ω is approximately 50rpm, then the BN separation tendency reduces as ω continues to increase. A butterfly pattern appears in the middle particles layer under the simultaneous stimulations of vibration and rotation.