Particle System Model Research Articles

On the Physical Consistency of an Open Quantum Region with a Classical Reservoir in Molecular Simulation

AbstractThe possibility of treating a molecular liquid in an open region at ab initio electronic resolution embedded in a classical reservoir of energy and particles, is investigated. Because of its challenging properties and its relevance in many field of current research, the system chosen as prototype of molecular liquid is water at room conditions. A numerical protocol based on the mathematical model of open particle system is applied and the results are compared with results of a full ab initio simulation of reference. The key conclusion is that one can claim the existence of a mandatory minimal size of the quantum region in which structural and electronic properties reproduce those of reference and, at the same time, the exchange of molecules with the environment takes place as expected. This work provides a proof of concept about the possibility to systematically define a physically well founded open quantum system embedded in a classical environment. In turn, the proof of concept is a key information for the design of numerically efficient algorithms for ab initio molecular dynamics simulations of open systems.

Research on the Application of Dynamic Simulation and 3D Modeling Technology for Ink Animation Performance

Abstract This paper mainly discusses the combination of 3D modeling technology and traditional characteristics of ink animation to promote the innovation and development of Chinese traditional animation. Aiming at the characteristics of ink painting, the 3D model construction algorithm of ink animation is proposed, which realizes the establishment of algorithms such as transforming the 2D model into a 3D model, constructing the 3D animation scene, imitating the virtual reality of ink painting and rendering the virtual reality of ink animation. The basic model of the particle system is proposed, including modules for particle generation, particle properties, particle motion change, particle extinction, and particle drawing. Combined with the basic principles based on the particle system model, randomly distributed particles break the regular rectangular shape in the overall distribution. More realistically simulates a variety of different animation forms for ink animation. The simulation speed and convergence time of this paper’s model are better than the other two models. The simulation results fulfill the demands of real-time ink animation performance. The FPS of the most complex animation image, the color ink staining of the cow, is 31FPS, which also meets the requirements of the animation image. It shows that the combination of 3D modeling technology, particle system-based dynamic simulation, and ink animation is perfect and has a broad application prospect.

Research and Innovation of Animated Movie Production Technology Based on Computer Graphic Design

Abstract The animation technology of computer graphic design can creatively integrate artificial intelligence technology and animation art, and use artificial intelligence technology to realize the creation of animation with the support of computer graphics. Based on this, this paper constructs a particle special effects system to realize the innovation of animation film production technology. This paper first analyzes the functions that need to be realized by the system and carries out the overall design of the system framework using modeling language. This includes the detailed design and graphical representation of the particle module, scene module, texture module, and so on in the particle special effects system. Then, simplify the mathematical model of snow, rain, fountain, etc., establish the particle system model of snow, rain and fountain, and realize the special effects simulation of snow, rain, fountain and other landscapes. Through the experiments, the performance of this system passes the standard of 70 frames per second, and the average score of the evaluation index of “whether there are common phenomena in animation” reaches 9.1 points, but the average score of the particle effects to express the emotions of the characters is only 6.3 points, which indicates that this system realizes the special effects simulation of snow, rain and fountain. This shows that the system in this paper has achieved the special effects simulation of snow, rain, and fountain phenomena, but there is still room for improvement in the expression of characters’ emotions with particle effects. On the whole, the system in this paper has achieved excellent special effects simulation and has realized the innovation of animation film production technology.

A study on light extinction model and inversion of mixed particle system based on Monte Carlo method

The extinction characteristics of mixed particles, which are composed of various types of particles, appear to be more complex. To statistically analyze photon destinations and investigate the extinction characteristics of mixed particles by tracing all underlying events in detail, a Monte Carlo method-based extinction model has been developed. Meanwhile, an extinction spectrum measurement system was designed. A series of experiments for both single-type particle and mixed-particle systems were performed. Afterwards, global optimization algorithms are introduced to perform simultaneous inversion of sizes of mixed particles and mixing ratio based on the experimental spectrum. The inversion results show that the error for any single parameter is <2%. Performing a simultaneous inversion for particle sizes and mixing ratios leads to an increase in the relative error, but it does not exceed 9%. It indicates that the model could simultaneously invert the mixing ratio and handle particle systems with two different sizes.

Development of nuclear de-excitation model EBITEM Ver.2

ABSTRACT The gamma de-excitation model of the general-purpose radiation transport code Particle and Heavy Ion Transport code System, called the Evaluated Nuclear Structure Data File (ENSDF)-Based Isomeric Transition and isomEr production Model (EBITEM) has been upgraded with a focus on precise neutron-capture reaction simulation. The first de-excitation subsequent to neutron capture of numerous nuclei, which was formerly simulated by a model based on the single particle model, is calculated using the Evaluated Gamma Activation File. The database used for further de-excitation, ENSDF, retrieved in 2013, was replaced with Reference Input Parameter Library 3 to consider internal conversion. The internal conversion process was interfaced with the atomic de-excitation model to assess the emission of Auger electrons and fluorescent X-rays. The spectra of gamma-rays from neutron-capture reactions calculated by the upgraded EBITEM correlate better with the evaluated cross-section data than those of the previous version.

Modelling Aero-Structural Deformation of Flexible Membrane Kites

Airborne wind energy systems using flexible membrane wings have the advantages of a low weight, small packing volume, high mobility and rapid deployability. This paper investigates the aero-structural deformation of a leading edge inflatable kite for airborne wind energy harvesting. In the first step, a triangular two-plate representation of the wing is introduced, leading to an analytical description of the wing geometry depending on the symmetric actuation state. In the second step, this geometric constraint-based model is refined to a multi-segment wing representation using a particle system approach. Each wing segment consists of four point masses kept at a constant distance along the tubular frame by linear spring-damper elements. An empirical correlation is used to model the billowing of the wing’s trailing edge. The linear spring-damper elements also the model line segments of the bridle line system, with each connecting two point masses. Three line segments can also be connected by a pulley model. The aerodynamic force acting on each wing segment is determined individually using the lift equation with a constant lift coefficient. The particle system model can predict the symmetric deformation of the wing in response to a symmetric actuation of the bridle lines used for depowering the kite (i.e., changing the pitch angle). The model also reproduces the typical twist deformation of the wing in response to an asymmetric line actuation used for steering the kite. The simulated wing geometries are compared with photogrammetric information taken by the onboard video camera of the kite control unit, focusing on the wing during flight. The results demonstrate that a particle system model can accurately predict the geometry of a soft wing at a low computational cost, making it an ideal structural building block for the next generation of soft wing kite models.

Simulation of various biofilm fractal morphologies by agent-based model

Biofilms are clusters of bacteria wrapped in extracellular matrix and polymers. The study of biofilm morphological transformation has been around for a long time and has attracted widespread attention. In this paper, we present a model for biofilm growth based on the interaction force, in which bacteria are treated as tiny particles and locations of particles are updated by calculating the repulsive forces among particles. We adapt a continuity equation to indicate nutrient concentration variation in the substrate. Based on the above, we study the morphological transformation of biofilms. We find that nutrient concentration and nutrient diffusion rate dominate different biofilm morphological transition processes, in which biofilms would grow into fractal morphology under the conditions of low nutrient concentration and nutrient diffusivity. At the same time, we expand our model by introducing a second particle to mimic extracellular polymeric substances (EPS) in biofilms. We find that the interaction between different particles can lead to phase separation patterns between cells and EPSs, and the adhesion effect of EPS can attenuate this phenomenon. In contrast to single particle system models, branches are inhibited due to EPS filling in dual particle system models, and this invalidation is boosted by the enhancement of the depletion effect.

Fast Aero-Structural Model of a Leading-Edge Inflatable Kite

Soft-wing kites for airborne wind-energy harvesting function as flying tensile membrane structures, each of whose shape depends on the aerodynamic load distribution and vice versa. The strong two-way coupling between shape and loading poses a complex fluid-structure interaction problem. Since computational models for such problems do not yet meet the requirements of being accurate and at the same time fast, kite designers usually work on the basis of intuition and experience, combined with extensive iterative flight testing. This paper presents a fast aero-structural model of leading-edge inflatable kites for the design phase of airborne wind-energy systems. The fluid-structure interaction solver couples two fast and modular models: a particle system model to capture the deformation of the wing and bridle-line system and a 3D nonlinear vortex step method coupled with viscous 2D airfoil polars to describe the aerodynamics. The flow solver was validated with several wing geometries and proved to be accurate and computationally inexpensive for pre-stall angles of attack. The coupled aero-structural model was validated using experimental data, showing good agreement in the deformations and aerodynamic forces. Therefore, the speed and accuracy of this model make it an excellent foundation for a kite design tool.

Deconvolution closure for mesoscopic continuum models of particle systems

We present a framework for derivation of closed‐form continuum equations governing mesoscale dynamics of large particle systems. Balance equations for spatial averages such as density, linear momentum, and energy were previously derived by a number of authors. These equations are exact, but are not in closed form because the stress and the heat flux cannot be evaluated without the knowledge of particle positions and velocities. Recently, we proposed a method for approximating exact fluxes by true constitutive equations, that is, using nonlocal operators acting only on the average density and velocity. In the paper, constitutive operators are obtained by using filtered regularization methods from the theory of ill‐posed problems. We also formulate conditions on fluctuation statistics which permit approximating these operators by local equations. The performance of the method is tested numerically using Fermi–Pasta–Ulam particle chains with two different potentials: the classical Lennard–Jones and the purely repulsive potential used in granular materials modeling. The initial conditions incorporate velocity fluctuations on scales that are smaller than the size of the averaging window. Simulation results show good agreement between the exact stress and its closed‐form approximation.

Learning anisotropic interaction rules from individual trajectories in a heterogeneous cellular population

Interacting particle system (IPS) models have proven to be highly successful for describing the spatial movement of organisms. However, it is challenging to infer the interaction rules directly from data. In the field of equation discovery, the weak-form sparse identification of nonlinear dynamics (WSINDy) methodology has been shown to be computationally efficient for identifying the governing equations of complex systems from noisy data. Motivated by the success of IPS models to describe the spatial movement of organisms, we develop WSINDy for the second-order IPS to learn equations for communities of cells. Our approach learns the directional interaction rules for each individual cell that in aggregate govern the dynamics of a heterogeneous population of migrating cells. To sort a cell according to the active classes present in its model, we also develop a novel ad hoc classification scheme (which accounts for the fact that some cells do not have enough evidence to accurately infer a model). Aggregated models are then constructed hierarchically to simultaneously identify different species of cells present in the population and determine best-fit models for each species. We demonstrate the efficiency and proficiency of the method on several test scenarios, motivated by common cell migration experiments.

Structure parameter design and bench test research of paddy field blades

Aiming at the problems of high labor intensity and low efficiency in manual operation during the pulping process of rice seedling nursing in thin mud in hilly and mountain areas, this paper designed a new type of paddy field blade for seedling nursing, and utilized a rice nursery pulper to help manual operation complete the pulping process. It created a mathematical model of mud-throwing mass and operating power in the operation process of paddy field blade, and obtained the main structure factors that influenced the mud-throwing mass and operating power of paddy field blade, which included the area of mud splashing board, the angle between the front cutting edge and the mud splashing board, and the inclination angle between the front cutting surface and the mud splashing board. To further analyze the degree of influence of the blade’s main structure parameters on mud-throwing mass and operating power, it used EDEM discrete element simulation software to establish a discrete element simulation model of paddy field blade and mud particle system, performed simulation analysis with the method of orthogonal experimental design, and conducted a bench test for comparison. The results showed that: (1) the degree of influence of the three structure parameters on mud-throwing mass and operating power from large to small in order was the area of mud splashing board > the inclination angle between front cutting surface and mud splashing board > the angle between front cutting edge and mud splashing board; (2) the maximum relative error for mud-throwing mass between simulation analysis and bench test was 4.53%, and that for operating power was 8.67%; and (3) three reference parameters combinations were selected by P2-1/M2 graph, the mud-throwing mass of the three combinations was 40.43%, 27.52% and 0.16% higher than that of the original blade, and the power consumed was 13.99%, 21.83% and 36.65% lower than that of the original blade, indicating that the new paddy field blade had good operating performance.

Phase Separation in Systems of Interacting Active Brownian Particles

The aim of this paper is to discuss the mathematical modeling of Brownian active particle systems, a recently popular paradigmatic system for self-propelled particles. We present four microscopic models with different types of repulsive interactions between particles and their associated macroscopic models, which are formally obtained using different coarse-graining methods. The macroscopic limits are integro-differential equations for the density in phase space (positions and orientations) of the particles and may include nonlinearities in both the diffusive and advective components. In contrast to passive particles, systems of active particles can undergo phase separation without any attractive interactions, a mechanism known as motility-induced phase separation (MIPS). We explore the onset of such a transition for each model in the parameter space of occupied volume fraction and P\'eclet number via a linear stability analysis and numerical simulations at both the microscopic and macroscopic levels. We establish that one of the models, namely the mean-field model which assumes long-range repulsive interactions, cannot explain the emergence of MIPS. In contrast, MIPS is observed for the remaining three models that assume short-range interactions that localize the interaction terms in space.

Real-Time Simulation Method of Flame Animation Based on the Deep Stripping Algorithm and Texture Mapping

With the gradual integration of computers into people’s work and life, it is no longer an unattainable goal to use the power of science and technology to simulate various states of matter. In the future, virtual simulation modeling technology will become more and more high-end with the improvement of the needs of the times. However, nowadays, there are many problems in generating real-time image animation. For traditional simulation methods, huge computation and realistic rendering have become technical bottlenecks. This topic takes the generation of flame animation as an example to illustrate. On the basis of the depth stripping algorithm and texture mapping method, not only particle system modeling is introduced, but also a new N-S equation is improved for research. The research results show the following. (1) The model constructed by this method has superior performance and has been greatly improved; after iteration, the error value is as low as 0.03 and the accuracy value is as high as 98%. (2) After 500 simulations, there are 399 kinds of static and 698 kinds of dynamic flames, respectively; it takes 24.01 s and 98.21 s to generate 500 incomplete animations. (3) Compared with the particle system and deep learning model for flame animation recognition and detection, the highest false alarm rate of this model is 4.6%, and the lowest is 0.9%, and the experimental effect is stable; the highest recognition of flame animation can reach 99.2%, and the lowest is 98.5%. (4) Generally speaking, experts and ordinary people have a high evaluation on the effect of this model; except for the first group, the scores are all over 80%, and the highest score can reach 85.936%. Finally, the experimental results are good, which proves the effectiveness and feasibility of this method, which has certain research contribution value. However, for the follow-up work, the algorithm and model have room for further improvement.

A Generic Particle Model with Topologic Modeling Capabilities for the Computational Form-Finding of Elastic Structures

Recent efforts on the research of bending- and tensile-active structures have shown the vast range of aesthetic and performative opportunities that elastic structures can offer for generating innovative architectural solutions. In this context, the task of conceptualizing and representing elastic structures is not trivial due to the presence of large deformations along the forming process. This condition demands to expand beyond current geometrical modeling schemes used in architecture and develop a more intuitive simulation-based design practice. Dynamic methods, such as Particle System and Dynamic Relaxation, have become an important topic on this subject with major efforts entirely focused on speeding up rates of numerical convergence. Fast simulations simplify the development of design iterations, but designers are still forced to break the integration process when topological changes need to be introduced for fulfilling a given design intention. As the exploration of elastic structures becomes more integrated within architectural design agendas, there is a growing necessity to introduce more flexible numerical models for design conceptualization. In this paper we introduce the conceptual framework for a generic Particle System model built on principles of combinatorial maps and graph theory that is designed to support topological transformations on the fly. The computational implementation of the proposed model is demonstrated with two types of data structures. The aim of this work is to enhance modeling capabilities when numerical simulations are used as design tools.

RetQSS: A novel methodology for efficient modeling and simulation of particle systems in reticulated geometries

This work presents retQSS, a novel methodology for efficient modeling and simulation of particle systems in reticulated meshed geometries. On the simulation side, retQSS profits from the discrete-event nature of Quantized State System (QSS) methods, which enable efficient particle tracking algorithms that are agnostic of the application domain. On the modeling side, retQSS relies on the standardized Modelica modeling language, yielding compact and elegant specifications of hybrid (continuous/discrete) dynamic systems. Combined together, these features offer a sound, general-purpose framework for modeling and simulation of particle systems. We show how the state-events that arise when particles interact with a reticulated mesh are seamlessly translated into easily tractable time-events. The latter can substantially improve simulation performance in scenarios where discontinuities dominate the computational demand. We showcase the flexibility of our approach by addressing four case studies arising from different application domains. Performance studies revealed that retQSS can perform similarly to, and even outperform, well-known domain-specific particle simulation toolkits while offering a clear and sound accuracy control interface.

A heat equation with memory: Large-time behavior

We study the large-time behavior in all Lp norms of solutions to a heat equation with a Caputo α-time derivative posed in RN (0<α<1). These are known as subdiffusion equations. The initial data are assumed to be integrable, and, when required, to be also in Lp.We find that the decay rate in all Lp norms, 1≤p≤∞, depends greatly on the space-time scale under consideration. This result explains in particular the so called “critical dimension phenomenon” (cf. [21]).Moreover, we find the final profiles (that strongly depend on the scale). The most striking result states that in compact sets the final profile (in all Lp norms) is a multiple of the Newtonian potential of the initial datum.Our results are very different from the ones for classical diffusion equations and show that, in accordance with the physics they have been proposed for, these are good models for particle systems with sticking and trapping phenomena or fluids with memory.

Modeling Food Particle Systems: A Review of Current Progress and Challenges.

For many years, food engineers have attempted to describe physical phenomena such as heat and mass transfer in food via mathematical models. Still, the impact and benefits of computer-aided engineering are less established in food than in most other industries today. Complexity in the structure and composition of food matrices are largely responsible for this gap. During processing of food, its temperature, moisture, and structure can change continuously, along with its physical properties. We summarize the knowledge foundation, recent progress, and remaining limitations in modeling food particle systems in four relevant areas: flowability, size reduction, drying, and granulation and agglomeration. Our goal is to enable researchers in academia and industry dealing with food powders to identify approaches to address their challenges with adequate model systems or through structural and compositional simplifications. With advances in computer simulation capacity, detailed particle-scale models are now available for many applications. Here, we discuss aspects that require further attention, especially related to physics-based contact models for discrete-element models of food particle systems.

The rapid assessment for three-dimensional potential model of large-scale particle system by a modified multilevel fast multipole algorithm

In this study, a modified multilevel fast multipole algorithm is constructed for investigating large-scale particle systems. The algorithm expands the number of levels of the modified dual-level fast multipole algorithm from dual-level grids to multipole levels by a layer-by-layer correction and recursive calculation. The linear equations on coarse grid are recursively solved by a two-level grid. The single sparse matrix having higher filling rate is decomposed into a set of sparse matrices with much lower filling rate. Subsequent theoretical analysis and examples demonstrate that the total storage space of sparse matrices is significantly reduced, yet efficiency of the algorithm is almost unaffected. The fast multipole method is applied to expedite the matrix–vector multiplications. Complexity analysis demonstrates the algorithm has O(N) operation efficiency and storage complexity for three-dimensional potential model. A potential example with 10 million degrees of freedom is accurately computed via a single laptop with 16GB RAM. Finally, the development process of the modified multilevel fast multipole algorithm is briefly overviewed.

Structure and defects in melting process of quasi-two-dimensional wet particle system

The study of structural defects in particle systems is of great value for studying solid-liquid melting. The volume fraction is a key parameter that can be used to accurately quantify the phase-transition process. The collective behavior and interaction form in a wet particle system are much more complex than that of a dry particle material because of the existence of liquid bridge force between the wet particles. In this paper, the structural defects and the critical value of solid-liquid transformation in the monolayer wet particles during solid-liquid melting under vertical vibration are experimentally studied. The contact model of the wet particle system is constructed according to experimental and theoretical analysis, and the structural changes of the particles in the melting process of the quasi-two-dimensional wet particle system are quantified. The Voronoi tessellation is established to study the phase transition of the particle system, and the local volume fraction is adopted to determine the state of structural defect change during melting. The experimental results indicate that the phase-transition process is caused by structural defects in the solid. The defects appear from the edge of the particle system, and the chain defect pairs spread to the center. The reason for structural defects at the edge of the cluster is that the particles at the edge of the cluster are subjected to less liquid bridge force, and the kinetic energy brought by the collision between the particles and the bottom wall makes the particles become active and begin to explore the available space. The chain defects are caused by the force chain generated by the fluid bridge force, which makes the particles tend to move together in rows. In addition, the local volume fraction of seven-phase defective particles decreases significantly and is much smaller than that of five-phase defective particles and six-phase defective particles when defects occur. Therefore, the evolution and the critical state of the structural defects can be quantified by measuring the change in the minimum local volume fraction (the local volume fraction of particles with 7-fold defects) in the particle system. The local volume fraction of the analysis shows that when the minimum local volume fraction &lt;i&gt;ϕ&lt;/i&gt; ≤ 0.6652 defects occur, and when &lt;i&gt;ϕ&lt;/i&gt; ≤ 0.4872 particle system transforms from solid to liquid.

Analysis of optical properties in particle curtains

Optical properties in particle curtains are investigated by means of a Monte Carlo Ray-Tracing (MCRT) model. The MCRT model calculates absorptance, transmittance and reflectance of curtains formed by discrete particles under different conditions. The effect of particle diameter, curtain thickness and solids volume fraction is studied for particles made of two materials with different absorptivity: sand (αp = 0.34) and CARBO (αp = 0.87). The absorptance of curtains with sand particles and CARBO particles can increase up to 0.75 and 0.97, respectively, in opaque curtains with solids volume fractions close to zero, which requires very thick curtains. If the opacity of the curtain decreases due to a smaller thickness, a greater particle diameter or a smaller solids volume fraction, the curtain absorptance decreases. Besides the MCRT model, an analytical model is developed to predict the optical properties of particle curtains in a simpler way than the MCRT method. The MCRT is used to validate the analytical model. The maximum difference in the curtain absorptance calculated by the MCRT model and the absorptance calculated by the analytical model is 0.048 in the case of sand and 0.02 in the case of CARBO particles. These small differences make the analytical model a very useful tool to integrate the calculation of optical properties in complex models of particle systems.